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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..d7b82bc --- /dev/null +++ b/.gitattributes @@ -0,0 +1,4 @@ +*.txt text eol=lf +*.htm text eol=lf +*.html text eol=lf +*.md text eol=lf diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..6312041 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,11 @@ +This eBook, including all associated images, markup, improvements, +metadata, and any other content or labor, has been confirmed to be +in the PUBLIC DOMAIN IN THE UNITED STATES. + +Procedures for determining public domain status are described in +the "Copyright How-To" at https://www.gutenberg.org. + +No investigation has been made concerning possible copyrights in +jurisdictions other than the United States. Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..4574e59 --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #50572 (https://www.gutenberg.org/ebooks/50572) diff --git a/old/50572-0.txt b/old/50572-0.txt deleted file mode 100644 index 344f7f4..0000000 --- a/old/50572-0.txt +++ /dev/null @@ -1,13279 +0,0 @@ -*** START OF THE PROJECT GUTENBERG EBOOK 50572 *** - -GOETHE'S - -THEORY OF COLOURS; - -TRANSLATED FROM THE GERMAN: - -WITH NOTES BY - -CHARLES LOCK EASTLAKE, R.A., F.R.S. - - - "Cicero varietatem propriè in coloribus nasci, hinc in - alienum migrare existimavit. Certè non alibi natura - copiosius aut majore lasciviâ opes suas commendavit. - Metalla, gemmas, marmora, flores, astra, omnia denique quæ - progenuit suis etiam coloribus distinxit; ut venia debeatur - si quis in tam numerosâ rerum sylvâ caligaverit." - - CELIO CALCAGNINI. - -LONDON: - -JOHN MURRAY, ALBEMARLE STREET. - -1840 - - - - - -TO - -JEREMIAH HARMAN, Esq. - - Dear Sir, - - I dedicate to you the following translation as a testimony - of my sincere gratitude and respect; in doing so, I but - follow the example of Portius, an Italian writer, who - inscribed his translation of Aristotle's Treatise on Colours - to one of the Medici. - - I have the honour to be, - - Dear Sir, - - Your most obliged and obedient Servant, - - C. L. EASTLAKE. - - - - -THE TRANSLATOR'S PREFACE. - - -English writers who have spoken of Goethe's "Doctrine of Colours,"[1] -have generally confined their remarks to those parts of the work in -which he has undertaken to account for the colours of the prismatic -spectrum, and of refraction altogether, on principles different -from the received theory of Newton. The less questionable merits -of the treatise consisting of a well-arranged mass of observations -and experiments, many of which are important and interesting, have -thus been in a great measure overlooked. The translator, aware of -the opposition which the theoretical views alluded to have met with, -intended at first to make a selection of such of the experiments as -seem more directly applicable to the theory and practice of painting. -Finding, however, that the alterations this would have involved would -have been incompatible with a clear and connected view of the author's -statements, he preferred giving the theory itself entire, reflecting, -at the same time, that some scientific readers may be curious to hear -the author speak for himself even on the points at issue. - -In reviewing the history and progress of his opinions and researches, -Goethe tells us that he first submitted his views to the public -in two short essays entitled "Contributions to Optics." Among the -circumstances which he supposes were unfavourable to him on that -occasion, he mentions the choice of his title, observing that by a -reference to optics he must have appeared to make pretensions to a -knowledge of mathematics, a science with which he admits he was very -imperfectly acquainted. Another cause to which he attributes the severe -treatment he experienced, was his having ventured so openly to question -the truth of the established theory: but this last provocation could -not be owing to mere inadvertence on his part; indeed the larger work, -in which he alludes to these circumstances, is still more remarkable -for the violence of his objections to the Newtonian doctrine. - -There can be no doubt, however, that much of the opposition Goethe met -with was to be attributed to the manner as well as to the substance -of his statements. Had he contented himself with merely detailing his -experiments and showing their application to the laws of chromatic -harmony, leaving it to others to reconcile them as they could with the -pre-established system, or even to doubt in consequence, the truth of -some of the Newtonian conclusions, he would have enjoyed the credit -he deserved for the accuracy and the utility of his investigations. -As it was, the uncompromising expression of his convictions only -exposed him to the resentment or silent neglect of a great portion -of the scientific world, so that for a time he could not even obtain -a fair hearing for the less objectionable or rather highly valuable -communications contained in his book. A specimen of his manner of -alluding to the Newtonian theory will be seen in the preface. - -It was quite natural that this spirit should call forth a somewhat -vindictive feeling, and with it not a little uncandid as well as -unsparing criticism. "The Doctrine of Colours" met with this reception -in Germany long before it was noticed in England, where a milder and -fairer treatment could hardly be expected, especially at a time when, -owing perhaps to the limited intercourse with the continent, German -literature was far less popular than it is at present. This last fact, -it is true, can be of little importance in the present instance, -for although the change of opinion with regard to the genius of an -enlightened nation must be acknowledged to be beneficial, it is to be -hoped there is no fashion in science, and the translator begs to state -once for all, that in advocating the neglected merits of the "Doctrine -of Colours," he is far from undertaking to defend its imputed errors. -Sufficient time has, however, now elapsed since the publication of this -work (in 1810) to allow a calmer and more candid examination of its -claims. In this more pleasing task Germany has again for some time led -the way, and many scientific investigators have followed up the hints -and observations of Goethe with a due acknowledgment of the acuteness -of his views.[2] - -It may require more magnanimity in English scientific readers to do -justice to the merits of one who was so open and, in many respects, it -is believed, so mistaken an opponent of Newton; but it must be admitted -that the statements of Goethe contain more useful principles in all -that relates to harmony of colour than any that have been derived from -the established doctrine. It is no derogation of the more important -truths of the Newtonian theory to say, that the views it contains -seldom appear in a form calculated for direct application to the arts. -The principle of contrast, so universally exhibited in nature, so -apparent in the action and re-action of the eye itself, is scarcely -hinted at. The equal pretensions of seven colours, as such, and the -fanciful analogies which their assumed proportions could suggest, have -rarely found favour with the votaries of taste,--indeed they have -long been abandoned even by scientific authorities.[3] And here the -translator stops: he is quite aware that the defects which make the -Newtonian theory so little available for æsthetic application, are -far from invalidating its more important conclusions in the opinion -of most scientific men. In carefully abstaining therefore from any -comparison between the two theories in these latter respects, he may -still be permitted to advocate the clearness and fulness of Goethe's -experiments. The German philosopher reduces the colours to their -origin and simplest elements; he sees and constantly bears in mind, and -sometimes ably elucidates, the phenomena of contrast and gradation, -two principles which may be said to make up the artist's world, and to -constitute the chief elements of beauty. These hints occur mostly in -what may be called the scientific part of the work. On the other hand, -in the portion expressly devoted to the æsthetic application of the -doctrine, the author seems to have made but an inadequate use of his -own principles. - -In that part of the chapter on chemical colours which relates to the -colours of plants and animals, the same genius and originality which -are displayed in the Essays on Morphology, and which have secured -to Goethe undisputed rank among the investigators of nature, are -frequently apparent. - -But one of the most interesting features of Goethe's theory, although -it cannot be a recommendation in a scientific point of view, is, that -it contains, undoubtedly with very great improvements, the general -doctrine of the ancients and of the Italians at the revival of letters. -The translator has endeavoured, in some notes, to point out the -connexion between this theory and the practice of the Italian painters. - -The "Doctrine of Colours," as first published in 1810, consists of -two volumes in 8vo., and sixteen plates, with descriptions, in 4to. -It is divided into three parts, a didactic, a controversial, and an -historical part; the present translation is confined to the first of -these, with such extracts from the other two as seemed necessary, -in fairness to the author, to explain some of his statements. The -polemical and historical parts are frequently alluded to in the -preface and elsewhere in the present work, but it has not been thought -advisable to omit these allusions. No alterations whatever seem to -have been made by Goethe in the didactic portion in later editions, -but he subsequently wrote an additional chapter on entoptic colours, -expressing his wish that it might be inserted in the theory itself at -a particular place which he points out. The form of this additional -essay is, however, very different from that of the rest of the work, -and the translator has therefore merely given some extracts from it in -the appendix. The polemical portion has been more than once omitted in -later editions. - -In the two first parts the author's statements are arranged -numerically, in the style of Bacon's Natural History. This, we are -told, was for the convenience of reference; but many passages are -thus separately numbered which hardly seem to have required it. The -same arrangement is, however, strictly followed in the translation to -facilitate a comparison with the original where it may be desired; and -here the translator observes, that although he has sometimes permitted -himself to make slight alterations, in order to avoid unnecessary -repetition, or to make the author's meaning clearer, he feels that an -apology may rather be expected from him for having omitted so little. -He was scrupulous on this point, having once determined to translate -the whole treatise, partly, as before stated, from a wish to deal -fairly with a controversial writer, and partly because many passages, -not directly bearing on the scientific views, are still characteristic -of Goethe. The observations which the translator has ventured to add -are inserted in the appendix: these observations are chiefly confined -to such of the author's opinions and conclusions as have direct -reference to the arts; they seldom interfere with the scientific -propositions, even where these have been considered most vulnerable. - - -[1] "Farbenlehre"--in the present translation generally rendered -"Theory of Colours." - -[2] Sixteen years after the appearance of the Farbenlehre, Dr. -Johannes Müller devoted a portion of his work, "Zur vergleichenden -Physiologie des Gesichtssinnes des Menschen und der Thiere," to the -critical examination of Goethe's theory. In his introductory remarks he -expresses himself as follows--"For my own part I readily acknowledge -that I have been greatly indebted to Goethe's treatise, and can truly -say that without having studied it for some years in connexion with the -actual phenomena, the present work would hardly have been undertaken. -I have no hesitation in confessing more particularly that I have full -faith in Goethe's statements, where they are merely descriptive of -the phenomena, and where the author does not enter into explanations -involving a decision on the great points of controversy." The names of -Hegel, Schelling, Seebeck, Steffens, may also be mentioned, and many -others might be added, as authorities more or less favourable to the -Farbenlehre. - -[3] "When Newton attempted to reckon up the rays of light decomposed -by the prism," says Sir John Leslie, "and ventured to assign the -famous number _seven_, he was apparently influenced by some lurking -disposition towards mysticism. If any unprejudiced person will fairly -repeat the experiment, he must soon be convinced that the various -coloured spaces which paint the spectrum slide into each other by -indefinite shadings: he may name four or five principal colours, but -the subordinate spaces are evidently so multiplied as to be incapable -of enumeration. The same illustrious mathematician, we can hardly -doubt, was betrayed by a passion for analogy, when he imagined that the -primary colours are distributed over the spectrum after the proportions -of the diatonic scale of music, since those intermediate spaces have -really no precise and defined limits."--_Treatises on Various Subjects -of Natural and Chemical Philosophy_, p. 59. - - - - -PREFACE TO THE FIRST EDITION OF 1810. - - -It may naturally be asked whether, in proposing to treat of colours, -light itself should not first engage our attention: to this we briefly -and frankly answer that since so much has already been said on the -subject of light, it can hardly be desirable to multiply repetitions by -again going over the same ground. - -Indeed, strictly speaking, it is useless to attempt to express the -nature of a thing abstractedly. Effects we can perceive, and a complete -history of those effects would, in fact, sufficiently define the -nature of the thing itself. We should try in vain to describe a man's -character, but let his acts be collected and an idea of the character -will be presented to us. - -The colours are acts of light; its active and passive modifications: -thus considered we may expect from them some explanation respecting -light itself. Colours and light, it is true, stand in the most intimate -relation to each other, but we should think of both as belonging to -nature as a whole, for it is nature as a whole which manifests itself -by their means in an especial manner to the sense of sight. - -The completeness of nature displays itself to another sense in a -similar way. Let the eye be closed, let the sense of hearing be -excited, and from the lightest breath to the wildest din, from the -simplest sound to the highest harmony, from the most vehement and -impassioned cry to the gentlest word of reason, still it is Nature that -speaks and manifests her presence, her power, her pervading life and -the vastness of her relations; so that a blind man to whom the infinite -visible is denied, can still comprehend an infinite vitality by means -of another organ. - -And thus as we descend the scale of being, Nature speaks to other -senses--to known, misunderstood, and unknown senses: so speaks she with -herself and to us in a thousand modes. To the attentive observer she -is nowhere dead nor silent; she has even a secret agent in inflexible -matter, in a metal, the smallest portions of which tell us what -is passing in the entire mass. However manifold, complicated, and -unintelligible this language may often seem to us, yet its elements -remain ever the same. With light poise and counterpoise, Nature -oscillates within her prescribed limits, yet thus arise all the -varieties and conditions of the phenomena which are presented to us in -space and time. - -Infinitely various are the means by which we become acquainted with -these general movements and tendencies: now as a simple repulsion and -attraction, now as an upsparkling and vanishing light, as undulation -in the air, as commotion in matter, as oxydation and de-oxydation; but -always, uniting or separating, the great purpose is found to be to -excite and promote existence in some form or other. - -The observers of nature finding, however, that this poise and -counterpoise are respectively unequal in effect, have endeavoured to -represent such a relation in terms. They have everywhere remarked and -spoken of a greater and lesser principle, an action and resistance, -a doing and suffering, an advancing and retiring, a violent and -moderating power; and thus a symbolical language has arisen, which, -from its close analogy, may be employed as equivalent to a direct and -appropriate terminology. - -To apply these designations, this language of Nature to the subject -we have undertaken: to enrich and amplify this language by means of -the theory of colours and the variety of their phenomena, and thus -facilitate the communication of higher theoretical views, was the -principal aim of the present treatise. - -The work itself is divided into three parts. The first contains the -outline of a theory of colours. In this, the innumerable cases which -present themselves to the observer are collected under certain leading -phenomena, according to an arrangement which will be explained in -the Introduction; and here it may be remarked, that although we have -adhered throughout to experiment, and throughout considered it as our -basis, yet the theoretical views which led to the arrangement alluded -to, could not but be stated. It is sometimes unreasonably required by -persons who do not even themselves attend to such a condition, that -experimental information should be submitted without any connecting -theory to the reader or scholar, who is himself to form his conclusions -as he may list. Surely the mere inspection of a subject can profit us -but little. Every act of seeing leads to consideration, consideration -to reflection, reflection to combination, and thus it may be said that -in every attentive look on nature we already theorise. But in order to -guard against the possible abuse of this abstract view, in order that -the practical deductions we look to should be really useful, we should -theorise without forgetting that we are so doing, we should theorise -with mental self-possession, and, to use a bold word, with irony. - -In the second part[1] we examine the Newtonian theory; a theory which -by its ascendancy and consideration has hitherto impeded a free inquiry -into the phenomena of colours. We combat that hypothesis, for although -it is no longer found available, it still retains a traditional -authority in the world. Its real relations to its subject will require -to be plainly pointed out; the old errors must be cleared away, if the -theory of colours is not still to remain in the rear of so many other -better investigated departments of natural science. Since, however, -this second part of our work may appear somewhat dry as regards its -matter, and perhaps too vehement and excited in its manner, we may here -be permitted to introduce a sort of allegory in a lighter style, as a -prelude to that graver portion, and as some excuse for the earnestness -alluded to. - -We compare the Newtonian theory of colours to an old castle, which -was at first constructed by its architect with youthful precipitation; -it was, however, gradually enlarged and equipped by him according -to the exigencies of time and circumstances, and moreover was still -further fortified and secured in consequence of feuds and hostile -demonstrations. - -The same system was pursued by his successors and heirs: their -increased wants within, the harassing vigilance of their opponents -without, and various accidents compelled them in some places to build -near, in others in connexion with the fabric, and thus to extend the -original plan. - -It became necessary to connect all these incongruous parts and -additions by the strangest galleries, halls and passages. All damages, -whether inflicted by the hand of the enemy or the power of time, were -quickly made good. As occasion required, they deepened the moats, -raised the walls, and took care there should be no lack of towers, -battlements, and embrasures. This care and these exertions gave rise -to a prejudice in favour of the great importance of the fortress, -and still upheld that prejudice, although the arts of building and -fortification were by this time very much advanced, and people had -learnt to construct much better dwellings and defences in other cases. -But the old castle was chiefly held in honour because it had never -been taken, because it had repulsed so many assaults, had baffled so -many hostile operations, and had always preserved its virgin renown. -This renown, this influence lasts even now: it occurs to no one that -the old castle is become uninhabitable. Its great duration, its costly -construction, are still constantly spoken of. Pilgrims wend their -way to it; hasty sketches of it are shown in all schools, and it is -thus recommended to the reverence of susceptible youth. Meanwhile, -the building itself is already abandoned; its only inmates are a few -invalids, who in simple seriousness imagine that they are prepared for -war. - -Thus there is no question here respecting a tedious siege or a -doubtful war; so far from it we find this eighth wonder of the world -already nodding to its fall as a deserted piece of antiquity, and -begin at once, without further ceremony, to dismantle it from gable -and roof downwards; that the sun may at last shine into the old nest -of rats and owls, and exhibit to the eye of the wondering traveller -that labyrinthine, incongruous style of building, with its scanty, -make-shift contrivances, the result of accident and emergency, its -intentional artifice and clumsy repairs. Such an inspection will, -however, only be possible when wall after wall, arch after arch, is -demolished, the rubbish being at once cleared away as well as it can be. - -To effect this, and to level the site where it is possible to do -so, to arrange the materials thus acquired, so that they can be -hereafter again employed for a new building, is the arduous duty -we have undertaken in this Second Part. Should we succeed, by a -cheerful application of all possible ability and dexterity, in razing -this Bastille, and in gaining a free space, it is thus by no means -intended at once to cover the site again and to encumber it with a new -structure; we propose rather to make use of this area for the purpose -of passing in review a pleasing and varied series of illustrative -figures. - -The third part is thus devoted to the historical account of early -inquirers and investigators. As we before expressed the opinion that -the history of an individual displays his character, so it may here be -well affirmed that the history of science is science itself. We cannot -clearly be aware of what we possess till we have the means of knowing -what others possessed before us. We cannot really and honestly rejoice -in the advantages of our own time if we know not how to appreciate -the advantages of former periods. But it was impossible to write, or -even to prepare the way for a history of the theory of colours while -the Newtonian theory existed; for no aristocratic presumption has ever -looked down on those who were not of its order, with such intolerable -arrogance as that betrayed by the Newtonian school in deciding on -all that had been done in earlier times and all that was done around -it. With disgust and indignation we find Priestley, in his History -of Optics, like many before and after him, dating the success of all -researches into the world of colours from the epoch of a decomposed ray -of light, or what pretended to be so; looking down with a supercilious -air on the ancient and less modern inquirers, who, after all, had -proceeded quietly in the right road, and who have transmitted to us -observations and thoughts in detail which we can neither arrange better -nor conceive more justly. - -We have a right to expect from one who proposes to give the history of -any science, that he inform us how the phenomena of which it treats -were gradually known, and what was imagined, conjectured, assumed, -or thought respecting them. To state all this in due connexion is by -no means an easy task; need we say that to write a history at all is -always a hazardous affair; with the most honest intention there is -always a danger of being dishonest; for in such an undertaking, a -writer tacitly announces at the outset that he means to place some -things in light, others in shade. The author has, nevertheless, long -derived pleasure from the prosecution of his task: but as it is the -intention only that presents itself to the mind as a whole, while the -execution is generally accomplished portion by portion, he is compelled -to admit that instead of a history he furnishes only materials for -one. These materials consist in translations, extracts, original and -borrowed comments, hints, and notes; a collection, in short, which, if -not answering all that is required, has at least the merit of having -been made with earnestness and interest. Lastly, such materials,--not -altogether untouched it is true, but still not exhausted,--may be more -satisfactory to the reflecting reader in the state in which they are, -as he can easily combine them according to his own judgment. - -This third part, containing the history of the science, does not, -however, thus conclude the subject: a fourth supplementary portion[2] -is added. This contains a recapitulation or revision; with a view -to which, chiefly, the paragraphs are headed numerically. In the -execution of a work of this kind some things may be forgotten, some -are of necessity omitted, so as not to distract the attention, some -can only be arrived at as corollaries, and others may require to be -exemplified and verified: on all these accounts, postscripts, additions -and corrections are indispensable. This part contains, besides, some -detached essays; for example, that on the atmospheric colours; for as -these are introduced in the theory itself without any classification, -they are here presented to the mind's eye at one view. Again, if this -essay invites the reader to consult Nature herself, another is intended -to recommend the artificial aids of science by circumstantially -describing the apparatus which will in future be necessary to assist -researches into the theory of colours. - -In conclusion, it only remains to speak of the plates which are added -at the end of the work;[3] and here we confess we are reminded of that -incompleteness and imperfection which the present undertaking has, -in common with all others of its class; for as a good play can be in -fact only half transmitted to writing, a great part of its effect -depending on the scene, the personal qualities of the actor, the powers -of his voice, the peculiarities of his gestures, and even the spirit -and favourable humour of the spectators; so it is, in a still greater -degree, with a book which treats of the appearances of nature. To be -enjoyed, to be turned to account, Nature herself must be present to -the reader, either really, or by the help of a lively imagination. -Indeed, the author should in such cases communicate his observations -orally, exhibiting the phenomena he describes--as a text, in the -first instance,--partly as they appear to us unsought, partly as they -may be presented by contrivance to serve in particular illustration. -Explanation and description could not then fail to produce a lively -impression. - -The plates which generally accompany works like the present are thus -a most inadequate substitute for all this; a physical phenomenon -exhibiting its effects on all sides is not to be arrested in lines -nor denoted by a section. No one ever dreams of explaining chemical -experiments with figures; yet it is customary in physical researches -nearly allied to these, because the object is thus found to be in -some degree answered. In many cases, however, such diagrams represent -mere notions; they are symbolical resources, hieroglyphic modes of -communication, which by degrees assume the place of the phenomena and -of Nature herself, and thus rather hinder than promote true knowledge. -In the present instance we could not dispense with plates, but we have -endeavoured so to construct them that they may be confidently referred -to for the explanation of the didactic and polemical portions. Some of -these may even be considered as forming part of the apparatus before -mentioned. - -We now therefore refer the reader to the work itself; first, only -repeating a request which many an author has already made in vain, and -which the modern German reader, especially, so seldom grants:-- - - Si quid novisti rectius istis - Candidus imperti; si non, his utere mecum. - - -[1] The Polemical part. - -[2] This preface must have been written before the work was finished, -for at the conclusion of the historical part there is only an apology -for the non-appearance of the supplement here alluded to. - -[3] In the present translation the necessary plates accompany the -text. - - - - -CONTENTS - - Introduction xxxvii - - - PART I. - - PHYSIOLOGICAL COLOURS. - - I. Effects of Light and Darkness on the Eye - II. Effects of Black and White Objects on the Eye - III. Grey Surfaces and Objects - IV. Dazzling Colourless Objects - V. Coloured Objects - VI. Coloured Shadows - VII. Faint Lights - VIII. Subjective Halos - Pathological Colours--Appendix - - - PART II. - - PHYSICAL COLOURS. - - IX. Dioptrical Colours - X. Dioptrical Colours of the First Class - XI. Dioptrical Colours of the Second Class--Refraction - Subjective Experiments - XII. Refraction without the Appearance of Colour - XIII. Conditions of the Appearance of Colour - XIV. Conditions under which the Appearance of Colour increases - XV. Explanation of the foregoing Phenomena - XVI. Decrease of the Appearance of Colour - XVII. Grey Objects displaced by Refraction - XVIII. Coloured Objects displaced by Refraction - XIX. Achromatism and Hyperchromatism - XX. Advantages of Subjective Experiments-- - Transition to the Objective - Objective Experiments - XXI. Refraction without the Appearance of Colour - XXII. Conditions of the Appearance of Colour - XXIII. Conditions of the Increase of Colour - XXIV. Explanation of the foregoing Phenomena - XXV. Decrease of the Appearance of Colour - XXVI. Grey Objects - XXVII. Coloured Objects - XXVIII. Achromatism and Hyperchromatism - XXIX. Combination of Subjective and Objective Experiments - XXX. Transition - XXXI. Catoptrical Colours - XXXII. Paroptical Colours - XXXIII. Epoptical Colours - - - PART III. - - CHEMICAL COLOURS. - - XXXIV. Chemical Contrast - XXXV. White - XXXVI. Black - XXXVII. First Excitation of Colour - XXXVIII. Augmentation of Colour - XXXIX. Culmination - XL. Fluctuation - XLI. Passage through the Whole Scale - XLII. Inversion - XLIII. Fixation - XLIV. Intermixture, Real - XLV. Intermixture, Apparent - XLVI. Communication, Actual - XLVII. Communication, Apparent - XLVIII. Extraction - XLIX. Nomenclature - L. Minerals - LI. Plants - LII. Worms, Insects, Fishes - LIII. Birds - LIV. Mammalia and Human Beings - LV. Physical and Chemical Effects of the Transmission - of Light through Coloured Mediums - LVI. Chemical Effect in Dioptrical Achromatism - - - PART IV. - - GENERAL CHARACTERISTICS. - - The Facility with which Colour appears - The Definite Nature of Colour - Combination of the Two Principles - Augmentation to Red - Junction of the Two Augmented Extremes - Completeness the Result of Variety in Colour - Harmony of the Complete State - Facility with which Colour may be made to tend either to - the Plus or Minus side - Evanescence of Colour - Permanence of Colour - - - PART V. - - RELATION TO OTHER PURSUITS. - - Relation to Philosophy - Relation to Mathematics - Relation to the Technical Operations of the Dyer - Relation to Physiology and Pathology - Relation to Natural History - Relation to General Physics - Relation to the Theory of Music - Concluding Observations on Terminology - - - PART VI. - - EFFECT OF COLOUR WITH REFERENCE TO MORAL ASSOCIATIONS. - - Yellow - Red-Yellow - Yellow-Red - Blue - Red-Blue - Blue-Red - Red - Green - Completeness and Harmony - Characteristic Combinations - Yellow and Blue - Yellow and Red - Blue and Red - Yellow-Red and Blue-Red - Combinations Non-Characteristic - Relation of the Combinations to Light and Dark - Considerations derived from the Evidence of Experience and History - Æsthetic Influence - Chiaro-Scuro - Tendency to Colour - Keeping - Colouring - Colour in General Nature - Colour of Particular Objects - Characteristic Colouring - Harmonious Colouring - Genuine Tone - False Tone - Weak Colouring - The Motley - Dread of Theory - Ultimate Aim - Grounds - Pigments - Allegorical, Symbolical, Mystical Application of Colour - Concluding Observations - - - - -OUTLINE - -OF A - -THEORY OF COLOURS. - - "Si vera nostra sunt aut falsa, erunt talia, licet nostra - per vitam defendimus. Post fata nostra pueri qui nunc ludunt - nostri judices erunt." - - - - -INTRODUCTION. - - -The desire of knowledge is first stimulated in us when remarkable -phenomena attract our attention. In order that this attention be -continued, it is necessary that we should feel some interest in -exercising it, and thus by degrees we become better acquainted with the -object of our curiosity. During this process of observation we remark -at first only a vast variety which presses indiscriminately on our -view; we are forced to separate, to distinguish, and again to combine; -by which means at last a certain order arises which admits of being -surveyed with more or less satisfaction. - -To accomplish this, only in a certain degree, in any department, -requires an unremitting and close application; and we find, for this -reason, that men prefer substituting a general theoretical view, or -some system of explanation, for the facts themselves, instead of taking -the trouble to make themselves first acquainted with cases in detail -and then constructing a whole. - -The attempt to describe and class the phenomena of colours has been -only twice made: first by Theophrastus,[1] and in modern times by -Boyle. The pretensions of the present essay to the third place will -hardly be disputed. - -Our historical survey enters into further details. Here we merely -observe that in the last century such a classification was not to be -thought of, because Newton had based his hypothesis on a phenomenon -exhibited in a complicated and secondary state; and to this the other -cases that forced themselves on the attention were contrived to be -referred, when they could not be passed over in silence; just as an -astronomer would do, if from whim he were to place the moon in the -centre of our system; he would be compelled to make the earth, sun, and -planets revolve round the lesser body, and be forced to disguise and -gloss over the error of his first assumption by ingenious calculations -and plausible statements. - -In our prefatory observations we assumed the reader to be acquainted -with what was known respecting light; here we assume the same with -regard to the eye. We observed that all nature manifests itself by -means of colours to the sense of sight. We now assert, extraordinary as -it may in some degree appear, that the eye sees no form, inasmuch as -light, shade, and colour together constitute that which to our vision -distinguishes object from object, and the parts of an object from each -other. From these three, light, shade, and colour, we construct the -visible world, and thus, at the same time, make painting possible, -an art which has the power of producing on a flat surface a much more -perfect visible world than the actual one can be. - -The eye may be said to owe its existence to light, which calls forth, -as it were, a sense that is akin to itself; the eye, in short, is -formed with reference to light, to be fit for the action of light; the -light it contains corresponding with the light without. - -We are here reminded of a significant adage in constant use with the -ancient Ionian school--"Like is only known by Like;" and again, of the -words of an old mystic writer, which may be thus rendered, "If the eye -were not sunny, how could we perceive light? If God's own strength -lived not in us, how could we delight in Divine things?" This immediate -affinity between light and the eye will be denied by none; to consider -them as identical in substance is less easy to comprehend. It will be -more intelligible to assert that a dormant light resides in the eye, -and that it may be excited by the slightest cause from within or from -without. In darkness we can, by an effort of imagination, call up the -brightest images; in dreams objects appear to us as in broad daylight; -awake, the slightest external action of light is perceptible, and if -the organ suffers an actual shock, light and colours spring forth. -Here, however, those who are wont to proceed according to a certain -method, may perhaps observe that as yet we have not decidedly explained -what colour is. This question, like the definition of light and the -eye, we would for the present evade, and would appeal to our inquiry -itself, where we have circumstantially shown how colour is produced. -We have only therefore to repeat that colour is a law of nature in -relation with the sense of sight. We must assume, too, that every one -has this sense, that every one knows the operation of nature on it, for -to a blind man it would be impossible to speak of colours. - -That we may not, however, appear too anxious to shun such an -explanation, we would restate what has been said as follows: colour is -an elementary phenomenon in nature adapted to the sense of vision; a -phenomenon which, like all others, exhibits itself by separation and -contrast, by commixture and union, by augmentation and neutralization, -by communication and dissolution: under these general terms its nature -may be best comprehended. - -We do not press this mode of stating the subject on any one. Those -who, like ourselves, find it convenient, will readily adopt it; but we -have no desire to enter the lists hereafter in its defence. From time -immemorial it has been dangerous to treat of colour; so much so, that -one of our predecessors ventured on a certain occasion to say, "The ox -becomes furious if a red cloth is shown to him; but the philosopher, -who speaks of colour only in a general way, begins to rave." - -Nevertheless, if we are to proceed to give some account of our work, to -which we have appealed, we must begin by explaining how we have classed -the different conditions under which colour is produced. We found three -modes in which it appears; three classes of colours, or rather three -exhibitions of them all. The distinctions of these classes are easily -expressed. - -Thus, in the first instance, we considered colours, as far as they -may be said to belong to the eye itself, and to depend on an action -and re-action of the organ; next, they attracted our attention as -perceived in, or by means of, colourless mediums; and lastly, where -we could consider them as belonging to particular substances. We have -denominated the first, physiological, the second, physical, the third, -chemical colours. The first are fleeting and not to be arrested; the -next are passing, but still for a while enduring; the last may be made -permanent for any length of time. - -Having separated these classes and kept them as distinct as possible, -with a view to a clear, didactic exposition, we have been enabled at -the same time to exhibit them in an unbroken series, to connect the -fleeting with the somewhat more enduring, and these again with the -permanent hues; and thus, after having carefully attended to a distinct -classification in the first instance, to do away with it again when a -larger view was desirable. - -In a fourth division of our work we have therefore treated generally -what was previously detailed under various particular conditions, and -have thus, in fact, given a sketch for a future theory of colours. We -will here only anticipate our statements so far as to observe, that -light and darkness, brightness and obscurity, or if a more general -expression is preferred, light and its absence, are necessary to the -production of colour. Next to the light, a colour appears which we call -yellow; another appears next to the darkness, which we name blue. When -these, in their purest state, are so mixed that they are exactly equal, -they produce a third colour called green. Each of the two first-named -colours can however of itself produce a new tint by being condensed or -darkened. They thus acquire a reddish appearance which can be increased -to so great a degree that the original blue or yellow is hardly to -be recognised in it: but the intensest and purest red, especially in -physical cases, is produced when the two extremes of the yellow-red -and blue-red are united. This is the actual state of the appearance -and generation of colours. But we can also assume an existing red in -addition to the definite existing blue and yellow, and we can produce -contrariwise, by mixing, what we directly produced by augmentation or -deepening. With these three or six colours, which may be conveniently -included in a circle, the elementary doctrine of colours is alone -concerned. All other modifications, which may be extended to infinity, -have reference more to the application,--have reference to the -technical operations of the painter and dyer, and the various purposes -of artificial life. To point out another general quality, we may -observe that colours throughout are to be considered as half-lights, as -half-shadows, on which account if they are so mixed as reciprocally to -destroy their specific hues, a shadowy tint, a grey, is produced. - -In the fifth division of our inquiry we had proposed to point out -the relations in which we should wish our doctrine of colours to -stand to other pursuits. Important as this part of our work is, it -is perhaps on this very account not so successful as we could wish. -Yet when we reflect that strictly speaking these relations cannot be -described before they exist, we may console ourselves if we have in -some degree failed in endeavouring for the first time to define them. -For undoubtedly we should first wait to see how those whom we have -endeavoured to serve, to whom we have intended to make an agreeable and -useful offering, how such persons, we say, will accept the result of -our utmost exertion: whether they will adopt it, whether they will make -use of it and follow it up, or whether they will repel, reject, and -suffer it to remain unassisted and neglected. - -Meanwhile, we venture to express what we believe and hope. From the -philosopher we believe we merit thanks for having traced the phenomena -of colours to their first sources, to the circumstances under which -they simply appear and are, and beyond which no further explanation -respecting them is possible. It will, besides, be gratifying to him -that we have arranged the appearances described in a form that admits -of being easily surveyed, even should he not altogether approve of the -arrangement itself. - -The medical practitioner, especially him whose study it is to watch -over the organ of sight, to preserve it, to assist its defects and to -cure its disorders, we reckon to make especially our friend. In the -chapter on the physiological colours, in the Appendix relating to those -that are more strictly pathological, he will find himself quite in his -own province. We are not without hopes of seeing the physiological -phenomena,--a hitherto neglected, and, we may add, most important -branch of the theory of colours,--completely investigated through the -exertions of those individuals who in our own times are treating this -department with success. - -The investigator of nature should receive us cordially, since we -enable him to exhibit the doctrine of colours in the series of other -elementary phenomena, and at the same time enable him to make use of a -corresponding nomenclature, nay, almost the same words and designations -as under the other rubrics. It is true we give him rather more trouble -as a teacher, for the chapter of colours is not now to be dismissed -as heretofore with a few paragraphs and experiments; nor will the -scholar submit to be so scantily entertained as he has hitherto been, -without murmuring. On the other hand, an advantage will afterwards -arise out of this: for if the Newtonian doctrine was easily learnt, -insurmountable difficulties presented themselves in its application. -Our theory is perhaps more difficult to comprehend, but once known, all -is accomplished, for it carries its application along with it. - -The chemist who looks upon colours as indications by which he may -detect the more secret properties of material things, has hitherto -found much inconvenience in the denomination and description of -colours; nay, some have been induced after closer and nicer examination -to look upon colour as an uncertain and fallacious criterion in -chemical operations. Yet we hope by means of our arrangement and the -nomenclature before alluded to, to bring colour again into credit, -and to awaken the conviction that a progressive, augmenting, mutable -quality, a quality which admits of alteration even to inversion, is not -fallacious, but rather calculated to bring to light the most delicate -operations of nature. - -In looking a little further round us, we are not without fears -that we may fail to satisfy another class of scientific men. By an -extraordinary combination of circumstances the theory of colours -has been drawn into the province and before the tribunal of the -mathematician, a tribunal to which it cannot be said to be amenable. -This was owing to its affinity with the other laws of vision which the -mathematician was legitimately called upon to treat. It was owing, -again, to another circumstance: a great mathematician had investigated -the theory of colours, and having been mistaken in his observations as -an experimentalist, he employed the whole force of his talent to give -consistency to this mistake. Were both these circumstances considered, -all misunderstanding would presently be removed, and the mathematician -would willingly co-operate with us, especially in the physical -department of the theory. - -To the practical man, to the dyer, on the other hand, our labour must -be altogether acceptable; for it was precisely those who reflected on -the facts resulting from the operations of dyeing who were the least -satisfied with the old theory: they were the first who perceived the -insufficiency of the Newtonian doctrine. The conclusions of men are -very different according to the mode in which they approach a science -or branch of knowledge; from which side, through which door they -enter. The literally practical man, the manufacturer, whose attention -is constantly and forcibly called to the facts which occur under his -eye, who experiences benefit or detriment from the application of his -convictions, to whom loss of time and money is not indifferent, who -is desirous of advancing, who aims at equalling or surpassing what -others have accomplished,--such a person feels the unsoundness and -erroneousness of a theory much sooner than the man of letters, in whose -eyes words consecrated by authority are at last equivalent to solid -coin; than the mathematician, whose formula always remains infallible, -even although the foundation on which it is constructed may not square -with it. Again, to carry on the figure before employed, in entering -this theory from the side of painting, from the side of æsthetic[2] -colouring generally, we shall be found to have accomplished a -most thank-worthy office for the artist. In the sixth part we have -endeavoured to define the effects of colour as addressed at once to -the eye and mind, with a view to making them more available for the -purposes of art. Although much in this portion, and indeed throughout, -has been suffered to remain as a sketch, it should be remembered that -all theory can in strictness only point out leading principles, under -the guidance of which, practice may proceed with vigour and be enabled -to attain legitimate results. - - -[1] The treatise to which the author alludes in more generally ascribed -to Aristotle.--T. - -[2] Æsthetic--belonging to taste as mere internal sense, from -αἰσθάνομαι, to feel; the word was first used by Wolf.--T. - - - - -PART I. - - -PHYSIOLOGICAL COLOURS. - - -1. - -We naturally place these colours first, because they belong altogether, -or in a great degree, to the _subject_[1]--to the eye itself. They -are the foundation of the whole doctrine, and open to our view the -chromatic harmony on which so much difference of opinion has existed. -They have been hitherto looked upon as extrinsic and casual, as -illusion and infirmity: their appearances have been known from ancient -date; but, as they were too evanescent to be arrested, they were -banished into the region of phantoms, and under this idea have been -very variously described. - -2. - -Thus they are called _colores adventicii_ by Boyle; _imaginarii_ and -_phantastici_ by Rizetti; by Buffon, _couleurs accidentelles_; by -Scherfer, _scheinfarben_ (apparent colours); _ocular illusions_ and -_deceptions of sight_ by many; by Hamberger, _vitia fugitiva_; by -Darwin, _ocular spectra_. - -3. - -We have called them physiological because they belong to the eye in a -healthy state; because we consider them as the necessary conditions -of vision; the lively alternating action of which, with reference to -external objects and a principle within it, is thus plainly indicated. - -4. - -To these we subjoin the pathological colours, which, like all -deviations from a constant law, afford a more complete insight into the -nature of the physiological colours. - - -EFFECTS OF LIGHT AND DARKNESS ON THE EYE. - - -5. - -The retina, after being acted upon by light or darkness, is found to be -in two different states, which are entirely opposed to each other. - -6. - -If we keep the eyes open in a totally dark place, a certain sense of -privation is experienced. The organ is abandoned to itself; it retires -into itself. That stimulating and grateful contact is wanting by means -of which it is connected with the external world, and becomes part of a -whole. - -7. - -If we look on a white, strongly illumined surface, the eye is dazzled, -and for a time is incapable of distinguishing objects moderately -lighted. - -8. - -The whole of the retina is acted on in each of these extreme states, -and thus we can only experience one of these effects at a time. In -the one case (6) we found the organ in the utmost relaxation and -susceptibility; in the other (7) in an overstrained state, and scarcely -susceptible at all. - -9. - -If we pass suddenly from the one state to the other, even without -supposing these to be the extremes, but only, perhaps, a change from -bright to dusky, the difference is remarkable, and we find that the -effects last for some time. - -10. - -In passing from bright daylight to a dusky place we distinguish nothing -at first: by degrees the eye recovers its susceptibility; strong eyes -sooner than weak ones; the former in a minute, while the latter may -require seven or eight minutes. - -11. - -The fact that the eye is not susceptible to faint impressions of -light, if we pass from light to comparative darkness, has led to -curious mistakes in scientific observations. Thus an observer, whose -eyes required some time to recover their tone, was long under the -impression that rotten wood did not emit light at noon-day, even in a -dark room. The fact was, he did not see the faint light, because he was -in the habit of passing from bright sunshine to the dark room, and only -subsequently remained so long there that the eye had time to recover -itself. - -The same may have happened to Doctor Wall, who, in the daytime, even in -a dark room, could hardly perceive the electric light of amber. - -Our not seeing the stars by day, as well as the improved appearance of -pictures seen through a double tube, is also to be attributed to the -same cause. - -12. - -If we pass from a totally dark place to one illumined by the sun, we -are dazzled. In coming from a lesser degree of darkness to light that -is not dazzling, we perceive all objects clearer and better: hence eyes -that have been in a state of repose are in all cases better able to -perceive moderately distinct appearances. - -Prisoners who have been long confined in darkness acquire so great -a susceptibility of the retina, that even in the dark (probably a -darkness very slightly illumined) they can still distinguish objects. - -13. - -In the act which we call seeing, the retina is at one and the same time -in different and even opposite states. The greatest brightness, short -of dazzling, acts near the greatest darkness. In this state we at once -perceive all the intermediate gradations of _chiaro-scuro_, and all the -varieties of hues. - -14. - -We will proceed in due order to consider and examine these elements of -the visible world, as well as the relation in which the organ itself -stands to them, and for this purpose we take the simplest objects. - - -[1] The German distinction between _subject_ and _object_ is so -generally understood and adopted, that it is hardly necessary to -explain that the subject is the _individual_, in this case the -_beholder_; the object, _all that is without him_.--T. - - - - -II. - - -EFFECTS OF BLACK AND WHITE OBJECTS ON THE EYE. - - -15. - -In the same manner as the retina generally is affected by brightness -and darkness, so it is affected by single bright or dark objects. -If light and dark produce different results on the whole retina, so -black and white objects seen at the same time produce the same states -together which light and dark occasioned in succession. - -16. - -A dark object appears smaller than a bright one of the same size. Let -a white disk be placed on a black ground, and a black disk on a white -ground, both being exactly similar in size; let them be seen together -at some distance, and we shall pronounce the last to be about a fifth -part smaller than the other. If the black circle be made larger by so -much, they will appear equal.[1] - -17. - -Thus Tycho de Brahe remarked that the moon in conjunction (the darker -state) appears about a fifth part smaller than when in opposition -(the bright full state). The first crescent appears to belong to a -larger disk than the remaining dark portion, which can sometimes be -distinguished at the period of the new moon. Black dresses make people -appear smaller than light ones. Lights seen behind an edge make an -apparent notch in it. A ruler, behind which the flame of a light just -appears, seems to us indented. The rising or setting sun appears to -make a notch in the horizon. - -[Illustration] - -18. - -Black, as the equivalent of darkness, leaves the organ in a state of -repose; white, as the representative of light, excites it. We may, -perhaps, conclude from the above experiment (16) that the unexcited -retina, if left to itself, is drawn together, and occupies a less space -than in its active state, produced by the excitement of light. - -Hence Kepler says very beautifully: "Certum est vel in retinâ caussâ -picturæ, vel in spiritibus caussâ impressionis, exsistere dilatationem -lucidorum."--_Paralip. in Vitellionem_, p. 220. Scherfer expresses a -similar conjecture.--Note A. - -19. - -However this may be, both impressions derived from such objects remain -in the organ itself, and last for some time, even when the external -cause is removed. In ordinary experience we scarcely notice this, for -objects are seldom presented to us which are very strongly relieved -from each other, and we avoid looking at those appearances that dazzle -the sight. In glancing from one object to another, the succession of -images appears to us distinct; we are not aware that some portion of -the impression derived from the object first contemplated passes to -that which is next looked at. - -20. - -If in the morning, on waking, when the eye is very susceptible, we look -intently at the bars of a window relieved against the dawning sky, and -then shut our eyes or look towards a totally dark place, we shall see a -dark cross on a light ground before us for some time. - -21. - -Every image occupies a certain space on the retina, and of course a -greater or less space in proportion as the object is seen near or at a -distance. If we shut the eyes immediately after looking at the sun we -shall be surprised to find how small the image it leaves appears. - -22. - -If, on the other hand, we turn the open eye towards the side of a -room, and consider the visionary image in relation to other objects, -we shall always see it larger in proportion to the distance of the -surface on which it is thrown. This is easily explained by the laws of -perspective, according to which a small object near covers a great one -at a distance. - -23. - -The duration of these visionary impressions varies with the powers -or structure of the eye in different individuals, just as the time -necessary for the recovery of the tone of the retina varies in passing -from brightness to darkness (10): it can be measured by minutes and -seconds, indeed much more exactly than it could formerly have been -by causing a lighted linstock to revolve rapidly, so as to appear a -circle.--Note B. - -24. - -But the force with which an impinging light impresses the eye is -especially worthy of attention. The image of the sun lasts longest; -other objects, of various degrees of brightness, leave the traces of -their appearance on the eye for a proportionate time. - -25. - -These images disappear by degrees, and diminish at once in distinctness -and in size. - -26. - -They are reduced from the contour inwards, and the impression on some -persons has been that in square images the angles become gradually -blunted till at last a diminished round image floats before the eye. - -27. - -Such an image, when its impression is no more observable, can, -immediately after, be again revived on the retina by opening and -shutting the eye, thus alternately exciting and resting it. - -28. - -Images may remain on the retina in morbid affections of the eye for -fourteen, seventeen minutes, or even longer. This indicates extreme -weakness of the organ, its inability to recover itself; while visions -of persons or things which are the objects of love or aversion indicate -the connexion between sense and thought. - -29. - -If, while the image of the window-bars before mentioned lasts, we -look upon a light grey surface, the cross will then appear light -and the panes dark. In the first case (20) the image was like the -original picture, so that the visionary impression also could continue -unchanged; but in the present instance our attention is excited by a -contrary effect being produced. Various examples have been given by -observers of nature. - -30. - -The scientific men who made observations in the Cordilleras saw a -bright appearance round the shadows of their heads on some clouds. This -example is a case in point; for, while they fixed their eyes on the -dark shadow, and at the same time moved from the spot, the compensatory -light image appeared to float round the real dark one. If we look at -a black disk on a light grey surface, we shall presently, by changing -the direction of the eyes in the slightest degree, see a bright halo -floating round the dark circle. - -A similar circumstance happened to myself: for while, as I sat in the -open air, I was talking to a man who stood at a little distance from me -relieved on a grey sky, it appeared to me, as I slightly altered the -direction of my eyes, after having for some time looked fixedly at him, -that his head was encircled with a dazzling light. - -In the same way probably might be explained the circumstance that -persons crossing dewy meadows at sunrise see a brightness round each -other's heads[2]; the brightness in this case may be also iridescent, -as the phenomena of refraction come into the account. - -Thus again it has been asserted that the shadows of a balloon thrown on -clouds were bordered with bright and somewhat variegated circles. - -Beccaria made use of a paper kite in some experiments on electricity. -Round this kite appeared a small shining cloud varying in size; the -same brightness was even observed round part of the string. Sometimes -it disappeared, and if the kite moved faster the light appeared to -float to and fro for a few moments on the place before occupied. This -appearance, which could not be explained by those who observed it at -the time, was the image which the eye retained of the kite relieved as -a dark mass on a bright sky; that image being changed into a light mass -on a comparatively dark background. - -In optical and especially in chromatic experiments, where the observer -has to do with bright lights whether colourless or coloured, great care -should be taken that the spectrum which the eye retains in consequence -of a previous observation does not mix with the succeeding one, and -thus affect the distinctness and purity of the impression. - -31. - -These appearances have been explained as follows: That portion of the -retina on which the dark cross (29) was impressed is to be considered -in a state of repose and susceptibility. On this portion therefore the -moderately light surface acted in a more lively manner than on the rest -of the retina, which had just been impressed with the light through -the panes, and which, having thus been excited by a much stronger -brightness, could only view the grey surface as a dark. - -32. - -This mode of explanation appears sufficient for the cases in question, -but, in the consideration of phenomena hereafter to be adduced, we are -forced to trace the effects to higher sources. - -33. - -The eye after sleep exhibits its vital elasticity more especially by -its tendency to alternate its impressions, which in the simplest form -change from dark to light, and from light to dark. The eye cannot for a -moment remain in a particular state determined by the object it looks -upon. On the contrary, it is forced to a sort of opposition, which, in -contrasting extreme with extreme, intermediate degree with intermediate -degree, at the same time combines these opposite impressions, and thus -ever tends to a whole, whether the impressions are successive, or -simultaneous and confined to one image. - -34. - -Perhaps the peculiarly grateful sensation which we experience in -looking at the skilfully treated chiaro-scuro of colourless pictures -and similar works of art arises chiefly from the _simultaneous_ -impression of a whole, which by the organ itself is sought, rather than -arrived at, in _succession_, and which, whatever may be the result, can -never be arrested. - - -[1] Plate 1. fig. 1. - -[2] See the Life of Benvenuto Cellini, vol. i. p. 453. Milan edition, -1806.--T. - - - - -III. - - -GREY SURFACES AND OBJECTS. - - -35. - -A moderate light is essential to many chromatic experiments. This can -be presently obtained by surfaces more or less grey, and thus we have -at once to make ourselves acquainted with this simplest kind of middle -tint, with regard to which it is hardly necessary to observe, that -in many cases a white surface in shadow, or in a low light, may be -considered equivalent to a grey. - -36. - -Since a grey surface is intermediate between brightness and darkness, -it admits of our illustrating a phenomenon before described (29) by an -easy experiment. - -37. - -Let a black object be held before a grey surface, and let the -spectator, after looking steadfastly at it, keep his eyes unmoved while -it is taken away: the space it occupied appears much lighter. Let a -white object be held up in the same manner: on taking it away the space -it occupied will appear much darker than the rest of the surface. Let -the spectator in both cases turn his eyes this way and that on the -surface, the visionary images will move in like manner. - -38. - -A grey object on a black ground appears much brighter than the same -object on a white ground. If both comparisons are seen together the -spectator can hardly persuade himself that the two greys are identical. -We believe this again to be a proof of the great excitability of the -retina, and of the silent resistance which every vital principle is -forced to exhibit when any definite or immutable state is presented to -it. Thus inspiration already presupposes expiration; thus every systole -its diastole. It is the universal formula of life which manifests -itself in this as in all other cases. When darkness is presented to -the eye it demands brightness, and _vice versâ_: it shows its vital -energy, its fitness to receive the impression of the object, precisely -by spontaneously tending to an opposite state. - - - - -IV. - - -DAZZLING COLOURLESS OBJECTS. - - -39. - -If we look at a dazzling, altogether colourless object, it makes a -strong lasting impression, and its after-vision is accompanied by an -appearance of colour. - -40. - -Let a room be made as dark as possible; let there be a circular opening -in the window-shutter about three inches in diameter, which may be -closed or not at pleasure. The sun being suffered to shine through this -on a white surface, let the spectator from some little distance fix his -eyes on the bright circle thus admitted. The hole being then closed, -let him look towards the darkest part of the room; a circular image -will now be seen to float before him. The middle of this circle will -appear bright, colourless, or somewhat yellow, but the border will at -the same moment appear red. - -After a time this red, increasing towards the centre, covers the whole -circle, and at last the bright central point. No sooner, however, is -the whole circle red than the edge begins to be blue, and the blue -gradually encroaches inwards on the red. When the whole is blue -the edge becomes dark and colourless. This darker edge again slowly -encroaches on the blue till the whole circle appears colourless. The -image then becomes gradually fainter, and at the same time diminishes -in size. Here again we see how the retina recovers itself by a -succession of vibrations after the powerful external impression it -received. (25, 26.) - -41. - -By several repetitions similar in result, I found the comparative -duration of these appearances in my own case to be as follows:-- - -I looked on the bright circle five seconds, and then, having closed -the aperture, saw the coloured visionary circle floating before me. -After thirteen seconds it was altogether red; twenty-nine seconds -next elapsed till the whole was blue, and forty-eight seconds till -it appeared colourless. By shutting and opening the eye I constantly -revived the image, so that it did not quite disappear till seven -minutes had elapsed. - -Future observers may find these periods shorter or longer as their -eyes may be stronger or weaker (23), but it would be very remarkable -if, notwithstanding such variations, a corresponding proportion as to -relative duration should be found to exist. - -42. - -But this remarkable phenomenon no sooner excites our attention than we -observe a new modification of it. - -If we receive the impression of the bright circle as before, and then -look on a light grey surface in a moderately lighted room, an image -again floats before us; but in this instance a dark one: by degrees it -is encircled by a green border that gradually spreads inwards over the -whole circle, as the red did in the former instance. As soon as this -has taken place a dingy yellow appears, and, filling the space as the -blue did before, is finally lost in a negative shade. - -43. - -These two experiments may be combined by placing a black and a white -plane surface next each other in a moderately lighted room, and then -looking alternately on one and the other as long as the impression of -the light circle lasts: the spectator will then perceive at first a red -and green image alternately, and afterwards the other changes. After a -little practice the two opposite colours may be perceived at once, by -causing the floating image to fall on the junction of the two planes. -This can be more conveniently done if the planes are at some distance, -for the spectrum then appears larger. - -44. - -I happened to be in a forge towards evening at the moment when a -glowing mass of iron was placed on the anvil; I had fixed my eyes -steadfastly on it, and, turning round, I looked accidentally into an -open coal-shed: a large red image now floated before my eyes, and, as I -turned them from the dark opening to the light boards of which the shed -was constructed, the image appeared half green, half red, according as -it had a lighter or darker ground behind it. I did not at that time -take notice of the subsequent changes of this appearance. - -45. - -The after-vision occasioned by a total dazzling of the retina -corresponds with that of a circumscribed bright object. The red colour -seen by persons who are dazzled with snow belongs to this class of -phenomena, as well as the singularly beautiful green colour which dark -objects seem to wear after looking long on white paper in the sun. The -details of such experiments may be investigated hereafter by those -whose young eyes are capable of enduring such trials further for the -sake of science. - -46. - -With these examples we may also class the black letters which in the -evening light appear red. Perhaps we might insert under the same -category the story that drops of blood appeared on the table at which -Henry IV. of France had seated himself with the Duc de Guise to play at -dice. - - - - -V. - - -COLOURED OBJECTS. - - -47. - -We have hitherto seen the physiological colours displayed in the -after-vision of colourless bright objects, and also in the after-vision -of general colourless brightness; we shall now find analogous -appearances if a given colour be presented to the eye: in considering -this, all that has been hitherto detailed must be present to our -recollection. - -48. - -The impression of coloured objects remains in the eye like that of -colourless ones, but in this case the energy of the retina, stimulated -as it is to produce the opposite colour, will be more apparent. - -49. - -Let a small piece of bright-coloured paper or silk stuff be held before -a moderately lighted white surface; let the observer look steadfastly -on the small coloured object, and let it be taken away after a time -while his eyes remain unmoved; the spectrum of another colour will then -be visible on the white plane. The coloured paper may be also left in -its place while the eye is directed to another part of the white plane; -the same spectrum will be visible there too, for it arises from an -image which now belongs to the eye. - -50. - -In order at once to see what colour will be evoked by this contrast, -the chromatic circle[1] may be referred to. The colours are here -arranged in a general way according to the natural order, and the -arrangement will be found to be directly applicable in the present -case; for the colours diametrically opposed to each other in this -diagram are those which reciprocally evoke each other in the eye. Thus, -yellow demands purple; orange, blue; red, green; and _vice versâ_: thus -again all intermediate gradations reciprocally evoke each other; the -simpler colour demanding the compound, and _vice versâ_.--Note C. - -51. - -The cases here under consideration occur oftener than we are aware in -ordinary life; indeed, an attentive observer sees these appearances -everywhere, while, on the other hand, the uninstructed, like our -predecessors, consider them as temporary visual defects, sometimes -even as symptoms of disorders in the eye, thus exciting serious -apprehensions. A few remarkable instances may here be inserted. - -52. - -I had entered an inn towards evening, and, as a well-favoured girl, -with a brilliantly fair complexion, black hair, and a scarlet bodice, -came into the room, I looked attentively at her as she stood before me -at some distance in half shadow. As she presently afterwards turned -away, I saw on the white wall, which was now before me, a black face -surrounded with a bright light, while the dress of the perfectly -distinct figure appeared of a beautiful sea-green. - -53. - -Among the materials for optical experiments, there are portraits with -colours and shadows exactly opposite to the appearance of nature. The -spectator, after having looked at one of these for a time, will see the -visionary figure tolerably true to nature. This is conformable to the -same principles, and consistent with experience, for, in the former -instance, a negress with a white head-dress would have given me a -white face surrounded with black. In the case of the painted figures, -however, which are commonly small, the parts are not distinguishable by -every one in the after-image. - -54. - -A phenomenon which has before excited attention among the observers of -nature is to be attributed, I am persuaded, to the same cause. - -It has been stated that certain flowers, towards evening in summer, -coruscate, become phosphorescent, or emit a momentary light. Some -persons have described their observation of this minutely. I had often -endeavoured to witness it myself, and had even resorted to artificial -contrivances to produce it. - -On the 19th of June, 1799, late in the evening, when the twilight was -deepening into a clear night, as I was walking up and down the garden -with a friend, we very distinctly observed a flame-like appearance -near the oriental poppy, the flowers of which are remarkable for their -powerful red colour. We approached the place and looked attentively -at the flowers, but could perceive nothing further, till at last, by -passing and repassing repeatedly, while we looked sideways on them, we -succeeded in renewing the appearance as often as we pleased. It proved -to be a physiological phenomenon, such as others we have described, and -the apparent coruscation was nothing but the spectrum of the flower in -the compensatory blue-green colour. - -In looking directly at a flower the image is not produced, but it -appears immediately as the direction of the eye is altered. Again, by -looking sideways on the object, a double image is seen for a moment, -for the spectrum then appears near and on the real object. - -The twilight accounts for the eye being in a perfect state of repose, -and thus very susceptible, and the colour of the poppy is sufficiently -powerful in the summer twilight of the longest days to act with -full effect and produce a compensatory image. I have no doubt these -appearances might be reduced to experiment, and the same effect -produced by pieces of coloured paper. Those who wish to take the most -effectual means for observing the appearance in nature--suppose in a -garden--should fix the eyes on the bright flowers selected for the -purpose, and, immediately after, look on the gravel path. This will -be seen studded with spots of the opposite colour. The experiment is -practicable on a cloudy day, and even in the brightest sunshine, for -the sun-light, by enhancing the brilliancy of the flower, renders it -fit to produce the compensatory colour sufficiently distinct to be -perceptible even in a bright light. Thus, peonies produce beautiful -green, marigolds vivid blue spectra. - -55. - -As the opposite colour is produced by a constant law in experiments -with coloured objects on portions of the retina, so the same effect -takes place when the whole retina is impressed with a single colour. We -may convince ourselves of this by means of coloured glasses. If we look -long through a blue pane of glass, everything will afterwards appear -in sunshine to the naked eye, even if the sky is grey and the scene -colourless. In like manner, in taking off green spectacles, we see all -objects in a red light. Every decided colour does a certain violence to -the eye, and forces the organ to opposition. - -56. - -We have hitherto seen the opposite colours producing each other -successively on the retina: it now remains to show by experiment -that the same effects can exist simultaneously. If a coloured object -impinges on one part of the retina, the remaining portion at the same -moment has a tendency to produce the compensatory colour. To pursue -a former experiment, if we look on a yellow piece of paper placed -on a white surface, the remaining part of the organ has already a -tendency to produce a purple hue on the colourless surface: in this -case the small portion of yellow is not powerful enough to produce -this appearance distinctly, but, if a white paper is placed on a yellow -wall, we shall see the white tinged with a purple hue. - -57. - -Although this experiment may be made with any colours, yet red and -green are particularly recommended for it, because these colours seem -powerfully to evoke each other. Numerous instances occur in daily -experience. If a green paper is seen through striped or flowered -muslin, the stripes or flowers will appear reddish. A grey building -seen through green pallisades appears in like manner reddish. A -modification of this tint in the agitated sea is also a compensatory -colour: the light side of the waves appears green in its own colour, -and the shadowed side is tinged with the opposite hue. The different -direction of the waves with reference to the eye produces the same -effect. Objects seen through an opening in a red or green curtain -appear to wear the opposite hue. These appearances will present -themselves to the attentive observer on all occasions, even to an -unpleasant degree. - -58. - -Having made ourselves acquainted with the simultaneous exhibition of -these effects in direct cases, we shall find that we can also observe -them by indirect means. If we place a piece of paper of a bright -orange colour on the white surface, we shall, after looking intently -at it, scarcely perceive the compensatory colour on the rest of the -surface: but when we take the orange paper away, and when the blue -spectrum appears in its place, immediately as this spectrum becomes -fully apparent, the rest of the surface will be overspread, as if by a -flash, with a reddish-yellow light, thus exhibiting to the spectator -in a lively manner the productive energy of the organ, in constant -conformity with the same law. - -59. - -As the compensatory colours easily appear, where they do not exist in -nature, near and after the original opposite ones, so they are rendered -more intense where they happen to mix with a similar real hue. In a -court which was paved with grey limestone flags, between which grass -had grown, the grass appeared of an extremely beautiful green when -the evening clouds threw a scarcely perceptible reddish light on the -pavement. In an opposite case we find, in walking through meadows, -where we see scarcely anything but green, the stems of trees and the -roads often gleam with a reddish hue. This tone is not uncommon in -the works of landscape painters, especially those who practice in -water-colours: they probably see it in nature, and thus, unconsciously -imitating it, their colouring is criticised as unnatural. - -60. - -These phenomena are of the greatest importance, since they direct our -attention to the laws of vision, and are a necessary preparation for -future observations on colours. They show that the eye especially -demands completeness, and seeks to eke out the colorific circle in -itself. The purple or violet colour suggested by yellow contains red -and blue; orange, which responds to blue, is composed of yellow and -red; green, uniting blue and yellow, demands red; and so through all -gradations of the most complicated combinations. That we are compelled -in this case to assume three leading colours has been already remarked -by other observers. - -61. - -When in this completeness the elements of which it is composed are -still appreciable by the eye, the result is justly called harmony. We -shall subsequently endeavour to show how the theory of the harmony of -colours may be deduced from these phenomena, and how, simply through -these qualities, colours may be capable of being applied to æsthetic -purposes. This will be shown when we have gone through the whole circle -of our observations, returning to the point from which we started. - - -[1] Plate 1, fig. 3. - - - - -VI. - - -COLOURED SHADOWS. - - -62. - -Before, however, we proceed further, we have yet to observe some very -remarkable cases of the vivacity with which the suggested colours -appear in the neighbourhood of others: we allude to coloured shadows. -To arrive at these we first turn our attention to shadows that are -colourless or negative. - -63. - -A shadow cast by the sun, in its full brightness, on a white surface, -gives us no impression of colour; it appears black, or, if a contrary -light (here assumed to differ only in degree) can act upon it, it is -only weaker, half-lighted, grey. - -64. - -Two conditions are necessary for the existence of coloured shadows: -first, that the principal light tinge the white surface with some hue; -secondly, that a contrary light illumine to a certain extent the cast -shadow. - -65. - -Let a short, lighted candle be placed at twilight on a sheet of white -paper. Between it and the declining daylight let a pencil be placed -upright, so that its shadow thrown by the candle may be lighted, but -not overcome, by the weak daylight: the shadow will appear of the most -beautiful blue. - -66. - -That this shadow is blue is immediately evident; but we can only -persuade ourselves by some attention that the white paper acts as a -reddish yellow, by means of which the complemental blue is excited in -the eye.--Note D. - -67. - -In all coloured shadows, therefore, we must presuppose a colour excited -or suggested by the hue of the surface on which the shadow is thrown. -This may be easily found to be the case by attentive consideration, but -we may convince ourselves at once by the following experiment. - -68. - -Place two candles at night opposite each other on a white surface; hold -a thin rod between them upright, so that two shadows be cast by it; -take a coloured glass and hold it before one of the lights, so that -the white paper appear coloured; at the same moment the shadow cast by -the coloured light and slightly illumined by the colourless one will -exhibit the complemental hue. - -69. - -An important consideration suggests itself here, to which we shall -frequently have occasion to return. Colour itself is a degree of -darkness _σκιερόν_; hence Kircher is perfectly right in calling it -_lumen opacatum_. As it is allied to shadow, so it combines readily -with it; it appears to us readily in and by means of shadow the -moment a suggesting cause presents itself. We could not refrain from -adverting at once to a fact which we propose to trace and develop -hereafter.--Note E. - -70. - -Select the moment in twilight when the light of the sky is still -powerful enough to cast a shadow which cannot be entirely effaced by -the light of a candle. The candle may be so placed that a double shadow -shall be visible, one from the candle towards the daylight, and another -from the daylight towards the candle. If the former is blue the latter -will appear orange-yellow: this orange-yellow is in fact, however, only -the yellow-red light of the candle diffused over the whole paper, and -which _becomes visible in shadow_. - -71. - -This is best exemplified by the former experiment with two candles and -coloured glasses. - -The surprising readiness with which shadow assumes a colour will again -invite our attention in the further consideration of reflections and -elsewhere. - -72. - -Thus the phenomena of coloured shadows may be traced to their cause -without difficulty. Henceforth let any one who sees an instance of -the kind observe only with what hue the light surface on which they -are thrown is tinged. Nay, the colour of the shadow may be considered -as a chromatoscope of the illumined surface, for the spectator may -always assume the colour of the light to be the opposite of that of the -shadow, and by an attentive examination may ascertain this to be the -fact in every instance. - -73. - -These appearances have been a source of great perplexity to former -observers: for, as they were remarked chiefly in the open air, where -they commonly appeared blue, they were attributed to a certain inherent -blue or blue colouring quality in the air. The inquirer can, however, -convince himself, by the experiment with the candle in a room, that no -kind of blue light or reflection is necessary to produce the effect -in question. The experiment may be made on a cloudy day with white -curtains drawn before the light, and in a room where no trace of blue -exists, and the blue shadow will be only so much the more beautiful. - -74. - -De Saussure, in the description of his ascent of Mont Blanc, says, "A -second remark, which may not be uninteresting, relates to the colour of -the shadows. These, notwithstanding the most attentive observation, we -never found dark blue, although this had been frequently the case in -the plain. On the contrary, in fifty-nine instances we saw them once -yellowish, six times pale bluish, eighteen times colourless or black, -and thirty-four times pale violet. Some natural philosophers suppose -that these colours arise from accidental vapours diffused in the air, -which communicate their own hues to the shadows; not that the colours -of the shadows are occasioned by the reflection of any given sky colour -or interposition of any given air colour: the above observations seem -to favour this opinion." The instances given by De Saussure may be now -explained and classed with analogous examples without difficulty. - -At a great elevation the sky was generally free from vapours, the sun -shone in full force on the snow, so that it appeared perfectly white -to the eye: in this case they saw the shadows quite colourless. If the -air was charged with a certain degree of vapour, in consequence of -which the light snow would assume a yellowish tone, the shadows were -violet-coloured, and this effect, it appears, occurred oftenest. They -saw also bluish shadows, but this happened less frequently; and that -the blue and violet were pale was owing to the surrounding brightness, -by which the strength of the shadows was mitigated. Once only they -saw the shadow yellowish: in this case, as we have already seen (70), -the shadow is cast by a colourless light, and slightly illumined by a -coloured one. - -75. - -In travelling over the Harz in winter, I happened to descend from the -Brocken towards evening; the wide slopes extending above and below me, -the heath, every insulated tree and projecting rock, and all masses of -both, were covered with snow or hoar-frost. The sun was sinking towards -the Oder ponds[1]. During the day, owing to the yellowish hue of the -snow, shadows tending to violet had already been observable; these -might now be pronounced to be decidedly blue, as the illumined parts -exhibited a yellow deepening to orange. - -But as the sun at last was about to set, and its rays, greatly -mitigated by the thicker vapours, began to diffuse a most beautiful -red colour over the whole scene around me, the shadow colour changed -to a green, in lightness to be compared to a sea-green, in beauty to -the green of the emerald. The appearance became more and more vivid: -one might have imagined oneself in a fairy world, for every object had -clothed itself in the two vivid and so beautifully harmonising colours, -till at last, as the sun went down, the magnificent spectacle was lost -in a grey twilight, and by degrees in a clear moon-and-starlight night. - -76. - -One of the most beautiful instances of coloured shadows may be -observed during the full moon. The candle-light and moon-light may be -contrived to be exactly equal in force; both shadows may be exhibited -with equal strength and clearness, so that both colours balance each -other perfectly. A white surface being placed opposite the full moon, -and the candle being placed a little on one side at a due distance, -an opaque body is held before the white plane, A double shadow will -then be seen: that cast by the moon and illumined by the candle-light -will be a powerful red-yellow; and contrariwise, that cast by the -candle and illumined by the moon will appear of the most beautiful -blue. The shadow, composed of the union of the two shadows, where -they cross each other, is black. The yellow shadow (74) cannot perhaps -be exhibited in a more striking manner. The immediate vicinity of -the blue and the interposing black shadow make the appearance the -more agreeable. It will even be found, if the eye dwells long on -these colours, that they mutually evoke and enhance each other, the -increasing red in the one still producing its contrast, viz. a kind of -sea-green. - -77. - -We are here led to remark that in this, and in all cases, a moment or -two may perhaps be necessary to produce the complemental colour. The -retina must be first thoroughly impressed with the demanding hue before -the responding one can be distinctly observable. - -78. - -When divers are under water, and the sunlight shines into the -diving-bell, everything is seen in a red light (the cause of which -will be explained hereafter), while the shadows appear green. The very -same phenomenon which I observed on a high mountain (75) is presented -to others in the depths of the sea, and thus Nature throughout is in -harmony with herself. - -79. - -Some observations and experiments which equally illustrate what has -been stated with regard to coloured objects and coloured shadows may -be here added. Let a white paper blind be fastened inside the window -on a winter evening; in this blind let there be an opening, through -which the snow of some neighbouring roof can be seen. Towards dusk let -a candle be brought into the room; the snow seen through the opening -will then appear perfectly blue, because the paper is tinged with warm -yellow by the candle-light. The snow seen through the aperture is here -equivalent to a shadow illumined by a contrary light (76), and may also -represent a grey disk on a coloured surface (56). - -80. - -Another very interesting experiment may conclude these examples. If we -take a piece of green glass of some thickness, and hold it so that the -window bars be reflected in it, they will appear double owing to the -thickness of the glass. The image which is reflected from the under -surface of the glass will be green; the image which is reflected from -the upper surface, and which should be colourless, will appear red. - -The experiment may be very satisfactorily made by pouring water into -a vessel, the inner surface of which can act as a mirror; for both -reflections may first be seen colourless while the water is pure, and -then by tinging it, they will exhibit two opposite hues. - - -[1] Reservoirs in which water is collected from various small streams, -to work the mines.--T. - - - - -VII. - - -FAINT LIGHTS. - - -81. - -Light, in its full force, appears purely white, and it gives this -impression also in its highest degree of dazzling splendour. Light, -which is not so powerful, can also, under various conditions, remain -colourless. Several naturalists and mathematicians have endeavoured to -measure its degrees--Lambert, Bouguer, Rumford. - -82. - -Yet an appearance of colour presently manifests itself in fainter -lights, for in their relation to absolute light they resemble the -coloured spectra of dazzling objects (39). - -83. - -A light of any kind becomes weaker, either when its own force, from -whatever cause, is diminished, or when the eye is so circumstanced or -placed, that it cannot be sufficiently impressed by the action of the -light. Those appearances which may be called objective, come under the -head of physical colours. We will only advert here to the transition -from white to red heat in glowing iron. We may also observe that the -flames of lights at night appear redder in proportion to their distance -from the eye.--Note F. - -84. - -Candle-light at night acts as yellow when seen near; we can perceive -this by the effect it produces on other colours. At night a pale yellow -is hardly to be distinguished from white; blue approaches to green, and -rose-colour to orange. - -85. - -Candle-light at twilight acts powerfully as a yellow light: this -is best proved by the purple blue shadows which, under these -circumstances, are evoked by the eye. - -86. - -The retina may be so excited by a strong light that it cannot perceive -fainter lights (11): if it perceive these they appear coloured: hence -candle-light by day appears reddish, thus resembling, in its relation -to fuller light, the spectrum of a dazzling object; nay, if at night we -look long and intently on the flame of a light, it appears to increase -in redness. - -87. - -There are faint lights which, notwithstanding their moderate lustre, -give an impression of a white, or, at the most, of a light yellow -appearance on the retina; such as the moon in its full splendour. -Rotten wood has even a kind of bluish light. All this will hereafter be -the subject of further remarks. - -88. - -If at night we place a light near a white or greyish wall so that the -surface be illumined from this central point to some extent, we find, -on observing the spreading light at some distance, that the boundary of -the illumined surface appears to be surrounded with a yellow circle, -which on the outside tends to red-yellow. We thus observe that when -light direct or reflected does not act in its full force, it gives an -impression of yellow, of reddish, and lastly even of red. Here we find -the transition to halos which we are accustomed to see in some mode or -other round luminous points. - - - - -VIII. - - -SUBJECTIVE HALOS. - - -89. - -Halos may be divided into subjective and objective. The latter will -be considered under the physical colours; the first only belong here. -These are distinguished from the objective halos by the circumstance -of their vanishing when the point of light which produces them on the -retina is covered. - -90. - -We have before noticed the impression of a luminous object on the -retina, and seen that it appears larger: but the effect is not at -an end here, it is not confined to the impression of the image; an -expansive action also takes place, spreading from the centre. - -91. - -That a nimbus of this kind is produced round the luminous image in the -eye may be best seen in a dark room, if we look towards a moderately -large opening in the window-shutter. In this case the bright image is -surrounded by a circular misty light. I saw such a halo bounded by a -yellow and yellow-red circle on opening my eyes at dawn, on an occasion -when I passed several nights in a bed-carriage. - -92. - -Halos appear most vivid when the eye is susceptible from having been in -a state of repose. A dark background also heightens their appearance. -Both causes account for our seeing them so strong if a light is -presented to the eyes on waking at night. These conditions were -combined when Descartes after sleeping, as he sat in a ship, remarked -such a vividly-coloured halo round the light. - -93. - -A light must shine moderately, not dazzle, in order to produce the -impression of a halo in the eye; at all events the halos of dazzling -lights cannot be observed. We see a splendour of this kind round the -image of the sun reflected from the surface of water. - -94. - -A halo of this description, attentively observed, is found to be -encircled towards its edge with a yellow border: but even here the -expansive action, before alluded to, is not at an end, but appears -still to extend in varied circles. - -95. - -Several cases seem to indicate a circular action of the retina, whether -owing to the round form of the eye itself and its different parts, or -to some other cause. - -96. - -If the eye is pressed only in a slight degree from the inner corner, -darker or lighter circles appear. At night, even without pressure, we -can sometimes perceive a succession of such circles emerging from, or -spreading over, each other. - -97. - -We have already seen that a yellow border is apparent round the white -space illumined by a light placed near it. This may be a kind of -objective halo. (88.) - -98. - -Subjective halos may be considered as the result of a conflict between -the light and a living surface. From the conflict between the exciting -principle and the excited, an undulating motion arises, which may be -illustrated by a comparison with the circles on water. The stone thrown -in drives the water in all directions; the effect attains a maximum, -it reacts, and being opposed, continues under the surface. The effect -goes on, culminates again, and thus the circles are repeated. If we -have ever remarked the concentric rings which appear in a glass of -water on trying to produce a tone by rubbing the edge; if we call to -mind the intermitting pulsations in the reverberations of bells, we -shall approach a conception of what may take place on the retina when -the image of a luminous object impinges on it, not to mention that as -a living and elastic structure, it has already a circular principle in -its organisation.--Note G. - -99. - -The bright circular space which appears round the shining object -is yellow, ending in red: then follows a greenish circle, which is -terminated by a red border. This appears to be the usual phenomenon -where the luminous body is somewhat considerable in size. These halos -become greater the more distant we are from the luminous object. - -100. - -Halos may, however, appear extremely small and numerous when the -impinging image is minute, yet powerful, in its effect. The experiment -is best made with a piece of gold-leaf placed on the ground and -illumined by the sun. In these cases the halos appear in variegated -rays. The iridescent appearance produced in the eye when the sun -pierces through the leaves of trees seems also to belong to the same -class of phenomena. - - - - -PATHOLOGICAL COLOURS. - - -APPENDIX. - - -101. - -We are now sufficiently acquainted with the physiological colours to -distinguish them from the pathological. We know what appearances belong -to the eye in a healthy state, and are necessary to enable the organ to -exert its complete vitality and activity. - -102. - -Morbid phenomena indicate in like manner the existence of organic -and physical laws: for if a living being deviates from those rules -with reference to which it is constructed, it still seeks to agree -with the general vitality of nature in conformity with general laws, -and throughout its whole course still proves the constancy of those -principles on which the universe has existed, and by which it is held -together. - -103. - -We will here first advert to a very remarkable state in which the -vision of many persons is found to be. As it presents a deviation -from the ordinary mode of seeing colours, it might be fairly classed -under morbid impressions; but as it is consistent in itself, as it -often occurs, may extend to several members of a family, and probably -does not admit of cure, we may consider it as bordering only on the -nosological cases, and therefore place it first. - -104. - -I was acquainted with two individuals not more than twenty years of -age, who were thus affected: both had bluish-grey eyes, an acute sight -for near and distant objects, by day-light and candle-light, and their -mode of seeing colours was in the main quite similar. - -105. - -They agreed with the rest of the world in denominating white, black, -and grey in the usual manner. Both saw white untinged with any hue. One -saw a somewhat brownish appearance in black, and in grey a somewhat -reddish tinge. In general they appeared to have a very delicate -perception of the gradations of light and dark. - -106. - -They appeared to see yellow, red-yellow, and yellow-red,[1] like -others: in the last case they said they saw the yellow passing as it -were over the red as if glazed: some thickly-ground carmine, which had -dried in a saucer, they called red. - -107. - -But now a striking difference presented itself. If the carmine was -passed thinly over the white saucer, they would compare the light -colour thus produced to the colour of the sky, and call it blue. If -a rose was shown them beside it, they would, in like manner, call it -blue; and in all the trials which were made, it appeared that they -could not distinguish light blue from rose-colour. They confounded -rose-colour, blue, and violet on all occasions: these colours only -appeared to them to be distinguished from each other by delicate shades -of lighter, darker, intenser, or fainter appearance. - -108. - -Again they could not distinguish green from dark orange, nor, more -especially, from a red brown. - -109. - -If any one, accidentally conversing with these individuals, happened -to question them about surrounding objects, their answers occasioned -the greatest perplexity, and the interrogator began to fancy his own -wits were out of order. With some method we may, however, approach to a -nearer knowledge of the law of this deviation from the general law. - -110. - -These persons, as may be gathered from what has been stated, saw fewer -colours than other people: hence arose the confusion of different -colours. They called the sky rose-colour, and the rose blue, or -_vice versâ_. The question now is: did they see both blue or both -rose-colour? did they see green orange, or orange green? - -111. - -This singular enigma appears to solve itself, if we assume that they -saw no blue, but, instead of it, a light pure red, a rose-colour. -We can comprehend what would be the result of this by means of the -chromatic diagram. - -112. - -If we take away blue from the chromatic circle we shall miss violet and -green as well. Pure red occupies the place of blue and violet, and in -again mixing with yellow the red produces orange where green should be. - -113. - -Professing to be satisfied with this mode of explanation, we have named -this remarkable deviation from ordinary vision "Acyanoblepsia."[2] -We have prepared some coloured figures for its further elucidation, -and in explaining these we shall add some further details. Among the -examples will be found a landscape, coloured in the mode in which the -individuals alluded to appeared to see nature: the sky rose-colour, and -all that should be green varying from yellow to brown red, nearly as -foliage appears to us in autumn[3].--Note H. - -114. - -We now proceed to speak of morbid and other extraordinary affections -of the retina, by which the eye may be susceptible of an appearance -of light without external light, reserving for a future occasion the -consideration of galvanic light. - -115. - -If the eye receives a blow, sparks seem to spread from it. In some -states of body, again, when the blood is heated, and the system much -excited, if the eye is pressed first gently, and then more and more -strongly, a dazzling and intolerable light may be excited. - -116. - -If those who have been recently couched experience pain and heat in the -eye, they frequently see fiery flashes and sparks: these symptoms last -sometimes for a week or fortnight, or till the pain and heat diminish. - -117. - -A person suffering from ear-ache saw sparks and balls of light in the -eye during each attack, as long as the pain lasted. - -118. - -Persons suffering from worms often experience extraordinary appearances -in the eye, sometimes sparks of fire, sometimes spectres of light, -sometimes frightful figures, which they cannot by an effort of the will -cease to see: sometimes these appearances are double. - -119. - -Hypochondriacs frequently see dark objects, such as threads, hairs, -spiders, flies, wasps. These appearances also exhibit themselves in the -incipient hard cataract. Many see semi-transparent small tubes, forms -like wings of insects, bubbles of water of various sizes, which fall -slowly down, if the eye is raised: sometimes these congregate together -so as to resemble the spawn of frogs; sometimes they appear as complete -spheres, sometimes in the form of lenses. - -120. - -As light appeared, in the former instances, without external light, -so also these images appear without corresponding external objects. -The images are sometimes transient, sometimes they last during -the patient's life. Colour, again, frequently accompanies these -impressions: for hypochondriacs often see yellow-red stripes in the -eye: these are generally more vivid and numerous in the morning, or -when lasting. - -121. - -We have before seen that the impression of any object may remain for a -time in the eye: this we have found to be a physiological phenomenon -(23): the excessive duration of such an impression, on the other band, -may be considered as morbid. - -122. - -The weaker the organ the longer the impression of the image lasts. -The retina does not so soon recover itself; and the effect may be -considered as a kind of paralysis (28). - -123. - -This is not to be wondered at in the case of dazzling lights. If any -one looks at the sun, he may retain the image in his eyes for several -days. Boyle relates an instance of ten years. - -124. - -The same takes place, in a certain degree, with regard to objects -that are not dazzling. Büsch relates of himself that the image of an -engraving, complete in all its parts, was impressed on his eye for -seventeen minutes. - -125. - -A person inclined to fulness of blood retained the image of a bright -red calico, with white spots, many minutes in the eye, and saw it float -before everything like a veil. It only disappeared by rubbing the eye -for some time. - -126. - -Scherfer observes that the red colour, which is the consequence of a -powerful impression of light, may last for some hours. - -127. - -As we can produce an appearance of light on the retina by pressure -on the eyeball, so by a gentle pressure a red colour appears, thus -corresponding with the after-image of an impression of light. - -128. - -Many sick persons, on awaking, see everything in the colour of the -morning sky, as if through a red veil: so, if in the evening they doze -and wake again, the same appearance presents itself. It remains for -some minutes, and always disappears if the eye is rubbed a little. Red -stars and balls sometimes accompany the impression. This state may last -for a considerable time. - -129. - -The aëronauts, particularly Zambeccari and his companions, relate -that they saw the moon blood-red at the highest elevation. As they -had ascended above the vapours of the earth, through which we see the -moon and sun naturally of such a colour, it may be suspected that this -appearance may be classed with the pathological colours. The senses, -namely, may be so influenced by an unusual state, that the whole -nervous system, and particularly the retina, may sink into a kind of -inertness and inexcitability. Hence it is not impossible that the moon -might act as a very subdued light, and thus produce the impression of -the red colour. The sun even appeared blood-red to the aëronauts of -Hamburgh. - -If those who are at some elevation in a balloon scarcely hear each -other speak, may not this, too, be attributed to the inexcitable state -of the nerves as well as to the thinness of the air? - -130. - -Objects are often seen by sick persons in variegated colours. Boyle -relates an instance of a lady, who, after a fall by which an eye was -bruised, saw all objects, but especially white objects, glittering in -colours, even to an intolerable degree. - -131. - -Physicians give the name of "Chrupsia" to an affection of the sight, -occurring in typhoid maladies. In these cases the patients state that -they see the boundaries of objects coloured where light and dark meet. -A change probably takes place in the humours of the eye, through which -their achromatism is affected. - -132. - -In cases of milky cataract, a very turbid crystalline lens causes -the patient to see a red light. In a case of this kind, which was -treated by the application of electricity, the red light changed by -degrees to yellow, and at last to white, when the patient again began -to distinguish objects. These changes of themselves warranted the -conclusion that the turbid state of the lens was gradually approaching -the transparent state. We shall be enabled easily to trace this effect -to its source as soon as we become better acquainted with the physical -colours. - -133. - -If again it may be assumed that a jaundiced patient sees through -an actually yellow-coloured humour, we are at once referred to the -department of chemical colours, and it is thus evident that we can only -thoroughly investigate the chapter of pathological colours when we -have made ourselves acquainted with the whole range of the remaining -phenomena. What has been adduced may therefore suffice for the present, -till we resume the further consideration of this portion of our subject. - -134. - -In conclusion we may, however, at once advert to some peculiar states -or dispositions of the organ. - -There are painters who, instead of rendering the colours of nature, -diffuse a general tone, a warm or cold hue, over the picture. In some, -again, a predilection for certain colours displays itself; in others a -want of feeling for harmony. - -135. - -Lastly, it is also worthy of remark, that savage nations, uneducated -people, and children have a great predilection for vivid colours; -that animals are excited to rage by certain colours; that people of -refinement avoid vivid colours in their dress and the objects that are -about them, and seem inclined to banish them altogether from their -presence.--Note I. - - -[1] It has been found necessary to follow the author's nomenclature -throughout--T. - -[2] Non-perception of blue. - -[3] It has not been thought necessary to copy the plates here referred -to.--T. - - - - -PART II. - - -PHYSICAL COLOURS. - - -136. - -We give this designation to colours which are produced by certain -material mediums: these mediums, however, have no colour themselves, -and may be either transparent, semi-transparent yet transmitting light, -or altogether opaque. The colours in question are thus produced in the -eye through such external given causes, or are merely reflected to -the eye when by whatever means they are already produced without us. -Although we thus ascribe to them a certain objective character, their -distinctive quality still consists in their being transient, and not to -be arrested. - -137. - -They are called by former investigators _colores apparentes, fluxi, -fugitivi, phantastici, falsi, variantes_. They are also called -_speciosi_ and _emphatici_, on account of their striking splendour. -They are immediately connected with the physiological colours, and -appear to have but little more reality: for, while in the production -of the physiological colours the eye itself was chiefly efficient, and -we could only perceive the phenomena thus evoked within ourselves, -but not without us, we have now to consider the fact that colours are -produced in the eye by means of colourless objects; that we thus too -have a colourless surface before us which is acted upon as the retina -itself is, and that we can perceive the appearance produced upon it -without us. In such a process, however, every observation will convince -us that we have to do with colours in a progressive and mutable, but -not in a final or complete, state. - -138. - -Hence, in directing our attention to these physical colours, we find -it quite possible to place an objective phenomenon beside a subjective -one, and often by means of the union of the two successfully to -penetrate farther into the nature of the appearance. - -139. - -Thus, in the observations by which we become acquainted with the -physical colours, the eye is not to be considered as acting alone; nor -is the light ever to be considered in immediate relation with the eye: -but we direct our attention especially to the various effects produced -by mediums, those mediums being themselves colourless. - -140. - -Light under these circumstances may be affected by three conditions. -First, when it flashes back from the surface of a medium; in -considering which _catoptrical_ experiments invite our attention. -Secondly, when it passes by the edge of a medium: the phenomena -thus produced were formerly called _perioptical_; we prefer the -term _paroptical_. Thirdly, when it passes through either a merely -light-transmitting or an actually transparent body; thus constituting -a class of appearances on which _dioptrical_ experiments are founded. -We have called a fourth class of physical colours _epoptical_, as the -phenomena exhibit themselves on the colourless surface of bodies under -various conditions, without previous or actual dye (βαφή).--Note K. - -141. - -In examining these categories with reference to our three leading -divisions, according to which we consider the phenomena of colours in a -physiological, physical, or chemical view, we find that the catoptrical -colours are closely connected with the physiological; the paroptical -are already somewhat more distinct and independent; the dioptrical -exhibit themselves as entirely and strictly physical, and as having -a decidedly objective character; the epoptical, although still only -apparent, may be considered as the transition to the chemical colours. - -142. - -If we were desirous of prosecuting our investigation strictly in the -order of nature, we ought to proceed according to the classification -which has just been made; but in didactic treatises it is not of -so much consequence to connect as to duly distinguish the various -divisions of a subject, in order that at last, when every single -class and case has been presented to the mind, the whole may be -embraced in one comprehensive view. We therefore turn our attention -forthwith to the dioptrical class, in order at once to give the reader -the full impression of the physical colours, and to exhibit their -characteristics the more strikingly. - - - - -IX. - - -DIOPTRICAL COLOURS. - - -143. - -Colours are called dioptrical when a colourless medium is necessary -to produce them; the medium must be such that light and darkness can -act through it either on the eye or on opposite surfaces. It is thus -required that the medium should be transparent, or at least capable, to -a certain degree, of transmitting light. - -144. - -According to these conditions we divide the dioptrical phenomena into -two classes, placing in the first those which are produced by means of -imperfectly transparent, yet light-transmitting mediums; and in the -second such as are exhibited when the medium is in the highest degree -transparent. - - - - -X. - -DIOPTRICAL COLOURS OF THE FIRST CLASS. - - -145. - -Space, if we assume it to be empty, would have the quality of absolute -transparency to our vision. If this space is filled so that the eye -cannot perceive that it is so, there exists a more or less material -transparent medium, which may be of the nature of air and gas, may be -fluid or even solid. - -146. - -The pure and light-transmitting semi-transparent medium is only an -accumulated form of the transparent medium. It may therefore be -presented to us in three modes. - -147. - -The extreme degree of this accumulation is white; the simplest, -brightest, first, opaque occupation of space. - -148. - -Transparency itself, empirically considered, is already the first -degree of the opposite state. The intermediate degrees from this point -to opaque white are infinite. - -149. - -At whatever point short of opacity we arrest the thickening medium, it -exhibits simple and remarkable phenomena when placed in relation with -light and darkness. - -150. - -The highest degree of light, such as that of the sun, of phosphorus -burning in oxygen, is dazzling and colourless: so the light of the -fixed stars is for the most part colourless. This light, however, seen -through a medium but very slightly thickened, appears to us yellow. -If the density of such a medium be increased, or if its volume become -greater, we shall see the light gradually assume a yellow-red hue, -which at last deepens to a ruby-colour.--Note L. - -151. - -If on the other hand darkness is seen through a semi-transparent -medium, which is itself illumined by a light striking on it, a blue -colour appears: this becomes lighter and paler as the density of the -medium is increased, but on the contrary appears darker and deeper the -more transparent the medium becomes: in the least degree of dimness -short of absolute transparence, always supposing a perfectly colourless -medium, this deep blue approaches the most beautiful violet. - -152. - -If this effect takes place in the eye as here described, and may -thus be pronounced to be subjective, it remains further to convince -ourselves of this by objective phenomena. For a light thus mitigated -and subdued illumines all objects in like manner with a yellow, -yellow-red, or red hue; and, although the effect of darkness through -the non-transparent medium does not exhibit itself so powerfully, yet -the blue sky displays itself in the camera obscura very distinctly on -white paper, as well as every other material colour. - -153. - -In examining the cases in which this important leading phenomenon -appears, we naturally mention the atmospheric colours first: most of -these may be here introduced in order. - -154. - -The sun seen through a certain degree of vapour appears with a yellow -disk; the centre is often dazzlingly yellow when the edges are already -red. The orb seen through a thick yellow mist appears ruby-red (as was -the case in 1794, even in the north); the same appearance is still -more decided, owing to the state of the atmosphere, when the scirocco -prevails in southern climates: the clouds generally surrounding the sun -in the latter case are of the same colour, which is reflected again on -all objects. - -The red hues of morning and evening are owing to the same cause. The -sun is announced by a red light, in shining through a greater mass -of vapours. The higher he rises, the yellower and brighter the light -becomes. - -155. - -If the darkness of infinite space is seen through atmospheric vapours -illumined by the day-light, the blue colour appears. On high mountains -the sky appears by day intensely blue, owing to the few thin vapours -that float before the endless dark space: as soon as we descend in the -valleys, the blue becomes lighter; till at last, in certain regions, -and in consequence of increasing vapours, it altogether changes to a -very pale blue. - -156. - -The mountains, in like manner, appear to us blue; for, as we see them -at so great a distance that we no longer distinguish the local tints, -and as no light reflected from their surface acts on our vision, they -are equivalent to mere dark objects, which, owing to the interposed -vapours, appear blue. - -157. - -So we find the shadowed parts of nearer objects are blue when the air -is charged with thin vapours. - -158. - -The snow-mountains, on the other hand, at a great distance, still -appear white, or approaching to a yellowish hue, because they act on -our eyes as brightness seen through atmospheric vapour. - -159. - -The blue appearance at the lower part of the flame of a candle belongs -to the same class of phenomena. If the flame be held before a white -ground, no blue will be seen, but this colour will immediately appear -if the flame is opposed to a black ground. This phenomenon may be -exhibited most strikingly with a spoonful of lighted spirits of wine. -We may thus consider the lower part of the flame as equivalent to the -vapour which, although infinitely thin, is still apparent before the -dark surface; it is so thin, that one may easily see to read through -it: on the other hand, the point of the flame which conceals objects -from our sight is to be considered as a self-illuminating body. - -160. - -Lastly, smoke is also to be considered as a semi-transparent medium, -which appears to us yellow or reddish before a light ground, but blue -before a dark one. - -161. - -If we now turn our attention to fluid mediums, we find that water, -deprived in a very slight degree of its transparency, produces the same -effects. - -162. - -The infusion of the lignum nephriticum (guilandina Linnæi), which -formerly excited so much attention, is only a semi-transparent liquor, -which in dark wooden cups must appear blue, but held towards the sun in -a transparent glass must exhibit a yellow appearance. - -163. - -A drop of scented water, of spirit varnish, of several metallic -solutions, may be employed to give various degrees of opacity to water -for such experiments. Spirit of soap perhaps answers best. - -164. - -The bottom of the sea appears to divers of a red colour in bright -sunshine: in this case the water, owing to its depth, acts as a -semi-transparent medium. Under these circumstances, they find the -shadows green, which is the complemental colour. - -165. - -Among solid mediums the opal attracts our attention first: its colours -are, at least, partly to be explained by the circumstance that it is, -in fact, a semi-transparent medium, through which sometimes light, -sometimes dark, substrata are visible. - -166. - -For these experiments, however, the opal-glass (vitrum astroides, -girasole) is the most desirable material. It is prepared in various -ways, and its semi-opacity is produced by metallic oxydes. The same -effect is produced also by melting pulverised and calcined bones -together with the glass, on which account it is also known by the name -of _beinglas_; but, prepared in this mode, it easily becomes too opaque. - -167. - -This glass may be adapted for experiments in various ways: it may -either be made in a very slight degree non-transparent, in which case -the light seen through various layers placed one upon the other may -be deepened from the lightest yellow to the deepest red, or, if made -originally more opaque, it may be employed in thinner or thicker -laminæ. The experiments may be successfully made in both ways: in -order, however, to see the bright blue colour, the glass should neither -be too opaque nor too thick. For, as it is quite natural that darkness -must act weakly through the semi-transparent medium, so this medium, if -too thick, soon approaches whiteness. - -168. - -Panes of glass throw a yellow light on objects through those parts -where they happen to be semi-opaque, and these same parts appear blue -if we look at a dark object through them. - -169. - -Smoked glass may be also mentioned here, and is, in like manner, to be -considered as a semi-opaque medium. It exhibits the sun more or less -ruby-coloured; and, although this appearance may be attributed to the -black-brown colour of the soot, we may still convince ourselves that a -semi-transparent medium here acts if we hold such a glass moderately -smoked, and lit by the sun on the unsmoked side, before a dark object, -for we shall then perceive a bluish appearance. - -170. - -A striking experiment may be made in a dark room with sheets of -parchment. If we fasten a piece of parchment before the opening in the -window-shutter when the sun shines, it will appear nearly white; by -adding a second, a yellowish colour appears, which still increases as -more leaves are added, till at last it changes to red. - -171. - -A similar effect, owing to the state of the crystalline lens in milky -cataract, has been already adverted to (131). - -172. - -Having now, in tracing these phenomena, arrived at the effect of a -degree of opacity scarcely capable of transmitting light, we may here -mention a singular appearance which was owing to a momentary state of -this kind. - -A portrait of a celebrated theologian had been painted some years -before the circumstance to which we allude, by an artist who was known -to have considerable skill in the management of his materials. The -very reverend individual was represented in a rich velvet dress, which -was not a little admired, and which attracted the eye of the spectator -almost more than the face. The picture, however, from the effect of the -smoke of lamps and dust, had lost much of its original vivacity. It -was, therefore, placed in the hands of a painter, who was to clean it, -and give it a fresh coat of varnish. This person began his operations -by carefully washing the picture with a sponge: no sooner, however, -had he gone over the surface once or twice, and wiped away the first -dirt, than to his amazement the black velvet dress changed suddenly to -a light blue plush, which gave the ecclesiastic a very secular, though -somewhat old-fashioned, appearance. The painter did not venture to go -on with his washing: he could not comprehend how a light blue should be -the ground of the deepest black, still less how he could so suddenly -have removed a glazing colour capable of converting the one tint to the -other. - -At all events, he was not a little disconcerted at having spoilt the -picture to such an extent. Nothing to characterize the ecclesiastic -remained but the richly-curled round wig, which made the exchange -of a faded plush for a handsome new velvet dress far from desirable. -Meanwhile, the mischief appeared irreparable, and the good artist, -having turned the picture to the wall, retired to rest with a mind ill -at ease. But what was his joy the next morning, when, on examining the -picture, he beheld the black velvet dress again in its full splendour. -He could not refrain from again wetting a corner, upon which the blue -colour again appeared, and after a time vanished. On hearing of this -phenomenon, I went at once to see the miraculous picture. A wet sponge -was passed over it in my presence, and the change quickly took place. I -saw a somewhat faded, but decidedly light blue plush dress, the folds -under the arm being indicated by some brown strokes. - -I explained this appearance to myself by the doctrine of the -semi-opaque medium. The painter, in order to give additional depth -to his black, may have passed some particular varnish over it: on -being washed, this varnish imbibed some moisture, and hence became -semi-opaque, in consequence of which the black underneath immediately -appeared blue. Perhaps those who are practically acquainted with the -effect of varnishes may, through accident or contrivance, arrive at -some means of exhibiting this singular appearance, as an experiment, to -those who are fond of investigating natural phenomena. Notwithstanding -many attempts, I could not myself succeed in re-producing it. - -173. - -Having now traced the most splendid instances of atmospheric -appearances, as well as other less striking yet sufficiently remarkable -cases, to the leading examples of semi-transparent mediums, we have no -doubt that attentive observers of nature will carry such researches -further, and accustom themselves to trace and explain the various -appearances which present themselves in every-day experience on the -same principle: we may also hope that such investigators will provide -themselves with an adequate apparatus in order to place remarkable -facts before the eyes of others who may be desirous of information. - -174. - -We venture, once for all, to call the leading appearance in question, -as generally described in the foregoing pages, a primordial and -elementary phenomenon; and we may here be permitted at once to state -what we understand by the term. - -175. - -The circumstances which come under our notice in ordinary observation -are, for the most part, insulated cases, which, with some attention, -admit of being classed under general leading facts. These again range -themselves under theoretical rubrics which are more comprehensive, and -through which we become better acquainted with certain indispensable -conditions of appearances in detail. From henceforth everything is -gradually arranged under higher rules and laws, which, however, are not -to be made intelligible by words and hypotheses to the understanding -merely, but, at the same time, by real phenomena to the senses. We -call these primordial phenomena, because nothing appreciable by the -senses lies beyond them, on the contrary, they are perfectly fit to be -considered as a fixed point to which we first ascended, step by step, -and from which we may, in like manner, descend to the commonest case -of every-day experience. Such an original phenomenon is that which has -lately engaged our attention. We see on the one side light, brightness; -on the other darkness, obscurity: we bring the semi-transparent medium -between the two, and from these contrasts and this medium the colours -develop themselves, contrasted, in like manner, but soon, through a -reciprocal relation, directly tending again to a point of union.[1] - -176. - -With this conviction we look upon the mistake that has been committed -in the investigation of this subject to be a very serious one, inasmuch -as a secondary phenomenon has been thus placed higher in order--the -primordial phenomenon has been degraded to an inferior place; nay, the -secondary phenomenon has been placed at the head, a compound effect has -been treated as simple, a simple appearance as compound: owing to this -contradiction, the most capricious complication and perplexity have -been introduced into physical inquiries, the effects of which are still -apparent. - -177. - -But when even such a primordial phenomenon is arrived at, the evil -still is that we refuse to recognise it as such, that we still aim at -something beyond, although it would become us to confess that we are -arrived at the limits of experimental knowledge. Let the observer of -nature suffer the primordial phenomenon to remain undisturbed in its -beauty; let the philosopher admit it into his department, and he will -find that important elementary facts are a worthier basis for further -operations than insulated cases, opinions, and hypotheses.--Note M. - - -[1] That is (according to the author's statement 150. 151.) both tend -to red; the yellow deepening to orange as the comparatively dark medium -is thickened before brightness; the blue deepening to violet as the -light medium is thinned before darkness.--T. - - - - -[Pg 74] - - - -XI. - -DIOPTRICAL COLOURS OF THE SECOND CLASS.--REFRACTION. - - -178. - -Dioptrical colours of both classes are closely connected, as will -presently appear on a little examination. Those of the first class -appeared through semi-transparent mediums, those of the second class -will now appear through transparent mediums. But since every substance, -however transparent, may be already considered to partake of the -opposite quality (as every accumulation of a medium called transparent -proves), so the near affinity of the two classes is sufficiently -manifest. - -179. - -We will, however, first consider transparent mediums abstractedly as -such, as entirely free from any degree of opacity, and direct our whole -attention to a phenomenon which here presents itself, and which is -known by the name of refraction. - -180. - -In treating of the physiological colours, we have already had occasion -to vindicate what [Pg 75] were formerly called illusions of sight, as -the active energies of the healthy and duly efficient eye (2), and we -are now again invited to consider similar instances confirming the -constancy of the laws of vision. - -181. - -Throughout nature, as presented to the senses, everything depends on -the relation which things bear to each other, but especially on the -relation which man, the most important of these, bears to the rest. -Hence the world divides itself into two parts, and the human being -as _subject_, stands opposed to the _object_. Thus the practical -man exhausts himself in the accumulation of facts, the thinker in -speculation; each being called upon to sustain a conflict which admits -of no peace and no decision. - -182. - -But still the main point always is, whether the relations are truly -seen. As our senses, if healthy, are the surest witnesses of external -relations, so we may be convinced that, in all instances where they -appear to contradict reality, they lay the greater and surer stress -on true relations. Thus a distant object appears to us smaller; and -precisely by this means we are aware of distance. We produced coloured -appearances on colourless objects, through colourless mediums, and at -the same moment our attention was called to the degree of opacity in -the medium. - -183. - -Thus the different degrees of opacity in so-called transparent mediums, -nay, even other physical and chemical properties belonging to them, -are known to our vision by means of refraction, and invite us to make -further trials in order to penetrate more completely by physical and -chemical means into those secrets which are already opened to our view -on one side. - -184. - -Objects seen through mediums more or less transparent do not appear -to us in the place which they should occupy according to the laws of -perspective. On this fact the dioptrical colours of the second class -depend. - -185. - -Those laws of vision which admit of being expressed in mathematical -formulæ are based on the principle that, as light proceeds in straight -lines, it must be possible to draw a straight line from the eye to any -given object in order that it be seen. If, therefore, a case arises in -which the light arrives to us in a bent or broken line, that we see the -object by means of a bent or broken line, we are at once informed that -the medium between the eye and the object is denser, or that it has -assumed this or that foreign nature. - -186. - -This deviation from the law of right-lined vision is known by the -general term of refraction; and, although we may take it for granted -that our readers are sufficiently acquainted with its effects, yet we -will here once more briefly exhibit it in its objective and subjective -point of view. - -187. - -Let the sun shine diagonally into an empty cubical vessel, so that -the opposite side be illumined, but not the bottom: let water be -then poured into this vessel, and the direction of the light will -be immediately altered; for a part of the bottom is shone upon. At -the point where the light enters the thicker medium it deviates from -its rectilinear direction, and appears broken: hence the phenomenon -is called the breaking (_brechung_) or refraction. Thus much of the -objective experiment. - -188. - -We arrive at the subjective fact in the following mode:--Let the eye -be substituted for the sun: let the sight be directed in like manner -[Pg 78] diagonally over one side, so that the opposite inner side be -entirely seen, while no part of the bottom is visible. On pouring in -water the eye will perceive a part of the bottom; and this takes place -without our being aware that we do not see in a straight line; for -the bottom appears to us raised, and hence we give the term elevation -(_hebung_) to the subjective phenomenon. Some points, which are -particularly remarkable with reference to this, will be adverted to -hereafter. - -189. - -Were we now to express this phenomenon generally, we might here repeat, -in conformity with the view lately taken, that the relation of the -objects is changed or deranged. - -190. - -But as it is our intention at present to separate the objective from -the subjective appearances, we first express the phenomenon in a -subjective form, and say,--a derangement or displacement of the object -seen, or to be seen, takes place. - -191. - -But that which is seen without a limiting outline may be thus affected -without our perceiving the change. On the other hand, if what we look -at has a visible termination, we have an evident indication that a -displacement occurs. If, therefore, [Pg 79] we wish to ascertain the -relation or degree of such a displacement, we must chiefly confine -ourselves to the alteration of surfaces with visible boundaries; in -other words, to the displacement of circumscribed objects. - -192. - -The general effect may take place through parallel mediums, for every -parallel medium displaces the object by bringing it perpendicularly -towards the eye. The apparent change of position is, however, more -observable through mediums that are not parallel. - -193. - -These latter may be perfectly spherical, or may be employed in the -form of convex or concave lenses. We shall make use of all these as -occasion may require in our experiments. But as they not only displace -the object from its position, but alter it in various ways, we shall, -in most cases, prefer employing mediums with surfaces, not, indeed, -parallel with reference to each other, but still altogether plane, -namely, prisms. These have a triangle for their base, and may, it is -true, be considered as portions of a lens, but they are particularly -available for our experiments, inasmuch as they very perceptibly -displace the object from its position, without producing a remarkable -distortion. - -194. - -And now, in order to conduct our observations with as much exactness -as possible, and to avoid all confusion and ambiguity, we confine -ourselves at first to - - -SUBJECTIVE EXPERIMENTS, - - -in which, namely, the object is seen by the observer through a -refracting medium. As soon as we have treated these in due series, the -objective experiments will follow in similar order. - - - - -XII. - - -REFRACTION WITHOUT THE APPEARANCE OF COLOUR. - - -195. - -Refraction can visibly take place without our perceiving an appearance -of colour. To whatever extent a colourless or uniformly coloured -surface may be altered as to its position by refraction, no colour -consequent upon refraction appears within it, provided it has no -outline or boundary. We may convince ourselves of this in various ways. - -196. - -Place a glass cube on any larger surface, and look through the glass -perpendicularly or obliquely, the unbroken surface opposite the eye -appears altogether raised, but no colour exhibits itself. If we look at -a pure grey or blue sky or a uniformly white or coloured wall through a -prism, the portion of the surface which the eye thus embraces will be -altogether changed as to its position, without our therefore observing -the smallest appearance of colour. - - - - -XIII. - - -CONDITIONS OF THE APPEARANCE OF COLOUR. - - -197. - -Although in the foregoing experiments we have found all unbroken -surfaces, large or small, colourless, yet at the outlines or -boundaries, where the surface is relieved upon a darker or lighter -object, we observe a coloured appearance. - -198. - -Outline, as well as surface, is necessary to constitute a figure or -circumscribed object. We therefore express the leading fact thus: -circumscribed objects must be displaced by refraction in order to the -exhibition of an appearance of colour. - -199. - -We place before us the simplest object, a light disk on a dark ground -(A).[1] A displacement occurs with regard to this object, if we -apparently extend its outline from the centre by magnifying it. This -may be done with any convex glass, and in this case we see a blue edge -(B). - -200. - -We can, to appearance, contract the circumference of the same light -disk towards the centre by diminishing the object; the edge will then -appear yellow (C). This may be done with a concave glass, which, -however, should not be ground thin like common eye-glasses, but must -have some substance. In order, however, to make this experiment at once -with the convex glass, let a smaller black disk be inserted within -the light disk on a black ground. If we magnify the black disk on a -white ground with a convex glass, the same result takes place as if we -diminished the white disk; for we extend the black outline upon the -white, and we thus perceive the yellow edge together with the blue edge -(D). - -201. - -These two appearances, the blue and yellow, exhibit themselves in and -upon the white: they both assume a reddish hue, in proportion as they -mingle with the black.[2] - -[Illustration] - -202. - -In this short statement we have described the primordial phenomena of -all appearance of colour occasioned by refraction. These undoubtedly -may be repeated, varied, and rendered more striking; may be combined, -complicated, confused; but, after all, may be still restored to their -original simplicity. - -203. - -In examining the process of the experiment just given, we find that -in the one case we have, to appearance, extended the white edge upon -the dark surface; in the other we have extended the dark edge upon -the white surface, supplanting one by the other, pushing one over -the other. We will now endeavour, step by step, to analyse these and -similar cases. - -204. - -If we cause the white disk to move, in appearance, entirely from its -place, which can be done effectually by prisms, it will be coloured -according to the direction in which it apparently moves, in conformity -with the above laws. If we look at the disk _a_[3] through a prism, -so that it appear moved to _b_, the outer edge will appear blue and -blue-red, according to the law of the figure B (fig. 1), the other -edge being yellow, and yellow-red, according to the law of the figure -C (fig. 1). For in the first case the white figure is, as it were, -extended over the dark boundary, and in the other case the dark -boundary is passed over the white figure. The same happens if the disk -is, to appearance, moved from _a_ to _c_, from _a_ to _d_, and so -throughout the circle. - -205. - -As it is with the simple effect, so it is with more complicated -appearances. If we look through a horizontal prism (_a b_[4]) at a -white disk placed at some distance behind it at _e_, the disk will -be raised to _f_, and coloured according to the above law. If we -remove this prism, and look through a vertical one (_c d_) at the same -disk, it will appear at _h_, and coloured according to the same law. -If we place the two prisms one upon the other, the disk will appear -displaced diagonally, in conformity with a general law of nature, and -will be coloured as before; that is, according to its movement in the -direction, _e.g._:[5] - -206. - -If we attentively examine these opposite coloured edges, we find that -they only appear in the direction of the apparent change of place. -A round figure leaves us in some degree uncertain as to this: a -quadrangular figure removes all doubt. - -207. - -The quadrangular figure _a_,[6] moved in the direction _a b_ or _a d_ -exhibits no colour on the sides which are parallel with the direction -in which it moves: on the other hand, if moved in the direction _a -c_, parallel with its diagonal, all the edges of the figure appear -coloured.[7] - -208. - -Thus, a former position (203) is here confirmed; viz. to produce -colour, an object must be so displaced that the light edges be -apparently carried over a dark surface, the dark edges over a light -surface, the figure over its boundary, the boundary over the figure. -But if the rectilinear boundaries of a figure could be indefinitely -extended by refraction, so that figure and background might only pursue -their course next, but not over each other, no colour would appear, not -even if they were prolonged to infinity. - - -[1] Plate 2, fig. 1. - -[2] The author has omitted the orange and purple in the coloured -diagrams which illustrate these first experiments, from a wish probably -to present the elementary contrast, on which he lays a stress, in -greater simplicity. The reddish tinge would be apparent, as stated -above, where the blue and yellow are in contact with the black.--T. - -[3] Plate 2, fig. 2 - -[4] Plate 2, fig. 4 - -[5] In this case, according to the author, the refracting medium being -increased in mass, the appearance of colour is increased, and the -displacement is greater.--T. - -[6] Plate 2, fig. 3. - -[7] Fig. 2, plate 1, contains a variety of forms, which, when viewed -through a prism, are intended to illustrate the statement in this and -the following paragraph. - - - - -XIV. - - -CONDITIONS UNDER WHICH THE APPEARANCE OF COLOUR INCREASES. - - -209. - -We have seen in the foregoing experiments that all appearance of colour -occasioned by refraction depends on the condition that the boundary or -edge be moved in upon the object itself, or the object itself over the -ground, that the figure should be, as it were, carried over itself, or -over the ground. And we shall now find that, by increased displacement -of the object, the appearance of colour exhibits itself in a greater -degree. This takes place in subjective experiments, to which, for the -present, we confine ourselves, under the following conditions. - -210. - -First, if, in looking through parallel mediums, the eye is directed -more obliquely. - -Secondly, if the surfaces of the medium are no longer parallel, but -form a more or less acute angle. - -Thirdly, owing to the increased proportion of the medium, whether -parallel mediums be increased in size, or whether the angle be -increased, provided it does not attain a right angle. - -Fourthly, owing to the distance of the eye armed with a refracting -medium from the object to be displaced. - -Fifthly, owing to a chemical property that may be communicated to the -glass, and which may be afterwards increased in effect. - -211. - -The greatest change of place, short of considerable distortion of the -object, is produced by means of prisms, and this is the reason why the -appearance of colour can be exhibited most powerfully through glasses -of this form. Yet we will not, in employing them, suffer ourselves to -be dazzled by the splendid appearances they exhibit, but keep the above -well-established, simple principles calmly in view. - -212. - -The colour which is outside, or foremost, in the apparent change of an -object by refraction, is always the broader, and we will henceforth -call this a _border_: the colour that remains next the outline is the -narrower, and this we will call an _edge_. - -213. - -If we move a dark boundary towards a light surface, the yellow broader -border is foremost, and the narrower yellow-red edge follows close to -the outline. If we move a light boundary towards a dark surface, the -broader violet border is foremost, and the narrower blue edge follows. - -214. - -If the object is large, its centre remains uncoloured. Its inner -surface is then to be considered as unlimited (195): it is displaced, -but not otherwise altered: but if the object is so narrow, that under -the above conditions the yellow border can reach the blue edge, the -space between the outlines will be entirely covered with colour. If we -make this experiment with a white stripe on a black ground,[1] the two -extremes will presently meet, and thus produce green. We shall then see -the following series of colours:-- - - Yellow-red. - Yellow. - Green. - Blue. - Blue-red. - -215. - -If we place a black band, or stripe, on white paper,[2] the violet -border will spread till it meets the yellow-red edge. In this case the -intermediate black is effaced (as the intermediate white was in the -last experiment), and in its stead a splendid pure red will appear.[3] -The series of colours will now be as follows:-- - - Blue. - Blue-red. - Red. - Yellow-red. - Yellow. - -216. - -The yellow and blue, in the first case (214), can by degrees meet so -fully, that the two colours blend entirely in green, and the order will -then be, - - Yellow-red. - Green. - Blue-red. - -In the second case (215), under similar circumstances, we see only - - Blue. - Red. - Yellow. - -This appearance is best exhibited by refracting the bars of a window -when they are relieved on a grey sky.[4] - -217. - -In all this we are never to forget that this appearance is not to be -considered as a complete or final state, but always as a progressive, -increasing, and, in many senses, controllable appearance. Thus we -find that, by the negation of the above five conditions, it gradually -decreases, and at last disappears altogether. - - -[1] Plate 2, fig. 5, _left_. - -[2] Plate 2, fig. 5, _right_. - -[3] This pure red, the union of orange and violet, is considered by the -author the maximum of the coloured appearance: he has appropriated the -term _purpur_ to it. See paragraph 703, and _note_.--T. - -[4] The bands or stripes in fig. 4, plate 1, when viewed through a -prism, exhibit the colours represented in plate 2, fig. 5. - - - - -XV. - - -EXPLANATION OF THE FOREGOING PHENOMENA. - - -218. - -Before we proceed further, it is incumbent on us to explain the first -tolerably simple phenomenon, and to show its connexion with the -principles first laid down, in order that the observer of nature may -be enabled clearly to comprehend the more complicated appearances that -follow. - -219. - -In the first place, it is necessary to remember that we have to do -with circumscribed objects. In the act of seeing, generally, it is -the circumscribed visible which chiefly invites our observation; and -in the present instance, in speaking of the appearance of colour, as -occasioned by refraction, the circumscribed visible, the detached -object solely occupies our attention. - -220. - -For our chromatic exhibitions we can, however, divide objects generally -into _primary_ and _secondary_. The expressions of themselves denote -what we understand by them, but our meaning will be rendered still more -plain by what follows. - -221. - -Primary objects may be considered firstly as _original_, as images -which are impressed on the eye by things before it, and which assure -us of their reality. To these the secondary images may be opposed -as _derived_ images, which remain in the organ when the object -itself is taken away; those apparent after-images, which have been -circumstantially treated of in the doctrine of physiological colours. - -222. - -The primary images, again, may be considered as _direct_ images, which, -like the original impressions, are conveyed immediately from the object -to the eye. In contradistinction to these, the secondary images may -be considered as _indirect_, being only conveyed to us, as it were, -at second-hand from a reflecting surface. These are the mirrored, or -catoptrical, images, which in certain cases can also become double -images: - -223. - -When, namely, the reflecting body is transparent, and has two parallel -surfaces, one behind the other: in such a case, an image may be -reflected to the eye from both surfaces, and thus arise double images, -inasmuch as the upper image does not quite cover the under one: this -may take place in various ways. - -Let a playing-card be held before a mirror. We shall at first see the -distinct image of the card, but the edge of the whole card, as well -as that of every spot upon it, will be bounded on one side with a -border, which is the beginning of the second reflection. This effect -varies in different mirrors, according to the different thickness of -the glass, and the accidents of polishing. If a person wearing a white -waistcoat, with the remaining part of his dress dark, stands before -certain mirrors, the border appears very distinctly, and in like manner -the metal buttons on dark cloth exhibit the double reflection very -evidently. - -224. - -The reader who has made himself acquainted with our former descriptions -of experiments (80) will the more readily follow the present statement. -The window-bars reflected by plates of glass appear double, and -by increased thickness of the glass, and a due adaptation of the -angle of reflection, the two reflections may be entirely separated -from each other. So a vase full of water, with a plane mirror-like -bottom, reflects any object twice, the two reflections being more or -less separated under the same conditions. In these cases it is to be -observed that, where the two reflections cover each other, the perfect -vivid image is reflected, but where they are separated they exhibit -only weak, transparent, and shadowy images. - -225. - -If we wish to know which is the under and which the upper image, we -have only to take a coloured medium, for then a light object reflected -from the under surface is of the colour of the medium, while that -reflected from the upper surface presents the complemental colour. With -dark objects it is the reverse; hence black and white surfaces may be -here also conveniently employed. How easily the double images assume -and evoke colours will here again be striking. - -226. - -Thirdly, the primary images may be considered as _principal_ images, -while the secondary can be, as it were, annexed to these as _accessory_ -images. Such an accessory image produces a sort of double form; except -that it does not separate itself from the principal object, although it -may be said to be always endeavouring to do so. It is with secondary -images of this last description that we have to do in prismatic -appearances. - -227. - -A surface without a boundary exhibits no appearance of colour when -refracted (195). Whatever is seen must be circumscribed by an -outline to produce this effect. In other words a figure, an object, -is required; this object undergoes an apparent change of place by -refraction: the change is however not complete, not clean, not sharp; -but incomplete, inasmuch as an accessory image only is produced. - -228. - -In examining every appearance of nature, but especially in examining -an important and striking one, we should not remain in one spot, we -should not confine ourselves to the insulated fact, nor dwell on it -exclusively, but look round through all nature to see where something -similar, something that has affinity to it, appears: for it is only by -combining analogies that we gradually arrive at a whole which speaks -for itself, and requires no further explanation. - -229. - -Thus we here call to mind that in certain cases refraction -unquestionably produces double images, as is the case in Iceland spar: -similar double images are also apparent in cases of refraction through -large rock crystals, and in other instances; phenomena which have not -hitherto been sufficiently observed.[1] - -230. - -But since in the case under consideration (227) the question relates -not to double but to accessory images, we refer to a phenomenon already -adverted to, but not yet thoroughly investigated. We allude to an -earlier experiment, in which it appeared that a sort of conflict took -place in regard to the retina between a light object and its dark -ground, and between a dark object and its light ground (16). The light -object in this case appeared larger, the dark one smaller. - -231. - -By a more exact observation of this phenomenon we may remark that the -forms are not sharply distinguished from the ground, but that they -appear with a kind of grey, in some degree, coloured edge; in short, -with an accessory image. If, then, objects seen only with the naked -eye produce such effects, what may not take place when a dense medium -is interposed? It is not that alone which presents itself to us in -obvious operation which produces and suffers effects, but likewise all -principles that have a mutual relation only of some sort are efficient -accordingly, and indeed often in a very high degree. - -232. - -Thus when refraction produces its effect on an object there appears an -accessory image next the object itself: the real form thus refracted -seems even to linger behind, as if resisting the change of place; but -the accessory image seems to advance, and extends itself more or less -in the mode already shown (212-216). - -233. - -We also remarked (224) that in double images the fainter appear only -half substantial, having a kind of transparent, evanescent character, -just as the fainter shades of double shadows must always appear as -half-shadows. These latter assume colours easily, and produce them -readily (69), the former also (80); and the same takes place in the -instance of accessory images, which, it is true, do not altogether -quit the real object, but still advance or extend from it as -half-substantial images, and hence can appear coloured so quickly and -so powerfully. - -234. - -That the prismatic appearance is in fact an accessory image we may -convince ourselves in more than one mode. It corresponds exactly with -the form of the object itself. Whether the object be bounded by a -straight line or a curve, indented or waving, the form of the accessory -image corresponds throughout exactly with the form of the object.[2] - -235. - -Again, not only the form but other qualities of the object are -communicated to the accessory image. If the object is sharply relieved -from its ground, like white on black, the coloured accessory image in -like manner appears in its greatest force. It is vivid, distinct, and -powerful; but it is most especially powerful when a luminous object is -shown on a dark ground, which may be contrived in various ways. - -236. - -But if the object is but faintly distinguished from the ground, like -grey objects on black or white, or even on each other, the accessory -image is also faint, and, when the original difference of tint or force -is slight, becomes hardly discernible. - -237. - -The appearances which are observable when coloured objects are relieved -on light, dark, or coloured grounds are, moreover, well worthy of -attention. In this case a union takes place between the apparent colour -of the accessory image and the real colour of the object; a compound -colour is the result, which is either assisted and enhanced by the -accordance, or neutralised by the opposition of its ingredients. - -238. - -But the common and general characteristic both of the double and -accessory image is semi-transparence. The tendency of a transparent -medium to become only half transparent, or merely light-transmitting, -has been before adverted to (147, 148). Let the reader assume that he -sees within or through such a medium a visionary image, and he will at -once pronounce this latter to be a semi-transparent image. - -239. - -Thus the colours produced by refraction may be fitly explained by the -doctrine of the semi-transparent mediums. For where dark passes over -light, as the border of the semi-transparent accessory image advances, -yellow appears; and, on the other hand, where a light outline passes -over the dark background, blue appears (150, 151). - -240. - -The advancing foremost colour is always the broader. Thus the yellow -spreads over the light with a broad border, but the yellow-red appears -as a narrower stripe and is next the dark, according to the doctrine of -augmentation, as an effect of shade.[3] - -241. - -On the opposite side the condensed blue is next the edge, while the -advancing border, spreading as a thinner veil over the black, produces -the violet colour, precisely on the principles before explained in -treating of semi-transparent mediums, principles which will hereafter -be found equally efficient in many other cases. - -242. - -Since an analysis like the present requires to be confirmed by ocular -demonstration, we beg every reader to make himself acquainted with the -experiments hitherto adduced, not in a superficial manner, but fairly -and thoroughly. We have not placed arbitrary signs before him instead -of the appearances themselves; no modes of expression are here proposed -for his adoption which may be repeated for ever without the exercise -of thought and without leading any one to think; but we invite him to -examine intelligible appearances, which must be present to the eye and -mind, in order to enable him clearly to trace these appearances to -their origin, and to explain them to himself and to others. - - -[1] The date of the publication, 1810, is sometimes to be -remembered.--T. - -[2] The forms in fig. 2, plate 1, when seen through a prism, are -again intended to exemplify this. In the plates to the original work -curvilinear figures are added, but the circles, fig. 1, in the same -plate, may answer the same end.--T. - -[3] The author has before observed that colour is a degree of darkness, -and he here means that increase of darkness, produced by transparent -mediums, is, to a certain extent, increase of colour.--T. - - - - -XVI. - - -DECREASE OF THE APPEARANCE OF COLOUR. - - -243. - -We need only take the five conditions (210) under which the appearance -of colour increases in the contrary order, to produce the contrary or -decreasing state; it may be as well, however, briefly to describe and -review the corresponding modifications which are presented to the eye. - -244. - -At the highest point of complete junction of the opposite edges, the -colours appear as follows (216):-- - - Yellow-red. Blue. - Green. Red. - Blue-red. Yellow. - -245. - -Where the junction is less complete, the appearance is as follows (214, -215):-- - - Yellow-red. Blue. - Yellow. Blue-red. - Green. Red. - Blue. Yellow-red. - Blue-red. Yellow. - -Here, therefore, the surface still appears completely coloured, but -neither series is to be considered as an elementary series, always -developing itself in the same manner and in the same degrees; on the -contrary, they can and should be resolved into their elements; and, in -doing this, we become better acquainted with their nature and character. - -246. - -These elements then are (199, 200, 201)-- - - Yellow-red. Blue. - Yellow. Blue-red. - White. Black. - Blue. Yellow-red. - Blue-red. Yellow. - -Here the surface itself, the original object, which has been hitherto -completely covered, and as it were lost, again appears in the centre of -the colours, asserts its right, and enables us fully to recognise the -secondary nature of the accessory images which exhibit themselves as -"edges" and "borders."--Note N. - -247. - -We can make these edges and borders as narrow as we please; nay, we -can still have refraction in reserve after having done away with all -appearance of colour at the boundary of the object. - -Having now sufficiently investigated the exhibition of colour in this -phenomenon, we repeat that we cannot admit it to be an elementary -phenomenon. On the contrary, we have traced it to an antecedent and -a simpler one; we have derived it, in connexion with the theory of -secondary images, from the primordial phenomenon of light and darkness, -as affected or acted upon by semi-transparent mediums. Thus prepared, -we proceed to describe the appearances which refraction produces on -grey and coloured objects, and this will complete the section of -subjective phenomena. - - - - -XVII. - -GREY OBJECTS DISPLACED BY REFRACTION. - - -248. - -Hitherto we have confined our attention to black and white objects -relieved on respectively opposite grounds, as seen through the prism, -because the coloured edges and borders are most clearly displayed in -such cases. We now repeat these experiments with grey objects, and -again find similar results. - -249. - -As we called black the equivalent of darkness, and white the -representative of light (18), so we now venture to say that grey -represents half-shadow, which partakes more or less of light and -darkness, and thus stands between the two. We invite the reader to call -to mind the following facts as bearing on our present view. - -250. - -Grey objects appear lighter on a black than on a white ground (33); -they appear as a light on a black ground, and larger; as a dark on the -white ground, and smaller. (16.) - -251. - -The darker the grey the more it appears as a faint light on black, as a -strong dark on white, and _vice versâ_; hence the accessory images of -dark-grey on black are faint, on white strong: so the accessory images -of light-grey on white are faint, on black strong. - -252. - -Grey on black, seen through the prism, will exhibit the same -appearances as white on black; the edges are coloured according to the -same law, only the borders appear fainter. If we relieve grey on white, -we have the same edges and borders which would be produced if we saw -black on white through the prism.--Note O. - -253. - -Various shades of grey placed next each other in gradation will exhibit -at their edges, either blue and violet only, or red and yellow only, -according as the darker grey is placed over or under. - -254. - -A series of such shades of grey placed horizontally next each other -will be coloured conformably to the same law according as the whole -series is relieved, on a black or white ground above or below. - -255. - -The observer may see the phenomena exhibited by the prism at one -glance, by enlarging the plate intended to illustrate this section.[1] - -256. - -It is of great importance duly to examine and consider another -experiment in which a grey object is placed partly on a black and -partly on a white surface, so that the line of division passes -vertically through the object. - -257. - -The colours will appear on this grey object in conformity with the -usual law, but according to the opposite relation of the light to the -dark, and will be contrasted in a line. For as the grey is as a light -to the black, so it exhibits the red and yellow above the blue and -violet below: again, as the grey is as a dark to the white, the blue -and violet appear above the red and yellow below. This experiment will -be found of great importance with reference to the next chapter. - - -[1] It has been thought unnecessary to give all the examples in the -plate alluded to, but the leading instance referred to in the next -paragraph will be found in plate 3, fig. 1. The grey square when seen -through a prism will exhibit the effects described in par. 257.--T. - - - - -XVIII. - - -COLOURED OBJECTS DISPLACED BY REFRACTION. - - -258. - -An unlimited coloured surface exhibits no prismatic colour in addition -to its own hue, thus not at all differing from a black, white, or -grey surface. To produce the appearance of colour, light and dark -boundaries must act on it either accidentally or by contrivance. Hence -experiments and observations on coloured surfaces, as seen through the -prism, can only be made when such surfaces are separated by an outline -from another differently tinted surface, in short when _circumscribed -objects_ are coloured. - -259. - -All colours, whatever they may be, correspond so far with grey, that -they appear darker than white and lighter than black. This shade-like -quality of colour (σκιέρον) has been already alluded to (69), and will -become more and more evident. If then we begin by placing coloured -objects on black and white surfaces, and examine them through the -prism, we shall again have all that we have seen exhibited with grey -surfaces. - - -[Illustration] - -260. - -If we displace a coloured object by refraction, there appears, as -in the case of colourless objects and according to the same laws, -an accessory image. This accessory image retains, as far as colour -is concerned, its usual nature, and acts on one side as a blue and -blue-red, on the opposite side as a yellow and yellow-red. Hence the -apparent colour of the edge and border will be either homogeneous -with the real colour of the object, or not so. In the first case the -apparent image identifies itself with the real one, and appears to -increase it, while, in the second case, the real image may be vitiated, -rendered indistinct, and reduced in size by the apparent image. We -proceed to review the cases in which these effects are most strikingly -exhibited. - -261. - -If we take a coloured drawing enlarged from the plate, which -illustrates this experiment[1], and examine the red and blue squares -placed next each other on a black ground, through the prism as usual, -we shall find that as both colours are lighter than the ground, -similarly coloured edges and borders will appear above and below, at -the outlines of both, only they will not appear equally distinct to the -eye. - -262. - -Red is proportionally much lighter on black than blue is. The colours -of the edges will therefore appear stronger on the red than on the -blue, which here acts as a dark-grey, but little different from black. -(251.) - -263. - -The extreme red edge will identify itself with the vermilion colour -of the square, which will thus appear a little elongated in this -direction; while the yellow border immediately underneath it only gives -the red surface a more brilliant appearance, and is not distinguished -without attentive observation. - -264. - -On the other hand the red edge and yellow border are heterogeneous -with the blue square; a dull red appears at the edge, and a dull green -mingles with the figure, and thus the blue square seems, at a hasty -glance, to be comparatively diminished on this side. - -265. - -At the lower outline of the two squares a blue edge and a violet border -will appear, and will produce the contrary effect; for the blue edge, -which is heterogeneous with the warm red surface, will vitiate it -and produce a neutral colour, so that the red on this side appears -comparatively reduced and driven upwards, and the violet border on the -black is scarcely perceptible. - -266. - -On the other hand, the blue apparent edge will identify itself with the -blue square, and not only not reduce, but extend it. The blue edge and -even the violet border next it have the apparent effect of increasing -the surface, and elongating it in that direction. - -267. - -The effect of homogeneous and heterogeneous edges, as I have now -minutely described it, is so powerful and singular that the two squares -at the first glance seem pushed out of their relative horizontal -position and moved in opposite directions, the red upwards, the blue -downwards. But no one who is accustomed to observe experiments in a -certain succession, and respectively to connect and trace them, will -suffer himself to be deceived by such an unreal effect. - -268. - -A just impression with regard to this important phenomenon will, -however, much depend on some nice and even troublesome conditions, -which are necessary to produce the illusion in question. Paper should -be tinged with vermilion or the best minium for the red square, and -with deep indigo for the blue square. The blue and red prismatic edges -will then unite imperceptibly with the real surfaces where they are -respectively homogeneous; where they are not, they vitiate the colours -of the squares without producing a very distinct middle tint. The real -red should not incline too much to yellow, otherwise the apparent deep -red edge above will be too distinct; at the same time it should be -somewhat yellow, otherwise the transition to the yellow border will be -too observable. The blue must not be light, otherwise the red edge will -be visible, and the yellow border will produce a too decided green, -while the violet border underneath would not give us the impression of -being part of an elongated light blue square. - -269. - -All this will be treated more circumstantially hereafter, when we speak -of the apparatus intended to facilitate the experiments connected with -this part of our subject.[2] Every inquirer should prepare the figures -himself, in order fairly to exhibit this specimen of ocular deception, -and at the same time to convince himself that the coloured edges, even -in this case, cannot escape accurate examination. - -270. - -Meanwhile various other combinations, as exhibited in the plate, are -fully calculated to remove all doubt on this point in the mind of every -attentive observer. - -271. - -If, for instance, we look at a white square, next the blue one, on a -black ground, the prismatic hues of the opposite edges of the white, -which here occupies the place of the red in the former experiment, will -exhibit themselves in their utmost force. The red edge extends itself -above the level of the blue almost in a greater degree than was the -case with the red square itself in the former experiment. The lower -blue edge, again, is visible in its full force next the white, while, -on the other hand, it cannot be distinguished next the blue square. The -violet border underneath is also much more apparent on the white than -on the blue. - -272. - -If the observer now compares these double squares, carefully prepared -and arranged one above the other, the red with the white, the two blue -squares together, the blue with the red, the blue with the white, he -will clearly perceive the relations of these surfaces to their coloured -edges and borders. - -273. - -The edges and their relations to the coloured surfaces appear still -more striking if we look at the coloured squares and a black square -on a white ground; for in this case the illusion before mentioned -ceases altogether, and the effect of the edges is as visible as in -any case that has come under our observation. Let the blue and red -squares be first examined through the prism. In both the blue edge now -appears above; this edge, homogeneous with the blue surface, unites -with it, and appears to extend it upwards, only the blue edge, owing -to its lightness, is somewhat too distinct in its upper portion; the -violet border underneath it is also sufficiently evident on the blue. -The apparent blue edge is, on the other hand, heterogeneous with the -red square; it is neutralised by contrast, and is scarcely visible; -meanwhile the violet border, uniting with the real red, produces a hue -resembling that of the peach-blossom. - -274. - -If thus, owing to the above causes, the upper outlines of these -squares do not appear level with each other, the correspondence of the -under outlines is the more observable; for since both colours, the red -and the blue, are darks compared with the white (as in the former case -they were light compared with the black), the red edge with its yellow -border appears very distinctly under both. It exhibits itself under the -warm red surface in its full force, and under the dark blue nearly as -it appears under the black: as may be seen if we compare the edges and -borders of the figures placed one above the other on the white ground. - -275. - -In order to present these experiments with the greatest variety and -perspicuity, squares of various colours are so arranged[3] that the -boundary of the black and white passes through them vertically. -According to the laws now known to us, especially in their application -to coloured objects, we shall find the squares as usual doubly coloured -at each edge; each square will appear to be split in two, and to be -elongated upwards or downwards. We may here call to mind the experiment -with the grey figure seen in like manner on the line of division -between black and white (257).[4] - -276. - -A phenomenon was before exhibited, even to illusion, in the instance of -a red and blue square on a black ground; in the present experiment the -elongation upwards and downwards of two differently coloured figures -is apparent in the two halves of one and the same figure of one and -the same colour. Thus we are still referred to the coloured edges and -borders, and to the effects of their homogeneous and heterogeneous -relations with respect to the real colours of the objects. - -277. - -I leave it to observers themselves to compare the various gradations -of coloured squares, placed half on black half on white, only inviting -their attention to the apparent alteration which takes place in -contrary directions; for red and yellow appear elongated upwards if -on a black ground, downwards if on a white; blue, downwards if on a -black ground, upwards if on a white. All which, however, is quite in -accordance with the diffusely detailed examples above given. - -278. - -Let the observer now turn the figures so that the before-mentioned -squares placed on the line of division between black and white may -be in a horizontal series; the black above, the white underneath. On -looking at these squares through the prism, he will observe that the -red square gains by the addition of two red edges; on more accurate -examination he will observe the yellow border on the red figure, and -the lower yellow border upon the white will be perfectly apparent. - -279. - -The upper red edge on the blue square is on the other hand hardly -visible; the yellow border next it produces a dull green by mingling -with the figure; the lower red edge and the yellow border are displayed -in lively colours. - -280. - -After observing that the red figure in these cases appears to gain by -an addition on both sides, while the dark blue, on one side at least, -loses something; we shall see the contrary effect produced by turning -the same figures upside down, so that the white ground be above, the -black below. - -281. - -For as the homogeneous edges and borders now appear above and below -the blue square, this appears elongated, and a portion of the surface -itself seems even more brilliantly coloured: it is only by attentive -observation that we can distinguish the edges and borders from the -colour of the figure itself. - -282. - -The yellow and red squares, on the other hand, are comparatively -reduced by the heterogeneous edges in this position of the figures, -and their colours are, to a certain extent, vitiated. The blue edge -in both is almost invisible. The violet border appears as a beautiful -peach-blossom hue on the red, as a very pale colour of the same kind on -the yellow; both the lower edges are green; dull on the red, vivid on -the yellow; the violet border is but faintly perceptible under the red, -but is more apparent under the yellow. - -283. - -Every inquirer should make it a point to be thoroughly acquainted with -all the appearances here adduced, and not consider it irksome to follow -out a single phenomenon through so many modifying circumstances. These -experiments, it is true, may be multiplied to infinity by differently -coloured figures, upon and between differently coloured grounds. Under -all such circumstances, however, it will be evident to every attentive -observer that coloured squares only appear relatively altered, or -elongated, or reduced by the prism, because an addition of homogeneous -or heterogeneous edges produces an illusion. The inquirer will now -be enabled to do away with this illusion if he has the patience to -go through the experiments one after the other, always comparing the -effects together, and satisfying himself of their correspondence. - -Experiments with coloured objects might have been contrived in various -ways: why they have been exhibited precisely in the above mode, and -with so much minuteness, will be seen hereafter. The phenomena, -although formerly not unknown, were much misunderstood; and it was -necessary to investigate them thoroughly to render some portions of our -intended historical view clearer. - -284. - -In conclusion, we will mention a contrivance by means of which our -scientific readers may be enabled to see these appearances distinctly -at one view, and even in their greatest splendour. Cut in a piece of -pasteboard five perfectly similar square openings of about an inch, -next each other, exactly in a horizontal line: behind these openings -place five coloured glasses in the natural order, orange, yellow, -green, blue, violet. Let the series thus adjusted be fastened in an -opening of the camera obscura, so that the bright sky may be seen -through the squares, or that the sun may shine on them; they will thus -appear very powerfully coloured. Let the spectator now examine them -through the prism, and observe the appearances, already familiar by -the foregoing experiments, with coloured objects, namely, the partly -assisting, partly neutralising effects of the edges and borders, and -the consequent apparent elongation or reduction of the coloured squares -with reference to the horizontal line. The results witnessed by the -observer in this case, entirely correspond with those in the cases -before analysed; we do not, therefore, go through them again in detail, -especially as we shall find frequent occasions hereafter to return to -the subject.--Note P. - - -[1] Plate 3, fig. 1. The author always recommends making the -experiments on an increased scale, in order to see the prismatic -effects distinctly. - -[2] Neither the description of the apparatus nor the recapitulation -of the whole theory, so often alluded to by the author, were ever -given.--T. - -[3] Plate 3. fig. 1. - -[4] The grey square is introduced in the same plate, fig. 1, above the -coloured squares. - - - - -XIX. - - -ACHROMATISM AND HYPERCHROMATISM. - - -285. - -Formerly when much that is regular and constant in nature was -considered as mere aberration and accident, the colours arising from -refraction were but little attended to, and were looked upon as an -appearance attributable to particular local circumstances. - -286. - -But after it had been assumed that this appearance of colour -accompanies refraction at all times, it was natural that it should -be considered as intimately and exclusively connected with that -phenomenon; the belief obtaining that the measure of the coloured -appearance was in proportion to the measure of the refraction, and that -they must advance _pari passu_ with each other. - -287. - -If, again, philosophers ascribed the phenomenon of a stronger or weaker -refraction, not indeed wholly, but in some degree, to the different -density of the medium, (as purer atmospheric air, air charged with -vapours, water, glass, according to their increasing density, increase -the so-called refraction, or displacement of the object;) so they -could hardly doubt that the appearance of colour must increase in the -same proportion; and hence took it for granted, in combining different -mediums which were to counteract refraction, that as long as refraction -existed, the appearance of colour must take place, and that as soon as -the colour disappeared, the refraction also must cease. - -288. - -Afterwards it was, however, discovered that this relation which was -assumed to correspond, was, in fact, dissimilar; that two mediums can -refract an object with equal power, and yet produce very dissimilar -coloured borders. - -289. - -It was found that, in addition to the physical principle to which -refraction was ascribed, a chemical one was also to be taken into the -account. We propose to pursue this subject hereafter, in the chemical -division of our inquiry, and we shall have to describe the particulars -of this important discovery in our history of the doctrine of colours. -What follows may suffice for the present. - -290. - -In mediums of similar or nearly similar refracting power, we find -the remarkable circumstance that a greater and lesser appearance of -colour can be produced by a chemical treatment; the greater effect is -owing, namely, to acids, the lesser to alkalis. If metallic oxydes are -introduced into a common mass of glass, the coloured appearance through -such glasses becomes greatly increased without any perceptible change -of refracting power. That the lesser effect, again, is produced by -alkalis, may be easily supposed. - -291. - -Those kinds of glass which were first employed after the discovery, -are called flint and crown glass; the first produces the stronger, the -second the fainter appearance of colour. - -292. - -We shall make use of both these denominations as technical terms in our -present statement, and assume that the refractive power of both is -the same, but that flint-glass produces the coloured appearance more -strongly by one-third than the crown-glass. The diagram (Plate 3, fig. -2,) may serve in illustration. - -293. - -A black surface is here divided into compartments for more convenient -demonstration: let the spectator imagine five white squares between the -parallel lines _a, b,_ and _c, d_. The square No. 1, is presented to -the naked eye unmoved from its place. - -294. - -But let the square No. 2, seen through a crown-glass prism _g_, be -supposed to be displaced by refraction three compartments, exhibiting -the coloured borders to a certain extent; again, let the square No. 3, -seen through a flint glass prism _h_, in like manner be moved downwards -three compartments, when it will exhibit the coloured borders by about -a third wider than No. 2. - -295. - -Again, let us suppose that the square No. 4, has, like No. 2, been -moved downwards three compartments by a prism of crown-glass, and that -then by an oppositely placed prism _h_, of flint-glass, it has been -again raised to its former situation, where it now stands. - -296. - -Here, it is true, the refraction is done away with by the opposition of -the two; but as the prism _h_, in displacing the square by refraction -through three compartments, produces coloured borders wider by a -third than those produced by the prism _g_, so, notwithstanding the -refraction is neutralised, there must be an excess of coloured border -remaining. (The position of this colour, as usual, depends on the -direction of the apparent motion (204) communicated to the square by -the prism _h_, and, consequently, it is the reverse of the appearance -in the two squares 2 and 3, which have been moved in an opposite -direction.) This excess of colour we have called Hyperchromatism, and -from this the achromatic state may be immediately arrived at. - -297. - -For assuming that it was the square No. 5 which was removed three -compartments from its first supposed place, like No. 2, by a prism of -crown-glass _g_, it would only be necessary to reduce the angle of a -prism of flint-glass _h_, and to connect it, reversed, to the prism -_g_, in order to raise the square No. 5 two degrees or compartments; -by which means the Hyperchromatism of the first case would cease, the -figure would not quite return to its first position, and yet be already -colourless. The prolonged lines of the united prisms, under No. 5, show -that a single complete prism remains: again, we have only to suppose -the lines curved, and an object-glass presents itself. Such is the -principle of the achromatic telescopes. - -298. - -For these experiments, a small prism composed of three different -prisms, as prepared in England, is extremely well adapted. It is to be -hoped our own opticians will in future enable every friend of science -to provide himself with this necessary instrument. - - - - -XX. - - -ADVANTAGES OF SUBJECTIVE EXPERIMENTS.--TRANSITION TO THE OBJECTIVE. - - -299. - -We have presented the appearances of colour as exhibited by refraction, -first, by means of subjective experiments; and we have so far arrived -at a definite result, that we have been enabled to deduce the phenomena -in question from the doctrine of semi-transparent mediums and double -images. - -300. - -In statements which have reference to nature, everything depends on -ocular inspection, and these experiments are the more satisfactory as -they may be easily and conveniently made. Every amateur can procure -his apparatus without much trouble or cost, and if he is a tolerable -adept in pasteboard contrivances, he may even prepare a great part of -his machinery himself. A few plain surfaces, on which black, white, -grey, and coloured objects may be exhibited alternately on a light and -dark ground, are all that is necessary. The spectator fixes them before -him, examines the appearances at the edge of the figures conveniently, -and as long as he pleases; he retires to a greater distance, again -approaches, and accurately observes the progressive states of the -phenomena. - -301. - -Besides this, the appearances may be observed with sufficient exactness -through small prisms, which need not be of the purest glass. The other -desirable requisites in these glass instruments will, however, be -pointed out in the section which treats of the apparatus.[1] - -302. - -A great advantage in these experiments, again, is, that they can be -made at any hour of the day in any room, whatever aspect it may have. -We have no need to wait for sunshine, which in general is not very -propitious to northern observers. - - -[1] This description of the apparatus was never given. - - - - -OBJECTIVE EXPERIMENTS. - - -303. - -The objective experiments, on the contrary, necessarily require the -sun-light which, even when it is to be had, may not always have the -most desirable relation with the apparatus placed opposite to it. -Sometimes the sun is too high, sometimes too low, and withal only a -short time in the meridian of the best situated room. It changes its -direction during the observation, the observer is forced to alter -his own position and that of his apparatus, in consequence of which -the experiments in many cases become uncertain. If the sun shines -through the prism it exhibits all inequalities, lines, and bubbles -in the glass, and thus the appearance is rendered confused, dim, and -discoloured. - -304. - -Yet both kinds of experiments must be investigated with equal accuracy. -They appear to be opposed to each other, and yet are always parallel. -What one order of experiments exhibits the other exhibits likewise, -and yet each has its peculiar capabilities, by means of which certain -effects of nature are made known to us in more than one way. - -305. - -In the next place there are important phenomena which may be exhibited -by the union of subjective and objective experiments. The latter -experiments again have this advantage, that we can in most cases -represent them by diagrams, and present to view the component relations -of the phenomena. In proceeding, therefore, to describe the objective -experiments, we shall so arrange them that they may always correspond -with the analogous subjective examples; for this reason, too, we annex -to the number of each paragraph the number of the former corresponding -one. But we set out by observing generally that the reader must consult -the plates, that the scientific investigator must be familiar with the -apparatus in order that the twin-phenomena in one mode or the other may -be placed before them. - - - - -XXI. - - -REFRACTION WITHOUT THE APPEARANCE OF COLOUR. - - -306 (195, 196). - -That refraction may exhibit its effects without producing an appearance -of colour, is not to be demonstrated so perfectly in objective as -in subjective experiments. We have, it is true, unlimited spaces -which we can look at through the prism, and thus convince ourselves -that no colour appears where there is no boundary; but we have no -unlimited source of light which we can cause to act through the prism. -Our light comes to us from circumscribed bodies; and the sun, which -chiefly produces our prismatic appearances, is itself only a small, -circumscribed, luminous object. - -307. - -We may, however, consider every larger opening through which the sun -shines, every larger medium through which the sun-light is transmitted -and made to deviate from its course, as so far unlimited that we can -confine our attention to the centre of the surface without considering -its boundaries. - -308 (197). - -If we place a large water-prism in the sun, a large bright space is -refracted upwards by it on the plane intended to receive the image, and -the middle of this illumined space will be colourless. The same effect -may be produced if we make the experiment with glass prisms having -angles of few degrees: the appearance may be produced even through -glass prisms, whose refracting angle is sixty degrees, provided we -place the recipient surface near enough. - - - - -XXII. - - -CONDITIONS OF THE APPEARANCE OF COLOUR. - - -309 (198). - -Although, then, the illumined space before mentioned appears indeed -refracted and moved from its place, but not coloured, yet on the -horizontal edges of this space we observe a coloured appearance. -That here again the colour is solely owing to the displacement of a -circumscribed object may require to be more fully proved. - -The luminous body which here acts is circumscribed: the sun, while it -shines and diffuses light, is still an insulated object. However small -the opening in the lid of a camera obscura be made, still the whole -image of the sun will penetrate it. The light which streams from all -parts of the sun's disk, will cross itself in the smallest opening, and -form the angle which corresponds with the sun's apparent diameter. On -the outside we have a cone narrowing to the orifice; within, this apex -spreads again, producing on an opposite surface a round image, which -still increases in size in proportion to the distance of the recipient -surface from the apex. This image, together with all other objects -of the external landscape, appears reversed on the white surface in -question in a dark room. - -310. - -How little therefore we have here to do with single sun-rays, bundles -or fasces of rays, cylinders of rays, pencils, or whatever else of the -kind may be imagined, is strikingly evident. For the convenience of -certain diagrams the sun-light may be assumed to arrive in parallel -lines, but it is known that this is only a fiction; a fiction quite -allowable where the difference between the assumption and the true -appearance is unimportant; but we should take care not to suffer such a -postulate to be equivalent to a fact, and proceed to further operations -on such a fictitious basis. - -311. - -Let the aperture in the window-shutter be now enlarged at pleasure, let -it be made round or square, nay, let the whole shutter be opened, and -let the sun shine into the room through the whole window; the space -which the sun illumines will always be larger according to the angle -which its diameter makes; and thus even the whole space illumined by -the sun through the largest window is only the image of the sun _plus_ -the size of the opening. We shall hereafter have occasion to return to -this. - -312 (199). - -If we transmit the image of the sun through convex glasses we contract -it towards the focus. In this case, according to the laws before -explained, a yellow border and a yellow-red edge must appear when the -spectrum is thrown on white paper. But as this experiment is dazzling -and inconvenient, it may be made more agreeably with the image of the -full moon. On contracting this orb by means of a convex glass, the -coloured edge appears in the greatest splendour; for the moon transmits -a mitigated light in the first instance, and can thus the more readily -produce colour which to a certain extent accompanies the subduing of -light: at the same time the eye of the observer is only gently and -agreeably excited. - -313 (200). - -If we transmit a luminous image through concave glasses, it is -dilated. Here the image appears edged with blue. - -314. - -The two opposite appearances may be produced by a convex glass, -simultaneously or in succession; simultaneously by fastening an opaque -disk in the centre of the convex glass, and then transmitting the sun's -image. In this case the luminous image and the black disk within it are -both contracted, and, consequently, the opposite colours must appear. -Again, we can present this contrast in succession by first contracting -the luminous image towards the focus, and then suffering it to expand -again beyond the focus, when it will immediately exhibit a blue edge. - -315 (201). - -Here too what was observed in the subjective experiments is again to be -remarked, namely, that blue and yellow appear in and upon the white, -and that both assume a reddish appearance in proportion as they mingle -with the black. - -316 (202, 203). - -These elementary phenomena occur in all subsequent objective -experiments, as they constituted the groundwork of the subjective -ones. The process too which takes place is the same; a light boundary -is carried over a dark surface, a dark surface is carried over a light -boundary. The edges must advance, and as it were push over each other -in these experiments as in the former ones. - -317 (204). - -If we admit the sun's image through a larger or smaller opening into -the dark room, if we transmit it through a prism so placed that its -refracting angle, as usual, is underneath; the luminous image, instead -of proceeding in a straight line to the floor, is refracted upwards on -a vertical surface placed to receive it. This is the moment to take -notice of the opposite modes in which the subjective and objective -refractions of the object appear. - -318. - -If we _look_ through a prism, held with its refracting angle -underneath, at an object above us, the object is moved downwards; -whereas a luminous image refracted through the same prism is moved -upwards. This, which we here merely mention as a matter of fact for -the sake of brevity, is easily explained by the laws of refraction and -elevation. - -319. - -The luminous object being moved from its place in this manner, the -coloured borders appear in the order, and according to the laws before -explained. The violet border is always foremost, and thus in objective -cases proceeds upwards, in subjective cases downwards. - -320 (205). - -The observer may convince himself in like manner of the mode in which -the appearance of colour takes place in the diagonal direction when the -displacement is effected by means of two prisms, as has been plainly -enough shown in the subjective example; for this experiment, however, -prisms should be procured of few degrees, say about fifteen. - -321(206, 207). - -That the colouring of the image takes place here too, according to the -direction in which it moves, will be apparent if we make a _square_ -opening of moderate size in a shutter, and cause the luminous image -to pass through a water-prism; the spectrum being moved first in the -horizontal and vertical directions, then diagonally, the coloured edges -will change their position accordingly. - -322(208). - -Whence it is again evident that to produce colour the boundaries must -be carried over each other, not merely move side by side. - - - - -XXIII. - -CONDITIONS OF THE INCREASE OF COLOUR. - - -323 (209). - -Here too an increased displacement of the object produces a greater -appearance of colour. - -324 (210). - -This increased displacement occurs, - -1. By a more oblique direction of the impinging luminous object through -mediums with parallel surfaces. - -2. By changing the parallel form for one more or less acute angled. - -3. By increased proportion of the medium, whether parallel or acute -angled; partly because the object is by this means more powerfully -displaced, partly because an effect depending on the mere mass -co-operates. - -4. By the distance of the recipient surface from the refracting medium -so that the coloured spectrum emerging from the prism may be said to -have a longer way to travel. - -5. When a chemical property produces its effects under all these -circumstances: this we have already entered into more fully under the -head of achromatism and hyperchromatism. - -325 (211). - -The objective experiments have this advantage that the progressive -states of the phenomenon may be arrested and clearly represented by -diagrams, which is not the case with the subjective experiments. - -326. - -We can observe the luminous image after it has emerged from the prism, -step by step, and mark its increasing colour by receiving it on a -plane at different distances, thus exhibiting before our eyes various -sections of this cone, with an elliptical base: again, the phenomenon -may at once be rendered beautifully visible throughout its whole course -in the following manner:--Let a cloud of fine white dust be excited -along the line in which the image passes through the dark space; the -cloud is best produced by fine, perfectly dry, hair-powder. The more or -less coloured appearance will now be painted on the white atoms, and -presented in its whole length and breadth to the eye of the spectator. - -327. - -By this means we have prepared some diagrams, which will be found among -the plates. In these the appearance is exhibited from its first origin, -and by these the spectator can clearly comprehend why the luminous -image is so much more powerfully coloured through prisms than through -parallel mediums. - -328 (212). - -At the two opposite outlines of the image an opposite appearance -presents itself, beginning from an acute angle;[1] the appearance -spreads as it proceeds further in space, according to this angle. On -one side, in the direction in which the luminous image is moved, a -violet border advances on the dark, a narrower blue edge remains next -the outline of the image. On the opposite side a yellow border advances -into the light of the image itself, and a yellow-red edge remains at -the outline. - -329 (213). - -Here, therefore, the movement of the dark against the light, of the -light against the dark, may be clearly observed. - - -[Illustration] - -330 (214). - -The centre of a large object remains long uncoloured, especially with -mediums of less density and smaller angles; but at last the opposite -borders and edges touch each other, upon which a green appears in the -centre of the luminous image. - -331 (215). - -Objective experiments have been usually made with the sun's image: an -objective experiment with a dark object has hitherto scarcely been -thought of. We have, however, prepared a convenient contrivance for -this also. Let the large water-prism before alluded to be placed in -the sun, and let a round pasteboard disk be fastened either inside or -outside. The coloured appearance will again take place at the outline, -beginning according to the usual law; the edges will appear, they will -spread in the same proportion, and when they meet, red will appear in -the centre[2]. An intercepting square may be added near the round disk, -and placed in any direction _ad libitum_, and the spectator can again -convince himself of what has been before so often described. - -332 (216). - -If we take away these dark objects from the prism, in which case, -however, the glass is to be carefully cleaned, and hold a rod or a -large pencil before the centre of the horizontal prism, we shall -then accomplish the complete immixture of the violet border and the -yellow-red edge, and see only the three colours, the external blue, and -yellow, and the central red. - -333. - -If again we cut a long horizontal opening in the middle of a piece of -pasteboard, fastened on the prism, and then cause the sun-light to pass -through it, we shall accomplish the complete union of the yellow border -with the blue edge upon the light, and only see yellow-red, green and -violet. The details of this are further entered into in the description -of the plates. - -334 (217). - -The prismatic appearance is thus by no means complete and final when -the luminous image emerges from the prism. It is then only that -we perceive its elements in contrast; for as it increases these -contrasting elements unite, and are at last intimately joined. The -section of this phenomenon arrested on a plane surface is different -at every degree of distance from the prism; so that the notion of an -immutable series of colours, or of a pervading similar proportion -between them, cannot be a question for a moment. - - -[1] Plate 4. fig. 1. - -[2] Plate 4. fig. 2. - - - - -XXIV. - - -EXPLANATION OF THE FOREGOING PHENOMENA. - - -335 (218). - -As we have already entered into this analysis circumstantially while -treating of the subjective experiments, as all that was of force there -is equally valid here, it will require no long details in addition to -show that the phenomena, which are entirely parallel in the two cases, -may also be traced precisely to the same sources. - -336 (219). - -That in objective experiments also we have to do with circumscribed -images, has been already demonstrated at large. The sun may shine -through the smallest opening, yet the image of the whole disk -penetrates beyond. The largest prism may be placed in the open -sun-light, yet it is still the sun's image that is bounded by the -edges of the refracting surfaces, and produces the accessory images -of this boundary. We may fasten pasteboard, with many openings cut in -it, before the water-prism, yet we still merely see multiplied images -which, after having been moved from their place by refraction, exhibit -coloured edges and borders, and in these mere accessory images. - -337 (235). - -In subjective experiments we have seen that objects strongly relieved -from each other produce a very lively appearance of colour, and this -will be the case in objective experiments in a much more vivid and -splendid degree. The sun's image is the most powerful brightness we -know; hence its accessory image will be energetic in proportion, and -notwithstanding its really secondary dimmed and darkened character, -must be still very brilliant. The colours thrown by the sun-light -through the prism on any object, carry a powerful light with them, for -they have the highest and most intense source of light, as it were, for -their ground. - -338. - -That we are warranted in calling even these accessory images -semi-transparent, thus deducing the appearances from the doctrine -of the semi-transparent mediums, will be clear to every one who has -followed us thus far, but particularly to those who have supplied -themselves with the necessary apparatus, so as to be enabled at all -times to witness the precision and vivacity with which semi-transparent -mediums act. - - - - -XXV. - - -DECREASE OF THE APPEARANCE OF COLOUR. - - -339 (243). - -If we could afford to be concise in the description of the decreasing -coloured appearance in subjective cases, we may here be permitted -to proceed with still greater brevity while we refer to the former -distinct statement. One circumstance, only on account of its great -importance, may be here recommended to the reader's especial attention -as a leading point of our whole thesis. - -340 (244, 247). - -The decline of the prismatic appearance must be preceded by its -separation, by its resolution into its elements. At a due distance from -the prism, the image of the sun being entirely coloured, the blue and -yellow at length mix completely, and we see only yellow-red, green, and -blue-red. If we bring the recipient surface nearer to the refracting -medium, yellow and blue appear again, and we see the five colours with -their gradations. At a still shorter distance the yellow and blue -separate from each other entirely, the green vanishes, and the image -itself appears, colourless, between the coloured edges and borders. The -nearer we bring the recipient surface to the prism, the narrower the -edges and borders become, till at last, when in contact with the prism, -they are reduced to nothing. - - - - -XXVI. - - -GREY OBJECTS. - - -341 (218). - -We have exhibited grey objects as very important to our inquiry in the -subjective experiments. They show, by the faintness of the accessory -images, that these same images are in all cases derived from the -principal object. If we wish here, too, to carry on the objective -experiments parallel with the others, we may conveniently do this by -placing a more or less dull ground glass before the opening through -which the sun's image enters. By this means a subdued image would be -produced, which on being refracted would exhibit much duller colours on -the recipient plane than those immediately derived from the sun's disk; -and thus, even from the intense sun-image, only a faint accessory image -would appear, proportioned to the mitigation of the light by the glass. -This experiment, it is true, will only again and again confirm what is -already sufficiently familiar to us. - - - - -XXVII. - - -COLOURED OBJECTS. - - -342 (260). - -There are various modes of producing coloured images in objective -experiments. In the first place, we can fix coloured glass before the -opening, by which means a coloured image is at once produced; secondly, -we can fill the water-prism with coloured fluids; thirdly, we can cause -the colours, already produced in their full vivacity by the prism, to -pass through proportionate small openings in a tin plate, and thus -prepare small circumscribed colours for a second operation. This last -mode is the most difficult; for owing to the continual progress of the -sun, the image cannot be arrested in any direction at will. The second -method has also its inconveniences, since not all coloured liquids can -be prepared perfectly bright and clear. On these accounts the first is -to be preferred, and deserves the more to be adopted because natural -philosophers have hitherto chosen to consider the colours produced -from the sun-light through the prism, those produced through liquids -and glasses, and those which are already fixed on paper or cloth, as -exhibiting effects equally to be depended on, and equally available in -demonstration. - -343. - -As it is thus merely necessary that the image should be coloured, so -the large water-prism before alluded to affords us the best means of -effecting this. A pasteboard screen may be contrived to slide before -the large surfaces of the prism, through which, in the first instance, -the light passes uncoloured. In this screen openings of various forms -may be cut, in order to produce different images, and consequently -different accessory images. This being done, we need only fix coloured -glasses before the openings, in order to observe what effect refraction -produces on coloured images in an objective sense. - -344. - -A series of glasses may be prepared in a mode similar to that before -described (284); these should be accurately contrived to slide in the -grooves of the large water-prism. Let the sun then shine through them, -and the coloured images refracted upwards will appear bordered and -edged, and will vary accordingly: for these borders and edges will be -exhibited quite distinctly on some images, and on others will be mixed -with the specific colour of the glass, which they will either enhance -or neutralize. Every observer will be enabled to convince himself -here again that we have only to do with the same simple phenomenon so -circumstantially described subjectively and objectively. - - - - -XXVIII. - - -ACHROMATISM AND HYPERCHROMATISM. - - -345 (285, 290). - -It is possible to make the hyperchromatic and achromatic experiments -objectively as well as subjectively. After what has been already -stated, a short description of the method will suffice, especially as -we take it for granted that the compound prism before mentioned is in -the hands of the observer. - -346. - -Let the sun's image pass through an acute-angled prism of few degrees, -prepared from crown-glass, so that the spectrum be refracted upwards on -an opposite surface; the edges will appear coloured, according to the -constant law, namely, the violet and blue above and outside, the yellow -and yellow-red below and within the image. As the refracting angle of -this prism is undermost, let another proportionate prism of flint-glass -be placed against it, with its refracting angle uppermost. The sun's -image will by this means be again moved to its place, where, owing to -the excess of the colouring power of the prism of flint-glass, it will -still appear a little coloured, and, in consequence of the direction -in which it has been moved, the blue and violet will now appear -underneath and outside, the yellow and yellow-red above and inside. - -347. - -If the whole image be now moved a little upwards by a proportionate -prism of crown-glass, the hyperchromatism will disappear, the sun's -image will be moved from its place, and yet will appear colourless. - -348. - -With an achromatic object-glass composed of three glasses, this -experiment may be made step by step, if we do not mind taking out the -glasses from their setting. The two convex glasses of crown-glass in -contracting the sun's image towards the focus, the concave glass of -flint-glass in dilating the image beyond it, exhibit at the edges the -usual colours. A convex glass united with a concave one exhibits the -colours according to the law of the latter. If all three glasses are -placed together, whether we contract the sun's image towards the focus, -or suffer it to dilate beyond the focus, coloured edges never appear, -and the achromatic effect intended by the optician is, in this case, -again attained. - -349. - -But as the crown-glass has always a greenish tint, and as a tendency -to this hue may be more decided in large and strong object-glasses, -and under certain circumstances produce the compensatory red, -(which, however, in repeated experiments with several instruments of -this kind did not occur to us,) philosophers have resorted to the -most extraordinary modes of explaining such a result; and having -been compelled, in support of their system, theoretically to prove -the impossibility of achromatic telescopes, have felt a kind of -satisfaction in having some apparent ground for denying so great an -improvement. Of this, however, we can only treat circumstantially in -our historical account of these discoveries. - - - - -XXIX. - - -COMBINATION OF SUBJECTIVE AND OBJECTIVE EXPERIMENTS. - - -350. - -Having shown above (318) that refraction, considered objectively and -subjectively, must act in opposite directions, it will follow that if -we combine the experiments, the effects will reciprocally destroy each -other. - -351. - -Let the sun's image be thrown upwards on a vertical plane, through -a horizontally-placed prism. If the prism is long enough to admit of -the spectator also looking through it, he will see the image elevated -by the objective refraction again depressed, and in the same place in -which it appeared without refraction. - -352. - -Here a remarkable case presents itself, but at the same time a natural -result of a general law. For since, as often before stated, the -objective sun's image thrown on the vertical plane is not an ultimate -or unchangeable state of the phenomenon, so in the above operation the -image is not only depressed when seen through the prism, but its edges -and borders are entirely robbed of their hues, and the spectrum is -reduced to a colourless circular form. - -353. - -By employing two perfectly similar prisms placed next each other, for -this experiment, we can transmit the sun's image through one, and look -through the other. - -354. - -If the spectator advances nearer with the prism through which he looks, -the image is again elevated, and by degrees becomes coloured according -to the law of the first prism. If he again retires till he has brought -the image to the neutralized point, and then retires still farther -away, the image, which had become round and colourless, moves still -more downwards and becomes coloured in the opposite sense, so that -if we look through the prism and upon the refracted spectrum at the -same time, we see the same image coloured according to subjective and -objective laws. - -355. - -The modes in which this experiment may be varied are obvious. If the -refracting angle of the prism, through which the sun's image was -objectively elevated, is greater than that of the prism through which -the observer looks, he must retire to a much greater distance, in order -to depress the coloured image so low on the vertical plane that it -shall appear colourless, and _vice versâ_. - -356. - -It will be easily seen that we may exhibit achromatic and -hyperchromatic effects in a similar manner, and we leave it to the -amateur to follow out such researches more fully. Other complicated -experiments in which prisms and lenses are employed together, others -again, in which objective and subjective experiments are variously -intermixed, we reserve for a future occasion, when it will be our -object to trace such effects to the simple phenomena with which we are -now sufficiently familiar. - - - - -XXX. - - -TRANSITION. - - -357. - -In looking back on the description and analysis of dioptrical colours, -we do not repent either that we have treated them so circumstantially, -or that we have taken them into consideration before the other physical -colours, out of the order we ourselves laid down. Yet, before we quit -this branch of our inquiry, it may be as well to state the reasons that -have weighed with us. - -358. - -If some apology is necessary for having treated the theory of the -dioptrical colours, particularly those of the second class, so -diffusely, we should observe, that the exposition of any branch of -knowledge is to be considered partly with reference to the intrinsic -importance of the subject, and partly with reference to the particular -necessities of the time in which the inquiry is undertaken. In our -own case we were forced to keep both these considerations constantly -in view. In the first place we had to state a mass of experiments with -our consequent convictions; next, it was our especial aim to exhibit -certain phenomena (known, it is true, but misunderstood, and above -all, exhibited in false connection,) in that natural and progressive -development which is strictly and truly conformable to observation; in -order that hereafter, in our polemical or historical investigations, -we might be enabled to bring a complete preparatory analysis to bear -on, and elucidate, our general view. The details we have entered into -were on this account unavoidable; they may be considered as a reluctant -consequence of the occasion. Hereafter, when philosophers will look -upon a simple principle as simple, a combined effect as combined; when -they will acknowledge the first elementary, and the second complicated -states, for what they are; then, indeed, all this statement may be -abridged to a narrower form; a labour which, should we ourselves -not be able to accomplish it, we bequeath to the active interest of -contemporaries and posterity. - -359. - -With respect to the order of the chapters, it should be remembered -that natural phenomena, which are even allied to each other, are -not connected in any particular sequence or constant series; their -efficient causes act in a narrow circle, so that it is in some sort -indifferent what phenomenon is first or last considered; the main point -is, that all should be as far as possible present to us, in order that -we may embrace them at last from one point of view, partly according to -their nature, partly according to generally received methods. - -360. - -Yet, in the present particular instance, it may be asserted that the -dioptrical colours are justly placed at the head of the physical -colours; not only on account of their striking splendour and their -importance in other respects, but because, in tracing these to their -source, much was necessarily entered into which will assist our -subsequent enquiries. - -361. - -For, hitherto, light has been considered as a kind of abstract -principle, existing and acting independently; to a certain extent -self-modified, and on the slightest cause, producing colours out of -itself. To divert the votaries of physical science from this mode -of viewing the subject; to make them attentive to the fact, that in -prismatic and other appearances we have not to do with light as an -uncircumscribed and modifying principle, but as circumscribed and -modified; that we have to do with a luminous image; with images or -circumscribed objects generally, whether light or dark: this was the -purpose we had in view, and such is the problem to be solved. - -362. - -All that takes place in dioptrical cases,--especially those of the -second class which are connected with the phenomena of refraction,--is -now sufficiently familiar to us, and will serve as an introduction to -what follows. - -363. - -Catoptrical appearances remind us of the physiological phenomena, but -as we ascribe a more objective character to the former, we thought -ourselves justified in classing them with the physical examples. It is -of importance, however, to remember that here again it is not light, in -an abstract sense, but a luminous image that we have to consider. - -364. - -In proceeding onwards to the paroptrical class, the reader, if duly -acquainted with the foregoing facts, will be pleased to find himself -once more in the region of circumscribed forms. The shadows of bodies, -especially, as secondary images, so exactly accompanying the object, -will serve greatly to elucidate analogous appearances. - -365. - -We will not, however, anticipate these statements, but proceed as -heretofore in what we consider the regular course. - - - - -XXXI. - - -CATOPTRICAL COLOURS. - - -366. - -Catoptrical colours are such as appear in consequence of a mirror-like -reflection. We assume, in the first place, that the light itself -as well as the surface from which it is reflected, is perfectly -colourless. In this sense the appearances in question come under the -head of physical colours. They arise in consequence of reflection, as -we found the dioptrical colours of the second class appear by means of -refraction. Without further general definitions, we turn our attention -at once to particular cases, and to the conditions which are essential -to the exhibition of these phenomena. - -367. - -If we unroll a coil of bright steel-wire, and after suffering it to -spring confusedly together again, place it at a window in the light, -we shall see the prominent parts of the circles and convolutions -illumined, but neither resplendent nor iridescent. But if the sun -shines on the wire, this light will be condensed into a point, and we -perceive a small resplendent image of the sun, which, when seen near, -exhibits no colour. On retiring a little, however, and fixing the eyes -on this refulgent appearance, we discern several small mirrored suns, -coloured in the most varied manner; and although the impression is that -green and red predominate, yet, on a more accurate inspection, we find -that the other colours are also present. - -368. - -If we take an eye-glass, and examine the appearance through it, we -find the colours have vanished, as well as the radiating splendour in -which they were seen, and we perceive only the small luminous points, -the repeated images of the sun. We thus find that the impression is -subjective in its nature, and that the appearance is allied to those -which we have adverted to under the name of radiating halos (100). - -369. - -We can, however, exhibit this phenomenon objectively. Let a piece -of white paper be fastened beneath a small aperture in the lid of a -camera-obscura, and when the sun shines through this aperture, let -the confusedly-rolled steel-wire be held in the light, so that it be -opposite to the paper. The sun-light will impinge on and in the circles -of the wire, and will not, as in the concentrating lens of the eye, -display itself in a point; but, as the paper can receive the reflection -of the light in every part of its surface will be seen in hair-like -lines, which are also iridescent. - -370. - -This experiment is purely catoptrical; for as we cannot imagine that -the light penetrates the surface of the steel, and thus undergoes a -change, we are soon convinced that we have here a mere reflection -which, in its subjective character, is connected with the theory of -faintly acting lights, and the after-image of dazzling lights, and as -far as it can be considered objective, announces even in the minutest -appearances, a real effect, independent of the action and reaction of -the eye. - -371. - -We have seen that to produce these effects not merely light but a -powerful light is necessary; that this powerful light again is not an -abstract and general quality, but a circumscribed light, a luminous -image. We can convince ourselves still further of this by analogous -cases. - -372. - -A polished surface of silver placed in the sun reflects a dazzling -light, but in this case no colour is seen. If, however, we slightly -scratch the surface, an iridescent appearance, in which green and red -are conspicuous, will be exhibited at a certain angle. In chased and -carved metals the effect is striking: yet it may be remarked throughout -that, in order to its appearance, some form, some alternation of light -and dark must co-operate with the reflection; thus a window-bar, -the stem of a tree, an accidentally or purposely interposed object -produces a perceptible effect. This appearance, too, may be exhibited -objectively in the camera-obscura. - -373. - -If we cause a polished plated surface to be so acted on by aqua fortis -that the copper within is touched, and the surface itself thus rendered -rough, and if the sun's image be then reflected from it, the splendour -will be reverberated from every minutest prominence, and the surface -will appear iridescent. So, if we hold a sheet of black unglazed paper -in the sun, and look at it attentively, it will be seen to glisten in -its minutest points with the most vivid colours. - -374. - -All these examples are referable to the same conditions. In the first -case the luminous image is reflected from a thin line; in the second -probably from sharp edges; in the third from very small points. In all -a very powerful and circumscribed light is requisite. For all these -appearances of colour again it is necessary that the eye should be at a -due distance from the reflecting points. - -375. - -If these observations are made with the microscope, the appearance -will be greatly increased in force and splendour, for we then see the -smallest portion of the surfaces, lit by the sun, glittering in these -colours of reflection, which, allied to the hues of refraction, now -attain their highest degree of brilliancy. In such cases we may observe -a vermiform iridescence on the surface of organic bodies, the further -description of which will be given hereafter. - -376. - -Lastly, the colours which are chiefly exhibited in reflection are red -and green, whence we may infer that the linear appearance especially -consists of a thin line of red, bounded by blue on one side and yellow -on the other. If these triple lines approach very near together, the -intermediate space must appear green; a phenomenon which will often -occur to us as we proceed. - -377. - -We frequently meet with these colours in nature. The colours of the -spider's web might be considered exactly of the same class with those -reflected from the steel wire, except that the non-translucent quality -of the former is not so certain as in the case of steel; on which -account some have been inclined to class the colours of the spider's -web with the phenomena of refraction. - -378. - -In mother-of-pearl we perceive infinitely fine organic fibres and -lamellæ in juxta-position, from which, as from the scratched silver -before alluded to, varied colours, but especially red and green, may -arise. - -379. - -The changing colours of the plumage of birds may also be mentioned -here, although in all organic instances a chemical principle -and an adaptation of the colour to the structure may be assumed; -considerations to which we shall return in treating of chemical colours. - -380. - -That the appearances of objective halos also approximate catoptrical -phenomena will be readily admitted, while we again do not deny that -refraction as well may here come into the account. For the present -we restrict ourselves to one or two observations; hereafter we may -be enabled to make a fuller application of general principles to -particular examples. - -381. - -We first call to mind the yellow and red circles produced on a white or -grey wall by a light placed near it (88). Light when reflected appears -subdued, and a subdued light excites the impression of yellow, and -subsequently of red. - -382. - -Let the wall be illumined by a candle placed quite close to it. The -farther the light is diffused the fainter it becomes; but it is still -the effect of the flame, the continuation of its action, the dilated -effect of its image. We might, therefore, very fairly call these -circles reiterated images, because they constitute the successive -boundaries of the action of the light, and yet at the same time only -present an extended image of the flame. - -383. - -If the sky is white and luminous round the sun owing to the atmosphere -being filled with light vapours; if mists or clouds pass before the -moon, the reflection of the disk mirrors itself in them; the halos we -then perceive are single or double, smaller or greater, sometimes very -large, often colourless, sometimes coloured. - -384. - -I witnessed a very beautiful halo round the moon the 15th of November, -1799, when the barometer stood high; the sky was cloudy and vapoury. -The halo was completely coloured, and the circles were concentric round -the light as in subjective halos. That this halo was objective I was -presently convinced by covering the moon's disk, when the same circles -were nevertheless perfectly visible. - -385. - -The different extent of the halos appears to have a relation with the -proximity or distance of the vapour from the eye of the observer. - -386. - -As window-panes lightly breathed upon increase the brilliancy of -subjective halos, and in some degree give them an objective character, -so, perhaps, with a simple contrivance in winter, during a quickly -freezing temperature, a more exact definition of this might be arrived -at. - -387. - -How much reason we have in considering these circles to insist on the -_image_ and its effects, is apparent in the phenomenon of the so-called -double suns. Similar double images always occur in certain points -of halos and circles, and only present in a circumscribed form what -takes place in a more general way in the whole circle. All this will -be more conveniently treated in connexion with the appearance of the -rainbow.--Note Q. - -388. - -In conclusion it is only necessary to point out the affinity between -the catoptrical and paroptical colours. - -We call those paroptical colours which appear when the light passes -by the edge of an opaque colourless body. How nearly these are allied -to the dioptrical colours of the second class will be easily seen by -those who are convinced with us that the colours of refraction [Pg 163] -take place only at the edges of objects. The affinity again between the -catoptrical and paroptical colours will be evident in the following -chapter. - - - - -XXXII. - - -PAROPTICAL COLOURS. - - -389. - -The paroptical colours have been hitherto called peri-optical, because -a peculiar effect of light was supposed to take place as it were round -the object, and was ascribed to a certain flexibility of the light to -and from the object. - -390. - -These colours again may be divided into subjective and objective, -because they appear partly without us, as it were, painted on surfaces, -and partly within us, immediately on the retina. In this chapter we -shall find it more to our purpose to take the objective cases first, -since the subjective are so closely connected with other appearances -already known to us, that it is hardly possible to separate them. - -391. - -The paroptical colours then are so called because the light must pass -by an outline or edge to produce them. They do not, however, always -appear in this case; to produce the effect very particular conditions -are necessary besides. - -392. - -It is also to be observed that in this instance again light does not -act as an abstract diffusion (361), the sun shines towards an edge. -The volume of light poured from the sun-image passes by the edge of -a substance, and occasions shadows. Within these shadows we shall -presently find colours appear. - -393. - -But, above all, we should make the experiments and observations that -bear upon our present inquiry in the fullest light. We, therefore, -place the observer in the open air before we conduct him to the limits -of a dark room. - -394. - -A person walking in sun-shine in a garden, or on any level path, may -observe that his shadow only appears sharply defined next the foot on -which he rests; farther from this point, especially round the head, it -melts away into the bright ground. For as the sun-light proceeds not -only from the middle of the sun, but also acts cross-wise from the two -extremes of every diameter, an objective parallax takes place which -produces a half-shadow on both sides of the object. - -395. - -If the person walking raises and spreads his hand, he distinctly sees -in the shadow of each finger the diverging separation of the two -half-shadows outwards, and the diminution of the principal shadow -inwards, both being effects of the cross action of the light. - -396. - -This experiment may be repeated and varied before a smooth wall, -with rods of different thicknesses, and again with balls; we shall -always find that the farther the object is removed from the surface of -the wall, the more the weak double shadow spreads, and the more the -forcible main shadow diminishes, till at last the main shadow appears -quite effaced, and even the double shadows become so faint, that they -almost disappear; at a still greater distance they are, in fact, -imperceptible. - -397. - -That this is caused by the cross-action of the light we may easily -convince ourselves; for the shadow of a pointed object plainly exhibits -two points. We must thus never lose sight of the fact that in this -case the whole sun-image acts, produces shadows, changes them to double -shadows, and finally obliterates them. - -398. - -Instead of solid bodies let us now take openings cut of various given -sizes next each other, and let the sun shine through them on a plane -surface at some little distance; we shall find that the bright image -produced by the sun on the surface, is larger than the opening; this -is because one edge of the sun shines towards the opposite edge of the -opening, while the other edge of the disk is excluded on that side. -Hence the bright image is more weakly lighted towards the edges. - -399. - -If we take square openings of any size we please, we shall find that -the bright image on a surface nine feet from the opening, is on every -side about an inch larger than the opening; thus nearly corresponding -with the angle of the apparent diameter of the sun. - -400. - -That the brightness should gradually diminish towards the edges of the -image is quite natural, for at last only a minimum of the light can -act cross-wise from the sun's circumference through the edge of the -aperture. - -401. - -Thus we here again see how much reason we have in actual observation to -guard against the assumption of parallel rays, bundles and fasces of -rays, and the like hypothetical notions. - -402. - -We might rather consider the splendour of the sun, or of any light, -as an infinite specular multiplication of the circumscribed luminous -image, whence it may be explained that all square openings through -which the sun shines, at certain distances, according as the apertures -are greater or smaller, must give a round image of light. - -403. - -The above experiments may be repeated through openings of various -shapes and sizes, and the same effect will always take place at -proportionate distances. In all these cases, however, we may still -observe that in a full light and while the sun merely shines past an -edge, no colour is apparent. - -404. - -We therefore proceed to experiments with a subdued light, which is -essential to the appearance of colour. Let a small opening be made in -the window-shutter of a dark room; let the crossing sun-light which -enters, be received on a surface of white paper, and we shall find that -the smaller the opening is, the dimmer the light image will be. This is -quite obvious, because the paper does not receive light from the whole -sun, but partially from single points of its disk. - -405. - -If we look attentively at this dim image of the sun, we find it still -dimmer towards the outlines where a yellow border is perceptible. The -colour is still more apparent if a vapour or a transparent cloud passes -before the sun, thus subduing and dimming its brightness. The halo on -the wall, the effect of the decreasing brightness of a light placed -near it, is here forced on our recollection. (88.) - -406. - -If we examine the image more accurately, we perceive that this yellow -border is not the only appearance of colour; we can see, besides, a -bluish circle, if not even a halo-like repetition of the coloured -border. If the room is quite dark, we discern that the sky next the -sun also has its effect: we see the blue sky, nay, even the whole -landscape, on the paper, and are thus again convinced that as far as -regards the sun, we have here only to do with a luminous image. - -407. - -If we take a somewhat larger square opening, so large that the image -of the sun shining through it does not immediately become round, we -may distinctly observe the half-shadows of every edge or side, the -junction of these in the corners, and their colours; just as in the -above-mentioned appearance with the round opening. - -408. - -We have now subdued a parallactic light by causing it to shine through -small apertures, but we have not taken from it its parallactic -character; so that it can produce double shadows of bodies, although -with diminished power. These double shadows which we have hitherto -been describing, follow each other in light and dark, coloured and -colourless circles, and produce repeated, nay, almost innumerable -halos. These effects have been often represented in drawings and -engravings. By placing needles, hairs, and other small bodies, in the -subdued light, the numerous halo-like double shadows may be increased; -thus observed, they have been ascribed to an alternating flexile action -of the light, and the same assumption has been employed to explain the -obliteration of the central shadow, and the appearance of a light in -the place of the dark. - -409. - -For ourselves, we maintain that these again are parallactic double -shadows, which appear edged with coloured borders and halos. - -410. - -After having seen and investigated the foregoing phenomena, we -can proceed to the experiments with knife-blades,[1] exhibiting -effects which may be referred to the contact and parallactic mutual -intersection of the half-shadows and halos already familiar to us. - -411. - -Lastly, the observer may follow out the experiments with hairs, -needles, and wires, in the half-light produced as before described by -the sun, as well as in that derived from the blue sky, and indicated on -the white paper. He will thus make himself still better acquainted with -the true nature of this phenomenon. - -412. - -But since in these experiments everything depends on our being -persuaded of the parallactic action of the light, we can make this more -evident by means of two sources of light, the two shadows from which -intersect each other, and may be altogether separated. By day this may -be contrived with two small openings in a window-shutter; by night, -with two candles. There are even accidental effects in interiors, on -opening and closing shutters, by means of which we can better observe -these appearances than with the most careful apparatus. But still, -all and each of these may be reduced to experiment by preparing a box -which the observer can look into from above, and gradually diminishing -the openings after having caused a double light to shine in. In this -case, as might be expected, the coloured shadow, considered under the -physiological colours, appears very easily. - -413. - -It is necessary to remember, generally, what has been before stated -with regard to the nature of double shadows, half-lights, and the like. -Experiments also should especially be made with different shades of -grey placed next each other, where every stripe will appear light by a -darker, and dark by a lighter stripe next it. If at night, with three -or more lights, we produce shadows which cross each other successively, -we can observe this phenomenon very distinctly, and we shall be -convinced that the physiological case before more fully treated, here -comes into the account (38). - -414. - -To what extent the appearances that accompany the paroptical colours, -may be derived from the doctrine of subdued lights, from half-shadows, -and from the physiological disposition of the retina, or whether we -shall be forced to take refuge in certain intrinsic qualities of light, -as has hitherto been done, time may teach. Suffice it here to have -pointed out the conditions under which the paroptical colours appear, -and we may hope that our allusion to their connexion with the facts -before adduced by us will not remain unnoticed by the observers of -nature. - -415. - -The affinity of the paroptical colours with the dioptrical of the -second class will also be readily seen and followed up by every -reflecting investigator. Here, as in those instances, we have to do -with edges or boundaries; here, as in those instances, with a light, -which appears at the outline. How natural, therefore, it is to conclude -that the paroptical effects may be heightened, strengthened, and -enriched by the dioptrical. Since, however, the luminous image actually -shines through the medium, we can here only have to do with objective -cases of refraction: it is these which are strictly allied to the -paroptical cases. The subjective cases of refraction, where we see -objects through the medium, are quite distinct from the paroptical. -We have already recommended them on account of their clearness and -simplicity. - -416. - -The connexion between the paroptical colours and the catoptrical may -be already inferred from what has been said: for as the catoptrical -colours only appear on scratches, points, steel-wire, and delicate -threads, so it is nearly the same case as if the light shone past an -edge. The light must always be reflected from an edge in order to -produce colour. Here again, as before pointed out, the partial action -of the luminous image and the subduing of the light are both to be -taken into the account. - -417. - -We add but few observations on the subjective paroptical colours, -because these may be classed partly with the physiological colours, -partly with the dioptrical of the second order. The greater part hardly -seem to belong here, but, when attentively considered, they still -diffuse a satisfactory light over the whole doctrine, and establish its -connexion. - -418. - -If we hold a ruler before the eyes so that the flame of a light just -appears above it, we see the ruler as it were indented and notched -at the place where the light appears. This seems deducible from the -expansive power of light acting on the retina (18). - -419. - -The same phenomenon on a large scale is exhibited at sun-rise; for when -the orb appears distinctly, but not too powerfully, so that we can -still look at it, it always makes a sharp indentation in the horizon. - -420. - -If, when the sky is grey, we approach a window, so that the dark cross -of the window-bars be relieved on the sky; if after fixing the eyes on -the horizontal bar we bend the head a little forward; on half closing -the eyes as we look up, we shall presently perceive a bright yellow-red -border under the bar, and a bright light-blue one above it. The duller -and more monotonous the grey of the sky, the more dusky the room, and, -consequently, the more previously unexcited the eye, the livelier the -appearance will be; but it may be seen by an attentive observer even in -bright daylight. - -421. - -If we move the head backwards while half closing the eyes, so that the -horizontal bar be seen below, the phenomenon will appear reversed. The -upper edge will appear yellow, the under edge blue. - -422. - -Such observations are best made in a dark room. If white paper is -spread before the opening where the solar microscope is commonly -fastened, the lower edge of the circle will appear blue, the upper -yellow, even while the eyes are quite open, or only by half-closing -them so far that a halo no longer appears round the white. If the head -is moved backwards the colours are reversed. - -423. - -These phenomena seem to prove that the humours of the eye are in fact -only really achromatic in the centre where vision takes place, but that -towards the circumference, and in unusual motions of the eyes, as in -looking horizontally when the head is bent backwards or forwards, a -chromatic tendency remains, especially when distinctly relieved objects -are thus looked at. Hence such phenomena may be considered as allied to -the dioptrical colours of the second class. - -424. - -Similar colours appear if we look on black and white objects, through a -pin-hole in a card. Instead of a white object we may take the minute -light aperture in the tin plate of a camera obscura, as prepared for -paroptical experiments. - -425. - -If we look through a tube, the farther end of which is contracted or -variously indented, the same colours appear. - -426. - -The following phenomena appear to me to be more nearly allied to the -paroptical appearances. If we hold up a needle near the eye, the point -appears double. A particularly remarkable effect again is produced if -we look towards a grey sky through the blades of knives prepared for -paroptical experiments. We seem to look through a gauze; a multitude of -threads appear to the eye; these are in fact only the reiterated images -of the sharp edges, each of which is successively modified by the next, -or perhaps modified in a parallactic sense by the oppositely acting -one, the whole mass being thus changed to a thread-like appearance. - -427. - -Lastly, it is to be remarked that if we look through the blades towards -a minute light in the window-shutter, coloured stripes and halos -appear on the retina as on the paper. - -428. - -The present chapter may be here terminated, the less reluctantly, -as a friend has undertaken to investigate this subject by further -experiments. In our recapitulation, in the description of the -plates and apparatus, we hope hereafter to give an account of his -observations.[2] - - -[1] See Newton's Optics, book iii. - -[2] The observations here alluded to never appeared. - - - - -XXXIII. - - -EPOPTICAL COLOURS. - - -429. - -We have hitherto had to do with colours which appear with vivacity, but -which immediately vanish again when certain conditions cease. We have -now to become acquainted with others, which it is true are still to be -considered as transient, but which, under certain circumstances, become -so fixed that, even after the conditions which first occasioned their -appearance cease, they still remain, and thus constitute the link -between the physical and the chemical colours. - -430. - -They appear from various causes on the surface of a colourless body, -originally, without communication, die or immersion (βαφή); and we now -proceed to trace them, from their faintest indication to their most -permanent state, through the different conditions of their appearance, -which for easier survey we here at once summarily state. - -431. - -First condition.--The contact of two smooth surfaces of hard -transparent bodies. - -First case: if masses or plates of glass, or if lenses are pressed -against each other. - -Second case: if a crack takes place in a solid mass of glass, chrystal, -or ice. - -Third case: if lamellæ of transparent stones become separated. - -Second condition.--If a surface of glass or a polished stone is -breathed upon. - -Third condition.--The combination of the two last; first, breathing on -the glass, then placing another plate of glass upon it, thus exciting -the colours by pressure; then removing the upper glass, upon which the -colours begin to fade and vanish with the breath. - -Fourth condition.--Bubbles of various liquids, soap, chocolate, beer, -wine, fine glass bubbles. - -Fifth condition.--Very fine pellicles and lamellæ, produced by the -decomposition of minerals and metals. The pellicles of lime, the -surface of stagnant water, especially if impregnated with iron, and -again pellicles of oil on water, especially of varnish on aqua fortis. - -Sixth condition.--If metals are heated; the operation of imparting -tints to steel and other metals. - -Seventh condition.--If the surface of glass is beginning to decompose. - -432. - -First condition, first case. If two convex glasses, or a convex and -plane glass, or, best of all, a convex and concave glass come in -contact, concentric coloured circles appear. The phenomenon exhibits -itself immediately on the slightest pressure, and may then be gradually -carried through various successive states. We will describe the -complete appearance at once, as we shall then be better enabled to -follow the different states through which it passes. - -433. - -The centre is colourless; where the glasses are, so to speak, united -in one by the strongest pressure, a dark grey point appears with a -silver white space round it: then follow, in decreasing distances, -various insulated rings, all consisting of three colours, which are -in immediate contact with each other. Each of these rings, of which -perhaps three or four might be counted, is yellow on the inner side, -blue on the outer, and red in the centre. Between two rings there -appears a silver white interval. The rings which are farthest from the -centre are always nearer together: they are composed of red and green -without a perceptible white space between them. - -434. - -We will now observe the appearances in their gradual formation, -beginning from the slightest pressure. - -435. - -On the slightest pressure the centre itself appears of a green colour. -Then follow as far as the concentric circles extend, red and green -rings. They are wide, accordingly, and no trace of a silver white -space is to be seen between them. The green is produced by the blue of -an imperfectly developed circle, mixing with the yellow of the first -circle. All the remaining circles are, in this slight contact, broad; -their yellow and blue edges mix together, thus producing a beautiful -green. The red, however, of each circle, remains pure and untouched; -hence the whole series is composed of these two colours. - -436. - -A somewhat stronger pressure separates the first circle by a slight -interval from the imperfectly developed one: it is thus detached, and -may be said to appear in a complete state. The centre is now a blue -point; for the yellow of the first circle is now separated from this -central point by a silver white space. From the centre of the blue a -red appears, which is thus, in all cases, bounded on the outside by -its blue edge. The second and third rings from the centre are quite -detached. Where deviations from this order present themselves, the -observer will be enabled to account for them, from what has been or -remains to be stated. - -437. - -On a stronger pressure the centre becomes yellow; this yellow is -surrounded by a red and blue edge: at last, the yellow also retires -from the centre; the innermost circle is formed and is bounded with -yellow. The whole centre itself now appears silver white, till at last, -on the strongest pressure, the dark point appears, and the phenomenon, -as described at first, is complete. - -438. - -The relative size of the concentric circles and their intervals depends -on the form of the glasses which are pressed together. - -439. - -We remarked above, that the coloured centre is, in fact, an undeveloped -circle. It is, however, often found, on the slightest pressure, that -several undeveloped circles exist there, as it were, in the germ; these -can be successively developed before the eye of the observer. - -440. - -The regularity of these rings is owing to the form of the convex -glasses, and the diameter of the coloured appearance depends on the -greater or lesser section of a circle on which a lens is polished. We -easily conclude from this, that by pressing plane glasses together, -irregular appearances only will be produced; the colours, in fact, -undulate like watered silks, and spread from the point of pressure in -all directions. Yet, the phenomenon as thus exhibited is much more -splendid than in the former instance, and cannot fail to strike every -spectator. If we make the experiment in this mode, we shall distinctly -see, as in the other case, that, on a slight pressure, the green and -red waves appear; on a stronger, stripes of blue, red, and yellow, -become detached. At first, the outer sides of these stripes touch; on -increased pressure they are separated by a silver white space. - -441. - -Before we proceed to a further description of this phenomenon, we may -point out the most convenient mode of exhibiting it. Place a large -convex glass on a table near the window; upon this glass lay a plate -of well-polished mirror-glass, about the size of a playing-card, and -the mere weight of the plate will press sufficiently to produce one -or other of the phenomena above described. So, also, by the different -weight of plates of glass, by other accidental circumstances, for -instance, by slipping the plate on the side of the convex glass where -the pressure cannot be so strong as in the centre, all the gradations -above described can be produced in succession. - -442. - -In order to observe the phenomenon it is necessary to look obliquely -on the surface where it appears. But, above all, it is to be remarked -that by stooping still more, and looking at the appearance under a more -acute angle, the circles not only grow larger but other circles are -developed from the centre, of which no trace is to be discovered when -we look perpendicularly, even through the strongest magnifiers. - -443. - -In order to exhibit the phenomenon in its greatest beauty, the utmost -attention should be paid to the cleanness of the glasses. If the -experiment is made with plate-glass adapted for mirrors, the glass -should be handled with gloves. The inner surfaces, which must come in -contact with the utmost nicety, may be most conveniently cleaned before -the experiment, and the outer surfaces should be kept clean while the -pressure is increased. - -444. - -From what has been said it will be seen that an exact contact of two -smooth surfaces is necessary. Polished glasses are best adapted for the -purpose. Plates of glass exhibit the most brilliant colours when they -fit closely together, and for this reason the phenomenon will increase -in beauty if exhibited under an air-pump, by exhausting the air. - -445. - -The appearance of the coloured rings may be produced in the greatest -perfection by placing a convex and concave glass together which have -been ground on similar segments of circles. I have never seen the -effect more brilliant than with the object-glass of an achromatic -telescope, in which the crown-glass and flint-glass were necessarily -in the closest contact. - -446. - -A remarkable appearance takes place when dissimilar surfaces are -pressed together; for example, a polished crystal and a plate of -glass. The appearance does not at all exhibit itself in large flowing -waves, as in the combination of glass with glass, but it is small and -angular, and, as it were, disjointed: thus it appears that the surface -of the polished crystal, which consists of infinitely small sections of -lamellæ, does not come so uninterruptedly in contact with the glass as -another glass-plate would. - -447. - -The appearance of colour vanishes on the strongest pressure, which so -intimately unites the two surfaces that they appear to make but one -substance. It is this which occasions the dark centre, because the -pressed lens no longer reflects any light from this point, for the -very same point, when seen against the light, is perfectly clear and -transparent. On relaxing the pressure, the colours, in like manner, -gradually diminish, and disappear entirely when the surfaces are -separated. - -448. - -These same appearances occur in two similar cases. If entirely -transparent masses become partially separated, the surfaces of their -parts being still sufficiently in contact, we see the same circles and -waves more or less. They may be produced in great beauty by plunging a -hot mass of glass in water; the different fissures and cracks enabling -us to observe the colours in various forms. Nature often exhibits the -same phenomena in split rock crystals. - -449. - -This appearance, again, frequently displays itself in the mineral world -in those kinds of stone which by nature have a tendency to exfoliate. -These original lamellæ are, it is true, so intimately united, that -stones of this kind appear altogether transparent and colourless, yet, -the internal layers become separated, from various accidental causes, -without altogether destroying the contact: thus the appearance, which -is now familiar to us by the foregoing description, often occurs in -nature, particularly in calcareous spars; the specularis, adularia, and -other minerals of similar structure. Hence it shows an ignorance of the -proximate causes of an appearance so often accidentally produced, to -consider it so important in mineralogy, and to attach especial value to -the specimens exhibiting it. - -450. - -We have yet to speak of the very remarkable inversion of this -appearance, as related by men of science. If, namely, instead of -looking at the colours by a reflected light, we examine them by a -transmitted light, the opposite colours are said to appear, and in -a mode corresponding with that which we have before described as -physiological; the colours evoking each other. Instead of blue, we -should thus see red-yellow; instead of red, green, &c., and _vice -versâ_. We reserve experiments in detail, the rather as we have -ourselves still some doubts on this point. - -451. - -If we were now called upon to give some general explanation of these -epoptical colours, as they appear under the first condition, and to -show their connexion with the previously detailed physical phenomena, -we might proceed to do so as follows:-- - -452. - -The glasses employed for the experiments are to be regarded as the -utmost possible practical approach to transparence. By the intimate -contact, however, occasioned by the pressure applied to them, their -surfaces, we are persuaded, immediately become in a very slight -degree dimmed. Within this semi-transparence the colours immediately -appear, and every circle comprehends the whole scale; for when the two -opposites, yellow and blue, are united by their red extremities, pure -red appears: the green, on the other hand, as in prismatic experiments, -when yellow and blue touch. - -453. - -We have already repeatedly found that where colour exists at all, the -whole scale is soon called into existence; a similar principle may be -said to lurk in the nature of every physical phenomenon; it already -follows, from the idea of polar opposition, from which an elementary -unity or completeness results. - -454. - -The fact that a colour exhibited by transmitted light is different -from that displayed by reflected light, reminds us of those dioptrical -colours of the first class which we found were produced precisely in -the same way through semi-opacity. That here, too, a diminution of -transparency exists there can scarcely be a doubt; for the adhesion -of the perfectly smooth plates of glass (an adhesion so strong that -they remain hanging to each other) produces a degree of union which -deprives each of the two surfaces, in some degree, of its smoothness -and transparence. The fullest proof may, however, be found in the -fact that in the centre, where the lens is most strongly pressed on -the other glass, and where a perfect union is accomplished, a complete -transparence takes place, in which we no longer perceive any colour. -All this may be hereafter confirmed in a recapitulation of the whole. - -455. - -Second condition.--If after breathing on a plate of glass, the breath -is merely wiped away with the finger, and if we then again immediately -breathe on the glass, we see very vivid colours gliding through each -other; these, as the moisture evaporates, change their place, and at -last vanish altogether. If this operation is repeated, the colours are -more vivid and beautiful, and remain longer than they did the first -time. - -456. - -Quickly as this appearance passes, and confused as it appears to be, I -have yet remarked the following effects:--At first all the principal -colours appear with their combinations; on breathing more strongly, the -appearance may be perceived in some order. In this succession it may be -remarked, that when the breath in evaporating becomes contracted from -all sides towards the centre, the blue colour vanishes last. - -457. - -The phenomenon appears most readily between the minute lines, which the -action of passing the fingers leaves on the clear surface; a somewhat -rough state of the surface of the glass is otherwise requisite. On -some glass the appearance may be produced by merely breathing; in -other cases the wiping with the fingers is necessary: I have even met -with polished mirror-glasses, one side of which immediately showed the -colours vividly; the other not. To judge from some remaining pieces, -the former was originally the front of the glass, the latter the side -which was covered with quicksilver. - -458. - -These experiments may be best made in cold weather, because the glass -may be more quickly and distinctly breathed upon, and the breath -evaporates more suddenly. In severe frost the phenomenon may be -observed on a large scale while travelling in a carriage; the glasses -being well cleaned, and all closed. The breath of the persons within is -very gently diffused over the glass, and immediately produces the most -vivid play of colours. How far they may present a regular succession I -have not been able to remark; but they appear particularly vivid when -they have a dark object as a background. This alternation of colours -does not, however, last long; for as soon as the breath gathers in -drops, or freezes to points of ice, the appearance is at once at an end. - -459. - -Third condition.--The two foregoing experiments of the pressure and -breathing may be united; namely, by breathing on a plate of glass, and -immediately after pressing the other upon it. The colours then appear -as in the case of two glasses unbreathed upon, with this difference, -that the moisture occasions here and there an interruption of the -undulations. On pushing one glass away from the other the moisture -appears iridescent as it evaporates. - -460. - -It might, however, be asserted that this combined experiment exhibits -no more than each single experiment; for it appears the colours excited -by pressure disappear in proportion as the glasses are less in contact, -and the moisture then evaporates with its own colours. - -461. - -Fourth condition.--Iridescent appearances are observable in almost all -bubbles; soap-bubbles are the most commonly known, and the effect in -question is thus exhibited in the easiest mode; but it may be observed -in wine, beer, in pure spirit, and again, especially, in the froth of -chocolate. - -462. - -As in the above cases we required an infinitely narrow space between -two surfaces which are in contact, so we can consider the pellicle -of the soap-bubble as an infinitely thin lamina between two elastic -bodies; for the appearance in fact takes place between the air within, -which distends the bubble, and the atmospheric air. - -463. - -The bubble when first produced is colourless; then coloured stripes, -like those in marble paper, begin to appear: these at length spread -over the whole surface, or rather are driven round it as it is -distended. - -464. - -In a single bubble, suffered to hang from the straw or tube, the -appearance of colour is difficult to observe, for the quick rotation -prevents any accurate observation, and all the colours seem to mix -together; yet we can perceive that the colours begin at the orifice of -the tube. The solution itself may, however, be blown into carefully, -so that only one bubble shall appear. This remains white (colourless) -if not much agitated; but if the solution is not too watery, circles -appear round the perpendicular axis of the bubble; these being near -each other, are commonly composed alternately of green and red. Lastly, -several bubbles may be produced together by the same means; in this -case the colours appear on the sides where two bubbles have pressed -each other flat. - -465. - -The bubbles of chocolate-froth may perhaps be even more conveniently -observed than those of soap; though smaller, they remain longer. In -these, owing to the heat, an impulse, a movement, is produced and -sustained, which appears necessary to the development and succession of -the appearances. - -466. - -If the bubble is small, or shut in between others, coloured lines -chase each other over the surface, resembling marbled paper; all the -colours of the scale are seen to pass through each other; the pure, the -augmented, the combined, all distinctly clear and beautiful. In small -bubbles the appearance lasts for a considerable time. - -467. - -If the bubble is larger, or if it becomes by degrees detached, owing -to the bursting of others near, we perceive that this impulsion and -attraction of the colours has, as it were, an end in view; for on -the highest point of the bubble we see a small circle appear, which -is yellow in the centre; the other remaining coloured lines move -constantly round this with a vermicular action. - -468. - -In a short time the circle enlarges and sinks downwards on all sides; -in the centre the yellow remains; below and on the outside it becomes -red, and soon blue; below this again appears a new circle of the -same series of colours: if they approximate sufficiently, a green is -produced by the union of the border-colours. - -469. - -When I could count three such leading circles, the centre was -colourless, and this space became by degrees larger as the circles sank -lower, till at last the bubble burst. - -470. - -Fifth condition.--Very delicate pellicles may be formed in various -ways: on these films we discover a very lively play of colours, either -in the usual order, or more confusedly passing through each other. The -water in which lime has been slaked soon skims over with a coloured -pellicle: the same happens on the surface of stagnant water, especially -if impregnated with iron. The lamellæ of the fine tartar which adheres -to bottles, especially in red French wine, exhibit the most brilliant -colours, on being exposed to the light, if carefully detached. Drops of -oil on water, brandy, and other fluids, produce also similar circles -and brilliant effects: but the most beautiful experiment that can be -made is the following:--Let aqua fortis, not too strong, be poured into -a flat saucer, and then with a brush drop on it some of the varnish -used by engravers to cover certain portions during the process of -biting their plates. After quick commotion there presently appears a -film which spreads itself out in circles, and immediately produces the -most vivid appearances of colour. - -471. - -Sixth condition.--When metals are heated, colours rapidly succeeding -each other appear on the surface: these colours can, however, be -arrested at will. - -472. - -If a piece of polished steel is heated, it will, at a certain degree -of warmth, be overspread with yellow. If taken suddenly away from the -fire, this yellow remains. - -473. - -As the steel becomes hotter, the yellow appears darker, intenser, and -presently passes into red. This is difficult to arrest, for it hastens -very quickly to bright blue. - -474. - -This beautiful blue is to be arrested if the steel is suddenly taken -out of the heat and buried in ashes. The blue steel works are produced -in this way. If, again, the steel is held longer over the fire, it soon -becomes a light blue, and so it remains. - -475. - -These colours pass like a breath over the plate of steel; each seems -to fly before the other, but, in reality, each successive hue is -constantly developed from the preceding one. - -476. - -If we hold a penknife in the flame of a light, a coloured stripe will -appear across the blade. The portion of the stripe which was nearest to -the flame is light blue; this melts into blue-red; the red is in the -centre; then follow yellow-red and yellow. - -477. - -This phenomenon is deducible from the preceding ones; for the portion -of the blade next the handle is less heated than the end which is in -the flame, and thus all the colours which in other cases exhibited -themselves in succession, must here appear at once, and may thus be -permanently preserved. - -478. - -Robert Boyle gives this succession of colours as follows:--"A florido -flavo ad flavum saturum et rubescentem (quem artifices sanguineum -vocant) inde ad languidum, postea ad saturiorem cyaneum." This would be -quite correct if the words "languidus" and "saturior" were to change -places. How far the observation is correct, that the different colours -have a relation to the degree of temper which the metal afterwards -acquires, we leave to others to decide. The colours are here only -indications of the different degrees of heat.--Note R. - -479. - -When lead is calcined, the surface is first greyish. This greyish -powder, with greater heat, becomes yellow, and then orange. Silver, -too, exhibits colours when heated; the fracture of silver in the -process of refining belongs to the same class of examples. When -metallic glasses melt, colours in like manner appear on the surface. - -480. - -Seventh condition.--When the surface of glass becomes decomposed. The -accidental opacity (blindwerden) of glass has been already noticed: the -term (blindwerden) is employed to denote that the surface of the glass -is so affected as to appear dim to us. - -481. - -White glass becomes "blind" soonest; cast, and afterwards polished -glass is also liable to be so affected; the bluish less, the green -least. - -482. - -Of the two sides of a plate of glass one is called the mirror side; -it is that which in the oven lies uppermost, on which one may observe -roundish elevations: it is smoother than the other, which is undermost -in the oven, and on which scratches may be sometimes observed. On this -account the mirror side is placed facing the interior of rooms, because -it is less affected by the moisture adhering to it from within, than -the other would be, and the glass is thus less liable to become "blind." - -483. - -This half-opacity or dimness of the glass assumes by degrees an -appearance of colour which may become very vivid, and in which perhaps -a certain succession, or otherwise regular order, might be discovered. - -484. - -Having thus traced the physical colours from their simplest effects to -the present instances, where these fleeting appearances are found to -be fixed in bodies, we are, in fact, arrived at the point where the -chemical colours begin; nay, we have in some sort already passed those -limits; a circumstance which may excite a favourable prejudice for the -consistency of our statement. By way of conclusion to this part of our -inquiry, we subjoin a general observation, which may not be without its -bearing on the common connecting principle of the phenomena that have -been adduced. - -485. - -The colouring of steel and the appearances analogous to it, might -perhaps be easily deduced from the doctrine of the semi-opaque mediums. -Polished steel reflects light powerfully: we may consider the colour -produced by the heat as a slight degree of dimness: hence a bright -yellow must immediately appear; this, as the dimness increases, must -still appear deeper, more condensed, and redder, and at last pure and -ruby-red. The colour has now reached the extreme point of depth, and -if we suppose the same degree of semi-opacity still to continue, the -dimness would now spread itself over a dark ground, first producing a -violet, then a dark-blue, and at last a light-blue, and thus complete -the series of the appearances. - -We will not assert that this mode of explanation will suffice in -all cases; our object is rather to point out the road by which the -all-comprehensive formula, the very key of the enigma, may be at last -discovered.--Note S. - - - - -PART III. - - -CHEMICAL COLOURS. - - -486. - -We give this denomination to colours which we can produce, and more -or less fix, in certain bodies; which we can render more intense, -which we can again take away and communicate to other bodies, and to -which, therefore, we ascribe a certain permanency: duration is their -prevailing characteristic. - -487. - -In this view the chemical colours were formerly distinguished with -various epithets; they were called _colores proprii, corporei, -materiales, veri, permanentes, fixi_. - -488. - -In the preceding chapter we observed how the fluctuating and transient -nature of the physical colours becomes gradually fixed, thus forming -the natural transition to our present subject. - -489. - -Colour becomes fixed in bodies more or less permanently; superficially, -or thoroughly. - -490. - -All bodies are susceptible of colour; it can either be excited, -rendered intense, and gradually fixed in them, or at least communicated -to them. - - - - -XXXIV. - - -CHEMICAL CONTRAST. - - -491. - -In the examination of coloured appearances we had occasion everywhere -to take notice of a principle of contrast: so again, in approaching the -precincts of chemistry, we find a chemical contrast of a remarkable -nature. We speak here, with reference to our present purpose, only of -that which is comprehended under the general names of acid and alkali. - -492. - -We characterised the chromatic contrast, in conformity with all other -physical contrasts as a _more_ and _less_; ascribing the _plus_ to -the yellow side, the _minus_ to the blue; and we now find that these -two divisions correspond with the chemical contrasts. The yellow and -yellow-red affect the acids, the blue and blue-red the alkalis; thus -the phenomena of chemical colours, although still necessarily mixed -up with other considerations, admit of being traced with sufficient -simplicity. - -493. - -The principal phenomena in chemical colours are produced by the -oxydation of metals, and it will be seen how important this -consideration is at the outset. Other facts which come into the -account, and which are worthy of attention, will be examined under -separate heads; in doing this we, however, expressly state that we only -propose to offer some preparatory suggestions to the chemist in a very -general way, without entering into the nicer chemical problems and -questions, or presuming to decide on them. Our object is only to give a -sketch of the mode in which, according to our conviction, the chemical -theory of colours may be connected with general physics. - - - - -XXXV. - - -WHITE. - - -494. - -In treating of the dioptrical colours of the first class (155) we -have already in some degree anticipated this subject. Transparent -substances may be said to be in the highest class of inorganic matter. -With these, colourless semi-transparence is closely connected, and -white may be considered the last opaque degree of this. - -495. - -Pure water crystallised to snow appears white, for the transparence of -the separate parts makes no transparent whole. Various crystallised -salts, when deprived to a certain extent of moisture, appear as a white -powder. The accidentally opaque state of a pure transparent substance -might be called white; thus pounded glass appears as a white powder. -The cessation of a combining power, and the exhibition of the atomic -quality of the substance might at the same time be taken into the -account. - -496. - -The known undecomposed earths are, in their pure state, all white. -They pass to a state of transparence by natural crystallization. Silex -becomes rock-crystal; argile, mica; magnesia, talc; calcareous earth -and barytes appear transparent in various spars.--Note T. - -497. - -As in the colouring of mineral bodies the metallic oxydes will often -invite our attention, we observe, in conclusion, that metals, when -slightly oxydated, at first appear white, as lead is converted to white -lead by vegetable acid. - - - - -XXXVI. - - -BLACK. - - -498. - -Black is not exhibited in so elementary a state as white. We meet -with it in the vegetable kingdom in semi-combustion; and charcoal, a -substance especially worthy of attention on other accounts, exhibits -a black colour. Again, if woods--for example, boards, owing to the -action of light, air, and moisture, are deprived in part of their -combustibility, there appears first the grey then the black colour. So -again, we can convert even portions of animal substance to charcoal by -semi-combustion. - -499. - -In the same manner we often find that a sub-oxydation takes place -in metals when the black colour is to be produced. Various metals, -particularly iron, become black by slight oxydation, by vinegar, by -mild acid fermentations; for example, a decoction of rice, &c. - -500. - -Again, it may be inferred that a de-oxydation may produce black. This -occurs in the preparation of ink, which becomes yellow by the solution -of iron in strong sulphuric acid, but when partly de-oxydised by the -infusion of gall-nuts, appears black. - - - - -XXXVII. - - -FIRST EXCITATION OF COLOUR. - - -501. - -In the division of physical colours, where semi-transparent mediums -were considered, we saw colours antecedently to white and black. In the -present case we assume a white and black already produced and fixed; -and the question is, how colour can be excited in them? - -502. - -Here, too, we can say, white that becomes darkened or dimmed inclines -to yellow; black, as it becomes lighter, inclines to blue.--Note U. - -503. - -Yellow appears on the active (plus) side, immediately in the light, the -bright, the white. All white surfaces easily assume a yellow tinge; -paper, linen, wool, silk, wax: transparent fluids again, which have -a tendency to combustion, easily become yellow; in other words they -easily pass into a very slight state of semi-transparence. - -504. - -So again the excitement on the passive side, the tendency to obscure, -dark, black, is immediately accompanied with blue, or rather with a -reddish-blue. Iron dissolved in sulphuric acid, and much diluted with -water, if held to the light in a glass, exhibits a beautiful violet -colour as soon as a few drops only of the infusion of gall-nuts are -added. This colour presents the peculiar hues of the dark topaz, the -_orphninon_ of a burnt-red, as the ancients expressed it. - -505. - -Whether any colour can be excited in the pure earths by the chemical -operations of nature and art, without the admixture of metallic oxydes, -is an important question, generally, indeed, answered in the negative. -It is perhaps connected with the question--to what extent changes may -be produced in the earths through oxydation? - -506. - -Undoubtedly the negation of the above question is confirmed by the -circumstance that wherever mineral colours are found, some trace of -metal, especially of iron, shows itself; we are thus naturally led -to consider how easily iron becomes oxydised, how easily the oxyde -of iron assumes different colours, how infinitely divisible it is, -and how quickly it communicates its colour. It were to be wished, -notwithstanding, that new experiments could be made in regard to the -above point, so as either to confirm or remove any doubt. - -507. - -However this may be, the susceptibility of the earths with regard -to colours already existing is very great; aluminous earth is thus -particularly distinguished. - -508. - -In proceeding to consider the metals, which in the inorganic world -have the almost exclusive prerogative of appearing coloured, we find -that, in their pure, independent, natural state, they are already -distinguished from the pure earths by a tendency to some one colour or -other. - -509. - -While silver approximates most to pure white,--nay, really represents -pure white, heightened by metallic splendour,--steel, tin, lead, and so -forth, incline towards pale blue-grey; gold, on the other hand, deepens -to pure yellow, copper approaches a red hue, which, under certain -circumstances, increases almost to bright red, but which again returns -to a yellow golden colour when combined with zinc. - -510. - -But if metals in their pure state have so specific a determination -towards this or that exhibition of colour, they are, through the effect -of oxydation, in some degree reduced to a common character; for the -elementary colours now come forth in their purity, and although this -or that metal appears to have a particular tendency to this or that -colour, we find some that can go through the whole circle of hues, -others, that are capable of exhibiting more than one colour; tin, -however, is distinguished by its comparative inaptitude to become -coloured. We propose to give a table hereafter, showing how far the -different metals can be more or less made to exhibit the different -colours. - -511. - -When the clean, smooth surface of a pure metal, on being heated, -becomes overspread with a mantling colour, which passes through a -series of appearances as the heat increases, this, we are persuaded, -indicates the aptitude of the metal to pass through the whole range of -colours. We find this phenomenon most beautifully exhibited in polished -steel; but silver, copper, brass, lead, and tin, easily present similar -appearances. A superficial oxydation is probably here taking place, -as may be inferred from the effects of the operation when continued, -especially in the more easily oxydizable metals. - -512. - -The same conclusion may be drawn from the fact that iron is more -easily oxydizable by acid liquids when it is red hot, for in this -case the two effects concur with each other. We observe, again, that -steel, accordingly as it is hardened in different stages of its -colorification, may exhibit a difference of elasticity: this is quite -natural, for the various appearances of colour indicate various degrees -of heat.[1] - -513. - -If we look beyond this superficial mantling, this pellicle of colour, -we observe that as metals are oxydized throughout their masses, white -or black appears with the first degree of heat, as may be seen in white -lead, iron, and quicksilver. - -514. - -If we examine further, and look for the actual exhibition of colour, -we find it most frequently on the _plus_ side. The mantling, so often -mentioned, of smooth metallic surfaces begins with yellow. Iron -passes presently into yellow ochre, lead from white lead to massicot, -quicksilver from æthiops to yellow turbith. The solutions of gold and -platinum in acids are yellow. - -515. - -The exhibitions on the _minus_ side are less frequent. Copper slightly -oxydized appears blue. In the preparation of Prussian-blue, alkalis are -employed. - -516. - -Generally, however, these appearances of colour are of so mutable a -nature that chemists look upon them as deceptive tests, at least in the -nicer gradations. For ourselves, as we can only treat of these matters -in a general way, we merely observe that the appearances of colour in -metals may be classed according to their origin, manifold appearance, -and cessation, as various results of oxydation, hyper-oxydation, -ab-oxydation, and de-oxydation.[2] - - -[1] See par. 478. - -[2] As these terms are afterwards referred to (par. 525), it was -necessary to preserve them. - - - - -XXXVIII. - - -AUGMENTATION OF COLOUR.[1] - - -517. - -The augmentation of colour exhibits itself as a condensation, a -fulness, a darkening of the hue. We have before seen, in treating of -colourless mediums, that by increasing the degree of opacity in the -medium, we can deepen a bright object from the lightest yellow to the -intensest ruby-red. Blue, on the other hand, increases to the most -beautiful violet, if we rarefy and diminish a semi-opaque medium, -itself lighted, but through which we see darkness (150, 151). - -518. - -If the colour is positive, a similar colour appears in the intenser -state. Thus if we fill a white porcelain cup with a pure yellow -liquor, the fluid will appear to become gradually redder towards the -bottom, and at last appears orange. If we pour a pure blue solution -into another cup, the upper portion will exhibit a sky-blue, that -towards the bottom, a beautiful violet. If the cup is placed in the -sun, the shadowed side, even of the upper portion, is already violet. -If we throw a shadow with the hand, or any other substance, over the -illumined portion, the shadow in like manner appears reddish. - -519. - -This is one of the most important appearances connected with the -doctrine of colours, for we here manifestly find that a difference of -quantity produces a corresponding qualified impression on our senses. -In speaking of the last class of epoptical colours (452, 485), we -stated our conjecture that the colouring of steel might perhaps be -traced to the doctrine of the semi-transparent mediums, and we would -here again recall this to the reader's recollection. - -520. - -All chemical augmentation of colour, again, is the immediate -consequence of continued excitation. The augmentation advances -constantly and unremittingly, and it is to be observed that the -increase of intenseness is most common on the _plus_ side. Yellow iron -ochre increases, as well by fire as by other operations, to a very -strong red: massicot is increased to red lead, turbith to vermilion, -which last attains a very high degree of the yellow-red. An intimate -saturation of the metal by the acid, and its separation to infinity, -take place together with the above effects. - -521. - -The augmentation on the _minus_ side is less frequent; but we observe -that the more pure and condensed the Prussian-blue or cobalt glass is -prepared, the more readily it assumes a reddish hue and inclines to the -violet. - -522. - -The French have a happy expression for the less perceptible tendency of -yellow and blue towards red: they say the colour has "un œil de rouge," -which we might perhaps express by a reddish glance (einen röthlichen -blick). - - -[1] Steigerung, literally _gradual ascent_. See the note to par. 523. - - - - -XXXIX. - - -CULMINATION[1] - - -523. - -This is the consequence of still progressing augmentation. Red, in -which neither yellow nor blue is to be detected, here constitutes the -acme. - -524. - -If we wish to select a striking example of a culmination on the _plus_ -side, we again find it in the coloured steel, which attains the bright -red acme, and can be arrested at this point. - -525. - -Were we here to employ the terminology before proposed, we should -say that the first oxydation produces yellow, the hyper-oxydation -yellow-red; that here a kind of maximum exists, and that then an -ab-oxydation, and lastly a de-oxydation takes place. - -526. - -High degrees of oxydation produce a bright red. Gold in solution, -precipitated by a solution of tin, appears bright red: oxyde of -arsenic, in combination, with sulphur, produces a ruby colour. - -527. - -How far, however, a kind of sub-oxydation may co-operate in some -culminations, is matter for inquiry; for an influence of alkalis on -yellow-red also appears to produce the culmination; the colour reaching -the acme by being forced towards the _minus_ side. - -528. - -The Dutch prepare a colour known by the name of vermilion, from the -best Hungarian cinnabar, which exhibits the brightest yellow-red. This -vermilion is still only a cinnabar, which, however, approximates the -pure red, and it may be conjectured that alkalis are used to bring it -nearer to the culminating point. - -529. - -Vegetable juices, treated in this way, offer very striking examples of -the above effects. The colouring-matter of turmeric, annotto, dyer's -saffron,[2] and other vegetables, being extracted with spirits of wine, -exhibits tints of yellow, yellow-red, and hyacinth-red; these, by the -admixture of alkalis, pass to the culminating point, and even beyond it -to blue-red. - -530. - -No instance of a culmination on the _minus_ side has come to my -knowledge in the mineral and vegetable kingdoms. In the animal -kingdom the juice of the murex is remarkable; of its augmentation and -culmination on the _minus_ side, we shall hereafter have occasion to -speak. - - -[1] _Culmination_, the original word. It might have been rendered -_maximum of colour_, but as the author supposes an _ascent_ through -yellow and blue to red, his meaning is better expressed by his own term. - -[2] Curcuma, Bixa Orellana, Carthamus Tinctorius. - - - - -XL. - - -FLUCTUATION. - - -531. - -The mutability of colour is so great, that even those pigments, which -may have been considered to be defined and arrested, still admit of -slight variations on one side or the other. This mutability is most -remarkable near the culminating point, and is effected in a very -striking manner by the alternate employment of acids and alkalis. - -532. - -To express this appearance in dyeing, the French make use of the word -"virer," to turn from one side to the other; they thus very adroitly -convey an idea which others attempt to express by terms indicating the -component hues. - -533. - -The effect produced with litmus is one of the most known and striking -of this kind. This colouring substance is tendered red-blue by means of -alkalis. The red-blue is very readily changed to red-yellow by means -of acids, and again returns to its first state by again employing -alkalis. The question whether a culminating point is to be discovered -and arrested by nice experiments, is left to those who are practised -in these operations. Dyeing, especially scarlet-dyeing, might afford a -variety of examples of this fluctuation. - - - - -XLI. - - -PASSAGE THROUGH THE WHOLE SCALE. - - -534. - -The first excitation and gradual increase of colour take place more on -the _plus_ than on the _minus_ side. So, also, in passing through the -whole scale, colour exhibits itself most on the _plus_ side. - -535. - -A passage of this kind, regular and evident to the senses, from yellow -through red to blue, is apparent in the colouring of steel. - -536. - -The metals may be arrested at various points of the colorific circle by -various degrees and kinds of oxydation. - -537. - -As they also appear green, a question arises whether chemists know any -instance in the mineral kingdom of a constant transition from yellow, -through green, to blue, and _vice versâ_. Oxyde of iron, melted with -glass, produces first a green, and with a more powerful heat, a blue -colour. - -538. - -We may here observe of green generally, that it appears, especially -in an atomic sense, and certainly in a pure state, when we mix blue -and yellow: but, again, an impure and dirty yellow soon gives us the -impression of green; yellow and black already produce green; this, -however, is owing to the affinity between black and blue. An imperfect -yellow, such as that of sulphur, gives us the impression of a greenish -hue: thus, again, an imperfect blue appears green. The green of wine -bottles arises, it appears, from an imperfect union of the oxyde of -iron with the glass. If we produce a more complete union by greater -heat, a beautiful blue-glass is the result. - -539. - -From all this it appears that a certain chasm exists in nature between -yellow and blue, the opposite characters of which, it is true, may be -done away atomically by due immixture, and, thus combined, to green; -but the true reconciliation between yellow and blue, it seems, only -takes place by means of red. - -540. - -The process, however, which appears unattainable in inorganic -substances, we shall find to be possible when we turn our attention to -organic productions; for in these, the passage through the whole circle -from yellow, through green and blue, to red, really takes place. - - - - -XLII. - - -INVERSION. - - -541. - -Again, an immediate inversion or change to the totally opposite hue, is -a very remarkable appearance which sometimes occurs; at present, we are -merely enabled to adduce what follows. - -542. - -The mineral chameleon, a name which has been given to an oxyde of -manganese, may be considered, in its perfectly dry state, as a green -powder. If we strew it in water, the green colour displays itself very -beautifully in the first moment of solution, but it changes presently -to the bright red opposite to green, without any apparent intermediate -state. - -543. - -The same occurs with the sympathetic ink, which may be considered a -reddish liquid, but which, when dried by warmth, appears as a green -colour on paper. - -544. - -In fact, this phenomenon appears to be owing to the conflict between -a dry and moist state, as has been already observed, if we are not -mistaken, by the chemists. We may look to the improvements of time to -point out what may further be deduced from these phenomena, and to show -what other facts they may be connected with. - - - - -XLIII. - - -FIXATION. - - -545. - -Mutable as we have hitherto found colour to be, even as a substance, -yet under certain circumstances it may at last be fixed. - -546. - -There are bodies capable of being entirely converted into colouring -matter: here it may be said that the colour fixes itself in its own -substance, stops at a certain point, and is there defined. Such -colouring substances are found throughout nature; the vegetable world -affords a great quantity of examples, among which some are particularly -distinguished, and may be considered as the representatives of the -rest; such as, on the active side, madder, on the passive side, indigo. - -547. - -In order to make these materials available in use, it is necessary -that the colouring quality in them should be intimately condensed, and -the tinging substance refined, practically speaking, to an infinite -divisibility. This is accomplished in various ways, and particularly by -the well-known means of fermentation and decomposition. - -548. - -These colouring substances now attach themselves again to other bodies. -Thus, in the mineral kingdom they adhere to earths and metallic oxydes; -they unite in melting with glasses; and in this case, as the light is -transmitted through them, they appear in the greatest beauty, while an -eternal duration may be ascribed to them. - -549. - -They fasten on vegetable and animal bodies with more or less power, and -remain more or less permanently; partly owing to their nature,--as -yellow, for instance, is more evanescent than blue,--or owing to -the nature of the substance on which they appear. They last less in -vegetable than in animal substances, and even within this latter -kingdom there are again varieties. Hemp or cotton threads, silk or -wool, exhibit very different relations to colouring substances. - -550. - -Here comes into the account the important operation of employing -mordants, which may be considered as the intermediate agents between -the colour and the recipient substance; various works on dyeing speak -of this circumstantially. Suffice it to have alluded to processes by -means of which the colour retains a permanency only to be destroyed -with the substance, and which may even increase in brightness and -beauty by use. - - - - -XLIV. - - -INTERMIXTURE, REAL. - - -551. - -Every intermixture pre-supposes a specific state of colour; and thus -when we speak of intermixture, we here understand it in an atomic -sense. We must first have before us certain bodies arrested at any -given point of the colorific circle, before we can produce gradations -by their union. - -552. - -Yellow, blue, and red, may be assumed as pure elementary colours, -already existing; from these, violet, orange, and green, are the -simplest combined results. - -553. - -Some persons have taken much pains to define these intermixtures more -accurately, by relations of number, measure, and weight, but nothing -very profitable has been thus accomplished. - -554. - -Painting consists, strictly speaking, in the intermixture of -such specific colouring bodies and their infinite possible -combinations--combinations which can only be appreciated by the nicest, -most practised eye, and only accomplished under its influence. - -555. - -The intimate combination of these ingredients is effected, in the first -instance, through the most perfect comminution of the material by means -of grinding, washing, &c., as well as by vehicles or liquid mediums -which hold together the pulverized substance, and combine organically, -as it were, the unorganic; such are the oils, resins, &c.--Note V. - -556. - -If all the colours are mixed together they retain their general -character as σκιερόν, and as they are no longer seen next each other, -no completeness, no harmony, is experienced; the result is grey, which, -like apparent colour, always appears somewhat darker than white, and -somewhat lighter than black. - -557. - -This grey may be produced in various ways. By mixing yellow and blue to -an emerald green, and then adding pure red, till all three neutralize -each other; or, by placing the primitive and intermediate colours next -each other in a certain proportion, and afterwards mixing them. - -558. - -That all the colours mixed together produce white, is an absurdity -which people have credulously been accustomed to repeat for a century, -in opposition to the evidence of their senses. - -559. - -Colours when mixed together retain their original darkness. The darker -the colours, the darker will be the grey resulting from their union, -till at last this grey approaches black. The lighter the colours the -lighter will be the grey, which at last approaches white. - - - - -XLV. - - -INTERMIXTURE, APPARENT. - - -560. - -The intermixture, which is only apparent, naturally invites our -attention in connexion with the foregoing; it is in many respects -important, and, indeed, the intermixture which we have distinguished as -real, might be considered as merely apparent. For the elements of which -the combined colour consists are only too small to be considered as -distinct parts. Yellow and blue powders mingled together appear green -to the naked eye, but through a magnifying glass we can still perceive -yellow and blue distinct from each other. Thus yellow and blue stripes -seen at a distance, present a green mass; the same observation is -applicable with regard to the intermixture of other specific colours. - -561. - -In the description of our apparatus we shall have occasion to mention -the wheel by means of which the apparent intermixture is produced by -rapid movement. Various colours are arranged near each other round -the edge of a disk, which is made to revolve with velocity, and thus -by having several such disks ready, every possible intermixture can -be presented to the eye, as well as the mixture of all colours to -grey, darker or lighter, according to the depth of the tints as above -explained. - -562. - -Physiological colours admit, in like manner, of being mixed with -others. If, for example, we produce the blue shadow (65) on a light -yellow paper, the surface will appear green. The same happens with -regard to the other colours if the necessary preparations are attended -to. - -563. - -If, when the eye is impressed with visionary images that last for a -while, we look on coloured surfaces, an intermixture also takes place; -the spectrum is determined to a new colour which is composed of the two. - -564. - -Physical colours also admit of combination. Here might be adduced the -experiments in which many-coloured images are seen through the prism, -as we have before shown in detail (258, 284). - -565. - -Those who have prosecuted these inquiries have, however, paid most -attention to the appearances which take place when the prismatic -colours are thrown on coloured surfaces. - -566. - -What is seen under these circumstances is quite simple. In the first -place it must be remembered that the prismatic colours are much more -vivid than the colours of the surface on which they are thrown. -Secondly, we have to consider that the prismatic colours may be either -homogeneous or heterogeneous, with the recipient surface. In the former -case the surface deepens and enhances them, and is itself enhanced in -return, as a coloured stone is displayed by a similarly coloured foil. -In the opposite case each vitiates, disturbs, and destroys the other. - -567. - -These experiments may be repeated with coloured glasses, by causing the -sun-light to shine through them on coloured surfaces. In every instance -similar results will appear. - -568. - -The same effect takes place when we look on coloured objects through -coloured glasses; the colours being thus according to the same -conditions enhanced, subdued, or neutralized. - -569. - -If the prismatic colours are suffered to pass through coloured glasses, -the appearances that take place are perfectly analogous; in these cases -more or less force, more or less light and dark, the clearness and -cleanness of the glass are all to be allowed for, as they produce many -delicate varieties of effect: these will not escape the notice of every -accurate observer who takes sufficient interest in the inquiry to go -through the experiments. - -570. - -It is scarcely necessary to mention that several coloured glasses, as -well as oiled or transparent papers, placed over each other, may be -made to produce and exhibit every kind of intermixture at pleasure. - -571. - -Lastly, the operation of glazing in painting belongs to this kind of -intermixture; by this means a much more refined union may be produced -than that arising from the mechanical, atomic mixture which is commonly -employed. - - - - -XLVI. - - -COMMUNICATION, ACTUAL. - - -572. - -Having now provided the colouring materials, as before shown, a further -question arises how to communicate these to colourless substances: -the answer is of the greatest importance from the connexion of the -object with the ordinary wants of men, with useful purposes, and with -commercial and technical interests. - -573. - -Here, again, the dark quality of every colour again comes into the -account. From a yellow, that is very near to white, through orange, -and the hue of minium to pure red and carmine, through all gradations -of violet to the deepest blue which is almost identified with black, -colour still increases in darkness. Blue once defined, admits of -being diluted, made light, united with yellow, and then, as green, -it approaches the light side of the scale: but this is by no means -according to its own nature. - -574. - -In the physiological colours we have already seen that they are less -than the light, inasmuch as they are a repetition of an impression -of light, nay, at last they leave this impression quite as a dark. In -physical experiments the employment of semi-transparent mediums, the -effect of semi-transparent accessory images, taught us that in such -cases we have to do with a subdued light, with a transition to darkness. - -575. - -In treating of the chemical origin of pigments we found that the same -effect was produced on the very first excitement. The yellow tinge -which mantles over the steel, already darkens the shining surface. In -changing white lead to massicot it is evident that the yellow is darker -than white. - -576. - -This process is in the highest degree delicate; the growing -intenseness, as it still increases, tinges the substance more and more -intimately and powerfully, and thus indicates the extreme fineness, and -the infinite divisibility of the coloured atoms. - -577. - -The colours which approach the dark side, and consequently, blue in -particular, can be made to approximate to black; in fact, a very -perfect Prussian blue, or an indigo acted on by vitriolic acid appears -almost as a black. - -578. - -A remarkable appearance may be here adverted to; pigments, in their -deepest and most condensed state, especially those produced from -the vegetable kingdom, such as the indigo just mentioned, or madder -carried to its intensest hue, no longer show their own colour; on the -contrary, a decided metallic shine is seen on their surface, in which -the physiological compensatory colour appears. - -579. - -All good indigo exhibits a copper-colour in its fracture, a -circumstance attended to, as a known characteristic, in trade. Again, -the indigo which has been acted on by sulphuric acid, if thickly laid -on, or suffered to dry so that neither white paper nor the porcelain -can appear through, exhibits a colour approaching to orange. - -580. - -The bright red Spanish rouge, probably prepared from madder, exhibits -on its surface a perfectly green, metallic shine. If this colour, or -the blue before mentioned, is washed with a pencil on porcelain or -paper, it is seen in its real state owing to the bright ground shining -through. - -581. - -Coloured liquids appear black when no light is transmitted through -them, as we may easily see in cubic tin vessels with glass bottoms. -In these every transparent-coloured infusion will appear black and -colourless if we place a black surface under them. - -582. - -If we contrive that the image of a flame be reflected from the bottom, -the image will appear coloured. If we lift up the vessel and suffer the -transmitted light to fall on white paper under it, the colour of the -liquid appears on the paper. Every light ground seen through such a -coloured medium exhibits the colour of the medium. - -583. - -Thus every colour, in order to be seen, must have a light within or -behind it. Hence the lighter and brighter the grounds are, the more -brilliant the colours appear. If we pass lac-varnish over a shining -white metal surface, as the so-called foils are prepared, the splendour -of the colour is displayed by this internally reflected light as -powerfully as in any prismatic experiment; nay, the force of the -physical colours is owing principally to the circumstance that light is -always acting with and behind them. - -584. - -Lichtenberg, who of necessity followed the received theory, owing -to the time and circumstances in which he lived, was yet too good an -observer, and too acute not to explain and classify, after his fashion, -what was evident to his senses. He says, in the preface to Delaval, -"It appears to me also, on other grounds, probable, that our organ, in -order to be impressed by a colour, must at the same time be impressed -by all light (white)." - -585. - -To procure white as a ground is the chief business of the dyer. Every -colour may be easily communicated to colourless earths, especially -to alum: but the dyer has especially to do with animal and vegetable -products as the ground of his operations. - -586. - -Everything living tends to colour--to local, specific colour, to -effect, to opacity--pervading the minutest atoms. Everything in which -life is extinct approximates to white (494), to the abstract, the -general state, to clearness[1], to transparence. - -587. - -How this is put in practice in technical operations remains to be -adverted to in the chapter on the privation of colour. With regard -to the communication of colour, we have especially to bear in mind -that animals and vegetables, in a living state, produce colours, and -hence their substances, if deprived of colours, can the more readily -re-assume them. - - -[1] Verklärung, literally _clarification_. - - - - -XLVII. - - -COMMUNICATION, APPARENT. - - -588. - -The communication of colours, real as well as apparent, corresponds, as -may easily be seen, with their intermixture: we need not, therefore, -repeat what has been already sufficiently entered into. - -589. - -Yet we may here point out more circumstantially the importance of an -apparent communication which takes place by means of reflection. This -phenomenon is well known, but still it is pregnant with inferences, and -is of the greatest importance both to the investigator of nature and to -the painter. - -590. - -Let a surface coloured with any one of the positive colours be placed -in the sun, and let its reflection be thrown on other colourless -objects. This reflection is a kind of subdued light, a half-light, -a half-shadow, which, in a subdued state, reflects the colours in -question. - -591. - -If this reflection acts on light surfaces, it is so far overpowered -that we can scarcely perceive the colour which accompanies it; but if -it acts on shadowed portions, a sort of magical union takes place with -the σκιερῷ. Shadow is the proper element of colour, and in this case -a subdued colour approaches it, lighting up, tinging, and enlivening -it. And thus arises an appearance, as powerful as agreeable, which may -render the most pleasing service to the painter who knows how to make -use of it. These are the types of the so-called reflexes, which were -only noticed late in the history of art, and which have been too seldom -employed in their full variety. - -592. - -The schoolmen called these colours _colores notionales_ and -_intentionales_, and the history of the doctrine of colours will -generally show that the old inquirers already observed the phenomena -well enough, and knew how to distinguish them properly, although the -whole method of treating such subjects is very different from ours. - - - - -XLVIII. - - -EXTRACTION. - - -593. - -Colour may be extracted from substances, whether they possess it -naturally or by communication, in various ways. We have thus the power -to remove it intentionally for a useful purpose, but, on the other -hand, it often flies contrary to our wish. - -594. - -Not only are the elementary earths in their natural state white, but -vegetable and animal substances can be reduced to a white state without -disturbing their texture. A pure white is very desirable for various -uses, as in the instance of our preferring to use linen and cotton -stuffs uncoloured. In like manner some silk stuffs, paper, and other -substances, are the more agreeable the whiter they can be. Again, -the chief basis of all dyeing consists in white grounds. For these -reasons manufacturers, aided by accident and contrivance, have devoted -themselves assiduously to discover means of extracting colour: infinite -experiments have been made in connexion with this object, and many -important facts have been arrived at. - -595. - -It is in accomplishing this entire extraction of colour that the -operation of bleaching consists, which is very generally practised -empirically or methodically. We will here shortly state the leading -principles. - -596. - -Light is considered as one of the first means of extracting colour -from substances, and not only the sun-light, but the mere powerless -day-light: for as both lights--the direct light of the sun, as well as -the derived light of the sky--kindle Bologna phosphorus, so both act on -coloured surfaces. Whether the light attacks the colour allied to it, -and, as it were, kindles and consumes it, thus reducing the definite -quality to a general state, or whether some other operation, unknown -to us, takes place, it is clear that light exercises a great power on -coloured surfaces, and bleaches them more or less. Here, however, the -different colours exhibit a different degree of durability; yellow, -especially if prepared from certain materials, is, in this case, the -first to fly. - -597. - -Not only light, but air, and especially water, act strongly in -destroying colour. It has been even asserted that thread, well soaked -and spread on the grass at night, bleaches better than that which is -exposed, after soaking, to the sun-light. Thus, in this case, water -proves to be a solving and conducting agent, removing the accidental -quality, and restoring the substance to a general or colourless state. - -598. - -The extraction of colour is also effected by re-agents. Spirits of wine -has a peculiar tendency to attract the juice which tinges plants, and -becomes coloured with it often in a very permanent manner. Sulphuric -acid is very efficient in removing colour, especially from wool and -silk, and every one is acquainted with the use of sulphur vapours in -bleaching. - -599. - -The strongest acids have been recommended more recently as more -expeditious agents in bleaching. - -600. - -The alkaline re-agents produce the same effects by contrary -means--lixiviums alone, oils and fat combined with lixiviums to soap, -and so forth. - -601. - -Before we dismiss this subject, we observe [Pg 240] that it may be -well worth while to make certain delicate experiments as to how far -light and air exhibit their action in the removal of colour. It might -be possible to expose coloured substances to the light under glass -bells, without air, or filled with common or particular kinds of air. -The colours might be those of known fugacity, and it might be observed -whether any of the volatilized colour attached itself to the glass or -was otherwise perceptible as a deposit or precipitate; whether, again, -in such a case, this appearance would be perfectly like that which had -gradually ceased to be visible, or whether it had suffered any change. -Skilful experimentalists might devise various contrivances with a view -to such researches. - -602. - -Having thus first considered the operations of nature as subservient to -our proposes, we add a few observations on the modes in which they act -against us. - -603. - -The art of painting is so circumstanced that the most beautiful results -of mind and labour are altered and destroyed in various ways by time. -Hence great pains have been always taken to find durable pigments, and -so to unite them with each other and with their ground, that their -permanency might be further insured. The technical history of the -schools of painting affords sufficient information on this point. - -604. - -We may here, too, mention a minor art, to which, in relation to -dyeing, we are much indebted, namely, the weaving of tapestry. As the -manufacturers were enabled to imitate the most delicate shades of -pictures, and hence often brought the most variously coloured materials -together, it was soon observed that the colours were not all equally -durable, but that some faded from the tapestry more quickly than -others. Hence the most diligent efforts were made to ensure an equal -permanency to all the colours and their gradations. This object was -especially promoted in France, under Colbert, whose regulations to this -effect constitute an epoch in the history of dyeing. The gay dye which -only aimed at a transient beauty, was practised by a particular guild. -On the other hand, great pains were taken to define the technical -processes which promised durability. - -And thus, after considering the artificial extraction, the evanescence, -and the perishable nature of brilliant appearances of colour, we are -again returned to the desideratum of permanency. - - - - -XLIX. - - -NOMENCLATURE. - - -605. - -After what has been adduced respecting the origin, the increase, -and the affinity of colours, we may be better enabled to judge what -nomenclature would be desirable in future, and what might be retained -of that hitherto in use. - -606. - -The nomenclature of colours, like all other modes of designation, -but especially those employed to distinguish the objects of sense, -proceeded in the first instance from particular to general, and from -general back again to particular terms. The name of the species became -a generic name to which the individual was again referred. - -607. - -This method might have been followed in consequence of the mutability -and uncertainty of ancient modes of expression, especially since, in -the early ages, more reliance may be supposed to have been placed on -the vivid impressions of sense. The qualities of objects were described -indistinctly, because they were impressed clearly on every imagination. - -608. - -The pure chromatic circle was limited, it is true; but, specific as it -was, it appears to have been applied to innumerable objects, while it -was circumscribed by qualifying characteristics. If we take a glance -at the copiousness of the Greek and Roman terms, we shall perceive how -mutable the words were, and how easily each was adapted to almost every -point in the colorific circle.--Note W. - -609. - -In modern ages terms for many new gradations were introduced in -consequence of the various operations of dyeing. Even the colours -of fashion and their designations, represented an endless series of -specific hues. We shall, on occasion, employ the chromatic terminology -of modern languages, whence it will appear that the aim has gradually -been to introduce more exact definitions, and to individualise and -arrest a fixed and specific state by language equally distinct. - -610. - -With regard to the German terminology, it has the advantage of -possessing four monosyllabic names no longer to be traced to their -origin, viz., yellow (Gelb), blue, red, green. They represent the most -general idea of colour to the imagination, without reference to any -very specific modification. - -611. - -If we were to add two other qualifying terms to each of these four, as -thus--red-yellow, and yellow-red, red-blue and blue-red, yellow-green -and green-yellow, blue-green and green-blue,[1] we should express the -gradations of the chromatic circle with sufficient distinctness; and if -we were to add the designations of light and dark, and again define, in -some measure, the degree of purity or its opposite by the monosyllables -black, white, grey, brown, we should have a tolerably sufficient range -of expressions to describe the ordinary appearances presented to us, -without troubling ourselves whether they were produced dynamically or -atomically. - -612. - -The specific and proper terms in use might, however, still be -conveniently employed, and we have thus made use of the words orange -and violet. We have in like manner employed the word "_purpur_" to -designate a pure central red, because the secretion of the murex or -"_purpura_" is to be carried to the highest point of culmination by the -action of the sun-light on fine linen saturated with the juice. - - -[1] This description is suffered to remain because it accounts for the -terminology employed throughout.--T. - - - - -L. - - -MINERALS. - - -613. - -The colours of minerals are all of a chemical nature, and thus the -modes in which they are produced may be explained in a general way by -what has been said on the subject of chemical colours. - -614. - -Among the external characteristics of minerals, the description of -their colours occupies the first place; and great pains have been -taken, in the spirit of modern times, to define and arrest every -such appearance exactly: by this means, however, new difficulties, -it appears to us, have been created, which occasion no little -inconvenience in practice. - -615. - -It is true, this precision, when we reflect how it arose, carries with -it its own excuse. The painter has at all times been privileged in -the use of colours. The few specific hues, in themselves, admitted of -no change; but from these, innumerable gradations were artificially -produced which imitated the surface of natural objects. It was, -therefore, not to be wondered at that these gradations should also be -adopted as criterions, and that the artist should be invited to produce -tinted patterns with which the objects of nature might be compared, and -according to which they were to receive their designations. - -616. - -But, after all, the terminology of colours which has been introduced in -mineralogy, is open to many objections. The terms, for instance, have -not been borrowed from the mineral kingdom, as was possible enough in -most cases, but from all kinds of visible objects. Too many specific -terms have been adopted; and in seeking to establish new definitions -by combining these, the nomenclators have not reflected that they thus -altogether efface the image from the imagination, and the idea from -the understanding. Lastly, these individual designations of colours, -employed to a certain extent as elementary definitions, are not -arranged in the best manner as regards their respective derivation from -each other: hence, the scholar must learn every single designation, -and impress an almost lifeless but positive language on his memory. -The further consideration of this would be too foreign to our present -subject.[1] - - -[1] These remarks have reference to the German mineralogical -terminology.--T. - - - - -LI. - - -PLANTS. - - -617. - -The colours of organic bodies in general may be considered as a higher -kind of chemical operation, for which reason the ancients employed the -word concoction, πέψις, to designate the process. All the elementary -colours, as well as the combined and secondary hues, appear on the -surface of organic productions, while on the other hand, the interior, -if not colourless, appears, strictly speaking, negative when brought to -the light. As we propose to communicate our views respecting organic -nature, to a certain extent, in another place, we only insert here -what has been before connected with the doctrine of colours, while it -may serve as an introduction to the further consideration of the views -alluded to: and first, of plants. - -618. - -Seeds, bulbs, roots, and what is generally shut out from the light, or -immediately surrounded by the earth, appear, for the most part, white. - -619. - -Plants reared from seed, in darkness, are white, or approaching to -yellow. Light, on the other hand, in acting on their colours, acts at -the same time on their form. - -620. - -Plants which grow in darkness make, it is true, long shoots from joint -to joint: but the stems between two joints are thus longer than they -should be; no side stems are produced, and the metamorphosis of the -plant does not take place. - -621. - -Light, on the other hand, places it at once in an active state; the -plant appears green, and the course of the metamorphosis proceeds -uninterruptedly to the period of reproduction. - -622. - -We know that the leaves of the stem are only preparations and -pre-significations of the instruments of florification and -fructification, and accordingly we can already see colours in the -leaves of the stem which, as it were, announce the flower from afar, as -is the case in the amaranthus. - -623. - -There are white flowers whose petals have wrought or refined themselves -to the greatest purity; there are coloured ones, in which the -elementary hues may be said to fluctuate to and fro. There are some -which, in tending to the higher state, have only partially emancipated -themselves from the green of the plant. - -624. - -Flowers of the same genus, and even of the same kind, are found of all -colours. Roses, and particularly mallows, for example, vary through -a great portion of the colorific circle from white to yellow, then -through red-yellow to bright red, and from thence to the darkest hue it -can exhibit as it approaches blue. - -625. - -Others already begin from a higher degree in the scale, as, for -example, the poppy, which is yellow-red in the first instance, and -which afterwards approaches a violet hue. - -626. - -Yet the same colours in species, varieties, and even in families and -classes, if not constant, are still predominant, especially the yellow -colour: blue is throughout rarer. - -627. - -A process somewhat similar takes place in the juicy capsule of -the fruit, for it increases in colour from the green, through the -yellowish and yellow, up to the highest red, the colour of the rind -thus indicating the degree of ripeness. Some are coloured all round, -some only on the sunny side, in which last case the augmentation of the -yellow into red,--the gradations crowding in and upon each other,--may -be very well observed. - -628. - -Many fruits, too, are coloured internally; pure red juices, especially, -are common. - -629. - -The colour which is found superficially in the flower and penetratingly -in the fruit, spreads itself through all the remaining parts, colouring -the roots and the juices of the stem, and this with a very rich and -powerful hue. - -630. - -So, again, the colour of the wood passes from yellow through the -different degrees of red up to pure red and on to brown. Blue woods are -unknown to me; and thus in this degree of organisation the active side -exhibits itself powerfully, although both principles appear balanced in -the general green of the plant. - -631. - -We have seen above that the germ pushing from the earth is generally -white and yellowish, but that by means of the action of light and air -it acquires a green colour. The same happens with young leaves of -trees, as may be seen, for example, in the birch, the young leaves of -which are yellowish, and if boiled, yield a beautiful yellow juice: -afterwards they become greener, while the leaves of other trees become -gradually blue-green. - -632. - -Thus a yellow ingredient appears to belong more essentially to leaves -than a blue one; for this last vanishes in the autumn, and the yellow -of the leaf appears changed to a brown colour. Still more remarkable, -however, are the particular cases where leaves in autumn again become -pure yellow, and others increase to the brightest red. - -633. - -Other plants, again, may, by artificial treatment be entirely converted -to a colouring matter, which is as fine, active, and infinitely -divisible as any other. Indigo and madder, with which so much is -effected, are examples: lichens are also used for dyes. - -634. - -To this fact another stands immediately opposed; we can, namely, -extract the colouring part of plants, and, as it were, exhibit it -apart, while the organisation does not on this account appear to suffer -at all. The colours of flowers may be extracted by spirits of wine, and -tinge it; the petals meanwhile becoming white. - -635. - -There are various modes of acting on flowers and their juices by -re-agents. This has been done by Boyle in many experiments. Roses are -bleached by sulphur, and may be restored to their first state by other -acids; roses are turned green by the smoke of tobacco. - - - - -LII. - - -WORMS, INSECTS, FISHES. - - -636. - -With regard to creatures belonging to the lower degrees of -organisation, we may first observe that worms, which live in the earth -and remain in darkness and cold moisture, are imperfectly negatively -coloured; worms bred in warm moisture and darkness are colourless; -light seems expressly necessary to the definite exhibition of colour. - -637. - -Creatures which live in water, which, although a very dense medium, -suffers sufficient light to pass through it, appear more or less -coloured. Zoophytes, which appear to animate the purest calcareous -earth, are mostly white; yet we find corals deepened into the most -beautiful yellow-red: in other cells of worms this colour increases -nearly to bright red. - -638. - -The shells of the crustaceous tribe are beautifully designed and -coloured, yet it is to be remarked that neither land-snails nor the -shells of crustacea of fresh water, are adorned with such bright -colours as those of the sea. - -639. - -In examining shells, particularly such as are spiral, we find that -a series of animal organs, similar to each other, must have moved -increasingly forward, and in turning on an axis produced the shell in -a series of chambers, divisions, tubes, and prominences, according to -a plan for ever growing larger. We remark, however, that a tinging -juice must have accompanied the development of these organs, a juice -which marked the surface of the shell, probably through the immediate -co-operation of the sea-water, with coloured lines, points, spots, and -shadings: this must have taken place at regular intervals, and thus -left the indications of increasing growth lastingly on the exterior; -meanwhile the interior is generally found white or only faintly -coloured. - -640. - -That such a juice is to be found in shell-fish is, besides, -sufficiently proved by experience; for the creatures furnish it in its -liquid and colouring state: the juice of the ink-fish is an example. -But a much stronger is exhibited in the red juice found in many -shell-fish, which was so famous in ancient times, and has been employed -with advantage by the moderns. There is, it appears, in the entrails of -many of the crustaceous tribe a certain vessel which is filled with a -red juice; this contains a very strong and durable colouring substance, -so much so that the entire creature may be crushed and boiled, and -yet out of this broth a sufficiently strong tinging liquid may be -extracted. But the little vessel filled with colour may be separated -from the animal, by which means of course a concentrated juice is -gained. - -641. - -This juice has the property that when exposed to light and air it -appears first yellowish, then greenish; it then passes to blue, then to -a violet, gradually growing redder; and lastly, by the action of the -sun, and especially if transferred to cambric, it assumes a pure bright -red colour. - -642. - -Thus we should here have an augmentation, even to culmination, on the -_minus_ side, which we cannot easily meet with in inorganic cases; -indeed, we might almost call this example a passage through the -whole scale, and we are persuaded that by due experiments the entire -revolution of the circle might really be effected, for there is no -doubt that by acids duly employed, the pure red may be pushed beyond -the culminating point towards scarlet. - -643. - -This juice appears on the one hand to be connected with the phenomena -of reproduction, eggs being found, the embryos of future shell-fish, -which contain a similar colouring principle. On the other hand, in -animals ranking higher in the scale of being, the secretion appears to -bear some relation to the development of the blood. The blood exhibits -similar properties in regard to colour; in its thinnest state it -appears yellow; thickened, as it is found in the veins, it appears red; -while the arterial blood exhibits a brighter red, probably owing to the -oxydation which takes place by means of breathing. The venous blood -approaches more to violet, and by this mutability denotes the tendency -to that augmentation and progression which are now familiar to us. - -644. - -Before we quit the element whence we derived the foregoing examples, -we may add a few observations on fishes, whose scaly surface is -coloured either altogether in stripes, or in spots, and still oftener -exhibits a certain iridescent appearance, indicating the affinity of -the scales with the coats of shell-fish, mother-of-pearl, and even -the pearl itself. At the same time it should not be forgotten that -warmer climates, the influence of which extends to the watery regions, -produce, embellish, and enhance these colours in fishes in a still -greater degree. - -645. - -In Otaheite, Forster observed fishes with beautifully iridescent -surfaces, and this effect was especially apparent at the moment when -the fish died. We may here call to mind the hues of the chameleon, -and other similar appearances; for when similar facts are presented -together, we are better enabled to trace them. - -646. - -Lastly, although not strictly in the same class, the iridescent -appearance of certain molluscæ may be mentioned, as well as the -phosphorescence which, in some marine creatures, it is said becomes -iridescent just before it vanishes. - -647. - -We now turn our attention to those creatures which belong to light, -air and dry warmth, and it is here that we first find ourselves in -the living region of colours. Here, in exquisitely organised parts, -the elementary colours present themselves in their greatest purity -and beauty. They indicate, however, that the creatures they adorn, -are still low in the scale of organisation, precisely because these -colours can thus appear, as it were, unwrought. Here, too, heat seems -to contribute much to their development. - -648. - -We find insects which may be considered altogether as concentrated -colouring matter; among these, the cochineals especially are -celebrated; with regard to these we observe that their mode of settling -on vegetables, and even nestling in them, at the same time produces -those excrescences which are so useful as mordants in fixing colours. - -649. - -But the power of colour, accompanied by regular organisation, exhibits -itself in the most striking manner in those insects which require a -perfect metamorphosis for their development--in scarabæ, and especially -in butterflies. - -650. - -These last, which might be called true productions of light and air, -often exhibit the most beautiful colours, even in their chrysalis -state, indicating the future colours of the butterfly; a consideration -which, if pursued further hereafter, must undoubtedly afford a -satisfactory insight into many a secret of organised being. - -651. - -If, again, we examine the wings of the butterfly more accurately, and -in its net-like web discover the rudiments of an arm, and observe -further the mode in which this, as it were, flattened arm is covered -with tender plumage and constituted an organ of flying; we believe -we recognise a law according to which the great variety of tints is -regulated. This will be a subject for further investigation hereafter. - -652. - -That, again, heat generally has an influence on the size of the -creature, on the accomplishment of the form, and on the greater beauty -of the colours, hardly needs to be remarked. - - - - -LIII. - - -BIRDS. - - -653. - -The more we approach the higher organisations, the more it becomes -necessary to limit ourselves to a few passing observations; for all the -natural conditions of such organised beings are the result of so many -premises, that, without having at least hinted at these, our remarks -would only appear daring, and at the same time insufficient. - -654. - -We find in plants, that the consummate flower and fruit are, as it -were, rooted in the stem, and that they are nourished by more perfect -juices than the original roots first afforded; we remark, too, -that parasitical plants which derive their support from organised -structures, exhibit themselves especially endowed as to their energies -and qualities. We might in some sense compare the feathers of birds -with plants of this description; the feathers spring up as a last -structural result from the surface of a body which has yet much in -reserve for the completion of the external economy, and thus are very -richly endowed organs. - -655. - -The quills not only grow proportionally to a considerable size, but are -throughout branched, by which means they properly become feathers, and -many of these feathered branches are again subdivided; thus, again, -recalling the structure of plants. - -656. - -The feathers are very different in shape and size, but each still -remains the same organ, forming and transforming itself according to -the constitution of the part of the body from which it springs. - -657. - -With the form, the colour also becomes changed, and a certain law -regulates the general order of hues as well as that particular -distribution by which a single feather becomes party coloured, It -is from this that all combination of variegated plumage arises, and -whence, at last, the eyes in the peacock's tail are produced. It is -a result similar to that which we have already unfolded in treating -of the metamorphosis of plants, and which we shall take an early -opportunity to prove. - -658. - -Although time and circumstances compel us here to pass by this organic -law, yet we are bound to refer to the chemical operations which -commonly exhibit themselves in the tinting of feathers in a mode now -sufficiently known to us. - -659. - -Plumage is of all colours, yet, on the whole, yellow deepening to red -is commoner than blue. - -660. - -The operation of light on the feathers and their colours, is to be -remarked in all cases. Thus, for example, the feathers on the breast of -certain parrots, are strictly yellow; the scale-like anterior portion, -which is acted on by the light, is deepened from yellow to red. The -breast of such a bird appears bright-red, but if we blow into the -feathers the yellow appears. - -661. - -The exposed portion of the feathers is in all cases very different -from that which, in a quiet state, is covered; it is only the exposed -portion, for instance, in ravens, which exhibits the iridescent -appearance; the covered portion does not: from which indication, the -feathers of the tail when ruffled together, may be at once placed in -the natural order again. - - - - -LIV. - - -MAMMALIA AND HUMAN BEINGS. - - -662. - -Here the elementary colours begin to leave us altogether. We are -arrived at the highest degree of the scale, and shall not dwell on its -characteristics long. - -663. - -An animal of this class is distinguished among the examples of -organised being. Every thing that exhibits itself about him is living. -Of the internal structure we do not speak, but confine ourselves -briefly to the surface. The hairs are already distinguished from -feathers, inasmuch as they belong more to the skin, inasmuch as they -are simple, thread-like, not branched. They are however, like feathers, -shorter, longer, softer, and firmer, colourless or coloured, and all -this in conformity to laws which might be defined. - -664. - -White and black, yellow, yellow-red and brown, alternate in various -modifications, but they never appear in such a state as to remind us -of the elementary hues. On the contrary, they are all broken colours -subdued by organic concoction, and thus denote, more or less, the -perfection of life in the being they belong to. - -665. - -One of the most important considerations connected with morphology, -so far as it relates to surfaces, is this, that even in quadrupeds -the spots of the skin have a relation with the parts underneath -them. Capriciously as nature here appears, on a hasty examination, -to operate, she nevertheless consistently observes a secret law. The -development and application of this, it is true, are reserved only for -accurate and careful investigation and sincere co-operation. - -666. - -If in some animals portions appear variegated with positive colours, -this of itself shows how far such creatures are removed from a perfect -organisation; for, it may be said, the nobler a creature is, the more -all the mere material of which he is composed, is disguised by being -wrought together; the more essentially his surface corresponds with the -internal organisation, the less can it exhibit the elementary colours. -Where all tends to make up a perfect whole, any detached specific -developments cannot take place. - -667. - -Of man we have little to say, for he is entirely distinct from the -general physiological results of which we now treat. So much in this -case is in affinity with the internal structure, that the surface can -only be sparingly endowed. - -668. - -When we consider that brutes are rather encumbered than advantageously -provided with intercutaneous muscles; when we see that much that is -superfluous tends to the surface, as, for instance, large ears and -tails, as well as hair, manes, tufts; we see that nature, in such -cases, had much to give away and to lavish. - -669. - -On the contrary, the general surface of the human form is smooth and -clean, and thus in the most perfect examples, the beautiful forms are -apparent; for it may be remarked in passing, that a superfluity of -hair on the chest, arms, and lower limbs, rather indicates weakness -than strength. Poets only have sometimes been induced, probably by the -example of the ferine nature, so strong in other respects, to extol -similar attributes in their rough heroes. - -670. - -But we have here chiefly to speak of colour, and observe that the -colour of the human skin, in all its varieties, is never an elementary -colour, but presents, by means of organic concoction, a highly -complicated result.--Note X. - -671. - -That the colour of the skin and hair has relation with the differences -of character, is beyond question; and we are led to conjecture that the -circumstance of one or other organic system predominating, produces -the varieties we see. A similar hypothesis may be applied to nations, -in which case it might perhaps be observed, that certain colours -correspond with certain confirmations, which has always been observed -of the negro physiognomy. - -672. - -Lastly, we might here consider the problematical question, whether all -human forms and hues are not equally beautiful, and whether custom -and self-conceit are not the causes why one is preferred to another? -We venture, however, after what has been adduced, to assert that the -white man, that is, he whose surface varies from white to reddish, -yellowish, brownish, in short, whose surface appears most neutral in -hue and least inclines to any particular or positive colour, is the -most beautiful. On the same principle a similar point of perfection in -human conformation may be defined hereafter, when the question relates -to form. We do not imagine that this long-disputed question is to be -thus, once for all, settled, for there are persons enough who have -reason to leave this significancy of the exterior in doubt; but we thus -express a conclusion, derived from observation and reflection, such -as might suggest itself to a mind aiming at a satisfactory decision. -We subjoin a few observations connected with the elementary chemical -doctrine of colours.--Note Y. - - - - -LV. - - -PHYSICAL AND CHEMICAL EFFECTS OF THE TRANSMISSION OF LIGHT THROUGH -COLOURED MEDIUMS. - - -673. - -The physical and chemical effects of colourless light are known, so -that it is unnecessary here to describe them at length. Colourless -light exhibits itself under various conditions as exciting warmth, as -imparting a luminous quality to certain bodies, as promoting oxydation -and de-oxydation. In the modes and degrees of these effects many -varieties take place, but no difference is found indicating a principle -of contrast such as we find in the transmission of coloured light. We -proceed briefly to advert to this. - -674. - -Let the temperature of a dark room be observed by means of a very -sensible air-thermometer; if the bulb is then brought to the direct sun -light as it shines into the room, nothing is more natural than that the -fluid should indicate a much higher degree of warmth. If upon this we -interpose coloured glasses, it follows again quite naturally that the -degree of warmth must be lowered; first, because the operation of the -direct light is already somewhat impeded by the glass, and again, more -especially, because a coloured glass, as a dark medium, admits less -light through it. - -675. - -But here a difference in the excitation of warmth exhibits itself to -the attentive observer, according to the colour of the glass. The -yellow and the yellow-red glasses produce a higher temperature than the -blue and blue-red, the difference being considerable. - -676. - -This experiment may be made with the prismatic spectrum. The -temperature of the room being first remarked on the thermometer, the -blue coloured light is made to fall on the bulb, when a somewhat higher -degree of warmth is exhibited, which still increases as the other -colours are gradually brought to act on the mercury. If the experiment -is made with the water-prism, so that the white light can be retained -in the centre, this, refracted indeed, but not yet coloured light, is -the warmest; the other colours, stand in relation to each other as -before. - -677. - -As we here merely describe, without undertaking to deduce or explain -this phenomenon, we only remark in passing, that the pure light is by -no means abruptly and entirely at an end with the red division in the -spectrum, but that a refracted light is still to be observed deviating -from its course and, as it were, insinuating itself beyond the -prismatic image, so that on closer examination it will hardly be found -necessary to take refuge in invisible rays and their refraction. - -678. - -The communication of light by means of coloured mediums exhibits the -same difference. The light communicates itself to Bologna phosphorus -through blue and violet glasses, but by no means through yellow and -yellow-red glasses. It has been even remarked that the phosphori which -have been rendered luminous under violet and blue glasses, become -sooner extinguished when afterwards placed under yellow and yellow-red -glasses than those which have been suffered to remain in a dark room -without any further influence. - -679. - -These experiments, like the foregoing, may also be made by means of the -prismatic spectrum, when the same results take place. - -680. - -To ascertain the effect of coloured light on oxydation and -de-oxydation, the following means may be employed:--Let moist, -perfectly white muriate of silver[1] be spread on a strip of paper; -place it in the light, so that it may become to a certain degree grey, -and then cut it in three portions. Of these, one may be preserved -in a book, as a specimen of this state; let another be placed under -a yellow-red, and the third under a blue-red glass. The last will -become a darker grey, and exhibit a de-oxydation; the other, under the -yellow-red glass, will, on the contrary, become a lighter grey, and -thus approach nearer to the original state of more perfect oxydation. -The change in both may be ascertained by a comparison with the -unaltered specimen. - -681. - -An excellent apparatus has been contrived to perform these experiments -with the prismatic image. The results are analogous to those already -mentioned, and we shall hereafter give the particulars, making use -of the labours of an accurate observer, who has been for some time -carefully prosecuting these experiments.[2] - - -[1] Now generally called chloride of silver: the term in the original -is Hornsilber.--T. - -[2] The individual alluded to was Seebeck: the result of his -experiments was published in the second volume.--T. - - - - -LVI. - - -CHEMICAL EFFECT IN DIOPTRICAL ACHROMATISM. - - -682. - -We first invite our readers to turn to what has been before observed on -this subject (285, 298), to avoid unnecessary repetition here. - -683. - -We can thus give a glass the property of producing much wider coloured -edges without refracting more strongly than before, that is, without -displacing the object much more perceptibly. - -684. - -This property is communicated to the glass by means of metallic oxydes. -Minium, melted and thoroughly united with a pure glass, produces this -effect, and thus flint-glass (291) is prepared with oxyde of lead. -Experiments of this kind have been carried farther, and the so-called -butter of antimony, which, according to a new preparation, may be -exhibited as a pure fluid, has been made use of in hollow lenses and -prisms, producing a very strong appearance of colour with a very -moderate refraction, and presenting the effect which we have called -hyperchromatism in a very vivid manner. - -685. - -In common glass, the alkaline nature obviously preponderates, since -it is chiefly composed of sand and alkaline salts; hence a series of -experiments, exhibiting the relation of perfectly alkaline fluids to -perfect acids, might lead to useful results. - -686. - -For, could the maximum and minimum be found, it would be a question -whether a refracting medium could not be discovered, in which the -increasing and diminishing appearance of colour, (an effect almost -independent of refraction,) could not be done away with altogether, -while the displacement of the object would be unaltered. - -687. - -How desirable, therefore, it would be with regard to this last point, -as well as for the elucidation of the whole of this third division of -our work, and, indeed, for the elucidation of the doctrine of colours -generally, that those who are occupied in chemical researches, with new -views ever opening to them, should take this subject in hand, pursuing -into more delicate combinations what we have only roughly hinted at, -and prosecuting their inquiries with reference to science as a whole. - - - - -PART IV. - - -GENERAL CHARACTERISTICS. - - -688. - -We have hitherto, in a manner forcibly, kept phenomena asunder, -which, partly from their nature, partly in accordance with our mental -habits, have, as it were, constantly sought to be reunited. We have -exhibited them in three divisions. We have considered colours, first, -as transient, the result of an action and re-action in the eye -itself; next, as passing effects of colourless, light-transmitting, -transparent, or opaque mediums on light; especially on the luminous -image; lastly, we arrived at the point where we could securely -pronounce them as permanent, and actually inherent in bodies. - -689. - -In following this order we have as far as possible endeavoured to -define, to separate, and to class the appearances. But now that we -need no longer be apprehensive of mixing or confounding them, we may -proceed, first, to state the general nature of these appearances -considered abstractedly, as an independent circle of facts, and, in the -next place, to show how this particular circle is connected with other -classes of analogous phenomena in nature. - - -THE FACILITY WITH WHICH COLOUR APPEARS. - - -690. - -We have observed that colour under many conditions appears very easily. -The susceptibility of the eye with regard to light, the constant -re-action of the retina against it, produce instantaneously a slight -iridescence. Every subdued light may be considered as coloured, nay, we -ought to call any light coloured, inasmuch as it is seen. Colourless -light, colourless surfaces, are, in some sort, abstract ideas; in -actual experience we can hardly be said to be aware of them.--Note Z. - -691. - -If light impinges on a colourless body, is reflected from it or passes -through it, colour immediately appears; but it is necessary here to -remember what has been so often urged by us, namely, that the leading -conditions of refraction, reflection, &c., are not of themselves -sufficient to produce the appearance. Sometimes, it is true, light acts -with these merely as light, but oftener as a defined, circumscribed -appearance, as a luminous image. The semi-opacity of the medium is -often a necessary condition; while half, and double shadows, are -required for many coloured appearances. In all cases, however, colour -appears instantaneously. We find, again, that by means of pressure, -breathing heat (432, 471), by various kinds of motion and alteration -on smooth clean surfaces (461), as well as on colourless fluids (470), -colour is immediately produced. - -692. - -The slightest change has only to take place in the component parts -of bodies, whether by immixture with other particles or other such -effects, and colour either makes its appearance or becomes changed. - - -THE FORCE OF COLOUR. - - -693. - -The physical colours, and especially those of the prism, were formerly -called "_colores emphatici_," on account of their extraordinary beauty -and force. Strictly speaking, however, a high degree of effect may be -ascribed to all appearances of colour, assuming that they are exhibited -under the purest and most perfect conditions. - -694. - -The dark nature of colour, its full rich quality, is what produces -the grave, and at the same time fascinating impression we sometimes -experience, and as colour is to be considered a condition of light, -so it cannot dispense with light as the co-operating cause of its -appearance, as its basis or ground; as a power thus displaying and -manifesting colour. - - -THE DEFINITE NATURE OF COLOUR. - - -695. - -The existence and the relatively definite character of colour are one -and the same thing. Light displays itself and the face of nature, as -it were, with a general indifference, informing us as to surrounding -objects perhaps devoid of interest or importance; but colour is at all -times specific, characteristic, significant. - -696. - -Considered in a general point of view, colour is determined towards one -of two sides. It thus presents a contrast which we call a polarity, and -which we may fitly designate by the expressions _plus_ and _minus_. - - _Plus. Minus_. - - Yellow. Blue. - Action. Negation.[1] - Light. Shadow. - Brightness. Darkness. - Force. Weakness. - Warmth. Coldness. - Proximity. Distance. - Repulsion Attraction. - Affinity with acids. Affinity with alkalis. - - -COMBINATION OF THE TWO PRINCIPLES. - - -697. - -If these specific, contrasted principles are combined, the respective -qualities do not therefore destroy each other: for if in this -intermixture the ingredients are so perfectly balanced that neither -is to be distinctly recognised, the union again acquires a specific -character; it appears as a quality by itself in which we no longer -think of combination. This union we call green. - -698. - -Thus, if two opposite phenomena springing from the same source do not -destroy each other when combined, but in their union present a third -appreciable and pleasing appearance, this result at once indicates -their harmonious relation. The more perfect result yet remains to be -adverted to. - - -AUGMENTATION TO RED. - - -699. - -Blue and yellow do not admit of increased intensity without presently -exhibiting a new appearance in addition to their own. Each colour, in -its lightest state, is a dark; if condensed it must become darker, but -this effect no sooner takes place than the hue assumes an appearance -which we designate by the word reddish. - -700. - -This appearance still increases, so that when the highest degree of -intensity is attained it predominates over the original hue. A powerful -impression of light leaves the sensation of red on the retina. In the -prismatic yellow-red which springs directly from the yellow, we hardly -recognise the yellow. - -701. - -This deepening takes place again by means of colourless -semi-transparent mediums, and here we see the effect in its utmost -purity and extent. Transparent fluids, coloured with any given hues, in -a series of glass-vessels, exhibit it very strikingly. The augmentation -is unremittingly rapid and constant; it is universal, and obtains in -physiological as well as in physical and chemical colours. - - -JUNCTION OF THE TWO AUGMENTED EXTREMES. - - -702. - -As the extremes of the simple contrast produce a beautiful and -agreeable appearance by their union, so the deepened extremes on being -united, will present a still more fascinating colour; indeed, it might -naturally be expected that we should here find the acme of the whole -phenomenon. - -COMPLETENESS THE RESULT OF VARIETY. - - -703. - -And such is the fact, for pure red appears; a colour to which, from its -excellence, we have appropriated the term "purpur."[2] - -704. - -There are various modes in which pure red may appear. By bringing -together the violet edge and yellow-red border in prismatic -experiments, by continued augmentation in chemical operations, and by -the organic contrast in physiological effects. - -705. - -As a pigment it cannot be produced by intermixture or union, but -only by arresting the hue in substances chemically acted on, at the -high culminating point. Hence the painter is justified in assuming -that there are _three_ primitive colours from which he combines all -the others. The natural philosopher, on the other hand, assumes only -_two_ elementary colours, from which he, in like manner, developes and -combines the rest. - - -COMPLETENESS THE RESULT OF VARIETY IN COLOUR. - - -706. - -The various appearances of colour arrested in their different degrees, -and seen in juxtaposition, produce a whole. This totality is harmony to -the eye. - -707. - -The chromatic circle has been gradually presented to us; the -various relations of its progression are apparent to us. Two pure -original principles in contrast, are the foundation of the whole; -an augmentation manifests itself by means of which both approach a -third state; hence there exists on both sides a lowest and highest, -a simplest and most qualified state. Again, two combinations present -themselves; first that of the simple primitive contrasts, then that of -the deepened contrasts. - - -HARMONY OF THE COMPLETE STATE. - - -708. - -The whole ingredients of the chromatic scale, seen in juxtaposition, -produce an harmonious impression on the eye. The difference between the -physical contrast and harmonious opposition in all its extent should -not be overlooked. The first resides in the pure restricted original -dualism, considered in its antagonizing elements; the other results -from the fully developed effects of the complete state. - -709. - -Every single opposition in order to be harmonious must comprehend the -whole. The physiological experiments are sufficiently convincing -on this point. A development of all the possible contrasts of the -chromatic scale will be shortly given.[3] - - -FACILITY WITH WHICH COLOUR MAY BE MADE TO TEND EITHER TO THE PLUS OR -MINUS SIDE. - - -710. - -We have already had occasion to take notice of the mutability of colour -in considering its so-called augmentation and progressive variations -round the whole circle; but the hues even pass and repass from one side -to the other, rapidly and of necessity. - -711. - -Physiological colours are different in appearance as they happen -to fall on a dark or on a light ground. In physical colours the -combination of the objective and subjective experiments is very -remarkable. The epoptical colours, it appears, are contrasted according -as the light shines through or upon them. To what extent the chemical -colours may be changed by fire and alkalis, has been sufficiently shown -in its proper place. - - -EVANESCENCE OF COLOUR. - - -712. - -All that has been adverted to as subsequent to the rapid excitation -and definition of colour, immixture, augmentation, combination, -separation, not forgetting the law of compensatory harmony, all takes -place with the greatest rapidity and facility; but with equal quickness -colour again altogether disappears. - -713. - -The physiological appearances are in no wise to be arrested; the -physical last only as long as the external condition lasts; even the -chemical colours have great mutability, they may be made to pass and -repass from one side to the other by means of opposite re-agents, and -may even be annihilated altogether. - - -PERMANENCE OF COLOUR. - - -714. - -The chemical colours afford evidence of very great duration. Colours -fixed in glass by fusion, and by nature in gems, defy all time and -re-action. - -715. - -The art of dyeing again fixes colour very powerfully. The hues of -pigments which might otherwise be easily rendered mutable by re-agents, -may be communicated to substances in the greatest permanency by means -of mordants. - - -[1] Wirkung, Beraubung; the last would be more literally rendered -_privation_. The author has already frequently made use of the terms -_active_ and _passive_ as equivalent to _plus_ and _minus_.--T. - -[2] Wherever this word occurs incidentally it is translated _pure red_, -the English word _purple_ being generally employed to denote a colour -similar to violet.--T. - -[3] No diagram or table of this kind was ever given by the author.--T. - - - - -PART V. - - -RELATION TO OTHER PURSUITS--RELATION TO PHILOSOPHY. - - -716. - -The investigator of nature cannot be required to be a philosopher, -but it is expected that he should so far have attained the habit of -philosophizing, as to distinguish himself essentially from the world, -in order to associate himself with it again in a higher sense. He -should form to himself a method in accordance with observation, but -he should take heed not to reduce observation to mere notion, to -substitute words for this notion, and to use and deal with these words -as if they were things. He should be acquainted with the labours of -philosophers, in order to follow up the phenomena which have been the -subject of his observation, into the philosophic region. - -717. - -It cannot be required that the philosopher should be a naturalist, and -yet his co-operation in physical researches is as necessary as it is -desirable. He needs not an acquaintance with details for this, but only -a clear view of those conclusions where insulated facts meet. - -718. - -We have before (175) alluded to this important consideration, and -repeat it here where it is in its place. The worst that can happen -to physical science as well as to many other kinds of knowledge is, -that men should treat a secondary phenomenon as a primordial one, and -(since it is impossible to derive the original fact from the secondary -state), seek to explain what is in reality the cause by an effect made -to usurp its place. Hence arises an endless confusion, a mere verbiage, -a constant endeavour to seek and to find subterfuges whenever truth -presents itself and threatens to be overpowering. - -719. - -While the observer, the investigator of nature, is thus dissatisfied -in finding that the appearances he sees still contradict a received -theory, the philosopher can calmly continue to operate in his abstract -department on a false result, for no result is so false but that it can -be made to appear valid, as form without substance, by some means or -other. - -720. - -If, on the other hand, the investigator of nature can attain to the -knowledge of that which we have called a primordial phenomenon, he is -safe; and the philosopher with him. The investigator of nature is -safe, since he is persuaded that he has here arrived at the limits -of his science, that he finds himself at the height of experimental -research; a height whence he can look back upon the details of -observation in all its steps, and forwards into, if he cannot enter, -the regions of theory. The philosopher is safe, for he receives -from the experimentalist an ultimate fact, which, in his hands, now -becomes an elementary one. He now justly pays little attention to -appearances which are understood to be secondary, whether he already -finds them scientifically arranged, or whether they present themselves -to his casual observation scattered and confused. Should he even be -inclined to go over this experimental ground himself, and not be -averse to examination in detail, he does this conveniently, instead of -lingering too long in the consideration of secondary and intermediate -circumstances, or hastily passing them over without becoming accurately -acquainted with them. - -721. - -To place the doctrine of colours nearer, in this sense, within the -philosopher's reach, was the author's wish; and although the execution -of his purpose, from various causes, does not correspond with his -intention, he will still keep this object in view in an intended -recapitulation, as well as in the polemical and historical portions of -his work; for he will have to return to the consideration of this point -hereafter, on an occasion where it will be necessary to speak with less -reserve. - - -RELATION TO MATHEMATICS. - - -722. - -It may be expected that the investigator of nature, who proposes to -treat the science of natural philosophy in its entire range, should be -a mathematician. In the middle ages, mathematics was the chief organ by -means of which men hoped to master the secrets of nature, and even now, -geometry in certain departments of physics, is justly considered of -first importance. - -723. - -The author can boast of no attainments of this kind, and on this -account confines himself to departments of science which are -independent of geometry; departments which in modern times have been -opened up far and wide. - -724. - -It will be universally allowed that mathematics, one of the noblest -auxiliaries which can be employed by man, has, in one point of view, -been of the greatest use to the physical sciences; but that, by a -false application of its methods, it has, in many respects, been -prejudicial to them, is also not to be denied; we find it here and -there reluctantly admitted. - -725. - -The theory of colours, in particular, has suffered much, and its -progress has been incalculably retarded by having been mixed up with -optics generally, a science which cannot dispense with mathematics; -whereas the theory of colours, in strictness, may be investigated quite -independently of optics. - -726. - -But besides this there was an additional evil. A great mathematician -was possessed with an entirely false notion on the physical origin of -colours; yet, owing to his great authority as a geometer, the mistakes -which he committed as an experimentalist long became sanctioned in the -eyes of a world ever fettered in prejudices. - -727. - -The author of the present inquiry has endeavoured throughout to keep -the theory of colours distinct from the mathematics, although there -are evidently certain points where the assistance of geometry would be -desirable. Had not the unprejudiced mathematicians, with whom he has -had, or still has, the good fortune to be acquainted, been prevented -by other occupations from making common cause with him, his work would -not have wanted some merit in this respect. But this very want may be -in the end advantageous, since it may now become the object of the -enlightened mathematician to ascertain where the doctrine of colours is -in need of his aid, and how he can contribute the means at his command -with a view to the complete elucidation of this branch of physics. - -728. - -In general it were to be wished that the Germans, who render such -good service to science, while they adopt all that is good from other -nations, could by degrees accustom themselves to work in concert. We -live, it must be confessed, in an age, the habits of which are directly -opposed to such a wish. Every one seeks, not only to be original in -his views, but to be independent of the labours of others, or at least -to persuade himself that he is so, even in the course of his life -and occupation. It is very often remarked that men who undoubtedly -have accomplished much, quote themselves only, their own writings, -journals, and compendiums; whereas it would be far more advantageous -for the individual, and for the world, if many were devoted to a common -pursuit. The conduct of our neighbours the French is, in this respect, -worthy of imitation; we have a pleasing instance in Cuvier's preface -to his "Tableau Élémentaire de l'Histoire Naturelle des Animaux." - -729. - -He who has observed science and its progress with an unprejudiced eye, -might even ask whether it is desirable that so many occupations and -aims, though allied to each other, should be united in one person, and -whether it would not be more suitable for the limited powers of the -human mind to distinguish, for example, the investigator and inventor, -from him who employs and applies the result of experiment? Astronomers, -who devote themselves to the observation of the heavens and the -discovery or enumeration of stars, have in modern times formed, to a -certain extent, a distinct class from those who calculate the orbits, -consider the universe in its connexion, and more accurately define its -laws. The history of the doctrine of colours will often lead us back to -these considerations. - - -RELATION TO THE TECHNICAL OPERATIONS OF THE DYER. - - -730. - -If in our labours we have gone out of the province of the -mathematician, we have, on the other hand, endeavoured to meet the -practical views of the dyer; and although the chapter which treats -of colour in a chemical point of view is not the most complete and -circumstantial, yet in that portion, as well as in our general -observations respecting colour, the dyer will find his views assisted -far more than by the theory hitherto in vogue, which failed to afford -him any assistance. - -731. - -It is curious, in this view, to take a glance at the works containing -directions on the art of dyeing. As the Catholic, on entering his -temple, sprinkles himself with holy water, and after bending the knee, -proceeds perhaps to converse with his friends on his affairs, without -any especial devotion; so all the treatises on dyeing begin with a -respectful allusion to the accredited theory, without afterwards -exhibiting a single trace of any principle deduced from this theory, -or showing that it has thrown light on any part of the art, or that it -offers any useful hints in furtherance of practical methods. - -732. - -On the other hand, there are men who, after having become thoroughly -and experimentally acquainted with the nature of dyes, have not been -able to reconcile their observations with the received theory; who -have, in short, discovered its weak points, and sought for a general -view more consonant to nature and experience. When we come to the names -of Castel and Gülich, in our historical review, we shall have occasion -to enter into this more fully, and an opportunity will then present -itself to show that an assiduous experience in taking advantage of -every accident may, in fact, be said almost to exhaust the knowledge -of the province to which it is confined. The high and complete result -is then submitted to the theorist, who, if he examines facts with -accuracy, and reasons with candour, will find such materials eminently -useful as a basis for his conclusions.--Note A A. - - -RELATION TO PHYSIOLOGY AND PATHOLOGY. - - -733. - -If the phenomena adduced in the chapter where colours were considered -in a physiological and pathological view are for the most part -generally known, still some new views, mixed up with them, will not be -unacceptable to the physiologist. We especially hope to have given him -cause to be satisfied by classing certain phenomena which stood alone, -under analogous facts, and thus, in some measure, to have prepared the -way for his further investigations. - -734. - -The appendix on pathological colours, again, is admitted to be scanty -and unconnected. We reflect, however, that Germany can boast of men who -are not only highly experienced in this department, but are likewise so -distinguished for general cultivation, that it can cost them but little -to revise this portion, to complete what has been sketched, and at the -same time to connect it with the higher facts of organisation. - - -RELATION TO NATURAL HISTORY. - - -735. - -If we may at all hope that natural history will gradually be modified -by the principle of deducing the ordinary appearances of nature from -higher phenomena, the author believes he may have given some hints -and introductory views bearing on this object also. As colour, in its -infinite variety, exhibits itself on the surface of living beings, it -becomes an important part of the outward indications, by means of which -we can discover what passes underneath. - -736. - -In one point of view it is certainly not to be too much relied on, on -account of its indefinite and mutable nature; yet even this mutability, -inasmuch as it exhibits itself as a constant quality, again becomes -a criterion of a mutable vitality; and the author wishes nothing -more than that time may be granted him to develop the results of his -observations on this subject more fully; here they would not be in -their place. - - -RELATION TO GENERAL PHYSICS. - - -737. - -The state in which general physics now is, appears, again, particularly -favourable to our labours; for natural philosophy, owing to -indefatigable and variously directed research, has gradually attained -such eminence, that it appears not impossible to refer a boundless -empiricism to one centre. - -738. - -Without referring to subjects which are too far removed from our own -province, we observe that the formulæ under which the elementary -appearances of nature are expressed, altogether tend in this direction; -and it is easy to see that through this correspondence of expression, a -correspondence in meaning will necessarily be soon arrived at. - -739. - -True observers of nature, however they may differ in opinion in other -respects, will agree that all which presents itself as appearance, all -that we meet with as phenomenon, must either indicate an original -division which is capable of union, or an original unity which admits -of division, and that the phenomenon will present itself accordingly. -To divide the united, to unite the divided, is the life of nature; -this is the eternal systole and diastole, the eternal collapsion and -expansion, the inspiration and expiration of the world in which we live -and move. - -740. - -It is hardly necessary to observe that what we here express as number -and restrict to dualism is to be understood in a higher sense; the -appearance of a third, a fourth order of facts progressively developing -themselves is to be similarly understood; but actual observation -should, above all, be the basis of all these expressions. - -741. - -Iron is known to us as a peculiar substance, different from other -substances: in its ordinary state we look upon it as a mere material -remarkable only on account of its fitness for various uses and -applications. How little, however, is necessary to do away with the -comparative insignificancy of this substance. A two-fold power is -called forth,[1] which, while it tends again to a state of union, and, -as it were, seeks itself, acquires a kind of magical relation with -its like, and propagates this double property, which is in fact but a -principle of reunion, throughout all bodies of the same kind. We here -first observe the mere substance, iron; we see the division that takes -place in it propagate itself and disappear, and again easily become -re-excited. This, according to our mode of thinking, is a primordial -phenomenon in immediate relation with its idea, and which acknowledges -nothing earthly beyond it. - -742. - -Electricity is again peculiarly characterised. As a mere quality we are -unacquainted with it; for us it is a nothing, a zero, a mere point, -which, however, dwells in all apparent existences, and at the same time -is the point of origin whence, on the slightest stimulus, a double -appearance presents itself, an appearance which only manifests itself -to vanish. The conditions under which this manifestation is excited -are infinitely varied, according to the nature of particular bodies. -From the rudest mechanical friction of very different substances with -one another, to the mere contiguity of two entirely similar bodies, -the phenomenon is present and stirring, nay, striking and powerful, -and so decided and specific, that when we employ the terms or formulæ -polarity, plus and minus, for north and south, for glass and resin, we -do so justifiably and in conformity with nature. - -743. - -This phenomenon, although it especially affects the surface, is yet by -no means superficial. It influences the tendency or determination of -material qualities, and connects itself in immediate co-operation with -the important double phenomenon which takes place so universally in -chemistry,--oxydation, and de-oxydation. - -744. - -To introduce and include the appearances of colour in this series, -this circle of phenomena was the object of our labours. What we have -not succeeded in others will accomplish. We found a primordial vast -contrast between light and darkness, which may be more generally -expressed by light and its absence. We looked for the intermediate -state, and sought by means of it to compose the visible world of light, -shade, and colour. In the prosecution of this we employed various terms -applicable to the development of the phenomena, terms which we adopted -from the theories of magnetism, of electricity, and of chemistry. It -was necessary, however, to extend this terminology, since we found -ourselves in an abstract region, and had to express more complicated -relations. - -745. - -If electricity and galvanism, in their general character, are -distinguished as superior to the more limited exhibition of magnetic -phenomena, it may be said that colour, although coming under similar -laws, is still superior; for since it addresses itself to the noble -sense of vision, its perfections are more generally displayed. Compare -the varied effects which result from the augmentation of yellow and -blue to red, from the combination of these two higher extremes to pure -red, and the union of the two inferior extremes to green. What a far -more varied scheme is apparent here than that in which magnetism and -electricity are comprehended. These last phenomena may be said to be -inferior again on another account; for though they penetrate and give -life to the universe, they cannot address themselves to man in a higher -sense in order to his employing them æsthetically. The general, simple, -physical law must first be elevated and diversified itself in order to -be available for elevated uses. - -746. - -If the reader, in this spirit, recalls what has been stated by us -throughout, generally and in detail, with regard to colour, he will -himself pursue and unfold what has been here only lightly hinted at. -He will augur well for science, technical processes, and art, if it -should prove possible to rescue the attractive subject of the doctrine -of colours from the atomic restriction and isolation in which it has -been banished, in order to restore it to the general dynamic flow of -life and action which the present age loves to recognise in nature. -These considerations will press upon us more strongly when, in the -historical portion, we shall have to speak of many an enterprising -and intelligent man who failed to possess his contemporaries with his -convictions. - - -RELATION TO THE THEORY OF MUSIC. - - -747. - -Before we proceed to the moral associations of colour, and the æsthetic -influences arising from them, we have here to say a few words on its -relation to melody. That a certain relation exists between the two, -has been always felt; this is proved by the frequent comparisons we -meet with, sometimes as passing allusions, sometimes as circumstantial -parallels. The error which writers have fallen into in trying to -establish this analogy we would thus define: - -748. - -Colour and sound do not admit of being directly compared together -in any way, but both are referable to a higher formula, both are -derivable, although each for itself, from this higher law. They are -like two rivers which have their source in one and the same mountain, -but subsequently pursue their way under totally different conditions -in two totally different regions, so that throughout the whole course -of both no two points can be compared. Both are general, elementary -effects acting according to the general law of separation and tendency -to union, of undulation and oscillation, yet acting thus in wholly -different provinces, in different modes, on different elementary -mediums, for different senses.--Note B B. - -749. - -Could some investigator rightly adopt the method in which we have -connected the doctrine of colours with natural philosophy generally, -and happily supply what has escaped or been missed by us, the theory -of sound, we are persuaded, might be perfectly connected with general -physics: at present it stands, as it were, isolated within the circle -of science. - -750. - -It is true it would be an undertaking of the greatest difficulty -to do away with the positive character which we are now accustomed -to attribute to music--a character resulting from the achievements -of practical skill, from accidental, mathematical, æsthetical -influences--and to substitute for all this a merely physical inquiry -tending to resolve the science into its first elements. Yet considering -the point at which science and art are now arrived, considering the -many excellent preparatory investigations that have been made relative -to this subject, we may perhaps still see it accomplished. - - -CONCLUDING OBSERVATIONS ON TERMINOLOGY. - - -751. - -We never sufficiently reflect that a language, strictly speaking, can -only be symbolical and figurative, that it can never express things -directly, but only, as it were, reflectedly. This is especially the -case in speaking of qualities which are only imperfectly presented -to observation, which might rather be called powers than objects, -and which are ever in movement throughout nature. They are not to be -arrested, and yet we find it necessary to describe them; hence we look -for all kinds of formulæ in order, figuratively at least, to define -them. - -752. - -Metaphysical formulæ have breadth as well as depth, but on this -very account they require a corresponding import; the danger -here is vagueness. Mathematical expressions may in many cases be -very conveniently and happily employed, but there is always an -inflexibility in them, and we presently feel their inadequacy; for even -in elementary cases we are very soon conscious of an incommensurable -idea; they are, besides, only intelligible to those who are especially -conversant in the sciences to which such formulæ are appropriated. The -terms of the science of mechanics are more addressed to the ordinary -mind, but they are ordinary in other senses, and always have something -unpolished; they destroy the inward life to offer from without an -insufficient substitute for it. The formulæ of the corpuscular theories -are nearly allied to the last; through them the mutable becomes rigid, -description and expression uncouth: while, again, moral terms, which -undoubtedly can express nicer relations, have the effect of mere -symbols in the end, and are in danger of being lost in a play of wit. - -753. - -If, however, a writer could use all these modes of description and -expression with perfect command, and thus give forth the result of his -observations on the phenomena of nature in a diversified language; -if he could preserve himself from predilections, still embodying a -lively meaning in as animated an expression, we might look for much -instruction communicated in the most agreeable of forms. - -754. - -Yet, how difficult it is to avoid substituting the sign for the thing; -how difficult to keep the essential quality still living before us, -and not to kill it with the word. With all this, we are exposed in -modern times to a still greater danger by adopting expressions and -terminologies from all branches of knowledge and science to embody our -views of simple nature. Astronomy, cosmology, geology, natural history, -nay religion and mysticism, are called in in aid; and how often do -we not find a general idea and an elementary state rather hidden and -obscured than elucidated and brought nearer to us by the employment of -terms, the application of which is strictly specific and secondary. -We are quite aware of the necessity which led to the introduction and -general adoption of such a language, we also know that it has become in -a certain sense indispensable; but it is only a moderate, unpretending -recourse to it, with an internal conviction of its fitness, that can -recommend it. - -755. - -After all, the most desirable principle would be that writers should -borrow the expressions employed to describe the details of a given -province of investigation from the province itself; treating the -simplest phenomenon as an elementary formula, and deriving and -developing the more complicated designations from this. - -756. - -The necessity and suitableness of such a conventional language where -the elementary sign expresses the appearance itself, has been duly -appreciated by extending, for instance, the application of the term -polarity, which is borrowed from the magnet to electricity, &c. The -_plus_ and _minus_ which may be substituted for this, have found as -suitable an application to many phenomena; even the musician, probably -without troubling himself about these other departments, has been -naturally led to express the leading difference in the modes of melody -by _major_ and _minor_. - -757. - -For ourselves we have long wished to introduce the term polarity into -the doctrine of colours; with what right and in what sense, the present -work may show. Perhaps we may hereafter find room to connect the -elementary phenomena together according to our mode, by a similar use -of symbolical terms, terms which must at all times convey the directly -corresponding idea; we shall thus render more explicit what has been -here only alluded to generally, and perhaps too vaguely expressed. - - -[1] Eine Entzweyung geht vor; literally, _a division takes place_. -According to some, the two magnetic powers are previously in the bar, -and are then separated at the ends.--T. - - - - -PART VI. - - -EFFECT OF COLOUR WITH REFERENCE TO MORAL ASSOCIATIONS. - - -758. - -Since colour occupies so important a place in the series of elementary -phenomena, filling as it does the limited circle assigned to it with -fullest variety, we shall not be surprised to find that its effects are -at all times decided and significant, and that they are immediately -associated with the emotions of the mind. We shall not be surprised -to find that these appearances presented singly, are specific, that -in combination they may produce an harmonious, characteristic, often -even an inharmonious effect on the eye, by means of which they act on -the mind; producing this impression in their most general elementary -character, without relation to the nature or form of the object on -whose surface they are apparent. Hence, colour considered as an element -of art, may be made subservient to the highest æsthetical ends.--Note C -C. - -759. - -People experience a great delight in colour, generally. The eye -requires it as much as it requires light. We have only to remember -the refreshing sensation we experience, if on a cloudy day the sun -illumines a single portion of the scene before us and displays its -colours. That healing powers were ascribed to coloured gems, may have -arisen from the experience of this indefinable pleasure. - -760. - -The colours which we see on objects are not qualities entirely -strange to the eye; the organ is not thus merely habituated to the -impression; no, it is always predisposed to produce colour of itself, -and experiences a sensation of delight if something analogous to its -own nature is offered to it from without; if its susceptibility is -distinctly determined towards a given state. - -761. - -From some of our earlier observations we can conclude, that general -impressions produced by single colours cannot be changed, that they act -specifically, and must produce definite, specific states in the living -organ. - -762. - -They likewise produce a corresponding influence on the mind. Experience -teaches us that particular colours excite particular states of feeling. -It is related of a witty Frenchman, "Il prétendoit que son ton de -conversation avec Madame étoit changé depuis qu'elle avoit changé en -cramoisi le meuble de son cabinet, qui étoit bleu." - -763. - -In order to experience these influences completely, the eye should be -entirely surrounded with one colour; we should be in a room of one -colour, or look through a coloured glass. We are then identified with -the hue, it attunes the eye and mind in mere unison with itself. - -764. - -The colours on the _plus_ side are yellow, red-yellow (orange), -yellow-red (minium, cinnabar). The feelings they excite are quick, -lively, aspiring. - - -YELLOW. - - -765. - -This is the colour nearest the light. It appears on the slightest -mitigation of light, whether by semi-transparent mediums or faint -reflection from white surfaces. In prismatic experiments it extends -itself alone and widely in the light space, and while the two poles -remain separated from each other, before it mixes with blue to -produce green it is to be seen in its utmost purity and beauty. How -the chemical yellow developes itself in and upon the white, has been -circumstantially described in its proper place. - -766. - -In its highest purity it always carries with it the nature of -brightness, and has a serene, gay, softly exciting character. - -767. - -In this state, applied to dress, hangings, carpeting, &c., it is -agreeable. Gold in its perfectly unmixed state, especially when the -effect of polish is superadded, gives us a new and high idea of this -colour; in like manner, a strong yellow, as it appears on satin, has a -magnificent and noble effect. - -768. - -We find from experience, again, that yellow excites a warm and -agreeable impression. Hence in painting it belongs to the illumined and -emphatic side. - -769. - -This impression of warmth may be experienced in a very lively manner if -we look at a landscape through a yellow glass, particularly on a grey -winter's day. The eye is gladdened, the heart expanded and cheered, a -glow seems at once to breathe towards us. - -770. - -If, however, this colour in its pure and bright state is agreeable -and gladdening, and in its utmost power is serene and noble, it is, on -the other hand, extremely liable to contamination, and produces a very -disagreeable effect if it is sullied, or in some degree tends to the -_minus_ side. Thus, the colour of sulphur, which inclines to green, has -a something unpleasant in it. - -771. - -When a yellow colour is communicated to dull and coarse surfaces, -such as common cloth, felt, or the like, on which it does not appear -with full energy, the disagreeable effect alluded to is apparent. By -a slight and scarcely perceptible change, the beautiful impression -of fire and gold is transformed into one not undeserving the epithet -foul; and the colour of honour and joy reversed to that of ignominy -and aversion. To this impression the yellow hats of bankrupts and the -yellow circles on the mantles of Jews, may have owed their origin. - - -RED-YELLOW. - - -772. - -As no colour can be considered as stationary, so we can very easily -augment yellow into reddish by condensing or darkening it. The colour -increases in energy, and appears in red-yellow more powerful and -splendid. - -773. - -All that we have said of yellow is applicable here in a higher -degree. The red-yellow gives an impression of warmth and gladness, -since it represents the hue of the intenser glow of fire, and of the -milder radiance of the setting sun. Hence it is agreeable around us, -and again, as clothing, in greater or less degrees is cheerful and -magnificent. A slight tendency to red immediately gives a new character -to yellow, and while the English and Germans content themselves -with bright pale yellow colours in leather, the French, as Castel -has remarked, prefer a yellow enhanced to red; indeed, in general, -everything in colour is agreeable to them which belongs to the active -side. - - -YELLOW-RED. - - -774. - -As pure yellow passes very easily to red-yellow, so the deepening of -this last to yellow-red is not to be arrested. The agreeable, cheerful -sensation which red-yellow excites, increases to an intolerably -powerful impression in bright yellow-red. - -775, - -The active side is here in its highest energy, and it is not to -be wondered at that impetuous, robust, uneducated men, should be -especially pleased with this colour. Among savage nations the -inclination for it has been universally remarked, and when children, -left to themselves, begin to use tints, they never spare vermilion and -minium. - -776. - -In looking steadfastly at a perfectly yellow-red surface, the colour -seems actually to penetrate the organ. It produces an extreme -excitement, and still acts thus when somewhat darkened. A yellow-red -cloth disturbs and enrages animals. I have known men of education to -whom its effect was intolerable if they chanced to see a person dressed -in a scarlet cloak on a grey, cloudy day. - -777. - -The colours on the _minus_ side are blue, red-blue, and blue-red. They -produce a restless, susceptible, anxious impression. - - -BLUE. - - -778. - -As yellow is always accompanied with light, so it may be said that blue -still brings a principle of darkness with it. - -779. - -This colour has a peculiar and almost indescribable effect on the eye. -As a hue it is powerful, but it is on the negative side, and in its -highest purity is, as it were, a stimulating negation. Its appearance, -then, is a kind of contradiction between excitement and repose. - -780. - -As the upper sky and distant mountains appear blue, so a blue surface -seems to retire from us. - -781. - -But as we readily follow an agreeable object that flies from us, so we -love to contemplate blue, not because it advances to us, but because it -draws us after it. - -782. - -Blue gives us an impression of cold, and thus, again, reminds us of -shade. We have before spoken of its affinity with black. - -783. - -Rooms which are hung with pure blue, appear in some degree larger, but -at the same time empty and cold. - -784. - -The appearance of objects seen through a blue glass is gloomy and -melancholy. - -785. - -When blue partakes in some degree of the _plus_ side, the effect is not -disagreeable. Sea-green is rather a pleasing colour. - - -RED-BLUE. - - -786. - -We found yellow very soon tending to the intense state, and we observe -the same progression in blue. - -787. - -Blue deepens very mildly into red, and thus acquires a somewhat active -character, although it is on the passive side. Its exciting power is, -however, of a very different kind from that of the red-yellow. It may -be said to disturb rather than enliven. - -788. - -As augmentation itself is not to be arrested, so we feel an inclination -to follow the progress of the colour, not, however, as in the case of -the red-yellow, to see it still increase in the active sense, but to -find a point to rest in. - -789. - -In a very attenuated state, this colour is known to us under the name -of lilac; but even in this degree it has a something lively without -gladness. - -790. - -This unquiet feeling increases as the hue progresses, and it may be -safely assumed, that a carpet of a perfectly pure deep blue-red would -be intolerable. On this account, when it is used for dress, ribbons, or -other ornaments, it is employed in a very attenuated and light state, -and thus displays its character as above defined, in a peculiarly -attractive manner. - -791. - -As the higher dignitaries of the church have appropriated this unquiet -colour to themselves, we may venture to say that it unceasingly aspires -to the cardinal's red through the restless degrees of a still impatient -progression. - - -RED. - - -792. - -We are here to forget everything that borders on yellow or blue. We -are to imagine an absolutely pure red, like fine carmine suffered to -dry on white porcelain. We have called this colour "purpur" by way -of distinction, although we are quite aware that the purple of the -ancients inclined more to blue. - -793. - -Whoever is acquainted with the prismatic origin of red, will not think -it paradoxical if we assert that this colour partly _actu_, partly -_potentiâ_, includes all the other colours. - -794. - -We have remarked a constant progress or augmentation in yellow and -blue, and seen what impressions were produced by the various states; -hence it may naturally be inferred that now, in the junction of the -deepened extremes, a feeling of satisfaction must succeed; and thus, in -physical phenomena, this highest of all appearances of colour arises -from the junction of two contrasted extremes which have gradually -prepared themselves for a union. - -795. - -As a pigment, on the other hand, it presents itself to us already -formed, and is most perfect as a hue in cochineal; a substance which, -however, by chemical action may be made to tend to the _plus_ or the -_minus_ side, and may be considered to have attained the central point -in the best carmine. - -796. - -The effect of this colour is as peculiar as its nature. It conveys an -impression of gravity and dignity, and at the same time of grace and -attractiveness. The first in its dark deep state, the latter in its -light attenuated tint; and thus the dignity of age and the amiableness -of youth may adorn itself with degrees of the same hue. - -797. - -History relates many instances of the jealousy of sovereigns with -regard to the quality of red. Surrounding accompaniments of this colour -have always a grave and magnificent effect. - -798. - -The red glass exhibits a bright landscape in so dreadful a hue as to -inspire sentiments of awe. - -799. - -Kermes and cochineal, the two materials chiefly employed in dyeing to -produce this colour, incline more or less to the _plus_ or _minus_ -state, and may be made to pass and repass the culminating point by -the action of acids and alkalis: it is to be observed that the French -arrest their operations on the active side, as is proved by the French -scarlet, which inclines to yellow. The Italians, on the other hand, -remain on the passive side, for their scarlet has a tinge of blue. - -800. - -By means of a similar alkaline treatment, the so-called crimson is -produced; a colour which the French must be particularly prejudiced -against, since they employ the expressions--"Sot en cramoisi, méchant -en cramoisi," to mark the extreme of the silly and the reprehensible. - - -GREEN. - - -801. - -If yellow and blue, which we consider as the most fundamental and -simple colours, are united as they first appear, in the first state of -their action, the colour which we call green is the result. - -802. - -The eye experiences a distinctly grateful impression from this colour. -If the two elementary colours are mixed in perfect equality so that -neither predominates, the eye and the mind repose on the result of this -junction as upon a simple colour. The beholder has neither the wish -nor the power to imagine a state beyond it. Hence for rooms to live in -constantly, the green colour is most generally selected. - - -COMPLETENESS AND HARMONY. - - -803. - -We have hitherto assumed, for the sake of clearer explanation, that the -eye can be compelled to assimilate or identify itself with a single -colour; but this can only be possible for an instant. - -804. - -For when we find ourselves surrounded by a given colour which excites -its corresponding sensation on the eye, and compels us by its presence -to remain in a state identical with it, this state is soon found to be -forced, and the organ unwillingly remains in it. - -805. - -When the eye sees a colour it is immediately excited, and it is its -nature, spontaneously and of necessity, at once to produce another, -which with the original colour comprehends the whole chromatic scale. -A single colour excites, by a specific sensation, the tendency to -universality. - -806. - -To experience this completeness, to satisfy itself, the eye seeks for -a colourless space next every hue in order to produce the complemental -hue upon it. - -807. - -In this resides the fundamental law of all harmony of colours, of which -every one may convince himself by making himself accurately acquainted -with the experiments which we have described in the chapter on the -physiological colours. - -808. - -If, again, the entire scale is presented to the eye externally, the -impression is gladdening, since the result of its own operation is -presented to it in reality. We turn our attention therefore, in the -first place, to this harmonious juxtaposition. - -809. - -As a very simple means of comprehending the principle of this, the -reader has only to imagine a moveable diametrical index in the -colorific circle.[1] The index, as it revolves round the whole circle, -indicates at its two extremes the complemental colours, which, after -all, may be reduced to three contrasts. - -810. - -Yellow demands Red-blue, -Blue demands Red-yellow, -Red demands Green, -and contrariwise. - -811. - -In proportion as one end of the supposed index deviates from the -central intensity of the colours, arranged as they are in the natural -order, so the opposite end changes its place in the contrasted -gradation, and by such a simple contrivance the complemental colours -may be indicated at any given point. A chromatic circle might be made -for this purpose, not confined, like our own, to the leading colours, -but exhibiting them with their transitions in an unbroken series. -This would not be without its use, for we are here considering a very -important point which deserves all our attention.[2] - -812. - -We before stated that the eye could be in some degree pathologically -affected by being long confined to a single colour; that, again, -definite moral impressions were thus produced, at one time lively and -aspiring, at another susceptible and anxious--now exalted to grand -associations, now reduced to ordinary ones. We now observe that the -demand for completeness, which is inherent in the organ, frees us from -this restraint; the eye relieves itself by producing the opposite -of the single colour forced upon it, and thus attains the entire -impression which is so satisfactory to it. - -813. - -Simple, therefore, as these strictly harmonious contrasts are, as -presented to us in the narrow circle, the hint is important, that -nature tends to emancipate the sense from confined impressions by -suggesting and producing the whole, and that in this instance we have a -natural phenomenon immediately applicable to æsthetic purposes. - -814. - -While, therefore, we may assert that the chromatic scale, as given by -us, produces an agreeable impression by its ingredient hues, we may -here remark that those have been mistaken who have hitherto adduced -the rainbow as an example of the entire scale; for the chief colour, -pure red, is deficient in it, and cannot be produced, since in this -phenomenon, as well as in the ordinary prismatic series, the yellow-red -and blue-red cannot attain to a union. - -815. - -Nature perhaps exhibits no general phenomenon where the scale is in -complete combination. By artificial experiments such an appearance may -be produced in its perfect splendour. The mode, however, in which the -entire series is connected in a circle, is rendered most intelligible -by tints on paper, till after much experience and practice, aided by -due susceptibility of the organ, we become penetrated with the idea of -this harmony, and feel it present in our minds. - -816. - -Besides these pure, harmonious, self-developed combinations, which -always carry the conditions of completeness with them, there are -others which may be arbitrarily produced, and which may be most easily -described by observing that they are to be found in the colorific -circle, not by diameters, but by chords, in such a manner that an -intermediate colour is passed over. - -817. - -We call these combinations characteristic because they have all a -certain significancy and tend to excite a definite impression; an -impression, however, which does not altogether satisfy, inasmuch as -every characteristic quality of necessity presents itself only as a -part of a whole, with which it has a relation, but into which it cannot -be resolved. - -818. - -As we are acquainted with the impressions produced by the colours -singly as well as in their harmonious relations, we may at once -conclude that the character of the arbitrary combinations will be very -different from each other as regards their significancy. We proceed to -review them separately. - - -YELLOW AND BLUE. - - -819. - -This is the simplest of such combinations. It may be said that it -contains too little, for since every trace of red is wanting in it, -it is defective as compared with the whole scale. In this view it -may be called poor, and as the two contrasting elements are in their -lowest state, may be said to be ordinary; yet it is recommended by -its proximity to green--in short, by containing the ingredients of an -ultimate state. - - -YELLOW AND RED. - - -820. - -This is a somewhat preponderating combination, but it has a serene -and magnificent effect. The two extremes of the active side are seen -together without conveying any idea of progression from one to the -other. As the result of their combination in pigments is yellow-red, so -they in some degree represent this colour. - - -BLUE AND RED. - - -821. - -The two ends of the passive side, with the excess of the upper end of -the active side. The effect of this juxtaposition approaches that of -the blue-red produced by their union. - - -YELLOW-RED AND BLUE-RED. - - -822. - -These, when placed together, as the deepened extremes of both sides, -have something exciting, elevated: they give us a presentiment of red, -which in physical experiments is produced by their union. - -823. - -These four combinations have also the common quality of producing the -intermediate colour of our colorific circle by their union, a union -which actually takes place if they are opposed to each other in small -quantities and seen from a distance. A surface covered with narrow blue -and yellow stripes appears green at a certain distance. - -824. - -If, again, the eye sees blue and yellow next each other, it finds -itself in a peculiar disposition to produce green without accomplishing -it, while it neither experiences a satisfactory sensation in -contemplating the detached colours, nor an impression of completeness -in the two. - -825. - -Thus it will be seen that it was not without reason we called these -combinations characteristic; the more so, since the character of each -combination must have a relation to that of the single colours of which -it consists. - - -COMBINATIONS NON-CHARACTERISTIC. - - -826. - -We now turn our attention to the last kind of combinations. These are -easily found in the circle; they are indicated by shorter chords, for -in this case we do not pass over an entire intermediate colour, but -only the transition from one to the other. - -827. - -These combinations may justly be called non-characteristic, inasmuch -as the colours are too nearly alike for their impression to be -significant. Yet most of these recommend themselves to a certain -degree, since they indicate a progressive state, though its relations -can hardly be appreciable. - -828. - -Thus yellow and yellow-red, yellow-red and red, blue and blue-red, -blue-red and red, represent the nearest degrees of augmentation and -culmination, and in certain relations as to quantity may produce no -unpleasant effect. - -829. - -The juxtaposition of yellow and green has always something ordinary, -but in a cheerful sense; blue and green, on the other hand, is ordinary -in a repulsive sense. Our good forefathers called these last fool's -colours. - - -RELATION OF THE COMBINATIONS TO LIGHT AND DARK. - - -830. - -These combinations may be very much varied by making both colours light -or both dark, or one light and the other dark; in which modifications, -however, all that has been found true in a general sense is applicable -to each particular case. With regard to the infinite variety thus -produced, we merely observe: - -831. - -The colours of the active side placed next to black gain in energy, -those of the passive side lose. The active conjoined with white and -brightness lose in strength, the passive gain in cheerfulness. Red and -green with black appear dark and grave; with white they appear gay. - -832. - -To this we may add that all colours may be more or less broken or -neutralised, may to a certain degree be rendered nameless, and thus -combined partly together and partly with pure colours; but although the -relations may thus be varied to infinity, still all that is applicable -with regard to the pure colours will be applicable in these cases. - - -CONSIDERATIONS DERIVED FROM THE EVIDENCE OF EXPERIENCE AND HISTORY. - - -833. - -The principles of the harmony of colours having been thus far defined, -it may not be irrelevant to review what has been adduced in connexion -with experience and historical examples. - -834. - -The principles in question have been derived from the constitution of -our nature and the constant relations which are found to obtain in -chromatic phenomena. In experience we find much that is in conformity -with these principles, and much that is opposed to them. - -835. - -Men in a state of nature, uncivilised nations, children, have a great -fondness for colours in their utmost brightness, and especially for -yellow-red: they are also pleased with the motley. By this expression -we understand the juxtaposition of vivid colours without an harmonious -balance; but if this balance is observed, through instinct or accident, -an agreeable effect may be produced. I remember a Hessian officer, -returned from America, who had painted his face with the positive -colours, in the manner of the Indians; a kind of completeness or due -balance was thus produced, the effect of which was not disagreeable. - -836. - -The inhabitants of the south of Europe make use of very brilliant -colours for their dresses. The circumstance of their procuring silk -stuffs at a cheap rate is favourable to this propensity. The women, -especially, with their bright-coloured bodices and ribbons, are always -in harmony with the scenery, since they cannot possibly surpass the -splendour of the sky and landscape. - -837. - -The history of dyeing teaches us that certain technical conveniences -and advantages have had great influence on the costume of nations. -We find that the Germans wear blue very generally because it is a -permanent colour in cloth; so in many districts all the country people -wear green twill, because that material takes a green dye well. If -a traveller were to pay attention to these circumstances, he might -collect some amusing and curious facts. - -838. - -Colours, as connected with particular frames of mind, are again a -consequence of peculiar character and circumstances. Lively nations, -the French for instance, love intense colours, especially on the active -side; sedate nations, like the English and Germans, wear straw-coloured -or leather-coloured yellow accompanied with dark blue. Nations aiming -at dignity of appearance, the Spaniards and Italians for instance, -suffer the red colour of their mantles to incline to the passive side. - -839. - -In dress we associate the character of the colour with the character of -the person. We may thus observe the relation of colours singly, and in -combination, to the colour of the complexion, age, and station. - -840. - -The female sex in youth is attached to rose-colour and sea-green, in -age to violet and dark-green. The fair-haired prefer violet, as opposed -to light yellow, the brunettes, blue, as opposed to yellow-red, and -all on good grounds. The Roman emperors were extremely jealous with -regard to their purple. The robe of the Chinese Emperor is orange -embroidered with red; his attendants and the ministers of religion wear -citron-yellow. - -841. - -People of refinement have a disinclination to colours. This may be -owing partly to weakness of sight, partly to the uncertainty of taste, -which readily takes refuge in absolute negation. Women now appear -almost universally in white and men in black. - -842. - -An observation, very generally applicable, may not be out of place -here, namely, that man, desirous as he is of being distinguished, is -quite as willing to be lost among his fellows. - -843. - -Black was intended to remind the Venetian noblemen of republican -equality. - -844. - -To what degree the cloudy sky of northern climates may have gradually -banished colour may also admit of explanation. - -845. - -The scale of positive colours is obviously soon exhausted; on the -other hand, the neutral, subdued, so-called fashionable colours -present infinitely varying degrees and shades, most of which are not -unpleasing. - -846. - -It is also to be remarked that ladies, in wearing positive colours, -are in danger of making a complexion which may not be very bright -still less so, and thus to preserve a due balance with such brilliant -accompaniments, they are induced to heighten their complexions -artificially. - -847. - -An amusing inquiry might be made which would lead to a critique of -uniforms, liveries, cockades, and other distinctions, according to the -principles above hinted at. It might be observed, generally, that such -dresses and insignia should not be composed of harmonious colours. -Uniforms should be characteristic and dignified; liveries might be -ordinary and striking to the eye. Examples both good and bad would -not be wanting, since the scale of colours usually employed for such -purposes is limited, and its varieties have been often enough tried.[3] - - -ÆSTHETIC INFLUENCE. - - -848. - -From the moral associations connected with the appearance of colours, -single or combined, their æsthetic influence may now be deduced for -the artist. We shall touch the most essential points to be attended -to after first considering the general condition of pictorial -representation, light and shade, with which the appearance of colour is -immediately connected. - - -CHIARO-SCURO. - - -849. - -We apply the term chiaro-scuro (Helldunkel) to the appearance of -material objects when the mere effect produced on them by light and -shade is considered.--Note D D. - -850. - -In a narrower sense a mass of shadow lighted by reflexes is often -thus designated; but we here use the expression in its first and more -general sense. - -851. - -The separation of light and dark from all appearance of colour is -possible and necessary. The artist will solve the mystery of imitation -sooner by first considering light and dark independently of colour, and -making himself acquainted with it in its whole extent. - -852. - -Chiaro-scuro exhibits the substance as substance, inasmuch as light and -shade inform us as to degrees of density. - -853. - -We have here to consider the highest light, the middle tint, and the -shadow, and in the last the shadow of the object itself, the shadow it -casts on other objects, and the illumined shadow or reflexion. - -854. - -The globe is well adapted for the general exemplification of the nature -of chiaro-scuro, but it is not altogether sufficient. The softened -unity of such complete rotundity tends to the vapoury, and in order to -serve as a principle for effects of art, it should be composed of plane -surfaces, so as to define the gradations more. - -855. - -The Italians call this manner "il piazzoso;" in German it might -be called "das Flächenhafte."[4] If, therefore, the sphere is a -perfect example of natural chiaro-scuro, a polygon would exhibit the -artist-like treatment in which all kinds of lights, half-lights, -shadows, and reflexions, would be appreciable.--Note E E. - -856. - -The bunch of grapes is recognised as a good example of a picturesque -completeness in chiaro-scuro, the more so as it is fitted, from its -form, to represent a principal group; but it is only available for the -master who can see in it what he has the power of producing. - -857. - -In order to make the first idea intelligible to the beginner, (for -it is difficult to consider it abstractedly even in a polygon,) we -may take a cube, the three sides of which that are seen represent the -light, the middle tint, and the shadow in distinct order. - -858. - -To proceed again to the chiaro-scuro of a more complicated figure, we -might select the example of an open book, which presents a greater -diversity. - -859. - -We find the antique statues of the best time treated very much with -reference to these effects. The parts intended to receive the light -are wrought with simplicity, the portion originally in shade is, on -the other hand, in more distinct surfaces to make them susceptible -of a variety of reflexions; here the example of the polygon will be -remembered.--Note F F. - -860. - -The pictures of Herculaneum and the Aldobrandini marriage are examples -of antique painting in the same style. - -861. - -Modern examples may be found in single figures by Raphael, in entire -works by Correggio, and also by the Flemish masters, especially Rubens. - - -TENDENCY TO COLOUR. - - -862. - -A picture in black and white seldom makes its appearance; some works -of Polidoro are examples of this kind of art. Such works, inasmuch as -they can attain form and keeping, are estimable, but they have little -attraction for the eye, since their very existence supposes a violent -abstraction. - -863. - -If the artist abandons himself to his feeling, colour presently -announces itself. Black no sooner inclines to blue than the eye demands -yellow, which the artist instinctively modifies, and introduces partly -pure in the light, partly reddened and subdued as brown, in the -reflexes, thus enlivening the whole.--Note G G. - -864. - -All kinds of _camayeu_, or colour on similar colour, end in the -introduction either of a complemental contrast, or some variety of hue. -Thus, Polidoro in his black and white frescoes sometimes introduced a -yellow vase, or something of the kind. - -865. - -In general it may be observed that men have at all times instinctively -striven after colour in the practice of the art. We need only observe -daily, how soon amateurs proceed from colourless to coloured materials. -Paolo Uccello painted coloured landscapes to colourless figures.--Note -H H. - -866. - -Even the sculpture of the ancients could not be exempt from the -influence of this propensity. The Egyptians painted their bas-reliefs; -statues had eyes of coloured stones. Porphyry draperies were added to -marble heads and extremities, and variegated stalactites were used -for the pedestals of busts. The Jesuits did not fail to compose the -statue of their S. Luigi, in Rome, in this manner, and the most modern -sculpture distinguishes the flesh from the drapery by staining the -latter. - - -KEEPING. - - -867. - -If linear perspective displays the gradation of objects in their -apparent size as affected by distance, aërial perspective shows us -their gradation in greater or less distinctness, as affected by the -same cause. - -868. - -Although from the nature of the organ of sight, we cannot see distant -objects so distinctly as nearer ones, yet aërial perspective is -grounded strictly on the important fact that all mediums called -transparent are in some degree dim. - -869. - -The atmosphere is thus always, more or less, semi-transparent. This -quality is remarkable in southern climates, even when the barometer is -high, the weather dry, and the sky cloudless, for a very pronounced -gradation is observable between objects but little removed from each -other. - -870. - -The appearance on a large scale is known to every one; the painter, -however, sees or believes he sees, the gradation in the slightest -varieties of distance. He exemplifies it practically by making a -distinction, for instance, in the features of a face according to their -relative position as regards the plane of the picture. The direction of -the light is attended to in like manner. This is considered to produce -a gradation from side to side, while keeping has reference to depth, to -the comparative distinctness of near and distant things. - -871. - -In proceeding to consider this subject, we assume that the painter is -generally acquainted with our sketch of the theory of colours, and that -he has made himself well acquainted with certain chapters and rubrics -which especially concern him. He will thus be enabled to make use of -theory as well as practice in recognising the principles of effect in -nature, and in employing the means of art. - - -COLOUR IN GENERAL NATURE. - - -872. - -The first indication of colour announces itself in nature together -with the gradations of aërial perspective; for aërial perspective is -intimately connected with the doctrine of semi-transparent mediums. We -see the sky, distant objects and even comparatively near shadows, blue. -At the same moment, the illuminating and illuminated objects appear -yellow, gradually deepening to red. In many cases the physiological -suggestion of contrasts comes into the account, and an entirely -colourless landscape, by means of these assisting and counteracting -tendencies, appears to our eyes completely coloured. - -873. - -Local colours are composed of the general elementary colours; but these -are determined or specified according to the properties of substances -and surfaces on which they appear: this specification is infinite. - -874. - -Thus, there is at once a great difference between silk and wool -similarly dyed. Every kind of preparation and texture produces -corresponding modifications. Roughness, smoothness, polish, all are to -be considered. - -875. - -It is therefore one of the pernicious prejudices of art that the -skilful painter must never attend to the material of draperies, -but always represent, as it were, only abstract folds. Is not all -characteristic variety thus done away with, and is the portrait of Leo -X. less excellent because velvet, satin, and moreen, are imitated in -their relative effect? - -876. - -In the productions of nature, colours appear more or less modified, -specified, even individualised: this may be readily observed in -minerals and plants, in the feathers of birds and the skins of beasts. - -877. - -The chief art of the painter is always to imitate the actual appearance -of the definite hue, doing away with the recollection of the elementary -ingredients of colour. This difficulty is in no instance greater than -in the imitation of the surface of the human figure. - -878. - -The colour of flesh, as a whole, belongs to the active side, yet the -bluish of the passive side mingles with it. The colour is altogether -removed from the elementary state and neutralised by organisation. - -879. - -To bring the colouring of general nature into harmony with the -colouring of a given object, will perhaps be more attainable for the -judicious artist after the consideration of what has been pointed out -in the foregoing theory. For the most fancifully beautiful and varied -appearances may still be made true to the principles of nature. - - -CHARACTERISTIC COLOURING. - - -880. - -The combination of coloured objects, as well as the colour of -their ground, should depend on considerations which the artist -pre-establishes for himself. Here a reference to the effect of colours -singly or combined, on the feelings, is especially necessary. On this -account the painter should possess himself with the idea of the general -dualism, as well as of particular contrasts, not forgetting what has -been adverted to with regard to the qualities of colours. - -881. - -The characteristic in colour may be comprehended under three leading -rubrics, which we here define as the powerful, the soft, and the -splendid. - -882. - -The first is produced by the preponderance of the active side, the -second by that of the passive side, and the third by completeness, by -the exhibition of the whole chromatic scale in due balance. - -883. - -The powerful impression is attained by yellow, yellow-red, and red, -which last colour is to be arrested on the plus side. But little violet -and blue, still less green, are admissible. The soft effect is produced -by blue, violet, and red, which in this case is arrested on the minus -side; a moderate addition of yellow and yellow-red, but much green may -be admitted. - -884. - -If it is proposed to produce both these effects in their full -significancy, the complemental colours may be excluded to a minimum, -and only so much of them may be suffered to appear as is indispensable -to convey an impression of completeness. - - -HARMONIOUS COLOURING. - - -885. - -Although the two characteristic divisions as above defined may in some -sense be also called harmonious, the harmonious effect, properly so -called, only takes place when all the colours are exhibited together in -due balance. - -886. - -In this way the splendid as well as the agreeable may be produced; both -of these, however, have of necessity a certain generalised effect, and -in this sense may be considered the reverse of the characteristic. - -887. - -This is the reason why the colouring of most modern painters is without -character, for, while they follow their general instinctive feeling -only, the last result of such a tendency must be mere completeness; -this, they more or less attain, but thus at the same time neglect the -characteristic impression which the subject might demand. - -888. - -But if the principles before alluded to are kept in view, it must be -apparent that a distinct style of colour may be adopted on safe grounds -for every subject. The application requires, it is true, infinite -modifications, which can only succeed in the hands of genius. - - -GENUINE TONE. - - -889. - -If the word tone, or rather tune, is to be still borrowed in future -from music, and applied to colouring, it might be used in a better -sense than heretofore. - -890. - -For it would not be unreasonable to compare a painting of powerful -effect, with a piece of music in a sharp key; a painting of soft effect -with a piece of music in a flat key, while other equivalents might be -found for the modifications of these two leading modes. - - -FALSE TONE. - - -891. - -The word tone has been hitherto understood to mean a veil of a -particular colour spread over the whole picture; it was generally -yellow, for the painter instinctively pushed the effect towards the -powerful side. - -892. - -If we look at a picture through a yellow glass it will appear in this -tone. It is worth while to make this experiment again and again, in -order to observe what takes place in such an operation. It is a sort of -artificial light, deepening, and at the same time darkening the _plus_ -side, and neutralising the _minus_ side. - -893. - -This spurious tone is produced instinctively through uncertainty -as to the means of attaining a genuine effect; so that instead of -completeness, monotony is the result. - - -WEAK COLOURING. - - -894. - -It is owing to the same uncertainty that the colours are sometimes so -much broken as to have the effect of a grey camayeu, the handling being -at the same time as delicate as possible. - -895. - -The harmonious contrasts are often found to be very happily felt in -such pictures, but without spirit, owing to a dread of the motley. - - -THE MOTLEY. - - -896. - -A picture may easily become party-coloured or motley, when the colours -are placed next each other in their full force, as it were only -mechanically and according to uncertain impressions. - -897. - -If, on the other hand, weak colours are combined, even although they -may be dissonant, the effect, as a matter of course, is not striking. -The uncertainty of the artist is communicated to the spectator, who, on -his side, can neither praise nor censure. - -898. - -It is also important to observe that the colours may be disposed -rightly in themselves, but that a work may still appear motley, if they -are falsely arranged in relation to light and shade. - -899. - -This may the more easily occur as light and shade are already defined -in the drawing, and are, as it were, comprehended in it, while the -colour still remains open to selection. - - -DREAD OF THEORY. - - -900. - -A dread of, nay, a decided aversion for all theoretical views -respecting colour and everything belonging to it, has been hitherto -found to exist among painters; a prejudice for which, after all, they -were not to be blamed; for what has been hitherto called theory was -groundless, vacillating, and akin to empiricism. We hope that our -labours may tend to diminish this prejudice, and stimulate the artist -practically to prove and embody the principles that have been explained. - - -ULTIMATE AIM. - - -901. - -But without a comprehensive view of the whole of our theory, the -ultimate object will not be attained. Let the artist penetrate himself -with all that we have stated. It is only by means of harmonious -relations in light and shade, in keeping, in true and characteristic -colouring, that a picture can be considered complete, in the sense we -have now learnt to attach to the term. - - -GROUNDS. - - -902. - -It was the practice of the earlier artists to paint on light grounds. -This ground consisted of gypsum, and was thickly spread on linen or -panel, and then levigated. After the outline was drawn, the subject was -washed in with a blackish or brownish colour. Pictures prepared in -this manner for colouring are still in existence, by Leonardo da Vinci, -and Fra Bartolomeo; there are also several by Guido.--Note I I. - -903. - -When the artist proceeded to colour, and had to represent white -draperies, he sometimes suffered the ground to remain untouched. -Titian did this latterly when he had attained the greatest certainty -in practice, and could accomplish much with little labour. The whitish -ground was left as a middle tint, the shadows painted in, and the high -lights touched on.--Note K K. - -904. - -In the process of colouring, the preparation merely washed as it were -underneath, was always effective. A drapery, for example, was painted -with a transparent colour, the white ground shone through it and gave -the colour life, so the parts previously prepared for shadows exhibited -the colour subdued, without being mixed or sullied. - -905. - -This method had many advantages; for the painter had a light ground -for the light portions of his work and a dark ground for the shadowed -portions. The whole picture was prepared; the artist could work with -thin colours in the shadows, and had always an internal light to give -value to his tints. In our own time painting in water colours depends -on the same principles. - -906. - -Indeed a light ground is now generally employed in oil-painting, -because middle tints are thus found to be more transparent, and are in -some degree enlivened by a bright ground; the shadows, again, do not so -easily become black. - -907. - -It was the practice for a time to paint on dark grounds. Tintoret -probably introduced them. Titian's best pictures are not painted on a -dark ground. - -908. - -The ground in question was red-brown, and when the subject was drawn -upon it, the strongest shadows were laid in; the colours of the lights -impasted very thickly in the bright parts, and scumbled towards the -shadows, so that the dark ground appeared through the thin colour as a -middle tint. Effect was attained in finishing by frequently going over -the bright parts and touching on the high lights. - -909. - -If this method especially recommended itself in practice on account -of the rapidity it allowed of, yet it had pernicious consequences. -The strong ground increased and became darker, and the light colours -losing their brightness by degrees, gave the shadowed portions more -and more preponderance. The middle tints became darker and darker, and -the shadows at last quite obscure. The strongly impasted lights alone -remained bright, and we now see only light spots on the painting. The -pictures of the Bolognese school, and of Caravaggio, afford sufficient -examples of these results. - -910. - -We may here in conclusion observe, that glazing derives its effect -from treating the prepared colour underneath as a light ground. By -this operation colours may have the effect of being mixed to the eye, -may be enhanced, and may acquire what is called tone; but they thus -necessarily become darker. - - -PIGMENTS. - - -911. - -We receive these from the hands of the chemist and the investigator of -nature. Much has been recorded respecting colouring substances, which -is familiar to all by means of the press. But such directions require -to be revised from time to time. The master meanwhile communicates his -experience in these matters to his scholar, and artists generally to -each other. - -912. - -Those pigments which according to their nature are the most permanent, -are naturally much sought after, but the mode of employing them also -contributes much to the duration of a picture. The fewest possible -colouring materials are to be employed, and the simplest methods of -using them cannot be sufficiently recommended. - -913. - -For from the multitude of pigments colouring has suffered much. Every -pigment has its peculiar nature as regards its effect on the eye; -besides this it has its peculiar quality, requiring a corresponding -technical method in its application. The former circumstance is a -reason why harmony is more difficult of attainment with many materials -than with few, the latter, why chemical action and re-action may take -place among the colouring substances. - -914. - -We may refer, besides, to some false tendencies which the artists -suffer themselves to be led away with. Painters are always looking -for new colouring substances, and believe when such a substance is -discovered that they have made an advance in the art. They have a -great curiosity to know the practical methods of the old masters, and -lose much time in the search. Towards the end of the last century -we were thus long tormented with wax-painting. Others turn their -attention to the discovery of new methods, through which nothing new is -accomplished; for, after all, it is the feeling of the artist only that -informs every kind of technical process. - - -ALLEGORICAL, SYMBOLICAL, MYSTICAL APPLICATION OF COLOUR. - - -915. - -It has been circumstantially shown above, that every colour produces -a distinct impression on the mind, and thus addresses at once the eye -and feelings. Hence it follows that colour may be employed for certain -moral and æsthetic ends. - -916. - -Such an application, coinciding entirely with nature, might be called -symbolical, since the colour would be employed in conformity with its -effect, and would at once express its meaning. If, for example, pure -red were assumed to designate majesty, there can be no doubt that this -would be admitted to be a just and expressive symbol. All this has been -already sufficiently entered into. - -917. - -Another application is nearly allied to this; it might be called the -allegorical application. In this there is more of accident and caprice, -inasmuch as the meaning of the sign must be first communicated to us -before we know what it is to signify; what idea, for instance, is -attached to the green colour, which has been appropriated to hope? - -918. - -That, lastly, colour may have a mystical allusion, may be readily -surmised, for since every diagram in which the variety of colours may -be represented points to those primordial relations which belong both -to nature and the organ of vision, there can be no doubt that these may -be made use of as a language, in cases where it is proposed to express -similar primordial relations which do not present themselves to the -senses in so powerful and varied a manner. The mathematician extols -the value and applicability of the triangle; the triangle is revered -by the mystic; much admits of being expressed in it by diagrams, and, -among other things, the law of the phenomena of colours; in this case, -indeed, we presently arrive at the ancient mysterious hexagon. - -919. - -When the distinction of yellow and blue is duly comprehended, and -especially the augmentation into red, by means of which the opposite -qualities tend towards each other and become united in a third; then, -certainly, an especially mysterious interpretation will suggest itself, -since a spiritual meaning may be connected with these facts; and when -we find the two separate principles producing green on the one hand and -red in their intenser state, we can hardly refrain from thinking in the -first case on the earthly, in the last on the heavenly, generation of -the Elohim.--Note L L. - -920. - -But we shall do better not to expose ourselves, in conclusion, to -the suspicion of enthusiasm; since, if our doctrine of colours finds -favour, applications and allusions, allegorical, symbolical, and -mystical, will not fail to be made, in conformity with the spirit of -the age. - - -CONCLUDING OBSERVATIONS. - - -In reviewing this labour, which has occupied me long, and which at -last I give but as a sketch, I am reminded of a wish once expressed -by a careful writer, who observed that he would gladly see his works -printed at once as he conceived them, in order then to go to the task -with a fresh eye; since everything defective presents itself to us more -obviously in print than even in the cleanest manuscript. This feeling -may be imagined to be stronger in my case, since I had not even an -opportunity of going through a fair transcript of my work before its -publication, these pages having been put together at a time when a -quiet, collected state of mind was out of the question.[5] - -Some of the explanations I was desirous of giving are to be found in -the introduction, but in the portion of my work to be devoted to the -history of the doctrine of colours, I hope to give a more detailed -account of my investigations and the vicissitudes they underwent. One -inquiry, however, may not be out of place here; the consideration, -namely, of the question, what can a man accomplish who cannot devote -his whole life to scientific pursuits? what can he perform as a -temporary guest on an estate not his own, for the advantage of the -proprietor? - -When we consider art in its higher character, we might wish that -masters only had to do with it, that scholars should be trained by -the severest study, that amateurs might feel themselves happy in -reverentially approaching its precincts. For a work of art should be -the effusion of genius, the artist should evoke its substance and form -from his inmost being, treat his materials with sovereign command, and -make use of external influences only to accomplish his powers. - -But if the professor in this case has many reasons for respecting -the dilettante, the man of science has every motive to be still more -indulgent, since the amateur here is capable of contributing what may -be satisfactory and useful. The sciences depend much more on experiment -than art, and for mere experiment many a votary is qualified. -Scientific results are arrived at by many means, and cannot dispense -with many hands, many heads. Science may be communicated, the treasure -may be inherited, and what is acquired by one may be appropriated -by many. Hence no one perhaps ought to be reluctant to offer his -contributions. How much do we not owe to accident, to mere practice, -to momentary observation. All who are endowed only with habits of -attention, women, children, are capable of communicating striking and -true remarks. - -In science it cannot therefore be required, that he who endeavours -to furnish something in its aid should devote his whole life to it, -should survey and investigate it in all its extent; for this, in most -cases, would be a severe condition even for the initiated. But if we -look through the history of science in general, especially the history -of physics, we shall find that many important acquisitions have been -made by single inquirers, in single departments, and very often by -unprofessional observers. - -To whatever direction a man may be determined by inclination or -accident, whatever class of phenomena especially strike him, excite -his interest, fix his attention, and occupy him, the result will still -be for the advantage of science: for every new relation that comes to -light, every new mode of investigation, even the imperfect attempt, -even error itself is available; it may stimulate other observers and is -never without its use as influencing future inquiry. - -With this feeling the author himself may look back without regret -on his endeavours. From this consideration he can derive some -encouragement for the prosecution of the remainder of his task; and -although not satisfied with the result of his efforts, yet re-assured -by the sincerity of his intentions, he ventures to recommend his past -and future labours to the interest of his contemporaries and posterity. - -Multi pertransibunt et augebitur scientia. - - -[1] Plate 1, fig. 3. - -[2] See Note C. - -[3] Some early Italian writers, Sicillo, Occolti, Rinaldi, and others, -have treated this subject in connexion with the supposed signification -of colours.--T. - -[4] The English technical expressions "flat" and "square" have an -association of mannerism.--T - -[5] Towards the close of 1806, when Weimar was occupied by Napoleon -after the battle of Jena.--T. - - - - -NOTES. - - -NOTE A.--Par. 18. - -Leonardo da Vinci observes that "a light object relieved on a dark -ground appears magnified;" and again, "Objects seen at a distance -appear out of proportion; this is because the light parts transmit -their rays to the eye more powerfully than the dark. A woman's white -head-dress once appeared to me much wider than her shoulders, owing -to their being dressed in black."[1] "It is now generally admitted -that the excitation produced by light is propagated on the retina a -little beyond the outline of the image. Professor Plateau, of Ghent, -has devoted a very interesting special memoir to the description -and explanation of phenomena of this nature. See his 'Mémoire sur -l'Irradiation,' published in the 11th vol. of the Transactions of the -Royal Academy of Sciences at Brussels."[2]--S. F. - - -NOTE B.--Par. 23. - -"The duration of ocular spectra produced by strongly exciting the -retina, may be conveniently measured by minutes and seconds; but to -ascertain the duration of more evanescent phenomena, recourse must be -had to other means. The Chevalier d'Arcy (Mém. de l'Acad. des Sc. -1765,) endeavoured to ascertain the duration of the impression produced -by a glowing coal in the following manner. He attached it to the -circumference of a wheel, the velocity of which was gradually increased -until the apparent trace of the object formed a complete circle, and -then measured the duration of a revolution, which was obviously that -of the impression. To ascertain the duration of a revolution it is -sufficient merely to know the number of revolutions described in a -given time. Recently more refined experiments of the same kind have -been made by Professors Plateau and Wheatstone."--S. F. - - -[1] "Trattato della Pittura, Roma, 1817," p. 143-223. This edition, -published from a Vatican MS., contains many observations not included -in former editions. - -[2] A few notes (marked with inverted commas and with the signature S. -F.) have been kindly furnished by a scientific friend. - - -NOTE C.--Par. 50. - -Every treatise on the harmonious combination of colours contains the -diagram of the chromatic circle more or less elaborately constructed. -These diagrams, if intended to exhibit the contrasts produced by -the action and re-action of the retina, have one common defect. The -opposite colours are made equal in intensity; whereas the complemental -colour pictured on the retina is always less vivid, and always darker -or lighter than the original colour. This variety undoubtedly accords -more with harmonious effects in painting. - -The opposition of two pure hues of equal intensity, differing only in -the abstract quality of colour, would immediately be pronounced crude -and inharmonious. It would not, however, be strictly correct to say -that such a contrast is too violent; on the contrary, it appears the -contrast is not carried far enough, for though differing in colour, -the two hues may be exactly similar in purity and intensity. Complete -contrast, on the other hand, supposes dissimilarity in all respects. - -In addition to the mere difference of hue, the eye, it seems, requires -difference in the lightness or darkness of the hue. The spectrum of a -colour relieved as a dark on a light ground, is a light colour on a -dark ground, and _vice versâ_. Thus, if we look at a bright red wafer -on the whitest surface, the complemental image will be still lighter -than the white surface; if the same wafer is placed on a black surface, -the complemental image will be still darker. The colour of both these -spectra may be called greenish, but it is evident that a colour must be -scarcely appreciable as such, if it is lighter than white and darker -than black. It is, however, to be remarked, that the white surface -round the light greenish image seems tinged with a reddish hue, and -the black surface round the dark image becomes slightly illuminated -with the same colour, thus in both cases assisting to render the image -apparent (58). - -The difficulty or impossibility of describing degrees of colour in -words, has also had a tendency to mislead, by conveying the idea of -more positive hues than the physiological contrast warrants. Thus, -supposing scarlet to be relieved as a dark, the complemental colour is -so light in degree and so faint in colour, that it should be called a -pearly grey; whereas the theorists, looking at the quality of colour -abstractedly, would call it a green-blue, and the diagram would falsely -present such a hue equal in intensity to scarlet, or as nearly equal as -possible. - -Even the difference of mass which good taste requires may be suggested -by the physiological phenomena, for unless the complemental image is -suffered to fall on a surface precisely as near to the eye as that on -which the original colour was displayed, it appears larger or smaller -than the original object (22), and this in a rapidly increasing -proportion. Lastly, the shape itself soon becomes changed (26). - -That vivid colour demands the comparative absence of colour, either -on a lighter or darker scale, as its contrast, may be inferred again -from the fact that bright colourless objects produce strongly coloured -spectra. In darkness, the spectrum which is first white, or nearly -white, is followed by red: in light, the spectrum which is first black, -is followed by green (39-44). All colour, as the author observes -(259), is to be considered as half-light, inasmuch as it is in every -case lighter than black and darker than white. Hence no contrast of -colour with colour, or even of colour with black or white, can be so -great (as regards lightness or darkness) as the contrast of black and -white, or light and dark abstractedly. This distinction between the -differences of degree and the differences of kind is important, since a -just application of contrast in colour may be counteracted by an undue -difference in lightness or darkness. The mere contrast of colour is -happily employed in some of Guido's lighter pictures, but if intense -darks had been opposed to his delicate carnations, their comparative -whiteness would have been unpleasantly apparent. On the other hand, the -flesh-colour in Giorgione, Sebastian del Piombo (his best imitator), -and Titian, was sometimes so extremely glowing[1] that the deepest -colours, and black, were indispensable accompaniments. The manner of -Titian as distinguished from his imitation of Giorgione, is golden -rather than fiery, and his biographers are quite correct in saying -that he was fond of opposing red (lake) and blue to his flesh[2]. The -correspondence of these contrasts with the physiological phenomena will -be immediately apparent, while the occasional practice of Rubens in -opposing bright red to a still cooler flesh-colour, will be seen to be -equally consistent. - -The effect of white drapery (the comparative absence of colour) in -enhancing the glow of Titian's flesh-colour, has been frequently -pointed out:[3] the shadows of white thus opposed to flesh, often -present, again, the physiological contrast, however delicately, -according to the hue of the carnation. The lights, on the other hand, -are not, and probably never were, quite white, but from the first, -partook of the quality of depth, a quality assumed by the colourists to -pervade every part of a picture more or less.[4] - -It was before observed that the description of colours in words may -often convey ideas of too positive a nature, and it may be remarked -generally that the colours employed by the great masters are, in their -ultimate effect, more or less subdued or broken. The physiological -contrasts are, however, still applicable in the most comparatively -neutral scale. - -Again, the works of the colourists show that these oppositions are -not confined to large masses (except perhaps in works to be seen only -at a great distance); on the contrary, they are more or less apparent -in every part, and when at last the direct and intentional operations -of the artist may have been insufficient to produce them in their -minuter degrees, the accidental results of glazing and other methods -may be said to extend the contrasts to infinity. In such productions, -where every smallest portion is an epitome of the whole, the eye -still appreciates the fascinating effect of contrast, and the work is -pronounced to be true and complete, in the best sense of the words. - -The Venetian method of scumbling and glazing exhibits these minuter -contrasts within each other, and is thus generally considered more -refined than the system of breaking the colours, since it ensures a -fuller gradation of hues, and produces another class of contrasts, -those, namely, which result from degrees of transparence and opacity. -In some of the Flemish and Dutch masters, and sometimes in Reynolds, -the two methods are combined in great perfection. - -The chromatic diagram does not appear to be older than the last -century. It is one of those happy adaptations of exacter principles to -the objects of taste which might have been expected from Leonardo da -Vinci. That its true principle was duly felt is abundantly evident from -the works of the colourists, as well as from the general observations -of early writers.[5] The more practical directions occasionally to be -met with in the treatises of Leon Battista Alberti, Leonardo da Vinci -and others, are conformable to the same system. Some Italian works, -not written by painters, which pretend to describe this harmony, are, -however, very imperfect.[6] A passage in Lodovico Dolce's Dialogue on -Colours is perhaps the only one worth quoting. "He," says that writer, -"who wishes to combine colours that are agreeable to the eye, will -put grey next dusky orange; yellow-green next rose-colour; blue next -orange; dark purple, black, next dark-green; white next black, and -white next flesh-colour."[7] The Dialogue on Painting, by the same -author, has the reputation of containing some of Titian's precepts: -if the above passage may be traced to the same source, it must be -confessed that it is almost the only one of the kind in the treatise -from which it is taken. - - -[1] "Ardito veramente alquanto, sanguigno, e quasi -fiammeggiante."--_Zanetti della Pittura Veneziana_, Ven. 1771, p. -90. Warm as the flesh colour of the colourists is, it still never -approaches a positive hue, if we except some examples in frescoes and -other works intended to be seen at a great distance. Zanetti, speaking -of a fresco by Giorgione, now almost obliterated, compares the colour -to "un vivo raggio di cocente sole."---_Varie Pitture a fresco dei -Principali Maestri Veneziani_. Ven. 1760. - -[2] Ridolfi. - -[3] Zanetti, I. ii. - -[4] Two great authorities, divided by more than three centuries, Leon -Battista Alberti and Reynolds, have recommended this subdued treatment -of white. "It is to be remembered," says the first, "that no surface -should be made so white that it cannot be made more so. In white -dresses again, it is necessary to stop far short of the last degree of -whiteness."--_Della Pittura_, I. ii., compare with Reynolds, vol. i. -dis. 8. - -[5] Vasari observes, "L'unione nella pittura è una discordanza -dicolori diversi accordati insième."--Vol. i. c. 18. This observation -is repeated by various writers on art in nearly the same words, and -at last appears in Sandrart: "Concordia, potissimum picturæ decus, -in discordiâ consistit, et quasi litigio colorum."--P. i. c. 5. The -source, perhaps, is Aristotle: he observes, "We are delighted with -harmony, because it is the union of contrary principles having a ratio -to each other."--_Problem._ - -[6] See "Occolti Trattato de' Colori." Parma, 1568. - -[7] "Volendo l'uomo accoppiare insième colori che all'occhio -dilettino--porrà insième il berrettino col leonato; il verde-giallo con -l'incarnato e rosso; il turchino con l'arangi; il morello col verde -oscuro; il nero col bianco; il bianco con l'incarnato."--_Dialogo di -M. Lodovico Dolce nel quale si ragiona della qualità, diversità, e -proprietà de' colori_. Venezia, 1565. - - - -NOTE D.--Par. 66. - -In some of these cases there can be no doubt that Goethe attributes -the contrast too exclusively to the physiological cause, without -making sufficient allowance for the actual difference in the colour of -the lights. The purely physical nature of some coloured shadows was -pointed out by Pohlmann; and Dr. Eckermann took some pains to convince -Goethe of the necessity of making such a distinction. Goethe at first -adhered to his extreme view, but some time afterwards confessed to -Dr. Eckermann, that in the case of the blue shadows of snow (74), the -reflection of the sky was undoubtedly to be taken into the account. -"Both causes may, however, operate together," he observed, "and the -contrast which a warm yellow light demands may heighten the effect of -the blue." This was all his opponent contended.[1] - -With a few such exceptions, the general theory of Goethe with regard -to coloured shadows is undoubtedly correct; the experiments with two -candles (68), and with coloured glass and fluids (80), as well as the -observations on the shadows of snow (75), are conclusive, for in all -these cases only one light is actually changed in colour, while the -other still assumes the complemental hue. "Coloured shadows," Dr. J. -Müller observes, "are usually ascribed to the physiological influence -of contrast; the complementary colour presented by the shadow being -regarded as the effect of internal causes acting on that part of the -retina, and not of the impression of coloured rays from without. This -explanation is the one adopted by Rumford, Goethe, Grotthuss, Brandes, -Tourtual, Pohlmann, and most authors who have studied the subject."[2] - -In the Historical Part the author gives an account of a scarce French -work, "Observations sur les Ombres Colorées," Paris, 1782. The -writer[3] concludes that "the colour of shadows is as much owing to -the light that causes them as to that which (more faintly) illumines -them." - - -[1] Eckermann's "Gespräche mit Goethe," vol. ii. p. 76 and 280. - -[2] "Elements of Physiology," by J. Müller, M. D., translated from the -German by William Baly, M.D. London, 1839. - -[3] Anonymous, having only given the initials H. F. T. - - - -NOTE E.--Par. 69. - -This opinion of the author is frequently repeated (201, 312, 591), and -as it seems at first sight to be at variance with a received principle -of art, it may be as well at once to examine it. - -In order to see the general proposition in its true point of view, -it will be necessary to forget the arbitrary distinctions of light -and shade, and to consider all such modifications between highest -brightness and absolute darkness only as so many lesser degrees of -light.[1] The author, indeed, by the word shadow, always understands a -lesser light. - -The received notion, as stated by Du Fresnoy,[2] is much too positive -and unconditional, and is only true when we understand the "displaying" -light to comprehend certain degrees of half or reflected light, and the -"destroying" shade to mean the intensest degree of obscurity. - -There are degrees of brightness which destroy colour as well as -degrees of darkness.[3] In general, colour resides in a mitigated -light, but a very little observation shows us that different colours -require different degrees of light to display them. Leonardo da Vinci -frequently inculcates the general principle above alluded to, but he -as frequently qualifies it; for he not only remarks that the highest -light may be comparative privation of colour, but observes, with great -truth, that some hues are best displayed in their fully illumined -parts, some in their reflections, and some in their half-lights; and -again, that every colour is most beautiful when lit by reflections from -its own surface, or from a hue similar to its own.[4] - -The Venetians went further than Leonardo in this view and practice; -and he seems to allude to them when he criticises certain painters, -who, in aiming at clearness and fulness of colour, neglected what, in -his eyes, was of superior importance, namely, gradation and force of -chiaro-scuro.[5] - -That increase of colour supposes increase of darkness, as so often -stated by Goethe, may be granted without difficulty. To what extent, on -the other hand, increase of darkness, or rather diminution of light, -is accompanied by increase of colour, is a question which has been -variously answered by various schools. Examples of the total negation -of the principle are not wanting, nor are they confined to the infancy -of the art. Instances, again, of the opposite tendency are frequent -in Venetian and early Flemish pictures resembling the augmenting -richness of gems or of stained glass:[6] indeed, it is not impossible -that the increase of colour in shade, which is so remarkable in the -pictures alluded to, may have been originally suggested by the rich -and fascinating effect of stained glass; and the Venetians, in this as -in many other respects, may have improved on a hint borrowed from the -early German painters, many of whom painted on glass.[7] - -At all events, the principle of still increasing in colour in certain -hues seems to have been adopted in Flanders and in Venice at an early -period;[8] while Giorgione, in carrying the style to the most daring -extent, still recommended it by corresponding grandeur of treatment in -other respects. - -The same general tendency, except that the technical methods are -less transparent, is, however, very striking in some of the painters -of the school of Umbria, the instructors or early companions of -Raphael.[9] The influence of these examples, as well as that of Fra -Bartolommeo, in Florence, is distinctly to be traced in the works of -the great artist just named, but neither is so marked as the effect -of his emulation of a Venetian painter at a later period. The glowing -colour, sometimes bordering on exaggeration, which Raphael adopted -in Rome, is undoubtedly to be attributed to the rivalry of Sebastian -del Piombo. This painter, the best of Giorgione's imitators, arrived -in Rome, invited by Agostini Chigi, in 1511, and the most powerful of -Raphael's frescoes, the Heliodorus and Mass of Bolsena, as well as -some portraits in the same style, were painted in the two following -years. In the hands of some of Raphael's scholars, again, this extreme -warmth was occasionally carried to excess, particularly by Pierino del -Vaga, with whom it often degenerated into redness. The representative -of the glowing manner in Florence was Fra Bartolommeo, and, in the -same quality, considered abstractedly, some painters of the school of -Ferrara were second to none. - -In another Note (par. 177) some further considerations are offered, -which may partly explain the prevalence of this style in the beginning -of the sixteenth century; here we merely add, that the conditions under -which the appearance itself is most apparent in nature are perhaps more -obvious in Venice than elsewhere. The colour of general nature may be -observed in all places with almost equal convenience, but with regard -to an important quality in living nature, namely, the colour of flesh, -perhaps there are no circumstances in which its effects at different -distances can be so conveniently compared as when the observer and the -observed gradually approach and glide past each other on so smooth an -element and in so undisturbed a manner as on the canals and in the -gondolas of Venice;[10] the complexions, from the peculiar mellow -carnations of the Italian women to the sun-burnt features and limbs -of the mariners, presenting at the same time the fullest variety in -another sense. - -At a certain distance--the colour being always assumed to be unimpaired -by interposed atmosphere--the reflections appear kindled to intenser -warmth; the fiery glow of Giorgione is strikingly apparent; the colour -is seen in its largest relation; the _macchia_,[11] an expression so -emphatically used by Italian writers, appears in all its quantity, and -the reflections being the focus of warmth, the hue seems to deepen in -shade. - -A nearer view gives the detail of cooler tints more perceptibly,[12] -and the forms are at the same time more distinct. Hence Lanzi is quite -correct when, in distinguishing the style of Titian from that of -Giorgione, he says that Titian's was at once more defined and less -fiery.[13] In a still nearer observation the eye detects the minute -lights which Leonardo da Vinci says are incompatible with effects such -as those we have described[14] and which, accordingly, we never find -in Giorgione and Titian. This large impression of colour, which seems -to require the condition of comparative distance for its full effect, -was most fitly employed by the same great artists in works painted in -the open air or for large altar-pieces. Their celebrated frescoes on -the exterior of the Fondaco de' Tedeschi at Venice, to judge from their -faint remains and the descriptions of earlier writers, were remarkable -for extreme warmth in the shadows. The old frescoes in the open air -throughout Friuli have often the same character, and, owing to the -fulness of effect which this treatment ensures, are conspicuous at a -very great distance.[15] - -In assuming that the Venetian painters may have acquired a taste for -this breadth[16] of colour under the circumstances above alluded to, -it is moreover to be remembered that the time for this agreeable -study was the evening; when the sun had already set behind the hills -of Bassano; when the light was glowing but diffused; when shadows -were soft--conditions all agreeing with the character of their -colouring:[17] above all, when the hour invited the fairer portion of -the population to betake themselves in their gondolas to the lagunes. -The scene of this "promenade" was to the north of Venice, the quarter -in which Titian at one time lived. A letter exists written by Francesco -Priscianese, giving an account of his supping with the great painter in -company with Jacopo Nardi, Pietro Aretino, the sculptor Sansovino, and -others. The writer speaks of the beauty of the garden, where the table -was prepared, looking over the lagunes towards Murano, "which part of -the sea," he continues, "as soon as the sun was down, was covered with -a thousand gondolas, graced with beautiful women, and enlivened by the -harmony of voices and instruments, which lasted till midnight, forming -a pleasing accompaniment to our cheerful repast."[18] - -To return to Goethe: perhaps the foregoing remarks may warrant the -conclusion that his idea of colour in shadow is not irreconcileable -with the occasional practice of the best painters. The highest examples -of the style thus defined are, or were, to be found in the works of -Giorgione[19] and Titian, and hence the style itself, though "within -that circle" few "dare walk" is to be considered the grandest and -most perfect. Its possible defects or abuse are not to be dissembled: -in addition to the danger of exaggeration[20] it is seldom united -with the plenitude of light and shade, or with roundness; yet, where -fine examples of both modes of treatment may be compared, the charm -of colour has perhaps the advantage.[21] The difficulty of uniting -qualities so different in their nature, is proved by the very rare -instances in which it has been accomplished. Tintoret in endeavouring -to add chiaro-scuro to Venetian colour, in almost every instance fell -short of the glowing richness of Titian.[22] - -Giacomo Bassan and his imitators, even in their dark effects, still had -the principle of the gem in view: their light, in certain hues, is the -minimum of colour, their lower tones are rich, their darks intense, -and all is sparkling.[23] Of the great painters who, beginning, on -the other hand, with chiaro-scuro, sought to combine with it the full -richness of colour, Correggio, in the opinion of many, approached -perfection nearest; but we may perhaps conclude with greater justice -that the desired excellence was more completely attained by Rembrandt -than by any of the Italians. - - -[1] Leonardo da Vinci observes: "L'ombra è diminuzione di luce, tenebre -è privazione di luce." And again: "Sempre il minor lume è ombra del -lume maggiore."--_Trattato della Pittura_, pp. 274-299. - -N. B. The same edition before described has been consulted throughout. - -[2] - - "Lux varium vivumque dabit, nullum umbra colorem." - _De Arte Graphicá_. - - "Know first that light displays and shade destroys - Refulgent nature's variegated dies."--Mason's _Translation_. - - -[3] A Spanish writer, Diego de Carvalho e Sampayo, quoted by Goethe -("Farbenlehre," vol. ii.), has a similar observation. This destroying -effect of light is striking in climates where the sun is powerful, and -was not likely to escape the notice of a Spaniard. - -[4] Trattato, pp. 103, 121, 123, 324, &c. - -[5] Ib. pp. 85, 134. - -[6] Absolute opacity, to judge from the older specimens of stained -glass, seems to have been considered inadmissible. The window was -to admit light, however modified and varied, in the form prescribed -by the architect, and that form was to be preserved. This has been -unfortunately lost sight of in some modern glass-painting, which, -by excluding the light in large masses, and adopting the opacity -of pictures (the reverse of the influence above alluded to), has -interfered with the architectural symmetry in a manner far from -desirable. On the other hand, if we suppose painting at any period -to have aimed at the imitation of stained glass, such an imitation -must of necessity have led to extreme force; for the painter sets -out by substituting a mere white ground for the real light of the -sky, and would thus be compelled to subdue every tone accordingly. -In such an imitation his colour would soon deepen to its intensest -state; indeed, considerable portions of the darker hues would be lost -in obscurity. The early Flemish pictures seldom err on the side of -a gay superabundance of colour; on the contrary, they are generally -remarkable for comparatively cool lights, for extreme depth, and a -certain subdued splendour, qualities which would necessarily result -from the imitation or influence in question. - -[7] See Langlois, "Peinture sur Verre." Rouen, 1832; Descamps, "La Vie -des Peintres Flamands;" and Gessert, "Geschichte der Glasmalerei." -Stutgard, 1839. The antiquity of the glass manufactory of Murano -(Venice) is also not to be forgotten. Vasari objects to the Venetian -glass, because it was darker in colour than that of Flanders, France, -and England; but this very quality was more likely to have an -advantageous influence on the style of the early oil-painters. The use -of stained glass was, however, at no period very general in Italy. - -[8] Zanetti, "Della Pittura Veneziana," marks the progress of the early -Venetian painters by the gradual use of the warm outline. There are -some mosaics in St. Mark's which have the effect of flesh-colour, but -on examination, the only red colour used is found to be in the outlines -and markings. Many of the drawings of the old masters, heightened with -red in the shadows, have the same effect. In these drawings the artists -judiciously avoided colouring the lips and cheeks much, for this would -only have betrayed the want of general colour, as is observable when -statues are so treated. - -[9] Andrea di Luigi, called L'Ingegno, and Niccolo di Fuligno, are -cited as the most prominent examples. See Rumohr, "Italienische -Forschungen." Perogino himself occasionally adopted a very glowing -colour. - -The early Italian schools which adhered most to the Byzantine types -appear to have been also the most remarkable for depth, or rather -darkness, of colour. This fidelity to customary representation was -sometimes, as in the schools of Umbria, and to a certain extent in -those of Siena and Bologna, the result of a religious veneration for -the ancient examples; in others, as in Venice, the circumstance of -frequent intercourse with the Levant is also to be taken into the -account. The Greek pictures of the Madonna, not to mention other -representations, were extremely dark, in exaggerated conformity, -it is supposed, with the tradition respecting her real complexion -(see D'Agincourt, vol. iv. p. 1); a belief which obtained so late as -Lomazzo's time, for, speaking of the Madonna, he observes, "Leggesi -però che fu alquanto bruna." Giotto, who with the independence of -genius betrayed a certain contempt for these traditions, failed perhaps -to unite improvement with novelty when he substituted a pale white -flesh-colour for the traditional brown. Some specimens of his works, -still existing at Padua, present a remarkable contrast in this respect -with the earliest productions of the Venetian and Paduan artists. His -works at Florence differ as widely from those of the earlier painters -of Tuscany. This peculiarity was inherited by his imitators, and at -one time almost characterised the Florentine school. Leon Battista -Alberti was not perhaps the first who objected to it ("Vorrei io -che dai pittori fosse comperato il color bianco assai più caro che -le presiosissime gemme."--_Della Pittura_, I. ii.) The attachment -of Fra Bartolommeo to the grave character of the Christian types is -exemplified in his deep colouring, as well as in other respects. - -[10] Holland might be excepted, and in Holland similar causes may have -had a similar influence. - -[11] Local colour; literally, the _blot_. - -[12] Zanetti ventures to single out the picture of Tobit and the Angel -in S. Marziale as the first example of Titian's own manner, and in -which a direct imitation of Giorgione is no longer apparent. In this -picture the lights are cool and the blood-tint very effective. - -[13] "Meno sfumato, men focoso."--_Storia Pittorica_. - -[14] "La prima cosa che de' colori si perde nelle distante è il lustro, -loro minima parte."--_Trattato_, p. 213; and elsewhere, "I lumi -principali in picciol luogo son quelli che in picciola distanza sono i -primi che si perdono all' occhio."--p. 128. - -[15] A colossal St. Christopher, the usual subject, is frequently seen -occupying the whole height of the external wall of a church. We have -here an example of the influence of religion, such as it was, even on -the style of colouring and practical methods of the art. The mere sight -of the image of St. Christopher, the type of strength, was considered -sufficient to reinvigorate those who were exhausted by the labours of -husbandry. The following is a specimen of the inscriptions inculcating -this belief:-- - - "Christophori Sancti speciem quicumque tuetur, - Illo namque die nullo languore tenetur." - -Hence the practice of painting the figure on the outside of churches, -hence its colossal size, and hence the powerful qualities in colour -above described. See Maniago, "Storia delle Belle Arti Friulane." - -[16] The authority of Fuseli sufficiently warrants the application of -the term breadth to colour; he speaks of Titian's "breadth of local -tint." - -[17] Zanetti quotes an opinion of the painters of his time to the same -effect:--"Teneano essi (alcuni maestri) per cosa certa, che in molte -opere Tiziano volesse fingere il lume--quale si vede nell' inclinarsi -del sole verso la sera. Gli orizzonti assai luminosi dietro le -montagne, le ombre incerte e più le carnagioni brunette e rosseggianti -delle figure, gl'induceano a creder questo."--Lib. ii. Leonardo da -Vinci observes, "Quel corpo che si troverà in mediocre lume fia in -lui poca differenza da' lumi all' ombre. E questo accade sul far -della sera--e queste opere sono dolci ed hacci grazia ogni qualità di -volto," &c.--p. 336. Elsewhere, "Le ombre fatte dal sole od altri lumi -particolari sono senza grazia."--p. 357; see also p. 247. - -[18] See "Francesco Priscianese De' Primi Principii della Lingua -Latina," Venice, 1550. The letter is at the end of the work. It is -quoted in Ticozzi's "Vite de' Pittori Vecelli," Milan, 1817. - -[19] The works of Giorgione are extremely rare. The pictures best -calculated to give an idea of the glowing manner for which he -is celebrated, are the somewhat early works and several of the -altar-pieces of Titian, the best specimens of Palma Vecchio, and the -portraits of Sebastian del Piombo. - -[20] Zanetti and Lodovico Dolce mention Lorenzo Lotto as an instance -of the excess of Giorgione's style. Titian himself sometimes -overstepped the mark, as his biographers confess, and as appears, -among other instances, from the head of St. Peter in the picture (now -in the Vatican) in which the celebrated St. Sebastian is introduced. -Raphael was criticised by some cardinals for a similar defect. See -"Castiglione, Il Cortigiano," 1. ii. - -In the same paragraph to which the present observations refer, the -authority of Kircher is quoted; his treatise, "Ars magna lucis et -umbrae," was published in Rome in 1646. In a portrait of Nicholas -Poussin, engraved by Clouet, the painter is represented holding a book, -which, from the title and the circumstance of Poussin having lived in -Rome in Kircher's time, Goethe supposes to be the work in question. The -abuse of the principle above alluded to, is perhaps exemplified in the -red half-tints observable in some of Poussin's figures. - -The augmentation of colour in subdued light was still more directly -taught by Lomazzo. He composes the half-tints of flesh merely by -diminishing the quantity of white, the proportions of the other colours -employed (for he enters into minute details) remaining unaltered. See -his "Trattato della arte della Pittura," Milan, 1584, p. 301. - -[21] In the Dresden Gallery, a picture attributed to Titian--at -all events a lucid Venetian picture--hangs next the St. George of -Correggio. After looking at the latter, the Venetian work appears -glassy and unsubstantial, but on reversing the order of comparison, -the Correggio may be said to suffer more, and for a moment its fine -transitions of light and shade seem changed to heaviness. - -[22] The finest works of Tintoret---the Crucifixion and the Miracolo -del Servo (considered here merely with reference to their colour,) -may be said to combine the excellences of Titian and Giacomo Bassan, -on a grand scale; the sparkling clearness of the latter is one of the -prominent characteristics of these pictures. Tintoret is reported to -have once said that a union of his own knowledge of form with Bassan's -colour would be the perfection of painting. See "Verei Notizie de' -Pittori di Bassano;" Ven. 1775, p. 61. - -[23] That this last quality, the characteristic of Bassan's best -pictures, was held in high estimation by Paul Veronese, is not only -evident from that painter's own works, but from the circumstance of his -preferring to place his sons with Bassan rather than with any other -painter. (See "Boschini Carta del Navegar," p. 280.) The Baptism of -Sta. Lucilla, in Boschini's time considered the finest of Giacomo's -works, is still in the church of S. Valentino, at Bassano, and may be -considered the type of the lucid and sparkling manner. - - - -NOTE F.--Par. 83. - -The author, in these instances, seems to be anticipating his -subsequent explanations on the effect of semi-transparent mediums. -For an explanation of the general view contained in these paragraphs -respecting the gradual increase of colour from high light, see the last -Note. - -The anonymous French work before alluded to, among other interesting -examples, contains a chapter on shadows cast by the upper light of the -sky and coloured by the setting sun. The effect of this remarkable -combination is, that the light on a wall is most coloured immediately -under a projecting roof, and becomes comparatively neutralised in -proportion to its distance from the edge of the darkest shade. - - -NOTE G.--Par. 98. - -"The simplest case of the phenomenon, which Goethe calls a subjective -halo, and one which at once explains its cause, is the following. -Regard a red wafer on a sheet of white paper, keeping the eye -stedfastly fixed on a point at its center. When the retina is -fatigued, withdraw the head a little from the paper, and a green halo -will appear to surround the wafer. By this slight increase of distance -the image of the wafer itself on the retina becomes smaller, and the -ocular spectrum which before coincided with the direct image, being -now relatively larger, is seen as a surrounding ring."--S. F. Goethe -mentions cases of this kind, but does not class them with subjective -halos. See Par. 30. - - -NOTE H.--Par. 113. - -"Cases of this kind are by no means uncommon. Several interesting -ones are related in Sir John Herschell's article on Light in the -Encyclopædia Metropolitana. Careful investigation has, however, shown -that this defect of vision arises in most, if not in all cases, from -an inability to perceive the red, not the blue rays. The terms are so -confounded by the individuals thus affected, that the comparison of -colours in their presence is the only criterion."--S. F. - - -NOTE I.--Par. 135. - -The author more than once admits that this chapter on "Pathological -Colours" is very incomplete, and expresses a wish (Par. 734) that some -medical physiologists would investigate the subject further. This was -afterwards in a great degree accomplished by Dr. Johannes Müller, in -his memoir "Über die Phantastischen Gesichtserscheinungen." Coblentz, -1826. Similar phenomena have been also investigated with great labour -and success by Purkinje. For a collection of extraordinary facts of the -kind recorded by these writers, the reader may consult Scott's Letters -on Demonology and Witchcraft.[1] The instances adduced by Müller and -others are, however, intended to prove the inherent capacity of the -organ of vision to produce light and colours. In some maladies of the -eye, the patient, it seems, suffers the constant presence of light -without external light. The exciting principle in this case is thus -proved to be within, and the conclusion of the physiologists is that -external light is only one of the causes which produce luminous and -coloured impressions. That this view was anticipated by Newton may be -gathered from the concluding "query" in the third book of his Optics. - - -[1] See also a curious passage on the beatific vision of the monks of -Mount Athos, in Gibbon, chap. 63. - - - -NOTE K.--Par. 140. - -"Catoptrical colours. The colours included under this head are -principally those of fibres and grooved surfaces; they can be produced -artificially by cutting parallel grooves on a surface of metal from -2000 to 10,000 in the inch. See 'Brewster's Optics,' p. 120. The -colours called by Goethe _paroptical_, correspond with those produced -by the diffraction or inflection of light in the received theory.--See -Brewster, p. 95. The phenomena included under the title 'Epoptical -Colours,' are generally known as the colours of thin plates. They vary -with the thickness of the film, and the colour seen by reflection -always differs from that seen by transmission. The laws of these -phenomena have been thoroughly investigated. See Nobili, and Brewster, -p. 100."--S. F. - -The colours produced by the transmission of polarised light through -chrystalised mediums, were described by Goethe, in his mode, -subsequently to the publication of his general theory, under the name -of Entoptic Colours. See note to Par. 485. - - -NOTE L.--Par. 150. - -We have in this and the next paragraph the outline of Goethe's system. -The examples that follow seem to establish the doctrine here laid -down, but there are many cases which it appears cannot be explained on -such principles: hence, philosophers generally prefer the theory of -absorption, according to which it appears that certain mediums "have -the property of absorbing some of the component rays of white light, -while they allow the passage of others."[1] - -Whether all the facts adduced by Goethe--for instance, that recorded -in Par. 172, are to be explained by this doctrine, we leave to the -investigators of nature to determine. Dr. Eckermann, in conversing with -Goethe, thus described the two leading phenomena (156, 158) as seen by -him in the Alps. "At a distance of eighteen or twenty miles at mid-day -in bright sunshine, the snow appeared yellow or even reddish, while the -dark parts of the mountain, free from snow, were of the most decided -blue. The appearances did not surprise me, for I could have predicted -that the mass of the interposed medium would give a deep yellow tone -to the white snow, but I was pleased to witness the effect, since it -so entirely contradicted the erroneous views of some philosophers, -who assert that the air has a blue-tinging quality. The observation, -said Goethe, is of importance, and contradicts the error you allude to -completely."[2] - -The same writer has some observations to the same effect on the colour -of the Rhone at Geneva. A circumstance of an amusing nature which he -relates in confirmation of Goethe's theory, deserves to be inserted. -"Here (at Strasburg), passing by a shop, I saw a little glass bust -of Napoleon, which, relieved as it was against the dark interior of -the room, exhibited every gradation of blue, from milky light blue -to deep violet. I foresaw that the bust seen from within the shop -with the light behind it, would present every degree of yellow, and I -could not resist walking in and addressing the owner, though perfectly -unknown to me. My first glance was directed to the bust, in which, to -my great joy, I saw at once the most brilliant colours of the warmer -kind, from the palest yellow to dark ruby red. I eagerly asked if I -might be allowed to purchase the bust; the owner replied that he had -only lately brought it with him from Paris, from a similar attachment -to the emperor to that which I appeared to feel, but, as my ardour -seemed far to surpass his, I deserved to possess it. So invaluable -did this treasure seem in my eyes, that I could not help looking at -the good man with wonder as he put the bust into my hands for a few -franks. I sent it, together with a curious medal which I had bought -in Milan, as a present to Goethe, and when at Frankfort received the -following letter from him." The letter, which Dr. Eckermann gives -entire, thus concludes--"When you return to Weimar you shall see the -bust in bright sunshine, and while the transparent countenance exhibits -a quiet blue,[3] the thick mass of the breast and epaulettes glows with -every gradation of warmth, from the most powerful ruby-red downwards; -and as the granite statue of Memnon uttered harmonious sounds, so the -dim glass image displays itself in the pomp of colours. The hero is -victorious still in supporting the Farbenlehre."[4] - -One effect of Goethe's theory has been to invite the attention of -scientific men to facts and appearances which had before been unnoticed -or unexplained. To the above cases may be added the very common, but -very important, fact in painting, that a light warm colour, passed in -a semi-transparent state over a dark one, produces a cold, bluish -hue, while the operation reversed, produces extreme warmth. On the -judicious application of both these effects, but especially of the -latter, the richness and brilliancy of the best-coloured pictures -greatly depends. The principle is to be recognised in the productions -of schools apparently opposite in their methods. Thus the practice -of leaving the ground, through which a light colour is apparent, as -a means of ensuring warmth and depth, is very common among the Dutch -and Flemish painters. The Italians, again, who preferred a solid -under-painting, speak of internal light as the most fascinating quality -in colour. When the ground is entirely covered by solid painting, as -in the works of some colourists, the warmest tints in shadows and -reflections have been found necessary to represent it. This was the -practice of Rembrandt frequently, and of Reynolds universally, but the -glow of their general colour is still owing to its being repeatedly -or ultimately enriched on the above principle. Lastly, the works of -those masters who were accustomed to paint on dark grounds are often -heavy and opaque; and even where this influence of the ground was -overcome, the effects of time must be constantly diminishing the warmth -of their colouring as the surface becomes rubbed and the dark ground -more apparent through it. The practice of painting on dark grounds was -intended by the Carracci to compel the students of their school to -aim at the direct imitation of the model, and to acquire the use of -the brush; for the dark ground could only be overcome by very solid -painting. The result answered their expectations as far as dexterity of -pencil was concerned, but the method was fatal to brilliancy of colour. -An intelligent writer of the seventeenth century[5] relates that Guido -adopted his extremely light style from seeing the rapid change in some -works of the Carracci soon after they were done. It is important, -however, to remark, that Guido's remedy was external rather than -internal brilliancy; and it is evident that so powerless a brightness -as white paint can only acquire the splendour of light by great -contrast, and, above all, by being seen through external darkness. The -secret of Van Eyck and his contemporaries is always assumed to consist -in the vehicle (varnish or oils) he employed; but a far more important -condition of the splendour of colour in the works of those masters was -the careful preservation of internal light by painting thinly, but -ultimately with great force, on white grounds. In some of the early -Flemish pictures in the Royal Gallery at Munich, it may be observed, -that wherever an alteration was made by the painter, so that a light -colour is painted over a dark one, the colour is as opaque as in any -of the more modern pictures which are generally contrasted with such -works. No quality in the vehicle could prevent this opacity under such -circumstances; and on the other hand, provided the internal splendour -is by any means preserved, the vehicle is comparatively unimportant. - -It matters not (say the authorities on these points) whether the effect -in question is attained by painting thinly over the ground, in the -manner of the early Flemish painters and sometimes of Rubens, or by -painting a solid light preparation to be afterwards toned to richness -in the manner of the Venetians. Among the mechanical causes of the -clearness of colours superposed on a light preparation may be mentioned -that of careful grinding. All writers on art who have descended to -practical details have insisted on this. From the appearance of some -Venetian pictures it may be conjectured that the colours of the -solid under-painting were sometimes less perfectly ground than the -scumbling colours (the light having to pass through the one and to -be reflected from the other). The Flemish painters appear to have -used carefully-ground pigments universally. This is very evident in -Flemish copies from Raphael, which, though equally impasted with -the originals, are to be detected, among other indications, by the -finely-ground colours employed. - - -[1] See "Müller's Elements of Physiology," translated from the German -by William Baly, M.D. "The laws of absorption," it has been observed, -"have not been studied with so much success as those of other phenomena -of physical optics, but some excellent observations on the subject -will be found in Herschell's Treatise on Light in the Encyclopædia -Metropolitana, § III." - -[2] "Eckermann's Gespräche mit Goethe," vol. ii. p. 280. Leonardo da -Vinci had made precisely the same observation. "A distant mountain will -appear of a more beautiful blue in proportion as it is dark in colour. -The illumined air, interposed between the eye and the dark mass, being -thinner towards the summit of the mountain, will exhibit the darkness -as a deeper blue and _vice versâ_."--_Trattato della Pittura_, p. 143. -Elsewhere--"The air which intervenes between the eye and dark mountains -becomes blue; but it does not become blue in (before) the light part, -and much less in (before) the portion that is covered with snow."--p. -244. - -[3] This supposes either that the mass was considerably thicker, or -that there was a dark ground behind the head, and a light ground behind -the rest of the figure. - -[4] "Eckermann's Gespräche mit Goethe," vol. ii. p. 242. - -[5] Scanelli, "Microcosmo della Pittura," Cesena, 1657, p. 114. - - - -NOTE M.--Par. 177. - -Without entering further into the scientific merits or demerits of -this chapter on the "First Class of Dioptrical Colours," it is to be -observed that several of the examples correspond with the observations -of Leonardo da Vinci, and again with those of a much older authority, -namely, Aristotle. Goethe himself admits, and it has been remarked by -others, that his theory, in many respects, closely resembles that of -Aristotle: indeed he confesses[1] that at one time he had an intention -of merely paraphrasing that philosopher's Treatise on Colours.[2] - -We have already remarked (Note on par. 150) that Goethe's notion with -regard to the production of warm colours, by the interposition of dark -transparent mediums before a light ground, agrees with the practice of -the best schools in colouring; and it is not impossible that the same -reasons which may make this part of the doctrine generally acceptable -to artists now, may have recommended the very similar theory of -Aristotle to the painters of the fifteenth and sixteenth centuries: -at all events, it appears that the ancient theory was known to those -painters. - -It is unnecessary to dwell on the fact that the doctrines of Aristotle -were enthusiastically embraced and generally inculcated at the period -in question;[3] but it has not been observed that the Italian writers -who translated, paraphrased, and commented on Aristotle's Treatise -on Colours in particular, were in several instances the personal -friends of distinguished painters. Celio Calcagnini[4] had the highest -admiration for Raphael; Lodovico Dolce[5] was the eulogist of Titian; -Portius,[6] whose amicable relations with the Florentine painters may -be inferred from various circumstances, lectured at Florence on the -Aristotelian doctrines early in the sixteenth century. The Italian -translations were later, but still prove that these studies were -undertaken with reference to the arts, for one of them is dedicated to -the painter Cigoli.[7] - -The writers on art, from Leon Battista Alberti to Borghini, without -mentioning later authorities, either tacitly coincide with the -Aristotelian doctrine, or openly profess to explain it. It is true this -is not always done in the clearest manner, and some of these writers -might say with Lodovico Dolce, "I speak of colours, not as a painter, -for that would be the province of the divine Titian." - -Leonardo da Vinci in his writings, as in everything else, appears as -an original genius. He now and then alludes generally to opinions -of "philosophers," but he quotes no authority ancient or modern. -Nevertheless, a passage on the nature of colours, particularly where -he speaks of the colours of the elements, appears to be copied from -Leon Battista Alberti,[8] and from the mode in which some of Leonardo's -propositions are stated, it has been supposed[9] that he had been -accustomed at Florence to the form of the Aristotelian philosophy. At -all events, some of the most important of his observations respecting -light and colours, have a great analogy with those contained in the -treatise in question. The following examples will be sufficient to -prove this coincidence; the corresponding passages in Goethe are -indicated, as usual, by the numbers of the paragraphs; the references -to Leonardo's treatise are given at the bottom of the page. - - Aristotle. - - "A vivid and brilliant red appears when the weak rays of the - sun are tempered by subdued and shadowy white,"--154. - - Leonardo - - "The air which is between the sun and the earth at sun-rise - or sun-set, always invests what is beyond it more than any - other (higher) portion of the air: this is because it is - whiter."[10] - - A bright object loses its whiteness in proportion to its - distance from the eye much more when it is illuminated by - the sun, for it partakes of the colour of the sun mingled - with the colour (tempered by the mass) of the air interposed - between the eye and the brightness.[11] - - Aristotle. - - "If light is overspread with much obscurity, a red colour - appears; if the light is brilliant and vivid, this red - changes to a flame-colour."[12]--150, 160. - - Leonardo. - - "This (the effect of transparent colours on various grounds) - is evident in smoke, which is blue when seen against black, - but when it is opposed to the (light) blue sky, it appears - brownish and reddening."[13] - - Aristotle. - - "White surfaces as a ground for colours, have the effect of - making the pigments[14] appear in greater splendour."--594, - 902. - - Leonardo. - - "To exhibit colours in their beauty, the whitest ground - should be prepared. I speak of colours that are (more or - less) transparent."[15] - - Aristotle. - - "The air near us appears colourless; but when seen in depth, - owing to its thinness it appears blue;[16] for where the - light is deficient (beyond it), the air is affected by the - darkness and appears blue: in a very accumulated state, - however, it appears, as is the case with water, quite - white."--155, 158. - - Leonardo. - - "The blue of the atmosphere is owing to the mass of - illuminated air interposed between the darkness above and - the earth. The air in itself has no colour, but assumes - qualities according to the nature of the objects which are - beyond it. The blue of the atmosphere will be the more - intense in proportion to the degree of darkness beyond it:" - elsewhere--"if the air had not darkness beyond it, it would - be white."[17] - - Aristotle. - - "We see no colour in its pure state, but every hue is - variously intermingled with others: even when it is - uninfluenced by other colours, the effect of light and - shade modifies it in various ways, so that it undergoes - alterations and appears unlike itself. Thus, bodies seen in - shade or in light, in more pronounced or softer sun-shine, - with their surfaces inclined this way or that, with every - change exhibit a different colour." - - Leonardo. - - "No substance will ever exhibit its own hue unless the light - which illumines it is entirely similar in colour. It very - rarely happens that the shadows of opaque bodies are really - similar (in colour) to the illumined parts. The surface of - every substance partakes of as many hues as are reflected - from surrounding objects."[18] - - Aristotle. - - "So, again, with regard to the light of fire, of the moon, - or of lamps, each has a different colour, which is variously - combined with differently coloured objects." - - Leonardo. - - "We can scarcely ever say that the surface of illumined - bodies exhibits the real colour of those bodies. Take a - white band and place it in the dark, and let it receive - light by means of three apertures from the sun, from fire, - and from the sky: the white band will be tricoloured."[19] - - Aristotle. - - "When the light falls on any object and assumes (for - example) a red or green tint, it is again reflected on other - substances, thus undergoing a new change. But this effect, - though it really takes place, is not appreciable by the - eye: though the light thus reflected to the eye is composed - of a variety of colours, the principal of these only are - distinguishable." - - Leonardo. - - "No colour reflected on the surface of another colour, - tinges that surface with its own colour (merely), but will - be mixed with various other reflections impinging on the - same surface:" but such effects, he observes elsewhere, "are - scarcely, if at all, distinguishable in a very diffused - light."[20] - - Aristotle. - - "Thus, all combinations of colours are owing to three - causes: the light, the medium through which the light - appears, such as water or air, and lastly the local colour - from which the light happens to be reflected." - - Leonardo. - - "All illumined objects partake of the colour of the light - they receive. - - "Every opaque surface partakes of the colour of the - intervening transparent medium, according to the density of - such medium and the distance between the eye and the object. - - "The medium is of two kinds; either it has a surface, like - water, &c., or it is without a common surface, like the - air."[21] - -In the observations on trees and plants more points of resemblance -might be quoted; the passages corresponding with Goethe's views are -much more numerous. - -It is remarkable that Leonardo, in opposition, it seems to some -authorities,[22] agrees with Aristotle in reckoning black and white -as colours, placing them at the beginning and end of the scale.[23] -Like Aristotle, again, he frequently makes use of the term black, for -obscurity; he even goes further, for he seems to consider that blue -may be produced by the actual mixture of black and white, provided they -are pure.[24] The ancient author, however, explains himself on this -point as follows--"We must not attempt to make our observations on -these effects by mixing colours as painters mix them, but by remarking -the appearances as produced by the rays of light mingling with each -other."[25] - -When we consider that Leonardo's Treatise professes to embrace the -subject of imitation in painting, and that Aristotle's briefly examines -the physical nature and appearance of colours, it must be admitted -that the latter sustains the above comparison with advantage; and it -is somewhat extraordinary that observations indicating so refined a -knowledge of nature, as regards the picturesque, should not have been -taken into the account, for such appears to be the fact, in the various -opinions and conjectures that have been expressed from time to time on -the painting of the Greeks. The treatise in question must have been -written when Apelles painted, or immediately before; and as a proof -that Aristotle's remarks on the effect of semi-transparent mediums were -not lost on the artists of his time, the following passage from Pliny -is subjoined, for, though it is well known, it acquires additional -interest from the foregoing extracts. - -"He (Apelles) passed a dark colour over his pictures when finished, so -thin that it increased the splendour of the tints, while it protected -the surface from dust and dirt: it could only be seen on looking into -the picture. The effect of this operation, judiciously managed, was to -prevent the colours from being too glaring, and to give the spectator -the impression of looking through a transparent crystal. At the same -time it seemed almost imperceptibly to add a certain dignity of tone to -colours that were too florid." "This," says Reynolds, "is a true and -artist-like description of glazing or scumbling, such as was practised -by Titian and the rest of the Venetian painters." - -The account of Pliny has, in this instance, internal evidence -of truth, but it is fully confirmed by the following passage in -Aristotle:--"Another mode in which the effect of colours is exhibited -is when they appear through each other, as painters employ them when -they glaze (ἐπαλειφοντες)[26] a (dark) colour over a lighter one; just -as the sun, which is in itself white, assumes a red colour when seen -through darkness and smoke. This operation also ensures a variety of -colours, for there will be a certain ratio between those which are on -the surface and those which are in depth."--_De Sensu et Sensili_. - -Aristotle's notion respecting the derivation of colours from white and -black may perhaps be illustrated by the following opinion on the very -similar theory of Goethe. - -"Goethe and Seebeck regard colour as resulting from the mixture of -white and black, and ascribe to the different colours a quality -of darkness (σκιερὸν), by the different degrees of which they are -distinguished, passing from white to black through the gradations -of yellow, orange, red, violet, and blue, while green appears to be -intermediate again between yellow and blue. This remark, though it has -no influence in weakening the theory of colours proposed by Newton, -is certainly correct, having been confirmed experimentally by the -researches of Herschell, who ascertained the relative intensity of the -different coloured rays by illuminating objects under the microscope by -their means, &c. - -"Another certain proof of the difference in brightness of the different -coloured rays is afforded by the phenomena of ocular spectra. If, after -gazing at the sun, the eyes are closed so as to exclude the light, the -image of the sun appears at first as a luminous or white spectrum upon -a dark ground, but it gradually passes through the series of colours to -black, that is to say, until it can no longer be distinguished from the -dark field of vision; and the colours which it assumes are successively -those intermediate between white and black in the order of their -illuminating power or brightness, namely, yellow, orange, red, violet, -and blue. If, on the other hand, after looking for some time at the -sun we turn our eyes towards a white surface, the image of the sun is -seen at first as a black spectrum upon the white surface, and gradually -passes through the different colours from the darkest to the lightest, -and at last becomes white, so that it can no longer be distinguished -from the white surface"[27]--See par 40, 44. - -It is not impossible that Aristotle's enumeration of the colours may -have been derived from, or confirmed by, this very experiment. Speaking -of the after-image of colours he says, "The impression not only exists -in the sensorium in the act of perceiving, but remains when the organ -is at rest. Thus if we look long and intently on any object, when -we change the direction of the eyes a responding colour follows. If -we look at the sun, or any other very bright object, and afterwards -shut our eyes, we shall, as if in ordinary vision, first see a colour -of the same kind; this will presently be changed to a red colour, -then to purple, and so on till it ends in black and disappears."--_De -Insomniis_. - - -[1] "Geschichte der Farbenlehre," in the "Nachgelassene Werke." Cotta, -1833. - -[2] The treatise in question is ascribed by Goethe to Theophrastus, -but it is included in most editions of Aristotle, and even attributed -to him in those which contain the works of both philosophers; for -instance, in the Aldine Princeps edition, 1496. Calcagnini says, the -treatise is made up of two separate works on the subject, both by -Aristotle. - -[3] His authority seems to have been equally great on subjects -connected with the phenomena of vision; the Italian translator of -a Latin treatise, by Portius, on the structure and colours of the -eye, thus opens his dedication to the Cardinal Ercole Gonzaga, of -Mantua:--"Grande anzi quasi infinito è l'obligo che ha il mondo con -quel più divino che umano spirito di Aristotile." - -[4] In a letter to Ziegler the mathematician, Calcagnini speaks of -Raphael as "the first of painters in the theory as well as in the -practice of his art." This expression may, however, have had reference -to a remarkable circumstance mentioned in the same letter, namely, -that Raphael entertained the learned Fabius of Ravenna as a constant -guest, and employed him to translate Vitruvius into Italian. This MS. -translation, with marginal notes, written by Raphael, is now in the -library at Munich. "Passavant, Rafael von Urbino." - -[5] Lodovico Dolce's Treatise on Colours (1565) is in the form of a -dialogue, like his "Aretino." The abridged theory of Aristotle is -followed by a translation of the Treatise of Antonius Thylesius on -Colours; this is adapted to the same colloquial form, and the author is -not acknowledged: the book ends with an absurd catalogue of emblems. -The "Somma della Filosofia d'Aristotile," published earlier by the same -author, is a very careless performance. - -[6] A Latin translation of Aristotle's Treatise on Colours, with -comments by Simon Portius, was first published, according to Goethe, -at Naples in 1537. In a later Florentine edition, 1548, dedicated to -Cosmo I., Portius alludes to his having lectured at an earlier period -in Florence on the doctrines of Aristotle, at which time he translated -the treatise in question. Another Latin translation, with notes, was -published later in the same century at Padua--"Emanuele Marguino -Interprete:" but by far the clearest view of the Aristotelian theory -is to be found in the treatise of Antonio Vidi Scarmiglione of Fuligno -("De Coloribus," Marpurgi, 1591). It is dedicated to the Emperor -Rudolph II. Of all the paraphrases of the ancient doctrine this comes -nearest to the system of Goethe; but neither this nor any other of the -works alluded to throughout this Note are mentioned by the author in -his History of the Doctrine of Colours, except that of Portius. - -[7] An earlier Italian translation appeared in Rome, 1535. See -"Argelatus Biblioteca degli Volgarizzatori." - -[8] "Della Pittura e della Statua," Lib. I, p. 16, Milan edition, -1804. Compare with the "Trattato della Pittura," p. 141. Other points -of resemblance are to be met with. The notion of certain colours -appropriated to the four elements, occurs in Aristotle, and is indeed -attributed to older writers. - -[9] See the notes to the Roman edition of the "Trattato della Pittura." - -[10] Page 237. - -[11] Page 301. - -[12] In the Treatise _De Igne_, by Theophrastus, we find the same -notion thus expressed: "Brightness (_τὸ λευκὸν_) seen through a -dark coloured medium (_διὰ του μέλανος_) appears red; as the sun -seen through smoke or soot: hence the coal is redder than the -flame." Scarmiglione, from whom Kircher seems to have copied, -observes:--"Itaque color realis est lux opaca; licet id e plurimis -apparentiis colligere. Luna enim in magnâ solis eclipsi rubra -conspicitur, quia tenebris lux præpeditur ac veluti tegitur."--_De -Coloribus_. - -[13] Page 122. - -[14] _Τὰ ἂνθη_: translated _flores_ by Calcagnini and the rest, by -Goethe, _die Blüthe_, the bloom. That the word sometimes signified -pigments is sufficiently apparent from the following passage of -Suidas (quoted by Emeric David, "Discours Historiques sur la Peinture -Moderne") _ἂνθεσι κεκοσμημέναι, οἶον ψιμμιωίῳ φύκει καὶ τοῖς ὸμοίοις_. -Variis pigmentis ornatæ, ut cerussâ, fuco, et aliis similibus. (Suid. -in voc. _Ἐξμηθισμένας_.) A panel prepared for painting, with a white -ground consolidated with wax, and perhaps mastic, was found in -Herculaneum. - -[15] Page 114. - -[16] _Ἐν βάθει δὲ θεωρουμίνου ιγγυτάτω φαίνεται τῶ χρώματι κυανονοειδὴς -διὰ τὴν ὰραιότητα._ "But when seen in depth, it appears (even) in its -nearest colour, blue, owing to its thinness." The Latin interpretations -vary very much throughout. The point which is chiefly important is -however plain enough, viz. that darkness seen through a light medium is -blue. - -[17] Page 136-430. - -[18] Page 121, 306, 326, 387. - -[19] Page 306. - -[20] Page 104, 369. - -[21] Page 236, 260, 328. - -[22] "De' semplici colori il primo è il bianco: beuchè i filosofi non -accettano nè il bianco nè il nero nel numero de' colori."--p. 125, 141. -Elsewhere, however, he sometimes adopts the received opinion. - -[23] Leon Battista Alberti, in like manner observes:--"Affermano (i -filosofi) che le spezie de' colori sono sette, cioè, che il bianco ed -il nero sono i duoi estremi, infra i quali ve n'è uno nel mezzo (rosso) -e che infra ciascuno di questi duoi estremi e quel del mezzo, da ogni -parte ve ne sono due altri." An absurd statement of Lomazzo, p. 190, -is copied verbatim from Lodovico Dolce (Somma della Filos. d'Arist.); -but elsewhere, p. 306, Lomazzo agrees with Alberti. Aristotle seems to -have misled the two first, for after saying there are seven colours, -he appears only to mention six: he says--"There are seven colours, if -brown is to be considered equivalent to black, which seems reasonable. -Yellow, again, may be said to be a modification of white. Between these -we find red, purple, green, and blue."--_De Sensu et Sensili_. Perhaps -it is in accordance with this passage that Leonardo da Vinci reckons -eight colours.--_Trattato_, p. 126. - -[24] Page 122, 142, 237. - -[25] On the authority of this explanation the word μιλάν has sometimes -been translated in the foregoing extracts _obscurity, darkness_. - -Raffaello Borghini, in his attempt to describe the doctrine of -Aristotle with a view to painting, observes--"There are two -principles which concur in the production of colour, namely, light -and transparence." But he soon loses this clue to the best part of -the ancient theory, and when he has to speak of the derivation of -colours from white and black, he evidently understands it in a mere -atomic sense, and adds--"I shall not at present pursue the opinion -of Aristotle, who assumes black and white as principal colours, and -considers all the rest as intermediate between them."--_Il Riposo_, 1. -ii. Accordingly, like Lodovico Dolce, he proceeds to a subject where he -was more at home, namely, the symbolical meaning of colours. - -[26] This word is only strictly applied to unctuous substances, and may -confirm the views of those writers who have conjectured that asphaltum -was a chief ingredient in the _atramentum_ of the ancients. - -[27] "Elements of Physiology," by J. Müller, M.D., translated from the -German by William Baly, M.D. London, 1839. - - - -NOTE N.--Par. 246. - -"The appearance of white in the centre, according to the Newtonian -theory, arises from each line of rays forming its own spectrum. -These spectra, superposing each other on all the middle part, leave -uncorrected (unneutralised) colours only at the two edges."--S. F.[1] - - -[1] This was objected to Goethe when his "Beyträge sur Optik" first -appeared; he answered the objection by a coloured diagram in the plates -to the "Farbenlehre:" in this he undertakes to show that the assumed -gradual "correction" of the colours would produce results different -from the actual appearance in nature. - - - -NOTE O.--Par. 252. - -These experiments with grey objects, which exhibit different colours -as they are on dark or light grounds, were suggested, Goethe tells -us, by an observation of Antonius Lucas, of Lüttich, one of Newton's -opponents, and, in the opinion of the author, one of the few who made -any well-founded objections. Lucas remarks, that the sun acts merely -as a circumscribed image in the prismatic experiments, and that if the -same sun had a lighter background than itself, the colours of the prism -would be reversed. Thus in Goethe's experiments, when the grey disk is -on a dark ground, it is edged with blue on being magnified; when on a -light ground it is edged with yellow. Goethe acknowledges that Lucas -had in some measure anticipated his own theory.--Vol. ii. p. 440. - - - -NOTE P.--Par. 284. - -The earnestness and pertinacity with which Goethe insisted that -the different colours are not subject to different degrees of -refrangibility are at least calculated to prove that he was himself -convinced on the subject, and, however extraordinary it may seem, his -conviction appears to have been the result of infinite experiments -and the fullest ocular evidence. He returns to the question in the -controversial division of his work, in the historical part, and again -in the description of the plates. In the first he endeavours to show -that Newton's experiment with the blue and red paper depends entirely -on the colours being so contrived as to appear elongated or curtailed -by the prismatic borders. "If," he says, "we take a light-blue instead -of a dark one, the illusion (in the latter case) is at once evident. -According to the Newtonian theory the yellow-red (red) is the least -refrangible colour, the violet the most refrangible. Why, then, does -Newton place a blue paper instead of a violet next the red? If the -fact were as he states it, the difference in the refrangibility of -the yellow-red and violet would be greater than in the case of the -yellow-red and blue. But here comes in the circumstance that a violet -paper conceals the prismatic borders less than a dark-blue paper, as -every observer may now easily convince himself," &c.--Polemischer -Theil, par. 45. Desaguliers, in repeating the experiment, confessed -that if the ground of the colours was not black, the effect did -not take place so well. Goethe adds, "not only not so well, but -not at all."--Historischer Theil, p. 459. Lucas of Lüttich, one of -Newton's first opponents, denied that two differently-coloured silks -are different in distinctness when seen in the microscope. Another -experiment proposed by him, to show the unsoundness of the doctrine of -various refrangibility, was the following:--Let a tin plate painted -with the prismatic colours in stripes be placed in an empty cubical -vessel, so that from the spectator's point of view the colours may be -just hidden by the rim. On pouring water into this vessel, all the -colours become visible in the same degree; whereas, it was contended, -if the Newtonian doctrine were true, some colours would be apparent -before others.--Historischer Theil, p. 434. - -Such are the arguments and experiments adduced by Goethe on this -subject; they have all probably been answered. In his analysis of -Newton's celebrated _Experimentum Crucis_, he shows again that by -reversing the prismatic colours (refracting a dark instead of a -light object), the colours that are the most refrangible in Newton's -experiment become the least so, and _vice versâ_. - -Without reference to this objection, it is now admitted that "the -difference of colour is not a test of difference of refrangibility, and -the conclusion deduced by Newton is no longer admissible as a general -truth, that to the same degree of refrangibility ever belongs the -same colour, and to the same colour ever belongs the same degree of -refrangibility."--Brewster's Optics, p. 72. - - - -NOTE Q--Par. 387. - -With the exception of two very inconclusive letters to Sulpice -Boisserée, and some incidental observations in the conclusion of the -historical portion under the head of entoptic colours, Goethe never -returned to the rainbow. Among the plates he gave the diagram of -Antonius de Dominis. An interesting chapter on halos, parhelia, and -paraselenæ, will be found in Brewster's Optics, p. 270. - - -NOTE R.--Par. 478. - -The most complete exhibition of the colouring or mantling of metals -was attained by the late Cav. Nobili, professor of physical science in -Florence. The general mode in which these colours are produced is thus -explained by him:[1]-- - -"A point of platinum is placed vertically at the distance of about -half a line above a lamina of the same metal laid horizontally at the -bottom of a vessel of glass or porcelain. Into this vessel a solution -of acetate of lead is poured so as to cover not only the lamina of -platinum, but two or three lines of the point as well. Lastly, the -point is put in communication with the negative pole of a battery, and -the lamina with the positive pole. At the moment in which the circuit -is completed a series of coloured rings is produced on the lamina -under the point similar to those observed by Newton in lenses pressed -together." - -The scale of colours thus produced corresponds very nearly with that -observed by Newton and others in thin plates and films, but it is -fuller, for it extends to forty-four tints. The following list, as -given by Nobili, is divided by him into four series to agree with -those of Newton: the numbers in brackets are those of Newton's scale. -The Italian terms are untranslated, because the colours in some cases -present very delicate transitions.[2] - - _First Series._ - - 1. Biondo argentino (4).[3] 6. Fulvo acceso. - 2. Biondo. 7. Rosso di rame (6). - 3. Biondo d'oro. 8. Ocria. - 4. Biondo acceso (5). 9. Ocria violacea. - 5. Fulvo. 10. Rosso violaceo (7). - - Second Series. - - 11. Violetto (8). 20. Giallo acceso. - 12. Indaco (10). 21. Giallo-rancio. - 13. Blu carico. 22. Rancio (13). - 14. Blu. 23. Rancio-rossiccio. - 15. Blu chiaro (11) 24. Rancio-rosso. - 16. Celeste. 25. Rosso-rancio. - 17. Celeste giallognolo. 26. Lacca-rancia (14). - 18. Giallo chiarissimo (12). 27. Lacca. - 19. Giallo. 28. Lacca accesa (15). - - Third Series. - - 29. Lacca-purpurea (16). 34. Verde-giallo (20). - 30. Lacca-turchiniccia (17). 35. Verde-rancio. - 31. Porpora-verdognola (18). 36. Rancio-verde (21). - 32. Verde (19). 37. Rancio-roseo. - 33. Verde giallognolo. 38. Lacca-rosea (22). - - - Fourth Series. - - 39. Lacca-violacea (24). 43. Verde-giallo rossiccio (28). - 40. Violaceo-verdognolo (25). 44. Lacca-rosea (30). - 41. Verde (26). - 42. Verde-giallo (27). - -"These tints," Professor Nobili observes, "are disposed according to -the order of the thin mantlings which occasion them; the colour of -the thinnest film is numbered 1; then follow in order those produced -by a gradual thickening of the medium. I cannot deceive myself in -this arrangement, for the thin films which produce the colours are -all applied with the same electro-chemical process. The battery, the -solution, the distances, &c., are always the same; the only difference -is the time the effect is suffered to last. This is a mere instant for -the colour of No. 1, a little longer for No. 2, and so on, increasing -for the succeeding numbers. Other criterions, however, are not wanting -to ascertain the place to which each tint belongs." - -The scale differs from that of Newton, inasmuch as there is no blue in -Nobili's first series and no green in the second: green only appears in -the third and fourth series. "The first series," says the Professor, -"is remarkable for the fire and metallic appearance of its tints, the -second for clearness and brilliancy, the third and fourth for force and -richness." The fourth, he observes, has the qualities of the third in a -somewhat lesser degree, but the two greens are very nearly alike. - -It is to be observed, that red and green are the principal ingredients -in the third and fourth series, blue and yellow in the second and first. - - -[1] See "Memorie ed Osservazioni, edite et inedite del Cav. Professor -Nobili," Firenze, 1834. - -[2] The colours in some of the compound terms are in a manner mutually -neutralising; such terms might, no doubt, be amended. - -[3] The three first numbers in Newton's scale are black, blue, and -white. - - - -NOTE S.--Par. 485. - -A chapter on entoptic colours, contained in the supplement to Goethe's -works, was translated with the intention of inserting it among the -notes, but on the whole it was thought most advisable to omit it. Like -many other parts of the "Doctrine of Colours" it might have served as -a specimen of what may be achieved by accurate observation unassisted -by a mathematical foundation. The whole theory of the polarization of -light has, however, been so fully investigated since Goethe's time, -that the chapter in question would probably have been found to contain -very little to interest scientific readers, for whom it seems chiefly -to have been intended. One observation occurs in it which indeed has -more reference to the arts; in order to make this intelligible, the -leading experiment must be first described, and for this purpose the -following extracts may serve. - -3.[1] - -"The experiment, in its simplest form, is to be made as follows:--let -a tolerably thick piece of plate-glass be cut into several squares of -an inch and a half; let these be heated to a red heat and then suddenly -cooled. The squares of glass which do not split in this operation are -now fit to produce the entoptic colours. - -4. - -"In our mode of exhibiting the phenomenon, the observer is, above all, -to betake himself, with his apparatus to the open air. All dark rooms, -all small apertures (foramina exigua),[2] are again to be given up. A -pure, cloudless sky is the source whence we are derive a satisfactory -insight into the appearances. - -5. - -"The atmosphere being clear, let the observer lay the squares above -described on a black surface, so placing them that two sides may -be parallel with the plane of vision. When the sun is low, let him -hold the squares so as to reflect to the eye that portion of the sky -opposite to the sun, and he will then perceive four dark points in -the four corners of a light space. If, after this, he turn towards -the quarters of the sky at right angles with that where his first -observation was made, he will see four bright points on a dark ground: -between the two regions the figures appear to fluctuate. - -6. - -"From this simple reflection we now proceed to another, which, but -little more complicated, exhibits the appearance much more distinctly. -A solid cube of glass, or in its stead a cube composed of several -plates, is placed on a black mirror, or held a little inclined -above it, at sun-rise or sun-set. The reflection of the sky being -now suffered to fall through the cube on the mirror, the appearance -above described will appear more distinctly. The reflection of the -sky opposite to the sun presents four dark points on a light ground; -the two lateral portions of the sky present the contrary appearance, -namely, four light points on a dark ground. The space not occupied by -the corner points appears in the first case as a white cross, in the -other as a black cross, expressions hereafter employed in describing -the phenomena. Before sun-rise or after sun-set, in a very subdued -light, the white cross appears on the side of the sun also.[3] - -"We thus conclude that the direct reflection of the sun produces a -light figure, which we call a white cross; the oblique reflection gives -a dark figure, which we call a black cross. If we make the experiment -all round the sky, we shall find that a fluctuation takes place in the -intermediate regions." - -We pass over a variety of observations on the modes of exhibiting this -phenomenon, the natural transparent substances which exhibit it best, -and the detail of the colours seen within[4] them, and proceed to an -instance where the author was enabled to distinguish the "direct" from -the "oblique" reflection by means of the entoptic apparatus, in a -painter's study. - -40. - -"An excellent artist, unfortunately too soon taken from us, Ferdinand -Jagemann, who, with other qualifications, had a fine eye for light and -shade, colour and keeping, had built himself a painting-room for large -as well as small works. The single high window was to the north, facing -the most open sky, and it was thought that all necessary requisites had -been sufficiently attended to. - -"But after our friend had worked for some time, it appeared to him, -in painting portraits, that the faces he copied were not equally well -lighted at all hours of the day, and yet his sitters always occupied -the same place, and the serenity of the atmosphere was unaltered. - -"The variations of the favourable and unfavourable light had their -periods during the day. Early in the morning the light appeared most -unpleasantly grey and unsatisfactory; it became better, till at last, -about an hour before noon, the objects had acquired a totally different -appearance. Everything presented itself to the eye of the artist in its -greatest perfection, as he would most wish to transfer it to canvas. -In the afternoon this beautiful appearance vanished--the light became -worse, even in the brightest day, without any change having taken place -in the atmosphere. - -"As soon as I heard of this circumstance, I at once connected it in -my own mind with the phenomena which I had been so long observing, -and hastened to prove, by a physical experiment, what a clear-sighted -artist had discovered entirely of himself, to his own surprise and -astonishment. - -"I had the second[5] entoptic apparatus brought to the spot, and the -effect on this was what might be conjectured from the above statement. -At mid-day, when the artist saw his model best lighted, the north, -direct reflection gave the white cross; in the morning and evening, on -the other hand, when the unfavourable oblique light was so unpleasant -to him, the cube showed the black cross; in the intermediate hours the -state of transition was apparent." - -The author proceeds to recall to his memory instances where works of -art had struck him by the beauty of their appearance owing to the light -coming from the quarter opposite the sun, in "direct reflection," and -adds, "Since these decided effects are thus traceable to their cause, -the friends of art, in looking at and exhibiting pictures, may enhance -the enjoyment to themselves and others by attending to a fortunate -reflection." - - -[1] The numbers, as usual, indicate the corresponding paragraphs in the -original. - -[2] In the historical part, Goethe has to speak of so many followers of -Newton who begin their statements with "Si per foramen exiguum," that -the term is a sort of by-word with him. - -[3] At mid-day on the 24th of June the author observed the white cross -reflected from every part of the horizon. At a certain distance from -the sun, corresponding, he supposes, with the extent of halos, the -black cross appeared. - -[4] Whence the term _entoptic_. - -[5] Before described: the author describes several others more or less -complicated, and suggests a portable one. "Such plates, which need -only be an inch and a quarter square, placed on each other to form a -cube, might be set in a brass case, open above and below. At one end of -this case a black mirror with a hinge, acting like a cover, might be -fastened. We recommend this simple apparatus, with which the principal -and original experiment may be readily made. With this we could, in the -longest days, better define the circle round the sun where the black -cross appears," &c. - - -NOTE T.--Par. 496. - -"Since Goethe wrote, all the earths have been decomposed, and have -been shown to be metallic bases united with oxygen; but this does not -invalidate his statement."--S. F. - - -NOTE U.--Par. 502. - -The cold nature of black and its affinity to blue are assumed by the -author throughout; if the quality is opaque, and consequently greyish, -such an affinity is obvious, but in many fine pictures, intense black -seems to be considered as the last effect of heat, and in accompanying -crimson and orange may be said rather to present a difference of -degree than a difference of kind. In looking at the great picture -of the globe, we find this last result produced in climates where -the sun has greatest power, as we find it the immediate effect of -fire. The light parts of black animals are often of a mellow colour; -the spots and stripes on skins and shells are generally surrounded -by a warm hue, and are brown before they are absolutely black. In -combustion, the blackness which announces the complete ignition, is -preceded always by the same mellow, orange colour. The representation -of this process was probably intended by the Greeks in the black and -subdued orange of their vases: indeed, the very colours may have been -first produced in the kiln. But without supposing that they were -retained merely from this accident, the fact that the combination -itself is extremely harmonious, would be sufficient to account for -its adoption. Many of the remarks of Aristotle[1] and Theophrastus[2] -on the production of black, are derived from the observation of the -action of fire, and on one occasion, the former distinctly alludes to -the terracotta kiln. That the above opinion as to the nature of black -was prevalent in the sixteenth century, may be inferred from Lomazzo, -who observes,--"Quanto all' origine e generazione de' colori, la -frigidità è la madre della bianchezza: il calore è padre del nero."[3] -The positive coldness of black may be said to begin when it approaches -grey. When Leonardo da Vinci says that black is most beautiful in -shade, he probably means to define its most intense and transparent -state, when it is furthest removed from grey. - - -[1] "De Coloribus." - -[2] "De Igne." - -[3] "Trattato," &c. p. 191, the rest of the passage, it must be -admitted, abounds with absurdities. - - - -NOTE V.--Par. 555. - -The nature of vehicles or liquid mediums to combine with the substance -of colours, has been frequently discussed by modern writers on art, -and may perhaps be said to have received as much attention as it -deserves. Reynolds smiles at the notion of our not having materials -equal to those of former times, and indeed, although the methods of -individuals will always differ, there seems no reason to suppose that -any great technical secret has been lost. In these inquiries, however, -which relate merely to the mechanical causes of bright and durable -colouring, the skill of the painter in the adequate employment of the -higher resources of his art is, as if by common consent, left out of -the account, and without departing from this mode of considering the -question, we would merely repeat a conviction before expressed, viz. -that the preservation of internal brightness, a quality compatible with -various methods, has had more to do with the splendour and durability -of finely coloured pictures than any vehicle. The observations that -follow are therefore merely intended to show how far the older -written authorities on this subject agree with the results of modern -investigation, without at all assuming that the old methods, if known, -need be implicitly followed. - -On a careful examination of the earlier pictures, it is said that -a resinous substance appears to have been mingled with the colours -together with the oil; that the fracture of the indurated pigment is -shining, and that the surface resists the ordinary solvents.[1] This -admixture of resinous solutions or varnishes with the solid is not -alluded to, as far as we have seen, by any of the writers on Italian -practice, but as the method corresponds with that now prevalent in -England, the above hypothesis is not likely to be objected to for the -present. - -Various local circumstances and relations might seem to warrant the -supposition that the Venetian painters used resinous substances. An -important branch of commerce between the mountains of Friuli and Venice -still consists in the turpentine or fir-resin.[2] Similar substances -produced from various trees, and known under the common name of -balsams,[3] were imported from the East through Venice, for general -use, before the American balsams[4] in some degree superseded them; -and a Venetian painter, Marco Boschini, in his description of the -Archipelago, does not omit to speak of the abundance of mastic produced -in the island of Scio.[5] - -The testimonies, direct or indirect, against the employment of any -such substances by the Venetian painters, in the solid part of their -work, seem, notwithstanding, very conclusive; we begin with the writer -just named. In his principal composition, a poem[6] describing the -practice and the productions of the Venetian painters, Boschini speaks -of certain colours which they shunned, and adds:--"In like manner -(they avoided) shining liquids and varnishes, which I should rather -call lackers;[7] for the surface of flesh, if natural and unadorned, -assuredly does not shine, nature speaks as to this plainly." After -alluding to the possible alteration of this natural appearance by -means of cosmetics, he continues: "Foreign artists set such great -store by these varnishes, that a shining surface seems to them the -only desirable quality in art. What trash it is they prize! fir-resin, -mastic, and sandarach, and larch-resin (not to say treacle), stuff fit -to polish boots.[8] If those great painters of ours had to represent -armour, a gold vase, a mirror, or anything of the kind, they made it -shine with (simple) colours."[9] - -This writer so frequently alludes to the Flemish painters, of whose -great reputation he sometimes seems jealous, that the above strong -expression of opinion may have been pointed at them. On the other hand -it is to be observed that the term _forestieri_, strangers, does not -necessarily mean transalpine foreigners, but includes those Italians -who were not of the Venetian state.[10] The directions given by -Raphael Borghini,[11] and after him by Armenini,[12] respecting the use -and preparation of varnishes made from the very materials in question, -may thus have been comprehended in the censure, especially as some of -these recipes were copied and republished in Venice by Bisagno,[13] in -1642--that is, only six years before Boschini's poem appeared. - -Ridolfi's Lives of the Venetian Painters[14] (1648) may be mentioned -with the two last. His only observation respecting the vehicle is, that -Giovanni Bellini, after introducing himself by an artifice into the -painting-room of Antonello da Messina, saw that painter dip his brush -from time to time in linseed oil. This story, related about two hundred -years after the supposed event, is certainly not to be adduced as very -striking evidence in any way.[15] - -Among the next writers, in order of time prior to Bisagno, may be -mentioned Canepario[16] (1619). His work, "De Atramentis" contains -a variety of recipes for different purposes: one chapter, _De -atramentis diversicoloribus_, has a more direct reference to painting. -His observations under this head are by no means confined to the -preparation of transparent colours, but he says little on the subject -of varnishes. After describing a mode of preserving white of egg, -he says, "Others are accustomed to mix colours in liquid varnish and -linseed, or nut-oil; for a liquid and oily varnish binds the (different -layers of) colours better together, and thus forms a very fit glazing -material."[17] On the subject of oils he observes, that linseed oil was -in great request among painters; who, however, were of opinion that -nut-oil-excelled it "in giving brilliancy to pictures, in preserving -them better, and in rendering the colours more vivid."[18] - -Lomazzo (a Milanese) says nothing on the subject of vehicles in his -principal work, but in his "Idea del Tempio della Pittura,"[19] he -speaks of grinding the colours "in nut-oil, and spike-oil, and other -things," the "and" here evidently means _or_, and by "other things" we -are perhaps to understand other oils, poppy oil, drying oils, &c. - -The directions of Raphael Borghini and Vasari[20] cannot certainly be -considered conclusive as to the practice of the Venetians, but they are -very clear on the subject of varnish. These writers may be considered -the earliest Italian authorities who have entered much into practical -methods. In the few observations on the subject of vehicles in Leonardo -da Vinci's treatise, "there is nothing," as M. Merimée observes, "to -show that he was in the habit of mixing varnish with his colours." -Cennini says but little on the subject of oil-painting; Leon Battista -Alberti is theoretical rather than practical, and the published -extracts of Lorenzo Ghiberti's MS. chiefly relate to sculpture. - -Borghini and Vasari agree in recommending nut-oil in preference to -linseed-oil; both recommend adding varnish to the colours in painting -on walls in oil, "because the work does not then require to be -varnished afterwards," but in the ordinary modes of painting on panel -or cloth, the varnish is omitted. Borghini expressly says, that oil -alone (senza più) is to be employed; he also recommends a very sparing -use of it. - -The treatise of Armenini (1587) was published at Ravenna, and he -himself was of Faenza, so that his authority, again, cannot be -considered decisive as to the Venetian practice. After all, he -recommends the addition of "common varnish" only for the ground or -preparation, as a consolidating medium, for the glazing colours, -and for those dark pigments which are slow in drying. Many of his -directions are copied from the writers last named; the recipes for -varnishes, in particular, are to be found in Borghini. Christoforo -Sorte[21] (1580) briefly alludes to the subject in question. After -speaking of the methods of distemper, he observes that the same colours -may be used in oil, except that instead of mixing them with size, they -are mixed on the palette with nut-oil, or (if slow in drying) with -boiled linseed-oil: he does not mention varnish. The Italian writers -next in order are earlier than Vasari, and may therefore be considered -original, but they are all very concise. - -The treatise of Michael Angelo Biondo[22] (1549), remarkable for -its historical mistakes, is not without interest in other respects. -The list of colours he gives is, in all probability, a catalogue of -those in general use in Venice at the period he wrote. With regard -to the vehicle, he merely mentions oil and size as the mediums for -the two distinct methods of oil-painting and distemper, and does not -speak of varnish. The passages in the Dialogue of Doni[23] (1549), -which relate to the subject in question, are to the same effect. "In -colouring in oil," he observes, "the most brilliant colours (that we -see in pictures) are prepared by merely mixing them with the end of a -knife on the palette." Speaking of the perishable nature of works in -oil-painting as compared with sculpture, he says, that the plaster of -Paris (gesso) and mastic, with other ingredients of which the ground -is prepared, are liable to decay, &c.; and elsewhere, in comparing -painting in general with mosaic, that in the former the colours "must -of necessity be mixed with various things, such as oils, gums, white -or yolk of egg, and juice of figs, all which tend to impair the beauty -of the tints." This catalogue of vehicles is derived from all kinds of -painting to enforce the argument, and is by no means to be understood -as belonging to one and the same method. - -An interesting little work,[24] still in the form of a dialogue (Fabio -and Lauro), appeared a year earlier; the author, Paolo Pino, was a -Venetian painter. In speaking of the practical methods Fabio observes, -as usual, that oil-painting is of all modes of imitation the most -perfect, but his reasons for this opinion seem to have a reference -to the Venetian practice of going over the work repeatedly. Lauro -asks whether it is not possible to paint in oil on the dry wall, as -Sebastian del Piombo did. Fabio answers, "the work cannot last, for the -solidity of the plaster is impenetrable, and the colours, whether in -oil or distemper, cannot pass the surface." This might seem to warrant -the inference that absorbent grounds were prepared for oil-painting, -but there are proofs enough that resins as well as oil were used with -the _gesso_ to make the preparation compact. See Doni, Armenini, &c. -This writer, again, does not speak of varnish. These appear to be the -chief Venetian and Italian authorities[25] of the sixteenth and part of -the following century; and although Boschini wrote latest, he appears -to have had his information from good sources, and more than once -distinctly quotes Palma Giovane. - -In all these instances it will be seen that there is no allusion to the -immixture of varnishes with the solid colours, except in painting on -walls in oil, and that the processes of distemper and oil are always -considered as separate arts.[26] On the other hand, the prohibition -of Boschini cannot be understood to be universal, for it is quite -certain that the Venetians varnished their pictures when done.[27] -After Titian had finished his whole-length portrait of Pope Paul III. -it was placed in the sun to be varnished.[28] Again, in the archives of -the church of S. Niccolo at Treviso a sum is noted (Sept. 21, 1521 ), -"per far la vernise da invernisar la Pala dell' altar grando," and the -same day a second entry appears of a payment to a painter, "per esser -venuto a dar la vernise alla Pala," &c.[29] It is to be observed that -in both these cases the pictures were varnished as soon as done;[30] -the varnish employed was perhaps the thin compound of naphtha (oglio di -sasso) and melted turpentine (oglio d'abezzo), described by Borghini, -and after him by Armenini: the last-named writer remarks that he had -seen this varnish used by the best painters in Lombardy, and had heard -that it was preferred by Correggio. The consequence of this immediate -varnishing may have been that the warm resinous liquid, whatever it -was, became united with the colours, and thus at a future time the -pigment may have acquired a consistency capable of resisting the -ordinary solvents. Not only was the surface of the picture required to -be warm, but the varnish was applied soon after it was taken from the -fire.[31] - -Many of the treatises above quoted contain directions for making the -colours dry:[32] some of these recipes, and many in addition, are to be -found in Palomino, who, however defective as an historian,[33] has left -very copious practical details, evidently of ancient date. His drying -recipes are numerous, and although sugar of lead does not appear, -cardenillo (verdigris), which is perhaps as objectionable, is admitted -to be the best of all dryers. It may excite some surprise that the -Spanish painters should have bestowed so much attention on this subject -in a climate like theirs, but the rapidity of their execution must have -often required such an assistance.[34] - -One circumstance alluded to by Palomino, in his very minute practical -directions, deserves to be mentioned. After saying what colours should -be preserved in their saucers under water, and what colours should be -merely covered with oiled paper because the water injures them, he -proceeds to communicate "a curious mode of preserving oil-colours," and -of transporting them from place to place. The important secret is to -tie them in bladders, the mode of doing which he enters into with great -minuteness, as if the invention was recent. It is true, Christoforo -Sorte, in describing his practice in water-colour drawing, says he was -in the habit of preserving a certain vegetable green with gum-water in -a bladder; but as the method was obviously new to Palomino, there seems -sufficient reason to believe that oil-colours, when once ground, had, -up to his time, been kept in saucers and preserved under water.[35] -Among the items of expense in the Treviso document before alluded to, -we find "a pan and saucers for the painters."[36] This is in accordance -with Cennini's directions, and the same system appears to have been -followed till after 1700.[37] - -The Flemish accounts of the early practice of oil-painting are all -later than Vasari. Van Mander, in correcting the Italian historian in -his dates, still follows his narrative in other respects verbatim. If -Vasari's story is to be accepted as true, it might be inferred that -the Flemish secret consisted in an oil varnish like copal.[38] Vasari -says, that Van Eyck boiled the oils with other ingredients; that the -colours, when mixed with this kind of oil, had a very firm consistence; -that the surface of the pictures so executed had a lustre, so that they -needed no varnish when done; and that the colours were in no danger -from water.[39] - -Certain colours, as is well known, if mixed with oil alone, may be -washed off after a considerable time. Leonardo da Vinci remarks, that -verdigris may be thus removed. Carmine, Palomino observes, may be -washed off after six years. It is on this account the Italian writers -recommend the use of varnish with certain colours, and it appears the -Venetians, and perhaps the Italians generally, employed it solely in -such cases. But it is somewhat extraordinary that Vasari should teach -a mode of painting in oil so different in its results (inasmuch as the -work thus required varnish at last) from the Flemish method which he so -much extols--a method which he says the Italians long endeavoured to -find out in vain. If they knew it, it is evident, assuming his account -to be correct, that they did not practice it. - - -[1] See "Marcucci Saggio Analitico-chimico sopra i colori," &c. Rome, -1816, and "Taylor's Translation of Merimée on Oil-painting," London, -1839. The last-named work contains much useful information. - -[2] Italian writers of the 16th century speak of three kinds. Cardanus -says, that of the _abies_ was esteemed most, that of the _larix_ next, -and that of the _picea_ least. The resin extracted by incision from -the last (the pinus abies Linnæi) is known by the name of Burgundy -pitch; when extracted by fire it is black. The three varieties occur -in Italian treatises on art, under the names of _oglio di abezzo_, -_trementina_ and _pece Greca_. - -[3] The concrete balsam _benzoe_, called by the Italians _beluzino_, -and _belzoino_, is sometimes spoken of as a varnish. - -[4] Marcucci supposes that balsam of copaiba was mixed with the -pigments by the (later) Venetians. - -[5] "L'Archipelago con tutte le Isole," Ven. 1658. The incidental -notices of the remains of antiquity in this work would be curious and -important if they could be relied on. In describing the island of -Samos, for instance, the author asserts that the temple of Juno was in -tolerable preservation, and that the statue was still there. - -[6] "La Carta del Navegar Pitoresco," Ven. 1660. It is in the Venetian -dialect. - -[7] Inveriadure (invetriature), literally the glazing applied to -earthenware. - -[8] - - "O de che strazze se fan cavedal! - D'ogio d'avezzo, mastici e sandraca; - E trementina (per no'dir triaca) - Robe, che ilustrerave ogni stival."--p. 338. - -The alliteration of the words _trementina_ and _triaca_ is of course -lost in a translation. - -[9] "I li ha fati straluser co' i colori." Boschini was at least -constant in his opinion. In the second edition of his "Ricche Minere -della Pittura Veneziana," which appeared fourteen years after the -publication of his poem, he repeats that the Venetian painters avoided -some colours in flesh "e similmente i lustri e le vernici." - -[10] Thus, in the introduction to the "Ricche Minere," Boschini calls -the Milanese, Florentine, Lombard, and Bolognese painters, _forestieri_. - -[11] "Il Riposo," Firenze, 1584. - -[12] "De' Veri Precetti della Pittura," Ravenna, 1587. - -[13] "Trattato della Pittura fondato nell' autorità di molti eccellenti -in questa professione." Venezia, 1642. Bisagno remarks in his preface, -that the books on art were few, and that painters were in the habit of -keeping them secret. He acknowledges that he has availed himself of the -labours of others, but without mentioning his sources: some passages -are copied from Lomazzo. He, however, lays claim to some original -observations, and says he had seen much and discoursed with many -excellent painters. - -[14] "Le Meraviglie dell' Arte," Venezia, 1648. - -[15] It has been conjectured by some that this story proved the -immixture of varnishes with the colours, and that the oil was only used -to dilute them. The epitaph on Antonello da Messina which existed in -Vasari's time, alludes to his having mixed the colours with oil. - -[16] "Petri Mariæ Caneparii De Atramentis cujuscumque generis," Venet. -1619. It was republished at Rotterdam in 1718. - -[17] "Ita quod magis ex hiis evadit atramentum picturæ summopere -idoneum." Thus, if _atramentum_ is to be understood, as usual, to -mean a glazing colour, the passage can only refer to the immixture of -varnish with the transparent colours applied last in order. - -[18] In a passage that follows respecting the mode of extracting -nut-oil, Caneparius appears to mistranslate Galen, c. 7--"De Simplicium -Medicamentorum facultatibus." The observations of Galen on this -subject, and on the drying property of linseed, may have given the -first hint to the inventors of oil-painting. The custom of dating -the origin of this art from Van Eyck is like that of dating the -commencement of modern painting from Cimabue. The improver is often -assumed to be the inventor. - -[19] Milan, 1590. - -[20] The particulars here alluded to are to be found in the first -edition of Vasari (1550) as well as the second.--v. i. c. 21, &c. - -[21] "Osservasioni nella Pittura." In Venezia, 1580. Sorte, who, it -appears, was a native of Verona, had worked in his youth with Giulio -Romano, at Mantua, and communicates the methods taught him by that -painter, for giving the true effects of perspective in compositions -of figures. He is, perhaps, the earliest who describes the process of -water-colour painting as distinguished from distemper and as adapted to -landscape, if the art he describes deserves the name. - -[22] "Della nobilissima Pittura e sua Arte," Venezia, 1549. Biondo is -so ignorant as to attribute the Last Supper, by Leonardo da Vinci, to -Mantegna. - -[23] "Disegno del Doni," in Venezia, 1549. - -[24] "Dialogo di Pittura," Venezia, 1548. Pino, in enumerating the -celebrated contemporary artists, does not include Paul Veronese, for a -very obvious reason, that painter being at the time only about 17 years -of age. Sorte, who wrote thirty years later, mentions "l'eccellente -Messer Paulino nostro," alone. - -[25] The Dialogues of Lodovico Dolce, and various other works, are not -referred to here, as they contain nothing on the subject in question. -The latest authority at all connected with the traditions of Venetian -practice, is a certain Giambatista Volpato, of Bassano: he died in -1706, and had been intimate with Ridolfi. The only circumstance he -has transmitted relating to practical details is that Giacomo Bassan, -in retouching on a dry surface, sometimes adopted a method commonly -practised, he says, by Paul Veronese (and commonly practised still), -namely, that of dipping his brush in spirits of turpentine; at other -times he oiled out the surface in the usual manner. Volpato left a MS. -which was announced for publication in Vicenza in 1685, but it never -appeared; it, however, afterwards formed the ground-work of Verci's -"Notizie intorno alla Vita e alle Opere de' Pittori di Bassano." -Venezia, 1775. See also "Lettera di Giambatista Roberti sopra Giacomo -da Ponte," Lugano, 1777. Another MS. by Natale Melchiori, of about the -same date, is preserved at Treviso and Castel Franco: it abounds with -historical mistakes; the author says, for instance, that the Pietro -Martyre was begun by Giorgione and finished by Titian. The recipes for -varnishes and colours are very numerous, but they are mostly copied -from earlier works. - -[26] That distemper was not very highly esteemed by the Venetians -may be inferred from the following observation of Pino:--"Il modo di -colorir à guazzo è imperfetto et più fragile et à me non diletta onde -lasciamolo all' oltremontani i quali sono privi della vera via." It is, -however, certain that the Venetians sometimes painted in this style, -and Volpato mentions several works of the kind by Bassan, but he never -hints that he began his oil pictures in distemper. - -[27] Boschini says, that the Venetians (he especially means Titian) -rendered their pictures sparkling by finally touching on a dry -surface (_à secco_). The absence of varnish in the solid colours, the -retouching with spirit of turpentine, and even _à secco_, all suppose a -dull surface, which would require varnish. The latter method, alluded -to by Boschini, was an exception to the general practice, and not -likely to be followed on account of its difficulty. Carlo Maratti, on -the authority of Palomino, used to say, "He must be a skilful painter -who can retouch without oiling out." - -[28] See a letter by Francesco Bocchi, and another by Vasari, in -the "Lettere Pittoriche" of Bottari. The circumstance is mentioned -incidentally; the point chiefly dwelt on is, that some persons who -passed were deceived, and bowed to the picture, supposing it to be the -pope. - -[29] Federici, "Memorie Trevigiane," Venezia, 1803. The altar-piece of -S. Niccolo at Treviso is attributed, in the document alluded to, to -Fra Marco Pensabene, a name unknown; the painting is so excellent as -to have been thought worthy of Sebastian del Piombo: for this opinion, -however, there are no historical grounds. It was begun in 1520, but -before it was quite finished the painter, whoever he was, absconded: it -was therefore completed by another. - -[30] Titian's stay in Rome was short, and with respect to the Treviso -altar-piece, a week or two only, at most, can have elapsed between the -completion and the varnishing. Cennini, who recommends delaying a year -at least before varnishing, speaks of pictures in distemper. - -[31] See Borghini, Armenini, their Venetian copyist Bisagno, and -Palomino. The last-named writer, though of another school and much -more modern, was evidently well acquainted with the ancient methods: -he says, "Se advierte que siempre que se huviere de barnizar alguna -cosa conviene que la pintura y el barniz estèn calientes."--_El Museo -Pictorico_, v. ii. - -[32] Burnt alum, one of the ingredients recommended, might perhaps -account for a shining fracture in the indurated pigment in some old -pictures. - -[33] Of the earlier Spanish writers Pacheco may be mentioned next to -Palomino as containing most practical information. Carducho, De Butron, -and others, seldom descend to such details. Palomino contains all the -directions of Pacheco, and many in addition. - -[34] See Cean Bermudez, "Sobre la Escuela Sevillana," Cadiz, 1806. The -same reasons induced the later Venetian machinists to paint on dark -grounds, and to make use of (drying) oil in excess. See Zanetti, _Della -Pittura Veneziana_, 1. iv. - -[35] Borghini, in describing the method of making a gold-size (the -same as Cennini's), speaks of boiling the "buccie de' colori" in oil; -this only means the skin or pellicle of the colour itself--in fact, he -proceeds to say that they dissolve in boiling. Vasari, in describing -the same process, uses the expression "colori seccaticci." - -[36] "Maggio 4 (1520) Per un cadin (catino) per depentori. Per -scudellini per li depentori."--_Mem. Trev._, vol. i. p. 131. Pungileoni -("Memorie Istoriche di Antonio Allegri") quotes a note of expenses -relating to two oil-pictures by Paolo Gianotti; among the items we find -"colori, telari, et brocchette."--vol. ii. p. 75. - -[37] Salmon, in his "Polygraphice" (1701), gives the following -direction:--"Oyl colors, if not presently used, will have a skin grow -over them, to prevent which put them into a glass, and put the glass -three or four inches under water," &c. - -[38] This varnish appears to have been known some centuries before Van -Eyck's time, but he may have been the first to mix it with the colours. - -[39] See Vasari, Life of Antonello da Messina. - - - -NOTE W.--Par. 608. - -In the second volume Goethe gives the nomenclature of the Greeks and -Romans at some length. The general notions of the ancients with regard -to colours are thus described:--"The ancients derive all colours from -white and black, from light and darkness. They say, all colours are -between white and black, and are mixed out of these. We must not, -however, suppose that they understand by this a mere atomic mixture, -although they occasionally use the word μίξις;[1] for in the remarkable -passages, where they wish to express a kind of reciprocal (dynamic) -action of the two contrasting principles, they employ the words κρᾶσις, -union, σύγκρισις, combination; thus, again, the mutual influence of -light and darkness, and of colours among each other, is described by -the word κεράννυστας, an expression of similar import. - -"The varieties of colours are differently enumerated; some mention -seven, others twelve, but without giving the complete list. From a -consideration of the terminology both of the Greeks and Romans, it -appears that they sometimes employed general for specific terms, and -_vice versâ_. - -"Their denominations of colours are not permanently and precisely -defined, but mutable and fluctuating, for they are employed even with -regard to similar colours both on the _plus_ and _minus_ side. Their -yellow, on the one hand, inclines to red, on the other to blue; the -blue is sometimes green, sometimes red; the red is at one time yellow, -at another blue. Pure red (purpur) fluctuates between warm red and -blue, sometimes inclining to scarlet, sometimes to violet. - -"Thus the ancients not only seem to have looked upon colour as a -mutable and fleeting quality, but appear to have had a presentiment of -the (physical and chemical) effects of augmentation and re-action. In -speaking of colours they make use of expressions which indicate this -knowledge; they make yellow redden, because its augmentation tends to -red; they make red become yellow, for it often returns thus to its -origin. - -"The hues thus specified undergo new modifications. The colours -arrested at a given point are attenuated by a stronger light darkened -by a shadow, nay, deepened and condensed in themselves. For the -gradations which thus arise the name of the species only is often -given, but the more generic terms are also employed. Every colour, of -whatever kind, can, according to the same view, be multiplied into -itself, condensed, enriched, and will in consequence appear more or -less dark. The ancients called colour in this state," &c. Then follow -the designations of general states of colour and those of specific hues. - -Another essay on the notions of the ancients respecting the origin -and nature of colour generally, shows how nearly Goethe himself has -followed in the same track. The dilating effect of light objects, -the action and reaction of the retina, the coloured after-image, the -general law of contrast, the effect of semi-transparent mediums in -producing warm or cold colours as they are interposed before a dark or -light background--all this is either distinctly expressed or hinted -at; "but," continues Goethe, "how a single element divides itself into -two, remained a secret for them. They knew the nature of the magnet, -in amber, only as attraction; polarity was not yet distinctly evident -to them. And in very modern times have we not found that scientific -men have still given their almost exclusive attention to attraction, -and considered the immediately excited repulsion only as a mere -after-action?" - -An essay on the Painting of the Ancients[2] was contributed by Heinrich -Meyer. - - -[1] See Note on Par. 177. - -[2] Vol. ii. p. 69, first edition. - - - -NOTE X.--Par. 670. - -This agrees with the general recommendation so often given by high -authorities in art, to avoid a tinted look in the colour of flesh. The -great example of Rubens, whose practice was sometimes an exception -to this, may however show that no rule of art is to be blindly or -exclusively adhered to. Reynolds, nevertheless, in the midst of his -admiration for this great painter, considered the example dangerous, -and more than once expresses himself to this effect, observing on one -occasion that Rubens, like Baroccio, is sometimes open to the criticism -made on an ancient painter, namely, that his figures looked as if they -fed on roses. - -Lodovico Dolce, who is supposed to have given the _vivâ voce_ precepts -of Titian in his Dialogue,[1] makes Aretino say: "I would generally -banish from my pictures those vermilion cheeks with coral lips; for -faces thus treated look like masks. Propertius, reproving his Cynthia -for using cosmetics, desires that her complexion might exhibit the -simplicity and purity of colour which is seen in the works of Apelles." - -Those who have written on the practice of painting have always -recommended the use of few colours for flesh. Reynolds and others quote -even ancient authorities as recorded by Pliny, and Boschini gives -several descriptions of the method of the Venetians, and particularly -of Titian, to the same effect. "They used," he says, "earths more than -any other colour, and at the utmost only added a little vermilion, -minium, and lake, abhorring as a pestilence _biadetti, gialli santi, -smaltini, verdi-azzurri, giallolini_."[2] Elsewhere he says,[3] "Earths -should be used rather than other colours:" after repeating the above -prohibited list he adds, "I speak of the imitation of flesh, for in -other things every colour is good;" again, "Our great Titian used to -say that he who wishes to be a painter should be acquainted with three -colours, white, black, and red."[4] Assuming this account to be a -little exaggerated, it is still to be observed that the monotony to -which the use of few colours would seem to tend, is prevented by the -nature of the Venetian process, which was sufficiently conformable to -Goethe's doctrine; the gradations being multiplied, and the effect -of the colours heightened by using them as semi-opaque mediums. -Immediately after the passage last quoted we read, "He also gave this -true precept, that to produce a lively colouring in flesh it is not -possible to finish at once."[5] As these particulars may not be known -to all, we add some further abridged extracts explaining the order and -methods of these different operations. - -"The Venetian painters," says this writer,[6] "after having drawn in -their subject, got in the masses with very solid colour, without making -use of nature or statues. Their great object in this stage of their -work was to distinguish the advancing and retiring portions, that the -figures might be relieved by means of chiaro-scuro--one of the most -important departments of colour and form, and indeed of invention. -Having decided on their scheme of effect, when this preparation was -dry, they consulted nature and the antique; not servilely, but with the -aid of a few lines on paper (_quattro segni in carta_) they corrected -their figures without any other model. Then returning to their brushes, -they began to paint smartly on this preparation, producing the colour -of flesh." The passage before quoted follows, stating that they used -earths chiefly, that they carefully avoided certain colours, "and -likewise varnishes and whatever produces a shining surface.[7] When -this second painting was dry, they proceeded to scumble over this or -that figure with a low tint to make the one next it come forward, -giving another, at the same time, an additional light--for example, on -a head, a hand, or a foot, thus detaching them, so to speak, from the -canvas." (Tintoret's _Prigionia di S. Rocco_ is here quoted.) "By thus -still multiplying these well-understood retouchings where required, on -the dry surface, _(à secco)_ they reduced the whole to harmony. In this -operation they took care not to cover entire figures, but rather went -on gemming them _(gioielandole)_ with vigorous touches. In the shadows, -too, they infused vigour frequently by glazing with asphaltum, always -leaving great masses in middle-tint, with many darks, in addition to -the partial glazings, and few lights." - -The introduction to the subject of Venetian colouring, in the poem by -the same author, is also worth transcribing, but as the style is quaint -and very concise, a translation is necessarily a paraphrase.[8] - -"The art of colouring has the imitation of qualities for its object; -not all qualities, but those secondary ones which are appreciable by -the sense of sight. The eye especially sees colours, the imitation -of nature in painting is therefore justly called colouring; but the -painter arrives at his end by indirect means. He gives the varieties -of tone in masses;[9] he smartly impinges lights, he clothes his -preparation with more delicate local hues, he unites, he glazes: thus -everything depends on the method, on the process. For if we look -at colour abstractedly, the most positive may be called the most -beautiful, but if we keep the end of imitation in view, this shallow -conclusion falls to the ground. The refined Venetian manner is very -different from mere direct, sedulous imitation. Every one who has -a good eye may arrive at such results, but to attain the manner of -Paolo, of Bassan, of Palma, Tintoret, or Titian, is a very different -undertaking."[10] - -The effects of semi-transparent mediums in some natural productions -seem alluded to in the following passage--"Nature sometimes -accidentally imitates figures in stones and other substances, and -although they are necessarily incomplete in form, yet the principle -of effect (depth) resembles the Venetian practice." In a passage that -follows there appears to be an allusion to the production of the -atmospheric colours by semi-transparent mediums.[11] - - -[1] "Dialogo della Pittura, intitolato l'Aretino." It was first -published at Venice in 1557; about twenty years before Titian's death. -In the dedication to the senator Loredano, Lodovico Dolce eulogises -the work, which he would hardly have done if it had been entirely his -own: again, the supposition that it may have been suggested by Aretino, -would be equally conclusive, coupled with internal evidence, as to the -original source. - -[2] Introduction to the "Ricche Minere della Pittura Veneziana," -Venezia, 1674. The Italian annotators on older works on painting are -sometimes at a loss to find modern terms equivalent to the obsolete -names of pigments. (See "Antologia dell 'Arte Pittorica.") The colours -now in use corresponding with Boschini's list, are probably yellow -lakes, smalt, verditer, and Naples yellow. Boschini often censures the -practice of other schools, and in this emphatic condemnation he seems -to have had an eye to certain precepts in Lomazzo, and perhaps, even -in Leonardo da Vinci, who, on one occasion, recommends Naples yellow, -lake, and white for flesh. The Venetian writer often speaks, too, in -no measured terms of certain Flemish pictures, probably because they -appeared to him too tinted. - -[3] "La Carta del Navegar Pitoresco," p. 338. - -[4] Ib. p. 341. In describing Titian's actual practice ("Ricche -Minere"), he, however, adds yellow (ochre). The red is also -particularised, viz., the common terra rossa. - -[5] High examples here again prove that the opposite system may attain -results quite as successful. - -[6] Introduction to the "Ricche Minere." - -[7] See Note to Par. 555. Here again, assuming the description to be -correct, high authorities might be opposed to the Venetians. - -[8] The following quatrain may serve as a specimen; the author is -speaking of the importance of the colour of flesh as conducive to -picturesque effect:-- - - "Importa el nudo; e come ben l'importa! - Un quadro senta nudo è come aponto - Un disnar senza pan, se ben ghe zonto, - Per più delicia, confetura e torta."--p. 346. - -In his preface he anticipates, and thus answers the objections to his -Venetian dialect--"Mi, che son Venetian in Venetia e che parlo de' -Pitori Venetiani hò da andarme a stravestir? Guarda el Cielo." - -[9] The word _Macchia_, literally a blot, is generally used by Italian -writers, by Vasari for instance, for the local colour. Boschini -understands by it the relative depth of tones rather than the mere -difference of hue. "By macchia," he says, "I understand that treatment -by which the figures are distinguished from each other by different -tones lighter or darker."--_La Carta del Navegar_, p. 328. Elsewhere, -"Colouring (as practised by the Venetians) comprehends both the macchia -and drawing;" (p. 300) that is, comprehends the gradations of light -and dark in objects, and the parts of objects, and consequently, their -essential form. "The macchia," he adds, "is the effect of practice, and -is dictated by the knowledge of what is requisite for effect." - -[10] - - "Ma l'arivar a la maniera, al trato - (Verbi gratia) de Paulo, del Bassan, - Del Vechio, Tentoreto, e di Tician, - Per Dio, l'è cosa da deventar mato."--p. 294, 297. - - -[11] The traces of the Aristotelian theory are quite as apparent in -Boschini as in the other Italian writers on art; but as he wrote in the -seventeenth century, his authority in this respect is only important as -an indication of the earlier prevalence of the doctrine. - - - -NOTE Y.--Par. 672. - -The author's conclusion here is unsatisfactory, for the colour of -the black races may be considered at least quite as negative as that -of Europeans. It would be safer to say that the white skin is more -beautiful than the black, because it is more capable of indications -of life, and indications of emotion. A degree of light which would -fail to exhibit the finer varieties of form on a dark surface, would -be sufficient to display them on a light one; and the delicate -mantlings of colour, whether the result of action or emotion, are more -perceptible for the same reason. - - - -NOTE Z.--Par. 690. - -The author appears to mean that a degree of brightness which the organ -can bear at all, must of necessity be removed from dazzling, white -light. The slightest tinge of colour to this brightness, implies that -it is seen through a medium, and thus, in painting, the lightest, -whitest surface should partake of the quality of depth. Goethe's view -here again accords, it must be admitted, with the practice of the best -colourists, and with the precepts of the highest authorities.--See Note -C. - - - -NOTE A A.--Par. 732. - -Ample details respecting the opinions of Louis Bertrand Castel, a -Jesuit, are given in the historical part. The coincidence of some -of his views with those of Goethe is often apparent: he objects, -for instance, to the arbitrary selection of the Newtonian spectrum; -observing that the colours change with every change of distance between -the prism and the recipient surface.--_Farbenl._ vol. ii. p. 527. -Jeremias Friedrich Gülich was a dyer in the neighbourhood of Stutgardt: -he published an elaborate work on the technical details of his own -pursuit.--_Farbenl._ vol. ii. p. 630. - - - -NOTE B B.--Par. 748. - -Goethe, in his account of Castel, suppresses the learned Jesuit's -attempt at colorific music (the claveçin oculaire), founded on the -Newtonian doctrine. Castel was complimented, perhaps ironically, on -having been the first to remark that there were but three principal -colours. In asserting his claim to the discovery, he admits that there -is nothing new. In fact, the notion of three colours is to be found in -Aristotle; for that philosopher enumerates no more in speaking of the -rainbow,[1] and Seneca calls them by their right names.[2] Compare with -Dante, Parad. c. 33. The relation between colours and sounds is in like -manner adverted to by Aristotle; he says--"It is possible that colours -may stand in relation to each other in the same manner as concords -in music, for the colours which are (to each other) in proportions -corresponding with the musical concords, are those which appear to -be the most agreeable."[3] In the latter part of the 16th century, -Arcimboldo, a Milanese painter, invented a colorific music; an account -of his principles and method will be found in a treatise on painting -which appeared about the same time. "Ammaestrato dal quai ordine Mauro -Cremonese dalla viola, musico dell' Imperadore Ridolfo II. trovò sul -gravicembalo tutte quelle consonanze che dall' Arcimboldo erano segnate -coi colori sopra una carta."[4] - -[1] "De Meteor.," lib. 3, c. ii. and iv. He observes that this is the -only effect of colour which painters cannot imitate. - -[2] "De Ignib. cœlest." The description of the prism by Seneca is -another instance of the truth of Castel's admission. The Roman -philosopher's words are--"Virgula solet fieri vitrea, stricta vel -pluribus angulis in modo clavæ tortuosæ; hæc si ex transverso solem -accipit colorem talem qualis in arcu videri solet, reddit," &c. - -[3] "De Sensu et sensili." - -[4] "Il Figino, overo del Fine della Pittura," Mantova, 1591, p. 249. -An account of the absurd invention of the same painter in composing -figures of flowers and animals, and even painting portraits in this -way, to the great delight of the emperor, will be found in the same -work. - - - -NOTE C C.--Par. 758. - -The moral associations of colours have always been a more favourite -subject with poets than with painters. This is to be traced to the -materials and means of description as distinguished from those of -representation. An image is more distinct for the mind when it is -compared with something that resembles it. An object is more distinct -for the eye when it is compared with something that differs from it. -Association is the auxiliary in the one case, contrast in the other. -The poet, of necessity, succeeds best in conveying the impression -of external things by the aid of analogous rather than of opposite -qualities: so far from losing their effect by this means, the images -gain in distinctness. Comparisons that are utterly false and groundless -never strike us as such if the great end is accomplished of placing -the thing described more vividly before the imagination. In the common -language of laudatory description the colour of flesh is like snow -mixed with vermilion: these are the words used by Aretino in one of -his letters in speaking of a figure of St. John, by Titian. Similar -instances without end might be quoted from poets: even a contrast can -only be strongly conveyed in description by another contrast that -resembles it.[1] On the other hand it would be easy to show that -whenever poets have attempted the painter's method of direct contrast, -the image has failed to be striking, for the mind's eye cannot see the -relation between two colours. - -Under the same category of effect produced by association may be -classed the moral qualities in which poets have judiciously taken -refuge when describing visible forms and colours, to avoid competition -with the painters' elements, or rather to attain their end more -completely. But a little examination would show that very pleasing -moral associations may be connected with colours which would be far -from agreeable to the eye. All light, positive colours, light-green, -light-purple, white, are pleasing to the mind's eye, and no degree -of dazzling splendour is offensive. The moment, however, we have to -do with the actual sense of vision, the susceptibility of the eye -itself is to be considered, the law of comparison is reversed, colours -become striking by being opposed to what they are not, and their moral -associations are not owing to the colours themselves, but to the -modifications such colours undergo in consequence of what surrounds -them. This view, so naturally consequent on the principles the author -has himself arrived at, appears to be overlooked in the chapter under -consideration, the remarks in which, in other respects, are acute and -ingenious. - - -[1] Such as-- - - "Her beauty hangs upon the cheek of night, - Like a rich jewel in an Ethiop's ear." - _Romeo and Juliet_. - - - - -NOTE D D.--Par. 849. - -According to the usual acceptation of the term chiaro-scuro in the -artist world, it means not only the mutable effects produced by light -and shade, but also the permanent differences in brightness and -darkness which are owing to the varieties of local colour. - - - -NOTE E E.--Par. 855. - -The mannered treatment of light and shade here alluded to by the -author is very seldom to be met with in the works of the colourists; -the taste may have first arisen from the use of plaster-casts, and -was most prevalent in France and Italy in the early part of the last -century. Piazzetta represented it in Venice, Subleyras in Rome. In -France "Restout taught his pupils that a globe ought to be represented -as a polyhedron. Greuze most implicitly adopted the doctrine, and in -practice showed that he considered the round cheeks of a young girl or -an infant as bodies cut into facettes."[1] - - -[1] See Taylor's translation of Merimée on oil-painting, p. 27. -Barry, in a letter from Paris, speaks of Restout as the only painter -who resembled the earlier French masters: the manner in question is -undoubtedly sometimes very observable in Poussin. The English artist -elsewhere speaks of the "broad, happy manner of Subleyras."--_Works_, -London, 1809. - - - -NOTE F F.--Par. 859. - -All this was no doubt suggested by Heinrich Meyer, whose chief -occupation in Rome, at one time, was making sepia drawings from -sculpture (see Goethe's Italiänische Reise). It is hardly necessary to -say that the observation respecting the treatment of the surface in the -antique statues is very fanciful. - - - -NOTE G G.--Par. 863. - -This observation might have been suggested by the drawings of Claude, -which, with the slightest means, exhibit an harmonious balance of warm -and cold. - - - -NOTE H H.--Par. 865. - -The colouring of Paolo Uccello, according to Vasari's account of him, -was occasionally so remarkable that he might perhaps have been fairly -included among the instances of defective vision given by the author. -His skill in perspective, indicating an eye for gradation, may be also -reckoned among the points of resemblance (see Par. 105). - - - -NOTE I I.--Par. 902. - -The quotation before given from Boschini shows that the method -described by the author, and which is true with regard to some of the -Florentine painters, was not practised by the Venetians, for their -first painting was very solid. It agrees, however, with the manner -of Rubens, many of whose works sufficiently corroborate the account -of his process given by Descamps. "In the early state of Rubens's -pictures," says that writer,[1] "everything appeared like a thin wash; -but although he often made use of the ground in producing his tones, -the canvas was entirely covered more or less with colour." In this -system of leaving the shadows transparent from the first, with the -ground shining through them, it would have been obviously destructive -of richness to use white mixed with the darks, the brightness, in -fact, already existed underneath. Hence the well-known precept of -Rubens to avoid white in the shadows, a precept, like many others, -belonging to a particular practice, and involving all the conditions of -that practice.[2] Scarmiglione, whose Aristotelian treatise on colour -was published in Germany when Rubens was three-and-twenty, observes, -"Painters, with consummate art, lock up the bright colours with dark -ones, and, on the other hand, employ white, the poison of a picture, -very sparingly." (Artificiosissimè pictores claros obscuris obsepiant -et contra candido picturarum veneno summè parcentes, &c.) - - -[1] "La Vie des Peintres Flamands," vol. i. - -[2] The method he recommended for keeping the colours pure in the -lights, viz. to place the tints next each other unmixed, and then -slightly to unite them, may have degenerated to a methodical manner -in the hands of his followers. Boschini, who speaks of Rubens himself -with due reverence, and is far from confounding him with his imitators, -contrasts such a system with that of the Venetians, and adds that -Titian used to say, "Chi de imbratar colori teme, imbrata e machia -si medemi."--_Carta del Navegar_, p. 341. The poem of Boschini is in -many respects polemical. He wrote at a time when the Flemish painters, -having adopted and modified the Venetian principles, threatened to -supersede the Italian masters in the opinion of the world. Their -excellence, too, had all the charm of novelty, for in the seventeenth -century Venice produced no remarkable talent, and it was precisely -the age for her to boast of past glories. The contemptuous manner in -which Boschini speaks of the Flemish varnishes, of the fear of mixing -tints, &c., is thus always to be considered with reference to the time -and circumstances. So also his boasting that the Venetian masters -painted without nature, which may be an exaggeration, is pointed at -the _Naturalisti_, Caravaggio and his followers, who copied nature -literally. - - - -NOTE K K.--Par. 903. - -The practice here alluded to is more frequently observable in slight -works by Paul Veronese. His ground was often pure white, and in some -of his works it is left as such. Titian's white ground was covered -with a light warm colour, probably at first, and appears to have -been similar to that to which Armenini gives the preference, namely, -"quella che tira al color di carne chiarissima con un non so che di -fiammeggiante."[1] - - -[1] "Veri Precetti della Pittura," p. 123. - - -NOTE L L.--Par. 919. - -The notion which the author has here ventured to express may have -been suggested by the remarkable passage in the last canto of Dante's -"Paradiso"-- - - "Nella profonda e chiara sussistenza, - Dell' alto lume parremi tre giri - Di tre colori e d'una continenza," &c. - -After the concluding paragraph the author inserts a letter from a -landscape-painter, Philipp Otto Runge, which is intended to show that -those who imitate nature may arrive at principles analogous to those of -the "Farbenlehre." - - -THE END. - - - - - -End of the Project Gutenberg EBook of Goethe's Theory of Colours, by -Johann, Wolfgang von Goethe - - -*** END OF THE PROJECT GUTENBERG EBOOK 50572 *** diff --git a/old/50572-h/50572-h.htm b/old/50572-h/50572-h.htm deleted file mode 100644 index 6cd189a..0000000 --- a/old/50572-h/50572-h.htm +++ /dev/null @@ -1,14230 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" - "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> -<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> - <head> - <meta http-equiv="Content-Type" content="text/html;charset=utf-8" /> - <meta http-equiv="Content-Style-Type" content="text/css" /> - <title> - The Project Gutenberg eBook of Goethe's Theory of Colours, by Johann Wolfgang von Goethe. - </title> - <style type="text/css"> - -body { - margin-left: 10%; - margin-right: 10%; -} - - h1,h2,h3,h4,h5,h6 { - text-align: center; /* all headings centered */ - clear: both; -} - -p { - margin-top: .51em; - text-align: justify; - margin-bottom: .49em; -} - -.p2 {margin-top: 2em;} -.p4 {margin-top: 4em;} -.p6 {margin-top: 6em;} - -hr { - width: 33%; - margin-top: 2em; - margin-bottom: 2em; - margin-left: auto; - margin-right: auto; - clear: both; -} - -hr.tb {width: 45%;} -hr.chap {width: 65%} -hr.full {width: 95%;} - -hr.r5 {width: 5%; margin-top: 1em; margin-bottom: 1em;} -hr.r65 {width: 65%; margin-top: 3em; margin-bottom: 3em;} - - -table { - margin-left: auto; - margin-right: auto; -} - - .tdl {text-align: left;} - .tdr {text-align: right;} - .tdc {text-align: center;} - -.pagenum { /* uncomment the next line for invisible page numbers */ - /* visibility: hidden; */ - position: absolute; - left: 92%; - font-size: smaller; - text-align: right; - color: #CCCCCC; -} /* page numbers */ - - -.blockquot { - margin-left: 5%; - margin-right: 10%; -} - -a:link {color: #800000; text-decoration: none; } - -v:link {color: #800000; text-decoration: none; } - -.para { font-size: 0.8em; - font-weight: bold; - text-align: center; - margin-top: 1.5em;} - -.center {text-align: center;} - -.right {text-align: right;} - -.tabnum {position: absolute; - left: 80%; - font-size: 0.8em;} - -.caption {font-weight: bold; - font-size: 0.8em; - text-align: center;} - -/* Images */ -.figcenter { - margin: auto; - text-align: center; -} - -.figleft { - float: left; - clear: left; - margin-left: 0; - margin-bottom: 1em; - margin-top: 1em; - margin-right: 1em; - padding: 0; - text-align: center; -} - -.figright { - float: right; - clear: right; - margin-left: 1em; - margin-bottom: - 1em; - margin-top: 1em; - margin-right: 0; - padding: 0; - text-align: center; -} - -/* Footnotes */ -.footnotes {border: dashed 1px;} - -.footnote {margin-left: 10%; margin-right: 10%; font-size: 0.9em;} - -.footnote .label {position: absolute; right: 84%; text-align: right;} - -.fnanchor { - vertical-align: super; - font-size: .8em; - text-decoration: - none; -} - - </style> - </head> -<body> - - -<div>*** START OF THE PROJECT GUTENBERG EBOOK 50572 ***</div> - - - -<div class="figcenter" style="width: 500px;"> -<img src="images/cover.jpg" width="500" alt="" /> -</div> - -<h2>GOETHE'S</h2> - -<h1>THEORY OF COLOURS;</h1> - -<h4>TRANSLATED FROM THE GERMAN:</h4> - -<h4>WITH NOTES BY</h4> - -<h4>CHARLES LOCK EASTLAKE, R.A., F.R.S.</h4> - -<hr class="r5" /> -<blockquote> - -<p>"Cicero varietatem propriè in coloribus nasci, hinc in -alienum migrare existimavit. Certè non alibi natura -copiosius aut majore lasciviâ opes suas commendavit. -Metalla, gemmas, marmora, flores, astra, omnia denique quæ -progenuit suis etiam coloribus distinxit; ut venia debeatur -si quis in tam numerosâ rerum sylvâ caligaverit."</p> - -<p style="margin-left: 65%; font-size: 0.8em;">CELIO CALCAGNINI.</p></blockquote> -<hr class="r5" /> -<h5>LONDON:</h5> - -<h5>JOHN MURRAY, ALBEMARLE STREET.</h5> - -<h5>1840</h5> - - - - -<hr class="chap" /> -<h5><a name="TO" id="TO">TO</a></h5> - -<h4>JEREMIAH HARMAN, Esq.</h4> - -<blockquote> - -<p style="margin-left: 10%;">Dear Sir,</p> - -<p style="margin-left: 10%;">I dedicate to you the following translation as a testimony -of my sincere gratitude and respect; in doing so, I but -follow the example of Portius, an Italian writer, who -inscribed his translation of Aristotle's Treatise on Colours -to one of the Medici.</p> - -<p style="margin-left: 40%;">I have the honour to be,</p> - -<p style="margin-left: 45%;">Dear Sir,</p> - -<p style="margin-left: 30%;">Your most obliged and obedient Servant,</p> - -<p style="margin-left: 65%; font-size: 0.8em;">C. L. EASTLAKE.</p></blockquote> - - - -<hr class="chap" /> -<h4><a name="THE_TRANSLATORS_PREFACE" id="THE_TRANSLATORS_PREFACE">THE TRANSLATOR'S PREFACE.</a></h4> - - -<p>English writers who have spoken of Goethe's "Doctrine of Colours,"<a name="FNanchor_1_1" id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">[1]</a> -have generally confined their remarks to those parts of the work in -which he has undertaken to account for the colours of the prismatic -spectrum, and of refraction altogether, on principles different -from the received theory of Newton. The less questionable merits -of the treatise consisting of a well-arranged mass of observations -and experiments, many of which are important and interesting, have -thus been in a great measure overlooked. The translator, aware of -the opposition which the theoretical views alluded to have met with, -intended at first to make a selection of such of the experiments as -seem more directly applicable to the theory and practice of painting. -Finding, however, that the alterations this would have involved would -have been incompatible with a clear and connected view of the author's -statements, he preferred giving the theory itself entire, reflecting, -at the same time, that some scientific readers may be curious to hear -the author speak for himself even on the points at issue.</p> - -<p>In reviewing the history and progress of his opinions and researches, -Goethe tells us that he first submitted his views to the public -in two short essays entitled "Contributions to Optics." Among the -circumstances which he supposes were unfavourable to him on that -occasion, he mentions the choice of his title, observing that by a -reference to optics he must have appeared to make pretensions to a -knowledge of mathematics, a science with which he admits he was very -imperfectly acquainted. Another cause to which he attributes the severe -treatment he experienced, was his having ventured so openly to question -the truth of the established theory: but this last provocation could -not be owing to mere inadvertence on his part; indeed the larger work, -in which he alludes to these circumstances,<span class="pagenum"><a name="Page_ix" id="Page_ix">[Pg ix]</a></span> is still more remarkable -for the violence of his objections to the Newtonian doctrine.</p> - -<p>There can be no doubt, however, that much of the opposition Goethe met -with was to be attributed to the manner as well as to the substance -of his statements. Had he contented himself with merely detailing his -experiments and showing their application to the laws of chromatic -harmony, leaving it to others to reconcile them as they could with the -pre-established system, or even to doubt in consequence, the truth of -some of the Newtonian conclusions, he would have enjoyed the credit -he deserved for the accuracy and the utility of his investigations. -As it was, the uncompromising expression of his convictions only -exposed him to the resentment or silent neglect of a great portion -of the scientific world, so that for a time he could not even obtain -a fair hearing for the less objectionable or rather highly valuable -communications contained in his book. A specimen of his manner of -alluding to the Newtonian theory will be seen in the preface.</p> - -<p>It was quite natural that this spirit should call forth a somewhat -vindictive feeling, and with it not a little uncandid as well as -unsparing criticism. "The Doctrine of Colours" met<span class="pagenum"><a name="Page_x" id="Page_x">[Pg x]</a></span> with this reception -in Germany long before it was noticed in England, where a milder and -fairer treatment could hardly be expected, especially at a time when, -owing perhaps to the limited intercourse with the continent, German -literature was far less popular than it is at present. This last fact, -it is true, can be of little importance in the present instance, -for although the change of opinion with regard to the genius of an -enlightened nation must be acknowledged to be beneficial, it is to be -hoped there is no fashion in science, and the translator begs to state -once for all, that in advocating the neglected merits of the "Doctrine -of Colours," he is far from undertaking to defend its imputed errors. -Sufficient time has, however, now elapsed since the publication of this -work (in 1810) to allow a calmer and more candid examination of its -claims. In this more pleasing task Germany has again for some time led -the way, and many scientific investigators have followed up the hints -and observations of Goethe with a due acknowledgment of the acuteness -of his views.<a name="FNanchor_2_2" id="FNanchor_2_2"></a><a href="#Footnote_2_2" class="fnanchor">[2]</a></p> - -<p><span class="pagenum"><a name="Page_xi" id="Page_xi">[Pg xi]</a></span></p> - -<p>It may require more magnanimity in English scientific readers to do -justice to the merits of one who was so open and, in many respects, it -is believed, so mistaken an opponent of Newton; but it must be admitted -that the statements of Goethe contain more useful principles in all -that relates to harmony of colour than any that have been derived from -the established doctrine. It is no derogation of the more important -truths of the Newtonian theory to say, that the views it contains -seldom appear in a form calculated for direct application to the arts. -The principle of contrast, so universally exhibited in nature, so -apparent in the action and re-action of the eye itself, is scarcely -hinted at. The equal pretensions of seven colours, as<span class="pagenum"><a name="Page_xii" id="Page_xii">[Pg xii]</a></span> such, and the -fanciful analogies which their assumed proportions could suggest, have -rarely found favour with the votaries of taste,—indeed they have -long been abandoned even by scientific authorities.<a name="FNanchor_3_3" id="FNanchor_3_3"></a><a href="#Footnote_3_3" class="fnanchor">[3]</a> And here the -translator stops: he is quite aware that the defects which make the -Newtonian theory so little available for æsthetic application, are -far from invalidating its more important conclusions in the opinion -of most scientific men. In carefully abstaining therefore from any -comparison between the two theories in these latter respects, he may -still be permitted to advocate the clearness and fulness of Goethe's -experiments. The German philosopher reduces the colours to their<span class="pagenum"><a name="Page_xiii" id="Page_xiii">[Pg xiii]</a></span> -origin and simplest elements; he sees and constantly bears in mind, and -sometimes ably elucidates, the phenomena of contrast and gradation, -two principles which may be said to make up the artist's world, and to -constitute the chief elements of beauty. These hints occur mostly in -what may be called the scientific part of the work. On the other hand, -in the portion expressly devoted to the æsthetic application of the -doctrine, the author seems to have made but an inadequate use of his -own principles.</p> - -<p>In that part of the chapter on chemical colours which relates to the -colours of plants and animals, the same genius and originality which -are displayed in the Essays on Morphology, and which have secured -to Goethe undisputed rank among the investigators of nature, are -frequently apparent.</p> - -<p>But one of the most interesting features of Goethe's theory, although -it cannot be a recommendation in a scientific point of view, is, that -it contains, undoubtedly with very great improvements, the general -doctrine of the ancients and of the Italians at the revival of letters. -The translator has endeavoured, in some notes, to point out the -connexion between this theory and the practice of the Italian painters.</p> - -<p><span class="pagenum"><a name="Page_xiv" id="Page_xiv">[Pg xiv]</a></span></p> - -<p>The "Doctrine of Colours," as first published in 1810, consists of -two volumes in 8vo., and sixteen plates, with descriptions, in 4to. -It is divided into three parts, a didactic, a controversial, and an -historical part; the present translation is confined to the first of -these, with such extracts from the other two as seemed necessary, -in fairness to the author, to explain some of his statements. The -polemical and historical parts are frequently alluded to in the -preface and elsewhere in the present work, but it has not been thought -advisable to omit these allusions. No alterations whatever seem to -have been made by Goethe in the didactic portion in later editions, -but he subsequently wrote an additional chapter on entoptic colours, -expressing his wish that it might be inserted in the theory itself at -a particular place which he points out. The form of this additional -essay is, however, very different from that of the rest of the work, -and the translator has therefore merely given some extracts from it in -the appendix. The polemical portion has been more than once omitted in -later editions.</p> - -<p>In the two first parts the author's statements are arranged -numerically, in the style of Bacon's Natural History. This, we are -told, was for the<span class="pagenum"><a name="Page_xv" id="Page_xv">[Pg xv]</a></span> convenience of reference; but many passages are -thus separately numbered which hardly seem to have required it. The -same arrangement is, however, strictly followed in the translation to -facilitate a comparison with the original where it may be desired; and -here the translator observes, that although he has sometimes permitted -himself to make slight alterations, in order to avoid unnecessary -repetition, or to make the author's meaning clearer, he feels that an -apology may rather be expected from him for having omitted so little. -He was scrupulous on this point, having once determined to translate -the whole treatise, partly, as before stated, from a wish to deal -fairly with a controversial writer, and partly because many passages, -not directly bearing on the scientific views, are still characteristic -of Goethe. The observations which the translator has ventured to add -are inserted in the appendix: these observations are chiefly confined -to such of the author's opinions and conclusions as have direct -reference to the arts; they seldom interfere with the scientific -propositions, even where these have been considered most vulnerable.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">[1]</span></a> "Farbenlehre"—in the present translation generally -rendered "Theory of Colours."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_2" id="Footnote_2_2"></a><a href="#FNanchor_2_2"><span class="label">[2]</span></a> Sixteen years after the appearance of the Farbenlehre, -Dr. Johannes Müller devoted a portion of his work, "Zur vergleichenden -Physiologie des Gesichtssinnes des Menschen und der Thiere," to the -critical examination of Goethe's theory. In his introductory remarks he -expresses himself as follows—"For my own part I readily acknowledge -that I have been greatly indebted to Goethe's treatise, and can truly -say that without having studied it for some years in connexion with the -actual phenomena, the present work would hardly have been undertaken. -I have no hesitation in confessing more particularly that I have full -faith in Goethe's statements, where they are merely descriptive of -the phenomena, and where the author does not enter into explanations -involving a decision on the great points of controversy." The names of -Hegel, Schelling, Seebeck, Steffens, may also be mentioned, and many -others might be added, as authorities more or less favourable to the -Farbenlehre.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_3" id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">[3]</span></a> "When Newton attempted to reckon up the rays of light -decomposed by the prism," says Sir John Leslie, "and ventured to assign -the famous number <i>seven</i>, he was apparently influenced by some lurking -disposition towards mysticism. If any unprejudiced person will fairly -repeat the experiment, he must soon be convinced that the various -coloured spaces which paint the spectrum slide into each other by -indefinite shadings: he may name four or five principal colours, but -the subordinate spaces are evidently so multiplied as to be incapable -of enumeration. The same illustrious mathematician, we can hardly -doubt, was betrayed by a passion for analogy, when he imagined that the -primary colours are distributed over the spectrum after the proportions -of the diatonic scale of music, since those intermediate spaces have -really no precise and defined limits."—<i>Treatises on Various Subjects -of Natural and Chemical Philosophy</i>, p. 59.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_xvii" id="Page_xvii">[Pg xvii]</a></span></p></div> - - - - -<h4><a name="PREFACE_TO_THE_FIRST_EDITION_OF_1810" id="PREFACE_TO_THE_FIRST_EDITION_OF_1810">PREFACE TO THE FIRST EDITION OF 1810.</a></h4> - - -<p>It may naturally be asked whether, in proposing to treat of colours, -light itself should not first engage our attention: to this we briefly -and frankly answer that since so much has already been said on the -subject of light, it can hardly be desirable to multiply repetitions by -again going over the same ground.</p> - -<p>Indeed, strictly speaking, it is useless to attempt to express the -nature of a thing abstractedly. Effects we can perceive, and a complete -history of those effects would, in fact, sufficiently define the -nature of the thing itself. We should try in vain to describe a man's -character, but let his acts be collected and an idea of the character -will be presented to us.</p> - -<p>The colours are acts of light; its active and passive modifications: -thus considered we may expect from them some explanation respecting -light itself. Colours and light, it is true, stand in the most intimate -relation to each other, but<span class="pagenum"><a name="Page_xviii" id="Page_xviii">[Pg xviii]</a></span> we should think of both as belonging to -nature as a whole, for it is nature as a whole which manifests itself -by their means in an especial manner to the sense of sight.</p> - -<p>The completeness of nature displays itself to another sense in a -similar way. Let the eye be closed, let the sense of hearing be -excited, and from the lightest breath to the wildest din, from the -simplest sound to the highest harmony, from the most vehement and -impassioned cry to the gentlest word of reason, still it is Nature that -speaks and manifests her presence, her power, her pervading life and -the vastness of her relations; so that a blind man to whom the infinite -visible is denied, can still comprehend an infinite vitality by means -of another organ.</p> - -<p>And thus as we descend the scale of being, Nature speaks to other -senses—to known, misunderstood, and unknown senses: so speaks she with -herself and to us in a thousand modes. To the attentive observer she -is nowhere dead nor silent; she has even a secret agent in inflexible -matter, in a metal, the smallest portions of which tell us what -is passing in the entire mass. However manifold, complicated, and -unintelligible this language may often seem to us, yet its elements -remain ever the same. With light poise<span class="pagenum"><a name="Page_xix" id="Page_xix">[Pg xix]</a></span> and counterpoise, Nature -oscillates within her prescribed limits, yet thus arise all the -varieties and conditions of the phenomena which are presented to us in -space and time.</p> - -<p>Infinitely various are the means by which we become acquainted with -these general movements and tendencies: now as a simple repulsion and -attraction, now as an upsparkling and vanishing light, as undulation -in the air, as commotion in matter, as oxydation and de-oxydation; but -always, uniting or separating, the great purpose is found to be to -excite and promote existence in some form or other.</p> - -<p>The observers of nature finding, however, that this poise and -counterpoise are respectively unequal in effect, have endeavoured to -represent such a relation in terms. They have everywhere remarked and -spoken of a greater and lesser principle, an action and resistance, -a doing and suffering, an advancing and retiring, a violent and -moderating power; and thus a symbolical language has arisen, which, -from its close analogy, may be employed as equivalent to a direct and -appropriate terminology.</p> - -<p>To apply these designations, this language of Nature to the subject -we have undertaken: to enrich and amplify this language by means of<span class="pagenum"><a name="Page_xx" id="Page_xx">[Pg xx]</a></span> -the theory of colours and the variety of their phenomena, and thus -facilitate the communication of higher theoretical views, was the -principal aim of the present treatise.</p> - -<p>The work itself is divided into three parts. The first contains the -outline of a theory of colours. In this, the innumerable cases which -present themselves to the observer are collected under certain leading -phenomena, according to an arrangement which will be explained in -the Introduction; and here it may be remarked, that although we have -adhered throughout to experiment, and throughout considered it as our -basis, yet the theoretical views which led to the arrangement alluded -to, could not but be stated. It is sometimes unreasonably required by -persons who do not even themselves attend to such a condition, that -experimental information should be submitted without any connecting -theory to the reader or scholar, who is himself to form his conclusions -as he may list. Surely the mere inspection of a subject can profit us -but little. Every act of seeing leads to consideration, consideration -to reflection, reflection to combination, and thus it may be said that -in every attentive look on nature we already theorise. But in order to -guard against the possible<span class="pagenum"><a name="Page_xxi" id="Page_xxi">[Pg xxi]</a></span> abuse of this abstract view, in order that -the practical deductions we look to should be really useful, we should -theorise without forgetting that we are so doing, we should theorise -with mental self-possession, and, to use a bold word, with irony.</p> - -<p>In the second part<a name="FNanchor_1_4" id="FNanchor_1_4"></a><a href="#Footnote_1_4" class="fnanchor">[1]</a> we examine the Newtonian theory; a theory which -by its ascendancy and consideration has hitherto impeded a free inquiry -into the phenomena of colours. We combat that hypothesis, for although -it is no longer found available, it still retains a traditional -authority in the world. Its real relations to its subject will require -to be plainly pointed out; the old errors must be cleared away, if the -theory of colours is not still to remain in the rear of so many other -better investigated departments of natural science. Since, however, -this second part of our work may appear somewhat dry as regards its -matter, and perhaps too vehement and excited in its manner, we may here -be permitted to introduce a sort of allegory in a lighter style, as a -prelude to that graver portion, and as some excuse for the earnestness -alluded to.</p> - -<p>We compare the Newtonian theory of colours<span class="pagenum"><a name="Page_xxii" id="Page_xxii">[Pg xxii]</a></span> to an old castle, which -was at first constructed by its architect with youthful precipitation; -it was, however, gradually enlarged and equipped by him according -to the exigencies of time and circumstances, and moreover was still -further fortified and secured in consequence of feuds and hostile -demonstrations.</p> - -<p>The same system was pursued by his successors and heirs: their -increased wants within, the harassing vigilance of their opponents -without, and various accidents compelled them in some places to build -near, in others in connexion with the fabric, and thus to extend the -original plan.</p> - -<p>It became necessary to connect all these incongruous parts and -additions by the strangest galleries, halls and passages. All damages, -whether inflicted by the hand of the enemy or the power of time, were -quickly made good. As occasion required, they deepened the moats, -raised the walls, and took care there should be no lack of towers, -battlements, and embrasures. This care and these exertions gave rise -to a prejudice in favour of the great importance of the fortress, -and still upheld that prejudice, although the arts of building and -fortification were by this time very much advanced, and people had<span class="pagenum"><a name="Page_xxiii" id="Page_xxiii">[Pg xxiii]</a></span> -learnt to construct much better dwellings and defences in other cases. -But the old castle was chiefly held in honour because it had never -been taken, because it had repulsed so many assaults, had baffled so -many hostile operations, and had always preserved its virgin renown. -This renown, this influence lasts even now: it occurs to no one that -the old castle is become uninhabitable. Its great duration, its costly -construction, are still constantly spoken of. Pilgrims wend their -way to it; hasty sketches of it are shown in all schools, and it is -thus recommended to the reverence of susceptible youth. Meanwhile, -the building itself is already abandoned; its only inmates are a few -invalids, who in simple seriousness imagine that they are prepared for -war.</p> - -<p>Thus there is no question here respecting a tedious siege or a -doubtful war; so far from it we find this eighth wonder of the world -already nodding to its fall as a deserted piece of antiquity, and -begin at once, without further ceremony, to dismantle it from gable -and roof downwards; that the sun may at last shine into the old nest -of rats and owls, and exhibit to the eye of the wondering traveller -that labyrinthine, incongruous style of building, with its scanty,<span class="pagenum"><a name="Page_xxiv" id="Page_xxiv">[Pg xxiv]</a></span> -make-shift contrivances, the result of accident and emergency, its -intentional artifice and clumsy repairs. Such an inspection will, -however, only be possible when wall after wall, arch after arch, is -demolished, the rubbish being at once cleared away as well as it can be.</p> - -<p>To effect this, and to level the site where it is possible to do -so, to arrange the materials thus acquired, so that they can be -hereafter again employed for a new building, is the arduous duty -we have undertaken in this Second Part. Should we succeed, by a -cheerful application of all possible ability and dexterity, in razing -this Bastille, and in gaining a free space, it is thus by no means -intended at once to cover the site again and to encumber it with a new -structure; we propose rather to make use of this area for the purpose -of passing in review a pleasing and varied series of illustrative -figures.</p> - -<p>The third part is thus devoted to the historical account of early -inquirers and investigators. As we before expressed the opinion that -the history of an individual displays his character, so it may here be -well affirmed that the history of science is science itself. We cannot -clearly be aware of what we possess till we have the means of knowing -what others possessed<span class="pagenum"><a name="Page_xxv" id="Page_xxv">[Pg xxv]</a></span> before us. We cannot really and honestly rejoice -in the advantages of our own time if we know not how to appreciate -the advantages of former periods. But it was impossible to write, or -even to prepare the way for a history of the theory of colours while -the Newtonian theory existed; for no aristocratic presumption has ever -looked down on those who were not of its order, with such intolerable -arrogance as that betrayed by the Newtonian school in deciding on -all that had been done in earlier times and all that was done around -it. With disgust and indignation we find Priestley, in his History -of Optics, like many before and after him, dating the success of all -researches into the world of colours from the epoch of a decomposed ray -of light, or what pretended to be so; looking down with a supercilious -air on the ancient and less modern inquirers, who, after all, had -proceeded quietly in the right road, and who have transmitted to us -observations and thoughts in detail which we can neither arrange better -nor conceive more justly.</p> - -<p>We have a right to expect from one who proposes to give the history of -any science, that he inform us how the phenomena of which it treats -were gradually known, and what was imagined,<span class="pagenum"><a name="Page_xxvi" id="Page_xxvi">[Pg xxvi]</a></span> conjectured, assumed, -or thought respecting them. To state all this in due connexion is by -no means an easy task; need we say that to write a history at all is -always a hazardous affair; with the most honest intention there is -always a danger of being dishonest; for in such an undertaking, a -writer tacitly announces at the outset that he means to place some -things in light, others in shade. The author has, nevertheless, long -derived pleasure from the prosecution of his task: but as it is the -intention only that presents itself to the mind as a whole, while the -execution is generally accomplished portion by portion, he is compelled -to admit that instead of a history he furnishes only materials for -one. These materials consist in translations, extracts, original and -borrowed comments, hints, and notes; a collection, in short, which, if -not answering all that is required, has at least the merit of having -been made with earnestness and interest. Lastly, such materials,—not -altogether untouched it is true, but still not exhausted,—may be more -satisfactory to the reflecting reader in the state in which they are, -as he can easily combine them according to his own judgment.</p> - -<p>This third part, containing the history of the<span class="pagenum"><a name="Page_xxvii" id="Page_xxvii">[Pg xxvii]</a></span> science, does not, -however, thus conclude the subject: a fourth supplementary portion<a name="FNanchor_2_5" id="FNanchor_2_5"></a><a href="#Footnote_2_5" class="fnanchor">[2]</a> -is added. This contains a recapitulation or revision; with a view -to which, chiefly, the paragraphs are headed numerically. In the -execution of a work of this kind some things may be forgotten, some -are of necessity omitted, so as not to distract the attention, some -can only be arrived at as corollaries, and others may require to be -exemplified and verified: on all these accounts, postscripts, additions -and corrections are indispensable. This part contains, besides, some -detached essays; for example, that on the atmospheric colours; for as -these are introduced in the theory itself without any classification, -they are here presented to the mind's eye at one view. Again, if this -essay invites the reader to consult Nature herself, another is intended -to recommend the artificial aids of science by circumstantially -describing the apparatus which will in future be necessary to assist -researches into the theory of colours.</p> - -<p>In conclusion, it only remains to speak of the<span class="pagenum"><a name="Page_xxviii" id="Page_xxviii">[Pg xxviii]</a></span> plates which are added -at the end of the work;<a name="FNanchor_3_6" id="FNanchor_3_6"></a><a href="#Footnote_3_6" class="fnanchor">[3]</a> and here we confess we are reminded of that -incompleteness and imperfection which the present undertaking has, -in common with all others of its class; for as a good play can be in -fact only half transmitted to writing, a great part of its effect -depending on the scene, the personal qualities of the actor, the powers -of his voice, the peculiarities of his gestures, and even the spirit -and favourable humour of the spectators; so it is, in a still greater -degree, with a book which treats of the appearances of nature. To be -enjoyed, to be turned to account, Nature herself must be present to -the reader, either really, or by the help of a lively imagination. -Indeed, the author should in such cases communicate his observations -orally, exhibiting the phenomena he describes—as a text, in the -first instance,—partly as they appear to us unsought, partly as they -may be presented by contrivance to serve in particular illustration. -Explanation and description could not then fail to produce a lively -impression.</p> - -<p>The plates which generally accompany works like the present are thus -a most inadequate substitute<span class="pagenum"><a name="Page_xxix" id="Page_xxix">[Pg xxix]</a></span> for all this; a physical phenomenon -exhibiting its effects on all sides is not to be arrested in lines -nor denoted by a section. No one ever dreams of explaining chemical -experiments with figures; yet it is customary in physical researches -nearly allied to these, because the object is thus found to be in -some degree answered. In many cases, however, such diagrams represent -mere notions; they are symbolical resources, hieroglyphic modes of -communication, which by degrees assume the place of the phenomena and -of Nature herself, and thus rather hinder than promote true knowledge. -In the present instance we could not dispense with plates, but we have -endeavoured so to construct them that they may be confidently referred -to for the explanation of the didactic and polemical portions. Some of -these may even be considered as forming part of the apparatus before -mentioned.</p> - -<p>We now therefore refer the reader to the work itself; first, only -repeating a request which many an author has already made in vain, and -which the modern German reader, especially, so seldom grants:—</p> - -<p style="margin-left: 20%;"> -<span style="margin-left: 6em;">Si quid novisti rectius istis</span><br /> -Candidus imperti; si non, his utere mecum.<br /> -</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_4" id="Footnote_1_4"></a><a href="#FNanchor_1_4"><span class="label">[1]</span></a> The Polemical part.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_5" id="Footnote_2_5"></a><a href="#FNanchor_2_5"><span class="label">[2]</span></a> This preface must have been written before the work was -finished, for at the conclusion of the historical part there is only an -apology for the non-appearance of the supplement here alluded to.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_6" id="Footnote_3_6"></a><a href="#FNanchor_3_6"><span class="label">[3]</span></a> In the present translation the necessary plates accompany -the text.</p></div> - -<hr class="chap" /> - - - - -<p><span class="pagenum"><a name="Page_xxxi" id="Page_xxxi">[Pg xxxi]</a></span></p> -<h5><a name="CONTENTS" id="CONTENTS">CONTENTS</a></h5> - - - -<table border="0" cellpadding="3" cellspacing="0" summary=""> -<tr><th style="font-size: 0.8em;" colspan="3">INTRODUCTION</th><td align="right">xxxvii</td></tr> -<tr><th style="font-size: 0.8em;" colspan="3">PART I.<br />PHYSIOLOGICAL COLOURS.</th></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">I.</span></td><td align="left">Effects of Light and Darkness on the Eye</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_2">2</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">II.</span></td><td align="left">Effects of Black and White Objects on the Eye</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_5">5</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">III</span>.</td><td align="left">Grey Surfaces and Objects</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_14">14</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">IV</span>.</td><td align="left">Dazzling Colourless Objects</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_16">16</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">V</span>.</td><td align="left">Coloured Objects</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_20">20</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">VI</span>.</td><td align="left">Coloured Shadows</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_29">29</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">VII</span>.</td><td align="left">Faint Lights</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_38">38</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">VIII</span>.</td><td align="left">Subjective Halos</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_40">40</a></span></td></tr> -<tr><td align="left"></td><td align="right"></td><td align="left">Pathological Colours—Appendix</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_45">45</a></span></td></tr> -<tr><th style="font-size: 0.8em;" colspan="3">PART II.<br />PHYSICAL COLOURS.</th></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">IX.</span></td><td align="left">Dioptrical Colours</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_59">59</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">X.</span></td><td align="left">Dioptrical Colours of the First Class</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_60">60</a></span></td></tr> -<tr><td align="left"></td><td align="right" valign="top"><span style="font-size: 0.8em;">XI</span>.</td><td align="left">Dioptrical Colours of the Second Class<br /> -—Refraction</td><td align="right"><span style="font-size: 0.8em;"><a href="#Pg_74">74</a></span></td></tr> -<tr><td align="left"></td><td align="left"></td><td align="left">Subjective Experiments</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_80">80</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XII.</span></td><td align="left">Refraction without the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_80">80</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XIII.</span></td><td align="left">Conditions of the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_81">81</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XIV.</span></td><td align="left">Conditions under which the Appearance of</td></tr> -<tr><td align="left"></td><td align="left"></td><td align="left">Colour increases</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_86">86</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XV.</span></td><td align="left">Explanation of the foregoing Phenomena</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_90">90</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XVI.</span></td><td align="left">Decrease of the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_100">100</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XVII.</span></td><td align="left">Grey Objects displaced by Refraction</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_103">103</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XVIII.</span></td><td align="left">Coloured Objects displaced by Refraction</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_106">106</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XIX.</span></td><td align="left">Achromatism and Hyperchromatism</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_118">118</a></span> -<span class="pagenum"><a name="Page_xxxii" id="Page_xxxii">[Pg xxxii]</a></span></td></tr> -<tr><td align="left"></td><td align="right" valign="top"><span style="font-size: 0.8em;">XX.</span></td><td align="left">Advantages of Subjective Experiments<br /> -—Transition to the Objective</td><td align="right" valign="bottom"><span style="font-size: 0.8em;"><a href="#Page_123">123</a></span></td></tr> -<tr><td align="left"></td><td align="left"></td><td align="left">Objective Experiments</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_125">125</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXI</span>.</td><td align="left">Refraction without the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_121">121</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXII</span>.</td><td align="left">Conditions of the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_128">128</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXIII</span>.</td><td align="left">Conditions of the Increase of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_134">134</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXIV</span>.</td><td align="left">Explanation of the foregoing Phenomena</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_139">139</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXV</span>.</td><td align="left">Decrease of the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_141">141</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXVI</span>.</td><td align="left">Grey Objects</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_142">142</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXVII</span>.</td><td align="left">Coloured Objects</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_143">143</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXVIII</span>.</td><td align="left">Achromatism and Hyperchromatism</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_145">145</a></span></td></tr> -<tr><td align="left"></td><td align="right" valign="top"><span style="font-size: 0.8em;">XXIX</span>.</td><td align="left">Combination of Subjective and Objective<br /> -Experiments</td><td align="right" valign="bottom"><span style="font-size: 0.8em;"><a href="#Page_147">147</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXX</span>.</td><td align="left">Transition</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_150">150</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXI</span>.</td><td align="left">Catoptrical Colours</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_154">154</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXII</span>.</td><td align="left">Paroptical Colours</td><td align="right"><span style="font-size: 0.8em;"><a href="#a163">163</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXIII</span>.</td><td align="left">Epoptical Colours</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_177">177</a></span></td></tr> -<tr><th style="font-size: 0.8em;" colspan="3">PART III.<br />CHEMICAL COLOURS.</th></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXIV</span>.</td><td align="left">Chemical Contrast</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_202">202</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXV</span>.</td><td align="left">White</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_203">203</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXVI</span>.</td><td align="left">Black</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_205">205</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXVII</span>.</td><td align="left">First Excitation of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_206">206</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXVIII</span>.</td><td align="left">Augmentation of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_212">212</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXIX</span>.</td><td align="left">Culmination</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_214">214</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XL</span>.</td><td align="left">Fluctuation</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_217">217</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLI</span>.</td><td align="left">Passage through the Whole Scale</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_218">218</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLII</span>.</td><td align="left">Inversion</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_220">220</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLIII</span>.</td><td align="left">Fixation</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_221">221</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLIV</span>.</td><td align="left">Intermixture, Real</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_223">223</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLV</span>.</td><td align="left">Intermixture, Apparent</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_226">226</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLVI</span>.</td><td align="left">Communication, Actual</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_230">230</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLVII</span>.</td><td align="left">Communication, Apparent</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_235">235</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLVIII</span>.</td><td align="left">Extraction</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_237">237</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLIX</span>.</td><td align="left">Nomenclature</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_242">242</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">L</span>.</td><td align="left">Minerals</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_245">245</a></span> -<span class="pagenum"><a name="Page_xxxiii" id="Page_xxxiii">[Pg xxxiii]</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">LI</span>.</td><td align="left">Plants</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_247">247</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">LII</span>.</td><td align="left">Worms, Insects, Fishes</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_252">252</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">LIII</span>.</td><td align="left">Birds</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_259">259</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">LIV</span>.</td><td align="left">Mammalia and Human Beings</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_262">262</a></span></td></tr> -<tr><td align="left"></td><td align="right" valign="top"><span style="font-size: 0.8em;">LV</span>.</td><td align="left">Physical and Chemical Effects of the -Transmission<br /> of Light through Coloured Mediums</td><td align="right" valign="bottom"><span style="font-size: 0.8em;"><a href="#Page_266">266</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">LVI</span>.</td><td align="left">Chemical Effect in Dioptrical Achromatism</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_270">270</a></span></td></tr> -</table> - -<p class="caption">PART IV.<br /> -GENERAL CHARACTERISTICS.</p> - -<p style="margin-left: 15%;"> -The Facility with which Colour appears <span class="tabnum"><a href="#Page_274">274</a></span><br /> -The Definite Nature of Colour <span class="tabnum"><a href="#Page_276">276</a></span><br /> -Combination of the Two Principles <span class="tabnum"><a href="#Page_277">277</a></span><br /> -Augmentation to Red <span class="tabnum"><a href="#Page_277">277</a></span><br /> -Junction of the Two Augmented Extremes <span class="tabnum"><a href="#Page_278">278</a></span><br /> -Completeness the Result of Variety in Colour <span class="tabnum"><a href="#Page_279">279</a></span><br /> -Harmony of the Complete State <span class="tabnum"><a href="#Page_280">280</a></span><br /> -Facility with which Colour may be made to tend either to<br /> -the Plus or Minus side <span class="tabnum"><a href="#Page_281">281</a></span><br /> -Evanescence of Colour <span class="tabnum"><a href="#Page_281">281</a></span><br /> -Permanence of Colour <span class="tabnum"><a href="#Page_282">282</a></span><br /> -</p> - - -<p class="caption">PART V.<br /> -RELATION TO OTHER PURSUITS.</p> - -<p style="margin-left: 15%;">Relation to Philosophy <span class="tabnum"><a href="#Page_283">283</a></span><br /> -Relation to Mathematics <span class="tabnum"><a href="#Page_286">286</a></span><br /> -Relation to the Technical Operations of the Dyer <span class="tabnum"><a href="#Page_289">289</a></span><br /> -Relation to Physiology and Pathology <span class="tabnum"><a href="#Page_291">291</a></span><br /> -Relation to Natural History <span class="tabnum"><a href="#Page_292">292</a></span><br /> -Relation to General Physics <span class="tabnum"><a href="#Page_293">293</a></span><br /> -Relation to the Theory of Music <span class="tabnum"><a href="#Page_298">298</a></span><br /> -Concluding Observations on Terminology <span class="tabnum"><a href="#Page_300">300</a></span><br /> -</p> - - -<p class="caption">PART VI.<br /> -EFFECT OF COLOUR WITH REFERENCE<br /> TO MORAL ASSOCIATIONS.</p> -<p class="pagenum"><a name="Page_xxxiv" id="Page_xxxiv">[Pg xxxiv]</a></p> -<p style="margin-left: 15%;"> -Yellow <span class="tabnum"><a href="#Page_306">306</a></span><br /> -Red-Yellow <span class="tabnum"><a href="#Page_308">308</a></span><br /> -Yellow-Red <span class="tabnum"><a href="#Page_309">309</a></span><br /> -Blue <span class="tabnum"><a href="#Page_310">310</a></span><br /> -Red-Blue <span class="tabnum"><a href="#Page_312">312</a></span><br /> -Blue-Red <span class="tabnum"><a href="#Page_313">313</a></span><br /> -Red <span class="tabnum"><a href="#Page_313">313</a></span><br /> -Green <span class="tabnum"><a href="#Page_316">316</a></span><br /> -Completeness and Harmony <span class="tabnum"><a href="#Page_316">316</a></span><br /> -Characteristic Combinations <span class="tabnum"><a href="#Page_321">321</a></span><br /> -Yellow and Blue <span class="tabnum"><a href="#Page_322">322</a></span><br /> -Yellow and Red <span class="tabnum"><a href="#Page_322">322</a></span><br /> -Blue and Red <span class="tabnum"><a href="#Page_322">322</a></span><br /> -Yellow-Red and Blue-Red <span class="tabnum"><a href="#Page_323">323</a></span><br /> -Combinations Non-Characteristic <span class="tabnum"><a href="#Page_324">324</a></span><br /> -Relation of the Combinations to Light and Dark <span class="tabnum"><a href="#Page_325">325</a></span><br /> -Considerations derived from the Evidence of Experience<br /> -and History <span class="tabnum"><a href="#Page_326">326</a></span><br /> -Æsthetic Influence <span class="tabnum"><a href="#Page_330">330</a></span><br /> -Chiaro-Scuro <span class="tabnum"><a href="#Page_331">331</a></span><br /> -Tendency to Colour <span class="tabnum"><a href="#Page_334">334</a></span><br /> -Keeping <span class="tabnum"><a href="#Page_335">335</a></span><br /> -Colouring <span class="tabnum"><a href="#Page_337">337</a></span><br /> -Colour in General Nature <span class="tabnum"><a href="#Page_337">337</a></span><br /> -Colour of Particular Objects <span class="tabnum"><a href="#Page_338">338</a></span><br /> -Characteristic Colouring <span class="tabnum"><a href="#Page_339">339</a></span><br /> -Harmonious Colouring <span class="tabnum"><a href="#Page_341">341</a></span><br /> -Genuine Tone <span class="tabnum"><a href="#Page_342">342</a></span><br /> -False Tone <span class="tabnum"><a href="#Page_342">342</a></span><br /> -Weak Colouring <span class="tabnum"><a href="#Page_343">343</a></span><br /> -The Motley <span class="tabnum"><a href="#Page_344">344</a></span><br /> -Dread of Theory <span class="tabnum"><a href="#Page_344">344</a></span><br /> -Ultimate Aim <span class="tabnum"><a href="#Page_345">345</a></span><br /> -Grounds <span class="tabnum"><a href="#Page_345">345</a></span><br /> -Pigments <span class="tabnum"><a href="#Page_348">348</a></span><br /> -Allegorical, Symbolical, Mystical Application of Colour <span class="tabnum"><a href="#Page_350">350</a></span><br /> -Concluding Observations <span class="tabnum"><a href="#Page_352">352</a></span><br /> -</p> -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_xxxv" id="Page_xxxv">[Pg xxxv]</a></span></p> - -<h3><a name="OUTLINE_OF_A_THEORY_OF_COLOURS" id="OUTLINE_OF_A_THEORY_OF_COLOURS">OUTLINE OF A THEORY OF COLOURS.</a></h3> - - -<blockquote> - -<p>"Si vera nostra sunt aut falsa, erunt talia, licet nostra -per vitam defendimus. Post fata nostra pueri qui nunc ludunt -nostri judices erunt."</p></blockquote> - -<hr class="tb" /> - -<p><span class="pagenum"><a name="Page_xxxvii" id="Page_xxxvii">[Pg xxxvii]</a></span></p> - - - - -<h4><a name="INTRODUCTION" id="INTRODUCTION">INTRODUCTION.</a></h4> - - -<p>The desire of knowledge is first stimulated in us when remarkable -phenomena attract our attention. In order that this attention be -continued, it is necessary that we should feel some interest in -exercising it, and thus by degrees we become better acquainted with the -object of our curiosity. During this process of observation we remark -at first only a vast variety which presses indiscriminately on our -view; we are forced to separate, to distinguish, and again to combine; -by which means at last a certain order arises which admits of being -surveyed with more or less satisfaction.</p> - -<p>To accomplish this, only in a certain degree, in any department, -requires an unremitting and close application; and we find, for this -reason, that men prefer substituting a general theoretical view, or -some system of explanation, for the facts themselves, instead of taking -the trouble to make themselves first acquainted with cases in detail -and then constructing a whole.</p> - -<p>The attempt to describe and class the phenomena of colours has been -only twice made: first by Theophrastus,<a name="FNanchor_1_7" id="FNanchor_1_7"></a><a href="#Footnote_1_7" class="fnanchor">[1]</a> and in modern times by<span class="pagenum"><a name="Page_xxxviii" id="Page_xxxviii">[Pg xxxviii]</a></span> -Boyle. The pretensions of the present essay to the third place will -hardly be disputed.</p> - -<p>Our historical survey enters into further details. Here we merely -observe that in the last century such a classification was not to be -thought of, because Newton had based his hypothesis on a phenomenon -exhibited in a complicated and secondary state; and to this the other -cases that forced themselves on the attention were contrived to be -referred, when they could not be passed over in silence; just as an -astronomer would do, if from whim he were to place the moon in the -centre of our system; he would be compelled to make the earth, sun, and -planets revolve round the lesser body, and be forced to disguise and -gloss over the error of his first assumption by ingenious calculations -and plausible statements.</p> - -<p>In our prefatory observations we assumed the reader to be acquainted -with what was known respecting light; here we assume the same with -regard to the eye. We observed that all nature manifests itself by -means of colours to the sense of sight. We now assert, extraordinary as -it may in some degree appear, that the eye sees no form, inasmuch as -light, shade, and colour together constitute that which to our vision -distinguishes object from object, and the parts of an object from each -other. From these three, light, shade, and colour, we construct the -visible<span class="pagenum"><a name="Page_xxxix" id="Page_xxxix">[Pg xxxix]</a></span> world, and thus, at the same time, make painting possible, -an art which has the power of producing on a flat surface a much more -perfect visible world than the actual one can be.</p> - -<p>The eye may be said to owe its existence to light, which calls forth, -as it were, a sense that is akin to itself; the eye, in short, is -formed with reference to light, to be fit for the action of light; the -light it contains corresponding with the light without.</p> - -<p>We are here reminded of a significant adage in constant use with the -ancient Ionian school—"Like is only known by Like;" and again, of the -words of an old mystic writer, which may be thus rendered, "If the eye -were not sunny, how could we perceive light? If God's own strength -lived not in us, how could we delight in Divine things?" This immediate -affinity between light and the eye will be denied by none; to consider -them as identical in substance is less easy to comprehend. It will be -more intelligible to assert that a dormant light resides in the eye, -and that it may be excited by the slightest cause from within or from -without. In darkness we can, by an effort of imagination, call up the -brightest images; in dreams objects appear to us as in broad daylight; -awake, the slightest external action of light is perceptible, and if -the organ suffers an actual shock, light and colours spring forth.<span class="pagenum"><a name="Page_xl" id="Page_xl">[Pg xl]</a></span> -Here, however, those who are wont to proceed according to a certain -method, may perhaps observe that as yet we have not decidedly explained -what colour is. This question, like the definition of light and the -eye, we would for the present evade, and would appeal to our inquiry -itself, where we have circumstantially shown how colour is produced. -We have only therefore to repeat that colour is a law of nature in -relation with the sense of sight. We must assume, too, that every one -has this sense, that every one knows the operation of nature on it, for -to a blind man it would be impossible to speak of colours.</p> - -<p>That we may not, however, appear too anxious to shun such an -explanation, we would restate what has been said as follows: colour is -an elementary phenomenon in nature adapted to the sense of vision; a -phenomenon which, like all others, exhibits itself by separation and -contrast, by commixture and union, by augmentation and neutralization, -by communication and dissolution: under these general terms its nature -may be best comprehended.</p> - -<p>We do not press this mode of stating the subject on any one. Those -who, like ourselves, find it convenient, will readily adopt it; but we -have no desire to enter the lists hereafter in its defence. From time -immemorial it has been dangerous to treat of colour; so much so, that<span class="pagenum"><a name="Page_xli" id="Page_xli">[Pg xli]</a></span> -one of our predecessors ventured on a certain occasion to say, "The ox -becomes furious if a red cloth is shown to him; but the philosopher, -who speaks of colour only in a general way, begins to rave."</p> - -<p>Nevertheless, if we are to proceed to give some account of our work, to -which we have appealed, we must begin by explaining how we have classed -the different conditions under which colour is produced. We found three -modes in which it appears; three classes of colours, or rather three -exhibitions of them all. The distinctions of these classes are easily -expressed.</p> - -<p>Thus, in the first instance, we considered colours, as far as they -may be said to belong to the eye itself, and to depend on an action -and re-action of the organ; next, they attracted our attention as -perceived in, or by means of, colourless mediums; and lastly, where -we could consider them as belonging to particular substances. We have -denominated the first, physiological, the second, physical, the third, -chemical colours. The first are fleeting and not to be arrested; the -next are passing, but still for a while enduring; the last may be made -permanent for any length of time.</p> - -<p>Having separated these classes and kept them as distinct as possible, -with a view to a clear, didactic exposition, we have been enabled at<span class="pagenum"><a name="Page_xlii" id="Page_xlii">[Pg xlii]</a></span> -the same time to exhibit them in an unbroken series, to connect the -fleeting with the somewhat more enduring, and these again with the -permanent hues; and thus, after having carefully attended to a distinct -classification in the first instance, to do away with it again when a -larger view was desirable.</p> - -<p>In a fourth division of our work we have therefore treated generally -what was previously detailed under various particular conditions, and -have thus, in fact, given a sketch for a future theory of colours. We -will here only anticipate our statements so far as to observe, that -light and darkness, brightness and obscurity, or if a more general -expression is preferred, light and its absence, are necessary to the -production of colour. Next to the light, a colour appears which we call -yellow; another appears next to the darkness, which we name blue. When -these, in their purest state, are so mixed that they are exactly equal, -they produce a third colour called green. Each of the two first-named -colours can however of itself produce a new tint by being condensed or -darkened. They thus acquire a reddish appearance which can be increased -to so great a degree that the original blue or yellow is hardly to -be recognised in it: but the intensest and purest red, especially in -physical cases, is produced when the two extremes of the yellow-red -and blue-red are<span class="pagenum"><a name="Page_xliii" id="Page_xliii">[Pg xliii]</a></span> united. This is the actual state of the appearance -and generation of colours. But we can also assume an existing red in -addition to the definite existing blue and yellow, and we can produce -contrariwise, by mixing, what we directly produced by augmentation or -deepening. With these three or six colours, which may be conveniently -included in a circle, the elementary doctrine of colours is alone -concerned. All other modifications, which may be extended to infinity, -have reference more to the application,—have reference to the -technical operations of the painter and dyer, and the various purposes -of artificial life. To point out another general quality, we may -observe that colours throughout are to be considered as half-lights, as -half-shadows, on which account if they are so mixed as reciprocally to -destroy their specific hues, a shadowy tint, a grey, is produced.</p> - -<p>In the fifth division of our inquiry we had proposed to point out -the relations in which we should wish our doctrine of colours to -stand to other pursuits. Important as this part of our work is, it -is perhaps on this very account not so successful as we could wish. -Yet when we reflect that strictly speaking these relations cannot be -described before they exist, we may console ourselves if we have in -some degree failed in endeavouring for the first time to define them. -For undoubtedly we should first<span class="pagenum"><a name="Page_xliv" id="Page_xliv">[Pg xliv]</a></span> wait to see how those whom we have -endeavoured to serve, to whom we have intended to make an agreeable and -useful offering, how such persons, we say, will accept the result of -our utmost exertion: whether they will adopt it, whether they will make -use of it and follow it up, or whether they will repel, reject, and -suffer it to remain unassisted and neglected.</p> - -<p>Meanwhile, we venture to express what we believe and hope. From the -philosopher we believe we merit thanks for having traced the phenomena -of colours to their first sources, to the circumstances under which -they simply appear and are, and beyond which no further explanation -respecting them is possible. It will, besides, be gratifying to him -that we have arranged the appearances described in a form that admits -of being easily surveyed, even should he not altogether approve of the -arrangement itself.</p> - -<p>The medical practitioner, especially him whose study it is to watch -over the organ of sight, to preserve it, to assist its defects and to -cure its disorders, we reckon to make especially our friend. In the -chapter on the physiological colours, in the Appendix relating to those -that are more strictly pathological, he will find himself quite in his -own province. We are not without hopes of seeing the physiological -phenomena,—a hitherto neglected, and, we may add, most important -branch of the theory of<span class="pagenum"><a name="Page_xlv" id="Page_xlv">[Pg xlv]</a></span> colours,—completely investigated through the -exertions of those individuals who in our own times are treating this -department with success.</p> - -<p>The investigator of nature should receive us cordially, since we -enable him to exhibit the doctrine of colours in the series of other -elementary phenomena, and at the same time enable him to make use of a -corresponding nomenclature, nay, almost the same words and designations -as under the other rubrics. It is true we give him rather more trouble -as a teacher, for the chapter of colours is not now to be dismissed -as heretofore with a few paragraphs and experiments; nor will the -scholar submit to be so scantily entertained as he has hitherto been, -without murmuring. On the other hand, an advantage will afterwards -arise out of this: for if the Newtonian doctrine was easily learnt, -insurmountable difficulties presented themselves in its application. -Our theory is perhaps more difficult to comprehend, but once known, all -is accomplished, for it carries its application along with it.</p> - -<p>The chemist who looks upon colours as indications by which he may -detect the more secret properties of material things, has hitherto -found much inconvenience in the denomination and description of -colours; nay, some have been induced after closer and nicer examination -to look upon colour as an uncertain and fallacious criterion<span class="pagenum"><a name="Page_xlvi" id="Page_xlvi">[Pg xlvi]</a></span> in -chemical operations. Yet we hope by means of our arrangement and the -nomenclature before alluded to, to bring colour again into credit, -and to awaken the conviction that a progressive, augmenting, mutable -quality, a quality which admits of alteration even to inversion, is not -fallacious, but rather calculated to bring to light the most delicate -operations of nature.</p> - -<p>In looking a little further round us, we are not without fears -that we may fail to satisfy another class of scientific men. By an -extraordinary combination of circumstances the theory of colours -has been drawn into the province and before the tribunal of the -mathematician, a tribunal to which it cannot be said to be amenable. -This was owing to its affinity with the other laws of vision which the -mathematician was legitimately called upon to treat. It was owing, -again, to another circumstance: a great mathematician had investigated -the theory of colours, and having been mistaken in his observations as -an experimentalist, he employed the whole force of his talent to give -consistency to this mistake. Were both these circumstances considered, -all misunderstanding would presently be removed, and the mathematician -would willingly co-operate with us, especially in the physical -department of the theory.</p> - -<p>To the practical man, to the dyer, on the other hand, our labour must -be altogether acceptable;<span class="pagenum"><a name="Page_xlvii" id="Page_xlvii">[Pg xlvii]</a></span> for it was precisely those who reflected on -the facts resulting from the operations of dyeing who were the least -satisfied with the old theory: they were the first who perceived the -insufficiency of the Newtonian doctrine. The conclusions of men are -very different according to the mode in which they approach a science -or branch of knowledge; from which side, through which door they -enter. The literally practical man, the manufacturer, whose attention -is constantly and forcibly called to the facts which occur under his -eye, who experiences benefit or detriment from the application of his -convictions, to whom loss of time and money is not indifferent, who -is desirous of advancing, who aims at equalling or surpassing what -others have accomplished,—such a person feels the unsoundness and -erroneousness of a theory much sooner than the man of letters, in whose -eyes words consecrated by authority are at last equivalent to solid -coin; than the mathematician, whose formula always remains infallible, -even although the foundation on which it is constructed may not square -with it. Again, to carry on the figure before employed, in entering -this theory from the side of painting, from the side of æsthetic<a name="FNanchor_2_8" id="FNanchor_2_8"></a><a href="#Footnote_2_8" class="fnanchor">[2]</a> -colouring generally, we shall be<span class="pagenum"><a name="Page_xlviii" id="Page_xlviii">[Pg xlviii]</a></span> found to have accomplished a -most thank-worthy office for the artist. In the sixth part we have -endeavoured to define the effects of colour as addressed at once to -the eye and mind, with a view to making them more available for the -purposes of art. Although much in this portion, and indeed throughout, -has been suffered to remain as a sketch, it should be remembered that -all theory can in strictness only point out leading principles, under -the guidance of which, practice may proceed with vigour and be enabled -to attain legitimate results.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_7" id="Footnote_1_7"></a><a href="#FNanchor_1_7"><span class="label">[1]</span></a> The treatise to which the author alludes in more generally -ascribed to Aristotle.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_8" id="Footnote_2_8"></a><a href="#FNanchor_2_8"><span class="label">[2]</span></a> Æsthetic—belonging to taste as mere internal sense, from -αἰσθάνομαι, to feel; the word was first used by Wolf.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_1" id="Page_1">[Pg 1]</a></span></p></div> - - - - -<h5><a name="PART_I" id="PART_I">PART I.</a></h5> - - -<h4>PHYSIOLOGICAL COLOURS.</h4> - - -<p class="para"><a id="a1"></a>1.</p> - -<p>We naturally place these colours first, because they belong altogether, -or in a great degree, to the <i>subject</i><a name="FNanchor_1_9" id="FNanchor_1_9"></a><a href="#Footnote_1_9" class="fnanchor">[1]</a>—to the eye itself. They -are the foundation of the whole doctrine, and open to our view the -chromatic harmony on which so much difference of opinion has existed. -They have been hitherto looked upon as extrinsic and casual, as -illusion and infirmity: their appearances have been known from ancient -date; but, as they were too evanescent to be arrested, they were -banished into the region of phantoms, and under this idea have been -very variously described.</p> - -<p class="para"><a id="a2">2.</a></p> - -<p>Thus they are called <i>colores adventicii</i> by Boyle; <i>imaginarii</i> and -<i>phantastici</i> by Rizetti; by Buffon, <i>couleurs accidentelles</i>; by -Scherfer, <i>scheinfarben</i> (apparent colours); <i>ocular illusions</i> and -<i>deceptions of sight</i><span class="pagenum"><a name="Page_2" id="Page_2">[Pg 2]</a></span> by many; by Hamberger, <i>vitia fugitiva</i>; by -Darwin, <i>ocular spectra</i>.</p> - -<p class="para"><a id="a3">3.</a></p> - -<p>We have called them physiological because they belong to the eye in a -healthy state; because we consider them as the necessary conditions -of vision; the lively alternating action of which, with reference to -external objects and a principle within it, is thus plainly indicated.</p> - -<p class="para"><a id="a4">4.</a></p> - -<p>To these we subjoin the pathological colours, which, like all -deviations from a constant law, afford a more complete insight into the -nature of the physiological colours.</p> - -<hr class="r5" /> - -<h5>I</h5> -<h5>EFFECTS OF LIGHT AND DARKNESS ON THE EYE.</h5> - - -<p class="para"><a id="a5">5.</a></p> - -<p>The retina, after being acted upon by light or darkness, is found to be -in two different states, which are entirely opposed to each other.</p> - -<p class="para"><a id="a6">6.</a></p> - -<p>If we keep the eyes open in a totally dark place, a certain sense of -privation is experienced. The organ is abandoned to itself; it retires -into itself. That stimulating and grateful contact is wanting by means -of which it is connected with the external world, and becomes part of a -whole.</p> - -<p><span class="pagenum"><a name="Page_3" id="Page_3">[Pg 3]</a></span></p> - -<p class="para"><a id="a7">7.</a></p> - -<p>If we look on a white, strongly illumined surface, the eye is dazzled, -and for a time is incapable of distinguishing objects moderately -lighted.</p> - -<p class="para"><a id="a8">8.</a></p> - -<p>The whole of the retina is acted on in each of these extreme states, -and thus we can only experience one of these effects at a time. In -the one case (6) we found the organ in the utmost relaxation and -susceptibility; in the other (7) in an overstrained state, and scarcely -susceptible at all.</p> - -<p class="para"><a id="a9">9.</a></p> - -<p>If we pass suddenly from the one state to the other, even without -supposing these to be the extremes, but only, perhaps, a change from -bright to dusky, the difference is remarkable, and we find that the -effects last for some time.</p> - -<p class="para"><a id="a10">10.</a></p> - -<p>In passing from bright daylight to a dusky place we distinguish nothing -at first: by degrees the eye recovers its susceptibility; strong eyes -sooner than weak ones; the former in a minute, while the latter may -require seven or eight minutes.</p> - -<p class="para"><a id="a11">11.</a></p> - -<p>The fact that the eye is not susceptible to faint<span class="pagenum"><a name="Page_4" id="Page_4">[Pg 4]</a></span> impressions of -light, if we pass from light to comparative darkness, has led to -curious mistakes in scientific observations. Thus an observer, whose -eyes required some time to recover their tone, was long under the -impression that rotten wood did not emit light at noon-day, even in a -dark room. The fact was, he did not see the faint light, because he was -in the habit of passing from bright sunshine to the dark room, and only -subsequently remained so long there that the eye had time to recover -itself.</p> - -<p>The same may have happened to Doctor Wall, who, in the daytime, even in -a dark room, could hardly perceive the electric light of amber.</p> - -<p>Our not seeing the stars by day, as well as the improved appearance of -pictures seen through a double tube, is also to be attributed to the -same cause.</p> - -<p class="para"><a id="a12">12.</a></p> - -<p>If we pass from a totally dark place to one illumined by the sun, we -are dazzled. In coming from a lesser degree of darkness to light that -is not dazzling, we perceive all objects clearer and better: hence eyes -that have been in a state of repose are in all cases better able to -perceive moderately distinct appearances.</p> - -<p>Prisoners who have been long confined in darkness acquire so great -a susceptibility of the retina, that even in the dark (probably a -darkness<span class="pagenum"><a name="Page_5" id="Page_5">[Pg 5]</a></span> very slightly illumined) they can still distinguish objects.</p> - -<p class="para"><a id="a13">13.</a></p> - -<p>In the act which we call seeing, the retina is at one and the same time -in different and even opposite states. The greatest brightness, short -of dazzling, acts near the greatest darkness. In this state we at once -perceive all the intermediate gradations of <i>chiaro-scuro</i>, and all the -varieties of hues.</p> - -<p class="para"><a id="a14">14.</a></p> - -<p>We will proceed in due order to consider and examine these elements of -the visible world, as well as the relation in which the organ itself -stands to them, and for this purpose we take the simplest objects.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_9" id="Footnote_1_9"></a><a href="#FNanchor_1_9"><span class="label">[1]</span></a> The German distinction between <i>subject</i> and <i>object</i> -is so generally understood and adopted, that it is hardly necessary -to explain that the subject is the <i>individual</i>, in this case the -<i>beholder</i>; the object, <i>all that is without him</i>.—T.</p></div> - - -<hr class="chap" /> - -<h5><a name="II" id="II">II.</a></h5> - - -<h5>EFFECTS OF BLACK AND WHITE OBJECTS ON THE EYE.</h5> - - -<p class="para"><a id="a15">15.</a></p> - -<p>In the same manner as the retina generally is affected by brightness -and darkness, so it is affected by single bright or dark objects. -If light and dark produce different results on the whole retina, so -black and white objects seen at<span class="pagenum"><a name="Page_6" id="Page_6">[Pg 6]</a></span> the same time produce the same states -together which light and dark occasioned in succession.</p> - -<p class="para"><a id="a16">16.</a></p> - -<p>A dark object appears smaller than a bright one of the same size. Let -a white disk be placed on a black ground, and a black disk on a white -ground, both being exactly similar in size; let them be seen together -at some distance, and we shall pronounce the last to be about a fifth -part smaller than the other. If the black circle be made larger by so -much, they will appear equal.<a name="FNanchor_1_10" id="FNanchor_1_10"></a><a href="#Footnote_1_10" class="fnanchor">[1]</a></p> - -<p class="para"><a id="a17">17.</a></p> - -<p>Thus Tycho de Brahe remarked that the moon in conjunction (the darker -state) appears about a fifth part smaller than when in opposition -(the bright full state). The first crescent appears to belong to a -larger disk than the remaining dark portion, which can sometimes be -distinguished at the period of the new moon. Black dresses make people -appear smaller than light ones. Lights seen behind an edge make an -apparent notch in it. A ruler, behind which the flame of a light just -appears, seems to us indented. The rising or setting sun appears to -make a notch in the horizon.</p> - -<div class="figcenter" style="width: 500px;"> -<a id="col000"></a> -<img src="images/col_000.jpg" width="500" alt="" /> -<p style="text-align: center; font-weight: bold;">Plate 1.</p> -</div> - -<p class="para"><a id="a18">18.</a></p> - -<p>Black, as the equivalent of darkness, leaves<span class="pagenum"><a name="Page_7" id="Page_7">[Pg 7]</a></span> the organ in a state of -repose; white, as the representative of light, excites it. We may, -perhaps, conclude from the above experiment (16) that the unexcited -retina, if left to itself, is drawn together, and occupies a less space -than in its active state, produced by the excitement of light.</p> - -<p>Hence Kepler says very beautifully: "Certum est vel in retinâ caussâ -picturæ, vel in spiritibus caussâ impressionis, exsistere dilatationem -lucidorum."—<i>Paralip. in Vitellionem</i>, p. 220. Scherfer expresses a -similar conjecture.—<a href="#NOTE_A">Note A</a>.</p> - -<p class="para"><a id="a19">19.</a></p> - -<p>However this may be, both impressions derived from such objects remain -in the organ itself, and last for some time, even when the external -cause is removed. In ordinary experience we scarcely notice this, for -objects are seldom presented to us which are very strongly relieved -from each other, and we avoid looking at those appearances that dazzle -the sight. In glancing from one object to another, the succession of -images appears to us distinct; we are not aware that some portion of -the impression derived from the object first contemplated passes to -that which is next looked at.</p> - -<p class="para"><a id="a20">20.</a></p> - -<p>If in the morning, on waking, when the eye is very susceptible, we look -intently at the bars<span class="pagenum"><a name="Page_8" id="Page_8">[Pg 8]</a></span> of a window relieved against the dawning sky, and -then shut our eyes or look towards a totally dark place, we shall see a -dark cross on a light ground before us for some time.</p> - -<p class="para"><a id="a21">21.</a></p> - -<p>Every image occupies a certain space on the retina, and of course a -greater or less space in proportion as the object is seen near or at a -distance. If we shut the eyes immediately after looking at the sun we -shall be surprised to find how small the image it leaves appears.</p> - -<p class="para"><a id="a22">22.</a></p> - -<p>If, on the other hand, we turn the open eye towards the side of a -room, and consider the visionary image in relation to other objects, -we shall always see it larger in proportion to the distance of the -surface on which it is thrown. This is easily explained by the laws of -perspective, according to which a small object near covers a great one -at a distance.</p> - -<p class="para"><a id="a23">23.</a></p> - -<p>The duration of these visionary impressions varies with the powers -or structure of the eye in different individuals, just as the time -necessary for the recovery of the tone of the retina varies in passing -from brightness to darkness (10): it can be measured by minutes and -seconds,<span class="pagenum"><a name="Page_9" id="Page_9">[Pg 9]</a></span> indeed much more exactly than it could formerly have been -by causing a lighted linstock to revolve rapidly, so as to appear a -circle.—<a href="#NOTE_B">Note B</a>.</p> - -<p class="para"><a id="a24">24.</a></p> - -<p>But the force with which an impinging light impresses the eye is -especially worthy of attention. The image of the sun lasts longest; -other objects, of various degrees of brightness, leave the traces of -their appearance on the eye for a proportionate time.</p> - -<p class="para"><a id="a25">25.</a></p> - -<p>These images disappear by degrees, and diminish at once in distinctness -and in size.</p> - -<p class="para"><a id="a26">26.</a></p> - -<p>They are reduced from the contour inwards, and the impression on some -persons has been that in square images the angles become gradually -blunted till at last a diminished round image floats before the eye.</p> - -<p class="para"><a id="a27">27.</a></p> - -<p>Such an image, when its impression is no more observable, can, -immediately after, be again revived on the retina by opening and -shutting the eye, thus alternately exciting and resting it.</p> - -<p><span class="pagenum"><a name="Page_10" id="Page_10">[Pg 10]</a></span></p> - -<p class="para"><a id="a28">28.</a></p> - -<p>Images may remain on the retina in morbid affections of the eye for -fourteen, seventeen minutes, or even longer. This indicates extreme -weakness of the organ, its inability to recover itself; while visions -of persons or things which are the objects of love or aversion indicate -the connexion between sense and thought.</p> - -<p class="para"><a id="a29">29.</a></p> - -<p>If, while the image of the window-bars before mentioned lasts, we -look upon a light grey surface, the cross will then appear light -and the panes dark. In the first case (20) the image was like the -original picture, so that the visionary impression also could continue -unchanged; but in the present instance our attention is excited by a -contrary effect being produced. Various examples have been given by -observers of nature.</p> - -<p class="para"><a id="a30">30.</a></p> - -<p>The scientific men who made observations in the Cordilleras saw a -bright appearance round the shadows of their heads on some clouds. This -example is a case in point; for, while they fixed their eyes on the -dark shadow, and at the same time moved from the spot, the compensatory -light image appeared to float round the<span class="pagenum"><a name="Page_11" id="Page_11">[Pg 11]</a></span> real dark one. If we look at -a black disk on a light grey surface, we shall presently, by changing -the direction of the eyes in the slightest degree, see a bright halo -floating round the dark circle.</p> - -<p>A similar circumstance happened to myself: for while, as I sat in the -open air, I was talking to a man who stood at a little distance from me -relieved on a grey sky, it appeared to me, as I slightly altered the -direction of my eyes, after having for some time looked fixedly at him, -that his head was encircled with a dazzling light.</p> - -<p>In the same way probably might be explained the circumstance that -persons crossing dewy meadows at sunrise see a brightness round each -other's heads<a name="FNanchor_2_11" id="FNanchor_2_11"></a><a href="#Footnote_2_11" class="fnanchor">[2]</a>; the brightness in this case may be also iridescent, -as the phenomena of refraction come into the account.</p> - -<p>Thus again it has been asserted that the shadows of a balloon thrown on -clouds were bordered with bright and somewhat variegated circles.</p> - -<p>Beccaria made use of a paper kite in some experiments on electricity. -Round this kite appeared a small shining cloud varying in size; the -same brightness was even observed round part of the string. Sometimes -it disappeared,<span class="pagenum"><a name="Page_12" id="Page_12">[Pg 12]</a></span> and if the kite moved faster the light appeared to -float to and fro for a few moments on the place before occupied. This -appearance, which could not be explained by those who observed it at -the time, was the image which the eye retained of the kite relieved as -a dark mass on a bright sky; that image being changed into a light mass -on a comparatively dark background.</p> - -<p>In optical and especially in chromatic experiments, where the observer -has to do with bright lights whether colourless or coloured, great care -should be taken that the spectrum which the eye retains in consequence -of a previous observation does not mix with the succeeding one, and -thus affect the distinctness and purity of the impression.</p> - -<p class="para"><a id="a31">31.</a></p> - -<p>These appearances have been explained as follows: That portion of the -retina on which the dark cross (29) was impressed is to be considered -in a state of repose and susceptibility. On this portion therefore the -moderately light surface acted in a more lively manner than on the rest -of the retina, which had just been impressed with the light through -the panes, and which, having thus been excited by a much stronger -brightness, could only view the grey surface as a dark.</p> - -<p><span class="pagenum"><a name="Page_13" id="Page_13">[Pg 13]</a></span></p> - -<p class="para"><a id="a32">32.</a></p> - -<p>This mode of explanation appears sufficient for the cases in question, -but, in the consideration of phenomena hereafter to be adduced, we are -forced to trace the effects to higher sources.</p> - -<p class="para"><a id="a33">33.</a></p> - -<p>The eye after sleep exhibits its vital elasticity more especially by -its tendency to alternate its impressions, which in the simplest form -change from dark to light, and from light to dark. The eye cannot for a -moment remain in a particular state determined by the object it looks -upon. On the contrary, it is forced to a sort of opposition, which, in -contrasting extreme with extreme, intermediate degree with intermediate -degree, at the same time combines these opposite impressions, and thus -ever tends to a whole, whether the impressions are successive, or -simultaneous and confined to one image.</p> - -<p class="para"><a id="a34">34.</a></p> - -<p>Perhaps the peculiarly grateful sensation which we experience in -looking at the skilfully treated chiaro-scuro of colourless pictures -and similar works of art arises chiefly from the <i>simultaneous</i> -impression of a whole, which by the organ itself is sought, rather than -arrived at, in <i>succession</i>, and which, whatever may be the result, can -never be arrested.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_10" id="Footnote_1_10"></a><a href="#FNanchor_1_10"><span class="label">[1]</span></a> <a href="#col000">Plate 1</a>. fig. 1.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_11" id="Footnote_2_11"></a><a href="#FNanchor_2_11"><span class="label">[2]</span></a> See the Life of Benvenuto Cellini, vol. i. p. 453. Milan -edition, 1806.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_14" id="Page_14">[Pg 14]</a></span></p></div> - - - - -<h5><a name="III" id="III">III.</a></h5> - - -<h5>GREY SURFACES AND OBJECTS.</h5> - - -<p class="para"><a id="a35">35.</a></p> - -<p>A moderate light is essential to many chromatic experiments. This can -be presently obtained by surfaces more or less grey, and thus we have -at once to make ourselves acquainted with this simplest kind of middle -tint, with regard to which it is hardly necessary to observe, that -in many cases a white surface in shadow, or in a low light, may be -considered equivalent to a grey.</p> - -<p class="para"><a id="a36">36.</a></p> - -<p>Since a grey surface is intermediate between brightness and darkness, -it admits of our illustrating a phenomenon before described (29) by an -easy experiment.</p> - -<p class="para"><a id="a37">37.</a></p> - -<p>Let a black object be held before a grey surface, and let the -spectator, after looking steadfastly at it, keep his eyes unmoved while -it is taken away: the space it occupied appears much lighter. Let a -white object be held up in the same manner: on taking it away the space -it occupied will appear much darker than the<span class="pagenum"><a name="Page_15" id="Page_15">[Pg 15]</a></span> rest of the surface. Let -the spectator in both cases turn his eyes this way and that on the -surface, the visionary images will move in like manner.</p> - -<p class="para"><a id="a38">38.</a></p> - -<p>A grey object on a black ground appears much brighter than the same -object on a white ground. If both comparisons are seen together the -spectator can hardly persuade himself that the two greys are identical. -We believe this again to be a proof of the great excitability of the -retina, and of the silent resistance which every vital principle is -forced to exhibit when any definite or immutable state is presented to -it. Thus inspiration already presupposes expiration; thus every systole -its diastole. It is the universal formula of life which manifests -itself in this as in all other cases. When darkness is presented to -the eye it demands brightness, and <i>vice versâ</i>: it shows its vital -energy, its fitness to receive the impression of the object, precisely -by spontaneously tending to an opposite state.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_16" id="Page_16">[Pg 16]</a></span></p> - - - - -<h5><a name="IV" id="IV">IV.</a></h5> - - -<h5>DAZZLING COLOURLESS OBJECTS.</h5> - - -<p class="para"><a id="a39">39.</a></p> - -<p>If we look at a dazzling, altogether colourless object, it makes a -strong lasting impression, and its after-vision is accompanied by an -appearance of colour.</p> - -<p class="para"><a id="a40">40.</a></p> - -<p>Let a room be made as dark as possible; let there be a circular opening -in the window-shutter about three inches in diameter, which may be -closed or not at pleasure. The sun being suffered to shine through this -on a white surface, let the spectator from some little distance fix his -eyes on the bright circle thus admitted. The hole being then closed, -let him look towards the darkest part of the room; a circular image -will now be seen to float before him. The middle of this circle will -appear bright, colourless, or somewhat yellow, but the border will at -the same moment appear red.</p> - -<p>After a time this red, increasing towards the centre, covers the whole -circle, and at last the bright central point. No sooner, however, is -the whole circle red than the edge begins to be blue, and the blue -gradually encroaches inwards<span class="pagenum"><a name="Page_17" id="Page_17">[Pg 17]</a></span> on the red. When the whole is blue -the edge becomes dark and colourless. This darker edge again slowly -encroaches on the blue till the whole circle appears colourless. The -image then becomes gradually fainter, and at the same time diminishes -in size. Here again we see how the retina recovers itself by a -succession of vibrations after the powerful external impression it -received. (<a href="#a25">25</a>, <a href="#a26">26</a>.)</p> - -<p class="para"><a id="a41">41.</a></p> - -<p>By several repetitions similar in result, I found the comparative -duration of these appearances in my own case to be as follows:—</p> - -<p>I looked on the bright circle five seconds, and then, having closed -the aperture, saw the coloured visionary circle floating before me. -After thirteen seconds it was altogether red; twenty-nine seconds -next elapsed till the whole was blue, and forty-eight seconds till -it appeared colourless. By shutting and opening the eye I constantly -revived the image, so that it did not quite disappear till seven -minutes had elapsed.</p> - -<p>Future observers may find these periods shorter or longer as their -eyes may be stronger or weaker (<a href="#a23">23</a>), but it would be very remarkable -if, notwithstanding such variations, a corresponding proportion as to -relative duration should be found to exist.</p> - -<p><span class="pagenum"><a name="Page_18" id="Page_18">[Pg 18]</a></span></p> - -<p class="para"><a id="a42">42.</a></p> - -<p>But this remarkable phenomenon no sooner excites our attention than we -observe a new modification of it.</p> - -<p>If we receive the impression of the bright circle as before, and then -look on a light grey surface in a moderately lighted room, an image -again floats before us; but in this instance a dark one: by degrees it -is encircled by a green border that gradually spreads inwards over the -whole circle, as the red did in the former instance. As soon as this -has taken place a dingy yellow appears, and, filling the space as the -blue did before, is finally lost in a negative shade.</p> - -<p class="para"><a id="a43">43.</a></p> - -<p>These two experiments may be combined by placing a black and a white -plane surface next each other in a moderately lighted room, and then -looking alternately on one and the other as long as the impression of -the light circle lasts: the spectator will then perceive at first a red -and green image alternately, and afterwards the other changes. After a -little practice the two opposite colours may be perceived at once, by -causing the floating image to fall on the junction of the two planes. -This can be more conveniently done if the planes are at some distance, -for the spectrum then appears larger.</p> - -<p><span class="pagenum"><a name="Page_19" id="Page_19">[Pg 19]</a></span></p> - -<p class="para"><a id="a44">44.</a></p> - -<p>I happened to be in a forge towards evening at the moment when a -glowing mass of iron was placed on the anvil; I had fixed my eyes -steadfastly on it, and, turning round, I looked accidentally into an -open coal-shed: a large red image now floated before my eyes, and, as I -turned them from the dark opening to the light boards of which the shed -was constructed, the image appeared half green, half red, according as -it had a lighter or darker ground behind it. I did not at that time -take notice of the subsequent changes of this appearance.</p> - -<p class="para"><a id="a45">45.</a></p> - -<p>The after-vision occasioned by a total dazzling of the retina -corresponds with that of a circumscribed bright object. The red colour -seen by persons who are dazzled with snow belongs to this class of -phenomena, as well as the singularly beautiful green colour which dark -objects seem to wear after looking long on white paper in the sun. The -details of such experiments may be investigated hereafter by those -whose young eyes are capable of enduring such trials further for the -sake of science.</p> - -<p class="para"><a id="a46">46.</a></p> - -<p>With these examples we may also class the black letters which in the -evening light appear<span class="pagenum"><a name="Page_20" id="Page_20">[Pg 20]</a></span> red. Perhaps we might insert under the same -category the story that drops of blood appeared on the table at which -Henry IV. of France had seated himself with the Duc de Guise to play at -dice.</p> - - - -<hr class="chap" /> -<h5><a name="V" id="V">V.</a></h5> - - -<h5>COLOURED OBJECTS.</h5> - - -<p class="para"><a id="a47">47.</a></p> - -<p>We have hitherto seen the physiological colours displayed in the -after-vision of colourless bright objects, and also in the after-vision -of general colourless brightness; we shall now find analogous -appearances if a given colour be presented to the eye: in considering -this, all that has been hitherto detailed must be present to our -recollection.</p> - -<p class="para"><a id="a48">48.</a></p> - -<p>The impression of coloured objects remains in the eye like that of -colourless ones, but in this case the energy of the retina, stimulated -as it is to produce the opposite colour, will be more apparent.</p> - -<p class="para"><a id="a49">49.</a></p> - -<p>Let a small piece of bright-coloured paper or silk stuff be held before -a moderately lighted white surface; let the observer look steadfastly<span class="pagenum"><a name="Page_21" id="Page_21">[Pg 21]</a></span> -on the small coloured object, and let it be taken away after a time -while his eyes remain unmoved; the spectrum of another colour will then -be visible on the white plane. The coloured paper may be also left in -its place while the eye is directed to another part of the white plane; -the same spectrum will be visible there too, for it arises from an -image which now belongs to the eye.</p> - -<p class="para"><a id="a50">50.</a></p> - -<p>In order at once to see what colour will be evoked by this contrast, -the chromatic circle<a name="FNanchor_1_12" id="FNanchor_1_12"></a><a href="#Footnote_1_12" class="fnanchor">[1]</a> may be referred to. The colours are here -arranged in a general way according to the natural order, and the -arrangement will be found to be directly applicable in the present -case; for the colours diametrically opposed to each other in this -diagram are those which reciprocally evoke each other in the eye. Thus, -yellow demands purple; orange, blue; red, green; and <i>vice versâ</i>: thus -again all intermediate gradations reciprocally evoke each other; the -simpler colour demanding the compound, and <i>vice versâ</i>.—<a href="#NOTE_C">Note C</a>.</p> - -<p class="para"><a id="a51">51.</a></p> - -<p>The cases here under consideration occur oftener than we are aware in -ordinary life; indeed,<span class="pagenum"><a name="Page_22" id="Page_22">[Pg 22]</a></span> an attentive observer sees these appearances -everywhere, while, on the other hand, the uninstructed, like our -predecessors, consider them as temporary visual defects, sometimes -even as symptoms of disorders in the eye, thus exciting serious -apprehensions. A few remarkable instances may here be inserted.</p> - -<p class="para"><a id="a52">52.</a></p> - -<p>I had entered an inn towards evening, and, as a well-favoured girl, -with a brilliantly fair complexion, black hair, and a scarlet bodice, -came into the room, I looked attentively at her as she stood before me -at some distance in half shadow. As she presently afterwards turned -away, I saw on the white wall, which was now before me, a black face -surrounded with a bright light, while the dress of the perfectly -distinct figure appeared of a beautiful sea-green.</p> - -<p class="para"><a id="a53">53.</a></p> - -<p>Among the materials for optical experiments, there are portraits with -colours and shadows exactly opposite to the appearance of nature. The -spectator, after having looked at one of these for a time, will see the -visionary figure tolerably true to nature. This is conformable to the -same principles, and consistent with experience, for, in the former -instance, a negress with a white head-dress would have given me a -white face surrounded with black. In the case<span class="pagenum"><a name="Page_23" id="Page_23">[Pg 23]</a></span> of the painted figures, -however, which are commonly small, the parts are not distinguishable by -every one in the after-image.</p> - -<p class="para"><a id="a54">54.</a></p> - -<p>A phenomenon which has before excited attention among the observers of -nature is to be attributed, I am persuaded, to the same cause.</p> - -<p>It has been stated that certain flowers, towards evening in summer, -coruscate, become phosphorescent, or emit a momentary light. Some -persons have described their observation of this minutely. I had often -endeavoured to witness it myself, and had even resorted to artificial -contrivances to produce it.</p> - -<p>On the 19th of June, 1799, late in the evening, when the twilight was -deepening into a clear night, as I was walking up and down the garden -with a friend, we very distinctly observed a flame-like appearance -near the oriental poppy, the flowers of which are remarkable for their -powerful red colour. We approached the place and looked attentively -at the flowers, but could perceive nothing further, till at last, by -passing and repassing repeatedly, while we looked sideways on them, we -succeeded in renewing the appearance as often as we pleased. It proved -to be a physiological phenomenon, such as others we have described, and -the apparent<span class="pagenum"><a name="Page_24" id="Page_24">[Pg 24]</a></span> coruscation was nothing but the spectrum of the flower in -the compensatory blue-green colour.</p> - -<p>In looking directly at a flower the image is not produced, but it -appears immediately as the direction of the eye is altered. Again, by -looking sideways on the object, a double image is seen for a moment, -for the spectrum then appears near and on the real object.</p> - -<p>The twilight accounts for the eye being in a perfect state of repose, -and thus very susceptible, and the colour of the poppy is sufficiently -powerful in the summer twilight of the longest days to act with -full effect and produce a compensatory image. I have no doubt these -appearances might be reduced to experiment, and the same effect -produced by pieces of coloured paper. Those who wish to take the most -effectual means for observing the appearance in nature—suppose in a -garden—should fix the eyes on the bright flowers selected for the -purpose, and, immediately after, look on the gravel path. This will -be seen studded with spots of the opposite colour. The experiment is -practicable on a cloudy day, and even in the brightest sunshine, for -the sun-light, by enhancing the brilliancy of the flower, renders it -fit to produce the compensatory colour sufficiently distinct to be -perceptible even in a bright light. Thus, peonies produce beautiful -green, marigolds vivid blue spectra.</p> - -<p><span class="pagenum"><a name="Page_25" id="Page_25">[Pg 25]</a></span></p> - -<p class="para"><a id="a55">55.</a></p> - -<p>As the opposite colour is produced by a constant law in experiments -with coloured objects on portions of the retina, so the same effect -takes place when the whole retina is impressed with a single colour. We -may convince ourselves of this by means of coloured glasses. If we look -long through a blue pane of glass, everything will afterwards appear -in sunshine to the naked eye, even if the sky is grey and the scene -colourless. In like manner, in taking off green spectacles, we see all -objects in a red light. Every decided colour does a certain violence to -the eye, and forces the organ to opposition.</p> - -<p class="para"><a id="a56">56.</a></p> - -<p>We have hitherto seen the opposite colours producing each other -successively on the retina: it now remains to show by experiment -that the same effects can exist simultaneously. If a coloured object -impinges on one part of the retina, the remaining portion at the same -moment has a tendency to produce the compensatory colour. To pursue -a former experiment, if we look on a yellow piece of paper placed -on a white surface, the remaining part of the organ has already a -tendency to produce a purple hue on the colourless surface: in this -case the small portion of yellow is not powerful enough to produce<span class="pagenum"><a name="Page_26" id="Page_26">[Pg 26]</a></span> -this appearance distinctly, but, if a white paper is placed on a yellow -wall, we shall see the white tinged with a purple hue.</p> - -<p class="para"><a id="a57">57.</a></p> - -<p>Although this experiment may be made with any colours, yet red and -green are particularly recommended for it, because these colours seem -powerfully to evoke each other. Numerous instances occur in daily -experience. If a green paper is seen through striped or flowered -muslin, the stripes or flowers will appear reddish. A grey building -seen through green pallisades appears in like manner reddish. A -modification of this tint in the agitated sea is also a compensatory -colour: the light side of the waves appears green in its own colour, -and the shadowed side is tinged with the opposite hue. The different -direction of the waves with reference to the eye produces the same -effect. Objects seen through an opening in a red or green curtain -appear to wear the opposite hue. These appearances will present -themselves to the attentive observer on all occasions, even to an -unpleasant degree.</p> - -<p class="para"><a id="a58">58.</a></p> - -<p>Having made ourselves acquainted with the simultaneous exhibition of -these effects in direct cases, we shall find that we can also observe -them by indirect means. If we place a piece of<span class="pagenum"><a name="Page_27" id="Page_27">[Pg 27]</a></span> paper of a bright -orange colour on the white surface, we shall, after looking intently -at it, scarcely perceive the compensatory colour on the rest of the -surface: but when we take the orange paper away, and when the blue -spectrum appears in its place, immediately as this spectrum becomes -fully apparent, the rest of the surface will be overspread, as if by a -flash, with a reddish-yellow light, thus exhibiting to the spectator -in a lively manner the productive energy of the organ, in constant -conformity with the same law.</p> - -<p class="para"><a id="a59">59.</a></p> - -<p>As the compensatory colours easily appear, where they do not exist in -nature, near and after the original opposite ones, so they are rendered -more intense where they happen to mix with a similar real hue. In a -court which was paved with grey limestone flags, between which grass -had grown, the grass appeared of an extremely beautiful green when -the evening clouds threw a scarcely perceptible reddish light on the -pavement. In an opposite case we find, in walking through meadows, -where we see scarcely anything but green, the stems of trees and the -roads often gleam with a reddish hue. This tone is not uncommon in -the works of landscape painters, especially those who practice in -water-colours: they probably see it in<span class="pagenum"><a name="Page_28" id="Page_28">[Pg 28]</a></span> nature, and thus, unconsciously -imitating it, their colouring is criticised as unnatural.</p> - -<p class="para"><a id="a60">60.</a></p> - -<p>These phenomena are of the greatest importance, since they direct our -attention to the laws of vision, and are a necessary preparation for -future observations on colours. They show that the eye especially -demands completeness, and seeks to eke out the colorific circle in -itself. The purple or violet colour suggested by yellow contains red -and blue; orange, which responds to blue, is composed of yellow and -red; green, uniting blue and yellow, demands red; and so through all -gradations of the most complicated combinations. That we are compelled -in this case to assume three leading colours has been already remarked -by other observers.</p> - -<p class="para"><a id="a61">61.</a></p> - -<p>When in this completeness the elements of which it is composed are -still appreciable by the eye, the result is justly called harmony. We -shall subsequently endeavour to show how the theory of the harmony of -colours may be deduced from these phenomena, and how, simply through -these qualities, colours may be capable of being applied to æsthetic -purposes. This will be shown when we have gone through the whole circle -of our observations, returning to the point from which we started.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_12" id="Footnote_1_12"></a><a href="#FNanchor_1_12"><span class="label">[1]</span></a> <a href="#col000">Plate 1</a>, fig. 3.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_29" id="Page_29">[Pg 29]</a></span></p></div> - - - - -<h5><a name="VI" id="VI">VI.</a></h5> - - -<h5>COLOURED SHADOWS.</h5> - - -<p class="para"><a id="a62">62.</a></p> - -<p>Before, however, we proceed further, we have yet to observe some very -remarkable cases of the vivacity with which the suggested colours -appear in the neighbourhood of others: we allude to coloured shadows. -To arrive at these we first turn our attention to shadows that are -colourless or negative.</p> - -<p class="para"><a id="a63">63.</a></p> - -<p>A shadow cast by the sun, in its full brightness, on a white surface, -gives us no impression of colour; it appears black, or, if a contrary -light (here assumed to differ only in degree) can act upon it, it is -only weaker, half-lighted, grey.</p> - -<p class="para"><a id="a64">64.</a></p> - -<p>Two conditions are necessary for the existence of coloured shadows: -first, that the principal light tinge the white surface with some hue; -secondly, that a contrary light illumine to a certain extent the cast -shadow.</p> - -<p class="para"><a id="a65">65.</a></p> - -<p>Let a short, lighted candle be placed at twilight on a sheet of white -paper. Between it and the declining daylight let a pencil be placed<span class="pagenum"><a name="Page_30" id="Page_30">[Pg 30]</a></span> -upright, so that its shadow thrown by the candle may be lighted, but -not overcome, by the weak daylight: the shadow will appear of the most -beautiful blue.</p> - -<p class="para"><a id="a66">66.</a></p> - -<p>That this shadow is blue is immediately evident; but we can only -persuade ourselves by some attention that the white paper acts as a -reddish yellow, by means of which the complemental blue is excited in -the eye.—<a href="#NOTE_D">Note D</a>.</p> - -<p class="para"><a id="a67">67.</a></p> - -<p>In all coloured shadows, therefore, we must presuppose a colour excited -or suggested by the hue of the surface on which the shadow is thrown. -This may be easily found to be the case by attentive consideration, but -we may convince ourselves at once by the following experiment.</p> - -<p class="para"><a id="a68">68.</a></p> - -<p>Place two candles at night opposite each other on a white surface; hold -a thin rod between them upright, so that two shadows be cast by it; -take a coloured glass and hold it before one of the lights, so that -the white paper appear coloured; at the same moment the shadow cast by -the coloured light and slightly illumined by the colourless one will -exhibit the complemental hue.</p> - -<p><span class="pagenum"><a name="Page_31" id="Page_31">[Pg 31]</a></span></p> - -<p class="para"><a id="a69">69.</a></p> - -<p>An important consideration suggests itself here, to which we shall -frequently have occasion to return. Colour itself is a degree of -darkness <i>σκιερόν</i>; hence Kircher is perfectly right in calling it -<i>lumen opacatum</i>. As it is allied to shadow, so it combines readily -with it; it appears to us readily in and by means of shadow the -moment a suggesting cause presents itself. We could not refrain from -adverting at once to a fact which we propose to trace and develop -hereafter.—<a href="#NOTE_E">Note E</a>.</p> - -<p class="para"><a id="a70">70.</a></p> - -<p>Select the moment in twilight when the light of the sky is still -powerful enough to cast a shadow which cannot be entirely effaced by -the light of a candle. The candle may be so placed that a double shadow -shall be visible, one from the candle towards the daylight, and another -from the daylight towards the candle. If the former is blue the latter -will appear orange-yellow: this orange-yellow is in fact, however, only -the yellow-red light of the candle diffused over the whole paper, and -which <i>becomes visible in shadow</i>.</p> - -<p class="para"><a id="a71">71.</a></p> - -<p>This is best exemplified by the former experiment with two candles and -coloured glasses.</p> - -<p><span class="pagenum"><a name="Page_32" id="Page_32">[Pg 32]</a></span></p> - -<p>The surprising readiness with which shadow assumes a colour will again -invite our attention in the further consideration of reflections and -elsewhere.</p> - -<p class="para"><a id="a72">72.</a></p> - -<p>Thus the phenomena of coloured shadows may be traced to their cause -without difficulty. Henceforth let any one who sees an instance of -the kind observe only with what hue the light surface on which they -are thrown is tinged. Nay, the colour of the shadow may be considered -as a chromatoscope of the illumined surface, for the spectator may -always assume the colour of the light to be the opposite of that of the -shadow, and by an attentive examination may ascertain this to be the -fact in every instance.</p> - -<p class="para"><a id="a73">73.</a></p> - -<p>These appearances have been a source of great perplexity to former -observers: for, as they were remarked chiefly in the open air, where -they commonly appeared blue, they were attributed to a certain inherent -blue or blue colouring quality in the air. The inquirer can, however, -convince himself, by the experiment with the candle in a room, that no -kind of blue light or reflection is necessary to produce the effect -in question. The experiment may be made on a cloudy day with white -curtains drawn<span class="pagenum"><a name="Page_33" id="Page_33">[Pg 33]</a></span> before the light, and in a room where no trace of blue -exists, and the blue shadow will be only so much the more beautiful.</p> - -<p class="para"><a id="a74">74.</a></p> - -<p>De Saussure, in the description of his ascent of Mont Blanc, says, "A -second remark, which may not be uninteresting, relates to the colour of -the shadows. These, notwithstanding the most attentive observation, we -never found dark blue, although this had been frequently the case in -the plain. On the contrary, in fifty-nine instances we saw them once -yellowish, six times pale bluish, eighteen times colourless or black, -and thirty-four times pale violet. Some natural philosophers suppose -that these colours arise from accidental vapours diffused in the air, -which communicate their own hues to the shadows; not that the colours -of the shadows are occasioned by the reflection of any given sky colour -or interposition of any given air colour: the above observations seem -to favour this opinion." The instances given by De Saussure may be now -explained and classed with analogous examples without difficulty.</p> - -<p>At a great elevation the sky was generally free from vapours, the sun -shone in full force on the snow, so that it appeared perfectly white -to the eye: in this case they saw the shadows quite colourless. If the -air was charged with a<span class="pagenum"><a name="Page_34" id="Page_34">[Pg 34]</a></span> certain degree of vapour, in consequence of -which the light snow would assume a yellowish tone, the shadows were -violet-coloured, and this effect, it appears, occurred oftenest. They -saw also bluish shadows, but this happened less frequently; and that -the blue and violet were pale was owing to the surrounding brightness, -by which the strength of the shadows was mitigated. Once only they -saw the shadow yellowish: in this case, as we have already seen (<a href="#a70">70</a>), -the shadow is cast by a colourless light, and slightly illumined by a -coloured one.</p> - -<p class="para"><a id="a75">75.</a></p> - -<p>In travelling over the Harz in winter, I happened to descend from the -Brocken towards evening; the wide slopes extending above and below me, -the heath, every insulated tree and projecting rock, and all masses of -both, were covered with snow or hoar-frost. The sun was sinking towards -the Oder ponds<a name="FNanchor_1_13" id="FNanchor_1_13"></a><a href="#Footnote_1_13" class="fnanchor">[1]</a>. During the day, owing to the yellowish hue of the -snow, shadows tending to violet had already been observable; these -might now be pronounced to be decidedly blue, as the illumined parts -exhibited a yellow deepening to orange.</p> - -<p>But as the sun at last was about to set, and its rays, greatly -mitigated by the thicker vapours,<span class="pagenum"><a name="Page_35" id="Page_35">[Pg 35]</a></span> began to diffuse a most beautiful -red colour over the whole scene around me, the shadow colour changed -to a green, in lightness to be compared to a sea-green, in beauty to -the green of the emerald. The appearance became more and more vivid: -one might have imagined oneself in a fairy world, for every object had -clothed itself in the two vivid and so beautifully harmonising colours, -till at last, as the sun went down, the magnificent spectacle was lost -in a grey twilight, and by degrees in a clear moon-and-starlight night.</p> - -<p class="para"><a id="a76">76.</a></p> - -<p>One of the most beautiful instances of coloured shadows may be -observed during the full moon. The candle-light and moon-light may be -contrived to be exactly equal in force; both shadows may be exhibited -with equal strength and clearness, so that both colours balance each -other perfectly. A white surface being placed opposite the full moon, -and the candle being placed a little on one side at a due distance, -an opaque body is held before the white plane, A double shadow will -then be seen: that cast by the moon and illumined by the candle-light -will be a powerful red-yellow; and contrariwise, that cast by the -candle and illumined by the moon will appear of the most beautiful -blue. The shadow, composed of the union of the two shadows, where<span class="pagenum"><a name="Page_36" id="Page_36">[Pg 36]</a></span> -they cross each other, is black. The yellow shadow (<a href="#a74">74</a>) cannot perhaps -be exhibited in a more striking manner. The immediate vicinity of -the blue and the interposing black shadow make the appearance the -more agreeable. It will even be found, if the eye dwells long on -these colours, that they mutually evoke and enhance each other, the -increasing red in the one still producing its contrast, viz. a kind of -sea-green.</p> - -<p class="para"><a id="a77">77.</a></p> - -<p>We are here led to remark that in this, and in all cases, a moment or -two may perhaps be necessary to produce the complemental colour. The -retina must be first thoroughly impressed with the demanding hue before -the responding one can be distinctly observable.</p> - -<p class="para"><a id="a78">78.</a></p> - -<p>When divers are under water, and the sunlight shines into the -diving-bell, everything is seen in a red light (the cause of which -will be explained hereafter), while the shadows appear green. The very -same phenomenon which I observed on a high mountain (<a href="#a75">75</a>) is presented -to others in the depths of the sea, and thus Nature throughout is in -harmony with herself.</p> - -<p class="para"><a id="a79">79.</a></p> - -<p>Some observations and experiments which equally illustrate what has -been stated with regard<span class="pagenum"><a name="Page_37" id="Page_37">[Pg 37]</a></span> to coloured objects and coloured shadows may -be here added. Let a white paper blind be fastened inside the window -on a winter evening; in this blind let there be an opening, through -which the snow of some neighbouring roof can be seen. Towards dusk let -a candle be brought into the room; the snow seen through the opening -will then appear perfectly blue, because the paper is tinged with warm -yellow by the candle-light. The snow seen through the aperture is here -equivalent to a shadow illumined by a contrary light (<a href="#a76">76</a>), and may also -represent a grey disk on a coloured surface (<a href="#a56">56</a>).</p> - -<p class="para"><a id="a80">80.</a></p> - -<p>Another very interesting experiment may conclude these examples. If we -take a piece of green glass of some thickness, and hold it so that the -window bars be reflected in it, they will appear double owing to the -thickness of the glass. The image which is reflected from the under -surface of the glass will be green; the image which is reflected from -the upper surface, and which should be colourless, will appear red.</p> - -<p>The experiment may be very satisfactorily made by pouring water into -a vessel, the inner surface of which can act as a mirror; for both -reflections may first be seen colourless while the water is pure, and -then by tinging it, they will exhibit two opposite hues.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_13" id="Footnote_1_13"></a><a href="#FNanchor_1_13"><span class="label">[1]</span></a> Reservoirs in which water is collected from various small -streams, to work the mines.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_38" id="Page_38">[Pg 38]</a></span></p></div> - - - - -<h5><a name="VII" id="VII">VII.</a></h5> - - -<h5>FAINT LIGHTS.</h5> - - -<p class="para"><a id="a81">81.</a></p> - -<p>Light, in its full force, appears purely white, and it gives this -impression also in its highest degree of dazzling splendour. Light, -which is not so powerful, can also, under various conditions, remain -colourless. Several naturalists and mathematicians have endeavoured to -measure its degrees—Lambert, Bouguer, Rumford.</p> - -<p class="para"><a id="a82">82.</a></p> - -<p>Yet an appearance of colour presently manifests itself in fainter -lights, for in their relation to absolute light they resemble the -coloured spectra of dazzling objects (<a href="#a39">39</a>).</p> - -<p class="para"><a id="a83">83.</a></p> - -<p>A light of any kind becomes weaker, either when its own force, from -whatever cause, is diminished, or when the eye is so circumstanced or -placed, that it cannot be sufficiently impressed by the action of the -light. Those appearances which may be called objective, come under the -head of physical colours. We will only advert here to the transition -from white to red heat in glowing iron. We may also observe<span class="pagenum"><a name="Page_39" id="Page_39">[Pg 39]</a></span> that the -flames of lights at night appear redder in proportion to their distance -from the eye.—<a href="#NOTE_F">Note F</a>.</p> - -<p class="para"><a id="a84">84.</a></p> - -<p>Candle-light at night acts as yellow when seen near; we can perceive -this by the effect it produces on other colours. At night a pale yellow -is hardly to be distinguished from white; blue approaches to green, and -rose-colour to orange.</p> - -<p class="para"><a id="a85">85.</a></p> - -<p>Candle-light at twilight acts powerfully as a yellow light: this -is best proved by the purple blue shadows which, under these -circumstances, are evoked by the eye.</p> - -<p class="para"><a id="a86">86.</a></p> - -<p>The retina may be so excited by a strong light that it cannot perceive -fainter lights (<a href="#a11">11</a>): if it perceive these they appear coloured: hence -candle-light by day appears reddish, thus resembling, in its relation -to fuller light, the spectrum of a dazzling object; nay, if at night we -look long and intently on the flame of a light, it appears to increase -in redness.</p> - -<p class="para"><a id="a87">87.</a></p> - -<p>There are faint lights which, notwithstanding their moderate lustre, -give an impression of a<span class="pagenum"><a name="Page_40" id="Page_40">[Pg 40]</a></span> white, or, at the most, of a light yellow -appearance on the retina; such as the moon in its full splendour. -Rotten wood has even a kind of bluish light. All this will hereafter be -the subject of further remarks.</p> - -<p class="para"><a id="a88">88.</a></p> - -<p>If at night we place a light near a white or greyish wall so that the -surface be illumined from this central point to some extent, we find, -on observing the spreading light at some distance, that the boundary of -the illumined surface appears to be surrounded with a yellow circle, -which on the outside tends to red-yellow. We thus observe that when -light direct or reflected does not act in its full force, it gives an -impression of yellow, of reddish, and lastly even of red. Here we find -the transition to halos which we are accustomed to see in some mode or -other round luminous points.</p> - - - -<hr class="chap" /> -<h5><a name="VIII" id="VIII">VIII.</a></h5> - - -<h5>SUBJECTIVE HALOS.</h5> - - -<p class="para"><a id="a89">89.</a></p> - -<p>Halos may be divided into subjective and objective. The latter will -be considered under the physical colours; the first only belong here. -These are distinguished from the objective<span class="pagenum"><a name="Page_41" id="Page_41">[Pg 41]</a></span> halos by the circumstance -of their vanishing when the point of light which produces them on the -retina is covered.</p> - -<p class="para"><a id="a90">90.</a></p> - -<p>We have before noticed the impression of a luminous object on the -retina, and seen that it appears larger: but the effect is not at -an end here, it is not confined to the impression of the image; an -expansive action also takes place, spreading from the centre.</p> - -<p class="para"><a id="a91">91.</a></p> - -<p>That a nimbus of this kind is produced round the luminous image in the -eye may be best seen in a dark room, if we look towards a moderately -large opening in the window-shutter. In this case the bright image is -surrounded by a circular misty light. I saw such a halo bounded by a -yellow and yellow-red circle on opening my eyes at dawn, on an occasion -when I passed several nights in a bed-carriage.</p> - -<p class="para"><a id="a92">92.</a></p> - -<p>Halos appear most vivid when the eye is susceptible from having been in -a state of repose. A dark background also heightens their appearance. -Both causes account for our seeing them so strong if a light is -presented to the eyes<span class="pagenum"><a name="Page_42" id="Page_42">[Pg 42]</a></span> on waking at night. These conditions were -combined when Descartes after sleeping, as he sat in a ship, remarked -such a vividly-coloured halo round the light.</p> - -<p class="para"><a id="a93">93.</a></p> - -<p>A light must shine moderately, not dazzle, in order to produce the -impression of a halo in the eye; at all events the halos of dazzling -lights cannot be observed. We see a splendour of this kind round the -image of the sun reflected from the surface of water.</p> - -<p class="para"><a id="a94">94.</a></p> - -<p>A halo of this description, attentively observed, is found to be -encircled towards its edge with a yellow border: but even here the -expansive action, before alluded to, is not at an end, but appears -still to extend in varied circles.</p> - -<p class="para"><a id="a95">95.</a></p> - -<p>Several cases seem to indicate a circular action of the retina, whether -owing to the round form of the eye itself and its different parts, or -to some other cause.</p> - -<p class="para"><a id="a96">96.</a></p> - -<p>If the eye is pressed only in a slight degree from the inner corner, -darker or lighter circles<span class="pagenum"><a name="Page_43" id="Page_43">[Pg 43]</a></span> appear. At night, even without pressure, we -can sometimes perceive a succession of such circles emerging from, or -spreading over, each other.</p> - -<p class="para"><a id="a97">97.</a></p> - -<p>We have already seen that a yellow border is apparent round the white -space illumined by a light placed near it. This may be a kind of -objective halo. (<a href="#a88">88</a>.)</p> - -<p class="para"><a id="a98">98.</a></p> - -<p>Subjective halos may be considered as the result of a conflict between -the light and a living surface. From the conflict between the exciting -principle and the excited, an undulating motion arises, which may be -illustrated by a comparison with the circles on water. The stone thrown -in drives the water in all directions; the effect attains a maximum, -it reacts, and being opposed, continues under the surface. The effect -goes on, culminates again, and thus the circles are repeated. If we -have ever remarked the concentric rings which appear in a glass of -water on trying to produce a tone by rubbing the edge; if we call to -mind the intermitting pulsations in the reverberations of bells, we -shall approach a conception of what may take place on the retina when -the image of a luminous object impinges on it, not to mention<span class="pagenum"><a name="Page_44" id="Page_44">[Pg 44]</a></span> that as -a living and elastic structure, it has already a circular principle in -its organisation.—<a href="#NOTE_G">Note G</a>.</p> - -<p class="para"><a id="a99">99.</a></p> - -<p>The bright circular space which appears round the shining object -is yellow, ending in red: then follows a greenish circle, which is -terminated by a red border. This appears to be the usual phenomenon -where the luminous body is somewhat considerable in size. These halos -become greater the more distant we are from the luminous object.</p> - -<p class="para"><a id="a100">100.</a></p> - -<p>Halos may, however, appear extremely small and numerous when the -impinging image is minute, yet powerful, in its effect. The experiment -is best made with a piece of gold-leaf placed on the ground and -illumined by the sun. In these cases the halos appear in variegated -rays. The iridescent appearance produced in the eye when the sun -pierces through the leaves of trees seems also to belong to the same -class of phenomena.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_45" id="Page_45">[Pg 45]</a></span></p> - - - - -<h5><a name="PATHOLOGICAL_COLOURS" id="PATHOLOGICAL_COLOURS">PATHOLOGICAL COLOURS.</a></h5> - - -<h5>APPENDIX.</h5> - - -<p class="para"><a id="a101">101.</a></p> - -<p>We are now sufficiently acquainted with the physiological colours to -distinguish them from the pathological. We know what appearances belong -to the eye in a healthy state, and are necessary to enable the organ to -exert its complete vitality and activity.</p> - -<p class="para"><a id="a102">102.</a></p> - -<p>Morbid phenomena indicate in like manner the existence of organic -and physical laws: for if a living being deviates from those rules -with reference to which it is constructed, it still seeks to agree -with the general vitality of nature in conformity with general laws, -and throughout its whole course still proves the constancy of those -principles on which the universe has existed, and by which it is held -together.</p> - -<p class="para"><a id="a103">103.</a></p> - -<p>We will here first advert to a very remarkable state in which the -vision of many persons is found to be. As it presents a deviation -from the ordinary mode of seeing colours, it might be fairly classed -under morbid impressions; but as it is consistent in itself, as it -often occurs,<span class="pagenum"><a name="Page_46" id="Page_46">[Pg 46]</a></span> may extend to several members of a family, and probably -does not admit of cure, we may consider it as bordering only on the -nosological cases, and therefore place it first.</p> - -<p class="para"><a id="a104">104.</a></p> - -<p>I was acquainted with two individuals not more than twenty years of -age, who were thus affected: both had bluish-grey eyes, an acute sight -for near and distant objects, by day-light and candle-light, and their -mode of seeing colours was in the main quite similar.</p> - -<p class="para"><a id="a105">105.</a></p> - -<p>They agreed with the rest of the world in denominating white, black, -and grey in the usual manner. Both saw white untinged with any hue. One -saw a somewhat brownish appearance in black, and in grey a somewhat -reddish tinge. In general they appeared to have a very delicate -perception of the gradations of light and dark.</p> - -<p class="para"><a id="a106">106.</a></p> - -<p>They appeared to see yellow, red-yellow, and yellow-red,<a name="FNanchor_1_14" id="FNanchor_1_14"></a><a href="#Footnote_1_14" class="fnanchor">[1]</a> like -others: in the last case they said they saw the yellow passing as it -were over the red as if glazed: some thickly-ground carmine, which had -dried in a saucer, they called red.</p> - -<p><span class="pagenum"><a name="Page_47" id="Page_47">[Pg 47]</a></span></p> - -<p class="para"><a id="a107">107.</a></p> - -<p>But now a striking difference presented itself. If the carmine was -passed thinly over the white saucer, they would compare the light -colour thus produced to the colour of the sky, and call it blue. If -a rose was shown them beside it, they would, in like manner, call it -blue; and in all the trials which were made, it appeared that they -could not distinguish light blue from rose-colour. They confounded -rose-colour, blue, and violet on all occasions: these colours only -appeared to them to be distinguished from each other by delicate shades -of lighter, darker, intenser, or fainter appearance.</p> - -<p class="para"><a id="a108">108.</a></p> - -<p>Again they could not distinguish green from dark orange, nor, more -especially, from a red brown.</p> - -<p class="para"><a id="a109">109.</a></p> - -<p>If any one, accidentally conversing with these individuals, happened -to question them about surrounding objects, their answers occasioned -the greatest perplexity, and the interrogator began to fancy his own -wits were out of order. With some method we may, however, approach to a -nearer knowledge of the law of this deviation from the general law.</p> - -<p><span class="pagenum"><a name="Page_48" id="Page_48">[Pg 48]</a></span></p> - -<p class="para"><a id="a110">110.</a></p> - -<p>These persons, as may be gathered from what has been stated, saw fewer -colours than other people: hence arose the confusion of different -colours. They called the sky rose-colour, and the rose blue, or -<i>vice versâ</i>. The question now is: did they see both blue or both -rose-colour? did they see green orange, or orange green?</p> - -<p class="para"><a id="a111">111.</a></p> - -<p>This singular enigma appears to solve itself, if we assume that they -saw no blue, but, instead of it, a light pure red, a rose-colour. -We can comprehend what would be the result of this by means of the -chromatic diagram.</p> - -<p class="para"><a id="a112">112.</a></p> - -<p>If we take away blue from the chromatic circle we shall miss violet and -green as well. Pure red occupies the place of blue and violet, and in -again mixing with yellow the red produces orange where green should be.</p> - -<p class="para"><a id="a113">113.</a></p> - -<p>Professing to be satisfied with this mode of explanation, we have named -this remarkable deviation from ordinary vision "Acyanoblepsia."<a name="FNanchor_2_15" id="FNanchor_2_15"></a><a href="#Footnote_2_15" class="fnanchor">[2]</a> -We have prepared some coloured figures for<span class="pagenum"><a name="Page_49" id="Page_49">[Pg 49]</a></span> its further elucidation, -and in explaining these we shall add some further details. Among the -examples will be found a landscape, coloured in the mode in which the -individuals alluded to appeared to see nature: the sky rose-colour, and -all that should be green varying from yellow to brown red, nearly as -foliage appears to us in autumn<a name="FNanchor_3_16" id="FNanchor_3_16"></a><a href="#Footnote_3_16" class="fnanchor">[3]</a>.—<a href="#NOTE_H">Note H</a>.</p> - -<p class="para"><a id="a114">114.</a></p> - -<p>We now proceed to speak of morbid and other extraordinary affections -of the retina, by which the eye may be susceptible of an appearance -of light without external light, reserving for a future occasion the -consideration of galvanic light.</p> - -<p class="para"><a id="a115">115.</a></p> - -<p>If the eye receives a blow, sparks seem to spread from it. In some -states of body, again, when the blood is heated, and the system much -excited, if the eye is pressed first gently, and then more and more -strongly, a dazzling and intolerable light may be excited.</p> - -<p class="para"><a id="a116">116.</a></p> - -<p>If those who have been recently couched experience pain and heat in the -eye, they frequently<span class="pagenum"><a name="Page_50" id="Page_50">[Pg 50]</a></span> see fiery flashes and sparks: these symptoms last -sometimes for a week or fortnight, or till the pain and heat diminish.</p> - -<p class="para"><a id="a117">117.</a></p> - -<p>A person suffering from ear-ache saw sparks and balls of light in the -eye during each attack, as long as the pain lasted.</p> - -<p class="para"><a id="a118">118.</a></p> - -<p>Persons suffering from worms often experience extraordinary appearances -in the eye, sometimes sparks of fire, sometimes spectres of light, -sometimes frightful figures, which they cannot by an effort of the will -cease to see: sometimes these appearances are double.</p> - -<p class="para"><a id="a119">119.</a></p> - -<p>Hypochondriacs frequently see dark objects, such as threads, hairs, -spiders, flies, wasps. These appearances also exhibit themselves in the -incipient hard cataract. Many see semi-transparent small tubes, forms -like wings of insects, bubbles of water of various sizes, which fall -slowly down, if the eye is raised: sometimes these congregate together -so as to resemble the spawn of frogs; sometimes they appear as complete -spheres, sometimes in the form of lenses.</p> - -<p class="para"><a id="a120">120.</a></p> - -<p>As light appeared, in the former instances,<span class="pagenum"><a name="Page_51" id="Page_51">[Pg 51]</a></span> without external light, -so also these images appear without corresponding external objects. -The images are sometimes transient, sometimes they last during -the patient's life. Colour, again, frequently accompanies these -impressions: for hypochondriacs often see yellow-red stripes in the -eye: these are generally more vivid and numerous in the morning, or -when lasting.</p> - -<p class="para"><a id="a121">121.</a></p> - -<p>We have before seen that the impression of any object may remain for a -time in the eye: this we have found to be a physiological phenomenon -(<a href="#a23">23</a>): the excessive duration of such an impression, on the other band, -may be considered as morbid.</p> - -<p class="para"><a id="a122">122.</a></p> - -<p>The weaker the organ the longer the impression of the image lasts. -The retina does not so soon recover itself; and the effect may be -considered as a kind of paralysis (<a href="#a28">28</a>).</p> - -<p class="para"><a id="a123">123.</a></p> - -<p>This is not to be wondered at in the case of dazzling lights. If any -one looks at the sun, he may retain the image in his eyes for several -days. Boyle relates an instance of ten years.</p> - -<p class="para"><a id="a124">124.</a></p> - -<p>The same takes place, in a certain degree, with<span class="pagenum"><a name="Page_52" id="Page_52">[Pg 52]</a></span> regard to objects -that are not dazzling. Büsch relates of himself that the image of an -engraving, complete in all its parts, was impressed on his eye for -seventeen minutes.</p> - -<p class="para"><a id="a125">125.</a></p> - -<p>A person inclined to fulness of blood retained the image of a bright -red calico, with white spots, many minutes in the eye, and saw it float -before everything like a veil. It only disappeared by rubbing the eye -for some time.</p> - -<p class="para"><a id="a126">126.</a></p> - -<p>Scherfer observes that the red colour, which is the consequence of a -powerful impression of light, may last for some hours.</p> - -<p class="para"><a id="a127">127.</a></p> - -<p>As we can produce an appearance of light on the retina by pressure -on the eyeball, so by a gentle pressure a red colour appears, thus -corresponding with the after-image of an impression of light.</p> - -<p class="para"><a id="a128">128.</a></p> - -<p>Many sick persons, on awaking, see everything in the colour of the -morning sky, as if through a red veil: so, if in the evening they doze -and wake again, the same appearance presents itself. It remains for -some minutes, and<span class="pagenum"><a name="Page_53" id="Page_53">[Pg 53]</a></span> always disappears if the eye is rubbed a little. Red -stars and balls sometimes accompany the impression. This state may last -for a considerable time.</p> - -<p class="para"><a id="a129">129.</a></p> - -<p>The aëronauts, particularly Zambeccari and his companions, relate -that they saw the moon blood-red at the highest elevation. As they -had ascended above the vapours of the earth, through which we see the -moon and sun naturally of such a colour, it may be suspected that this -appearance may be classed with the pathological colours. The senses, -namely, may be so influenced by an unusual state, that the whole -nervous system, and particularly the retina, may sink into a kind of -inertness and inexcitability. Hence it is not impossible that the moon -might act as a very subdued light, and thus produce the impression of -the red colour. The sun even appeared blood-red to the aëronauts of -Hamburgh.</p> - -<p>If those who are at some elevation in a balloon scarcely hear each -other speak, may not this, too, be attributed to the inexcitable state -of the nerves as well as to the thinness of the air?</p> - -<p class="para"><a id="a130">130.</a></p> - -<p>Objects are often seen by sick persons in variegated colours. Boyle -relates an instance<span class="pagenum"><a name="Page_54" id="Page_54">[Pg 54]</a></span> of a lady, who, after a fall by which an eye was -bruised, saw all objects, but especially white objects, glittering in -colours, even to an intolerable degree.</p> - -<p class="para"><a id="a131">131.</a></p> - -<p>Physicians give the name of "Chrupsia" to an affection of the sight, -occurring in typhoid maladies. In these cases the patients state that -they see the boundaries of objects coloured where light and dark meet. -A change probably takes place in the humours of the eye, through which -their achromatism is affected.</p> - -<p class="para"><a id="a132">132.</a></p> - -<p>In cases of milky cataract, a very turbid crystalline lens causes -the patient to see a red light. In a case of this kind, which was -treated by the application of electricity, the red light changed by -degrees to yellow, and at last to white, when the patient again began -to distinguish objects. These changes of themselves warranted the -conclusion that the turbid state of the lens was gradually approaching -the transparent state. We shall be enabled easily to trace this effect -to its source as soon as we become better acquainted with the physical -colours.</p> - -<p class="para"><a id="a133">133.</a></p> - -<p>If again it may be assumed that a jaundiced<span class="pagenum"><a name="Page_55" id="Page_55">[Pg 55]</a></span> patient sees through -an actually yellow-coloured humour, we are at once referred to the -department of chemical colours, and it is thus evident that we can only -thoroughly investigate the chapter of pathological colours when we -have made ourselves acquainted with the whole range of the remaining -phenomena. What has been adduced may therefore suffice for the present, -till we resume the further consideration of this portion of our subject.</p> - -<p class="para"><a id="a134">134.</a></p> - -<p>In conclusion we may, however, at once advert to some peculiar states -or dispositions of the organ.</p> - -<p>There are painters who, instead of rendering the colours of nature, -diffuse a general tone, a warm or cold hue, over the picture. In some, -again, a predilection for certain colours displays itself; in others a -want of feeling for harmony.</p> - -<p class="para"><a id="a135">135.</a></p> - -<p>Lastly, it is also worthy of remark, that savage nations, uneducated -people, and children have a great predilection for vivid colours; -that animals are excited to rage by certain colours; that people of -refinement avoid vivid colours in their dress and the objects that are -about them, and seem inclined to banish them altogether from their -presence.—<a href="#NOTE_I">Note I</a>.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_14" id="Footnote_1_14"></a><a href="#FNanchor_1_14"><span class="label">[1]</span></a> It has been found necessary to follow the author's -nomenclature throughout—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_15" id="Footnote_2_15"></a><a href="#FNanchor_2_15"><span class="label">[2]</span></a> Non-perception of blue.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_16" id="Footnote_3_16"></a><a href="#FNanchor_3_16"><span class="label">[3]</span></a> It has not been thought necessary to copy the plates here -referred to.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_56" id="Page_56">[Pg 56]</a></span></p></div> - - - - -<h5><a name="PART_II" id="PART_II">PART II.</a></h5> - - -<h4>PHYSICAL COLOURS.</h4> - - -<p class="para"><a id="a136">136.</a></p> - -<p>We give this designation to colours which are produced by certain -material mediums: these mediums, however, have no colour themselves, -and may be either transparent, semi-transparent yet transmitting light, -or altogether opaque. The colours in question are thus produced in the -eye through such external given causes, or are merely reflected to -the eye when by whatever means they are already produced without us. -Although we thus ascribe to them a certain objective character, their -distinctive quality still consists in their being transient, and not to -be arrested.</p> - -<p class="para"><a id="a137">137.</a></p> - -<p>They are called by former investigators <i>colores apparentes, fluxi, -fugitivi, phantastici, falsi, variantes</i>. They are also called -<i>speciosi</i> and <i>emphatici</i>, on account of their striking splendour. -They are immediately connected with the physiological colours, and -appear to have but little more reality: for, while in the production<span class="pagenum"><a name="Page_57" id="Page_57">[Pg 57]</a></span> -of the physiological colours the eye itself was chiefly efficient, and -we could only perceive the phenomena thus evoked within ourselves, -but not without us, we have now to consider the fact that colours are -produced in the eye by means of colourless objects; that we thus too -have a colourless surface before us which is acted upon as the retina -itself is, and that we can perceive the appearance produced upon it -without us. In such a process, however, every observation will convince -us that we have to do with colours in a progressive and mutable, but -not in a final or complete, state.</p> - -<p class="para"><a id="a138">138.</a></p> - -<p>Hence, in directing our attention to these physical colours, we find -it quite possible to place an objective phenomenon beside a subjective -one, and often by means of the union of the two successfully to -penetrate farther into the nature of the appearance.</p> - -<p class="para"><a id="a139">139.</a></p> - -<p>Thus, in the observations by which we become acquainted with the -physical colours, the eye is not to be considered as acting alone; nor -is the light ever to be considered in immediate relation with the eye: -but we direct our attention especially to the various effects produced -by mediums, those mediums being themselves colourless.</p> - -<p><span class="pagenum"><a name="Page_58" id="Page_58">[Pg 58]</a></span></p> - -<p class="para"><a id="a140">140.</a></p> - -<p>Light under these circumstances may be affected by three conditions. -First, when it flashes back from the surface of a medium; in -considering which <i>catoptrical</i> experiments invite our attention. -Secondly, when it passes by the edge of a medium: the phenomena -thus produced were formerly called <i>perioptical</i>; we prefer the -term <i>paroptical</i>. Thirdly, when it passes through either a merely -light-transmitting or an actually transparent body; thus constituting -a class of appearances on which <i>dioptrical</i> experiments are founded. -We have called a fourth class of physical colours <i>epoptical</i>, as the -phenomena exhibit themselves on the colourless surface of bodies under -various conditions, without previous or actual dye (βαφή).—<a href="#NOTE_K">Note K</a>.</p> - -<p class="para"><a id="a141">141.</a></p> - -<p>In examining these categories with reference to our three leading -divisions, according to which we consider the phenomena of colours in a -physiological, physical, or chemical view, we find that the catoptrical -colours are closely connected with the physiological; the paroptical -are already somewhat more distinct and independent; the dioptrical -exhibit themselves as entirely and strictly physical, and as having -a decidedly objective character; the epoptical, although still only -apparent, may be considered as the transition to the chemical colours.</p> - -<p><span class="pagenum"><a name="Page_59" id="Page_59">[Pg 59]</a></span></p> - -<p class="para"><a id="a142">142.</a></p> - -<p>If we were desirous of prosecuting our investigation strictly in the -order of nature, we ought to proceed according to the classification -which has just been made; but in didactic treatises it is not of -so much consequence to connect as to duly distinguish the various -divisions of a subject, in order that at last, when every single -class and case has been presented to the mind, the whole may be -embraced in one comprehensive view. We therefore turn our attention -forthwith to the dioptrical class, in order at once to give the reader -the full impression of the physical colours, and to exhibit their -characteristics the more strikingly.</p> - - - -<hr class="chap" /> -<h5><a name="IX" id="IX">IX.</a></h5> - - -<h5>DIOPTRICAL COLOURS.</h5> - - -<p class="para"><a id="a143">143.</a></p> - -<p>Colours are called dioptrical when a colourless medium is necessary -to produce them; the medium must be such that light and darkness can -act through it either on the eye or on opposite surfaces. It is thus -required that the medium should be transparent, or at least capable, to -a certain degree, of transmitting light.</p> - -<p><span class="pagenum"><a name="Page_60" id="Page_60">[Pg 60]</a></span></p> - -<p class="para"><a id="a144">144.</a></p> - -<p>According to these conditions we divide the dioptrical phenomena into -two classes, placing in the first those which are produced by means of -imperfectly transparent, yet light-transmitting mediums; and in the -second such as are exhibited when the medium is in the highest degree -transparent.</p> - - - -<hr class="chap" /> -<h5><a name="X" id="X">X.</a></h5> - -<h5>DIOPTRICAL COLOURS OF THE FIRST CLASS.</h5> - - -<p class="para"><a id="a145">145.</a></p> - -<p>Space, if we assume it to be empty, would have the quality of absolute -transparency to our vision. If this space is filled so that the eye -cannot perceive that it is so, there exists a more or less material -transparent medium, which may be of the nature of air and gas, may be -fluid or even solid.</p> - -<p class="para"><a id="a146">146.</a></p> - -<p>The pure and light-transmitting semi-transparent medium is only an -accumulated form of the transparent medium. It may therefore be -presented to us in three modes.</p> - -<p><span class="pagenum"><a name="Page_61" id="Page_61">[Pg 61]</a></span></p> - -<p class="para"><a id="a147">147.</a></p> - -<p>The extreme degree of this accumulation is white; the simplest, -brightest, first, opaque occupation of space.</p> - -<p class="para"><a id="a148">148.</a></p> - -<p>Transparency itself, empirically considered, is already the first -degree of the opposite state. The intermediate degrees from this point -to opaque white are infinite.</p> - -<p class="para"><a id="a149">149.</a></p> - -<p>At whatever point short of opacity we arrest the thickening medium, it -exhibits simple and remarkable phenomena when placed in relation with -light and darkness.</p> - -<p class="para"><a id="a150">150.</a></p> - -<p>The highest degree of light, such as that of the sun, of phosphorus -burning in oxygen, is dazzling and colourless: so the light of the -fixed stars is for the most part colourless. This light, however, seen -through a medium but very slightly thickened, appears to us yellow. -If the density of such a medium be increased, or if its volume become -greater, we shall see the light gradually assume a yellow-red hue, -which at last deepens to a ruby-colour.—<a href="#NOTE_L">Note L</a>.</p> - -<p><span class="pagenum"><a name="Page_62" id="Page_62">[Pg 62]</a></span></p> - -<p class="para"><a id="a151">151.</a></p> - -<p>If on the other hand darkness is seen through a semi-transparent -medium, which is itself illumined by a light striking on it, a blue -colour appears: this becomes lighter and paler as the density of the -medium is increased, but on the contrary appears darker and deeper the -more transparent the medium becomes: in the least degree of dimness -short of absolute transparence, always supposing a perfectly colourless -medium, this deep blue approaches the most beautiful violet.</p> - -<p class="para"><a id="a152">152.</a></p> - -<p>If this effect takes place in the eye as here described, and may -thus be pronounced to be subjective, it remains further to convince -ourselves of this by objective phenomena. For a light thus mitigated -and subdued illumines all objects in like manner with a yellow, -yellow-red, or red hue; and, although the effect of darkness through -the non-transparent medium does not exhibit itself so powerfully, yet -the blue sky displays itself in the camera obscura very distinctly on -white paper, as well as every other material colour.</p> - -<p class="para"><a id="a153">153.</a></p> - -<p>In examining the cases in which this important<span class="pagenum"><a name="Page_63" id="Page_63">[Pg 63]</a></span> leading phenomenon -appears, we naturally mention the atmospheric colours first: most of -these may be here introduced in order.</p> - -<p class="para"><a id="a154">154.</a></p> - -<p>The sun seen through a certain degree of vapour appears with a yellow -disk; the centre is often dazzlingly yellow when the edges are already -red. The orb seen through a thick yellow mist appears ruby-red (as was -the case in 1794, even in the north); the same appearance is still -more decided, owing to the state of the atmosphere, when the scirocco -prevails in southern climates: the clouds generally surrounding the sun -in the latter case are of the same colour, which is reflected again on -all objects.</p> - -<p>The red hues of morning and evening are owing to the same cause. The -sun is announced by a red light, in shining through a greater mass -of vapours. The higher he rises, the yellower and brighter the light -becomes.</p> - -<p class="para"><a id="a155">155.</a></p> - -<p>If the darkness of infinite space is seen through atmospheric vapours -illumined by the day-light, the blue colour appears. On high mountains -the sky appears by day intensely blue, owing to the few thin vapours -that float before the endless dark space: as soon as we descend in the<span class="pagenum"><a name="Page_64" id="Page_64">[Pg 64]</a></span> -valleys, the blue becomes lighter; till at last, in certain regions, -and in consequence of increasing vapours, it altogether changes to a -very pale blue.</p> - -<p class="para"><a id="a156">156.</a></p> - -<p>The mountains, in like manner, appear to us blue; for, as we see them -at so great a distance that we no longer distinguish the local tints, -and as no light reflected from their surface acts on our vision, they -are equivalent to mere dark objects, which, owing to the interposed -vapours, appear blue.</p> - -<p class="para"><a id="a157">157.</a></p> - -<p>So we find the shadowed parts of nearer objects are blue when the air -is charged with thin vapours.</p> - -<p class="para"><a id="a158">158.</a></p> - -<p>The snow-mountains, on the other hand, at a great distance, still -appear white, or approaching to a yellowish hue, because they act on -our eyes as brightness seen through atmospheric vapour.</p> - -<p class="para"><a id="a159">159.</a></p> - -<p>The blue appearance at the lower part of the flame of a candle belongs -to the same class of phenomena. If the flame be held before a white -ground, no blue will be seen, but this colour will immediately appear -if the flame is opposed<span class="pagenum"><a name="Page_65" id="Page_65">[Pg 65]</a></span> to a black ground. This phenomenon may be -exhibited most strikingly with a spoonful of lighted spirits of wine. -We may thus consider the lower part of the flame as equivalent to the -vapour which, although infinitely thin, is still apparent before the -dark surface; it is so thin, that one may easily see to read through -it: on the other hand, the point of the flame which conceals objects -from our sight is to be considered as a self-illuminating body.</p> - -<p class="para"><a id="a160">160.</a></p> - -<p>Lastly, smoke is also to be considered as a semi-transparent medium, -which appears to us yellow or reddish before a light ground, but blue -before a dark one.</p> - -<p class="para"><a id="a161">161.</a></p> - -<p>If we now turn our attention to fluid mediums, we find that water, -deprived in a very slight degree of its transparency, produces the same -effects.</p> - -<p class="para"><a id="a162">162.</a></p> - -<p>The infusion of the lignum nephriticum (guilandina Linnæi), which -formerly excited so much attention, is only a semi-transparent liquor, -which in dark wooden cups must appear blue, but held towards the sun in -a transparent glass must exhibit a yellow appearance.</p> - -<p><span class="pagenum"><a name="Page_66" id="Page_66">[Pg 66]</a></span></p> - -<p class="para"><a id="a163">163.</a></p> - -<p>A drop of scented water, of spirit varnish, of several metallic -solutions, may be employed to give various degrees of opacity to water -for such experiments. Spirit of soap perhaps answers best.</p> - -<p class="para"><a id="a164">164.</a></p> - -<p>The bottom of the sea appears to divers of a red colour in bright -sunshine: in this case the water, owing to its depth, acts as a -semi-transparent medium. Under these circumstances, they find the -shadows green, which is the complemental colour.</p> - -<p class="para"><a id="a165">165.</a></p> - -<p>Among solid mediums the opal attracts our attention first: its colours -are, at least, partly to be explained by the circumstance that it is, -in fact, a semi-transparent medium, through which sometimes light, -sometimes dark, substrata are visible.</p> - -<p class="para"><a id="a166">166.</a></p> - -<p>For these experiments, however, the opal-glass (vitrum astroides, -girasole) is the most desirable material. It is prepared in various -ways, and its semi-opacity is produced by metallic oxydes. The same -effect is produced also by melting pulverised and calcined bones -together<span class="pagenum"><a name="Page_67" id="Page_67">[Pg 67]</a></span> with the glass, on which account it is also known by the name -of <i>beinglas</i>; but, prepared in this mode, it easily becomes too opaque.</p> - -<p class="para"><a id="a167">167.</a></p> - -<p>This glass may be adapted for experiments in various ways: it may -either be made in a very slight degree non-transparent, in which case -the light seen through various layers placed one upon the other may -be deepened from the lightest yellow to the deepest red, or, if made -originally more opaque, it may be employed in thinner or thicker -laminæ. The experiments may be successfully made in both ways: in -order, however, to see the bright blue colour, the glass should neither -be too opaque nor too thick. For, as it is quite natural that darkness -must act weakly through the semi-transparent medium, so this medium, if -too thick, soon approaches whiteness.</p> - -<p class="para"><a id="a168">168.</a></p> - -<p>Panes of glass throw a yellow light on objects through those parts -where they happen to be semi-opaque, and these same parts appear blue -if we look at a dark object through them.</p> - -<p class="para"><a id="a169">169.</a></p> - -<p>Smoked glass may be also mentioned here, and is, in like manner, to be -considered as a semi-opaque medium. It exhibits the sun more<span class="pagenum"><a name="Page_68" id="Page_68">[Pg 68]</a></span> or less -ruby-coloured; and, although this appearance may be attributed to the -black-brown colour of the soot, we may still convince ourselves that a -semi-transparent medium here acts if we hold such a glass moderately -smoked, and lit by the sun on the unsmoked side, before a dark object, -for we shall then perceive a bluish appearance.</p> - -<p class="para"><a id="a170">170.</a></p> - -<p>A striking experiment may be made in a dark room with sheets of -parchment. If we fasten a piece of parchment before the opening in the -window-shutter when the sun shines, it will appear nearly white; by -adding a second, a yellowish colour appears, which still increases as -more leaves are added, till at last it changes to red.</p> - -<p class="para"><a id="a171">171.</a></p> - -<p>A similar effect, owing to the state of the crystalline lens in milky -cataract, has been already adverted to (131).</p> - -<p class="para"><a id="a172">172.</a></p> - -<p>Having now, in tracing these phenomena, arrived at the effect of a -degree of opacity scarcely capable of transmitting light, we may here -mention a singular appearance which was owing to a momentary state of -this kind.</p> - -<p><span class="pagenum"><a name="Page_69" id="Page_69">[Pg 69]</a></span></p> - -<p>A portrait of a celebrated theologian had been painted some years -before the circumstance to which we allude, by an artist who was known -to have considerable skill in the management of his materials. The -very reverend individual was represented in a rich velvet dress, which -was not a little admired, and which attracted the eye of the spectator -almost more than the face. The picture, however, from the effect of the -smoke of lamps and dust, had lost much of its original vivacity. It -was, therefore, placed in the hands of a painter, who was to clean it, -and give it a fresh coat of varnish. This person began his operations -by carefully washing the picture with a sponge: no sooner, however, -had he gone over the surface once or twice, and wiped away the first -dirt, than to his amazement the black velvet dress changed suddenly to -a light blue plush, which gave the ecclesiastic a very secular, though -somewhat old-fashioned, appearance. The painter did not venture to go -on with his washing: he could not comprehend how a light blue should be -the ground of the deepest black, still less how he could so suddenly -have removed a glazing colour capable of converting the one tint to the -other.</p> - -<p>At all events, he was not a little disconcerted at having spoilt the -picture to such an extent. Nothing to characterize the ecclesiastic -remained<span class="pagenum"><a name="Page_70" id="Page_70">[Pg 70]</a></span> but the richly-curled round wig, which made the exchange -of a faded plush for a handsome new velvet dress far from desirable. -Meanwhile, the mischief appeared irreparable, and the good artist, -having turned the picture to the wall, retired to rest with a mind ill -at ease. But what was his joy the next morning, when, on examining the -picture, he beheld the black velvet dress again in its full splendour. -He could not refrain from again wetting a corner, upon which the blue -colour again appeared, and after a time vanished. On hearing of this -phenomenon, I went at once to see the miraculous picture. A wet sponge -was passed over it in my presence, and the change quickly took place. I -saw a somewhat faded, but decidedly light blue plush dress, the folds -under the arm being indicated by some brown strokes.</p> - -<p>I explained this appearance to myself by the doctrine of the -semi-opaque medium. The painter, in order to give additional depth -to his black, may have passed some particular varnish over it: on -being washed, this varnish imbibed some moisture, and hence became -semi-opaque, in consequence of which the black underneath immediately -appeared blue. Perhaps those who are practically acquainted with the -effect of varnishes may, through accident or contrivance, arrive at -some means of exhibiting this singular appearance, as an experiment, to -those<span class="pagenum"><a name="Page_71" id="Page_71">[Pg 71]</a></span> who are fond of investigating natural phenomena. Notwithstanding -many attempts, I could not myself succeed in re-producing it.</p> - -<p class="para"><a id="a173">173.</a></p> - -<p>Having now traced the most splendid instances of atmospheric -appearances, as well as other less striking yet sufficiently remarkable -cases, to the leading examples of semi-transparent mediums, we have no -doubt that attentive observers of nature will carry such researches -further, and accustom themselves to trace and explain the various -appearances which present themselves in every-day experience on the -same principle: we may also hope that such investigators will provide -themselves with an adequate apparatus in order to place remarkable -facts before the eyes of others who may be desirous of information.</p> - -<p class="para"><a id="a174">174.</a></p> - -<p>We venture, once for all, to call the leading appearance in question, -as generally described in the foregoing pages, a primordial and -elementary phenomenon; and we may here be permitted at once to state -what we understand by the term.</p> - -<p class="para"><a id="a175">175.</a></p> - -<p>The circumstances which come under our notice in ordinary observation -are, for the most part, insulated cases, which, with some attention, -admit<span class="pagenum"><a name="Page_72" id="Page_72">[Pg 72]</a></span> of being classed under general leading facts. These again range -themselves under theoretical rubrics which are more comprehensive, and -through which we become better acquainted with certain indispensable -conditions of appearances in detail. From henceforth everything is -gradually arranged under higher rules and laws, which, however, are not -to be made intelligible by words and hypotheses to the understanding -merely, but, at the same time, by real phenomena to the senses. We -call these primordial phenomena, because nothing appreciable by the -senses lies beyond them, on the contrary, they are perfectly fit to be -considered as a fixed point to which we first ascended, step by step, -and from which we may, in like manner, descend to the commonest case -of every-day experience. Such an original phenomenon is that which has -lately engaged our attention. We see on the one side light, brightness; -on the other darkness, obscurity: we bring the semi-transparent medium -between the two, and from these contrasts and this medium the colours -develop themselves, contrasted, in like manner, but soon, through a -reciprocal relation, directly tending again to a point of union.<a name="FNanchor_1_17" id="FNanchor_1_17"></a><a href="#Footnote_1_17" class="fnanchor">[1]</a></p> - -<p><span class="pagenum"><a name="Page_73" id="Page_73">[Pg 73]</a></span></p> - -<p class="para"><a id="a176">176.</a></p> - -<p>With this conviction we look upon the mistake that has been committed -in the investigation of this subject to be a very serious one, inasmuch -as a secondary phenomenon has been thus placed higher in order—the -primordial phenomenon has been degraded to an inferior place; nay, the -secondary phenomenon has been placed at the head, a compound effect has -been treated as simple, a simple appearance as compound: owing to this -contradiction, the most capricious complication and perplexity have -been introduced into physical inquiries, the effects of which are still -apparent.</p> - -<p class="para"><a id="a177">177.</a></p> - -<p>But when even such a primordial phenomenon is arrived at, the evil -still is that we refuse to recognise it as such, that we still aim at -something beyond, although it would become us to confess that we are -arrived at the limits of experimental knowledge. Let the observer of -nature suffer the primordial phenomenon to remain undisturbed in its -beauty; let the philosopher admit it into his department, and he will -find that important elementary facts are a worthier basis for further -operations than insulated cases, opinions, and hypotheses.—<a href="#NOTE_M">Note M</a>.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_17" id="Footnote_1_17"></a><a href="#FNanchor_1_17"><span class="label">[1]</span></a> That is (according to the author's statement 150. 151.) -both tend to red; the yellow deepening to orange as the comparatively -dark medium is thickened before brightness; the blue deepening to -violet as the light medium is thinned before darkness.—T.</p></div> - - - -<hr class="chap" /> - -<p class="pagenum"><a name="Pg_74" id="Pg_74">[Pg 74]</a></p> - - - -<h5>XI.</h5> - -<h5>DIOPTRICAL COLOURS OF THE SECOND CLASS.—REFRACTION.</h5> - - -<p class="para"><a id="a178">178.</a></p> - -<p>Dioptrical colours of both classes are closely connected, as will -presently appear on a little examination. Those of the first class -appeared through semi-transparent mediums, those of the second class -will now appear through transparent mediums. But since every substance, -however transparent, may be already considered to partake of the -opposite quality (as every accumulation of a medium called transparent -proves), so the near affinity of the two classes is sufficiently -manifest.</p> - -<p class="para"><a id="a179">179.</a></p> - -<p>We will, however, first consider transparent mediums abstractedly as -such, as entirely free from any degree of opacity, and direct our whole -attention to a phenomenon which here presents itself, and which is -known by the name of refraction.</p> - -<p class="para"><a id="a180">180.</a></p> - -<p>In treating of the physiological colours, we have already had occasion -to vindicate what<span class="pagenum"><a name="Pg_75" id="Pg_75">[Pg 75]</a></span> were formerly called illusions of sight, as -the active energies of the healthy and duly efficient eye (<a href="#a2">2</a>), and we -are now again invited to consider similar instances confirming the -constancy of the laws of vision.</p> - -<p class="para"><a id="a181">181.</a></p> - -<p>Throughout nature, as presented to the senses, everything depends on -the relation which things bear to each other, but especially on the -relation which man, the most important of these, bears to the rest. -Hence the world divides itself into two parts, and the human being -as <i>subject</i>, stands opposed to the <i>object</i>. Thus the practical -man exhausts himself in the accumulation of facts, the thinker in -speculation; each being called upon to sustain a conflict which admits -of no peace and no decision.</p> - -<p class="para"><a id="a182">182.</a></p> - -<p>But still the main point always is, whether the relations are truly -seen. As our senses, if healthy, are the surest witnesses of external -relations, so we may be convinced that, in all instances where they -appear to contradict reality, they lay the greater and surer stress -on true relations. Thus a distant object appears to us smaller; and -precisely by this means we are aware of distance. We produced coloured -appearances on colourless objects, through colourless mediums, and at -the same moment our<span class="pagenum"><a name="Page_76" id="Page_76">[Pg 76]</a></span> attention was called to the degree of opacity in -the medium.</p> - -<p class="para"><a id="a183">183.</a></p> - -<p>Thus the different degrees of opacity in so-called transparent mediums, -nay, even other physical and chemical properties belonging to them, -are known to our vision by means of refraction, and invite us to make -further trials in order to penetrate more completely by physical and -chemical means into those secrets which are already opened to our view -on one side.</p> - -<p class="para"><a id="a184">184.</a></p> - -<p>Objects seen through mediums more or less transparent do not appear -to us in the place which they should occupy according to the laws of -perspective. On this fact the dioptrical colours of the second class -depend.</p> - -<p class="para"><a id="a185">185.</a></p> - -<p>Those laws of vision which admit of being expressed in mathematical -formulæ are based on the principle that, as light proceeds in straight -lines, it must be possible to draw a straight line from the eye to any -given object in order that it be seen. If, therefore, a case arises in -which the light arrives to us in a bent or broken line, that we see the -object by means of a bent or broken line, we are at once informed that -the<span class="pagenum"><a name="Page_77" id="Page_77">[Pg 77]</a></span> medium between the eye and the object is denser, or that it has -assumed this or that foreign nature.</p> - -<p class="para"><a id="a186">186.</a></p> - -<p>This deviation from the law of right-lined vision is known by the -general term of refraction; and, although we may take it for granted -that our readers are sufficiently acquainted with its effects, yet we -will here once more briefly exhibit it in its objective and subjective -point of view.</p> - -<p class="para"><a id="a187">187.</a></p> - -<p>Let the sun shine diagonally into an empty cubical vessel, so that -the opposite side be illumined, but not the bottom: let water be -then poured into this vessel, and the direction of the light will -be immediately altered; for a part of the bottom is shone upon. At -the point where the light enters the thicker medium it deviates from -its rectilinear direction, and appears broken: hence the phenomenon -is called the breaking (<i>brechung</i>) or refraction. Thus much of the -objective experiment.</p> - -<p class="para"><a id="a188">188.</a></p> - -<p>We arrive at the subjective fact in the following mode:—Let the eye -be substituted for the sun: let the sight be directed in like manner -<span class="pagenum"><a name="Page_78" id="Page_78">[Pg 78]</a></span> diagonally over one side, so that the opposite inner side be -entirely seen, while no part of the bottom is visible. On pouring in -water the eye will perceive a part of the bottom; and this takes place -without our being aware that we do not see in a straight line; for -the bottom appears to us raised, and hence we give the term elevation -(<i>hebung</i>) to the subjective phenomenon. Some points, which are -particularly remarkable with reference to this, will be adverted to -hereafter.</p> - -<p class="para"><a id="a189">189.</a></p> - -<p>Were we now to express this phenomenon generally, we might here repeat, -in conformity with the view lately taken, that the relation of the -objects is changed or deranged.</p> - -<p class="para"><a id="a190">190.</a></p> - -<p>But as it is our intention at present to separate the objective from -the subjective appearances, we first express the phenomenon in a -subjective form, and say,—a derangement or displacement of the object -seen, or to be seen, takes place.</p> - -<p class="para"><a id="a191">191.</a></p> - -<p>But that which is seen without a limiting outline may be thus affected -without our perceiving the change. On the other hand, if what we look -at has a visible termination, we have an evident indication that a -displacement occurs. If, therefore,<span class="pagenum"><a name="Page_79" id="Page_79">[Pg 79]</a></span> we wish to ascertain the -relation or degree of such a displacement, we must chiefly confine -ourselves to the alteration of surfaces with visible boundaries; in -other words, to the displacement of circumscribed objects.</p> - -<p class="para"><a id="a192">192.</a></p> - -<p>The general effect may take place through parallel mediums, for every -parallel medium displaces the object by bringing it perpendicularly -towards the eye. The apparent change of position is, however, more -observable through mediums that are not parallel.</p> - -<p class="para"><a id="a193">193.</a></p> - -<p>These latter may be perfectly spherical, or may be employed in the -form of convex or concave lenses. We shall make use of all these as -occasion may require in our experiments. But as they not only displace -the object from its position, but alter it in various ways, we shall, -in most cases, prefer employing mediums with surfaces, not, indeed, -parallel with reference to each other, but still altogether plane, -namely, prisms. These have a triangle for their base, and may, it is -true, be considered as portions of a lens, but they are particularly -available for our experiments, inasmuch as they very perceptibly -displace the object from its position, without producing a remarkable -distortion.</p> - -<p><span class="pagenum"><a name="Page_80" id="Page_80">[Pg 80]</a></span></p> - -<p class="para"><a id="a194">194.</a></p> - -<p>And now, in order to conduct our observations with as much exactness -as possible, and to avoid all confusion and ambiguity, we confine -ourselves at first to</p> - - -<h5>SUBJECTIVE EXPERIMENTS,</h5> - - -<p>in which, namely, the object is seen by the observer through a -refracting medium. As soon as we have treated these in due series, the -objective experiments will follow in similar order.</p> - - - -<hr class="chap" /> -<h5><a name="XII" id="XII">XII.</a></h5> - - -<h5>REFRACTION WITHOUT THE APPEARANCE OF COLOUR.</h5> - - -<p class="para"><a id="a195">195.</a></p> - -<p>Refraction can visibly take place without our perceiving an appearance -of colour. To whatever extent a colourless or uniformly coloured -surface may be altered as to its position by refraction, no colour -consequent upon refraction appears within it, provided it has no -outline or boundary. We may convince ourselves of this in various ways.</p> - -<p><span class="pagenum"><a name="Page_81" id="Page_81">[Pg 81]</a></span></p> - -<p class="para"><a id="a196">196.</a></p> - -<p>Place a glass cube on any larger surface, and look through the glass -perpendicularly or obliquely, the unbroken surface opposite the eye -appears altogether raised, but no colour exhibits itself. If we look at -a pure grey or blue sky or a uniformly white or coloured wall through a -prism, the portion of the surface which the eye thus embraces will be -altogether changed as to its position, without our therefore observing -the smallest appearance of colour.</p> - - - -<hr class="chap" /> -<h5><a name="XIII" id="XIII">XIII.</a></h5> - - -<h5>CONDITIONS OF THE APPEARANCE OF COLOUR.</h5> - - -<p class="para"><a id="a197">197.</a></p> - -<p>Although in the foregoing experiments we have found all unbroken -surfaces, large or small, colourless, yet at the outlines or -boundaries, where the surface is relieved upon a darker or lighter -object, we observe a coloured appearance.</p> - -<p class="para"><a id="a198">198.</a></p> - -<p>Outline, as well as surface, is necessary to constitute a figure or -circumscribed object. We therefore express the leading fact thus: -circumscribed objects must be displaced by refraction in order to the -exhibition of an appearance of colour.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_82" id="Page_82">[Pg 82]</a></span></p> - -<p class="para"><a id="a199">199.</a></p> - -<p>We place before us the simplest object, a light disk on a dark ground -(A).<a name="FNanchor_1_18" id="FNanchor_1_18"></a><a href="#Footnote_1_18" class="fnanchor">[1]</a> A displacement occurs with regard to this object, if we -apparently extend its outline from the centre by magnifying it. This -may be done with any convex glass, and in this case we see a blue edge -(B).</p> - -<p class="para"><a id="a200">200.</a></p> - -<p>We can, to appearance, contract the circumference of the same light -disk towards the centre by diminishing the object; the edge will then -appear yellow (C). This may be done with a concave glass, which, -however, should not be ground thin like common eye-glasses, but must -have some substance. In order, however, to make this experiment at once -with the convex glass, let a smaller black disk be inserted within -the light disk on a black ground. If we magnify the black disk on a -white ground with a convex glass, the same result takes place as if we -diminished the white disk; for we extend the black outline upon the -white, and we thus perceive the yellow edge together with the blue edge -(D).</p> - -<p class="para"><a id="a201">201.</a></p> - -<p>These two appearances, the blue and yellow, exhibit themselves in and -upon the white: they<span class="pagenum"><a name="Page_83" id="Page_83">[Pg 83]</a></span> both assume a reddish hue, in proportion as they -mingle with the black.<a name="FNanchor_2_19" id="FNanchor_2_19"></a><a href="#Footnote_2_19" class="fnanchor">[2]</a></p> - -<div class="figcenter" style="width: 500px;"> -<a id="col001"></a> -<img src="images/col_001.jpg" width="500" alt="" /> -<p style="text-align: center; font-weight: bold;">Plate 2.</p> -</div> - -<p class="para"><a id="a202">202.</a></p> - -<p>In this short statement we have described the primordial phenomena of -all appearance of colour occasioned by refraction. These undoubtedly -may be repeated, varied, and rendered more striking; may be combined, -complicated, confused; but, after all, may be still restored to their -original simplicity.</p> - -<p class="para"><a id="a203">203.</a></p> - -<p>In examining the process of the experiment just given, we find that -in the one case we have, to appearance, extended the white edge upon -the dark surface; in the other we have extended the dark edge upon -the white surface, supplanting one by the other, pushing one over -the other. We will now endeavour, step by step, to analyse these and -similar cases.</p> - -<p class="para"><a id="a204">204.</a></p> - -<p>If we cause the white disk to move, in appearance, entirely from its -place, which can be done<span class="pagenum"><a name="Page_84" id="Page_84">[Pg 84]</a></span> effectually by prisms, it will be coloured -according to the direction in which it apparently moves, in conformity -with the above laws. If we look at the disk <i>a</i><a name="FNanchor_3_20" id="FNanchor_3_20"></a><a href="#Footnote_3_20" class="fnanchor">[3]</a> through a prism, -so that it appear moved to <i>b</i>, the outer edge will appear blue and -blue-red, according to the law of the figure B (fig. 1), the other -edge being yellow, and yellow-red, according to the law of the figure -C (fig. 1). For in the first case the white figure is, as it were, -extended over the dark boundary, and in the other case the dark -boundary is passed over the white figure. The same happens if the disk -is, to appearance, moved from <i>a</i> to <i>c</i>, from <i>a</i> to <i>d</i>, and so -throughout the circle.</p> - -<p class="para"><a id="a205">205.</a></p> - -<p>As it is with the simple effect, so it is with more complicated -appearances. If we look through a horizontal prism (<i>a b</i><a name="FNanchor_4_21" id="FNanchor_4_21"></a><a href="#Footnote_4_21" class="fnanchor">[4]</a>) at a -white disk placed at some distance behind it at <i>e</i>, the disk will -be raised to <i>f</i>, and coloured according to the above law. If we -remove this prism, and look through a vertical one (<i>c d</i>) at the same -disk, it will appear at <i>h</i>, and coloured according to the same law. -If we place the two prisms one upon the other, the disk will appear -displaced diagonally, in conformity with a general law of nature, and -will be coloured as<span class="pagenum"><a name="Page_85" id="Page_85">[Pg 85]</a></span> before; that is, according to its movement in the -direction, <i>e.g.</i>:<a name="FNanchor_5_22" id="FNanchor_5_22"></a><a href="#Footnote_5_22" class="fnanchor">[5]</a></p> - -<p class="para"><a id="a206">206.</a></p> - -<p>If we attentively examine these opposite coloured edges, we find that -they only appear in the direction of the apparent change of place. -A round figure leaves us in some degree uncertain as to this: a -quadrangular figure removes all doubt.</p> - -<p class="para"><a id="a207">207.</a></p> - -<p>The quadrangular figure <i>a</i>,<a name="FNanchor_6_23" id="FNanchor_6_23"></a><a href="#Footnote_6_23" class="fnanchor">[6]</a> moved in the direction <i>a b</i> or <i>a d</i> -exhibits no colour on the sides which are parallel with the direction -in which it moves: on the other hand, if moved in the direction <i>a -c</i>, parallel with its diagonal, all the edges of the figure appear -coloured.<a name="FNanchor_7_24" id="FNanchor_7_24"></a><a href="#Footnote_7_24" class="fnanchor">[7]</a></p> - -<p class="para"><a id="a208">208.</a></p> - -<p>Thus, a former position (203) is here confirmed; viz. to produce -colour, an object must be so displaced that the light edges be -apparently carried over a dark surface, the dark edges over a light -surface, the figure over its boundary, the boundary over the figure. -But<span class="pagenum"><a name="Page_86" id="Page_86">[Pg 86]</a></span> if the rectilinear boundaries of a figure could be indefinitely -extended by refraction, so that figure and background might only pursue -their course next, but not over each other, no colour would appear, not -even if they were prolonged to infinity.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_18" id="Footnote_1_18"></a><a href="#FNanchor_1_18"><span class="label">[1]</span></a> <a href="#col001">Plate 2</a>, fig. 1.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_19" id="Footnote_2_19"></a><a href="#FNanchor_2_19"><span class="label">[2]</span></a> The author has omitted the orange and purple in the -coloured diagrams which illustrate these first experiments, from a wish -probably to present the elementary contrast, on which he lays a stress, -in greater simplicity. The reddish tinge would be apparent, as stated -above, where the blue and yellow are in contact with the black.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_20" id="Footnote_3_20"></a><a href="#FNanchor_3_20"><span class="label">[3]</span></a> <a href="#col001">Plate 2</a>, fig. 2</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_21" id="Footnote_4_21"></a><a href="#FNanchor_4_21"><span class="label">[4]</span></a> <a href="#col001">Plate 2</a>, fig. 4</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_22" id="Footnote_5_22"></a><a href="#FNanchor_5_22"><span class="label">[5]</span></a> In this case, according to the author, the refracting -medium being increased in mass, the appearance of colour is increased, -and the displacement is greater.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_23" id="Footnote_6_23"></a><a href="#FNanchor_6_23"><span class="label">[6]</span></a> <a href="#col001">Plate 2</a>, fig. 3.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_24" id="Footnote_7_24"></a><a href="#FNanchor_7_24"><span class="label">[7]</span></a> Fig. 2, <a href="#col000">plate 1</a>, contains a variety of forms, which, when -viewed through a prism, are intended to illustrate the statement in -this and the following paragraph.</p></div> - - -<hr class="chap" /> - -<h5><a name="XIV" id="XIV">XIV.</a></h5> - - -<h5>CONDITIONS UNDER WHICH THE APPEARANCE OF COLOUR INCREASES.</h5> - - -<p class="para"><a id="a209">209.</a></p> - -<p>We have seen in the foregoing experiments that all appearance of colour -occasioned by refraction depends on the condition that the boundary or -edge be moved in upon the object itself, or the object itself over the -ground, that the figure should be, as it were, carried over itself, or -over the ground. And we shall now find that, by increased displacement -of the object, the appearance of colour exhibits itself in a greater -degree. This takes place in subjective experiments, to which, for the -present, we confine ourselves, under the following conditions.</p> - -<p class="para"><a id="a210">210.</a></p> - -<p>First, if, in looking through parallel mediums, the eye is directed -more obliquely.</p> - -<p>Secondly, if the surfaces of the medium are no longer parallel, but -form a more or less acute angle.</p> - -<p><span class="pagenum"><a name="Page_87" id="Page_87">[Pg 87]</a></span></p> - -<p>Thirdly, owing to the increased proportion of the medium, whether -parallel mediums be increased in size, or whether the angle be -increased, provided it does not attain a right angle.</p> - -<p>Fourthly, owing to the distance of the eye armed with a refracting -medium from the object to be displaced.</p> - -<p>Fifthly, owing to a chemical property that may be communicated to the -glass, and which may be afterwards increased in effect.</p> - -<p class="para"><a id="a211">211.</a></p> - -<p>The greatest change of place, short of considerable distortion of the -object, is produced by means of prisms, and this is the reason why the -appearance of colour can be exhibited most powerfully through glasses -of this form. Yet we will not, in employing them, suffer ourselves to -be dazzled by the splendid appearances they exhibit, but keep the above -well-established, simple principles calmly in view.</p> - -<p class="para"><a id="a212">212.</a></p> - -<p>The colour which is outside, or foremost, in the apparent change of an -object by refraction, is always the broader, and we will henceforth -call this a <i>border</i>: the colour that remains next the outline is the -narrower, and this we will call an <i>edge</i>.</p> - -<p><span class="pagenum"><a name="Page_88" id="Page_88">[Pg 88]</a></span></p> - -<p class="para"><a id="a213">213.</a></p> - -<p>If we move a dark boundary towards a light surface, the yellow broader -border is foremost, and the narrower yellow-red edge follows close to -the outline. If we move a light boundary towards a dark surface, the -broader violet border is foremost, and the narrower blue edge follows.</p> - -<p class="para"><a id="a214">214.</a></p> - -<p>If the object is large, its centre remains uncoloured. Its inner -surface is then to be considered as unlimited (195): it is displaced, -but not otherwise altered: but if the object is so narrow, that under -the above conditions the yellow border can reach the blue edge, the -space between the outlines will be entirely covered with colour. If we -make this experiment with a white stripe on a black ground,<a name="FNanchor_1_25" id="FNanchor_1_25"></a><a href="#Footnote_1_25" class="fnanchor">[1]</a> the two -extremes will presently meet, and thus produce green. We shall then see -the following series of colours:—</p> - -<p style="margin-left: 20%;"> -Yellow-red.<br /> -Yellow.<br /> -Green.<br /> -Blue.<br /> -Blue-red.<br /> -</p> - -<p class="para"><a id="a215">215.</a></p> - -<p>If we place a black band, or stripe, on white paper,<a name="FNanchor_2_26" id="FNanchor_2_26"></a><a href="#Footnote_2_26" class="fnanchor">[2]</a> the violet -border will spread till it meets<span class="pagenum"><a name="Page_89" id="Page_89">[Pg 89]</a></span> the yellow-red edge. In this case the -intermediate black is effaced (as the intermediate white was in the -last experiment), and in its stead a splendid pure red will appear.<a name="FNanchor_3_27" id="FNanchor_3_27"></a><a href="#Footnote_3_27" class="fnanchor">[3]</a> -The series of colours will now be as follows:—</p> - -<p style="margin-left: 20%;"> -Blue.<br /> -Blue-red.<br /> -Red.<br /> -Yellow-red.<br /> -Yellow.<br /> -</p> - -<p class="para"><a id="a216">216.</a></p> - -<p>The yellow and blue, in the first case (214), can by degrees meet so -fully, that the two colours blend entirely in green, and the order will -then be,</p> - -<p style="margin-left: 20%;"> -Yellow-red.<br /> -Green.<br /> -Blue-red.<br /> -</p> - -<p>In the second case (215), under similar circumstances, we see only</p> - -<p style="margin-left: 20%;"> -Blue.<br /> -Red.<br /> -Yellow.<br /> -</p> - -<p>This appearance is best exhibited by refracting the bars of a window -when they are relieved on a grey sky.<a name="FNanchor_4_28" id="FNanchor_4_28"></a><a href="#Footnote_4_28" class="fnanchor">[4]</a></p> - -<p><span class="pagenum"><a name="Page_90" id="Page_90">[Pg 90]</a></span></p> - -<p class="para"><a id="a217">217.</a></p> - -<p>In all this we are never to forget that this appearance is not to be -considered as a complete or final state, but always as a progressive, -increasing, and, in many senses, controllable appearance. Thus we -find that, by the negation of the above five conditions, it gradually -decreases, and at last disappears altogether.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_25" id="Footnote_1_25"></a><a href="#FNanchor_1_25"><span class="label">[1]</span></a> <a href="#col001">Plate 2</a>, fig. 5, <i>left</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_26" id="Footnote_2_26"></a><a href="#FNanchor_2_26"><span class="label">[2]</span></a> <a href="#col001">Plate 2</a>, fig. 5, <i>right</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_27" id="Footnote_3_27"></a><a href="#FNanchor_3_27"><span class="label">[3]</span></a> This pure red, the union of orange and violet, is -considered by the author the maximum of the coloured appearance: he -has appropriated the term <i>purpur</i> to it. See paragraph <a href="#a703">703</a>, and -<i>note</i>.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_28" id="Footnote_4_28"></a><a href="#FNanchor_4_28"><span class="label">[4]</span></a> The bands or stripes in fig. 4, <a href="#col000">plate 1</a>, when viewed -through a prism, exhibit the colours represented in <a href="#col001">plate 2</a>, fig. 5.</p></div> - - -<hr class="chap" /> - -<h5><a name="XV" id="XV">XV.</a></h5> - - -<h5>EXPLANATION OF THE FOREGOING PHENOMENA.</h5> - - -<p class="para"><a id="a218">218.</a></p> - -<p>Before we proceed further, it is incumbent on us to explain the first -tolerably simple phenomenon, and to show its connexion with the -principles first laid down, in order that the observer of nature may -be enabled clearly to comprehend the more complicated appearances that -follow.</p> - -<p class="para"><a id="a219">219.</a></p> - -<p>In the first place, it is necessary to remember that we have to do -with circumscribed objects. In the act of seeing, generally, it is -the circumscribed visible which chiefly invites our observation; and -in the present instance, in speaking of the appearance of colour, as -occasioned by refraction, the circumscribed visible, the detached -object solely occupies our attention.</p> - -<p><span class="pagenum"><a name="Page_91" id="Page_91">[Pg 91]</a></span></p> - -<p class="para"><a id="a220">220.</a></p> - -<p>For our chromatic exhibitions we can, however, divide objects generally -into <i>primary</i> and <i>secondary</i>. The expressions of themselves denote -what we understand by them, but our meaning will be rendered still more -plain by what follows.</p> - -<p class="para"><a id="a221">221.</a></p> - -<p>Primary objects may be considered firstly as <i>original</i>, as images -which are impressed on the eye by things before it, and which assure -us of their reality. To these the secondary images may be opposed -as <i>derived</i> images, which remain in the organ when the object -itself is taken away; those apparent after-images, which have been -circumstantially treated of in the doctrine of physiological colours.</p> - -<p class="para"><a id="a222">222.</a></p> - -<p>The primary images, again, may be considered as <i>direct</i> images, which, -like the original impressions, are conveyed immediately from the object -to the eye. In contradistinction to these, the secondary images may -be considered as <i>indirect</i>, being only conveyed to us, as it were, -at second-hand from a reflecting surface. These are the mirrored, or -catoptrical, images, which in certain cases can also become double -images:</p> - -<p class="para"><a id="a223">223.</a></p> - -<p>When, namely, the reflecting body is transparent,<span class="pagenum"><a name="Page_92" id="Page_92">[Pg 92]</a></span> and has two parallel -surfaces, one behind the other: in such a case, an image may be -reflected to the eye from both surfaces, and thus arise double images, -inasmuch as the upper image does not quite cover the under one: this -may take place in various ways.</p> - -<p>Let a playing-card be held before a mirror. We shall at first see the -distinct image of the card, but the edge of the whole card, as well -as that of every spot upon it, will be bounded on one side with a -border, which is the beginning of the second reflection. This effect -varies in different mirrors, according to the different thickness of -the glass, and the accidents of polishing. If a person wearing a white -waistcoat, with the remaining part of his dress dark, stands before -certain mirrors, the border appears very distinctly, and in like manner -the metal buttons on dark cloth exhibit the double reflection very -evidently.</p> - -<p class="para"><a id="a224">224.</a></p> - -<p>The reader who has made himself acquainted with our former descriptions -of experiments (<a href="#a80">80</a>) will the more readily follow the present statement. -The window-bars reflected by plates of glass appear double, and -by increased thickness of the glass, and a due adaptation of the -angle of reflection, the two reflections may be entirely separated -from each other. So a vase full of<span class="pagenum"><a name="Page_93" id="Page_93">[Pg 93]</a></span> water, with a plane mirror-like -bottom, reflects any object twice, the two reflections being more or -less separated under the same conditions. In these cases it is to be -observed that, where the two reflections cover each other, the perfect -vivid image is reflected, but where they are separated they exhibit -only weak, transparent, and shadowy images.</p> - -<p class="para"><a id="a225">225.</a></p> - -<p>If we wish to know which is the under and which the upper image, we -have only to take a coloured medium, for then a light object reflected -from the under surface is of the colour of the medium, while that -reflected from the upper surface presents the complemental colour. With -dark objects it is the reverse; hence black and white surfaces may be -here also conveniently employed. How easily the double images assume -and evoke colours will here again be striking.</p> - -<p class="para"><a id="a226">226.</a></p> - -<p>Thirdly, the primary images may be considered as <i>principal</i> images, -while the secondary can be, as it were, annexed to these as <i>accessory</i> -images. Such an accessory image produces a sort of double form; except -that it does not separate itself from the principal object, although it -may be said to be always endeavouring to do so. It is<span class="pagenum"><a name="Page_94" id="Page_94">[Pg 94]</a></span> with secondary -images of this last description that we have to do in prismatic -appearances.</p> - -<p class="para"><a id="a227">227.</a></p> - -<p>A surface without a boundary exhibits no appearance of colour when -refracted (<a href="#a195">195</a>). Whatever is seen must be circumscribed by an -outline to produce this effect. In other words a figure, an object, -is required; this object undergoes an apparent change of place by -refraction: the change is however not complete, not clean, not sharp; -but incomplete, inasmuch as an accessory image only is produced.</p> - -<p class="para"><a id="a228">228.</a></p> - -<p>In examining every appearance of nature, but especially in examining -an important and striking one, we should not remain in one spot, we -should not confine ourselves to the insulated fact, nor dwell on it -exclusively, but look round through all nature to see where something -similar, something that has affinity to it, appears: for it is only by -combining analogies that we gradually arrive at a whole which speaks -for itself, and requires no further explanation.</p> - -<p class="para"><a id="a229">229.</a></p> - -<p>Thus we here call to mind that in certain cases refraction -unquestionably produces double images, as is the case in Iceland spar: -similar<span class="pagenum"><a name="Page_95" id="Page_95">[Pg 95]</a></span> double images are also apparent in cases of refraction through -large rock crystals, and in other instances; phenomena which have not -hitherto been sufficiently observed.<a name="FNanchor_1_29" id="FNanchor_1_29"></a><a href="#Footnote_1_29" class="fnanchor">[1]</a></p> - -<p class="para"><a id="a230">230.</a></p> - -<p>But since in the case under consideration (227) the question relates -not to double but to accessory images, we refer to a phenomenon already -adverted to, but not yet thoroughly investigated. We allude to an -earlier experiment, in which it appeared that a sort of conflict took -place in regard to the retina between a light object and its dark -ground, and between a dark object and its light ground (<a href="#a16">16</a>). The light -object in this case appeared larger, the dark one smaller.</p> - -<p class="para"><a id="a231">231.</a></p> - -<p>By a more exact observation of this phenomenon we may remark that the -forms are not sharply distinguished from the ground, but that they -appear with a kind of grey, in some degree, coloured edge; in short, -with an accessory image. If, then, objects seen only with the naked -eye produce such effects, what may not take place when a dense medium -is interposed? It is not that alone which presents itself to us<span class="pagenum"><a name="Page_96" id="Page_96">[Pg 96]</a></span> in -obvious operation which produces and suffers effects, but likewise all -principles that have a mutual relation only of some sort are efficient -accordingly, and indeed often in a very high degree.</p> - -<p class="para"><a id="a232">232.</a></p> - -<p>Thus when refraction produces its effect on an object there appears an -accessory image next the object itself: the real form thus refracted -seems even to linger behind, as if resisting the change of place; but -the accessory image seems to advance, and extends itself more or less -in the mode already shown (<a href="#a212">212</a>-<a href="#a216">216</a>).</p> - -<p class="para"><a id="a233">233.</a></p> - -<p>We also remarked (<a href="#a224">224</a>) that in double images the fainter appear only -half substantial, having a kind of transparent, evanescent character, -just as the fainter shades of double shadows must always appear as -half-shadows. These latter assume colours easily, and produce them -readily (<a href="#a69">69</a>), the former also (80); and the same takes place in the -instance of accessory images, which, it is true, do not altogether -quit the real object, but still advance or extend from it as -half-substantial images, and hence can appear coloured so quickly and -so powerfully.</p> - -<p class="para"><a id="a234">234.</a></p> - -<p>That the prismatic appearance is in fact an<span class="pagenum"><a name="Page_97" id="Page_97">[Pg 97]</a></span> accessory image we may -convince ourselves in more than one mode. It corresponds exactly with -the form of the object itself. Whether the object be bounded by a -straight line or a curve, indented or waving, the form of the accessory -image corresponds throughout exactly with the form of the object.<a name="FNanchor_2_30" id="FNanchor_2_30"></a><a href="#Footnote_2_30" class="fnanchor">[2]</a></p> - -<p class="para"><a id="a235">235.</a></p> - -<p>Again, not only the form but other qualities of the object are -communicated to the accessory image. If the object is sharply relieved -from its ground, like white on black, the coloured accessory image in -like manner appears in its greatest force. It is vivid, distinct, and -powerful; but it is most especially powerful when a luminous object is -shown on a dark ground, which may be contrived in various ways.</p> - -<p class="para"><a id="a236">236.</a></p> - -<p>But if the object is but faintly distinguished from the ground, like -grey objects on black or white, or even on each other, the accessory -image is also faint, and, when the original difference of tint or force -is slight, becomes hardly discernible.</p> - -<p><span class="pagenum"><a name="Page_98" id="Page_98">[Pg 98]</a></span></p> - -<p class="para"><a id="a237">237.</a></p> - -<p>The appearances which are observable when coloured objects are relieved -on light, dark, or coloured grounds are, moreover, well worthy of -attention. In this case a union takes place between the apparent colour -of the accessory image and the real colour of the object; a compound -colour is the result, which is either assisted and enhanced by the -accordance, or neutralised by the opposition of its ingredients.</p> - -<p class="para"><a id="a238">238.</a></p> - -<p>But the common and general characteristic both of the double and -accessory image is semi-transparence. The tendency of a transparent -medium to become only half transparent, or merely light-transmitting, -has been before adverted to (<a href="#a147">147</a>, <a href="#a148">148</a>). Let the reader assume that he -sees within or through such a medium a visionary image, and he will at -once pronounce this latter to be a semi-transparent image.</p> - -<p class="para"><a id="a239">239.</a></p> - -<p>Thus the colours produced by refraction may be fitly explained by the -doctrine of the semi-transparent mediums. For where dark passes over -light, as the border of the semi-transparent accessory image advances, -yellow appears; and, on the other hand, where a light outline passes -over the dark background, blue appears (<a href="#a150">150</a>, <a href="#a151">151</a>).</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_99" id="Page_99">[Pg 99]</a></span></p> - -<p class="para"><a id="a240">240.</a></p> - -<p>The advancing foremost colour is always the broader. Thus the yellow -spreads over the light with a broad border, but the yellow-red appears -as a narrower stripe and is next the dark, according to the doctrine of -augmentation, as an effect of shade.<a name="FNanchor_3_31" id="FNanchor_3_31"></a><a href="#Footnote_3_31" class="fnanchor">[3]</a></p> - -<p class="para"><a id="a241">241.</a></p> - -<p>On the opposite side the condensed blue is next the edge, while the -advancing border, spreading as a thinner veil over the black, produces -the violet colour, precisely on the principles before explained in -treating of semi-transparent mediums, principles which will hereafter -be found equally efficient in many other cases.</p> - -<p class="para"><a id="a242">242.</a></p> - -<p>Since an analysis like the present requires to be confirmed by ocular -demonstration, we beg every reader to make himself acquainted with the -experiments hitherto adduced, not in a superficial manner, but fairly -and thoroughly. We have not placed arbitrary signs before him instead -of the appearances themselves; no modes of expression are here proposed -for his<span class="pagenum"><a name="Page_100" id="Page_100">[Pg 100]</a></span> adoption which may be repeated for ever without the exercise -of thought and without leading any one to think; but we invite him to -examine intelligible appearances, which must be present to the eye and -mind, in order to enable him clearly to trace these appearances to -their origin, and to explain them to himself and to others.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_29" id="Footnote_1_29"></a><a href="#FNanchor_1_29"><span class="label">[1]</span></a> The date of the publication, 1810, is sometimes to be -remembered.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_30" id="Footnote_2_30"></a><a href="#FNanchor_2_30"><span class="label">[2]</span></a> The forms in fig. 2, <a href="#col000">plate 1</a>, when seen through a prism, -are again intended to exemplify this. In the plates to the original -work curvilinear figures are added, but the circles, fig. 1, in the -same plate, may answer the same end.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_31" id="Footnote_3_31"></a><a href="#FNanchor_3_31"><span class="label">[3]</span></a> The author has before observed that colour is a degree -of darkness, and he here means that increase of darkness, produced by -transparent mediums, is, to a certain extent, increase of colour.—T.</p></div> - - - -<hr class="r5" /> -<h5><a name="XVI" id="XVI">XVI.</a></h5> - - -<h5>DECREASE OF THE APPEARANCE OF COLOUR.</h5> - - -<p class="para"><a id="a243">243.</a></p> - -<p>We need only take the five conditions (<a href="#a210">210</a>) under which the appearance -of colour increases in the contrary order, to produce the contrary or -decreasing state; it may be as well, however, briefly to describe and -review the corresponding modifications which are presented to the eye.</p> - -<p class="para"><a id="a244">244.</a></p> - -<p>At the highest point of complete junction of the opposite edges, the -colours appear as follows (<a href="#a216">216</a>):—</p> - -<table border="0" cellpadding="2" cellspacing="0" summary=""> -<tr><td align="left">Yellow-red. </td><td align="left">Blue.</td></tr> -<tr><td align="left">Green.</td><td align="left">Red.</td></tr> -<tr><td align="left">Blue-red.</td><td align="left">Yellow.</td></tr> -</table> - -<p><span class="pagenum"><a name="Page_101" id="Page_101">[Pg 101]</a></span></p> - -<p class="para"><a id="a245">245.</a></p> - -<p>Where the junction is less complete, the appearance is as follows (<a href="#a214">214</a>, -<a href="#a215">215</a>):—</p> - -<table border="0" cellpadding="2" cellspacing="0" summary=""> -<tr><td align="left">Yellow-red. </td><td align="left">Blue.</td></tr> -<tr><td align="left">Yellow.</td><td align="left">Blue-red.</td></tr> -<tr><td align="left">Green.</td><td align="left">Red.</td></tr> -<tr><td align="left">Blue.</td><td align="left">Yellow-red.</td></tr> -<tr><td align="left">Blue-red.</td><td align="left">Yellow.</td></tr> -</table> - -<p>Here, therefore, the surface still appears completely coloured, but -neither series is to be considered as an elementary series, always -developing itself in the same manner and in the same degrees; on the -contrary, they can and should be resolved into their elements; and, in -doing this, we become better acquainted with their nature and character.</p> - -<p class="para"><a id="a246">246.</a></p> - -<p>These elements then are (<a href="#a199">199</a>, <a href="#a200">200</a>, <a href="#a201">201</a>)—</p> - -<table border="0" cellpadding="4" cellspacing="0" summary=""> -<tr><td align="left">Yellow-red. </td><td align="left">Blue.</td></tr> -<tr><td align="left">Yellow.</td><td align="left">Blue-red.</td></tr> -<tr><td align="left">White.</td><td align="left">Black.</td></tr> -<tr><td align="left">Blue.</td><td align="left">Yellow-red.</td></tr> -<tr><td align="left">Blue-red.</td><td align="left">Yellow.</td></tr> -</table> - -<p>Here the surface itself, the original object, which has been hitherto -completely covered, and as it were lost, again appears in the centre of -the colours, asserts its right, and enables us<span class="pagenum"><a name="Page_102" id="Page_102">[Pg 102]</a></span> fully to recognise the -secondary nature of the accessory images which exhibit themselves as -"edges" and "borders."—<a href="#NOTE_N">Note N.</a></p> - -<p class="para"><a id="a247">247.</a></p> - -<p>We can make these edges and borders as narrow as we please; nay, we -can still have refraction in reserve after having done away with all -appearance of colour at the boundary of the object.</p> - -<p>Having now sufficiently investigated the exhibition of colour in this -phenomenon, we repeat that we cannot admit it to be an elementary -phenomenon. On the contrary, we have traced it to an antecedent and -a simpler one; we have derived it, in connexion with the theory of -secondary images, from the primordial phenomenon of light and darkness, -as affected or acted upon by semi-transparent mediums. Thus prepared, -we proceed to describe the appearances which refraction produces on -grey and coloured objects, and this will complete the section of -subjective phenomena.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_103" id="Page_103">[Pg 103]</a></span></p> - - - - -<h5><a name="XVII" id="XVII">XVII.</a></h5> - -<h5>GREY OBJECTS DISPLACED BY REFRACTION.</h5> - - -<p class="para"><a id="a248">248.</a></p> - -<p>Hitherto we have confined our attention to black and white objects -relieved on respectively opposite grounds, as seen through the prism, -because the coloured edges and borders are most clearly displayed in -such cases. We now repeat these experiments with grey objects, and -again find similar results.</p> - -<p class="para"><a id="a249">249.</a></p> - -<p>As we called black the equivalent of darkness, and white the -representative of light (<a href="#a18">18</a>), so we now venture to say that grey -represents half-shadow, which partakes more or less of light and -darkness, and thus stands between the two. We invite the reader to call -to mind the following facts as bearing on our present view.</p> - -<p class="para"><a id="a250">250.</a></p> - -<p>Grey objects appear lighter on a black than on a white ground (<a href="#a33">33</a>); -they appear as a light on a black ground, and larger; as a dark on the -white ground, and smaller. (<a href="#a16">16</a>.)</p> - -<p><span class="pagenum"><a name="Page_104" id="Page_104">[Pg 104]</a></span></p> - -<p class="para"><a id="a251">251.</a></p> - -<p>The darker the grey the more it appears as a faint light on black, as a -strong dark on white, and <i>vice versâ</i>; hence the accessory images of -dark-grey on black are faint, on white strong: so the accessory images -of light-grey on white are faint, on black strong.</p> - -<p class="para"><a id="a252">252.</a></p> - -<p>Grey on black, seen through the prism, will exhibit the same -appearances as white on black; the edges are coloured according to the -same law, only the borders appear fainter. If we relieve grey on white, -we have the same edges and borders which would be produced if we saw -black on white through the prism.—<a href="#NOTE_O">Note O.</a></p> - -<p class="para"><a id="a253">253.</a></p> - -<p>Various shades of grey placed next each other in gradation will exhibit -at their edges, either blue and violet only, or red and yellow only, -according as the darker grey is placed over or under.</p> - -<p class="para"><a id="a254">254.</a></p> - -<p>A series of such shades of grey placed horizontally next each other -will be coloured conformably to the same law according as the whole -series is relieved, on a black or white ground above or below.</p> - -<p><span class="pagenum"><a name="Page_105" id="Page_105">[Pg 105]</a></span></p> - -<p class="para"><a id="a255">255.</a></p> - -<p>The observer may see the phenomena exhibited by the prism at one -glance, by enlarging the plate intended to illustrate this section.<a name="FNanchor_1_32" id="FNanchor_1_32"></a><a href="#Footnote_1_32" class="fnanchor">[1]</a></p> - -<p class="para"><a id="a256">256.</a></p> - -<p>It is of great importance duly to examine and consider another -experiment in which a grey object is placed partly on a black and -partly on a white surface, so that the line of division passes -vertically through the object.</p> - -<p class="para"><a id="a257">257.</a></p> - -<p>The colours will appear on this grey object in conformity with the -usual law, but according to the opposite relation of the light to the -dark, and will be contrasted in a line. For as the grey is as a light -to the black, so it exhibits the red and yellow above the blue and -violet below: again, as the grey is as a dark to the white, the blue -and violet appear above the red and yellow below. This experiment will -be found of great importance with reference to the next chapter.</p> - - -<div class="footnote"> - -<p><a name="Footnote_1_32" id="Footnote_1_32"></a><a href="#FNanchor_1_32"><span class="label">[1]</span></a> It has been thought unnecessary to give all the examples -in the plate alluded to, but the leading instance referred to in the -next paragraph will be found in <a href="#col002">plate 3</a>, fig. 1. The grey square -when seen through a prism will exhibit the effects described in par. -<a href="#a257">257</a>.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_106" id="Page_106">[Pg 106]</a></span></p></div> - - - - -<h5><a name="XVIII" id="XVIII">XVIII.</a></h5> - - -<h5>COLOURED OBJECTS DISPLACED BY REFRACTION.</h5> - - -<p class="para"><a id="a258">258.</a></p> - -<p>An unlimited coloured surface exhibits no prismatic colour in addition -to its own hue, thus not at all differing from a black, white, or -grey surface. To produce the appearance of colour, light and dark -boundaries must act on it either accidentally or by contrivance. Hence -experiments and observations on coloured surfaces, as seen through the -prism, can only be made when such surfaces are separated by an outline -from another differently tinted surface, in short when <i>circumscribed -objects</i> are coloured.</p> - -<p class="para"><a id="a259">259.</a></p> - -<p>All colours, whatever they may be, correspond so far with grey, that -they appear darker than white and lighter than black. This shade-like -quality of colour (σκιέρον) has been already alluded to (<a href="#a69">69</a>), and will -become more and more evident. If then we begin by placing coloured -objects on black and white surfaces, and examine them through the -prism, we shall again have all that we have seen exhibited with grey -surfaces.</p> - - -<div class="figcenter" style="width: 500px;"> -<a id="col002"></a> -<img src="images/col_002.jpg" width="500" alt="" /> -<p style="text-align: center; font-weight: bold;">Plate 3.</p> -</div> - -<p><span class="pagenum"><a name="Page_107" id="Page_107">[Pg 107]</a></span></p> - -<p class="para"><a id="a260">260.</a></p> - -<p>If we displace a coloured object by refraction, there appears, as -in the case of colourless objects and according to the same laws, -an accessory image. This accessory image retains, as far as colour -is concerned, its usual nature, and acts on one side as a blue and -blue-red, on the opposite side as a yellow and yellow-red. Hence the -apparent colour of the edge and border will be either homogeneous -with the real colour of the object, or not so. In the first case the -apparent image identifies itself with the real one, and appears to -increase it, while, in the second case, the real image may be vitiated, -rendered indistinct, and reduced in size by the apparent image. We -proceed to review the cases in which these effects are most strikingly -exhibited.</p> - -<p class="para"><a id="a261">261.</a></p> - -<p>If we take a coloured drawing enlarged from the plate, which -illustrates this experiment<a name="FNanchor_1_33" id="FNanchor_1_33"></a><a href="#Footnote_1_33" class="fnanchor">[1]</a>, and examine the red and blue squares -placed next each other on a black ground, through the prism as usual, -we shall find that as both colours are lighter than the ground, -similarly coloured edges and borders will appear above and below,<span class="pagenum"><a name="Page_108" id="Page_108">[Pg 108]</a></span> at -the outlines of both, only they will not appear equally distinct to the -eye.</p> - -<p class="para"><a id="a262">262.</a></p> - -<p>Red is proportionally much lighter on black than blue is. The colours -of the edges will therefore appear stronger on the red than on the -blue, which here acts as a dark-grey, but little different from black. -(<a href="#a251">251</a>.)</p> - -<p class="para"><a id="a263">263.</a></p> - -<p>The extreme red edge will identify itself with the vermilion colour -of the square, which will thus appear a little elongated in this -direction; while the yellow border immediately underneath it only gives -the red surface a more brilliant appearance, and is not distinguished -without attentive observation.</p> - -<p class="para"><a id="a264">264.</a></p> - -<p>On the other hand the red edge and yellow border are heterogeneous -with the blue square; a dull red appears at the edge, and a dull green -mingles with the figure, and thus the blue square seems, at a hasty -glance, to be comparatively diminished on this side.</p> - -<p class="para"><a id="a265">265.</a></p> - -<p>At the lower outline of the two squares a blue edge and a violet border -will appear, and will<span class="pagenum"><a name="Page_109" id="Page_109">[Pg 109]</a></span> produce the contrary effect; for the blue edge, -which is heterogeneous with the warm red surface, will vitiate it -and produce a neutral colour, so that the red on this side appears -comparatively reduced and driven upwards, and the violet border on the -black is scarcely perceptible.</p> - -<p class="para"><a id="a266">266.</a></p> - -<p>On the other hand, the blue apparent edge will identify itself with the -blue square, and not only not reduce, but extend it. The blue edge and -even the violet border next it have the apparent effect of increasing -the surface, and elongating it in that direction.</p> - -<p class="para"><a id="a267">267.</a></p> - -<p>The effect of homogeneous and heterogeneous edges, as I have now -minutely described it, is so powerful and singular that the two squares -at the first glance seem pushed out of their relative horizontal -position and moved in opposite directions, the red upwards, the blue -downwards. But no one who is accustomed to observe experiments in a -certain succession, and respectively to connect and trace them, will -suffer himself to be deceived by such an unreal effect.</p> - -<p class="para"><a id="a268">268.</a></p> - -<p>A just impression with regard to this important<span class="pagenum"><a name="Page_110" id="Page_110">[Pg 110]</a></span> phenomenon will, -however, much depend on some nice and even troublesome conditions, -which are necessary to produce the illusion in question. Paper should -be tinged with vermilion or the best minium for the red square, and -with deep indigo for the blue square. The blue and red prismatic edges -will then unite imperceptibly with the real surfaces where they are -respectively homogeneous; where they are not, they vitiate the colours -of the squares without producing a very distinct middle tint. The real -red should not incline too much to yellow, otherwise the apparent deep -red edge above will be too distinct; at the same time it should be -somewhat yellow, otherwise the transition to the yellow border will be -too observable. The blue must not be light, otherwise the red edge will -be visible, and the yellow border will produce a too decided green, -while the violet border underneath would not give us the impression of -being part of an elongated light blue square.</p> - -<p class="para"><a id="a269">269.</a></p> - -<p>All this will be treated more circumstantially hereafter, when we speak -of the apparatus intended to facilitate the experiments connected with -this part of our subject.<a name="FNanchor_2_34" id="FNanchor_2_34"></a><a href="#Footnote_2_34" class="fnanchor">[2]</a> Every inquirer<span class="pagenum"><a name="Page_111" id="Page_111">[Pg 111]</a></span> should prepare the figures -himself, in order fairly to exhibit this specimen of ocular deception, -and at the same time to convince himself that the coloured edges, even -in this case, cannot escape accurate examination.</p> - -<p class="para"><a id="a270">270.</a></p> - -<p>Meanwhile various other combinations, as exhibited in the plate, are -fully calculated to remove all doubt on this point in the mind of every -attentive observer.</p> - -<p class="para"><a id="a271">271.</a></p> - -<p>If, for instance, we look at a white square, next the blue one, on a -black ground, the prismatic hues of the opposite edges of the white, -which here occupies the place of the red in the former experiment, will -exhibit themselves in their utmost force. The red edge extends itself -above the level of the blue almost in a greater degree than was the -case with the red square itself in the former experiment. The lower -blue edge, again, is visible in its full force next the white, while, -on the other hand, it cannot be distinguished next the blue square. The -violet border underneath is also much more apparent on the white than -on the blue.</p> - -<p class="para"><a id="a272">272.</a></p> - -<p>If the observer now compares these double<span class="pagenum"><a name="Page_112" id="Page_112">[Pg 112]</a></span> squares, carefully prepared -and arranged one above the other, the red with the white, the two blue -squares together, the blue with the red, the blue with the white, he -will clearly perceive the relations of these surfaces to their coloured -edges and borders.</p> - -<p class="para"><a id="a273">273.</a></p> - -<p>The edges and their relations to the coloured surfaces appear still -more striking if we look at the coloured squares and a black square -on a white ground; for in this case the illusion before mentioned -ceases altogether, and the effect of the edges is as visible as in -any case that has come under our observation. Let the blue and red -squares be first examined through the prism. In both the blue edge now -appears above; this edge, homogeneous with the blue surface, unites -with it, and appears to extend it upwards, only the blue edge, owing -to its lightness, is somewhat too distinct in its upper portion; the -violet border underneath it is also sufficiently evident on the blue. -The apparent blue edge is, on the other hand, heterogeneous with the -red square; it is neutralised by contrast, and is scarcely visible; -meanwhile the violet border, uniting with the real red, produces a hue -resembling that of the peach-blossom.</p> - -<p class="para"><a id="a274">274.</a></p> - -<p>If thus, owing to the above causes, the upper<span class="pagenum"><a name="Page_113" id="Page_113">[Pg 113]</a></span> outlines of these -squares do not appear level with each other, the correspondence of the -under outlines is the more observable; for since both colours, the red -and the blue, are darks compared with the white (as in the former case -they were light compared with the black), the red edge with its yellow -border appears very distinctly under both. It exhibits itself under the -warm red surface in its full force, and under the dark blue nearly as -it appears under the black: as may be seen if we compare the edges and -borders of the figures placed one above the other on the white ground.</p> - -<p class="para"><a id="a275">275.</a></p> - -<p>In order to present these experiments with the greatest variety and -perspicuity, squares of various colours are so arranged<a name="FNanchor_3_35" id="FNanchor_3_35"></a><a href="#Footnote_3_35" class="fnanchor">[3]</a> that the -boundary of the black and white passes through them vertically. -According to the laws now known to us, especially in their application -to coloured objects, we shall find the squares as usual doubly coloured -at each edge; each square will appear to be split in two, and to be -elongated upwards or downwards. We may here call to mind the experiment -with the grey figure seen in like manner on the line of division -between black and white (257).<a name="FNanchor_4_36" id="FNanchor_4_36"></a><a href="#Footnote_4_36" class="fnanchor">[4]</a></p> - -<p><span class="pagenum"><a name="Page_114" id="Page_114">[Pg 114]</a></span></p> - -<p class="para"><a id="a276">276.</a></p> - -<p>A phenomenon was before exhibited, even to illusion, in the instance of -a red and blue square on a black ground; in the present experiment the -elongation upwards and downwards of two differently coloured figures -is apparent in the two halves of one and the same figure of one and -the same colour. Thus we are still referred to the coloured edges and -borders, and to the effects of their homogeneous and heterogeneous -relations with respect to the real colours of the objects.</p> - -<p class="para"><a id="a277">277.</a></p> - -<p>I leave it to observers themselves to compare the various gradations -of coloured squares, placed half on black half on white, only inviting -their attention to the apparent alteration which takes place in -contrary directions; for red and yellow appear elongated upwards if -on a black ground, downwards if on a white; blue, downwards if on a -black ground, upwards if on a white. All which, however, is quite in -accordance with the diffusely detailed examples above given.</p> - -<p class="para"><a id="a278">278.</a></p> - -<p>Let the observer now turn the figures so that the before-mentioned -squares placed on the line of division between black and white may -be in a horizontal series; the black above, the white underneath. On -looking at these squares<span class="pagenum"><a name="Page_115" id="Page_115">[Pg 115]</a></span> through the prism, he will observe that the -red square gains by the addition of two red edges; on more accurate -examination he will observe the yellow border on the red figure, and -the lower yellow border upon the white will be perfectly apparent.</p> - -<p class="para"><a id="a279">279.</a></p> - -<p>The upper red edge on the blue square is on the other hand hardly -visible; the yellow border next it produces a dull green by mingling -with the figure; the lower red edge and the yellow border are displayed -in lively colours.</p> - -<p class="para"><a id="a280">280.</a></p> - -<p>After observing that the red figure in these cases appears to gain by -an addition on both sides, while the dark blue, on one side at least, -loses something; we shall see the contrary effect produced by turning -the same figures upside down, so that the white ground be above, the -black below.</p> - -<p class="para"><a id="a281">281.</a></p> - -<p>For as the homogeneous edges and borders now appear above and below -the blue square, this appears elongated, and a portion of the surface -itself seems even more brilliantly coloured: it is only by attentive -observation that we can distinguish the edges and borders from the -colour of the figure itself.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_116" id="Page_116">[Pg 116]</a></span></p> - -<p class="para"><a id="a282">282.</a></p> - -<p>The yellow and red squares, on the other hand, are comparatively -reduced by the heterogeneous edges in this position of the figures, -and their colours are, to a certain extent, vitiated. The blue edge -in both is almost invisible. The violet border appears as a beautiful -peach-blossom hue on the red, as a very pale colour of the same kind on -the yellow; both the lower edges are green; dull on the red, vivid on -the yellow; the violet border is but faintly perceptible under the red, -but is more apparent under the yellow.</p> - -<p class="para"><a id="a283">283.</a></p> - -<p>Every inquirer should make it a point to be thoroughly acquainted with -all the appearances here adduced, and not consider it irksome to follow -out a single phenomenon through so many modifying circumstances. These -experiments, it is true, may be multiplied to infinity by differently -coloured figures, upon and between differently coloured grounds. Under -all such circumstances, however, it will be evident to every attentive -observer that coloured squares only appear relatively altered, or -elongated, or reduced by the prism, because an addition of homogeneous -or heterogeneous edges produces an illusion. The inquirer will now -be enabled to do away with this illusion if he has the<span class="pagenum"><a name="Page_117" id="Page_117">[Pg 117]</a></span> patience to -go through the experiments one after the other, always comparing the -effects together, and satisfying himself of their correspondence.</p> - -<p>Experiments with coloured objects might have been contrived in various -ways: why they have been exhibited precisely in the above mode, and -with so much minuteness, will be seen hereafter. The phenomena, -although formerly not unknown, were much misunderstood; and it was -necessary to investigate them thoroughly to render some portions of our -intended historical view clearer.</p> - -<p class="para"><a id="a284">284.</a></p> - -<p>In conclusion, we will mention a contrivance by means of which our -scientific readers may be enabled to see these appearances distinctly -at one view, and even in their greatest splendour. Cut in a piece of -pasteboard five perfectly similar square openings of about an inch, -next each other, exactly in a horizontal line: behind these openings -place five coloured glasses in the natural order, orange, yellow, -green, blue, violet. Let the series thus adjusted be fastened in an -opening of the camera obscura, so that the bright sky may be seen -through the squares, or that the sun may shine on them; they will thus -appear very powerfully coloured. Let the spectator now examine them -through the prism, and observe the appearances, already<span class="pagenum"><a name="Page_118" id="Page_118">[Pg 118]</a></span> familiar by -the foregoing experiments, with coloured objects, namely, the partly -assisting, partly neutralising effects of the edges and borders, and -the consequent apparent elongation or reduction of the coloured squares -with reference to the horizontal line. The results witnessed by the -observer in this case, entirely correspond with those in the cases -before analysed; we do not, therefore, go through them again in detail, -especially as we shall find frequent occasions hereafter to return to -the subject.—<a href="#NOTE_P">Note P.</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_33" id="Footnote_1_33"></a><a href="#FNanchor_1_33"><span class="label">[1]</span></a> <a href="#col002">Plate 3</a>, fig. 1. The author always recommends making -the experiments on an increased scale, in order to see the prismatic -effects distinctly.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_34" id="Footnote_2_34"></a><a href="#FNanchor_2_34"><span class="label">[2]</span></a> Neither the description of the apparatus nor the -recapitulation of the whole theory, so often alluded to by the author, -were ever given.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_35" id="Footnote_3_35"></a><a href="#FNanchor_3_35"><span class="label">[3]</span></a> <a href="#col002">Plate 3</a>. fig. 1.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_36" id="Footnote_4_36"></a><a href="#FNanchor_4_36"><span class="label">[4]</span></a> The grey square is introduced in the same <a href="#col002">plate</a>, fig. 1, -above the coloured squares.</p></div> - - -<hr class="chap" /> - -<h5><a name="XIX" id="XIX">XIX.</a></h5> - - -<h5>ACHROMATISM AND HYPERCHROMATISM.</h5> - - -<p class="para"><a id="a285">285.</a></p> - -<p>Formerly when much that is regular and constant in nature was -considered as mere aberration and accident, the colours arising from -refraction were but little attended to, and were looked upon as an -appearance attributable to particular local circumstances.</p> - -<p class="para"><a id="a286">286.</a></p> - -<p>But after it had been assumed that this appearance of colour -accompanies refraction at all times, it was natural that it should -be considered as intimately and exclusively connected with that -phenomenon; the belief obtaining that the<span class="pagenum"><a name="Page_119" id="Page_119">[Pg 119]</a></span> measure of the coloured -appearance was in proportion to the measure of the refraction, and that -they must advance <i>pari passu</i> with each other.</p> - -<p class="para"><a id="a287">287.</a></p> - -<p>If, again, philosophers ascribed the phenomenon of a stronger or weaker -refraction, not indeed wholly, but in some degree, to the different -density of the medium, (as purer atmospheric air, air charged with -vapours, water, glass, according to their increasing density, increase -the so-called refraction, or displacement of the object;) so they -could hardly doubt that the appearance of colour must increase in the -same proportion; and hence took it for granted, in combining different -mediums which were to counteract refraction, that as long as refraction -existed, the appearance of colour must take place, and that as soon as -the colour disappeared, the refraction also must cease.</p> - -<p class="para"><a id="a288">288.</a></p> - -<p>Afterwards it was, however, discovered that this relation which was -assumed to correspond, was, in fact, dissimilar; that two mediums can -refract an object with equal power, and yet produce very dissimilar -coloured borders.</p> - -<p class="para"><a id="a289">289.</a></p> - -<p>It was found that, in addition to the physical principle to which -refraction was ascribed, a<span class="pagenum"><a name="Page_120" id="Page_120">[Pg 120]</a></span> chemical one was also to be taken into the -account. We propose to pursue this subject hereafter, in the chemical -division of our inquiry, and we shall have to describe the particulars -of this important discovery in our history of the doctrine of colours. -What follows may suffice for the present.</p> - -<p class="para"><a id="a290">290.</a></p> - -<p>In mediums of similar or nearly similar refracting power, we find -the remarkable circumstance that a greater and lesser appearance of -colour can be produced by a chemical treatment; the greater effect is -owing, namely, to acids, the lesser to alkalis. If metallic oxydes are -introduced into a common mass of glass, the coloured appearance through -such glasses becomes greatly increased without any perceptible change -of refracting power. That the lesser effect, again, is produced by -alkalis, may be easily supposed.</p> - -<p class="para"><a id="a291">291.</a></p> - -<p>Those kinds of glass which were first employed after the discovery, -are called flint and crown glass; the first produces the stronger, the -second the fainter appearance of colour.</p> - -<p class="para"><a id="a292">292.</a></p> - -<p>We shall make use of both these denominations as technical terms in our -present statement,<span class="pagenum"><a name="Page_121" id="Page_121">[Pg 121]</a></span> and assume that the refractive power of both is -the same, but that flint-glass produces the coloured appearance more -strongly by one-third than the crown-glass. The diagram (<a href="#col002">Plate 3</a>, fig. -2,) may serve in illustration.</p> - -<p class="para"><a id="a293">293.</a></p> - -<p>A black surface is here divided into compartments for more convenient -demonstration: let the spectator imagine five white squares between the -parallel lines <i>a, b,</i> and <i>c, d</i>. The square No. 1, is presented to -the naked eye unmoved from its place.</p> - -<p class="para"><a id="a294">294.</a></p> - -<p>But let the square No. 2, seen through a crown-glass prism <i>g</i>, be -supposed to be displaced by refraction three compartments, exhibiting -the coloured borders to a certain extent; again, let the square No. 3, -seen through a flint glass prism <i>h</i>, in like manner be moved downwards -three compartments, when it will exhibit the coloured borders by about -a third wider than No. 2.</p> - -<p class="para"><a id="a295">295.</a></p> - -<p>Again, let us suppose that the square No. 4, has, like No. 2, been -moved downwards three compartments by a prism of crown-glass, and that -then by an oppositely placed prism <i>h</i>, of<span class="pagenum"><a name="Page_122" id="Page_122">[Pg 122]</a></span> flint-glass, it has been -again raised to its former situation, where it now stands.</p> - -<p class="para"><a id="a296">296.</a></p> - -<p>Here, it is true, the refraction is done away with by the opposition of -the two; but as the prism <i>h</i>, in displacing the square by refraction -through three compartments, produces coloured borders wider by a -third than those produced by the prism <i>g</i>, so, notwithstanding the -refraction is neutralised, there must be an excess of coloured border -remaining. (The position of this colour, as usual, depends on the -direction of the apparent motion (<a href="#a204">204</a>) communicated to the square by -the prism <i>h</i>, and, consequently, it is the reverse of the appearance -in the two squares 2 and 3, which have been moved in an opposite -direction.) This excess of colour we have called Hyperchromatism, and -from this the achromatic state may be immediately arrived at.</p> - -<p class="para"><a id="a297">297.</a></p> - -<p>For assuming that it was the square No. 5 which was removed three -compartments from its first supposed place, like No. 2, by a prism of -crown-glass <i>g</i>, it would only be necessary to reduce the angle of a -prism of flint-glass <i>h</i>, and to connect it, reversed, to the prism -<i>g</i>, in order to raise the square No. 5 two degrees or compartments; -by which means the Hyperchromatism<span class="pagenum"><a name="Page_123" id="Page_123">[Pg 123]</a></span> of the first case would cease, the -figure would not quite return to its first position, and yet be already -colourless. The prolonged lines of the united prisms, under No. 5, show -that a single complete prism remains: again, we have only to suppose -the lines curved, and an object-glass presents itself. Such is the -principle of the achromatic telescopes.</p> - -<p class="para"><a id="a298">298.</a></p> - -<p>For these experiments, a small prism composed of three different -prisms, as prepared in England, is extremely well adapted. It is to be -hoped our own opticians will in future enable every friend of science -to provide himself with this necessary instrument.</p> - - - -<hr class="chap" /> -<h5><a name="XX" id="XX">XX.</a></h5> - - -<h5>ADVANTAGES OF SUBJECTIVE EXPERIMENTS.—TRANSITION TO THE OBJECTIVE.</h5> - - -<p class="para"><a id="a299">299.</a></p> - -<p>We have presented the appearances of colour as exhibited by refraction, -first, by means of subjective experiments; and we have so far arrived -at a definite result, that we have been enabled to deduce the phenomena -in question<span class="pagenum"><a name="Page_124" id="Page_124">[Pg 124]</a></span> from the doctrine of semi-transparent mediums and double -images.</p> - -<p class="para"><a id="a300">300.</a></p> - -<p>In statements which have reference to nature, everything depends on -ocular inspection, and these experiments are the more satisfactory as -they may be easily and conveniently made. Every amateur can procure -his apparatus without much trouble or cost, and if he is a tolerable -adept in pasteboard contrivances, he may even prepare a great part of -his machinery himself. A few plain surfaces, on which black, white, -grey, and coloured objects may be exhibited alternately on a light and -dark ground, are all that is necessary. The spectator fixes them before -him, examines the appearances at the edge of the figures conveniently, -and as long as he pleases; he retires to a greater distance, again -approaches, and accurately observes the progressive states of the -phenomena.</p> - -<p class="para"><a id="a301">301.</a></p> - -<p>Besides this, the appearances may be observed with sufficient exactness -through small prisms, which need not be of the purest glass. The other -desirable requisites in these glass instruments will, however, be -pointed out in the section which treats of the apparatus.<a name="FNanchor_1_37" id="FNanchor_1_37"></a><a href="#Footnote_1_37" class="fnanchor">[1]</a></p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_125" id="Page_125">[Pg 125]</a></span></p> - -<p class="para"><a id="a302">302.</a></p> - -<p>A great advantage in these experiments, again, is, that they can be -made at any hour of the day in any room, whatever aspect it may have. -We have no need to wait for sunshine, which in general is not very -propitious to northern observers.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_37" id="Footnote_1_37"></a><a href="#FNanchor_1_37"><span class="label">[1]</span></a> This description of the apparatus was never given.</p></div> - - - - -<h5><a name="OBJECTIVE_EXPERIMENTS" id="OBJECTIVE_EXPERIMENTS">OBJECTIVE EXPERIMENTS.</a></h5> - - -<p class="para"><a id="a303">303.</a></p> - -<p>The objective experiments, on the contrary, necessarily require the -sun-light which, even when it is to be had, may not always have the -most desirable relation with the apparatus placed opposite to it. -Sometimes the sun is too high, sometimes too low, and withal only a -short time in the meridian of the best situated room. It changes its -direction during the observation, the observer is forced to alter -his own position and that of his apparatus, in consequence of which -the experiments in many cases become uncertain. If the sun shines -through the prism it exhibits all inequalities, lines, and bubbles -in the glass, and thus the appearance is rendered confused, dim, and -discoloured.</p> - -<p class="para"><a id="a304">304.</a></p> - -<p>Yet both kinds of experiments must be investigated with equal accuracy. -They appear to<span class="pagenum"><a name="Page_126" id="Page_126">[Pg 126]</a></span> be opposed to each other, and yet are always parallel. -What one order of experiments exhibits the other exhibits likewise, -and yet each has its peculiar capabilities, by means of which certain -effects of nature are made known to us in more than one way.</p> - -<p class="para"><a id="a305">305.</a></p> - -<p>In the next place there are important phenomena which may be exhibited -by the union of subjective and objective experiments. The latter -experiments again have this advantage, that we can in most cases -represent them by diagrams, and present to view the component relations -of the phenomena. In proceeding, therefore, to describe the objective -experiments, we shall so arrange them that they may always correspond -with the analogous subjective examples; for this reason, too, we annex -to the number of each paragraph the number of the former corresponding -one. But we set out by observing generally that the reader must consult -the plates, that the scientific investigator must be familiar with the -apparatus in order that the twin-phenomena in one mode or the other may -be placed before them.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_127" id="Page_127">[Pg 127]</a></span></p> - - - - -<h5><a name="XXI" id="XXI">XXI.</a></h5> - - -<h5>REFRACTION WITHOUT THE APPEARANCE OF COLOUR.</h5> - -<p class="para"><a id="a306">306</a> (<a href="#a195">195</a>, <a href="#a196">196</a>).</p> - -<p>That refraction may exhibit its effects without producing an appearance -of colour, is not to be demonstrated so perfectly in objective as -in subjective experiments. We have, it is true, unlimited spaces -which we can look at through the prism, and thus convince ourselves -that no colour appears where there is no boundary; but we have no -unlimited source of light which we can cause to act through the prism. -Our light comes to us from circumscribed bodies; and the sun, which -chiefly produces our prismatic appearances, is itself only a small, -circumscribed, luminous object.</p> - -<p class="para"><a id="a307">307.</a></p> - -<p>We may, however, consider every larger opening through which the sun -shines, every larger medium through which the sun-light is transmitted -and made to deviate from its course, as so far unlimited that we can -confine our attention to the centre of the surface without considering -its boundaries.</p> - -<p class="para"><a id="a308">308</a> (<a href="#a197">197</a>).</p> - -<p>If we place a large water-prism in the sun, a<span class="pagenum"><a name="Page_128" id="Page_128">[Pg 128]</a></span> large bright space is -refracted upwards by it on the plane intended to receive the image, and -the middle of this illumined space will be colourless. The same effect -may be produced if we make the experiment with glass prisms having -angles of few degrees: the appearance may be produced even through -glass prisms, whose refracting angle is sixty degrees, provided we -place the recipient surface near enough.</p> - - - -<hr class="chap" /> -<h5><a name="XXII" id="XXII">XXII.</a></h5> - - -<h5>CONDITIONS OF THE APPEARANCE OF COLOUR.</h5> - - -<p class="para"><a id="a309">309</a> (<a href="#a198">198</a>).</p> - -<p>Although, then, the illumined space before mentioned appears indeed -refracted and moved from its place, but not coloured, yet on the -horizontal edges of this space we observe a coloured appearance. -That here again the colour is solely owing to the displacement of a -circumscribed object may require to be more fully proved.</p> - -<p>The luminous body which here acts is circumscribed: the sun, while it -shines and diffuses light, is still an insulated object. However small -the opening in the lid of a camera obscura be made, still the whole -image of the sun will<span class="pagenum"><a name="Page_129" id="Page_129">[Pg 129]</a></span> penetrate it. The light which streams from all -parts of the sun's disk, will cross itself in the smallest opening, and -form the angle which corresponds with the sun's apparent diameter. On -the outside we have a cone narrowing to the orifice; within, this apex -spreads again, producing on an opposite surface a round image, which -still increases in size in proportion to the distance of the recipient -surface from the apex. This image, together with all other objects -of the external landscape, appears reversed on the white surface in -question in a dark room.</p> - -<p class="para"><a id="a310">310.</a></p> - -<p>How little therefore we have here to do with single sun-rays, bundles -or fasces of rays, cylinders of rays, pencils, or whatever else of the -kind may be imagined, is strikingly evident. For the convenience of -certain diagrams the sun-light may be assumed to arrive in parallel -lines, but it is known that this is only a fiction; a fiction quite -allowable where the difference between the assumption and the true -appearance is unimportant; but we should take care not to suffer such a -postulate to be equivalent to a fact, and proceed to further operations -on such a fictitious basis.</p> - -<p class="para"><a id="a311">311.</a></p> - -<p>Let the aperture in the window-shutter be now enlarged at pleasure, let -it be made round<span class="pagenum"><a name="Page_130" id="Page_130">[Pg 130]</a></span> or square, nay, let the whole shutter be opened, and -let the sun shine into the room through the whole window; the space -which the sun illumines will always be larger according to the angle -which its diameter makes; and thus even the whole space illumined by -the sun through the largest window is only the image of the sun <i>plus</i> -the size of the opening. We shall hereafter have occasion to return to -this.</p> - -<p class="para"><a id="a312">312</a> (<a href="#a199">199</a>).</p> - -<p>If we transmit the image of the sun through convex glasses we contract -it towards the focus. In this case, according to the laws before -explained, a yellow border and a yellow-red edge must appear when the -spectrum is thrown on white paper. But as this experiment is dazzling -and inconvenient, it may be made more agreeably with the image of the -full moon. On contracting this orb by means of a convex glass, the -coloured edge appears in the greatest splendour; for the moon transmits -a mitigated light in the first instance, and can thus the more readily -produce colour which to a certain extent accompanies the subduing of -light: at the same time the eye of the observer is only gently and -agreeably excited.</p> - -<p class="para"><a id="a313">313</a> (<a href="#a200">200</a>).</p> - -<p>If we transmit a luminous image through concave<span class="pagenum"><a name="Page_131" id="Page_131">[Pg 131]</a></span> glasses, it is -dilated. Here the image appears edged with blue.</p> - -<p class="para"><a id="a314">314.</a></p> - -<p>The two opposite appearances may be produced by a convex glass, -simultaneously or in succession; simultaneously by fastening an opaque -disk in the centre of the convex glass, and then transmitting the sun's -image. In this case the luminous image and the black disk within it are -both contracted, and, consequently, the opposite colours must appear. -Again, we can present this contrast in succession by first contracting -the luminous image towards the focus, and then suffering it to expand -again beyond the focus, when it will immediately exhibit a blue edge.</p> - -<p class="para"><a id="a315">315</a> (<a href="#a201">201</a>).</p> - -<p>Here too what was observed in the subjective experiments is again to be -remarked, namely, that blue and yellow appear in and upon the white, -and that both assume a reddish appearance in proportion as they mingle -with the black.</p> - -<p class="para"><a id="a316">316</a> (<a href="#a202">202</a>, <a href="#a203">203</a>).</p> - -<p>These elementary phenomena occur in all subsequent objective -experiments, as they constituted the groundwork of the subjective -ones.<span class="pagenum"><a name="Page_132" id="Page_132">[Pg 132]</a></span> The process too which takes place is the same; a light boundary -is carried over a dark surface, a dark surface is carried over a light -boundary. The edges must advance, and as it were push over each other -in these experiments as in the former ones.</p> - -<p class="para"><a id="a317">317</a> (<a href="#a204">204</a>).</p> - -<p>If we admit the sun's image through a larger or smaller opening into -the dark room, if we transmit it through a prism so placed that its -refracting angle, as usual, is underneath; the luminous image, instead -of proceeding in a straight line to the floor, is refracted upwards on -a vertical surface placed to receive it. This is the moment to take -notice of the opposite modes in which the subjective and objective -refractions of the object appear.</p> - -<p class="para"><a id="a318">318.</a></p> - -<p>If we <i>look</i> through a prism, held with its refracting angle -underneath, at an object above us, the object is moved downwards; -whereas a luminous image refracted through the same prism is moved -upwards. This, which we here merely mention as a matter of fact for -the sake of brevity, is easily explained by the laws of refraction and -elevation.</p> - -<p><span class="pagenum"><a name="Page_133" id="Page_133">[Pg 133]</a></span></p> - -<p class="para"><a id="a319">319.</a></p> - -<p>The luminous object being moved from its place in this manner, the -coloured borders appear in the order, and according to the laws before -explained. The violet border is always foremost, and thus in objective -cases proceeds upwards, in subjective cases downwards.</p> - -<p class="para"><a id="a320">320</a> (<a href="#a205">205</a>).</p> - -<p>The observer may convince himself in like manner of the mode in which -the appearance of colour takes place in the diagonal direction when the -displacement is effected by means of two prisms, as has been plainly -enough shown in the subjective example; for this experiment, however, -prisms should be procured of few degrees, say about fifteen.</p> - -<p class="para"><a id="a321">321</a> (<a href="#a206">206</a>, <a href="#a207">207</a>).</p> - -<p>That the colouring of the image takes place here too, according to the -direction in which it moves, will be apparent if we make a <i>square</i> -opening of moderate size in a shutter, and cause the luminous image -to pass through a water-prism; the spectrum being moved first in the -horizontal and vertical directions, then diagonally, the coloured edges -will change their position accordingly.</p> - -<p><span class="pagenum"><a name="Page_134" id="Page_134">[Pg 134]</a></span></p> - -<p class="para"><a id="a322">322</a> (<a href="#a208">208</a>).</p> - -<p>Whence it is again evident that to produce colour the boundaries must -be carried over each other, not merely move side by side.</p> - - - -<hr class="chap" /> -<h5><a name="XXIII" id="XXIII">XXIII.</a></h5> - -<h5>CONDITIONS OF THE INCREASE OF COLOUR.</h5> - - -<p class="para"><a id="a323">323</a> (<a href="#a209">209</a>).</p> - -<p>Here too an increased displacement of the object produces a greater -appearance of colour.</p> - -<p class="para"><a id="a324">324</a> (<a href="#a210">210</a>).</p> - -<p>This increased displacement occurs,</p> - -<p>1. By a more oblique direction of the impinging luminous object through -mediums with parallel surfaces.</p> - -<p>2. By changing the parallel form for one more or less acute angled.</p> - -<p>3. By increased proportion of the medium, whether parallel or acute -angled; partly because the object is by this means more powerfully -displaced, partly because an effect depending on the mere mass -co-operates.</p> - -<p>4. By the distance of the recipient surface from the refracting medium -so that the coloured <span class="pagenum"><a name="Page_135" id="Page_135">[Pg 135]</a></span> spectrum emerging from the prism may be said to -have a longer way to travel.</p> - -<p>5. When a chemical property produces its effects under all these -circumstances: this we have already entered into more fully under the -head of achromatism and hyperchromatism.</p> - -<p class="para"><a id="a325">325</a> (<a href="#a211">211</a>).</p> - -<p>The objective experiments have this advantage that the progressive -states of the phenomenon may be arrested and clearly represented by -diagrams, which is not the case with the subjective experiments.</p> - -<p class="para"><a id="a326">326.</a></p> - -<p>We can observe the luminous image after it has emerged from the prism, -step by step, and mark its increasing colour by receiving it on a -plane at different distances, thus exhibiting before our eyes various -sections of this cone, with an elliptical base: again, the phenomenon -may at once be rendered beautifully visible throughout its whole course -in the following manner:—Let a cloud of fine white dust be excited -along the line in which the image passes through the dark space; the -cloud is best produced by fine, perfectly dry, hair-powder. The more or -less coloured appearance will now be painted on the white atoms, and -presented in<span class="pagenum"><a name="Page_136" id="Page_136">[Pg 136]</a></span> its whole length and breadth to the eye of the spectator.</p> - -<p class="para"><a id="a327">327.</a></p> - -<p>By this means we have prepared some diagrams, which will be found among -the plates. In these the appearance is exhibited from its first origin, -and by these the spectator can clearly comprehend why the luminous -image is so much more powerfully coloured through prisms than through -parallel mediums.</p> - -<p class="para"><a id="a328">328</a> (<a href="#a212">212</a>).</p> - -<p>At the two opposite outlines of the image an opposite appearance -presents itself, beginning from an acute angle;<a name="FNanchor_1_38" id="FNanchor_1_38"></a><a href="#Footnote_1_38" class="fnanchor">[1]</a> the appearance -spreads as it proceeds further in space, according to this angle. On -one side, in the direction in which the luminous image is moved, a -violet border advances on the dark, a narrower blue edge remains next -the outline of the image. On the opposite side a yellow border advances -into the light of the image itself, and a yellow-red edge remains at -the outline.</p> - -<p class="para"><a id="a329">329</a> (<a href="#a213">213</a>).</p> - -<p>Here, therefore, the movement of the dark against the light, of the -light against the dark, may be clearly observed.</p> - -<div class="figcenter" style="width: 500px;"> -<a id="col003"></a> -<img src="images/col_003.jpg" width="500" alt="" /> -<p style="text-align: center; font-weight: bold;">Plate 4.</p> -</div> - -<p><span class="pagenum"><a name="Page_137" id="Page_137">[Pg 137]</a></span></p> - -<p class="para"><a id="a330">330</a> (<a href="#a214">214</a>).</p> - -<p>The centre of a large object remains long uncoloured, especially with -mediums of less density and smaller angles; but at last the opposite -borders and edges touch each other, upon which a green appears in the -centre of the luminous image.</p> - -<p class="para"><a id="a331">331</a> (<a href="#a215">215</a>).</p> - -<p>Objective experiments have been usually made with the sun's image: an -objective experiment with a dark object has hitherto scarcely been -thought of. We have, however, prepared a convenient contrivance for -this also. Let the large water-prism before alluded to be placed in -the sun, and let a round pasteboard disk be fastened either inside or -outside. The coloured appearance will again take place at the outline, -beginning according to the usual law; the edges will appear, they will -spread in the same proportion, and when they meet, red will appear in -the centre<a name="FNanchor_2_39" id="FNanchor_2_39"></a><a href="#Footnote_2_39" class="fnanchor">[2]</a>. An intercepting square may be added near the round disk, -and placed in any direction <i>ad libitum</i>, and the spectator can again -convince himself of what has been before so often described.</p> - -<p class="para"><a id="a332">332</a> (<a href="#a216">216</a>).</p> - -<p>If we take away these dark objects from the<span class="pagenum"><a name="Page_138" id="Page_138">[Pg 138]</a></span> prism, in which case, -however, the glass is to be carefully cleaned, and hold a rod or a -large pencil before the centre of the horizontal prism, we shall -then accomplish the complete immixture of the violet border and the -yellow-red edge, and see only the three colours, the external blue, and -yellow, and the central red.</p> - -<p class="para"><a id="a333">333.</a></p> - -<p>If again we cut a long horizontal opening in the middle of a piece of -pasteboard, fastened on the prism, and then cause the sun-light to pass -through it, we shall accomplish the complete union of the yellow border -with the blue edge upon the light, and only see yellow-red, green and -violet. The details of this are further entered into in the description -of the plates.</p> - -<p class="para"><a id="a334">334</a> (<a href="#a217">217</a>).</p> - -<p>The prismatic appearance is thus by no means complete and final when -the luminous image emerges from the prism. It is then only that -we perceive its elements in contrast; for as it increases these -contrasting elements unite, and are at last intimately joined. The -section of this phenomenon arrested on a plane surface is different -at every degree of distance from the prism; so that the notion of an -immutable series of colours, or of a pervading similar proportion -between them, cannot be a question for a moment.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_38" id="Footnote_1_38"></a><a href="#FNanchor_1_38"><span class="label">[1]</span></a> <a href="#col003">Plate 4</a>. fig. 1.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_39" id="Footnote_2_39"></a><a href="#FNanchor_2_39"><span class="label">[2]</span></a> <a href="#col003">Plate 4</a>. fig. 2.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_139" id="Page_139">[Pg 139]</a></span></p></div> - - - - -<h5><a name="XXIV" id="XXIV">XXIV.</a></h5> - - -<h5>EXPLANATION OF THE FOREGOING PHENOMENA.</h5> - - -<p class="para"><a id="a335">335</a> (<a href="#a218">218</a>).</p> - -<p>As we have already entered into this analysis circumstantially while -treating of the subjective experiments, as all that was of force there -is equally valid here, it will require no long details in addition to -show that the phenomena, which are entirely parallel in the two cases, -may also be traced precisely to the same sources.</p> - -<p class="para"><a id="a336">336</a> (<a href="#a219">219</a>).</p> - -<p>That in objective experiments also we have to do with circumscribed -images, has been already demonstrated at large. The sun may shine -through the smallest opening, yet the image of the whole disk -penetrates beyond. The largest prism may be placed in the open -sun-light, yet it is still the sun's image that is bounded by the -edges of the refracting surfaces, and produces the accessory images -of this boundary. We may fasten pasteboard, with many openings cut in -it, before the water-prism, yet we still merely see multiplied images -which, after having been moved from their place by refraction, exhibit -coloured edges and borders, and in these mere accessory images.</p> - -<p><span class="pagenum"><a name="Page_140" id="Page_140">[Pg 140]</a></span></p> - -<p class="para"><a id="a337">337</a> (<a href="#a235">235</a>).</p> - -<p>In subjective experiments we have seen that objects strongly relieved -from each other produce a very lively appearance of colour, and this -will be the case in objective experiments in a much more vivid and -splendid degree. The sun's image is the most powerful brightness we -know; hence its accessory image will be energetic in proportion, and -notwithstanding its really secondary dimmed and darkened character, -must be still very brilliant. The colours thrown by the sun-light -through the prism on any object, carry a powerful light with them, for -they have the highest and most intense source of light, as it were, for -their ground.</p> - -<p class="para"><a id="a338">338.</a></p> - -<p>That we are warranted in calling even these accessory images -semi-transparent, thus deducing the appearances from the doctrine -of the semi-transparent mediums, will be clear to every one who has -followed us thus far, but particularly to those who have supplied -themselves with the necessary apparatus, so as to be enabled at all -times to witness the precision and vivacity with which semi-transparent -mediums act.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_141" id="Page_141">[Pg 141]</a></span></p> - - - - -<h5><a name="XXV" id="XXV">XXV.</a></h5> - - -<h5>DECREASE OF THE APPEARANCE OF COLOUR.</h5> - - -<p class="para"><a id="a339">339</a> (243).</p> - -<p>If we could afford to be concise in the description of the decreasing -coloured appearance in subjective cases, we may here be permitted -to proceed with still greater brevity while we refer to the former -distinct statement. One circumstance, only on account of its great -importance, may be here recommended to the reader's especial attention -as a leading point of our whole thesis.</p> - -<p class="para"><a id="a340">340</a> (<a href="#a244">244</a>, <a href="#a247">247</a>).</p> - -<p>The decline of the prismatic appearance must be preceded by its -separation, by its resolution into its elements. At a due distance from -the prism, the image of the sun being entirely coloured, the blue and -yellow at length mix completely, and we see only yellow-red, green, and -blue-red. If we bring the recipient surface nearer to the refracting -medium, yellow and blue appear again, and we see the five colours with -their gradations. At a still shorter distance the yellow and blue -separate from each other entirely, the green vanishes, and the image -itself appears, colourless, between the coloured edges and borders. The -nearer we bring the recipient surface to the prism, the<span class="pagenum"><a name="Page_142" id="Page_142">[Pg 142]</a></span> narrower the -edges and borders become, till at last, when in contact with the prism, -they are reduced to nothing.</p> - - - -<hr class="chap" /> -<h5><a name="XXVI" id="XXVI">XXVI.</a></h5> - - -<h5>GREY OBJECTS.</h5> - - -<p class="para"><a id="a341">341</a> (<a href="#a218">218</a>).</p> - -<p>We have exhibited grey objects as very important to our inquiry in the -subjective experiments. They show, by the faintness of the accessory -images, that these same images are in all cases derived from the -principal object. If we wish here, too, to carry on the objective -experiments parallel with the others, we may conveniently do this by -placing a more or less dull ground glass before the opening through -which the sun's image enters. By this means a subdued image would be -produced, which on being refracted would exhibit much duller colours on -the recipient plane than those immediately derived from the sun's disk; -and thus, even from the intense sun-image, only a faint accessory image -would appear, proportioned to the mitigation of the light by the glass. -This experiment, it is true, will only again and again confirm what is -already sufficiently familiar to us.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_143" id="Page_143">[Pg 143]</a></span></p> - - - - -<h5><a name="XXVII" id="XXVII">XXVII.</a></h5> - - -<h5>COLOURED OBJECTS.</h5> - - -<p class="para"><a id="a342">342</a> (<a href="#a260">260</a>).</p> - -<p>There are various modes of producing coloured images in objective -experiments. In the first place, we can fix coloured glass before the -opening, by which means a coloured image is at once produced; secondly, -we can fill the water-prism with coloured fluids; thirdly, we can cause -the colours, already produced in their full vivacity by the prism, to -pass through proportionate small openings in a tin plate, and thus -prepare small circumscribed colours for a second operation. This last -mode is the most difficult; for owing to the continual progress of the -sun, the image cannot be arrested in any direction at will. The second -method has also its inconveniences, since not all coloured liquids can -be prepared perfectly bright and clear. On these accounts the first is -to be preferred, and deserves the more to be adopted because natural -philosophers have hitherto chosen to consider the colours produced -from the sun-light through the prism, those produced through liquids -and glasses, and those which are already fixed on paper or cloth, as -exhibiting effects equally to be depended on, and equally available in -demonstration.</p> - -<p class="para"><a id="a343">343.</a></p> - -<p>As it is thus merely necessary that the image<span class="pagenum"><a name="Page_144" id="Page_144">[Pg 144]</a></span> should be coloured, so -the large water-prism before alluded to affords us the best means of -effecting this. A pasteboard screen may be contrived to slide before -the large surfaces of the prism, through which, in the first instance, -the light passes uncoloured. In this screen openings of various forms -may be cut, in order to produce different images, and consequently -different accessory images. This being done, we need only fix coloured -glasses before the openings, in order to observe what effect refraction -produces on coloured images in an objective sense.</p> - -<p class="para"><a id="a344">344.</a></p> - -<p>A series of glasses may be prepared in a mode similar to that before -described (<a href="#a284">284</a>); these should be accurately contrived to slide in the -grooves of the large water-prism. Let the sun then shine through them, -and the coloured images refracted upwards will appear bordered and -edged, and will vary accordingly: for these borders and edges will be -exhibited quite distinctly on some images, and on others will be mixed -with the specific colour of the glass, which they will either enhance -or neutralize. Every observer will be enabled to convince himself -here again that we have only to do with the same simple phenomenon so -circumstantially described subjectively and objectively.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_145" id="Page_145">[Pg 145]</a></span></p> - - - - -<h5><a name="XXVIII" id="XXVIII">XXVIII.</a></h5> - - -<h5>ACHROMATISM AND HYPERCHROMATISM.</h5> - - -<p class="para"><a id="a345">345</a> (<a href="#a285">285</a>, <a href="#a290">290</a>).</p> - -<p>It is possible to make the hyperchromatic and achromatic experiments -objectively as well as subjectively. After what has been already -stated, a short description of the method will suffice, especially as -we take it for granted that the compound prism before mentioned is in -the hands of the observer.</p> - -<p class="para"><a id="a346">346.</a></p> - -<p>Let the sun's image pass through an acute-angled prism of few degrees, -prepared from crown-glass, so that the spectrum be refracted upwards on -an opposite surface; the edges will appear coloured, according to the -constant law, namely, the violet and blue above and outside, the yellow -and yellow-red below and within the image. As the refracting angle of -this prism is undermost, let another proportionate prism of flint-glass -be placed against it, with its refracting angle uppermost. The sun's -image will by this means be again moved to its place, where, owing to -the excess of the colouring power of the prism of flint-glass, it will -still appear a little coloured, and, in consequence of the direction -in which it has been moved, the blue and violet<span class="pagenum"><a name="Page_146" id="Page_146">[Pg 146]</a></span> will now appear -underneath and outside, the yellow and yellow-red above and inside.</p> - -<p class="para"><a id="a347">347.</a></p> - -<p>If the whole image be now moved a little upwards by a proportionate -prism of crown-glass, the hyperchromatism will disappear, the sun's -image will be moved from its place, and yet will appear colourless.</p> - -<p class="para"><a id="a348">348.</a></p> - -<p>With an achromatic object-glass composed of three glasses, this -experiment may be made step by step, if we do not mind taking out the -glasses from their setting. The two convex glasses of crown-glass in -contracting the sun's image towards the focus, the concave glass of -flint-glass in dilating the image beyond it, exhibit at the edges the -usual colours. A convex glass united with a concave one exhibits the -colours according to the law of the latter. If all three glasses are -placed together, whether we contract the sun's image towards the focus, -or suffer it to dilate beyond the focus, coloured edges never appear, -and the achromatic effect intended by the optician is, in this case, -again attained.</p> - -<p class="para"><a id="a349">349.</a></p> - -<p>But as the crown-glass has always a greenish tint, and as a tendency -to this hue may be more<span class="pagenum"><a name="Page_147" id="Page_147">[Pg 147]</a></span> decided in large and strong object-glasses, -and under certain circumstances produce the compensatory red, -(which, however, in repeated experiments with several instruments of -this kind did not occur to us,) philosophers have resorted to the -most extraordinary modes of explaining such a result; and having -been compelled, in support of their system, theoretically to prove -the impossibility of achromatic telescopes, have felt a kind of -satisfaction in having some apparent ground for denying so great an -improvement. Of this, however, we can only treat circumstantially in -our historical account of these discoveries.</p> - - - -<hr class="chap" /> -<h5><a name="XXIX" id="XXIX">XXIX.</a></h5> - - -<h5>COMBINATION OF SUBJECTIVE AND OBJECTIVE EXPERIMENTS.</h5> - - -<p class="para"><a id="a350">350.</a></p> - -<p>Having shown above (<a href="#a318">318</a>) that refraction, considered objectively and -subjectively, must act in opposite directions, it will follow that if -we combine the experiments, the effects will reciprocally destroy each -other.</p> - -<p class="para"><a id="a351">351.</a></p> - -<p>Let the sun's image be thrown upwards on a<span class="pagenum"><a name="Page_148" id="Page_148">[Pg 148]</a></span> vertical plane, through -a horizontally-placed prism. If the prism is long enough to admit of -the spectator also looking through it, he will see the image elevated -by the objective refraction again depressed, and in the same place in -which it appeared without refraction.</p> - -<p class="para"><a id="a352">352.</a></p> - -<p>Here a remarkable case presents itself, but at the same time a natural -result of a general law. For since, as often before stated, the -objective sun's image thrown on the vertical plane is not an ultimate -or unchangeable state of the phenomenon, so in the above operation the -image is not only depressed when seen through the prism, but its edges -and borders are entirely robbed of their hues, and the spectrum is -reduced to a colourless circular form.</p> - -<p class="para"><a id="a353">353.</a></p> - -<p>By employing two perfectly similar prisms placed next each other, for -this experiment, we can transmit the sun's image through one, and look -through the other.</p> - -<p class="para"><a id="a354">354.</a></p> - -<p>If the spectator advances nearer with the prism through which he looks, -the image is again elevated, and by degrees becomes coloured according -to the law of the first prism. If he<span class="pagenum"><a name="Page_149" id="Page_149">[Pg 149]</a></span> again retires till he has brought -the image to the neutralized point, and then retires still farther -away, the image, which had become round and colourless, moves still -more downwards and becomes coloured in the opposite sense, so that -if we look through the prism and upon the refracted spectrum at the -same time, we see the same image coloured according to subjective and -objective laws.</p> - -<p class="para"><a id="a355">355.</a></p> - -<p>The modes in which this experiment may be varied are obvious. If the -refracting angle of the prism, through which the sun's image was -objectively elevated, is greater than that of the prism through which -the observer looks, he must retire to a much greater distance, in order -to depress the coloured image so low on the vertical plane that it -shall appear colourless, and <i>vice versâ</i>.</p> - -<p class="para"><a id="a356">356.</a></p> - -<p>It will be easily seen that we may exhibit achromatic and -hyperchromatic effects in a similar manner, and we leave it to the -amateur to follow out such researches more fully. Other complicated -experiments in which prisms and lenses are employed together, others -again, in which objective and subjective experiments are variously -intermixed, we reserve for a future<span class="pagenum"><a name="Page_150" id="Page_150">[Pg 150]</a></span> occasion, when it will be our -object to trace such effects to the simple phenomena with which we are -now sufficiently familiar.</p> - - - -<hr class="chap" /> -<h5><a name="XXX" id="XXX">XXX.</a></h5> - - -<h5>TRANSITION.</h5> - - -<p class="para"><a id="a357">357.</a></p> - -<p>In looking back on the description and analysis of dioptrical colours, -we do not repent either that we have treated them so circumstantially, -or that we have taken them into consideration before the other physical -colours, out of the order we ourselves laid down. Yet, before we quit -this branch of our inquiry, it may be as well to state the reasons that -have weighed with us.</p> - -<p class="para"><a id="a358">358.</a></p> - -<p>If some apology is necessary for having treated the theory of the -dioptrical colours, particularly those of the second class, so -diffusely, we should observe, that the exposition of any branch of -knowledge is to be considered partly with reference to the intrinsic -importance of the subject, and partly with reference to the particular -necessities of the time in which the<span class="pagenum"><a name="Page_151" id="Page_151">[Pg 151]</a></span> inquiry is undertaken. In our -own case we were forced to keep both these considerations constantly -in view. In the first place we had to state a mass of experiments with -our consequent convictions; next, it was our especial aim to exhibit -certain phenomena (known, it is true, but misunderstood, and above -all, exhibited in false connection,) in that natural and progressive -development which is strictly and truly conformable to observation; in -order that hereafter, in our polemical or historical investigations, -we might be enabled to bring a complete preparatory analysis to bear -on, and elucidate, our general view. The details we have entered into -were on this account unavoidable; they may be considered as a reluctant -consequence of the occasion. Hereafter, when philosophers will look -upon a simple principle as simple, a combined effect as combined; when -they will acknowledge the first elementary, and the second complicated -states, for what they are; then, indeed, all this statement may be -abridged to a narrower form; a labour which, should we ourselves -not be able to accomplish it, we bequeath to the active interest of -contemporaries and posterity.</p> - -<p class="para"><a id="a359">359.</a></p> - -<p>With respect to the order of the chapters, it should be remembered -that natural phenomena,<span class="pagenum"><a name="Page_152" id="Page_152">[Pg 152]</a></span> which are even allied to each other, are -not connected in any particular sequence or constant series; their -efficient causes act in a narrow circle, so that it is in some sort -indifferent what phenomenon is first or last considered; the main point -is, that all should be as far as possible present to us, in order that -we may embrace them at last from one point of view, partly according to -their nature, partly according to generally received methods.</p> - -<p class="para"><a id="a360">360.</a></p> - -<p>Yet, in the present particular instance, it may be asserted that the -dioptrical colours are justly placed at the head of the physical -colours; not only on account of their striking splendour and their -importance in other respects, but because, in tracing these to their -source, much was necessarily entered into which will assist our -subsequent enquiries.</p> - -<p class="para"><a id="a361">361.</a></p> - -<p>For, hitherto, light has been considered as a kind of abstract -principle, existing and acting independently; to a certain extent -self-modified, and on the slightest cause, producing colours out of -itself. To divert the votaries of physical science from this mode -of viewing the subject; to make them attentive to the fact, that in -prismatic and other appearances we have not to do<span class="pagenum"><a name="Page_153" id="Page_153">[Pg 153]</a></span> with light as an -uncircumscribed and modifying principle, but as circumscribed and -modified; that we have to do with a luminous image; with images or -circumscribed objects generally, whether light or dark: this was the -purpose we had in view, and such is the problem to be solved.</p> - -<p class="para"><a id="a362">362.</a></p> - -<p>All that takes place in dioptrical cases,—especially those of the -second class which are connected with the phenomena of refraction,—is -now sufficiently familiar to us, and will serve as an introduction to -what follows.</p> - -<p class="para"><a id="a363">363.</a></p> - -<p>Catoptrical appearances remind us of the physiological phenomena, but -as we ascribe a more objective character to the former, we thought -ourselves justified in classing them with the physical examples. It is -of importance, however, to remember that here again it is not light, in -an abstract sense, but a luminous image that we have to consider.</p> - -<p class="para"><a id="a364">364.</a></p> - -<p>In proceeding onwards to the paroptrical class, the reader, if duly -acquainted with the foregoing facts, will be pleased to find himself -once more in the region of circumscribed forms. The shadows of bodies, -especially, as secondary<span class="pagenum"><a name="Page_154" id="Page_154">[Pg 154]</a></span> images, so exactly accompanying the object, -will serve greatly to elucidate analogous appearances.</p> - -<p class="para"><a id="a365">365.</a></p> - -<p>We will not, however, anticipate these statements, but proceed as -heretofore in what we consider the regular course.</p> - - - -<hr class="chap" /> -<h5><a name="XXXI" id="XXXI">XXXI.</a></h5> - - -<h5>CATOPTRICAL COLOURS.</h5> - - -<p class="para"><a id="a366">366.</a></p> - -<p>Catoptrical colours are such as appear in consequence of a mirror-like -reflection. We assume, in the first place, that the light itself -as well as the surface from which it is reflected, is perfectly -colourless. In this sense the appearances in question come under the -head of physical colours. They arise in consequence of reflection, as -we found the dioptrical colours of the second class appear by means of -refraction. Without further general definitions, we turn our attention -at once to particular cases, and to the conditions which are essential -to the exhibition of these phenomena.</p> - -<p><span class="pagenum"><a name="Page_155" id="Page_155">[Pg 155]</a></span></p> - -<p class="para"><a id="a367">367.</a></p> - -<p>If we unroll a coil of bright steel-wire, and after suffering it to -spring confusedly together again, place it at a window in the light, -we shall see the prominent parts of the circles and convolutions -illumined, but neither resplendent nor iridescent. But if the sun -shines on the wire, this light will be condensed into a point, and we -perceive a small resplendent image of the sun, which, when seen near, -exhibits no colour. On retiring a little, however, and fixing the eyes -on this refulgent appearance, we discern several small mirrored suns, -coloured in the most varied manner; and although the impression is that -green and red predominate, yet, on a more accurate inspection, we find -that the other colours are also present.</p> - -<p class="para"><a id="a368">368.</a></p> - -<p>If we take an eye-glass, and examine the appearance through it, we -find the colours have vanished, as well as the radiating splendour in -which they were seen, and we perceive only the small luminous points, -the repeated images of the sun. We thus find that the impression is -subjective in its nature, and that the appearance is allied to those -which we have adverted to under the name of radiating halos (<a href="#a100">100</a>).</p> - -<p><span class="pagenum"><a name="Page_156" id="Page_156">[Pg 156]</a></span></p> - -<p class="para"><a id="a369">369.</a></p> - -<p>We can, however, exhibit this phenomenon objectively. Let a piece -of white paper be fastened beneath a small aperture in the lid of a -camera-obscura, and when the sun shines through this aperture, let -the confusedly-rolled steel-wire be held in the light, so that it be -opposite to the paper. The sun-light will impinge on and in the circles -of the wire, and will not, as in the concentrating lens of the eye, -display itself in a point; but, as the paper can receive the reflection -of the light in every part of its surface will be seen in hair-like -lines, which are also iridescent.</p> - -<p class="para"><a id="a370">370.</a></p> - -<p>This experiment is purely catoptrical; for as we cannot imagine that -the light penetrates the surface of the steel, and thus undergoes a -change, we are soon convinced that we have here a mere reflection -which, in its subjective character, is connected with the theory of -faintly acting lights, and the after-image of dazzling lights, and as -far as it can be considered objective, announces even in the minutest -appearances, a real effect, independent of the action and reaction of -the eye.</p> - -<p class="para"><a id="a371">371.</a></p> - -<p>We have seen that to produce these effects<span class="pagenum"><a name="Page_157" id="Page_157">[Pg 157]</a></span> not merely light but a -powerful light is necessary; that this powerful light again is not an -abstract and general quality, but a circumscribed light, a luminous -image. We can convince ourselves still further of this by analogous -cases.</p> - -<p class="para"><a id="a372">372.</a></p> - -<p>A polished surface of silver placed in the sun reflects a dazzling -light, but in this case no colour is seen. If, however, we slightly -scratch the surface, an iridescent appearance, in which green and red -are conspicuous, will be exhibited at a certain angle. In chased and -carved metals the effect is striking: yet it may be remarked throughout -that, in order to its appearance, some form, some alternation of light -and dark must co-operate with the reflection; thus a window-bar, -the stem of a tree, an accidentally or purposely interposed object -produces a perceptible effect. This appearance, too, may be exhibited -objectively in the camera-obscura.</p> - -<p class="para"><a id="a373">373.</a></p> - -<p>If we cause a polished plated surface to be so acted on by aqua fortis -that the copper within is touched, and the surface itself thus rendered -rough, and if the sun's image be then reflected from it, the splendour -will be reverberated from every minutest prominence, and the surface -will appear iridescent. So, if we hold a sheet of<span class="pagenum"><a name="Page_158" id="Page_158">[Pg 158]</a></span> black unglazed paper -in the sun, and look at it attentively, it will be seen to glisten in -its minutest points with the most vivid colours.</p> - -<p class="para"><a id="a374">374.</a></p> - -<p>All these examples are referable to the same conditions. In the first -case the luminous image is reflected from a thin line; in the second -probably from sharp edges; in the third from very small points. In all -a very powerful and circumscribed light is requisite. For all these -appearances of colour again it is necessary that the eye should be at a -due distance from the reflecting points.</p> - -<p class="para"><a id="a375">375.</a></p> - -<p>If these observations are made with the microscope, the appearance -will be greatly increased in force and splendour, for we then see the -smallest portion of the surfaces, lit by the sun, glittering in these -colours of reflection, which, allied to the hues of refraction, now -attain their highest degree of brilliancy. In such cases we may observe -a vermiform iridescence on the surface of organic bodies, the further -description of which will be given hereafter.</p> - -<p class="para"><a id="a376">376.</a></p> - -<p>Lastly, the colours which are chiefly exhibited<span class="pagenum"><a name="Page_159" id="Page_159">[Pg 159]</a></span> in reflection are red -and green, whence we may infer that the linear appearance especially -consists of a thin line of red, bounded by blue on one side and yellow -on the other. If these triple lines approach very near together, the -intermediate space must appear green; a phenomenon which will often -occur to us as we proceed.</p> - -<p class="para"><a id="a377">377.</a></p> - -<p>We frequently meet with these colours in nature. The colours of the -spider's web might be considered exactly of the same class with those -reflected from the steel wire, except that the non-translucent quality -of the former is not so certain as in the case of steel; on which -account some have been inclined to class the colours of the spider's -web with the phenomena of refraction.</p> - -<p class="para"><a id="a378">378.</a></p> - -<p>In mother-of-pearl we perceive infinitely fine organic fibres and -lamellæ in juxta-position, from which, as from the scratched silver -before alluded to, varied colours, but especially red and green, may -arise.</p> - -<p class="para"><a id="a379">379.</a></p> - -<p>The changing colours of the plumage of birds may also be mentioned -here, although in all organic<span class="pagenum"><a name="Page_160" id="Page_160">[Pg 160]</a></span> instances a chemical principle -and an adaptation of the colour to the structure may be assumed; -considerations to which we shall return in treating of chemical colours.</p> - -<p class="para"><a id="a380">380.</a></p> - -<p>That the appearances of objective halos also approximate catoptrical -phenomena will be readily admitted, while we again do not deny that -refraction as well may here come into the account. For the present -we restrict ourselves to one or two observations; hereafter we may -be enabled to make a fuller application of general principles to -particular examples.</p> - -<p class="para"><a id="a381">381.</a></p> - -<p>We first call to mind the yellow and red circles produced on a white or -grey wall by a light placed near it (<a href="#a88">88</a>). Light when reflected appears -subdued, and a subdued light excites the impression of yellow, and -subsequently of red.</p> - -<p class="para"><a id="a382">382.</a></p> - -<p>Let the wall be illumined by a candle placed quite close to it. The -farther the light is diffused the fainter it becomes; but it is still -the effect of the flame, the continuation of its action, the dilated -effect of its image. We might, therefore, very fairly call these -circles<span class="pagenum"><a name="Page_161" id="Page_161">[Pg 161]</a></span> reiterated images, because they constitute the successive -boundaries of the action of the light, and yet at the same time only -present an extended image of the flame.</p> - -<p class="para"><a id="a383">383.</a></p> - -<p>If the sky is white and luminous round the sun owing to the atmosphere -being filled with light vapours; if mists or clouds pass before the -moon, the reflection of the disk mirrors itself in them; the halos we -then perceive are single or double, smaller or greater, sometimes very -large, often colourless, sometimes coloured.</p> - -<p class="para"><a id="a384">384.</a></p> - -<p>I witnessed a very beautiful halo round the moon the 15th of November, -1799, when the barometer stood high; the sky was cloudy and vapoury. -The halo was completely coloured, and the circles were concentric round -the light as in subjective halos. That this halo was objective I was -presently convinced by covering the moon's disk, when the same circles -were nevertheless perfectly visible.</p> - -<p class="para"><a id="a385">385.</a></p> - -<p>The different extent of the halos appears to have a relation with the -proximity or distance of the vapour from the eye of the observer.</p> - -<p><span class="pagenum"><a name="Page_162" id="Page_162">[Pg 162]</a></span></p> - -<p class="para"><a id="a386">386.</a></p> - -<p>As window-panes lightly breathed upon increase the brilliancy of -subjective halos, and in some degree give them an objective character, -so, perhaps, with a simple contrivance in winter, during a quickly -freezing temperature, a more exact definition of this might be arrived -at.</p> - -<p class="para"><a id="a387">387.</a></p> - -<p>How much reason we have in considering these circles to insist on the -<i>image</i> and its effects, is apparent in the phenomenon of the so-called -double suns. Similar double images always occur in certain points -of halos and circles, and only present in a circumscribed form what -takes place in a more general way in the whole circle. All this will -be more conveniently treated in connexion with the appearance of the -rainbow.—<a href="#NOTE_Q">Note Q</a>.</p> - -<p class="para"><a id="a388">388.</a></p> - -<p>In conclusion it is only necessary to point out the affinity between -the catoptrical and paroptical colours.</p> - -<p>We call those paroptical colours which appear when the light passes -by the edge of an opaque colourless body. How nearly these are allied -to the dioptrical colours of the second class will be easily seen by -those who are convinced with us that the colours of refraction<span class="pagenum"><a name="Page_163" id="Page_163">[Pg 163]</a></span> -take place only at the edges of objects. The affinity again between the -catoptrical and paroptical colours will be evident in the following -chapter.</p> - - - -<hr class="chap" /> -<h5><a name="XXXII" id="XXXII">XXXII.</a></h5> - -<h5> -PAROPTICAL COLOURS.</h5> - - -<p class="para"><a id="a389">389.</a></p> - -<p>The paroptical colours have been hitherto called peri-optical, because -a peculiar effect of light was supposed to take place as it were round -the object, and was ascribed to a certain flexibility of the light to -and from the object.</p> - -<p class="para"><a id="a390">390.</a></p> - -<p>These colours again may be divided into subjective and objective, -because they appear partly without us, as it were, painted on surfaces, -and partly within us, immediately on the retina. In this chapter we -shall find it more to our purpose to take the objective cases first, -since the subjective are so closely connected with other appearances -already known to us, that it is hardly possible to separate them.</p> - -<p class="para"><a id="a391">391.</a></p> - -<p>The paroptical colours then are so called because<span class="pagenum"><a name="Page_164" id="Page_164">[Pg 164]</a></span> the light must pass -by an outline or edge to produce them. They do not, however, always -appear in this case; to produce the effect very particular conditions -are necessary besides.</p> - -<p class="para"><a id="a392">392.</a></p> - -<p>It is also to be observed that in this instance again light does not -act as an abstract diffusion (361), the sun shines towards an edge. -The volume of light poured from the sun-image passes by the edge of -a substance, and occasions shadows. Within these shadows we shall -presently find colours appear.</p> - -<p class="para"><a id="a393">393.</a></p> - -<p>But, above all, we should make the experiments and observations that -bear upon our present inquiry in the fullest light. We, therefore, -place the observer in the open air before we conduct him to the limits -of a dark room.</p> - -<p class="para"><a id="a394">394.</a></p> - -<p>A person walking in sun-shine in a garden, or on any level path, may -observe that his shadow only appears sharply defined next the foot on -which he rests; farther from this point, especially round the head, it -melts away into the bright ground. For as the sun-light proceeds not -only from the middle of the sun, but also acts cross-wise from the two -extremes of every<span class="pagenum"><a name="Page_165" id="Page_165">[Pg 165]</a></span> diameter, an objective parallax takes place which -produces a half-shadow on both sides of the object.</p> - -<p class="para"><a id="a395">395.</a></p> - -<p>If the person walking raises and spreads his hand, he distinctly sees -in the shadow of each finger the diverging separation of the two -half-shadows outwards, and the diminution of the principal shadow -inwards, both being effects of the cross action of the light.</p> - -<p class="para"><a id="a396">396.</a></p> - -<p>This experiment may be repeated and varied before a smooth wall, -with rods of different thicknesses, and again with balls; we shall -always find that the farther the object is removed from the surface of -the wall, the more the weak double shadow spreads, and the more the -forcible main shadow diminishes, till at last the main shadow appears -quite effaced, and even the double shadows become so faint, that they -almost disappear; at a still greater distance they are, in fact, -imperceptible.</p> - -<p class="para"><a id="a397">397.</a></p> - -<p>That this is caused by the cross-action of the light we may easily -convince ourselves; for the shadow of a pointed object plainly exhibits -two points. We must thus never lose sight of the<span class="pagenum"><a name="Page_166" id="Page_166">[Pg 166]</a></span> fact that in this -case the whole sun-image acts, produces shadows, changes them to double -shadows, and finally obliterates them.</p> - -<p class="para"><a id="a398">398.</a></p> - -<p>Instead of solid bodies let us now take openings cut of various given -sizes next each other, and let the sun shine through them on a plane -surface at some little distance; we shall find that the bright image -produced by the sun on the surface, is larger than the opening; this -is because one edge of the sun shines towards the opposite edge of the -opening, while the other edge of the disk is excluded on that side. -Hence the bright image is more weakly lighted towards the edges.</p> - -<p class="para"><a id="a399">399.</a></p> - -<p>If we take square openings of any size we please, we shall find that -the bright image on a surface nine feet from the opening, is on every -side about an inch larger than the opening; thus nearly corresponding -with the angle of the apparent diameter of the sun.</p> - -<p class="para"><a id="a400">400.</a></p> - -<p>That the brightness should gradually diminish towards the edges of the -image is quite natural, for at last only a minimum of the light can -act cross-wise from the sun's circumference through the edge of the -aperture.</p> - -<p><span class="pagenum"><a name="Page_167" id="Page_167">[Pg 167]</a></span></p> - -<p class="para"><a id="a401">401.</a></p> - -<p>Thus we here again see how much reason we have in actual observation to -guard against the assumption of parallel rays, bundles and fasces of -rays, and the like hypothetical notions.</p> - -<p class="para"><a id="a402">402.</a></p> - -<p>We might rather consider the splendour of the sun, or of any light, -as an infinite specular multiplication of the circumscribed luminous -image, whence it may be explained that all square openings through -which the sun shines, at certain distances, according as the apertures -are greater or smaller, must give a round image of light.</p> - -<p class="para"><a id="a403">403.</a></p> - -<p>The above experiments may be repeated through openings of various -shapes and sizes, and the same effect will always take place at -proportionate distances. In all these cases, however, we may still -observe that in a full light and while the sun merely shines past an -edge, no colour is apparent.</p> - -<p class="para"><a id="a404">404.</a></p> - -<p>We therefore proceed to experiments with a subdued light, which is -essential to the appearance of colour. Let a small opening be made in -the window-shutter of a dark room; let the<span class="pagenum"><a name="Page_168" id="Page_168">[Pg 168]</a></span> crossing sun-light which -enters, be received on a surface of white paper, and we shall find that -the smaller the opening is, the dimmer the light image will be. This is -quite obvious, because the paper does not receive light from the whole -sun, but partially from single points of its disk.</p> - -<p class="para"><a id="a405">405.</a></p> - -<p>If we look attentively at this dim image of the sun, we find it still -dimmer towards the outlines where a yellow border is perceptible. The -colour is still more apparent if a vapour or a transparent cloud passes -before the sun, thus subduing and dimming its brightness. The halo on -the wall, the effect of the decreasing brightness of a light placed -near it, is here forced on our recollection. (<a href="#a88">88</a>.)</p> - -<p class="para"><a id="a406">406.</a></p> - -<p>If we examine the image more accurately, we perceive that this yellow -border is not the only appearance of colour; we can see, besides, a -bluish circle, if not even a halo-like repetition of the coloured -border. If the room is quite dark, we discern that the sky next the -sun also has its effect: we see the blue sky, nay, even the whole -landscape, on the paper, and are thus again convinced that as far as -regards the sun, we have here only to do with a luminous image.</p> - -<p><span class="pagenum"><a name="Page_169" id="Page_169">[Pg 169]</a></span></p> - -<p class="para"><a id="a407">407.</a></p> - -<p>If we take a somewhat larger square opening, so large that the image -of the sun shining through it does not immediately become round, we -may distinctly observe the half-shadows of every edge or side, the -junction of these in the corners, and their colours; just as in the -above-mentioned appearance with the round opening.</p> - -<p class="para"><a id="a408">408.</a></p> - -<p>We have now subdued a parallactic light by causing it to shine through -small apertures, but we have not taken from it its parallactic -character; so that it can produce double shadows of bodies, although -with diminished power. These double shadows which we have hitherto -been describing, follow each other in light and dark, coloured and -colourless circles, and produce repeated, nay, almost innumerable -halos. These effects have been often represented in drawings and -engravings. By placing needles, hairs, and other small bodies, in the -subdued light, the numerous halo-like double shadows may be increased; -thus observed, they have been ascribed to an alternating flexile action -of the light, and the same assumption has been employed to explain the -obliteration of the central shadow, and the appearance of a light in -the place of the dark.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_170" id="Page_170">[Pg 170]</a></span></p> - -<p class="para"><a id="a409">409.</a></p> - -<p>For ourselves, we maintain that these again are parallactic double -shadows, which appear edged with coloured borders and halos.</p> - -<p class="para"><a id="a410">410.</a></p> - -<p>After having seen and investigated the foregoing phenomena, we -can proceed to the experiments with knife-blades,<a name="FNanchor_1_40" id="FNanchor_1_40"></a><a href="#Footnote_1_40" class="fnanchor">[1]</a> exhibiting -effects which may be referred to the contact and parallactic mutual -intersection of the half-shadows and halos already familiar to us.</p> - -<p class="para"><a id="a411">411.</a></p> - -<p>Lastly, the observer may follow out the experiments with hairs, -needles, and wires, in the half-light produced as before described by -the sun, as well as in that derived from the blue sky, and indicated on -the white paper. He will thus make himself still better acquainted with -the true nature of this phenomenon.</p> - -<p class="para"><a id="a412">412.</a></p> - -<p>But since in these experiments everything depends on our being -persuaded of the parallactic action of the light, we can make this more -evident by means of two sources of light, the two shadows from which -intersect each other, and may be altogether separated. By day this may -be contrived with two small<span class="pagenum"><a name="Page_171" id="Page_171">[Pg 171]</a></span> openings in a window-shutter; by night, -with two candles. There are even accidental effects in interiors, on -opening and closing shutters, by means of which we can better observe -these appearances than with the most careful apparatus. But still, -all and each of these may be reduced to experiment by preparing a box -which the observer can look into from above, and gradually diminishing -the openings after having caused a double light to shine in. In this -case, as might be expected, the coloured shadow, considered under the -physiological colours, appears very easily.</p> - -<p class="para"><a id="a413">413.</a></p> - -<p>It is necessary to remember, generally, what has been before stated -with regard to the nature of double shadows, half-lights, and the like. -Experiments also should especially be made with different shades of -grey placed next each other, where every stripe will appear light by a -darker, and dark by a lighter stripe next it. If at night, with three -or more lights, we produce shadows which cross each other successively, -we can observe this phenomenon very distinctly, and we shall be -convinced that the physiological case before more fully treated, here -comes into the account (<a href="#a38">38</a>).</p> - -<p class="para"><a id="a414">414.</a></p> - -<p>To what extent the appearances that accompany<span class="pagenum"><a name="Page_172" id="Page_172">[Pg 172]</a></span> the paroptical colours, -may be derived from the doctrine of subdued lights, from half-shadows, -and from the physiological disposition of the retina, or whether we -shall be forced to take refuge in certain intrinsic qualities of light, -as has hitherto been done, time may teach. Suffice it here to have -pointed out the conditions under which the paroptical colours appear, -and we may hope that our allusion to their connexion with the facts -before adduced by us will not remain unnoticed by the observers of -nature.</p> - -<p class="para"><a id="a415">415.</a></p> - -<p>The affinity of the paroptical colours with the dioptrical of the -second class will also be readily seen and followed up by every -reflecting investigator. Here, as in those instances, we have to do -with edges or boundaries; here, as in those instances, with a light, -which appears at the outline. How natural, therefore, it is to conclude -that the paroptical effects may be heightened, strengthened, and -enriched by the dioptrical. Since, however, the luminous image actually -shines through the medium, we can here only have to do with objective -cases of refraction: it is these which are strictly allied to the -paroptical cases. The subjective cases of refraction, where we see -objects through the medium, are quite distinct from the paroptical.<span class="pagenum"><a name="Page_173" id="Page_173">[Pg 173]</a></span> -We have already recommended them on account of their clearness and -simplicity.</p> - -<p class="para"><a id="a416">416.</a></p> - -<p>The connexion between the paroptical colours and the catoptrical may -be already inferred from what has been said: for as the catoptrical -colours only appear on scratches, points, steel-wire, and delicate -threads, so it is nearly the same case as if the light shone past an -edge. The light must always be reflected from an edge in order to -produce colour. Here again, as before pointed out, the partial action -of the luminous image and the subduing of the light are both to be -taken into the account.</p> - -<p class="para"><a id="a417">417.</a></p> - -<p>We add but few observations on the subjective paroptical colours, -because these may be classed partly with the physiological colours, -partly with the dioptrical of the second order. The greater part hardly -seem to belong here, but, when attentively considered, they still -diffuse a satisfactory light over the whole doctrine, and establish its -connexion.</p> - -<p class="para"><a id="a418">418.</a></p> - -<p>If we hold a ruler before the eyes so that the flame of a light just -appears above it, we see the ruler as it were indented and notched -at the<span class="pagenum"><a name="Page_174" id="Page_174">[Pg 174]</a></span> place where the light appears. This seems deducible from the -expansive power of light acting on the retina (<a href="#a18">18</a>).</p> - -<p class="para"><a id="a419">419.</a></p> - -<p>The same phenomenon on a large scale is exhibited at sun-rise; for when -the orb appears distinctly, but not too powerfully, so that we can -still look at it, it always makes a sharp indentation in the horizon.</p> - -<p class="para"><a id="a420">420.</a></p> - -<p>If, when the sky is grey, we approach a window, so that the dark cross -of the window-bars be relieved on the sky; if after fixing the eyes on -the horizontal bar we bend the head a little forward; on half closing -the eyes as we look up, we shall presently perceive a bright yellow-red -border under the bar, and a bright light-blue one above it. The duller -and more monotonous the grey of the sky, the more dusky the room, and, -consequently, the more previously unexcited the eye, the livelier the -appearance will be; but it may be seen by an attentive observer even in -bright daylight.</p> - -<p class="para"><a id="a421">421.</a></p> - -<p>If we move the head backwards while half closing the eyes, so that the -horizontal bar be seen below, the phenomenon will appear reversed.<span class="pagenum"><a name="Page_175" id="Page_175">[Pg 175]</a></span> The -upper edge will appear yellow, the under edge blue.</p> - -<p class="para"><a id="a422">422.</a></p> - -<p>Such observations are best made in a dark room. If white paper is -spread before the opening where the solar microscope is commonly -fastened, the lower edge of the circle will appear blue, the upper -yellow, even while the eyes are quite open, or only by half-closing -them so far that a halo no longer appears round the white. If the head -is moved backwards the colours are reversed.</p> - -<p class="para"><a id="a423">423.</a></p> - -<p>These phenomena seem to prove that the humours of the eye are in fact -only really achromatic in the centre where vision takes place, but that -towards the circumference, and in unusual motions of the eyes, as in -looking horizontally when the head is bent backwards or forwards, a -chromatic tendency remains, especially when distinctly relieved objects -are thus looked at. Hence such phenomena may be considered as allied to -the dioptrical colours of the second class.</p> - -<p class="para"><a id="a424">424.</a></p> - -<p>Similar colours appear if we look on black and white objects, through a -pin-hole in a card.<span class="pagenum"><a name="Page_176" id="Page_176">[Pg 176]</a></span> Instead of a white object we may take the minute -light aperture in the tin plate of a camera obscura, as prepared for -paroptical experiments.</p> - -<p class="para"><a id="a425">425.</a></p> - -<p>If we look through a tube, the farther end of which is contracted or -variously indented, the same colours appear.</p> - -<p class="para"><a id="a426">426.</a></p> - -<p>The following phenomena appear to me to be more nearly allied to the -paroptical appearances. If we hold up a needle near the eye, the point -appears double. A particularly remarkable effect again is produced if -we look towards a grey sky through the blades of knives prepared for -paroptical experiments. We seem to look through a gauze; a multitude of -threads appear to the eye; these are in fact only the reiterated images -of the sharp edges, each of which is successively modified by the next, -or perhaps modified in a parallactic sense by the oppositely acting -one, the whole mass being thus changed to a thread-like appearance.</p> - -<p class="para"><a id="a427">427.</a></p> - -<p>Lastly, it is to be remarked that if we look through the blades towards -a minute light in<span class="pagenum"><a name="Page_177" id="Page_177">[Pg 177]</a></span> the window-shutter, coloured stripes and halos -appear on the retina as on the paper.</p> - -<p class="para"><a id="a428">428.</a></p> - -<p>The present chapter may be here terminated, the less reluctantly, -as a friend has undertaken to investigate this subject by further -experiments. In our recapitulation, in the description of the -plates and apparatus, we hope hereafter to give an account of his -observations.<a name="FNanchor_2_41" id="FNanchor_2_41"></a><a href="#Footnote_2_41" class="fnanchor">[2]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_40" id="Footnote_1_40"></a><a href="#FNanchor_1_40"><span class="label">[1]</span></a> See Newton's Optics, book iii.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_41" id="Footnote_2_41"></a><a href="#FNanchor_2_41"><span class="label">[2]</span></a> The observations here alluded to never appeared.</p></div> - - -<hr class="chap" /> - -<h5><a name="XXXIII" id="XXXIII">XXXIII.</a></h5> - - -<h5>EPOPTICAL COLOURS.</h5> - - -<p class="para"><a id="a429">429.</a></p> - -<p>We have hitherto had to do with colours which appear with vivacity, but -which immediately vanish again when certain conditions cease. We have -now to become acquainted with others, which it is true are still to be -considered as transient, but which, under certain circumstances, become -so fixed that, even after the conditions which first occasioned their -appearance cease, they still remain, and thus constitute<span class="pagenum"><a name="Page_178" id="Page_178">[Pg 178]</a></span> the link -between the physical and the chemical colours.</p> - -<p class="para"><a id="a430">430.</a></p> - -<p>They appear from various causes on the surface of a colourless body, -originally, without communication, die or immersion (βαφή); and we now -proceed to trace them, from their faintest indication to their most -permanent state, through the different conditions of their appearance, -which for easier survey we here at once summarily state.</p> - -<p class="para"><a id="a431">431.</a></p> - -<p>First condition.—The contact of two smooth surfaces of hard -transparent bodies.</p> - -<p>First case: if masses or plates of glass, or if lenses are pressed -against each other.</p> - -<p>Second case: if a crack takes place in a solid mass of glass, chrystal, -or ice.</p> - -<p>Third case: if lamellæ of transparent stones become separated.</p> - -<p>Second condition.—If a surface of glass or a polished stone is -breathed upon.</p> - -<p>Third condition.—The combination of the two last; first, breathing on -the glass, then placing another plate of glass upon it, thus exciting -the colours by pressure; then removing the upper glass, upon which the -colours begin to fade and vanish with the breath.</p> - -<p><span class="pagenum"><a name="Page_179" id="Page_179">[Pg 179]</a></span></p> - -<p>Fourth condition.—Bubbles of various liquids, soap, chocolate, beer, -wine, fine glass bubbles.</p> - -<p>Fifth condition.—Very fine pellicles and lamellæ, produced by the -decomposition of minerals and metals. The pellicles of lime, the -surface of stagnant water, especially if impregnated with iron, and -again pellicles of oil on water, especially of varnish on aqua fortis.</p> - -<p>Sixth condition.—If metals are heated; the operation of imparting -tints to steel and other metals.</p> - -<p>Seventh condition.—If the surface of glass is beginning to decompose.</p> - -<p class="para"><a id="a432">432.</a></p> - -<p>First condition, first case. If two convex glasses, or a convex and -plane glass, or, best of all, a convex and concave glass come in -contact, concentric coloured circles appear. The phenomenon exhibits -itself immediately on the slightest pressure, and may then be gradually -carried through various successive states. We will describe the -complete appearance at once, as we shall then be better enabled to -follow the different states through which it passes.</p> - -<p class="para"><a id="a433">433.</a></p> - -<p>The centre is colourless; where the glasses are, so to speak, united -in one by the strongest pressure, a dark grey point appears with a -silver<span class="pagenum"><a name="Page_180" id="Page_180">[Pg 180]</a></span> white space round it: then follow, in decreasing distances, -various insulated rings, all consisting of three colours, which are -in immediate contact with each other. Each of these rings, of which -perhaps three or four might be counted, is yellow on the inner side, -blue on the outer, and red in the centre. Between two rings there -appears a silver white interval. The rings which are farthest from the -centre are always nearer together: they are composed of red and green -without a perceptible white space between them.</p> - -<p class="para"><a id="a434">434.</a></p> - -<p>We will now observe the appearances in their gradual formation, -beginning from the slightest pressure.</p> - -<p class="para"><a id="a435">435.</a></p> - -<p>On the slightest pressure the centre itself appears of a green colour. -Then follow as far as the concentric circles extend, red and green -rings. They are wide, accordingly, and no trace of a silver white -space is to be seen between them. The green is produced by the blue of -an imperfectly developed circle, mixing with the yellow of the first -circle. All the remaining circles are, in this slight contact, broad; -their yellow and blue edges mix together, thus producing a beautiful -green. The red, however, of<span class="pagenum"><a name="Page_181" id="Page_181">[Pg 181]</a></span> each circle, remains pure and untouched; -hence the whole series is composed of these two colours.</p> - -<p class="para"><a id="a436">436.</a></p> - -<p>A somewhat stronger pressure separates the first circle by a slight -interval from the imperfectly developed one: it is thus detached, and -may be said to appear in a complete state. The centre is now a blue -point; for the yellow of the first circle is now separated from this -central point by a silver white space. From the centre of the blue a -red appears, which is thus, in all cases, bounded on the outside by -its blue edge. The second and third rings from the centre are quite -detached. Where deviations from this order present themselves, the -observer will be enabled to account for them, from what has been or -remains to be stated.</p> - -<p class="para"><a id="a437">437.</a></p> - -<p>On a stronger pressure the centre becomes yellow; this yellow is -surrounded by a red and blue edge: at last, the yellow also retires -from the centre; the innermost circle is formed and is bounded with -yellow. The whole centre itself now appears silver white, till at last, -on the strongest pressure, the dark point appears, and the phenomenon, -as described at first, is complete.</p> - -<p><span class="pagenum"><a name="Page_182" id="Page_182">[Pg 182]</a></span></p> - -<p class="para"><a id="a438">438.</a></p> - -<p>The relative size of the concentric circles and their intervals depends -on the form of the glasses which are pressed together.</p> - -<p class="para"><a id="a439">439.</a></p> - -<p>We remarked above, that the coloured centre is, in fact, an undeveloped -circle. It is, however, often found, on the slightest pressure, that -several undeveloped circles exist there, as it were, in the germ; these -can be successively developed before the eye of the observer.</p> - -<p class="para"><a id="a440">440.</a></p> - -<p>The regularity of these rings is owing to the form of the convex -glasses, and the diameter of the coloured appearance depends on the -greater or lesser section of a circle on which a lens is polished. We -easily conclude from this, that by pressing plane glasses together, -irregular appearances only will be produced; the colours, in fact, -undulate like watered silks, and spread from the point of pressure in -all directions. Yet, the phenomenon as thus exhibited is much more -splendid than in the former instance, and cannot fail to strike every -spectator. If we make the experiment in this mode, we shall distinctly -see, as in the other case, that, on a slight pressure, the green and -red waves appear; on a stronger, stripes of blue, red, and yellow, -become detached.<span class="pagenum"><a name="Page_183" id="Page_183">[Pg 183]</a></span> At first, the outer sides of these stripes touch; on -increased pressure they are separated by a silver white space.</p> - -<p class="para"><a id="a441">441.</a></p> - -<p>Before we proceed to a further description of this phenomenon, we may -point out the most convenient mode of exhibiting it. Place a large -convex glass on a table near the window; upon this glass lay a plate -of well-polished mirror-glass, about the size of a playing-card, and -the mere weight of the plate will press sufficiently to produce one -or other of the phenomena above described. So, also, by the different -weight of plates of glass, by other accidental circumstances, for -instance, by slipping the plate on the side of the convex glass where -the pressure cannot be so strong as in the centre, all the gradations -above described can be produced in succession.</p> - -<p class="para"><a id="a442">442.</a></p> - -<p>In order to observe the phenomenon it is necessary to look obliquely -on the surface where it appears. But, above all, it is to be remarked -that by stooping still more, and looking at the appearance under a more -acute angle, the circles not only grow larger but other circles are -developed from the centre, of which no trace is to be discovered when -we look perpendicularly, even through the strongest magnifiers.</p> - -<p><span class="pagenum"><a name="Page_184" id="Page_184">[Pg 184]</a></span></p> - -<p class="para"><a id="a443">443.</a></p> - -<p>In order to exhibit the phenomenon in its greatest beauty, the utmost -attention should be paid to the cleanness of the glasses. If the -experiment is made with plate-glass adapted for mirrors, the glass -should be handled with gloves. The inner surfaces, which must come in -contact with the utmost nicety, may be most conveniently cleaned before -the experiment, and the outer surfaces should be kept clean while the -pressure is increased.</p> - -<p class="para"><a id="a444">444.</a></p> - -<p>From what has been said it will be seen that an exact contact of two -smooth surfaces is necessary. Polished glasses are best adapted for the -purpose. Plates of glass exhibit the most brilliant colours when they -fit closely together, and for this reason the phenomenon will increase -in beauty if exhibited under an air-pump, by exhausting the air.</p> - -<p class="para"><a id="a445">445.</a></p> - -<p>The appearance of the coloured rings may be produced in the greatest -perfection by placing a convex and concave glass together which have -been ground on similar segments of circles. I have never seen the -effect more brilliant than with the object-glass of an achromatic -telescope,<span class="pagenum"><a name="Page_185" id="Page_185">[Pg 185]</a></span> in which the crown-glass and flint-glass were necessarily -in the closest contact.</p> - -<p class="para"><a id="a446">446.</a></p> - -<p>A remarkable appearance takes place when dissimilar surfaces are -pressed together; for example, a polished crystal and a plate of -glass. The appearance does not at all exhibit itself in large flowing -waves, as in the combination of glass with glass, but it is small and -angular, and, as it were, disjointed: thus it appears that the surface -of the polished crystal, which consists of infinitely small sections of -lamellæ, does not come so uninterruptedly in contact with the glass as -another glass-plate would.</p> - -<p class="para"><a id="a447">447.</a></p> - -<p>The appearance of colour vanishes on the strongest pressure, which so -intimately unites the two surfaces that they appear to make but one -substance. It is this which occasions the dark centre, because the -pressed lens no longer reflects any light from this point, for the -very same point, when seen against the light, is perfectly clear and -transparent. On relaxing the pressure, the colours, in like manner, -gradually diminish, and disappear entirely when the surfaces are -separated.</p> - -<p><span class="pagenum"><a name="Page_186" id="Page_186">[Pg 186]</a></span></p> - -<p class="para"><a id="a448">448.</a></p> - -<p>These same appearances occur in two similar cases. If entirely -transparent masses become partially separated, the surfaces of their -parts being still sufficiently in contact, we see the same circles and -waves more or less. They may be produced in great beauty by plunging a -hot mass of glass in water; the different fissures and cracks enabling -us to observe the colours in various forms. Nature often exhibits the -same phenomena in split rock crystals.</p> - -<p class="para"><a id="a449">449.</a></p> - -<p>This appearance, again, frequently displays itself in the mineral world -in those kinds of stone which by nature have a tendency to exfoliate. -These original lamellæ are, it is true, so intimately united, that -stones of this kind appear altogether transparent and colourless, yet, -the internal layers become separated, from various accidental causes, -without altogether destroying the contact: thus the appearance, which -is now familiar to us by the foregoing description, often occurs in -nature, particularly in calcareous spars; the specularis, adularia, and -other minerals of similar structure. Hence it shows an ignorance of the -proximate causes of an appearance so often accidentally produced, to -consider it so important in mineralogy, and to attach especial value to -the specimens exhibiting it.</p> - -<p><span class="pagenum"><a name="Page_187" id="Page_187">[Pg 187]</a></span></p> - -<p class="para"><a id="a450">450.</a></p> - -<p>We have yet to speak of the very remarkable inversion of this -appearance, as related by men of science. If, namely, instead of -looking at the colours by a reflected light, we examine them by a -transmitted light, the opposite colours are said to appear, and in -a mode corresponding with that which we have before described as -physiological; the colours evoking each other. Instead of blue, we -should thus see red-yellow; instead of red, green, &c., and <i>vice -versâ</i>. We reserve experiments in detail, the rather as we have -ourselves still some doubts on this point.</p> - -<p class="para"><a id="a451">451.</a></p> - -<p>If we were now called upon to give some general explanation of these -epoptical colours, as they appear under the first condition, and to -show their connexion with the previously detailed physical phenomena, -we might proceed to do so as follows:—</p> - -<p class="para"><a id="a452">452.</a></p> - -<p>The glasses employed for the experiments are to be regarded as the -utmost possible practical approach to transparence. By the intimate -contact, however, occasioned by the pressure applied to them, their -surfaces, we are persuaded, immediately become in a very slight -degree dimmed. Within this semi-transparence<span class="pagenum"><a name="Page_188" id="Page_188">[Pg 188]</a></span> the colours immediately -appear, and every circle comprehends the whole scale; for when the two -opposites, yellow and blue, are united by their red extremities, pure -red appears: the green, on the other hand, as in prismatic experiments, -when yellow and blue touch.</p> - -<p class="para"><a id="a453">453.</a></p> - -<p>We have already repeatedly found that where colour exists at all, the -whole scale is soon called into existence; a similar principle may be -said to lurk in the nature of every physical phenomenon; it already -follows, from the idea of polar opposition, from which an elementary -unity or completeness results.</p> - -<p class="para"><a id="a454">454.</a></p> - -<p>The fact that a colour exhibited by transmitted light is different -from that displayed by reflected light, reminds us of those dioptrical -colours of the first class which we found were produced precisely in -the same way through semi-opacity. That here, too, a diminution of -transparency exists there can scarcely be a doubt; for the adhesion -of the perfectly smooth plates of glass (an adhesion so strong that -they remain hanging to each other) produces a degree of union which -deprives each of the two surfaces, in some degree, of its smoothness -and transparence. The fullest proof may, however,<span class="pagenum"><a name="Page_189" id="Page_189">[Pg 189]</a></span> be found in the -fact that in the centre, where the lens is most strongly pressed on -the other glass, and where a perfect union is accomplished, a complete -transparence takes place, in which we no longer perceive any colour. -All this may be hereafter confirmed in a recapitulation of the whole.</p> - -<p class="para"><a id="a455">455.</a></p> - -<p>Second condition.—If after breathing on a plate of glass, the breath -is merely wiped away with the finger, and if we then again immediately -breathe on the glass, we see very vivid colours gliding through each -other; these, as the moisture evaporates, change their place, and at -last vanish altogether. If this operation is repeated, the colours are -more vivid and beautiful, and remain longer than they did the first -time.</p> - -<p class="para"><a id="a456">456.</a></p> - -<p>Quickly as this appearance passes, and confused as it appears to be, I -have yet remarked the following effects:—At first all the principal -colours appear with their combinations; on breathing more strongly, the -appearance may be perceived in some order. In this succession it may be -remarked, that when the breath in evaporating becomes contracted from -all sides<span class="pagenum"><a name="Page_190" id="Page_190">[Pg 190]</a></span> towards the centre, the blue colour vanishes last.</p> - -<p class="para"><a id="a457">457.</a></p> - -<p>The phenomenon appears most readily between the minute lines, which the -action of passing the fingers leaves on the clear surface; a somewhat -rough state of the surface of the glass is otherwise requisite. On -some glass the appearance may be produced by merely breathing; in -other cases the wiping with the fingers is necessary: I have even met -with polished mirror-glasses, one side of which immediately showed the -colours vividly; the other not. To judge from some remaining pieces, -the former was originally the front of the glass, the latter the side -which was covered with quicksilver.</p> - -<p class="para"><a id="a458">458.</a></p> - -<p>These experiments may be best made in cold weather, because the glass -may be more quickly and distinctly breathed upon, and the breath -evaporates more suddenly. In severe frost the phenomenon may be -observed on a large scale while travelling in a carriage; the glasses -being well cleaned, and all closed. The breath of the persons within is -very gently diffused over the glass, and immediately produces the most -vivid play of colours. How far they may present a regular succession I -have not been able to remark;<span class="pagenum"><a name="Page_191" id="Page_191">[Pg 191]</a></span> but they appear particularly vivid when -they have a dark object as a background. This alternation of colours -does not, however, last long; for as soon as the breath gathers in -drops, or freezes to points of ice, the appearance is at once at an end.</p> - -<p class="para"><a id="a459">459.</a></p> - -<p>Third condition.—The two foregoing experiments of the pressure and -breathing may be united; namely, by breathing on a plate of glass, and -immediately after pressing the other upon it. The colours then appear -as in the case of two glasses unbreathed upon, with this difference, -that the moisture occasions here and there an interruption of the -undulations. On pushing one glass away from the other the moisture -appears iridescent as it evaporates.</p> - -<p class="para"><a id="a460">460.</a></p> - -<p>It might, however, be asserted that this combined experiment exhibits -no more than each single experiment; for it appears the colours excited -by pressure disappear in proportion as the glasses are less in contact, -and the moisture then evaporates with its own colours.</p> - -<p class="para"><a id="a461">461.</a></p> - -<p>Fourth condition.—Iridescent appearances are observable in almost all -bubbles; soap-bubbles<span class="pagenum"><a name="Page_192" id="Page_192">[Pg 192]</a></span> are the most commonly known, and the effect in -question is thus exhibited in the easiest mode; but it may be observed -in wine, beer, in pure spirit, and again, especially, in the froth of -chocolate.</p> - -<p class="para"><a id="a462">462.</a></p> - -<p>As in the above cases we required an infinitely narrow space between -two surfaces which are in contact, so we can consider the pellicle -of the soap-bubble as an infinitely thin lamina between two elastic -bodies; for the appearance in fact takes place between the air within, -which distends the bubble, and the atmospheric air.</p> - -<p class="para"><a id="a463">463.</a></p> - -<p>The bubble when first produced is colourless; then coloured stripes, -like those in marble paper, begin to appear: these at length spread -over the whole surface, or rather are driven round it as it is -distended.</p> - -<p class="para"><a id="a464">464.</a></p> - -<p>In a single bubble, suffered to hang from the straw or tube, the -appearance of colour is difficult to observe, for the quick rotation -prevents any accurate observation, and all the colours seem to mix -together; yet we can perceive that the colours begin at the orifice of -the tube. The solution itself may, however, be blown into carefully,<span class="pagenum"><a name="Page_193" id="Page_193">[Pg 193]</a></span> -so that only one bubble shall appear. This remains white (colourless) -if not much agitated; but if the solution is not too watery, circles -appear round the perpendicular axis of the bubble; these being near -each other, are commonly composed alternately of green and red. Lastly, -several bubbles may be produced together by the same means; in this -case the colours appear on the sides where two bubbles have pressed -each other flat.</p> - -<p class="para"><a id="a465">465.</a></p> - -<p>The bubbles of chocolate-froth may perhaps be even more conveniently -observed than those of soap; though smaller, they remain longer. In -these, owing to the heat, an impulse, a movement, is produced and -sustained, which appears necessary to the development and succession of -the appearances.</p> - -<p class="para"><a id="a466">466.</a></p> - -<p>If the bubble is small, or shut in between others, coloured lines -chase each other over the surface, resembling marbled paper; all the -colours of the scale are seen to pass through each other; the pure, the -augmented, the combined, all distinctly clear and beautiful. In small -bubbles the appearance lasts for a considerable time.</p> - -<p><span class="pagenum"><a name="Page_194" id="Page_194">[Pg 194]</a></span></p> - -<p class="para"><a id="a467">467.</a></p> - -<p>If the bubble is larger, or if it becomes by degrees detached, owing -to the bursting of others near, we perceive that this impulsion and -attraction of the colours has, as it were, an end in view; for on -the highest point of the bubble we see a small circle appear, which -is yellow in the centre; the other remaining coloured lines move -constantly round this with a vermicular action.</p> - -<p class="para"><a id="a468">468.</a></p> - -<p>In a short time the circle enlarges and sinks downwards on all sides; -in the centre the yellow remains; below and on the outside it becomes -red, and soon blue; below this again appears a new circle of the -same series of colours: if they approximate sufficiently, a green is -produced by the union of the border-colours.</p> - -<p class="para"><a id="a469">469.</a></p> - -<p>When I could count three such leading circles, the centre was -colourless, and this space became by degrees larger as the circles sank -lower, till at last the bubble burst.</p> - -<p class="para"><a id="a470">470.</a></p> - -<p>Fifth condition.—Very delicate pellicles may be formed in various -ways: on these films we discover a very lively play of colours, either -in the usual order, or more confusedly passing through each other. The -water in which lime<span class="pagenum"><a name="Page_195" id="Page_195">[Pg 195]</a></span> has been slaked soon skims over with a coloured -pellicle: the same happens on the surface of stagnant water, especially -if impregnated with iron. The lamellæ of the fine tartar which adheres -to bottles, especially in red French wine, exhibit the most brilliant -colours, on being exposed to the light, if carefully detached. Drops of -oil on water, brandy, and other fluids, produce also similar circles -and brilliant effects: but the most beautiful experiment that can be -made is the following:—Let aqua fortis, not too strong, be poured into -a flat saucer, and then with a brush drop on it some of the varnish -used by engravers to cover certain portions during the process of -biting their plates. After quick commotion there presently appears a -film which spreads itself out in circles, and immediately produces the -most vivid appearances of colour.</p> - -<p class="para"><a id="a471">471.</a></p> - -<p>Sixth condition.—When metals are heated, colours rapidly succeeding -each other appear on the surface: these colours can, however, be -arrested at will.</p> - -<p class="para"><a id="a472">472.</a></p> - -<p>If a piece of polished steel is heated, it will, at a certain degree -of warmth, be overspread with yellow. If taken suddenly away from the -fire, this yellow remains.</p> - -<p><span class="pagenum"><a name="Page_196" id="Page_196">[Pg 196]</a></span></p> - -<p class="para"><a id="a473">473.</a></p> - -<p>As the steel becomes hotter, the yellow appears darker, intenser, and -presently passes into red. This is difficult to arrest, for it hastens -very quickly to bright blue.</p> - -<p class="para"><a id="a474">474.</a></p> - -<p>This beautiful blue is to be arrested if the steel is suddenly taken -out of the heat and buried in ashes. The blue steel works are produced -in this way. If, again, the steel is held longer over the fire, it soon -becomes a light blue, and so it remains.</p> - -<p class="para"><a id="a475">475.</a></p> - -<p>These colours pass like a breath over the plate of steel; each seems -to fly before the other, but, in reality, each successive hue is -constantly developed from the preceding one.</p> - -<p class="para"><a id="a476">476.</a></p> - -<p>If we hold a penknife in the flame of a light, a coloured stripe will -appear across the blade. The portion of the stripe which was nearest to -the flame is light blue; this melts into blue-red; the red is in the -centre; then follow yellow-red and yellow.</p> - -<p class="para"><a id="a477">477.</a></p> - -<p>This phenomenon is deducible from the preceding<span class="pagenum"><a name="Page_197" id="Page_197">[Pg 197]</a></span> ones; for the portion -of the blade next the handle is less heated than the end which is in -the flame, and thus all the colours which in other cases exhibited -themselves in succession, must here appear at once, and may thus be -permanently preserved.</p> - -<p class="para"><a id="a478">478.</a></p> - -<p>Robert Boyle gives this succession of colours as follows:—"A florido -flavo ad flavum saturum et rubescentem (quem artifices sanguineum -vocant) inde ad languidum, postea ad saturiorem cyaneum." This would be -quite correct if the words "languidus" and "saturior" were to change -places. How far the observation is correct, that the different colours -have a relation to the degree of temper which the metal afterwards -acquires, we leave to others to decide. The colours are here only -indications of the different degrees of heat.—<a href="#NOTE_R">Note R</a>.</p> - -<p class="para"><a id="a479">479.</a></p> - -<p>When lead is calcined, the surface is first greyish. This greyish -powder, with greater heat, becomes yellow, and then orange. Silver, -too, exhibits colours when heated; the fracture of silver in the -process of refining belongs to the same class of examples. When -metallic glasses melt, colours in like manner appear on the surface.</p> - -<p><span class="pagenum"><a name="Page_198" id="Page_198">[Pg 198]</a></span></p> - -<p class="para"><a id="a480">480.</a></p> - -<p>Seventh condition.—When the surface of glass becomes decomposed. The -accidental opacity (blindwerden) of glass has been already noticed: the -term (blindwerden) is employed to denote that the surface of the glass -is so affected as to appear dim to us.</p> - -<p class="para"><a id="a481">481.</a></p> - -<p>White glass becomes "blind" soonest; cast, and afterwards polished -glass is also liable to be so affected; the bluish less, the green -least.</p> - -<p class="para"><a id="a482">482.</a></p> - -<p>Of the two sides of a plate of glass one is called the mirror side; -it is that which in the oven lies uppermost, on which one may observe -roundish elevations: it is smoother than the other, which is undermost -in the oven, and on which scratches may be sometimes observed. On this -account the mirror side is placed facing the interior of rooms, because -it is less affected by the moisture adhering to it from within, than -the other would be, and the glass is thus less liable to become "blind."</p> - -<p class="para"><a id="a483">483.</a></p> - -<p>This half-opacity or dimness of the glass assumes by degrees an -appearance of colour which may become very vivid, and in which<span class="pagenum"><a name="Page_199" id="Page_199">[Pg 199]</a></span> perhaps -a certain succession, or otherwise regular order, might be discovered.</p> - -<p class="para"><a id="a484">484.</a></p> - -<p>Having thus traced the physical colours from their simplest effects to -the present instances, where these fleeting appearances are found to -be fixed in bodies, we are, in fact, arrived at the point where the -chemical colours begin; nay, we have in some sort already passed those -limits; a circumstance which may excite a favourable prejudice for the -consistency of our statement. By way of conclusion to this part of our -inquiry, we subjoin a general observation, which may not be without its -bearing on the common connecting principle of the phenomena that have -been adduced.</p> - -<p class="para"><a id="a485">485.</a></p> - -<p>The colouring of steel and the appearances analogous to it, might -perhaps be easily deduced from the doctrine of the semi-opaque mediums. -Polished steel reflects light powerfully: we may consider the colour -produced by the heat as a slight degree of dimness: hence a bright -yellow must immediately appear; this, as the dimness increases, must -still appear deeper, more condensed, and redder, and at last pure and -ruby-red. The colour has now reached the extreme point of depth, and -if we suppose the same degree<span class="pagenum"><a name="Page_200" id="Page_200">[Pg 200]</a></span> of semi-opacity still to continue, the -dimness would now spread itself over a dark ground, first producing a -violet, then a dark-blue, and at last a light-blue, and thus complete -the series of the appearances.</p> - -<p>We will not assert that this mode of explanation will suffice in -all cases; our object is rather to point out the road by which the -all-comprehensive formula, the very key of the enigma, may be at last -discovered.—<a href="#NOTE_S">Note S</a>.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_201" id="Page_201">[Pg 201]</a></span></p> - - - - -<h5><a name="PART_III" id="PART_III">PART III.</a></h5> - - -<h5>CHEMICAL COLOURS.</h5> - - -<p class="para"><a id="a486">486.</a></p> - -<p>We give this denomination to colours which we can produce, and more -or less fix, in certain bodies; which we can render more intense, -which we can again take away and communicate to other bodies, and to -which, therefore, we ascribe a certain permanency: duration is their -prevailing characteristic.</p> - -<p class="para"><a id="a487">487.</a></p> - -<p>In this view the chemical colours were formerly distinguished with -various epithets; they were called <i>colores proprii, corporei, -materiales, veri, permanentes, fixi</i>.</p> - -<p class="para"><a id="a488">488.</a></p> - -<p>In the preceding chapter we observed how the fluctuating and transient -nature of the physical colours becomes gradually fixed, thus forming -the natural transition to our present subject.</p> - -<p class="para"><a id="a489">489.</a></p> - -<p>Colour becomes fixed in bodies more or less permanently; superficially, -or thoroughly.</p> - -<p class="para"><a id="a490">490.</a></p> - -<p>All bodies are susceptible of colour; it can<span class="pagenum"><a name="Page_202" id="Page_202">[Pg 202]</a></span> either be excited, -rendered intense, and gradually fixed in them, or at least communicated -to them.</p> - - - -<hr class="chap" /> -<h5><a name="XXXIV" id="XXXIV">XXXIV.</a></h5> - - -<h5>CHEMICAL CONTRAST.</h5> - - -<p class="para"><a id="a491">491.</a></p> - -<p>In the examination of coloured appearances we had occasion everywhere -to take notice of a principle of contrast: so again, in approaching the -precincts of chemistry, we find a chemical contrast of a remarkable -nature. We speak here, with reference to our present purpose, only of -that which is comprehended under the general names of acid and alkali.</p> - -<p class="para"><a id="a492">492.</a></p> - -<p>We characterised the chromatic contrast, in conformity with all other -physical contrasts as a <i>more</i> and <i>less</i>; ascribing the <i>plus</i> to -the yellow side, the <i>minus</i> to the blue; and we now find that these -two divisions correspond with the chemical contrasts. The yellow and -yellow-red affect the acids, the blue and blue-red the alkalis; thus -the phenomena of chemical colours, although still necessarily mixed -up with<span class="pagenum"><a name="Page_203" id="Page_203">[Pg 203]</a></span> other considerations, admit of being traced with sufficient -simplicity.</p> - -<p class="para"><a id="a493">493.</a></p> - -<p>The principal phenomena in chemical colours are produced by the -oxydation of metals, and it will be seen how important this -consideration is at the outset. Other facts which come into the -account, and which are worthy of attention, will be examined under -separate heads; in doing this we, however, expressly state that we only -propose to offer some preparatory suggestions to the chemist in a very -general way, without entering into the nicer chemical problems and -questions, or presuming to decide on them. Our object is only to give a -sketch of the mode in which, according to our conviction, the chemical -theory of colours may be connected with general physics.</p> - - - -<hr class="chap" /> -<h5><a name="XXXV" id="XXXV">XXXV.</a></h5> - - -<h5>WHITE.</h5> - - -<p class="para"><a id="a494">494.</a></p> - -<p>In treating of the dioptrical colours of the first class (155) we -have already in some degree anticipated this subject. Transparent -substances<span class="pagenum"><a name="Page_204" id="Page_204">[Pg 204]</a></span> may be said to be in the highest class of inorganic matter. -With these, colourless semi-transparence is closely connected, and -white may be considered the last opaque degree of this.</p> - -<p class="para"><a id="a495">495.</a></p> - -<p>Pure water crystallised to snow appears white, for the transparence of -the separate parts makes no transparent whole. Various crystallised -salts, when deprived to a certain extent of moisture, appear as a white -powder. The accidentally opaque state of a pure transparent substance -might be called white; thus pounded glass appears as a white powder. -The cessation of a combining power, and the exhibition of the atomic -quality of the substance might at the same time be taken into the -account.</p> - -<p class="para"><a id="a496">496.</a></p> - -<p>The known undecomposed earths are, in their pure state, all white. -They pass to a state of transparence by natural crystallization. Silex -becomes rock-crystal; argile, mica; magnesia, talc; calcareous earth -and barytes appear transparent in various spars.—<a href="#NOTE_T">Note T</a>.</p> - -<p class="para"><a id="a497">497.</a></p> - -<p>As in the colouring of mineral bodies the<span class="pagenum"><a name="Page_205" id="Page_205">[Pg 205]</a></span> metallic oxydes will often -invite our attention, we observe, in conclusion, that metals, when -slightly oxydated, at first appear white, as lead is converted to white -lead by vegetable acid.</p> - - - -<hr class="chap" /> -<h5><a name="XXXVI" id="XXXVI">XXXVI.</a></h5> - - -<h5>BLACK.</h5> - - -<p class="para"><a id="a498">498.</a></p> - -<p>Black is not exhibited in so elementary a state as white. We meet -with it in the vegetable kingdom in semi-combustion; and charcoal, a -substance especially worthy of attention on other accounts, exhibits -a black colour. Again, if woods—for example, boards, owing to the -action of light, air, and moisture, are deprived in part of their -combustibility, there appears first the grey then the black colour. So -again, we can convert even portions of animal substance to charcoal by -semi-combustion.</p> - -<p class="para"><a id="a499">499.</a></p> - -<p>In the same manner we often find that a sub-oxydation takes place -in metals when the black colour is to be produced. Various metals, -particularly iron, become black by slight oxydation,<span class="pagenum"><a name="Page_206" id="Page_206">[Pg 206]</a></span> by vinegar, by -mild acid fermentations; for example, a decoction of rice, &c.</p> - -<p class="para"><a id="a500">500.</a></p> - -<p>Again, it may be inferred that a de-oxydation may produce black. This -occurs in the preparation of ink, which becomes yellow by the solution -of iron in strong sulphuric acid, but when partly de-oxydised by the -infusion of gall-nuts, appears black.</p> - - - -<hr class="chap" /> -<h5><a name="XXXVII" id="XXXVII">XXXVII.</a></h5> - - -<h5>FIRST EXCITATION OF COLOUR.</h5> - - -<p class="para"><a id="a501">501.</a></p> - -<p>In the division of physical colours, where semi-transparent mediums -were considered, we saw colours antecedently to white and black. In the -present case we assume a white and black already produced and fixed; -and the question is, how colour can be excited in them?</p> - -<p class="para"><a id="a502">502.</a></p> - -<p>Here, too, we can say, white that becomes darkened or dimmed inclines -to yellow; black, as it becomes lighter, inclines to blue.—<a href="#NOTE_U">Note U</a>.</p> - -<p><span class="pagenum"><a name="Page_207" id="Page_207">[Pg 207]</a></span></p> - -<p class="para"><a id="a503">503.</a></p> - -<p>Yellow appears on the active (plus) side, immediately in the light, the -bright, the white. All white surfaces easily assume a yellow tinge; -paper, linen, wool, silk, wax: transparent fluids again, which have -a tendency to combustion, easily become yellow; in other words they -easily pass into a very slight state of semi-transparence.</p> - -<p class="para"><a id="a504">504.</a></p> - -<p>So again the excitement on the passive side, the tendency to obscure, -dark, black, is immediately accompanied with blue, or rather with a -reddish-blue. Iron dissolved in sulphuric acid, and much diluted with -water, if held to the light in a glass, exhibits a beautiful violet -colour as soon as a few drops only of the infusion of gall-nuts are -added. This colour presents the peculiar hues of the dark topaz, the -<i>orphninon</i> of a burnt-red, as the ancients expressed it.</p> - -<p class="para"><a id="a505">505.</a></p> - -<p>Whether any colour can be excited in the pure earths by the chemical -operations of nature and art, without the admixture of metallic oxydes, -is an important question, generally, indeed, answered in the negative. -It is perhaps connected with the question—to what extent<span class="pagenum"><a name="Page_208" id="Page_208">[Pg 208]</a></span> changes may -be produced in the earths through oxydation?</p> - -<p class="para"><a id="a506">506.</a></p> - -<p>Undoubtedly the negation of the above question is confirmed by the -circumstance that wherever mineral colours are found, some trace of -metal, especially of iron, shows itself; we are thus naturally led -to consider how easily iron becomes oxydised, how easily the oxyde -of iron assumes different colours, how infinitely divisible it is, -and how quickly it communicates its colour. It were to be wished, -notwithstanding, that new experiments could be made in regard to the -above point, so as either to confirm or remove any doubt.</p> - -<p class="para"><a id="a507">507.</a></p> - -<p>However this may be, the susceptibility of the earths with regard -to colours already existing is very great; aluminous earth is thus -particularly distinguished.</p> - -<p class="para"><a id="a508">508.</a></p> - -<p>In proceeding to consider the metals, which in the inorganic world -have the almost exclusive prerogative of appearing coloured, we find -that, in their pure, independent, natural state, they are already -distinguished from the<span class="pagenum"><a name="Page_209" id="Page_209">[Pg 209]</a></span> pure earths by a tendency to some one colour or -other.</p> - -<p class="para"><a id="a509">509.</a></p> - -<p>While silver approximates most to pure white,—nay, really represents -pure white, heightened by metallic splendour,—steel, tin, lead, and so -forth, incline towards pale blue-grey; gold, on the other hand, deepens -to pure yellow, copper approaches a red hue, which, under certain -circumstances, increases almost to bright red, but which again returns -to a yellow golden colour when combined with zinc.</p> - -<p class="para"><a id="a510">510.</a></p> - -<p>But if metals in their pure state have so specific a determination -towards this or that exhibition of colour, they are, through the effect -of oxydation, in some degree reduced to a common character; for the -elementary colours now come forth in their purity, and although this -or that metal appears to have a particular tendency to this or that -colour, we find some that can go through the whole circle of hues, -others, that are capable of exhibiting more than one colour; tin, -however, is distinguished by its comparative inaptitude to become -coloured. We propose to give a table hereafter, showing how far the -different metals can be more or less made to exhibit the different -colours.</p> - - -<p><span class="pagenum"><a name="Page_210" id="Page_210">[Pg 210]</a></span></p> - -<p class="para"><a id="a511">511.</a></p> - -<p>When the clean, smooth surface of a pure metal, on being heated, -becomes overspread with a mantling colour, which passes through a -series of appearances as the heat increases, this, we are persuaded, -indicates the aptitude of the metal to pass through the whole range of -colours. We find this phenomenon most beautifully exhibited in polished -steel; but silver, copper, brass, lead, and tin, easily present similar -appearances. A superficial oxydation is probably here taking place, -as may be inferred from the effects of the operation when continued, -especially in the more easily oxydizable metals.</p> - -<p class="para"><a id="a512">512.</a></p> - -<p>The same conclusion may be drawn from the fact that iron is more -easily oxydizable by acid liquids when it is red hot, for in this -case the two effects concur with each other. We observe, again, that -steel, accordingly as it is hardened in different stages of its -colorification, may exhibit a difference of elasticity: this is quite -natural, for the various appearances of colour indicate various degrees -of heat.<a name="FNanchor_1_42" id="FNanchor_1_42"></a><a href="#Footnote_1_42" class="fnanchor">[1]</a></p> - -<p class="para"><a id="a513">513.</a></p> - -<p>If we look beyond this superficial mantling,<span class="pagenum"><a name="Page_211" id="Page_211">[Pg 211]</a></span> this pellicle of colour, -we observe that as metals are oxydized throughout their masses, white -or black appears with the first degree of heat, as may be seen in white -lead, iron, and quicksilver.</p> - -<p class="para"><a id="a514">514.</a></p> - -<p>If we examine further, and look for the actual exhibition of colour, -we find it most frequently on the <i>plus</i> side. The mantling, so often -mentioned, of smooth metallic surfaces begins with yellow. Iron -passes presently into yellow ochre, lead from white lead to massicot, -quicksilver from æthiops to yellow turbith. The solutions of gold and -platinum in acids are yellow.</p> - -<p class="para"><a id="a515">515.</a></p> - -<p>The exhibitions on the <i>minus</i> side are less frequent. Copper slightly -oxydized appears blue. In the preparation of Prussian-blue, alkalis are -employed.</p> - -<p class="para"><a id="a516">516.</a></p> - -<p>Generally, however, these appearances of colour are of so mutable a -nature that chemists look upon them as deceptive tests, at least in the -nicer gradations. For ourselves, as we can only treat of these matters -in a general way, we merely observe that the appearances of colour in -metals may be classed according to their<span class="pagenum"><a name="Page_212" id="Page_212">[Pg 212]</a></span> origin, manifold appearance, -and cessation, as various results of oxydation, hyper-oxydation, -ab-oxydation, and de-oxydation.<a name="FNanchor_2_43" id="FNanchor_2_43"></a><a href="#Footnote_2_43" class="fnanchor">[2]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_42" id="Footnote_1_42"></a><a href="#FNanchor_1_42"><span class="label">[1]</span></a> See par. <a href="#a478">478</a>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_43" id="Footnote_2_43"></a><a href="#FNanchor_2_43"><span class="label">[2]</span></a> As these terms are afterwards referred to (par. <a href="#a525">525</a>), it -was necessary to preserve them.</p></div> - -<hr class="chap" /> - - -<h5><a name="XXXVIII" id="XXXVIII">XXXVIII.</a></h5> - - -<h5>AUGMENTATION OF COLOUR.<a name="FNanchor_1_44" id="FNanchor_1_44"></a><a href="#Footnote_1_44" class="fnanchor">[1]</a></h5> - - -<p class="para"><a id="a517">517.</a></p> - -<p>The augmentation of colour exhibits itself as a condensation, a -fulness, a darkening of the hue. We have before seen, in treating of -colourless mediums, that by increasing the degree of opacity in the -medium, we can deepen a bright object from the lightest yellow to the -intensest ruby-red. Blue, on the other hand, increases to the most -beautiful violet, if we rarefy and diminish a semi-opaque medium, -itself lighted, but through which we see darkness (150, 151).</p> - -<p class="para"><a id="a518">518.</a></p> - -<p>If the colour is positive, a similar colour appears in the intenser -state. Thus if we fill a white porcelain cup with a pure yellow -liquor, the fluid will appear to become gradually redder<span class="pagenum"><a name="Page_213" id="Page_213">[Pg 213]</a></span> towards the -bottom, and at last appears orange. If we pour a pure blue solution -into another cup, the upper portion will exhibit a sky-blue, that -towards the bottom, a beautiful violet. If the cup is placed in the -sun, the shadowed side, even of the upper portion, is already violet. -If we throw a shadow with the hand, or any other substance, over the -illumined portion, the shadow in like manner appears reddish.</p> - -<p class="para"><a id="a519">519.</a></p> - -<p>This is one of the most important appearances connected with the -doctrine of colours, for we here manifestly find that a difference of -quantity produces a corresponding qualified impression on our senses. -In speaking of the last class of epoptical colours (<a href="#a452">452</a>, <a href="#a485">485</a>), we -stated our conjecture that the colouring of steel might perhaps be -traced to the doctrine of the semi-transparent mediums, and we would -here again recall this to the reader's recollection.</p> - -<p class="para"><a id="a520">520.</a></p> - -<p>All chemical augmentation of colour, again, is the immediate -consequence of continued excitation. The augmentation advances -constantly and unremittingly, and it is to be observed that the -increase of intenseness is most common on the <i>plus</i> side. Yellow iron -ochre increases, as well by fire as by other operations, to a very<span class="pagenum"><a name="Page_214" id="Page_214">[Pg 214]</a></span> -strong red: massicot is increased to red lead, turbith to vermilion, -which last attains a very high degree of the yellow-red. An intimate -saturation of the metal by the acid, and its separation to infinity, -take place together with the above effects.</p> - -<p class="para"><a id="a521">521.</a></p> - -<p>The augmentation on the <i>minus</i> side is less frequent; but we observe -that the more pure and condensed the Prussian-blue or cobalt glass is -prepared, the more readily it assumes a reddish hue and inclines to the -violet.</p> - -<p class="para"><a id="a522">522.</a></p> - -<p>The French have a happy expression for the less perceptible tendency of -yellow and blue towards red: they say the colour has "un œil de rouge," -which we might perhaps express by a reddish glance (einen röthlichen -blick).</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_44" id="Footnote_1_44"></a><a href="#FNanchor_1_44"><span class="label">[1]</span></a> Steigerung, literally <i>gradual ascent</i>. See the note to -par. 523.</p></div> - - -<hr class="chap" /> - -<h5><a name="XXXIX" id="XXXIX">XXXIX.</a></h5> - - -<h5>CULMINATION<a name="FNanchor_1_45" id="FNanchor_1_45"></a><a href="#Footnote_1_45" class="fnanchor">[1]</a></h5> - - -<p class="para"><a id="a523">523.</a></p> - -<p>This is the consequence of still progressing augmentation. Red, in -which neither yellow nor<span class="pagenum"><a name="Page_215" id="Page_215">[Pg 215]</a></span> blue is to be detected, here constitutes the -acme.</p> - -<p class="para"><a id="a524">524.</a></p> - -<p>If we wish to select a striking example of a culmination on the <i>plus</i> -side, we again find it in the coloured steel, which attains the bright -red acme, and can be arrested at this point.</p> - -<p class="para"><a id="a525">525.</a></p> - -<p>Were we here to employ the terminology before proposed, we should -say that the first oxydation produces yellow, the hyper-oxydation -yellow-red; that here a kind of maximum exists, and that then an -ab-oxydation, and lastly a de-oxydation takes place.</p> - -<p class="para"><a id="a526">526.</a></p> - -<p>High degrees of oxydation produce a bright red. Gold in solution, -precipitated by a solution of tin, appears bright red: oxyde of -arsenic, in combination, with sulphur, produces a ruby colour.</p> - -<p class="para"><a id="a527">527.</a></p> - -<p>How far, however, a kind of sub-oxydation may co-operate in some -culminations, is matter for inquiry; for an influence of alkalis on<span class="pagenum"><a name="Page_216" id="Page_216">[Pg 216]</a></span> -yellow-red also appears to produce the culmination; the colour reaching -the acme by being forced towards the <i>minus</i> side.</p> - -<p class="para"><a id="a528">528.</a></p> - -<p>The Dutch prepare a colour known by the name of vermilion, from the -best Hungarian cinnabar, which exhibits the brightest yellow-red. This -vermilion is still only a cinnabar, which, however, approximates the -pure red, and it may be conjectured that alkalis are used to bring it -nearer to the culminating point.</p> - -<p class="para"><a id="a529">529.</a></p> - -<p>Vegetable juices, treated in this way, offer very striking examples of -the above effects. The colouring-matter of turmeric, annotto, dyer's -saffron,<a name="FNanchor_2_46" id="FNanchor_2_46"></a><a href="#Footnote_2_46" class="fnanchor">[2]</a> and other vegetables, being extracted with spirits of wine, -exhibits tints of yellow, yellow-red, and hyacinth-red; these, by the -admixture of alkalis, pass to the culminating point, and even beyond it -to blue-red.</p> - -<p class="para"><a id="a530">530.</a></p> - -<p>No instance of a culmination on the <i>minus</i> side has come to my -knowledge in the mineral and vegetable kingdoms. In the animal -kingdom the juice of the murex is remarkable; of its augmentation and -culmination on the <i>minus</i> side, we shall hereafter have occasion to -speak.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_45" id="Footnote_1_45"></a><a href="#FNanchor_1_45"><span class="label">[1]</span></a> <i>Culmination</i>, the original word. It might have been -rendered <i>maximum of colour</i>, but as the author supposes an <i>ascent</i> -through yellow and blue to red, his meaning is better expressed by his -own term.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_46" id="Footnote_2_46"></a><a href="#FNanchor_2_46"><span class="label">[2]</span></a> Curcuma, Bixa Orellana, Carthamus Tinctorius.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_217" id="Page_217">[Pg 217]</a></span></p></div> - - - - -<h5><a name="XL" id="XL">XL.</a></h5> - - -<h5>FLUCTUATION.</h5> - - -<p class="para"><a id="a531">531.</a></p> - -<p>The mutability of colour is so great, that even those pigments, which -may have been considered to be defined and arrested, still admit of -slight variations on one side or the other. This mutability is most -remarkable near the culminating point, and is effected in a very -striking manner by the alternate employment of acids and alkalis.</p> - -<p class="para"><a id="a532">532.</a></p> - -<p>To express this appearance in dyeing, the French make use of the word -"virer," to turn from one side to the other; they thus very adroitly -convey an idea which others attempt to express by terms indicating the -component hues.</p> - -<p class="para"><a id="a533">533.</a></p> - -<p>The effect produced with litmus is one of the most known and striking -of this kind. This colouring substance is tendered red-blue by means of -alkalis. The red-blue is very readily changed to red-yellow by means -of acids, and again returns to its first state by again employing -alkalis. The question whether a culminating point is to be discovered -and arrested by<span class="pagenum"><a name="Page_218" id="Page_218">[Pg 218]</a></span> nice experiments, is left to those who are practised -in these operations. Dyeing, especially scarlet-dyeing, might afford a -variety of examples of this fluctuation.</p> - - - -<hr class="chap" /> -<h5><a name="XLI" id="XLI">XLI.</a></h5> - - -<h5>PASSAGE THROUGH THE WHOLE SCALE.</h5> - - -<p class="para"><a id="a534">534.</a></p> - -<p>The first excitation and gradual increase of colour take place more on -the <i>plus</i> than on the <i>minus</i> side. So, also, in passing through the -whole scale, colour exhibits itself most on the <i>plus</i> side.</p> - -<p class="para"><a id="a535">535.</a></p> - -<p>A passage of this kind, regular and evident to the senses, from yellow -through red to blue, is apparent in the colouring of steel.</p> - -<p class="para"><a id="a536">536.</a></p> - -<p>The metals may be arrested at various points of the colorific circle by -various degrees and kinds of oxydation.</p> - -<p class="para"><a id="a537">537.</a></p> - -<p>As they also appear green, a question arises whether chemists know any -instance in the<span class="pagenum"><a name="Page_219" id="Page_219">[Pg 219]</a></span> mineral kingdom of a constant transition from yellow, -through green, to blue, and <i>vice versâ</i>. Oxyde of iron, melted with -glass, produces first a green, and with a more powerful heat, a blue -colour.</p> - -<p class="para"><a id="a538">538.</a></p> - -<p>We may here observe of green generally, that it appears, especially -in an atomic sense, and certainly in a pure state, when we mix blue -and yellow: but, again, an impure and dirty yellow soon gives us the -impression of green; yellow and black already produce green; this, -however, is owing to the affinity between black and blue. An imperfect -yellow, such as that of sulphur, gives us the impression of a greenish -hue: thus, again, an imperfect blue appears green. The green of wine -bottles arises, it appears, from an imperfect union of the oxyde of -iron with the glass. If we produce a more complete union by greater -heat, a beautiful blue-glass is the result.</p> - -<p class="para"><a id="a539">539.</a></p> - -<p>From all this it appears that a certain chasm exists in nature between -yellow and blue, the opposite characters of which, it is true, may be -done away atomically by due immixture, and, thus combined, to green; -but the true reconciliation between yellow and blue, it seems, only -takes place by means of red.</p> - -<p><span class="pagenum"><a name="Page_220" id="Page_220">[Pg 220]</a></span></p> - -<p class="para"><a id="a540">540.</a></p> - -<p>The process, however, which appears unattainable in inorganic -substances, we shall find to be possible when we turn our attention to -organic productions; for in these, the passage through the whole circle -from yellow, through green and blue, to red, really takes place.</p> - - - -<hr class="chap" /> -<h5><a name="XLII" id="XLII">XLII.</a></h5> - - -<h5>INVERSION.</h5> - - -<p class="para"><a id="a541">541.</a></p> - -<p>Again, an immediate inversion or change to the totally opposite hue, is -a very remarkable appearance which sometimes occurs; at present, we are -merely enabled to adduce what follows.</p> - -<p class="para"><a id="a542">542.</a></p> - -<p>The mineral chameleon, a name which has been given to an oxyde of -manganese, may be considered, in its perfectly dry state, as a green -powder. If we strew it in water, the green colour displays itself very -beautifully in the first moment of solution, but it changes presently -to the bright red opposite to green, without any apparent intermediate -state.</p> - -<p><span class="pagenum"><a name="Page_221" id="Page_221">[Pg 221]</a></span></p> - -<p class="para"><a id="a543">543.</a></p> - -<p>The same occurs with the sympathetic ink, which may be considered a -reddish liquid, but which, when dried by warmth, appears as a green -colour on paper.</p> - -<p class="para"><a id="a544">544.</a></p> - -<p>In fact, this phenomenon appears to be owing to the conflict between -a dry and moist state, as has been already observed, if we are not -mistaken, by the chemists. We may look to the improvements of time to -point out what may further be deduced from these phenomena, and to show -what other facts they may be connected with.</p> - - - -<hr class="chap" /> -<h5><a name="XLIII" id="XLIII">XLIII.</a></h5> - - -<h5>FIXATION.</h5> - - -<p class="para"><a id="a545">545.</a></p> - -<p>Mutable as we have hitherto found colour to be, even as a substance, -yet under certain circumstances it may at last be fixed.</p> - -<p class="para"><a id="a546">546.</a></p> - -<p>There are bodies capable of being entirely converted into colouring -matter: here it may be said that the colour fixes itself in its own -substance,<span class="pagenum"><a name="Page_222" id="Page_222">[Pg 222]</a></span> stops at a certain point, and is there defined. Such -colouring substances are found throughout nature; the vegetable world -affords a great quantity of examples, among which some are particularly -distinguished, and may be considered as the representatives of the -rest; such as, on the active side, madder, on the passive side, indigo.</p> - -<p class="para"><a id="a547">547.</a></p> - -<p>In order to make these materials available in use, it is necessary -that the colouring quality in them should be intimately condensed, and -the tinging substance refined, practically speaking, to an infinite -divisibility. This is accomplished in various ways, and particularly by -the well-known means of fermentation and decomposition.</p> - -<p class="para"><a id="a548">548.</a></p> - -<p>These colouring substances now attach themselves again to other bodies. -Thus, in the mineral kingdom they adhere to earths and metallic oxydes; -they unite in melting with glasses; and in this case, as the light is -transmitted through them, they appear in the greatest beauty, while an -eternal duration may be ascribed to them.</p> - -<p class="para"><a id="a549">549.</a></p> - -<p>They fasten on vegetable and animal bodies with more or less power, and -remain more or less<span class="pagenum"><a name="Page_223" id="Page_223">[Pg 223]</a></span> permanently; partly owing to their nature,—as -yellow, for instance, is more evanescent than blue,—or owing to -the nature of the substance on which they appear. They last less in -vegetable than in animal substances, and even within this latter -kingdom there are again varieties. Hemp or cotton threads, silk or -wool, exhibit very different relations to colouring substances.</p> - -<p class="para"><a id="a550">550.</a></p> - -<p>Here comes into the account the important operation of employing -mordants, which may be considered as the intermediate agents between -the colour and the recipient substance; various works on dyeing speak -of this circumstantially. Suffice it to have alluded to processes by -means of which the colour retains a permanency only to be destroyed -with the substance, and which may even increase in brightness and -beauty by use.</p> - - - -<hr class="chap" /> -<h5><a name="XLIV" id="XLIV">XLIV.</a></h5> - - -<h5>INTERMIXTURE, REAL.</h5> - - -<p class="para"><a id="a551">551.</a></p> - -<p>Every intermixture pre-supposes a specific state of colour; and thus -when we speak of intermixture, we here understand it in an atomic<span class="pagenum"><a name="Page_224" id="Page_224">[Pg 224]</a></span> -sense. We must first have before us certain bodies arrested at any -given point of the colorific circle, before we can produce gradations -by their union.</p> - -<p class="para"><a id="a552">552.</a></p> - -<p>Yellow, blue, and red, may be assumed as pure elementary colours, -already existing; from these, violet, orange, and green, are the -simplest combined results.</p> - -<p class="para"><a id="a553">553.</a></p> - -<p>Some persons have taken much pains to define these intermixtures more -accurately, by relations of number, measure, and weight, but nothing -very profitable has been thus accomplished.</p> - -<p class="para"><a id="a554">554.</a></p> - -<p>Painting consists, strictly speaking, in the intermixture of -such specific colouring bodies and their infinite possible -combinations—combinations which can only be appreciated by the nicest, -most practised eye, and only accomplished under its influence.</p> - -<p class="para"><a id="a555">555.</a></p> - -<p>The intimate combination of these ingredients is effected, in the first -instance, through the most perfect comminution of the material by means -of grinding, washing, &c., as well as by vehicles<span class="pagenum"><a name="Page_225" id="Page_225">[Pg 225]</a></span> or liquid mediums -which hold together the pulverized substance, and combine organically, -as it were, the unorganic; such are the oils, resins, &c.—<a href="#NOTE_V">Note V</a>.</p> - -<p class="para"><a id="a556">556.</a></p> - -<p>If all the colours are mixed together they retain their general -character as σκιερόν, and as they are no longer seen next each other, -no completeness, no harmony, is experienced; the result is grey, which, -like apparent colour, always appears somewhat darker than white, and -somewhat lighter than black.</p> - -<p class="para"><a id="a557">557.</a></p> - -<p>This grey may be produced in various ways. By mixing yellow and blue to -an emerald green, and then adding pure red, till all three neutralize -each other; or, by placing the primitive and intermediate colours next -each other in a certain proportion, and afterwards mixing them.</p> - -<p class="para"><a id="a558">558.</a></p> - -<p>That all the colours mixed together produce white, is an absurdity -which people have credulously been accustomed to repeat for a century, -in opposition to the evidence of their senses.</p> - -<p class="para"><a id="a559">559.</a></p> - -<p>Colours when mixed together retain their<span class="pagenum"><a name="Page_226" id="Page_226">[Pg 226]</a></span> original darkness. The darker -the colours, the darker will be the grey resulting from their union, -till at last this grey approaches black. The lighter the colours the -lighter will be the grey, which at last approaches white.</p> - - - -<hr class="chap" /> -<h5><a name="XLV" id="XLV">XLV.</a></h5> - - -<h5>INTERMIXTURE, APPARENT.</h5> - - -<p class="para"><a id="a560">560.</a></p> - -<p>The intermixture, which is only apparent, naturally invites our -attention in connexion with the foregoing; it is in many respects -important, and, indeed, the intermixture which we have distinguished as -real, might be considered as merely apparent. For the elements of which -the combined colour consists are only too small to be considered as -distinct parts. Yellow and blue powders mingled together appear green -to the naked eye, but through a magnifying glass we can still perceive -yellow and blue distinct from each other. Thus yellow and blue stripes -seen at a distance, present a green mass; the same observation is -applicable with regard to the intermixture of other specific colours.</p> - -<p class="para"><a id="a561">561.</a></p> - -<p>In the description of our apparatus we shall<span class="pagenum"><a name="Page_227" id="Page_227">[Pg 227]</a></span> have occasion to mention -the wheel by means of which the apparent intermixture is produced by -rapid movement. Various colours are arranged near each other round -the edge of a disk, which is made to revolve with velocity, and thus -by having several such disks ready, every possible intermixture can -be presented to the eye, as well as the mixture of all colours to -grey, darker or lighter, according to the depth of the tints as above -explained.</p> - -<p class="para"><a id="a562">562.</a></p> - -<p>Physiological colours admit, in like manner, of being mixed with -others. If, for example, we produce the blue shadow (<a href="#a65">65</a>) on a light -yellow paper, the surface will appear green. The same happens with -regard to the other colours if the necessary preparations are attended -to.</p> - -<p class="para"><a id="a563">563.</a></p> - -<p>If, when the eye is impressed with visionary images that last for a -while, we look on coloured surfaces, an intermixture also takes place; -the spectrum is determined to a new colour which is composed of the two.</p> - -<p class="para"><a id="a564">564.</a></p> - -<p>Physical colours also admit of combination. Here might be adduced the -experiments in<span class="pagenum"><a name="Page_228" id="Page_228">[Pg 228]</a></span> which many-coloured images are seen through the prism, -as we have before shown in detail (<a href="#a258">258</a>, <a href="#a284">284</a>).</p> - -<p class="para"><a id="a565">565.</a></p> - -<p>Those who have prosecuted these inquiries have, however, paid most -attention to the appearances which take place when the prismatic -colours are thrown on coloured surfaces.</p> - -<p class="para"><a id="a566">566.</a></p> - -<p>What is seen under these circumstances is quite simple. In the first -place it must be remembered that the prismatic colours are much more -vivid than the colours of the surface on which they are thrown. -Secondly, we have to consider that the prismatic colours may be either -homogeneous or heterogeneous, with the recipient surface. In the former -case the surface deepens and enhances them, and is itself enhanced in -return, as a coloured stone is displayed by a similarly coloured foil. -In the opposite case each vitiates, disturbs, and destroys the other.</p> - -<p class="para"><a id="a567">567.</a></p> - -<p>These experiments may be repeated with coloured glasses, by causing the -sun-light to shine through them on coloured surfaces. In every instance -similar results will appear.</p> - -<p><span class="pagenum"><a name="Page_229" id="Page_229">[Pg 229]</a></span></p> - -<p class="para"><a id="a568">568.</a></p> - -<p>The same effect takes place when we look on coloured objects through -coloured glasses; the colours being thus according to the same -conditions enhanced, subdued, or neutralized.</p> - -<p class="para"><a id="a569">569.</a></p> - -<p>If the prismatic colours are suffered to pass through coloured glasses, -the appearances that take place are perfectly analogous; in these cases -more or less force, more or less light and dark, the clearness and -cleanness of the glass are all to be allowed for, as they produce many -delicate varieties of effect: these will not escape the notice of every -accurate observer who takes sufficient interest in the inquiry to go -through the experiments.</p> - -<p class="para"><a id="a570">570.</a></p> - -<p>It is scarcely necessary to mention that several coloured glasses, as -well as oiled or transparent papers, placed over each other, may be -made to produce and exhibit every kind of intermixture at pleasure.</p> - -<p class="para"><a id="a571">571.</a></p> - -<p>Lastly, the operation of glazing in painting belongs to this kind of -intermixture; by this means a much more refined union may be produced -than that arising from the mechanical, atomic mixture which is commonly -employed.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_230" id="Page_230">[Pg 230]</a></span></p> - - - - -<h5><a name="XLVI" id="XLVI">XLVI.</a></h5> - - -<h5>COMMUNICATION, ACTUAL.</h5> - - -<p class="para"><a id="a572">572.</a></p> - -<p>Having now provided the colouring materials, as before shown, a further -question arises how to communicate these to colourless substances: -the answer is of the greatest importance from the connexion of the -object with the ordinary wants of men, with useful purposes, and with -commercial and technical interests.</p> - -<p class="para"><a id="a573">573.</a></p> - -<p>Here, again, the dark quality of every colour again comes into the -account. From a yellow, that is very near to white, through orange, -and the hue of minium to pure red and carmine, through all gradations -of violet to the deepest blue which is almost identified with black, -colour still increases in darkness. Blue once defined, admits of -being diluted, made light, united with yellow, and then, as green, -it approaches the light side of the scale: but this is by no means -according to its own nature.</p> - -<p class="para"><a id="a574">574.</a></p> - -<p>In the physiological colours we have already seen that they are less -than the light, inasmuch<span class="pagenum"><a name="Page_231" id="Page_231">[Pg 231]</a></span> as they are a repetition of an impression -of light, nay, at last they leave this impression quite as a dark. In -physical experiments the employment of semi-transparent mediums, the -effect of semi-transparent accessory images, taught us that in such -cases we have to do with a subdued light, with a transition to darkness.</p> - -<p class="para"><a id="a575">575.</a></p> - -<p>In treating of the chemical origin of pigments we found that the same -effect was produced on the very first excitement. The yellow tinge -which mantles over the steel, already darkens the shining surface. In -changing white lead to massicot it is evident that the yellow is darker -than white.</p> - -<p class="para"><a id="a576">576.</a></p> - -<p>This process is in the highest degree delicate; the growing -intenseness, as it still increases, tinges the substance more and more -intimately and powerfully, and thus indicates the extreme fineness, and -the infinite divisibility of the coloured atoms.</p> - -<p class="para"><a id="a577">577.</a></p> - -<p>The colours which approach the dark side, and consequently, blue in -particular, can be made to approximate to black; in fact, a very -perfect Prussian blue, or an indigo acted on by vitriolic acid appears -almost as a black.</p> - -<p><span class="pagenum"><a name="Page_232" id="Page_232">[Pg 232]</a></span></p> - -<p class="para"><a id="a578">578.</a></p> - -<p>A remarkable appearance may be here adverted to; pigments, in their -deepest and most condensed state, especially those produced from -the vegetable kingdom, such as the indigo just mentioned, or madder -carried to its intensest hue, no longer show their own colour; on the -contrary, a decided metallic shine is seen on their surface, in which -the physiological compensatory colour appears.</p> - -<p class="para"><a id="a579">579.</a></p> - -<p>All good indigo exhibits a copper-colour in its fracture, a -circumstance attended to, as a known characteristic, in trade. Again, -the indigo which has been acted on by sulphuric acid, if thickly laid -on, or suffered to dry so that neither white paper nor the porcelain -can appear through, exhibits a colour approaching to orange.</p> - -<p class="para"><a id="a580">580.</a></p> - -<p>The bright red Spanish rouge, probably prepared from madder, exhibits -on its surface a perfectly green, metallic shine. If this colour, or -the blue before mentioned, is washed with a pencil on porcelain or -paper, it is seen in its real state owing to the bright ground shining -through.</p> - -<p class="para"><a id="a581">581.</a></p> - -<p>Coloured liquids appear black when no light<span class="pagenum"><a name="Page_233" id="Page_233">[Pg 233]</a></span> is transmitted through -them, as we may easily see in cubic tin vessels with glass bottoms. -In these every transparent-coloured infusion will appear black and -colourless if we place a black surface under them.</p> - -<p class="para"><a id="a582">582.</a></p> - -<p>If we contrive that the image of a flame be reflected from the bottom, -the image will appear coloured. If we lift up the vessel and suffer the -transmitted light to fall on white paper under it, the colour of the -liquid appears on the paper. Every light ground seen through such a -coloured medium exhibits the colour of the medium.</p> - -<p class="para"><a id="a583">583.</a></p> - -<p>Thus every colour, in order to be seen, must have a light within or -behind it. Hence the lighter and brighter the grounds are, the more -brilliant the colours appear. If we pass lac-varnish over a shining -white metal surface, as the so-called foils are prepared, the splendour -of the colour is displayed by this internally reflected light as -powerfully as in any prismatic experiment; nay, the force of the -physical colours is owing principally to the circumstance that light is -always acting with and behind them.</p> - -<p class="para"><a id="a584">584.</a></p> - -<p>Lichtenberg, who of necessity followed the<span class="pagenum"><a name="Page_234" id="Page_234">[Pg 234]</a></span> received theory, owing -to the time and circumstances in which he lived, was yet too good an -observer, and too acute not to explain and classify, after his fashion, -what was evident to his senses. He says, in the preface to Delaval, -"It appears to me also, on other grounds, probable, that our organ, in -order to be impressed by a colour, must at the same time be impressed -by all light (white)."</p> - -<p class="para"><a id="a585">585.</a></p> - -<p>To procure white as a ground is the chief business of the dyer. Every -colour may be easily communicated to colourless earths, especially -to alum: but the dyer has especially to do with animal and vegetable -products as the ground of his operations.</p> - -<p class="para"><a id="a586">586.</a></p> - -<p>Everything living tends to colour—to local, specific colour, to -effect, to opacity—pervading the minutest atoms. Everything in which -life is extinct approximates to white (<a href="#a494">494</a>), to the abstract, the -general state, to clearness<a name="FNanchor_1_47" id="FNanchor_1_47"></a><a href="#Footnote_1_47" class="fnanchor">[1]</a>, to transparence.</p> - -<p class="para"><a id="a587">587.</a></p> - -<p>How this is put in practice in technical operations remains to be -adverted to in the chapter on the privation of colour. With regard -to the<span class="pagenum"><a name="Page_235" id="Page_235">[Pg 235]</a></span> communication of colour, we have especially to bear in mind -that animals and vegetables, in a living state, produce colours, and -hence their substances, if deprived of colours, can the more readily -re-assume them.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_47" id="Footnote_1_47"></a><a href="#FNanchor_1_47"><span class="label">[1]</span></a> Verklärung, literally <i>clarification</i>.</p></div> - - - -<hr class="chap" /> -<h5><a name="XLVII" id="XLVII">XLVII.</a></h5> - - -<h5>COMMUNICATION, APPARENT.</h5> - - -<p class="para"><a id="a588">588.</a></p> - -<p>The communication of colours, real as well as apparent, corresponds, as -may easily be seen, with their intermixture: we need not, therefore, -repeat what has been already sufficiently entered into.</p> - -<p class="para"><a id="a589">589.</a></p> - -<p>Yet we may here point out more circumstantially the importance of an -apparent communication which takes place by means of reflection. This -phenomenon is well known, but still it is pregnant with inferences, and -is of the greatest importance both to the investigator of nature and to -the painter.</p> - -<p class="para"><a id="a590">590.</a></p> - -<p>Let a surface coloured with any one of the positive colours be placed -in the sun, and let its<span class="pagenum"><a name="Page_236" id="Page_236">[Pg 236]</a></span> reflection be thrown on other colourless -objects. This reflection is a kind of subdued light, a half-light, -a half-shadow, which, in a subdued state, reflects the colours in -question.</p> - -<p class="para"><a id="a591">591.</a></p> - -<p>If this reflection acts on light surfaces, it is so far overpowered -that we can scarcely perceive the colour which accompanies it; but if -it acts on shadowed portions, a sort of magical union takes place with -the σκιερῷ. Shadow is the proper element of colour, and in this case -a subdued colour approaches it, lighting up, tinging, and enlivening -it. And thus arises an appearance, as powerful as agreeable, which may -render the most pleasing service to the painter who knows how to make -use of it. These are the types of the so-called reflexes, which were -only noticed late in the history of art, and which have been too seldom -employed in their full variety.</p> - -<p class="para"><a id="a592">592.</a></p> - -<p>The schoolmen called these colours <i>colores notionales</i> and -<i>intentionales</i>, and the history of the doctrine of colours will -generally show that the old inquirers already observed the phenomena -well enough, and knew how to distinguish them properly, although the -whole method of treating such subjects is very different from ours.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_237" id="Page_237">[Pg 237]</a></span></p> - - - - -<h5><a name="XLVIII" id="XLVIII">XLVIII.</a></h5> - - -<h5>EXTRACTION.</h5> - - -<p class="para"><a id="a593">593.</a></p> - -<p>Colour may be extracted from substances, whether they possess it -naturally or by communication, in various ways. We have thus the power -to remove it intentionally for a useful purpose, but, on the other -hand, it often flies contrary to our wish.</p> - -<p class="para"><a id="a594">594.</a></p> - -<p>Not only are the elementary earths in their natural state white, but -vegetable and animal substances can be reduced to a white state without -disturbing their texture. A pure white is very desirable for various -uses, as in the instance of our preferring to use linen and cotton -stuffs uncoloured. In like manner some silk stuffs, paper, and other -substances, are the more agreeable the whiter they can be. Again, -the chief basis of all dyeing consists in white grounds. For these -reasons manufacturers, aided by accident and contrivance, have devoted -themselves assiduously to discover means of extracting colour: infinite -experiments have been made in connexion with this object, and many -important facts have been arrived at.</p> - -<p><span class="pagenum"><a name="Page_238" id="Page_238">[Pg 238]</a></span></p> - -<p class="para"><a id="a595">595.</a></p> - -<p>It is in accomplishing this entire extraction of colour that the -operation of bleaching consists, which is very generally practised -empirically or methodically. We will here shortly state the leading -principles.</p> - -<p class="para"><a id="a596">596.</a></p> - -<p>Light is considered as one of the first means of extracting colour -from substances, and not only the sun-light, but the mere powerless -day-light: for as both lights—the direct light of the sun, as well as -the derived light of the sky—kindle Bologna phosphorus, so both act on -coloured surfaces. Whether the light attacks the colour allied to it, -and, as it were, kindles and consumes it, thus reducing the definite -quality to a general state, or whether some other operation, unknown -to us, takes place, it is clear that light exercises a great power on -coloured surfaces, and bleaches them more or less. Here, however, the -different colours exhibit a different degree of durability; yellow, -especially if prepared from certain materials, is, in this case, the -first to fly.</p> - -<p class="para"><a id="a597">597.</a></p> - -<p>Not only light, but air, and especially water, act strongly in -destroying colour. It has been even asserted that thread, well soaked -and<span class="pagenum"><a name="Page_239" id="Page_239">[Pg 239]</a></span> spread on the grass at night, bleaches better than that which is -exposed, after soaking, to the sun-light. Thus, in this case, water -proves to be a solving and conducting agent, removing the accidental -quality, and restoring the substance to a general or colourless state.</p> - -<p class="para"><a id="a598">598.</a></p> - -<p>The extraction of colour is also effected by re-agents. Spirits of wine -has a peculiar tendency to attract the juice which tinges plants, and -becomes coloured with it often in a very permanent manner. Sulphuric -acid is very efficient in removing colour, especially from wool and -silk, and every one is acquainted with the use of sulphur vapours in -bleaching.</p> - -<p class="para"><a id="a599">599.</a></p> - -<p>The strongest acids have been recommended more recently as more -expeditious agents in bleaching.</p> - -<p class="para"><a id="a600">600.</a></p> - -<p>The alkaline re-agents produce the same effects by contrary -means—lixiviums alone, oils and fat combined with lixiviums to soap, -and so forth.</p> - -<p class="para"><a id="a601">601.</a></p> - -<p>Before we dismiss this subject, we observe [Pg 240] that it may be -well worth while to make certain delicate experiments as to how far -light and air exhibit their action in the removal of colour. It might -be possible to expose coloured substances to the light under glass -bells, without air, or filled with common or particular kinds of air. -The colours might be those of known fugacity, and it might be observed -whether any of the volatilized colour attached itself to the glass or -was otherwise perceptible as a deposit or precipitate; whether, again, -in such a case, this appearance would be perfectly like that which had -gradually ceased to be visible, or whether it had suffered any change. -Skilful experimentalists might devise various contrivances with a view -to such researches.</p> - -<p class="para"><a id="a602">602.</a></p> - -<p>Having thus first considered the operations of nature as subservient to -our proposes, we add a few observations on the modes in which they act -against us.</p> - -<p class="para"><a id="a603">603.</a></p> - -<p>The art of painting is so circumstanced that the most beautiful results -of mind and labour are altered and destroyed in various ways by time. -Hence great pains have been always taken to find durable pigments, and -so to unite them with each other and with their ground, that their<span class="pagenum"><a name="Page_241" id="Page_241">[Pg 241]</a></span> -permanency might be further insured. The technical history of the -schools of painting affords sufficient information on this point.</p> - -<p class="para"><a id="a604">604.</a></p> - -<p>We may here, too, mention a minor art, to which, in relation to -dyeing, we are much indebted, namely, the weaving of tapestry. As the -manufacturers were enabled to imitate the most delicate shades of -pictures, and hence often brought the most variously coloured materials -together, it was soon observed that the colours were not all equally -durable, but that some faded from the tapestry more quickly than -others. Hence the most diligent efforts were made to ensure an equal -permanency to all the colours and their gradations. This object was -especially promoted in France, under Colbert, whose regulations to this -effect constitute an epoch in the history of dyeing. The gay dye which -only aimed at a transient beauty, was practised by a particular guild. -On the other hand, great pains were taken to define the technical -processes which promised durability.</p> - -<p>And thus, after considering the artificial extraction, the evanescence, -and the perishable nature of brilliant appearances of colour, we are -again returned to the desideratum of permanency.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_242" id="Page_242">[Pg 242]</a></span></p> - - - - -<h5><a name="XLIX" id="XLIX">XLIX.</a></h5> - - -<h5>NOMENCLATURE.</h5> - - -<p class="para"><a id="a605">605.</a></p> - -<p>After what has been adduced respecting the origin, the increase, -and the affinity of colours, we may be better enabled to judge what -nomenclature would be desirable in future, and what might be retained -of that hitherto in use.</p> - -<p class="para"><a id="a606">606.</a></p> - -<p>The nomenclature of colours, like all other modes of designation, -but especially those employed to distinguish the objects of sense, -proceeded in the first instance from particular to general, and from -general back again to particular terms. The name of the species became -a generic name to which the individual was again referred.</p> - -<p class="para"><a id="a607">607.</a></p> - -<p>This method might have been followed in consequence of the mutability -and uncertainty of ancient modes of expression, especially since, in -the early ages, more reliance may be supposed to have been placed on -the vivid impressions of sense. The qualities of objects were described -indistinctly, because they were impressed clearly on every imagination.</p> - -<p><span class="pagenum"><a name="Page_243" id="Page_243">[Pg 243]</a></span></p> - -<p class="para"><a id="a608">608.</a></p> - -<p>The pure chromatic circle was limited, it is true; but, specific as it -was, it appears to have been applied to innumerable objects, while it -was circumscribed by qualifying characteristics. If we take a glance -at the copiousness of the Greek and Roman terms, we shall perceive how -mutable the words were, and how easily each was adapted to almost every -point in the colorific circle.—<a href="#NOTE_W">Note W</a>.</p> - -<p class="para"><a id="a609">609.</a></p> - -<p>In modern ages terms for many new gradations were introduced in -consequence of the various operations of dyeing. Even the colours -of fashion and their designations, represented an endless series of -specific hues. We shall, on occasion, employ the chromatic terminology -of modern languages, whence it will appear that the aim has gradually -been to introduce more exact definitions, and to individualise and -arrest a fixed and specific state by language equally distinct.</p> - -<p class="para"><a id="a610">610.</a></p> - -<p>With regard to the German terminology, it has the advantage of -possessing four monosyllabic names no longer to be traced to their -origin, viz., yellow (Gelb), blue, red, green. They represent the most -general idea of colour to the imagination, without reference to any -very specific modification.</p> - -<p><span class="pagenum"><a name="Page_244" id="Page_244">[Pg 244]</a></span></p> - -<p class="para"><a id="a611">611.</a></p> - -<p>If we were to add two other qualifying terms to each of these four, as -thus—red-yellow, and yellow-red, red-blue and blue-red, yellow-green -and green-yellow, blue-green and green-blue,<a name="FNanchor_1_48" id="FNanchor_1_48"></a><a href="#Footnote_1_48" class="fnanchor">[1]</a> we should express the -gradations of the chromatic circle with sufficient distinctness; and if -we were to add the designations of light and dark, and again define, in -some measure, the degree of purity or its opposite by the monosyllables -black, white, grey, brown, we should have a tolerably sufficient range -of expressions to describe the ordinary appearances presented to us, -without troubling ourselves whether they were produced dynamically or -atomically.</p> - -<p class="para"><a id="a612">612.</a></p> - -<p>The specific and proper terms in use might, however, still be -conveniently employed, and we have thus made use of the words orange -and violet. We have in like manner employed the word "<i>purpur</i>" to -designate a pure central red, because the secretion of the murex or -"<i>purpura</i>" is to be carried to the highest point of culmination by the -action of the sun-light on fine linen saturated with the juice.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_48" id="Footnote_1_48"></a><a href="#FNanchor_1_48"><span class="label">[1]</span></a> This description is suffered to remain because it accounts -for the terminology employed throughout.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_245" id="Page_245">[Pg 245]</a></span></p></div> - - - - -<h5><a name="L" id="L">L.</a></h5> - - -<h5>MINERALS.</h5> - - -<p class="para"><a id="a613">613.</a></p> - -<p>The colours of minerals are all of a chemical nature, and thus the -modes in which they are produced may be explained in a general way by -what has been said on the subject of chemical colours.</p> - -<p class="para"><a id="a614">614.</a></p> - -<p>Among the external characteristics of minerals, the description of -their colours occupies the first place; and great pains have been -taken, in the spirit of modern times, to define and arrest every -such appearance exactly: by this means, however, new difficulties, -it appears to us, have been created, which occasion no little -inconvenience in practice.</p> - -<p class="para"><a id="a615">615.</a></p> - -<p>It is true, this precision, when we reflect how it arose, carries with -it its own excuse. The painter has at all times been privileged in -the use of colours. The few specific hues, in themselves, admitted of -no change; but from these, innumerable gradations were artificially -produced which imitated the surface of natural objects. It was, -therefore, not to be wondered<span class="pagenum"><a name="Page_246" id="Page_246">[Pg 246]</a></span> at that these gradations should also be -adopted as criterions, and that the artist should be invited to produce -tinted patterns with which the objects of nature might be compared, and -according to which they were to receive their designations.</p> - -<p class="para"><a id="a616">616.</a></p> - -<p>But, after all, the terminology of colours which has been introduced in -mineralogy, is open to many objections. The terms, for instance, have -not been borrowed from the mineral kingdom, as was possible enough in -most cases, but from all kinds of visible objects. Too many specific -terms have been adopted; and in seeking to establish new definitions -by combining these, the nomenclators have not reflected that they thus -altogether efface the image from the imagination, and the idea from -the understanding. Lastly, these individual designations of colours, -employed to a certain extent as elementary definitions, are not -arranged in the best manner as regards their respective derivation from -each other: hence, the scholar must learn every single designation, -and impress an almost lifeless but positive language on his memory. -The further consideration of this would be too foreign to our present -subject.<a name="FNanchor_1_49" id="FNanchor_1_49"></a><a href="#Footnote_1_49" class="fnanchor">[1]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_49" id="Footnote_1_49"></a><a href="#FNanchor_1_49"><span class="label">[1]</span></a> These remarks have reference to the German mineralogical -terminology.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_247" id="Page_247">[Pg 247]</a></span></p></div> - - - - -<h5><a name="LI" id="LI">LI.</a></h5> - - -<h5>PLANTS.</h5> - - -<p class="para"><a id="a617">617.</a></p> - -<p>The colours of organic bodies in general may be considered as a higher -kind of chemical operation, for which reason the ancients employed the -word concoction, πέψις, to designate the process. All the elementary -colours, as well as the combined and secondary hues, appear on the -surface of organic productions, while on the other hand, the interior, -if not colourless, appears, strictly speaking, negative when brought to -the light. As we propose to communicate our views respecting organic -nature, to a certain extent, in another place, we only insert here -what has been before connected with the doctrine of colours, while it -may serve as an introduction to the further consideration of the views -alluded to: and first, of plants.</p> - -<p class="para"><a id="a618">618.</a></p> - -<p>Seeds, bulbs, roots, and what is generally shut out from the light, or -immediately surrounded by the earth, appear, for the most part, white.</p> - -<p class="para"><a id="a619">619.</a></p> - -<p>Plants reared from seed, in darkness, are white, or approaching to -yellow. Light, on the<span class="pagenum"><a name="Page_248" id="Page_248">[Pg 248]</a></span> other hand, in acting on their colours, acts at -the same time on their form.</p> - -<p class="para"><a id="a620">620.</a></p> - -<p>Plants which grow in darkness make, it is true, long shoots from joint -to joint: but the stems between two joints are thus longer than they -should be; no side stems are produced, and the metamorphosis of the -plant does not take place.</p> - -<p class="para"><a id="a621">621.</a></p> - -<p>Light, on the other hand, places it at once in an active state; the -plant appears green, and the course of the metamorphosis proceeds -uninterruptedly to the period of reproduction.</p> - -<p class="para"><a id="a622">622.</a></p> - -<p>We know that the leaves of the stem are only preparations and -pre-significations of the instruments of florification and -fructification, and accordingly we can already see colours in the -leaves of the stem which, as it were, announce the flower from afar, as -is the case in the amaranthus.</p> - -<p class="para"><a id="a623">623.</a></p> - -<p>There are white flowers whose petals have wrought or refined themselves -to the greatest purity; there are coloured ones, in which the<span class="pagenum"><a name="Page_249" id="Page_249">[Pg 249]</a></span> -elementary hues may be said to fluctuate to and fro. There are some -which, in tending to the higher state, have only partially emancipated -themselves from the green of the plant.</p> - -<p class="para"><a id="a624">624.</a></p> - -<p>Flowers of the same genus, and even of the same kind, are found of all -colours. Roses, and particularly mallows, for example, vary through -a great portion of the colorific circle from white to yellow, then -through red-yellow to bright red, and from thence to the darkest hue it -can exhibit as it approaches blue.</p> - -<p class="para"><a id="a625">625.</a></p> - -<p>Others already begin from a higher degree in the scale, as, for -example, the poppy, which is yellow-red in the first instance, and -which afterwards approaches a violet hue.</p> - -<p class="para"><a id="a626">626.</a></p> - -<p>Yet the same colours in species, varieties, and even in families and -classes, if not constant, are still predominant, especially the yellow -colour: blue is throughout rarer.</p> - -<p class="para"><a id="a627">627.</a></p> - -<p>A process somewhat similar takes place in the juicy capsule of -the fruit, for it increases in colour from the green, through the -yellowish<span class="pagenum"><a name="Page_250" id="Page_250">[Pg 250]</a></span> and yellow, up to the highest red, the colour of the rind -thus indicating the degree of ripeness. Some are coloured all round, -some only on the sunny side, in which last case the augmentation of the -yellow into red,—the gradations crowding in and upon each other,—may -be very well observed.</p> - -<p class="para"><a id="a628">628.</a></p> - -<p>Many fruits, too, are coloured internally; pure red juices, especially, -are common.</p> - -<p class="para"><a id="a629">629.</a></p> - -<p>The colour which is found superficially in the flower and penetratingly -in the fruit, spreads itself through all the remaining parts, colouring -the roots and the juices of the stem, and this with a very rich and -powerful hue.</p> - -<p class="para"><a id="a630">630.</a></p> - -<p>So, again, the colour of the wood passes from yellow through the -different degrees of red up to pure red and on to brown. Blue woods are -unknown to me; and thus in this degree of organisation the active side -exhibits itself powerfully, although both principles appear balanced in -the general green of the plant.</p> - -<p class="para"><a id="a631">631.</a></p> - -<p>We have seen above that the germ pushing<span class="pagenum"><a name="Page_251" id="Page_251">[Pg 251]</a></span> from the earth is generally -white and yellowish, but that by means of the action of light and air -it acquires a green colour. The same happens with young leaves of -trees, as may be seen, for example, in the birch, the young leaves of -which are yellowish, and if boiled, yield a beautiful yellow juice: -afterwards they become greener, while the leaves of other trees become -gradually blue-green.</p> - -<p class="para"><a id="a632">632.</a></p> - -<p>Thus a yellow ingredient appears to belong more essentially to leaves -than a blue one; for this last vanishes in the autumn, and the yellow -of the leaf appears changed to a brown colour. Still more remarkable, -however, are the particular cases where leaves in autumn again become -pure yellow, and others increase to the brightest red.</p> - -<p class="para"><a id="a633">633.</a></p> - -<p>Other plants, again, may, by artificial treatment be entirely converted -to a colouring matter, which is as fine, active, and infinitely -divisible as any other. Indigo and madder, with which so much is -effected, are examples: lichens are also used for dyes.</p> - -<p class="para"><a id="a634">634.</a></p> - -<p>To this fact another stands immediately opposed;<span class="pagenum"><a name="Page_252" id="Page_252">[Pg 252]</a></span> we can, namely, -extract the colouring part of plants, and, as it were, exhibit it -apart, while the organisation does not on this account appear to suffer -at all. The colours of flowers may be extracted by spirits of wine, and -tinge it; the petals meanwhile becoming white.</p> - -<p class="para"><a id="a635">635.</a></p> - -<p>There are various modes of acting on flowers and their juices by -re-agents. This has been done by Boyle in many experiments. Roses are -bleached by sulphur, and may be restored to their first state by other -acids; roses are turned green by the smoke of tobacco.</p> - - - -<hr class="chap" /> -<h5><a name="LII" id="LII">LII.</a></h5> - - -<h5>WORMS, INSECTS, FISHES.</h5> - - -<p class="para"><a id="a636">636.</a></p> - -<p>With regard to creatures belonging to the lower degrees of -organisation, we may first observe that worms, which live in the earth -and remain in darkness and cold moisture, are imperfectly negatively -coloured; worms bred in warm moisture and darkness are colourless; -light seems expressly necessary to the definite exhibition of colour.</p> - -<p><span class="pagenum"><a name="Page_253" id="Page_253">[Pg 253]</a></span></p> - -<p class="para"><a id="a637">637.</a></p> - -<p>Creatures which live in water, which, although a very dense medium, -suffers sufficient light to pass through it, appear more or less -coloured. Zoophytes, which appear to animate the purest calcareous -earth, are mostly white; yet we find corals deepened into the most -beautiful yellow-red: in other cells of worms this colour increases -nearly to bright red.</p> - -<p class="para"><a id="a638">638.</a></p> - -<p>The shells of the crustaceous tribe are beautifully designed and -coloured, yet it is to be remarked that neither land-snails nor the -shells of crustacea of fresh water, are adorned with such bright -colours as those of the sea.</p> - -<p class="para"><a id="a639">639.</a></p> - -<p>In examining shells, particularly such as are spiral, we find that -a series of animal organs, similar to each other, must have moved -increasingly forward, and in turning on an axis produced the shell in -a series of chambers, divisions, tubes, and prominences, according to -a plan for ever growing larger. We remark, however, that a tinging -juice must have accompanied the development of these organs, a juice -which marked the surface of the shell, probably through the immediate -co-operation of the sea-water, with coloured lines, points, spots, and -shadings:<span class="pagenum"><a name="Page_254" id="Page_254">[Pg 254]</a></span> this must have taken place at regular intervals, and thus -left the indications of increasing growth lastingly on the exterior; -meanwhile the interior is generally found white or only faintly -coloured.</p> - -<p class="para"><a id="a640">640.</a></p> - -<p>That such a juice is to be found in shell-fish is, besides, -sufficiently proved by experience; for the creatures furnish it in its -liquid and colouring state: the juice of the ink-fish is an example. -But a much stronger is exhibited in the red juice found in many -shell-fish, which was so famous in ancient times, and has been employed -with advantage by the moderns. There is, it appears, in the entrails of -many of the crustaceous tribe a certain vessel which is filled with a -red juice; this contains a very strong and durable colouring substance, -so much so that the entire creature may be crushed and boiled, and -yet out of this broth a sufficiently strong tinging liquid may be -extracted. But the little vessel filled with colour may be separated -from the animal, by which means of course a concentrated juice is -gained.</p> - -<p class="para"><a id="a641">641.</a></p> - -<p>This juice has the property that when exposed to light and air it -appears first yellowish, then greenish; it then passes to blue, then to -a<span class="pagenum"><a name="Page_255" id="Page_255">[Pg 255]</a></span> violet, gradually growing redder; and lastly, by the action of the -sun, and especially if transferred to cambric, it assumes a pure bright -red colour.</p> - -<p class="para"><a id="a642">642.</a></p> - -<p>Thus we should here have an augmentation, even to culmination, on the -<i>minus</i> side, which we cannot easily meet with in inorganic cases; -indeed, we might almost call this example a passage through the -whole scale, and we are persuaded that by due experiments the entire -revolution of the circle might really be effected, for there is no -doubt that by acids duly employed, the pure red may be pushed beyond -the culminating point towards scarlet.</p> - -<p class="para"><a id="a643">643.</a></p> - -<p>This juice appears on the one hand to be connected with the phenomena -of reproduction, eggs being found, the embryos of future shell-fish, -which contain a similar colouring principle. On the other hand, in -animals ranking higher in the scale of being, the secretion appears to -bear some relation to the development of the blood. The blood exhibits -similar properties in regard to colour; in its thinnest state it -appears yellow; thickened, as it is found in the veins, it appears red; -while the arterial blood exhibits a brighter red, probably owing to the -oxydation<span class="pagenum"><a name="Page_256" id="Page_256">[Pg 256]</a></span> which takes place by means of breathing. The venous blood -approaches more to violet, and by this mutability denotes the tendency -to that augmentation and progression which are now familiar to us.</p> - -<p class="para"><a id="a644">644.</a></p> - -<p>Before we quit the element whence we derived the foregoing examples, -we may add a few observations on fishes, whose scaly surface is -coloured either altogether in stripes, or in spots, and still oftener -exhibits a certain iridescent appearance, indicating the affinity of -the scales with the coats of shell-fish, mother-of-pearl, and even -the pearl itself. At the same time it should not be forgotten that -warmer climates, the influence of which extends to the watery regions, -produce, embellish, and enhance these colours in fishes in a still -greater degree.</p> - -<p class="para"><a id="a645">645.</a></p> - -<p>In Otaheite, Forster observed fishes with beautifully iridescent -surfaces, and this effect was especially apparent at the moment when -the fish died. We may here call to mind the hues of the chameleon, -and other similar appearances; for when similar facts are presented -together, we are better enabled to trace them.</p> - -<p class="para"><a id="a646">646.</a></p> - -<p>Lastly, although not strictly in the same<span class="pagenum"><a name="Page_257" id="Page_257">[Pg 257]</a></span> class, the iridescent -appearance of certain molluscæ may be mentioned, as well as the -phosphorescence which, in some marine creatures, it is said becomes -iridescent just before it vanishes.</p> - -<p class="para"><a id="a647">647.</a></p> - -<p>We now turn our attention to those creatures which belong to light, -air and dry warmth, and it is here that we first find ourselves in -the living region of colours. Here, in exquisitely organised parts, -the elementary colours present themselves in their greatest purity -and beauty. They indicate, however, that the creatures they adorn, -are still low in the scale of organisation, precisely because these -colours can thus appear, as it were, unwrought. Here, too, heat seems -to contribute much to their development.</p> - -<p class="para"><a id="a648">648.</a></p> - -<p>We find insects which may be considered altogether as concentrated -colouring matter; among these, the cochineals especially are -celebrated; with regard to these we observe that their mode of settling -on vegetables, and even nestling in them, at the same time produces -those excrescences which are so useful as mordants in fixing colours.</p> - -<p><span class="pagenum"><a name="Page_258" id="Page_258">[Pg 258]</a></span></p> - -<p class="para"><a id="a649">649.</a></p> - -<p>But the power of colour, accompanied by regular organisation, exhibits -itself in the most striking manner in those insects which require a -perfect metamorphosis for their development—in scarabæ, and especially -in butterflies.</p> - -<p class="para"><a id="a650">650.</a></p> - -<p>These last, which might be called true productions of light and air, -often exhibit the most beautiful colours, even in their chrysalis -state, indicating the future colours of the butterfly; a consideration -which, if pursued further hereafter, must undoubtedly afford a -satisfactory insight into many a secret of organised being.</p> - -<p class="para"><a id="a651">651.</a></p> - -<p>If, again, we examine the wings of the butterfly more accurately, and -in its net-like web discover the rudiments of an arm, and observe -further the mode in which this, as it were, flattened arm is covered -with tender plumage and constituted an organ of flying; we believe -we recognise a law according to which the great variety of tints is -regulated. This will be a subject for further investigation hereafter.</p> - -<p class="para"><a id="a652">652.</a></p> - -<p>That, again, heat generally has an influence<span class="pagenum"><a name="Page_259" id="Page_259">[Pg 259]</a></span> on the size of the -creature, on the accomplishment of the form, and on the greater beauty -of the colours, hardly needs to be remarked.</p> - - - -<hr class="chap" /> -<h5><a name="LIII" id="LIII">LIII.</a></h5> - -<h5>BIRDS.</h5> - - -<p class="para"><a id="a653">653.</a></p> - -<p>The more we approach the higher organisations, the more it becomes -necessary to limit ourselves to a few passing observations; for all the -natural conditions of such organised beings are the result of so many -premises, that, without having at least hinted at these, our remarks -would only appear daring, and at the same time insufficient.</p> - -<p class="para"><a id="a654">654.</a></p> - -<p>We find in plants, that the consummate flower and fruit are, as it -were, rooted in the stem, and that they are nourished by more perfect -juices than the original roots first afforded; we remark, too, -that parasitical plants which derive their support from organised -structures, exhibit themselves especially endowed as to their energies -and qualities. We might in some sense compare the feathers of birds -with plants of this description; the feathers spring up as a last -structural result from the surface of a body<span class="pagenum"><a name="Page_260" id="Page_260">[Pg 260]</a></span> which has yet much in -reserve for the completion of the external economy, and thus are very -richly endowed organs.</p> - -<p class="para"><a id="a655">655.</a></p> - -<p>The quills not only grow proportionally to a considerable size, but are -throughout branched, by which means they properly become feathers, and -many of these feathered branches are again subdivided; thus, again, -recalling the structure of plants.</p> - -<p class="para"><a id="a656">656.</a></p> - -<p>The feathers are very different in shape and size, but each still -remains the same organ, forming and transforming itself according to -the constitution of the part of the body from which it springs.</p> - -<p class="para"><a id="a657">657.</a></p> - -<p>With the form, the colour also becomes changed, and a certain law -regulates the general order of hues as well as that particular -distribution by which a single feather becomes party coloured, It -is from this that all combination of variegated plumage arises, and -whence, at last, the eyes in the peacock's tail are produced. It is -a result similar to that which we have already unfolded in treating -of the metamorphosis of plants, and which we shall take an early -opportunity to prove.</p> - -<p><span class="pagenum"><a name="Page_261" id="Page_261">[Pg 261]</a></span></p> - -<p class="para"><a id="a658">658.</a></p> - -<p>Although time and circumstances compel us here to pass by this organic -law, yet we are bound to refer to the chemical operations which -commonly exhibit themselves in the tinting of feathers in a mode now -sufficiently known to us.</p> - -<p class="para"><a id="a659">659.</a></p> - -<p>Plumage is of all colours, yet, on the whole, yellow deepening to red -is commoner than blue.</p> - -<p class="para"><a id="a660">660.</a></p> - -<p>The operation of light on the feathers and their colours, is to be -remarked in all cases. Thus, for example, the feathers on the breast of -certain parrots, are strictly yellow; the scale-like anterior portion, -which is acted on by the light, is deepened from yellow to red. The -breast of such a bird appears bright-red, but if we blow into the -feathers the yellow appears.</p> - -<p class="para"><a id="a661">661.</a></p> - -<p>The exposed portion of the feathers is in all cases very different -from that which, in a quiet state, is covered; it is only the exposed -portion, for instance, in ravens, which exhibits the iridescent -appearance; the covered portion does not: from which indication, the -feathers of the tail when ruffled together, may be at once placed in -the natural order again.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_262" id="Page_262">[Pg 262]</a></span></p> - - - - -<h5><a name="LIV" id="LIV">LIV.</a></h5> - - -<h5>MAMMALIA AND HUMAN BEINGS.</h5> - - -<p class="para"><a id="a662">662.</a></p> - -<p>Here the elementary colours begin to leave us altogether. We are -arrived at the highest degree of the scale, and shall not dwell on its -characteristics long.</p> - -<p class="para"><a id="a663">663.</a></p> - -<p>An animal of this class is distinguished among the examples of -organised being. Every thing that exhibits itself about him is living. -Of the internal structure we do not speak, but confine ourselves -briefly to the surface. The hairs are already distinguished from -feathers, inasmuch as they belong more to the skin, inasmuch as they -are simple, thread-like, not branched. They are however, like feathers, -shorter, longer, softer, and firmer, colourless or coloured, and all -this in conformity to laws which might be defined.</p> - -<p class="para"><a id="a664">664.</a></p> - -<p>White and black, yellow, yellow-red and brown, alternate in various -modifications, but they never appear in such a state as to remind us -of the elementary hues. On the contrary,<span class="pagenum"><a name="Page_263" id="Page_263">[Pg 263]</a></span> they are all broken colours -subdued by organic concoction, and thus denote, more or less, the -perfection of life in the being they belong to.</p> - -<p class="para"><a id="a665">665.</a></p> - -<p>One of the most important considerations connected with morphology, -so far as it relates to surfaces, is this, that even in quadrupeds -the spots of the skin have a relation with the parts underneath -them. Capriciously as nature here appears, on a hasty examination, -to operate, she nevertheless consistently observes a secret law. The -development and application of this, it is true, are reserved only for -accurate and careful investigation and sincere co-operation.</p> - -<p class="para"><a id="a666">666.</a></p> - -<p>If in some animals portions appear variegated with positive colours, -this of itself shows how far such creatures are removed from a perfect -organisation; for, it may be said, the nobler a creature is, the more -all the mere material of which he is composed, is disguised by being -wrought together; the more essentially his surface corresponds with the -internal organisation, the less can it exhibit the elementary colours. -Where all tends to make up a perfect whole, any detached specific -developments cannot take place.</p> - -<p class="para"><a id="a667">667.</a></p> - -<p>Of man we have little to say, for he is entirely<span class="pagenum"><a name="Page_264" id="Page_264">[Pg 264]</a></span> distinct from the -general physiological results of which we now treat. So much in this -case is in affinity with the internal structure, that the surface can -only be sparingly endowed.</p> - -<p class="para"><a id="a668">668.</a></p> - -<p>When we consider that brutes are rather encumbered than advantageously -provided with intercutaneous muscles; when we see that much that is -superfluous tends to the surface, as, for instance, large ears and -tails, as well as hair, manes, tufts; we see that nature, in such -cases, had much to give away and to lavish.</p> - -<p class="para"><a id="a669">669.</a></p> - -<p>On the contrary, the general surface of the human form is smooth and -clean, and thus in the most perfect examples, the beautiful forms are -apparent; for it may be remarked in passing, that a superfluity of -hair on the chest, arms, and lower limbs, rather indicates weakness -than strength. Poets only have sometimes been induced, probably by the -example of the ferine nature, so strong in other respects, to extol -similar attributes in their rough heroes.</p> - -<p class="para"><a id="a670">670.</a></p> - -<p>But we have here chiefly to speak of colour, and observe that the -colour of the human skin, in all its varieties, is never an elementary -colour,<span class="pagenum"><a name="Page_265" id="Page_265">[Pg 265]</a></span> but presents, by means of organic concoction, a highly -complicated result.—<a href="#NOTE_X">Note X</a>.</p> - -<p class="para"><a id="a671">671.</a></p> - -<p>That the colour of the skin and hair has relation with the differences -of character, is beyond question; and we are led to conjecture that the -circumstance of one or other organic system predominating, produces -the varieties we see. A similar hypothesis may be applied to nations, -in which case it might perhaps be observed, that certain colours -correspond with certain confirmations, which has always been observed -of the negro physiognomy.</p> - -<p class="para"><a id="a672">672.</a></p> - -<p>Lastly, we might here consider the problematical question, whether all -human forms and hues are not equally beautiful, and whether custom -and self-conceit are not the causes why one is preferred to another? -We venture, however, after what has been adduced, to assert that the -white man, that is, he whose surface varies from white to reddish, -yellowish, brownish, in short, whose surface appears most neutral in -hue and least inclines to any particular or positive colour, is the -most beautiful. On the same principle a similar point of perfection in -human conformation may be defined hereafter, when the question relates -to form. We do not<span class="pagenum"><a name="Page_266" id="Page_266">[Pg 266]</a></span> imagine that this long-disputed question is to be -thus, once for all, settled, for there are persons enough who have -reason to leave this significancy of the exterior in doubt; but we thus -express a conclusion, derived from observation and reflection, such -as might suggest itself to a mind aiming at a satisfactory decision. -We subjoin a few observations connected with the elementary chemical -doctrine of colours.—<a href="#NOTE_Y">Note Y</a>.</p> - - - -<hr class="chap" /> -<h5><a name="LV" id="LV">LV.</a></h5> - - -<h5>PHYSICAL AND CHEMICAL EFFECTS OF THE TRANSMISSION OF LIGHT THROUGH -COLOURED MEDIUMS.</h5> - - -<p class="para"><a id="a673">673.</a></p> - -<p>The physical and chemical effects of colourless light are known, so -that it is unnecessary here to describe them at length. Colourless -light exhibits itself under various conditions as exciting warmth, as -imparting a luminous quality to certain bodies, as promoting oxydation -and de-oxydation. In the modes and degrees of these effects many -varieties take place, but no difference is found indicating a principle -of contrast such as we find in the transmission of coloured light. We -proceed briefly to advert to this.</p> - -<p><span class="pagenum"><a name="Page_267" id="Page_267">[Pg 267]</a></span></p> - -<p class="para"><a id="a674">674.</a></p> - -<p>Let the temperature of a dark room be observed by means of a very -sensible air-thermometer; if the bulb is then brought to the direct sun -light as it shines into the room, nothing is more natural than that the -fluid should indicate a much higher degree of warmth. If upon this we -interpose coloured glasses, it follows again quite naturally that the -degree of warmth must be lowered; first, because the operation of the -direct light is already somewhat impeded by the glass, and again, more -especially, because a coloured glass, as a dark medium, admits less -light through it.</p> - -<p class="para"><a id="a675">675.</a></p> - -<p>But here a difference in the excitation of warmth exhibits itself to -the attentive observer, according to the colour of the glass. The -yellow and the yellow-red glasses produce a higher temperature than the -blue and blue-red, the difference being considerable.</p> - -<p class="para"><a id="a676">676.</a></p> - -<p>This experiment may be made with the prismatic spectrum. The -temperature of the room being first remarked on the thermometer, the -blue coloured light is made to fall on the bulb, when a somewhat higher -degree of warmth is exhibited, which still increases as the other -colours<span class="pagenum"><a name="Page_268" id="Page_268">[Pg 268]</a></span> are gradually brought to act on the mercury. If the experiment -is made with the water-prism, so that the white light can be retained -in the centre, this, refracted indeed, but not yet coloured light, is -the warmest; the other colours, stand in relation to each other as -before.</p> - -<p class="para"><a id="a677">677.</a></p> - -<p>As we here merely describe, without undertaking to deduce or explain -this phenomenon, we only remark in passing, that the pure light is by -no means abruptly and entirely at an end with the red division in the -spectrum, but that a refracted light is still to be observed deviating -from its course and, as it were, insinuating itself beyond the -prismatic image, so that on closer examination it will hardly be found -necessary to take refuge in invisible rays and their refraction.</p> - -<p class="para"><a id="a678">678.</a></p> - -<p>The communication of light by means of coloured mediums exhibits the -same difference. The light communicates itself to Bologna phosphorus -through blue and violet glasses, but by no means through yellow and -yellow-red glasses. It has been even remarked that the phosphori which -have been rendered luminous under violet and blue glasses, become -sooner extinguished when afterwards placed under yellow and yellow-red -glasses than those which have been<span class="pagenum"><a name="Page_269" id="Page_269">[Pg 269]</a></span> suffered to remain in a dark room -without any further influence.</p> - -<p class="para"><a id="a679">679.</a></p> - -<p>These experiments, like the foregoing, may also be made by means of the -prismatic spectrum, when the same results take place.</p> - -<p class="para"><a id="a680">680.</a></p> - -<p>To ascertain the effect of coloured light on oxydation and -de-oxydation, the following means may be employed:—Let moist, -perfectly white muriate of silver<a name="FNanchor_1_50" id="FNanchor_1_50"></a><a href="#Footnote_1_50" class="fnanchor">[1]</a> be spread on a strip of paper; -place it in the light, so that it may become to a certain degree grey, -and then cut it in three portions. Of these, one may be preserved -in a book, as a specimen of this state; let another be placed under -a yellow-red, and the third under a blue-red glass. The last will -become a darker grey, and exhibit a de-oxydation; the other, under the -yellow-red glass, will, on the contrary, become a lighter grey, and -thus approach nearer to the original state of more perfect oxydation. -The change in both may be ascertained by a comparison with the -unaltered specimen.</p> - -<p class="para"><a id="a681">681.</a></p> - -<p>An excellent apparatus has been contrived to<span class="pagenum"><a name="Page_270" id="Page_270">[Pg 270]</a></span> perform these experiments -with the prismatic image. The results are analogous to those already -mentioned, and we shall hereafter give the particulars, making use -of the labours of an accurate observer, who has been for some time -carefully prosecuting these experiments.<a name="FNanchor_2_51" id="FNanchor_2_51"></a><a href="#Footnote_2_51" class="fnanchor">[2]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_50" id="Footnote_1_50"></a><a href="#FNanchor_1_50"><span class="label">[1]</span></a> Now generally called chloride of silver: the term in the -original is Hornsilber.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_51" id="Footnote_2_51"></a><a href="#FNanchor_2_51"><span class="label">[2]</span></a> The individual alluded to was Seebeck: the result of his -experiments was published in the second volume.—T.</p></div> - - -<hr class="chap" /> - -<h5><a name="LVI" id="LVI">LVI.</a></h5> - - -<h5>CHEMICAL EFFECT IN DIOPTRICAL ACHROMATISM.</h5> - - -<p class="para"><a id="a682">682.</a></p> - -<p>We first invite our readers to turn to what has been before observed on -this subject (<a href="#a285">285</a>, <a href="#a298">298</a>), to avoid unnecessary repetition here.</p> - -<p class="para"><a id="a683">683.</a></p> - -<p>We can thus give a glass the property of producing much wider coloured -edges without refracting more strongly than before, that is, without -displacing the object much more perceptibly.</p> - -<p class="para"><a id="a684">684.</a></p> - -<p>This property is communicated to the glass by means of metallic oxydes. -Minium, melted and thoroughly united with a pure glass, produces<span class="pagenum"><a name="Page_271" id="Page_271">[Pg 271]</a></span> this -effect, and thus flint-glass (<a href="#a291">291</a>) is prepared with oxyde of lead. -Experiments of this kind have been carried farther, and the so-called -butter of antimony, which, according to a new preparation, may be -exhibited as a pure fluid, has been made use of in hollow lenses and -prisms, producing a very strong appearance of colour with a very -moderate refraction, and presenting the effect which we have called -hyperchromatism in a very vivid manner.</p> - -<p class="para"><a id="a685">685.</a></p> - -<p>In common glass, the alkaline nature obviously preponderates, since -it is chiefly composed of sand and alkaline salts; hence a series of -experiments, exhibiting the relation of perfectly alkaline fluids to -perfect acids, might lead to useful results.</p> - -<p class="para"><a id="a686">686.</a></p> - -<p>For, could the maximum and minimum be found, it would be a question -whether a refracting medium could not be discovered, in which the -increasing and diminishing appearance of colour, (an effect almost -independent of refraction,) could not be done away with altogether, -while the displacement of the object would be unaltered.</p> - -<p class="para"><a id="a687">687.</a></p> - -<p>How desirable, therefore, it would be with<span class="pagenum"><a name="Page_272" id="Page_272">[Pg 272]</a></span> regard to this last point, -as well as for the elucidation of the whole of this third division of -our work, and, indeed, for the elucidation of the doctrine of colours -generally, that those who are occupied in chemical researches, with new -views ever opening to them, should take this subject in hand, pursuing -into more delicate combinations what we have only roughly hinted at, -and prosecuting their inquiries with reference to science as a whole.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_273" id="Page_273">[Pg 273]</a></span></p> - - - - -<h5><a name="PART_IV" id="PART_IV">PART IV.</a></h5> - - -<h5>GENERAL CHARACTERISTICS.</h5> - - -<p class="para"><a id="a688">688.</a></p> - -<p>We have hitherto, in a manner forcibly, kept phenomena asunder, -which, partly from their nature, partly in accordance with our mental -habits, have, as it were, constantly sought to be reunited. We have -exhibited them in three divisions. We have considered colours, first, -as transient, the result of an action and re-action in the eye -itself; next, as passing effects of colourless, light-transmitting, -transparent, or opaque mediums on light; especially on the luminous -image; lastly, we arrived at the point where we could securely -pronounce them as permanent, and actually inherent in bodies.</p> - -<p class="para"><a id="a689">689.</a></p> - -<p>In following this order we have as far as possible endeavoured to -define, to separate, and to class the appearances. But now that we -need no longer be apprehensive of mixing or confounding them, we may -proceed, first, to state the general nature of these appearances -considered abstractedly, as an independent circle of facts, and, in the -next place, to show how this particular circle is connected with other -classes of analogous phenomena in nature.</p> -<hr class="tb" /> -<p><span class="pagenum"><a name="Page_274" id="Page_274">[Pg 274]</a></span></p> - - -<h5>THE FACILITY WITH WHICH COLOUR APPEARS.</h5> - - -<p class="para"><a id="a690">690.</a></p> - -<p>We have observed that colour under many conditions appears very easily. -The susceptibility of the eye with regard to light, the constant -re-action of the retina against it, produce instantaneously a slight -iridescence. Every subdued light may be considered as coloured, nay, we -ought to call any light coloured, inasmuch as it is seen. Colourless -light, colourless surfaces, are, in some sort, abstract ideas; in -actual experience we can hardly be said to be aware of them.—<a href="#NOTE_Z">Note Z</a>.</p> - -<p class="para"><a id="a691">691.</a></p> - -<p>If light impinges on a colourless body, is reflected from it or passes -through it, colour immediately appears; but it is necessary here to -remember what has been so often urged by us, namely, that the leading -conditions of refraction, reflection, &c., are not of themselves -sufficient to produce the appearance. Sometimes, it is true, light acts -with these merely as light, but oftener as a defined, circumscribed -appearance, as a luminous image. The semi-opacity of the medium is -often a necessary condition; while half, and double shadows, are -required for many coloured appearances. In all cases, however, colour -appears instantaneously. We find, again, that by means of pressure, -breathing heat (<a href="#a432">432</a>, <a href="#a471">471</a>), by various kinds of motion and<span class="pagenum"><a name="Page_275" id="Page_275">[Pg 275]</a></span> alteration -on smooth clean surfaces (<a href="#a461">461</a>), as well as on colourless fluids (<a href="#a470">470</a>), -colour is immediately produced.</p> - -<p class="para"><a id="a692">692.</a></p> - -<p>The slightest change has only to take place in the component parts -of bodies, whether by immixture with other particles or other such -effects, and colour either makes its appearance or becomes changed.</p> - -<hr class="tb" /> -<h5>THE FORCE OF COLOUR.</h5> - - -<p class="para"><a id="a693">693.</a></p> - -<p>The physical colours, and especially those of the prism, were formerly -called "<i>colores emphatici</i>," on account of their extraordinary beauty -and force. Strictly speaking, however, a high degree of effect may be -ascribed to all appearances of colour, assuming that they are exhibited -under the purest and most perfect conditions.</p> - -<p class="para"><a id="a694">694.</a></p> - -<p>The dark nature of colour, its full rich quality, is what produces -the grave, and at the same time fascinating impression we sometimes -experience, and as colour is to be considered a condition of light, -so it cannot dispense with light as the co-operating cause of its -appearance, as its basis or ground; as a power thus displaying and -manifesting colour.</p> - -<p><span class="pagenum"><a name="Page_276" id="Page_276">[Pg 276]</a></span></p> - -<hr class="tb" /> -<h5>THE DEFINITE NATURE OF COLOUR.</h5> - - -<p class="para"><a id="a695">695.</a></p> - -<p>The existence and the relatively definite character of colour are one -and the same thing. Light displays itself and the face of nature, as -it were, with a general indifference, informing us as to surrounding -objects perhaps devoid of interest or importance; but colour is at all -times specific, characteristic, significant.</p> - -<p class="para"><a id="a696">696.</a></p> - -<p>Considered in a general point of view, colour is determined towards one -of two sides. It thus presents a contrast which we call a polarity, and -which we may fitly designate by the expressions <i>plus</i> and <i>minus</i>.</p> - -<table border="0" cellpadding="2" cellspacing="0" summary=""> -<tr><th align="left" colspan="1"><i>Plus</i>.</th><th align="left" colspan="1"><i>Minus</i>.</th></tr> -<tr><td align="left">Yellow.</td><td align="left">Blue.</td></tr> -<tr><td align="left">Action.</td><td align="left">Negation.<a name="FNanchor_1_52" id="FNanchor_1_52"></a><a href="#Footnote_1_52" class="fnanchor">[1]</a></td></tr> -<tr><td align="left">Light.</td><td align="left">Shadow.</td></tr> -<tr><td align="left">Brightness.</td><td align="left">Darkness.</td></tr> -<tr><td align="left">Force.</td><td align="left">Weakness.</td></tr> -<tr><td align="left">Warmth.</td><td align="left">Coldness.</td></tr> -<tr><td align="left">Proximity.</td><td align="left">Distance.</td></tr> -<tr><td align="left">Repulsion</td><td align="left">Attraction.</td></tr> -<tr><td align="left">Affinity with acids. </td><td align="left">Affinity with alkalis.</td></tr> -</table> - -<p><span class="pagenum"><a name="Page_277" id="Page_277">[Pg 277]</a></span></p> - - -<hr class="tb" /> -<h5>COMBINATION OF THE TWO PRINCIPLES.</h5> - - -<p class="para"><a id="a697">697.</a></p> - -<p>If these specific, contrasted principles are combined, the respective -qualities do not therefore destroy each other: for if in this -intermixture the ingredients are so perfectly balanced that neither -is to be distinctly recognised, the union again acquires a specific -character; it appears as a quality by itself in which we no longer -think of combination. This union we call green.</p> - -<p class="para"><a id="a698">698.</a></p> - -<p>Thus, if two opposite phenomena springing from the same source do not -destroy each other when combined, but in their union present a third -appreciable and pleasing appearance, this result at once indicates -their harmonious relation. The more perfect result yet remains to be -adverted to.</p> - -<hr class="tb" /> -<h5>AUGMENTATION TO RED.</h5> - - -<p class="para"><a id="a699">699.</a></p> - -<p>Blue and yellow do not admit of increased intensity without presently -exhibiting a new appearance in addition to their own. Each colour, in -its lightest state, is a dark; if condensed it must become darker, but -this effect no sooner takes place than the hue assumes an appearance -which we designate by the word reddish.</p> - -<p><span class="pagenum"><a name="Page_278" id="Page_278">[Pg 278]</a></span></p> - -<p class="para"><a id="a700">700.</a></p> - -<p>This appearance still increases, so that when the highest degree of -intensity is attained it predominates over the original hue. A powerful -impression of light leaves the sensation of red on the retina. In the -prismatic yellow-red which springs directly from the yellow, we hardly -recognise the yellow.</p> - -<p class="para"><a id="a701">701.</a></p> - -<p>This deepening takes place again by means of colourless -semi-transparent mediums, and here we see the effect in its utmost -purity and extent. Transparent fluids, coloured with any given hues, in -a series of glass-vessels, exhibit it very strikingly. The augmentation -is unremittingly rapid and constant; it is universal, and obtains in -physiological as well as in physical and chemical colours.</p> - -<hr class="tb" /> -<h5>JUNCTION OF THE TWO AUGMENTED EXTREMES.</h5> - - -<p class="para"><a id="a702">702.</a></p> - -<p>As the extremes of the simple contrast produce a beautiful and -agreeable appearance by their union, so the deepened extremes on being -united, will present a still more fascinating colour; indeed, it might -naturally be expected that we should here find the acme of the whole -phenomenon.</p> - -<p><span class="pagenum"><a name="Page_279" id="Page_279">[Pg 279]</a></span></p> -<hr class="tb" /> -<h5>COMPLETENESS THE RESULT OF VARIETY.</h5> - - -<p class="para"><a id="a703">703.</a></p> - -<p>And such is the fact, for pure red appears; a colour to which, from its -excellence, we have appropriated the term "purpur."<a name="FNanchor_2_53" id="FNanchor_2_53"></a><a href="#Footnote_2_53" class="fnanchor">[2]</a></p> - -<p class="para"><a id="a704">704.</a></p> - -<p>There are various modes in which pure red may appear. By bringing -together the violet edge and yellow-red border in prismatic -experiments, by continued augmentation in chemical operations, and by -the organic contrast in physiological effects.</p> - -<p class="para"><a id="a705">705.</a></p> - -<p>As a pigment it cannot be produced by intermixture or union, but -only by arresting the hue in substances chemically acted on, at the -high culminating point. Hence the painter is justified in assuming -that there are <i>three</i> primitive colours from which he combines all -the others. The natural philosopher, on the other hand, assumes only -<i>two</i> elementary colours, from which he, in like manner, developes and -combines the rest.</p> - -<hr class="tb" /> -<h5>COMPLETENESS THE RESULT OF VARIETY IN COLOUR.</h5> - - -<p class="para"><a id="a706">706.</a></p> - -<p>The various appearances of colour arrested in<span class="pagenum"><a name="Page_280" id="Page_280">[Pg 280]</a></span> their different degrees, -and seen in juxtaposition, produce a whole. This totality is harmony to -the eye.</p> - -<p class="para"><a id="a707">707.</a></p> - -<p>The chromatic circle has been gradually presented to us; the -various relations of its progression are apparent to us. Two pure -original principles in contrast, are the foundation of the whole; -an augmentation manifests itself by means of which both approach a -third state; hence there exists on both sides a lowest and highest, -a simplest and most qualified state. Again, two combinations present -themselves; first that of the simple primitive contrasts, then that of -the deepened contrasts.</p> - -<hr class="tb" /> -<h5>HARMONY OF THE COMPLETE STATE.</h5> - - -<p class="para"><a id="a708">708.</a></p> - -<p>The whole ingredients of the chromatic scale, seen in juxtaposition, -produce an harmonious impression on the eye. The difference between the -physical contrast and harmonious opposition in all its extent should -not be overlooked. The first resides in the pure restricted original -dualism, considered in its antagonizing elements; the other results -from the fully developed effects of the complete state.</p> - -<p class="para"><a id="a709">709.</a></p> - -<p>Every single opposition in order to be harmonious must comprehend the -whole. The<span class="pagenum"><a name="Page_281" id="Page_281">[Pg 281]</a></span> physiological experiments are sufficiently convincing -on this point. A development of all the possible contrasts of the -chromatic scale will be shortly given.<a name="FNanchor_3_54" id="FNanchor_3_54"></a><a href="#Footnote_3_54" class="fnanchor">[3]</a></p> - -<hr class="tb" /> -<h5>FACILITY WITH WHICH COLOUR MAY BE MADE TO TEND EITHER TO THE PLUS OR -MINUS SIDE.</h5> - - -<p class="para"><a id="a710">710.</a></p> - -<p>We have already had occasion to take notice of the mutability of colour -in considering its so-called augmentation and progressive variations -round the whole circle; but the hues even pass and repass from one side -to the other, rapidly and of necessity.</p> - -<p class="para"><a id="a711">711.</a></p> - -<p>Physiological colours are different in appearance as they happen -to fall on a dark or on a light ground. In physical colours the -combination of the objective and subjective experiments is very -remarkable. The epoptical colours, it appears, are contrasted according -as the light shines through or upon them. To what extent the chemical -colours may be changed by fire and alkalis, has been sufficiently shown -in its proper place.</p> - -<hr class="tb" /> -<h5>EVANESCENCE OF COLOUR.</h5> - - -<p class="para"><a id="a712">712.</a></p> - -<p>All that has been adverted to as subsequent<span class="pagenum"><a name="Page_282" id="Page_282">[Pg 282]</a></span> to the rapid excitation -and definition of colour, immixture, augmentation, combination, -separation, not forgetting the law of compensatory harmony, all takes -place with the greatest rapidity and facility; but with equal quickness -colour again altogether disappears.</p> - -<p class="para"><a id="a713">713.</a></p> - -<p>The physiological appearances are in no wise to be arrested; the -physical last only as long as the external condition lasts; even the -chemical colours have great mutability, they may be made to pass and -repass from one side to the other by means of opposite re-agents, and -may even be annihilated altogether.</p> - -<hr class="tb" /> -<h5>PERMANENCE OF COLOUR.</h5> - - -<p class="para"><a id="a714">714.</a></p> - -<p>The chemical colours afford evidence of very great duration. Colours -fixed in glass by fusion, and by nature in gems, defy all time and -re-action.</p> - -<p class="para"><a id="a715">715.</a></p> - -<p>The art of dyeing again fixes colour very powerfully. The hues of -pigments which might otherwise be easily rendered mutable by re-agents, -may be communicated to substances in the greatest permanency by means -of mordants.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_52" id="Footnote_1_52"></a><a href="#FNanchor_1_52"><span class="label">[1]</span></a> Wirkung, Beraubung; the last would be more literally -rendered <i>privation</i>. The author has already frequently made use of the -terms <i>active</i> and <i>passive</i> as equivalent to <i>plus</i> and <i>minus</i>.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_53" id="Footnote_2_53"></a><a href="#FNanchor_2_53"><span class="label">[2]</span></a> Wherever this word occurs incidentally it is translated -<i>pure red</i>, the English word <i>purple</i> being generally employed to -denote a colour similar to violet.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_54" id="Footnote_3_54"></a><a href="#FNanchor_3_54"><span class="label">[3]</span></a> No diagram or table of this kind was ever given by the -author.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_283" id="Page_283">[Pg 283]</a></span></p></div> - - - - -<h5><a name="PART_V" id="PART_V">PART V.</a></h5> - - -<h5>RELATION TO OTHER PURSUITS—RELATION TO PHILOSOPHY.</h5> - - -<p class="para"><a id="a716">716.</a></p> - -<p>The investigator of nature cannot be required to be a philosopher, -but it is expected that he should so far have attained the habit of -philosophizing, as to distinguish himself essentially from the world, -in order to associate himself with it again in a higher sense. He -should form to himself a method in accordance with observation, but -he should take heed not to reduce observation to mere notion, to -substitute words for this notion, and to use and deal with these words -as if they were things. He should be acquainted with the labours of -philosophers, in order to follow up the phenomena which have been the -subject of his observation, into the philosophic region.</p> - -<p class="para"><a id="a717">717.</a></p> - -<p>It cannot be required that the philosopher should be a naturalist, and -yet his co-operation in physical researches is as necessary as it is -desirable. He needs not an acquaintance with details for this, but only -a clear view of those conclusions where insulated facts meet.</p> - -<p><span class="pagenum"><a name="Page_284" id="Page_284">[Pg 284]</a></span></p> - -<p class="para"><a id="a718">718.</a></p> - -<p>We have before (<a href="#a175">175</a>) alluded to this important consideration, and -repeat it here where it is in its place. The worst that can happen -to physical science as well as to many other kinds of knowledge is, -that men should treat a secondary phenomenon as a primordial one, and -(since it is impossible to derive the original fact from the secondary -state), seek to explain what is in reality the cause by an effect made -to usurp its place. Hence arises an endless confusion, a mere verbiage, -a constant endeavour to seek and to find subterfuges whenever truth -presents itself and threatens to be overpowering.</p> - -<p class="para"><a id="a719">719.</a></p> - -<p>While the observer, the investigator of nature, is thus dissatisfied -in finding that the appearances he sees still contradict a received -theory, the philosopher can calmly continue to operate in his abstract -department on a false result, for no result is so false but that it can -be made to appear valid, as form without substance, by some means or -other.</p> - -<p class="para"><a id="a720">720.</a></p> - -<p>If, on the other hand, the investigator of nature can attain to the -knowledge of that which we have called a primordial phenomenon, he is -safe; and the philosopher with him. The investigator<span class="pagenum"><a name="Page_285" id="Page_285">[Pg 285]</a></span> of nature is -safe, since he is persuaded that he has here arrived at the limits -of his science, that he finds himself at the height of experimental -research; a height whence he can look back upon the details of -observation in all its steps, and forwards into, if he cannot enter, -the regions of theory. The philosopher is safe, for he receives -from the experimentalist an ultimate fact, which, in his hands, now -becomes an elementary one. He now justly pays little attention to -appearances which are understood to be secondary, whether he already -finds them scientifically arranged, or whether they present themselves -to his casual observation scattered and confused. Should he even be -inclined to go over this experimental ground himself, and not be -averse to examination in detail, he does this conveniently, instead of -lingering too long in the consideration of secondary and intermediate -circumstances, or hastily passing them over without becoming accurately -acquainted with them.</p> - -<p class="para"><a id="a721">721.</a></p> - -<p>To place the doctrine of colours nearer, in this sense, within the -philosopher's reach, was the author's wish; and although the execution -of his purpose, from various causes, does not correspond with his -intention, he will still keep this object in view in an intended -recapitulation,<span class="pagenum"><a name="Page_286" id="Page_286">[Pg 286]</a></span> as well as in the polemical and historical portions of -his work; for he will have to return to the consideration of this point -hereafter, on an occasion where it will be necessary to speak with less -reserve.</p> - -<hr class="tb" /> -<h5>RELATION TO MATHEMATICS.</h5> - - -<p class="para"><a id="a722">722.</a></p> - -<p>It may be expected that the investigator of nature, who proposes to -treat the science of natural philosophy in its entire range, should be -a mathematician. In the middle ages, mathematics was the chief organ by -means of which men hoped to master the secrets of nature, and even now, -geometry in certain departments of physics, is justly considered of -first importance.</p> - -<p class="para"><a id="a723">723.</a></p> - -<p>The author can boast of no attainments of this kind, and on this -account confines himself to departments of science which are -independent of geometry; departments which in modern times have been -opened up far and wide.</p> - -<p class="para"><a id="a724">724.</a></p> - -<p>It will be universally allowed that mathematics, one of the noblest -auxiliaries which can be employed by man, has, in one point of view, -been of the greatest use to the physical sciences; but that, by a -false application of its methods,<span class="pagenum"><a name="Page_287" id="Page_287">[Pg 287]</a></span> it has, in many respects, been -prejudicial to them, is also not to be denied; we find it here and -there reluctantly admitted.</p> - -<p class="para"><a id="a725">725.</a></p> - -<p>The theory of colours, in particular, has suffered much, and its -progress has been incalculably retarded by having been mixed up with -optics generally, a science which cannot dispense with mathematics; -whereas the theory of colours, in strictness, may be investigated quite -independently of optics.</p> - -<p class="para"><a id="a726">726.</a></p> - -<p>But besides this there was an additional evil. A great mathematician -was possessed with an entirely false notion on the physical origin of -colours; yet, owing to his great authority as a geometer, the mistakes -which he committed as an experimentalist long became sanctioned in the -eyes of a world ever fettered in prejudices.</p> - -<p class="para"><a id="a727">727.</a></p> - -<p>The author of the present inquiry has endeavoured throughout to keep -the theory of colours distinct from the mathematics, although there -are evidently certain points where the assistance of geometry would be -desirable. Had not the unprejudiced mathematicians, with whom he has -had, or still has, the good fortune to be acquainted,<span class="pagenum"><a name="Page_288" id="Page_288">[Pg 288]</a></span> been prevented -by other occupations from making common cause with him, his work would -not have wanted some merit in this respect. But this very want may be -in the end advantageous, since it may now become the object of the -enlightened mathematician to ascertain where the doctrine of colours is -in need of his aid, and how he can contribute the means at his command -with a view to the complete elucidation of this branch of physics.</p> - -<p class="para"><a id="a728">728.</a></p> - -<p>In general it were to be wished that the Germans, who render such -good service to science, while they adopt all that is good from other -nations, could by degrees accustom themselves to work in concert. We -live, it must be confessed, in an age, the habits of which are directly -opposed to such a wish. Every one seeks, not only to be original in -his views, but to be independent of the labours of others, or at least -to persuade himself that he is so, even in the course of his life -and occupation. It is very often remarked that men who undoubtedly -have accomplished much, quote themselves only, their own writings, -journals, and compendiums; whereas it would be far more advantageous -for the individual, and for the world, if many were devoted to a common -pursuit. The conduct of our neighbours the French is, in this respect, -worthy<span class="pagenum"><a name="Page_289" id="Page_289">[Pg 289]</a></span> of imitation; we have a pleasing instance in Cuvier's preface -to his "Tableau Élémentaire de l'Histoire Naturelle des Animaux."</p> - -<p class="para"><a id="a729">729.</a></p> - -<p>He who has observed science and its progress with an unprejudiced eye, -might even ask whether it is desirable that so many occupations and -aims, though allied to each other, should be united in one person, and -whether it would not be more suitable for the limited powers of the -human mind to distinguish, for example, the investigator and inventor, -from him who employs and applies the result of experiment? Astronomers, -who devote themselves to the observation of the heavens and the -discovery or enumeration of stars, have in modern times formed, to a -certain extent, a distinct class from those who calculate the orbits, -consider the universe in its connexion, and more accurately define its -laws. The history of the doctrine of colours will often lead us back to -these considerations.</p> - -<hr class="tb" /> -<h5>RELATION TO THE TECHNICAL OPERATIONS OF THE DYER.</h5> - - -<p class="para"><a id="a730">730.</a></p> - -<p>If in our labours we have gone out of the province of the -mathematician, we have, on the other hand, endeavoured to meet the -practical<span class="pagenum"><a name="Page_290" id="Page_290">[Pg 290]</a></span> views of the dyer; and although the chapter which treats -of colour in a chemical point of view is not the most complete and -circumstantial, yet in that portion, as well as in our general -observations respecting colour, the dyer will find his views assisted -far more than by the theory hitherto in vogue, which failed to afford -him any assistance.</p> - -<p class="para"><a id="a731">731.</a></p> - -<p>It is curious, in this view, to take a glance at the works containing -directions on the art of dyeing. As the Catholic, on entering his -temple, sprinkles himself with holy water, and after bending the knee, -proceeds perhaps to converse with his friends on his affairs, without -any especial devotion; so all the treatises on dyeing begin with a -respectful allusion to the accredited theory, without afterwards -exhibiting a single trace of any principle deduced from this theory, -or showing that it has thrown light on any part of the art, or that it -offers any useful hints in furtherance of practical methods.</p> - -<p class="para"><a id="a732">732.</a></p> - -<p>On the other hand, there are men who, after having become thoroughly -and experimentally acquainted with the nature of dyes, have not been -able to reconcile their observations with the received theory; who -have, in short, discovered<span class="pagenum"><a name="Page_291" id="Page_291">[Pg 291]</a></span> its weak points, and sought for a general -view more consonant to nature and experience. When we come to the names -of Castel and Gülich, in our historical review, we shall have occasion -to enter into this more fully, and an opportunity will then present -itself to show that an assiduous experience in taking advantage of -every accident may, in fact, be said almost to exhaust the knowledge -of the province to which it is confined. The high and complete result -is then submitted to the theorist, who, if he examines facts with -accuracy, and reasons with candour, will find such materials eminently -useful as a basis for his conclusions.—<a href="#NOTE_AA">Note AA</a>.</p> - -<hr class="tb" /> -<h5>RELATION TO PHYSIOLOGY AND PATHOLOGY.</h5> - - -<p class="para"><a id="a733">733.</a></p> - -<p>If the phenomena adduced in the chapter where colours were considered -in a physiological and pathological view are for the most part -generally known, still some new views, mixed up with them, will not be -unacceptable to the physiologist. We especially hope to have given him -cause to be satisfied by classing certain phenomena which stood alone, -under analogous facts, and thus, in some measure, to have prepared the -way for his further investigations.</p> - -<p class="para"><a id="a734">734.</a></p> - -<p>The appendix on pathological colours, again,<span class="pagenum"><a name="Page_292" id="Page_292">[Pg 292]</a></span> is admitted to be scanty -and unconnected. We reflect, however, that Germany can boast of men who -are not only highly experienced in this department, but are likewise so -distinguished for general cultivation, that it can cost them but little -to revise this portion, to complete what has been sketched, and at the -same time to connect it with the higher facts of organisation.</p> - -<hr class="tb" /> -<h5>RELATION TO NATURAL HISTORY.</h5> - - -<p class="para"><a id="a735">735.</a></p> - -<p>If we may at all hope that natural history will gradually be modified -by the principle of deducing the ordinary appearances of nature from -higher phenomena, the author believes he may have given some hints -and introductory views bearing on this object also. As colour, in its -infinite variety, exhibits itself on the surface of living beings, it -becomes an important part of the outward indications, by means of which -we can discover what passes underneath.</p> - -<p class="para"><a id="a736">736.</a></p> - -<p>In one point of view it is certainly not to be too much relied on, on -account of its indefinite and mutable nature; yet even this mutability, -inasmuch as it exhibits itself as a constant quality, again becomes -a criterion of a mutable vitality; and the author wishes nothing -more<span class="pagenum"><a name="Page_293" id="Page_293">[Pg 293]</a></span> than that time may be granted him to develop the results of his -observations on this subject more fully; here they would not be in -their place.</p> - -<hr class="tb" /> -<h5>RELATION TO GENERAL PHYSICS.</h5> - - -<p class="para"><a id="a737">737.</a></p> - -<p>The state in which general physics now is, appears, again, particularly -favourable to our labours; for natural philosophy, owing to -indefatigable and variously directed research, has gradually attained -such eminence, that it appears not impossible to refer a boundless -empiricism to one centre.</p> - -<p class="para"><a id="a738">738.</a></p> - -<p>Without referring to subjects which are too far removed from our own -province, we observe that the formulæ under which the elementary -appearances of nature are expressed, altogether tend in this direction; -and it is easy to see that through this correspondence of expression, a -correspondence in meaning will necessarily be soon arrived at.</p> - -<p class="para"><a id="a739">739.</a></p> - -<p>True observers of nature, however they may differ in opinion in other -respects, will agree that all which presents itself as appearance, all -that we meet with as phenomenon, must either<span class="pagenum"><a name="Page_294" id="Page_294">[Pg 294]</a></span> indicate an original -division which is capable of union, or an original unity which admits -of division, and that the phenomenon will present itself accordingly. -To divide the united, to unite the divided, is the life of nature; -this is the eternal systole and diastole, the eternal collapsion and -expansion, the inspiration and expiration of the world in which we live -and move.</p> - -<p class="para"><a id="a740">740.</a></p> - -<p>It is hardly necessary to observe that what we here express as number -and restrict to dualism is to be understood in a higher sense; the -appearance of a third, a fourth order of facts progressively developing -themselves is to be similarly understood; but actual observation -should, above all, be the basis of all these expressions.</p> - -<p class="para"><a id="a741">741.</a></p> - -<p>Iron is known to us as a peculiar substance, different from other -substances: in its ordinary state we look upon it as a mere material -remarkable only on account of its fitness for various uses and -applications. How little, however, is necessary to do away with the -comparative insignificancy of this substance. A two-fold power is -called forth,<a name="FNanchor_1_55" id="FNanchor_1_55"></a><a href="#Footnote_1_55" class="fnanchor">[1]</a> which, while it tends again to a<span class="pagenum"><a name="Page_295" id="Page_295">[Pg 295]</a></span> state of union, and, -as it were, seeks itself, acquires a kind of magical relation with -its like, and propagates this double property, which is in fact but a -principle of reunion, throughout all bodies of the same kind. We here -first observe the mere substance, iron; we see the division that takes -place in it propagate itself and disappear, and again easily become -re-excited. This, according to our mode of thinking, is a primordial -phenomenon in immediate relation with its idea, and which acknowledges -nothing earthly beyond it.</p> - -<p class="para"><a id="a742">742.</a></p> - -<p>Electricity is again peculiarly characterised. As a mere quality we are -unacquainted with it; for us it is a nothing, a zero, a mere point, -which, however, dwells in all apparent existences, and at the same time -is the point of origin whence, on the slightest stimulus, a double -appearance presents itself, an appearance which only manifests itself -to vanish. The conditions under which this manifestation is excited -are infinitely varied, according to the nature of particular bodies. -From the rudest mechanical friction of very different substances with -one another, to the mere contiguity of two entirely similar bodies, -the phenomenon is present and stirring, nay, striking and powerful, -and so decided and specific, that when we employ the terms or formulæ<span class="pagenum"><a name="Page_296" id="Page_296">[Pg 296]</a></span> -polarity, plus and minus, for north and south, for glass and resin, we -do so justifiably and in conformity with nature.</p> - -<p class="para"><a id="a743">743.</a></p> - -<p>This phenomenon, although it especially affects the surface, is yet by -no means superficial. It influences the tendency or determination of -material qualities, and connects itself in immediate co-operation with -the important double phenomenon which takes place so universally in -chemistry,—oxydation, and de-oxydation.</p> - -<p class="para"><a id="a744">744.</a></p> - -<p>To introduce and include the appearances of colour in this series, -this circle of phenomena was the object of our labours. What we have -not succeeded in others will accomplish. We found a primordial vast -contrast between light and darkness, which may be more generally -expressed by light and its absence. We looked for the intermediate -state, and sought by means of it to compose the visible world of light, -shade, and colour. In the prosecution of this we employed various terms -applicable to the development of the phenomena, terms which we adopted -from the theories of magnetism, of electricity, and of chemistry. It -was necessary, however, to extend this terminology, since we found -ourselves in an abstract region, and had to express more complicated -relations.</p> - -<p><span class="pagenum"><a name="Page_297" id="Page_297">[Pg 297]</a></span></p> - -<p class="para"><a id="a745">745.</a></p> - -<p>If electricity and galvanism, in their general character, are -distinguished as superior to the more limited exhibition of magnetic -phenomena, it may be said that colour, although coming under similar -laws, is still superior; for since it addresses itself to the noble -sense of vision, its perfections are more generally displayed. Compare -the varied effects which result from the augmentation of yellow and -blue to red, from the combination of these two higher extremes to pure -red, and the union of the two inferior extremes to green. What a far -more varied scheme is apparent here than that in which magnetism and -electricity are comprehended. These last phenomena may be said to be -inferior again on another account; for though they penetrate and give -life to the universe, they cannot address themselves to man in a higher -sense in order to his employing them æsthetically. The general, simple, -physical law must first be elevated and diversified itself in order to -be available for elevated uses.</p> - -<p class="para"><a id="a746">746.</a></p> - -<p>If the reader, in this spirit, recalls what has been stated by us -throughout, generally and in detail, with regard to colour, he will -himself pursue and unfold what has been here only lightly hinted at. -He will augur well for<span class="pagenum"><a name="Page_298" id="Page_298">[Pg 298]</a></span> science, technical processes, and art, if it -should prove possible to rescue the attractive subject of the doctrine -of colours from the atomic restriction and isolation in which it has -been banished, in order to restore it to the general dynamic flow of -life and action which the present age loves to recognise in nature. -These considerations will press upon us more strongly when, in the -historical portion, we shall have to speak of many an enterprising -and intelligent man who failed to possess his contemporaries with his -convictions.</p> - -<hr class="tb" /> -<h5>RELATION TO THE THEORY OF MUSIC.</h5> - - -<p class="para"><a id="a747">747.</a></p> - -<p>Before we proceed to the moral associations of colour, and the æsthetic -influences arising from them, we have here to say a few words on its -relation to melody. That a certain relation exists between the two, -has been always felt; this is proved by the frequent comparisons we -meet with, sometimes as passing allusions, sometimes as circumstantial -parallels. The error which writers have fallen into in trying to -establish this analogy we would thus define:</p> - -<p class="para"><a id="a748">748.</a></p> - -<p>Colour and sound do not admit of being directly compared together -in any way, but both are referable to a higher formula, both are -derivable,<span class="pagenum"><a name="Page_299" id="Page_299">[Pg 299]</a></span> although each for itself, from this higher law. They are -like two rivers which have their source in one and the same mountain, -but subsequently pursue their way under totally different conditions -in two totally different regions, so that throughout the whole course -of both no two points can be compared. Both are general, elementary -effects acting according to the general law of separation and tendency -to union, of undulation and oscillation, yet acting thus in wholly -different provinces, in different modes, on different elementary -mediums, for different senses.—<a href="#NOTE_BB">Note BB</a>.</p> - -<p class="para"><a id="a749">749.</a></p> - -<p>Could some investigator rightly adopt the method in which we have -connected the doctrine of colours with natural philosophy generally, -and happily supply what has escaped or been missed by us, the theory -of sound, we are persuaded, might be perfectly connected with general -physics: at present it stands, as it were, isolated within the circle -of science.</p> - -<p class="para"><a id="a750">750.</a></p> - -<p>It is true it would be an undertaking of the greatest difficulty -to do away with the positive character which we are now accustomed -to attribute to music—a character resulting from the achievements -of practical skill, from accidental,<span class="pagenum"><a name="Page_300" id="Page_300">[Pg 300]</a></span> mathematical, æsthetical -influences—and to substitute for all this a merely physical inquiry -tending to resolve the science into its first elements. Yet considering -the point at which science and art are now arrived, considering the -many excellent preparatory investigations that have been made relative -to this subject, we may perhaps still see it accomplished.</p> - -<hr class="tb" /> -<h5>CONCLUDING OBSERVATIONS ON TERMINOLOGY.</h5> - - -<p class="para"><a id="a751">751.</a></p> - -<p>We never sufficiently reflect that a language, strictly speaking, can -only be symbolical and figurative, that it can never express things -directly, but only, as it were, reflectedly. This is especially the -case in speaking of qualities which are only imperfectly presented -to observation, which might rather be called powers than objects, -and which are ever in movement throughout nature. They are not to be -arrested, and yet we find it necessary to describe them; hence we look -for all kinds of formulæ in order, figuratively at least, to define -them.</p> - -<p class="para"><a id="a752">752.</a></p> - -<p>Metaphysical formulæ have breadth as well as depth, but on this -very account they require a corresponding import; the danger -here is vagueness. Mathematical expressions may in many cases be -very conveniently and happily<span class="pagenum"><a name="Page_301" id="Page_301">[Pg 301]</a></span> employed, but there is always an -inflexibility in them, and we presently feel their inadequacy; for even -in elementary cases we are very soon conscious of an incommensurable -idea; they are, besides, only intelligible to those who are especially -conversant in the sciences to which such formulæ are appropriated. The -terms of the science of mechanics are more addressed to the ordinary -mind, but they are ordinary in other senses, and always have something -unpolished; they destroy the inward life to offer from without an -insufficient substitute for it. The formulæ of the corpuscular theories -are nearly allied to the last; through them the mutable becomes rigid, -description and expression uncouth: while, again, moral terms, which -undoubtedly can express nicer relations, have the effect of mere -symbols in the end, and are in danger of being lost in a play of wit.</p> - -<p class="para"><a id="a753">753.</a></p> - -<p>If, however, a writer could use all these modes of description and -expression with perfect command, and thus give forth the result of his -observations on the phenomena of nature in a diversified language; -if he could preserve himself from predilections, still embodying a -lively meaning in as animated an expression, we might look for much -instruction communicated in the most agreeable of forms.</p> - -<p><span class="pagenum"><a name="Page_302" id="Page_302">[Pg 302]</a></span></p> - -<p class="para"><a id="a754">754.</a></p> - -<p>Yet, how difficult it is to avoid substituting the sign for the thing; -how difficult to keep the essential quality still living before us, -and not to kill it with the word. With all this, we are exposed in -modern times to a still greater danger by adopting expressions and -terminologies from all branches of knowledge and science to embody our -views of simple nature. Astronomy, cosmology, geology, natural history, -nay religion and mysticism, are called in in aid; and how often do -we not find a general idea and an elementary state rather hidden and -obscured than elucidated and brought nearer to us by the employment of -terms, the application of which is strictly specific and secondary. -We are quite aware of the necessity which led to the introduction and -general adoption of such a language, we also know that it has become in -a certain sense indispensable; but it is only a moderate, unpretending -recourse to it, with an internal conviction of its fitness, that can -recommend it.</p> - -<p class="para"><a id="a755">755.</a></p> - -<p>After all, the most desirable principle would be that writers should -borrow the expressions employed to describe the details of a given -province of investigation from the province itself; treating the -simplest phenomenon as an elementary<span class="pagenum"><a name="Page_303" id="Page_303">[Pg 303]</a></span> formula, and deriving and -developing the more complicated designations from this.</p> - -<p class="para"><a id="a756">756.</a></p> - -<p>The necessity and suitableness of such a conventional language where -the elementary sign expresses the appearance itself, has been duly -appreciated by extending, for instance, the application of the term -polarity, which is borrowed from the magnet to electricity, &c. The -<i>plus</i> and <i>minus</i> which may be substituted for this, have found as -suitable an application to many phenomena; even the musician, probably -without troubling himself about these other departments, has been -naturally led to express the leading difference in the modes of melody -by <i>major</i> and <i>minor</i>.</p> - -<p class="para"><a id="a757">757.</a></p> - -<p>For ourselves we have long wished to introduce the term polarity into -the doctrine of colours; with what right and in what sense, the present -work may show. Perhaps we may hereafter find room to connect the -elementary phenomena together according to our mode, by a similar use -of symbolical terms, terms which must at all times convey the directly -corresponding idea; we shall thus render more explicit what has been -here only alluded to generally, and perhaps too vaguely expressed.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_55" id="Footnote_1_55"></a><a href="#FNanchor_1_55"><span class="label">[1]</span></a> Eine Entzweyung geht vor; literally, <i>a division takes -place</i>. According to some, the two magnetic powers are previously in -the bar, and are then separated at the ends.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_304" id="Page_304">[Pg 304]</a></span></p></div> - - - - -<h5><a name="PART_VI" id="PART_VI">PART VI.</a></h5> - - -<h5>EFFECT OF COLOUR WITH REFERENCE TO MORAL ASSOCIATIONS.</h5> - - -<p class="para"><a id="a758">758.</a></p> - -<p>Since colour occupies so important a place in the series of elementary -phenomena, filling as it does the limited circle assigned to it with -fullest variety, we shall not be surprised to find that its effects are -at all times decided and significant, and that they are immediately -associated with the emotions of the mind. We shall not be surprised -to find that these appearances presented singly, are specific, that -in combination they may produce an harmonious, characteristic, often -even an inharmonious effect on the eye, by means of which they act on -the mind; producing this impression in their most general elementary -character, without relation to the nature or form of the object on -whose surface they are apparent. Hence, colour considered as an element -of art, may be made subservient to the highest æsthetical ends.—<a href="#NOTE_CC">Note CC</a>.</p> - -<p class="para"><a id="a759">759.</a></p> - -<p>People experience a great delight in colour, generally. The eye -requires it as much as it requires light. We have only to remember -the<span class="pagenum"><a name="Page_305" id="Page_305">[Pg 305]</a></span> refreshing sensation we experience, if on a cloudy day the sun -illumines a single portion of the scene before us and displays its -colours. That healing powers were ascribed to coloured gems, may have -arisen from the experience of this indefinable pleasure.</p> - -<p class="para"><a id="a760">760.</a></p> - -<p>The colours which we see on objects are not qualities entirely -strange to the eye; the organ is not thus merely habituated to the -impression; no, it is always predisposed to produce colour of itself, -and experiences a sensation of delight if something analogous to its -own nature is offered to it from without; if its susceptibility is -distinctly determined towards a given state.</p> - -<p class="para"><a id="a761">761.</a></p> - -<p>From some of our earlier observations we can conclude, that general -impressions produced by single colours cannot be changed, that they act -specifically, and must produce definite, specific states in the living -organ.</p> - -<p class="para"><a id="a762">762.</a></p> - -<p>They likewise produce a corresponding influence on the mind. Experience -teaches us that particular colours excite particular states of feeling. -It is related of a witty Frenchman, "Il prétendoit que son ton de -conversation avec<span class="pagenum"><a name="Page_306" id="Page_306">[Pg 306]</a></span> Madame étoit changé depuis qu'elle avoit changé en -cramoisi le meuble de son cabinet, qui étoit bleu."</p> - -<p class="para"><a id="a763">763.</a></p> - -<p>In order to experience these influences completely, the eye should be -entirely surrounded with one colour; we should be in a room of one -colour, or look through a coloured glass. We are then identified with -the hue, it attunes the eye and mind in mere unison with itself.</p> - -<p class="para"><a id="a764">764.</a></p> - -<p>The colours on the <i>plus</i> side are yellow, red-yellow (orange), -yellow-red (minium, cinnabar). The feelings they excite are quick, -lively, aspiring.</p> - -<hr class="r5" /> -<h5>YELLOW.</h5> - - -<p class="para"><a id="a765">765.</a></p> - -<p>This is the colour nearest the light. It appears on the slightest -mitigation of light, whether by semi-transparent mediums or faint -reflection from white surfaces. In prismatic experiments it extends -itself alone and widely in the light space, and while the two poles -remain separated from each other, before it mixes with blue to -produce green it is to be seen in its utmost purity and beauty. How -the chemical yellow developes itself in and upon the white, has been -circumstantially described in its proper place.</p> - -<p><span class="pagenum"><a name="Page_307" id="Page_307">[Pg 307]</a></span></p> - -<p class="para"><a id="a766">766.</a></p> - -<p>In its highest purity it always carries with it the nature of -brightness, and has a serene, gay, softly exciting character.</p> - -<p class="para"><a id="a767">767.</a></p> - -<p>In this state, applied to dress, hangings, carpeting, &c., it is -agreeable. Gold in its perfectly unmixed state, especially when the -effect of polish is superadded, gives us a new and high idea of this -colour; in like manner, a strong yellow, as it appears on satin, has a -magnificent and noble effect.</p> - -<p class="para"><a id="a768">768.</a></p> - -<p>We find from experience, again, that yellow excites a warm and -agreeable impression. Hence in painting it belongs to the illumined and -emphatic side.</p> - -<p class="para"><a id="a769">769.</a></p> - -<p>This impression of warmth may be experienced in a very lively manner if -we look at a landscape through a yellow glass, particularly on a grey -winter's day. The eye is gladdened, the heart expanded and cheered, a -glow seems at once to breathe towards us.</p> - -<p class="para"><a id="a770">770.</a></p> - -<p>If, however, this colour in its pure and bright<span class="pagenum"><a name="Page_308" id="Page_308">[Pg 308]</a></span> state is agreeable -and gladdening, and in its utmost power is serene and noble, it is, on -the other hand, extremely liable to contamination, and produces a very -disagreeable effect if it is sullied, or in some degree tends to the -<i>minus</i> side. Thus, the colour of sulphur, which inclines to green, has -a something unpleasant in it.</p> - -<p class="para"><a id="a771">771.</a></p> - -<p>When a yellow colour is communicated to dull and coarse surfaces, -such as common cloth, felt, or the like, on which it does not appear -with full energy, the disagreeable effect alluded to is apparent. By -a slight and scarcely perceptible change, the beautiful impression -of fire and gold is transformed into one not undeserving the epithet -foul; and the colour of honour and joy reversed to that of ignominy -and aversion. To this impression the yellow hats of bankrupts and the -yellow circles on the mantles of Jews, may have owed their origin.</p> - -<hr class="r5" /> -<h5>RED-YELLOW.</h5> - - -<p class="para"><a id="a772">772.</a></p> - -<p>As no colour can be considered as stationary, so we can very easily -augment yellow into reddish by condensing or darkening it. The colour -increases in energy, and appears in red-yellow more powerful and -splendid.</p> - -<p><span class="pagenum"><a name="Page_309" id="Page_309">[Pg 309]</a></span></p> - -<p class="para"><a id="a773">773.</a></p> - -<p>All that we have said of yellow is applicable here in a higher -degree. The red-yellow gives an impression of warmth and gladness, -since it represents the hue of the intenser glow of fire, and of the -milder radiance of the setting sun. Hence it is agreeable around us, -and again, as clothing, in greater or less degrees is cheerful and -magnificent. A slight tendency to red immediately gives a new character -to yellow, and while the English and Germans content themselves -with bright pale yellow colours in leather, the French, as Castel -has remarked, prefer a yellow enhanced to red; indeed, in general, -everything in colour is agreeable to them which belongs to the active -side.</p> - -<hr class="r5" /> -<h5>YELLOW-RED.</h5> - - -<p class="para"><a id="a774">774.</a></p> - -<p>As pure yellow passes very easily to red-yellow, so the deepening of -this last to yellow-red is not to be arrested. The agreeable, cheerful -sensation which red-yellow excites, increases to an intolerably -powerful impression in bright yellow-red.</p> - -<p class="para"><a id="a775">775.</a></p> - -<p>The active side is here in its highest energy, and it is not to -be wondered at that impetuous, robust, uneducated men, should be -especially<span class="pagenum"><a name="Page_310" id="Page_310">[Pg 310]</a></span> pleased with this colour. Among savage nations the -inclination for it has been universally remarked, and when children, -left to themselves, begin to use tints, they never spare vermilion and -minium.</p> - -<p class="para"><a id="a776">776.</a></p> - -<p>In looking steadfastly at a perfectly yellow-red surface, the colour -seems actually to penetrate the organ. It produces an extreme -excitement, and still acts thus when somewhat darkened. A yellow-red -cloth disturbs and enrages animals. I have known men of education to -whom its effect was intolerable if they chanced to see a person dressed -in a scarlet cloak on a grey, cloudy day.</p> - -<p class="para"><a id="a777">777.</a></p> - -<p>The colours on the <i>minus</i> side are blue, red-blue, and blue-red. They -produce a restless, susceptible, anxious impression.</p> - -<hr class="r5" /> -<h5>BLUE.</h5> - - -<p class="para"><a id="a778">778.</a></p> - -<p>As yellow is always accompanied with light, so it may be said that blue -still brings a principle of darkness with it.</p> - -<p class="para"><a id="a779">779.</a></p> - -<p>This colour has a peculiar and almost indescribable<span class="pagenum"><a name="Page_311" id="Page_311">[Pg 311]</a></span> effect on the eye. -As a hue it is powerful, but it is on the negative side, and in its -highest purity is, as it were, a stimulating negation. Its appearance, -then, is a kind of contradiction between excitement and repose.</p> - -<p class="para"><a id="a780">780.</a></p> - -<p>As the upper sky and distant mountains appear blue, so a blue surface -seems to retire from us.</p> - -<p class="para"><a id="a781">781.</a></p> - -<p>But as we readily follow an agreeable object that flies from us, so we -love to contemplate blue, not because it advances to us, but because it -draws us after it.</p> - -<p class="para"><a id="a782">782.</a></p> - -<p>Blue gives us an impression of cold, and thus, again, reminds us of -shade. We have before spoken of its affinity with black.</p> - -<p class="para"><a id="a783">783.</a></p> - -<p>Rooms which are hung with pure blue, appear in some degree larger, but -at the same time empty and cold.</p> - -<p class="para"><a id="a784">784.</a></p> - -<p>The appearance of objects seen through a blue glass is gloomy and -melancholy.</p> - -<p><span class="pagenum"><a name="Page_312" id="Page_312">[Pg 312]</a></span></p> - -<p class="para"><a id="a785">785.</a></p> - -<p>When blue partakes in some degree of the <i>plus</i> side, the effect is not -disagreeable. Sea-green is rather a pleasing colour.</p> - -<hr class="r5" /> -<h5>RED-BLUE.</h5> - - -<p class="para"><a id="a786">786.</a></p> - -<p>We found yellow very soon tending to the intense state, and we observe -the same progression in blue.</p> - -<p class="para"><a id="a787">787.</a></p> - -<p>Blue deepens very mildly into red, and thus acquires a somewhat active -character, although it is on the passive side. Its exciting power is, -however, of a very different kind from that of the red-yellow. It may -be said to disturb rather than enliven.</p> - -<p class="para"><a id="a788">788.</a></p> - -<p>As augmentation itself is not to be arrested, so we feel an inclination -to follow the progress of the colour, not, however, as in the case of -the red-yellow, to see it still increase in the active sense, but to -find a point to rest in.</p> - -<p class="para"><a id="a789">789.</a></p> - -<p>In a very attenuated state, this colour is known to us under the name -of lilac; but even in this degree it has a something lively without -gladness.</p> - -<p><span class="pagenum"><a name="Page_313" id="Page_313">[Pg 313]</a></span></p> - -<p class="para"><a id="a790">790.</a></p> - -<p>This unquiet feeling increases as the hue progresses, and it may be -safely assumed, that a carpet of a perfectly pure deep blue-red would -be intolerable. On this account, when it is used for dress, ribbons, or -other ornaments, it is employed in a very attenuated and light state, -and thus displays its character as above defined, in a peculiarly -attractive manner.</p> - -<p class="para"><a id="a791">791.</a></p> - -<p>As the higher dignitaries of the church have appropriated this unquiet -colour to themselves, we may venture to say that it unceasingly aspires -to the cardinal's red through the restless degrees of a still impatient -progression.</p> - -<hr class="r5" /> -<h5>RED.</h5> - - -<p class="para"><a id="a792">792.</a></p> - -<p>We are here to forget everything that borders on yellow or blue. We -are to imagine an absolutely pure red, like fine carmine suffered to -dry on white porcelain. We have called this colour "purpur" by way -of distinction, although we are quite aware that the purple of the -ancients inclined more to blue.</p> - -<p class="para"><a id="a793">793.</a></p> - -<p>Whoever is acquainted with the prismatic<span class="pagenum"><a name="Page_314" id="Page_314">[Pg 314]</a></span> origin of red, will not think -it paradoxical if we assert that this colour partly <i>actu</i>, partly -<i>potentiâ</i>, includes all the other colours.</p> - -<p class="para"><a id="a794">794.</a></p> - -<p>We have remarked a constant progress or augmentation in yellow and -blue, and seen what impressions were produced by the various states; -hence it may naturally be inferred that now, in the junction of the -deepened extremes, a feeling of satisfaction must succeed; and thus, in -physical phenomena, this highest of all appearances of colour arises -from the junction of two contrasted extremes which have gradually -prepared themselves for a union.</p> - -<p class="para"><a id="a795">795.</a></p> - -<p>As a pigment, on the other hand, it presents itself to us already -formed, and is most perfect as a hue in cochineal; a substance which, -however, by chemical action may be made to tend to the <i>plus</i> or the -<i>minus</i> side, and may be considered to have attained the central point -in the best carmine.</p> - -<p class="para"><a id="a796">796.</a></p> - -<p>The effect of this colour is as peculiar as its nature. It conveys an -impression of gravity and dignity, and at the same time of grace and -attractiveness. The first in its dark deep state,<span class="pagenum"><a name="Page_315" id="Page_315">[Pg 315]</a></span> the latter in its -light attenuated tint; and thus the dignity of age and the amiableness -of youth may adorn itself with degrees of the same hue.</p> - -<p class="para"><a id="a797">797.</a></p> - -<p>History relates many instances of the jealousy of sovereigns with -regard to the quality of red. Surrounding accompaniments of this colour -have always a grave and magnificent effect.</p> - -<p class="para"><a id="a798">798.</a></p> - -<p>The red glass exhibits a bright landscape in so dreadful a hue as to -inspire sentiments of awe.</p> - -<p class="para"><a id="a799">799.</a></p> - -<p>Kermes and cochineal, the two materials chiefly employed in dyeing to -produce this colour, incline more or less to the <i>plus</i> or <i>minus</i> -state, and may be made to pass and repass the culminating point by -the action of acids and alkalis: it is to be observed that the French -arrest their operations on the active side, as is proved by the French -scarlet, which inclines to yellow. The Italians, on the other hand, -remain on the passive side, for their scarlet has a tinge of blue.</p> - -<p class="para"><a id="a800">800.</a></p> - -<p>By means of a similar alkaline treatment, the so-called crimson is -produced; a colour which the French must be particularly prejudiced<span class="pagenum"><a name="Page_316" id="Page_316">[Pg 316]</a></span> -against, since they employ the expressions—"Sot en cramoisi, méchant -en cramoisi," to mark the extreme of the silly and the reprehensible.</p> - -<hr class="r5" /> -<h5>GREEN.</h5> - - -<p class="para"><a id="a801">801.</a></p> - -<p>If yellow and blue, which we consider as the most fundamental and -simple colours, are united as they first appear, in the first state of -their action, the colour which we call green is the result.</p> - -<p class="para"><a id="a802">802.</a></p> - -<p>The eye experiences a distinctly grateful impression from this colour. -If the two elementary colours are mixed in perfect equality so that -neither predominates, the eye and the mind repose on the result of this -junction as upon a simple colour. The beholder has neither the wish -nor the power to imagine a state beyond it. Hence for rooms to live in -constantly, the green colour is most generally selected.</p> - -<hr class="r5" /> -<h5>COMPLETENESS AND HARMONY.</h5> - - -<p class="para"><a id="a803">803.</a></p> - -<p>We have hitherto assumed, for the sake of clearer explanation, that the -eye can be compelled to assimilate or identify itself with a single -colour; but this can only be possible for an instant.</p> - -<p><span class="pagenum"><a name="Page_317" id="Page_317">[Pg 317]</a></span></p> - -<p class="para"><a id="a804">804.</a></p> - -<p>For when we find ourselves surrounded by a given colour which excites -its corresponding sensation on the eye, and compels us by its presence -to remain in a state identical with it, this state is soon found to be -forced, and the organ unwillingly remains in it.</p> - -<p class="para"><a id="a805">805.</a></p> - -<p>When the eye sees a colour it is immediately excited, and it is its -nature, spontaneously and of necessity, at once to produce another, -which with the original colour comprehends the whole chromatic scale. -A single colour excites, by a specific sensation, the tendency to -universality.</p> - -<p class="para"><a id="a806">806.</a></p> - -<p>To experience this completeness, to satisfy itself, the eye seeks for -a colourless space next every hue in order to produce the complemental -hue upon it.</p> - -<p class="para"><a id="a807">807.</a></p> - -<p>In this resides the fundamental law of all harmony of colours, of which -every one may convince himself by making himself accurately acquainted -with the experiments which we have described in the chapter on the -physiological colours.</p> - -<p><span class="pagenum"><a name="Page_318" id="Page_318">[Pg 318]</a></span></p> - -<p class="para"><a id="a808">808.</a></p> - -<p>If, again, the entire scale is presented to the eye externally, the -impression is gladdening, since the result of its own operation is -presented to it in reality. We turn our attention therefore, in the -first place, to this harmonious juxtaposition.</p> - -<p class="para"><a id="a809">809.</a></p> - -<p>As a very simple means of comprehending the principle of this, the -reader has only to imagine a moveable diametrical index in the -colorific circle.<a name="FNanchor_1_56" id="FNanchor_1_56"></a><a href="#Footnote_1_56" class="fnanchor">[1]</a> The index, as it revolves round the whole circle, -indicates at its two extremes the complemental colours, which, after -all, may be reduced to three contrasts.</p> - -<p class="para"><a id="a810">810.</a></p> - -<p style="margin-left: 10%;"> -Yellow demands Red-blue,<br /> -Blue demands Red-yellow,<br /> -Red demands Green,<br /> -and contrariwise.<br /> -</p> - -<p class="para"><a id="a811">811.</a></p> - -<p>In proportion as one end of the supposed index deviates from the -central intensity of the colours, arranged as they are in the natural -order, so the opposite end changes its place in the contrasted -gradation, and by such a simple<span class="pagenum"><a name="Page_319" id="Page_319">[Pg 319]</a></span> contrivance the complemental colours -may be indicated at any given point. A chromatic circle might be made -for this purpose, not confined, like our own, to the leading colours, -but exhibiting them with their transitions in an unbroken series. -This would not be without its use, for we are here considering a very -important point which deserves all our attention.<a name="FNanchor_2_57" id="FNanchor_2_57"></a><a href="#Footnote_2_57" class="fnanchor">[2]</a></p> - -<p class="para"><a id="a812">812.</a></p> - -<p>We before stated that the eye could be in some degree pathologically -affected by being long confined to a single colour; that, again, -definite moral impressions were thus produced, at one time lively and -aspiring, at another susceptible and anxious—now exalted to grand -associations, now reduced to ordinary ones. We now observe that the -demand for completeness, which is inherent in the organ, frees us from -this restraint; the eye relieves itself by producing the opposite -of the single colour forced upon it, and thus attains the entire -impression which is so satisfactory to it.</p> - -<p class="para"><a id="a813">813.</a></p> - -<p>Simple, therefore, as these strictly harmonious contrasts are, as -presented to us in the narrow circle, the hint is important, that -nature tends to emancipate the sense from confined<span class="pagenum"><a name="Page_320" id="Page_320">[Pg 320]</a></span> impressions by -suggesting and producing the whole, and that in this instance we have a -natural phenomenon immediately applicable to æsthetic purposes.</p> - -<p class="para"><a id="a814">814.</a></p> - -<p>While, therefore, we may assert that the chromatic scale, as given by -us, produces an agreeable impression by its ingredient hues, we may -here remark that those have been mistaken who have hitherto adduced -the rainbow as an example of the entire scale; for the chief colour, -pure red, is deficient in it, and cannot be produced, since in this -phenomenon, as well as in the ordinary prismatic series, the yellow-red -and blue-red cannot attain to a union.</p> - -<p class="para"><a id="a815">815.</a></p> - -<p>Nature perhaps exhibits no general phenomenon where the scale is in -complete combination. By artificial experiments such an appearance may -be produced in its perfect splendour. The mode, however, in which the -entire series is connected in a circle, is rendered most intelligible -by tints on paper, till after much experience and practice, aided by -due susceptibility of the organ, we become penetrated with the idea of -this harmony, and feel it present in our minds.</p> - -<p><span class="pagenum"><a name="Page_321" id="Page_321">[Pg 321]</a></span></p> - -<p class="para"><a id="a816">816.</a></p> - -<p>Besides these pure, harmonious, self-developed combinations, which -always carry the conditions of completeness with them, there are -others which may be arbitrarily produced, and which may be most easily -described by observing that they are to be found in the colorific -circle, not by diameters, but by chords, in such a manner that an -intermediate colour is passed over.</p> - -<p class="para"><a id="a817">817.</a></p> - -<p>We call these combinations characteristic because they have all a -certain significancy and tend to excite a definite impression; an -impression, however, which does not altogether satisfy, inasmuch as -every characteristic quality of necessity presents itself only as a -part of a whole, with which it has a relation, but into which it cannot -be resolved.</p> - -<p class="para"><a id="a818">818.</a></p> - -<p>As we are acquainted with the impressions produced by the colours -singly as well as in their harmonious relations, we may at once -conclude that the character of the arbitrary combinations will be very -different from each other as regards their significancy. We proceed to -review them separately.</p> - -<p><span class="pagenum"><a name="Page_322" id="Page_322">[Pg 322]</a></span></p> - -<hr class="r5" /> -<h5>YELLOW AND BLUE.</h5> - - -<p class="para"><a id="a819">819.</a></p> - -<p>This is the simplest of such combinations. It may be said that it -contains too little, for since every trace of red is wanting in it, -it is defective as compared with the whole scale. In this view it -may be called poor, and as the two contrasting elements are in their -lowest state, may be said to be ordinary; yet it is recommended by -its proximity to green—in short, by containing the ingredients of an -ultimate state.</p> - -<hr class="r5" /> -<h5>YELLOW AND RED.</h5> - - -<p class="para"><a id="a820">820.</a></p> - -<p>This is a somewhat preponderating combination, but it has a serene -and magnificent effect. The two extremes of the active side are seen -together without conveying any idea of progression from one to the -other. As the result of their combination in pigments is yellow-red, so -they in some degree represent this colour.</p> - -<hr class="r5" /> -<h5>BLUE AND RED.</h5> - - -<p class="para"><a id="a821">821.</a></p> - -<p>The two ends of the passive side, with the excess of the upper end of -the active side. The effect of this juxtaposition approaches that of -the blue-red produced by their union.</p> - -<p><span class="pagenum"><a name="Page_323" id="Page_323">[Pg 323]</a></span></p> - -<hr class="r5" /> -<h5>YELLOW-RED AND BLUE-RED.</h5> - - -<p class="para"><a id="a822">822.</a></p> - -<p>These, when placed together, as the deepened extremes of both sides, -have something exciting, elevated: they give us a presentiment of red, -which in physical experiments is produced by their union.</p> - -<p class="para"><a id="a823">823.</a></p> - -<p>These four combinations have also the common quality of producing the -intermediate colour of our colorific circle by their union, a union -which actually takes place if they are opposed to each other in small -quantities and seen from a distance. A surface covered with narrow blue -and yellow stripes appears green at a certain distance.</p> - -<p class="para"><a id="a824">824.</a></p> - -<p>If, again, the eye sees blue and yellow next each other, it finds -itself in a peculiar disposition to produce green without accomplishing -it, while it neither experiences a satisfactory sensation in -contemplating the detached colours, nor an impression of completeness -in the two.</p> - -<p class="para"><a id="a825">825.</a></p> - -<p>Thus it will be seen that it was not without reason we called these -combinations characteristic; the more so, since the character of each<span class="pagenum"><a name="Page_324" id="Page_324">[Pg 324]</a></span> -combination must have a relation to that of the single colours of which -it consists.</p> - -<hr class="r5" /> -<h5>COMBINATIONS NON-CHARACTERISTIC.</h5> - - -<p class="para"><a id="a826">826.</a></p> - -<p>We now turn our attention to the last kind of combinations. These are -easily found in the circle; they are indicated by shorter chords, for -in this case we do not pass over an entire intermediate colour, but -only the transition from one to the other.</p> - -<p class="para"><a id="a827">827.</a></p> - -<p>These combinations may justly be called non-characteristic, inasmuch -as the colours are too nearly alike for their impression to be -significant. Yet most of these recommend themselves to a certain -degree, since they indicate a progressive state, though its relations -can hardly be appreciable.</p> - -<p class="para"><a id="a828">828.</a></p> - -<p>Thus yellow and yellow-red, yellow-red and red, blue and blue-red, -blue-red and red, represent the nearest degrees of augmentation and -culmination, and in certain relations as to quantity may produce no -unpleasant effect.</p> - -<p class="para"><a id="a829">829.</a></p> - -<p>The juxtaposition of yellow and green has<span class="pagenum"><a name="Page_325" id="Page_325">[Pg 325]</a></span> always something ordinary, -but in a cheerful sense; blue and green, on the other hand, is ordinary -in a repulsive sense. Our good forefathers called these last fool's -colours.</p> - -<hr class="r5" /> -<h5>RELATION OF THE COMBINATIONS TO LIGHT AND DARK.</h5> - - -<p class="para"><a id="a830">830.</a></p> - -<p>These combinations may be very much varied by making both colours light -or both dark, or one light and the other dark; in which modifications, -however, all that has been found true in a general sense is applicable -to each particular case. With regard to the infinite variety thus -produced, we merely observe:</p> - -<p class="para"><a id="a831">831.</a></p> - -<p>The colours of the active side placed next to black gain in energy, -those of the passive side lose. The active conjoined with white and -brightness lose in strength, the passive gain in cheerfulness. Red and -green with black appear dark and grave; with white they appear gay.</p> - -<p class="para"><a id="a832">832.</a></p> - -<p>To this we may add that all colours may be more or less broken or -neutralised, may to a certain degree be rendered nameless, and thus -combined partly together and partly with pure colours; but although the -relations may thus<span class="pagenum"><a name="Page_326" id="Page_326">[Pg 326]</a></span> be varied to infinity, still all that is applicable -with regard to the pure colours will be applicable in these cases.</p> - -<hr class="r5" /> -<h5>CONSIDERATIONS DERIVED FROM THE EVIDENCE OF EXPERIENCE AND HISTORY.</h5> - - -<p class="para"><a id="a833">833.</a></p> - -<p>The principles of the harmony of colours having been thus far defined, -it may not be irrelevant to review what has been adduced in connexion -with experience and historical examples.</p> - -<p class="para"><a id="a834">834.</a></p> - -<p>The principles in question have been derived from the constitution of -our nature and the constant relations which are found to obtain in -chromatic phenomena. In experience we find much that is in conformity -with these principles, and much that is opposed to them.</p> - -<p class="para"><a id="a835">835.</a></p> - -<p>Men in a state of nature, uncivilised nations, children, have a great -fondness for colours in their utmost brightness, and especially for -yellow-red: they are also pleased with the motley. By this expression -we understand the juxtaposition of vivid colours without an harmonious -balance; but if this balance is observed, through instinct or accident, -an agreeable effect may be produced. I remember a Hessian officer, -returned<span class="pagenum"><a name="Page_327" id="Page_327">[Pg 327]</a></span> from America, who had painted his face with the positive -colours, in the manner of the Indians; a kind of completeness or due -balance was thus produced, the effect of which was not disagreeable.</p> - -<p class="para"><a id="a836">836.</a></p> - -<p>The inhabitants of the south of Europe make use of very brilliant -colours for their dresses. The circumstance of their procuring silk -stuffs at a cheap rate is favourable to this propensity. The women, -especially, with their bright-coloured bodices and ribbons, are always -in harmony with the scenery, since they cannot possibly surpass the -splendour of the sky and landscape.</p> - -<p class="para"><a id="a837">837.</a></p> - -<p>The history of dyeing teaches us that certain technical conveniences -and advantages have had great influence on the costume of nations. -We find that the Germans wear blue very generally because it is a -permanent colour in cloth; so in many districts all the country people -wear green twill, because that material takes a green dye well. If -a traveller were to pay attention to these circumstances, he might -collect some amusing and curious facts.</p> - -<p class="para"><a id="a838">838.</a></p> - -<p>Colours, as connected with particular frames<span class="pagenum"><a name="Page_328" id="Page_328">[Pg 328]</a></span> of mind, are again a -consequence of peculiar character and circumstances. Lively nations, -the French for instance, love intense colours, especially on the active -side; sedate nations, like the English and Germans, wear straw-coloured -or leather-coloured yellow accompanied with dark blue. Nations aiming -at dignity of appearance, the Spaniards and Italians for instance, -suffer the red colour of their mantles to incline to the passive side.</p> - -<p class="para"><a id="a839">839.</a></p> - -<p>In dress we associate the character of the colour with the character of -the person. We may thus observe the relation of colours singly, and in -combination, to the colour of the complexion, age, and station.</p> - -<p class="para"><a id="a840">840.</a></p> - -<p>The female sex in youth is attached to rose-colour and sea-green, in -age to violet and dark-green. The fair-haired prefer violet, as opposed -to light yellow, the brunettes, blue, as opposed to yellow-red, and -all on good grounds. The Roman emperors were extremely jealous with -regard to their purple. The robe of the Chinese Emperor is orange -embroidered with red; his attendants and the ministers of religion wear -citron-yellow.</p> - -<p><span class="pagenum"><a name="Page_329" id="Page_329">[Pg 329]</a></span></p> - -<p class="para"><a id="a841">841.</a></p> - -<p>People of refinement have a disinclination to colours. This may be -owing partly to weakness of sight, partly to the uncertainty of taste, -which readily takes refuge in absolute negation. Women now appear -almost universally in white and men in black.</p> - -<p class="para"><a id="a842">842.</a></p> - -<p>An observation, very generally applicable, may not be out of place -here, namely, that man, desirous as he is of being distinguished, is -quite as willing to be lost among his fellows.</p> - -<p class="para"><a id="a843">843.</a></p> - -<p>Black was intended to remind the Venetian noblemen of republican -equality.</p> - -<p class="para"><a id="a844">844.</a></p> - -<p>To what degree the cloudy sky of northern climates may have gradually -banished colour may also admit of explanation.</p> - -<p class="para"><a id="a845">845.</a></p> - -<p>The scale of positive colours is obviously soon exhausted; on the -other hand, the neutral, subdued, so-called fashionable colours -present infinitely varying degrees and shades, most of which are not -unpleasing.</p> - -<p><span class="pagenum"><a name="Page_330" id="Page_330">[Pg 330]</a></span></p> - -<p class="para"><a id="a846">846.</a></p> - -<p>It is also to be remarked that ladies, in wearing positive colours, -are in danger of making a complexion which may not be very bright -still less so, and thus to preserve a due balance with such brilliant -accompaniments, they are induced to heighten their complexions -artificially.</p> - -<p class="para"><a id="a847">847.</a></p> - -<p>An amusing inquiry might be made which would lead to a critique of -uniforms, liveries, cockades, and other distinctions, according to the -principles above hinted at. It might be observed, generally, that such -dresses and insignia should not be composed of harmonious colours. -Uniforms should be characteristic and dignified; liveries might be -ordinary and striking to the eye. Examples both good and bad would -not be wanting, since the scale of colours usually employed for such -purposes is limited, and its varieties have been often enough tried.<a name="FNanchor_3_58" id="FNanchor_3_58"></a><a href="#Footnote_3_58" class="fnanchor">[3]</a></p> - -<hr class="r5" /> -<h5>ÆSTHETIC INFLUENCE.</h5> - - -<p class="para"><a id="a848">848.</a></p> - -<p>From the moral associations connected with the appearance of colours, -single or combined, their æsthetic influence may now be deduced<span class="pagenum"><a name="Page_331" id="Page_331">[Pg 331]</a></span> for -the artist. We shall touch the most essential points to be attended -to after first considering the general condition of pictorial -representation, light and shade, with which the appearance of colour is -immediately connected.</p> - -<hr class="r5" /> -<h5>CHIARO-SCURO.</h5> - - -<p class="para"><a id="a849">849.</a></p> - -<p>We apply the term chiaro-scuro (Helldunkel) to the appearance of -material objects when the mere effect produced on them by light and -shade is considered.—<a href="#NOTE_DD">Note DD</a>.</p> - -<p class="para"><a id="a850">850.</a></p> - -<p>In a narrower sense a mass of shadow lighted by reflexes is often -thus designated; but we here use the expression in its first and more -general sense.</p> - -<p class="para"><a id="a851">851.</a></p> - -<p>The separation of light and dark from all appearance of colour is -possible and necessary. The artist will solve the mystery of imitation -sooner by first considering light and dark independently of colour, and -making himself acquainted with it in its whole extent.</p> - -<p class="para"><a id="a852">852.</a></p> - -<p>Chiaro-scuro exhibits the substance as substance, inasmuch as light and -shade inform us as to degrees of density.</p> - -<p><span class="pagenum"><a name="Page_332" id="Page_332">[Pg 332]</a></span></p> - -<p class="para"><a id="a853">853.</a></p> - -<p>We have here to consider the highest light, the middle tint, and the -shadow, and in the last the shadow of the object itself, the shadow it -casts on other objects, and the illumined shadow or reflexion.</p> - -<p class="para"><a id="a854">854.</a></p> - -<p>The globe is well adapted for the general exemplification of the nature -of chiaro-scuro, but it is not altogether sufficient. The softened -unity of such complete rotundity tends to the vapoury, and in order to -serve as a principle for effects of art, it should be composed of plane -surfaces, so as to define the gradations more.</p> - -<p class="para"><a id="a855">855.</a></p> - -<p>The Italians call this manner "il piazzoso;" in German it might -be called "das Flächenhafte."<a name="FNanchor_4_59" id="FNanchor_4_59"></a><a href="#Footnote_4_59" class="fnanchor">[4]</a> If, therefore, the sphere is a -perfect example of natural chiaro-scuro, a polygon would exhibit the -artist-like treatment in which all kinds of lights, half-lights, -shadows, and reflexions, would be appreciable.—<a href="#NOTE_EE">Note EE</a>.</p> - -<p class="para"><a id="a856">856.</a></p> - -<p>The bunch of grapes is recognised as a good example of a picturesque -completeness in chiaro-scuro, the more so as it is fitted, from its -form, to represent a principal group; but it is only<span class="pagenum"><a name="Page_333" id="Page_333">[Pg 333]</a></span> available for the -master who can see in it what he has the power of producing.</p> - -<p class="para"><a id="a857">857.</a></p> - -<p>In order to make the first idea intelligible to the beginner, (for -it is difficult to consider it abstractedly even in a polygon,) we -may take a cube, the three sides of which that are seen represent the -light, the middle tint, and the shadow in distinct order.</p> - -<p class="para"><a id="a858">858.</a></p> - -<p>To proceed again to the chiaro-scuro of a more complicated figure, we -might select the example of an open book, which presents a greater -diversity.</p> - -<p class="para"><a id="a859">859.</a></p> - -<p>We find the antique statues of the best time treated very much with -reference to these effects. The parts intended to receive the light -are wrought with simplicity, the portion originally in shade is, on -the other hand, in more distinct surfaces to make them susceptible -of a variety of reflexions; here the example of the polygon will be -remembered.—<a href="#NOTE_FF">Note FF</a>.</p> - -<p class="para"><a id="a860">860.</a></p> - -<p>The pictures of Herculaneum and the Aldobrandini marriage are examples -of antique painting in the same style.</p> - -<p><span class="pagenum"><a name="Page_334" id="Page_334">[Pg 334]</a></span></p> - -<p class="para"><a id="a861">861.</a></p> - -<p>Modern examples may be found in single figures by Raphael, in entire -works by Correggio, and also by the Flemish masters, especially Rubens.</p> - -<hr class="r5" /> -<h5>TENDENCY TO COLOUR.</h5> - - -<p class="para"><a id="a862">862.</a></p> - -<p>A picture in black and white seldom makes its appearance; some works -of Polidoro are examples of this kind of art. Such works, inasmuch as -they can attain form and keeping, are estimable, but they have little -attraction for the eye, since their very existence supposes a violent -abstraction.</p> - -<p class="para"><a id="a863">863.</a></p> - -<p>If the artist abandons himself to his feeling, colour presently -announces itself. Black no sooner inclines to blue than the eye demands -yellow, which the artist instinctively modifies, and introduces partly -pure in the light, partly reddened and subdued as brown, in the -reflexes, thus enlivening the whole.—<a href="#NOTE_GG">Note GG</a>.</p> - -<p class="para"><a id="a864">864.</a></p> - -<p>All kinds of <i>camayeu</i>, or colour on similar colour, end in the -introduction either of a complemental contrast, or some variety of hue. -Thus, Polidoro in his black and white frescoes<span class="pagenum"><a name="Page_335" id="Page_335">[Pg 335]</a></span> sometimes introduced a -yellow vase, or something of the kind.</p> - -<p class="para"><a id="a865">865.</a></p> - -<p>In general it may be observed that men have at all times instinctively -striven after colour in the practice of the art. We need only observe -daily, how soon amateurs proceed from colourless to coloured materials. -Paolo Uccello painted coloured landscapes to colourless figures.—<a href="#NOTE_HH">Note HH</a>.</p> - -<p class="para"><a id="a866">866.</a></p> - -<p>Even the sculpture of the ancients could not be exempt from the -influence of this propensity. The Egyptians painted their bas-reliefs; -statues had eyes of coloured stones. Porphyry draperies were added to -marble heads and extremities, and variegated stalactites were used -for the pedestals of busts. The Jesuits did not fail to compose the -statue of their S. Luigi, in Rome, in this manner, and the most modern -sculpture distinguishes the flesh from the drapery by staining the -latter.</p> - -<hr class="r5" /> -<h5>KEEPING.</h5> - - -<p class="para"><a id="a867">867.</a></p> - -<p>If linear perspective displays the gradation of objects in their -apparent size as affected by distance, aërial perspective shows us -their gradation<span class="pagenum"><a name="Page_336" id="Page_336">[Pg 336]</a></span> in greater or less distinctness, as affected by the -same cause.</p> - -<p class="para"><a id="a868">868.</a></p> - -<p>Although from the nature of the organ of sight, we cannot see distant -objects so distinctly as nearer ones, yet aërial perspective is -grounded strictly on the important fact that all mediums called -transparent are in some degree dim.</p> - -<p class="para"><a id="a869">869.</a></p> - -<p>The atmosphere is thus always, more or less, semi-transparent. This -quality is remarkable in southern climates, even when the barometer is -high, the weather dry, and the sky cloudless, for a very pronounced -gradation is observable between objects but little removed from each -other.</p> - -<p class="para"><a id="a870">870.</a></p> - -<p>The appearance on a large scale is known to every one; the painter, -however, sees or believes he sees, the gradation in the slightest -varieties of distance. He exemplifies it practically by making a -distinction, for instance, in the features of a face according to their -relative position as regards the plane of the picture. The direction of -the light is attended to in like manner. This is considered to produce -a gradation from side to side, while keeping has reference to depth, to -the comparative distinctness of near and distant things.</p> - -<p><span class="pagenum"><a name="Page_337" id="Page_337">[Pg 337]</a></span></p> - -<p class="para"><a id="a871">871.</a></p> - -<p>In proceeding to consider this subject, we assume that the painter is -generally acquainted with our sketch of the theory of colours, and that -he has made himself well acquainted with certain chapters and rubrics -which especially concern him. He will thus be enabled to make use of -theory as well as practice in recognising the principles of effect in -nature, and in employing the means of art.</p> - -<hr class="r5" /> -<h5>COLOUR IN GENERAL NATURE.</h5> - - -<p class="para"><a id="a872">872.</a></p> - -<p>The first indication of colour announces itself in nature together -with the gradations of aërial perspective; for aërial perspective is -intimately connected with the doctrine of semi-transparent mediums. We -see the sky, distant objects and even comparatively near shadows, blue. -At the same moment, the illuminating and illuminated objects appear -yellow, gradually deepening to red. In many cases the physiological -suggestion of contrasts comes into the account, and an entirely -colourless landscape, by means of these assisting and counteracting -tendencies, appears to our eyes completely coloured.</p> - -<p><span class="pagenum"><a name="Page_338" id="Page_338">[Pg 338]</a></span></p> - -<p class="para"><a id="a873">873.</a></p> - -<p>Local colours are composed of the general elementary colours; but these -are determined or specified according to the properties of substances -and surfaces on which they appear: this specification is infinite.</p> - -<p class="para"><a id="a874">874.</a></p> - -<p>Thus, there is at once a great difference between silk and wool -similarly dyed. Every kind of preparation and texture produces -corresponding modifications. Roughness, smoothness, polish, all are to -be considered.</p> - -<p class="para"><a id="a875">875.</a></p> - -<p>It is therefore one of the pernicious prejudices of art that the -skilful painter must never attend to the material of draperies, -but always represent, as it were, only abstract folds. Is not all -characteristic variety thus done away with, and is the portrait of Leo -X. less excellent because velvet, satin, and moreen, are imitated in -their relative effect?</p> - -<p class="para"><a id="a876">876.</a></p> - -<p>In the productions of nature, colours appear more or less modified, -specified, even individualised: this may be readily observed in -minerals<span class="pagenum"><a name="Page_339" id="Page_339">[Pg 339]</a></span> and plants, in the feathers of birds and the skins of beasts.</p> - -<p class="para"><a id="a877">877.</a></p> - -<p>The chief art of the painter is always to imitate the actual appearance -of the definite hue, doing away with the recollection of the elementary -ingredients of colour. This difficulty is in no instance greater than -in the imitation of the surface of the human figure.</p> - -<p class="para"><a id="a878">878.</a></p> - -<p>The colour of flesh, as a whole, belongs to the active side, yet the -bluish of the passive side mingles with it. The colour is altogether -removed from the elementary state and neutralised by organisation.</p> - -<p class="para"><a id="a879">879.</a></p> - -<p>To bring the colouring of general nature into harmony with the -colouring of a given object, will perhaps be more attainable for the -judicious artist after the consideration of what has been pointed out -in the foregoing theory. For the most fancifully beautiful and varied -appearances may still be made true to the principles of nature.</p> - -<hr class="r5" /> -<h5>CHARACTERISTIC COLOURING.</h5> - - -<p class="para"><a id="a880">880.</a></p> - -<p>The combination of coloured objects, as well as the colour of -their ground, should depend on<span class="pagenum"><a name="Page_340" id="Page_340">[Pg 340]</a></span> considerations which the artist -pre-establishes for himself. Here a reference to the effect of colours -singly or combined, on the feelings, is especially necessary. On this -account the painter should possess himself with the idea of the general -dualism, as well as of particular contrasts, not forgetting what has -been adverted to with regard to the qualities of colours.</p> - -<p class="para"><a id="a881">881.</a></p> - -<p>The characteristic in colour may be comprehended under three leading -rubrics, which we here define as the powerful, the soft, and the -splendid.</p> - -<p class="para"><a id="a882">882.</a></p> - -<p>The first is produced by the preponderance of the active side, the -second by that of the passive side, and the third by completeness, by -the exhibition of the whole chromatic scale in due balance.</p> - -<p class="para"><a id="a883">883.</a></p> - -<p>The powerful impression is attained by yellow, yellow-red, and red, -which last colour is to be arrested on the plus side. But little violet -and blue, still less green, are admissible. The soft effect is produced -by blue, violet, and red, which in this case is arrested on the minus -side; a moderate addition of yellow and yellow-red, but much green may -be admitted.</p> - -<p><span class="pagenum"><a name="Page_341" id="Page_341">[Pg 341]</a></span></p> - -<p class="para"><a id="a884">884.</a></p> - -<p>If it is proposed to produce both these effects in their full -significancy, the complemental colours may be excluded to a minimum, -and only so much of them may be suffered to appear as is indispensable -to convey an impression of completeness.</p> - -<hr class="r5" /> -<h5>HARMONIOUS COLOURING.</h5> - - -<p class="para"><a id="a885">885.</a></p> - -<p>Although the two characteristic divisions as above defined may in some -sense be also called harmonious, the harmonious effect, properly so -called, only takes place when all the colours are exhibited together in -due balance.</p> - -<p class="para"><a id="a886">886.</a></p> - -<p>In this way the splendid as well as the agreeable may be produced; both -of these, however, have of necessity a certain generalised effect, and -in this sense may be considered the reverse of the characteristic.</p> - -<p class="para"><a id="a887">887.</a></p> - -<p>This is the reason why the colouring of most modern painters is without -character, for, while they follow their general instinctive feeling -only, the last result of such a tendency must be mere completeness; -this, they more or less attain, but thus at the same time neglect the -characteristic<span class="pagenum"><a name="Page_342" id="Page_342">[Pg 342]</a></span> impression which the subject might demand.</p> - -<p class="para"><a id="a888">888.</a></p> - -<p>But if the principles before alluded to are kept in view, it must be -apparent that a distinct style of colour may be adopted on safe grounds -for every subject. The application requires, it is true, infinite -modifications, which can only succeed in the hands of genius.</p> - -<hr class="r5" /> -<h5>GENUINE TONE.</h5> - - -<p class="para"><a id="a889">889.</a></p> - -<p>If the word tone, or rather tune, is to be still borrowed in future -from music, and applied to colouring, it might be used in a better -sense than heretofore.</p> - -<p class="para"><a id="a890">890.</a></p> - -<p>For it would not be unreasonable to compare a painting of powerful -effect, with a piece of music in a sharp key; a painting of soft effect -with a piece of music in a flat key, while other equivalents might be -found for the modifications of these two leading modes.</p> - -<hr class="r5" /> -<h5>FALSE TONE.</h5> - - -<p class="para"><a id="a891">891.</a></p> - -<p>The word tone has been hitherto understood to mean a veil of a -particular colour spread over<span class="pagenum"><a name="Page_343" id="Page_343">[Pg 343]</a></span> the whole picture; it was generally -yellow, for the painter instinctively pushed the effect towards the -powerful side.</p> - -<p class="para"><a id="a892">892.</a></p> - -<p>If we look at a picture through a yellow glass it will appear in this -tone. It is worth while to make this experiment again and again, in -order to observe what takes place in such an operation. It is a sort of -artificial light, deepening, and at the same time darkening the <i>plus</i> -side, and neutralising the <i>minus</i> side.</p> - -<p class="para"><a id="a893">893.</a></p> - -<p>This spurious tone is produced instinctively through uncertainty -as to the means of attaining a genuine effect; so that instead of -completeness, monotony is the result.</p> - -<hr class="r5" /> -<h5>WEAK COLOURING.</h5> - - -<p class="para"><a id="a894">894.</a></p> - -<p>It is owing to the same uncertainty that the colours are sometimes so -much broken as to have the effect of a grey camayeu, the handling being -at the same time as delicate as possible.</p> - -<p class="para"><a id="a895">895.</a></p> - -<p>The harmonious contrasts are often found to be very happily felt in -such pictures, but without spirit, owing to a dread of the motley.</p> - -<p><span class="pagenum"><a name="Page_344" id="Page_344">[Pg 344]</a></span></p> - -<hr class="r5" /> -<h5>THE MOTLEY.</h5> - - -<p class="para"><a id="a896">896.</a></p> - -<p>A picture may easily become party-coloured or motley, when the colours -are placed next each other in their full force, as it were only -mechanically and according to uncertain impressions.</p> - -<p class="para"><a id="a897">897.</a></p> - -<p>If, on the other hand, weak colours are combined, even although they -may be dissonant, the effect, as a matter of course, is not striking. -The uncertainty of the artist is communicated to the spectator, who, on -his side, can neither praise nor censure.</p> - -<p class="para"><a id="a898">898.</a></p> - -<p>It is also important to observe that the colours may be disposed -rightly in themselves, but that a work may still appear motley, if they -are falsely arranged in relation to light and shade.</p> - -<p class="para"><a id="a899">899.</a></p> - -<p>This may the more easily occur as light and shade are already defined -in the drawing, and are, as it were, comprehended in it, while the -colour still remains open to selection.</p> - -<hr class="r5" /> -<h5>DREAD OF THEORY.</h5> - - -<p class="para"><a id="a900">900.</a></p> - -<p>A dread of, nay, a decided aversion for all<span class="pagenum"><a name="Page_345" id="Page_345">[Pg 345]</a></span> theoretical views -respecting colour and everything belonging to it, has been hitherto -found to exist among painters; a prejudice for which, after all, they -were not to be blamed; for what has been hitherto called theory was -groundless, vacillating, and akin to empiricism. We hope that our -labours may tend to diminish this prejudice, and stimulate the artist -practically to prove and embody the principles that have been explained.</p> - -<hr class="r5" /> -<h5>ULTIMATE AIM.</h5> - - -<p class="para"><a id="a901">901.</a></p> - -<p>But without a comprehensive view of the whole of our theory, the -ultimate object will not be attained. Let the artist penetrate himself -with all that we have stated. It is only by means of harmonious -relations in light and shade, in keeping, in true and characteristic -colouring, that a picture can be considered complete, in the sense we -have now learnt to attach to the term.</p> - -<hr class="r5" /> -<h5>GROUNDS.</h5> - - -<p class="para"><a id="a902">902.</a></p> - -<p>It was the practice of the earlier artists to paint on light grounds. -This ground consisted of gypsum, and was thickly spread on linen or -panel, and then levigated. After the outline was drawn, the subject was -washed in with a<span class="pagenum"><a name="Page_346" id="Page_346">[Pg 346]</a></span> blackish or brownish colour. Pictures prepared in -this manner for colouring are still in existence, by Leonardo da Vinci, -and Fra Bartolomeo; there are also several by Guido.—<a href="#NOTE_II">Note II</a>.</p> - -<p class="para"><a id="a903">903.</a></p> - -<p>When the artist proceeded to colour, and had to represent white -draperies, he sometimes suffered the ground to remain untouched. -Titian did this latterly when he had attained the greatest certainty -in practice, and could accomplish much with little labour. The whitish -ground was left as a middle tint, the shadows painted in, and the high -lights touched on.—<a href="#NOTE_KK">Note KK</a>.</p> - -<p class="para"><a id="a904">904.</a></p> - -<p>In the process of colouring, the preparation merely washed as it were -underneath, was always effective. A drapery, for example, was painted -with a transparent colour, the white ground shone through it and gave -the colour life, so the parts previously prepared for shadows exhibited -the colour subdued, without being mixed or sullied.</p> - -<p class="para"><a id="a905">905.</a></p> - -<p>This method had many advantages; for the painter had a light ground -for the light portions of his work and a dark ground for the shadowed -portions. The whole picture was prepared; the<span class="pagenum"><a name="Page_347" id="Page_347">[Pg 347]</a></span> artist could work with -thin colours in the shadows, and had always an internal light to give -value to his tints. In our own time painting in water colours depends -on the same principles.</p> - -<p class="para"><a id="a906">906.</a></p> - -<p>Indeed a light ground is now generally employed in oil-painting, -because middle tints are thus found to be more transparent, and are in -some degree enlivened by a bright ground; the shadows, again, do not so -easily become black.</p> - -<p class="para"><a id="a907">907.</a></p> - -<p>It was the practice for a time to paint on dark grounds. Tintoret -probably introduced them. Titian's best pictures are not painted on a -dark ground.</p> - -<p class="para"><a id="a908">908.</a></p> - -<p>The ground in question was red-brown, and when the subject was drawn -upon it, the strongest shadows were laid in; the colours of the lights -impasted very thickly in the bright parts, and scumbled towards the -shadows, so that the dark ground appeared through the thin colour as a -middle tint. Effect was attained in finishing by frequently going over -the bright parts and touching on the high lights.</p> - -<p><span class="pagenum"><a name="Page_348" id="Page_348">[Pg 348]</a></span></p> - -<p class="para"><a id="a909">909.</a></p> - -<p>If this method especially recommended itself in practice on account -of the rapidity it allowed of, yet it had pernicious consequences. -The strong ground increased and became darker, and the light colours -losing their brightness by degrees, gave the shadowed portions more -and more preponderance. The middle tints became darker and darker, and -the shadows at last quite obscure. The strongly impasted lights alone -remained bright, and we now see only light spots on the painting. The -pictures of the Bolognese school, and of Caravaggio, afford sufficient -examples of these results.</p> - -<p class="para"><a id="a910">910.</a></p> - -<p>We may here in conclusion observe, that glazing derives its effect -from treating the prepared colour underneath as a light ground. By -this operation colours may have the effect of being mixed to the eye, -may be enhanced, and may acquire what is called tone; but they thus -necessarily become darker.</p> - -<hr class="r5" /> -<h5>PIGMENTS.</h5> - - -<p class="para"><a id="a911">911.</a></p> - -<p>We receive these from the hands of the chemist and the investigator of -nature. Much has been recorded respecting colouring substances,<span class="pagenum"><a name="Page_349" id="Page_349">[Pg 349]</a></span> which -is familiar to all by means of the press. But such directions require -to be revised from time to time. The master meanwhile communicates his -experience in these matters to his scholar, and artists generally to -each other.</p> - -<p class="para"><a id="a912">912.</a></p> - -<p>Those pigments which according to their nature are the most permanent, -are naturally much sought after, but the mode of employing them also -contributes much to the duration of a picture. The fewest possible -colouring materials are to be employed, and the simplest methods of -using them cannot be sufficiently recommended.</p> - -<p class="para"><a id="a913">913.</a></p> - -<p>For from the multitude of pigments colouring has suffered much. Every -pigment has its peculiar nature as regards its effect on the eye; -besides this it has its peculiar quality, requiring a corresponding -technical method in its application. The former circumstance is a -reason why harmony is more difficult of attainment with many materials -than with few, the latter, why chemical action and re-action may take -place among the colouring substances.</p> - -<p class="para"><a id="a914">914.</a></p> - -<p>We may refer, besides, to some false tendencies<span class="pagenum"><a name="Page_350" id="Page_350">[Pg 350]</a></span> which the artists -suffer themselves to be led away with. Painters are always looking -for new colouring substances, and believe when such a substance is -discovered that they have made an advance in the art. They have a -great curiosity to know the practical methods of the old masters, and -lose much time in the search. Towards the end of the last century -we were thus long tormented with wax-painting. Others turn their -attention to the discovery of new methods, through which nothing new is -accomplished; for, after all, it is the feeling of the artist only that -informs every kind of technical process.</p> - -<hr class="r5" /> -<h5>ALLEGORICAL, SYMBOLICAL, MYSTICAL APPLICATION OF COLOUR.</h5> - - -<p class="para"><a id="a915">915.</a></p> - -<p>It has been circumstantially shown above, that every colour produces -a distinct impression on the mind, and thus addresses at once the eye -and feelings. Hence it follows that colour may be employed for certain -moral and æsthetic ends.</p> - -<p class="para"><a id="a916">916.</a></p> - -<p>Such an application, coinciding entirely with nature, might be called -symbolical, since the colour would be employed in conformity with its -effect, and would at once express its meaning. If, for example, pure -red were assumed to<span class="pagenum"><a name="Page_351" id="Page_351">[Pg 351]</a></span> designate majesty, there can be no doubt that this -would be admitted to be a just and expressive symbol. All this has been -already sufficiently entered into.</p> - -<p class="para"><a id="a917">917.</a></p> - -<p>Another application is nearly allied to this; it might be called the -allegorical application. In this there is more of accident and caprice, -inasmuch as the meaning of the sign must be first communicated to us -before we know what it is to signify; what idea, for instance, is -attached to the green colour, which has been appropriated to hope?</p> - -<p class="para"><a id="a918">918.</a></p> - -<p>That, lastly, colour may have a mystical allusion, may be readily -surmised, for since every diagram in which the variety of colours may -be represented points to those primordial relations which belong both -to nature and the organ of vision, there can be no doubt that these may -be made use of as a language, in cases where it is proposed to express -similar primordial relations which do not present themselves to the -senses in so powerful and varied a manner. The mathematician extols -the value and applicability of the triangle; the triangle is revered -by the mystic; much admits of being expressed in it by diagrams, and, -among other things, the law<span class="pagenum"><a name="Page_352" id="Page_352">[Pg 352]</a></span> of the phenomena of colours; in this case, -indeed, we presently arrive at the ancient mysterious hexagon.</p> - -<p class="para"><a id="a919">919.</a></p> - -<p>When the distinction of yellow and blue is duly comprehended, and -especially the augmentation into red, by means of which the opposite -qualities tend towards each other and become united in a third; then, -certainly, an especially mysterious interpretation will suggest itself, -since a spiritual meaning may be connected with these facts; and when -we find the two separate principles producing green on the one hand and -red in their intenser state, we can hardly refrain from thinking in the -first case on the earthly, in the last on the heavenly, generation of -the Elohim.—<a href="#NOTE_LL">Note LL</a>.</p> - -<p class="para"><a id="a920">920.</a></p> - -<p>But we shall do better not to expose ourselves, in conclusion, to -the suspicion of enthusiasm; since, if our doctrine of colours finds -favour, applications and allusions, allegorical, symbolical, and -mystical, will not fail to be made, in conformity with the spirit of -the age.</p> - -<hr class="r5" /> -<h5>CONCLUDING OBSERVATIONS.</h5> - - -<p>In reviewing this labour, which has occupied me long, and which at -last I give but as a<span class="pagenum"><a name="Page_353" id="Page_353">[Pg 353]</a></span> sketch, I am reminded of a wish once expressed -by a careful writer, who observed that he would gladly see his works -printed at once as he conceived them, in order then to go to the task -with a fresh eye; since everything defective presents itself to us more -obviously in print than even in the cleanest manuscript. This feeling -may be imagined to be stronger in my case, since I had not even an -opportunity of going through a fair transcript of my work before its -publication, these pages having been put together at a time when a -quiet, collected state of mind was out of the question.<a name="FNanchor_5_60" id="FNanchor_5_60"></a><a href="#Footnote_5_60" class="fnanchor">[5]</a></p> - -<p>Some of the explanations I was desirous of giving are to be found in -the introduction, but in the portion of my work to be devoted to the -history of the doctrine of colours, I hope to give a more detailed -account of my investigations and the vicissitudes they underwent. One -inquiry, however, may not be out of place here; the consideration, -namely, of the question, what can a man accomplish who cannot devote -his whole life to scientific pursuits? what can he perform as a -temporary guest on an estate not his own, for the advantage of the -proprietor?</p> - -<p>When we consider art in its higher character, we might wish that -masters only had to do with<span class="pagenum"><a name="Page_354" id="Page_354">[Pg 354]</a></span> it, that scholars should be trained by -the severest study, that amateurs might feel themselves happy in -reverentially approaching its precincts. For a work of art should be -the effusion of genius, the artist should evoke its substance and form -from his inmost being, treat his materials with sovereign command, and -make use of external influences only to accomplish his powers.</p> - -<p>But if the professor in this case has many reasons for respecting -the dilettante, the man of science has every motive to be still more -indulgent, since the amateur here is capable of contributing what may -be satisfactory and useful. The sciences depend much more on experiment -than art, and for mere experiment many a votary is qualified. -Scientific results are arrived at by many means, and cannot dispense -with many hands, many heads. Science may be communicated, the treasure -may be inherited, and what is acquired by one may be appropriated -by many. Hence no one perhaps ought to be reluctant to offer his -contributions. How much do we not owe to accident, to mere practice, -to momentary observation. All who are endowed only with habits of -attention, women, children, are capable of communicating striking and -true remarks.</p> - -<p>In science it cannot therefore be required, that he who endeavours -to furnish something in<span class="pagenum"><a name="Page_355" id="Page_355">[Pg 355]</a></span> its aid should devote his whole life to it, -should survey and investigate it in all its extent; for this, in most -cases, would be a severe condition even for the initiated. But if we -look through the history of science in general, especially the history -of physics, we shall find that many important acquisitions have been -made by single inquirers, in single departments, and very often by -unprofessional observers.</p> - -<p>To whatever direction a man may be determined by inclination or -accident, whatever class of phenomena especially strike him, excite -his interest, fix his attention, and occupy him, the result will still -be for the advantage of science: for every new relation that comes to -light, every new mode of investigation, even the imperfect attempt, -even error itself is available; it may stimulate other observers and is -never without its use as influencing future inquiry.</p> - -<p>With this feeling the author himself may look back without regret -on his endeavours. From this consideration he can derive some -encouragement for the prosecution of the remainder of his task; and -although not satisfied with the result of his efforts, yet re-assured -by the sincerity of his intentions, he ventures to recommend his past -and future labours to the interest of his contemporaries and posterity.</p> - -<p style="margin-left: 20%;"> -Multi pertransibunt et augebitur scientia.<br /> -</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_56" id="Footnote_1_56"></a><a href="#FNanchor_1_56"><span class="label">[1]</span></a> <a href="#col000">Plate 1</a>, fig. 3.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_57" id="Footnote_2_57"></a><a href="#FNanchor_2_57"><span class="label">[2]</span></a> See <a href="#NOTE_C">Note C</a>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_58" id="Footnote_3_58"></a><a href="#FNanchor_3_58"><span class="label">[3]</span></a> Some early Italian writers, Sicillo, Occolti, Rinaldi, -and others, have treated this subject in connexion with the supposed -signification of colours.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_59" id="Footnote_4_59"></a><a href="#FNanchor_4_59"><span class="label">[4]</span></a> The English technical expressions "flat" and "square" have -an association of mannerism.—T</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_60" id="Footnote_5_60"></a><a href="#FNanchor_5_60"><span class="label">[5]</span></a> Towards the close of 1806, when Weimar was occupied by -Napoleon after the battle of Jena.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_357" id="Page_357">[Pg 357]</a></span></p></div> - - - - -<h4><a name="NOTES" id="NOTES">NOTES.</a></h4> - - -<p class="para"><a id="NOTE_A"></a>NOTE A.—<a href="#a18">Par. 18.</a></p> - -<p>Leonardo da Vinci observes that "a light object relieved on a dark -ground appears magnified;" and again, "Objects seen at a distance -appear out of proportion; this is because the light parts transmit -their rays to the eye more powerfully than the dark. A woman's white -head-dress once appeared to me much wider than her shoulders, owing -to their being dressed in black."<a name="FNanchor_1_61" id="FNanchor_1_61"></a><a href="#Footnote_1_61" class="fnanchor">[1]</a> "It is now generally admitted -that the excitation produced by light is propagated on the retina a -little beyond the outline of the image. Professor Plateau, of Ghent, -has devoted a very interesting special memoir to the description -and explanation of phenomena of this nature. See his 'Mémoire sur -l'Irradiation,' published in the 11th vol. of the Transactions of the -Royal Academy of Sciences at Brussels."<a name="FNanchor_2_62" id="FNanchor_2_62"></a><a href="#Footnote_2_62" class="fnanchor">[2]</a>—S. F.</p> - - -<p class="para"><a id="NOTE_B"></a>NOTE B.—<a href="#a23">Par. 23.</a></p> - -<p>"The duration of ocular spectra produced by strongly exciting the -retina, may be conveniently measured by minutes and seconds; but to -ascertain the duration of more evanescent phenomena, recourse must be -had to other means. The Chevalier d'Arcy (Mém. de l'Acad. des Sc.<span class="pagenum"><a name="Page_358" id="Page_358">[Pg 358]</a></span> -1765,) endeavoured to ascertain the duration of the impression produced -by a glowing coal in the following manner. He attached it to the -circumference of a wheel, the velocity of which was gradually increased -until the apparent trace of the object formed a complete circle, and -then measured the duration of a revolution, which was obviously that -of the impression. To ascertain the duration of a revolution it is -sufficient merely to know the number of revolutions described in a -given time. Recently more refined experiments of the same kind have -been made by Professors Plateau and Wheatstone."—S. F.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_61" id="Footnote_1_61"></a><a href="#FNanchor_1_61"><span class="label">[1]</span></a> "Trattato della Pittura, Roma, 1817," p. 143-223. This -edition, published from a Vatican MS., contains many observations not -included in former editions.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_62" id="Footnote_2_62"></a><a href="#FNanchor_2_62"><span class="label">[2]</span></a> A few notes (marked with inverted commas and with the -signature S. F.) have been kindly furnished by a scientific friend.</p></div> - - -<p class="para"><a id="NOTE_C"></a>NOTE C.—<a href="#a50">Par. 50.</a></p> - -<p>Every treatise on the harmonious combination of colours contains the -diagram of the chromatic circle more or less elaborately constructed. -These diagrams, if intended to exhibit the contrasts produced by -the action and re-action of the retina, have one common defect. The -opposite colours are made equal in intensity; whereas the complemental -colour pictured on the retina is always less vivid, and always darker -or lighter than the original colour. This variety undoubtedly accords -more with harmonious effects in painting.</p> - -<p>The opposition of two pure hues of equal intensity, differing only in -the abstract quality of colour, would immediately be pronounced crude -and inharmonious. It would not, however, be strictly correct to say -that such a contrast is too violent; on the contrary, it appears the -contrast is not carried far enough, for though differing in colour, -the two hues may be exactly similar in purity and intensity. Complete -contrast, on the other hand, supposes dissimilarity in all respects.</p> - -<p>In addition to the mere difference of hue, the eye, it seems, requires -difference in the lightness or darkness of the hue. The spectrum of a -colour relieved as a dark on a light ground, is a light colour on a -dark ground, and <i>vice versâ</i>. Thus, if we look at a bright red wafer -on the whitest<span class="pagenum"><a name="Page_359" id="Page_359">[Pg 359]</a></span> surface, the complemental image will be still lighter -than the white surface; if the same wafer is placed on a black surface, -the complemental image will be still darker. The colour of both these -spectra may be called greenish, but it is evident that a colour must be -scarcely appreciable as such, if it is lighter than white and darker -than black. It is, however, to be remarked, that the white surface -round the light greenish image seems tinged with a reddish hue, and -the black surface round the dark image becomes slightly illuminated -with the same colour, thus in both cases assisting to render the image -apparent (<a href="#a58">58</a>).</p> - -<p>The difficulty or impossibility of describing degrees of colour in -words, has also had a tendency to mislead, by conveying the idea of -more positive hues than the physiological contrast warrants. Thus, -supposing scarlet to be relieved as a dark, the complemental colour is -so light in degree and so faint in colour, that it should be called a -pearly grey; whereas the theorists, looking at the quality of colour -abstractedly, would call it a green-blue, and the diagram would falsely -present such a hue equal in intensity to scarlet, or as nearly equal as -possible.</p> - -<p>Even the difference of mass which good taste requires may be suggested -by the physiological phenomena, for unless the complemental image is -suffered to fall on a surface precisely as near to the eye as that on -which the original colour was displayed, it appears larger or smaller -than the original object (<a href="#a22">22</a>), and this in a rapidly increasing -proportion. Lastly, the shape itself soon becomes changed (26).</p> - -<p>That vivid colour demands the comparative absence of colour, either -on a lighter or darker scale, as its contrast, may be inferred again -from the fact that bright colourless objects produce strongly coloured -spectra. In darkness, the spectrum which is first white, or nearly -white, is followed by red: in light, the spectrum which is first black, -is followed by green (<a href="#Page_39">39</a>-<a href="#a44">44</a>). All colour, as the author observes -(<a href="#a259">259</a>), is to be considered as half-light, inasmuch as it<span class="pagenum"><a name="Page_360" id="Page_360">[Pg 360]</a></span> is in every -case lighter than black and darker than white. Hence no contrast of -colour with colour, or even of colour with black or white, can be so -great (as regards lightness or darkness) as the contrast of black and -white, or light and dark abstractedly. This distinction between the -differences of degree and the differences of kind is important, since a -just application of contrast in colour may be counteracted by an undue -difference in lightness or darkness. The mere contrast of colour is -happily employed in some of Guido's lighter pictures, but if intense -darks had been opposed to his delicate carnations, their comparative -whiteness would have been unpleasantly apparent. On the other hand, the -flesh-colour in Giorgione, Sebastian del Piombo (his best imitator), -and Titian, was sometimes so extremely glowing<a name="FNanchor_1_63" id="FNanchor_1_63"></a><a href="#Footnote_1_63" class="fnanchor">[1]</a> that the deepest -colours, and black, were indispensable accompaniments. The manner of -Titian as distinguished from his imitation of Giorgione, is golden -rather than fiery, and his biographers are quite correct in saying -that he was fond of opposing red (lake) and blue to his flesh<a name="FNanchor_2_64" id="FNanchor_2_64"></a><a href="#Footnote_2_64" class="fnanchor">[2]</a>. The -correspondence of these contrasts with the physiological phenomena will -be immediately apparent, while the occasional practice of Rubens in -opposing bright red to a still cooler flesh-colour, will be seen to be -equally consistent.</p> - -<p>The effect of white drapery (the comparative absence of colour) in -enhancing the glow of Titian's flesh-colour, has been frequently -pointed out:<a name="FNanchor_3_65" id="FNanchor_3_65"></a><a href="#Footnote_3_65" class="fnanchor">[3]</a> the shadows of white thus opposed to flesh, often -present, again, the physiological contrast, however delicately, -according to the hue of the carnation.<span class="pagenum"><a name="Page_361" id="Page_361">[Pg 361]</a></span> The lights, on the other hand, -are not, and probably never were, quite white, but from the first, -partook of the quality of depth, a quality assumed by the colourists to -pervade every part of a picture more or less.<a name="FNanchor_4_66" id="FNanchor_4_66"></a><a href="#Footnote_4_66" class="fnanchor">[4]</a></p> - -<p>It was before observed that the description of colours in words may -often convey ideas of too positive a nature, and it may be remarked -generally that the colours employed by the great masters are, in their -ultimate effect, more or less subdued or broken. The physiological -contrasts are, however, still applicable in the most comparatively -neutral scale.</p> - -<p>Again, the works of the colourists show that these oppositions are -not confined to large masses (except perhaps in works to be seen only -at a great distance); on the contrary, they are more or less apparent -in every part, and when at last the direct and intentional operations -of the artist may have been insufficient to produce them in their -minuter degrees, the accidental results of glazing and other methods -may be said to extend the contrasts to infinity. In such productions, -where every smallest portion is an epitome of the whole, the eye -still appreciates the fascinating effect of contrast, and the work is -pronounced to be true and complete, in the best sense of the words.</p> - -<p>The Venetian method of scumbling and glazing exhibits these minuter -contrasts within each other, and is thus generally considered more -refined than the system of breaking the colours, since it ensures a -fuller gradation of hues, and produces another class of contrasts, -those, namely, which result from degrees of transparence and opacity. -In some of the Flemish and Dutch masters, and sometimes in Reynolds, -the two methods are combined in great perfection.</p> - -<p><span class="pagenum"><a name="Page_362" id="Page_362">[Pg 362]</a></span></p> - -<p>The chromatic diagram does not appear to be older than the last -century. It is one of those happy adaptations of exacter principles to -the objects of taste which might have been expected from Leonardo da -Vinci. That its true principle was duly felt is abundantly evident from -the works of the colourists, as well as from the general observations -of early writers.<a name="FNanchor_5_67" id="FNanchor_5_67"></a><a href="#Footnote_5_67" class="fnanchor">[5]</a> The more practical directions occasionally to be -met with in the treatises of Leon Battista Alberti, Leonardo da Vinci -and others, are conformable to the same system. Some Italian works, -not written by painters, which pretend to describe this harmony, are, -however, very imperfect.<a name="FNanchor_6_68" id="FNanchor_6_68"></a><a href="#Footnote_6_68" class="fnanchor">[6]</a> A passage in Lodovico Dolce's Dialogue on -Colours is perhaps the only one worth quoting. "He," says that writer, -"who wishes to combine colours that are agreeable to the eye, will -put grey next dusky orange; yellow-green next rose-colour; blue next -orange; dark purple, black, next dark-green; white next black, and -white next flesh-colour."<a name="FNanchor_7_69" id="FNanchor_7_69"></a><a href="#Footnote_7_69" class="fnanchor">[7]</a> The Dialogue on Painting, by the same -author, has the reputation of containing some of Titian's precepts: -if the above passage may be traced to the same source, it must be -confessed that it is almost the only one of the kind in the treatise -from which it is taken.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_63" id="Footnote_1_63"></a><a href="#FNanchor_1_63"><span class="label">[1]</span></a> "Ardito veramente alquanto, sanguigno, e quasi -fiammeggiante."—<i>Zanetti della Pittura Veneziana</i>, Ven. 1771, p. -90. Warm as the flesh colour of the colourists is, it still never -approaches a positive hue, if we except some examples in frescoes and -other works intended to be seen at a great distance. Zanetti, speaking -of a fresco by Giorgione, now almost obliterated, compares the colour -to "un vivo raggio di cocente sole."—-<i>Varie Pitture a fresco dei -Principali Maestri Veneziani</i>. Ven. 1760.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_64" id="Footnote_2_64"></a><a href="#FNanchor_2_64"><span class="label">[2]</span></a> Ridolfi.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_65" id="Footnote_3_65"></a><a href="#FNanchor_3_65"><span class="label">[3]</span></a> Zanetti, I. ii.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_66" id="Footnote_4_66"></a><a href="#FNanchor_4_66"><span class="label">[4]</span></a> Two great authorities, divided by more than three -centuries, Leon Battista Alberti and Reynolds, have recommended this -subdued treatment of white. "It is to be remembered," says the first, -"that no surface should be made so white that it cannot be made more -so. In white dresses again, it is necessary to stop far short of the -last degree of whiteness."—<i>Della Pittura</i>, I. ii., compare with -Reynolds, vol. i. dis. 8.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_67" id="Footnote_5_67"></a><a href="#FNanchor_5_67"><span class="label">[5]</span></a> Vasari observes, "L'unione nella pittura è una discordanza -dicolori diversi accordati insième."—Vol. i. c. 18. This observation -is repeated by various writers on art in nearly the same words, and -at last appears in Sandrart: "Concordia, potissimum picturæ decus, -in discordiâ consistit, et quasi litigio colorum."—P. i. c. 5. The -source, perhaps, is Aristotle: he observes, "We are delighted with -harmony, because it is the union of contrary principles having a ratio -to each other."—<i>Problem.</i></p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_68" id="Footnote_6_68"></a><a href="#FNanchor_6_68"><span class="label">[6]</span></a> See "Occolti Trattato de' Colori." Parma, 1568.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_69" id="Footnote_7_69"></a><a href="#FNanchor_7_69"><span class="label">[7]</span></a> "Volendo l'uomo accoppiare insième colori che all'occhio -dilettino—porrà insième il berrettino col leonato; il verde-giallo con -l'incarnato e rosso; il turchino con l'arangi; il morello col verde -oscuro; il nero col bianco; il bianco con l'incarnato."—<i>Dialogo di -M. Lodovico Dolce nel quale si ragiona della qualità, diversità, e -proprietà de' colori</i>. Venezia, 1565.</p></div> - - - -<p class="para"><a id="NOTE_D"></a>NOTE D.—<a href="#a66">Par. 66.</a></p> - -<p>In some of these cases there can be no doubt that Goethe<span class="pagenum"><a name="Page_363" id="Page_363">[Pg 363]</a></span> attributes -the contrast too exclusively to the physiological cause, without -making sufficient allowance for the actual difference in the colour of -the lights. The purely physical nature of some coloured shadows was -pointed out by Pohlmann; and Dr. Eckermann took some pains to convince -Goethe of the necessity of making such a distinction. Goethe at first -adhered to his extreme view, but some time afterwards confessed to -Dr. Eckermann, that in the case of the blue shadows of snow (<a href="#a74">74</a>), the -reflection of the sky was undoubtedly to be taken into the account. -"Both causes may, however, operate together," he observed, "and the -contrast which a warm yellow light demands may heighten the effect of -the blue." This was all his opponent contended.<a name="FNanchor_1_70" id="FNanchor_1_70"></a><a href="#Footnote_1_70" class="fnanchor">[1]</a></p> - -<p>With a few such exceptions, the general theory of Goethe with regard -to coloured shadows is undoubtedly correct; the experiments with two -candles (68), and with coloured glass and fluids (80), as well as the -observations on the shadows of snow (75), are conclusive, for in all -these cases only one light is actually changed in colour, while the -other still assumes the complemental hue. "Coloured shadows," Dr. J. -Müller observes, "are usually ascribed to the physiological influence -of contrast; the complementary colour presented by the shadow being -regarded as the effect of internal causes acting on that part of the -retina, and not of the impression of coloured rays from without. This -explanation is the one adopted by Rumford, Goethe, Grotthuss, Brandes, -Tourtual, Pohlmann, and most authors who have studied the subject."<a name="FNanchor_2_71" id="FNanchor_2_71"></a><a href="#Footnote_2_71" class="fnanchor">[2]</a></p> - -<p>In the Historical Part the author gives an account of a scarce French -work, "Observations sur les Ombres Colorées," Paris, 1782. The -writer<a name="FNanchor_3_72" id="FNanchor_3_72"></a><a href="#Footnote_3_72" class="fnanchor">[3]</a> concludes that "the colour<span class="pagenum"><a name="Page_364" id="Page_364">[Pg 364]</a></span> of shadows is as much owing to -the light that causes them as to that which (more faintly) illumines -them."</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_70" id="Footnote_1_70"></a><a href="#FNanchor_1_70"><span class="label">[1]</span></a> Eckermann's "Gespräche mit Goethe," vol. ii. p. 76 and -280.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_71" id="Footnote_2_71"></a><a href="#FNanchor_2_71"><span class="label">[2]</span></a> "Elements of Physiology," by J. Müller, M. D., translated -from the German by William Baly, M.D. London, 1839.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_72" id="Footnote_3_72"></a><a href="#FNanchor_3_72"><span class="label">[3]</span></a> Anonymous, having only given the initials H. F. T.</p></div> - - - -<p class="para"><a id="NOTE_E"></a>NOTE E.—<a href="#a69">Par. 69.</a></p> - -<p>This opinion of the author is frequently repeated (<a href="#a201">201</a>, <a href="#a312">312</a>, <a href="#a591">591</a>), and -as it seems at first sight to be at variance with a received principle -of art, it may be as well at once to examine it.</p> - -<p>In order to see the general proposition in its true point of view, -it will be necessary to forget the arbitrary distinctions of light -and shade, and to consider all such modifications between highest -brightness and absolute darkness only as so many lesser degrees of -light.<a name="FNanchor_1_73" id="FNanchor_1_73"></a><a href="#Footnote_1_73" class="fnanchor">[1]</a> The author, indeed, by the word shadow, always understands a -lesser light.</p> - -<p>The received notion, as stated by Du Fresnoy,<a name="FNanchor_2_74" id="FNanchor_2_74"></a><a href="#Footnote_2_74" class="fnanchor">[2]</a> is much too positive -and unconditional, and is only true when we understand the "displaying" -light to comprehend certain degrees of half or reflected light, and the -"destroying" shade to mean the intensest degree of obscurity.</p> - -<p>There are degrees of brightness which destroy colour as well as -degrees of darkness.<a name="FNanchor_3_75" id="FNanchor_3_75"></a><a href="#Footnote_3_75" class="fnanchor">[3]</a> In general, colour resides in a mitigated -light, but a very little observation shows us that different colours -require different degrees of light to display them. Leonardo da Vinci -frequently inculcates the general principle above alluded to, but he -as frequently qualifies it; for he not only remarks that the highest -light may be comparative<span class="pagenum"><a name="Page_365" id="Page_365">[Pg 365]</a></span> privation of colour, but observes, with great -truth, that some hues are best displayed in their fully illumined -parts, some in their reflections, and some in their half-lights; and -again, that every colour is most beautiful when lit by reflections from -its own surface, or from a hue similar to its own.<a name="FNanchor_4_76" id="FNanchor_4_76"></a><a href="#Footnote_4_76" class="fnanchor">[4]</a></p> - -<p>The Venetians went further than Leonardo in this view and practice; -and he seems to allude to them when he criticises certain painters, -who, in aiming at clearness and fulness of colour, neglected what, in -his eyes, was of superior importance, namely, gradation and force of -chiaro-scuro.<a name="FNanchor_5_77" id="FNanchor_5_77"></a><a href="#Footnote_5_77" class="fnanchor">[5]</a></p> - -<p>That increase of colour supposes increase of darkness, as so often -stated by Goethe, may be granted without difficulty. To what extent, on -the other hand, increase of darkness, or rather diminution of light, -is accompanied by increase of colour, is a question which has been -variously answered by various schools. Examples of the total negation -of the principle are not wanting, nor are they confined to the infancy -of the art. Instances, again, of the opposite tendency are frequent -in Venetian and early Flemish pictures resembling the augmenting -richness of gems or of stained glass:<a name="FNanchor_6_78" id="FNanchor_6_78"></a><a href="#Footnote_6_78" class="fnanchor">[6]</a><span class="pagenum"><a name="Page_366" id="Page_366">[Pg 366]</a></span> indeed, it is not impossible -that the increase of colour in shade, which is so remarkable in the -pictures alluded to, may have been originally suggested by the rich -and fascinating effect of stained glass; and the Venetians, in this as -in many other respects, may have improved on a hint borrowed from the -early German painters, many of whom painted on glass.<a name="FNanchor_7_79" id="FNanchor_7_79"></a><a href="#Footnote_7_79" class="fnanchor">[7]</a></p> - -<p>At all events, the principle of still increasing in colour in certain -hues seems to have been adopted in Flanders and in Venice at an early -period;<a name="FNanchor_8_80" id="FNanchor_8_80"></a><a href="#Footnote_8_80" class="fnanchor">[8]</a> while Giorgione, in carrying the style to the most daring -extent, still recommended it by corresponding grandeur of treatment in -other respects.</p> - -<p>The same general tendency, except that the technical methods are -less transparent, is, however, very striking in some of the painters -of the school of Umbria, the instructors or early companions of -Raphael.<a name="FNanchor_9_81" id="FNanchor_9_81"></a><a href="#Footnote_9_81" class="fnanchor">[9]</a> The influence of<span class="pagenum"><a name="Page_367" id="Page_367">[Pg 367]</a></span> these examples, as well as that of Fra -Bartolommeo, in Florence, is distinctly to be traced in the works of -the great artist just named, but neither is so marked as the effect -of his emulation of a Venetian painter at a later period. The glowing -colour, sometimes bordering on exaggeration, which Raphael adopted -in Rome, is undoubtedly to be attributed to the rivalry of Sebastian -del Piombo. This painter, the best of Giorgione's imitators, arrived -in Rome, invited by Agostini Chigi, in 1511, and the most powerful of -Raphael's frescoes, the Heliodorus and Mass of Bolsena, as well as -some portraits in the same style, were painted in the two following -years. In the hands of some of Raphael's scholars, again, this extreme -warmth was occasionally carried to excess, particularly by Pierino del -Vaga, with whom it often degenerated into redness. The representative -of the glowing manner in Florence was Fra Bartolommeo, and, in the -same quality, considered abstractedly, some painters of the school of -Ferrara were second to none.</p> - -<p>In another Note (par. <a href="#a177">177</a>) some further considerations<span class="pagenum"><a name="Page_368" id="Page_368">[Pg 368]</a></span> are offered, -which may partly explain the prevalence of this style in the beginning -of the sixteenth century; here we merely add, that the conditions under -which the appearance itself is most apparent in nature are perhaps more -obvious in Venice than elsewhere. The colour of general nature may be -observed in all places with almost equal convenience, but with regard -to an important quality in living nature, namely, the colour of flesh, -perhaps there are no circumstances in which its effects at different -distances can be so conveniently compared as when the observer and the -observed gradually approach and glide past each other on so smooth an -element and in so undisturbed a manner as on the canals and in the -gondolas of Venice;<a name="FNanchor_10_82" id="FNanchor_10_82"></a><a href="#Footnote_10_82" class="fnanchor">[10]</a> the complexions, from the peculiar mellow -carnations of the Italian women to the sun-burnt features and limbs -of the mariners, presenting at the same time the fullest variety in -another sense.</p> - -<p>At a certain distance—the colour being always assumed to be unimpaired -by interposed atmosphere—the reflections appear kindled to intenser -warmth; the fiery glow of Giorgione is strikingly apparent; the colour -is seen in its largest relation; the <i>macchia</i>,<a name="FNanchor_11_83" id="FNanchor_11_83"></a><a href="#Footnote_11_83" class="fnanchor">[11]</a> an expression so -emphatically used by Italian writers, appears in all its quantity, and -the reflections being the focus of warmth, the hue seems to deepen in -shade.</p> - -<p>A nearer view gives the detail of cooler tints more perceptibly,<a name="FNanchor_12_84" id="FNanchor_12_84"></a><a href="#Footnote_12_84" class="fnanchor">[12]</a> -and the forms are at the same time more distinct. Hence Lanzi is quite -correct when, in distinguishing the style of Titian from that of -Giorgione, he says that Titian's<span class="pagenum"><a name="Page_369" id="Page_369">[Pg 369]</a></span> was at once more defined and less -fiery.<a name="FNanchor_13_85" id="FNanchor_13_85"></a><a href="#Footnote_13_85" class="fnanchor">[13]</a> In a still nearer observation the eye detects the minute -lights which Leonardo da Vinci says are incompatible with effects such -as those we have described<a name="FNanchor_14_86" id="FNanchor_14_86"></a><a href="#Footnote_14_86" class="fnanchor">[14]</a> and which, accordingly, we never find -in Giorgione and Titian. This large impression of colour, which seems -to require the condition of comparative distance for its full effect, -was most fitly employed by the same great artists in works painted in -the open air or for large altar-pieces. Their celebrated frescoes on -the exterior of the Fondaco de' Tedeschi at Venice, to judge from their -faint remains and the descriptions of earlier writers, were remarkable -for extreme warmth in the shadows. The old frescoes in the open air -throughout Friuli have often the same character, and, owing to the -fulness of effect which this treatment ensures, are conspicuous at a -very great distance.<a name="FNanchor_15_87" id="FNanchor_15_87"></a><a href="#Footnote_15_87" class="fnanchor">[15]</a></p> - -<p>In assuming that the Venetian painters may have acquired a taste for -this breadth<a name="FNanchor_16_88" id="FNanchor_16_88"></a><a href="#Footnote_16_88" class="fnanchor">[16]</a> of colour under the circumstances above alluded to, -it is moreover to be remembered that the time for this agreeable -study was the evening; when the sun had already set behind the hills -of Bassano; when the light was glowing but diffused; when shadows<span class="pagenum"><a name="Page_370" id="Page_370">[Pg 370]</a></span> -were soft—conditions all agreeing with the character of their -colouring:<a name="FNanchor_17_89" id="FNanchor_17_89"></a><a href="#Footnote_17_89" class="fnanchor">[17]</a> above all, when the hour invited the fairer portion of -the population to betake themselves in their gondolas to the lagunes. -The scene of this "promenade" was to the north of Venice, the quarter -in which Titian at one time lived. A letter exists written by Francesco -Priscianese, giving an account of his supping with the great painter in -company with Jacopo Nardi, Pietro Aretino, the sculptor Sansovino, and -others. The writer speaks of the beauty of the garden, where the table -was prepared, looking over the lagunes towards Murano, "which part of -the sea," he continues, "as soon as the sun was down, was covered with -a thousand gondolas, graced with beautiful women, and enlivened by the -harmony of voices and instruments, which lasted till midnight, forming -a pleasing accompaniment to our cheerful repast."<a name="FNanchor_18_90" id="FNanchor_18_90"></a><a href="#Footnote_18_90" class="fnanchor">[18]</a></p> - -<p>To return to Goethe: perhaps the foregoing remarks may warrant the -conclusion that his idea of colour in shadow is not irreconcileable -with the occasional practice of the best painters. The highest examples -of the style thus defined are, or were, to be found in the works of -Giorgione<a name="FNanchor_19_91" id="FNanchor_19_91"></a><a href="#Footnote_19_91" class="fnanchor">[19]</a> and Titian, and hence the style itself, though "within -that circle"<span class="pagenum"><a name="Page_371" id="Page_371">[Pg 371]</a></span> few "dare walk" is to be considered the grandest and -most perfect. Its possible defects or abuse are not to be dissembled: -in addition to the danger of exaggeration<a name="FNanchor_20_92" id="FNanchor_20_92"></a><a href="#Footnote_20_92" class="fnanchor">[20]</a> it is seldom united -with the plenitude of light and shade, or with roundness; yet, where -fine examples of both modes of treatment may be compared, the charm -of colour has perhaps the advantage.<a name="FNanchor_21_93" id="FNanchor_21_93"></a><a href="#Footnote_21_93" class="fnanchor">[21]</a> The difficulty of uniting -qualities so different in their nature, is proved by the very rare -instances in which it has been accomplished. Tintoret in endeavouring -to add chiaro-scuro to Venetian colour, in almost every instance fell -short of the glowing richness of Titian.<a name="FNanchor_22_94" id="FNanchor_22_94"></a><a href="#Footnote_22_94" class="fnanchor">[22]</a></p> - -<p><span class="pagenum"><a name="Page_372" id="Page_372">[Pg 372]</a></span></p> - -<p>Giacomo Bassan and his imitators, even in their dark effects, still had -the principle of the gem in view: their light, in certain hues, is the -minimum of colour, their lower tones are rich, their darks intense, -and all is sparkling.<a name="FNanchor_23_95" id="FNanchor_23_95"></a><a href="#Footnote_23_95" class="fnanchor">[23]</a> Of the great painters who, beginning, on -the other hand, with chiaro-scuro, sought to combine with it the full -richness of colour, Correggio, in the opinion of many, approached -perfection nearest; but we may perhaps conclude with greater justice -that the desired excellence was more completely attained by Rembrandt -than by any of the Italians.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_73" id="Footnote_1_73"></a><a href="#FNanchor_1_73"><span class="label">[1]</span></a> Leonardo da Vinci observes: "L'ombra è diminuzione di -luce, tenebre è privazione di luce." And again: "Sempre il minor lume è -ombra del lume maggiore."—<i>Trattato della Pittura</i>, pp. 274-299. -</p> -<p> -N. B. The same edition before described has been consulted throughout.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_74" id="Footnote_2_74"></a><a href="#FNanchor_2_74"><span class="label">[2]</span></a> -</p> -<p> -"Lux varium vivumque dabit, nullum umbra colorem."<br /> -<span style="margin-left: 20.5em;"><i>De Arte Graphicá</i>.</span><br /> -</p> -<p> -"Know first that light displays and shade destroys<br /> -Refulgent nature's variegated dies."—Mason's <i>Translation</i>.<br /> -</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_75" id="Footnote_3_75"></a><a href="#FNanchor_3_75"><span class="label">[3]</span></a> A Spanish writer, Diego de Carvalho e Sampayo, quoted -by Goethe ("Farbenlehre," vol. ii.), has a similar observation. This -destroying effect of light is striking in climates where the sun is -powerful, and was not likely to escape the notice of a Spaniard.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_76" id="Footnote_4_76"></a><a href="#FNanchor_4_76"><span class="label">[4]</span></a> Trattato, pp. 103, 121, 123, 324, &c.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_77" id="Footnote_5_77"></a><a href="#FNanchor_5_77"><span class="label">[5]</span></a> Ib. pp. 85, 134.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_78" id="Footnote_6_78"></a><a href="#FNanchor_6_78"><span class="label">[6]</span></a> Absolute opacity, to judge from the older specimens -of stained glass, seems to have been considered inadmissible. The -window was to admit light, however modified and varied, in the form -prescribed by the architect, and that form was to be preserved. This -has been unfortunately lost sight of in some modern glass-painting, -which, by excluding the light in large masses, and adopting the -opacity of pictures (the reverse of the influence above alluded to), -has interfered with the architectural symmetry in a manner far from -desirable. On the other hand, if we suppose painting at any period -to have aimed at the imitation of stained glass, such an imitation -must of necessity have led to extreme force; for the painter sets -out by substituting a mere white ground for the real light of the -sky, and would thus be compelled to subdue every tone accordingly. -In such an imitation his colour would soon deepen to its intensest -state; indeed, considerable portions of the darker hues would be lost -in obscurity. The early Flemish pictures seldom err on the side of -a gay superabundance of colour; on the contrary, they are generally -remarkable for comparatively cool lights, for extreme depth, and a -certain subdued splendour, qualities which would necessarily result -from the imitation or influence in question.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_79" id="Footnote_7_79"></a><a href="#FNanchor_7_79"><span class="label">[7]</span></a> See Langlois, "Peinture sur Verre." Rouen, 1832; -Descamps, "La Vie des Peintres Flamands;" and Gessert, "Geschichte der -Glasmalerei." Stutgard, 1839. The antiquity of the glass manufactory -of Murano (Venice) is also not to be forgotten. Vasari objects to the -Venetian glass, because it was darker in colour than that of Flanders, -France, and England; but this very quality was more likely to have an -advantageous influence on the style of the early oil-painters. The use -of stained glass was, however, at no period very general in Italy.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_8_80" id="Footnote_8_80"></a><a href="#FNanchor_8_80"><span class="label">[8]</span></a> Zanetti, "Della Pittura Veneziana," marks the progress of -the early Venetian painters by the gradual use of the warm outline. -There are some mosaics in St. Mark's which have the effect of -flesh-colour, but on examination, the only red colour used is found -to be in the outlines and markings. Many of the drawings of the old -masters, heightened with red in the shadows, have the same effect. In -these drawings the artists judiciously avoided colouring the lips and -cheeks much, for this would only have betrayed the want of general -colour, as is observable when statues are so treated.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_9_81" id="Footnote_9_81"></a><a href="#FNanchor_9_81"><span class="label">[9]</span></a> Andrea di Luigi, called L'Ingegno, and Niccolo di Fuligno, -are cited as the most prominent examples. See Rumohr, "Italienische -Forschungen." Perogino himself occasionally adopted a very glowing -colour. -</p> -<p> -The early Italian schools which adhered most to the Byzantine types -appear to have been also the most remarkable for depth, or rather -darkness, of colour. This fidelity to customary representation was -sometimes, as in the schools of Umbria, and to a certain extent in -those of Siena and Bologna, the result of a religious veneration for -the ancient examples; in others, as in Venice, the circumstance of -frequent intercourse with the Levant is also to be taken into the -account. The Greek pictures of the Madonna, not to mention other -representations, were extremely dark, in exaggerated conformity, -it is supposed, with the tradition respecting her real complexion -(see D'Agincourt, vol. iv. p. 1); a belief which obtained so late as -Lomazzo's time, for, speaking of the Madonna, he observes, "Leggesi -però che fu alquanto bruna." Giotto, who with the independence of -genius betrayed a certain contempt for these traditions, failed perhaps -to unite improvement with novelty when he substituted a pale white -flesh-colour for the traditional brown. Some specimens of his works, -still existing at Padua, present a remarkable contrast in this respect -with the earliest productions of the Venetian and Paduan artists. His -works at Florence differ as widely from those of the earlier painters -of Tuscany. This peculiarity was inherited by his imitators, and at -one time almost characterised the Florentine school. Leon Battista -Alberti was not perhaps the first who objected to it ("Vorrei io -che dai pittori fosse comperato il color bianco assai più caro che -le presiosissime gemme."—<i>Della Pittura</i>, I. ii.) The attachment -of Fra Bartolommeo to the grave character of the Christian types is -exemplified in his deep colouring, as well as in other respects.</p></div> -<hr class="r5" /> -<div class="footnote"> - -<p><a name="Footnote_10_82" id="Footnote_10_82"></a><a href="#FNanchor_10_82"><span class="label">[10]</span></a> Holland might be excepted, and in Holland similar causes -may have had a similar influence.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_11_83" id="Footnote_11_83"></a><a href="#FNanchor_11_83"><span class="label">[11]</span></a> Local colour; literally, the <i>blot</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_12_84" id="Footnote_12_84"></a><a href="#FNanchor_12_84"><span class="label">[12]</span></a> Zanetti ventures to single out the picture of Tobit and -the Angel in S. Marziale as the first example of Titian's own manner, -and in which a direct imitation of Giorgione is no longer apparent. In -this picture the lights are cool and the blood-tint very effective.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_13_85" id="Footnote_13_85"></a><a href="#FNanchor_13_85"><span class="label">[13]</span></a> "Meno sfumato, men focoso."—<i>Storia Pittorica</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_14_86" id="Footnote_14_86"></a><a href="#FNanchor_14_86"><span class="label">[14]</span></a> "La prima cosa che de' colori si perde nelle distante è -il lustro, loro minima parte."—<i>Trattato</i>, p. 213; and elsewhere, "I -lumi principali in picciol luogo son quelli che in picciola distanza -sono i primi che si perdono all' occhio."—p. 128.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_15_87" id="Footnote_15_87"></a><a href="#FNanchor_15_87"><span class="label">[15]</span></a> A colossal St. Christopher, the usual subject, is -frequently seen occupying the whole height of the external wall of a -church. We have here an example of the influence of religion, such -as it was, even on the style of colouring and practical methods of -the art. The mere sight of the image of St. Christopher, the type of -strength, was considered sufficient to reinvigorate those who were -exhausted by the labours of husbandry. The following is a specimen of -the inscriptions inculcating this belief:— -</p> -<p style="margin-left: 20%;"> -"Christophori Sancti speciem quicumque tuetur,<br /> -Illo namque die nullo languore tenetur."<br /> -</p> -<p> -Hence the practice of painting the figure on the outside of churches, -hence its colossal size, and hence the powerful qualities in colour -above described. See Maniago, "Storia delle Belle Arti Friulane."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_16_88" id="Footnote_16_88"></a><a href="#FNanchor_16_88"><span class="label">[16]</span></a> The authority of Fuseli sufficiently warrants the -application of the term breadth to colour; he speaks of Titian's -"breadth of local tint."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_17_89" id="Footnote_17_89"></a><a href="#FNanchor_17_89"><span class="label">[17]</span></a> Zanetti quotes an opinion of the painters of his time -to the same effect:—"Teneano essi (alcuni maestri) per cosa certa, -che in molte opere Tiziano volesse fingere il lume—quale si vede -nell' inclinarsi del sole verso la sera. Gli orizzonti assai luminosi -dietro le montagne, le ombre incerte e più le carnagioni brunette e -rosseggianti delle figure, gl'induceano a creder questo."—Lib. ii. -Leonardo da Vinci observes, "Quel corpo che si troverà in mediocre lume -fia in lui poca differenza da' lumi all' ombre. E questo accade sul far -della sera—e queste opere sono dolci ed hacci grazia ogni qualità di -volto," &c.—p. 336. Elsewhere, "Le ombre fatte dal sole od altri lumi -particolari sono senza grazia."—p. 357; see also p. 247.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_18_90" id="Footnote_18_90"></a><a href="#FNanchor_18_90"><span class="label">[18]</span></a> See "Francesco Priscianese De' Primi Principii della -Lingua Latina," Venice, 1550. The letter is at the end of the work. It -is quoted in Ticozzi's "Vite de' Pittori Vecelli," Milan, 1817.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_19_91" id="Footnote_19_91"></a><a href="#FNanchor_19_91"><span class="label">[19]</span></a> The works of Giorgione are extremely rare. The pictures -best calculated to give an idea of the glowing manner for which -he is celebrated, are the somewhat early works and several of the -altar-pieces of Titian, the best specimens of Palma Vecchio, and the -portraits of Sebastian del Piombo.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_20_92" id="Footnote_20_92"></a><a href="#FNanchor_20_92"><span class="label">[20]</span></a> Zanetti and Lodovico Dolce mention Lorenzo Lotto as an -instance of the excess of Giorgione's style. Titian himself sometimes -overstepped the mark, as his biographers confess, and as appears, -among other instances, from the head of St. Peter in the picture (now -in the Vatican) in which the celebrated St. Sebastian is introduced. -Raphael was criticised by some cardinals for a similar defect. See -"Castiglione, Il Cortigiano," 1. ii. -</p> -<p> -In the same paragraph to which the present observations refer, the -authority of Kircher is quoted; his treatise, "Ars magna lucis et -umbrae," was published in Rome in 1646. In a portrait of Nicholas -Poussin, engraved by Clouet, the painter is represented holding a book, -which, from the title and the circumstance of Poussin having lived in -Rome in Kircher's time, Goethe supposes to be the work in question. The -abuse of the principle above alluded to, is perhaps exemplified in the -red half-tints observable in some of Poussin's figures. -</p> -<p> -The augmentation of colour in subdued light was still more directly -taught by Lomazzo. He composes the half-tints of flesh merely by -diminishing the quantity of white, the proportions of the other colours -employed (for he enters into minute details) remaining unaltered. See -his "Trattato della arte della Pittura," Milan, 1584, p. 301.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_21_93" id="Footnote_21_93"></a><a href="#FNanchor_21_93"><span class="label">[21]</span></a> In the Dresden Gallery, a picture attributed to -Titian—at all events a lucid Venetian picture—hangs next the St. -George of Correggio. After looking at the latter, the Venetian work -appears glassy and unsubstantial, but on reversing the order of -comparison, the Correggio may be said to suffer more, and for a moment -its fine transitions of light and shade seem changed to heaviness.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_22_94" id="Footnote_22_94"></a><a href="#FNanchor_22_94"><span class="label">[22]</span></a> The finest works of Tintoret—-the Crucifixion and the -Miracolo del Servo (considered here merely with reference to their -colour,) may be said to combine the excellences of Titian and Giacomo -Bassan, on a grand scale; the sparkling clearness of the latter is -one of the prominent characteristics of these pictures. Tintoret is -reported to have once said that a union of his own knowledge of form -with Bassan's colour would be the perfection of painting. See "Verei -Notizie de' Pittori di Bassano;" Ven. 1775, p. 61.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_23_95" id="Footnote_23_95"></a><a href="#FNanchor_23_95"><span class="label">[23]</span></a> That this last quality, the characteristic of Bassan's -best pictures, was held in high estimation by Paul Veronese, is not -only evident from that painter's own works, but from the circumstance -of his preferring to place his sons with Bassan rather than with any -other painter. (See "Boschini Carta del Navegar," p. 280.) The Baptism -of Sta. Lucilla, in Boschini's time considered the finest of Giacomo's -works, is still in the church of S. Valentino, at Bassano, and may be -considered the type of the lucid and sparkling manner.</p></div> - - - -<p class="para"><a id="NOTE_F"></a>NOTE F.—<a href="#a83">Par. 83.</a></p> - -<p>The author, in these instances, seems to be anticipating his -subsequent explanations on the effect of semi-transparent mediums. -For an explanation of the general view contained in these paragraphs -respecting the gradual increase of colour from high light, see the last -Note.</p> - -<p>The anonymous French work before alluded to, among other interesting -examples, contains a chapter on shadows cast by the upper light of the -sky and coloured by the setting sun. The effect of this remarkable -combination is, that the light on a wall is most coloured immediately -under a projecting roof, and becomes comparatively neutralised in -proportion to its distance from the edge of the darkest shade.</p> - - -<p class="para"><a id="NOTE_G"></a>NOTE G.—<a href="#a98">Par. 98.</a></p> - -<p>"The simplest case of the phenomenon, which Goethe calls a subjective -halo, and one which at once explains its cause, is the following. -Regard a red wafer on a sheet of white paper, keeping the eye -stedfastly fixed on a point at<span class="pagenum"><a name="Page_373" id="Page_373">[Pg 373]</a></span> its center. When the retina is -fatigued, withdraw the head a little from the paper, and a green halo -will appear to surround the wafer. By this slight increase of distance -the image of the wafer itself on the retina becomes smaller, and the -ocular spectrum which before coincided with the direct image, being -now relatively larger, is seen as a surrounding ring."—S. F. Goethe -mentions cases of this kind, but does not class them with subjective -halos. See Par. 30.</p> - - -<p class="para"><a id="NOTE_H"></a>NOTE H.—<a href="#a113">Par. 113.</a></p> - -<p>"Cases of this kind are by no means uncommon. Several interesting -ones are related in Sir John Herschell's article on Light in the -Encyclopædia Metropolitana. Careful investigation has, however, shown -that this defect of vision arises in most, if not in all cases, from -an inability to perceive the red, not the blue rays. The terms are so -confounded by the individuals thus affected, that the comparison of -colours in their presence is the only criterion."—S. F.</p> - - -<p class="para"><a id="NOTE_I"></a>NOTE I.—<a href="#a135">Par. 135.</a></p> - -<p>The author more than once admits that this chapter on "Pathological -Colours" is very incomplete, and expresses a wish (Par. 734) that some -medical physiologists would investigate the subject further. This was -afterwards in a great degree accomplished by Dr. Johannes Müller, in -his memoir "Über die Phantastischen Gesichtserscheinungen." Coblentz, -1826. Similar phenomena have been also investigated with great labour -and success by Purkinje. For a collection of extraordinary facts of the -kind recorded by these writers, the reader may consult Scott's Letters -on Demonology and Witchcraft.<a name="FNanchor_1_96" id="FNanchor_1_96"></a><a href="#Footnote_1_96" class="fnanchor">[1]</a> The instances adduced by Müller and -others are, however, intended to prove the inherent capacity of the -organ of vision to produce light and colours. In some maladies of the -eye, the patient, it seems,<span class="pagenum"><a name="Page_374" id="Page_374">[Pg 374]</a></span> suffers the constant presence of light -without external light. The exciting principle in this case is thus -proved to be within, and the conclusion of the physiologists is that -external light is only one of the causes which produce luminous and -coloured impressions. That this view was anticipated by Newton may be -gathered from the concluding "query" in the third book of his Optics. -</p> -<hr class="r5" /> -<div class="footnote"> - -<p><a name="Footnote_1_96" id="Footnote_1_96"></a><a href="#FNanchor_1_96"><span class="label">[1]</span></a> See also a curious passage on the beatific vision of the -monks of Mount Athos, in Gibbon, chap. 63.</p></div> - - - -<p class="para"><a id="NOTE_K"></a>NOTE K.—<a href="#a140">Par. 140.</a></p> - -<p>"Catoptrical colours. The colours included under this head are -principally those of fibres and grooved surfaces; they can be produced -artificially by cutting parallel grooves on a surface of metal from -2000 to 10,000 in the inch. See 'Brewster's Optics,' p. 120. The -colours called by Goethe <i>paroptical</i>, correspond with those produced -by the diffraction or inflection of light in the received theory.—See -Brewster, p. 95. The phenomena included under the title 'Epoptical -Colours,' are generally known as the colours of thin plates. They vary -with the thickness of the film, and the colour seen by reflection -always differs from that seen by transmission. The laws of these -phenomena have been thoroughly investigated. See Nobili, and Brewster, -p. 100."—S. F.</p> - -<p>The colours produced by the transmission of polarised light through -chrystalised mediums, were described by Goethe, in his mode, -subsequently to the publication of his general theory, under the name -of Entoptic Colours. See note to Par. 485.</p> - - -<p class="para"><a id="NOTE_L"></a>NOTE L.—<a href="#a150">Par. 150.</a></p> - -<p>We have in this and the next paragraph the outline of Goethe's system. -The examples that follow seem to establish the doctrine here laid -down, but there are many cases which it appears cannot be explained on -such principles: hence, philosophers generally prefer the theory of -absorption, according to which it appears that certain mediums "have -the property of absorbing some of the component<span class="pagenum"><a name="Page_375" id="Page_375">[Pg 375]</a></span> rays of white light, -while they allow the passage of others."<a name="FNanchor_1_97" id="FNanchor_1_97"></a><a href="#Footnote_1_97" class="fnanchor">[1]</a></p> - -<p>Whether all the facts adduced by Goethe—for instance, that recorded -in Par. <a href="#a172">172</a>, are to be explained by this doctrine, we leave to the -investigators of nature to determine. Dr. Eckermann, in conversing with -Goethe, thus described the two leading phenomena (156, 158) as seen by -him in the Alps. "At a distance of eighteen or twenty miles at mid-day -in bright sunshine, the snow appeared yellow or even reddish, while the -dark parts of the mountain, free from snow, were of the most decided -blue. The appearances did not surprise me, for I could have predicted -that the mass of the interposed medium would give a deep yellow tone -to the white snow, but I was pleased to witness the effect, since it -so entirely contradicted the erroneous views of some philosophers, -who assert that the air has a blue-tinging quality. The observation, -said Goethe, is of importance, and contradicts the error you allude to -completely."<a name="FNanchor_2_98" id="FNanchor_2_98"></a><a href="#Footnote_2_98" class="fnanchor">[2]</a></p> - -<p>The same writer has some observations to the same effect on the colour -of the Rhone at Geneva. A circumstance of an amusing nature which he -relates in confirmation of Goethe's theory, deserves to be inserted. -"Here (at Strasburg), passing by a shop, I saw a little glass bust -of Napoleon, which, relieved as it was against the dark interior<span class="pagenum"><a name="Page_376" id="Page_376">[Pg 376]</a></span> of -the room, exhibited every gradation of blue, from milky light blue -to deep violet. I foresaw that the bust seen from within the shop -with the light behind it, would present every degree of yellow, and I -could not resist walking in and addressing the owner, though perfectly -unknown to me. My first glance was directed to the bust, in which, to -my great joy, I saw at once the most brilliant colours of the warmer -kind, from the palest yellow to dark ruby red. I eagerly asked if I -might be allowed to purchase the bust; the owner replied that he had -only lately brought it with him from Paris, from a similar attachment -to the emperor to that which I appeared to feel, but, as my ardour -seemed far to surpass his, I deserved to possess it. So invaluable -did this treasure seem in my eyes, that I could not help looking at -the good man with wonder as he put the bust into my hands for a few -franks. I sent it, together with a curious medal which I had bought -in Milan, as a present to Goethe, and when at Frankfort received the -following letter from him." The letter, which Dr. Eckermann gives -entire, thus concludes—"When you return to Weimar you shall see the -bust in bright sunshine, and while the transparent countenance exhibits -a quiet blue,<a name="FNanchor_3_99" id="FNanchor_3_99"></a><a href="#Footnote_3_99" class="fnanchor">[3]</a> the thick mass of the breast and epaulettes glows with -every gradation of warmth, from the most powerful ruby-red downwards; -and as the granite statue of Memnon uttered harmonious sounds, so the -dim glass image displays itself in the pomp of colours. The hero is -victorious still in supporting the Farbenlehre."<a name="FNanchor_4_100" id="FNanchor_4_100"></a><a href="#Footnote_4_100" class="fnanchor">[4]</a></p> - -<p>One effect of Goethe's theory has been to invite the attention of -scientific men to facts and appearances which had before been unnoticed -or unexplained. To the above cases may be added the very common, but -very important, fact in painting, that a light warm colour, passed in -a semi-transparent<span class="pagenum"><a name="Page_377" id="Page_377">[Pg 377]</a></span> state over a dark one, produces a cold, bluish -hue, while the operation reversed, produces extreme warmth. On the -judicious application of both these effects, but especially of the -latter, the richness and brilliancy of the best-coloured pictures -greatly depends. The principle is to be recognised in the productions -of schools apparently opposite in their methods. Thus the practice -of leaving the ground, through which a light colour is apparent, as -a means of ensuring warmth and depth, is very common among the Dutch -and Flemish painters. The Italians, again, who preferred a solid -under-painting, speak of internal light as the most fascinating quality -in colour. When the ground is entirely covered by solid painting, as -in the works of some colourists, the warmest tints in shadows and -reflections have been found necessary to represent it. This was the -practice of Rembrandt frequently, and of Reynolds universally, but the -glow of their general colour is still owing to its being repeatedly -or ultimately enriched on the above principle. Lastly, the works of -those masters who were accustomed to paint on dark grounds are often -heavy and opaque; and even where this influence of the ground was -overcome, the effects of time must be constantly diminishing the warmth -of their colouring as the surface becomes rubbed and the dark ground -more apparent through it. The practice of painting on dark grounds was -intended by the Carracci to compel the students of their school to -aim at the direct imitation of the model, and to acquire the use of -the brush; for the dark ground could only be overcome by very solid -painting. The result answered their expectations as far as dexterity of -pencil was concerned, but the method was fatal to brilliancy of colour. -An intelligent writer of the seventeenth century<a name="FNanchor_5_101" id="FNanchor_5_101"></a><a href="#Footnote_5_101" class="fnanchor">[5]</a> relates that Guido -adopted his extremely light style from seeing the rapid change in some -works of the Carracci soon after they were done. It<span class="pagenum"><a name="Page_378" id="Page_378">[Pg 378]</a></span> is important, -however, to remark, that Guido's remedy was external rather than -internal brilliancy; and it is evident that so powerless a brightness -as white paint can only acquire the splendour of light by great -contrast, and, above all, by being seen through external darkness. The -secret of Van Eyck and his contemporaries is always assumed to consist -in the vehicle (varnish or oils) he employed; but a far more important -condition of the splendour of colour in the works of those masters was -the careful preservation of internal light by painting thinly, but -ultimately with great force, on white grounds. In some of the early -Flemish pictures in the Royal Gallery at Munich, it may be observed, -that wherever an alteration was made by the painter, so that a light -colour is painted over a dark one, the colour is as opaque as in any -of the more modern pictures which are generally contrasted with such -works. No quality in the vehicle could prevent this opacity under such -circumstances; and on the other hand, provided the internal splendour -is by any means preserved, the vehicle is comparatively unimportant.</p> - -<p>It matters not (say the authorities on these points) whether the effect -in question is attained by painting thinly over the ground, in the -manner of the early Flemish painters and sometimes of Rubens, or by -painting a solid light preparation to be afterwards toned to richness -in the manner of the Venetians. Among the mechanical causes of the -clearness of colours superposed on a light preparation may be mentioned -that of careful grinding. All writers on art who have descended to -practical details have insisted on this. From the appearance of some -Venetian pictures it may be conjectured that the colours of the -solid under-painting were sometimes less perfectly ground than the -scumbling colours (the light having to pass through the one and to -be reflected from the other). The Flemish painters appear to have -used carefully-ground pigments universally. This is very evident in -Flemish copies from Raphael, which, though<span class="pagenum"><a name="Page_379" id="Page_379">[Pg 379]</a></span> equally impasted with -the originals, are to be detected, among other indications, by the -finely-ground colours employed.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_97" id="Footnote_1_97"></a><a href="#FNanchor_1_97"><span class="label">[1]</span></a> See "Müller's Elements of Physiology," translated from -the German by William Baly, M.D. "The laws of absorption," it has been -observed, "have not been studied with so much success as those of -other phenomena of physical optics, but some excellent observations -on the subject will be found in Herschell's Treatise on Light in the -Encyclopædia Metropolitana, § III."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_98" id="Footnote_2_98"></a><a href="#FNanchor_2_98"><span class="label">[2]</span></a> "Eckermann's Gespräche mit Goethe," vol. ii. p. 280. -Leonardo da Vinci had made precisely the same observation. "A distant -mountain will appear of a more beautiful blue in proportion as it is -dark in colour. The illumined air, interposed between the eye and the -dark mass, being thinner towards the summit of the mountain, will -exhibit the darkness as a deeper blue and <i>vice versâ</i>."—<i>Trattato -della Pittura</i>, p. 143. Elsewhere—"The air which intervenes between -the eye and dark mountains becomes blue; but it does not become blue in -(before) the light part, and much less in (before) the portion that is -covered with snow."—p. 244.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_99" id="Footnote_3_99"></a><a href="#FNanchor_3_99"><span class="label">[3]</span></a> This supposes either that the mass was considerably -thicker, or that there was a dark ground behind the head, and a light -ground behind the rest of the figure.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_100" id="Footnote_4_100"></a><a href="#FNanchor_4_100"><span class="label">[4]</span></a> "Eckermann's Gespräche mit Goethe," vol. ii. p. 242.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_101" id="Footnote_5_101"></a><a href="#FNanchor_5_101"><span class="label">[5]</span></a> Scanelli, "Microcosmo della Pittura," Cesena, 1657, p. -114.</p></div> - - - -<p class="para"><a id="NOTE_M"></a>NOTE M.—<a href="#a177">Par. 177.</a></p> - -<p>Without entering further into the scientific merits or demerits of -this chapter on the "First Class of Dioptrical Colours," it is to be -observed that several of the examples correspond with the observations -of Leonardo da Vinci, and again with those of a much older authority, -namely, Aristotle. Goethe himself admits, and it has been remarked by -others, that his theory, in many respects, closely resembles that of -Aristotle: indeed he confesses<a name="FNanchor_1_102" id="FNanchor_1_102"></a><a href="#Footnote_1_102" class="fnanchor">[1]</a> that at one time he had an intention -of merely paraphrasing that philosopher's Treatise on Colours.<a name="FNanchor_2_103" id="FNanchor_2_103"></a><a href="#Footnote_2_103" class="fnanchor">[2]</a></p> - -<p>We have already remarked (Note on par. <a href="#a150">150</a>) that Goethe's notion with -regard to the production of warm colours, by the interposition of dark -transparent mediums before a light ground, agrees with the practice of -the best schools in colouring; and it is not impossible that the same -reasons which may make this part of the doctrine generally acceptable -to artists now, may have recommended the very similar theory of -Aristotle to the painters of the fifteenth and sixteenth centuries: -at all events, it appears that the ancient theory was known to those -painters.</p> - -<p>It is unnecessary to dwell on the fact that the doctrines of Aristotle -were enthusiastically embraced and generally inculcated at the period -in question;<a name="FNanchor_3_104" id="FNanchor_3_104"></a><a href="#Footnote_3_104" class="fnanchor">[3]</a> but it has not been<span class="pagenum"><a name="Page_380" id="Page_380">[Pg 380]</a></span> observed that the Italian writers -who translated, paraphrased, and commented on Aristotle's Treatise -on Colours in particular, were in several instances the personal -friends of distinguished painters. Celio Calcagnini<a name="FNanchor_4_105" id="FNanchor_4_105"></a><a href="#Footnote_4_105" class="fnanchor">[4]</a> had the highest -admiration for Raphael; Lodovico Dolce<a name="FNanchor_5_106" id="FNanchor_5_106"></a><a href="#Footnote_5_106" class="fnanchor">[5]</a> was the eulogist of Titian; -Portius,<a name="FNanchor_6_107" id="FNanchor_6_107"></a><a href="#Footnote_6_107" class="fnanchor">[6]</a> whose amicable relations with the Florentine painters may -be inferred from various circumstances, lectured at Florence on the -Aristotelian doctrines early in the sixteenth century. The Italian -translations were later, but still prove that these studies were -undertaken with reference to the arts, for one of them is dedicated to -the painter Cigoli.<a name="FNanchor_7_108" id="FNanchor_7_108"></a><a href="#Footnote_7_108" class="fnanchor">[7]</a></p> - -<p><span class="pagenum"><a name="Page_381" id="Page_381">[Pg 381]</a></span></p> - -<p>The writers on art, from Leon Battista Alberti to Borghini, without -mentioning later authorities, either tacitly coincide with the -Aristotelian doctrine, or openly profess to explain it. It is true this -is not always done in the clearest manner, and some of these writers -might say with Lodovico Dolce, "I speak of colours, not as a painter, -for that would be the province of the divine Titian."</p> - -<p>Leonardo da Vinci in his writings, as in everything else, appears as -an original genius. He now and then alludes generally to opinions -of "philosophers," but he quotes no authority ancient or modern. -Nevertheless, a passage on the nature of colours, particularly where -he speaks of the colours of the elements, appears to be copied from -Leon Battista Alberti,<a name="FNanchor_8_109" id="FNanchor_8_109"></a><a href="#Footnote_8_109" class="fnanchor">[8]</a> and from the mode in which some of Leonardo's -propositions are stated, it has been supposed<a name="FNanchor_9_110" id="FNanchor_9_110"></a><a href="#Footnote_9_110" class="fnanchor">[9]</a> that he had been -accustomed at Florence to the form of the Aristotelian philosophy. At -all events, some of the most important of his observations respecting -light and colours, have a great analogy with those contained in the -treatise in question. The following examples will be sufficient to -prove this coincidence; the corresponding passages in Goethe are -indicated, as usual, by the numbers of the paragraphs; the references -to Leonardo's treatise are given at the bottom of the page.</p> - -<blockquote> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"A vivid and brilliant red appears when the weak rays of the -sun are tempered by subdued and shadowy white,"—154.</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO</p> - -<p>"The air which is between the sun and the earth at sun-rise<span class="pagenum"><a name="Page_382" id="Page_382">[Pg 382]</a></span> -or sun-set, always invests what is beyond it more than any -other (higher) portion of the air: this is because it is -whiter."<a name="FNanchor_10_111" id="FNanchor_10_111"></a><a href="#Footnote_10_111" class="fnanchor">[10]</a></p> - -<p>A bright object loses its whiteness in proportion to its -distance from the eye much more when it is illuminated by -the sun, for it partakes of the colour of the sun mingled -with the colour (tempered by the mass) of the air interposed -between the eye and the brightness.<a name="FNanchor_11_112" id="FNanchor_11_112"></a><a href="#Footnote_11_112" class="fnanchor">[11]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"If light is overspread with much obscurity, a red colour -appears; if the light is brilliant and vivid, this red -changes to a flame-colour."<a name="FNanchor_12_113" id="FNanchor_12_113"></a><a href="#Footnote_12_113" class="fnanchor">[12]</a>—150, 160.</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"This (the effect of transparent colours on various grounds) -is evident in smoke, which is blue when seen against black, -but when it is opposed to the (light) blue sky, it appears -brownish and reddening."<a name="FNanchor_13_114" id="FNanchor_13_114"></a><a href="#Footnote_13_114" class="fnanchor">[13]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"White surfaces as a ground for colours, have the effect of -making the pigments<a name="FNanchor_14_115" id="FNanchor_14_115"></a><a href="#Footnote_14_115" class="fnanchor">[14]</a> appear in greater splendour."—594, -902.</p> - -<p><span class="pagenum"><a name="Page_383" id="Page_383">[Pg 383]</a></span></p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"To exhibit colours in their beauty, the whitest ground -should be prepared. I speak of colours that are (more or -less) transparent."<a name="FNanchor_15_116" id="FNanchor_15_116"></a><a href="#Footnote_15_116" class="fnanchor">[15]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"The air near us appears colourless; but when seen in depth, -owing to its thinness it appears blue;<a name="FNanchor_16_117" id="FNanchor_16_117"></a><a href="#Footnote_16_117" class="fnanchor">[16]</a> for where the -light is deficient (beyond it), the air is affected by the -darkness and appears blue: in a very accumulated state, -however, it appears, as is the case with water, quite -white."—155, 158.</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"The blue of the atmosphere is owing to the mass of -illuminated air interposed between the darkness above and -the earth. The air in itself has no colour, but assumes -qualities according to the nature of the objects which are -beyond it. The blue of the atmosphere will be the more -intense in proportion to the degree of darkness beyond it:" -elsewhere—"if the air had not darkness beyond it, it would -be white."<a name="FNanchor_17_118" id="FNanchor_17_118"></a><a href="#Footnote_17_118" class="fnanchor">[17]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"We see no colour in its pure state, but every hue is -variously intermingled with others: even when it is -uninfluenced by other colours, the effect of light and -shade modifies it in various ways, so that it undergoes -alterations and appears unlike itself. Thus, bodies seen in -shade or in<span class="pagenum"><a name="Page_384" id="Page_384">[Pg 384]</a></span> light, in more pronounced or softer sun-shine, -with their surfaces inclined this way or that, with every -change exhibit a different colour."</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"No substance will ever exhibit its own hue unless the light -which illumines it is entirely similar in colour. It very -rarely happens that the shadows of opaque bodies are really -similar (in colour) to the illumined parts. The surface of -every substance partakes of as many hues as are reflected -from surrounding objects."<a name="FNanchor_18_119" id="FNanchor_18_119"></a><a href="#Footnote_18_119" class="fnanchor">[18]</a></p> - -<p>Aristotle.</p> - -<p>"So, again, with regard to the light of fire, of the moon, -or of lamps, each has a different colour, which is variously -combined with differently coloured objects."</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"We can scarcely ever say that the surface of illumined -bodies exhibits the real colour of those bodies. Take a -white band and place it in the dark, and let it receive -light by means of three apertures from the sun, from fire, -and from the sky: the white band will be tricoloured."<a name="FNanchor_19_120" id="FNanchor_19_120"></a><a href="#Footnote_19_120" class="fnanchor">[19]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"When the light falls on any object and assumes (for -example) a red or green tint, it is again reflected on other -substances, thus undergoing a new change. But this effect, -though it really takes place, is not appreciable by the -eye: though the light thus reflected to the eye is composed -of a variety of colours, the principal of these only are -distinguishable."</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"No colour reflected on the surface of another colour, -tinges that surface with its own colour (merely), but will -be<span class="pagenum"><a name="Page_385" id="Page_385">[Pg 385]</a></span> mixed with various other reflections impinging on the -same surface:" but such effects, he observes elsewhere, "are -scarcely, if at all, distinguishable in a very diffused -light."<a name="FNanchor_20_121" id="FNanchor_20_121"></a><a href="#Footnote_20_121" class="fnanchor">[20]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"Thus, all combinations of colours are owing to three -causes: the light, the medium through which the light -appears, such as water or air, and lastly the local colour -from which the light happens to be reflected."</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"All illumined objects partake of the colour of the light -they receive.</p> - -<p>"Every opaque surface partakes of the colour of the -intervening transparent medium, according to the density of -such medium and the distance between the eye and the object.</p> - -<p>"The medium is of two kinds; either it has a surface, like -water, &c., or it is without a common surface, like the -air."<a name="FNanchor_21_122" id="FNanchor_21_122"></a><a href="#Footnote_21_122" class="fnanchor">[21]</a></p></blockquote> - -<hr class="r5" /> -<p>In the observations on trees and plants more points of resemblance -might be quoted; the passages corresponding with Goethe's views are -much more numerous.</p> - -<p>It is remarkable that Leonardo, in opposition, it seems to some -authorities,<a name="FNanchor_22_123" id="FNanchor_22_123"></a><a href="#Footnote_22_123" class="fnanchor">[22]</a> agrees with Aristotle in reckoning black and white -as colours, placing them at the beginning and end of the scale.<a name="FNanchor_23_124" id="FNanchor_23_124"></a><a href="#Footnote_23_124" class="fnanchor">[23]</a> -Like Aristotle, again, he frequently makes use of the term black, for -obscurity; he even goes further,<span class="pagenum"><a name="Page_386" id="Page_386">[Pg 386]</a></span> for he seems to consider that blue -may be produced by the actual mixture of black and white, provided they -are pure.<a name="FNanchor_24_125" id="FNanchor_24_125"></a><a href="#Footnote_24_125" class="fnanchor">[24]</a> The ancient author, however, explains himself on this -point as follows—"We must not attempt to make our observations on -these effects by mixing colours as painters mix them, but by remarking -the appearances as produced by the rays of light mingling with each -other."<a name="FNanchor_25_126" id="FNanchor_25_126"></a><a href="#Footnote_25_126" class="fnanchor">[25]</a></p> - -<p>When we consider that Leonardo's Treatise professes to embrace the -subject of imitation in painting, and that Aristotle's briefly examines -the physical nature and appearance of colours, it must be admitted -that the latter sustains the above comparison with advantage; and it -is somewhat extraordinary that observations indicating so refined a -knowledge of nature, as regards the picturesque, should not have been -taken into the account, for such appears to be the fact, in the various -opinions and conjectures that have been expressed from time to time on -the painting of the Greeks. The treatise in question must have been -written when Apelles painted, or immediately before; and as a proof<span class="pagenum"><a name="Page_387" id="Page_387">[Pg 387]</a></span> -that Aristotle's remarks on the effect of semi-transparent mediums were -not lost on the artists of his time, the following passage from Pliny -is subjoined, for, though it is well known, it acquires additional -interest from the foregoing extracts.</p> - -<p>"He (Apelles) passed a dark colour over his pictures when finished, so -thin that it increased the splendour of the tints, while it protected -the surface from dust and dirt: it could only be seen on looking into -the picture. The effect of this operation, judiciously managed, was to -prevent the colours from being too glaring, and to give the spectator -the impression of looking through a transparent crystal. At the same -time it seemed almost imperceptibly to add a certain dignity of tone to -colours that were too florid." "This," says Reynolds, "is a true and -artist-like description of glazing or scumbling, such as was practised -by Titian and the rest of the Venetian painters."</p> - -<p>The account of Pliny has, in this instance, internal evidence -of truth, but it is fully confirmed by the following passage in -Aristotle:—"Another mode in which the effect of colours is exhibited -is when they appear through each other, as painters employ them when -they glaze (ἐπαλειφοντες)<a name="FNanchor_26_127" id="FNanchor_26_127"></a><a href="#Footnote_26_127" class="fnanchor">[26]</a> a (dark) colour over a lighter one; just -as the sun, which is in itself white, assumes a red colour when seen -through darkness and smoke. This operation also ensures a variety of -colours, for there will be a certain ratio between those which are on -the surface and those which are in depth."—<i>De Sensu et Sensili</i>.</p> - -<p>Aristotle's notion respecting the derivation of colours from white and -black may perhaps be illustrated by the following opinion on the very -similar theory of Goethe.</p> - -<p>"Goethe and Seebeck regard colour as resulting from the mixture of -white and black, and ascribe to the different<span class="pagenum"><a name="Page_388" id="Page_388">[Pg 388]</a></span> colours a quality -of darkness (σκιερὸν), by the different degrees of which they are -distinguished, passing from white to black through the gradations -of yellow, orange, red, violet, and blue, while green appears to be -intermediate again between yellow and blue. This remark, though it has -no influence in weakening the theory of colours proposed by Newton, -is certainly correct, having been confirmed experimentally by the -researches of Herschell, who ascertained the relative intensity of the -different coloured rays by illuminating objects under the microscope by -their means, &c.</p> - -<p>"Another certain proof of the difference in brightness of the different -coloured rays is afforded by the phenomena of ocular spectra. If, after -gazing at the sun, the eyes are closed so as to exclude the light, the -image of the sun appears at first as a luminous or white spectrum upon -a dark ground, but it gradually passes through the series of colours to -black, that is to say, until it can no longer be distinguished from the -dark field of vision; and the colours which it assumes are successively -those intermediate between white and black in the order of their -illuminating power or brightness, namely, yellow, orange, red, violet, -and blue. If, on the other hand, after looking for some time at the -sun we turn our eyes towards a white surface, the image of the sun is -seen at first as a black spectrum upon the white surface, and gradually -passes through the different colours from the darkest to the lightest, -and at last becomes white, so that it can no longer be distinguished -from the white surface"<a name="FNanchor_27_128" id="FNanchor_27_128"></a><a href="#Footnote_27_128" class="fnanchor">[27]</a>—See par 40, 44.</p> - -<p>It is not impossible that Aristotle's enumeration of the colours may -have been derived from, or confirmed by, this very experiment. Speaking -of the after-image of colours he says, "The impression not only exists -in the sensorium in the act of perceiving, but remains when the organ -is at rest. Thus if we look long and intently on any object,<span class="pagenum"><a name="Page_389" id="Page_389">[Pg 389]</a></span> when -we change the direction of the eyes a responding colour follows. If -we look at the sun, or any other very bright object, and afterwards -shut our eyes, we shall, as if in ordinary vision, first see a colour -of the same kind; this will presently be changed to a red colour, -then to purple, and so on till it ends in black and disappears."—<i>De -Insomniis</i>.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_102" id="Footnote_1_102"></a><a href="#FNanchor_1_102"><span class="label">[1]</span></a> "Geschichte der Farbenlehre," in the "Nachgelassene -Werke." Cotta, 1833.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_103" id="Footnote_2_103"></a><a href="#FNanchor_2_103"><span class="label">[2]</span></a> The treatise in question is ascribed by Goethe to -Theophrastus, but it is included in most editions of Aristotle, and -even attributed to him in those which contain the works of both -philosophers; for instance, in the Aldine Princeps edition, 1496. -Calcagnini says, the treatise is made up of two separate works on the -subject, both by Aristotle.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_104" id="Footnote_3_104"></a><a href="#FNanchor_3_104"><span class="label">[3]</span></a> His authority seems to have been equally great on subjects -connected with the phenomena of vision; the Italian translator of -a Latin treatise, by Portius, on the structure and colours of the -eye, thus opens his dedication to the Cardinal Ercole Gonzaga, of -Mantua:—"Grande anzi quasi infinito è l'obligo che ha il mondo con -quel più divino che umano spirito di Aristotile."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_105" id="Footnote_4_105"></a><a href="#FNanchor_4_105"><span class="label">[4]</span></a> In a letter to Ziegler the mathematician, Calcagnini -speaks of Raphael as "the first of painters in the theory as well as -in the practice of his art." This expression may, however, have had -reference to a remarkable circumstance mentioned in the same letter, -namely, that Raphael entertained the learned Fabius of Ravenna as a -constant guest, and employed him to translate Vitruvius into Italian. -This MS. translation, with marginal notes, written by Raphael, is now -in the library at Munich. "Passavant, Rafael von Urbino."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_106" id="Footnote_5_106"></a><a href="#FNanchor_5_106"><span class="label">[5]</span></a> Lodovico Dolce's Treatise on Colours (1565) is in the form -of a dialogue, like his "Aretino." The abridged theory of Aristotle -is followed by a translation of the Treatise of Antonius Thylesius on -Colours; this is adapted to the same colloquial form, and the author is -not acknowledged: the book ends with an absurd catalogue of emblems. -The "Somma della Filosofia d'Aristotile," published earlier by the same -author, is a very careless performance.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_107" id="Footnote_6_107"></a><a href="#FNanchor_6_107"><span class="label">[6]</span></a> A Latin translation of Aristotle's Treatise on Colours, -with comments by Simon Portius, was first published, according to -Goethe, at Naples in 1537. In a later Florentine edition, 1548, -dedicated to Cosmo I., Portius alludes to his having lectured at an -earlier period in Florence on the doctrines of Aristotle, at which time -he translated the treatise in question. Another Latin translation, with -notes, was published later in the same century at Padua—"Emanuele -Marguino Interprete:" but by far the clearest view of the Aristotelian -theory is to be found in the treatise of Antonio Vidi Scarmiglione -of Fuligno ("De Coloribus," Marpurgi, 1591). It is dedicated to the -Emperor Rudolph II. Of all the paraphrases of the ancient doctrine -this comes nearest to the system of Goethe; but neither this nor any -other of the works alluded to throughout this Note are mentioned by -the author in his History of the Doctrine of Colours, except that of -Portius.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_108" id="Footnote_7_108"></a><a href="#FNanchor_7_108"><span class="label">[7]</span></a> An earlier Italian translation appeared in Rome, 1535. See -"Argelatus Biblioteca degli Volgarizzatori."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_8_109" id="Footnote_8_109"></a><a href="#FNanchor_8_109"><span class="label">[8]</span></a> "Della Pittura e della Statua," Lib. I, p. 16, Milan -edition, 1804. Compare with the "Trattato della Pittura," p. 141. Other -points of resemblance are to be met with. The notion of certain colours -appropriated to the four elements, occurs in Aristotle, and is indeed -attributed to older writers.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_9_110" id="Footnote_9_110"></a><a href="#FNanchor_9_110"><span class="label">[9]</span></a> See the notes to the Roman edition of the "Trattato della -Pittura."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_10_111" id="Footnote_10_111"></a><a href="#FNanchor_10_111"><span class="label">[10]</span></a> Page 237.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_11_112" id="Footnote_11_112"></a><a href="#FNanchor_11_112"><span class="label">[11]</span></a> Page 301.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_12_113" id="Footnote_12_113"></a><a href="#FNanchor_12_113"><span class="label">[12]</span></a> In the Treatise <i>De Igne</i>, by Theophrastus, we find -the same notion thus expressed: "Brightness (<i>τὸ λευκὸν</i>) seen -through a dark coloured medium (<i>διὰ του μέλανος</i>) appears red; as -the sun seen through smoke or soot: hence the coal is redder than -the flame." Scarmiglione, from whom Kircher seems to have copied, -observes:—"Itaque color realis est lux opaca; licet id e plurimis -apparentiis colligere. Luna enim in magnâ solis eclipsi rubra -conspicitur, quia tenebris lux præpeditur ac veluti tegitur."—<i>De -Coloribus</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_13_114" id="Footnote_13_114"></a><a href="#FNanchor_13_114"><span class="label">[13]</span></a> Page 122.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_14_115" id="Footnote_14_115"></a><a href="#FNanchor_14_115"><span class="label">[14]</span></a> <i>Τὰ ἂνθη</i>: translated <i>flores</i> by Calcagnini and the -rest, by Goethe, <i>die Blüthe</i>, the bloom. That the word sometimes -signified pigments is sufficiently apparent from the following -passage of Suidas (quoted by Emeric David, "Discours Historiques -sur la Peinture Moderne") <i>ἂνθεσι κεκοσμημέναι, οἶον ψιμμιωίῳ φύκει -καὶ τοῖς ὸμοίοις</i>. Variis pigmentis ornatæ, ut cerussâ, fuco, et -aliis similibus. (Suid. in voc. <i>Ἐξμηθισμένας</i>.) A panel prepared -for painting, with a white ground consolidated with wax, and perhaps -mastic, was found in Herculaneum.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_15_116" id="Footnote_15_116"></a><a href="#FNanchor_15_116"><span class="label">[15]</span></a> Page 114.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_16_117" id="Footnote_16_117"></a><a href="#FNanchor_16_117"><span class="label">[16]</span></a> <i>Ἐν βάθει δὲ θεωρουμίνου ιγγυτάτω φαίνεται τῶ χρώματι -κυανονοειδὴς διὰ τὴν ὰραιότητα.</i> "But when seen in depth, it appears -(even) in its nearest colour, blue, owing to its thinness." The Latin -interpretations vary very much throughout. The point which is chiefly -important is however plain enough, viz. that darkness seen through a -light medium is blue.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_17_118" id="Footnote_17_118"></a><a href="#FNanchor_17_118"><span class="label">[17]</span></a> Page 136-430.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_18_119" id="Footnote_18_119"></a><a href="#FNanchor_18_119"><span class="label">[18]</span></a> Page 121, 306, 326, 387.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_19_120" id="Footnote_19_120"></a><a href="#FNanchor_19_120"><span class="label">[19]</span></a> Page 306.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_20_121" id="Footnote_20_121"></a><a href="#FNanchor_20_121"><span class="label">[20]</span></a> Page 104, 369.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_21_122" id="Footnote_21_122"></a><a href="#FNanchor_21_122"><span class="label">[21]</span></a> Page 236, 260, 328.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_22_123" id="Footnote_22_123"></a><a href="#FNanchor_22_123"><span class="label">[22]</span></a> "De' semplici colori il primo è il bianco: beuchè -i filosofi non accettano nè il bianco nè il nero nel numero de' -colori."—p. 125, 141. Elsewhere, however, he sometimes adopts the -received opinion.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_23_124" id="Footnote_23_124"></a><a href="#FNanchor_23_124"><span class="label">[23]</span></a> Leon Battista Alberti, in like manner -observes:—"Affermano (i filosofi) che le spezie de' colori sono sette, -cioè, che il bianco ed il nero sono i duoi estremi, infra i quali ve -n'è uno nel mezzo (rosso) e che infra ciascuno di questi duoi estremi -e quel del mezzo, da ogni parte ve ne sono due altri." An absurd -statement of Lomazzo, p. 190, is copied verbatim from Lodovico Dolce -(Somma della Filos. d'Arist.); but elsewhere, p. 306, Lomazzo agrees -with Alberti. Aristotle seems to have misled the two first, for after -saying there are seven colours, he appears only to mention six: he -says—"There are seven colours, if brown is to be considered equivalent -to black, which seems reasonable. Yellow, again, may be said to be a -modification of white. Between these we find red, purple, green, and -blue."—<i>De Sensu et Sensili</i>. Perhaps it is in accordance with this -passage that Leonardo da Vinci reckons eight colours.—<i>Trattato</i>, p. -126.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_24_125" id="Footnote_24_125"></a><a href="#FNanchor_24_125"><span class="label">[24]</span></a> Page 122, 142, 237.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_25_126" id="Footnote_25_126"></a><a href="#FNanchor_25_126"><span class="label">[25]</span></a> On the authority of this explanation the word μιλάν -has sometimes been translated in the foregoing extracts <i>obscurity, -darkness</i>. -</p> -<p> -Raffaello Borghini, in his attempt to describe the doctrine of -Aristotle with a view to painting, observes—"There are two -principles which concur in the production of colour, namely, light -and transparence." But he soon loses this clue to the best part of -the ancient theory, and when he has to speak of the derivation of -colours from white and black, he evidently understands it in a mere -atomic sense, and adds—"I shall not at present pursue the opinion -of Aristotle, who assumes black and white as principal colours, and -considers all the rest as intermediate between them."—<i>Il Riposo</i>, 1. -ii. Accordingly, like Lodovico Dolce, he proceeds to a subject where he -was more at home, namely, the symbolical meaning of colours.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_26_127" id="Footnote_26_127"></a><a href="#FNanchor_26_127"><span class="label">[26]</span></a> This word is only strictly applied to unctuous -substances, and may confirm the views of those writers who have -conjectured that asphaltum was a chief ingredient in the <i>atramentum</i> -of the ancients.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_27_128" id="Footnote_27_128"></a><a href="#FNanchor_27_128"><span class="label">[27]</span></a> "Elements of Physiology," by J. Müller, M.D., translated -from the German by William Baly, M.D. London, 1839.</p></div> - - - -<p class="para"><a id="NOTE_N"></a>NOTE N.—Par. 246.</p> - -<p>"The appearance of white in the centre, according to the Newtonian -theory, arises from each line of rays forming its own spectrum. -These spectra, superposing each other on all the middle part, leave -uncorrected (unneutralised) colours only at the two edges."—S.F.<a name="FNanchor_1_129" id="FNanchor_1_129"></a><a href="#Footnote_1_129" class="fnanchor">[1]</a></p> - - -<div class="footnote"> - -<p><a name="Footnote_1_129" id="Footnote_1_129"></a><a href="#FNanchor_1_129"><span class="label">[1]</span></a> This was objected to Goethe when his "Beyträge sur Optik" -first appeared; he answered the objection by a coloured diagram in -the plates to the "Farbenlehre:" in this he undertakes to show that -the assumed gradual "correction" of the colours would produce results -different from the actual appearance in nature.</p></div> - - - -<p class="para"><a id="NOTE_O"></a>NOTE O.—<a href="#a252">Par. 252.</a></p> - -<p>These experiments with grey objects, which exhibit different colours -as they are on dark or light grounds, were suggested, Goethe tells -us, by an observation of Antonius Lucas, of Lüttich, one of Newton's -opponents, and, in the opinion of the author, one of the few who made -any well-founded objections. Lucas remarks, that the sun acts merely -as a circumscribed image in the prismatic experiments, and that if the -same sun had a lighter background than itself, the colours of the prism -would be reversed. Thus in Goethe's experiments, when the grey disk is -on a dark ground, it is edged with blue on being magnified; when on a -light ground it is edged with yellow. Goethe acknowledges that Lucas -had in some measure anticipated his own theory.—Vol. ii. p. 440.</p> - - - -<p class="para"><a id="NOTE_P"></a>NOTE P.—<a href="#a284">Par. 284.</a></p> - -<p>The earnestness and pertinacity with which Goethe insisted<span class="pagenum"><a name="Page_390" id="Page_390">[Pg 390]</a></span> that -the different colours are not subject to different degrees of -refrangibility are at least calculated to prove that he was himself -convinced on the subject, and, however extraordinary it may seem, his -conviction appears to have been the result of infinite experiments -and the fullest ocular evidence. He returns to the question in the -controversial division of his work, in the historical part, and again -in the description of the plates. In the first he endeavours to show -that Newton's experiment with the blue and red paper depends entirely -on the colours being so contrived as to appear elongated or curtailed -by the prismatic borders. "If," he says, "we take a light-blue instead -of a dark one, the illusion (in the latter case) is at once evident. -According to the Newtonian theory the yellow-red (red) is the least -refrangible colour, the violet the most refrangible. Why, then, does -Newton place a blue paper instead of a violet next the red? If the -fact were as he states it, the difference in the refrangibility of -the yellow-red and violet would be greater than in the case of the -yellow-red and blue. But here comes in the circumstance that a violet -paper conceals the prismatic borders less than a dark-blue paper, as -every observer may now easily convince himself," &c.—Polemischer -Theil, par. 45. Desaguliers, in repeating the experiment, confessed -that if the ground of the colours was not black, the effect did -not take place so well. Goethe adds, "not only not so well, but -not at all."—Historischer Theil, p. 459. Lucas of Lüttich, one of -Newton's first opponents, denied that two differently-coloured silks -are different in distinctness when seen in the microscope. Another -experiment proposed by him, to show the unsoundness of the doctrine of -various refrangibility, was the following:—Let a tin plate painted -with the prismatic colours in stripes be placed in an empty cubical -vessel, so that from the spectator's point of view the colours may be -just hidden by the rim. On pouring water into this vessel, all the -colours become visible in the same degree; whereas, it was contended, -if the Newtonian doctrine were true, some<span class="pagenum"><a name="Page_391" id="Page_391">[Pg 391]</a></span> colours would be apparent -before others.—Historischer Theil, p. 434.</p> - -<p>Such are the arguments and experiments adduced by Goethe on this -subject; they have all probably been answered. In his analysis of -Newton's celebrated <i>Experimentum Crucis</i>, he shows again that by -reversing the prismatic colours (refracting a dark instead of a -light object), the colours that are the most refrangible in Newton's -experiment become the least so, and <i>vice versâ</i>.</p> - -<p>Without reference to this objection, it is now admitted that "the -difference of colour is not a test of difference of refrangibility, and -the conclusion deduced by Newton is no longer admissible as a general -truth, that to the same degree of refrangibility ever belongs the -same colour, and to the same colour ever belongs the same degree of -refrangibility."—Brewster's Optics, p. 72.</p> - - - -<p class="para"><a id="NOTE_Q"></a>NOTE Q—<a href="#a387">Par. 387.</a></p> - -<p>With the exception of two very inconclusive letters to Sulpice -Boisserée, and some incidental observations in the conclusion of the -historical portion under the head of entoptic colours, Goethe never -returned to the rainbow. Among the plates he gave the diagram of -Antonius de Dominis. An interesting chapter on halos, parhelia, and -paraselenæ, will be found in Brewster's Optics, p. 270.</p> - - -<p class="para"><a id="NOTE_R"></a>NOTE R.—<a href="#a478">Par. 478.</a></p> - -<p>The most complete exhibition of the colouring or mantling of metals -was attained by the late Cav. Nobili, professor of physical science in -Florence. The general mode in which these colours are produced is thus -explained by him:<a name="FNanchor_1_130" id="FNanchor_1_130"></a><a href="#Footnote_1_130" class="fnanchor">[1]</a>—</p> - -<p>"A point of platinum is placed vertically at the distance of about -half a line above a lamina of the same metal laid<span class="pagenum"><a name="Page_392" id="Page_392">[Pg 392]</a></span> horizontally at the -bottom of a vessel of glass or porcelain. Into this vessel a solution -of acetate of lead is poured so as to cover not only the lamina of -platinum, but two or three lines of the point as well. Lastly, the -point is put in communication with the negative pole of a battery, and -the lamina with the positive pole. At the moment in which the circuit -is completed a series of coloured rings is produced on the lamina -under the point similar to those observed by Newton in lenses pressed -together."</p> - -<p>The scale of colours thus produced corresponds very nearly with that -observed by Newton and others in thin plates and films, but it is -fuller, for it extends to forty-four tints. The following list, as -given by Nobili, is divided by him into four series to agree with -those of Newton: the numbers in brackets are those of Newton's scale. -The Italian terms are untranslated, because the colours in some cases -present very delicate transitions.<a name="FNanchor_2_131" id="FNanchor_2_131"></a><a href="#Footnote_2_131" class="fnanchor">[2]</a></p> - - -<div class="p2"> -<table border="0" cellpadding="2" cellspacing="0" summary=""> -<tr><th colspan="4">First Series.</th></tr> -<tr><td align="left">1.</td><td align="left">Biondo argentino (4)<a name="FNanchor_3_132" id="FNanchor_3_132"></a><a href="#Footnote_3_132" class="fnanchor">[3]</a> -.</td><td align="left">6.</td><td align="left">Fulvo acceso.</td></tr> -<tr><td align="left">2.</td><td align="left">Biondo.</td><td align="left">7.</td><td align="left">Rosso di rame (6).</td></tr> -<tr><td align="left">3.</td><td align="left">Biondo d'oro.</td><td align="left">8.</td><td align="left">Ocria.</td></tr> -<tr><td align="left">4.</td><td align="left">Biondo acceso (5).</td><td align="left">9.</td><td align="left">Ocria violacea.</td></tr> -<tr><td align="left">5.</td><td align="left">Fulvo.</td><td align="left">10.</td><td align="left">Rosso violaceo (7).</td></tr> -<tr><th colspan="4">Second Series.</th></tr> -<tr><td align="left">11.</td><td align="left">Violetto (8).</td><td align="left">20.</td><td align="left">Giallo acceso.</td></tr> -<tr><td align="left">12.</td><td align="left">Indaco (10).</td><td align="left">21.</td><td align="left">Giallo-rancio.</td></tr> -<tr><td align="left">13.</td><td align="left">Blu carico.</td><td align="left">22.</td><td align="left">Rancio (13).</td></tr> -<tr><td align="left">14.</td><td align="left">Blu.</td><td align="left">23.</td><td align="left">Rancio-rossiccio.</td></tr> -<tr><td align="left">15.</td><td align="left">Blu chiaro (11)</td><td align="left">24.</td><td align="left">Rancio-rosso.</td></tr> -<tr><td align="left">16.</td><td align="left">Celeste.</td><td align="left">25.</td><td align="left">Rosso-rancio.</td></tr> -<tr><td align="left">17.</td><td align="left">Celeste giallognolo.</td><td align="left">26.</td><td align="left">Lacca-rancia (14).</td></tr> -<tr><td align="left">18.</td><td align="left">Giallo chiarissimo (12).</td><td align="left">27.</td><td align="left">Lacca.</td></tr> -<tr><td align="left">19.</td><td align="left">Giallo.</td><td align="left">28.</td><td align="left">Lacca accesa (15).</td></tr> -<tr><th colspan="4">Third Series.<span class="pagenum"><a name="Page_393" id="Page_393">[Pg 393]</a></span></th></tr> -<tr><td align="left">29.</td><td align="left">Lacca-purpurea (16).</td><td align="left">34.</td> <td align="left">Verde-giallo (20).</td></tr> -<tr><td align="left">30.</td><td align="left">Lacca-turchiniccia (17).</td><td align="left">35.</td> <td align="left">Verde-rancio.</td></tr> -<tr><td align="left">31.</td><td align="left">Porpora-verdognola (18).</td><td align="left">36.</td> <td align="left">Rancio-verde (21).</td></tr> -<tr><td align="left">32.</td><td align="left">Verde (19).</td><td align="left">37.</td> <td align="left">Rancio-roseo.</td></tr> -<tr><td align="left">33.</td><td align="left">Verde giallognolo.</td><td align="left">38.</td><td align="left">Lacca-rosea (22).</td></tr> -<tr><th colspan="4">Fourth Series.</th></tr> -<tr><td align="left">39.</td><td align="left">Lacca-violacea (24).</td><td align="left">43.</td><td align="left">Verde-giallo rossiccio (28).</td></tr> -<tr><td align="left">40.</td><td align="left">Violaceo-verdognolo (25). </td><td align="left">44.</td><td align="left">Lacca-rosea (30).</td></tr> -<tr><td align="left">41.</td><td align="left">Verde (26).</td></tr> -<tr><td align="left">42.</td><td align="left">Verde-giallo (27).</td></tr> -</table></div> - -<p class="p2">"These tints," Professor Nobili observes, "are disposed according to -the order of the thin mantlings which occasion them; the colour of -the thinnest film is numbered 1; then follow in order those produced -by a gradual thickening of the medium. I cannot deceive myself in -this arrangement, for the thin films which produce the colours are -all applied with the same electro-chemical process. The battery, the -solution, the distances, &c., are always the same; the only difference -is the time the effect is suffered to last. This is a mere instant for -the colour of No. 1, a little longer for No. 2, and so on, increasing -for the succeeding numbers. Other criterions, however, are not wanting -to ascertain the place to which each tint belongs."</p> - -<p>The scale differs from that of Newton, inasmuch as there is no blue in -Nobili's first series and no green in the second: green only appears in -the third and fourth series. "The first series," says the Professor, -"is remarkable for the fire and metallic appearance of its tints, the -second for clearness and brilliancy, the third and fourth for force and -richness." The fourth, he observes, has the qualities of the third in a -somewhat lesser degree, but the two greens are very nearly alike.</p> - -<p>It is to be observed, that red and green are the principal<span class="pagenum"><a name="Page_394" id="Page_394">[Pg 394]</a></span> ingredients -in the third and fourth series, blue and yellow in the second and first.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_130" id="Footnote_1_130"></a><a href="#FNanchor_1_130"><span class="label">[1]</span></a> See "Memorie ed Osservazioni, edite et inedite del Cav. -Professor Nobili," Firenze, 1834.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_131" id="Footnote_2_131"></a><a href="#FNanchor_2_131"><span class="label">[2]</span></a> The colours in some of the compound terms are in a manner -mutually neutralising; such terms might, no doubt, be amended.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_132" id="Footnote_3_132"></a><a href="#FNanchor_3_132"><span class="label">[3]</span></a> The three first numbers in Newton's scale are black, blue, -and white.</p></div> - - - -<p class="para"><a id="NOTE_S"></a>NOTE S.—<a href="#a485">Par. 485.</a></p> - -<p>A chapter on entoptic colours, contained in the supplement to Goethe's -works, was translated with the intention of inserting it among the -notes, but on the whole it was thought most advisable to omit it. Like -many other parts of the "Doctrine of Colours" it might have served as -a specimen of what may be achieved by accurate observation unassisted -by a mathematical foundation. The whole theory of the polarization of -light has, however, been so fully investigated since Goethe's time, -that the chapter in question would probably have been found to contain -very little to interest scientific readers, for whom it seems chiefly -to have been intended. One observation occurs in it which indeed has -more reference to the arts; in order to make this intelligible, the -leading experiment must be first described, and for this purpose the -following extracts may serve.</p> - -<p>3.<a name="FNanchor_1_133" id="FNanchor_1_133"></a><a href="#Footnote_1_133" class="fnanchor">[1]</a></p> - -<p>"The experiment, in its simplest form, is to be made as follows:—let -a tolerably thick piece of plate-glass be cut into several squares of -an inch and a half; let these be heated to a red heat and then suddenly -cooled. The squares of glass which do not split in this operation are -now fit to produce the entoptic colours.</p> - -<p>4.</p> - -<p>"In our mode of exhibiting the phenomenon, the observer is, above all, -to betake himself, with his apparatus to the open air. All dark rooms, -all small apertures<span class="pagenum"><a name="Page_395" id="Page_395">[Pg 395]</a></span> (foramina exigua),<a name="FNanchor_2_134" id="FNanchor_2_134"></a><a href="#Footnote_2_134" class="fnanchor">[2]</a> are again to be given up. A -pure, cloudless sky is the source whence we are derive a satisfactory -insight into the appearances.</p> - -<p>5.</p> - -<p>"The atmosphere being clear, let the observer lay the squares above -described on a black surface, so placing them that two sides may -be parallel with the plane of vision. When the sun is low, let him -hold the squares so as to reflect to the eye that portion of the sky -opposite to the sun, and he will then perceive four dark points in -the four corners of a light space. If, after this, he turn towards -the quarters of the sky at right angles with that where his first -observation was made, he will see four bright points on a dark ground: -between the two regions the figures appear to fluctuate.</p> - -<p>6.</p> - -<p>"From this simple reflection we now proceed to another, which, but -little more complicated, exhibits the appearance much more distinctly. -A solid cube of glass, or in its stead a cube composed of several -plates, is placed on a black mirror, or held a little inclined -above it, at sun-rise or sun-set. The reflection of the sky being -now suffered to fall through the cube on the mirror, the appearance -above described will appear more distinctly. The reflection of the -sky opposite to the sun presents four dark points on a light ground; -the two lateral portions of the sky present the contrary appearance, -namely, four light points on a dark ground. The space not occupied by -the corner points appears in the first case as a white cross, in the -other as a black cross, expressions hereafter employed in describing -the phenomena. Before sun-rise or after sun-set, in a very<span class="pagenum"><a name="Page_396" id="Page_396">[Pg 396]</a></span> subdued -light, the white cross appears on the side of the sun also.<a name="FNanchor_3_135" id="FNanchor_3_135"></a><a href="#Footnote_3_135" class="fnanchor">[3]</a></p> - -<p>"We thus conclude that the direct reflection of the sun produces a -light figure, which we call a white cross; the oblique reflection gives -a dark figure, which we call a black cross. If we make the experiment -all round the sky, we shall find that a fluctuation takes place in the -intermediate regions."</p> - -<p>We pass over a variety of observations on the modes of exhibiting this -phenomenon, the natural transparent substances which exhibit it best, -and the detail of the colours seen within<a name="FNanchor_4_136" id="FNanchor_4_136"></a><a href="#Footnote_4_136" class="fnanchor">[4]</a> them, and proceed to an -instance where the author was enabled to distinguish the "direct" from -the "oblique" reflection by means of the entoptic apparatus, in a -painter's study.</p> - -<p>40.</p> - -<p>"An excellent artist, unfortunately too soon taken from us, Ferdinand -Jagemann, who, with other qualifications, had a fine eye for light and -shade, colour and keeping, had built himself a painting-room for large -as well as small works. The single high window was to the north, facing -the most open sky, and it was thought that all necessary requisites had -been sufficiently attended to.</p> - -<p>"But after our friend had worked for some time, it appeared to him, -in painting portraits, that the faces he copied were not equally well -lighted at all hours of the day, and yet his sitters always occupied -the same place, and the serenity of the atmosphere was unaltered.</p> - -<p>"The variations of the favourable and unfavourable light had their -periods during the day. Early in the morning the light appeared most -unpleasantly grey and unsatisfactory;<span class="pagenum"><a name="Page_397" id="Page_397">[Pg 397]</a></span> it became better, till at last, -about an hour before noon, the objects had acquired a totally different -appearance. Everything presented itself to the eye of the artist in its -greatest perfection, as he would most wish to transfer it to canvas. -In the afternoon this beautiful appearance vanished—the light became -worse, even in the brightest day, without any change having taken place -in the atmosphere.</p> - -<p>"As soon as I heard of this circumstance, I at once connected it in -my own mind with the phenomena which I had been so long observing, -and hastened to prove, by a physical experiment, what a clear-sighted -artist had discovered entirely of himself, to his own surprise and -astonishment.</p> - -<p>"I had the second<a name="FNanchor_5_137" id="FNanchor_5_137"></a><a href="#Footnote_5_137" class="fnanchor">[5]</a> entoptic apparatus brought to the spot, and the -effect on this was what might be conjectured from the above statement. -At mid-day, when the artist saw his model best lighted, the north, -direct reflection gave the white cross; in the morning and evening, on -the other hand, when the unfavourable oblique light was so unpleasant -to him, the cube showed the black cross; in the intermediate hours the -state of transition was apparent."</p> - -<p>The author proceeds to recall to his memory instances where works of -art had struck him by the beauty of their appearance owing to the light -coming from the quarter opposite the sun, in "direct reflection," and -adds, "Since these decided effects are thus traceable to their cause, -the friends of art, in looking at and exhibiting pictures, may enhance -the enjoyment to themselves and others by attending to a fortunate -reflection."</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_133" id="Footnote_1_133"></a><a href="#FNanchor_1_133"><span class="label">[1]</span></a> The numbers, as usual, indicate the corresponding -paragraphs in the original.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_134" id="Footnote_2_134"></a><a href="#FNanchor_2_134"><span class="label">[2]</span></a> In the historical part, Goethe has to speak of so many -followers of Newton who begin their statements with "Si per foramen -exiguum," that the term is a sort of by-word with him.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_135" id="Footnote_3_135"></a><a href="#FNanchor_3_135"><span class="label">[3]</span></a> At mid-day on the 24th of June the author observed the -white cross reflected from every part of the horizon. At a certain -distance from the sun, corresponding, he supposes, with the extent of -halos, the black cross appeared.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_136" id="Footnote_4_136"></a><a href="#FNanchor_4_136"><span class="label">[4]</span></a> Whence the term <i>entoptic</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_137" id="Footnote_5_137"></a><a href="#FNanchor_5_137"><span class="label">[5]</span></a> Before described: the author describes several others more -or less complicated, and suggests a portable one. "Such plates, which -need only be an inch and a quarter square, placed on each other to form -a cube, might be set in a brass case, open above and below. At one end -of this case a black mirror with a hinge, acting like a cover, might be -fastened. We recommend this simple apparatus, with which the principal -and original experiment may be readily made. With this we could, in the -longest days, better define the circle round the sun where the black -cross appears," &c.</p> - -<p><span class="pagenum"><a name="Page_398" id="Page_398">[Pg 398]</a></span></p></div> - - -<p class="para"><a id="NOTE_T"></a>NOTE T.—<a href="#a496">Par. 496.</a></p> - -<p>"Since Goethe wrote, all the earths have been decomposed, and have -been shown to be metallic bases united with oxygen; but this does not -invalidate his statement."—S. F.</p> - - -<p class="para"><a id="NOTE_U"></a>NOTE U.—<a href="#a502">Par. 502.</a></p> - -<p>The cold nature of black and its affinity to blue are assumed by the -author throughout; if the quality is opaque, and consequently greyish, -such an affinity is obvious, but in many fine pictures, intense black -seems to be considered as the last effect of heat, and in accompanying -crimson and orange may be said rather to present a difference of -degree than a difference of kind. In looking at the great picture -of the globe, we find this last result produced in climates where -the sun has greatest power, as we find it the immediate effect of -fire. The light parts of black animals are often of a mellow colour; -the spots and stripes on skins and shells are generally surrounded -by a warm hue, and are brown before they are absolutely black. In -combustion, the blackness which announces the complete ignition, is -preceded always by the same mellow, orange colour. The representation -of this process was probably intended by the Greeks in the black and -subdued orange of their vases: indeed, the very colours may have been -first produced in the kiln. But without supposing that they were -retained merely from this accident, the fact that the combination -itself is extremely harmonious, would be sufficient to account for -its adoption. Many of the remarks of Aristotle<a name="FNanchor_1_138" id="FNanchor_1_138"></a><a href="#Footnote_1_138" class="fnanchor">[1]</a> and Theophrastus<a name="FNanchor_2_139" id="FNanchor_2_139"></a><a href="#Footnote_2_139" class="fnanchor">[2]</a> -on the production of black, are derived from the observation of the -action of fire, and on one occasion, the former distinctly alludes to -the terracotta kiln. That the above opinion as to the nature of black -was prevalent in the sixteenth century, may be inferred<span class="pagenum"><a name="Page_399" id="Page_399">[Pg 399]</a></span> from Lomazzo, -who observes,—"Quanto all' origine e generazione de' colori, la -frigidità è la madre della bianchezza: il calore è padre del nero."<a name="FNanchor_3_140" id="FNanchor_3_140"></a><a href="#Footnote_3_140" class="fnanchor">[3]</a> -The positive coldness of black may be said to begin when it approaches -grey. When Leonardo da Vinci says that black is most beautiful in -shade, he probably means to define its most intense and transparent -state, when it is furthest removed from grey.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_138" id="Footnote_1_138"></a><a href="#FNanchor_1_138"><span class="label">[1]</span></a> "De Coloribus."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_139" id="Footnote_2_139"></a><a href="#FNanchor_2_139"><span class="label">[2]</span></a> "De Igne."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_140" id="Footnote_3_140"></a><a href="#FNanchor_3_140"><span class="label">[3]</span></a> "Trattato," &c. p. 191, the rest of the passage, it must -be admitted, abounds with absurdities.</p></div> - - - -<p class="para"><a id="NOTE_V"></a>NOTE V.—<a href="#a555">Par. 555.</a></p> - -<p>The nature of vehicles or liquid mediums to combine with the substance -of colours, has been frequently discussed by modern writers on art, -and may perhaps be said to have received as much attention as it -deserves. Reynolds smiles at the notion of our not having materials -equal to those of former times, and indeed, although the methods of -individuals will always differ, there seems no reason to suppose that -any great technical secret has been lost. In these inquiries, however, -which relate merely to the mechanical causes of bright and durable -colouring, the skill of the painter in the adequate employment of the -higher resources of his art is, as if by common consent, left out of -the account, and without departing from this mode of considering the -question, we would merely repeat a conviction before expressed, viz. -that the preservation of internal brightness, a quality compatible with -various methods, has had more to do with the splendour and durability -of finely coloured pictures than any vehicle. The observations that -follow are therefore merely intended to show how far the older -written authorities on this subject agree with the results of modern -investigation, without at all assuming that the old methods, if known, -need be implicitly followed.</p> - -<p>On a careful examination of the earlier pictures, it is said<span class="pagenum"><a name="Page_400" id="Page_400">[Pg 400]</a></span> that -a resinous substance appears to have been mingled with the colours -together with the oil; that the fracture of the indurated pigment is -shining, and that the surface resists the ordinary solvents.<a name="FNanchor_1_141" id="FNanchor_1_141"></a><a href="#Footnote_1_141" class="fnanchor">[1]</a> This -admixture of resinous solutions or varnishes with the solid is not -alluded to, as far as we have seen, by any of the writers on Italian -practice, but as the method corresponds with that now prevalent in -England, the above hypothesis is not likely to be objected to for the -present.</p> - -<p>Various local circumstances and relations might seem to warrant the -supposition that the Venetian painters used resinous substances. An -important branch of commerce between the mountains of Friuli and Venice -still consists in the turpentine or fir-resin.<a name="FNanchor_2_142" id="FNanchor_2_142"></a><a href="#Footnote_2_142" class="fnanchor">[2]</a> Similar substances -produced from various trees, and known under the common name of -balsams,<a name="FNanchor_3_143" id="FNanchor_3_143"></a><a href="#Footnote_3_143" class="fnanchor">[3]</a> were imported from the East through Venice, for general -use, before the American balsams<a name="FNanchor_4_144" id="FNanchor_4_144"></a><a href="#Footnote_4_144" class="fnanchor">[4]</a> in some degree superseded them; -and a Venetian painter, Marco Boschini, in his description of the -Archipelago, does not omit to speak of the abundance of mastic produced -in the island of Scio.<a name="FNanchor_5_145" id="FNanchor_5_145"></a><a href="#Footnote_5_145" class="fnanchor">[5]</a></p> - -<p>The testimonies, direct or indirect, against the employment<span class="pagenum"><a name="Page_401" id="Page_401">[Pg 401]</a></span> of any -such substances by the Venetian painters, in the solid part of their -work, seem, notwithstanding, very conclusive; we begin with the writer -just named. In his principal composition, a poem<a name="FNanchor_6_146" id="FNanchor_6_146"></a><a href="#Footnote_6_146" class="fnanchor">[6]</a> describing the -practice and the productions of the Venetian painters, Boschini speaks -of certain colours which they shunned, and adds:—"In like manner -(they avoided) shining liquids and varnishes, which I should rather -call lackers;<a name="FNanchor_7_147" id="FNanchor_7_147"></a><a href="#Footnote_7_147" class="fnanchor">[7]</a> for the surface of flesh, if natural and unadorned, -assuredly does not shine, nature speaks as to this plainly." After -alluding to the possible alteration of this natural appearance by -means of cosmetics, he continues: "Foreign artists set such great -store by these varnishes, that a shining surface seems to them the -only desirable quality in art. What trash it is they prize! fir-resin, -mastic, and sandarach, and larch-resin (not to say treacle), stuff fit -to polish boots.<a name="FNanchor_8_148" id="FNanchor_8_148"></a><a href="#Footnote_8_148" class="fnanchor">[8]</a> If those great painters of ours had to represent -armour, a gold vase, a mirror, or anything of the kind, they made it -shine with (simple) colours."<a name="FNanchor_9_149" id="FNanchor_9_149"></a><a href="#Footnote_9_149" class="fnanchor">[9]</a></p> - -<p>This writer so frequently alludes to the Flemish painters, of whose -great reputation he sometimes seems jealous, that the above strong -expression of opinion may have been pointed at them. On the other hand -it is to be observed that the term <i>forestieri</i>, strangers, does not -necessarily mean transalpine foreigners, but includes those Italians -who were<span class="pagenum"><a name="Page_402" id="Page_402">[Pg 402]</a></span> not of the Venetian state.<a name="FNanchor_10_150" id="FNanchor_10_150"></a><a href="#Footnote_10_150" class="fnanchor">[10]</a> The directions given by -Raphael Borghini,<a name="FNanchor_11_151" id="FNanchor_11_151"></a><a href="#Footnote_11_151" class="fnanchor">[11]</a> and after him by Armenini,<a name="FNanchor_12_152" id="FNanchor_12_152"></a><a href="#Footnote_12_152" class="fnanchor">[12]</a> respecting the use -and preparation of varnishes made from the very materials in question, -may thus have been comprehended in the censure, especially as some of -these recipes were copied and republished in Venice by Bisagno,<a name="FNanchor_13_153" id="FNanchor_13_153"></a><a href="#Footnote_13_153" class="fnanchor">[13]</a> in -1642—that is, only six years before Boschini's poem appeared.</p> - -<p>Ridolfi's Lives of the Venetian Painters<a name="FNanchor_14_154" id="FNanchor_14_154"></a><a href="#Footnote_14_154" class="fnanchor">[14]</a> (1648) may be mentioned -with the two last. His only observation respecting the vehicle is, that -Giovanni Bellini, after introducing himself by an artifice into the -painting-room of Antonello da Messina, saw that painter dip his brush -from time to time in linseed oil. This story, related about two hundred -years after the supposed event, is certainly not to be adduced as very -striking evidence in any way.<a name="FNanchor_15_155" id="FNanchor_15_155"></a><a href="#Footnote_15_155" class="fnanchor">[15]</a></p> - -<p>Among the next writers, in order of time prior to Bisagno, may be -mentioned Canepario<a name="FNanchor_16_156" id="FNanchor_16_156"></a><a href="#Footnote_16_156" class="fnanchor">[16]</a> (1619). His work, "De Atramentis" contains -a variety of recipes for different purposes: one chapter, <i>De -atramentis diversicoloribus</i>, has a more direct reference to painting. -His observations under this head are by no means confined to the -preparation of transparent colours, but he says little on the subject -of<span class="pagenum"><a name="Page_403" id="Page_403">[Pg 403]</a></span> varnishes. After describing a mode of preserving white of egg, -he says, "Others are accustomed to mix colours in liquid varnish and -linseed, or nut-oil; for a liquid and oily varnish binds the (different -layers of) colours better together, and thus forms a very fit glazing -material."<a name="FNanchor_17_157" id="FNanchor_17_157"></a><a href="#Footnote_17_157" class="fnanchor">[17]</a> On the subject of oils he observes, that linseed oil was -in great request among painters; who, however, were of opinion that -nut-oil-excelled it "in giving brilliancy to pictures, in preserving -them better, and in rendering the colours more vivid."<a name="FNanchor_18_158" id="FNanchor_18_158"></a><a href="#Footnote_18_158" class="fnanchor">[18]</a></p> - -<p>Lomazzo (a Milanese) says nothing on the subject of vehicles in his -principal work, but in his "Idea del Tempio della Pittura,"<a name="FNanchor_19_159" id="FNanchor_19_159"></a><a href="#Footnote_19_159" class="fnanchor">[19]</a> he -speaks of grinding the colours "in nut-oil, and spike-oil, and other -things," the "and" here evidently means <i>or</i>, and by "other things" we -are perhaps to understand other oils, poppy oil, drying oils, &c.</p> - -<p>The directions of Raphael Borghini and Vasari<a name="FNanchor_20_160" id="FNanchor_20_160"></a><a href="#Footnote_20_160" class="fnanchor">[20]</a> cannot certainly be -considered conclusive as to the practice of the Venetians, but they are -very clear on the subject of varnish. These writers may be considered -the earliest Italian authorities who have entered much into practical -methods. In the few observations on the subject of vehicles in Leonardo -da Vinci's treatise, "there is nothing," as M. Merimée observes, "to -show that he was in the habit of mixing varnish with his colours." -Cennini says but little on the subject<span class="pagenum"><a name="Page_404" id="Page_404">[Pg 404]</a></span> of oil-painting; Leon Battista -Alberti is theoretical rather than practical, and the published -extracts of Lorenzo Ghiberti's MS. chiefly relate to sculpture.</p> - -<p>Borghini and Vasari agree in recommending nut-oil in preference to -linseed-oil; both recommend adding varnish to the colours in painting -on walls in oil, "because the work does not then require to be -varnished afterwards," but in the ordinary modes of painting on panel -or cloth, the varnish is omitted. Borghini expressly says, that oil -alone (senza più) is to be employed; he also recommends a very sparing -use of it.</p> - -<p>The treatise of Armenini (1587) was published at Ravenna, and he -himself was of Faenza, so that his authority, again, cannot be -considered decisive as to the Venetian practice. After all, he -recommends the addition of "common varnish" only for the ground or -preparation, as a consolidating medium, for the glazing colours, -and for those dark pigments which are slow in drying. Many of his -directions are copied from the writers last named; the recipes for -varnishes, in particular, are to be found in Borghini. Christoforo -Sorte<a name="FNanchor_21_161" id="FNanchor_21_161"></a><a href="#Footnote_21_161" class="fnanchor">[21]</a> (1580) briefly alludes to the subject in question. After -speaking of the methods of distemper, he observes that the same colours -may be used in oil, except that instead of mixing them with size, they -are mixed on the palette with nut-oil, or (if slow in drying) with -boiled linseed-oil: he does not mention varnish. The Italian writers -next in order are earlier than Vasari, and may therefore be considered -original, but they are all very concise.</p> - -<p><span class="pagenum"><a name="Page_405" id="Page_405">[Pg 405]</a></span></p> - -<p>The treatise of Michael Angelo Biondo<a name="FNanchor_22_162" id="FNanchor_22_162"></a><a href="#Footnote_22_162" class="fnanchor">[22]</a> (1549), remarkable for -its historical mistakes, is not without interest in other respects. -The list of colours he gives is, in all probability, a catalogue of -those in general use in Venice at the period he wrote. With regard -to the vehicle, he merely mentions oil and size as the mediums for -the two distinct methods of oil-painting and distemper, and does not -speak of varnish. The passages in the Dialogue of Doni<a name="FNanchor_23_163" id="FNanchor_23_163"></a><a href="#Footnote_23_163" class="fnanchor">[23]</a> (1549), -which relate to the subject in question, are to the same effect. "In -colouring in oil," he observes, "the most brilliant colours (that we -see in pictures) are prepared by merely mixing them with the end of a -knife on the palette." Speaking of the perishable nature of works in -oil-painting as compared with sculpture, he says, that the plaster of -Paris (gesso) and mastic, with other ingredients of which the ground -is prepared, are liable to decay, &c.; and elsewhere, in comparing -painting in general with mosaic, that in the former the colours "must -of necessity be mixed with various things, such as oils, gums, white -or yolk of egg, and juice of figs, all which tend to impair the beauty -of the tints." This catalogue of vehicles is derived from all kinds of -painting to enforce the argument, and is by no means to be understood -as belonging to one and the same method.</p> - -<p>An interesting little work,<a name="FNanchor_24_164" id="FNanchor_24_164"></a><a href="#Footnote_24_164" class="fnanchor">[24]</a> still in the form of a dialogue (Fabio -and Lauro), appeared a year earlier; the author, Paolo Pino, was a -Venetian painter. In speaking of the practical methods Fabio observes, -as usual, that oil-painting is of all modes of imitation the most -perfect, but his reasons for this opinion seem to have a reference -to the Venetian<span class="pagenum"><a name="Page_406" id="Page_406">[Pg 406]</a></span> practice of going over the work repeatedly. Lauro -asks whether it is not possible to paint in oil on the dry wall, as -Sebastian del Piombo did. Fabio answers, "the work cannot last, for the -solidity of the plaster is impenetrable, and the colours, whether in -oil or distemper, cannot pass the surface." This might seem to warrant -the inference that absorbent grounds were prepared for oil-painting, -but there are proofs enough that resins as well as oil were used with -the <i>gesso</i> to make the preparation compact. See Doni, Armenini, &c. -This writer, again, does not speak of varnish. These appear to be the -chief Venetian and Italian authorities<a name="FNanchor_25_165" id="FNanchor_25_165"></a><a href="#Footnote_25_165" class="fnanchor">[25]</a> of the sixteenth and part of -the following century; and although Boschini wrote latest, he appears -to have had his information from good sources, and more than once -distinctly quotes Palma Giovane.</p> - -<p>In all these instances it will be seen that there is no allusion to the -immixture of varnishes with the solid colours, except in painting on -walls in oil, and that the processes of distemper and oil are always -considered as separate arts.<a name="FNanchor_26_166" id="FNanchor_26_166"></a><a href="#Footnote_26_166" class="fnanchor">[26]</a><span class="pagenum"><a name="Page_407" id="Page_407">[Pg 407]</a></span> On the other hand, the prohibition -of Boschini cannot be understood to be universal, for it is quite -certain that the Venetians varnished their pictures when done.<a name="FNanchor_27_167" id="FNanchor_27_167"></a><a href="#Footnote_27_167" class="fnanchor">[27]</a> -After Titian had finished his whole-length portrait of Pope Paul III. -it was placed in the sun to be varnished.<a name="FNanchor_28_168" id="FNanchor_28_168"></a><a href="#Footnote_28_168" class="fnanchor">[28]</a> Again, in the archives of -the church of S. Niccolo at Treviso a sum is noted (Sept. 21, 1521 ), -"per far la vernise da invernisar la Pala dell' altar grando," and the -same day a second entry appears of a payment to a painter, "per esser -venuto a dar la vernise alla Pala," &c.<a name="FNanchor_29_169" id="FNanchor_29_169"></a><a href="#Footnote_29_169" class="fnanchor">[29]</a> It is to be observed that -in both these cases the pictures were varnished as soon as done;<a name="FNanchor_30_170" id="FNanchor_30_170"></a><a href="#Footnote_30_170" class="fnanchor">[30]</a> -the varnish employed was perhaps the thin compound of naphtha (oglio di -sasso) and melted turpentine (oglio d'abezzo), described by Borghini, -and after him by Armenini: the last-named writer remarks that he had -seen<span class="pagenum"><a name="Page_408" id="Page_408">[Pg 408]</a></span> this varnish used by the best painters in Lombardy, and had heard -that it was preferred by Correggio. The consequence of this immediate -varnishing may have been that the warm resinous liquid, whatever it -was, became united with the colours, and thus at a future time the -pigment may have acquired a consistency capable of resisting the -ordinary solvents. Not only was the surface of the picture required to -be warm, but the varnish was applied soon after it was taken from the -fire.<a name="FNanchor_31_171" id="FNanchor_31_171"></a><a href="#Footnote_31_171" class="fnanchor">[31]</a></p> - -<p>Many of the treatises above quoted contain directions for making the -colours dry:<a name="FNanchor_32_172" id="FNanchor_32_172"></a><a href="#Footnote_32_172" class="fnanchor">[32]</a> some of these recipes, and many in addition, are to be -found in Palomino, who, however defective as an historian,<a name="FNanchor_33_173" id="FNanchor_33_173"></a><a href="#Footnote_33_173" class="fnanchor">[33]</a> has left -very copious practical details, evidently of ancient date. His drying -recipes are numerous, and although sugar of lead does not appear, -cardenillo (verdigris), which is perhaps as objectionable, is admitted -to be the best of all dryers. It may excite some surprise that the -Spanish painters should have bestowed so much attention on this subject -in a climate like theirs, but the rapidity of their execution must have -often required such an assistance.<a name="FNanchor_34_174" id="FNanchor_34_174"></a><a href="#Footnote_34_174" class="fnanchor">[34]</a></p> - -<p>One circumstance alluded to by Palomino, in his very minute practical -directions, deserves to be mentioned. After<span class="pagenum"><a name="Page_409" id="Page_409">[Pg 409]</a></span> saying what colours should -be preserved in their saucers under water, and what colours should be -merely covered with oiled paper because the water injures them, he -proceeds to communicate "a curious mode of preserving oil-colours," and -of transporting them from place to place. The important secret is to -tie them in bladders, the mode of doing which he enters into with great -minuteness, as if the invention was recent. It is true, Christoforo -Sorte, in describing his practice in water-colour drawing, says he was -in the habit of preserving a certain vegetable green with gum-water in -a bladder; but as the method was obviously new to Palomino, there seems -sufficient reason to believe that oil-colours, when once ground, had, -up to his time, been kept in saucers and preserved under water.<a name="FNanchor_35_175" id="FNanchor_35_175"></a><a href="#Footnote_35_175" class="fnanchor">[35]</a> -Among the items of expense in the Treviso document before alluded to, -we find "a pan and saucers for the painters."<a name="FNanchor_36_176" id="FNanchor_36_176"></a><a href="#Footnote_36_176" class="fnanchor">[36]</a> This is in accordance -with Cennini's directions, and the same system appears to have been -followed till after 1700.<a name="FNanchor_37_177" id="FNanchor_37_177"></a><a href="#Footnote_37_177" class="fnanchor">[37]</a></p> - -<p>The Flemish accounts of the early practice of oil-painting are all -later than Vasari. Van Mander, in correcting the Italian historian in -his dates, still follows his narrative in other respects verbatim. If -Vasari's story is to be accepted as true, it might be inferred that -the Flemish secret consisted in an oil varnish like copal.<a name="FNanchor_38_178" id="FNanchor_38_178"></a><a href="#Footnote_38_178" class="fnanchor">[38]</a> Vasari -says, that Van<span class="pagenum"><a name="Page_410" id="Page_410">[Pg 410]</a></span> Eyck boiled the oils with other ingredients; that the -colours, when mixed with this kind of oil, had a very firm consistence; -that the surface of the pictures so executed had a lustre, so that they -needed no varnish when done; and that the colours were in no danger -from water.<a name="FNanchor_39_179" id="FNanchor_39_179"></a><a href="#Footnote_39_179" class="fnanchor">[39]</a></p> - -<p>Certain colours, as is well known, if mixed with oil alone, may be -washed off after a considerable time. Leonardo da Vinci remarks, that -verdigris may be thus removed. Carmine, Palomino observes, may be -washed off after six years. It is on this account the Italian writers -recommend the use of varnish with certain colours, and it appears the -Venetians, and perhaps the Italians generally, employed it solely in -such cases. But it is somewhat extraordinary that Vasari should teach -a mode of painting in oil so different in its results (inasmuch as the -work thus required varnish at last) from the Flemish method which he so -much extols—a method which he says the Italians long endeavoured to -find out in vain. If they knew it, it is evident, assuming his account -to be correct, that they did not practice it.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_141" id="Footnote_1_141"></a><a href="#FNanchor_1_141"><span class="label">[1]</span></a> See "Marcucci Saggio Analitico-chimico sopra i colori," -&c. Rome, 1816, and "Taylor's Translation of Merimée on Oil-painting," -London, 1839. The last-named work contains much useful information.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_142" id="Footnote_2_142"></a><a href="#FNanchor_2_142"><span class="label">[2]</span></a> Italian writers of the 16th century speak of three kinds. -Cardanus says, that of the <i>abies</i> was esteemed most, that of the -<i>larix</i> next, and that of the <i>picea</i> least. The resin extracted by -incision from the last (the pinus abies Linnæi) is known by the name -of Burgundy pitch; when extracted by fire it is black. The three -varieties occur in Italian treatises on art, under the names of <i>oglio -di abezzo</i>, <i>trementina</i> and <i>pece Greca</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_143" id="Footnote_3_143"></a><a href="#FNanchor_3_143"><span class="label">[3]</span></a> The concrete balsam <i>benzoe</i>, called by the Italians -<i>beluzino</i>, and <i>belzoino</i>, is sometimes spoken of as a varnish.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_144" id="Footnote_4_144"></a><a href="#FNanchor_4_144"><span class="label">[4]</span></a> Marcucci supposes that balsam of copaiba was mixed with -the pigments by the (later) Venetians.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_145" id="Footnote_5_145"></a><a href="#FNanchor_5_145"><span class="label">[5]</span></a> "L'Archipelago con tutte le Isole," Ven. 1658. The -incidental notices of the remains of antiquity in this work would be -curious and important if they could be relied on. In describing the -island of Samos, for instance, the author asserts that the temple of -Juno was in tolerable preservation, and that the statue was still -there.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_146" id="Footnote_6_146"></a><a href="#FNanchor_6_146"><span class="label">[6]</span></a> "La Carta del Navegar Pitoresco," Ven. 1660. It is in the -Venetian dialect.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_147" id="Footnote_7_147"></a><a href="#FNanchor_7_147"><span class="label">[7]</span></a> Inveriadure (invetriature), literally the glazing applied -to earthenware.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_8_148" id="Footnote_8_148"></a><a href="#FNanchor_8_148"><span class="label">[8]</span></a> -</p> -<p style="margin-left: 20%;"> -"O de che strazze se fan cavedal!<br /> -D'ogio d'avezzo, mastici e sandraca;<br /> -E trementina (per no'dir triaca)<br /> -Robe, che ilustrerave ogni stival."—p. 338.<br /> -</p> -<p> -The alliteration of the words <i>trementina</i> and <i>triaca</i> is of course -lost in a translation.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_9_149" id="Footnote_9_149"></a><a href="#FNanchor_9_149"><span class="label">[9]</span></a> "I li ha fati straluser co' i colori." Boschini was at -least constant in his opinion. In the second edition of his "Ricche -Minere della Pittura Veneziana," which appeared fourteen years after -the publication of his poem, he repeats that the Venetian painters -avoided some colours in flesh "e similmente i lustri e le vernici."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_10_150" id="Footnote_10_150"></a><a href="#FNanchor_10_150"><span class="label">[10]</span></a> Thus, in the introduction to the "Ricche Minere," -Boschini calls the Milanese, Florentine, Lombard, and Bolognese -painters, <i>forestieri</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_11_151" id="Footnote_11_151"></a><a href="#FNanchor_11_151"><span class="label">[11]</span></a> "Il Riposo," Firenze, 1584.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_12_152" id="Footnote_12_152"></a><a href="#FNanchor_12_152"><span class="label">[12]</span></a> "De' Veri Precetti della Pittura," Ravenna, 1587.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_13_153" id="Footnote_13_153"></a><a href="#FNanchor_13_153"><span class="label">[13]</span></a> "Trattato della Pittura fondato nell' autorità di molti -eccellenti in questa professione." Venezia, 1642. Bisagno remarks in -his preface, that the books on art were few, and that painters were in -the habit of keeping them secret. He acknowledges that he has availed -himself of the labours of others, but without mentioning his sources: -some passages are copied from Lomazzo. He, however, lays claim to some -original observations, and says he had seen much and discoursed with -many excellent painters.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_14_154" id="Footnote_14_154"></a><a href="#FNanchor_14_154"><span class="label">[14]</span></a> "Le Meraviglie dell' Arte," Venezia, 1648.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_15_155" id="Footnote_15_155"></a><a href="#FNanchor_15_155"><span class="label">[15]</span></a> It has been conjectured by some that this story proved -the immixture of varnishes with the colours, and that the oil was only -used to dilute them. The epitaph on Antonello da Messina which existed -in Vasari's time, alludes to his having mixed the colours with oil.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_16_156" id="Footnote_16_156"></a><a href="#FNanchor_16_156"><span class="label">[16]</span></a> "Petri Mariæ Caneparii De Atramentis cujuscumque -generis," Venet. 1619. It was republished at Rotterdam in 1718.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_17_157" id="Footnote_17_157"></a><a href="#FNanchor_17_157"><span class="label">[17]</span></a> "Ita quod magis ex hiis evadit atramentum picturæ -summopere idoneum." Thus, if <i>atramentum</i> is to be understood, as -usual, to mean a glazing colour, the passage can only refer to the -immixture of varnish with the transparent colours applied last in -order.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_18_158" id="Footnote_18_158"></a><a href="#FNanchor_18_158"><span class="label">[18]</span></a> In a passage that follows respecting the mode of -extracting nut-oil, Caneparius appears to mistranslate Galen, c. -7—"De Simplicium Medicamentorum facultatibus." The observations of -Galen on this subject, and on the drying property of linseed, may have -given the first hint to the inventors of oil-painting. The custom of -dating the origin of this art from Van Eyck is like that of dating the -commencement of modern painting from Cimabue. The improver is often -assumed to be the inventor.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_19_159" id="Footnote_19_159"></a><a href="#FNanchor_19_159"><span class="label">[19]</span></a> Milan, 1590.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_20_160" id="Footnote_20_160"></a><a href="#FNanchor_20_160"><span class="label">[20]</span></a> The particulars here alluded to are to be found in the -first edition of Vasari (1550) as well as the second.—v. i. c. 21, &c.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_21_161" id="Footnote_21_161"></a><a href="#FNanchor_21_161"><span class="label">[21]</span></a> "Osservasioni nella Pittura." In Venezia, 1580. Sorte, -who, it appears, was a native of Verona, had worked in his youth -with Giulio Romano, at Mantua, and communicates the methods taught -him by that painter, for giving the true effects of perspective in -compositions of figures. He is, perhaps, the earliest who describes the -process of water-colour painting as distinguished from distemper and as -adapted to landscape, if the art he describes deserves the name.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_22_162" id="Footnote_22_162"></a><a href="#FNanchor_22_162"><span class="label">[22]</span></a> "Della nobilissima Pittura e sua Arte," Venezia, 1549. -Biondo is so ignorant as to attribute the Last Supper, by Leonardo da -Vinci, to Mantegna.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_23_163" id="Footnote_23_163"></a><a href="#FNanchor_23_163"><span class="label">[23]</span></a> "Disegno del Doni," in Venezia, 1549.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_24_164" id="Footnote_24_164"></a><a href="#FNanchor_24_164"><span class="label">[24]</span></a> "Dialogo di Pittura," Venezia, 1548. Pino, in enumerating -the celebrated contemporary artists, does not include Paul Veronese, -for a very obvious reason, that painter being at the time only about -17 years of age. Sorte, who wrote thirty years later, mentions -"l'eccellente Messer Paulino nostro," alone.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_25_165" id="Footnote_25_165"></a><a href="#FNanchor_25_165"><span class="label">[25]</span></a> The Dialogues of Lodovico Dolce, and various other works, -are not referred to here, as they contain nothing on the subject in -question. The latest authority at all connected with the traditions of -Venetian practice, is a certain Giambatista Volpato, of Bassano: he -died in 1706, and had been intimate with Ridolfi. The only circumstance -he has transmitted relating to practical details is that Giacomo -Bassan, in retouching on a dry surface, sometimes adopted a method -commonly practised, he says, by Paul Veronese (and commonly practised -still), namely, that of dipping his brush in spirits of turpentine; -at other times he oiled out the surface in the usual manner. Volpato -left a MS. which was announced for publication in Vicenza in 1685, -but it never appeared; it, however, afterwards formed the ground-work -of Verci's "Notizie intorno alla Vita e alle Opere de' Pittori di -Bassano." Venezia, 1775. See also "Lettera di Giambatista Roberti sopra -Giacomo da Ponte," Lugano, 1777. Another MS. by Natale Melchiori, of -about the same date, is preserved at Treviso and Castel Franco: it -abounds with historical mistakes; the author says, for instance, that -the Pietro Martyre was begun by Giorgione and finished by Titian. The -recipes for varnishes and colours are very numerous, but they are -mostly copied from earlier works.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_26_166" id="Footnote_26_166"></a><a href="#FNanchor_26_166"><span class="label">[26]</span></a> That distemper was not very highly esteemed by the -Venetians may be inferred from the following observation of Pino:—"Il -modo di colorir à guazzo è imperfetto et più fragile et à me non -diletta onde lasciamolo all' oltremontani i quali sono privi della vera -via." It is, however, certain that the Venetians sometimes painted in -this style, and Volpato mentions several works of the kind by Bassan, -but he never hints that he began his oil pictures in distemper.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_27_167" id="Footnote_27_167"></a><a href="#FNanchor_27_167"><span class="label">[27]</span></a> Boschini says, that the Venetians (he especially means -Titian) rendered their pictures sparkling by finally touching on a dry -surface (<i>à secco</i>). The absence of varnish in the solid colours, the -retouching with spirit of turpentine, and even <i>à secco</i>, all suppose a -dull surface, which would require varnish. The latter method, alluded -to by Boschini, was an exception to the general practice, and not -likely to be followed on account of its difficulty. Carlo Maratti, on -the authority of Palomino, used to say, "He must be a skilful painter -who can retouch without oiling out."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_28_168" id="Footnote_28_168"></a><a href="#FNanchor_28_168"><span class="label">[28]</span></a> See a letter by Francesco Bocchi, and another by Vasari, -in the "Lettere Pittoriche" of Bottari. The circumstance is mentioned -incidentally; the point chiefly dwelt on is, that some persons who -passed were deceived, and bowed to the picture, supposing it to be the -pope.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_29_169" id="Footnote_29_169"></a><a href="#FNanchor_29_169"><span class="label">[29]</span></a> Federici, "Memorie Trevigiane," Venezia, 1803. The -altar-piece of S. Niccolo at Treviso is attributed, in the document -alluded to, to Fra Marco Pensabene, a name unknown; the painting is so -excellent as to have been thought worthy of Sebastian del Piombo: for -this opinion, however, there are no historical grounds. It was begun -in 1520, but before it was quite finished the painter, whoever he was, -absconded: it was therefore completed by another.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_30_170" id="Footnote_30_170"></a><a href="#FNanchor_30_170"><span class="label">[30]</span></a> Titian's stay in Rome was short, and with respect to the -Treviso altar-piece, a week or two only, at most, can have elapsed -between the completion and the varnishing. Cennini, who recommends -delaying a year at least before varnishing, speaks of pictures in -distemper.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_31_171" id="Footnote_31_171"></a><a href="#FNanchor_31_171"><span class="label">[31]</span></a> See Borghini, Armenini, their Venetian copyist Bisagno, -and Palomino. The last-named writer, though of another school and much -more modern, was evidently well acquainted with the ancient methods: -he says, "Se advierte que siempre que se huviere de barnizar alguna -cosa conviene que la pintura y el barniz estèn calientes."—<i>El Museo -Pictorico</i>, v. ii.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_32_172" id="Footnote_32_172"></a><a href="#FNanchor_32_172"><span class="label">[32]</span></a> Burnt alum, one of the ingredients recommended, might -perhaps account for a shining fracture in the indurated pigment in some -old pictures.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_33_173" id="Footnote_33_173"></a><a href="#FNanchor_33_173"><span class="label">[33]</span></a> Of the earlier Spanish writers Pacheco may be mentioned -next to Palomino as containing most practical information. Carducho, De -Butron, and others, seldom descend to such details. Palomino contains -all the directions of Pacheco, and many in addition.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_34_174" id="Footnote_34_174"></a><a href="#FNanchor_34_174"><span class="label">[34]</span></a> See Cean Bermudez, "Sobre la Escuela Sevillana," Cadiz, -1806. The same reasons induced the later Venetian machinists to paint -on dark grounds, and to make use of (drying) oil in excess. See -Zanetti, <i>Della Pittura Veneziana</i>, 1. iv.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_35_175" id="Footnote_35_175"></a><a href="#FNanchor_35_175"><span class="label">[35]</span></a> Borghini, in describing the method of making a gold-size -(the same as Cennini's), speaks of boiling the "buccie de' colori" in -oil; this only means the skin or pellicle of the colour itself—in -fact, he proceeds to say that they dissolve in boiling. Vasari, in -describing the same process, uses the expression "colori seccaticci."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_36_176" id="Footnote_36_176"></a><a href="#FNanchor_36_176"><span class="label">[36]</span></a> "Maggio 4 (1520) Per un cadin (catino) per depentori. Per -scudellini per li depentori."—<i>Mem. Trev.</i>, vol. i. p. 131. Pungileoni -("Memorie Istoriche di Antonio Allegri") quotes a note of expenses -relating to two oil-pictures by Paolo Gianotti; among the items we find -"colori, telari, et brocchette."—vol. ii. p. 75.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_37_177" id="Footnote_37_177"></a><a href="#FNanchor_37_177"><span class="label">[37]</span></a> Salmon, in his "Polygraphice" (1701), gives the following -direction:—"Oyl colors, if not presently used, will have a skin grow -over them, to prevent which put them into a glass, and put the glass -three or four inches under water," &c.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_38_178" id="Footnote_38_178"></a><a href="#FNanchor_38_178"><span class="label">[38]</span></a> This varnish appears to have been known some centuries -before Van Eyck's time, but he may have been the first to mix it with -the colours.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_39_179" id="Footnote_39_179"></a><a href="#FNanchor_39_179"><span class="label">[39]</span></a> See Vasari, Life of Antonello da Messina.</p></div> - - - -<p class="para"><a id="NOTE_W"></a>NOTE W.—<a href="#a608">Par. 608.</a></p> - -<p>In the second volume Goethe gives the nomenclature of the Greeks and -Romans at some length. The general notions of the ancients with regard -to colours are thus described:—"The ancients derive all colours from -white and black, from light and darkness. They say, all colours are -between white and black, and are mixed out of these. We must not, -however, suppose that they understand by this a mere atomic mixture, -although they occasionally use the word μίξις;<a name="FNanchor_1_180" id="FNanchor_1_180"></a><a href="#Footnote_1_180" class="fnanchor">[1]</a> for in the remarkable -passages, where they wish to express a kind of reciprocal (dynamic) -action of the two contrasting principles, they employ the words κρᾶσις, -union, σύγκρισις, combination; thus, again, the mutual influence of -light and darkness, and of colours among each<span class="pagenum"><a name="Page_411" id="Page_411">[Pg 411]</a></span> other, is described by -the word κεράννυστας, an expression of similar import.</p> - -<p>"The varieties of colours are differently enumerated; some mention -seven, others twelve, but without giving the complete list. From a -consideration of the terminology both of the Greeks and Romans, it -appears that they sometimes employed general for specific terms, and -<i>vice versâ</i>.</p> - -<p>"Their denominations of colours are not permanently and precisely -defined, but mutable and fluctuating, for they are employed even with -regard to similar colours both on the <i>plus</i> and <i>minus</i> side. Their -yellow, on the one hand, inclines to red, on the other to blue; the -blue is sometimes green, sometimes red; the red is at one time yellow, -at another blue. Pure red (purpur) fluctuates between warm red and -blue, sometimes inclining to scarlet, sometimes to violet.</p> - -<p>"Thus the ancients not only seem to have looked upon colour as a -mutable and fleeting quality, but appear to have had a presentiment of -the (physical and chemical) effects of augmentation and re-action. In -speaking of colours they make use of expressions which indicate this -knowledge; they make yellow redden, because its augmentation tends to -red; they make red become yellow, for it often returns thus to its -origin.</p> - -<p>"The hues thus specified undergo new modifications. The colours -arrested at a given point are attenuated by a stronger light darkened -by a shadow, nay, deepened and condensed in themselves. For the -gradations which thus arise the name of the species only is often -given, but the more generic terms are also employed. Every colour, of -whatever kind, can, according to the same view, be multiplied into -itself, condensed, enriched, and will in consequence appear more or -less dark. The ancients called colour in this state," &c. Then follow -the designations of general states of colour and those of specific hues.</p> - -<p>Another essay on the notions of the ancients respecting<span class="pagenum"><a name="Page_412" id="Page_412">[Pg 412]</a></span> the origin -and nature of colour generally, shows how nearly Goethe himself has -followed in the same track. The dilating effect of light objects, -the action and reaction of the retina, the coloured after-image, the -general law of contrast, the effect of semi-transparent mediums in -producing warm or cold colours as they are interposed before a dark or -light background—all this is either distinctly expressed or hinted -at; "but," continues Goethe, "how a single element divides itself into -two, remained a secret for them. They knew the nature of the magnet, -in amber, only as attraction; polarity was not yet distinctly evident -to them. And in very modern times have we not found that scientific -men have still given their almost exclusive attention to attraction, -and considered the immediately excited repulsion only as a mere -after-action?"</p> - -<p>An essay on the Painting of the Ancients<a name="FNanchor_2_181" id="FNanchor_2_181"></a><a href="#Footnote_2_181" class="fnanchor">[2]</a> was contributed by Heinrich -Meyer.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_180" id="Footnote_1_180"></a><a href="#FNanchor_1_180"><span class="label">[1]</span></a> See Note on Par. 177.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_181" id="Footnote_2_181"></a><a href="#FNanchor_2_181"><span class="label">[2]</span></a> Vol. ii. p. 69, first edition.</p></div> - - - -<p class="para"><a id="NOTE_X"></a>NOTE X.—<a href="#a670">Par. 670.</a></p> - -<p>This agrees with the general recommendation so often given by high -authorities in art, to avoid a tinted look in the colour of flesh. The -great example of Rubens, whose practice was sometimes an exception -to this, may however show that no rule of art is to be blindly or -exclusively adhered to. Reynolds, nevertheless, in the midst of his -admiration for this great painter, considered the example dangerous, -and more than once expresses himself to this effect, observing on one -occasion that Rubens, like Baroccio, is sometimes open to the criticism -made on an ancient painter, namely, that his figures looked as if they -fed on roses.</p> - -<p>Lodovico Dolce, who is supposed to have given the <i>vivâ voce</i> precepts -of Titian in his Dialogue,<a name="FNanchor_1_182" id="FNanchor_1_182"></a><a href="#Footnote_1_182" class="fnanchor">[1]</a> makes Aretino<span class="pagenum"><a name="Page_413" id="Page_413">[Pg 413]</a></span> say: "I would generally -banish from my pictures those vermilion cheeks with coral lips; for -faces thus treated look like masks. Propertius, reproving his Cynthia -for using cosmetics, desires that her complexion might exhibit the -simplicity and purity of colour which is seen in the works of Apelles."</p> - -<p>Those who have written on the practice of painting have always -recommended the use of few colours for flesh. Reynolds and others quote -even ancient authorities as recorded by Pliny, and Boschini gives -several descriptions of the method of the Venetians, and particularly -of Titian, to the same effect. "They used," he says, "earths more than -any other colour, and at the utmost only added a little vermilion, -minium, and lake, abhorring as a pestilence <i>biadetti, gialli santi, -smaltini, verdi-azzurri, giallolini</i>."<a name="FNanchor_2_183" id="FNanchor_2_183"></a><a href="#Footnote_2_183" class="fnanchor">[2]</a> Elsewhere he says,<a name="FNanchor_3_184" id="FNanchor_3_184"></a><a href="#Footnote_3_184" class="fnanchor">[3]</a> "Earths -should be used rather than other colours:" after repeating the above -prohibited list he adds, "I speak of the imitation of flesh, for in -other things every colour is good;" again, "Our great Titian used to -say that he who wishes to be a painter should be acquainted with three -colours, white, black, and red."<a name="FNanchor_4_185" id="FNanchor_4_185"></a><a href="#Footnote_4_185" class="fnanchor">[4]</a> Assuming this<span class="pagenum"><a name="Page_414" id="Page_414">[Pg 414]</a></span> account to be a -little exaggerated, it is still to be observed that the monotony to -which the use of few colours would seem to tend, is prevented by the -nature of the Venetian process, which was sufficiently conformable to -Goethe's doctrine; the gradations being multiplied, and the effect -of the colours heightened by using them as semi-opaque mediums. -Immediately after the passage last quoted we read, "He also gave this -true precept, that to produce a lively colouring in flesh it is not -possible to finish at once."<a name="FNanchor_5_186" id="FNanchor_5_186"></a><a href="#Footnote_5_186" class="fnanchor">[5]</a> As these particulars may not be known -to all, we add some further abridged extracts explaining the order and -methods of these different operations.</p> - -<p>"The Venetian painters," says this writer,<a name="FNanchor_6_187" id="FNanchor_6_187"></a><a href="#Footnote_6_187" class="fnanchor">[6]</a> "after having drawn in -their subject, got in the masses with very solid colour, without making -use of nature or statues. Their great object in this stage of their -work was to distinguish the advancing and retiring portions, that the -figures might be relieved by means of chiaro-scuro—one of the most -important departments of colour and form, and indeed of invention. -Having decided on their scheme of effect, when this preparation was -dry, they consulted nature and the antique; not servilely, but with the -aid of a few lines on paper (<i>quattro segni in carta</i>) they corrected -their figures without any other model. Then returning to their brushes, -they began to paint smartly on this preparation, producing the colour -of flesh." The passage before quoted follows, stating that they used -earths chiefly, that they carefully avoided certain colours, "and -likewise varnishes and whatever produces a shining surface.<a name="FNanchor_7_188" id="FNanchor_7_188"></a><a href="#Footnote_7_188" class="fnanchor">[7]</a> When -this second painting was dry, they proceeded to scumble over this or -that figure with a low tint to make the one next it come forward, -giving another, at the same time, an additional light—for example,<span class="pagenum"><a name="Page_415" id="Page_415">[Pg 415]</a></span> on -a head, a hand, or a foot, thus detaching them, so to speak, from the -canvas." (Tintoret's <i>Prigionia di S. Rocco</i> is here quoted.) "By thus -still multiplying these well-understood retouchings where required, on -the dry surface, <i>(à secco)</i> they reduced the whole to harmony. In this -operation they took care not to cover entire figures, but rather went -on gemming them <i>(gioielandole)</i> with vigorous touches. In the shadows, -too, they infused vigour frequently by glazing with asphaltum, always -leaving great masses in middle-tint, with many darks, in addition to -the partial glazings, and few lights."</p> - -<p>The introduction to the subject of Venetian colouring, in the poem by -the same author, is also worth transcribing, but as the style is quaint -and very concise, a translation is necessarily a paraphrase.<a name="FNanchor_8_189" id="FNanchor_8_189"></a><a href="#Footnote_8_189" class="fnanchor">[8]</a></p> - -<p>"The art of colouring has the imitation of qualities for its object; -not all qualities, but those secondary ones which are appreciable by -the sense of sight. The eye especially sees colours, the imitation -of nature in painting is therefore justly called colouring; but the -painter arrives at his end by indirect means. He gives the varieties -of tone in masses;<a name="FNanchor_9_190" id="FNanchor_9_190"></a><a href="#Footnote_9_190" class="fnanchor">[9]</a><span class="pagenum"><a name="Page_416" id="Page_416">[Pg 416]</a></span> he smartly impinges lights, he clothes his -preparation with more delicate local hues, he unites, he glazes: thus -everything depends on the method, on the process. For if we look -at colour abstractedly, the most positive may be called the most -beautiful, but if we keep the end of imitation in view, this shallow -conclusion falls to the ground. The refined Venetian manner is very -different from mere direct, sedulous imitation. Every one who has -a good eye may arrive at such results, but to attain the manner of -Paolo, of Bassan, of Palma, Tintoret, or Titian, is a very different -undertaking."<a name="FNanchor_10_191" id="FNanchor_10_191"></a><a href="#Footnote_10_191" class="fnanchor">[10]</a></p> - -<p>The effects of semi-transparent mediums in some natural productions -seem alluded to in the following passage—"Nature sometimes -accidentally imitates figures in stones and other substances, and -although they are necessarily incomplete in form, yet the principle -of effect (depth) resembles the Venetian practice." In a passage that -follows there appears to be an allusion to the production of the -atmospheric colours by semi-transparent mediums.<a name="FNanchor_11_192" id="FNanchor_11_192"></a><a href="#Footnote_11_192" class="fnanchor">[11]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_182" id="Footnote_1_182"></a><a href="#FNanchor_1_182"><span class="label">[1]</span></a> "Dialogo della Pittura, intitolato l'Aretino." It -was first published at Venice in 1557; about twenty years before -Titian's death. In the dedication to the senator Loredano, Lodovico -Dolce eulogises the work, which he would hardly have done if it had -been entirely his own: again, the supposition that it may have been -suggested by Aretino, would be equally conclusive, coupled with -internal evidence, as to the original source.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_183" id="Footnote_2_183"></a><a href="#FNanchor_2_183"><span class="label">[2]</span></a> Introduction to the "Ricche Minere della Pittura -Veneziana," Venezia, 1674. The Italian annotators on older works on -painting are sometimes at a loss to find modern terms equivalent to the -obsolete names of pigments. (See "Antologia dell 'Arte Pittorica.") -The colours now in use corresponding with Boschini's list, are -probably yellow lakes, smalt, verditer, and Naples yellow. Boschini -often censures the practice of other schools, and in this emphatic -condemnation he seems to have had an eye to certain precepts in -Lomazzo, and perhaps, even in Leonardo da Vinci, who, on one occasion, -recommends Naples yellow, lake, and white for flesh. The Venetian -writer often speaks, too, in no measured terms of certain Flemish -pictures, probably because they appeared to him too tinted.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_184" id="Footnote_3_184"></a><a href="#FNanchor_3_184"><span class="label">[3]</span></a> "La Carta del Navegar Pitoresco," p. 338.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_185" id="Footnote_4_185"></a><a href="#FNanchor_4_185"><span class="label">[4]</span></a> Ib. p. 341. In describing Titian's actual practice -("Ricche Minere"), he, however, adds yellow (ochre). The red is also -particularised, viz., the common terra rossa.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_186" id="Footnote_5_186"></a><a href="#FNanchor_5_186"><span class="label">[5]</span></a> High examples here again prove that the opposite system -may attain results quite as successful.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_187" id="Footnote_6_187"></a><a href="#FNanchor_6_187"><span class="label">[6]</span></a> Introduction to the "Ricche Minere."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_188" id="Footnote_7_188"></a><a href="#FNanchor_7_188"><span class="label">[7]</span></a> See Note to Par. <a href="#a555">555</a>. Here again, assuming the description -to be correct, high authorities might be opposed to the Venetians.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_8_189" id="Footnote_8_189"></a><a href="#FNanchor_8_189"><span class="label">[8]</span></a> The following quatrain may serve as a specimen; the author -is speaking of the importance of the colour of flesh as conducive to -picturesque effect:— -</p> -<p style="margin-left: 20%;"> -"Importa el nudo; e come ben l'importa!<br /> -Un quadro senta nudo è come aponto<br /> -Un disnar senza pan, se ben ghe zonto,<br /> -Per più delicia, confetura e torta."—p. 346.<br /> -</p> -<p> -In his preface he anticipates, and thus answers the objections to his -Venetian dialect—"Mi, che son Venetian in Venetia e che parlo de' -Pitori Venetiani hò da andarme a stravestir? Guarda el Cielo."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_9_190" id="Footnote_9_190"></a><a href="#FNanchor_9_190"><span class="label">[9]</span></a> The word <i>Macchia</i>, literally a blot, is generally used by -Italian writers, by Vasari for instance, for the local colour. Boschini -understands by it the relative depth of tones rather than the mere -difference of hue. "By macchia," he says, "I understand that treatment -by which the figures are distinguished from each other by different -tones lighter or darker."—<i>La Carta del Navegar</i>, p. 328. Elsewhere, -"Colouring (as practised by the Venetians) comprehends both the macchia -and drawing;" (p. 300) that is, comprehends the gradations of light -and dark in objects, and the parts of objects, and consequently, their -essential form. "The macchia," he adds, "is the effect of practice, and -is dictated by the knowledge of what is requisite for effect."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_10_191" id="Footnote_10_191"></a><a href="#FNanchor_10_191"><span class="label">[10]</span></a> -</p> -<p style="margin-left: 20%;"> -"Ma l'arivar a la maniera, al trato<br /> -(Verbi gratia) de Paulo, del Bassan,<br /> -Del Vechio, Tentoreto, e di Tician,<br /> -Per Dio, l'è cosa da deventar mato."—p. 294, 297.<br /> -</p></div> - -<div class="footnote"> - -<p><a name="Footnote_11_192" id="Footnote_11_192"></a><a href="#FNanchor_11_192"><span class="label">[11]</span></a> The traces of the Aristotelian theory are quite as -apparent in Boschini as in the other Italian writers on art; but as he -wrote in the seventeenth century, his authority in this respect is only -important as an indication of the earlier prevalence of the doctrine.</p></div> - - - -<p class="para"><a id="NOTE_Y"></a>NOTE Y.—Par. 672.</p> - -<p>The author's conclusion here is unsatisfactory, for the colour of -the black races may be considered at least quite as negative as that -of Europeans. It would be safer to say that the white skin is more -beautiful than the black, because it is more capable of indications -of life, and indications of emotion. A degree of light which would -fail to exhibit the finer varieties of form on a dark surface, would -be sufficient to display them on a light one; and the delicate -mantlings<span class="pagenum"><a name="Page_417" id="Page_417">[Pg 417]</a></span> of colour, whether the result of action or emotion, are more -perceptible for the same reason.</p> - - - -<p class="para"><a id="NOTE_Z"></a>NOTE Z.—Par. 690.</p> - -<p>The author appears to mean that a degree of brightness which the organ -can bear at all, must of necessity be removed from dazzling, white -light. The slightest tinge of colour to this brightness, implies that -it is seen through a medium, and thus, in painting, the lightest, -whitest surface should partake of the quality of depth. Goethe's view -here again accords, it must be admitted, with the practice of the best -colourists, and with the precepts of the highest authorities.—See <a href="#NOTE_C">Note C</a>.</p> - - - -<p class="para"><a id="NOTE_AA"></a>NOTE AA.—<a href="#a732">Par. 732.</a></p> - -<p>Ample details respecting the opinions of Louis Bertrand Castel, a -Jesuit, are given in the historical part. The coincidence of some -of his views with those of Goethe is often apparent: he objects, -for instance, to the arbitrary selection of the Newtonian spectrum; -observing that the colours change with every change of distance between -the prism and the recipient surface.—<i>Farbenl.</i> vol. ii. p. 527. -Jeremias Friedrich Gülich was a dyer in the neighbourhood of Stutgardt: -he published an elaborate work on the technical details of his own -pursuit.—<i>Farbenl.</i> vol. ii. p. 630.</p> - - - -<p class="para"><a id="NOTE_BB"></a>NOTE BB.—<a href="#a748">Par. 748.</a></p> - -<p>Goethe, in his account of Castel, suppresses the learned Jesuit's -attempt at colorific music (the claveçin oculaire), founded on the -Newtonian doctrine. Castel was complimented, perhaps ironically, on -having been the first to remark that there were but three principal -colours. In asserting his claim to the discovery, he admits that there -is nothing new. In fact, the notion of three colours is to be found in -Aristotle; for that philosopher enumerates no<span class="pagenum"><a name="Page_418" id="Page_418">[Pg 418]</a></span> more in speaking of the -rainbow,<a name="FNanchor_1_193" id="FNanchor_1_193"></a><a href="#Footnote_1_193" class="fnanchor">[1]</a> and Seneca calls them by their right names.<a name="FNanchor_2_194" id="FNanchor_2_194"></a><a href="#Footnote_2_194" class="fnanchor">[2]</a> Compare with -Dante, Parad. c. 33. The relation between colours and sounds is in like -manner adverted to by Aristotle; he says—"It is possible that colours -may stand in relation to each other in the same manner as concords -in music, for the colours which are (to each other) in proportions -corresponding with the musical concords, are those which appear to -be the most agreeable."<a name="FNanchor_3_195" id="FNanchor_3_195"></a><a href="#Footnote_3_195" class="fnanchor">[3]</a> In the latter part of the 16th century, -Arcimboldo, a Milanese painter, invented a colorific music; an account -of his principles and method will be found in a treatise on painting -which appeared about the same time. "Ammaestrato dal quai ordine Mauro -Cremonese dalla viola, musico dell' Imperadore Ridolfo II. trovò sul -gravicembalo tutte quelle consonanze che dall' Arcimboldo erano segnate -coi colori sopra una carta."<a name="FNanchor_4_196" id="FNanchor_4_196"></a><a href="#Footnote_4_196" class="fnanchor">[4]</a></p> -<hr class="r5" /> -<div class="footnote"> - -<p><a name="Footnote_1_193" id="Footnote_1_193"></a><a href="#FNanchor_1_193"><span class="label">[1]</span></a> "De Meteor.," lib. 3, c. ii. and iv. He observes that this -is the only effect of colour which painters cannot imitate.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_194" id="Footnote_2_194"></a><a href="#FNanchor_2_194"><span class="label">[2]</span></a> "De Ignib. cœlest." The description of the prism by Seneca -is another instance of the truth of Castel's admission. The Roman -philosopher's words are—"Virgula solet fieri vitrea, stricta vel -pluribus angulis in modo clavæ tortuosæ; hæc si ex transverso solem -accipit colorem talem qualis in arcu videri solet, reddit," &c.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_195" id="Footnote_3_195"></a><a href="#FNanchor_3_195"><span class="label">[3]</span></a> "De Sensu et sensili."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_196" id="Footnote_4_196"></a><a href="#FNanchor_4_196"><span class="label">[4]</span></a> "Il Figino, overo del Fine della Pittura," Mantova, 1591, -p. 249. An account of the absurd invention of the same painter in -composing figures of flowers and animals, and even painting portraits -in this way, to the great delight of the emperor, will be found in the -same work.</p></div> - - - -<p class="para"><a id="NOTE_CC"></a>NOTE CC.—<a href="#a758">Par. 758.</a></p> - -<p>The moral associations of colours have always been a more favourite -subject with poets than with painters. This is to be traced to the -materials and means of description as distinguished from those of -representation. An image is more distinct for the mind when it is -compared with something that resembles it. An object is more distinct -for the eye when it is compared with something that differs from it. -Association is the auxiliary in the one case, contrast in the<span class="pagenum"><a name="Page_419" id="Page_419">[Pg 419]</a></span> other. -The poet, of necessity, succeeds best in conveying the impression -of external things by the aid of analogous rather than of opposite -qualities: so far from losing their effect by this means, the images -gain in distinctness. Comparisons that are utterly false and groundless -never strike us as such if the great end is accomplished of placing -the thing described more vividly before the imagination. In the common -language of laudatory description the colour of flesh is like snow -mixed with vermilion: these are the words used by Aretino in one of -his letters in speaking of a figure of St. John, by Titian. Similar -instances without end might be quoted from poets: even a contrast can -only be strongly conveyed in description by another contrast that -resembles it.<a name="FNanchor_1_197" id="FNanchor_1_197"></a><a href="#Footnote_1_197" class="fnanchor">[1]</a> On the other hand it would be easy to show that -whenever poets have attempted the painter's method of direct contrast, -the image has failed to be striking, for the mind's eye cannot see the -relation between two colours.</p> - -<p>Under the same category of effect produced by association may be -classed the moral qualities in which poets have judiciously taken -refuge when describing visible forms and colours, to avoid competition -with the painters' elements, or rather to attain their end more -completely. But a little examination would show that very pleasing -moral associations may be connected with colours which would be far -from agreeable to the eye. All light, positive colours, light-green, -light-purple, white, are pleasing to the mind's eye, and no degree -of dazzling splendour is offensive. The moment, however, we have to -do with the actual sense of vision, the susceptibility of the eye -itself is to be considered, the law of comparison is reversed, colours -become striking by being opposed to what they are not, and their moral -associations are not owing to the colours themselves,<span class="pagenum"><a name="Page_420" id="Page_420">[Pg 420]</a></span> but to the -modifications such colours undergo in consequence of what surrounds -them. This view, so naturally consequent on the principles the author -has himself arrived at, appears to be overlooked in the chapter under -consideration, the remarks in which, in other respects, are acute and -ingenious.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_197" id="Footnote_1_197"></a><a href="#FNanchor_1_197"><span class="label">[1]</span></a> Such as— -</p> -<p style="margin-left: 20%;"> -"Her beauty hangs upon the cheek of night,<br /> -Like a rich jewel in an Ethiop's ear."<br /> -<span style="margin-left: 11em;"><i>Romeo and Juliet</i>.</span><br /> -</p></div> - - - -<p class="para"><a id="NOTE_DD"></a>NOTE DD.—Par. 849.</p> - -<p>According to the usual acceptation of the term chiaro-scuro in the -artist world, it means not only the mutable effects produced by light -and shade, but also the permanent differences in brightness and -darkness which are owing to the varieties of local colour.</p> - - - -<p class="para"><a id="NOTE_EE"></a>NOTE EE.—Par. 855.</p> - -<p>The mannered treatment of light and shade here alluded to by the -author is very seldom to be met with in the works of the colourists; -the taste may have first arisen from the use of plaster-casts, and -was most prevalent in France and Italy in the early part of the last -century. Piazzetta represented it in Venice, Subleyras in Rome. In -France "Restout taught his pupils that a globe ought to be represented -as a polyhedron. Greuze most implicitly adopted the doctrine, and in -practice showed that he considered the round cheeks of a young girl or -an infant as bodies cut into facettes."<a name="FNanchor_1_198" id="FNanchor_1_198"></a><a href="#Footnote_1_198" class="fnanchor">[1]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_198" id="Footnote_1_198"></a><a href="#FNanchor_1_198"><span class="label">[1]</span></a> See Taylor's translation of Merimée on oil-painting, -p. 27. Barry, in a letter from Paris, speaks of Restout as the -only painter who resembled the earlier French masters: the manner -in question is undoubtedly sometimes very observable in Poussin. -The English artist elsewhere speaks of the "broad, happy manner of -Subleyras."—<i>Works</i>, London, 1809.</p></div> - - - -<p class="para"><a id="NOTE_FF"></a>NOTE FF.—<a href="#a859">Par. 859.</a></p> - -<p>All this was no doubt suggested by Heinrich Meyer, whose chief -occupation in Rome, at one time, was making<span class="pagenum"><a name="Page_421" id="Page_421">[Pg 421]</a></span> sepia drawings from -sculpture (see Goethe's Italiänische Reise). It is hardly necessary to -say that the observation respecting the treatment of the surface in the -antique statues is very fanciful.</p> - - - -<p class="para"><a id="NOTE_GG"></a>NOTE GG.—<a href="#a863">Par. 863.</a></p> - -<p>This observation might have been suggested by the drawings of Claude, -which, with the slightest means, exhibit an harmonious balance of warm -and cold.</p> - - - -<p class="para"><a id="NOTE_HH"></a>NOTE HH.—<a href="#a865">Par. 865.</a></p> - -<p>The colouring of Paolo Uccello, according to Vasari's account of him, -was occasionally so remarkable that he might perhaps have been fairly -included among the instances of defective vision given by the author. -His skill in perspective, indicating an eye for gradation, may be also -reckoned among the points of resemblance (see Par. 105).</p> - - - -<p class="para"><a id="NOTE_II"></a>NOTE II.—<a href="#a902">Par. 902.</a></p> - -<p>The quotation before given from Boschini shows that the method -described by the author, and which is true with regard to some of the -Florentine painters, was not practised by the Venetians, for their -first painting was very solid. It agrees, however, with the manner -of Rubens, many of whose works sufficiently corroborate the account -of his process given by Descamps. "In the early state of Rubens's -pictures," says that writer,<a name="FNanchor_1_199" id="FNanchor_1_199"></a><a href="#Footnote_1_199" class="fnanchor">[1]</a> "everything appeared like a thin wash; -but although he often made use of the ground in producing his tones, -the canvas was entirely covered more or less with colour." In this -system of leaving the shadows transparent from the first, with the -ground shining through them, it would have been obviously destructive -of richness to use white mixed with the darks, the brightness, in -fact, already existed underneath. Hence the<span class="pagenum"><a name="Page_422" id="Page_422">[Pg 422]</a></span> well-known precept of -Rubens to avoid white in the shadows, a precept, like many others, -belonging to a particular practice, and involving all the conditions of -that practice.<a name="FNanchor_2_200" id="FNanchor_2_200"></a><a href="#Footnote_2_200" class="fnanchor">[2]</a> Scarmiglione, whose Aristotelian treatise on colour -was published in Germany when Rubens was three-and-twenty, observes, -"Painters, with consummate art, lock up the bright colours with dark -ones, and, on the other hand, employ white, the poison of a picture, -very sparingly." (Artificiosissimè pictores claros obscuris obsepiant -et contra candido picturarum veneno summè parcentes, &c.)</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_199" id="Footnote_1_199"></a><a href="#FNanchor_1_199"><span class="label">[1]</span></a> "La Vie des Peintres Flamands," vol. i.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_200" id="Footnote_2_200"></a><a href="#FNanchor_2_200"><span class="label">[2]</span></a> The method he recommended for keeping the colours pure in -the lights, viz. to place the tints next each other unmixed, and then -slightly to unite them, may have degenerated to a methodical manner -in the hands of his followers. Boschini, who speaks of Rubens himself -with due reverence, and is far from confounding him with his imitators, -contrasts such a system with that of the Venetians, and adds that -Titian used to say, "Chi de imbratar colori teme, imbrata e machia -si medemi."—<i>Carta del Navegar</i>, p. 341. The poem of Boschini is in -many respects polemical. He wrote at a time when the Flemish painters, -having adopted and modified the Venetian principles, threatened to -supersede the Italian masters in the opinion of the world. Their -excellence, too, had all the charm of novelty, for in the seventeenth -century Venice produced no remarkable talent, and it was precisely -the age for her to boast of past glories. The contemptuous manner in -which Boschini speaks of the Flemish varnishes, of the fear of mixing -tints, &c., is thus always to be considered with reference to the time -and circumstances. So also his boasting that the Venetian masters -painted without nature, which may be an exaggeration, is pointed at -the <i>Naturalisti</i>, Caravaggio and his followers, who copied nature -literally.</p></div> - - - -<p class="para"><span style="font-size: 0.8em;"><a id="NOTE_KK"></a>NOTE KK</span>.—Par. 903.</p> - -<p>The practice here alluded to is more frequently observable in slight -works by Paul Veronese. His ground was often pure white, and in some -of his works it is left as such. Titian's white ground was covered -with a light warm colour, probably at first, and appears to have -been similar to that to which Armenini gives the preference, namely, -"quella che tira al color di carne chiarissima con un non so che di -fiammeggiante."<a name="FNanchor_1_201" id="FNanchor_1_201"></a><a href="#Footnote_1_201" class="fnanchor">[1]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_201" id="Footnote_1_201"></a><a href="#FNanchor_1_201"><span class="label">[1]</span></a> "Veri Precetti della Pittura," p. 123.</p> - -<p><span class="pagenum"><a name="Page_423" id="Page_423">[Pg 423]</a></span></p></div> - - -<p class="para"><span style="font-size: 0.8em;"><a id="NOTE_LL"></a>NOTE LL.</span>—<a href="#a919">Par. 919.</a></p> - -<p>The notion which the author has here ventured to express may have -been suggested by the remarkable passage in the last canto of Dante's -"Paradiso"—</p> - -<p style="margin-left: 20%;"> -"Nella profonda e chiara sussistenza,<br /> -Dell' alto lume parremi tre giri<br /> -Di tre colori e d'una continenza," &c.<br /> -</p> - -<p>After the concluding paragraph the author inserts a letter from a -landscape-painter, Philipp Otto Runge, which is intended to show that -those who imitate nature may arrive at principles analogous to those of -the "Farbenlehre."</p> - - -<h4>THE END.</h4> - - - - - - - - -<div>*** END OF THE PROJECT GUTENBERG EBOOK 50572 ***</div> - - - -</body> -</html> -</div> - -</div> diff --git a/old/50572-h/images/col_000.jpg b/old/50572-h/images/col_000.jpg Binary files differdeleted file mode 100644 index 0156fd8..0000000 --- a/old/50572-h/images/col_000.jpg +++ /dev/null diff --git a/old/50572-h/images/col_001.jpg b/old/50572-h/images/col_001.jpg Binary files differdeleted file mode 100644 index 37b4162..0000000 --- a/old/50572-h/images/col_001.jpg +++ /dev/null diff --git a/old/50572-h/images/col_002.jpg b/old/50572-h/images/col_002.jpg Binary files differdeleted file mode 100644 index b273fd8..0000000 --- a/old/50572-h/images/col_002.jpg +++ /dev/null diff --git a/old/50572-h/images/col_003.jpg b/old/50572-h/images/col_003.jpg Binary files differdeleted file mode 100644 index c52487e..0000000 --- a/old/50572-h/images/col_003.jpg +++ /dev/null diff --git a/old/50572-h/images/cover.jpg b/old/50572-h/images/cover.jpg Binary files differdeleted file mode 100644 index 0e901d2..0000000 --- a/old/50572-h/images/cover.jpg +++ /dev/null diff --git a/old/old/50572-0.txt b/old/old/50572-0.txt deleted file mode 100644 index fbdca7a..0000000 --- a/old/old/50572-0.txt +++ /dev/null @@ -1,13673 +0,0 @@ -The Project Gutenberg EBook of Goethe's Theory of Colours, by -Johann, Wolfgang von Goethe - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms of -the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: Goethe's Theory of Colours - -Author: Johann, Wolfgang von Goethe - -Translator: Charles Lock Eastlake - -Release Date: November 29, 2015 [EBook #50572] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK GOETHE'S THEORY OF COLOURS *** - - - - -Produced by Annemie Arnst, Clare Graham & Marc D'Hooghe -at http://.freeliterature.org (Images generously made -available by the Internet Archive.) - - - - - -GOETHE'S - -THEORY OF COLOURS; - -TRANSLATED FROM THE GERMAN: - -WITH NOTES BY - -CHARLES LOCK EASTLAKE, R.A., F.R.S. - - - "Cicero varietatem propriè in coloribus nasci, hinc in - alienum migrare existimavit. Certè non alibi natura - copiosius aut majore lasciviâ opes suas commendavit. - Metalla, gemmas, marmora, flores, astra, omnia denique quæ - progenuit suis etiam coloribus distinxit; ut venia debeatur - si quis in tam numerosâ rerum sylvâ caligaverit." - - CELIO CALCAGNINI. - -LONDON: - -JOHN MURRAY, ALBEMARLE STREET. - -1840 - - - - - -TO - -JEREMIAH HARMAN, Esq. - - Dear Sir, - - I dedicate to you the following translation as a testimony - of my sincere gratitude and respect; in doing so, I but - follow the example of Portius, an Italian writer, who - inscribed his translation of Aristotle's Treatise on Colours - to one of the Medici. - - I have the honour to be, - - Dear Sir, - - Your most obliged and obedient Servant, - - C. L. EASTLAKE. - - - - -THE TRANSLATOR'S PREFACE. - - -English writers who have spoken of Goethe's "Doctrine of Colours,"[1] -have generally confined their remarks to those parts of the work in -which he has undertaken to account for the colours of the prismatic -spectrum, and of refraction altogether, on principles different -from the received theory of Newton. The less questionable merits -of the treatise consisting of a well-arranged mass of observations -and experiments, many of which are important and interesting, have -thus been in a great measure overlooked. The translator, aware of -the opposition which the theoretical views alluded to have met with, -intended at first to make a selection of such of the experiments as -seem more directly applicable to the theory and practice of painting. -Finding, however, that the alterations this would have involved would -have been incompatible with a clear and connected view of the author's -statements, he preferred giving the theory itself entire, reflecting, -at the same time, that some scientific readers may be curious to hear -the author speak for himself even on the points at issue. - -In reviewing the history and progress of his opinions and researches, -Goethe tells us that he first submitted his views to the public -in two short essays entitled "Contributions to Optics." Among the -circumstances which he supposes were unfavourable to him on that -occasion, he mentions the choice of his title, observing that by a -reference to optics he must have appeared to make pretensions to a -knowledge of mathematics, a science with which he admits he was very -imperfectly acquainted. Another cause to which he attributes the severe -treatment he experienced, was his having ventured so openly to question -the truth of the established theory: but this last provocation could -not be owing to mere inadvertence on his part; indeed the larger work, -in which he alludes to these circumstances, is still more remarkable -for the violence of his objections to the Newtonian doctrine. - -There can be no doubt, however, that much of the opposition Goethe met -with was to be attributed to the manner as well as to the substance -of his statements. Had he contented himself with merely detailing his -experiments and showing their application to the laws of chromatic -harmony, leaving it to others to reconcile them as they could with the -pre-established system, or even to doubt in consequence, the truth of -some of the Newtonian conclusions, he would have enjoyed the credit -he deserved for the accuracy and the utility of his investigations. -As it was, the uncompromising expression of his convictions only -exposed him to the resentment or silent neglect of a great portion -of the scientific world, so that for a time he could not even obtain -a fair hearing for the less objectionable or rather highly valuable -communications contained in his book. A specimen of his manner of -alluding to the Newtonian theory will be seen in the preface. - -It was quite natural that this spirit should call forth a somewhat -vindictive feeling, and with it not a little uncandid as well as -unsparing criticism. "The Doctrine of Colours" met with this reception -in Germany long before it was noticed in England, where a milder and -fairer treatment could hardly be expected, especially at a time when, -owing perhaps to the limited intercourse with the continent, German -literature was far less popular than it is at present. This last fact, -it is true, can be of little importance in the present instance, -for although the change of opinion with regard to the genius of an -enlightened nation must be acknowledged to be beneficial, it is to be -hoped there is no fashion in science, and the translator begs to state -once for all, that in advocating the neglected merits of the "Doctrine -of Colours," he is far from undertaking to defend its imputed errors. -Sufficient time has, however, now elapsed since the publication of this -work (in 1810) to allow a calmer and more candid examination of its -claims. In this more pleasing task Germany has again for some time led -the way, and many scientific investigators have followed up the hints -and observations of Goethe with a due acknowledgment of the acuteness -of his views.[2] - -It may require more magnanimity in English scientific readers to do -justice to the merits of one who was so open and, in many respects, it -is believed, so mistaken an opponent of Newton; but it must be admitted -that the statements of Goethe contain more useful principles in all -that relates to harmony of colour than any that have been derived from -the established doctrine. It is no derogation of the more important -truths of the Newtonian theory to say, that the views it contains -seldom appear in a form calculated for direct application to the arts. -The principle of contrast, so universally exhibited in nature, so -apparent in the action and re-action of the eye itself, is scarcely -hinted at. The equal pretensions of seven colours, as such, and the -fanciful analogies which their assumed proportions could suggest, have -rarely found favour with the votaries of taste,--indeed they have -long been abandoned even by scientific authorities.[3] And here the -translator stops: he is quite aware that the defects which make the -Newtonian theory so little available for æsthetic application, are -far from invalidating its more important conclusions in the opinion -of most scientific men. In carefully abstaining therefore from any -comparison between the two theories in these latter respects, he may -still be permitted to advocate the clearness and fulness of Goethe's -experiments. The German philosopher reduces the colours to their -origin and simplest elements; he sees and constantly bears in mind, and -sometimes ably elucidates, the phenomena of contrast and gradation, -two principles which may be said to make up the artist's world, and to -constitute the chief elements of beauty. These hints occur mostly in -what may be called the scientific part of the work. On the other hand, -in the portion expressly devoted to the æsthetic application of the -doctrine, the author seems to have made but an inadequate use of his -own principles. - -In that part of the chapter on chemical colours which relates to the -colours of plants and animals, the same genius and originality which -are displayed in the Essays on Morphology, and which have secured -to Goethe undisputed rank among the investigators of nature, are -frequently apparent. - -But one of the most interesting features of Goethe's theory, although -it cannot be a recommendation in a scientific point of view, is, that -it contains, undoubtedly with very great improvements, the general -doctrine of the ancients and of the Italians at the revival of letters. -The translator has endeavoured, in some notes, to point out the -connexion between this theory and the practice of the Italian painters. - -The "Doctrine of Colours," as first published in 1810, consists of -two volumes in 8vo., and sixteen plates, with descriptions, in 4to. -It is divided into three parts, a didactic, a controversial, and an -historical part; the present translation is confined to the first of -these, with such extracts from the other two as seemed necessary, -in fairness to the author, to explain some of his statements. The -polemical and historical parts are frequently alluded to in the -preface and elsewhere in the present work, but it has not been thought -advisable to omit these allusions. No alterations whatever seem to -have been made by Goethe in the didactic portion in later editions, -but he subsequently wrote an additional chapter on entoptic colours, -expressing his wish that it might be inserted in the theory itself at -a particular place which he points out. The form of this additional -essay is, however, very different from that of the rest of the work, -and the translator has therefore merely given some extracts from it in -the appendix. The polemical portion has been more than once omitted in -later editions. - -In the two first parts the author's statements are arranged -numerically, in the style of Bacon's Natural History. This, we are -told, was for the convenience of reference; but many passages are -thus separately numbered which hardly seem to have required it. The -same arrangement is, however, strictly followed in the translation to -facilitate a comparison with the original where it may be desired; and -here the translator observes, that although he has sometimes permitted -himself to make slight alterations, in order to avoid unnecessary -repetition, or to make the author's meaning clearer, he feels that an -apology may rather be expected from him for having omitted so little. -He was scrupulous on this point, having once determined to translate -the whole treatise, partly, as before stated, from a wish to deal -fairly with a controversial writer, and partly because many passages, -not directly bearing on the scientific views, are still characteristic -of Goethe. The observations which the translator has ventured to add -are inserted in the appendix: these observations are chiefly confined -to such of the author's opinions and conclusions as have direct -reference to the arts; they seldom interfere with the scientific -propositions, even where these have been considered most vulnerable. - - -[1] "Farbenlehre"--in the present translation generally rendered -"Theory of Colours." - -[2] Sixteen years after the appearance of the Farbenlehre, Dr. -Johannes Müller devoted a portion of his work, "Zur vergleichenden -Physiologie des Gesichtssinnes des Menschen und der Thiere," to the -critical examination of Goethe's theory. In his introductory remarks he -expresses himself as follows--"For my own part I readily acknowledge -that I have been greatly indebted to Goethe's treatise, and can truly -say that without having studied it for some years in connexion with the -actual phenomena, the present work would hardly have been undertaken. -I have no hesitation in confessing more particularly that I have full -faith in Goethe's statements, where they are merely descriptive of -the phenomena, and where the author does not enter into explanations -involving a decision on the great points of controversy." The names of -Hegel, Schelling, Seebeck, Steffens, may also be mentioned, and many -others might be added, as authorities more or less favourable to the -Farbenlehre. - -[3] "When Newton attempted to reckon up the rays of light decomposed -by the prism," says Sir John Leslie, "and ventured to assign the -famous number _seven_, he was apparently influenced by some lurking -disposition towards mysticism. If any unprejudiced person will fairly -repeat the experiment, he must soon be convinced that the various -coloured spaces which paint the spectrum slide into each other by -indefinite shadings: he may name four or five principal colours, but -the subordinate spaces are evidently so multiplied as to be incapable -of enumeration. The same illustrious mathematician, we can hardly -doubt, was betrayed by a passion for analogy, when he imagined that the -primary colours are distributed over the spectrum after the proportions -of the diatonic scale of music, since those intermediate spaces have -really no precise and defined limits."--_Treatises on Various Subjects -of Natural and Chemical Philosophy_, p. 59. - - - - -PREFACE TO THE FIRST EDITION OF 1810. - - -It may naturally be asked whether, in proposing to treat of colours, -light itself should not first engage our attention: to this we briefly -and frankly answer that since so much has already been said on the -subject of light, it can hardly be desirable to multiply repetitions by -again going over the same ground. - -Indeed, strictly speaking, it is useless to attempt to express the -nature of a thing abstractedly. Effects we can perceive, and a complete -history of those effects would, in fact, sufficiently define the -nature of the thing itself. We should try in vain to describe a man's -character, but let his acts be collected and an idea of the character -will be presented to us. - -The colours are acts of light; its active and passive modifications: -thus considered we may expect from them some explanation respecting -light itself. Colours and light, it is true, stand in the most intimate -relation to each other, but we should think of both as belonging to -nature as a whole, for it is nature as a whole which manifests itself -by their means in an especial manner to the sense of sight. - -The completeness of nature displays itself to another sense in a -similar way. Let the eye be closed, let the sense of hearing be -excited, and from the lightest breath to the wildest din, from the -simplest sound to the highest harmony, from the most vehement and -impassioned cry to the gentlest word of reason, still it is Nature that -speaks and manifests her presence, her power, her pervading life and -the vastness of her relations; so that a blind man to whom the infinite -visible is denied, can still comprehend an infinite vitality by means -of another organ. - -And thus as we descend the scale of being, Nature speaks to other -senses--to known, misunderstood, and unknown senses: so speaks she with -herself and to us in a thousand modes. To the attentive observer she -is nowhere dead nor silent; she has even a secret agent in inflexible -matter, in a metal, the smallest portions of which tell us what -is passing in the entire mass. However manifold, complicated, and -unintelligible this language may often seem to us, yet its elements -remain ever the same. With light poise and counterpoise, Nature -oscillates within her prescribed limits, yet thus arise all the -varieties and conditions of the phenomena which are presented to us in -space and time. - -Infinitely various are the means by which we become acquainted with -these general movements and tendencies: now as a simple repulsion and -attraction, now as an upsparkling and vanishing light, as undulation -in the air, as commotion in matter, as oxydation and de-oxydation; but -always, uniting or separating, the great purpose is found to be to -excite and promote existence in some form or other. - -The observers of nature finding, however, that this poise and -counterpoise are respectively unequal in effect, have endeavoured to -represent such a relation in terms. They have everywhere remarked and -spoken of a greater and lesser principle, an action and resistance, -a doing and suffering, an advancing and retiring, a violent and -moderating power; and thus a symbolical language has arisen, which, -from its close analogy, may be employed as equivalent to a direct and -appropriate terminology. - -To apply these designations, this language of Nature to the subject -we have undertaken: to enrich and amplify this language by means of -the theory of colours and the variety of their phenomena, and thus -facilitate the communication of higher theoretical views, was the -principal aim of the present treatise. - -The work itself is divided into three parts. The first contains the -outline of a theory of colours. In this, the innumerable cases which -present themselves to the observer are collected under certain leading -phenomena, according to an arrangement which will be explained in -the Introduction; and here it may be remarked, that although we have -adhered throughout to experiment, and throughout considered it as our -basis, yet the theoretical views which led to the arrangement alluded -to, could not but be stated. It is sometimes unreasonably required by -persons who do not even themselves attend to such a condition, that -experimental information should be submitted without any connecting -theory to the reader or scholar, who is himself to form his conclusions -as he may list. Surely the mere inspection of a subject can profit us -but little. Every act of seeing leads to consideration, consideration -to reflection, reflection to combination, and thus it may be said that -in every attentive look on nature we already theorise. But in order to -guard against the possible abuse of this abstract view, in order that -the practical deductions we look to should be really useful, we should -theorise without forgetting that we are so doing, we should theorise -with mental self-possession, and, to use a bold word, with irony. - -In the second part[1] we examine the Newtonian theory; a theory which -by its ascendancy and consideration has hitherto impeded a free inquiry -into the phenomena of colours. We combat that hypothesis, for although -it is no longer found available, it still retains a traditional -authority in the world. Its real relations to its subject will require -to be plainly pointed out; the old errors must be cleared away, if the -theory of colours is not still to remain in the rear of so many other -better investigated departments of natural science. Since, however, -this second part of our work may appear somewhat dry as regards its -matter, and perhaps too vehement and excited in its manner, we may here -be permitted to introduce a sort of allegory in a lighter style, as a -prelude to that graver portion, and as some excuse for the earnestness -alluded to. - -We compare the Newtonian theory of colours to an old castle, which -was at first constructed by its architect with youthful precipitation; -it was, however, gradually enlarged and equipped by him according -to the exigencies of time and circumstances, and moreover was still -further fortified and secured in consequence of feuds and hostile -demonstrations. - -The same system was pursued by his successors and heirs: their -increased wants within, the harassing vigilance of their opponents -without, and various accidents compelled them in some places to build -near, in others in connexion with the fabric, and thus to extend the -original plan. - -It became necessary to connect all these incongruous parts and -additions by the strangest galleries, halls and passages. All damages, -whether inflicted by the hand of the enemy or the power of time, were -quickly made good. As occasion required, they deepened the moats, -raised the walls, and took care there should be no lack of towers, -battlements, and embrasures. This care and these exertions gave rise -to a prejudice in favour of the great importance of the fortress, -and still upheld that prejudice, although the arts of building and -fortification were by this time very much advanced, and people had -learnt to construct much better dwellings and defences in other cases. -But the old castle was chiefly held in honour because it had never -been taken, because it had repulsed so many assaults, had baffled so -many hostile operations, and had always preserved its virgin renown. -This renown, this influence lasts even now: it occurs to no one that -the old castle is become uninhabitable. Its great duration, its costly -construction, are still constantly spoken of. Pilgrims wend their -way to it; hasty sketches of it are shown in all schools, and it is -thus recommended to the reverence of susceptible youth. Meanwhile, -the building itself is already abandoned; its only inmates are a few -invalids, who in simple seriousness imagine that they are prepared for -war. - -Thus there is no question here respecting a tedious siege or a -doubtful war; so far from it we find this eighth wonder of the world -already nodding to its fall as a deserted piece of antiquity, and -begin at once, without further ceremony, to dismantle it from gable -and roof downwards; that the sun may at last shine into the old nest -of rats and owls, and exhibit to the eye of the wondering traveller -that labyrinthine, incongruous style of building, with its scanty, -make-shift contrivances, the result of accident and emergency, its -intentional artifice and clumsy repairs. Such an inspection will, -however, only be possible when wall after wall, arch after arch, is -demolished, the rubbish being at once cleared away as well as it can be. - -To effect this, and to level the site where it is possible to do -so, to arrange the materials thus acquired, so that they can be -hereafter again employed for a new building, is the arduous duty -we have undertaken in this Second Part. Should we succeed, by a -cheerful application of all possible ability and dexterity, in razing -this Bastille, and in gaining a free space, it is thus by no means -intended at once to cover the site again and to encumber it with a new -structure; we propose rather to make use of this area for the purpose -of passing in review a pleasing and varied series of illustrative -figures. - -The third part is thus devoted to the historical account of early -inquirers and investigators. As we before expressed the opinion that -the history of an individual displays his character, so it may here be -well affirmed that the history of science is science itself. We cannot -clearly be aware of what we possess till we have the means of knowing -what others possessed before us. We cannot really and honestly rejoice -in the advantages of our own time if we know not how to appreciate -the advantages of former periods. But it was impossible to write, or -even to prepare the way for a history of the theory of colours while -the Newtonian theory existed; for no aristocratic presumption has ever -looked down on those who were not of its order, with such intolerable -arrogance as that betrayed by the Newtonian school in deciding on -all that had been done in earlier times and all that was done around -it. With disgust and indignation we find Priestley, in his History -of Optics, like many before and after him, dating the success of all -researches into the world of colours from the epoch of a decomposed ray -of light, or what pretended to be so; looking down with a supercilious -air on the ancient and less modern inquirers, who, after all, had -proceeded quietly in the right road, and who have transmitted to us -observations and thoughts in detail which we can neither arrange better -nor conceive more justly. - -We have a right to expect from one who proposes to give the history of -any science, that he inform us how the phenomena of which it treats -were gradually known, and what was imagined, conjectured, assumed, -or thought respecting them. To state all this in due connexion is by -no means an easy task; need we say that to write a history at all is -always a hazardous affair; with the most honest intention there is -always a danger of being dishonest; for in such an undertaking, a -writer tacitly announces at the outset that he means to place some -things in light, others in shade. The author has, nevertheless, long -derived pleasure from the prosecution of his task: but as it is the -intention only that presents itself to the mind as a whole, while the -execution is generally accomplished portion by portion, he is compelled -to admit that instead of a history he furnishes only materials for -one. These materials consist in translations, extracts, original and -borrowed comments, hints, and notes; a collection, in short, which, if -not answering all that is required, has at least the merit of having -been made with earnestness and interest. Lastly, such materials,--not -altogether untouched it is true, but still not exhausted,--may be more -satisfactory to the reflecting reader in the state in which they are, -as he can easily combine them according to his own judgment. - -This third part, containing the history of the science, does not, -however, thus conclude the subject: a fourth supplementary portion[2] -is added. This contains a recapitulation or revision; with a view -to which, chiefly, the paragraphs are headed numerically. In the -execution of a work of this kind some things may be forgotten, some -are of necessity omitted, so as not to distract the attention, some -can only be arrived at as corollaries, and others may require to be -exemplified and verified: on all these accounts, postscripts, additions -and corrections are indispensable. This part contains, besides, some -detached essays; for example, that on the atmospheric colours; for as -these are introduced in the theory itself without any classification, -they are here presented to the mind's eye at one view. Again, if this -essay invites the reader to consult Nature herself, another is intended -to recommend the artificial aids of science by circumstantially -describing the apparatus which will in future be necessary to assist -researches into the theory of colours. - -In conclusion, it only remains to speak of the plates which are added -at the end of the work;[3] and here we confess we are reminded of that -incompleteness and imperfection which the present undertaking has, -in common with all others of its class; for as a good play can be in -fact only half transmitted to writing, a great part of its effect -depending on the scene, the personal qualities of the actor, the powers -of his voice, the peculiarities of his gestures, and even the spirit -and favourable humour of the spectators; so it is, in a still greater -degree, with a book which treats of the appearances of nature. To be -enjoyed, to be turned to account, Nature herself must be present to -the reader, either really, or by the help of a lively imagination. -Indeed, the author should in such cases communicate his observations -orally, exhibiting the phenomena he describes--as a text, in the -first instance,--partly as they appear to us unsought, partly as they -may be presented by contrivance to serve in particular illustration. -Explanation and description could not then fail to produce a lively -impression. - -The plates which generally accompany works like the present are thus -a most inadequate substitute for all this; a physical phenomenon -exhibiting its effects on all sides is not to be arrested in lines -nor denoted by a section. No one ever dreams of explaining chemical -experiments with figures; yet it is customary in physical researches -nearly allied to these, because the object is thus found to be in -some degree answered. In many cases, however, such diagrams represent -mere notions; they are symbolical resources, hieroglyphic modes of -communication, which by degrees assume the place of the phenomena and -of Nature herself, and thus rather hinder than promote true knowledge. -In the present instance we could not dispense with plates, but we have -endeavoured so to construct them that they may be confidently referred -to for the explanation of the didactic and polemical portions. Some of -these may even be considered as forming part of the apparatus before -mentioned. - -We now therefore refer the reader to the work itself; first, only -repeating a request which many an author has already made in vain, and -which the modern German reader, especially, so seldom grants:-- - - Si quid novisti rectius istis - Candidus imperti; si non, his utere mecum. - - -[1] The Polemical part. - -[2] This preface must have been written before the work was finished, -for at the conclusion of the historical part there is only an apology -for the non-appearance of the supplement here alluded to. - -[3] In the present translation the necessary plates accompany the -text. - - - - -CONTENTS - - Introduction xxxvii - - - PART I. - - PHYSIOLOGICAL COLOURS. - - I. Effects of Light and Darkness on the Eye - II. Effects of Black and White Objects on the Eye - III. Grey Surfaces and Objects - IV. Dazzling Colourless Objects - V. Coloured Objects - VI. Coloured Shadows - VII. Faint Lights - VIII. Subjective Halos - Pathological Colours--Appendix - - - PART II. - - PHYSICAL COLOURS. - - IX. Dioptrical Colours - X. Dioptrical Colours of the First Class - XI. Dioptrical Colours of the Second Class--Refraction - Subjective Experiments - XII. Refraction without the Appearance of Colour - XIII. Conditions of the Appearance of Colour - XIV. Conditions under which the Appearance of Colour increases - XV. Explanation of the foregoing Phenomena - XVI. Decrease of the Appearance of Colour - XVII. Grey Objects displaced by Refraction - XVIII. Coloured Objects displaced by Refraction - XIX. Achromatism and Hyperchromatism - XX. Advantages of Subjective Experiments-- - Transition to the Objective - Objective Experiments - XXI. Refraction without the Appearance of Colour - XXII. Conditions of the Appearance of Colour - XXIII. Conditions of the Increase of Colour - XXIV. Explanation of the foregoing Phenomena - XXV. Decrease of the Appearance of Colour - XXVI. Grey Objects - XXVII. Coloured Objects - XXVIII. Achromatism and Hyperchromatism - XXIX. Combination of Subjective and Objective Experiments - XXX. Transition - XXXI. Catoptrical Colours - XXXII. Paroptical Colours - XXXIII. Epoptical Colours - - - PART III. - - CHEMICAL COLOURS. - - XXXIV. Chemical Contrast - XXXV. White - XXXVI. Black - XXXVII. First Excitation of Colour - XXXVIII. Augmentation of Colour - XXXIX. Culmination - XL. Fluctuation - XLI. Passage through the Whole Scale - XLII. Inversion - XLIII. Fixation - XLIV. Intermixture, Real - XLV. Intermixture, Apparent - XLVI. Communication, Actual - XLVII. Communication, Apparent - XLVIII. Extraction - XLIX. Nomenclature - L. Minerals - LI. Plants - LII. Worms, Insects, Fishes - LIII. Birds - LIV. Mammalia and Human Beings - LV. Physical and Chemical Effects of the Transmission - of Light through Coloured Mediums - LVI. Chemical Effect in Dioptrical Achromatism - - - PART IV. - - GENERAL CHARACTERISTICS. - - The Facility with which Colour appears - The Definite Nature of Colour - Combination of the Two Principles - Augmentation to Red - Junction of the Two Augmented Extremes - Completeness the Result of Variety in Colour - Harmony of the Complete State - Facility with which Colour may be made to tend either to - the Plus or Minus side - Evanescence of Colour - Permanence of Colour - - - PART V. - - RELATION TO OTHER PURSUITS. - - Relation to Philosophy - Relation to Mathematics - Relation to the Technical Operations of the Dyer - Relation to Physiology and Pathology - Relation to Natural History - Relation to General Physics - Relation to the Theory of Music - Concluding Observations on Terminology - - - PART VI. - - EFFECT OF COLOUR WITH REFERENCE TO MORAL ASSOCIATIONS. - - Yellow - Red-Yellow - Yellow-Red - Blue - Red-Blue - Blue-Red - Red - Green - Completeness and Harmony - Characteristic Combinations - Yellow and Blue - Yellow and Red - Blue and Red - Yellow-Red and Blue-Red - Combinations Non-Characteristic - Relation of the Combinations to Light and Dark - Considerations derived from the Evidence of Experience and History - Æsthetic Influence - Chiaro-Scuro - Tendency to Colour - Keeping - Colouring - Colour in General Nature - Colour of Particular Objects - Characteristic Colouring - Harmonious Colouring - Genuine Tone - False Tone - Weak Colouring - The Motley - Dread of Theory - Ultimate Aim - Grounds - Pigments - Allegorical, Symbolical, Mystical Application of Colour - Concluding Observations - - - - -OUTLINE - -OF A - -THEORY OF COLOURS. - - "Si vera nostra sunt aut falsa, erunt talia, licet nostra - per vitam defendimus. Post fata nostra pueri qui nunc ludunt - nostri judices erunt." - - - - -INTRODUCTION. - - -The desire of knowledge is first stimulated in us when remarkable -phenomena attract our attention. In order that this attention be -continued, it is necessary that we should feel some interest in -exercising it, and thus by degrees we become better acquainted with the -object of our curiosity. During this process of observation we remark -at first only a vast variety which presses indiscriminately on our -view; we are forced to separate, to distinguish, and again to combine; -by which means at last a certain order arises which admits of being -surveyed with more or less satisfaction. - -To accomplish this, only in a certain degree, in any department, -requires an unremitting and close application; and we find, for this -reason, that men prefer substituting a general theoretical view, or -some system of explanation, for the facts themselves, instead of taking -the trouble to make themselves first acquainted with cases in detail -and then constructing a whole. - -The attempt to describe and class the phenomena of colours has been -only twice made: first by Theophrastus,[1] and in modern times by -Boyle. The pretensions of the present essay to the third place will -hardly be disputed. - -Our historical survey enters into further details. Here we merely -observe that in the last century such a classification was not to be -thought of, because Newton had based his hypothesis on a phenomenon -exhibited in a complicated and secondary state; and to this the other -cases that forced themselves on the attention were contrived to be -referred, when they could not be passed over in silence; just as an -astronomer would do, if from whim he were to place the moon in the -centre of our system; he would be compelled to make the earth, sun, and -planets revolve round the lesser body, and be forced to disguise and -gloss over the error of his first assumption by ingenious calculations -and plausible statements. - -In our prefatory observations we assumed the reader to be acquainted -with what was known respecting light; here we assume the same with -regard to the eye. We observed that all nature manifests itself by -means of colours to the sense of sight. We now assert, extraordinary as -it may in some degree appear, that the eye sees no form, inasmuch as -light, shade, and colour together constitute that which to our vision -distinguishes object from object, and the parts of an object from each -other. From these three, light, shade, and colour, we construct the -visible world, and thus, at the same time, make painting possible, -an art which has the power of producing on a flat surface a much more -perfect visible world than the actual one can be. - -The eye may be said to owe its existence to light, which calls forth, -as it were, a sense that is akin to itself; the eye, in short, is -formed with reference to light, to be fit for the action of light; the -light it contains corresponding with the light without. - -We are here reminded of a significant adage in constant use with the -ancient Ionian school--"Like is only known by Like;" and again, of the -words of an old mystic writer, which may be thus rendered, "If the eye -were not sunny, how could we perceive light? If God's own strength -lived not in us, how could we delight in Divine things?" This immediate -affinity between light and the eye will be denied by none; to consider -them as identical in substance is less easy to comprehend. It will be -more intelligible to assert that a dormant light resides in the eye, -and that it may be excited by the slightest cause from within or from -without. In darkness we can, by an effort of imagination, call up the -brightest images; in dreams objects appear to us as in broad daylight; -awake, the slightest external action of light is perceptible, and if -the organ suffers an actual shock, light and colours spring forth. -Here, however, those who are wont to proceed according to a certain -method, may perhaps observe that as yet we have not decidedly explained -what colour is. This question, like the definition of light and the -eye, we would for the present evade, and would appeal to our inquiry -itself, where we have circumstantially shown how colour is produced. -We have only therefore to repeat that colour is a law of nature in -relation with the sense of sight. We must assume, too, that every one -has this sense, that every one knows the operation of nature on it, for -to a blind man it would be impossible to speak of colours. - -That we may not, however, appear too anxious to shun such an -explanation, we would restate what has been said as follows: colour is -an elementary phenomenon in nature adapted to the sense of vision; a -phenomenon which, like all others, exhibits itself by separation and -contrast, by commixture and union, by augmentation and neutralization, -by communication and dissolution: under these general terms its nature -may be best comprehended. - -We do not press this mode of stating the subject on any one. Those -who, like ourselves, find it convenient, will readily adopt it; but we -have no desire to enter the lists hereafter in its defence. From time -immemorial it has been dangerous to treat of colour; so much so, that -one of our predecessors ventured on a certain occasion to say, "The ox -becomes furious if a red cloth is shown to him; but the philosopher, -who speaks of colour only in a general way, begins to rave." - -Nevertheless, if we are to proceed to give some account of our work, to -which we have appealed, we must begin by explaining how we have classed -the different conditions under which colour is produced. We found three -modes in which it appears; three classes of colours, or rather three -exhibitions of them all. The distinctions of these classes are easily -expressed. - -Thus, in the first instance, we considered colours, as far as they -may be said to belong to the eye itself, and to depend on an action -and re-action of the organ; next, they attracted our attention as -perceived in, or by means of, colourless mediums; and lastly, where -we could consider them as belonging to particular substances. We have -denominated the first, physiological, the second, physical, the third, -chemical colours. The first are fleeting and not to be arrested; the -next are passing, but still for a while enduring; the last may be made -permanent for any length of time. - -Having separated these classes and kept them as distinct as possible, -with a view to a clear, didactic exposition, we have been enabled at -the same time to exhibit them in an unbroken series, to connect the -fleeting with the somewhat more enduring, and these again with the -permanent hues; and thus, after having carefully attended to a distinct -classification in the first instance, to do away with it again when a -larger view was desirable. - -In a fourth division of our work we have therefore treated generally -what was previously detailed under various particular conditions, and -have thus, in fact, given a sketch for a future theory of colours. We -will here only anticipate our statements so far as to observe, that -light and darkness, brightness and obscurity, or if a more general -expression is preferred, light and its absence, are necessary to the -production of colour. Next to the light, a colour appears which we call -yellow; another appears next to the darkness, which we name blue. When -these, in their purest state, are so mixed that they are exactly equal, -they produce a third colour called green. Each of the two first-named -colours can however of itself produce a new tint by being condensed or -darkened. They thus acquire a reddish appearance which can be increased -to so great a degree that the original blue or yellow is hardly to -be recognised in it: but the intensest and purest red, especially in -physical cases, is produced when the two extremes of the yellow-red -and blue-red are united. This is the actual state of the appearance -and generation of colours. But we can also assume an existing red in -addition to the definite existing blue and yellow, and we can produce -contrariwise, by mixing, what we directly produced by augmentation or -deepening. With these three or six colours, which may be conveniently -included in a circle, the elementary doctrine of colours is alone -concerned. All other modifications, which may be extended to infinity, -have reference more to the application,--have reference to the -technical operations of the painter and dyer, and the various purposes -of artificial life. To point out another general quality, we may -observe that colours throughout are to be considered as half-lights, as -half-shadows, on which account if they are so mixed as reciprocally to -destroy their specific hues, a shadowy tint, a grey, is produced. - -In the fifth division of our inquiry we had proposed to point out -the relations in which we should wish our doctrine of colours to -stand to other pursuits. Important as this part of our work is, it -is perhaps on this very account not so successful as we could wish. -Yet when we reflect that strictly speaking these relations cannot be -described before they exist, we may console ourselves if we have in -some degree failed in endeavouring for the first time to define them. -For undoubtedly we should first wait to see how those whom we have -endeavoured to serve, to whom we have intended to make an agreeable and -useful offering, how such persons, we say, will accept the result of -our utmost exertion: whether they will adopt it, whether they will make -use of it and follow it up, or whether they will repel, reject, and -suffer it to remain unassisted and neglected. - -Meanwhile, we venture to express what we believe and hope. From the -philosopher we believe we merit thanks for having traced the phenomena -of colours to their first sources, to the circumstances under which -they simply appear and are, and beyond which no further explanation -respecting them is possible. It will, besides, be gratifying to him -that we have arranged the appearances described in a form that admits -of being easily surveyed, even should he not altogether approve of the -arrangement itself. - -The medical practitioner, especially him whose study it is to watch -over the organ of sight, to preserve it, to assist its defects and to -cure its disorders, we reckon to make especially our friend. In the -chapter on the physiological colours, in the Appendix relating to those -that are more strictly pathological, he will find himself quite in his -own province. We are not without hopes of seeing the physiological -phenomena,--a hitherto neglected, and, we may add, most important -branch of the theory of colours,--completely investigated through the -exertions of those individuals who in our own times are treating this -department with success. - -The investigator of nature should receive us cordially, since we -enable him to exhibit the doctrine of colours in the series of other -elementary phenomena, and at the same time enable him to make use of a -corresponding nomenclature, nay, almost the same words and designations -as under the other rubrics. It is true we give him rather more trouble -as a teacher, for the chapter of colours is not now to be dismissed -as heretofore with a few paragraphs and experiments; nor will the -scholar submit to be so scantily entertained as he has hitherto been, -without murmuring. On the other hand, an advantage will afterwards -arise out of this: for if the Newtonian doctrine was easily learnt, -insurmountable difficulties presented themselves in its application. -Our theory is perhaps more difficult to comprehend, but once known, all -is accomplished, for it carries its application along with it. - -The chemist who looks upon colours as indications by which he may -detect the more secret properties of material things, has hitherto -found much inconvenience in the denomination and description of -colours; nay, some have been induced after closer and nicer examination -to look upon colour as an uncertain and fallacious criterion in -chemical operations. Yet we hope by means of our arrangement and the -nomenclature before alluded to, to bring colour again into credit, -and to awaken the conviction that a progressive, augmenting, mutable -quality, a quality which admits of alteration even to inversion, is not -fallacious, but rather calculated to bring to light the most delicate -operations of nature. - -In looking a little further round us, we are not without fears -that we may fail to satisfy another class of scientific men. By an -extraordinary combination of circumstances the theory of colours -has been drawn into the province and before the tribunal of the -mathematician, a tribunal to which it cannot be said to be amenable. -This was owing to its affinity with the other laws of vision which the -mathematician was legitimately called upon to treat. It was owing, -again, to another circumstance: a great mathematician had investigated -the theory of colours, and having been mistaken in his observations as -an experimentalist, he employed the whole force of his talent to give -consistency to this mistake. Were both these circumstances considered, -all misunderstanding would presently be removed, and the mathematician -would willingly co-operate with us, especially in the physical -department of the theory. - -To the practical man, to the dyer, on the other hand, our labour must -be altogether acceptable; for it was precisely those who reflected on -the facts resulting from the operations of dyeing who were the least -satisfied with the old theory: they were the first who perceived the -insufficiency of the Newtonian doctrine. The conclusions of men are -very different according to the mode in which they approach a science -or branch of knowledge; from which side, through which door they -enter. The literally practical man, the manufacturer, whose attention -is constantly and forcibly called to the facts which occur under his -eye, who experiences benefit or detriment from the application of his -convictions, to whom loss of time and money is not indifferent, who -is desirous of advancing, who aims at equalling or surpassing what -others have accomplished,--such a person feels the unsoundness and -erroneousness of a theory much sooner than the man of letters, in whose -eyes words consecrated by authority are at last equivalent to solid -coin; than the mathematician, whose formula always remains infallible, -even although the foundation on which it is constructed may not square -with it. Again, to carry on the figure before employed, in entering -this theory from the side of painting, from the side of æsthetic[2] -colouring generally, we shall be found to have accomplished a -most thank-worthy office for the artist. In the sixth part we have -endeavoured to define the effects of colour as addressed at once to -the eye and mind, with a view to making them more available for the -purposes of art. Although much in this portion, and indeed throughout, -has been suffered to remain as a sketch, it should be remembered that -all theory can in strictness only point out leading principles, under -the guidance of which, practice may proceed with vigour and be enabled -to attain legitimate results. - - -[1] The treatise to which the author alludes in more generally ascribed -to Aristotle.--T. - -[2] Æsthetic--belonging to taste as mere internal sense, from -αἰσθάνομαι, to feel; the word was first used by Wolf.--T. - - - - -PART I. - - -PHYSIOLOGICAL COLOURS. - - -1. - -We naturally place these colours first, because they belong altogether, -or in a great degree, to the _subject_[1]--to the eye itself. They -are the foundation of the whole doctrine, and open to our view the -chromatic harmony on which so much difference of opinion has existed. -They have been hitherto looked upon as extrinsic and casual, as -illusion and infirmity: their appearances have been known from ancient -date; but, as they were too evanescent to be arrested, they were -banished into the region of phantoms, and under this idea have been -very variously described. - -2. - -Thus they are called _colores adventicii_ by Boyle; _imaginarii_ and -_phantastici_ by Rizetti; by Buffon, _couleurs accidentelles_; by -Scherfer, _scheinfarben_ (apparent colours); _ocular illusions_ and -_deceptions of sight_ by many; by Hamberger, _vitia fugitiva_; by -Darwin, _ocular spectra_. - -3. - -We have called them physiological because they belong to the eye in a -healthy state; because we consider them as the necessary conditions -of vision; the lively alternating action of which, with reference to -external objects and a principle within it, is thus plainly indicated. - -4. - -To these we subjoin the pathological colours, which, like all -deviations from a constant law, afford a more complete insight into the -nature of the physiological colours. - - -EFFECTS OF LIGHT AND DARKNESS ON THE EYE. - - -5. - -The retina, after being acted upon by light or darkness, is found to be -in two different states, which are entirely opposed to each other. - -6. - -If we keep the eyes open in a totally dark place, a certain sense of -privation is experienced. The organ is abandoned to itself; it retires -into itself. That stimulating and grateful contact is wanting by means -of which it is connected with the external world, and becomes part of a -whole. - -7. - -If we look on a white, strongly illumined surface, the eye is dazzled, -and for a time is incapable of distinguishing objects moderately -lighted. - -8. - -The whole of the retina is acted on in each of these extreme states, -and thus we can only experience one of these effects at a time. In -the one case (6) we found the organ in the utmost relaxation and -susceptibility; in the other (7) in an overstrained state, and scarcely -susceptible at all. - -9. - -If we pass suddenly from the one state to the other, even without -supposing these to be the extremes, but only, perhaps, a change from -bright to dusky, the difference is remarkable, and we find that the -effects last for some time. - -10. - -In passing from bright daylight to a dusky place we distinguish nothing -at first: by degrees the eye recovers its susceptibility; strong eyes -sooner than weak ones; the former in a minute, while the latter may -require seven or eight minutes. - -11. - -The fact that the eye is not susceptible to faint impressions of -light, if we pass from light to comparative darkness, has led to -curious mistakes in scientific observations. Thus an observer, whose -eyes required some time to recover their tone, was long under the -impression that rotten wood did not emit light at noon-day, even in a -dark room. The fact was, he did not see the faint light, because he was -in the habit of passing from bright sunshine to the dark room, and only -subsequently remained so long there that the eye had time to recover -itself. - -The same may have happened to Doctor Wall, who, in the daytime, even in -a dark room, could hardly perceive the electric light of amber. - -Our not seeing the stars by day, as well as the improved appearance of -pictures seen through a double tube, is also to be attributed to the -same cause. - -12. - -If we pass from a totally dark place to one illumined by the sun, we -are dazzled. In coming from a lesser degree of darkness to light that -is not dazzling, we perceive all objects clearer and better: hence eyes -that have been in a state of repose are in all cases better able to -perceive moderately distinct appearances. - -Prisoners who have been long confined in darkness acquire so great -a susceptibility of the retina, that even in the dark (probably a -darkness very slightly illumined) they can still distinguish objects. - -13. - -In the act which we call seeing, the retina is at one and the same time -in different and even opposite states. The greatest brightness, short -of dazzling, acts near the greatest darkness. In this state we at once -perceive all the intermediate gradations of _chiaro-scuro_, and all the -varieties of hues. - -14. - -We will proceed in due order to consider and examine these elements of -the visible world, as well as the relation in which the organ itself -stands to them, and for this purpose we take the simplest objects. - - -[1] The German distinction between _subject_ and _object_ is so -generally understood and adopted, that it is hardly necessary to -explain that the subject is the _individual_, in this case the -_beholder_; the object, _all that is without him_.--T. - - - - -II. - - -EFFECTS OF BLACK AND WHITE OBJECTS ON THE EYE. - - -15. - -In the same manner as the retina generally is affected by brightness -and darkness, so it is affected by single bright or dark objects. -If light and dark produce different results on the whole retina, so -black and white objects seen at the same time produce the same states -together which light and dark occasioned in succession. - -16. - -A dark object appears smaller than a bright one of the same size. Let -a white disk be placed on a black ground, and a black disk on a white -ground, both being exactly similar in size; let them be seen together -at some distance, and we shall pronounce the last to be about a fifth -part smaller than the other. If the black circle be made larger by so -much, they will appear equal.[1] - -17. - -Thus Tycho de Brahe remarked that the moon in conjunction (the darker -state) appears about a fifth part smaller than when in opposition -(the bright full state). The first crescent appears to belong to a -larger disk than the remaining dark portion, which can sometimes be -distinguished at the period of the new moon. Black dresses make people -appear smaller than light ones. Lights seen behind an edge make an -apparent notch in it. A ruler, behind which the flame of a light just -appears, seems to us indented. The rising or setting sun appears to -make a notch in the horizon. - -[Illustration] - -18. - -Black, as the equivalent of darkness, leaves the organ in a state of -repose; white, as the representative of light, excites it. We may, -perhaps, conclude from the above experiment (16) that the unexcited -retina, if left to itself, is drawn together, and occupies a less space -than in its active state, produced by the excitement of light. - -Hence Kepler says very beautifully: "Certum est vel in retinâ caussâ -picturæ, vel in spiritibus caussâ impressionis, exsistere dilatationem -lucidorum."--_Paralip. in Vitellionem_, p. 220. Scherfer expresses a -similar conjecture.--Note A. - -19. - -However this may be, both impressions derived from such objects remain -in the organ itself, and last for some time, even when the external -cause is removed. In ordinary experience we scarcely notice this, for -objects are seldom presented to us which are very strongly relieved -from each other, and we avoid looking at those appearances that dazzle -the sight. In glancing from one object to another, the succession of -images appears to us distinct; we are not aware that some portion of -the impression derived from the object first contemplated passes to -that which is next looked at. - -20. - -If in the morning, on waking, when the eye is very susceptible, we look -intently at the bars of a window relieved against the dawning sky, and -then shut our eyes or look towards a totally dark place, we shall see a -dark cross on a light ground before us for some time. - -21. - -Every image occupies a certain space on the retina, and of course a -greater or less space in proportion as the object is seen near or at a -distance. If we shut the eyes immediately after looking at the sun we -shall be surprised to find how small the image it leaves appears. - -22. - -If, on the other hand, we turn the open eye towards the side of a -room, and consider the visionary image in relation to other objects, -we shall always see it larger in proportion to the distance of the -surface on which it is thrown. This is easily explained by the laws of -perspective, according to which a small object near covers a great one -at a distance. - -23. - -The duration of these visionary impressions varies with the powers -or structure of the eye in different individuals, just as the time -necessary for the recovery of the tone of the retina varies in passing -from brightness to darkness (10): it can be measured by minutes and -seconds, indeed much more exactly than it could formerly have been -by causing a lighted linstock to revolve rapidly, so as to appear a -circle.--Note B. - -24. - -But the force with which an impinging light impresses the eye is -especially worthy of attention. The image of the sun lasts longest; -other objects, of various degrees of brightness, leave the traces of -their appearance on the eye for a proportionate time. - -25. - -These images disappear by degrees, and diminish at once in distinctness -and in size. - -26. - -They are reduced from the contour inwards, and the impression on some -persons has been that in square images the angles become gradually -blunted till at last a diminished round image floats before the eye. - -27. - -Such an image, when its impression is no more observable, can, -immediately after, be again revived on the retina by opening and -shutting the eye, thus alternately exciting and resting it. - -28. - -Images may remain on the retina in morbid affections of the eye for -fourteen, seventeen minutes, or even longer. This indicates extreme -weakness of the organ, its inability to recover itself; while visions -of persons or things which are the objects of love or aversion indicate -the connexion between sense and thought. - -29. - -If, while the image of the window-bars before mentioned lasts, we -look upon a light grey surface, the cross will then appear light -and the panes dark. In the first case (20) the image was like the -original picture, so that the visionary impression also could continue -unchanged; but in the present instance our attention is excited by a -contrary effect being produced. Various examples have been given by -observers of nature. - -30. - -The scientific men who made observations in the Cordilleras saw a -bright appearance round the shadows of their heads on some clouds. This -example is a case in point; for, while they fixed their eyes on the -dark shadow, and at the same time moved from the spot, the compensatory -light image appeared to float round the real dark one. If we look at -a black disk on a light grey surface, we shall presently, by changing -the direction of the eyes in the slightest degree, see a bright halo -floating round the dark circle. - -A similar circumstance happened to myself: for while, as I sat in the -open air, I was talking to a man who stood at a little distance from me -relieved on a grey sky, it appeared to me, as I slightly altered the -direction of my eyes, after having for some time looked fixedly at him, -that his head was encircled with a dazzling light. - -In the same way probably might be explained the circumstance that -persons crossing dewy meadows at sunrise see a brightness round each -other's heads[2]; the brightness in this case may be also iridescent, -as the phenomena of refraction come into the account. - -Thus again it has been asserted that the shadows of a balloon thrown on -clouds were bordered with bright and somewhat variegated circles. - -Beccaria made use of a paper kite in some experiments on electricity. -Round this kite appeared a small shining cloud varying in size; the -same brightness was even observed round part of the string. Sometimes -it disappeared, and if the kite moved faster the light appeared to -float to and fro for a few moments on the place before occupied. This -appearance, which could not be explained by those who observed it at -the time, was the image which the eye retained of the kite relieved as -a dark mass on a bright sky; that image being changed into a light mass -on a comparatively dark background. - -In optical and especially in chromatic experiments, where the observer -has to do with bright lights whether colourless or coloured, great care -should be taken that the spectrum which the eye retains in consequence -of a previous observation does not mix with the succeeding one, and -thus affect the distinctness and purity of the impression. - -31. - -These appearances have been explained as follows: That portion of the -retina on which the dark cross (29) was impressed is to be considered -in a state of repose and susceptibility. On this portion therefore the -moderately light surface acted in a more lively manner than on the rest -of the retina, which had just been impressed with the light through -the panes, and which, having thus been excited by a much stronger -brightness, could only view the grey surface as a dark. - -32. - -This mode of explanation appears sufficient for the cases in question, -but, in the consideration of phenomena hereafter to be adduced, we are -forced to trace the effects to higher sources. - -33. - -The eye after sleep exhibits its vital elasticity more especially by -its tendency to alternate its impressions, which in the simplest form -change from dark to light, and from light to dark. The eye cannot for a -moment remain in a particular state determined by the object it looks -upon. On the contrary, it is forced to a sort of opposition, which, in -contrasting extreme with extreme, intermediate degree with intermediate -degree, at the same time combines these opposite impressions, and thus -ever tends to a whole, whether the impressions are successive, or -simultaneous and confined to one image. - -34. - -Perhaps the peculiarly grateful sensation which we experience in -looking at the skilfully treated chiaro-scuro of colourless pictures -and similar works of art arises chiefly from the _simultaneous_ -impression of a whole, which by the organ itself is sought, rather than -arrived at, in _succession_, and which, whatever may be the result, can -never be arrested. - - -[1] Plate 1. fig. 1. - -[2] See the Life of Benvenuto Cellini, vol. i. p. 453. Milan edition, -1806.--T. - - - - -III. - - -GREY SURFACES AND OBJECTS. - - -35. - -A moderate light is essential to many chromatic experiments. This can -be presently obtained by surfaces more or less grey, and thus we have -at once to make ourselves acquainted with this simplest kind of middle -tint, with regard to which it is hardly necessary to observe, that -in many cases a white surface in shadow, or in a low light, may be -considered equivalent to a grey. - -36. - -Since a grey surface is intermediate between brightness and darkness, -it admits of our illustrating a phenomenon before described (29) by an -easy experiment. - -37. - -Let a black object be held before a grey surface, and let the -spectator, after looking steadfastly at it, keep his eyes unmoved while -it is taken away: the space it occupied appears much lighter. Let a -white object be held up in the same manner: on taking it away the space -it occupied will appear much darker than the rest of the surface. Let -the spectator in both cases turn his eyes this way and that on the -surface, the visionary images will move in like manner. - -38. - -A grey object on a black ground appears much brighter than the same -object on a white ground. If both comparisons are seen together the -spectator can hardly persuade himself that the two greys are identical. -We believe this again to be a proof of the great excitability of the -retina, and of the silent resistance which every vital principle is -forced to exhibit when any definite or immutable state is presented to -it. Thus inspiration already presupposes expiration; thus every systole -its diastole. It is the universal formula of life which manifests -itself in this as in all other cases. When darkness is presented to -the eye it demands brightness, and _vice versâ_: it shows its vital -energy, its fitness to receive the impression of the object, precisely -by spontaneously tending to an opposite state. - - - - -IV. - - -DAZZLING COLOURLESS OBJECTS. - - -39. - -If we look at a dazzling, altogether colourless object, it makes a -strong lasting impression, and its after-vision is accompanied by an -appearance of colour. - -40. - -Let a room be made as dark as possible; let there be a circular opening -in the window-shutter about three inches in diameter, which may be -closed or not at pleasure. The sun being suffered to shine through this -on a white surface, let the spectator from some little distance fix his -eyes on the bright circle thus admitted. The hole being then closed, -let him look towards the darkest part of the room; a circular image -will now be seen to float before him. The middle of this circle will -appear bright, colourless, or somewhat yellow, but the border will at -the same moment appear red. - -After a time this red, increasing towards the centre, covers the whole -circle, and at last the bright central point. No sooner, however, is -the whole circle red than the edge begins to be blue, and the blue -gradually encroaches inwards on the red. When the whole is blue -the edge becomes dark and colourless. This darker edge again slowly -encroaches on the blue till the whole circle appears colourless. The -image then becomes gradually fainter, and at the same time diminishes -in size. Here again we see how the retina recovers itself by a -succession of vibrations after the powerful external impression it -received. (25, 26.) - -41. - -By several repetitions similar in result, I found the comparative -duration of these appearances in my own case to be as follows:-- - -I looked on the bright circle five seconds, and then, having closed -the aperture, saw the coloured visionary circle floating before me. -After thirteen seconds it was altogether red; twenty-nine seconds -next elapsed till the whole was blue, and forty-eight seconds till -it appeared colourless. By shutting and opening the eye I constantly -revived the image, so that it did not quite disappear till seven -minutes had elapsed. - -Future observers may find these periods shorter or longer as their -eyes may be stronger or weaker (23), but it would be very remarkable -if, notwithstanding such variations, a corresponding proportion as to -relative duration should be found to exist. - -42. - -But this remarkable phenomenon no sooner excites our attention than we -observe a new modification of it. - -If we receive the impression of the bright circle as before, and then -look on a light grey surface in a moderately lighted room, an image -again floats before us; but in this instance a dark one: by degrees it -is encircled by a green border that gradually spreads inwards over the -whole circle, as the red did in the former instance. As soon as this -has taken place a dingy yellow appears, and, filling the space as the -blue did before, is finally lost in a negative shade. - -43. - -These two experiments may be combined by placing a black and a white -plane surface next each other in a moderately lighted room, and then -looking alternately on one and the other as long as the impression of -the light circle lasts: the spectator will then perceive at first a red -and green image alternately, and afterwards the other changes. After a -little practice the two opposite colours may be perceived at once, by -causing the floating image to fall on the junction of the two planes. -This can be more conveniently done if the planes are at some distance, -for the spectrum then appears larger. - -44. - -I happened to be in a forge towards evening at the moment when a -glowing mass of iron was placed on the anvil; I had fixed my eyes -steadfastly on it, and, turning round, I looked accidentally into an -open coal-shed: a large red image now floated before my eyes, and, as I -turned them from the dark opening to the light boards of which the shed -was constructed, the image appeared half green, half red, according as -it had a lighter or darker ground behind it. I did not at that time -take notice of the subsequent changes of this appearance. - -45. - -The after-vision occasioned by a total dazzling of the retina -corresponds with that of a circumscribed bright object. The red colour -seen by persons who are dazzled with snow belongs to this class of -phenomena, as well as the singularly beautiful green colour which dark -objects seem to wear after looking long on white paper in the sun. The -details of such experiments may be investigated hereafter by those -whose young eyes are capable of enduring such trials further for the -sake of science. - -46. - -With these examples we may also class the black letters which in the -evening light appear red. Perhaps we might insert under the same -category the story that drops of blood appeared on the table at which -Henry IV. of France had seated himself with the Duc de Guise to play at -dice. - - - - -V. - - -COLOURED OBJECTS. - - -47. - -We have hitherto seen the physiological colours displayed in the -after-vision of colourless bright objects, and also in the after-vision -of general colourless brightness; we shall now find analogous -appearances if a given colour be presented to the eye: in considering -this, all that has been hitherto detailed must be present to our -recollection. - -48. - -The impression of coloured objects remains in the eye like that of -colourless ones, but in this case the energy of the retina, stimulated -as it is to produce the opposite colour, will be more apparent. - -49. - -Let a small piece of bright-coloured paper or silk stuff be held before -a moderately lighted white surface; let the observer look steadfastly -on the small coloured object, and let it be taken away after a time -while his eyes remain unmoved; the spectrum of another colour will then -be visible on the white plane. The coloured paper may be also left in -its place while the eye is directed to another part of the white plane; -the same spectrum will be visible there too, for it arises from an -image which now belongs to the eye. - -50. - -In order at once to see what colour will be evoked by this contrast, -the chromatic circle[1] may be referred to. The colours are here -arranged in a general way according to the natural order, and the -arrangement will be found to be directly applicable in the present -case; for the colours diametrically opposed to each other in this -diagram are those which reciprocally evoke each other in the eye. Thus, -yellow demands purple; orange, blue; red, green; and _vice versâ_: thus -again all intermediate gradations reciprocally evoke each other; the -simpler colour demanding the compound, and _vice versâ_.--Note C. - -51. - -The cases here under consideration occur oftener than we are aware in -ordinary life; indeed, an attentive observer sees these appearances -everywhere, while, on the other hand, the uninstructed, like our -predecessors, consider them as temporary visual defects, sometimes -even as symptoms of disorders in the eye, thus exciting serious -apprehensions. A few remarkable instances may here be inserted. - -52. - -I had entered an inn towards evening, and, as a well-favoured girl, -with a brilliantly fair complexion, black hair, and a scarlet bodice, -came into the room, I looked attentively at her as she stood before me -at some distance in half shadow. As she presently afterwards turned -away, I saw on the white wall, which was now before me, a black face -surrounded with a bright light, while the dress of the perfectly -distinct figure appeared of a beautiful sea-green. - -53. - -Among the materials for optical experiments, there are portraits with -colours and shadows exactly opposite to the appearance of nature. The -spectator, after having looked at one of these for a time, will see the -visionary figure tolerably true to nature. This is conformable to the -same principles, and consistent with experience, for, in the former -instance, a negress with a white head-dress would have given me a -white face surrounded with black. In the case of the painted figures, -however, which are commonly small, the parts are not distinguishable by -every one in the after-image. - -54. - -A phenomenon which has before excited attention among the observers of -nature is to be attributed, I am persuaded, to the same cause. - -It has been stated that certain flowers, towards evening in summer, -coruscate, become phosphorescent, or emit a momentary light. Some -persons have described their observation of this minutely. I had often -endeavoured to witness it myself, and had even resorted to artificial -contrivances to produce it. - -On the 19th of June, 1799, late in the evening, when the twilight was -deepening into a clear night, as I was walking up and down the garden -with a friend, we very distinctly observed a flame-like appearance -near the oriental poppy, the flowers of which are remarkable for their -powerful red colour. We approached the place and looked attentively -at the flowers, but could perceive nothing further, till at last, by -passing and repassing repeatedly, while we looked sideways on them, we -succeeded in renewing the appearance as often as we pleased. It proved -to be a physiological phenomenon, such as others we have described, and -the apparent coruscation was nothing but the spectrum of the flower in -the compensatory blue-green colour. - -In looking directly at a flower the image is not produced, but it -appears immediately as the direction of the eye is altered. Again, by -looking sideways on the object, a double image is seen for a moment, -for the spectrum then appears near and on the real object. - -The twilight accounts for the eye being in a perfect state of repose, -and thus very susceptible, and the colour of the poppy is sufficiently -powerful in the summer twilight of the longest days to act with -full effect and produce a compensatory image. I have no doubt these -appearances might be reduced to experiment, and the same effect -produced by pieces of coloured paper. Those who wish to take the most -effectual means for observing the appearance in nature--suppose in a -garden--should fix the eyes on the bright flowers selected for the -purpose, and, immediately after, look on the gravel path. This will -be seen studded with spots of the opposite colour. The experiment is -practicable on a cloudy day, and even in the brightest sunshine, for -the sun-light, by enhancing the brilliancy of the flower, renders it -fit to produce the compensatory colour sufficiently distinct to be -perceptible even in a bright light. Thus, peonies produce beautiful -green, marigolds vivid blue spectra. - -55. - -As the opposite colour is produced by a constant law in experiments -with coloured objects on portions of the retina, so the same effect -takes place when the whole retina is impressed with a single colour. We -may convince ourselves of this by means of coloured glasses. If we look -long through a blue pane of glass, everything will afterwards appear -in sunshine to the naked eye, even if the sky is grey and the scene -colourless. In like manner, in taking off green spectacles, we see all -objects in a red light. Every decided colour does a certain violence to -the eye, and forces the organ to opposition. - -56. - -We have hitherto seen the opposite colours producing each other -successively on the retina: it now remains to show by experiment -that the same effects can exist simultaneously. If a coloured object -impinges on one part of the retina, the remaining portion at the same -moment has a tendency to produce the compensatory colour. To pursue -a former experiment, if we look on a yellow piece of paper placed -on a white surface, the remaining part of the organ has already a -tendency to produce a purple hue on the colourless surface: in this -case the small portion of yellow is not powerful enough to produce -this appearance distinctly, but, if a white paper is placed on a yellow -wall, we shall see the white tinged with a purple hue. - -57. - -Although this experiment may be made with any colours, yet red and -green are particularly recommended for it, because these colours seem -powerfully to evoke each other. Numerous instances occur in daily -experience. If a green paper is seen through striped or flowered -muslin, the stripes or flowers will appear reddish. A grey building -seen through green pallisades appears in like manner reddish. A -modification of this tint in the agitated sea is also a compensatory -colour: the light side of the waves appears green in its own colour, -and the shadowed side is tinged with the opposite hue. The different -direction of the waves with reference to the eye produces the same -effect. Objects seen through an opening in a red or green curtain -appear to wear the opposite hue. These appearances will present -themselves to the attentive observer on all occasions, even to an -unpleasant degree. - -58. - -Having made ourselves acquainted with the simultaneous exhibition of -these effects in direct cases, we shall find that we can also observe -them by indirect means. If we place a piece of paper of a bright -orange colour on the white surface, we shall, after looking intently -at it, scarcely perceive the compensatory colour on the rest of the -surface: but when we take the orange paper away, and when the blue -spectrum appears in its place, immediately as this spectrum becomes -fully apparent, the rest of the surface will be overspread, as if by a -flash, with a reddish-yellow light, thus exhibiting to the spectator -in a lively manner the productive energy of the organ, in constant -conformity with the same law. - -59. - -As the compensatory colours easily appear, where they do not exist in -nature, near and after the original opposite ones, so they are rendered -more intense where they happen to mix with a similar real hue. In a -court which was paved with grey limestone flags, between which grass -had grown, the grass appeared of an extremely beautiful green when -the evening clouds threw a scarcely perceptible reddish light on the -pavement. In an opposite case we find, in walking through meadows, -where we see scarcely anything but green, the stems of trees and the -roads often gleam with a reddish hue. This tone is not uncommon in -the works of landscape painters, especially those who practice in -water-colours: they probably see it in nature, and thus, unconsciously -imitating it, their colouring is criticised as unnatural. - -60. - -These phenomena are of the greatest importance, since they direct our -attention to the laws of vision, and are a necessary preparation for -future observations on colours. They show that the eye especially -demands completeness, and seeks to eke out the colorific circle in -itself. The purple or violet colour suggested by yellow contains red -and blue; orange, which responds to blue, is composed of yellow and -red; green, uniting blue and yellow, demands red; and so through all -gradations of the most complicated combinations. That we are compelled -in this case to assume three leading colours has been already remarked -by other observers. - -61. - -When in this completeness the elements of which it is composed are -still appreciable by the eye, the result is justly called harmony. We -shall subsequently endeavour to show how the theory of the harmony of -colours may be deduced from these phenomena, and how, simply through -these qualities, colours may be capable of being applied to æsthetic -purposes. This will be shown when we have gone through the whole circle -of our observations, returning to the point from which we started. - - -[1] Plate 1, fig. 3. - - - - -VI. - - -COLOURED SHADOWS. - - -62. - -Before, however, we proceed further, we have yet to observe some very -remarkable cases of the vivacity with which the suggested colours -appear in the neighbourhood of others: we allude to coloured shadows. -To arrive at these we first turn our attention to shadows that are -colourless or negative. - -63. - -A shadow cast by the sun, in its full brightness, on a white surface, -gives us no impression of colour; it appears black, or, if a contrary -light (here assumed to differ only in degree) can act upon it, it is -only weaker, half-lighted, grey. - -64. - -Two conditions are necessary for the existence of coloured shadows: -first, that the principal light tinge the white surface with some hue; -secondly, that a contrary light illumine to a certain extent the cast -shadow. - -65. - -Let a short, lighted candle be placed at twilight on a sheet of white -paper. Between it and the declining daylight let a pencil be placed -upright, so that its shadow thrown by the candle may be lighted, but -not overcome, by the weak daylight: the shadow will appear of the most -beautiful blue. - -66. - -That this shadow is blue is immediately evident; but we can only -persuade ourselves by some attention that the white paper acts as a -reddish yellow, by means of which the complemental blue is excited in -the eye.--Note D. - -67. - -In all coloured shadows, therefore, we must presuppose a colour excited -or suggested by the hue of the surface on which the shadow is thrown. -This may be easily found to be the case by attentive consideration, but -we may convince ourselves at once by the following experiment. - -68. - -Place two candles at night opposite each other on a white surface; hold -a thin rod between them upright, so that two shadows be cast by it; -take a coloured glass and hold it before one of the lights, so that -the white paper appear coloured; at the same moment the shadow cast by -the coloured light and slightly illumined by the colourless one will -exhibit the complemental hue. - -69. - -An important consideration suggests itself here, to which we shall -frequently have occasion to return. Colour itself is a degree of -darkness _σκιερόν_; hence Kircher is perfectly right in calling it -_lumen opacatum_. As it is allied to shadow, so it combines readily -with it; it appears to us readily in and by means of shadow the -moment a suggesting cause presents itself. We could not refrain from -adverting at once to a fact which we propose to trace and develop -hereafter.--Note E. - -70. - -Select the moment in twilight when the light of the sky is still -powerful enough to cast a shadow which cannot be entirely effaced by -the light of a candle. The candle may be so placed that a double shadow -shall be visible, one from the candle towards the daylight, and another -from the daylight towards the candle. If the former is blue the latter -will appear orange-yellow: this orange-yellow is in fact, however, only -the yellow-red light of the candle diffused over the whole paper, and -which _becomes visible in shadow_. - -71. - -This is best exemplified by the former experiment with two candles and -coloured glasses. - -The surprising readiness with which shadow assumes a colour will again -invite our attention in the further consideration of reflections and -elsewhere. - -72. - -Thus the phenomena of coloured shadows may be traced to their cause -without difficulty. Henceforth let any one who sees an instance of -the kind observe only with what hue the light surface on which they -are thrown is tinged. Nay, the colour of the shadow may be considered -as a chromatoscope of the illumined surface, for the spectator may -always assume the colour of the light to be the opposite of that of the -shadow, and by an attentive examination may ascertain this to be the -fact in every instance. - -73. - -These appearances have been a source of great perplexity to former -observers: for, as they were remarked chiefly in the open air, where -they commonly appeared blue, they were attributed to a certain inherent -blue or blue colouring quality in the air. The inquirer can, however, -convince himself, by the experiment with the candle in a room, that no -kind of blue light or reflection is necessary to produce the effect -in question. The experiment may be made on a cloudy day with white -curtains drawn before the light, and in a room where no trace of blue -exists, and the blue shadow will be only so much the more beautiful. - -74. - -De Saussure, in the description of his ascent of Mont Blanc, says, "A -second remark, which may not be uninteresting, relates to the colour of -the shadows. These, notwithstanding the most attentive observation, we -never found dark blue, although this had been frequently the case in -the plain. On the contrary, in fifty-nine instances we saw them once -yellowish, six times pale bluish, eighteen times colourless or black, -and thirty-four times pale violet. Some natural philosophers suppose -that these colours arise from accidental vapours diffused in the air, -which communicate their own hues to the shadows; not that the colours -of the shadows are occasioned by the reflection of any given sky colour -or interposition of any given air colour: the above observations seem -to favour this opinion." The instances given by De Saussure may be now -explained and classed with analogous examples without difficulty. - -At a great elevation the sky was generally free from vapours, the sun -shone in full force on the snow, so that it appeared perfectly white -to the eye: in this case they saw the shadows quite colourless. If the -air was charged with a certain degree of vapour, in consequence of -which the light snow would assume a yellowish tone, the shadows were -violet-coloured, and this effect, it appears, occurred oftenest. They -saw also bluish shadows, but this happened less frequently; and that -the blue and violet were pale was owing to the surrounding brightness, -by which the strength of the shadows was mitigated. Once only they -saw the shadow yellowish: in this case, as we have already seen (70), -the shadow is cast by a colourless light, and slightly illumined by a -coloured one. - -75. - -In travelling over the Harz in winter, I happened to descend from the -Brocken towards evening; the wide slopes extending above and below me, -the heath, every insulated tree and projecting rock, and all masses of -both, were covered with snow or hoar-frost. The sun was sinking towards -the Oder ponds[1]. During the day, owing to the yellowish hue of the -snow, shadows tending to violet had already been observable; these -might now be pronounced to be decidedly blue, as the illumined parts -exhibited a yellow deepening to orange. - -But as the sun at last was about to set, and its rays, greatly -mitigated by the thicker vapours, began to diffuse a most beautiful -red colour over the whole scene around me, the shadow colour changed -to a green, in lightness to be compared to a sea-green, in beauty to -the green of the emerald. The appearance became more and more vivid: -one might have imagined oneself in a fairy world, for every object had -clothed itself in the two vivid and so beautifully harmonising colours, -till at last, as the sun went down, the magnificent spectacle was lost -in a grey twilight, and by degrees in a clear moon-and-starlight night. - -76. - -One of the most beautiful instances of coloured shadows may be -observed during the full moon. The candle-light and moon-light may be -contrived to be exactly equal in force; both shadows may be exhibited -with equal strength and clearness, so that both colours balance each -other perfectly. A white surface being placed opposite the full moon, -and the candle being placed a little on one side at a due distance, -an opaque body is held before the white plane, A double shadow will -then be seen: that cast by the moon and illumined by the candle-light -will be a powerful red-yellow; and contrariwise, that cast by the -candle and illumined by the moon will appear of the most beautiful -blue. The shadow, composed of the union of the two shadows, where -they cross each other, is black. The yellow shadow (74) cannot perhaps -be exhibited in a more striking manner. The immediate vicinity of -the blue and the interposing black shadow make the appearance the -more agreeable. It will even be found, if the eye dwells long on -these colours, that they mutually evoke and enhance each other, the -increasing red in the one still producing its contrast, viz. a kind of -sea-green. - -77. - -We are here led to remark that in this, and in all cases, a moment or -two may perhaps be necessary to produce the complemental colour. The -retina must be first thoroughly impressed with the demanding hue before -the responding one can be distinctly observable. - -78. - -When divers are under water, and the sunlight shines into the -diving-bell, everything is seen in a red light (the cause of which -will be explained hereafter), while the shadows appear green. The very -same phenomenon which I observed on a high mountain (75) is presented -to others in the depths of the sea, and thus Nature throughout is in -harmony with herself. - -79. - -Some observations and experiments which equally illustrate what has -been stated with regard to coloured objects and coloured shadows may -be here added. Let a white paper blind be fastened inside the window -on a winter evening; in this blind let there be an opening, through -which the snow of some neighbouring roof can be seen. Towards dusk let -a candle be brought into the room; the snow seen through the opening -will then appear perfectly blue, because the paper is tinged with warm -yellow by the candle-light. The snow seen through the aperture is here -equivalent to a shadow illumined by a contrary light (76), and may also -represent a grey disk on a coloured surface (56). - -80. - -Another very interesting experiment may conclude these examples. If we -take a piece of green glass of some thickness, and hold it so that the -window bars be reflected in it, they will appear double owing to the -thickness of the glass. The image which is reflected from the under -surface of the glass will be green; the image which is reflected from -the upper surface, and which should be colourless, will appear red. - -The experiment may be very satisfactorily made by pouring water into -a vessel, the inner surface of which can act as a mirror; for both -reflections may first be seen colourless while the water is pure, and -then by tinging it, they will exhibit two opposite hues. - - -[1] Reservoirs in which water is collected from various small streams, -to work the mines.--T. - - - - -VII. - - -FAINT LIGHTS. - - -81. - -Light, in its full force, appears purely white, and it gives this -impression also in its highest degree of dazzling splendour. Light, -which is not so powerful, can also, under various conditions, remain -colourless. Several naturalists and mathematicians have endeavoured to -measure its degrees--Lambert, Bouguer, Rumford. - -82. - -Yet an appearance of colour presently manifests itself in fainter -lights, for in their relation to absolute light they resemble the -coloured spectra of dazzling objects (39). - -83. - -A light of any kind becomes weaker, either when its own force, from -whatever cause, is diminished, or when the eye is so circumstanced or -placed, that it cannot be sufficiently impressed by the action of the -light. Those appearances which may be called objective, come under the -head of physical colours. We will only advert here to the transition -from white to red heat in glowing iron. We may also observe that the -flames of lights at night appear redder in proportion to their distance -from the eye.--Note F. - -84. - -Candle-light at night acts as yellow when seen near; we can perceive -this by the effect it produces on other colours. At night a pale yellow -is hardly to be distinguished from white; blue approaches to green, and -rose-colour to orange. - -85. - -Candle-light at twilight acts powerfully as a yellow light: this -is best proved by the purple blue shadows which, under these -circumstances, are evoked by the eye. - -86. - -The retina may be so excited by a strong light that it cannot perceive -fainter lights (11): if it perceive these they appear coloured: hence -candle-light by day appears reddish, thus resembling, in its relation -to fuller light, the spectrum of a dazzling object; nay, if at night we -look long and intently on the flame of a light, it appears to increase -in redness. - -87. - -There are faint lights which, notwithstanding their moderate lustre, -give an impression of a white, or, at the most, of a light yellow -appearance on the retina; such as the moon in its full splendour. -Rotten wood has even a kind of bluish light. All this will hereafter be -the subject of further remarks. - -88. - -If at night we place a light near a white or greyish wall so that the -surface be illumined from this central point to some extent, we find, -on observing the spreading light at some distance, that the boundary of -the illumined surface appears to be surrounded with a yellow circle, -which on the outside tends to red-yellow. We thus observe that when -light direct or reflected does not act in its full force, it gives an -impression of yellow, of reddish, and lastly even of red. Here we find -the transition to halos which we are accustomed to see in some mode or -other round luminous points. - - - - -VIII. - - -SUBJECTIVE HALOS. - - -89. - -Halos may be divided into subjective and objective. The latter will -be considered under the physical colours; the first only belong here. -These are distinguished from the objective halos by the circumstance -of their vanishing when the point of light which produces them on the -retina is covered. - -90. - -We have before noticed the impression of a luminous object on the -retina, and seen that it appears larger: but the effect is not at -an end here, it is not confined to the impression of the image; an -expansive action also takes place, spreading from the centre. - -91. - -That a nimbus of this kind is produced round the luminous image in the -eye may be best seen in a dark room, if we look towards a moderately -large opening in the window-shutter. In this case the bright image is -surrounded by a circular misty light. I saw such a halo bounded by a -yellow and yellow-red circle on opening my eyes at dawn, on an occasion -when I passed several nights in a bed-carriage. - -92. - -Halos appear most vivid when the eye is susceptible from having been in -a state of repose. A dark background also heightens their appearance. -Both causes account for our seeing them so strong if a light is -presented to the eyes on waking at night. These conditions were -combined when Descartes after sleeping, as he sat in a ship, remarked -such a vividly-coloured halo round the light. - -93. - -A light must shine moderately, not dazzle, in order to produce the -impression of a halo in the eye; at all events the halos of dazzling -lights cannot be observed. We see a splendour of this kind round the -image of the sun reflected from the surface of water. - -94. - -A halo of this description, attentively observed, is found to be -encircled towards its edge with a yellow border: but even here the -expansive action, before alluded to, is not at an end, but appears -still to extend in varied circles. - -95. - -Several cases seem to indicate a circular action of the retina, whether -owing to the round form of the eye itself and its different parts, or -to some other cause. - -96. - -If the eye is pressed only in a slight degree from the inner corner, -darker or lighter circles appear. At night, even without pressure, we -can sometimes perceive a succession of such circles emerging from, or -spreading over, each other. - -97. - -We have already seen that a yellow border is apparent round the white -space illumined by a light placed near it. This may be a kind of -objective halo. (88.) - -98. - -Subjective halos may be considered as the result of a conflict between -the light and a living surface. From the conflict between the exciting -principle and the excited, an undulating motion arises, which may be -illustrated by a comparison with the circles on water. The stone thrown -in drives the water in all directions; the effect attains a maximum, -it reacts, and being opposed, continues under the surface. The effect -goes on, culminates again, and thus the circles are repeated. If we -have ever remarked the concentric rings which appear in a glass of -water on trying to produce a tone by rubbing the edge; if we call to -mind the intermitting pulsations in the reverberations of bells, we -shall approach a conception of what may take place on the retina when -the image of a luminous object impinges on it, not to mention that as -a living and elastic structure, it has already a circular principle in -its organisation.--Note G. - -99. - -The bright circular space which appears round the shining object -is yellow, ending in red: then follows a greenish circle, which is -terminated by a red border. This appears to be the usual phenomenon -where the luminous body is somewhat considerable in size. These halos -become greater the more distant we are from the luminous object. - -100. - -Halos may, however, appear extremely small and numerous when the -impinging image is minute, yet powerful, in its effect. The experiment -is best made with a piece of gold-leaf placed on the ground and -illumined by the sun. In these cases the halos appear in variegated -rays. The iridescent appearance produced in the eye when the sun -pierces through the leaves of trees seems also to belong to the same -class of phenomena. - - - - -PATHOLOGICAL COLOURS. - - -APPENDIX. - - -101. - -We are now sufficiently acquainted with the physiological colours to -distinguish them from the pathological. We know what appearances belong -to the eye in a healthy state, and are necessary to enable the organ to -exert its complete vitality and activity. - -102. - -Morbid phenomena indicate in like manner the existence of organic -and physical laws: for if a living being deviates from those rules -with reference to which it is constructed, it still seeks to agree -with the general vitality of nature in conformity with general laws, -and throughout its whole course still proves the constancy of those -principles on which the universe has existed, and by which it is held -together. - -103. - -We will here first advert to a very remarkable state in which the -vision of many persons is found to be. As it presents a deviation -from the ordinary mode of seeing colours, it might be fairly classed -under morbid impressions; but as it is consistent in itself, as it -often occurs, may extend to several members of a family, and probably -does not admit of cure, we may consider it as bordering only on the -nosological cases, and therefore place it first. - -104. - -I was acquainted with two individuals not more than twenty years of -age, who were thus affected: both had bluish-grey eyes, an acute sight -for near and distant objects, by day-light and candle-light, and their -mode of seeing colours was in the main quite similar. - -105. - -They agreed with the rest of the world in denominating white, black, -and grey in the usual manner. Both saw white untinged with any hue. One -saw a somewhat brownish appearance in black, and in grey a somewhat -reddish tinge. In general they appeared to have a very delicate -perception of the gradations of light and dark. - -106. - -They appeared to see yellow, red-yellow, and yellow-red,[1] like -others: in the last case they said they saw the yellow passing as it -were over the red as if glazed: some thickly-ground carmine, which had -dried in a saucer, they called red. - -107. - -But now a striking difference presented itself. If the carmine was -passed thinly over the white saucer, they would compare the light -colour thus produced to the colour of the sky, and call it blue. If -a rose was shown them beside it, they would, in like manner, call it -blue; and in all the trials which were made, it appeared that they -could not distinguish light blue from rose-colour. They confounded -rose-colour, blue, and violet on all occasions: these colours only -appeared to them to be distinguished from each other by delicate shades -of lighter, darker, intenser, or fainter appearance. - -108. - -Again they could not distinguish green from dark orange, nor, more -especially, from a red brown. - -109. - -If any one, accidentally conversing with these individuals, happened -to question them about surrounding objects, their answers occasioned -the greatest perplexity, and the interrogator began to fancy his own -wits were out of order. With some method we may, however, approach to a -nearer knowledge of the law of this deviation from the general law. - -110. - -These persons, as may be gathered from what has been stated, saw fewer -colours than other people: hence arose the confusion of different -colours. They called the sky rose-colour, and the rose blue, or -_vice versâ_. The question now is: did they see both blue or both -rose-colour? did they see green orange, or orange green? - -111. - -This singular enigma appears to solve itself, if we assume that they -saw no blue, but, instead of it, a light pure red, a rose-colour. -We can comprehend what would be the result of this by means of the -chromatic diagram. - -112. - -If we take away blue from the chromatic circle we shall miss violet and -green as well. Pure red occupies the place of blue and violet, and in -again mixing with yellow the red produces orange where green should be. - -113. - -Professing to be satisfied with this mode of explanation, we have named -this remarkable deviation from ordinary vision "Acyanoblepsia."[2] -We have prepared some coloured figures for its further elucidation, -and in explaining these we shall add some further details. Among the -examples will be found a landscape, coloured in the mode in which the -individuals alluded to appeared to see nature: the sky rose-colour, and -all that should be green varying from yellow to brown red, nearly as -foliage appears to us in autumn[3].--Note H. - -114. - -We now proceed to speak of morbid and other extraordinary affections -of the retina, by which the eye may be susceptible of an appearance -of light without external light, reserving for a future occasion the -consideration of galvanic light. - -115. - -If the eye receives a blow, sparks seem to spread from it. In some -states of body, again, when the blood is heated, and the system much -excited, if the eye is pressed first gently, and then more and more -strongly, a dazzling and intolerable light may be excited. - -116. - -If those who have been recently couched experience pain and heat in the -eye, they frequently see fiery flashes and sparks: these symptoms last -sometimes for a week or fortnight, or till the pain and heat diminish. - -117. - -A person suffering from ear-ache saw sparks and balls of light in the -eye during each attack, as long as the pain lasted. - -118. - -Persons suffering from worms often experience extraordinary appearances -in the eye, sometimes sparks of fire, sometimes spectres of light, -sometimes frightful figures, which they cannot by an effort of the will -cease to see: sometimes these appearances are double. - -119. - -Hypochondriacs frequently see dark objects, such as threads, hairs, -spiders, flies, wasps. These appearances also exhibit themselves in the -incipient hard cataract. Many see semi-transparent small tubes, forms -like wings of insects, bubbles of water of various sizes, which fall -slowly down, if the eye is raised: sometimes these congregate together -so as to resemble the spawn of frogs; sometimes they appear as complete -spheres, sometimes in the form of lenses. - -120. - -As light appeared, in the former instances, without external light, -so also these images appear without corresponding external objects. -The images are sometimes transient, sometimes they last during -the patient's life. Colour, again, frequently accompanies these -impressions: for hypochondriacs often see yellow-red stripes in the -eye: these are generally more vivid and numerous in the morning, or -when lasting. - -121. - -We have before seen that the impression of any object may remain for a -time in the eye: this we have found to be a physiological phenomenon -(23): the excessive duration of such an impression, on the other band, -may be considered as morbid. - -122. - -The weaker the organ the longer the impression of the image lasts. -The retina does not so soon recover itself; and the effect may be -considered as a kind of paralysis (28). - -123. - -This is not to be wondered at in the case of dazzling lights. If any -one looks at the sun, he may retain the image in his eyes for several -days. Boyle relates an instance of ten years. - -124. - -The same takes place, in a certain degree, with regard to objects -that are not dazzling. Büsch relates of himself that the image of an -engraving, complete in all its parts, was impressed on his eye for -seventeen minutes. - -125. - -A person inclined to fulness of blood retained the image of a bright -red calico, with white spots, many minutes in the eye, and saw it float -before everything like a veil. It only disappeared by rubbing the eye -for some time. - -126. - -Scherfer observes that the red colour, which is the consequence of a -powerful impression of light, may last for some hours. - -127. - -As we can produce an appearance of light on the retina by pressure -on the eyeball, so by a gentle pressure a red colour appears, thus -corresponding with the after-image of an impression of light. - -128. - -Many sick persons, on awaking, see everything in the colour of the -morning sky, as if through a red veil: so, if in the evening they doze -and wake again, the same appearance presents itself. It remains for -some minutes, and always disappears if the eye is rubbed a little. Red -stars and balls sometimes accompany the impression. This state may last -for a considerable time. - -129. - -The aëronauts, particularly Zambeccari and his companions, relate -that they saw the moon blood-red at the highest elevation. As they -had ascended above the vapours of the earth, through which we see the -moon and sun naturally of such a colour, it may be suspected that this -appearance may be classed with the pathological colours. The senses, -namely, may be so influenced by an unusual state, that the whole -nervous system, and particularly the retina, may sink into a kind of -inertness and inexcitability. Hence it is not impossible that the moon -might act as a very subdued light, and thus produce the impression of -the red colour. The sun even appeared blood-red to the aëronauts of -Hamburgh. - -If those who are at some elevation in a balloon scarcely hear each -other speak, may not this, too, be attributed to the inexcitable state -of the nerves as well as to the thinness of the air? - -130. - -Objects are often seen by sick persons in variegated colours. Boyle -relates an instance of a lady, who, after a fall by which an eye was -bruised, saw all objects, but especially white objects, glittering in -colours, even to an intolerable degree. - -131. - -Physicians give the name of "Chrupsia" to an affection of the sight, -occurring in typhoid maladies. In these cases the patients state that -they see the boundaries of objects coloured where light and dark meet. -A change probably takes place in the humours of the eye, through which -their achromatism is affected. - -132. - -In cases of milky cataract, a very turbid crystalline lens causes -the patient to see a red light. In a case of this kind, which was -treated by the application of electricity, the red light changed by -degrees to yellow, and at last to white, when the patient again began -to distinguish objects. These changes of themselves warranted the -conclusion that the turbid state of the lens was gradually approaching -the transparent state. We shall be enabled easily to trace this effect -to its source as soon as we become better acquainted with the physical -colours. - -133. - -If again it may be assumed that a jaundiced patient sees through -an actually yellow-coloured humour, we are at once referred to the -department of chemical colours, and it is thus evident that we can only -thoroughly investigate the chapter of pathological colours when we -have made ourselves acquainted with the whole range of the remaining -phenomena. What has been adduced may therefore suffice for the present, -till we resume the further consideration of this portion of our subject. - -134. - -In conclusion we may, however, at once advert to some peculiar states -or dispositions of the organ. - -There are painters who, instead of rendering the colours of nature, -diffuse a general tone, a warm or cold hue, over the picture. In some, -again, a predilection for certain colours displays itself; in others a -want of feeling for harmony. - -135. - -Lastly, it is also worthy of remark, that savage nations, uneducated -people, and children have a great predilection for vivid colours; -that animals are excited to rage by certain colours; that people of -refinement avoid vivid colours in their dress and the objects that are -about them, and seem inclined to banish them altogether from their -presence.--Note I. - - -[1] It has been found necessary to follow the author's nomenclature -throughout--T. - -[2] Non-perception of blue. - -[3] It has not been thought necessary to copy the plates here referred -to.--T. - - - - -PART II. - - -PHYSICAL COLOURS. - - -136. - -We give this designation to colours which are produced by certain -material mediums: these mediums, however, have no colour themselves, -and may be either transparent, semi-transparent yet transmitting light, -or altogether opaque. The colours in question are thus produced in the -eye through such external given causes, or are merely reflected to -the eye when by whatever means they are already produced without us. -Although we thus ascribe to them a certain objective character, their -distinctive quality still consists in their being transient, and not to -be arrested. - -137. - -They are called by former investigators _colores apparentes, fluxi, -fugitivi, phantastici, falsi, variantes_. They are also called -_speciosi_ and _emphatici_, on account of their striking splendour. -They are immediately connected with the physiological colours, and -appear to have but little more reality: for, while in the production -of the physiological colours the eye itself was chiefly efficient, and -we could only perceive the phenomena thus evoked within ourselves, -but not without us, we have now to consider the fact that colours are -produced in the eye by means of colourless objects; that we thus too -have a colourless surface before us which is acted upon as the retina -itself is, and that we can perceive the appearance produced upon it -without us. In such a process, however, every observation will convince -us that we have to do with colours in a progressive and mutable, but -not in a final or complete, state. - -138. - -Hence, in directing our attention to these physical colours, we find -it quite possible to place an objective phenomenon beside a subjective -one, and often by means of the union of the two successfully to -penetrate farther into the nature of the appearance. - -139. - -Thus, in the observations by which we become acquainted with the -physical colours, the eye is not to be considered as acting alone; nor -is the light ever to be considered in immediate relation with the eye: -but we direct our attention especially to the various effects produced -by mediums, those mediums being themselves colourless. - -140. - -Light under these circumstances may be affected by three conditions. -First, when it flashes back from the surface of a medium; in -considering which _catoptrical_ experiments invite our attention. -Secondly, when it passes by the edge of a medium: the phenomena -thus produced were formerly called _perioptical_; we prefer the -term _paroptical_. Thirdly, when it passes through either a merely -light-transmitting or an actually transparent body; thus constituting -a class of appearances on which _dioptrical_ experiments are founded. -We have called a fourth class of physical colours _epoptical_, as the -phenomena exhibit themselves on the colourless surface of bodies under -various conditions, without previous or actual dye (βαφή).--Note K. - -141. - -In examining these categories with reference to our three leading -divisions, according to which we consider the phenomena of colours in a -physiological, physical, or chemical view, we find that the catoptrical -colours are closely connected with the physiological; the paroptical -are already somewhat more distinct and independent; the dioptrical -exhibit themselves as entirely and strictly physical, and as having -a decidedly objective character; the epoptical, although still only -apparent, may be considered as the transition to the chemical colours. - -142. - -If we were desirous of prosecuting our investigation strictly in the -order of nature, we ought to proceed according to the classification -which has just been made; but in didactic treatises it is not of -so much consequence to connect as to duly distinguish the various -divisions of a subject, in order that at last, when every single -class and case has been presented to the mind, the whole may be -embraced in one comprehensive view. We therefore turn our attention -forthwith to the dioptrical class, in order at once to give the reader -the full impression of the physical colours, and to exhibit their -characteristics the more strikingly. - - - - -IX. - - -DIOPTRICAL COLOURS. - - -143. - -Colours are called dioptrical when a colourless medium is necessary -to produce them; the medium must be such that light and darkness can -act through it either on the eye or on opposite surfaces. It is thus -required that the medium should be transparent, or at least capable, to -a certain degree, of transmitting light. - -144. - -According to these conditions we divide the dioptrical phenomena into -two classes, placing in the first those which are produced by means of -imperfectly transparent, yet light-transmitting mediums; and in the -second such as are exhibited when the medium is in the highest degree -transparent. - - - - -X. - -DIOPTRICAL COLOURS OF THE FIRST CLASS. - - -145. - -Space, if we assume it to be empty, would have the quality of absolute -transparency to our vision. If this space is filled so that the eye -cannot perceive that it is so, there exists a more or less material -transparent medium, which may be of the nature of air and gas, may be -fluid or even solid. - -146. - -The pure and light-transmitting semi-transparent medium is only an -accumulated form of the transparent medium. It may therefore be -presented to us in three modes. - -147. - -The extreme degree of this accumulation is white; the simplest, -brightest, first, opaque occupation of space. - -148. - -Transparency itself, empirically considered, is already the first -degree of the opposite state. The intermediate degrees from this point -to opaque white are infinite. - -149. - -At whatever point short of opacity we arrest the thickening medium, it -exhibits simple and remarkable phenomena when placed in relation with -light and darkness. - -150. - -The highest degree of light, such as that of the sun, of phosphorus -burning in oxygen, is dazzling and colourless: so the light of the -fixed stars is for the most part colourless. This light, however, seen -through a medium but very slightly thickened, appears to us yellow. -If the density of such a medium be increased, or if its volume become -greater, we shall see the light gradually assume a yellow-red hue, -which at last deepens to a ruby-colour.--Note L. - -151. - -If on the other hand darkness is seen through a semi-transparent -medium, which is itself illumined by a light striking on it, a blue -colour appears: this becomes lighter and paler as the density of the -medium is increased, but on the contrary appears darker and deeper the -more transparent the medium becomes: in the least degree of dimness -short of absolute transparence, always supposing a perfectly colourless -medium, this deep blue approaches the most beautiful violet. - -152. - -If this effect takes place in the eye as here described, and may -thus be pronounced to be subjective, it remains further to convince -ourselves of this by objective phenomena. For a light thus mitigated -and subdued illumines all objects in like manner with a yellow, -yellow-red, or red hue; and, although the effect of darkness through -the non-transparent medium does not exhibit itself so powerfully, yet -the blue sky displays itself in the camera obscura very distinctly on -white paper, as well as every other material colour. - -153. - -In examining the cases in which this important leading phenomenon -appears, we naturally mention the atmospheric colours first: most of -these may be here introduced in order. - -154. - -The sun seen through a certain degree of vapour appears with a yellow -disk; the centre is often dazzlingly yellow when the edges are already -red. The orb seen through a thick yellow mist appears ruby-red (as was -the case in 1794, even in the north); the same appearance is still -more decided, owing to the state of the atmosphere, when the scirocco -prevails in southern climates: the clouds generally surrounding the sun -in the latter case are of the same colour, which is reflected again on -all objects. - -The red hues of morning and evening are owing to the same cause. The -sun is announced by a red light, in shining through a greater mass -of vapours. The higher he rises, the yellower and brighter the light -becomes. - -155. - -If the darkness of infinite space is seen through atmospheric vapours -illumined by the day-light, the blue colour appears. On high mountains -the sky appears by day intensely blue, owing to the few thin vapours -that float before the endless dark space: as soon as we descend in the -valleys, the blue becomes lighter; till at last, in certain regions, -and in consequence of increasing vapours, it altogether changes to a -very pale blue. - -156. - -The mountains, in like manner, appear to us blue; for, as we see them -at so great a distance that we no longer distinguish the local tints, -and as no light reflected from their surface acts on our vision, they -are equivalent to mere dark objects, which, owing to the interposed -vapours, appear blue. - -157. - -So we find the shadowed parts of nearer objects are blue when the air -is charged with thin vapours. - -158. - -The snow-mountains, on the other hand, at a great distance, still -appear white, or approaching to a yellowish hue, because they act on -our eyes as brightness seen through atmospheric vapour. - -159. - -The blue appearance at the lower part of the flame of a candle belongs -to the same class of phenomena. If the flame be held before a white -ground, no blue will be seen, but this colour will immediately appear -if the flame is opposed to a black ground. This phenomenon may be -exhibited most strikingly with a spoonful of lighted spirits of wine. -We may thus consider the lower part of the flame as equivalent to the -vapour which, although infinitely thin, is still apparent before the -dark surface; it is so thin, that one may easily see to read through -it: on the other hand, the point of the flame which conceals objects -from our sight is to be considered as a self-illuminating body. - -160. - -Lastly, smoke is also to be considered as a semi-transparent medium, -which appears to us yellow or reddish before a light ground, but blue -before a dark one. - -161. - -If we now turn our attention to fluid mediums, we find that water, -deprived in a very slight degree of its transparency, produces the same -effects. - -162. - -The infusion of the lignum nephriticum (guilandina Linnæi), which -formerly excited so much attention, is only a semi-transparent liquor, -which in dark wooden cups must appear blue, but held towards the sun in -a transparent glass must exhibit a yellow appearance. - -163. - -A drop of scented water, of spirit varnish, of several metallic -solutions, may be employed to give various degrees of opacity to water -for such experiments. Spirit of soap perhaps answers best. - -164. - -The bottom of the sea appears to divers of a red colour in bright -sunshine: in this case the water, owing to its depth, acts as a -semi-transparent medium. Under these circumstances, they find the -shadows green, which is the complemental colour. - -165. - -Among solid mediums the opal attracts our attention first: its colours -are, at least, partly to be explained by the circumstance that it is, -in fact, a semi-transparent medium, through which sometimes light, -sometimes dark, substrata are visible. - -166. - -For these experiments, however, the opal-glass (vitrum astroides, -girasole) is the most desirable material. It is prepared in various -ways, and its semi-opacity is produced by metallic oxydes. The same -effect is produced also by melting pulverised and calcined bones -together with the glass, on which account it is also known by the name -of _beinglas_; but, prepared in this mode, it easily becomes too opaque. - -167. - -This glass may be adapted for experiments in various ways: it may -either be made in a very slight degree non-transparent, in which case -the light seen through various layers placed one upon the other may -be deepened from the lightest yellow to the deepest red, or, if made -originally more opaque, it may be employed in thinner or thicker -laminæ. The experiments may be successfully made in both ways: in -order, however, to see the bright blue colour, the glass should neither -be too opaque nor too thick. For, as it is quite natural that darkness -must act weakly through the semi-transparent medium, so this medium, if -too thick, soon approaches whiteness. - -168. - -Panes of glass throw a yellow light on objects through those parts -where they happen to be semi-opaque, and these same parts appear blue -if we look at a dark object through them. - -169. - -Smoked glass may be also mentioned here, and is, in like manner, to be -considered as a semi-opaque medium. It exhibits the sun more or less -ruby-coloured; and, although this appearance may be attributed to the -black-brown colour of the soot, we may still convince ourselves that a -semi-transparent medium here acts if we hold such a glass moderately -smoked, and lit by the sun on the unsmoked side, before a dark object, -for we shall then perceive a bluish appearance. - -170. - -A striking experiment may be made in a dark room with sheets of -parchment. If we fasten a piece of parchment before the opening in the -window-shutter when the sun shines, it will appear nearly white; by -adding a second, a yellowish colour appears, which still increases as -more leaves are added, till at last it changes to red. - -171. - -A similar effect, owing to the state of the crystalline lens in milky -cataract, has been already adverted to (131). - -172. - -Having now, in tracing these phenomena, arrived at the effect of a -degree of opacity scarcely capable of transmitting light, we may here -mention a singular appearance which was owing to a momentary state of -this kind. - -A portrait of a celebrated theologian had been painted some years -before the circumstance to which we allude, by an artist who was known -to have considerable skill in the management of his materials. The -very reverend individual was represented in a rich velvet dress, which -was not a little admired, and which attracted the eye of the spectator -almost more than the face. The picture, however, from the effect of the -smoke of lamps and dust, had lost much of its original vivacity. It -was, therefore, placed in the hands of a painter, who was to clean it, -and give it a fresh coat of varnish. This person began his operations -by carefully washing the picture with a sponge: no sooner, however, -had he gone over the surface once or twice, and wiped away the first -dirt, than to his amazement the black velvet dress changed suddenly to -a light blue plush, which gave the ecclesiastic a very secular, though -somewhat old-fashioned, appearance. The painter did not venture to go -on with his washing: he could not comprehend how a light blue should be -the ground of the deepest black, still less how he could so suddenly -have removed a glazing colour capable of converting the one tint to the -other. - -At all events, he was not a little disconcerted at having spoilt the -picture to such an extent. Nothing to characterize the ecclesiastic -remained but the richly-curled round wig, which made the exchange -of a faded plush for a handsome new velvet dress far from desirable. -Meanwhile, the mischief appeared irreparable, and the good artist, -having turned the picture to the wall, retired to rest with a mind ill -at ease. But what was his joy the next morning, when, on examining the -picture, he beheld the black velvet dress again in its full splendour. -He could not refrain from again wetting a corner, upon which the blue -colour again appeared, and after a time vanished. On hearing of this -phenomenon, I went at once to see the miraculous picture. A wet sponge -was passed over it in my presence, and the change quickly took place. I -saw a somewhat faded, but decidedly light blue plush dress, the folds -under the arm being indicated by some brown strokes. - -I explained this appearance to myself by the doctrine of the -semi-opaque medium. The painter, in order to give additional depth -to his black, may have passed some particular varnish over it: on -being washed, this varnish imbibed some moisture, and hence became -semi-opaque, in consequence of which the black underneath immediately -appeared blue. Perhaps those who are practically acquainted with the -effect of varnishes may, through accident or contrivance, arrive at -some means of exhibiting this singular appearance, as an experiment, to -those who are fond of investigating natural phenomena. Notwithstanding -many attempts, I could not myself succeed in re-producing it. - -173. - -Having now traced the most splendid instances of atmospheric -appearances, as well as other less striking yet sufficiently remarkable -cases, to the leading examples of semi-transparent mediums, we have no -doubt that attentive observers of nature will carry such researches -further, and accustom themselves to trace and explain the various -appearances which present themselves in every-day experience on the -same principle: we may also hope that such investigators will provide -themselves with an adequate apparatus in order to place remarkable -facts before the eyes of others who may be desirous of information. - -174. - -We venture, once for all, to call the leading appearance in question, -as generally described in the foregoing pages, a primordial and -elementary phenomenon; and we may here be permitted at once to state -what we understand by the term. - -175. - -The circumstances which come under our notice in ordinary observation -are, for the most part, insulated cases, which, with some attention, -admit of being classed under general leading facts. These again range -themselves under theoretical rubrics which are more comprehensive, and -through which we become better acquainted with certain indispensable -conditions of appearances in detail. From henceforth everything is -gradually arranged under higher rules and laws, which, however, are not -to be made intelligible by words and hypotheses to the understanding -merely, but, at the same time, by real phenomena to the senses. We -call these primordial phenomena, because nothing appreciable by the -senses lies beyond them, on the contrary, they are perfectly fit to be -considered as a fixed point to which we first ascended, step by step, -and from which we may, in like manner, descend to the commonest case -of every-day experience. Such an original phenomenon is that which has -lately engaged our attention. We see on the one side light, brightness; -on the other darkness, obscurity: we bring the semi-transparent medium -between the two, and from these contrasts and this medium the colours -develop themselves, contrasted, in like manner, but soon, through a -reciprocal relation, directly tending again to a point of union.[1] - -176. - -With this conviction we look upon the mistake that has been committed -in the investigation of this subject to be a very serious one, inasmuch -as a secondary phenomenon has been thus placed higher in order--the -primordial phenomenon has been degraded to an inferior place; nay, the -secondary phenomenon has been placed at the head, a compound effect has -been treated as simple, a simple appearance as compound: owing to this -contradiction, the most capricious complication and perplexity have -been introduced into physical inquiries, the effects of which are still -apparent. - -177. - -But when even such a primordial phenomenon is arrived at, the evil -still is that we refuse to recognise it as such, that we still aim at -something beyond, although it would become us to confess that we are -arrived at the limits of experimental knowledge. Let the observer of -nature suffer the primordial phenomenon to remain undisturbed in its -beauty; let the philosopher admit it into his department, and he will -find that important elementary facts are a worthier basis for further -operations than insulated cases, opinions, and hypotheses.--Note M. - - -[1] That is (according to the author's statement 150. 151.) both tend -to red; the yellow deepening to orange as the comparatively dark medium -is thickened before brightness; the blue deepening to violet as the -light medium is thinned before darkness.--T. - - - - -[Pg 74] - - - -XI. - -DIOPTRICAL COLOURS OF THE SECOND CLASS.--REFRACTION. - - -178. - -Dioptrical colours of both classes are closely connected, as will -presently appear on a little examination. Those of the first class -appeared through semi-transparent mediums, those of the second class -will now appear through transparent mediums. But since every substance, -however transparent, may be already considered to partake of the -opposite quality (as every accumulation of a medium called transparent -proves), so the near affinity of the two classes is sufficiently -manifest. - -179. - -We will, however, first consider transparent mediums abstractedly as -such, as entirely free from any degree of opacity, and direct our whole -attention to a phenomenon which here presents itself, and which is -known by the name of refraction. - -180. - -In treating of the physiological colours, we have already had occasion -to vindicate what [Pg 75] were formerly called illusions of sight, as -the active energies of the healthy and duly efficient eye (2), and we -are now again invited to consider similar instances confirming the -constancy of the laws of vision. - -181. - -Throughout nature, as presented to the senses, everything depends on -the relation which things bear to each other, but especially on the -relation which man, the most important of these, bears to the rest. -Hence the world divides itself into two parts, and the human being -as _subject_, stands opposed to the _object_. Thus the practical -man exhausts himself in the accumulation of facts, the thinker in -speculation; each being called upon to sustain a conflict which admits -of no peace and no decision. - -182. - -But still the main point always is, whether the relations are truly -seen. As our senses, if healthy, are the surest witnesses of external -relations, so we may be convinced that, in all instances where they -appear to contradict reality, they lay the greater and surer stress -on true relations. Thus a distant object appears to us smaller; and -precisely by this means we are aware of distance. We produced coloured -appearances on colourless objects, through colourless mediums, and at -the same moment our attention was called to the degree of opacity in -the medium. - -183. - -Thus the different degrees of opacity in so-called transparent mediums, -nay, even other physical and chemical properties belonging to them, -are known to our vision by means of refraction, and invite us to make -further trials in order to penetrate more completely by physical and -chemical means into those secrets which are already opened to our view -on one side. - -184. - -Objects seen through mediums more or less transparent do not appear -to us in the place which they should occupy according to the laws of -perspective. On this fact the dioptrical colours of the second class -depend. - -185. - -Those laws of vision which admit of being expressed in mathematical -formulæ are based on the principle that, as light proceeds in straight -lines, it must be possible to draw a straight line from the eye to any -given object in order that it be seen. If, therefore, a case arises in -which the light arrives to us in a bent or broken line, that we see the -object by means of a bent or broken line, we are at once informed that -the medium between the eye and the object is denser, or that it has -assumed this or that foreign nature. - -186. - -This deviation from the law of right-lined vision is known by the -general term of refraction; and, although we may take it for granted -that our readers are sufficiently acquainted with its effects, yet we -will here once more briefly exhibit it in its objective and subjective -point of view. - -187. - -Let the sun shine diagonally into an empty cubical vessel, so that -the opposite side be illumined, but not the bottom: let water be -then poured into this vessel, and the direction of the light will -be immediately altered; for a part of the bottom is shone upon. At -the point where the light enters the thicker medium it deviates from -its rectilinear direction, and appears broken: hence the phenomenon -is called the breaking (_brechung_) or refraction. Thus much of the -objective experiment. - -188. - -We arrive at the subjective fact in the following mode:--Let the eye -be substituted for the sun: let the sight be directed in like manner -[Pg 78] diagonally over one side, so that the opposite inner side be -entirely seen, while no part of the bottom is visible. On pouring in -water the eye will perceive a part of the bottom; and this takes place -without our being aware that we do not see in a straight line; for -the bottom appears to us raised, and hence we give the term elevation -(_hebung_) to the subjective phenomenon. Some points, which are -particularly remarkable with reference to this, will be adverted to -hereafter. - -189. - -Were we now to express this phenomenon generally, we might here repeat, -in conformity with the view lately taken, that the relation of the -objects is changed or deranged. - -190. - -But as it is our intention at present to separate the objective from -the subjective appearances, we first express the phenomenon in a -subjective form, and say,--a derangement or displacement of the object -seen, or to be seen, takes place. - -191. - -But that which is seen without a limiting outline may be thus affected -without our perceiving the change. On the other hand, if what we look -at has a visible termination, we have an evident indication that a -displacement occurs. If, therefore, [Pg 79] we wish to ascertain the -relation or degree of such a displacement, we must chiefly confine -ourselves to the alteration of surfaces with visible boundaries; in -other words, to the displacement of circumscribed objects. - -192. - -The general effect may take place through parallel mediums, for every -parallel medium displaces the object by bringing it perpendicularly -towards the eye. The apparent change of position is, however, more -observable through mediums that are not parallel. - -193. - -These latter may be perfectly spherical, or may be employed in the -form of convex or concave lenses. We shall make use of all these as -occasion may require in our experiments. But as they not only displace -the object from its position, but alter it in various ways, we shall, -in most cases, prefer employing mediums with surfaces, not, indeed, -parallel with reference to each other, but still altogether plane, -namely, prisms. These have a triangle for their base, and may, it is -true, be considered as portions of a lens, but they are particularly -available for our experiments, inasmuch as they very perceptibly -displace the object from its position, without producing a remarkable -distortion. - -194. - -And now, in order to conduct our observations with as much exactness -as possible, and to avoid all confusion and ambiguity, we confine -ourselves at first to - - -SUBJECTIVE EXPERIMENTS, - - -in which, namely, the object is seen by the observer through a -refracting medium. As soon as we have treated these in due series, the -objective experiments will follow in similar order. - - - - -XII. - - -REFRACTION WITHOUT THE APPEARANCE OF COLOUR. - - -195. - -Refraction can visibly take place without our perceiving an appearance -of colour. To whatever extent a colourless or uniformly coloured -surface may be altered as to its position by refraction, no colour -consequent upon refraction appears within it, provided it has no -outline or boundary. We may convince ourselves of this in various ways. - -196. - -Place a glass cube on any larger surface, and look through the glass -perpendicularly or obliquely, the unbroken surface opposite the eye -appears altogether raised, but no colour exhibits itself. If we look at -a pure grey or blue sky or a uniformly white or coloured wall through a -prism, the portion of the surface which the eye thus embraces will be -altogether changed as to its position, without our therefore observing -the smallest appearance of colour. - - - - -XIII. - - -CONDITIONS OF THE APPEARANCE OF COLOUR. - - -197. - -Although in the foregoing experiments we have found all unbroken -surfaces, large or small, colourless, yet at the outlines or -boundaries, where the surface is relieved upon a darker or lighter -object, we observe a coloured appearance. - -198. - -Outline, as well as surface, is necessary to constitute a figure or -circumscribed object. We therefore express the leading fact thus: -circumscribed objects must be displaced by refraction in order to the -exhibition of an appearance of colour. - -199. - -We place before us the simplest object, a light disk on a dark ground -(A).[1] A displacement occurs with regard to this object, if we -apparently extend its outline from the centre by magnifying it. This -may be done with any convex glass, and in this case we see a blue edge -(B). - -200. - -We can, to appearance, contract the circumference of the same light -disk towards the centre by diminishing the object; the edge will then -appear yellow (C). This may be done with a concave glass, which, -however, should not be ground thin like common eye-glasses, but must -have some substance. In order, however, to make this experiment at once -with the convex glass, let a smaller black disk be inserted within -the light disk on a black ground. If we magnify the black disk on a -white ground with a convex glass, the same result takes place as if we -diminished the white disk; for we extend the black outline upon the -white, and we thus perceive the yellow edge together with the blue edge -(D). - -201. - -These two appearances, the blue and yellow, exhibit themselves in and -upon the white: they both assume a reddish hue, in proportion as they -mingle with the black.[2] - -[Illustration] - -202. - -In this short statement we have described the primordial phenomena of -all appearance of colour occasioned by refraction. These undoubtedly -may be repeated, varied, and rendered more striking; may be combined, -complicated, confused; but, after all, may be still restored to their -original simplicity. - -203. - -In examining the process of the experiment just given, we find that -in the one case we have, to appearance, extended the white edge upon -the dark surface; in the other we have extended the dark edge upon -the white surface, supplanting one by the other, pushing one over -the other. We will now endeavour, step by step, to analyse these and -similar cases. - -204. - -If we cause the white disk to move, in appearance, entirely from its -place, which can be done effectually by prisms, it will be coloured -according to the direction in which it apparently moves, in conformity -with the above laws. If we look at the disk _a_[3] through a prism, -so that it appear moved to _b_, the outer edge will appear blue and -blue-red, according to the law of the figure B (fig. 1), the other -edge being yellow, and yellow-red, according to the law of the figure -C (fig. 1). For in the first case the white figure is, as it were, -extended over the dark boundary, and in the other case the dark -boundary is passed over the white figure. The same happens if the disk -is, to appearance, moved from _a_ to _c_, from _a_ to _d_, and so -throughout the circle. - -205. - -As it is with the simple effect, so it is with more complicated -appearances. If we look through a horizontal prism (_a b_[4]) at a -white disk placed at some distance behind it at _e_, the disk will -be raised to _f_, and coloured according to the above law. If we -remove this prism, and look through a vertical one (_c d_) at the same -disk, it will appear at _h_, and coloured according to the same law. -If we place the two prisms one upon the other, the disk will appear -displaced diagonally, in conformity with a general law of nature, and -will be coloured as before; that is, according to its movement in the -direction, _e.g._:[5] - -206. - -If we attentively examine these opposite coloured edges, we find that -they only appear in the direction of the apparent change of place. -A round figure leaves us in some degree uncertain as to this: a -quadrangular figure removes all doubt. - -207. - -The quadrangular figure _a_,[6] moved in the direction _a b_ or _a d_ -exhibits no colour on the sides which are parallel with the direction -in which it moves: on the other hand, if moved in the direction _a -c_, parallel with its diagonal, all the edges of the figure appear -coloured.[7] - -208. - -Thus, a former position (203) is here confirmed; viz. to produce -colour, an object must be so displaced that the light edges be -apparently carried over a dark surface, the dark edges over a light -surface, the figure over its boundary, the boundary over the figure. -But if the rectilinear boundaries of a figure could be indefinitely -extended by refraction, so that figure and background might only pursue -their course next, but not over each other, no colour would appear, not -even if they were prolonged to infinity. - - -[1] Plate 2, fig. 1. - -[2] The author has omitted the orange and purple in the coloured -diagrams which illustrate these first experiments, from a wish probably -to present the elementary contrast, on which he lays a stress, in -greater simplicity. The reddish tinge would be apparent, as stated -above, where the blue and yellow are in contact with the black.--T. - -[3] Plate 2, fig. 2 - -[4] Plate 2, fig. 4 - -[5] In this case, according to the author, the refracting medium being -increased in mass, the appearance of colour is increased, and the -displacement is greater.--T. - -[6] Plate 2, fig. 3. - -[7] Fig. 2, plate 1, contains a variety of forms, which, when viewed -through a prism, are intended to illustrate the statement in this and -the following paragraph. - - - - -XIV. - - -CONDITIONS UNDER WHICH THE APPEARANCE OF COLOUR INCREASES. - - -209. - -We have seen in the foregoing experiments that all appearance of colour -occasioned by refraction depends on the condition that the boundary or -edge be moved in upon the object itself, or the object itself over the -ground, that the figure should be, as it were, carried over itself, or -over the ground. And we shall now find that, by increased displacement -of the object, the appearance of colour exhibits itself in a greater -degree. This takes place in subjective experiments, to which, for the -present, we confine ourselves, under the following conditions. - -210. - -First, if, in looking through parallel mediums, the eye is directed -more obliquely. - -Secondly, if the surfaces of the medium are no longer parallel, but -form a more or less acute angle. - -Thirdly, owing to the increased proportion of the medium, whether -parallel mediums be increased in size, or whether the angle be -increased, provided it does not attain a right angle. - -Fourthly, owing to the distance of the eye armed with a refracting -medium from the object to be displaced. - -Fifthly, owing to a chemical property that may be communicated to the -glass, and which may be afterwards increased in effect. - -211. - -The greatest change of place, short of considerable distortion of the -object, is produced by means of prisms, and this is the reason why the -appearance of colour can be exhibited most powerfully through glasses -of this form. Yet we will not, in employing them, suffer ourselves to -be dazzled by the splendid appearances they exhibit, but keep the above -well-established, simple principles calmly in view. - -212. - -The colour which is outside, or foremost, in the apparent change of an -object by refraction, is always the broader, and we will henceforth -call this a _border_: the colour that remains next the outline is the -narrower, and this we will call an _edge_. - -213. - -If we move a dark boundary towards a light surface, the yellow broader -border is foremost, and the narrower yellow-red edge follows close to -the outline. If we move a light boundary towards a dark surface, the -broader violet border is foremost, and the narrower blue edge follows. - -214. - -If the object is large, its centre remains uncoloured. Its inner -surface is then to be considered as unlimited (195): it is displaced, -but not otherwise altered: but if the object is so narrow, that under -the above conditions the yellow border can reach the blue edge, the -space between the outlines will be entirely covered with colour. If we -make this experiment with a white stripe on a black ground,[1] the two -extremes will presently meet, and thus produce green. We shall then see -the following series of colours:-- - - Yellow-red. - Yellow. - Green. - Blue. - Blue-red. - -215. - -If we place a black band, or stripe, on white paper,[2] the violet -border will spread till it meets the yellow-red edge. In this case the -intermediate black is effaced (as the intermediate white was in the -last experiment), and in its stead a splendid pure red will appear.[3] -The series of colours will now be as follows:-- - - Blue. - Blue-red. - Red. - Yellow-red. - Yellow. - -216. - -The yellow and blue, in the first case (214), can by degrees meet so -fully, that the two colours blend entirely in green, and the order will -then be, - - Yellow-red. - Green. - Blue-red. - -In the second case (215), under similar circumstances, we see only - - Blue. - Red. - Yellow. - -This appearance is best exhibited by refracting the bars of a window -when they are relieved on a grey sky.[4] - -217. - -In all this we are never to forget that this appearance is not to be -considered as a complete or final state, but always as a progressive, -increasing, and, in many senses, controllable appearance. Thus we -find that, by the negation of the above five conditions, it gradually -decreases, and at last disappears altogether. - - -[1] Plate 2, fig. 5, _left_. - -[2] Plate 2, fig. 5, _right_. - -[3] This pure red, the union of orange and violet, is considered by the -author the maximum of the coloured appearance: he has appropriated the -term _purpur_ to it. See paragraph 703, and _note_.--T. - -[4] The bands or stripes in fig. 4, plate 1, when viewed through a -prism, exhibit the colours represented in plate 2, fig. 5. - - - - -XV. - - -EXPLANATION OF THE FOREGOING PHENOMENA. - - -218. - -Before we proceed further, it is incumbent on us to explain the first -tolerably simple phenomenon, and to show its connexion with the -principles first laid down, in order that the observer of nature may -be enabled clearly to comprehend the more complicated appearances that -follow. - -219. - -In the first place, it is necessary to remember that we have to do -with circumscribed objects. In the act of seeing, generally, it is -the circumscribed visible which chiefly invites our observation; and -in the present instance, in speaking of the appearance of colour, as -occasioned by refraction, the circumscribed visible, the detached -object solely occupies our attention. - -220. - -For our chromatic exhibitions we can, however, divide objects generally -into _primary_ and _secondary_. The expressions of themselves denote -what we understand by them, but our meaning will be rendered still more -plain by what follows. - -221. - -Primary objects may be considered firstly as _original_, as images -which are impressed on the eye by things before it, and which assure -us of their reality. To these the secondary images may be opposed -as _derived_ images, which remain in the organ when the object -itself is taken away; those apparent after-images, which have been -circumstantially treated of in the doctrine of physiological colours. - -222. - -The primary images, again, may be considered as _direct_ images, which, -like the original impressions, are conveyed immediately from the object -to the eye. In contradistinction to these, the secondary images may -be considered as _indirect_, being only conveyed to us, as it were, -at second-hand from a reflecting surface. These are the mirrored, or -catoptrical, images, which in certain cases can also become double -images: - -223. - -When, namely, the reflecting body is transparent, and has two parallel -surfaces, one behind the other: in such a case, an image may be -reflected to the eye from both surfaces, and thus arise double images, -inasmuch as the upper image does not quite cover the under one: this -may take place in various ways. - -Let a playing-card be held before a mirror. We shall at first see the -distinct image of the card, but the edge of the whole card, as well -as that of every spot upon it, will be bounded on one side with a -border, which is the beginning of the second reflection. This effect -varies in different mirrors, according to the different thickness of -the glass, and the accidents of polishing. If a person wearing a white -waistcoat, with the remaining part of his dress dark, stands before -certain mirrors, the border appears very distinctly, and in like manner -the metal buttons on dark cloth exhibit the double reflection very -evidently. - -224. - -The reader who has made himself acquainted with our former descriptions -of experiments (80) will the more readily follow the present statement. -The window-bars reflected by plates of glass appear double, and -by increased thickness of the glass, and a due adaptation of the -angle of reflection, the two reflections may be entirely separated -from each other. So a vase full of water, with a plane mirror-like -bottom, reflects any object twice, the two reflections being more or -less separated under the same conditions. In these cases it is to be -observed that, where the two reflections cover each other, the perfect -vivid image is reflected, but where they are separated they exhibit -only weak, transparent, and shadowy images. - -225. - -If we wish to know which is the under and which the upper image, we -have only to take a coloured medium, for then a light object reflected -from the under surface is of the colour of the medium, while that -reflected from the upper surface presents the complemental colour. With -dark objects it is the reverse; hence black and white surfaces may be -here also conveniently employed. How easily the double images assume -and evoke colours will here again be striking. - -226. - -Thirdly, the primary images may be considered as _principal_ images, -while the secondary can be, as it were, annexed to these as _accessory_ -images. Such an accessory image produces a sort of double form; except -that it does not separate itself from the principal object, although it -may be said to be always endeavouring to do so. It is with secondary -images of this last description that we have to do in prismatic -appearances. - -227. - -A surface without a boundary exhibits no appearance of colour when -refracted (195). Whatever is seen must be circumscribed by an -outline to produce this effect. In other words a figure, an object, -is required; this object undergoes an apparent change of place by -refraction: the change is however not complete, not clean, not sharp; -but incomplete, inasmuch as an accessory image only is produced. - -228. - -In examining every appearance of nature, but especially in examining -an important and striking one, we should not remain in one spot, we -should not confine ourselves to the insulated fact, nor dwell on it -exclusively, but look round through all nature to see where something -similar, something that has affinity to it, appears: for it is only by -combining analogies that we gradually arrive at a whole which speaks -for itself, and requires no further explanation. - -229. - -Thus we here call to mind that in certain cases refraction -unquestionably produces double images, as is the case in Iceland spar: -similar double images are also apparent in cases of refraction through -large rock crystals, and in other instances; phenomena which have not -hitherto been sufficiently observed.[1] - -230. - -But since in the case under consideration (227) the question relates -not to double but to accessory images, we refer to a phenomenon already -adverted to, but not yet thoroughly investigated. We allude to an -earlier experiment, in which it appeared that a sort of conflict took -place in regard to the retina between a light object and its dark -ground, and between a dark object and its light ground (16). The light -object in this case appeared larger, the dark one smaller. - -231. - -By a more exact observation of this phenomenon we may remark that the -forms are not sharply distinguished from the ground, but that they -appear with a kind of grey, in some degree, coloured edge; in short, -with an accessory image. If, then, objects seen only with the naked -eye produce such effects, what may not take place when a dense medium -is interposed? It is not that alone which presents itself to us in -obvious operation which produces and suffers effects, but likewise all -principles that have a mutual relation only of some sort are efficient -accordingly, and indeed often in a very high degree. - -232. - -Thus when refraction produces its effect on an object there appears an -accessory image next the object itself: the real form thus refracted -seems even to linger behind, as if resisting the change of place; but -the accessory image seems to advance, and extends itself more or less -in the mode already shown (212-216). - -233. - -We also remarked (224) that in double images the fainter appear only -half substantial, having a kind of transparent, evanescent character, -just as the fainter shades of double shadows must always appear as -half-shadows. These latter assume colours easily, and produce them -readily (69), the former also (80); and the same takes place in the -instance of accessory images, which, it is true, do not altogether -quit the real object, but still advance or extend from it as -half-substantial images, and hence can appear coloured so quickly and -so powerfully. - -234. - -That the prismatic appearance is in fact an accessory image we may -convince ourselves in more than one mode. It corresponds exactly with -the form of the object itself. Whether the object be bounded by a -straight line or a curve, indented or waving, the form of the accessory -image corresponds throughout exactly with the form of the object.[2] - -235. - -Again, not only the form but other qualities of the object are -communicated to the accessory image. If the object is sharply relieved -from its ground, like white on black, the coloured accessory image in -like manner appears in its greatest force. It is vivid, distinct, and -powerful; but it is most especially powerful when a luminous object is -shown on a dark ground, which may be contrived in various ways. - -236. - -But if the object is but faintly distinguished from the ground, like -grey objects on black or white, or even on each other, the accessory -image is also faint, and, when the original difference of tint or force -is slight, becomes hardly discernible. - -237. - -The appearances which are observable when coloured objects are relieved -on light, dark, or coloured grounds are, moreover, well worthy of -attention. In this case a union takes place between the apparent colour -of the accessory image and the real colour of the object; a compound -colour is the result, which is either assisted and enhanced by the -accordance, or neutralised by the opposition of its ingredients. - -238. - -But the common and general characteristic both of the double and -accessory image is semi-transparence. The tendency of a transparent -medium to become only half transparent, or merely light-transmitting, -has been before adverted to (147, 148). Let the reader assume that he -sees within or through such a medium a visionary image, and he will at -once pronounce this latter to be a semi-transparent image. - -239. - -Thus the colours produced by refraction may be fitly explained by the -doctrine of the semi-transparent mediums. For where dark passes over -light, as the border of the semi-transparent accessory image advances, -yellow appears; and, on the other hand, where a light outline passes -over the dark background, blue appears (150, 151). - -240. - -The advancing foremost colour is always the broader. Thus the yellow -spreads over the light with a broad border, but the yellow-red appears -as a narrower stripe and is next the dark, according to the doctrine of -augmentation, as an effect of shade.[3] - -241. - -On the opposite side the condensed blue is next the edge, while the -advancing border, spreading as a thinner veil over the black, produces -the violet colour, precisely on the principles before explained in -treating of semi-transparent mediums, principles which will hereafter -be found equally efficient in many other cases. - -242. - -Since an analysis like the present requires to be confirmed by ocular -demonstration, we beg every reader to make himself acquainted with the -experiments hitherto adduced, not in a superficial manner, but fairly -and thoroughly. We have not placed arbitrary signs before him instead -of the appearances themselves; no modes of expression are here proposed -for his adoption which may be repeated for ever without the exercise -of thought and without leading any one to think; but we invite him to -examine intelligible appearances, which must be present to the eye and -mind, in order to enable him clearly to trace these appearances to -their origin, and to explain them to himself and to others. - - -[1] The date of the publication, 1810, is sometimes to be -remembered.--T. - -[2] The forms in fig. 2, plate 1, when seen through a prism, are -again intended to exemplify this. In the plates to the original work -curvilinear figures are added, but the circles, fig. 1, in the same -plate, may answer the same end.--T. - -[3] The author has before observed that colour is a degree of darkness, -and he here means that increase of darkness, produced by transparent -mediums, is, to a certain extent, increase of colour.--T. - - - - -XVI. - - -DECREASE OF THE APPEARANCE OF COLOUR. - - -243. - -We need only take the five conditions (210) under which the appearance -of colour increases in the contrary order, to produce the contrary or -decreasing state; it may be as well, however, briefly to describe and -review the corresponding modifications which are presented to the eye. - -244. - -At the highest point of complete junction of the opposite edges, the -colours appear as follows (216):-- - - Yellow-red. Blue. - Green. Red. - Blue-red. Yellow. - -245. - -Where the junction is less complete, the appearance is as follows (214, -215):-- - - Yellow-red. Blue. - Yellow. Blue-red. - Green. Red. - Blue. Yellow-red. - Blue-red. Yellow. - -Here, therefore, the surface still appears completely coloured, but -neither series is to be considered as an elementary series, always -developing itself in the same manner and in the same degrees; on the -contrary, they can and should be resolved into their elements; and, in -doing this, we become better acquainted with their nature and character. - -246. - -These elements then are (199, 200, 201)-- - - Yellow-red. Blue. - Yellow. Blue-red. - White. Black. - Blue. Yellow-red. - Blue-red. Yellow. - -Here the surface itself, the original object, which has been hitherto -completely covered, and as it were lost, again appears in the centre of -the colours, asserts its right, and enables us fully to recognise the -secondary nature of the accessory images which exhibit themselves as -"edges" and "borders."--Note N. - -247. - -We can make these edges and borders as narrow as we please; nay, we -can still have refraction in reserve after having done away with all -appearance of colour at the boundary of the object. - -Having now sufficiently investigated the exhibition of colour in this -phenomenon, we repeat that we cannot admit it to be an elementary -phenomenon. On the contrary, we have traced it to an antecedent and -a simpler one; we have derived it, in connexion with the theory of -secondary images, from the primordial phenomenon of light and darkness, -as affected or acted upon by semi-transparent mediums. Thus prepared, -we proceed to describe the appearances which refraction produces on -grey and coloured objects, and this will complete the section of -subjective phenomena. - - - - -XVII. - -GREY OBJECTS DISPLACED BY REFRACTION. - - -248. - -Hitherto we have confined our attention to black and white objects -relieved on respectively opposite grounds, as seen through the prism, -because the coloured edges and borders are most clearly displayed in -such cases. We now repeat these experiments with grey objects, and -again find similar results. - -249. - -As we called black the equivalent of darkness, and white the -representative of light (18), so we now venture to say that grey -represents half-shadow, which partakes more or less of light and -darkness, and thus stands between the two. We invite the reader to call -to mind the following facts as bearing on our present view. - -250. - -Grey objects appear lighter on a black than on a white ground (33); -they appear as a light on a black ground, and larger; as a dark on the -white ground, and smaller. (16.) - -251. - -The darker the grey the more it appears as a faint light on black, as a -strong dark on white, and _vice versâ_; hence the accessory images of -dark-grey on black are faint, on white strong: so the accessory images -of light-grey on white are faint, on black strong. - -252. - -Grey on black, seen through the prism, will exhibit the same -appearances as white on black; the edges are coloured according to the -same law, only the borders appear fainter. If we relieve grey on white, -we have the same edges and borders which would be produced if we saw -black on white through the prism.--Note O. - -253. - -Various shades of grey placed next each other in gradation will exhibit -at their edges, either blue and violet only, or red and yellow only, -according as the darker grey is placed over or under. - -254. - -A series of such shades of grey placed horizontally next each other -will be coloured conformably to the same law according as the whole -series is relieved, on a black or white ground above or below. - -255. - -The observer may see the phenomena exhibited by the prism at one -glance, by enlarging the plate intended to illustrate this section.[1] - -256. - -It is of great importance duly to examine and consider another -experiment in which a grey object is placed partly on a black and -partly on a white surface, so that the line of division passes -vertically through the object. - -257. - -The colours will appear on this grey object in conformity with the -usual law, but according to the opposite relation of the light to the -dark, and will be contrasted in a line. For as the grey is as a light -to the black, so it exhibits the red and yellow above the blue and -violet below: again, as the grey is as a dark to the white, the blue -and violet appear above the red and yellow below. This experiment will -be found of great importance with reference to the next chapter. - - -[1] It has been thought unnecessary to give all the examples in the -plate alluded to, but the leading instance referred to in the next -paragraph will be found in plate 3, fig. 1. The grey square when seen -through a prism will exhibit the effects described in par. 257.--T. - - - - -XVIII. - - -COLOURED OBJECTS DISPLACED BY REFRACTION. - - -258. - -An unlimited coloured surface exhibits no prismatic colour in addition -to its own hue, thus not at all differing from a black, white, or -grey surface. To produce the appearance of colour, light and dark -boundaries must act on it either accidentally or by contrivance. Hence -experiments and observations on coloured surfaces, as seen through the -prism, can only be made when such surfaces are separated by an outline -from another differently tinted surface, in short when _circumscribed -objects_ are coloured. - -259. - -All colours, whatever they may be, correspond so far with grey, that -they appear darker than white and lighter than black. This shade-like -quality of colour (σκιέρον) has been already alluded to (69), and will -become more and more evident. If then we begin by placing coloured -objects on black and white surfaces, and examine them through the -prism, we shall again have all that we have seen exhibited with grey -surfaces. - - -[Illustration] - -260. - -If we displace a coloured object by refraction, there appears, as -in the case of colourless objects and according to the same laws, -an accessory image. This accessory image retains, as far as colour -is concerned, its usual nature, and acts on one side as a blue and -blue-red, on the opposite side as a yellow and yellow-red. Hence the -apparent colour of the edge and border will be either homogeneous -with the real colour of the object, or not so. In the first case the -apparent image identifies itself with the real one, and appears to -increase it, while, in the second case, the real image may be vitiated, -rendered indistinct, and reduced in size by the apparent image. We -proceed to review the cases in which these effects are most strikingly -exhibited. - -261. - -If we take a coloured drawing enlarged from the plate, which -illustrates this experiment[1], and examine the red and blue squares -placed next each other on a black ground, through the prism as usual, -we shall find that as both colours are lighter than the ground, -similarly coloured edges and borders will appear above and below, at -the outlines of both, only they will not appear equally distinct to the -eye. - -262. - -Red is proportionally much lighter on black than blue is. The colours -of the edges will therefore appear stronger on the red than on the -blue, which here acts as a dark-grey, but little different from black. -(251.) - -263. - -The extreme red edge will identify itself with the vermilion colour -of the square, which will thus appear a little elongated in this -direction; while the yellow border immediately underneath it only gives -the red surface a more brilliant appearance, and is not distinguished -without attentive observation. - -264. - -On the other hand the red edge and yellow border are heterogeneous -with the blue square; a dull red appears at the edge, and a dull green -mingles with the figure, and thus the blue square seems, at a hasty -glance, to be comparatively diminished on this side. - -265. - -At the lower outline of the two squares a blue edge and a violet border -will appear, and will produce the contrary effect; for the blue edge, -which is heterogeneous with the warm red surface, will vitiate it -and produce a neutral colour, so that the red on this side appears -comparatively reduced and driven upwards, and the violet border on the -black is scarcely perceptible. - -266. - -On the other hand, the blue apparent edge will identify itself with the -blue square, and not only not reduce, but extend it. The blue edge and -even the violet border next it have the apparent effect of increasing -the surface, and elongating it in that direction. - -267. - -The effect of homogeneous and heterogeneous edges, as I have now -minutely described it, is so powerful and singular that the two squares -at the first glance seem pushed out of their relative horizontal -position and moved in opposite directions, the red upwards, the blue -downwards. But no one who is accustomed to observe experiments in a -certain succession, and respectively to connect and trace them, will -suffer himself to be deceived by such an unreal effect. - -268. - -A just impression with regard to this important phenomenon will, -however, much depend on some nice and even troublesome conditions, -which are necessary to produce the illusion in question. Paper should -be tinged with vermilion or the best minium for the red square, and -with deep indigo for the blue square. The blue and red prismatic edges -will then unite imperceptibly with the real surfaces where they are -respectively homogeneous; where they are not, they vitiate the colours -of the squares without producing a very distinct middle tint. The real -red should not incline too much to yellow, otherwise the apparent deep -red edge above will be too distinct; at the same time it should be -somewhat yellow, otherwise the transition to the yellow border will be -too observable. The blue must not be light, otherwise the red edge will -be visible, and the yellow border will produce a too decided green, -while the violet border underneath would not give us the impression of -being part of an elongated light blue square. - -269. - -All this will be treated more circumstantially hereafter, when we speak -of the apparatus intended to facilitate the experiments connected with -this part of our subject.[2] Every inquirer should prepare the figures -himself, in order fairly to exhibit this specimen of ocular deception, -and at the same time to convince himself that the coloured edges, even -in this case, cannot escape accurate examination. - -270. - -Meanwhile various other combinations, as exhibited in the plate, are -fully calculated to remove all doubt on this point in the mind of every -attentive observer. - -271. - -If, for instance, we look at a white square, next the blue one, on a -black ground, the prismatic hues of the opposite edges of the white, -which here occupies the place of the red in the former experiment, will -exhibit themselves in their utmost force. The red edge extends itself -above the level of the blue almost in a greater degree than was the -case with the red square itself in the former experiment. The lower -blue edge, again, is visible in its full force next the white, while, -on the other hand, it cannot be distinguished next the blue square. The -violet border underneath is also much more apparent on the white than -on the blue. - -272. - -If the observer now compares these double squares, carefully prepared -and arranged one above the other, the red with the white, the two blue -squares together, the blue with the red, the blue with the white, he -will clearly perceive the relations of these surfaces to their coloured -edges and borders. - -273. - -The edges and their relations to the coloured surfaces appear still -more striking if we look at the coloured squares and a black square -on a white ground; for in this case the illusion before mentioned -ceases altogether, and the effect of the edges is as visible as in -any case that has come under our observation. Let the blue and red -squares be first examined through the prism. In both the blue edge now -appears above; this edge, homogeneous with the blue surface, unites -with it, and appears to extend it upwards, only the blue edge, owing -to its lightness, is somewhat too distinct in its upper portion; the -violet border underneath it is also sufficiently evident on the blue. -The apparent blue edge is, on the other hand, heterogeneous with the -red square; it is neutralised by contrast, and is scarcely visible; -meanwhile the violet border, uniting with the real red, produces a hue -resembling that of the peach-blossom. - -274. - -If thus, owing to the above causes, the upper outlines of these -squares do not appear level with each other, the correspondence of the -under outlines is the more observable; for since both colours, the red -and the blue, are darks compared with the white (as in the former case -they were light compared with the black), the red edge with its yellow -border appears very distinctly under both. It exhibits itself under the -warm red surface in its full force, and under the dark blue nearly as -it appears under the black: as may be seen if we compare the edges and -borders of the figures placed one above the other on the white ground. - -275. - -In order to present these experiments with the greatest variety and -perspicuity, squares of various colours are so arranged[3] that the -boundary of the black and white passes through them vertically. -According to the laws now known to us, especially in their application -to coloured objects, we shall find the squares as usual doubly coloured -at each edge; each square will appear to be split in two, and to be -elongated upwards or downwards. We may here call to mind the experiment -with the grey figure seen in like manner on the line of division -between black and white (257).[4] - -276. - -A phenomenon was before exhibited, even to illusion, in the instance of -a red and blue square on a black ground; in the present experiment the -elongation upwards and downwards of two differently coloured figures -is apparent in the two halves of one and the same figure of one and -the same colour. Thus we are still referred to the coloured edges and -borders, and to the effects of their homogeneous and heterogeneous -relations with respect to the real colours of the objects. - -277. - -I leave it to observers themselves to compare the various gradations -of coloured squares, placed half on black half on white, only inviting -their attention to the apparent alteration which takes place in -contrary directions; for red and yellow appear elongated upwards if -on a black ground, downwards if on a white; blue, downwards if on a -black ground, upwards if on a white. All which, however, is quite in -accordance with the diffusely detailed examples above given. - -278. - -Let the observer now turn the figures so that the before-mentioned -squares placed on the line of division between black and white may -be in a horizontal series; the black above, the white underneath. On -looking at these squares through the prism, he will observe that the -red square gains by the addition of two red edges; on more accurate -examination he will observe the yellow border on the red figure, and -the lower yellow border upon the white will be perfectly apparent. - -279. - -The upper red edge on the blue square is on the other hand hardly -visible; the yellow border next it produces a dull green by mingling -with the figure; the lower red edge and the yellow border are displayed -in lively colours. - -280. - -After observing that the red figure in these cases appears to gain by -an addition on both sides, while the dark blue, on one side at least, -loses something; we shall see the contrary effect produced by turning -the same figures upside down, so that the white ground be above, the -black below. - -281. - -For as the homogeneous edges and borders now appear above and below -the blue square, this appears elongated, and a portion of the surface -itself seems even more brilliantly coloured: it is only by attentive -observation that we can distinguish the edges and borders from the -colour of the figure itself. - -282. - -The yellow and red squares, on the other hand, are comparatively -reduced by the heterogeneous edges in this position of the figures, -and their colours are, to a certain extent, vitiated. The blue edge -in both is almost invisible. The violet border appears as a beautiful -peach-blossom hue on the red, as a very pale colour of the same kind on -the yellow; both the lower edges are green; dull on the red, vivid on -the yellow; the violet border is but faintly perceptible under the red, -but is more apparent under the yellow. - -283. - -Every inquirer should make it a point to be thoroughly acquainted with -all the appearances here adduced, and not consider it irksome to follow -out a single phenomenon through so many modifying circumstances. These -experiments, it is true, may be multiplied to infinity by differently -coloured figures, upon and between differently coloured grounds. Under -all such circumstances, however, it will be evident to every attentive -observer that coloured squares only appear relatively altered, or -elongated, or reduced by the prism, because an addition of homogeneous -or heterogeneous edges produces an illusion. The inquirer will now -be enabled to do away with this illusion if he has the patience to -go through the experiments one after the other, always comparing the -effects together, and satisfying himself of their correspondence. - -Experiments with coloured objects might have been contrived in various -ways: why they have been exhibited precisely in the above mode, and -with so much minuteness, will be seen hereafter. The phenomena, -although formerly not unknown, were much misunderstood; and it was -necessary to investigate them thoroughly to render some portions of our -intended historical view clearer. - -284. - -In conclusion, we will mention a contrivance by means of which our -scientific readers may be enabled to see these appearances distinctly -at one view, and even in their greatest splendour. Cut in a piece of -pasteboard five perfectly similar square openings of about an inch, -next each other, exactly in a horizontal line: behind these openings -place five coloured glasses in the natural order, orange, yellow, -green, blue, violet. Let the series thus adjusted be fastened in an -opening of the camera obscura, so that the bright sky may be seen -through the squares, or that the sun may shine on them; they will thus -appear very powerfully coloured. Let the spectator now examine them -through the prism, and observe the appearances, already familiar by -the foregoing experiments, with coloured objects, namely, the partly -assisting, partly neutralising effects of the edges and borders, and -the consequent apparent elongation or reduction of the coloured squares -with reference to the horizontal line. The results witnessed by the -observer in this case, entirely correspond with those in the cases -before analysed; we do not, therefore, go through them again in detail, -especially as we shall find frequent occasions hereafter to return to -the subject.--Note P. - - -[1] Plate 3, fig. 1. The author always recommends making the -experiments on an increased scale, in order to see the prismatic -effects distinctly. - -[2] Neither the description of the apparatus nor the recapitulation -of the whole theory, so often alluded to by the author, were ever -given.--T. - -[3] Plate 3. fig. 1. - -[4] The grey square is introduced in the same plate, fig. 1, above the -coloured squares. - - - - -XIX. - - -ACHROMATISM AND HYPERCHROMATISM. - - -285. - -Formerly when much that is regular and constant in nature was -considered as mere aberration and accident, the colours arising from -refraction were but little attended to, and were looked upon as an -appearance attributable to particular local circumstances. - -286. - -But after it had been assumed that this appearance of colour -accompanies refraction at all times, it was natural that it should -be considered as intimately and exclusively connected with that -phenomenon; the belief obtaining that the measure of the coloured -appearance was in proportion to the measure of the refraction, and that -they must advance _pari passu_ with each other. - -287. - -If, again, philosophers ascribed the phenomenon of a stronger or weaker -refraction, not indeed wholly, but in some degree, to the different -density of the medium, (as purer atmospheric air, air charged with -vapours, water, glass, according to their increasing density, increase -the so-called refraction, or displacement of the object;) so they -could hardly doubt that the appearance of colour must increase in the -same proportion; and hence took it for granted, in combining different -mediums which were to counteract refraction, that as long as refraction -existed, the appearance of colour must take place, and that as soon as -the colour disappeared, the refraction also must cease. - -288. - -Afterwards it was, however, discovered that this relation which was -assumed to correspond, was, in fact, dissimilar; that two mediums can -refract an object with equal power, and yet produce very dissimilar -coloured borders. - -289. - -It was found that, in addition to the physical principle to which -refraction was ascribed, a chemical one was also to be taken into the -account. We propose to pursue this subject hereafter, in the chemical -division of our inquiry, and we shall have to describe the particulars -of this important discovery in our history of the doctrine of colours. -What follows may suffice for the present. - -290. - -In mediums of similar or nearly similar refracting power, we find -the remarkable circumstance that a greater and lesser appearance of -colour can be produced by a chemical treatment; the greater effect is -owing, namely, to acids, the lesser to alkalis. If metallic oxydes are -introduced into a common mass of glass, the coloured appearance through -such glasses becomes greatly increased without any perceptible change -of refracting power. That the lesser effect, again, is produced by -alkalis, may be easily supposed. - -291. - -Those kinds of glass which were first employed after the discovery, -are called flint and crown glass; the first produces the stronger, the -second the fainter appearance of colour. - -292. - -We shall make use of both these denominations as technical terms in our -present statement, and assume that the refractive power of both is -the same, but that flint-glass produces the coloured appearance more -strongly by one-third than the crown-glass. The diagram (Plate 3, fig. -2,) may serve in illustration. - -293. - -A black surface is here divided into compartments for more convenient -demonstration: let the spectator imagine five white squares between the -parallel lines _a, b,_ and _c, d_. The square No. 1, is presented to -the naked eye unmoved from its place. - -294. - -But let the square No. 2, seen through a crown-glass prism _g_, be -supposed to be displaced by refraction three compartments, exhibiting -the coloured borders to a certain extent; again, let the square No. 3, -seen through a flint glass prism _h_, in like manner be moved downwards -three compartments, when it will exhibit the coloured borders by about -a third wider than No. 2. - -295. - -Again, let us suppose that the square No. 4, has, like No. 2, been -moved downwards three compartments by a prism of crown-glass, and that -then by an oppositely placed prism _h_, of flint-glass, it has been -again raised to its former situation, where it now stands. - -296. - -Here, it is true, the refraction is done away with by the opposition of -the two; but as the prism _h_, in displacing the square by refraction -through three compartments, produces coloured borders wider by a -third than those produced by the prism _g_, so, notwithstanding the -refraction is neutralised, there must be an excess of coloured border -remaining. (The position of this colour, as usual, depends on the -direction of the apparent motion (204) communicated to the square by -the prism _h_, and, consequently, it is the reverse of the appearance -in the two squares 2 and 3, which have been moved in an opposite -direction.) This excess of colour we have called Hyperchromatism, and -from this the achromatic state may be immediately arrived at. - -297. - -For assuming that it was the square No. 5 which was removed three -compartments from its first supposed place, like No. 2, by a prism of -crown-glass _g_, it would only be necessary to reduce the angle of a -prism of flint-glass _h_, and to connect it, reversed, to the prism -_g_, in order to raise the square No. 5 two degrees or compartments; -by which means the Hyperchromatism of the first case would cease, the -figure would not quite return to its first position, and yet be already -colourless. The prolonged lines of the united prisms, under No. 5, show -that a single complete prism remains: again, we have only to suppose -the lines curved, and an object-glass presents itself. Such is the -principle of the achromatic telescopes. - -298. - -For these experiments, a small prism composed of three different -prisms, as prepared in England, is extremely well adapted. It is to be -hoped our own opticians will in future enable every friend of science -to provide himself with this necessary instrument. - - - - -XX. - - -ADVANTAGES OF SUBJECTIVE EXPERIMENTS.--TRANSITION TO THE OBJECTIVE. - - -299. - -We have presented the appearances of colour as exhibited by refraction, -first, by means of subjective experiments; and we have so far arrived -at a definite result, that we have been enabled to deduce the phenomena -in question from the doctrine of semi-transparent mediums and double -images. - -300. - -In statements which have reference to nature, everything depends on -ocular inspection, and these experiments are the more satisfactory as -they may be easily and conveniently made. Every amateur can procure -his apparatus without much trouble or cost, and if he is a tolerable -adept in pasteboard contrivances, he may even prepare a great part of -his machinery himself. A few plain surfaces, on which black, white, -grey, and coloured objects may be exhibited alternately on a light and -dark ground, are all that is necessary. The spectator fixes them before -him, examines the appearances at the edge of the figures conveniently, -and as long as he pleases; he retires to a greater distance, again -approaches, and accurately observes the progressive states of the -phenomena. - -301. - -Besides this, the appearances may be observed with sufficient exactness -through small prisms, which need not be of the purest glass. The other -desirable requisites in these glass instruments will, however, be -pointed out in the section which treats of the apparatus.[1] - -302. - -A great advantage in these experiments, again, is, that they can be -made at any hour of the day in any room, whatever aspect it may have. -We have no need to wait for sunshine, which in general is not very -propitious to northern observers. - - -[1] This description of the apparatus was never given. - - - - -OBJECTIVE EXPERIMENTS. - - -303. - -The objective experiments, on the contrary, necessarily require the -sun-light which, even when it is to be had, may not always have the -most desirable relation with the apparatus placed opposite to it. -Sometimes the sun is too high, sometimes too low, and withal only a -short time in the meridian of the best situated room. It changes its -direction during the observation, the observer is forced to alter -his own position and that of his apparatus, in consequence of which -the experiments in many cases become uncertain. If the sun shines -through the prism it exhibits all inequalities, lines, and bubbles -in the glass, and thus the appearance is rendered confused, dim, and -discoloured. - -304. - -Yet both kinds of experiments must be investigated with equal accuracy. -They appear to be opposed to each other, and yet are always parallel. -What one order of experiments exhibits the other exhibits likewise, -and yet each has its peculiar capabilities, by means of which certain -effects of nature are made known to us in more than one way. - -305. - -In the next place there are important phenomena which may be exhibited -by the union of subjective and objective experiments. The latter -experiments again have this advantage, that we can in most cases -represent them by diagrams, and present to view the component relations -of the phenomena. In proceeding, therefore, to describe the objective -experiments, we shall so arrange them that they may always correspond -with the analogous subjective examples; for this reason, too, we annex -to the number of each paragraph the number of the former corresponding -one. But we set out by observing generally that the reader must consult -the plates, that the scientific investigator must be familiar with the -apparatus in order that the twin-phenomena in one mode or the other may -be placed before them. - - - - -XXI. - - -REFRACTION WITHOUT THE APPEARANCE OF COLOUR. - - -306 (195, 196). - -That refraction may exhibit its effects without producing an appearance -of colour, is not to be demonstrated so perfectly in objective as -in subjective experiments. We have, it is true, unlimited spaces -which we can look at through the prism, and thus convince ourselves -that no colour appears where there is no boundary; but we have no -unlimited source of light which we can cause to act through the prism. -Our light comes to us from circumscribed bodies; and the sun, which -chiefly produces our prismatic appearances, is itself only a small, -circumscribed, luminous object. - -307. - -We may, however, consider every larger opening through which the sun -shines, every larger medium through which the sun-light is transmitted -and made to deviate from its course, as so far unlimited that we can -confine our attention to the centre of the surface without considering -its boundaries. - -308 (197). - -If we place a large water-prism in the sun, a large bright space is -refracted upwards by it on the plane intended to receive the image, and -the middle of this illumined space will be colourless. The same effect -may be produced if we make the experiment with glass prisms having -angles of few degrees: the appearance may be produced even through -glass prisms, whose refracting angle is sixty degrees, provided we -place the recipient surface near enough. - - - - -XXII. - - -CONDITIONS OF THE APPEARANCE OF COLOUR. - - -309 (198). - -Although, then, the illumined space before mentioned appears indeed -refracted and moved from its place, but not coloured, yet on the -horizontal edges of this space we observe a coloured appearance. -That here again the colour is solely owing to the displacement of a -circumscribed object may require to be more fully proved. - -The luminous body which here acts is circumscribed: the sun, while it -shines and diffuses light, is still an insulated object. However small -the opening in the lid of a camera obscura be made, still the whole -image of the sun will penetrate it. The light which streams from all -parts of the sun's disk, will cross itself in the smallest opening, and -form the angle which corresponds with the sun's apparent diameter. On -the outside we have a cone narrowing to the orifice; within, this apex -spreads again, producing on an opposite surface a round image, which -still increases in size in proportion to the distance of the recipient -surface from the apex. This image, together with all other objects -of the external landscape, appears reversed on the white surface in -question in a dark room. - -310. - -How little therefore we have here to do with single sun-rays, bundles -or fasces of rays, cylinders of rays, pencils, or whatever else of the -kind may be imagined, is strikingly evident. For the convenience of -certain diagrams the sun-light may be assumed to arrive in parallel -lines, but it is known that this is only a fiction; a fiction quite -allowable where the difference between the assumption and the true -appearance is unimportant; but we should take care not to suffer such a -postulate to be equivalent to a fact, and proceed to further operations -on such a fictitious basis. - -311. - -Let the aperture in the window-shutter be now enlarged at pleasure, let -it be made round or square, nay, let the whole shutter be opened, and -let the sun shine into the room through the whole window; the space -which the sun illumines will always be larger according to the angle -which its diameter makes; and thus even the whole space illumined by -the sun through the largest window is only the image of the sun _plus_ -the size of the opening. We shall hereafter have occasion to return to -this. - -312 (199). - -If we transmit the image of the sun through convex glasses we contract -it towards the focus. In this case, according to the laws before -explained, a yellow border and a yellow-red edge must appear when the -spectrum is thrown on white paper. But as this experiment is dazzling -and inconvenient, it may be made more agreeably with the image of the -full moon. On contracting this orb by means of a convex glass, the -coloured edge appears in the greatest splendour; for the moon transmits -a mitigated light in the first instance, and can thus the more readily -produce colour which to a certain extent accompanies the subduing of -light: at the same time the eye of the observer is only gently and -agreeably excited. - -313 (200). - -If we transmit a luminous image through concave glasses, it is -dilated. Here the image appears edged with blue. - -314. - -The two opposite appearances may be produced by a convex glass, -simultaneously or in succession; simultaneously by fastening an opaque -disk in the centre of the convex glass, and then transmitting the sun's -image. In this case the luminous image and the black disk within it are -both contracted, and, consequently, the opposite colours must appear. -Again, we can present this contrast in succession by first contracting -the luminous image towards the focus, and then suffering it to expand -again beyond the focus, when it will immediately exhibit a blue edge. - -315 (201). - -Here too what was observed in the subjective experiments is again to be -remarked, namely, that blue and yellow appear in and upon the white, -and that both assume a reddish appearance in proportion as they mingle -with the black. - -316 (202, 203). - -These elementary phenomena occur in all subsequent objective -experiments, as they constituted the groundwork of the subjective -ones. The process too which takes place is the same; a light boundary -is carried over a dark surface, a dark surface is carried over a light -boundary. The edges must advance, and as it were push over each other -in these experiments as in the former ones. - -317 (204). - -If we admit the sun's image through a larger or smaller opening into -the dark room, if we transmit it through a prism so placed that its -refracting angle, as usual, is underneath; the luminous image, instead -of proceeding in a straight line to the floor, is refracted upwards on -a vertical surface placed to receive it. This is the moment to take -notice of the opposite modes in which the subjective and objective -refractions of the object appear. - -318. - -If we _look_ through a prism, held with its refracting angle -underneath, at an object above us, the object is moved downwards; -whereas a luminous image refracted through the same prism is moved -upwards. This, which we here merely mention as a matter of fact for -the sake of brevity, is easily explained by the laws of refraction and -elevation. - -319. - -The luminous object being moved from its place in this manner, the -coloured borders appear in the order, and according to the laws before -explained. The violet border is always foremost, and thus in objective -cases proceeds upwards, in subjective cases downwards. - -320 (205). - -The observer may convince himself in like manner of the mode in which -the appearance of colour takes place in the diagonal direction when the -displacement is effected by means of two prisms, as has been plainly -enough shown in the subjective example; for this experiment, however, -prisms should be procured of few degrees, say about fifteen. - -321(206, 207). - -That the colouring of the image takes place here too, according to the -direction in which it moves, will be apparent if we make a _square_ -opening of moderate size in a shutter, and cause the luminous image -to pass through a water-prism; the spectrum being moved first in the -horizontal and vertical directions, then diagonally, the coloured edges -will change their position accordingly. - -322(208). - -Whence it is again evident that to produce colour the boundaries must -be carried over each other, not merely move side by side. - - - - -XXIII. - -CONDITIONS OF THE INCREASE OF COLOUR. - - -323 (209). - -Here too an increased displacement of the object produces a greater -appearance of colour. - -324 (210). - -This increased displacement occurs, - -1. By a more oblique direction of the impinging luminous object through -mediums with parallel surfaces. - -2. By changing the parallel form for one more or less acute angled. - -3. By increased proportion of the medium, whether parallel or acute -angled; partly because the object is by this means more powerfully -displaced, partly because an effect depending on the mere mass -co-operates. - -4. By the distance of the recipient surface from the refracting medium -so that the coloured spectrum emerging from the prism may be said to -have a longer way to travel. - -5. When a chemical property produces its effects under all these -circumstances: this we have already entered into more fully under the -head of achromatism and hyperchromatism. - -325 (211). - -The objective experiments have this advantage that the progressive -states of the phenomenon may be arrested and clearly represented by -diagrams, which is not the case with the subjective experiments. - -326. - -We can observe the luminous image after it has emerged from the prism, -step by step, and mark its increasing colour by receiving it on a -plane at different distances, thus exhibiting before our eyes various -sections of this cone, with an elliptical base: again, the phenomenon -may at once be rendered beautifully visible throughout its whole course -in the following manner:--Let a cloud of fine white dust be excited -along the line in which the image passes through the dark space; the -cloud is best produced by fine, perfectly dry, hair-powder. The more or -less coloured appearance will now be painted on the white atoms, and -presented in its whole length and breadth to the eye of the spectator. - -327. - -By this means we have prepared some diagrams, which will be found among -the plates. In these the appearance is exhibited from its first origin, -and by these the spectator can clearly comprehend why the luminous -image is so much more powerfully coloured through prisms than through -parallel mediums. - -328 (212). - -At the two opposite outlines of the image an opposite appearance -presents itself, beginning from an acute angle;[1] the appearance -spreads as it proceeds further in space, according to this angle. On -one side, in the direction in which the luminous image is moved, a -violet border advances on the dark, a narrower blue edge remains next -the outline of the image. On the opposite side a yellow border advances -into the light of the image itself, and a yellow-red edge remains at -the outline. - -329 (213). - -Here, therefore, the movement of the dark against the light, of the -light against the dark, may be clearly observed. - - -[Illustration] - -330 (214). - -The centre of a large object remains long uncoloured, especially with -mediums of less density and smaller angles; but at last the opposite -borders and edges touch each other, upon which a green appears in the -centre of the luminous image. - -331 (215). - -Objective experiments have been usually made with the sun's image: an -objective experiment with a dark object has hitherto scarcely been -thought of. We have, however, prepared a convenient contrivance for -this also. Let the large water-prism before alluded to be placed in -the sun, and let a round pasteboard disk be fastened either inside or -outside. The coloured appearance will again take place at the outline, -beginning according to the usual law; the edges will appear, they will -spread in the same proportion, and when they meet, red will appear in -the centre[2]. An intercepting square may be added near the round disk, -and placed in any direction _ad libitum_, and the spectator can again -convince himself of what has been before so often described. - -332 (216). - -If we take away these dark objects from the prism, in which case, -however, the glass is to be carefully cleaned, and hold a rod or a -large pencil before the centre of the horizontal prism, we shall -then accomplish the complete immixture of the violet border and the -yellow-red edge, and see only the three colours, the external blue, and -yellow, and the central red. - -333. - -If again we cut a long horizontal opening in the middle of a piece of -pasteboard, fastened on the prism, and then cause the sun-light to pass -through it, we shall accomplish the complete union of the yellow border -with the blue edge upon the light, and only see yellow-red, green and -violet. The details of this are further entered into in the description -of the plates. - -334 (217). - -The prismatic appearance is thus by no means complete and final when -the luminous image emerges from the prism. It is then only that -we perceive its elements in contrast; for as it increases these -contrasting elements unite, and are at last intimately joined. The -section of this phenomenon arrested on a plane surface is different -at every degree of distance from the prism; so that the notion of an -immutable series of colours, or of a pervading similar proportion -between them, cannot be a question for a moment. - - -[1] Plate 4. fig. 1. - -[2] Plate 4. fig. 2. - - - - -XXIV. - - -EXPLANATION OF THE FOREGOING PHENOMENA. - - -335 (218). - -As we have already entered into this analysis circumstantially while -treating of the subjective experiments, as all that was of force there -is equally valid here, it will require no long details in addition to -show that the phenomena, which are entirely parallel in the two cases, -may also be traced precisely to the same sources. - -336 (219). - -That in objective experiments also we have to do with circumscribed -images, has been already demonstrated at large. The sun may shine -through the smallest opening, yet the image of the whole disk -penetrates beyond. The largest prism may be placed in the open -sun-light, yet it is still the sun's image that is bounded by the -edges of the refracting surfaces, and produces the accessory images -of this boundary. We may fasten pasteboard, with many openings cut in -it, before the water-prism, yet we still merely see multiplied images -which, after having been moved from their place by refraction, exhibit -coloured edges and borders, and in these mere accessory images. - -337 (235). - -In subjective experiments we have seen that objects strongly relieved -from each other produce a very lively appearance of colour, and this -will be the case in objective experiments in a much more vivid and -splendid degree. The sun's image is the most powerful brightness we -know; hence its accessory image will be energetic in proportion, and -notwithstanding its really secondary dimmed and darkened character, -must be still very brilliant. The colours thrown by the sun-light -through the prism on any object, carry a powerful light with them, for -they have the highest and most intense source of light, as it were, for -their ground. - -338. - -That we are warranted in calling even these accessory images -semi-transparent, thus deducing the appearances from the doctrine -of the semi-transparent mediums, will be clear to every one who has -followed us thus far, but particularly to those who have supplied -themselves with the necessary apparatus, so as to be enabled at all -times to witness the precision and vivacity with which semi-transparent -mediums act. - - - - -XXV. - - -DECREASE OF THE APPEARANCE OF COLOUR. - - -339 (243). - -If we could afford to be concise in the description of the decreasing -coloured appearance in subjective cases, we may here be permitted -to proceed with still greater brevity while we refer to the former -distinct statement. One circumstance, only on account of its great -importance, may be here recommended to the reader's especial attention -as a leading point of our whole thesis. - -340 (244, 247). - -The decline of the prismatic appearance must be preceded by its -separation, by its resolution into its elements. At a due distance from -the prism, the image of the sun being entirely coloured, the blue and -yellow at length mix completely, and we see only yellow-red, green, and -blue-red. If we bring the recipient surface nearer to the refracting -medium, yellow and blue appear again, and we see the five colours with -their gradations. At a still shorter distance the yellow and blue -separate from each other entirely, the green vanishes, and the image -itself appears, colourless, between the coloured edges and borders. The -nearer we bring the recipient surface to the prism, the narrower the -edges and borders become, till at last, when in contact with the prism, -they are reduced to nothing. - - - - -XXVI. - - -GREY OBJECTS. - - -341 (218). - -We have exhibited grey objects as very important to our inquiry in the -subjective experiments. They show, by the faintness of the accessory -images, that these same images are in all cases derived from the -principal object. If we wish here, too, to carry on the objective -experiments parallel with the others, we may conveniently do this by -placing a more or less dull ground glass before the opening through -which the sun's image enters. By this means a subdued image would be -produced, which on being refracted would exhibit much duller colours on -the recipient plane than those immediately derived from the sun's disk; -and thus, even from the intense sun-image, only a faint accessory image -would appear, proportioned to the mitigation of the light by the glass. -This experiment, it is true, will only again and again confirm what is -already sufficiently familiar to us. - - - - -XXVII. - - -COLOURED OBJECTS. - - -342 (260). - -There are various modes of producing coloured images in objective -experiments. In the first place, we can fix coloured glass before the -opening, by which means a coloured image is at once produced; secondly, -we can fill the water-prism with coloured fluids; thirdly, we can cause -the colours, already produced in their full vivacity by the prism, to -pass through proportionate small openings in a tin plate, and thus -prepare small circumscribed colours for a second operation. This last -mode is the most difficult; for owing to the continual progress of the -sun, the image cannot be arrested in any direction at will. The second -method has also its inconveniences, since not all coloured liquids can -be prepared perfectly bright and clear. On these accounts the first is -to be preferred, and deserves the more to be adopted because natural -philosophers have hitherto chosen to consider the colours produced -from the sun-light through the prism, those produced through liquids -and glasses, and those which are already fixed on paper or cloth, as -exhibiting effects equally to be depended on, and equally available in -demonstration. - -343. - -As it is thus merely necessary that the image should be coloured, so -the large water-prism before alluded to affords us the best means of -effecting this. A pasteboard screen may be contrived to slide before -the large surfaces of the prism, through which, in the first instance, -the light passes uncoloured. In this screen openings of various forms -may be cut, in order to produce different images, and consequently -different accessory images. This being done, we need only fix coloured -glasses before the openings, in order to observe what effect refraction -produces on coloured images in an objective sense. - -344. - -A series of glasses may be prepared in a mode similar to that before -described (284); these should be accurately contrived to slide in the -grooves of the large water-prism. Let the sun then shine through them, -and the coloured images refracted upwards will appear bordered and -edged, and will vary accordingly: for these borders and edges will be -exhibited quite distinctly on some images, and on others will be mixed -with the specific colour of the glass, which they will either enhance -or neutralize. Every observer will be enabled to convince himself -here again that we have only to do with the same simple phenomenon so -circumstantially described subjectively and objectively. - - - - -XXVIII. - - -ACHROMATISM AND HYPERCHROMATISM. - - -345 (285, 290). - -It is possible to make the hyperchromatic and achromatic experiments -objectively as well as subjectively. After what has been already -stated, a short description of the method will suffice, especially as -we take it for granted that the compound prism before mentioned is in -the hands of the observer. - -346. - -Let the sun's image pass through an acute-angled prism of few degrees, -prepared from crown-glass, so that the spectrum be refracted upwards on -an opposite surface; the edges will appear coloured, according to the -constant law, namely, the violet and blue above and outside, the yellow -and yellow-red below and within the image. As the refracting angle of -this prism is undermost, let another proportionate prism of flint-glass -be placed against it, with its refracting angle uppermost. The sun's -image will by this means be again moved to its place, where, owing to -the excess of the colouring power of the prism of flint-glass, it will -still appear a little coloured, and, in consequence of the direction -in which it has been moved, the blue and violet will now appear -underneath and outside, the yellow and yellow-red above and inside. - -347. - -If the whole image be now moved a little upwards by a proportionate -prism of crown-glass, the hyperchromatism will disappear, the sun's -image will be moved from its place, and yet will appear colourless. - -348. - -With an achromatic object-glass composed of three glasses, this -experiment may be made step by step, if we do not mind taking out the -glasses from their setting. The two convex glasses of crown-glass in -contracting the sun's image towards the focus, the concave glass of -flint-glass in dilating the image beyond it, exhibit at the edges the -usual colours. A convex glass united with a concave one exhibits the -colours according to the law of the latter. If all three glasses are -placed together, whether we contract the sun's image towards the focus, -or suffer it to dilate beyond the focus, coloured edges never appear, -and the achromatic effect intended by the optician is, in this case, -again attained. - -349. - -But as the crown-glass has always a greenish tint, and as a tendency -to this hue may be more decided in large and strong object-glasses, -and under certain circumstances produce the compensatory red, -(which, however, in repeated experiments with several instruments of -this kind did not occur to us,) philosophers have resorted to the -most extraordinary modes of explaining such a result; and having -been compelled, in support of their system, theoretically to prove -the impossibility of achromatic telescopes, have felt a kind of -satisfaction in having some apparent ground for denying so great an -improvement. Of this, however, we can only treat circumstantially in -our historical account of these discoveries. - - - - -XXIX. - - -COMBINATION OF SUBJECTIVE AND OBJECTIVE EXPERIMENTS. - - -350. - -Having shown above (318) that refraction, considered objectively and -subjectively, must act in opposite directions, it will follow that if -we combine the experiments, the effects will reciprocally destroy each -other. - -351. - -Let the sun's image be thrown upwards on a vertical plane, through -a horizontally-placed prism. If the prism is long enough to admit of -the spectator also looking through it, he will see the image elevated -by the objective refraction again depressed, and in the same place in -which it appeared without refraction. - -352. - -Here a remarkable case presents itself, but at the same time a natural -result of a general law. For since, as often before stated, the -objective sun's image thrown on the vertical plane is not an ultimate -or unchangeable state of the phenomenon, so in the above operation the -image is not only depressed when seen through the prism, but its edges -and borders are entirely robbed of their hues, and the spectrum is -reduced to a colourless circular form. - -353. - -By employing two perfectly similar prisms placed next each other, for -this experiment, we can transmit the sun's image through one, and look -through the other. - -354. - -If the spectator advances nearer with the prism through which he looks, -the image is again elevated, and by degrees becomes coloured according -to the law of the first prism. If he again retires till he has brought -the image to the neutralized point, and then retires still farther -away, the image, which had become round and colourless, moves still -more downwards and becomes coloured in the opposite sense, so that -if we look through the prism and upon the refracted spectrum at the -same time, we see the same image coloured according to subjective and -objective laws. - -355. - -The modes in which this experiment may be varied are obvious. If the -refracting angle of the prism, through which the sun's image was -objectively elevated, is greater than that of the prism through which -the observer looks, he must retire to a much greater distance, in order -to depress the coloured image so low on the vertical plane that it -shall appear colourless, and _vice versâ_. - -356. - -It will be easily seen that we may exhibit achromatic and -hyperchromatic effects in a similar manner, and we leave it to the -amateur to follow out such researches more fully. Other complicated -experiments in which prisms and lenses are employed together, others -again, in which objective and subjective experiments are variously -intermixed, we reserve for a future occasion, when it will be our -object to trace such effects to the simple phenomena with which we are -now sufficiently familiar. - - - - -XXX. - - -TRANSITION. - - -357. - -In looking back on the description and analysis of dioptrical colours, -we do not repent either that we have treated them so circumstantially, -or that we have taken them into consideration before the other physical -colours, out of the order we ourselves laid down. Yet, before we quit -this branch of our inquiry, it may be as well to state the reasons that -have weighed with us. - -358. - -If some apology is necessary for having treated the theory of the -dioptrical colours, particularly those of the second class, so -diffusely, we should observe, that the exposition of any branch of -knowledge is to be considered partly with reference to the intrinsic -importance of the subject, and partly with reference to the particular -necessities of the time in which the inquiry is undertaken. In our -own case we were forced to keep both these considerations constantly -in view. In the first place we had to state a mass of experiments with -our consequent convictions; next, it was our especial aim to exhibit -certain phenomena (known, it is true, but misunderstood, and above -all, exhibited in false connection,) in that natural and progressive -development which is strictly and truly conformable to observation; in -order that hereafter, in our polemical or historical investigations, -we might be enabled to bring a complete preparatory analysis to bear -on, and elucidate, our general view. The details we have entered into -were on this account unavoidable; they may be considered as a reluctant -consequence of the occasion. Hereafter, when philosophers will look -upon a simple principle as simple, a combined effect as combined; when -they will acknowledge the first elementary, and the second complicated -states, for what they are; then, indeed, all this statement may be -abridged to a narrower form; a labour which, should we ourselves -not be able to accomplish it, we bequeath to the active interest of -contemporaries and posterity. - -359. - -With respect to the order of the chapters, it should be remembered -that natural phenomena, which are even allied to each other, are -not connected in any particular sequence or constant series; their -efficient causes act in a narrow circle, so that it is in some sort -indifferent what phenomenon is first or last considered; the main point -is, that all should be as far as possible present to us, in order that -we may embrace them at last from one point of view, partly according to -their nature, partly according to generally received methods. - -360. - -Yet, in the present particular instance, it may be asserted that the -dioptrical colours are justly placed at the head of the physical -colours; not only on account of their striking splendour and their -importance in other respects, but because, in tracing these to their -source, much was necessarily entered into which will assist our -subsequent enquiries. - -361. - -For, hitherto, light has been considered as a kind of abstract -principle, existing and acting independently; to a certain extent -self-modified, and on the slightest cause, producing colours out of -itself. To divert the votaries of physical science from this mode -of viewing the subject; to make them attentive to the fact, that in -prismatic and other appearances we have not to do with light as an -uncircumscribed and modifying principle, but as circumscribed and -modified; that we have to do with a luminous image; with images or -circumscribed objects generally, whether light or dark: this was the -purpose we had in view, and such is the problem to be solved. - -362. - -All that takes place in dioptrical cases,--especially those of the -second class which are connected with the phenomena of refraction,--is -now sufficiently familiar to us, and will serve as an introduction to -what follows. - -363. - -Catoptrical appearances remind us of the physiological phenomena, but -as we ascribe a more objective character to the former, we thought -ourselves justified in classing them with the physical examples. It is -of importance, however, to remember that here again it is not light, in -an abstract sense, but a luminous image that we have to consider. - -364. - -In proceeding onwards to the paroptrical class, the reader, if duly -acquainted with the foregoing facts, will be pleased to find himself -once more in the region of circumscribed forms. The shadows of bodies, -especially, as secondary images, so exactly accompanying the object, -will serve greatly to elucidate analogous appearances. - -365. - -We will not, however, anticipate these statements, but proceed as -heretofore in what we consider the regular course. - - - - -XXXI. - - -CATOPTRICAL COLOURS. - - -366. - -Catoptrical colours are such as appear in consequence of a mirror-like -reflection. We assume, in the first place, that the light itself -as well as the surface from which it is reflected, is perfectly -colourless. In this sense the appearances in question come under the -head of physical colours. They arise in consequence of reflection, as -we found the dioptrical colours of the second class appear by means of -refraction. Without further general definitions, we turn our attention -at once to particular cases, and to the conditions which are essential -to the exhibition of these phenomena. - -367. - -If we unroll a coil of bright steel-wire, and after suffering it to -spring confusedly together again, place it at a window in the light, -we shall see the prominent parts of the circles and convolutions -illumined, but neither resplendent nor iridescent. But if the sun -shines on the wire, this light will be condensed into a point, and we -perceive a small resplendent image of the sun, which, when seen near, -exhibits no colour. On retiring a little, however, and fixing the eyes -on this refulgent appearance, we discern several small mirrored suns, -coloured in the most varied manner; and although the impression is that -green and red predominate, yet, on a more accurate inspection, we find -that the other colours are also present. - -368. - -If we take an eye-glass, and examine the appearance through it, we -find the colours have vanished, as well as the radiating splendour in -which they were seen, and we perceive only the small luminous points, -the repeated images of the sun. We thus find that the impression is -subjective in its nature, and that the appearance is allied to those -which we have adverted to under the name of radiating halos (100). - -369. - -We can, however, exhibit this phenomenon objectively. Let a piece -of white paper be fastened beneath a small aperture in the lid of a -camera-obscura, and when the sun shines through this aperture, let -the confusedly-rolled steel-wire be held in the light, so that it be -opposite to the paper. The sun-light will impinge on and in the circles -of the wire, and will not, as in the concentrating lens of the eye, -display itself in a point; but, as the paper can receive the reflection -of the light in every part of its surface will be seen in hair-like -lines, which are also iridescent. - -370. - -This experiment is purely catoptrical; for as we cannot imagine that -the light penetrates the surface of the steel, and thus undergoes a -change, we are soon convinced that we have here a mere reflection -which, in its subjective character, is connected with the theory of -faintly acting lights, and the after-image of dazzling lights, and as -far as it can be considered objective, announces even in the minutest -appearances, a real effect, independent of the action and reaction of -the eye. - -371. - -We have seen that to produce these effects not merely light but a -powerful light is necessary; that this powerful light again is not an -abstract and general quality, but a circumscribed light, a luminous -image. We can convince ourselves still further of this by analogous -cases. - -372. - -A polished surface of silver placed in the sun reflects a dazzling -light, but in this case no colour is seen. If, however, we slightly -scratch the surface, an iridescent appearance, in which green and red -are conspicuous, will be exhibited at a certain angle. In chased and -carved metals the effect is striking: yet it may be remarked throughout -that, in order to its appearance, some form, some alternation of light -and dark must co-operate with the reflection; thus a window-bar, -the stem of a tree, an accidentally or purposely interposed object -produces a perceptible effect. This appearance, too, may be exhibited -objectively in the camera-obscura. - -373. - -If we cause a polished plated surface to be so acted on by aqua fortis -that the copper within is touched, and the surface itself thus rendered -rough, and if the sun's image be then reflected from it, the splendour -will be reverberated from every minutest prominence, and the surface -will appear iridescent. So, if we hold a sheet of black unglazed paper -in the sun, and look at it attentively, it will be seen to glisten in -its minutest points with the most vivid colours. - -374. - -All these examples are referable to the same conditions. In the first -case the luminous image is reflected from a thin line; in the second -probably from sharp edges; in the third from very small points. In all -a very powerful and circumscribed light is requisite. For all these -appearances of colour again it is necessary that the eye should be at a -due distance from the reflecting points. - -375. - -If these observations are made with the microscope, the appearance -will be greatly increased in force and splendour, for we then see the -smallest portion of the surfaces, lit by the sun, glittering in these -colours of reflection, which, allied to the hues of refraction, now -attain their highest degree of brilliancy. In such cases we may observe -a vermiform iridescence on the surface of organic bodies, the further -description of which will be given hereafter. - -376. - -Lastly, the colours which are chiefly exhibited in reflection are red -and green, whence we may infer that the linear appearance especially -consists of a thin line of red, bounded by blue on one side and yellow -on the other. If these triple lines approach very near together, the -intermediate space must appear green; a phenomenon which will often -occur to us as we proceed. - -377. - -We frequently meet with these colours in nature. The colours of the -spider's web might be considered exactly of the same class with those -reflected from the steel wire, except that the non-translucent quality -of the former is not so certain as in the case of steel; on which -account some have been inclined to class the colours of the spider's -web with the phenomena of refraction. - -378. - -In mother-of-pearl we perceive infinitely fine organic fibres and -lamellæ in juxta-position, from which, as from the scratched silver -before alluded to, varied colours, but especially red and green, may -arise. - -379. - -The changing colours of the plumage of birds may also be mentioned -here, although in all organic instances a chemical principle -and an adaptation of the colour to the structure may be assumed; -considerations to which we shall return in treating of chemical colours. - -380. - -That the appearances of objective halos also approximate catoptrical -phenomena will be readily admitted, while we again do not deny that -refraction as well may here come into the account. For the present -we restrict ourselves to one or two observations; hereafter we may -be enabled to make a fuller application of general principles to -particular examples. - -381. - -We first call to mind the yellow and red circles produced on a white or -grey wall by a light placed near it (88). Light when reflected appears -subdued, and a subdued light excites the impression of yellow, and -subsequently of red. - -382. - -Let the wall be illumined by a candle placed quite close to it. The -farther the light is diffused the fainter it becomes; but it is still -the effect of the flame, the continuation of its action, the dilated -effect of its image. We might, therefore, very fairly call these -circles reiterated images, because they constitute the successive -boundaries of the action of the light, and yet at the same time only -present an extended image of the flame. - -383. - -If the sky is white and luminous round the sun owing to the atmosphere -being filled with light vapours; if mists or clouds pass before the -moon, the reflection of the disk mirrors itself in them; the halos we -then perceive are single or double, smaller or greater, sometimes very -large, often colourless, sometimes coloured. - -384. - -I witnessed a very beautiful halo round the moon the 15th of November, -1799, when the barometer stood high; the sky was cloudy and vapoury. -The halo was completely coloured, and the circles were concentric round -the light as in subjective halos. That this halo was objective I was -presently convinced by covering the moon's disk, when the same circles -were nevertheless perfectly visible. - -385. - -The different extent of the halos appears to have a relation with the -proximity or distance of the vapour from the eye of the observer. - -386. - -As window-panes lightly breathed upon increase the brilliancy of -subjective halos, and in some degree give them an objective character, -so, perhaps, with a simple contrivance in winter, during a quickly -freezing temperature, a more exact definition of this might be arrived -at. - -387. - -How much reason we have in considering these circles to insist on the -_image_ and its effects, is apparent in the phenomenon of the so-called -double suns. Similar double images always occur in certain points -of halos and circles, and only present in a circumscribed form what -takes place in a more general way in the whole circle. All this will -be more conveniently treated in connexion with the appearance of the -rainbow.--Note Q. - -388. - -In conclusion it is only necessary to point out the affinity between -the catoptrical and paroptical colours. - -We call those paroptical colours which appear when the light passes -by the edge of an opaque colourless body. How nearly these are allied -to the dioptrical colours of the second class will be easily seen by -those who are convinced with us that the colours of refraction [Pg 163] -take place only at the edges of objects. The affinity again between the -catoptrical and paroptical colours will be evident in the following -chapter. - - - - -XXXII. - - -PAROPTICAL COLOURS. - - -389. - -The paroptical colours have been hitherto called peri-optical, because -a peculiar effect of light was supposed to take place as it were round -the object, and was ascribed to a certain flexibility of the light to -and from the object. - -390. - -These colours again may be divided into subjective and objective, -because they appear partly without us, as it were, painted on surfaces, -and partly within us, immediately on the retina. In this chapter we -shall find it more to our purpose to take the objective cases first, -since the subjective are so closely connected with other appearances -already known to us, that it is hardly possible to separate them. - -391. - -The paroptical colours then are so called because the light must pass -by an outline or edge to produce them. They do not, however, always -appear in this case; to produce the effect very particular conditions -are necessary besides. - -392. - -It is also to be observed that in this instance again light does not -act as an abstract diffusion (361), the sun shines towards an edge. -The volume of light poured from the sun-image passes by the edge of -a substance, and occasions shadows. Within these shadows we shall -presently find colours appear. - -393. - -But, above all, we should make the experiments and observations that -bear upon our present inquiry in the fullest light. We, therefore, -place the observer in the open air before we conduct him to the limits -of a dark room. - -394. - -A person walking in sun-shine in a garden, or on any level path, may -observe that his shadow only appears sharply defined next the foot on -which he rests; farther from this point, especially round the head, it -melts away into the bright ground. For as the sun-light proceeds not -only from the middle of the sun, but also acts cross-wise from the two -extremes of every diameter, an objective parallax takes place which -produces a half-shadow on both sides of the object. - -395. - -If the person walking raises and spreads his hand, he distinctly sees -in the shadow of each finger the diverging separation of the two -half-shadows outwards, and the diminution of the principal shadow -inwards, both being effects of the cross action of the light. - -396. - -This experiment may be repeated and varied before a smooth wall, -with rods of different thicknesses, and again with balls; we shall -always find that the farther the object is removed from the surface of -the wall, the more the weak double shadow spreads, and the more the -forcible main shadow diminishes, till at last the main shadow appears -quite effaced, and even the double shadows become so faint, that they -almost disappear; at a still greater distance they are, in fact, -imperceptible. - -397. - -That this is caused by the cross-action of the light we may easily -convince ourselves; for the shadow of a pointed object plainly exhibits -two points. We must thus never lose sight of the fact that in this -case the whole sun-image acts, produces shadows, changes them to double -shadows, and finally obliterates them. - -398. - -Instead of solid bodies let us now take openings cut of various given -sizes next each other, and let the sun shine through them on a plane -surface at some little distance; we shall find that the bright image -produced by the sun on the surface, is larger than the opening; this -is because one edge of the sun shines towards the opposite edge of the -opening, while the other edge of the disk is excluded on that side. -Hence the bright image is more weakly lighted towards the edges. - -399. - -If we take square openings of any size we please, we shall find that -the bright image on a surface nine feet from the opening, is on every -side about an inch larger than the opening; thus nearly corresponding -with the angle of the apparent diameter of the sun. - -400. - -That the brightness should gradually diminish towards the edges of the -image is quite natural, for at last only a minimum of the light can -act cross-wise from the sun's circumference through the edge of the -aperture. - -401. - -Thus we here again see how much reason we have in actual observation to -guard against the assumption of parallel rays, bundles and fasces of -rays, and the like hypothetical notions. - -402. - -We might rather consider the splendour of the sun, or of any light, -as an infinite specular multiplication of the circumscribed luminous -image, whence it may be explained that all square openings through -which the sun shines, at certain distances, according as the apertures -are greater or smaller, must give a round image of light. - -403. - -The above experiments may be repeated through openings of various -shapes and sizes, and the same effect will always take place at -proportionate distances. In all these cases, however, we may still -observe that in a full light and while the sun merely shines past an -edge, no colour is apparent. - -404. - -We therefore proceed to experiments with a subdued light, which is -essential to the appearance of colour. Let a small opening be made in -the window-shutter of a dark room; let the crossing sun-light which -enters, be received on a surface of white paper, and we shall find that -the smaller the opening is, the dimmer the light image will be. This is -quite obvious, because the paper does not receive light from the whole -sun, but partially from single points of its disk. - -405. - -If we look attentively at this dim image of the sun, we find it still -dimmer towards the outlines where a yellow border is perceptible. The -colour is still more apparent if a vapour or a transparent cloud passes -before the sun, thus subduing and dimming its brightness. The halo on -the wall, the effect of the decreasing brightness of a light placed -near it, is here forced on our recollection. (88.) - -406. - -If we examine the image more accurately, we perceive that this yellow -border is not the only appearance of colour; we can see, besides, a -bluish circle, if not even a halo-like repetition of the coloured -border. If the room is quite dark, we discern that the sky next the -sun also has its effect: we see the blue sky, nay, even the whole -landscape, on the paper, and are thus again convinced that as far as -regards the sun, we have here only to do with a luminous image. - -407. - -If we take a somewhat larger square opening, so large that the image -of the sun shining through it does not immediately become round, we -may distinctly observe the half-shadows of every edge or side, the -junction of these in the corners, and their colours; just as in the -above-mentioned appearance with the round opening. - -408. - -We have now subdued a parallactic light by causing it to shine through -small apertures, but we have not taken from it its parallactic -character; so that it can produce double shadows of bodies, although -with diminished power. These double shadows which we have hitherto -been describing, follow each other in light and dark, coloured and -colourless circles, and produce repeated, nay, almost innumerable -halos. These effects have been often represented in drawings and -engravings. By placing needles, hairs, and other small bodies, in the -subdued light, the numerous halo-like double shadows may be increased; -thus observed, they have been ascribed to an alternating flexile action -of the light, and the same assumption has been employed to explain the -obliteration of the central shadow, and the appearance of a light in -the place of the dark. - -409. - -For ourselves, we maintain that these again are parallactic double -shadows, which appear edged with coloured borders and halos. - -410. - -After having seen and investigated the foregoing phenomena, we -can proceed to the experiments with knife-blades,[1] exhibiting -effects which may be referred to the contact and parallactic mutual -intersection of the half-shadows and halos already familiar to us. - -411. - -Lastly, the observer may follow out the experiments with hairs, -needles, and wires, in the half-light produced as before described by -the sun, as well as in that derived from the blue sky, and indicated on -the white paper. He will thus make himself still better acquainted with -the true nature of this phenomenon. - -412. - -But since in these experiments everything depends on our being -persuaded of the parallactic action of the light, we can make this more -evident by means of two sources of light, the two shadows from which -intersect each other, and may be altogether separated. By day this may -be contrived with two small openings in a window-shutter; by night, -with two candles. There are even accidental effects in interiors, on -opening and closing shutters, by means of which we can better observe -these appearances than with the most careful apparatus. But still, -all and each of these may be reduced to experiment by preparing a box -which the observer can look into from above, and gradually diminishing -the openings after having caused a double light to shine in. In this -case, as might be expected, the coloured shadow, considered under the -physiological colours, appears very easily. - -413. - -It is necessary to remember, generally, what has been before stated -with regard to the nature of double shadows, half-lights, and the like. -Experiments also should especially be made with different shades of -grey placed next each other, where every stripe will appear light by a -darker, and dark by a lighter stripe next it. If at night, with three -or more lights, we produce shadows which cross each other successively, -we can observe this phenomenon very distinctly, and we shall be -convinced that the physiological case before more fully treated, here -comes into the account (38). - -414. - -To what extent the appearances that accompany the paroptical colours, -may be derived from the doctrine of subdued lights, from half-shadows, -and from the physiological disposition of the retina, or whether we -shall be forced to take refuge in certain intrinsic qualities of light, -as has hitherto been done, time may teach. Suffice it here to have -pointed out the conditions under which the paroptical colours appear, -and we may hope that our allusion to their connexion with the facts -before adduced by us will not remain unnoticed by the observers of -nature. - -415. - -The affinity of the paroptical colours with the dioptrical of the -second class will also be readily seen and followed up by every -reflecting investigator. Here, as in those instances, we have to do -with edges or boundaries; here, as in those instances, with a light, -which appears at the outline. How natural, therefore, it is to conclude -that the paroptical effects may be heightened, strengthened, and -enriched by the dioptrical. Since, however, the luminous image actually -shines through the medium, we can here only have to do with objective -cases of refraction: it is these which are strictly allied to the -paroptical cases. The subjective cases of refraction, where we see -objects through the medium, are quite distinct from the paroptical. -We have already recommended them on account of their clearness and -simplicity. - -416. - -The connexion between the paroptical colours and the catoptrical may -be already inferred from what has been said: for as the catoptrical -colours only appear on scratches, points, steel-wire, and delicate -threads, so it is nearly the same case as if the light shone past an -edge. The light must always be reflected from an edge in order to -produce colour. Here again, as before pointed out, the partial action -of the luminous image and the subduing of the light are both to be -taken into the account. - -417. - -We add but few observations on the subjective paroptical colours, -because these may be classed partly with the physiological colours, -partly with the dioptrical of the second order. The greater part hardly -seem to belong here, but, when attentively considered, they still -diffuse a satisfactory light over the whole doctrine, and establish its -connexion. - -418. - -If we hold a ruler before the eyes so that the flame of a light just -appears above it, we see the ruler as it were indented and notched -at the place where the light appears. This seems deducible from the -expansive power of light acting on the retina (18). - -419. - -The same phenomenon on a large scale is exhibited at sun-rise; for when -the orb appears distinctly, but not too powerfully, so that we can -still look at it, it always makes a sharp indentation in the horizon. - -420. - -If, when the sky is grey, we approach a window, so that the dark cross -of the window-bars be relieved on the sky; if after fixing the eyes on -the horizontal bar we bend the head a little forward; on half closing -the eyes as we look up, we shall presently perceive a bright yellow-red -border under the bar, and a bright light-blue one above it. The duller -and more monotonous the grey of the sky, the more dusky the room, and, -consequently, the more previously unexcited the eye, the livelier the -appearance will be; but it may be seen by an attentive observer even in -bright daylight. - -421. - -If we move the head backwards while half closing the eyes, so that the -horizontal bar be seen below, the phenomenon will appear reversed. The -upper edge will appear yellow, the under edge blue. - -422. - -Such observations are best made in a dark room. If white paper is -spread before the opening where the solar microscope is commonly -fastened, the lower edge of the circle will appear blue, the upper -yellow, even while the eyes are quite open, or only by half-closing -them so far that a halo no longer appears round the white. If the head -is moved backwards the colours are reversed. - -423. - -These phenomena seem to prove that the humours of the eye are in fact -only really achromatic in the centre where vision takes place, but that -towards the circumference, and in unusual motions of the eyes, as in -looking horizontally when the head is bent backwards or forwards, a -chromatic tendency remains, especially when distinctly relieved objects -are thus looked at. Hence such phenomena may be considered as allied to -the dioptrical colours of the second class. - -424. - -Similar colours appear if we look on black and white objects, through a -pin-hole in a card. Instead of a white object we may take the minute -light aperture in the tin plate of a camera obscura, as prepared for -paroptical experiments. - -425. - -If we look through a tube, the farther end of which is contracted or -variously indented, the same colours appear. - -426. - -The following phenomena appear to me to be more nearly allied to the -paroptical appearances. If we hold up a needle near the eye, the point -appears double. A particularly remarkable effect again is produced if -we look towards a grey sky through the blades of knives prepared for -paroptical experiments. We seem to look through a gauze; a multitude of -threads appear to the eye; these are in fact only the reiterated images -of the sharp edges, each of which is successively modified by the next, -or perhaps modified in a parallactic sense by the oppositely acting -one, the whole mass being thus changed to a thread-like appearance. - -427. - -Lastly, it is to be remarked that if we look through the blades towards -a minute light in the window-shutter, coloured stripes and halos -appear on the retina as on the paper. - -428. - -The present chapter may be here terminated, the less reluctantly, -as a friend has undertaken to investigate this subject by further -experiments. In our recapitulation, in the description of the -plates and apparatus, we hope hereafter to give an account of his -observations.[2] - - -[1] See Newton's Optics, book iii. - -[2] The observations here alluded to never appeared. - - - - -XXXIII. - - -EPOPTICAL COLOURS. - - -429. - -We have hitherto had to do with colours which appear with vivacity, but -which immediately vanish again when certain conditions cease. We have -now to become acquainted with others, which it is true are still to be -considered as transient, but which, under certain circumstances, become -so fixed that, even after the conditions which first occasioned their -appearance cease, they still remain, and thus constitute the link -between the physical and the chemical colours. - -430. - -They appear from various causes on the surface of a colourless body, -originally, without communication, die or immersion (βαφή); and we now -proceed to trace them, from their faintest indication to their most -permanent state, through the different conditions of their appearance, -which for easier survey we here at once summarily state. - -431. - -First condition.--The contact of two smooth surfaces of hard -transparent bodies. - -First case: if masses or plates of glass, or if lenses are pressed -against each other. - -Second case: if a crack takes place in a solid mass of glass, chrystal, -or ice. - -Third case: if lamellæ of transparent stones become separated. - -Second condition.--If a surface of glass or a polished stone is -breathed upon. - -Third condition.--The combination of the two last; first, breathing on -the glass, then placing another plate of glass upon it, thus exciting -the colours by pressure; then removing the upper glass, upon which the -colours begin to fade and vanish with the breath. - -Fourth condition.--Bubbles of various liquids, soap, chocolate, beer, -wine, fine glass bubbles. - -Fifth condition.--Very fine pellicles and lamellæ, produced by the -decomposition of minerals and metals. The pellicles of lime, the -surface of stagnant water, especially if impregnated with iron, and -again pellicles of oil on water, especially of varnish on aqua fortis. - -Sixth condition.--If metals are heated; the operation of imparting -tints to steel and other metals. - -Seventh condition.--If the surface of glass is beginning to decompose. - -432. - -First condition, first case. If two convex glasses, or a convex and -plane glass, or, best of all, a convex and concave glass come in -contact, concentric coloured circles appear. The phenomenon exhibits -itself immediately on the slightest pressure, and may then be gradually -carried through various successive states. We will describe the -complete appearance at once, as we shall then be better enabled to -follow the different states through which it passes. - -433. - -The centre is colourless; where the glasses are, so to speak, united -in one by the strongest pressure, a dark grey point appears with a -silver white space round it: then follow, in decreasing distances, -various insulated rings, all consisting of three colours, which are -in immediate contact with each other. Each of these rings, of which -perhaps three or four might be counted, is yellow on the inner side, -blue on the outer, and red in the centre. Between two rings there -appears a silver white interval. The rings which are farthest from the -centre are always nearer together: they are composed of red and green -without a perceptible white space between them. - -434. - -We will now observe the appearances in their gradual formation, -beginning from the slightest pressure. - -435. - -On the slightest pressure the centre itself appears of a green colour. -Then follow as far as the concentric circles extend, red and green -rings. They are wide, accordingly, and no trace of a silver white -space is to be seen between them. The green is produced by the blue of -an imperfectly developed circle, mixing with the yellow of the first -circle. All the remaining circles are, in this slight contact, broad; -their yellow and blue edges mix together, thus producing a beautiful -green. The red, however, of each circle, remains pure and untouched; -hence the whole series is composed of these two colours. - -436. - -A somewhat stronger pressure separates the first circle by a slight -interval from the imperfectly developed one: it is thus detached, and -may be said to appear in a complete state. The centre is now a blue -point; for the yellow of the first circle is now separated from this -central point by a silver white space. From the centre of the blue a -red appears, which is thus, in all cases, bounded on the outside by -its blue edge. The second and third rings from the centre are quite -detached. Where deviations from this order present themselves, the -observer will be enabled to account for them, from what has been or -remains to be stated. - -437. - -On a stronger pressure the centre becomes yellow; this yellow is -surrounded by a red and blue edge: at last, the yellow also retires -from the centre; the innermost circle is formed and is bounded with -yellow. The whole centre itself now appears silver white, till at last, -on the strongest pressure, the dark point appears, and the phenomenon, -as described at first, is complete. - -438. - -The relative size of the concentric circles and their intervals depends -on the form of the glasses which are pressed together. - -439. - -We remarked above, that the coloured centre is, in fact, an undeveloped -circle. It is, however, often found, on the slightest pressure, that -several undeveloped circles exist there, as it were, in the germ; these -can be successively developed before the eye of the observer. - -440. - -The regularity of these rings is owing to the form of the convex -glasses, and the diameter of the coloured appearance depends on the -greater or lesser section of a circle on which a lens is polished. We -easily conclude from this, that by pressing plane glasses together, -irregular appearances only will be produced; the colours, in fact, -undulate like watered silks, and spread from the point of pressure in -all directions. Yet, the phenomenon as thus exhibited is much more -splendid than in the former instance, and cannot fail to strike every -spectator. If we make the experiment in this mode, we shall distinctly -see, as in the other case, that, on a slight pressure, the green and -red waves appear; on a stronger, stripes of blue, red, and yellow, -become detached. At first, the outer sides of these stripes touch; on -increased pressure they are separated by a silver white space. - -441. - -Before we proceed to a further description of this phenomenon, we may -point out the most convenient mode of exhibiting it. Place a large -convex glass on a table near the window; upon this glass lay a plate -of well-polished mirror-glass, about the size of a playing-card, and -the mere weight of the plate will press sufficiently to produce one -or other of the phenomena above described. So, also, by the different -weight of plates of glass, by other accidental circumstances, for -instance, by slipping the plate on the side of the convex glass where -the pressure cannot be so strong as in the centre, all the gradations -above described can be produced in succession. - -442. - -In order to observe the phenomenon it is necessary to look obliquely -on the surface where it appears. But, above all, it is to be remarked -that by stooping still more, and looking at the appearance under a more -acute angle, the circles not only grow larger but other circles are -developed from the centre, of which no trace is to be discovered when -we look perpendicularly, even through the strongest magnifiers. - -443. - -In order to exhibit the phenomenon in its greatest beauty, the utmost -attention should be paid to the cleanness of the glasses. If the -experiment is made with plate-glass adapted for mirrors, the glass -should be handled with gloves. The inner surfaces, which must come in -contact with the utmost nicety, may be most conveniently cleaned before -the experiment, and the outer surfaces should be kept clean while the -pressure is increased. - -444. - -From what has been said it will be seen that an exact contact of two -smooth surfaces is necessary. Polished glasses are best adapted for the -purpose. Plates of glass exhibit the most brilliant colours when they -fit closely together, and for this reason the phenomenon will increase -in beauty if exhibited under an air-pump, by exhausting the air. - -445. - -The appearance of the coloured rings may be produced in the greatest -perfection by placing a convex and concave glass together which have -been ground on similar segments of circles. I have never seen the -effect more brilliant than with the object-glass of an achromatic -telescope, in which the crown-glass and flint-glass were necessarily -in the closest contact. - -446. - -A remarkable appearance takes place when dissimilar surfaces are -pressed together; for example, a polished crystal and a plate of -glass. The appearance does not at all exhibit itself in large flowing -waves, as in the combination of glass with glass, but it is small and -angular, and, as it were, disjointed: thus it appears that the surface -of the polished crystal, which consists of infinitely small sections of -lamellæ, does not come so uninterruptedly in contact with the glass as -another glass-plate would. - -447. - -The appearance of colour vanishes on the strongest pressure, which so -intimately unites the two surfaces that they appear to make but one -substance. It is this which occasions the dark centre, because the -pressed lens no longer reflects any light from this point, for the -very same point, when seen against the light, is perfectly clear and -transparent. On relaxing the pressure, the colours, in like manner, -gradually diminish, and disappear entirely when the surfaces are -separated. - -448. - -These same appearances occur in two similar cases. If entirely -transparent masses become partially separated, the surfaces of their -parts being still sufficiently in contact, we see the same circles and -waves more or less. They may be produced in great beauty by plunging a -hot mass of glass in water; the different fissures and cracks enabling -us to observe the colours in various forms. Nature often exhibits the -same phenomena in split rock crystals. - -449. - -This appearance, again, frequently displays itself in the mineral world -in those kinds of stone which by nature have a tendency to exfoliate. -These original lamellæ are, it is true, so intimately united, that -stones of this kind appear altogether transparent and colourless, yet, -the internal layers become separated, from various accidental causes, -without altogether destroying the contact: thus the appearance, which -is now familiar to us by the foregoing description, often occurs in -nature, particularly in calcareous spars; the specularis, adularia, and -other minerals of similar structure. Hence it shows an ignorance of the -proximate causes of an appearance so often accidentally produced, to -consider it so important in mineralogy, and to attach especial value to -the specimens exhibiting it. - -450. - -We have yet to speak of the very remarkable inversion of this -appearance, as related by men of science. If, namely, instead of -looking at the colours by a reflected light, we examine them by a -transmitted light, the opposite colours are said to appear, and in -a mode corresponding with that which we have before described as -physiological; the colours evoking each other. Instead of blue, we -should thus see red-yellow; instead of red, green, &c., and _vice -versâ_. We reserve experiments in detail, the rather as we have -ourselves still some doubts on this point. - -451. - -If we were now called upon to give some general explanation of these -epoptical colours, as they appear under the first condition, and to -show their connexion with the previously detailed physical phenomena, -we might proceed to do so as follows:-- - -452. - -The glasses employed for the experiments are to be regarded as the -utmost possible practical approach to transparence. By the intimate -contact, however, occasioned by the pressure applied to them, their -surfaces, we are persuaded, immediately become in a very slight -degree dimmed. Within this semi-transparence the colours immediately -appear, and every circle comprehends the whole scale; for when the two -opposites, yellow and blue, are united by their red extremities, pure -red appears: the green, on the other hand, as in prismatic experiments, -when yellow and blue touch. - -453. - -We have already repeatedly found that where colour exists at all, the -whole scale is soon called into existence; a similar principle may be -said to lurk in the nature of every physical phenomenon; it already -follows, from the idea of polar opposition, from which an elementary -unity or completeness results. - -454. - -The fact that a colour exhibited by transmitted light is different -from that displayed by reflected light, reminds us of those dioptrical -colours of the first class which we found were produced precisely in -the same way through semi-opacity. That here, too, a diminution of -transparency exists there can scarcely be a doubt; for the adhesion -of the perfectly smooth plates of glass (an adhesion so strong that -they remain hanging to each other) produces a degree of union which -deprives each of the two surfaces, in some degree, of its smoothness -and transparence. The fullest proof may, however, be found in the -fact that in the centre, where the lens is most strongly pressed on -the other glass, and where a perfect union is accomplished, a complete -transparence takes place, in which we no longer perceive any colour. -All this may be hereafter confirmed in a recapitulation of the whole. - -455. - -Second condition.--If after breathing on a plate of glass, the breath -is merely wiped away with the finger, and if we then again immediately -breathe on the glass, we see very vivid colours gliding through each -other; these, as the moisture evaporates, change their place, and at -last vanish altogether. If this operation is repeated, the colours are -more vivid and beautiful, and remain longer than they did the first -time. - -456. - -Quickly as this appearance passes, and confused as it appears to be, I -have yet remarked the following effects:--At first all the principal -colours appear with their combinations; on breathing more strongly, the -appearance may be perceived in some order. In this succession it may be -remarked, that when the breath in evaporating becomes contracted from -all sides towards the centre, the blue colour vanishes last. - -457. - -The phenomenon appears most readily between the minute lines, which the -action of passing the fingers leaves on the clear surface; a somewhat -rough state of the surface of the glass is otherwise requisite. On -some glass the appearance may be produced by merely breathing; in -other cases the wiping with the fingers is necessary: I have even met -with polished mirror-glasses, one side of which immediately showed the -colours vividly; the other not. To judge from some remaining pieces, -the former was originally the front of the glass, the latter the side -which was covered with quicksilver. - -458. - -These experiments may be best made in cold weather, because the glass -may be more quickly and distinctly breathed upon, and the breath -evaporates more suddenly. In severe frost the phenomenon may be -observed on a large scale while travelling in a carriage; the glasses -being well cleaned, and all closed. The breath of the persons within is -very gently diffused over the glass, and immediately produces the most -vivid play of colours. How far they may present a regular succession I -have not been able to remark; but they appear particularly vivid when -they have a dark object as a background. This alternation of colours -does not, however, last long; for as soon as the breath gathers in -drops, or freezes to points of ice, the appearance is at once at an end. - -459. - -Third condition.--The two foregoing experiments of the pressure and -breathing may be united; namely, by breathing on a plate of glass, and -immediately after pressing the other upon it. The colours then appear -as in the case of two glasses unbreathed upon, with this difference, -that the moisture occasions here and there an interruption of the -undulations. On pushing one glass away from the other the moisture -appears iridescent as it evaporates. - -460. - -It might, however, be asserted that this combined experiment exhibits -no more than each single experiment; for it appears the colours excited -by pressure disappear in proportion as the glasses are less in contact, -and the moisture then evaporates with its own colours. - -461. - -Fourth condition.--Iridescent appearances are observable in almost all -bubbles; soap-bubbles are the most commonly known, and the effect in -question is thus exhibited in the easiest mode; but it may be observed -in wine, beer, in pure spirit, and again, especially, in the froth of -chocolate. - -462. - -As in the above cases we required an infinitely narrow space between -two surfaces which are in contact, so we can consider the pellicle -of the soap-bubble as an infinitely thin lamina between two elastic -bodies; for the appearance in fact takes place between the air within, -which distends the bubble, and the atmospheric air. - -463. - -The bubble when first produced is colourless; then coloured stripes, -like those in marble paper, begin to appear: these at length spread -over the whole surface, or rather are driven round it as it is -distended. - -464. - -In a single bubble, suffered to hang from the straw or tube, the -appearance of colour is difficult to observe, for the quick rotation -prevents any accurate observation, and all the colours seem to mix -together; yet we can perceive that the colours begin at the orifice of -the tube. The solution itself may, however, be blown into carefully, -so that only one bubble shall appear. This remains white (colourless) -if not much agitated; but if the solution is not too watery, circles -appear round the perpendicular axis of the bubble; these being near -each other, are commonly composed alternately of green and red. Lastly, -several bubbles may be produced together by the same means; in this -case the colours appear on the sides where two bubbles have pressed -each other flat. - -465. - -The bubbles of chocolate-froth may perhaps be even more conveniently -observed than those of soap; though smaller, they remain longer. In -these, owing to the heat, an impulse, a movement, is produced and -sustained, which appears necessary to the development and succession of -the appearances. - -466. - -If the bubble is small, or shut in between others, coloured lines -chase each other over the surface, resembling marbled paper; all the -colours of the scale are seen to pass through each other; the pure, the -augmented, the combined, all distinctly clear and beautiful. In small -bubbles the appearance lasts for a considerable time. - -467. - -If the bubble is larger, or if it becomes by degrees detached, owing -to the bursting of others near, we perceive that this impulsion and -attraction of the colours has, as it were, an end in view; for on -the highest point of the bubble we see a small circle appear, which -is yellow in the centre; the other remaining coloured lines move -constantly round this with a vermicular action. - -468. - -In a short time the circle enlarges and sinks downwards on all sides; -in the centre the yellow remains; below and on the outside it becomes -red, and soon blue; below this again appears a new circle of the -same series of colours: if they approximate sufficiently, a green is -produced by the union of the border-colours. - -469. - -When I could count three such leading circles, the centre was -colourless, and this space became by degrees larger as the circles sank -lower, till at last the bubble burst. - -470. - -Fifth condition.--Very delicate pellicles may be formed in various -ways: on these films we discover a very lively play of colours, either -in the usual order, or more confusedly passing through each other. The -water in which lime has been slaked soon skims over with a coloured -pellicle: the same happens on the surface of stagnant water, especially -if impregnated with iron. The lamellæ of the fine tartar which adheres -to bottles, especially in red French wine, exhibit the most brilliant -colours, on being exposed to the light, if carefully detached. Drops of -oil on water, brandy, and other fluids, produce also similar circles -and brilliant effects: but the most beautiful experiment that can be -made is the following:--Let aqua fortis, not too strong, be poured into -a flat saucer, and then with a brush drop on it some of the varnish -used by engravers to cover certain portions during the process of -biting their plates. After quick commotion there presently appears a -film which spreads itself out in circles, and immediately produces the -most vivid appearances of colour. - -471. - -Sixth condition.--When metals are heated, colours rapidly succeeding -each other appear on the surface: these colours can, however, be -arrested at will. - -472. - -If a piece of polished steel is heated, it will, at a certain degree -of warmth, be overspread with yellow. If taken suddenly away from the -fire, this yellow remains. - -473. - -As the steel becomes hotter, the yellow appears darker, intenser, and -presently passes into red. This is difficult to arrest, for it hastens -very quickly to bright blue. - -474. - -This beautiful blue is to be arrested if the steel is suddenly taken -out of the heat and buried in ashes. The blue steel works are produced -in this way. If, again, the steel is held longer over the fire, it soon -becomes a light blue, and so it remains. - -475. - -These colours pass like a breath over the plate of steel; each seems -to fly before the other, but, in reality, each successive hue is -constantly developed from the preceding one. - -476. - -If we hold a penknife in the flame of a light, a coloured stripe will -appear across the blade. The portion of the stripe which was nearest to -the flame is light blue; this melts into blue-red; the red is in the -centre; then follow yellow-red and yellow. - -477. - -This phenomenon is deducible from the preceding ones; for the portion -of the blade next the handle is less heated than the end which is in -the flame, and thus all the colours which in other cases exhibited -themselves in succession, must here appear at once, and may thus be -permanently preserved. - -478. - -Robert Boyle gives this succession of colours as follows:--"A florido -flavo ad flavum saturum et rubescentem (quem artifices sanguineum -vocant) inde ad languidum, postea ad saturiorem cyaneum." This would be -quite correct if the words "languidus" and "saturior" were to change -places. How far the observation is correct, that the different colours -have a relation to the degree of temper which the metal afterwards -acquires, we leave to others to decide. The colours are here only -indications of the different degrees of heat.--Note R. - -479. - -When lead is calcined, the surface is first greyish. This greyish -powder, with greater heat, becomes yellow, and then orange. Silver, -too, exhibits colours when heated; the fracture of silver in the -process of refining belongs to the same class of examples. When -metallic glasses melt, colours in like manner appear on the surface. - -480. - -Seventh condition.--When the surface of glass becomes decomposed. The -accidental opacity (blindwerden) of glass has been already noticed: the -term (blindwerden) is employed to denote that the surface of the glass -is so affected as to appear dim to us. - -481. - -White glass becomes "blind" soonest; cast, and afterwards polished -glass is also liable to be so affected; the bluish less, the green -least. - -482. - -Of the two sides of a plate of glass one is called the mirror side; -it is that which in the oven lies uppermost, on which one may observe -roundish elevations: it is smoother than the other, which is undermost -in the oven, and on which scratches may be sometimes observed. On this -account the mirror side is placed facing the interior of rooms, because -it is less affected by the moisture adhering to it from within, than -the other would be, and the glass is thus less liable to become "blind." - -483. - -This half-opacity or dimness of the glass assumes by degrees an -appearance of colour which may become very vivid, and in which perhaps -a certain succession, or otherwise regular order, might be discovered. - -484. - -Having thus traced the physical colours from their simplest effects to -the present instances, where these fleeting appearances are found to -be fixed in bodies, we are, in fact, arrived at the point where the -chemical colours begin; nay, we have in some sort already passed those -limits; a circumstance which may excite a favourable prejudice for the -consistency of our statement. By way of conclusion to this part of our -inquiry, we subjoin a general observation, which may not be without its -bearing on the common connecting principle of the phenomena that have -been adduced. - -485. - -The colouring of steel and the appearances analogous to it, might -perhaps be easily deduced from the doctrine of the semi-opaque mediums. -Polished steel reflects light powerfully: we may consider the colour -produced by the heat as a slight degree of dimness: hence a bright -yellow must immediately appear; this, as the dimness increases, must -still appear deeper, more condensed, and redder, and at last pure and -ruby-red. The colour has now reached the extreme point of depth, and -if we suppose the same degree of semi-opacity still to continue, the -dimness would now spread itself over a dark ground, first producing a -violet, then a dark-blue, and at last a light-blue, and thus complete -the series of the appearances. - -We will not assert that this mode of explanation will suffice in -all cases; our object is rather to point out the road by which the -all-comprehensive formula, the very key of the enigma, may be at last -discovered.--Note S. - - - - -PART III. - - -CHEMICAL COLOURS. - - -486. - -We give this denomination to colours which we can produce, and more -or less fix, in certain bodies; which we can render more intense, -which we can again take away and communicate to other bodies, and to -which, therefore, we ascribe a certain permanency: duration is their -prevailing characteristic. - -487. - -In this view the chemical colours were formerly distinguished with -various epithets; they were called _colores proprii, corporei, -materiales, veri, permanentes, fixi_. - -488. - -In the preceding chapter we observed how the fluctuating and transient -nature of the physical colours becomes gradually fixed, thus forming -the natural transition to our present subject. - -489. - -Colour becomes fixed in bodies more or less permanently; superficially, -or thoroughly. - -490. - -All bodies are susceptible of colour; it can either be excited, -rendered intense, and gradually fixed in them, or at least communicated -to them. - - - - -XXXIV. - - -CHEMICAL CONTRAST. - - -491. - -In the examination of coloured appearances we had occasion everywhere -to take notice of a principle of contrast: so again, in approaching the -precincts of chemistry, we find a chemical contrast of a remarkable -nature. We speak here, with reference to our present purpose, only of -that which is comprehended under the general names of acid and alkali. - -492. - -We characterised the chromatic contrast, in conformity with all other -physical contrasts as a _more_ and _less_; ascribing the _plus_ to -the yellow side, the _minus_ to the blue; and we now find that these -two divisions correspond with the chemical contrasts. The yellow and -yellow-red affect the acids, the blue and blue-red the alkalis; thus -the phenomena of chemical colours, although still necessarily mixed -up with other considerations, admit of being traced with sufficient -simplicity. - -493. - -The principal phenomena in chemical colours are produced by the -oxydation of metals, and it will be seen how important this -consideration is at the outset. Other facts which come into the -account, and which are worthy of attention, will be examined under -separate heads; in doing this we, however, expressly state that we only -propose to offer some preparatory suggestions to the chemist in a very -general way, without entering into the nicer chemical problems and -questions, or presuming to decide on them. Our object is only to give a -sketch of the mode in which, according to our conviction, the chemical -theory of colours may be connected with general physics. - - - - -XXXV. - - -WHITE. - - -494. - -In treating of the dioptrical colours of the first class (155) we -have already in some degree anticipated this subject. Transparent -substances may be said to be in the highest class of inorganic matter. -With these, colourless semi-transparence is closely connected, and -white may be considered the last opaque degree of this. - -495. - -Pure water crystallised to snow appears white, for the transparence of -the separate parts makes no transparent whole. Various crystallised -salts, when deprived to a certain extent of moisture, appear as a white -powder. The accidentally opaque state of a pure transparent substance -might be called white; thus pounded glass appears as a white powder. -The cessation of a combining power, and the exhibition of the atomic -quality of the substance might at the same time be taken into the -account. - -496. - -The known undecomposed earths are, in their pure state, all white. -They pass to a state of transparence by natural crystallization. Silex -becomes rock-crystal; argile, mica; magnesia, talc; calcareous earth -and barytes appear transparent in various spars.--Note T. - -497. - -As in the colouring of mineral bodies the metallic oxydes will often -invite our attention, we observe, in conclusion, that metals, when -slightly oxydated, at first appear white, as lead is converted to white -lead by vegetable acid. - - - - -XXXVI. - - -BLACK. - - -498. - -Black is not exhibited in so elementary a state as white. We meet -with it in the vegetable kingdom in semi-combustion; and charcoal, a -substance especially worthy of attention on other accounts, exhibits -a black colour. Again, if woods--for example, boards, owing to the -action of light, air, and moisture, are deprived in part of their -combustibility, there appears first the grey then the black colour. So -again, we can convert even portions of animal substance to charcoal by -semi-combustion. - -499. - -In the same manner we often find that a sub-oxydation takes place -in metals when the black colour is to be produced. Various metals, -particularly iron, become black by slight oxydation, by vinegar, by -mild acid fermentations; for example, a decoction of rice, &c. - -500. - -Again, it may be inferred that a de-oxydation may produce black. This -occurs in the preparation of ink, which becomes yellow by the solution -of iron in strong sulphuric acid, but when partly de-oxydised by the -infusion of gall-nuts, appears black. - - - - -XXXVII. - - -FIRST EXCITATION OF COLOUR. - - -501. - -In the division of physical colours, where semi-transparent mediums -were considered, we saw colours antecedently to white and black. In the -present case we assume a white and black already produced and fixed; -and the question is, how colour can be excited in them? - -502. - -Here, too, we can say, white that becomes darkened or dimmed inclines -to yellow; black, as it becomes lighter, inclines to blue.--Note U. - -503. - -Yellow appears on the active (plus) side, immediately in the light, the -bright, the white. All white surfaces easily assume a yellow tinge; -paper, linen, wool, silk, wax: transparent fluids again, which have -a tendency to combustion, easily become yellow; in other words they -easily pass into a very slight state of semi-transparence. - -504. - -So again the excitement on the passive side, the tendency to obscure, -dark, black, is immediately accompanied with blue, or rather with a -reddish-blue. Iron dissolved in sulphuric acid, and much diluted with -water, if held to the light in a glass, exhibits a beautiful violet -colour as soon as a few drops only of the infusion of gall-nuts are -added. This colour presents the peculiar hues of the dark topaz, the -_orphninon_ of a burnt-red, as the ancients expressed it. - -505. - -Whether any colour can be excited in the pure earths by the chemical -operations of nature and art, without the admixture of metallic oxydes, -is an important question, generally, indeed, answered in the negative. -It is perhaps connected with the question--to what extent changes may -be produced in the earths through oxydation? - -506. - -Undoubtedly the negation of the above question is confirmed by the -circumstance that wherever mineral colours are found, some trace of -metal, especially of iron, shows itself; we are thus naturally led -to consider how easily iron becomes oxydised, how easily the oxyde -of iron assumes different colours, how infinitely divisible it is, -and how quickly it communicates its colour. It were to be wished, -notwithstanding, that new experiments could be made in regard to the -above point, so as either to confirm or remove any doubt. - -507. - -However this may be, the susceptibility of the earths with regard -to colours already existing is very great; aluminous earth is thus -particularly distinguished. - -508. - -In proceeding to consider the metals, which in the inorganic world -have the almost exclusive prerogative of appearing coloured, we find -that, in their pure, independent, natural state, they are already -distinguished from the pure earths by a tendency to some one colour or -other. - -509. - -While silver approximates most to pure white,--nay, really represents -pure white, heightened by metallic splendour,--steel, tin, lead, and so -forth, incline towards pale blue-grey; gold, on the other hand, deepens -to pure yellow, copper approaches a red hue, which, under certain -circumstances, increases almost to bright red, but which again returns -to a yellow golden colour when combined with zinc. - -510. - -But if metals in their pure state have so specific a determination -towards this or that exhibition of colour, they are, through the effect -of oxydation, in some degree reduced to a common character; for the -elementary colours now come forth in their purity, and although this -or that metal appears to have a particular tendency to this or that -colour, we find some that can go through the whole circle of hues, -others, that are capable of exhibiting more than one colour; tin, -however, is distinguished by its comparative inaptitude to become -coloured. We propose to give a table hereafter, showing how far the -different metals can be more or less made to exhibit the different -colours. - -511. - -When the clean, smooth surface of a pure metal, on being heated, -becomes overspread with a mantling colour, which passes through a -series of appearances as the heat increases, this, we are persuaded, -indicates the aptitude of the metal to pass through the whole range of -colours. We find this phenomenon most beautifully exhibited in polished -steel; but silver, copper, brass, lead, and tin, easily present similar -appearances. A superficial oxydation is probably here taking place, -as may be inferred from the effects of the operation when continued, -especially in the more easily oxydizable metals. - -512. - -The same conclusion may be drawn from the fact that iron is more -easily oxydizable by acid liquids when it is red hot, for in this -case the two effects concur with each other. We observe, again, that -steel, accordingly as it is hardened in different stages of its -colorification, may exhibit a difference of elasticity: this is quite -natural, for the various appearances of colour indicate various degrees -of heat.[1] - -513. - -If we look beyond this superficial mantling, this pellicle of colour, -we observe that as metals are oxydized throughout their masses, white -or black appears with the first degree of heat, as may be seen in white -lead, iron, and quicksilver. - -514. - -If we examine further, and look for the actual exhibition of colour, -we find it most frequently on the _plus_ side. The mantling, so often -mentioned, of smooth metallic surfaces begins with yellow. Iron -passes presently into yellow ochre, lead from white lead to massicot, -quicksilver from æthiops to yellow turbith. The solutions of gold and -platinum in acids are yellow. - -515. - -The exhibitions on the _minus_ side are less frequent. Copper slightly -oxydized appears blue. In the preparation of Prussian-blue, alkalis are -employed. - -516. - -Generally, however, these appearances of colour are of so mutable a -nature that chemists look upon them as deceptive tests, at least in the -nicer gradations. For ourselves, as we can only treat of these matters -in a general way, we merely observe that the appearances of colour in -metals may be classed according to their origin, manifold appearance, -and cessation, as various results of oxydation, hyper-oxydation, -ab-oxydation, and de-oxydation.[2] - - -[1] See par. 478. - -[2] As these terms are afterwards referred to (par. 525), it was -necessary to preserve them. - - - - -XXXVIII. - - -AUGMENTATION OF COLOUR.[1] - - -517. - -The augmentation of colour exhibits itself as a condensation, a -fulness, a darkening of the hue. We have before seen, in treating of -colourless mediums, that by increasing the degree of opacity in the -medium, we can deepen a bright object from the lightest yellow to the -intensest ruby-red. Blue, on the other hand, increases to the most -beautiful violet, if we rarefy and diminish a semi-opaque medium, -itself lighted, but through which we see darkness (150, 151). - -518. - -If the colour is positive, a similar colour appears in the intenser -state. Thus if we fill a white porcelain cup with a pure yellow -liquor, the fluid will appear to become gradually redder towards the -bottom, and at last appears orange. If we pour a pure blue solution -into another cup, the upper portion will exhibit a sky-blue, that -towards the bottom, a beautiful violet. If the cup is placed in the -sun, the shadowed side, even of the upper portion, is already violet. -If we throw a shadow with the hand, or any other substance, over the -illumined portion, the shadow in like manner appears reddish. - -519. - -This is one of the most important appearances connected with the -doctrine of colours, for we here manifestly find that a difference of -quantity produces a corresponding qualified impression on our senses. -In speaking of the last class of epoptical colours (452, 485), we -stated our conjecture that the colouring of steel might perhaps be -traced to the doctrine of the semi-transparent mediums, and we would -here again recall this to the reader's recollection. - -520. - -All chemical augmentation of colour, again, is the immediate -consequence of continued excitation. The augmentation advances -constantly and unremittingly, and it is to be observed that the -increase of intenseness is most common on the _plus_ side. Yellow iron -ochre increases, as well by fire as by other operations, to a very -strong red: massicot is increased to red lead, turbith to vermilion, -which last attains a very high degree of the yellow-red. An intimate -saturation of the metal by the acid, and its separation to infinity, -take place together with the above effects. - -521. - -The augmentation on the _minus_ side is less frequent; but we observe -that the more pure and condensed the Prussian-blue or cobalt glass is -prepared, the more readily it assumes a reddish hue and inclines to the -violet. - -522. - -The French have a happy expression for the less perceptible tendency of -yellow and blue towards red: they say the colour has "un œil de rouge," -which we might perhaps express by a reddish glance (einen röthlichen -blick). - - -[1] Steigerung, literally _gradual ascent_. See the note to par. 523. - - - - -XXXIX. - - -CULMINATION[1] - - -523. - -This is the consequence of still progressing augmentation. Red, in -which neither yellow nor blue is to be detected, here constitutes the -acme. - -524. - -If we wish to select a striking example of a culmination on the _plus_ -side, we again find it in the coloured steel, which attains the bright -red acme, and can be arrested at this point. - -525. - -Were we here to employ the terminology before proposed, we should -say that the first oxydation produces yellow, the hyper-oxydation -yellow-red; that here a kind of maximum exists, and that then an -ab-oxydation, and lastly a de-oxydation takes place. - -526. - -High degrees of oxydation produce a bright red. Gold in solution, -precipitated by a solution of tin, appears bright red: oxyde of -arsenic, in combination, with sulphur, produces a ruby colour. - -527. - -How far, however, a kind of sub-oxydation may co-operate in some -culminations, is matter for inquiry; for an influence of alkalis on -yellow-red also appears to produce the culmination; the colour reaching -the acme by being forced towards the _minus_ side. - -528. - -The Dutch prepare a colour known by the name of vermilion, from the -best Hungarian cinnabar, which exhibits the brightest yellow-red. This -vermilion is still only a cinnabar, which, however, approximates the -pure red, and it may be conjectured that alkalis are used to bring it -nearer to the culminating point. - -529. - -Vegetable juices, treated in this way, offer very striking examples of -the above effects. The colouring-matter of turmeric, annotto, dyer's -saffron,[2] and other vegetables, being extracted with spirits of wine, -exhibits tints of yellow, yellow-red, and hyacinth-red; these, by the -admixture of alkalis, pass to the culminating point, and even beyond it -to blue-red. - -530. - -No instance of a culmination on the _minus_ side has come to my -knowledge in the mineral and vegetable kingdoms. In the animal -kingdom the juice of the murex is remarkable; of its augmentation and -culmination on the _minus_ side, we shall hereafter have occasion to -speak. - - -[1] _Culmination_, the original word. It might have been rendered -_maximum of colour_, but as the author supposes an _ascent_ through -yellow and blue to red, his meaning is better expressed by his own term. - -[2] Curcuma, Bixa Orellana, Carthamus Tinctorius. - - - - -XL. - - -FLUCTUATION. - - -531. - -The mutability of colour is so great, that even those pigments, which -may have been considered to be defined and arrested, still admit of -slight variations on one side or the other. This mutability is most -remarkable near the culminating point, and is effected in a very -striking manner by the alternate employment of acids and alkalis. - -532. - -To express this appearance in dyeing, the French make use of the word -"virer," to turn from one side to the other; they thus very adroitly -convey an idea which others attempt to express by terms indicating the -component hues. - -533. - -The effect produced with litmus is one of the most known and striking -of this kind. This colouring substance is tendered red-blue by means of -alkalis. The red-blue is very readily changed to red-yellow by means -of acids, and again returns to its first state by again employing -alkalis. The question whether a culminating point is to be discovered -and arrested by nice experiments, is left to those who are practised -in these operations. Dyeing, especially scarlet-dyeing, might afford a -variety of examples of this fluctuation. - - - - -XLI. - - -PASSAGE THROUGH THE WHOLE SCALE. - - -534. - -The first excitation and gradual increase of colour take place more on -the _plus_ than on the _minus_ side. So, also, in passing through the -whole scale, colour exhibits itself most on the _plus_ side. - -535. - -A passage of this kind, regular and evident to the senses, from yellow -through red to blue, is apparent in the colouring of steel. - -536. - -The metals may be arrested at various points of the colorific circle by -various degrees and kinds of oxydation. - -537. - -As they also appear green, a question arises whether chemists know any -instance in the mineral kingdom of a constant transition from yellow, -through green, to blue, and _vice versâ_. Oxyde of iron, melted with -glass, produces first a green, and with a more powerful heat, a blue -colour. - -538. - -We may here observe of green generally, that it appears, especially -in an atomic sense, and certainly in a pure state, when we mix blue -and yellow: but, again, an impure and dirty yellow soon gives us the -impression of green; yellow and black already produce green; this, -however, is owing to the affinity between black and blue. An imperfect -yellow, such as that of sulphur, gives us the impression of a greenish -hue: thus, again, an imperfect blue appears green. The green of wine -bottles arises, it appears, from an imperfect union of the oxyde of -iron with the glass. If we produce a more complete union by greater -heat, a beautiful blue-glass is the result. - -539. - -From all this it appears that a certain chasm exists in nature between -yellow and blue, the opposite characters of which, it is true, may be -done away atomically by due immixture, and, thus combined, to green; -but the true reconciliation between yellow and blue, it seems, only -takes place by means of red. - -540. - -The process, however, which appears unattainable in inorganic -substances, we shall find to be possible when we turn our attention to -organic productions; for in these, the passage through the whole circle -from yellow, through green and blue, to red, really takes place. - - - - -XLII. - - -INVERSION. - - -541. - -Again, an immediate inversion or change to the totally opposite hue, is -a very remarkable appearance which sometimes occurs; at present, we are -merely enabled to adduce what follows. - -542. - -The mineral chameleon, a name which has been given to an oxyde of -manganese, may be considered, in its perfectly dry state, as a green -powder. If we strew it in water, the green colour displays itself very -beautifully in the first moment of solution, but it changes presently -to the bright red opposite to green, without any apparent intermediate -state. - -543. - -The same occurs with the sympathetic ink, which may be considered a -reddish liquid, but which, when dried by warmth, appears as a green -colour on paper. - -544. - -In fact, this phenomenon appears to be owing to the conflict between -a dry and moist state, as has been already observed, if we are not -mistaken, by the chemists. We may look to the improvements of time to -point out what may further be deduced from these phenomena, and to show -what other facts they may be connected with. - - - - -XLIII. - - -FIXATION. - - -545. - -Mutable as we have hitherto found colour to be, even as a substance, -yet under certain circumstances it may at last be fixed. - -546. - -There are bodies capable of being entirely converted into colouring -matter: here it may be said that the colour fixes itself in its own -substance, stops at a certain point, and is there defined. Such -colouring substances are found throughout nature; the vegetable world -affords a great quantity of examples, among which some are particularly -distinguished, and may be considered as the representatives of the -rest; such as, on the active side, madder, on the passive side, indigo. - -547. - -In order to make these materials available in use, it is necessary -that the colouring quality in them should be intimately condensed, and -the tinging substance refined, practically speaking, to an infinite -divisibility. This is accomplished in various ways, and particularly by -the well-known means of fermentation and decomposition. - -548. - -These colouring substances now attach themselves again to other bodies. -Thus, in the mineral kingdom they adhere to earths and metallic oxydes; -they unite in melting with glasses; and in this case, as the light is -transmitted through them, they appear in the greatest beauty, while an -eternal duration may be ascribed to them. - -549. - -They fasten on vegetable and animal bodies with more or less power, and -remain more or less permanently; partly owing to their nature,--as -yellow, for instance, is more evanescent than blue,--or owing to -the nature of the substance on which they appear. They last less in -vegetable than in animal substances, and even within this latter -kingdom there are again varieties. Hemp or cotton threads, silk or -wool, exhibit very different relations to colouring substances. - -550. - -Here comes into the account the important operation of employing -mordants, which may be considered as the intermediate agents between -the colour and the recipient substance; various works on dyeing speak -of this circumstantially. Suffice it to have alluded to processes by -means of which the colour retains a permanency only to be destroyed -with the substance, and which may even increase in brightness and -beauty by use. - - - - -XLIV. - - -INTERMIXTURE, REAL. - - -551. - -Every intermixture pre-supposes a specific state of colour; and thus -when we speak of intermixture, we here understand it in an atomic -sense. We must first have before us certain bodies arrested at any -given point of the colorific circle, before we can produce gradations -by their union. - -552. - -Yellow, blue, and red, may be assumed as pure elementary colours, -already existing; from these, violet, orange, and green, are the -simplest combined results. - -553. - -Some persons have taken much pains to define these intermixtures more -accurately, by relations of number, measure, and weight, but nothing -very profitable has been thus accomplished. - -554. - -Painting consists, strictly speaking, in the intermixture of -such specific colouring bodies and their infinite possible -combinations--combinations which can only be appreciated by the nicest, -most practised eye, and only accomplished under its influence. - -555. - -The intimate combination of these ingredients is effected, in the first -instance, through the most perfect comminution of the material by means -of grinding, washing, &c., as well as by vehicles or liquid mediums -which hold together the pulverized substance, and combine organically, -as it were, the unorganic; such are the oils, resins, &c.--Note V. - -556. - -If all the colours are mixed together they retain their general -character as σκιερόν, and as they are no longer seen next each other, -no completeness, no harmony, is experienced; the result is grey, which, -like apparent colour, always appears somewhat darker than white, and -somewhat lighter than black. - -557. - -This grey may be produced in various ways. By mixing yellow and blue to -an emerald green, and then adding pure red, till all three neutralize -each other; or, by placing the primitive and intermediate colours next -each other in a certain proportion, and afterwards mixing them. - -558. - -That all the colours mixed together produce white, is an absurdity -which people have credulously been accustomed to repeat for a century, -in opposition to the evidence of their senses. - -559. - -Colours when mixed together retain their original darkness. The darker -the colours, the darker will be the grey resulting from their union, -till at last this grey approaches black. The lighter the colours the -lighter will be the grey, which at last approaches white. - - - - -XLV. - - -INTERMIXTURE, APPARENT. - - -560. - -The intermixture, which is only apparent, naturally invites our -attention in connexion with the foregoing; it is in many respects -important, and, indeed, the intermixture which we have distinguished as -real, might be considered as merely apparent. For the elements of which -the combined colour consists are only too small to be considered as -distinct parts. Yellow and blue powders mingled together appear green -to the naked eye, but through a magnifying glass we can still perceive -yellow and blue distinct from each other. Thus yellow and blue stripes -seen at a distance, present a green mass; the same observation is -applicable with regard to the intermixture of other specific colours. - -561. - -In the description of our apparatus we shall have occasion to mention -the wheel by means of which the apparent intermixture is produced by -rapid movement. Various colours are arranged near each other round -the edge of a disk, which is made to revolve with velocity, and thus -by having several such disks ready, every possible intermixture can -be presented to the eye, as well as the mixture of all colours to -grey, darker or lighter, according to the depth of the tints as above -explained. - -562. - -Physiological colours admit, in like manner, of being mixed with -others. If, for example, we produce the blue shadow (65) on a light -yellow paper, the surface will appear green. The same happens with -regard to the other colours if the necessary preparations are attended -to. - -563. - -If, when the eye is impressed with visionary images that last for a -while, we look on coloured surfaces, an intermixture also takes place; -the spectrum is determined to a new colour which is composed of the two. - -564. - -Physical colours also admit of combination. Here might be adduced the -experiments in which many-coloured images are seen through the prism, -as we have before shown in detail (258, 284). - -565. - -Those who have prosecuted these inquiries have, however, paid most -attention to the appearances which take place when the prismatic -colours are thrown on coloured surfaces. - -566. - -What is seen under these circumstances is quite simple. In the first -place it must be remembered that the prismatic colours are much more -vivid than the colours of the surface on which they are thrown. -Secondly, we have to consider that the prismatic colours may be either -homogeneous or heterogeneous, with the recipient surface. In the former -case the surface deepens and enhances them, and is itself enhanced in -return, as a coloured stone is displayed by a similarly coloured foil. -In the opposite case each vitiates, disturbs, and destroys the other. - -567. - -These experiments may be repeated with coloured glasses, by causing the -sun-light to shine through them on coloured surfaces. In every instance -similar results will appear. - -568. - -The same effect takes place when we look on coloured objects through -coloured glasses; the colours being thus according to the same -conditions enhanced, subdued, or neutralized. - -569. - -If the prismatic colours are suffered to pass through coloured glasses, -the appearances that take place are perfectly analogous; in these cases -more or less force, more or less light and dark, the clearness and -cleanness of the glass are all to be allowed for, as they produce many -delicate varieties of effect: these will not escape the notice of every -accurate observer who takes sufficient interest in the inquiry to go -through the experiments. - -570. - -It is scarcely necessary to mention that several coloured glasses, as -well as oiled or transparent papers, placed over each other, may be -made to produce and exhibit every kind of intermixture at pleasure. - -571. - -Lastly, the operation of glazing in painting belongs to this kind of -intermixture; by this means a much more refined union may be produced -than that arising from the mechanical, atomic mixture which is commonly -employed. - - - - -XLVI. - - -COMMUNICATION, ACTUAL. - - -572. - -Having now provided the colouring materials, as before shown, a further -question arises how to communicate these to colourless substances: -the answer is of the greatest importance from the connexion of the -object with the ordinary wants of men, with useful purposes, and with -commercial and technical interests. - -573. - -Here, again, the dark quality of every colour again comes into the -account. From a yellow, that is very near to white, through orange, -and the hue of minium to pure red and carmine, through all gradations -of violet to the deepest blue which is almost identified with black, -colour still increases in darkness. Blue once defined, admits of -being diluted, made light, united with yellow, and then, as green, -it approaches the light side of the scale: but this is by no means -according to its own nature. - -574. - -In the physiological colours we have already seen that they are less -than the light, inasmuch as they are a repetition of an impression -of light, nay, at last they leave this impression quite as a dark. In -physical experiments the employment of semi-transparent mediums, the -effect of semi-transparent accessory images, taught us that in such -cases we have to do with a subdued light, with a transition to darkness. - -575. - -In treating of the chemical origin of pigments we found that the same -effect was produced on the very first excitement. The yellow tinge -which mantles over the steel, already darkens the shining surface. In -changing white lead to massicot it is evident that the yellow is darker -than white. - -576. - -This process is in the highest degree delicate; the growing -intenseness, as it still increases, tinges the substance more and more -intimately and powerfully, and thus indicates the extreme fineness, and -the infinite divisibility of the coloured atoms. - -577. - -The colours which approach the dark side, and consequently, blue in -particular, can be made to approximate to black; in fact, a very -perfect Prussian blue, or an indigo acted on by vitriolic acid appears -almost as a black. - -578. - -A remarkable appearance may be here adverted to; pigments, in their -deepest and most condensed state, especially those produced from -the vegetable kingdom, such as the indigo just mentioned, or madder -carried to its intensest hue, no longer show their own colour; on the -contrary, a decided metallic shine is seen on their surface, in which -the physiological compensatory colour appears. - -579. - -All good indigo exhibits a copper-colour in its fracture, a -circumstance attended to, as a known characteristic, in trade. Again, -the indigo which has been acted on by sulphuric acid, if thickly laid -on, or suffered to dry so that neither white paper nor the porcelain -can appear through, exhibits a colour approaching to orange. - -580. - -The bright red Spanish rouge, probably prepared from madder, exhibits -on its surface a perfectly green, metallic shine. If this colour, or -the blue before mentioned, is washed with a pencil on porcelain or -paper, it is seen in its real state owing to the bright ground shining -through. - -581. - -Coloured liquids appear black when no light is transmitted through -them, as we may easily see in cubic tin vessels with glass bottoms. -In these every transparent-coloured infusion will appear black and -colourless if we place a black surface under them. - -582. - -If we contrive that the image of a flame be reflected from the bottom, -the image will appear coloured. If we lift up the vessel and suffer the -transmitted light to fall on white paper under it, the colour of the -liquid appears on the paper. Every light ground seen through such a -coloured medium exhibits the colour of the medium. - -583. - -Thus every colour, in order to be seen, must have a light within or -behind it. Hence the lighter and brighter the grounds are, the more -brilliant the colours appear. If we pass lac-varnish over a shining -white metal surface, as the so-called foils are prepared, the splendour -of the colour is displayed by this internally reflected light as -powerfully as in any prismatic experiment; nay, the force of the -physical colours is owing principally to the circumstance that light is -always acting with and behind them. - -584. - -Lichtenberg, who of necessity followed the received theory, owing -to the time and circumstances in which he lived, was yet too good an -observer, and too acute not to explain and classify, after his fashion, -what was evident to his senses. He says, in the preface to Delaval, -"It appears to me also, on other grounds, probable, that our organ, in -order to be impressed by a colour, must at the same time be impressed -by all light (white)." - -585. - -To procure white as a ground is the chief business of the dyer. Every -colour may be easily communicated to colourless earths, especially -to alum: but the dyer has especially to do with animal and vegetable -products as the ground of his operations. - -586. - -Everything living tends to colour--to local, specific colour, to -effect, to opacity--pervading the minutest atoms. Everything in which -life is extinct approximates to white (494), to the abstract, the -general state, to clearness[1], to transparence. - -587. - -How this is put in practice in technical operations remains to be -adverted to in the chapter on the privation of colour. With regard -to the communication of colour, we have especially to bear in mind -that animals and vegetables, in a living state, produce colours, and -hence their substances, if deprived of colours, can the more readily -re-assume them. - - -[1] Verklärung, literally _clarification_. - - - - -XLVII. - - -COMMUNICATION, APPARENT. - - -588. - -The communication of colours, real as well as apparent, corresponds, as -may easily be seen, with their intermixture: we need not, therefore, -repeat what has been already sufficiently entered into. - -589. - -Yet we may here point out more circumstantially the importance of an -apparent communication which takes place by means of reflection. This -phenomenon is well known, but still it is pregnant with inferences, and -is of the greatest importance both to the investigator of nature and to -the painter. - -590. - -Let a surface coloured with any one of the positive colours be placed -in the sun, and let its reflection be thrown on other colourless -objects. This reflection is a kind of subdued light, a half-light, -a half-shadow, which, in a subdued state, reflects the colours in -question. - -591. - -If this reflection acts on light surfaces, it is so far overpowered -that we can scarcely perceive the colour which accompanies it; but if -it acts on shadowed portions, a sort of magical union takes place with -the σκιερῷ. Shadow is the proper element of colour, and in this case -a subdued colour approaches it, lighting up, tinging, and enlivening -it. And thus arises an appearance, as powerful as agreeable, which may -render the most pleasing service to the painter who knows how to make -use of it. These are the types of the so-called reflexes, which were -only noticed late in the history of art, and which have been too seldom -employed in their full variety. - -592. - -The schoolmen called these colours _colores notionales_ and -_intentionales_, and the history of the doctrine of colours will -generally show that the old inquirers already observed the phenomena -well enough, and knew how to distinguish them properly, although the -whole method of treating such subjects is very different from ours. - - - - -XLVIII. - - -EXTRACTION. - - -593. - -Colour may be extracted from substances, whether they possess it -naturally or by communication, in various ways. We have thus the power -to remove it intentionally for a useful purpose, but, on the other -hand, it often flies contrary to our wish. - -594. - -Not only are the elementary earths in their natural state white, but -vegetable and animal substances can be reduced to a white state without -disturbing their texture. A pure white is very desirable for various -uses, as in the instance of our preferring to use linen and cotton -stuffs uncoloured. In like manner some silk stuffs, paper, and other -substances, are the more agreeable the whiter they can be. Again, -the chief basis of all dyeing consists in white grounds. For these -reasons manufacturers, aided by accident and contrivance, have devoted -themselves assiduously to discover means of extracting colour: infinite -experiments have been made in connexion with this object, and many -important facts have been arrived at. - -595. - -It is in accomplishing this entire extraction of colour that the -operation of bleaching consists, which is very generally practised -empirically or methodically. We will here shortly state the leading -principles. - -596. - -Light is considered as one of the first means of extracting colour -from substances, and not only the sun-light, but the mere powerless -day-light: for as both lights--the direct light of the sun, as well as -the derived light of the sky--kindle Bologna phosphorus, so both act on -coloured surfaces. Whether the light attacks the colour allied to it, -and, as it were, kindles and consumes it, thus reducing the definite -quality to a general state, or whether some other operation, unknown -to us, takes place, it is clear that light exercises a great power on -coloured surfaces, and bleaches them more or less. Here, however, the -different colours exhibit a different degree of durability; yellow, -especially if prepared from certain materials, is, in this case, the -first to fly. - -597. - -Not only light, but air, and especially water, act strongly in -destroying colour. It has been even asserted that thread, well soaked -and spread on the grass at night, bleaches better than that which is -exposed, after soaking, to the sun-light. Thus, in this case, water -proves to be a solving and conducting agent, removing the accidental -quality, and restoring the substance to a general or colourless state. - -598. - -The extraction of colour is also effected by re-agents. Spirits of wine -has a peculiar tendency to attract the juice which tinges plants, and -becomes coloured with it often in a very permanent manner. Sulphuric -acid is very efficient in removing colour, especially from wool and -silk, and every one is acquainted with the use of sulphur vapours in -bleaching. - -599. - -The strongest acids have been recommended more recently as more -expeditious agents in bleaching. - -600. - -The alkaline re-agents produce the same effects by contrary -means--lixiviums alone, oils and fat combined with lixiviums to soap, -and so forth. - -601. - -Before we dismiss this subject, we observe [Pg 240] that it may be -well worth while to make certain delicate experiments as to how far -light and air exhibit their action in the removal of colour. It might -be possible to expose coloured substances to the light under glass -bells, without air, or filled with common or particular kinds of air. -The colours might be those of known fugacity, and it might be observed -whether any of the volatilized colour attached itself to the glass or -was otherwise perceptible as a deposit or precipitate; whether, again, -in such a case, this appearance would be perfectly like that which had -gradually ceased to be visible, or whether it had suffered any change. -Skilful experimentalists might devise various contrivances with a view -to such researches. - -602. - -Having thus first considered the operations of nature as subservient to -our proposes, we add a few observations on the modes in which they act -against us. - -603. - -The art of painting is so circumstanced that the most beautiful results -of mind and labour are altered and destroyed in various ways by time. -Hence great pains have been always taken to find durable pigments, and -so to unite them with each other and with their ground, that their -permanency might be further insured. The technical history of the -schools of painting affords sufficient information on this point. - -604. - -We may here, too, mention a minor art, to which, in relation to -dyeing, we are much indebted, namely, the weaving of tapestry. As the -manufacturers were enabled to imitate the most delicate shades of -pictures, and hence often brought the most variously coloured materials -together, it was soon observed that the colours were not all equally -durable, but that some faded from the tapestry more quickly than -others. Hence the most diligent efforts were made to ensure an equal -permanency to all the colours and their gradations. This object was -especially promoted in France, under Colbert, whose regulations to this -effect constitute an epoch in the history of dyeing. The gay dye which -only aimed at a transient beauty, was practised by a particular guild. -On the other hand, great pains were taken to define the technical -processes which promised durability. - -And thus, after considering the artificial extraction, the evanescence, -and the perishable nature of brilliant appearances of colour, we are -again returned to the desideratum of permanency. - - - - -XLIX. - - -NOMENCLATURE. - - -605. - -After what has been adduced respecting the origin, the increase, -and the affinity of colours, we may be better enabled to judge what -nomenclature would be desirable in future, and what might be retained -of that hitherto in use. - -606. - -The nomenclature of colours, like all other modes of designation, -but especially those employed to distinguish the objects of sense, -proceeded in the first instance from particular to general, and from -general back again to particular terms. The name of the species became -a generic name to which the individual was again referred. - -607. - -This method might have been followed in consequence of the mutability -and uncertainty of ancient modes of expression, especially since, in -the early ages, more reliance may be supposed to have been placed on -the vivid impressions of sense. The qualities of objects were described -indistinctly, because they were impressed clearly on every imagination. - -608. - -The pure chromatic circle was limited, it is true; but, specific as it -was, it appears to have been applied to innumerable objects, while it -was circumscribed by qualifying characteristics. If we take a glance -at the copiousness of the Greek and Roman terms, we shall perceive how -mutable the words were, and how easily each was adapted to almost every -point in the colorific circle.--Note W. - -609. - -In modern ages terms for many new gradations were introduced in -consequence of the various operations of dyeing. Even the colours -of fashion and their designations, represented an endless series of -specific hues. We shall, on occasion, employ the chromatic terminology -of modern languages, whence it will appear that the aim has gradually -been to introduce more exact definitions, and to individualise and -arrest a fixed and specific state by language equally distinct. - -610. - -With regard to the German terminology, it has the advantage of -possessing four monosyllabic names no longer to be traced to their -origin, viz., yellow (Gelb), blue, red, green. They represent the most -general idea of colour to the imagination, without reference to any -very specific modification. - -611. - -If we were to add two other qualifying terms to each of these four, as -thus--red-yellow, and yellow-red, red-blue and blue-red, yellow-green -and green-yellow, blue-green and green-blue,[1] we should express the -gradations of the chromatic circle with sufficient distinctness; and if -we were to add the designations of light and dark, and again define, in -some measure, the degree of purity or its opposite by the monosyllables -black, white, grey, brown, we should have a tolerably sufficient range -of expressions to describe the ordinary appearances presented to us, -without troubling ourselves whether they were produced dynamically or -atomically. - -612. - -The specific and proper terms in use might, however, still be -conveniently employed, and we have thus made use of the words orange -and violet. We have in like manner employed the word "_purpur_" to -designate a pure central red, because the secretion of the murex or -"_purpura_" is to be carried to the highest point of culmination by the -action of the sun-light on fine linen saturated with the juice. - - -[1] This description is suffered to remain because it accounts for the -terminology employed throughout.--T. - - - - -L. - - -MINERALS. - - -613. - -The colours of minerals are all of a chemical nature, and thus the -modes in which they are produced may be explained in a general way by -what has been said on the subject of chemical colours. - -614. - -Among the external characteristics of minerals, the description of -their colours occupies the first place; and great pains have been -taken, in the spirit of modern times, to define and arrest every -such appearance exactly: by this means, however, new difficulties, -it appears to us, have been created, which occasion no little -inconvenience in practice. - -615. - -It is true, this precision, when we reflect how it arose, carries with -it its own excuse. The painter has at all times been privileged in -the use of colours. The few specific hues, in themselves, admitted of -no change; but from these, innumerable gradations were artificially -produced which imitated the surface of natural objects. It was, -therefore, not to be wondered at that these gradations should also be -adopted as criterions, and that the artist should be invited to produce -tinted patterns with which the objects of nature might be compared, and -according to which they were to receive their designations. - -616. - -But, after all, the terminology of colours which has been introduced in -mineralogy, is open to many objections. The terms, for instance, have -not been borrowed from the mineral kingdom, as was possible enough in -most cases, but from all kinds of visible objects. Too many specific -terms have been adopted; and in seeking to establish new definitions -by combining these, the nomenclators have not reflected that they thus -altogether efface the image from the imagination, and the idea from -the understanding. Lastly, these individual designations of colours, -employed to a certain extent as elementary definitions, are not -arranged in the best manner as regards their respective derivation from -each other: hence, the scholar must learn every single designation, -and impress an almost lifeless but positive language on his memory. -The further consideration of this would be too foreign to our present -subject.[1] - - -[1] These remarks have reference to the German mineralogical -terminology.--T. - - - - -LI. - - -PLANTS. - - -617. - -The colours of organic bodies in general may be considered as a higher -kind of chemical operation, for which reason the ancients employed the -word concoction, πέψις, to designate the process. All the elementary -colours, as well as the combined and secondary hues, appear on the -surface of organic productions, while on the other hand, the interior, -if not colourless, appears, strictly speaking, negative when brought to -the light. As we propose to communicate our views respecting organic -nature, to a certain extent, in another place, we only insert here -what has been before connected with the doctrine of colours, while it -may serve as an introduction to the further consideration of the views -alluded to: and first, of plants. - -618. - -Seeds, bulbs, roots, and what is generally shut out from the light, or -immediately surrounded by the earth, appear, for the most part, white. - -619. - -Plants reared from seed, in darkness, are white, or approaching to -yellow. Light, on the other hand, in acting on their colours, acts at -the same time on their form. - -620. - -Plants which grow in darkness make, it is true, long shoots from joint -to joint: but the stems between two joints are thus longer than they -should be; no side stems are produced, and the metamorphosis of the -plant does not take place. - -621. - -Light, on the other hand, places it at once in an active state; the -plant appears green, and the course of the metamorphosis proceeds -uninterruptedly to the period of reproduction. - -622. - -We know that the leaves of the stem are only preparations and -pre-significations of the instruments of florification and -fructification, and accordingly we can already see colours in the -leaves of the stem which, as it were, announce the flower from afar, as -is the case in the amaranthus. - -623. - -There are white flowers whose petals have wrought or refined themselves -to the greatest purity; there are coloured ones, in which the -elementary hues may be said to fluctuate to and fro. There are some -which, in tending to the higher state, have only partially emancipated -themselves from the green of the plant. - -624. - -Flowers of the same genus, and even of the same kind, are found of all -colours. Roses, and particularly mallows, for example, vary through -a great portion of the colorific circle from white to yellow, then -through red-yellow to bright red, and from thence to the darkest hue it -can exhibit as it approaches blue. - -625. - -Others already begin from a higher degree in the scale, as, for -example, the poppy, which is yellow-red in the first instance, and -which afterwards approaches a violet hue. - -626. - -Yet the same colours in species, varieties, and even in families and -classes, if not constant, are still predominant, especially the yellow -colour: blue is throughout rarer. - -627. - -A process somewhat similar takes place in the juicy capsule of -the fruit, for it increases in colour from the green, through the -yellowish and yellow, up to the highest red, the colour of the rind -thus indicating the degree of ripeness. Some are coloured all round, -some only on the sunny side, in which last case the augmentation of the -yellow into red,--the gradations crowding in and upon each other,--may -be very well observed. - -628. - -Many fruits, too, are coloured internally; pure red juices, especially, -are common. - -629. - -The colour which is found superficially in the flower and penetratingly -in the fruit, spreads itself through all the remaining parts, colouring -the roots and the juices of the stem, and this with a very rich and -powerful hue. - -630. - -So, again, the colour of the wood passes from yellow through the -different degrees of red up to pure red and on to brown. Blue woods are -unknown to me; and thus in this degree of organisation the active side -exhibits itself powerfully, although both principles appear balanced in -the general green of the plant. - -631. - -We have seen above that the germ pushing from the earth is generally -white and yellowish, but that by means of the action of light and air -it acquires a green colour. The same happens with young leaves of -trees, as may be seen, for example, in the birch, the young leaves of -which are yellowish, and if boiled, yield a beautiful yellow juice: -afterwards they become greener, while the leaves of other trees become -gradually blue-green. - -632. - -Thus a yellow ingredient appears to belong more essentially to leaves -than a blue one; for this last vanishes in the autumn, and the yellow -of the leaf appears changed to a brown colour. Still more remarkable, -however, are the particular cases where leaves in autumn again become -pure yellow, and others increase to the brightest red. - -633. - -Other plants, again, may, by artificial treatment be entirely converted -to a colouring matter, which is as fine, active, and infinitely -divisible as any other. Indigo and madder, with which so much is -effected, are examples: lichens are also used for dyes. - -634. - -To this fact another stands immediately opposed; we can, namely, -extract the colouring part of plants, and, as it were, exhibit it -apart, while the organisation does not on this account appear to suffer -at all. The colours of flowers may be extracted by spirits of wine, and -tinge it; the petals meanwhile becoming white. - -635. - -There are various modes of acting on flowers and their juices by -re-agents. This has been done by Boyle in many experiments. Roses are -bleached by sulphur, and may be restored to their first state by other -acids; roses are turned green by the smoke of tobacco. - - - - -LII. - - -WORMS, INSECTS, FISHES. - - -636. - -With regard to creatures belonging to the lower degrees of -organisation, we may first observe that worms, which live in the earth -and remain in darkness and cold moisture, are imperfectly negatively -coloured; worms bred in warm moisture and darkness are colourless; -light seems expressly necessary to the definite exhibition of colour. - -637. - -Creatures which live in water, which, although a very dense medium, -suffers sufficient light to pass through it, appear more or less -coloured. Zoophytes, which appear to animate the purest calcareous -earth, are mostly white; yet we find corals deepened into the most -beautiful yellow-red: in other cells of worms this colour increases -nearly to bright red. - -638. - -The shells of the crustaceous tribe are beautifully designed and -coloured, yet it is to be remarked that neither land-snails nor the -shells of crustacea of fresh water, are adorned with such bright -colours as those of the sea. - -639. - -In examining shells, particularly such as are spiral, we find that -a series of animal organs, similar to each other, must have moved -increasingly forward, and in turning on an axis produced the shell in -a series of chambers, divisions, tubes, and prominences, according to -a plan for ever growing larger. We remark, however, that a tinging -juice must have accompanied the development of these organs, a juice -which marked the surface of the shell, probably through the immediate -co-operation of the sea-water, with coloured lines, points, spots, and -shadings: this must have taken place at regular intervals, and thus -left the indications of increasing growth lastingly on the exterior; -meanwhile the interior is generally found white or only faintly -coloured. - -640. - -That such a juice is to be found in shell-fish is, besides, -sufficiently proved by experience; for the creatures furnish it in its -liquid and colouring state: the juice of the ink-fish is an example. -But a much stronger is exhibited in the red juice found in many -shell-fish, which was so famous in ancient times, and has been employed -with advantage by the moderns. There is, it appears, in the entrails of -many of the crustaceous tribe a certain vessel which is filled with a -red juice; this contains a very strong and durable colouring substance, -so much so that the entire creature may be crushed and boiled, and -yet out of this broth a sufficiently strong tinging liquid may be -extracted. But the little vessel filled with colour may be separated -from the animal, by which means of course a concentrated juice is -gained. - -641. - -This juice has the property that when exposed to light and air it -appears first yellowish, then greenish; it then passes to blue, then to -a violet, gradually growing redder; and lastly, by the action of the -sun, and especially if transferred to cambric, it assumes a pure bright -red colour. - -642. - -Thus we should here have an augmentation, even to culmination, on the -_minus_ side, which we cannot easily meet with in inorganic cases; -indeed, we might almost call this example a passage through the -whole scale, and we are persuaded that by due experiments the entire -revolution of the circle might really be effected, for there is no -doubt that by acids duly employed, the pure red may be pushed beyond -the culminating point towards scarlet. - -643. - -This juice appears on the one hand to be connected with the phenomena -of reproduction, eggs being found, the embryos of future shell-fish, -which contain a similar colouring principle. On the other hand, in -animals ranking higher in the scale of being, the secretion appears to -bear some relation to the development of the blood. The blood exhibits -similar properties in regard to colour; in its thinnest state it -appears yellow; thickened, as it is found in the veins, it appears red; -while the arterial blood exhibits a brighter red, probably owing to the -oxydation which takes place by means of breathing. The venous blood -approaches more to violet, and by this mutability denotes the tendency -to that augmentation and progression which are now familiar to us. - -644. - -Before we quit the element whence we derived the foregoing examples, -we may add a few observations on fishes, whose scaly surface is -coloured either altogether in stripes, or in spots, and still oftener -exhibits a certain iridescent appearance, indicating the affinity of -the scales with the coats of shell-fish, mother-of-pearl, and even -the pearl itself. At the same time it should not be forgotten that -warmer climates, the influence of which extends to the watery regions, -produce, embellish, and enhance these colours in fishes in a still -greater degree. - -645. - -In Otaheite, Forster observed fishes with beautifully iridescent -surfaces, and this effect was especially apparent at the moment when -the fish died. We may here call to mind the hues of the chameleon, -and other similar appearances; for when similar facts are presented -together, we are better enabled to trace them. - -646. - -Lastly, although not strictly in the same class, the iridescent -appearance of certain molluscæ may be mentioned, as well as the -phosphorescence which, in some marine creatures, it is said becomes -iridescent just before it vanishes. - -647. - -We now turn our attention to those creatures which belong to light, -air and dry warmth, and it is here that we first find ourselves in -the living region of colours. Here, in exquisitely organised parts, -the elementary colours present themselves in their greatest purity -and beauty. They indicate, however, that the creatures they adorn, -are still low in the scale of organisation, precisely because these -colours can thus appear, as it were, unwrought. Here, too, heat seems -to contribute much to their development. - -648. - -We find insects which may be considered altogether as concentrated -colouring matter; among these, the cochineals especially are -celebrated; with regard to these we observe that their mode of settling -on vegetables, and even nestling in them, at the same time produces -those excrescences which are so useful as mordants in fixing colours. - -649. - -But the power of colour, accompanied by regular organisation, exhibits -itself in the most striking manner in those insects which require a -perfect metamorphosis for their development--in scarabæ, and especially -in butterflies. - -650. - -These last, which might be called true productions of light and air, -often exhibit the most beautiful colours, even in their chrysalis -state, indicating the future colours of the butterfly; a consideration -which, if pursued further hereafter, must undoubtedly afford a -satisfactory insight into many a secret of organised being. - -651. - -If, again, we examine the wings of the butterfly more accurately, and -in its net-like web discover the rudiments of an arm, and observe -further the mode in which this, as it were, flattened arm is covered -with tender plumage and constituted an organ of flying; we believe -we recognise a law according to which the great variety of tints is -regulated. This will be a subject for further investigation hereafter. - -652. - -That, again, heat generally has an influence on the size of the -creature, on the accomplishment of the form, and on the greater beauty -of the colours, hardly needs to be remarked. - - - - -LIII. - - -BIRDS. - - -653. - -The more we approach the higher organisations, the more it becomes -necessary to limit ourselves to a few passing observations; for all the -natural conditions of such organised beings are the result of so many -premises, that, without having at least hinted at these, our remarks -would only appear daring, and at the same time insufficient. - -654. - -We find in plants, that the consummate flower and fruit are, as it -were, rooted in the stem, and that they are nourished by more perfect -juices than the original roots first afforded; we remark, too, -that parasitical plants which derive their support from organised -structures, exhibit themselves especially endowed as to their energies -and qualities. We might in some sense compare the feathers of birds -with plants of this description; the feathers spring up as a last -structural result from the surface of a body which has yet much in -reserve for the completion of the external economy, and thus are very -richly endowed organs. - -655. - -The quills not only grow proportionally to a considerable size, but are -throughout branched, by which means they properly become feathers, and -many of these feathered branches are again subdivided; thus, again, -recalling the structure of plants. - -656. - -The feathers are very different in shape and size, but each still -remains the same organ, forming and transforming itself according to -the constitution of the part of the body from which it springs. - -657. - -With the form, the colour also becomes changed, and a certain law -regulates the general order of hues as well as that particular -distribution by which a single feather becomes party coloured, It -is from this that all combination of variegated plumage arises, and -whence, at last, the eyes in the peacock's tail are produced. It is -a result similar to that which we have already unfolded in treating -of the metamorphosis of plants, and which we shall take an early -opportunity to prove. - -658. - -Although time and circumstances compel us here to pass by this organic -law, yet we are bound to refer to the chemical operations which -commonly exhibit themselves in the tinting of feathers in a mode now -sufficiently known to us. - -659. - -Plumage is of all colours, yet, on the whole, yellow deepening to red -is commoner than blue. - -660. - -The operation of light on the feathers and their colours, is to be -remarked in all cases. Thus, for example, the feathers on the breast of -certain parrots, are strictly yellow; the scale-like anterior portion, -which is acted on by the light, is deepened from yellow to red. The -breast of such a bird appears bright-red, but if we blow into the -feathers the yellow appears. - -661. - -The exposed portion of the feathers is in all cases very different -from that which, in a quiet state, is covered; it is only the exposed -portion, for instance, in ravens, which exhibits the iridescent -appearance; the covered portion does not: from which indication, the -feathers of the tail when ruffled together, may be at once placed in -the natural order again. - - - - -LIV. - - -MAMMALIA AND HUMAN BEINGS. - - -662. - -Here the elementary colours begin to leave us altogether. We are -arrived at the highest degree of the scale, and shall not dwell on its -characteristics long. - -663. - -An animal of this class is distinguished among the examples of -organised being. Every thing that exhibits itself about him is living. -Of the internal structure we do not speak, but confine ourselves -briefly to the surface. The hairs are already distinguished from -feathers, inasmuch as they belong more to the skin, inasmuch as they -are simple, thread-like, not branched. They are however, like feathers, -shorter, longer, softer, and firmer, colourless or coloured, and all -this in conformity to laws which might be defined. - -664. - -White and black, yellow, yellow-red and brown, alternate in various -modifications, but they never appear in such a state as to remind us -of the elementary hues. On the contrary, they are all broken colours -subdued by organic concoction, and thus denote, more or less, the -perfection of life in the being they belong to. - -665. - -One of the most important considerations connected with morphology, -so far as it relates to surfaces, is this, that even in quadrupeds -the spots of the skin have a relation with the parts underneath -them. Capriciously as nature here appears, on a hasty examination, -to operate, she nevertheless consistently observes a secret law. The -development and application of this, it is true, are reserved only for -accurate and careful investigation and sincere co-operation. - -666. - -If in some animals portions appear variegated with positive colours, -this of itself shows how far such creatures are removed from a perfect -organisation; for, it may be said, the nobler a creature is, the more -all the mere material of which he is composed, is disguised by being -wrought together; the more essentially his surface corresponds with the -internal organisation, the less can it exhibit the elementary colours. -Where all tends to make up a perfect whole, any detached specific -developments cannot take place. - -667. - -Of man we have little to say, for he is entirely distinct from the -general physiological results of which we now treat. So much in this -case is in affinity with the internal structure, that the surface can -only be sparingly endowed. - -668. - -When we consider that brutes are rather encumbered than advantageously -provided with intercutaneous muscles; when we see that much that is -superfluous tends to the surface, as, for instance, large ears and -tails, as well as hair, manes, tufts; we see that nature, in such -cases, had much to give away and to lavish. - -669. - -On the contrary, the general surface of the human form is smooth and -clean, and thus in the most perfect examples, the beautiful forms are -apparent; for it may be remarked in passing, that a superfluity of -hair on the chest, arms, and lower limbs, rather indicates weakness -than strength. Poets only have sometimes been induced, probably by the -example of the ferine nature, so strong in other respects, to extol -similar attributes in their rough heroes. - -670. - -But we have here chiefly to speak of colour, and observe that the -colour of the human skin, in all its varieties, is never an elementary -colour, but presents, by means of organic concoction, a highly -complicated result.--Note X. - -671. - -That the colour of the skin and hair has relation with the differences -of character, is beyond question; and we are led to conjecture that the -circumstance of one or other organic system predominating, produces -the varieties we see. A similar hypothesis may be applied to nations, -in which case it might perhaps be observed, that certain colours -correspond with certain confirmations, which has always been observed -of the negro physiognomy. - -672. - -Lastly, we might here consider the problematical question, whether all -human forms and hues are not equally beautiful, and whether custom -and self-conceit are not the causes why one is preferred to another? -We venture, however, after what has been adduced, to assert that the -white man, that is, he whose surface varies from white to reddish, -yellowish, brownish, in short, whose surface appears most neutral in -hue and least inclines to any particular or positive colour, is the -most beautiful. On the same principle a similar point of perfection in -human conformation may be defined hereafter, when the question relates -to form. We do not imagine that this long-disputed question is to be -thus, once for all, settled, for there are persons enough who have -reason to leave this significancy of the exterior in doubt; but we thus -express a conclusion, derived from observation and reflection, such -as might suggest itself to a mind aiming at a satisfactory decision. -We subjoin a few observations connected with the elementary chemical -doctrine of colours.--Note Y. - - - - -LV. - - -PHYSICAL AND CHEMICAL EFFECTS OF THE TRANSMISSION OF LIGHT THROUGH -COLOURED MEDIUMS. - - -673. - -The physical and chemical effects of colourless light are known, so -that it is unnecessary here to describe them at length. Colourless -light exhibits itself under various conditions as exciting warmth, as -imparting a luminous quality to certain bodies, as promoting oxydation -and de-oxydation. In the modes and degrees of these effects many -varieties take place, but no difference is found indicating a principle -of contrast such as we find in the transmission of coloured light. We -proceed briefly to advert to this. - -674. - -Let the temperature of a dark room be observed by means of a very -sensible air-thermometer; if the bulb is then brought to the direct sun -light as it shines into the room, nothing is more natural than that the -fluid should indicate a much higher degree of warmth. If upon this we -interpose coloured glasses, it follows again quite naturally that the -degree of warmth must be lowered; first, because the operation of the -direct light is already somewhat impeded by the glass, and again, more -especially, because a coloured glass, as a dark medium, admits less -light through it. - -675. - -But here a difference in the excitation of warmth exhibits itself to -the attentive observer, according to the colour of the glass. The -yellow and the yellow-red glasses produce a higher temperature than the -blue and blue-red, the difference being considerable. - -676. - -This experiment may be made with the prismatic spectrum. The -temperature of the room being first remarked on the thermometer, the -blue coloured light is made to fall on the bulb, when a somewhat higher -degree of warmth is exhibited, which still increases as the other -colours are gradually brought to act on the mercury. If the experiment -is made with the water-prism, so that the white light can be retained -in the centre, this, refracted indeed, but not yet coloured light, is -the warmest; the other colours, stand in relation to each other as -before. - -677. - -As we here merely describe, without undertaking to deduce or explain -this phenomenon, we only remark in passing, that the pure light is by -no means abruptly and entirely at an end with the red division in the -spectrum, but that a refracted light is still to be observed deviating -from its course and, as it were, insinuating itself beyond the -prismatic image, so that on closer examination it will hardly be found -necessary to take refuge in invisible rays and their refraction. - -678. - -The communication of light by means of coloured mediums exhibits the -same difference. The light communicates itself to Bologna phosphorus -through blue and violet glasses, but by no means through yellow and -yellow-red glasses. It has been even remarked that the phosphori which -have been rendered luminous under violet and blue glasses, become -sooner extinguished when afterwards placed under yellow and yellow-red -glasses than those which have been suffered to remain in a dark room -without any further influence. - -679. - -These experiments, like the foregoing, may also be made by means of the -prismatic spectrum, when the same results take place. - -680. - -To ascertain the effect of coloured light on oxydation and -de-oxydation, the following means may be employed:--Let moist, -perfectly white muriate of silver[1] be spread on a strip of paper; -place it in the light, so that it may become to a certain degree grey, -and then cut it in three portions. Of these, one may be preserved -in a book, as a specimen of this state; let another be placed under -a yellow-red, and the third under a blue-red glass. The last will -become a darker grey, and exhibit a de-oxydation; the other, under the -yellow-red glass, will, on the contrary, become a lighter grey, and -thus approach nearer to the original state of more perfect oxydation. -The change in both may be ascertained by a comparison with the -unaltered specimen. - -681. - -An excellent apparatus has been contrived to perform these experiments -with the prismatic image. The results are analogous to those already -mentioned, and we shall hereafter give the particulars, making use -of the labours of an accurate observer, who has been for some time -carefully prosecuting these experiments.[2] - - -[1] Now generally called chloride of silver: the term in the original -is Hornsilber.--T. - -[2] The individual alluded to was Seebeck: the result of his -experiments was published in the second volume.--T. - - - - -LVI. - - -CHEMICAL EFFECT IN DIOPTRICAL ACHROMATISM. - - -682. - -We first invite our readers to turn to what has been before observed on -this subject (285, 298), to avoid unnecessary repetition here. - -683. - -We can thus give a glass the property of producing much wider coloured -edges without refracting more strongly than before, that is, without -displacing the object much more perceptibly. - -684. - -This property is communicated to the glass by means of metallic oxydes. -Minium, melted and thoroughly united with a pure glass, produces this -effect, and thus flint-glass (291) is prepared with oxyde of lead. -Experiments of this kind have been carried farther, and the so-called -butter of antimony, which, according to a new preparation, may be -exhibited as a pure fluid, has been made use of in hollow lenses and -prisms, producing a very strong appearance of colour with a very -moderate refraction, and presenting the effect which we have called -hyperchromatism in a very vivid manner. - -685. - -In common glass, the alkaline nature obviously preponderates, since -it is chiefly composed of sand and alkaline salts; hence a series of -experiments, exhibiting the relation of perfectly alkaline fluids to -perfect acids, might lead to useful results. - -686. - -For, could the maximum and minimum be found, it would be a question -whether a refracting medium could not be discovered, in which the -increasing and diminishing appearance of colour, (an effect almost -independent of refraction,) could not be done away with altogether, -while the displacement of the object would be unaltered. - -687. - -How desirable, therefore, it would be with regard to this last point, -as well as for the elucidation of the whole of this third division of -our work, and, indeed, for the elucidation of the doctrine of colours -generally, that those who are occupied in chemical researches, with new -views ever opening to them, should take this subject in hand, pursuing -into more delicate combinations what we have only roughly hinted at, -and prosecuting their inquiries with reference to science as a whole. - - - - -PART IV. - - -GENERAL CHARACTERISTICS. - - -688. - -We have hitherto, in a manner forcibly, kept phenomena asunder, -which, partly from their nature, partly in accordance with our mental -habits, have, as it were, constantly sought to be reunited. We have -exhibited them in three divisions. We have considered colours, first, -as transient, the result of an action and re-action in the eye -itself; next, as passing effects of colourless, light-transmitting, -transparent, or opaque mediums on light; especially on the luminous -image; lastly, we arrived at the point where we could securely -pronounce them as permanent, and actually inherent in bodies. - -689. - -In following this order we have as far as possible endeavoured to -define, to separate, and to class the appearances. But now that we -need no longer be apprehensive of mixing or confounding them, we may -proceed, first, to state the general nature of these appearances -considered abstractedly, as an independent circle of facts, and, in the -next place, to show how this particular circle is connected with other -classes of analogous phenomena in nature. - - -THE FACILITY WITH WHICH COLOUR APPEARS. - - -690. - -We have observed that colour under many conditions appears very easily. -The susceptibility of the eye with regard to light, the constant -re-action of the retina against it, produce instantaneously a slight -iridescence. Every subdued light may be considered as coloured, nay, we -ought to call any light coloured, inasmuch as it is seen. Colourless -light, colourless surfaces, are, in some sort, abstract ideas; in -actual experience we can hardly be said to be aware of them.--Note Z. - -691. - -If light impinges on a colourless body, is reflected from it or passes -through it, colour immediately appears; but it is necessary here to -remember what has been so often urged by us, namely, that the leading -conditions of refraction, reflection, &c., are not of themselves -sufficient to produce the appearance. Sometimes, it is true, light acts -with these merely as light, but oftener as a defined, circumscribed -appearance, as a luminous image. The semi-opacity of the medium is -often a necessary condition; while half, and double shadows, are -required for many coloured appearances. In all cases, however, colour -appears instantaneously. We find, again, that by means of pressure, -breathing heat (432, 471), by various kinds of motion and alteration -on smooth clean surfaces (461), as well as on colourless fluids (470), -colour is immediately produced. - -692. - -The slightest change has only to take place in the component parts -of bodies, whether by immixture with other particles or other such -effects, and colour either makes its appearance or becomes changed. - - -THE FORCE OF COLOUR. - - -693. - -The physical colours, and especially those of the prism, were formerly -called "_colores emphatici_," on account of their extraordinary beauty -and force. Strictly speaking, however, a high degree of effect may be -ascribed to all appearances of colour, assuming that they are exhibited -under the purest and most perfect conditions. - -694. - -The dark nature of colour, its full rich quality, is what produces -the grave, and at the same time fascinating impression we sometimes -experience, and as colour is to be considered a condition of light, -so it cannot dispense with light as the co-operating cause of its -appearance, as its basis or ground; as a power thus displaying and -manifesting colour. - - -THE DEFINITE NATURE OF COLOUR. - - -695. - -The existence and the relatively definite character of colour are one -and the same thing. Light displays itself and the face of nature, as -it were, with a general indifference, informing us as to surrounding -objects perhaps devoid of interest or importance; but colour is at all -times specific, characteristic, significant. - -696. - -Considered in a general point of view, colour is determined towards one -of two sides. It thus presents a contrast which we call a polarity, and -which we may fitly designate by the expressions _plus_ and _minus_. - - _Plus. Minus_. - - Yellow. Blue. - Action. Negation.[1] - Light. Shadow. - Brightness. Darkness. - Force. Weakness. - Warmth. Coldness. - Proximity. Distance. - Repulsion Attraction. - Affinity with acids. Affinity with alkalis. - - -COMBINATION OF THE TWO PRINCIPLES. - - -697. - -If these specific, contrasted principles are combined, the respective -qualities do not therefore destroy each other: for if in this -intermixture the ingredients are so perfectly balanced that neither -is to be distinctly recognised, the union again acquires a specific -character; it appears as a quality by itself in which we no longer -think of combination. This union we call green. - -698. - -Thus, if two opposite phenomena springing from the same source do not -destroy each other when combined, but in their union present a third -appreciable and pleasing appearance, this result at once indicates -their harmonious relation. The more perfect result yet remains to be -adverted to. - - -AUGMENTATION TO RED. - - -699. - -Blue and yellow do not admit of increased intensity without presently -exhibiting a new appearance in addition to their own. Each colour, in -its lightest state, is a dark; if condensed it must become darker, but -this effect no sooner takes place than the hue assumes an appearance -which we designate by the word reddish. - -700. - -This appearance still increases, so that when the highest degree of -intensity is attained it predominates over the original hue. A powerful -impression of light leaves the sensation of red on the retina. In the -prismatic yellow-red which springs directly from the yellow, we hardly -recognise the yellow. - -701. - -This deepening takes place again by means of colourless -semi-transparent mediums, and here we see the effect in its utmost -purity and extent. Transparent fluids, coloured with any given hues, in -a series of glass-vessels, exhibit it very strikingly. The augmentation -is unremittingly rapid and constant; it is universal, and obtains in -physiological as well as in physical and chemical colours. - - -JUNCTION OF THE TWO AUGMENTED EXTREMES. - - -702. - -As the extremes of the simple contrast produce a beautiful and -agreeable appearance by their union, so the deepened extremes on being -united, will present a still more fascinating colour; indeed, it might -naturally be expected that we should here find the acme of the whole -phenomenon. - -COMPLETENESS THE RESULT OF VARIETY. - - -703. - -And such is the fact, for pure red appears; a colour to which, from its -excellence, we have appropriated the term "purpur."[2] - -704. - -There are various modes in which pure red may appear. By bringing -together the violet edge and yellow-red border in prismatic -experiments, by continued augmentation in chemical operations, and by -the organic contrast in physiological effects. - -705. - -As a pigment it cannot be produced by intermixture or union, but -only by arresting the hue in substances chemically acted on, at the -high culminating point. Hence the painter is justified in assuming -that there are _three_ primitive colours from which he combines all -the others. The natural philosopher, on the other hand, assumes only -_two_ elementary colours, from which he, in like manner, developes and -combines the rest. - - -COMPLETENESS THE RESULT OF VARIETY IN COLOUR. - - -706. - -The various appearances of colour arrested in their different degrees, -and seen in juxtaposition, produce a whole. This totality is harmony to -the eye. - -707. - -The chromatic circle has been gradually presented to us; the -various relations of its progression are apparent to us. Two pure -original principles in contrast, are the foundation of the whole; -an augmentation manifests itself by means of which both approach a -third state; hence there exists on both sides a lowest and highest, -a simplest and most qualified state. Again, two combinations present -themselves; first that of the simple primitive contrasts, then that of -the deepened contrasts. - - -HARMONY OF THE COMPLETE STATE. - - -708. - -The whole ingredients of the chromatic scale, seen in juxtaposition, -produce an harmonious impression on the eye. The difference between the -physical contrast and harmonious opposition in all its extent should -not be overlooked. The first resides in the pure restricted original -dualism, considered in its antagonizing elements; the other results -from the fully developed effects of the complete state. - -709. - -Every single opposition in order to be harmonious must comprehend the -whole. The physiological experiments are sufficiently convincing -on this point. A development of all the possible contrasts of the -chromatic scale will be shortly given.[3] - - -FACILITY WITH WHICH COLOUR MAY BE MADE TO TEND EITHER TO THE PLUS OR -MINUS SIDE. - - -710. - -We have already had occasion to take notice of the mutability of colour -in considering its so-called augmentation and progressive variations -round the whole circle; but the hues even pass and repass from one side -to the other, rapidly and of necessity. - -711. - -Physiological colours are different in appearance as they happen -to fall on a dark or on a light ground. In physical colours the -combination of the objective and subjective experiments is very -remarkable. The epoptical colours, it appears, are contrasted according -as the light shines through or upon them. To what extent the chemical -colours may be changed by fire and alkalis, has been sufficiently shown -in its proper place. - - -EVANESCENCE OF COLOUR. - - -712. - -All that has been adverted to as subsequent to the rapid excitation -and definition of colour, immixture, augmentation, combination, -separation, not forgetting the law of compensatory harmony, all takes -place with the greatest rapidity and facility; but with equal quickness -colour again altogether disappears. - -713. - -The physiological appearances are in no wise to be arrested; the -physical last only as long as the external condition lasts; even the -chemical colours have great mutability, they may be made to pass and -repass from one side to the other by means of opposite re-agents, and -may even be annihilated altogether. - - -PERMANENCE OF COLOUR. - - -714. - -The chemical colours afford evidence of very great duration. Colours -fixed in glass by fusion, and by nature in gems, defy all time and -re-action. - -715. - -The art of dyeing again fixes colour very powerfully. The hues of -pigments which might otherwise be easily rendered mutable by re-agents, -may be communicated to substances in the greatest permanency by means -of mordants. - - -[1] Wirkung, Beraubung; the last would be more literally rendered -_privation_. The author has already frequently made use of the terms -_active_ and _passive_ as equivalent to _plus_ and _minus_.--T. - -[2] Wherever this word occurs incidentally it is translated _pure red_, -the English word _purple_ being generally employed to denote a colour -similar to violet.--T. - -[3] No diagram or table of this kind was ever given by the author.--T. - - - - -PART V. - - -RELATION TO OTHER PURSUITS--RELATION TO PHILOSOPHY. - - -716. - -The investigator of nature cannot be required to be a philosopher, -but it is expected that he should so far have attained the habit of -philosophizing, as to distinguish himself essentially from the world, -in order to associate himself with it again in a higher sense. He -should form to himself a method in accordance with observation, but -he should take heed not to reduce observation to mere notion, to -substitute words for this notion, and to use and deal with these words -as if they were things. He should be acquainted with the labours of -philosophers, in order to follow up the phenomena which have been the -subject of his observation, into the philosophic region. - -717. - -It cannot be required that the philosopher should be a naturalist, and -yet his co-operation in physical researches is as necessary as it is -desirable. He needs not an acquaintance with details for this, but only -a clear view of those conclusions where insulated facts meet. - -718. - -We have before (175) alluded to this important consideration, and -repeat it here where it is in its place. The worst that can happen -to physical science as well as to many other kinds of knowledge is, -that men should treat a secondary phenomenon as a primordial one, and -(since it is impossible to derive the original fact from the secondary -state), seek to explain what is in reality the cause by an effect made -to usurp its place. Hence arises an endless confusion, a mere verbiage, -a constant endeavour to seek and to find subterfuges whenever truth -presents itself and threatens to be overpowering. - -719. - -While the observer, the investigator of nature, is thus dissatisfied -in finding that the appearances he sees still contradict a received -theory, the philosopher can calmly continue to operate in his abstract -department on a false result, for no result is so false but that it can -be made to appear valid, as form without substance, by some means or -other. - -720. - -If, on the other hand, the investigator of nature can attain to the -knowledge of that which we have called a primordial phenomenon, he is -safe; and the philosopher with him. The investigator of nature is -safe, since he is persuaded that he has here arrived at the limits -of his science, that he finds himself at the height of experimental -research; a height whence he can look back upon the details of -observation in all its steps, and forwards into, if he cannot enter, -the regions of theory. The philosopher is safe, for he receives -from the experimentalist an ultimate fact, which, in his hands, now -becomes an elementary one. He now justly pays little attention to -appearances which are understood to be secondary, whether he already -finds them scientifically arranged, or whether they present themselves -to his casual observation scattered and confused. Should he even be -inclined to go over this experimental ground himself, and not be -averse to examination in detail, he does this conveniently, instead of -lingering too long in the consideration of secondary and intermediate -circumstances, or hastily passing them over without becoming accurately -acquainted with them. - -721. - -To place the doctrine of colours nearer, in this sense, within the -philosopher's reach, was the author's wish; and although the execution -of his purpose, from various causes, does not correspond with his -intention, he will still keep this object in view in an intended -recapitulation, as well as in the polemical and historical portions of -his work; for he will have to return to the consideration of this point -hereafter, on an occasion where it will be necessary to speak with less -reserve. - - -RELATION TO MATHEMATICS. - - -722. - -It may be expected that the investigator of nature, who proposes to -treat the science of natural philosophy in its entire range, should be -a mathematician. In the middle ages, mathematics was the chief organ by -means of which men hoped to master the secrets of nature, and even now, -geometry in certain departments of physics, is justly considered of -first importance. - -723. - -The author can boast of no attainments of this kind, and on this -account confines himself to departments of science which are -independent of geometry; departments which in modern times have been -opened up far and wide. - -724. - -It will be universally allowed that mathematics, one of the noblest -auxiliaries which can be employed by man, has, in one point of view, -been of the greatest use to the physical sciences; but that, by a -false application of its methods, it has, in many respects, been -prejudicial to them, is also not to be denied; we find it here and -there reluctantly admitted. - -725. - -The theory of colours, in particular, has suffered much, and its -progress has been incalculably retarded by having been mixed up with -optics generally, a science which cannot dispense with mathematics; -whereas the theory of colours, in strictness, may be investigated quite -independently of optics. - -726. - -But besides this there was an additional evil. A great mathematician -was possessed with an entirely false notion on the physical origin of -colours; yet, owing to his great authority as a geometer, the mistakes -which he committed as an experimentalist long became sanctioned in the -eyes of a world ever fettered in prejudices. - -727. - -The author of the present inquiry has endeavoured throughout to keep -the theory of colours distinct from the mathematics, although there -are evidently certain points where the assistance of geometry would be -desirable. Had not the unprejudiced mathematicians, with whom he has -had, or still has, the good fortune to be acquainted, been prevented -by other occupations from making common cause with him, his work would -not have wanted some merit in this respect. But this very want may be -in the end advantageous, since it may now become the object of the -enlightened mathematician to ascertain where the doctrine of colours is -in need of his aid, and how he can contribute the means at his command -with a view to the complete elucidation of this branch of physics. - -728. - -In general it were to be wished that the Germans, who render such -good service to science, while they adopt all that is good from other -nations, could by degrees accustom themselves to work in concert. We -live, it must be confessed, in an age, the habits of which are directly -opposed to such a wish. Every one seeks, not only to be original in -his views, but to be independent of the labours of others, or at least -to persuade himself that he is so, even in the course of his life -and occupation. It is very often remarked that men who undoubtedly -have accomplished much, quote themselves only, their own writings, -journals, and compendiums; whereas it would be far more advantageous -for the individual, and for the world, if many were devoted to a common -pursuit. The conduct of our neighbours the French is, in this respect, -worthy of imitation; we have a pleasing instance in Cuvier's preface -to his "Tableau Élémentaire de l'Histoire Naturelle des Animaux." - -729. - -He who has observed science and its progress with an unprejudiced eye, -might even ask whether it is desirable that so many occupations and -aims, though allied to each other, should be united in one person, and -whether it would not be more suitable for the limited powers of the -human mind to distinguish, for example, the investigator and inventor, -from him who employs and applies the result of experiment? Astronomers, -who devote themselves to the observation of the heavens and the -discovery or enumeration of stars, have in modern times formed, to a -certain extent, a distinct class from those who calculate the orbits, -consider the universe in its connexion, and more accurately define its -laws. The history of the doctrine of colours will often lead us back to -these considerations. - - -RELATION TO THE TECHNICAL OPERATIONS OF THE DYER. - - -730. - -If in our labours we have gone out of the province of the -mathematician, we have, on the other hand, endeavoured to meet the -practical views of the dyer; and although the chapter which treats -of colour in a chemical point of view is not the most complete and -circumstantial, yet in that portion, as well as in our general -observations respecting colour, the dyer will find his views assisted -far more than by the theory hitherto in vogue, which failed to afford -him any assistance. - -731. - -It is curious, in this view, to take a glance at the works containing -directions on the art of dyeing. As the Catholic, on entering his -temple, sprinkles himself with holy water, and after bending the knee, -proceeds perhaps to converse with his friends on his affairs, without -any especial devotion; so all the treatises on dyeing begin with a -respectful allusion to the accredited theory, without afterwards -exhibiting a single trace of any principle deduced from this theory, -or showing that it has thrown light on any part of the art, or that it -offers any useful hints in furtherance of practical methods. - -732. - -On the other hand, there are men who, after having become thoroughly -and experimentally acquainted with the nature of dyes, have not been -able to reconcile their observations with the received theory; who -have, in short, discovered its weak points, and sought for a general -view more consonant to nature and experience. When we come to the names -of Castel and Gülich, in our historical review, we shall have occasion -to enter into this more fully, and an opportunity will then present -itself to show that an assiduous experience in taking advantage of -every accident may, in fact, be said almost to exhaust the knowledge -of the province to which it is confined. The high and complete result -is then submitted to the theorist, who, if he examines facts with -accuracy, and reasons with candour, will find such materials eminently -useful as a basis for his conclusions.--Note A A. - - -RELATION TO PHYSIOLOGY AND PATHOLOGY. - - -733. - -If the phenomena adduced in the chapter where colours were considered -in a physiological and pathological view are for the most part -generally known, still some new views, mixed up with them, will not be -unacceptable to the physiologist. We especially hope to have given him -cause to be satisfied by classing certain phenomena which stood alone, -under analogous facts, and thus, in some measure, to have prepared the -way for his further investigations. - -734. - -The appendix on pathological colours, again, is admitted to be scanty -and unconnected. We reflect, however, that Germany can boast of men who -are not only highly experienced in this department, but are likewise so -distinguished for general cultivation, that it can cost them but little -to revise this portion, to complete what has been sketched, and at the -same time to connect it with the higher facts of organisation. - - -RELATION TO NATURAL HISTORY. - - -735. - -If we may at all hope that natural history will gradually be modified -by the principle of deducing the ordinary appearances of nature from -higher phenomena, the author believes he may have given some hints -and introductory views bearing on this object also. As colour, in its -infinite variety, exhibits itself on the surface of living beings, it -becomes an important part of the outward indications, by means of which -we can discover what passes underneath. - -736. - -In one point of view it is certainly not to be too much relied on, on -account of its indefinite and mutable nature; yet even this mutability, -inasmuch as it exhibits itself as a constant quality, again becomes -a criterion of a mutable vitality; and the author wishes nothing -more than that time may be granted him to develop the results of his -observations on this subject more fully; here they would not be in -their place. - - -RELATION TO GENERAL PHYSICS. - - -737. - -The state in which general physics now is, appears, again, particularly -favourable to our labours; for natural philosophy, owing to -indefatigable and variously directed research, has gradually attained -such eminence, that it appears not impossible to refer a boundless -empiricism to one centre. - -738. - -Without referring to subjects which are too far removed from our own -province, we observe that the formulæ under which the elementary -appearances of nature are expressed, altogether tend in this direction; -and it is easy to see that through this correspondence of expression, a -correspondence in meaning will necessarily be soon arrived at. - -739. - -True observers of nature, however they may differ in opinion in other -respects, will agree that all which presents itself as appearance, all -that we meet with as phenomenon, must either indicate an original -division which is capable of union, or an original unity which admits -of division, and that the phenomenon will present itself accordingly. -To divide the united, to unite the divided, is the life of nature; -this is the eternal systole and diastole, the eternal collapsion and -expansion, the inspiration and expiration of the world in which we live -and move. - -740. - -It is hardly necessary to observe that what we here express as number -and restrict to dualism is to be understood in a higher sense; the -appearance of a third, a fourth order of facts progressively developing -themselves is to be similarly understood; but actual observation -should, above all, be the basis of all these expressions. - -741. - -Iron is known to us as a peculiar substance, different from other -substances: in its ordinary state we look upon it as a mere material -remarkable only on account of its fitness for various uses and -applications. How little, however, is necessary to do away with the -comparative insignificancy of this substance. A two-fold power is -called forth,[1] which, while it tends again to a state of union, and, -as it were, seeks itself, acquires a kind of magical relation with -its like, and propagates this double property, which is in fact but a -principle of reunion, throughout all bodies of the same kind. We here -first observe the mere substance, iron; we see the division that takes -place in it propagate itself and disappear, and again easily become -re-excited. This, according to our mode of thinking, is a primordial -phenomenon in immediate relation with its idea, and which acknowledges -nothing earthly beyond it. - -742. - -Electricity is again peculiarly characterised. As a mere quality we are -unacquainted with it; for us it is a nothing, a zero, a mere point, -which, however, dwells in all apparent existences, and at the same time -is the point of origin whence, on the slightest stimulus, a double -appearance presents itself, an appearance which only manifests itself -to vanish. The conditions under which this manifestation is excited -are infinitely varied, according to the nature of particular bodies. -From the rudest mechanical friction of very different substances with -one another, to the mere contiguity of two entirely similar bodies, -the phenomenon is present and stirring, nay, striking and powerful, -and so decided and specific, that when we employ the terms or formulæ -polarity, plus and minus, for north and south, for glass and resin, we -do so justifiably and in conformity with nature. - -743. - -This phenomenon, although it especially affects the surface, is yet by -no means superficial. It influences the tendency or determination of -material qualities, and connects itself in immediate co-operation with -the important double phenomenon which takes place so universally in -chemistry,--oxydation, and de-oxydation. - -744. - -To introduce and include the appearances of colour in this series, -this circle of phenomena was the object of our labours. What we have -not succeeded in others will accomplish. We found a primordial vast -contrast between light and darkness, which may be more generally -expressed by light and its absence. We looked for the intermediate -state, and sought by means of it to compose the visible world of light, -shade, and colour. In the prosecution of this we employed various terms -applicable to the development of the phenomena, terms which we adopted -from the theories of magnetism, of electricity, and of chemistry. It -was necessary, however, to extend this terminology, since we found -ourselves in an abstract region, and had to express more complicated -relations. - -745. - -If electricity and galvanism, in their general character, are -distinguished as superior to the more limited exhibition of magnetic -phenomena, it may be said that colour, although coming under similar -laws, is still superior; for since it addresses itself to the noble -sense of vision, its perfections are more generally displayed. Compare -the varied effects which result from the augmentation of yellow and -blue to red, from the combination of these two higher extremes to pure -red, and the union of the two inferior extremes to green. What a far -more varied scheme is apparent here than that in which magnetism and -electricity are comprehended. These last phenomena may be said to be -inferior again on another account; for though they penetrate and give -life to the universe, they cannot address themselves to man in a higher -sense in order to his employing them æsthetically. The general, simple, -physical law must first be elevated and diversified itself in order to -be available for elevated uses. - -746. - -If the reader, in this spirit, recalls what has been stated by us -throughout, generally and in detail, with regard to colour, he will -himself pursue and unfold what has been here only lightly hinted at. -He will augur well for science, technical processes, and art, if it -should prove possible to rescue the attractive subject of the doctrine -of colours from the atomic restriction and isolation in which it has -been banished, in order to restore it to the general dynamic flow of -life and action which the present age loves to recognise in nature. -These considerations will press upon us more strongly when, in the -historical portion, we shall have to speak of many an enterprising -and intelligent man who failed to possess his contemporaries with his -convictions. - - -RELATION TO THE THEORY OF MUSIC. - - -747. - -Before we proceed to the moral associations of colour, and the æsthetic -influences arising from them, we have here to say a few words on its -relation to melody. That a certain relation exists between the two, -has been always felt; this is proved by the frequent comparisons we -meet with, sometimes as passing allusions, sometimes as circumstantial -parallels. The error which writers have fallen into in trying to -establish this analogy we would thus define: - -748. - -Colour and sound do not admit of being directly compared together -in any way, but both are referable to a higher formula, both are -derivable, although each for itself, from this higher law. They are -like two rivers which have their source in one and the same mountain, -but subsequently pursue their way under totally different conditions -in two totally different regions, so that throughout the whole course -of both no two points can be compared. Both are general, elementary -effects acting according to the general law of separation and tendency -to union, of undulation and oscillation, yet acting thus in wholly -different provinces, in different modes, on different elementary -mediums, for different senses.--Note B B. - -749. - -Could some investigator rightly adopt the method in which we have -connected the doctrine of colours with natural philosophy generally, -and happily supply what has escaped or been missed by us, the theory -of sound, we are persuaded, might be perfectly connected with general -physics: at present it stands, as it were, isolated within the circle -of science. - -750. - -It is true it would be an undertaking of the greatest difficulty -to do away with the positive character which we are now accustomed -to attribute to music--a character resulting from the achievements -of practical skill, from accidental, mathematical, æsthetical -influences--and to substitute for all this a merely physical inquiry -tending to resolve the science into its first elements. Yet considering -the point at which science and art are now arrived, considering the -many excellent preparatory investigations that have been made relative -to this subject, we may perhaps still see it accomplished. - - -CONCLUDING OBSERVATIONS ON TERMINOLOGY. - - -751. - -We never sufficiently reflect that a language, strictly speaking, can -only be symbolical and figurative, that it can never express things -directly, but only, as it were, reflectedly. This is especially the -case in speaking of qualities which are only imperfectly presented -to observation, which might rather be called powers than objects, -and which are ever in movement throughout nature. They are not to be -arrested, and yet we find it necessary to describe them; hence we look -for all kinds of formulæ in order, figuratively at least, to define -them. - -752. - -Metaphysical formulæ have breadth as well as depth, but on this -very account they require a corresponding import; the danger -here is vagueness. Mathematical expressions may in many cases be -very conveniently and happily employed, but there is always an -inflexibility in them, and we presently feel their inadequacy; for even -in elementary cases we are very soon conscious of an incommensurable -idea; they are, besides, only intelligible to those who are especially -conversant in the sciences to which such formulæ are appropriated. The -terms of the science of mechanics are more addressed to the ordinary -mind, but they are ordinary in other senses, and always have something -unpolished; they destroy the inward life to offer from without an -insufficient substitute for it. The formulæ of the corpuscular theories -are nearly allied to the last; through them the mutable becomes rigid, -description and expression uncouth: while, again, moral terms, which -undoubtedly can express nicer relations, have the effect of mere -symbols in the end, and are in danger of being lost in a play of wit. - -753. - -If, however, a writer could use all these modes of description and -expression with perfect command, and thus give forth the result of his -observations on the phenomena of nature in a diversified language; -if he could preserve himself from predilections, still embodying a -lively meaning in as animated an expression, we might look for much -instruction communicated in the most agreeable of forms. - -754. - -Yet, how difficult it is to avoid substituting the sign for the thing; -how difficult to keep the essential quality still living before us, -and not to kill it with the word. With all this, we are exposed in -modern times to a still greater danger by adopting expressions and -terminologies from all branches of knowledge and science to embody our -views of simple nature. Astronomy, cosmology, geology, natural history, -nay religion and mysticism, are called in in aid; and how often do -we not find a general idea and an elementary state rather hidden and -obscured than elucidated and brought nearer to us by the employment of -terms, the application of which is strictly specific and secondary. -We are quite aware of the necessity which led to the introduction and -general adoption of such a language, we also know that it has become in -a certain sense indispensable; but it is only a moderate, unpretending -recourse to it, with an internal conviction of its fitness, that can -recommend it. - -755. - -After all, the most desirable principle would be that writers should -borrow the expressions employed to describe the details of a given -province of investigation from the province itself; treating the -simplest phenomenon as an elementary formula, and deriving and -developing the more complicated designations from this. - -756. - -The necessity and suitableness of such a conventional language where -the elementary sign expresses the appearance itself, has been duly -appreciated by extending, for instance, the application of the term -polarity, which is borrowed from the magnet to electricity, &c. The -_plus_ and _minus_ which may be substituted for this, have found as -suitable an application to many phenomena; even the musician, probably -without troubling himself about these other departments, has been -naturally led to express the leading difference in the modes of melody -by _major_ and _minor_. - -757. - -For ourselves we have long wished to introduce the term polarity into -the doctrine of colours; with what right and in what sense, the present -work may show. Perhaps we may hereafter find room to connect the -elementary phenomena together according to our mode, by a similar use -of symbolical terms, terms which must at all times convey the directly -corresponding idea; we shall thus render more explicit what has been -here only alluded to generally, and perhaps too vaguely expressed. - - -[1] Eine Entzweyung geht vor; literally, _a division takes place_. -According to some, the two magnetic powers are previously in the bar, -and are then separated at the ends.--T. - - - - -PART VI. - - -EFFECT OF COLOUR WITH REFERENCE TO MORAL ASSOCIATIONS. - - -758. - -Since colour occupies so important a place in the series of elementary -phenomena, filling as it does the limited circle assigned to it with -fullest variety, we shall not be surprised to find that its effects are -at all times decided and significant, and that they are immediately -associated with the emotions of the mind. We shall not be surprised -to find that these appearances presented singly, are specific, that -in combination they may produce an harmonious, characteristic, often -even an inharmonious effect on the eye, by means of which they act on -the mind; producing this impression in their most general elementary -character, without relation to the nature or form of the object on -whose surface they are apparent. Hence, colour considered as an element -of art, may be made subservient to the highest æsthetical ends.--Note C -C. - -759. - -People experience a great delight in colour, generally. The eye -requires it as much as it requires light. We have only to remember -the refreshing sensation we experience, if on a cloudy day the sun -illumines a single portion of the scene before us and displays its -colours. That healing powers were ascribed to coloured gems, may have -arisen from the experience of this indefinable pleasure. - -760. - -The colours which we see on objects are not qualities entirely -strange to the eye; the organ is not thus merely habituated to the -impression; no, it is always predisposed to produce colour of itself, -and experiences a sensation of delight if something analogous to its -own nature is offered to it from without; if its susceptibility is -distinctly determined towards a given state. - -761. - -From some of our earlier observations we can conclude, that general -impressions produced by single colours cannot be changed, that they act -specifically, and must produce definite, specific states in the living -organ. - -762. - -They likewise produce a corresponding influence on the mind. Experience -teaches us that particular colours excite particular states of feeling. -It is related of a witty Frenchman, "Il prétendoit que son ton de -conversation avec Madame étoit changé depuis qu'elle avoit changé en -cramoisi le meuble de son cabinet, qui étoit bleu." - -763. - -In order to experience these influences completely, the eye should be -entirely surrounded with one colour; we should be in a room of one -colour, or look through a coloured glass. We are then identified with -the hue, it attunes the eye and mind in mere unison with itself. - -764. - -The colours on the _plus_ side are yellow, red-yellow (orange), -yellow-red (minium, cinnabar). The feelings they excite are quick, -lively, aspiring. - - -YELLOW. - - -765. - -This is the colour nearest the light. It appears on the slightest -mitigation of light, whether by semi-transparent mediums or faint -reflection from white surfaces. In prismatic experiments it extends -itself alone and widely in the light space, and while the two poles -remain separated from each other, before it mixes with blue to -produce green it is to be seen in its utmost purity and beauty. How -the chemical yellow developes itself in and upon the white, has been -circumstantially described in its proper place. - -766. - -In its highest purity it always carries with it the nature of -brightness, and has a serene, gay, softly exciting character. - -767. - -In this state, applied to dress, hangings, carpeting, &c., it is -agreeable. Gold in its perfectly unmixed state, especially when the -effect of polish is superadded, gives us a new and high idea of this -colour; in like manner, a strong yellow, as it appears on satin, has a -magnificent and noble effect. - -768. - -We find from experience, again, that yellow excites a warm and -agreeable impression. Hence in painting it belongs to the illumined and -emphatic side. - -769. - -This impression of warmth may be experienced in a very lively manner if -we look at a landscape through a yellow glass, particularly on a grey -winter's day. The eye is gladdened, the heart expanded and cheered, a -glow seems at once to breathe towards us. - -770. - -If, however, this colour in its pure and bright state is agreeable -and gladdening, and in its utmost power is serene and noble, it is, on -the other hand, extremely liable to contamination, and produces a very -disagreeable effect if it is sullied, or in some degree tends to the -_minus_ side. Thus, the colour of sulphur, which inclines to green, has -a something unpleasant in it. - -771. - -When a yellow colour is communicated to dull and coarse surfaces, -such as common cloth, felt, or the like, on which it does not appear -with full energy, the disagreeable effect alluded to is apparent. By -a slight and scarcely perceptible change, the beautiful impression -of fire and gold is transformed into one not undeserving the epithet -foul; and the colour of honour and joy reversed to that of ignominy -and aversion. To this impression the yellow hats of bankrupts and the -yellow circles on the mantles of Jews, may have owed their origin. - - -RED-YELLOW. - - -772. - -As no colour can be considered as stationary, so we can very easily -augment yellow into reddish by condensing or darkening it. The colour -increases in energy, and appears in red-yellow more powerful and -splendid. - -773. - -All that we have said of yellow is applicable here in a higher -degree. The red-yellow gives an impression of warmth and gladness, -since it represents the hue of the intenser glow of fire, and of the -milder radiance of the setting sun. Hence it is agreeable around us, -and again, as clothing, in greater or less degrees is cheerful and -magnificent. A slight tendency to red immediately gives a new character -to yellow, and while the English and Germans content themselves -with bright pale yellow colours in leather, the French, as Castel -has remarked, prefer a yellow enhanced to red; indeed, in general, -everything in colour is agreeable to them which belongs to the active -side. - - -YELLOW-RED. - - -774. - -As pure yellow passes very easily to red-yellow, so the deepening of -this last to yellow-red is not to be arrested. The agreeable, cheerful -sensation which red-yellow excites, increases to an intolerably -powerful impression in bright yellow-red. - -775, - -The active side is here in its highest energy, and it is not to -be wondered at that impetuous, robust, uneducated men, should be -especially pleased with this colour. Among savage nations the -inclination for it has been universally remarked, and when children, -left to themselves, begin to use tints, they never spare vermilion and -minium. - -776. - -In looking steadfastly at a perfectly yellow-red surface, the colour -seems actually to penetrate the organ. It produces an extreme -excitement, and still acts thus when somewhat darkened. A yellow-red -cloth disturbs and enrages animals. I have known men of education to -whom its effect was intolerable if they chanced to see a person dressed -in a scarlet cloak on a grey, cloudy day. - -777. - -The colours on the _minus_ side are blue, red-blue, and blue-red. They -produce a restless, susceptible, anxious impression. - - -BLUE. - - -778. - -As yellow is always accompanied with light, so it may be said that blue -still brings a principle of darkness with it. - -779. - -This colour has a peculiar and almost indescribable effect on the eye. -As a hue it is powerful, but it is on the negative side, and in its -highest purity is, as it were, a stimulating negation. Its appearance, -then, is a kind of contradiction between excitement and repose. - -780. - -As the upper sky and distant mountains appear blue, so a blue surface -seems to retire from us. - -781. - -But as we readily follow an agreeable object that flies from us, so we -love to contemplate blue, not because it advances to us, but because it -draws us after it. - -782. - -Blue gives us an impression of cold, and thus, again, reminds us of -shade. We have before spoken of its affinity with black. - -783. - -Rooms which are hung with pure blue, appear in some degree larger, but -at the same time empty and cold. - -784. - -The appearance of objects seen through a blue glass is gloomy and -melancholy. - -785. - -When blue partakes in some degree of the _plus_ side, the effect is not -disagreeable. Sea-green is rather a pleasing colour. - - -RED-BLUE. - - -786. - -We found yellow very soon tending to the intense state, and we observe -the same progression in blue. - -787. - -Blue deepens very mildly into red, and thus acquires a somewhat active -character, although it is on the passive side. Its exciting power is, -however, of a very different kind from that of the red-yellow. It may -be said to disturb rather than enliven. - -788. - -As augmentation itself is not to be arrested, so we feel an inclination -to follow the progress of the colour, not, however, as in the case of -the red-yellow, to see it still increase in the active sense, but to -find a point to rest in. - -789. - -In a very attenuated state, this colour is known to us under the name -of lilac; but even in this degree it has a something lively without -gladness. - -790. - -This unquiet feeling increases as the hue progresses, and it may be -safely assumed, that a carpet of a perfectly pure deep blue-red would -be intolerable. On this account, when it is used for dress, ribbons, or -other ornaments, it is employed in a very attenuated and light state, -and thus displays its character as above defined, in a peculiarly -attractive manner. - -791. - -As the higher dignitaries of the church have appropriated this unquiet -colour to themselves, we may venture to say that it unceasingly aspires -to the cardinal's red through the restless degrees of a still impatient -progression. - - -RED. - - -792. - -We are here to forget everything that borders on yellow or blue. We -are to imagine an absolutely pure red, like fine carmine suffered to -dry on white porcelain. We have called this colour "purpur" by way -of distinction, although we are quite aware that the purple of the -ancients inclined more to blue. - -793. - -Whoever is acquainted with the prismatic origin of red, will not think -it paradoxical if we assert that this colour partly _actu_, partly -_potentiâ_, includes all the other colours. - -794. - -We have remarked a constant progress or augmentation in yellow and -blue, and seen what impressions were produced by the various states; -hence it may naturally be inferred that now, in the junction of the -deepened extremes, a feeling of satisfaction must succeed; and thus, in -physical phenomena, this highest of all appearances of colour arises -from the junction of two contrasted extremes which have gradually -prepared themselves for a union. - -795. - -As a pigment, on the other hand, it presents itself to us already -formed, and is most perfect as a hue in cochineal; a substance which, -however, by chemical action may be made to tend to the _plus_ or the -_minus_ side, and may be considered to have attained the central point -in the best carmine. - -796. - -The effect of this colour is as peculiar as its nature. It conveys an -impression of gravity and dignity, and at the same time of grace and -attractiveness. The first in its dark deep state, the latter in its -light attenuated tint; and thus the dignity of age and the amiableness -of youth may adorn itself with degrees of the same hue. - -797. - -History relates many instances of the jealousy of sovereigns with -regard to the quality of red. Surrounding accompaniments of this colour -have always a grave and magnificent effect. - -798. - -The red glass exhibits a bright landscape in so dreadful a hue as to -inspire sentiments of awe. - -799. - -Kermes and cochineal, the two materials chiefly employed in dyeing to -produce this colour, incline more or less to the _plus_ or _minus_ -state, and may be made to pass and repass the culminating point by -the action of acids and alkalis: it is to be observed that the French -arrest their operations on the active side, as is proved by the French -scarlet, which inclines to yellow. The Italians, on the other hand, -remain on the passive side, for their scarlet has a tinge of blue. - -800. - -By means of a similar alkaline treatment, the so-called crimson is -produced; a colour which the French must be particularly prejudiced -against, since they employ the expressions--"Sot en cramoisi, méchant -en cramoisi," to mark the extreme of the silly and the reprehensible. - - -GREEN. - - -801. - -If yellow and blue, which we consider as the most fundamental and -simple colours, are united as they first appear, in the first state of -their action, the colour which we call green is the result. - -802. - -The eye experiences a distinctly grateful impression from this colour. -If the two elementary colours are mixed in perfect equality so that -neither predominates, the eye and the mind repose on the result of this -junction as upon a simple colour. The beholder has neither the wish -nor the power to imagine a state beyond it. Hence for rooms to live in -constantly, the green colour is most generally selected. - - -COMPLETENESS AND HARMONY. - - -803. - -We have hitherto assumed, for the sake of clearer explanation, that the -eye can be compelled to assimilate or identify itself with a single -colour; but this can only be possible for an instant. - -804. - -For when we find ourselves surrounded by a given colour which excites -its corresponding sensation on the eye, and compels us by its presence -to remain in a state identical with it, this state is soon found to be -forced, and the organ unwillingly remains in it. - -805. - -When the eye sees a colour it is immediately excited, and it is its -nature, spontaneously and of necessity, at once to produce another, -which with the original colour comprehends the whole chromatic scale. -A single colour excites, by a specific sensation, the tendency to -universality. - -806. - -To experience this completeness, to satisfy itself, the eye seeks for -a colourless space next every hue in order to produce the complemental -hue upon it. - -807. - -In this resides the fundamental law of all harmony of colours, of which -every one may convince himself by making himself accurately acquainted -with the experiments which we have described in the chapter on the -physiological colours. - -808. - -If, again, the entire scale is presented to the eye externally, the -impression is gladdening, since the result of its own operation is -presented to it in reality. We turn our attention therefore, in the -first place, to this harmonious juxtaposition. - -809. - -As a very simple means of comprehending the principle of this, the -reader has only to imagine a moveable diametrical index in the -colorific circle.[1] The index, as it revolves round the whole circle, -indicates at its two extremes the complemental colours, which, after -all, may be reduced to three contrasts. - -810. - -Yellow demands Red-blue, -Blue demands Red-yellow, -Red demands Green, -and contrariwise. - -811. - -In proportion as one end of the supposed index deviates from the -central intensity of the colours, arranged as they are in the natural -order, so the opposite end changes its place in the contrasted -gradation, and by such a simple contrivance the complemental colours -may be indicated at any given point. A chromatic circle might be made -for this purpose, not confined, like our own, to the leading colours, -but exhibiting them with their transitions in an unbroken series. -This would not be without its use, for we are here considering a very -important point which deserves all our attention.[2] - -812. - -We before stated that the eye could be in some degree pathologically -affected by being long confined to a single colour; that, again, -definite moral impressions were thus produced, at one time lively and -aspiring, at another susceptible and anxious--now exalted to grand -associations, now reduced to ordinary ones. We now observe that the -demand for completeness, which is inherent in the organ, frees us from -this restraint; the eye relieves itself by producing the opposite -of the single colour forced upon it, and thus attains the entire -impression which is so satisfactory to it. - -813. - -Simple, therefore, as these strictly harmonious contrasts are, as -presented to us in the narrow circle, the hint is important, that -nature tends to emancipate the sense from confined impressions by -suggesting and producing the whole, and that in this instance we have a -natural phenomenon immediately applicable to æsthetic purposes. - -814. - -While, therefore, we may assert that the chromatic scale, as given by -us, produces an agreeable impression by its ingredient hues, we may -here remark that those have been mistaken who have hitherto adduced -the rainbow as an example of the entire scale; for the chief colour, -pure red, is deficient in it, and cannot be produced, since in this -phenomenon, as well as in the ordinary prismatic series, the yellow-red -and blue-red cannot attain to a union. - -815. - -Nature perhaps exhibits no general phenomenon where the scale is in -complete combination. By artificial experiments such an appearance may -be produced in its perfect splendour. The mode, however, in which the -entire series is connected in a circle, is rendered most intelligible -by tints on paper, till after much experience and practice, aided by -due susceptibility of the organ, we become penetrated with the idea of -this harmony, and feel it present in our minds. - -816. - -Besides these pure, harmonious, self-developed combinations, which -always carry the conditions of completeness with them, there are -others which may be arbitrarily produced, and which may be most easily -described by observing that they are to be found in the colorific -circle, not by diameters, but by chords, in such a manner that an -intermediate colour is passed over. - -817. - -We call these combinations characteristic because they have all a -certain significancy and tend to excite a definite impression; an -impression, however, which does not altogether satisfy, inasmuch as -every characteristic quality of necessity presents itself only as a -part of a whole, with which it has a relation, but into which it cannot -be resolved. - -818. - -As we are acquainted with the impressions produced by the colours -singly as well as in their harmonious relations, we may at once -conclude that the character of the arbitrary combinations will be very -different from each other as regards their significancy. We proceed to -review them separately. - - -YELLOW AND BLUE. - - -819. - -This is the simplest of such combinations. It may be said that it -contains too little, for since every trace of red is wanting in it, -it is defective as compared with the whole scale. In this view it -may be called poor, and as the two contrasting elements are in their -lowest state, may be said to be ordinary; yet it is recommended by -its proximity to green--in short, by containing the ingredients of an -ultimate state. - - -YELLOW AND RED. - - -820. - -This is a somewhat preponderating combination, but it has a serene -and magnificent effect. The two extremes of the active side are seen -together without conveying any idea of progression from one to the -other. As the result of their combination in pigments is yellow-red, so -they in some degree represent this colour. - - -BLUE AND RED. - - -821. - -The two ends of the passive side, with the excess of the upper end of -the active side. The effect of this juxtaposition approaches that of -the blue-red produced by their union. - - -YELLOW-RED AND BLUE-RED. - - -822. - -These, when placed together, as the deepened extremes of both sides, -have something exciting, elevated: they give us a presentiment of red, -which in physical experiments is produced by their union. - -823. - -These four combinations have also the common quality of producing the -intermediate colour of our colorific circle by their union, a union -which actually takes place if they are opposed to each other in small -quantities and seen from a distance. A surface covered with narrow blue -and yellow stripes appears green at a certain distance. - -824. - -If, again, the eye sees blue and yellow next each other, it finds -itself in a peculiar disposition to produce green without accomplishing -it, while it neither experiences a satisfactory sensation in -contemplating the detached colours, nor an impression of completeness -in the two. - -825. - -Thus it will be seen that it was not without reason we called these -combinations characteristic; the more so, since the character of each -combination must have a relation to that of the single colours of which -it consists. - - -COMBINATIONS NON-CHARACTERISTIC. - - -826. - -We now turn our attention to the last kind of combinations. These are -easily found in the circle; they are indicated by shorter chords, for -in this case we do not pass over an entire intermediate colour, but -only the transition from one to the other. - -827. - -These combinations may justly be called non-characteristic, inasmuch -as the colours are too nearly alike for their impression to be -significant. Yet most of these recommend themselves to a certain -degree, since they indicate a progressive state, though its relations -can hardly be appreciable. - -828. - -Thus yellow and yellow-red, yellow-red and red, blue and blue-red, -blue-red and red, represent the nearest degrees of augmentation and -culmination, and in certain relations as to quantity may produce no -unpleasant effect. - -829. - -The juxtaposition of yellow and green has always something ordinary, -but in a cheerful sense; blue and green, on the other hand, is ordinary -in a repulsive sense. Our good forefathers called these last fool's -colours. - - -RELATION OF THE COMBINATIONS TO LIGHT AND DARK. - - -830. - -These combinations may be very much varied by making both colours light -or both dark, or one light and the other dark; in which modifications, -however, all that has been found true in a general sense is applicable -to each particular case. With regard to the infinite variety thus -produced, we merely observe: - -831. - -The colours of the active side placed next to black gain in energy, -those of the passive side lose. The active conjoined with white and -brightness lose in strength, the passive gain in cheerfulness. Red and -green with black appear dark and grave; with white they appear gay. - -832. - -To this we may add that all colours may be more or less broken or -neutralised, may to a certain degree be rendered nameless, and thus -combined partly together and partly with pure colours; but although the -relations may thus be varied to infinity, still all that is applicable -with regard to the pure colours will be applicable in these cases. - - -CONSIDERATIONS DERIVED FROM THE EVIDENCE OF EXPERIENCE AND HISTORY. - - -833. - -The principles of the harmony of colours having been thus far defined, -it may not be irrelevant to review what has been adduced in connexion -with experience and historical examples. - -834. - -The principles in question have been derived from the constitution of -our nature and the constant relations which are found to obtain in -chromatic phenomena. In experience we find much that is in conformity -with these principles, and much that is opposed to them. - -835. - -Men in a state of nature, uncivilised nations, children, have a great -fondness for colours in their utmost brightness, and especially for -yellow-red: they are also pleased with the motley. By this expression -we understand the juxtaposition of vivid colours without an harmonious -balance; but if this balance is observed, through instinct or accident, -an agreeable effect may be produced. I remember a Hessian officer, -returned from America, who had painted his face with the positive -colours, in the manner of the Indians; a kind of completeness or due -balance was thus produced, the effect of which was not disagreeable. - -836. - -The inhabitants of the south of Europe make use of very brilliant -colours for their dresses. The circumstance of their procuring silk -stuffs at a cheap rate is favourable to this propensity. The women, -especially, with their bright-coloured bodices and ribbons, are always -in harmony with the scenery, since they cannot possibly surpass the -splendour of the sky and landscape. - -837. - -The history of dyeing teaches us that certain technical conveniences -and advantages have had great influence on the costume of nations. -We find that the Germans wear blue very generally because it is a -permanent colour in cloth; so in many districts all the country people -wear green twill, because that material takes a green dye well. If -a traveller were to pay attention to these circumstances, he might -collect some amusing and curious facts. - -838. - -Colours, as connected with particular frames of mind, are again a -consequence of peculiar character and circumstances. Lively nations, -the French for instance, love intense colours, especially on the active -side; sedate nations, like the English and Germans, wear straw-coloured -or leather-coloured yellow accompanied with dark blue. Nations aiming -at dignity of appearance, the Spaniards and Italians for instance, -suffer the red colour of their mantles to incline to the passive side. - -839. - -In dress we associate the character of the colour with the character of -the person. We may thus observe the relation of colours singly, and in -combination, to the colour of the complexion, age, and station. - -840. - -The female sex in youth is attached to rose-colour and sea-green, in -age to violet and dark-green. The fair-haired prefer violet, as opposed -to light yellow, the brunettes, blue, as opposed to yellow-red, and -all on good grounds. The Roman emperors were extremely jealous with -regard to their purple. The robe of the Chinese Emperor is orange -embroidered with red; his attendants and the ministers of religion wear -citron-yellow. - -841. - -People of refinement have a disinclination to colours. This may be -owing partly to weakness of sight, partly to the uncertainty of taste, -which readily takes refuge in absolute negation. Women now appear -almost universally in white and men in black. - -842. - -An observation, very generally applicable, may not be out of place -here, namely, that man, desirous as he is of being distinguished, is -quite as willing to be lost among his fellows. - -843. - -Black was intended to remind the Venetian noblemen of republican -equality. - -844. - -To what degree the cloudy sky of northern climates may have gradually -banished colour may also admit of explanation. - -845. - -The scale of positive colours is obviously soon exhausted; on the -other hand, the neutral, subdued, so-called fashionable colours -present infinitely varying degrees and shades, most of which are not -unpleasing. - -846. - -It is also to be remarked that ladies, in wearing positive colours, -are in danger of making a complexion which may not be very bright -still less so, and thus to preserve a due balance with such brilliant -accompaniments, they are induced to heighten their complexions -artificially. - -847. - -An amusing inquiry might be made which would lead to a critique of -uniforms, liveries, cockades, and other distinctions, according to the -principles above hinted at. It might be observed, generally, that such -dresses and insignia should not be composed of harmonious colours. -Uniforms should be characteristic and dignified; liveries might be -ordinary and striking to the eye. Examples both good and bad would -not be wanting, since the scale of colours usually employed for such -purposes is limited, and its varieties have been often enough tried.[3] - - -ÆSTHETIC INFLUENCE. - - -848. - -From the moral associations connected with the appearance of colours, -single or combined, their æsthetic influence may now be deduced for -the artist. We shall touch the most essential points to be attended -to after first considering the general condition of pictorial -representation, light and shade, with which the appearance of colour is -immediately connected. - - -CHIARO-SCURO. - - -849. - -We apply the term chiaro-scuro (Helldunkel) to the appearance of -material objects when the mere effect produced on them by light and -shade is considered.--Note D D. - -850. - -In a narrower sense a mass of shadow lighted by reflexes is often -thus designated; but we here use the expression in its first and more -general sense. - -851. - -The separation of light and dark from all appearance of colour is -possible and necessary. The artist will solve the mystery of imitation -sooner by first considering light and dark independently of colour, and -making himself acquainted with it in its whole extent. - -852. - -Chiaro-scuro exhibits the substance as substance, inasmuch as light and -shade inform us as to degrees of density. - -853. - -We have here to consider the highest light, the middle tint, and the -shadow, and in the last the shadow of the object itself, the shadow it -casts on other objects, and the illumined shadow or reflexion. - -854. - -The globe is well adapted for the general exemplification of the nature -of chiaro-scuro, but it is not altogether sufficient. The softened -unity of such complete rotundity tends to the vapoury, and in order to -serve as a principle for effects of art, it should be composed of plane -surfaces, so as to define the gradations more. - -855. - -The Italians call this manner "il piazzoso;" in German it might -be called "das Flächenhafte."[4] If, therefore, the sphere is a -perfect example of natural chiaro-scuro, a polygon would exhibit the -artist-like treatment in which all kinds of lights, half-lights, -shadows, and reflexions, would be appreciable.--Note E E. - -856. - -The bunch of grapes is recognised as a good example of a picturesque -completeness in chiaro-scuro, the more so as it is fitted, from its -form, to represent a principal group; but it is only available for the -master who can see in it what he has the power of producing. - -857. - -In order to make the first idea intelligible to the beginner, (for -it is difficult to consider it abstractedly even in a polygon,) we -may take a cube, the three sides of which that are seen represent the -light, the middle tint, and the shadow in distinct order. - -858. - -To proceed again to the chiaro-scuro of a more complicated figure, we -might select the example of an open book, which presents a greater -diversity. - -859. - -We find the antique statues of the best time treated very much with -reference to these effects. The parts intended to receive the light -are wrought with simplicity, the portion originally in shade is, on -the other hand, in more distinct surfaces to make them susceptible -of a variety of reflexions; here the example of the polygon will be -remembered.--Note F F. - -860. - -The pictures of Herculaneum and the Aldobrandini marriage are examples -of antique painting in the same style. - -861. - -Modern examples may be found in single figures by Raphael, in entire -works by Correggio, and also by the Flemish masters, especially Rubens. - - -TENDENCY TO COLOUR. - - -862. - -A picture in black and white seldom makes its appearance; some works -of Polidoro are examples of this kind of art. Such works, inasmuch as -they can attain form and keeping, are estimable, but they have little -attraction for the eye, since their very existence supposes a violent -abstraction. - -863. - -If the artist abandons himself to his feeling, colour presently -announces itself. Black no sooner inclines to blue than the eye demands -yellow, which the artist instinctively modifies, and introduces partly -pure in the light, partly reddened and subdued as brown, in the -reflexes, thus enlivening the whole.--Note G G. - -864. - -All kinds of _camayeu_, or colour on similar colour, end in the -introduction either of a complemental contrast, or some variety of hue. -Thus, Polidoro in his black and white frescoes sometimes introduced a -yellow vase, or something of the kind. - -865. - -In general it may be observed that men have at all times instinctively -striven after colour in the practice of the art. We need only observe -daily, how soon amateurs proceed from colourless to coloured materials. -Paolo Uccello painted coloured landscapes to colourless figures.--Note -H H. - -866. - -Even the sculpture of the ancients could not be exempt from the -influence of this propensity. The Egyptians painted their bas-reliefs; -statues had eyes of coloured stones. Porphyry draperies were added to -marble heads and extremities, and variegated stalactites were used -for the pedestals of busts. The Jesuits did not fail to compose the -statue of their S. Luigi, in Rome, in this manner, and the most modern -sculpture distinguishes the flesh from the drapery by staining the -latter. - - -KEEPING. - - -867. - -If linear perspective displays the gradation of objects in their -apparent size as affected by distance, aërial perspective shows us -their gradation in greater or less distinctness, as affected by the -same cause. - -868. - -Although from the nature of the organ of sight, we cannot see distant -objects so distinctly as nearer ones, yet aërial perspective is -grounded strictly on the important fact that all mediums called -transparent are in some degree dim. - -869. - -The atmosphere is thus always, more or less, semi-transparent. This -quality is remarkable in southern climates, even when the barometer is -high, the weather dry, and the sky cloudless, for a very pronounced -gradation is observable between objects but little removed from each -other. - -870. - -The appearance on a large scale is known to every one; the painter, -however, sees or believes he sees, the gradation in the slightest -varieties of distance. He exemplifies it practically by making a -distinction, for instance, in the features of a face according to their -relative position as regards the plane of the picture. The direction of -the light is attended to in like manner. This is considered to produce -a gradation from side to side, while keeping has reference to depth, to -the comparative distinctness of near and distant things. - -871. - -In proceeding to consider this subject, we assume that the painter is -generally acquainted with our sketch of the theory of colours, and that -he has made himself well acquainted with certain chapters and rubrics -which especially concern him. He will thus be enabled to make use of -theory as well as practice in recognising the principles of effect in -nature, and in employing the means of art. - - -COLOUR IN GENERAL NATURE. - - -872. - -The first indication of colour announces itself in nature together -with the gradations of aërial perspective; for aërial perspective is -intimately connected with the doctrine of semi-transparent mediums. We -see the sky, distant objects and even comparatively near shadows, blue. -At the same moment, the illuminating and illuminated objects appear -yellow, gradually deepening to red. In many cases the physiological -suggestion of contrasts comes into the account, and an entirely -colourless landscape, by means of these assisting and counteracting -tendencies, appears to our eyes completely coloured. - -873. - -Local colours are composed of the general elementary colours; but these -are determined or specified according to the properties of substances -and surfaces on which they appear: this specification is infinite. - -874. - -Thus, there is at once a great difference between silk and wool -similarly dyed. Every kind of preparation and texture produces -corresponding modifications. Roughness, smoothness, polish, all are to -be considered. - -875. - -It is therefore one of the pernicious prejudices of art that the -skilful painter must never attend to the material of draperies, -but always represent, as it were, only abstract folds. Is not all -characteristic variety thus done away with, and is the portrait of Leo -X. less excellent because velvet, satin, and moreen, are imitated in -their relative effect? - -876. - -In the productions of nature, colours appear more or less modified, -specified, even individualised: this may be readily observed in -minerals and plants, in the feathers of birds and the skins of beasts. - -877. - -The chief art of the painter is always to imitate the actual appearance -of the definite hue, doing away with the recollection of the elementary -ingredients of colour. This difficulty is in no instance greater than -in the imitation of the surface of the human figure. - -878. - -The colour of flesh, as a whole, belongs to the active side, yet the -bluish of the passive side mingles with it. The colour is altogether -removed from the elementary state and neutralised by organisation. - -879. - -To bring the colouring of general nature into harmony with the -colouring of a given object, will perhaps be more attainable for the -judicious artist after the consideration of what has been pointed out -in the foregoing theory. For the most fancifully beautiful and varied -appearances may still be made true to the principles of nature. - - -CHARACTERISTIC COLOURING. - - -880. - -The combination of coloured objects, as well as the colour of -their ground, should depend on considerations which the artist -pre-establishes for himself. Here a reference to the effect of colours -singly or combined, on the feelings, is especially necessary. On this -account the painter should possess himself with the idea of the general -dualism, as well as of particular contrasts, not forgetting what has -been adverted to with regard to the qualities of colours. - -881. - -The characteristic in colour may be comprehended under three leading -rubrics, which we here define as the powerful, the soft, and the -splendid. - -882. - -The first is produced by the preponderance of the active side, the -second by that of the passive side, and the third by completeness, by -the exhibition of the whole chromatic scale in due balance. - -883. - -The powerful impression is attained by yellow, yellow-red, and red, -which last colour is to be arrested on the plus side. But little violet -and blue, still less green, are admissible. The soft effect is produced -by blue, violet, and red, which in this case is arrested on the minus -side; a moderate addition of yellow and yellow-red, but much green may -be admitted. - -884. - -If it is proposed to produce both these effects in their full -significancy, the complemental colours may be excluded to a minimum, -and only so much of them may be suffered to appear as is indispensable -to convey an impression of completeness. - - -HARMONIOUS COLOURING. - - -885. - -Although the two characteristic divisions as above defined may in some -sense be also called harmonious, the harmonious effect, properly so -called, only takes place when all the colours are exhibited together in -due balance. - -886. - -In this way the splendid as well as the agreeable may be produced; both -of these, however, have of necessity a certain generalised effect, and -in this sense may be considered the reverse of the characteristic. - -887. - -This is the reason why the colouring of most modern painters is without -character, for, while they follow their general instinctive feeling -only, the last result of such a tendency must be mere completeness; -this, they more or less attain, but thus at the same time neglect the -characteristic impression which the subject might demand. - -888. - -But if the principles before alluded to are kept in view, it must be -apparent that a distinct style of colour may be adopted on safe grounds -for every subject. The application requires, it is true, infinite -modifications, which can only succeed in the hands of genius. - - -GENUINE TONE. - - -889. - -If the word tone, or rather tune, is to be still borrowed in future -from music, and applied to colouring, it might be used in a better -sense than heretofore. - -890. - -For it would not be unreasonable to compare a painting of powerful -effect, with a piece of music in a sharp key; a painting of soft effect -with a piece of music in a flat key, while other equivalents might be -found for the modifications of these two leading modes. - - -FALSE TONE. - - -891. - -The word tone has been hitherto understood to mean a veil of a -particular colour spread over the whole picture; it was generally -yellow, for the painter instinctively pushed the effect towards the -powerful side. - -892. - -If we look at a picture through a yellow glass it will appear in this -tone. It is worth while to make this experiment again and again, in -order to observe what takes place in such an operation. It is a sort of -artificial light, deepening, and at the same time darkening the _plus_ -side, and neutralising the _minus_ side. - -893. - -This spurious tone is produced instinctively through uncertainty -as to the means of attaining a genuine effect; so that instead of -completeness, monotony is the result. - - -WEAK COLOURING. - - -894. - -It is owing to the same uncertainty that the colours are sometimes so -much broken as to have the effect of a grey camayeu, the handling being -at the same time as delicate as possible. - -895. - -The harmonious contrasts are often found to be very happily felt in -such pictures, but without spirit, owing to a dread of the motley. - - -THE MOTLEY. - - -896. - -A picture may easily become party-coloured or motley, when the colours -are placed next each other in their full force, as it were only -mechanically and according to uncertain impressions. - -897. - -If, on the other hand, weak colours are combined, even although they -may be dissonant, the effect, as a matter of course, is not striking. -The uncertainty of the artist is communicated to the spectator, who, on -his side, can neither praise nor censure. - -898. - -It is also important to observe that the colours may be disposed -rightly in themselves, but that a work may still appear motley, if they -are falsely arranged in relation to light and shade. - -899. - -This may the more easily occur as light and shade are already defined -in the drawing, and are, as it were, comprehended in it, while the -colour still remains open to selection. - - -DREAD OF THEORY. - - -900. - -A dread of, nay, a decided aversion for all theoretical views -respecting colour and everything belonging to it, has been hitherto -found to exist among painters; a prejudice for which, after all, they -were not to be blamed; for what has been hitherto called theory was -groundless, vacillating, and akin to empiricism. We hope that our -labours may tend to diminish this prejudice, and stimulate the artist -practically to prove and embody the principles that have been explained. - - -ULTIMATE AIM. - - -901. - -But without a comprehensive view of the whole of our theory, the -ultimate object will not be attained. Let the artist penetrate himself -with all that we have stated. It is only by means of harmonious -relations in light and shade, in keeping, in true and characteristic -colouring, that a picture can be considered complete, in the sense we -have now learnt to attach to the term. - - -GROUNDS. - - -902. - -It was the practice of the earlier artists to paint on light grounds. -This ground consisted of gypsum, and was thickly spread on linen or -panel, and then levigated. After the outline was drawn, the subject was -washed in with a blackish or brownish colour. Pictures prepared in -this manner for colouring are still in existence, by Leonardo da Vinci, -and Fra Bartolomeo; there are also several by Guido.--Note I I. - -903. - -When the artist proceeded to colour, and had to represent white -draperies, he sometimes suffered the ground to remain untouched. -Titian did this latterly when he had attained the greatest certainty -in practice, and could accomplish much with little labour. The whitish -ground was left as a middle tint, the shadows painted in, and the high -lights touched on.--Note K K. - -904. - -In the process of colouring, the preparation merely washed as it were -underneath, was always effective. A drapery, for example, was painted -with a transparent colour, the white ground shone through it and gave -the colour life, so the parts previously prepared for shadows exhibited -the colour subdued, without being mixed or sullied. - -905. - -This method had many advantages; for the painter had a light ground -for the light portions of his work and a dark ground for the shadowed -portions. The whole picture was prepared; the artist could work with -thin colours in the shadows, and had always an internal light to give -value to his tints. In our own time painting in water colours depends -on the same principles. - -906. - -Indeed a light ground is now generally employed in oil-painting, -because middle tints are thus found to be more transparent, and are in -some degree enlivened by a bright ground; the shadows, again, do not so -easily become black. - -907. - -It was the practice for a time to paint on dark grounds. Tintoret -probably introduced them. Titian's best pictures are not painted on a -dark ground. - -908. - -The ground in question was red-brown, and when the subject was drawn -upon it, the strongest shadows were laid in; the colours of the lights -impasted very thickly in the bright parts, and scumbled towards the -shadows, so that the dark ground appeared through the thin colour as a -middle tint. Effect was attained in finishing by frequently going over -the bright parts and touching on the high lights. - -909. - -If this method especially recommended itself in practice on account -of the rapidity it allowed of, yet it had pernicious consequences. -The strong ground increased and became darker, and the light colours -losing their brightness by degrees, gave the shadowed portions more -and more preponderance. The middle tints became darker and darker, and -the shadows at last quite obscure. The strongly impasted lights alone -remained bright, and we now see only light spots on the painting. The -pictures of the Bolognese school, and of Caravaggio, afford sufficient -examples of these results. - -910. - -We may here in conclusion observe, that glazing derives its effect -from treating the prepared colour underneath as a light ground. By -this operation colours may have the effect of being mixed to the eye, -may be enhanced, and may acquire what is called tone; but they thus -necessarily become darker. - - -PIGMENTS. - - -911. - -We receive these from the hands of the chemist and the investigator of -nature. Much has been recorded respecting colouring substances, which -is familiar to all by means of the press. But such directions require -to be revised from time to time. The master meanwhile communicates his -experience in these matters to his scholar, and artists generally to -each other. - -912. - -Those pigments which according to their nature are the most permanent, -are naturally much sought after, but the mode of employing them also -contributes much to the duration of a picture. The fewest possible -colouring materials are to be employed, and the simplest methods of -using them cannot be sufficiently recommended. - -913. - -For from the multitude of pigments colouring has suffered much. Every -pigment has its peculiar nature as regards its effect on the eye; -besides this it has its peculiar quality, requiring a corresponding -technical method in its application. The former circumstance is a -reason why harmony is more difficult of attainment with many materials -than with few, the latter, why chemical action and re-action may take -place among the colouring substances. - -914. - -We may refer, besides, to some false tendencies which the artists -suffer themselves to be led away with. Painters are always looking -for new colouring substances, and believe when such a substance is -discovered that they have made an advance in the art. They have a -great curiosity to know the practical methods of the old masters, and -lose much time in the search. Towards the end of the last century -we were thus long tormented with wax-painting. Others turn their -attention to the discovery of new methods, through which nothing new is -accomplished; for, after all, it is the feeling of the artist only that -informs every kind of technical process. - - -ALLEGORICAL, SYMBOLICAL, MYSTICAL APPLICATION OF COLOUR. - - -915. - -It has been circumstantially shown above, that every colour produces -a distinct impression on the mind, and thus addresses at once the eye -and feelings. Hence it follows that colour may be employed for certain -moral and æsthetic ends. - -916. - -Such an application, coinciding entirely with nature, might be called -symbolical, since the colour would be employed in conformity with its -effect, and would at once express its meaning. If, for example, pure -red were assumed to designate majesty, there can be no doubt that this -would be admitted to be a just and expressive symbol. All this has been -already sufficiently entered into. - -917. - -Another application is nearly allied to this; it might be called the -allegorical application. In this there is more of accident and caprice, -inasmuch as the meaning of the sign must be first communicated to us -before we know what it is to signify; what idea, for instance, is -attached to the green colour, which has been appropriated to hope? - -918. - -That, lastly, colour may have a mystical allusion, may be readily -surmised, for since every diagram in which the variety of colours may -be represented points to those primordial relations which belong both -to nature and the organ of vision, there can be no doubt that these may -be made use of as a language, in cases where it is proposed to express -similar primordial relations which do not present themselves to the -senses in so powerful and varied a manner. The mathematician extols -the value and applicability of the triangle; the triangle is revered -by the mystic; much admits of being expressed in it by diagrams, and, -among other things, the law of the phenomena of colours; in this case, -indeed, we presently arrive at the ancient mysterious hexagon. - -919. - -When the distinction of yellow and blue is duly comprehended, and -especially the augmentation into red, by means of which the opposite -qualities tend towards each other and become united in a third; then, -certainly, an especially mysterious interpretation will suggest itself, -since a spiritual meaning may be connected with these facts; and when -we find the two separate principles producing green on the one hand and -red in their intenser state, we can hardly refrain from thinking in the -first case on the earthly, in the last on the heavenly, generation of -the Elohim.--Note L L. - -920. - -But we shall do better not to expose ourselves, in conclusion, to -the suspicion of enthusiasm; since, if our doctrine of colours finds -favour, applications and allusions, allegorical, symbolical, and -mystical, will not fail to be made, in conformity with the spirit of -the age. - - -CONCLUDING OBSERVATIONS. - - -In reviewing this labour, which has occupied me long, and which at -last I give but as a sketch, I am reminded of a wish once expressed -by a careful writer, who observed that he would gladly see his works -printed at once as he conceived them, in order then to go to the task -with a fresh eye; since everything defective presents itself to us more -obviously in print than even in the cleanest manuscript. This feeling -may be imagined to be stronger in my case, since I had not even an -opportunity of going through a fair transcript of my work before its -publication, these pages having been put together at a time when a -quiet, collected state of mind was out of the question.[5] - -Some of the explanations I was desirous of giving are to be found in -the introduction, but in the portion of my work to be devoted to the -history of the doctrine of colours, I hope to give a more detailed -account of my investigations and the vicissitudes they underwent. One -inquiry, however, may not be out of place here; the consideration, -namely, of the question, what can a man accomplish who cannot devote -his whole life to scientific pursuits? what can he perform as a -temporary guest on an estate not his own, for the advantage of the -proprietor? - -When we consider art in its higher character, we might wish that -masters only had to do with it, that scholars should be trained by -the severest study, that amateurs might feel themselves happy in -reverentially approaching its precincts. For a work of art should be -the effusion of genius, the artist should evoke its substance and form -from his inmost being, treat his materials with sovereign command, and -make use of external influences only to accomplish his powers. - -But if the professor in this case has many reasons for respecting -the dilettante, the man of science has every motive to be still more -indulgent, since the amateur here is capable of contributing what may -be satisfactory and useful. The sciences depend much more on experiment -than art, and for mere experiment many a votary is qualified. -Scientific results are arrived at by many means, and cannot dispense -with many hands, many heads. Science may be communicated, the treasure -may be inherited, and what is acquired by one may be appropriated -by many. Hence no one perhaps ought to be reluctant to offer his -contributions. How much do we not owe to accident, to mere practice, -to momentary observation. All who are endowed only with habits of -attention, women, children, are capable of communicating striking and -true remarks. - -In science it cannot therefore be required, that he who endeavours -to furnish something in its aid should devote his whole life to it, -should survey and investigate it in all its extent; for this, in most -cases, would be a severe condition even for the initiated. But if we -look through the history of science in general, especially the history -of physics, we shall find that many important acquisitions have been -made by single inquirers, in single departments, and very often by -unprofessional observers. - -To whatever direction a man may be determined by inclination or -accident, whatever class of phenomena especially strike him, excite -his interest, fix his attention, and occupy him, the result will still -be for the advantage of science: for every new relation that comes to -light, every new mode of investigation, even the imperfect attempt, -even error itself is available; it may stimulate other observers and is -never without its use as influencing future inquiry. - -With this feeling the author himself may look back without regret -on his endeavours. From this consideration he can derive some -encouragement for the prosecution of the remainder of his task; and -although not satisfied with the result of his efforts, yet re-assured -by the sincerity of his intentions, he ventures to recommend his past -and future labours to the interest of his contemporaries and posterity. - -Multi pertransibunt et augebitur scientia. - - -[1] Plate 1, fig. 3. - -[2] See Note C. - -[3] Some early Italian writers, Sicillo, Occolti, Rinaldi, and others, -have treated this subject in connexion with the supposed signification -of colours.--T. - -[4] The English technical expressions "flat" and "square" have an -association of mannerism.--T - -[5] Towards the close of 1806, when Weimar was occupied by Napoleon -after the battle of Jena.--T. - - - - -NOTES. - - -NOTE A.--Par. 18. - -Leonardo da Vinci observes that "a light object relieved on a dark -ground appears magnified;" and again, "Objects seen at a distance -appear out of proportion; this is because the light parts transmit -their rays to the eye more powerfully than the dark. A woman's white -head-dress once appeared to me much wider than her shoulders, owing -to their being dressed in black."[1] "It is now generally admitted -that the excitation produced by light is propagated on the retina a -little beyond the outline of the image. Professor Plateau, of Ghent, -has devoted a very interesting special memoir to the description -and explanation of phenomena of this nature. See his 'Mémoire sur -l'Irradiation,' published in the 11th vol. of the Transactions of the -Royal Academy of Sciences at Brussels."[2]--S. F. - - -NOTE B.--Par. 23. - -"The duration of ocular spectra produced by strongly exciting the -retina, may be conveniently measured by minutes and seconds; but to -ascertain the duration of more evanescent phenomena, recourse must be -had to other means. The Chevalier d'Arcy (Mém. de l'Acad. des Sc. -1765,) endeavoured to ascertain the duration of the impression produced -by a glowing coal in the following manner. He attached it to the -circumference of a wheel, the velocity of which was gradually increased -until the apparent trace of the object formed a complete circle, and -then measured the duration of a revolution, which was obviously that -of the impression. To ascertain the duration of a revolution it is -sufficient merely to know the number of revolutions described in a -given time. Recently more refined experiments of the same kind have -been made by Professors Plateau and Wheatstone."--S. F. - - -[1] "Trattato della Pittura, Roma, 1817," p. 143-223. This edition, -published from a Vatican MS., contains many observations not included -in former editions. - -[2] A few notes (marked with inverted commas and with the signature S. -F.) have been kindly furnished by a scientific friend. - - -NOTE C.--Par. 50. - -Every treatise on the harmonious combination of colours contains the -diagram of the chromatic circle more or less elaborately constructed. -These diagrams, if intended to exhibit the contrasts produced by -the action and re-action of the retina, have one common defect. The -opposite colours are made equal in intensity; whereas the complemental -colour pictured on the retina is always less vivid, and always darker -or lighter than the original colour. This variety undoubtedly accords -more with harmonious effects in painting. - -The opposition of two pure hues of equal intensity, differing only in -the abstract quality of colour, would immediately be pronounced crude -and inharmonious. It would not, however, be strictly correct to say -that such a contrast is too violent; on the contrary, it appears the -contrast is not carried far enough, for though differing in colour, -the two hues may be exactly similar in purity and intensity. Complete -contrast, on the other hand, supposes dissimilarity in all respects. - -In addition to the mere difference of hue, the eye, it seems, requires -difference in the lightness or darkness of the hue. The spectrum of a -colour relieved as a dark on a light ground, is a light colour on a -dark ground, and _vice versâ_. Thus, if we look at a bright red wafer -on the whitest surface, the complemental image will be still lighter -than the white surface; if the same wafer is placed on a black surface, -the complemental image will be still darker. The colour of both these -spectra may be called greenish, but it is evident that a colour must be -scarcely appreciable as such, if it is lighter than white and darker -than black. It is, however, to be remarked, that the white surface -round the light greenish image seems tinged with a reddish hue, and -the black surface round the dark image becomes slightly illuminated -with the same colour, thus in both cases assisting to render the image -apparent (58). - -The difficulty or impossibility of describing degrees of colour in -words, has also had a tendency to mislead, by conveying the idea of -more positive hues than the physiological contrast warrants. Thus, -supposing scarlet to be relieved as a dark, the complemental colour is -so light in degree and so faint in colour, that it should be called a -pearly grey; whereas the theorists, looking at the quality of colour -abstractedly, would call it a green-blue, and the diagram would falsely -present such a hue equal in intensity to scarlet, or as nearly equal as -possible. - -Even the difference of mass which good taste requires may be suggested -by the physiological phenomena, for unless the complemental image is -suffered to fall on a surface precisely as near to the eye as that on -which the original colour was displayed, it appears larger or smaller -than the original object (22), and this in a rapidly increasing -proportion. Lastly, the shape itself soon becomes changed (26). - -That vivid colour demands the comparative absence of colour, either -on a lighter or darker scale, as its contrast, may be inferred again -from the fact that bright colourless objects produce strongly coloured -spectra. In darkness, the spectrum which is first white, or nearly -white, is followed by red: in light, the spectrum which is first black, -is followed by green (39-44). All colour, as the author observes -(259), is to be considered as half-light, inasmuch as it is in every -case lighter than black and darker than white. Hence no contrast of -colour with colour, or even of colour with black or white, can be so -great (as regards lightness or darkness) as the contrast of black and -white, or light and dark abstractedly. This distinction between the -differences of degree and the differences of kind is important, since a -just application of contrast in colour may be counteracted by an undue -difference in lightness or darkness. The mere contrast of colour is -happily employed in some of Guido's lighter pictures, but if intense -darks had been opposed to his delicate carnations, their comparative -whiteness would have been unpleasantly apparent. On the other hand, the -flesh-colour in Giorgione, Sebastian del Piombo (his best imitator), -and Titian, was sometimes so extremely glowing[1] that the deepest -colours, and black, were indispensable accompaniments. The manner of -Titian as distinguished from his imitation of Giorgione, is golden -rather than fiery, and his biographers are quite correct in saying -that he was fond of opposing red (lake) and blue to his flesh[2]. The -correspondence of these contrasts with the physiological phenomena will -be immediately apparent, while the occasional practice of Rubens in -opposing bright red to a still cooler flesh-colour, will be seen to be -equally consistent. - -The effect of white drapery (the comparative absence of colour) in -enhancing the glow of Titian's flesh-colour, has been frequently -pointed out:[3] the shadows of white thus opposed to flesh, often -present, again, the physiological contrast, however delicately, -according to the hue of the carnation. The lights, on the other hand, -are not, and probably never were, quite white, but from the first, -partook of the quality of depth, a quality assumed by the colourists to -pervade every part of a picture more or less.[4] - -It was before observed that the description of colours in words may -often convey ideas of too positive a nature, and it may be remarked -generally that the colours employed by the great masters are, in their -ultimate effect, more or less subdued or broken. The physiological -contrasts are, however, still applicable in the most comparatively -neutral scale. - -Again, the works of the colourists show that these oppositions are -not confined to large masses (except perhaps in works to be seen only -at a great distance); on the contrary, they are more or less apparent -in every part, and when at last the direct and intentional operations -of the artist may have been insufficient to produce them in their -minuter degrees, the accidental results of glazing and other methods -may be said to extend the contrasts to infinity. In such productions, -where every smallest portion is an epitome of the whole, the eye -still appreciates the fascinating effect of contrast, and the work is -pronounced to be true and complete, in the best sense of the words. - -The Venetian method of scumbling and glazing exhibits these minuter -contrasts within each other, and is thus generally considered more -refined than the system of breaking the colours, since it ensures a -fuller gradation of hues, and produces another class of contrasts, -those, namely, which result from degrees of transparence and opacity. -In some of the Flemish and Dutch masters, and sometimes in Reynolds, -the two methods are combined in great perfection. - -The chromatic diagram does not appear to be older than the last -century. It is one of those happy adaptations of exacter principles to -the objects of taste which might have been expected from Leonardo da -Vinci. That its true principle was duly felt is abundantly evident from -the works of the colourists, as well as from the general observations -of early writers.[5] The more practical directions occasionally to be -met with in the treatises of Leon Battista Alberti, Leonardo da Vinci -and others, are conformable to the same system. Some Italian works, -not written by painters, which pretend to describe this harmony, are, -however, very imperfect.[6] A passage in Lodovico Dolce's Dialogue on -Colours is perhaps the only one worth quoting. "He," says that writer, -"who wishes to combine colours that are agreeable to the eye, will -put grey next dusky orange; yellow-green next rose-colour; blue next -orange; dark purple, black, next dark-green; white next black, and -white next flesh-colour."[7] The Dialogue on Painting, by the same -author, has the reputation of containing some of Titian's precepts: -if the above passage may be traced to the same source, it must be -confessed that it is almost the only one of the kind in the treatise -from which it is taken. - - -[1] "Ardito veramente alquanto, sanguigno, e quasi -fiammeggiante."--_Zanetti della Pittura Veneziana_, Ven. 1771, p. -90. Warm as the flesh colour of the colourists is, it still never -approaches a positive hue, if we except some examples in frescoes and -other works intended to be seen at a great distance. Zanetti, speaking -of a fresco by Giorgione, now almost obliterated, compares the colour -to "un vivo raggio di cocente sole."---_Varie Pitture a fresco dei -Principali Maestri Veneziani_. Ven. 1760. - -[2] Ridolfi. - -[3] Zanetti, I. ii. - -[4] Two great authorities, divided by more than three centuries, Leon -Battista Alberti and Reynolds, have recommended this subdued treatment -of white. "It is to be remembered," says the first, "that no surface -should be made so white that it cannot be made more so. In white -dresses again, it is necessary to stop far short of the last degree of -whiteness."--_Della Pittura_, I. ii., compare with Reynolds, vol. i. -dis. 8. - -[5] Vasari observes, "L'unione nella pittura è una discordanza -dicolori diversi accordati insième."--Vol. i. c. 18. This observation -is repeated by various writers on art in nearly the same words, and -at last appears in Sandrart: "Concordia, potissimum picturæ decus, -in discordiâ consistit, et quasi litigio colorum."--P. i. c. 5. The -source, perhaps, is Aristotle: he observes, "We are delighted with -harmony, because it is the union of contrary principles having a ratio -to each other."--_Problem._ - -[6] See "Occolti Trattato de' Colori." Parma, 1568. - -[7] "Volendo l'uomo accoppiare insième colori che all'occhio -dilettino--porrà insième il berrettino col leonato; il verde-giallo con -l'incarnato e rosso; il turchino con l'arangi; il morello col verde -oscuro; il nero col bianco; il bianco con l'incarnato."--_Dialogo di -M. Lodovico Dolce nel quale si ragiona della qualità, diversità, e -proprietà de' colori_. Venezia, 1565. - - - -NOTE D.--Par. 66. - -In some of these cases there can be no doubt that Goethe attributes -the contrast too exclusively to the physiological cause, without -making sufficient allowance for the actual difference in the colour of -the lights. The purely physical nature of some coloured shadows was -pointed out by Pohlmann; and Dr. Eckermann took some pains to convince -Goethe of the necessity of making such a distinction. Goethe at first -adhered to his extreme view, but some time afterwards confessed to -Dr. Eckermann, that in the case of the blue shadows of snow (74), the -reflection of the sky was undoubtedly to be taken into the account. -"Both causes may, however, operate together," he observed, "and the -contrast which a warm yellow light demands may heighten the effect of -the blue." This was all his opponent contended.[1] - -With a few such exceptions, the general theory of Goethe with regard -to coloured shadows is undoubtedly correct; the experiments with two -candles (68), and with coloured glass and fluids (80), as well as the -observations on the shadows of snow (75), are conclusive, for in all -these cases only one light is actually changed in colour, while the -other still assumes the complemental hue. "Coloured shadows," Dr. J. -Müller observes, "are usually ascribed to the physiological influence -of contrast; the complementary colour presented by the shadow being -regarded as the effect of internal causes acting on that part of the -retina, and not of the impression of coloured rays from without. This -explanation is the one adopted by Rumford, Goethe, Grotthuss, Brandes, -Tourtual, Pohlmann, and most authors who have studied the subject."[2] - -In the Historical Part the author gives an account of a scarce French -work, "Observations sur les Ombres Colorées," Paris, 1782. The -writer[3] concludes that "the colour of shadows is as much owing to -the light that causes them as to that which (more faintly) illumines -them." - - -[1] Eckermann's "Gespräche mit Goethe," vol. ii. p. 76 and 280. - -[2] "Elements of Physiology," by J. Müller, M. D., translated from the -German by William Baly, M.D. London, 1839. - -[3] Anonymous, having only given the initials H. F. T. - - - -NOTE E.--Par. 69. - -This opinion of the author is frequently repeated (201, 312, 591), and -as it seems at first sight to be at variance with a received principle -of art, it may be as well at once to examine it. - -In order to see the general proposition in its true point of view, -it will be necessary to forget the arbitrary distinctions of light -and shade, and to consider all such modifications between highest -brightness and absolute darkness only as so many lesser degrees of -light.[1] The author, indeed, by the word shadow, always understands a -lesser light. - -The received notion, as stated by Du Fresnoy,[2] is much too positive -and unconditional, and is only true when we understand the "displaying" -light to comprehend certain degrees of half or reflected light, and the -"destroying" shade to mean the intensest degree of obscurity. - -There are degrees of brightness which destroy colour as well as -degrees of darkness.[3] In general, colour resides in a mitigated -light, but a very little observation shows us that different colours -require different degrees of light to display them. Leonardo da Vinci -frequently inculcates the general principle above alluded to, but he -as frequently qualifies it; for he not only remarks that the highest -light may be comparative privation of colour, but observes, with great -truth, that some hues are best displayed in their fully illumined -parts, some in their reflections, and some in their half-lights; and -again, that every colour is most beautiful when lit by reflections from -its own surface, or from a hue similar to its own.[4] - -The Venetians went further than Leonardo in this view and practice; -and he seems to allude to them when he criticises certain painters, -who, in aiming at clearness and fulness of colour, neglected what, in -his eyes, was of superior importance, namely, gradation and force of -chiaro-scuro.[5] - -That increase of colour supposes increase of darkness, as so often -stated by Goethe, may be granted without difficulty. To what extent, on -the other hand, increase of darkness, or rather diminution of light, -is accompanied by increase of colour, is a question which has been -variously answered by various schools. Examples of the total negation -of the principle are not wanting, nor are they confined to the infancy -of the art. Instances, again, of the opposite tendency are frequent -in Venetian and early Flemish pictures resembling the augmenting -richness of gems or of stained glass:[6] indeed, it is not impossible -that the increase of colour in shade, which is so remarkable in the -pictures alluded to, may have been originally suggested by the rich -and fascinating effect of stained glass; and the Venetians, in this as -in many other respects, may have improved on a hint borrowed from the -early German painters, many of whom painted on glass.[7] - -At all events, the principle of still increasing in colour in certain -hues seems to have been adopted in Flanders and in Venice at an early -period;[8] while Giorgione, in carrying the style to the most daring -extent, still recommended it by corresponding grandeur of treatment in -other respects. - -The same general tendency, except that the technical methods are -less transparent, is, however, very striking in some of the painters -of the school of Umbria, the instructors or early companions of -Raphael.[9] The influence of these examples, as well as that of Fra -Bartolommeo, in Florence, is distinctly to be traced in the works of -the great artist just named, but neither is so marked as the effect -of his emulation of a Venetian painter at a later period. The glowing -colour, sometimes bordering on exaggeration, which Raphael adopted -in Rome, is undoubtedly to be attributed to the rivalry of Sebastian -del Piombo. This painter, the best of Giorgione's imitators, arrived -in Rome, invited by Agostini Chigi, in 1511, and the most powerful of -Raphael's frescoes, the Heliodorus and Mass of Bolsena, as well as -some portraits in the same style, were painted in the two following -years. In the hands of some of Raphael's scholars, again, this extreme -warmth was occasionally carried to excess, particularly by Pierino del -Vaga, with whom it often degenerated into redness. The representative -of the glowing manner in Florence was Fra Bartolommeo, and, in the -same quality, considered abstractedly, some painters of the school of -Ferrara were second to none. - -In another Note (par. 177) some further considerations are offered, -which may partly explain the prevalence of this style in the beginning -of the sixteenth century; here we merely add, that the conditions under -which the appearance itself is most apparent in nature are perhaps more -obvious in Venice than elsewhere. The colour of general nature may be -observed in all places with almost equal convenience, but with regard -to an important quality in living nature, namely, the colour of flesh, -perhaps there are no circumstances in which its effects at different -distances can be so conveniently compared as when the observer and the -observed gradually approach and glide past each other on so smooth an -element and in so undisturbed a manner as on the canals and in the -gondolas of Venice;[10] the complexions, from the peculiar mellow -carnations of the Italian women to the sun-burnt features and limbs -of the mariners, presenting at the same time the fullest variety in -another sense. - -At a certain distance--the colour being always assumed to be unimpaired -by interposed atmosphere--the reflections appear kindled to intenser -warmth; the fiery glow of Giorgione is strikingly apparent; the colour -is seen in its largest relation; the _macchia_,[11] an expression so -emphatically used by Italian writers, appears in all its quantity, and -the reflections being the focus of warmth, the hue seems to deepen in -shade. - -A nearer view gives the detail of cooler tints more perceptibly,[12] -and the forms are at the same time more distinct. Hence Lanzi is quite -correct when, in distinguishing the style of Titian from that of -Giorgione, he says that Titian's was at once more defined and less -fiery.[13] In a still nearer observation the eye detects the minute -lights which Leonardo da Vinci says are incompatible with effects such -as those we have described[14] and which, accordingly, we never find -in Giorgione and Titian. This large impression of colour, which seems -to require the condition of comparative distance for its full effect, -was most fitly employed by the same great artists in works painted in -the open air or for large altar-pieces. Their celebrated frescoes on -the exterior of the Fondaco de' Tedeschi at Venice, to judge from their -faint remains and the descriptions of earlier writers, were remarkable -for extreme warmth in the shadows. The old frescoes in the open air -throughout Friuli have often the same character, and, owing to the -fulness of effect which this treatment ensures, are conspicuous at a -very great distance.[15] - -In assuming that the Venetian painters may have acquired a taste for -this breadth[16] of colour under the circumstances above alluded to, -it is moreover to be remembered that the time for this agreeable -study was the evening; when the sun had already set behind the hills -of Bassano; when the light was glowing but diffused; when shadows -were soft--conditions all agreeing with the character of their -colouring:[17] above all, when the hour invited the fairer portion of -the population to betake themselves in their gondolas to the lagunes. -The scene of this "promenade" was to the north of Venice, the quarter -in which Titian at one time lived. A letter exists written by Francesco -Priscianese, giving an account of his supping with the great painter in -company with Jacopo Nardi, Pietro Aretino, the sculptor Sansovino, and -others. The writer speaks of the beauty of the garden, where the table -was prepared, looking over the lagunes towards Murano, "which part of -the sea," he continues, "as soon as the sun was down, was covered with -a thousand gondolas, graced with beautiful women, and enlivened by the -harmony of voices and instruments, which lasted till midnight, forming -a pleasing accompaniment to our cheerful repast."[18] - -To return to Goethe: perhaps the foregoing remarks may warrant the -conclusion that his idea of colour in shadow is not irreconcileable -with the occasional practice of the best painters. The highest examples -of the style thus defined are, or were, to be found in the works of -Giorgione[19] and Titian, and hence the style itself, though "within -that circle" few "dare walk" is to be considered the grandest and -most perfect. Its possible defects or abuse are not to be dissembled: -in addition to the danger of exaggeration[20] it is seldom united -with the plenitude of light and shade, or with roundness; yet, where -fine examples of both modes of treatment may be compared, the charm -of colour has perhaps the advantage.[21] The difficulty of uniting -qualities so different in their nature, is proved by the very rare -instances in which it has been accomplished. Tintoret in endeavouring -to add chiaro-scuro to Venetian colour, in almost every instance fell -short of the glowing richness of Titian.[22] - -Giacomo Bassan and his imitators, even in their dark effects, still had -the principle of the gem in view: their light, in certain hues, is the -minimum of colour, their lower tones are rich, their darks intense, -and all is sparkling.[23] Of the great painters who, beginning, on -the other hand, with chiaro-scuro, sought to combine with it the full -richness of colour, Correggio, in the opinion of many, approached -perfection nearest; but we may perhaps conclude with greater justice -that the desired excellence was more completely attained by Rembrandt -than by any of the Italians. - - -[1] Leonardo da Vinci observes: "L'ombra è diminuzione di luce, tenebre -è privazione di luce." And again: "Sempre il minor lume è ombra del -lume maggiore."--_Trattato della Pittura_, pp. 274-299. - -N. B. The same edition before described has been consulted throughout. - -[2] - - "Lux varium vivumque dabit, nullum umbra colorem." - _De Arte Graphicá_. - - "Know first that light displays and shade destroys - Refulgent nature's variegated dies."--Mason's _Translation_. - - -[3] A Spanish writer, Diego de Carvalho e Sampayo, quoted by Goethe -("Farbenlehre," vol. ii.), has a similar observation. This destroying -effect of light is striking in climates where the sun is powerful, and -was not likely to escape the notice of a Spaniard. - -[4] Trattato, pp. 103, 121, 123, 324, &c. - -[5] Ib. pp. 85, 134. - -[6] Absolute opacity, to judge from the older specimens of stained -glass, seems to have been considered inadmissible. The window was -to admit light, however modified and varied, in the form prescribed -by the architect, and that form was to be preserved. This has been -unfortunately lost sight of in some modern glass-painting, which, -by excluding the light in large masses, and adopting the opacity -of pictures (the reverse of the influence above alluded to), has -interfered with the architectural symmetry in a manner far from -desirable. On the other hand, if we suppose painting at any period -to have aimed at the imitation of stained glass, such an imitation -must of necessity have led to extreme force; for the painter sets -out by substituting a mere white ground for the real light of the -sky, and would thus be compelled to subdue every tone accordingly. -In such an imitation his colour would soon deepen to its intensest -state; indeed, considerable portions of the darker hues would be lost -in obscurity. The early Flemish pictures seldom err on the side of -a gay superabundance of colour; on the contrary, they are generally -remarkable for comparatively cool lights, for extreme depth, and a -certain subdued splendour, qualities which would necessarily result -from the imitation or influence in question. - -[7] See Langlois, "Peinture sur Verre." Rouen, 1832; Descamps, "La Vie -des Peintres Flamands;" and Gessert, "Geschichte der Glasmalerei." -Stutgard, 1839. The antiquity of the glass manufactory of Murano -(Venice) is also not to be forgotten. Vasari objects to the Venetian -glass, because it was darker in colour than that of Flanders, France, -and England; but this very quality was more likely to have an -advantageous influence on the style of the early oil-painters. The use -of stained glass was, however, at no period very general in Italy. - -[8] Zanetti, "Della Pittura Veneziana," marks the progress of the early -Venetian painters by the gradual use of the warm outline. There are -some mosaics in St. Mark's which have the effect of flesh-colour, but -on examination, the only red colour used is found to be in the outlines -and markings. Many of the drawings of the old masters, heightened with -red in the shadows, have the same effect. In these drawings the artists -judiciously avoided colouring the lips and cheeks much, for this would -only have betrayed the want of general colour, as is observable when -statues are so treated. - -[9] Andrea di Luigi, called L'Ingegno, and Niccolo di Fuligno, are -cited as the most prominent examples. See Rumohr, "Italienische -Forschungen." Perogino himself occasionally adopted a very glowing -colour. - -The early Italian schools which adhered most to the Byzantine types -appear to have been also the most remarkable for depth, or rather -darkness, of colour. This fidelity to customary representation was -sometimes, as in the schools of Umbria, and to a certain extent in -those of Siena and Bologna, the result of a religious veneration for -the ancient examples; in others, as in Venice, the circumstance of -frequent intercourse with the Levant is also to be taken into the -account. The Greek pictures of the Madonna, not to mention other -representations, were extremely dark, in exaggerated conformity, -it is supposed, with the tradition respecting her real complexion -(see D'Agincourt, vol. iv. p. 1); a belief which obtained so late as -Lomazzo's time, for, speaking of the Madonna, he observes, "Leggesi -però che fu alquanto bruna." Giotto, who with the independence of -genius betrayed a certain contempt for these traditions, failed perhaps -to unite improvement with novelty when he substituted a pale white -flesh-colour for the traditional brown. Some specimens of his works, -still existing at Padua, present a remarkable contrast in this respect -with the earliest productions of the Venetian and Paduan artists. His -works at Florence differ as widely from those of the earlier painters -of Tuscany. This peculiarity was inherited by his imitators, and at -one time almost characterised the Florentine school. Leon Battista -Alberti was not perhaps the first who objected to it ("Vorrei io -che dai pittori fosse comperato il color bianco assai più caro che -le presiosissime gemme."--_Della Pittura_, I. ii.) The attachment -of Fra Bartolommeo to the grave character of the Christian types is -exemplified in his deep colouring, as well as in other respects. - -[10] Holland might be excepted, and in Holland similar causes may have -had a similar influence. - -[11] Local colour; literally, the _blot_. - -[12] Zanetti ventures to single out the picture of Tobit and the Angel -in S. Marziale as the first example of Titian's own manner, and in -which a direct imitation of Giorgione is no longer apparent. In this -picture the lights are cool and the blood-tint very effective. - -[13] "Meno sfumato, men focoso."--_Storia Pittorica_. - -[14] "La prima cosa che de' colori si perde nelle distante è il lustro, -loro minima parte."--_Trattato_, p. 213; and elsewhere, "I lumi -principali in picciol luogo son quelli che in picciola distanza sono i -primi che si perdono all' occhio."--p. 128. - -[15] A colossal St. Christopher, the usual subject, is frequently seen -occupying the whole height of the external wall of a church. We have -here an example of the influence of religion, such as it was, even on -the style of colouring and practical methods of the art. The mere sight -of the image of St. Christopher, the type of strength, was considered -sufficient to reinvigorate those who were exhausted by the labours of -husbandry. The following is a specimen of the inscriptions inculcating -this belief:-- - - "Christophori Sancti speciem quicumque tuetur, - Illo namque die nullo languore tenetur." - -Hence the practice of painting the figure on the outside of churches, -hence its colossal size, and hence the powerful qualities in colour -above described. See Maniago, "Storia delle Belle Arti Friulane." - -[16] The authority of Fuseli sufficiently warrants the application of -the term breadth to colour; he speaks of Titian's "breadth of local -tint." - -[17] Zanetti quotes an opinion of the painters of his time to the same -effect:--"Teneano essi (alcuni maestri) per cosa certa, che in molte -opere Tiziano volesse fingere il lume--quale si vede nell' inclinarsi -del sole verso la sera. Gli orizzonti assai luminosi dietro le -montagne, le ombre incerte e più le carnagioni brunette e rosseggianti -delle figure, gl'induceano a creder questo."--Lib. ii. Leonardo da -Vinci observes, "Quel corpo che si troverà in mediocre lume fia in -lui poca differenza da' lumi all' ombre. E questo accade sul far -della sera--e queste opere sono dolci ed hacci grazia ogni qualità di -volto," &c.--p. 336. Elsewhere, "Le ombre fatte dal sole od altri lumi -particolari sono senza grazia."--p. 357; see also p. 247. - -[18] See "Francesco Priscianese De' Primi Principii della Lingua -Latina," Venice, 1550. The letter is at the end of the work. It is -quoted in Ticozzi's "Vite de' Pittori Vecelli," Milan, 1817. - -[19] The works of Giorgione are extremely rare. The pictures best -calculated to give an idea of the glowing manner for which he -is celebrated, are the somewhat early works and several of the -altar-pieces of Titian, the best specimens of Palma Vecchio, and the -portraits of Sebastian del Piombo. - -[20] Zanetti and Lodovico Dolce mention Lorenzo Lotto as an instance -of the excess of Giorgione's style. Titian himself sometimes -overstepped the mark, as his biographers confess, and as appears, -among other instances, from the head of St. Peter in the picture (now -in the Vatican) in which the celebrated St. Sebastian is introduced. -Raphael was criticised by some cardinals for a similar defect. See -"Castiglione, Il Cortigiano," 1. ii. - -In the same paragraph to which the present observations refer, the -authority of Kircher is quoted; his treatise, "Ars magna lucis et -umbrae," was published in Rome in 1646. In a portrait of Nicholas -Poussin, engraved by Clouet, the painter is represented holding a book, -which, from the title and the circumstance of Poussin having lived in -Rome in Kircher's time, Goethe supposes to be the work in question. The -abuse of the principle above alluded to, is perhaps exemplified in the -red half-tints observable in some of Poussin's figures. - -The augmentation of colour in subdued light was still more directly -taught by Lomazzo. He composes the half-tints of flesh merely by -diminishing the quantity of white, the proportions of the other colours -employed (for he enters into minute details) remaining unaltered. See -his "Trattato della arte della Pittura," Milan, 1584, p. 301. - -[21] In the Dresden Gallery, a picture attributed to Titian--at -all events a lucid Venetian picture--hangs next the St. George of -Correggio. After looking at the latter, the Venetian work appears -glassy and unsubstantial, but on reversing the order of comparison, -the Correggio may be said to suffer more, and for a moment its fine -transitions of light and shade seem changed to heaviness. - -[22] The finest works of Tintoret---the Crucifixion and the Miracolo -del Servo (considered here merely with reference to their colour,) -may be said to combine the excellences of Titian and Giacomo Bassan, -on a grand scale; the sparkling clearness of the latter is one of the -prominent characteristics of these pictures. Tintoret is reported to -have once said that a union of his own knowledge of form with Bassan's -colour would be the perfection of painting. See "Verei Notizie de' -Pittori di Bassano;" Ven. 1775, p. 61. - -[23] That this last quality, the characteristic of Bassan's best -pictures, was held in high estimation by Paul Veronese, is not only -evident from that painter's own works, but from the circumstance of his -preferring to place his sons with Bassan rather than with any other -painter. (See "Boschini Carta del Navegar," p. 280.) The Baptism of -Sta. Lucilla, in Boschini's time considered the finest of Giacomo's -works, is still in the church of S. Valentino, at Bassano, and may be -considered the type of the lucid and sparkling manner. - - - -NOTE F.--Par. 83. - -The author, in these instances, seems to be anticipating his -subsequent explanations on the effect of semi-transparent mediums. -For an explanation of the general view contained in these paragraphs -respecting the gradual increase of colour from high light, see the last -Note. - -The anonymous French work before alluded to, among other interesting -examples, contains a chapter on shadows cast by the upper light of the -sky and coloured by the setting sun. The effect of this remarkable -combination is, that the light on a wall is most coloured immediately -under a projecting roof, and becomes comparatively neutralised in -proportion to its distance from the edge of the darkest shade. - - -NOTE G.--Par. 98. - -"The simplest case of the phenomenon, which Goethe calls a subjective -halo, and one which at once explains its cause, is the following. -Regard a red wafer on a sheet of white paper, keeping the eye -stedfastly fixed on a point at its center. When the retina is -fatigued, withdraw the head a little from the paper, and a green halo -will appear to surround the wafer. By this slight increase of distance -the image of the wafer itself on the retina becomes smaller, and the -ocular spectrum which before coincided with the direct image, being -now relatively larger, is seen as a surrounding ring."--S. F. Goethe -mentions cases of this kind, but does not class them with subjective -halos. See Par. 30. - - -NOTE H.--Par. 113. - -"Cases of this kind are by no means uncommon. Several interesting -ones are related in Sir John Herschell's article on Light in the -Encyclopædia Metropolitana. Careful investigation has, however, shown -that this defect of vision arises in most, if not in all cases, from -an inability to perceive the red, not the blue rays. The terms are so -confounded by the individuals thus affected, that the comparison of -colours in their presence is the only criterion."--S. F. - - -NOTE I.--Par. 135. - -The author more than once admits that this chapter on "Pathological -Colours" is very incomplete, and expresses a wish (Par. 734) that some -medical physiologists would investigate the subject further. This was -afterwards in a great degree accomplished by Dr. Johannes Müller, in -his memoir "Über die Phantastischen Gesichtserscheinungen." Coblentz, -1826. Similar phenomena have been also investigated with great labour -and success by Purkinje. For a collection of extraordinary facts of the -kind recorded by these writers, the reader may consult Scott's Letters -on Demonology and Witchcraft.[1] The instances adduced by Müller and -others are, however, intended to prove the inherent capacity of the -organ of vision to produce light and colours. In some maladies of the -eye, the patient, it seems, suffers the constant presence of light -without external light. The exciting principle in this case is thus -proved to be within, and the conclusion of the physiologists is that -external light is only one of the causes which produce luminous and -coloured impressions. That this view was anticipated by Newton may be -gathered from the concluding "query" in the third book of his Optics. - - -[1] See also a curious passage on the beatific vision of the monks of -Mount Athos, in Gibbon, chap. 63. - - - -NOTE K.--Par. 140. - -"Catoptrical colours. The colours included under this head are -principally those of fibres and grooved surfaces; they can be produced -artificially by cutting parallel grooves on a surface of metal from -2000 to 10,000 in the inch. See 'Brewster's Optics,' p. 120. The -colours called by Goethe _paroptical_, correspond with those produced -by the diffraction or inflection of light in the received theory.--See -Brewster, p. 95. The phenomena included under the title 'Epoptical -Colours,' are generally known as the colours of thin plates. They vary -with the thickness of the film, and the colour seen by reflection -always differs from that seen by transmission. The laws of these -phenomena have been thoroughly investigated. See Nobili, and Brewster, -p. 100."--S. F. - -The colours produced by the transmission of polarised light through -chrystalised mediums, were described by Goethe, in his mode, -subsequently to the publication of his general theory, under the name -of Entoptic Colours. See note to Par. 485. - - -NOTE L.--Par. 150. - -We have in this and the next paragraph the outline of Goethe's system. -The examples that follow seem to establish the doctrine here laid -down, but there are many cases which it appears cannot be explained on -such principles: hence, philosophers generally prefer the theory of -absorption, according to which it appears that certain mediums "have -the property of absorbing some of the component rays of white light, -while they allow the passage of others."[1] - -Whether all the facts adduced by Goethe--for instance, that recorded -in Par. 172, are to be explained by this doctrine, we leave to the -investigators of nature to determine. Dr. Eckermann, in conversing with -Goethe, thus described the two leading phenomena (156, 158) as seen by -him in the Alps. "At a distance of eighteen or twenty miles at mid-day -in bright sunshine, the snow appeared yellow or even reddish, while the -dark parts of the mountain, free from snow, were of the most decided -blue. The appearances did not surprise me, for I could have predicted -that the mass of the interposed medium would give a deep yellow tone -to the white snow, but I was pleased to witness the effect, since it -so entirely contradicted the erroneous views of some philosophers, -who assert that the air has a blue-tinging quality. The observation, -said Goethe, is of importance, and contradicts the error you allude to -completely."[2] - -The same writer has some observations to the same effect on the colour -of the Rhone at Geneva. A circumstance of an amusing nature which he -relates in confirmation of Goethe's theory, deserves to be inserted. -"Here (at Strasburg), passing by a shop, I saw a little glass bust -of Napoleon, which, relieved as it was against the dark interior of -the room, exhibited every gradation of blue, from milky light blue -to deep violet. I foresaw that the bust seen from within the shop -with the light behind it, would present every degree of yellow, and I -could not resist walking in and addressing the owner, though perfectly -unknown to me. My first glance was directed to the bust, in which, to -my great joy, I saw at once the most brilliant colours of the warmer -kind, from the palest yellow to dark ruby red. I eagerly asked if I -might be allowed to purchase the bust; the owner replied that he had -only lately brought it with him from Paris, from a similar attachment -to the emperor to that which I appeared to feel, but, as my ardour -seemed far to surpass his, I deserved to possess it. So invaluable -did this treasure seem in my eyes, that I could not help looking at -the good man with wonder as he put the bust into my hands for a few -franks. I sent it, together with a curious medal which I had bought -in Milan, as a present to Goethe, and when at Frankfort received the -following letter from him." The letter, which Dr. Eckermann gives -entire, thus concludes--"When you return to Weimar you shall see the -bust in bright sunshine, and while the transparent countenance exhibits -a quiet blue,[3] the thick mass of the breast and epaulettes glows with -every gradation of warmth, from the most powerful ruby-red downwards; -and as the granite statue of Memnon uttered harmonious sounds, so the -dim glass image displays itself in the pomp of colours. The hero is -victorious still in supporting the Farbenlehre."[4] - -One effect of Goethe's theory has been to invite the attention of -scientific men to facts and appearances which had before been unnoticed -or unexplained. To the above cases may be added the very common, but -very important, fact in painting, that a light warm colour, passed in -a semi-transparent state over a dark one, produces a cold, bluish -hue, while the operation reversed, produces extreme warmth. On the -judicious application of both these effects, but especially of the -latter, the richness and brilliancy of the best-coloured pictures -greatly depends. The principle is to be recognised in the productions -of schools apparently opposite in their methods. Thus the practice -of leaving the ground, through which a light colour is apparent, as -a means of ensuring warmth and depth, is very common among the Dutch -and Flemish painters. The Italians, again, who preferred a solid -under-painting, speak of internal light as the most fascinating quality -in colour. When the ground is entirely covered by solid painting, as -in the works of some colourists, the warmest tints in shadows and -reflections have been found necessary to represent it. This was the -practice of Rembrandt frequently, and of Reynolds universally, but the -glow of their general colour is still owing to its being repeatedly -or ultimately enriched on the above principle. Lastly, the works of -those masters who were accustomed to paint on dark grounds are often -heavy and opaque; and even where this influence of the ground was -overcome, the effects of time must be constantly diminishing the warmth -of their colouring as the surface becomes rubbed and the dark ground -more apparent through it. The practice of painting on dark grounds was -intended by the Carracci to compel the students of their school to -aim at the direct imitation of the model, and to acquire the use of -the brush; for the dark ground could only be overcome by very solid -painting. The result answered their expectations as far as dexterity of -pencil was concerned, but the method was fatal to brilliancy of colour. -An intelligent writer of the seventeenth century[5] relates that Guido -adopted his extremely light style from seeing the rapid change in some -works of the Carracci soon after they were done. It is important, -however, to remark, that Guido's remedy was external rather than -internal brilliancy; and it is evident that so powerless a brightness -as white paint can only acquire the splendour of light by great -contrast, and, above all, by being seen through external darkness. The -secret of Van Eyck and his contemporaries is always assumed to consist -in the vehicle (varnish or oils) he employed; but a far more important -condition of the splendour of colour in the works of those masters was -the careful preservation of internal light by painting thinly, but -ultimately with great force, on white grounds. In some of the early -Flemish pictures in the Royal Gallery at Munich, it may be observed, -that wherever an alteration was made by the painter, so that a light -colour is painted over a dark one, the colour is as opaque as in any -of the more modern pictures which are generally contrasted with such -works. No quality in the vehicle could prevent this opacity under such -circumstances; and on the other hand, provided the internal splendour -is by any means preserved, the vehicle is comparatively unimportant. - -It matters not (say the authorities on these points) whether the effect -in question is attained by painting thinly over the ground, in the -manner of the early Flemish painters and sometimes of Rubens, or by -painting a solid light preparation to be afterwards toned to richness -in the manner of the Venetians. Among the mechanical causes of the -clearness of colours superposed on a light preparation may be mentioned -that of careful grinding. All writers on art who have descended to -practical details have insisted on this. From the appearance of some -Venetian pictures it may be conjectured that the colours of the -solid under-painting were sometimes less perfectly ground than the -scumbling colours (the light having to pass through the one and to -be reflected from the other). The Flemish painters appear to have -used carefully-ground pigments universally. This is very evident in -Flemish copies from Raphael, which, though equally impasted with -the originals, are to be detected, among other indications, by the -finely-ground colours employed. - - -[1] See "Müller's Elements of Physiology," translated from the German -by William Baly, M.D. "The laws of absorption," it has been observed, -"have not been studied with so much success as those of other phenomena -of physical optics, but some excellent observations on the subject -will be found in Herschell's Treatise on Light in the Encyclopædia -Metropolitana, § III." - -[2] "Eckermann's Gespräche mit Goethe," vol. ii. p. 280. Leonardo da -Vinci had made precisely the same observation. "A distant mountain will -appear of a more beautiful blue in proportion as it is dark in colour. -The illumined air, interposed between the eye and the dark mass, being -thinner towards the summit of the mountain, will exhibit the darkness -as a deeper blue and _vice versâ_."--_Trattato della Pittura_, p. 143. -Elsewhere--"The air which intervenes between the eye and dark mountains -becomes blue; but it does not become blue in (before) the light part, -and much less in (before) the portion that is covered with snow."--p. -244. - -[3] This supposes either that the mass was considerably thicker, or -that there was a dark ground behind the head, and a light ground behind -the rest of the figure. - -[4] "Eckermann's Gespräche mit Goethe," vol. ii. p. 242. - -[5] Scanelli, "Microcosmo della Pittura," Cesena, 1657, p. 114. - - - -NOTE M.--Par. 177. - -Without entering further into the scientific merits or demerits of -this chapter on the "First Class of Dioptrical Colours," it is to be -observed that several of the examples correspond with the observations -of Leonardo da Vinci, and again with those of a much older authority, -namely, Aristotle. Goethe himself admits, and it has been remarked by -others, that his theory, in many respects, closely resembles that of -Aristotle: indeed he confesses[1] that at one time he had an intention -of merely paraphrasing that philosopher's Treatise on Colours.[2] - -We have already remarked (Note on par. 150) that Goethe's notion with -regard to the production of warm colours, by the interposition of dark -transparent mediums before a light ground, agrees with the practice of -the best schools in colouring; and it is not impossible that the same -reasons which may make this part of the doctrine generally acceptable -to artists now, may have recommended the very similar theory of -Aristotle to the painters of the fifteenth and sixteenth centuries: -at all events, it appears that the ancient theory was known to those -painters. - -It is unnecessary to dwell on the fact that the doctrines of Aristotle -were enthusiastically embraced and generally inculcated at the period -in question;[3] but it has not been observed that the Italian writers -who translated, paraphrased, and commented on Aristotle's Treatise -on Colours in particular, were in several instances the personal -friends of distinguished painters. Celio Calcagnini[4] had the highest -admiration for Raphael; Lodovico Dolce[5] was the eulogist of Titian; -Portius,[6] whose amicable relations with the Florentine painters may -be inferred from various circumstances, lectured at Florence on the -Aristotelian doctrines early in the sixteenth century. The Italian -translations were later, but still prove that these studies were -undertaken with reference to the arts, for one of them is dedicated to -the painter Cigoli.[7] - -The writers on art, from Leon Battista Alberti to Borghini, without -mentioning later authorities, either tacitly coincide with the -Aristotelian doctrine, or openly profess to explain it. It is true this -is not always done in the clearest manner, and some of these writers -might say with Lodovico Dolce, "I speak of colours, not as a painter, -for that would be the province of the divine Titian." - -Leonardo da Vinci in his writings, as in everything else, appears as -an original genius. He now and then alludes generally to opinions -of "philosophers," but he quotes no authority ancient or modern. -Nevertheless, a passage on the nature of colours, particularly where -he speaks of the colours of the elements, appears to be copied from -Leon Battista Alberti,[8] and from the mode in which some of Leonardo's -propositions are stated, it has been supposed[9] that he had been -accustomed at Florence to the form of the Aristotelian philosophy. At -all events, some of the most important of his observations respecting -light and colours, have a great analogy with those contained in the -treatise in question. The following examples will be sufficient to -prove this coincidence; the corresponding passages in Goethe are -indicated, as usual, by the numbers of the paragraphs; the references -to Leonardo's treatise are given at the bottom of the page. - - Aristotle. - - "A vivid and brilliant red appears when the weak rays of the - sun are tempered by subdued and shadowy white,"--154. - - Leonardo - - "The air which is between the sun and the earth at sun-rise - or sun-set, always invests what is beyond it more than any - other (higher) portion of the air: this is because it is - whiter."[10] - - A bright object loses its whiteness in proportion to its - distance from the eye much more when it is illuminated by - the sun, for it partakes of the colour of the sun mingled - with the colour (tempered by the mass) of the air interposed - between the eye and the brightness.[11] - - Aristotle. - - "If light is overspread with much obscurity, a red colour - appears; if the light is brilliant and vivid, this red - changes to a flame-colour."[12]--150, 160. - - Leonardo. - - "This (the effect of transparent colours on various grounds) - is evident in smoke, which is blue when seen against black, - but when it is opposed to the (light) blue sky, it appears - brownish and reddening."[13] - - Aristotle. - - "White surfaces as a ground for colours, have the effect of - making the pigments[14] appear in greater splendour."--594, - 902. - - Leonardo. - - "To exhibit colours in their beauty, the whitest ground - should be prepared. I speak of colours that are (more or - less) transparent."[15] - - Aristotle. - - "The air near us appears colourless; but when seen in depth, - owing to its thinness it appears blue;[16] for where the - light is deficient (beyond it), the air is affected by the - darkness and appears blue: in a very accumulated state, - however, it appears, as is the case with water, quite - white."--155, 158. - - Leonardo. - - "The blue of the atmosphere is owing to the mass of - illuminated air interposed between the darkness above and - the earth. The air in itself has no colour, but assumes - qualities according to the nature of the objects which are - beyond it. The blue of the atmosphere will be the more - intense in proportion to the degree of darkness beyond it:" - elsewhere--"if the air had not darkness beyond it, it would - be white."[17] - - Aristotle. - - "We see no colour in its pure state, but every hue is - variously intermingled with others: even when it is - uninfluenced by other colours, the effect of light and - shade modifies it in various ways, so that it undergoes - alterations and appears unlike itself. Thus, bodies seen in - shade or in light, in more pronounced or softer sun-shine, - with their surfaces inclined this way or that, with every - change exhibit a different colour." - - Leonardo. - - "No substance will ever exhibit its own hue unless the light - which illumines it is entirely similar in colour. It very - rarely happens that the shadows of opaque bodies are really - similar (in colour) to the illumined parts. The surface of - every substance partakes of as many hues as are reflected - from surrounding objects."[18] - - Aristotle. - - "So, again, with regard to the light of fire, of the moon, - or of lamps, each has a different colour, which is variously - combined with differently coloured objects." - - Leonardo. - - "We can scarcely ever say that the surface of illumined - bodies exhibits the real colour of those bodies. Take a - white band and place it in the dark, and let it receive - light by means of three apertures from the sun, from fire, - and from the sky: the white band will be tricoloured."[19] - - Aristotle. - - "When the light falls on any object and assumes (for - example) a red or green tint, it is again reflected on other - substances, thus undergoing a new change. But this effect, - though it really takes place, is not appreciable by the - eye: though the light thus reflected to the eye is composed - of a variety of colours, the principal of these only are - distinguishable." - - Leonardo. - - "No colour reflected on the surface of another colour, - tinges that surface with its own colour (merely), but will - be mixed with various other reflections impinging on the - same surface:" but such effects, he observes elsewhere, "are - scarcely, if at all, distinguishable in a very diffused - light."[20] - - Aristotle. - - "Thus, all combinations of colours are owing to three - causes: the light, the medium through which the light - appears, such as water or air, and lastly the local colour - from which the light happens to be reflected." - - Leonardo. - - "All illumined objects partake of the colour of the light - they receive. - - "Every opaque surface partakes of the colour of the - intervening transparent medium, according to the density of - such medium and the distance between the eye and the object. - - "The medium is of two kinds; either it has a surface, like - water, &c., or it is without a common surface, like the - air."[21] - -In the observations on trees and plants more points of resemblance -might be quoted; the passages corresponding with Goethe's views are -much more numerous. - -It is remarkable that Leonardo, in opposition, it seems to some -authorities,[22] agrees with Aristotle in reckoning black and white -as colours, placing them at the beginning and end of the scale.[23] -Like Aristotle, again, he frequently makes use of the term black, for -obscurity; he even goes further, for he seems to consider that blue -may be produced by the actual mixture of black and white, provided they -are pure.[24] The ancient author, however, explains himself on this -point as follows--"We must not attempt to make our observations on -these effects by mixing colours as painters mix them, but by remarking -the appearances as produced by the rays of light mingling with each -other."[25] - -When we consider that Leonardo's Treatise professes to embrace the -subject of imitation in painting, and that Aristotle's briefly examines -the physical nature and appearance of colours, it must be admitted -that the latter sustains the above comparison with advantage; and it -is somewhat extraordinary that observations indicating so refined a -knowledge of nature, as regards the picturesque, should not have been -taken into the account, for such appears to be the fact, in the various -opinions and conjectures that have been expressed from time to time on -the painting of the Greeks. The treatise in question must have been -written when Apelles painted, or immediately before; and as a proof -that Aristotle's remarks on the effect of semi-transparent mediums were -not lost on the artists of his time, the following passage from Pliny -is subjoined, for, though it is well known, it acquires additional -interest from the foregoing extracts. - -"He (Apelles) passed a dark colour over his pictures when finished, so -thin that it increased the splendour of the tints, while it protected -the surface from dust and dirt: it could only be seen on looking into -the picture. The effect of this operation, judiciously managed, was to -prevent the colours from being too glaring, and to give the spectator -the impression of looking through a transparent crystal. At the same -time it seemed almost imperceptibly to add a certain dignity of tone to -colours that were too florid." "This," says Reynolds, "is a true and -artist-like description of glazing or scumbling, such as was practised -by Titian and the rest of the Venetian painters." - -The account of Pliny has, in this instance, internal evidence -of truth, but it is fully confirmed by the following passage in -Aristotle:--"Another mode in which the effect of colours is exhibited -is when they appear through each other, as painters employ them when -they glaze (ἐπαλειφοντες)[26] a (dark) colour over a lighter one; just -as the sun, which is in itself white, assumes a red colour when seen -through darkness and smoke. This operation also ensures a variety of -colours, for there will be a certain ratio between those which are on -the surface and those which are in depth."--_De Sensu et Sensili_. - -Aristotle's notion respecting the derivation of colours from white and -black may perhaps be illustrated by the following opinion on the very -similar theory of Goethe. - -"Goethe and Seebeck regard colour as resulting from the mixture of -white and black, and ascribe to the different colours a quality -of darkness (σκιερὸν), by the different degrees of which they are -distinguished, passing from white to black through the gradations -of yellow, orange, red, violet, and blue, while green appears to be -intermediate again between yellow and blue. This remark, though it has -no influence in weakening the theory of colours proposed by Newton, -is certainly correct, having been confirmed experimentally by the -researches of Herschell, who ascertained the relative intensity of the -different coloured rays by illuminating objects under the microscope by -their means, &c. - -"Another certain proof of the difference in brightness of the different -coloured rays is afforded by the phenomena of ocular spectra. If, after -gazing at the sun, the eyes are closed so as to exclude the light, the -image of the sun appears at first as a luminous or white spectrum upon -a dark ground, but it gradually passes through the series of colours to -black, that is to say, until it can no longer be distinguished from the -dark field of vision; and the colours which it assumes are successively -those intermediate between white and black in the order of their -illuminating power or brightness, namely, yellow, orange, red, violet, -and blue. If, on the other hand, after looking for some time at the -sun we turn our eyes towards a white surface, the image of the sun is -seen at first as a black spectrum upon the white surface, and gradually -passes through the different colours from the darkest to the lightest, -and at last becomes white, so that it can no longer be distinguished -from the white surface"[27]--See par 40, 44. - -It is not impossible that Aristotle's enumeration of the colours may -have been derived from, or confirmed by, this very experiment. Speaking -of the after-image of colours he says, "The impression not only exists -in the sensorium in the act of perceiving, but remains when the organ -is at rest. Thus if we look long and intently on any object, when -we change the direction of the eyes a responding colour follows. If -we look at the sun, or any other very bright object, and afterwards -shut our eyes, we shall, as if in ordinary vision, first see a colour -of the same kind; this will presently be changed to a red colour, -then to purple, and so on till it ends in black and disappears."--_De -Insomniis_. - - -[1] "Geschichte der Farbenlehre," in the "Nachgelassene Werke." Cotta, -1833. - -[2] The treatise in question is ascribed by Goethe to Theophrastus, -but it is included in most editions of Aristotle, and even attributed -to him in those which contain the works of both philosophers; for -instance, in the Aldine Princeps edition, 1496. Calcagnini says, the -treatise is made up of two separate works on the subject, both by -Aristotle. - -[3] His authority seems to have been equally great on subjects -connected with the phenomena of vision; the Italian translator of -a Latin treatise, by Portius, on the structure and colours of the -eye, thus opens his dedication to the Cardinal Ercole Gonzaga, of -Mantua:--"Grande anzi quasi infinito è l'obligo che ha il mondo con -quel più divino che umano spirito di Aristotile." - -[4] In a letter to Ziegler the mathematician, Calcagnini speaks of -Raphael as "the first of painters in the theory as well as in the -practice of his art." This expression may, however, have had reference -to a remarkable circumstance mentioned in the same letter, namely, -that Raphael entertained the learned Fabius of Ravenna as a constant -guest, and employed him to translate Vitruvius into Italian. This MS. -translation, with marginal notes, written by Raphael, is now in the -library at Munich. "Passavant, Rafael von Urbino." - -[5] Lodovico Dolce's Treatise on Colours (1565) is in the form of a -dialogue, like his "Aretino." The abridged theory of Aristotle is -followed by a translation of the Treatise of Antonius Thylesius on -Colours; this is adapted to the same colloquial form, and the author is -not acknowledged: the book ends with an absurd catalogue of emblems. -The "Somma della Filosofia d'Aristotile," published earlier by the same -author, is a very careless performance. - -[6] A Latin translation of Aristotle's Treatise on Colours, with -comments by Simon Portius, was first published, according to Goethe, -at Naples in 1537. In a later Florentine edition, 1548, dedicated to -Cosmo I., Portius alludes to his having lectured at an earlier period -in Florence on the doctrines of Aristotle, at which time he translated -the treatise in question. Another Latin translation, with notes, was -published later in the same century at Padua--"Emanuele Marguino -Interprete:" but by far the clearest view of the Aristotelian theory -is to be found in the treatise of Antonio Vidi Scarmiglione of Fuligno -("De Coloribus," Marpurgi, 1591). It is dedicated to the Emperor -Rudolph II. Of all the paraphrases of the ancient doctrine this comes -nearest to the system of Goethe; but neither this nor any other of the -works alluded to throughout this Note are mentioned by the author in -his History of the Doctrine of Colours, except that of Portius. - -[7] An earlier Italian translation appeared in Rome, 1535. See -"Argelatus Biblioteca degli Volgarizzatori." - -[8] "Della Pittura e della Statua," Lib. I, p. 16, Milan edition, -1804. Compare with the "Trattato della Pittura," p. 141. Other points -of resemblance are to be met with. The notion of certain colours -appropriated to the four elements, occurs in Aristotle, and is indeed -attributed to older writers. - -[9] See the notes to the Roman edition of the "Trattato della Pittura." - -[10] Page 237. - -[11] Page 301. - -[12] In the Treatise _De Igne_, by Theophrastus, we find the same -notion thus expressed: "Brightness (_τὸ λευκὸν_) seen through a -dark coloured medium (_διὰ του μέλανος_) appears red; as the sun -seen through smoke or soot: hence the coal is redder than the -flame." Scarmiglione, from whom Kircher seems to have copied, -observes:--"Itaque color realis est lux opaca; licet id e plurimis -apparentiis colligere. Luna enim in magnâ solis eclipsi rubra -conspicitur, quia tenebris lux præpeditur ac veluti tegitur."--_De -Coloribus_. - -[13] Page 122. - -[14] _Τὰ ἂνθη_: translated _flores_ by Calcagnini and the rest, by -Goethe, _die Blüthe_, the bloom. That the word sometimes signified -pigments is sufficiently apparent from the following passage of -Suidas (quoted by Emeric David, "Discours Historiques sur la Peinture -Moderne") _ἂνθεσι κεκοσμημέναι, οἶον ψιμμιωίῳ φύκει καὶ τοῖς ὸμοίοις_. -Variis pigmentis ornatæ, ut cerussâ, fuco, et aliis similibus. (Suid. -in voc. _Ἐξμηθισμένας_.) A panel prepared for painting, with a white -ground consolidated with wax, and perhaps mastic, was found in -Herculaneum. - -[15] Page 114. - -[16] _Ἐν βάθει δὲ θεωρουμίνου ιγγυτάτω φαίνεται τῶ χρώματι κυανονοειδὴς -διὰ τὴν ὰραιότητα._ "But when seen in depth, it appears (even) in its -nearest colour, blue, owing to its thinness." The Latin interpretations -vary very much throughout. The point which is chiefly important is -however plain enough, viz. that darkness seen through a light medium is -blue. - -[17] Page 136-430. - -[18] Page 121, 306, 326, 387. - -[19] Page 306. - -[20] Page 104, 369. - -[21] Page 236, 260, 328. - -[22] "De' semplici colori il primo è il bianco: beuchè i filosofi non -accettano nè il bianco nè il nero nel numero de' colori."--p. 125, 141. -Elsewhere, however, he sometimes adopts the received opinion. - -[23] Leon Battista Alberti, in like manner observes:--"Affermano (i -filosofi) che le spezie de' colori sono sette, cioè, che il bianco ed -il nero sono i duoi estremi, infra i quali ve n'è uno nel mezzo (rosso) -e che infra ciascuno di questi duoi estremi e quel del mezzo, da ogni -parte ve ne sono due altri." An absurd statement of Lomazzo, p. 190, -is copied verbatim from Lodovico Dolce (Somma della Filos. d'Arist.); -but elsewhere, p. 306, Lomazzo agrees with Alberti. Aristotle seems to -have misled the two first, for after saying there are seven colours, -he appears only to mention six: he says--"There are seven colours, if -brown is to be considered equivalent to black, which seems reasonable. -Yellow, again, may be said to be a modification of white. Between these -we find red, purple, green, and blue."--_De Sensu et Sensili_. Perhaps -it is in accordance with this passage that Leonardo da Vinci reckons -eight colours.--_Trattato_, p. 126. - -[24] Page 122, 142, 237. - -[25] On the authority of this explanation the word μιλάν has sometimes -been translated in the foregoing extracts _obscurity, darkness_. - -Raffaello Borghini, in his attempt to describe the doctrine of -Aristotle with a view to painting, observes--"There are two -principles which concur in the production of colour, namely, light -and transparence." But he soon loses this clue to the best part of -the ancient theory, and when he has to speak of the derivation of -colours from white and black, he evidently understands it in a mere -atomic sense, and adds--"I shall not at present pursue the opinion -of Aristotle, who assumes black and white as principal colours, and -considers all the rest as intermediate between them."--_Il Riposo_, 1. -ii. Accordingly, like Lodovico Dolce, he proceeds to a subject where he -was more at home, namely, the symbolical meaning of colours. - -[26] This word is only strictly applied to unctuous substances, and may -confirm the views of those writers who have conjectured that asphaltum -was a chief ingredient in the _atramentum_ of the ancients. - -[27] "Elements of Physiology," by J. Müller, M.D., translated from the -German by William Baly, M.D. London, 1839. - - - -NOTE N.--Par. 246. - -"The appearance of white in the centre, according to the Newtonian -theory, arises from each line of rays forming its own spectrum. -These spectra, superposing each other on all the middle part, leave -uncorrected (unneutralised) colours only at the two edges."--S. F.[1] - - -[1] This was objected to Goethe when his "Beyträge sur Optik" first -appeared; he answered the objection by a coloured diagram in the plates -to the "Farbenlehre:" in this he undertakes to show that the assumed -gradual "correction" of the colours would produce results different -from the actual appearance in nature. - - - -NOTE O.--Par. 252. - -These experiments with grey objects, which exhibit different colours -as they are on dark or light grounds, were suggested, Goethe tells -us, by an observation of Antonius Lucas, of Lüttich, one of Newton's -opponents, and, in the opinion of the author, one of the few who made -any well-founded objections. Lucas remarks, that the sun acts merely -as a circumscribed image in the prismatic experiments, and that if the -same sun had a lighter background than itself, the colours of the prism -would be reversed. Thus in Goethe's experiments, when the grey disk is -on a dark ground, it is edged with blue on being magnified; when on a -light ground it is edged with yellow. Goethe acknowledges that Lucas -had in some measure anticipated his own theory.--Vol. ii. p. 440. - - - -NOTE P.--Par. 284. - -The earnestness and pertinacity with which Goethe insisted that -the different colours are not subject to different degrees of -refrangibility are at least calculated to prove that he was himself -convinced on the subject, and, however extraordinary it may seem, his -conviction appears to have been the result of infinite experiments -and the fullest ocular evidence. He returns to the question in the -controversial division of his work, in the historical part, and again -in the description of the plates. In the first he endeavours to show -that Newton's experiment with the blue and red paper depends entirely -on the colours being so contrived as to appear elongated or curtailed -by the prismatic borders. "If," he says, "we take a light-blue instead -of a dark one, the illusion (in the latter case) is at once evident. -According to the Newtonian theory the yellow-red (red) is the least -refrangible colour, the violet the most refrangible. Why, then, does -Newton place a blue paper instead of a violet next the red? If the -fact were as he states it, the difference in the refrangibility of -the yellow-red and violet would be greater than in the case of the -yellow-red and blue. But here comes in the circumstance that a violet -paper conceals the prismatic borders less than a dark-blue paper, as -every observer may now easily convince himself," &c.--Polemischer -Theil, par. 45. Desaguliers, in repeating the experiment, confessed -that if the ground of the colours was not black, the effect did -not take place so well. Goethe adds, "not only not so well, but -not at all."--Historischer Theil, p. 459. Lucas of Lüttich, one of -Newton's first opponents, denied that two differently-coloured silks -are different in distinctness when seen in the microscope. Another -experiment proposed by him, to show the unsoundness of the doctrine of -various refrangibility, was the following:--Let a tin plate painted -with the prismatic colours in stripes be placed in an empty cubical -vessel, so that from the spectator's point of view the colours may be -just hidden by the rim. On pouring water into this vessel, all the -colours become visible in the same degree; whereas, it was contended, -if the Newtonian doctrine were true, some colours would be apparent -before others.--Historischer Theil, p. 434. - -Such are the arguments and experiments adduced by Goethe on this -subject; they have all probably been answered. In his analysis of -Newton's celebrated _Experimentum Crucis_, he shows again that by -reversing the prismatic colours (refracting a dark instead of a -light object), the colours that are the most refrangible in Newton's -experiment become the least so, and _vice versâ_. - -Without reference to this objection, it is now admitted that "the -difference of colour is not a test of difference of refrangibility, and -the conclusion deduced by Newton is no longer admissible as a general -truth, that to the same degree of refrangibility ever belongs the -same colour, and to the same colour ever belongs the same degree of -refrangibility."--Brewster's Optics, p. 72. - - - -NOTE Q--Par. 387. - -With the exception of two very inconclusive letters to Sulpice -Boisserée, and some incidental observations in the conclusion of the -historical portion under the head of entoptic colours, Goethe never -returned to the rainbow. Among the plates he gave the diagram of -Antonius de Dominis. An interesting chapter on halos, parhelia, and -paraselenæ, will be found in Brewster's Optics, p. 270. - - -NOTE R.--Par. 478. - -The most complete exhibition of the colouring or mantling of metals -was attained by the late Cav. Nobili, professor of physical science in -Florence. The general mode in which these colours are produced is thus -explained by him:[1]-- - -"A point of platinum is placed vertically at the distance of about -half a line above a lamina of the same metal laid horizontally at the -bottom of a vessel of glass or porcelain. Into this vessel a solution -of acetate of lead is poured so as to cover not only the lamina of -platinum, but two or three lines of the point as well. Lastly, the -point is put in communication with the negative pole of a battery, and -the lamina with the positive pole. At the moment in which the circuit -is completed a series of coloured rings is produced on the lamina -under the point similar to those observed by Newton in lenses pressed -together." - -The scale of colours thus produced corresponds very nearly with that -observed by Newton and others in thin plates and films, but it is -fuller, for it extends to forty-four tints. The following list, as -given by Nobili, is divided by him into four series to agree with -those of Newton: the numbers in brackets are those of Newton's scale. -The Italian terms are untranslated, because the colours in some cases -present very delicate transitions.[2] - - _First Series._ - - 1. Biondo argentino (4).[3] 6. Fulvo acceso. - 2. Biondo. 7. Rosso di rame (6). - 3. Biondo d'oro. 8. Ocria. - 4. Biondo acceso (5). 9. Ocria violacea. - 5. Fulvo. 10. Rosso violaceo (7). - - Second Series. - - 11. Violetto (8). 20. Giallo acceso. - 12. Indaco (10). 21. Giallo-rancio. - 13. Blu carico. 22. Rancio (13). - 14. Blu. 23. Rancio-rossiccio. - 15. Blu chiaro (11) 24. Rancio-rosso. - 16. Celeste. 25. Rosso-rancio. - 17. Celeste giallognolo. 26. Lacca-rancia (14). - 18. Giallo chiarissimo (12). 27. Lacca. - 19. Giallo. 28. Lacca accesa (15). - - Third Series. - - 29. Lacca-purpurea (16). 34. Verde-giallo (20). - 30. Lacca-turchiniccia (17). 35. Verde-rancio. - 31. Porpora-verdognola (18). 36. Rancio-verde (21). - 32. Verde (19). 37. Rancio-roseo. - 33. Verde giallognolo. 38. Lacca-rosea (22). - - - Fourth Series. - - 39. Lacca-violacea (24). 43. Verde-giallo rossiccio (28). - 40. Violaceo-verdognolo (25). 44. Lacca-rosea (30). - 41. Verde (26). - 42. Verde-giallo (27). - -"These tints," Professor Nobili observes, "are disposed according to -the order of the thin mantlings which occasion them; the colour of -the thinnest film is numbered 1; then follow in order those produced -by a gradual thickening of the medium. I cannot deceive myself in -this arrangement, for the thin films which produce the colours are -all applied with the same electro-chemical process. The battery, the -solution, the distances, &c., are always the same; the only difference -is the time the effect is suffered to last. This is a mere instant for -the colour of No. 1, a little longer for No. 2, and so on, increasing -for the succeeding numbers. Other criterions, however, are not wanting -to ascertain the place to which each tint belongs." - -The scale differs from that of Newton, inasmuch as there is no blue in -Nobili's first series and no green in the second: green only appears in -the third and fourth series. "The first series," says the Professor, -"is remarkable for the fire and metallic appearance of its tints, the -second for clearness and brilliancy, the third and fourth for force and -richness." The fourth, he observes, has the qualities of the third in a -somewhat lesser degree, but the two greens are very nearly alike. - -It is to be observed, that red and green are the principal ingredients -in the third and fourth series, blue and yellow in the second and first. - - -[1] See "Memorie ed Osservazioni, edite et inedite del Cav. Professor -Nobili," Firenze, 1834. - -[2] The colours in some of the compound terms are in a manner mutually -neutralising; such terms might, no doubt, be amended. - -[3] The three first numbers in Newton's scale are black, blue, and -white. - - - -NOTE S.--Par. 485. - -A chapter on entoptic colours, contained in the supplement to Goethe's -works, was translated with the intention of inserting it among the -notes, but on the whole it was thought most advisable to omit it. Like -many other parts of the "Doctrine of Colours" it might have served as -a specimen of what may be achieved by accurate observation unassisted -by a mathematical foundation. The whole theory of the polarization of -light has, however, been so fully investigated since Goethe's time, -that the chapter in question would probably have been found to contain -very little to interest scientific readers, for whom it seems chiefly -to have been intended. One observation occurs in it which indeed has -more reference to the arts; in order to make this intelligible, the -leading experiment must be first described, and for this purpose the -following extracts may serve. - -3.[1] - -"The experiment, in its simplest form, is to be made as follows:--let -a tolerably thick piece of plate-glass be cut into several squares of -an inch and a half; let these be heated to a red heat and then suddenly -cooled. The squares of glass which do not split in this operation are -now fit to produce the entoptic colours. - -4. - -"In our mode of exhibiting the phenomenon, the observer is, above all, -to betake himself, with his apparatus to the open air. All dark rooms, -all small apertures (foramina exigua),[2] are again to be given up. A -pure, cloudless sky is the source whence we are derive a satisfactory -insight into the appearances. - -5. - -"The atmosphere being clear, let the observer lay the squares above -described on a black surface, so placing them that two sides may -be parallel with the plane of vision. When the sun is low, let him -hold the squares so as to reflect to the eye that portion of the sky -opposite to the sun, and he will then perceive four dark points in -the four corners of a light space. If, after this, he turn towards -the quarters of the sky at right angles with that where his first -observation was made, he will see four bright points on a dark ground: -between the two regions the figures appear to fluctuate. - -6. - -"From this simple reflection we now proceed to another, which, but -little more complicated, exhibits the appearance much more distinctly. -A solid cube of glass, or in its stead a cube composed of several -plates, is placed on a black mirror, or held a little inclined -above it, at sun-rise or sun-set. The reflection of the sky being -now suffered to fall through the cube on the mirror, the appearance -above described will appear more distinctly. The reflection of the -sky opposite to the sun presents four dark points on a light ground; -the two lateral portions of the sky present the contrary appearance, -namely, four light points on a dark ground. The space not occupied by -the corner points appears in the first case as a white cross, in the -other as a black cross, expressions hereafter employed in describing -the phenomena. Before sun-rise or after sun-set, in a very subdued -light, the white cross appears on the side of the sun also.[3] - -"We thus conclude that the direct reflection of the sun produces a -light figure, which we call a white cross; the oblique reflection gives -a dark figure, which we call a black cross. If we make the experiment -all round the sky, we shall find that a fluctuation takes place in the -intermediate regions." - -We pass over a variety of observations on the modes of exhibiting this -phenomenon, the natural transparent substances which exhibit it best, -and the detail of the colours seen within[4] them, and proceed to an -instance where the author was enabled to distinguish the "direct" from -the "oblique" reflection by means of the entoptic apparatus, in a -painter's study. - -40. - -"An excellent artist, unfortunately too soon taken from us, Ferdinand -Jagemann, who, with other qualifications, had a fine eye for light and -shade, colour and keeping, had built himself a painting-room for large -as well as small works. The single high window was to the north, facing -the most open sky, and it was thought that all necessary requisites had -been sufficiently attended to. - -"But after our friend had worked for some time, it appeared to him, -in painting portraits, that the faces he copied were not equally well -lighted at all hours of the day, and yet his sitters always occupied -the same place, and the serenity of the atmosphere was unaltered. - -"The variations of the favourable and unfavourable light had their -periods during the day. Early in the morning the light appeared most -unpleasantly grey and unsatisfactory; it became better, till at last, -about an hour before noon, the objects had acquired a totally different -appearance. Everything presented itself to the eye of the artist in its -greatest perfection, as he would most wish to transfer it to canvas. -In the afternoon this beautiful appearance vanished--the light became -worse, even in the brightest day, without any change having taken place -in the atmosphere. - -"As soon as I heard of this circumstance, I at once connected it in -my own mind with the phenomena which I had been so long observing, -and hastened to prove, by a physical experiment, what a clear-sighted -artist had discovered entirely of himself, to his own surprise and -astonishment. - -"I had the second[5] entoptic apparatus brought to the spot, and the -effect on this was what might be conjectured from the above statement. -At mid-day, when the artist saw his model best lighted, the north, -direct reflection gave the white cross; in the morning and evening, on -the other hand, when the unfavourable oblique light was so unpleasant -to him, the cube showed the black cross; in the intermediate hours the -state of transition was apparent." - -The author proceeds to recall to his memory instances where works of -art had struck him by the beauty of their appearance owing to the light -coming from the quarter opposite the sun, in "direct reflection," and -adds, "Since these decided effects are thus traceable to their cause, -the friends of art, in looking at and exhibiting pictures, may enhance -the enjoyment to themselves and others by attending to a fortunate -reflection." - - -[1] The numbers, as usual, indicate the corresponding paragraphs in the -original. - -[2] In the historical part, Goethe has to speak of so many followers of -Newton who begin their statements with "Si per foramen exiguum," that -the term is a sort of by-word with him. - -[3] At mid-day on the 24th of June the author observed the white cross -reflected from every part of the horizon. At a certain distance from -the sun, corresponding, he supposes, with the extent of halos, the -black cross appeared. - -[4] Whence the term _entoptic_. - -[5] Before described: the author describes several others more or less -complicated, and suggests a portable one. "Such plates, which need -only be an inch and a quarter square, placed on each other to form a -cube, might be set in a brass case, open above and below. At one end of -this case a black mirror with a hinge, acting like a cover, might be -fastened. We recommend this simple apparatus, with which the principal -and original experiment may be readily made. With this we could, in the -longest days, better define the circle round the sun where the black -cross appears," &c. - - -NOTE T.--Par. 496. - -"Since Goethe wrote, all the earths have been decomposed, and have -been shown to be metallic bases united with oxygen; but this does not -invalidate his statement."--S. F. - - -NOTE U.--Par. 502. - -The cold nature of black and its affinity to blue are assumed by the -author throughout; if the quality is opaque, and consequently greyish, -such an affinity is obvious, but in many fine pictures, intense black -seems to be considered as the last effect of heat, and in accompanying -crimson and orange may be said rather to present a difference of -degree than a difference of kind. In looking at the great picture -of the globe, we find this last result produced in climates where -the sun has greatest power, as we find it the immediate effect of -fire. The light parts of black animals are often of a mellow colour; -the spots and stripes on skins and shells are generally surrounded -by a warm hue, and are brown before they are absolutely black. In -combustion, the blackness which announces the complete ignition, is -preceded always by the same mellow, orange colour. The representation -of this process was probably intended by the Greeks in the black and -subdued orange of their vases: indeed, the very colours may have been -first produced in the kiln. But without supposing that they were -retained merely from this accident, the fact that the combination -itself is extremely harmonious, would be sufficient to account for -its adoption. Many of the remarks of Aristotle[1] and Theophrastus[2] -on the production of black, are derived from the observation of the -action of fire, and on one occasion, the former distinctly alludes to -the terracotta kiln. That the above opinion as to the nature of black -was prevalent in the sixteenth century, may be inferred from Lomazzo, -who observes,--"Quanto all' origine e generazione de' colori, la -frigidità è la madre della bianchezza: il calore è padre del nero."[3] -The positive coldness of black may be said to begin when it approaches -grey. When Leonardo da Vinci says that black is most beautiful in -shade, he probably means to define its most intense and transparent -state, when it is furthest removed from grey. - - -[1] "De Coloribus." - -[2] "De Igne." - -[3] "Trattato," &c. p. 191, the rest of the passage, it must be -admitted, abounds with absurdities. - - - -NOTE V.--Par. 555. - -The nature of vehicles or liquid mediums to combine with the substance -of colours, has been frequently discussed by modern writers on art, -and may perhaps be said to have received as much attention as it -deserves. Reynolds smiles at the notion of our not having materials -equal to those of former times, and indeed, although the methods of -individuals will always differ, there seems no reason to suppose that -any great technical secret has been lost. In these inquiries, however, -which relate merely to the mechanical causes of bright and durable -colouring, the skill of the painter in the adequate employment of the -higher resources of his art is, as if by common consent, left out of -the account, and without departing from this mode of considering the -question, we would merely repeat a conviction before expressed, viz. -that the preservation of internal brightness, a quality compatible with -various methods, has had more to do with the splendour and durability -of finely coloured pictures than any vehicle. The observations that -follow are therefore merely intended to show how far the older -written authorities on this subject agree with the results of modern -investigation, without at all assuming that the old methods, if known, -need be implicitly followed. - -On a careful examination of the earlier pictures, it is said that -a resinous substance appears to have been mingled with the colours -together with the oil; that the fracture of the indurated pigment is -shining, and that the surface resists the ordinary solvents.[1] This -admixture of resinous solutions or varnishes with the solid is not -alluded to, as far as we have seen, by any of the writers on Italian -practice, but as the method corresponds with that now prevalent in -England, the above hypothesis is not likely to be objected to for the -present. - -Various local circumstances and relations might seem to warrant the -supposition that the Venetian painters used resinous substances. An -important branch of commerce between the mountains of Friuli and Venice -still consists in the turpentine or fir-resin.[2] Similar substances -produced from various trees, and known under the common name of -balsams,[3] were imported from the East through Venice, for general -use, before the American balsams[4] in some degree superseded them; -and a Venetian painter, Marco Boschini, in his description of the -Archipelago, does not omit to speak of the abundance of mastic produced -in the island of Scio.[5] - -The testimonies, direct or indirect, against the employment of any -such substances by the Venetian painters, in the solid part of their -work, seem, notwithstanding, very conclusive; we begin with the writer -just named. In his principal composition, a poem[6] describing the -practice and the productions of the Venetian painters, Boschini speaks -of certain colours which they shunned, and adds:--"In like manner -(they avoided) shining liquids and varnishes, which I should rather -call lackers;[7] for the surface of flesh, if natural and unadorned, -assuredly does not shine, nature speaks as to this plainly." After -alluding to the possible alteration of this natural appearance by -means of cosmetics, he continues: "Foreign artists set such great -store by these varnishes, that a shining surface seems to them the -only desirable quality in art. What trash it is they prize! fir-resin, -mastic, and sandarach, and larch-resin (not to say treacle), stuff fit -to polish boots.[8] If those great painters of ours had to represent -armour, a gold vase, a mirror, or anything of the kind, they made it -shine with (simple) colours."[9] - -This writer so frequently alludes to the Flemish painters, of whose -great reputation he sometimes seems jealous, that the above strong -expression of opinion may have been pointed at them. On the other hand -it is to be observed that the term _forestieri_, strangers, does not -necessarily mean transalpine foreigners, but includes those Italians -who were not of the Venetian state.[10] The directions given by -Raphael Borghini,[11] and after him by Armenini,[12] respecting the use -and preparation of varnishes made from the very materials in question, -may thus have been comprehended in the censure, especially as some of -these recipes were copied and republished in Venice by Bisagno,[13] in -1642--that is, only six years before Boschini's poem appeared. - -Ridolfi's Lives of the Venetian Painters[14] (1648) may be mentioned -with the two last. His only observation respecting the vehicle is, that -Giovanni Bellini, after introducing himself by an artifice into the -painting-room of Antonello da Messina, saw that painter dip his brush -from time to time in linseed oil. This story, related about two hundred -years after the supposed event, is certainly not to be adduced as very -striking evidence in any way.[15] - -Among the next writers, in order of time prior to Bisagno, may be -mentioned Canepario[16] (1619). His work, "De Atramentis" contains -a variety of recipes for different purposes: one chapter, _De -atramentis diversicoloribus_, has a more direct reference to painting. -His observations under this head are by no means confined to the -preparation of transparent colours, but he says little on the subject -of varnishes. After describing a mode of preserving white of egg, -he says, "Others are accustomed to mix colours in liquid varnish and -linseed, or nut-oil; for a liquid and oily varnish binds the (different -layers of) colours better together, and thus forms a very fit glazing -material."[17] On the subject of oils he observes, that linseed oil was -in great request among painters; who, however, were of opinion that -nut-oil-excelled it "in giving brilliancy to pictures, in preserving -them better, and in rendering the colours more vivid."[18] - -Lomazzo (a Milanese) says nothing on the subject of vehicles in his -principal work, but in his "Idea del Tempio della Pittura,"[19] he -speaks of grinding the colours "in nut-oil, and spike-oil, and other -things," the "and" here evidently means _or_, and by "other things" we -are perhaps to understand other oils, poppy oil, drying oils, &c. - -The directions of Raphael Borghini and Vasari[20] cannot certainly be -considered conclusive as to the practice of the Venetians, but they are -very clear on the subject of varnish. These writers may be considered -the earliest Italian authorities who have entered much into practical -methods. In the few observations on the subject of vehicles in Leonardo -da Vinci's treatise, "there is nothing," as M. Merimée observes, "to -show that he was in the habit of mixing varnish with his colours." -Cennini says but little on the subject of oil-painting; Leon Battista -Alberti is theoretical rather than practical, and the published -extracts of Lorenzo Ghiberti's MS. chiefly relate to sculpture. - -Borghini and Vasari agree in recommending nut-oil in preference to -linseed-oil; both recommend adding varnish to the colours in painting -on walls in oil, "because the work does not then require to be -varnished afterwards," but in the ordinary modes of painting on panel -or cloth, the varnish is omitted. Borghini expressly says, that oil -alone (senza più) is to be employed; he also recommends a very sparing -use of it. - -The treatise of Armenini (1587) was published at Ravenna, and he -himself was of Faenza, so that his authority, again, cannot be -considered decisive as to the Venetian practice. After all, he -recommends the addition of "common varnish" only for the ground or -preparation, as a consolidating medium, for the glazing colours, -and for those dark pigments which are slow in drying. Many of his -directions are copied from the writers last named; the recipes for -varnishes, in particular, are to be found in Borghini. Christoforo -Sorte[21] (1580) briefly alludes to the subject in question. After -speaking of the methods of distemper, he observes that the same colours -may be used in oil, except that instead of mixing them with size, they -are mixed on the palette with nut-oil, or (if slow in drying) with -boiled linseed-oil: he does not mention varnish. The Italian writers -next in order are earlier than Vasari, and may therefore be considered -original, but they are all very concise. - -The treatise of Michael Angelo Biondo[22] (1549), remarkable for -its historical mistakes, is not without interest in other respects. -The list of colours he gives is, in all probability, a catalogue of -those in general use in Venice at the period he wrote. With regard -to the vehicle, he merely mentions oil and size as the mediums for -the two distinct methods of oil-painting and distemper, and does not -speak of varnish. The passages in the Dialogue of Doni[23] (1549), -which relate to the subject in question, are to the same effect. "In -colouring in oil," he observes, "the most brilliant colours (that we -see in pictures) are prepared by merely mixing them with the end of a -knife on the palette." Speaking of the perishable nature of works in -oil-painting as compared with sculpture, he says, that the plaster of -Paris (gesso) and mastic, with other ingredients of which the ground -is prepared, are liable to decay, &c.; and elsewhere, in comparing -painting in general with mosaic, that in the former the colours "must -of necessity be mixed with various things, such as oils, gums, white -or yolk of egg, and juice of figs, all which tend to impair the beauty -of the tints." This catalogue of vehicles is derived from all kinds of -painting to enforce the argument, and is by no means to be understood -as belonging to one and the same method. - -An interesting little work,[24] still in the form of a dialogue (Fabio -and Lauro), appeared a year earlier; the author, Paolo Pino, was a -Venetian painter. In speaking of the practical methods Fabio observes, -as usual, that oil-painting is of all modes of imitation the most -perfect, but his reasons for this opinion seem to have a reference -to the Venetian practice of going over the work repeatedly. Lauro -asks whether it is not possible to paint in oil on the dry wall, as -Sebastian del Piombo did. Fabio answers, "the work cannot last, for the -solidity of the plaster is impenetrable, and the colours, whether in -oil or distemper, cannot pass the surface." This might seem to warrant -the inference that absorbent grounds were prepared for oil-painting, -but there are proofs enough that resins as well as oil were used with -the _gesso_ to make the preparation compact. See Doni, Armenini, &c. -This writer, again, does not speak of varnish. These appear to be the -chief Venetian and Italian authorities[25] of the sixteenth and part of -the following century; and although Boschini wrote latest, he appears -to have had his information from good sources, and more than once -distinctly quotes Palma Giovane. - -In all these instances it will be seen that there is no allusion to the -immixture of varnishes with the solid colours, except in painting on -walls in oil, and that the processes of distemper and oil are always -considered as separate arts.[26] On the other hand, the prohibition -of Boschini cannot be understood to be universal, for it is quite -certain that the Venetians varnished their pictures when done.[27] -After Titian had finished his whole-length portrait of Pope Paul III. -it was placed in the sun to be varnished.[28] Again, in the archives of -the church of S. Niccolo at Treviso a sum is noted (Sept. 21, 1521 ), -"per far la vernise da invernisar la Pala dell' altar grando," and the -same day a second entry appears of a payment to a painter, "per esser -venuto a dar la vernise alla Pala," &c.[29] It is to be observed that -in both these cases the pictures were varnished as soon as done;[30] -the varnish employed was perhaps the thin compound of naphtha (oglio di -sasso) and melted turpentine (oglio d'abezzo), described by Borghini, -and after him by Armenini: the last-named writer remarks that he had -seen this varnish used by the best painters in Lombardy, and had heard -that it was preferred by Correggio. The consequence of this immediate -varnishing may have been that the warm resinous liquid, whatever it -was, became united with the colours, and thus at a future time the -pigment may have acquired a consistency capable of resisting the -ordinary solvents. Not only was the surface of the picture required to -be warm, but the varnish was applied soon after it was taken from the -fire.[31] - -Many of the treatises above quoted contain directions for making the -colours dry:[32] some of these recipes, and many in addition, are to be -found in Palomino, who, however defective as an historian,[33] has left -very copious practical details, evidently of ancient date. His drying -recipes are numerous, and although sugar of lead does not appear, -cardenillo (verdigris), which is perhaps as objectionable, is admitted -to be the best of all dryers. It may excite some surprise that the -Spanish painters should have bestowed so much attention on this subject -in a climate like theirs, but the rapidity of their execution must have -often required such an assistance.[34] - -One circumstance alluded to by Palomino, in his very minute practical -directions, deserves to be mentioned. After saying what colours should -be preserved in their saucers under water, and what colours should be -merely covered with oiled paper because the water injures them, he -proceeds to communicate "a curious mode of preserving oil-colours," and -of transporting them from place to place. The important secret is to -tie them in bladders, the mode of doing which he enters into with great -minuteness, as if the invention was recent. It is true, Christoforo -Sorte, in describing his practice in water-colour drawing, says he was -in the habit of preserving a certain vegetable green with gum-water in -a bladder; but as the method was obviously new to Palomino, there seems -sufficient reason to believe that oil-colours, when once ground, had, -up to his time, been kept in saucers and preserved under water.[35] -Among the items of expense in the Treviso document before alluded to, -we find "a pan and saucers for the painters."[36] This is in accordance -with Cennini's directions, and the same system appears to have been -followed till after 1700.[37] - -The Flemish accounts of the early practice of oil-painting are all -later than Vasari. Van Mander, in correcting the Italian historian in -his dates, still follows his narrative in other respects verbatim. If -Vasari's story is to be accepted as true, it might be inferred that -the Flemish secret consisted in an oil varnish like copal.[38] Vasari -says, that Van Eyck boiled the oils with other ingredients; that the -colours, when mixed with this kind of oil, had a very firm consistence; -that the surface of the pictures so executed had a lustre, so that they -needed no varnish when done; and that the colours were in no danger -from water.[39] - -Certain colours, as is well known, if mixed with oil alone, may be -washed off after a considerable time. Leonardo da Vinci remarks, that -verdigris may be thus removed. Carmine, Palomino observes, may be -washed off after six years. It is on this account the Italian writers -recommend the use of varnish with certain colours, and it appears the -Venetians, and perhaps the Italians generally, employed it solely in -such cases. But it is somewhat extraordinary that Vasari should teach -a mode of painting in oil so different in its results (inasmuch as the -work thus required varnish at last) from the Flemish method which he so -much extols--a method which he says the Italians long endeavoured to -find out in vain. If they knew it, it is evident, assuming his account -to be correct, that they did not practice it. - - -[1] See "Marcucci Saggio Analitico-chimico sopra i colori," &c. Rome, -1816, and "Taylor's Translation of Merimée on Oil-painting," London, -1839. The last-named work contains much useful information. - -[2] Italian writers of the 16th century speak of three kinds. Cardanus -says, that of the _abies_ was esteemed most, that of the _larix_ next, -and that of the _picea_ least. The resin extracted by incision from -the last (the pinus abies Linnæi) is known by the name of Burgundy -pitch; when extracted by fire it is black. The three varieties occur -in Italian treatises on art, under the names of _oglio di abezzo_, -_trementina_ and _pece Greca_. - -[3] The concrete balsam _benzoe_, called by the Italians _beluzino_, -and _belzoino_, is sometimes spoken of as a varnish. - -[4] Marcucci supposes that balsam of copaiba was mixed with the -pigments by the (later) Venetians. - -[5] "L'Archipelago con tutte le Isole," Ven. 1658. The incidental -notices of the remains of antiquity in this work would be curious and -important if they could be relied on. In describing the island of -Samos, for instance, the author asserts that the temple of Juno was in -tolerable preservation, and that the statue was still there. - -[6] "La Carta del Navegar Pitoresco," Ven. 1660. It is in the Venetian -dialect. - -[7] Inveriadure (invetriature), literally the glazing applied to -earthenware. - -[8] - - "O de che strazze se fan cavedal! - D'ogio d'avezzo, mastici e sandraca; - E trementina (per no'dir triaca) - Robe, che ilustrerave ogni stival."--p. 338. - -The alliteration of the words _trementina_ and _triaca_ is of course -lost in a translation. - -[9] "I li ha fati straluser co' i colori." Boschini was at least -constant in his opinion. In the second edition of his "Ricche Minere -della Pittura Veneziana," which appeared fourteen years after the -publication of his poem, he repeats that the Venetian painters avoided -some colours in flesh "e similmente i lustri e le vernici." - -[10] Thus, in the introduction to the "Ricche Minere," Boschini calls -the Milanese, Florentine, Lombard, and Bolognese painters, _forestieri_. - -[11] "Il Riposo," Firenze, 1584. - -[12] "De' Veri Precetti della Pittura," Ravenna, 1587. - -[13] "Trattato della Pittura fondato nell' autorità di molti eccellenti -in questa professione." Venezia, 1642. Bisagno remarks in his preface, -that the books on art were few, and that painters were in the habit of -keeping them secret. He acknowledges that he has availed himself of the -labours of others, but without mentioning his sources: some passages -are copied from Lomazzo. He, however, lays claim to some original -observations, and says he had seen much and discoursed with many -excellent painters. - -[14] "Le Meraviglie dell' Arte," Venezia, 1648. - -[15] It has been conjectured by some that this story proved the -immixture of varnishes with the colours, and that the oil was only used -to dilute them. The epitaph on Antonello da Messina which existed in -Vasari's time, alludes to his having mixed the colours with oil. - -[16] "Petri Mariæ Caneparii De Atramentis cujuscumque generis," Venet. -1619. It was republished at Rotterdam in 1718. - -[17] "Ita quod magis ex hiis evadit atramentum picturæ summopere -idoneum." Thus, if _atramentum_ is to be understood, as usual, to -mean a glazing colour, the passage can only refer to the immixture of -varnish with the transparent colours applied last in order. - -[18] In a passage that follows respecting the mode of extracting -nut-oil, Caneparius appears to mistranslate Galen, c. 7--"De Simplicium -Medicamentorum facultatibus." The observations of Galen on this -subject, and on the drying property of linseed, may have given the -first hint to the inventors of oil-painting. The custom of dating -the origin of this art from Van Eyck is like that of dating the -commencement of modern painting from Cimabue. The improver is often -assumed to be the inventor. - -[19] Milan, 1590. - -[20] The particulars here alluded to are to be found in the first -edition of Vasari (1550) as well as the second.--v. i. c. 21, &c. - -[21] "Osservasioni nella Pittura." In Venezia, 1580. Sorte, who, it -appears, was a native of Verona, had worked in his youth with Giulio -Romano, at Mantua, and communicates the methods taught him by that -painter, for giving the true effects of perspective in compositions -of figures. He is, perhaps, the earliest who describes the process of -water-colour painting as distinguished from distemper and as adapted to -landscape, if the art he describes deserves the name. - -[22] "Della nobilissima Pittura e sua Arte," Venezia, 1549. Biondo is -so ignorant as to attribute the Last Supper, by Leonardo da Vinci, to -Mantegna. - -[23] "Disegno del Doni," in Venezia, 1549. - -[24] "Dialogo di Pittura," Venezia, 1548. Pino, in enumerating the -celebrated contemporary artists, does not include Paul Veronese, for a -very obvious reason, that painter being at the time only about 17 years -of age. Sorte, who wrote thirty years later, mentions "l'eccellente -Messer Paulino nostro," alone. - -[25] The Dialogues of Lodovico Dolce, and various other works, are not -referred to here, as they contain nothing on the subject in question. -The latest authority at all connected with the traditions of Venetian -practice, is a certain Giambatista Volpato, of Bassano: he died in -1706, and had been intimate with Ridolfi. The only circumstance he -has transmitted relating to practical details is that Giacomo Bassan, -in retouching on a dry surface, sometimes adopted a method commonly -practised, he says, by Paul Veronese (and commonly practised still), -namely, that of dipping his brush in spirits of turpentine; at other -times he oiled out the surface in the usual manner. Volpato left a MS. -which was announced for publication in Vicenza in 1685, but it never -appeared; it, however, afterwards formed the ground-work of Verci's -"Notizie intorno alla Vita e alle Opere de' Pittori di Bassano." -Venezia, 1775. See also "Lettera di Giambatista Roberti sopra Giacomo -da Ponte," Lugano, 1777. Another MS. by Natale Melchiori, of about the -same date, is preserved at Treviso and Castel Franco: it abounds with -historical mistakes; the author says, for instance, that the Pietro -Martyre was begun by Giorgione and finished by Titian. The recipes for -varnishes and colours are very numerous, but they are mostly copied -from earlier works. - -[26] That distemper was not very highly esteemed by the Venetians -may be inferred from the following observation of Pino:--"Il modo di -colorir à guazzo è imperfetto et più fragile et à me non diletta onde -lasciamolo all' oltremontani i quali sono privi della vera via." It is, -however, certain that the Venetians sometimes painted in this style, -and Volpato mentions several works of the kind by Bassan, but he never -hints that he began his oil pictures in distemper. - -[27] Boschini says, that the Venetians (he especially means Titian) -rendered their pictures sparkling by finally touching on a dry -surface (_à secco_). The absence of varnish in the solid colours, the -retouching with spirit of turpentine, and even _à secco_, all suppose a -dull surface, which would require varnish. The latter method, alluded -to by Boschini, was an exception to the general practice, and not -likely to be followed on account of its difficulty. Carlo Maratti, on -the authority of Palomino, used to say, "He must be a skilful painter -who can retouch without oiling out." - -[28] See a letter by Francesco Bocchi, and another by Vasari, in -the "Lettere Pittoriche" of Bottari. The circumstance is mentioned -incidentally; the point chiefly dwelt on is, that some persons who -passed were deceived, and bowed to the picture, supposing it to be the -pope. - -[29] Federici, "Memorie Trevigiane," Venezia, 1803. The altar-piece of -S. Niccolo at Treviso is attributed, in the document alluded to, to -Fra Marco Pensabene, a name unknown; the painting is so excellent as -to have been thought worthy of Sebastian del Piombo: for this opinion, -however, there are no historical grounds. It was begun in 1520, but -before it was quite finished the painter, whoever he was, absconded: it -was therefore completed by another. - -[30] Titian's stay in Rome was short, and with respect to the Treviso -altar-piece, a week or two only, at most, can have elapsed between the -completion and the varnishing. Cennini, who recommends delaying a year -at least before varnishing, speaks of pictures in distemper. - -[31] See Borghini, Armenini, their Venetian copyist Bisagno, and -Palomino. The last-named writer, though of another school and much -more modern, was evidently well acquainted with the ancient methods: -he says, "Se advierte que siempre que se huviere de barnizar alguna -cosa conviene que la pintura y el barniz estèn calientes."--_El Museo -Pictorico_, v. ii. - -[32] Burnt alum, one of the ingredients recommended, might perhaps -account for a shining fracture in the indurated pigment in some old -pictures. - -[33] Of the earlier Spanish writers Pacheco may be mentioned next to -Palomino as containing most practical information. Carducho, De Butron, -and others, seldom descend to such details. Palomino contains all the -directions of Pacheco, and many in addition. - -[34] See Cean Bermudez, "Sobre la Escuela Sevillana," Cadiz, 1806. The -same reasons induced the later Venetian machinists to paint on dark -grounds, and to make use of (drying) oil in excess. See Zanetti, _Della -Pittura Veneziana_, 1. iv. - -[35] Borghini, in describing the method of making a gold-size (the -same as Cennini's), speaks of boiling the "buccie de' colori" in oil; -this only means the skin or pellicle of the colour itself--in fact, he -proceeds to say that they dissolve in boiling. Vasari, in describing -the same process, uses the expression "colori seccaticci." - -[36] "Maggio 4 (1520) Per un cadin (catino) per depentori. Per -scudellini per li depentori."--_Mem. Trev._, vol. i. p. 131. Pungileoni -("Memorie Istoriche di Antonio Allegri") quotes a note of expenses -relating to two oil-pictures by Paolo Gianotti; among the items we find -"colori, telari, et brocchette."--vol. ii. p. 75. - -[37] Salmon, in his "Polygraphice" (1701), gives the following -direction:--"Oyl colors, if not presently used, will have a skin grow -over them, to prevent which put them into a glass, and put the glass -three or four inches under water," &c. - -[38] This varnish appears to have been known some centuries before Van -Eyck's time, but he may have been the first to mix it with the colours. - -[39] See Vasari, Life of Antonello da Messina. - - - -NOTE W.--Par. 608. - -In the second volume Goethe gives the nomenclature of the Greeks and -Romans at some length. The general notions of the ancients with regard -to colours are thus described:--"The ancients derive all colours from -white and black, from light and darkness. They say, all colours are -between white and black, and are mixed out of these. We must not, -however, suppose that they understand by this a mere atomic mixture, -although they occasionally use the word μίξις;[1] for in the remarkable -passages, where they wish to express a kind of reciprocal (dynamic) -action of the two contrasting principles, they employ the words κρᾶσις, -union, σύγκρισις, combination; thus, again, the mutual influence of -light and darkness, and of colours among each other, is described by -the word κεράννυστας, an expression of similar import. - -"The varieties of colours are differently enumerated; some mention -seven, others twelve, but without giving the complete list. From a -consideration of the terminology both of the Greeks and Romans, it -appears that they sometimes employed general for specific terms, and -_vice versâ_. - -"Their denominations of colours are not permanently and precisely -defined, but mutable and fluctuating, for they are employed even with -regard to similar colours both on the _plus_ and _minus_ side. Their -yellow, on the one hand, inclines to red, on the other to blue; the -blue is sometimes green, sometimes red; the red is at one time yellow, -at another blue. Pure red (purpur) fluctuates between warm red and -blue, sometimes inclining to scarlet, sometimes to violet. - -"Thus the ancients not only seem to have looked upon colour as a -mutable and fleeting quality, but appear to have had a presentiment of -the (physical and chemical) effects of augmentation and re-action. In -speaking of colours they make use of expressions which indicate this -knowledge; they make yellow redden, because its augmentation tends to -red; they make red become yellow, for it often returns thus to its -origin. - -"The hues thus specified undergo new modifications. The colours -arrested at a given point are attenuated by a stronger light darkened -by a shadow, nay, deepened and condensed in themselves. For the -gradations which thus arise the name of the species only is often -given, but the more generic terms are also employed. Every colour, of -whatever kind, can, according to the same view, be multiplied into -itself, condensed, enriched, and will in consequence appear more or -less dark. The ancients called colour in this state," &c. Then follow -the designations of general states of colour and those of specific hues. - -Another essay on the notions of the ancients respecting the origin -and nature of colour generally, shows how nearly Goethe himself has -followed in the same track. The dilating effect of light objects, -the action and reaction of the retina, the coloured after-image, the -general law of contrast, the effect of semi-transparent mediums in -producing warm or cold colours as they are interposed before a dark or -light background--all this is either distinctly expressed or hinted -at; "but," continues Goethe, "how a single element divides itself into -two, remained a secret for them. They knew the nature of the magnet, -in amber, only as attraction; polarity was not yet distinctly evident -to them. And in very modern times have we not found that scientific -men have still given their almost exclusive attention to attraction, -and considered the immediately excited repulsion only as a mere -after-action?" - -An essay on the Painting of the Ancients[2] was contributed by Heinrich -Meyer. - - -[1] See Note on Par. 177. - -[2] Vol. ii. p. 69, first edition. - - - -NOTE X.--Par. 670. - -This agrees with the general recommendation so often given by high -authorities in art, to avoid a tinted look in the colour of flesh. The -great example of Rubens, whose practice was sometimes an exception -to this, may however show that no rule of art is to be blindly or -exclusively adhered to. Reynolds, nevertheless, in the midst of his -admiration for this great painter, considered the example dangerous, -and more than once expresses himself to this effect, observing on one -occasion that Rubens, like Baroccio, is sometimes open to the criticism -made on an ancient painter, namely, that his figures looked as if they -fed on roses. - -Lodovico Dolce, who is supposed to have given the _vivâ voce_ precepts -of Titian in his Dialogue,[1] makes Aretino say: "I would generally -banish from my pictures those vermilion cheeks with coral lips; for -faces thus treated look like masks. Propertius, reproving his Cynthia -for using cosmetics, desires that her complexion might exhibit the -simplicity and purity of colour which is seen in the works of Apelles." - -Those who have written on the practice of painting have always -recommended the use of few colours for flesh. Reynolds and others quote -even ancient authorities as recorded by Pliny, and Boschini gives -several descriptions of the method of the Venetians, and particularly -of Titian, to the same effect. "They used," he says, "earths more than -any other colour, and at the utmost only added a little vermilion, -minium, and lake, abhorring as a pestilence _biadetti, gialli santi, -smaltini, verdi-azzurri, giallolini_."[2] Elsewhere he says,[3] "Earths -should be used rather than other colours:" after repeating the above -prohibited list he adds, "I speak of the imitation of flesh, for in -other things every colour is good;" again, "Our great Titian used to -say that he who wishes to be a painter should be acquainted with three -colours, white, black, and red."[4] Assuming this account to be a -little exaggerated, it is still to be observed that the monotony to -which the use of few colours would seem to tend, is prevented by the -nature of the Venetian process, which was sufficiently conformable to -Goethe's doctrine; the gradations being multiplied, and the effect -of the colours heightened by using them as semi-opaque mediums. -Immediately after the passage last quoted we read, "He also gave this -true precept, that to produce a lively colouring in flesh it is not -possible to finish at once."[5] As these particulars may not be known -to all, we add some further abridged extracts explaining the order and -methods of these different operations. - -"The Venetian painters," says this writer,[6] "after having drawn in -their subject, got in the masses with very solid colour, without making -use of nature or statues. Their great object in this stage of their -work was to distinguish the advancing and retiring portions, that the -figures might be relieved by means of chiaro-scuro--one of the most -important departments of colour and form, and indeed of invention. -Having decided on their scheme of effect, when this preparation was -dry, they consulted nature and the antique; not servilely, but with the -aid of a few lines on paper (_quattro segni in carta_) they corrected -their figures without any other model. Then returning to their brushes, -they began to paint smartly on this preparation, producing the colour -of flesh." The passage before quoted follows, stating that they used -earths chiefly, that they carefully avoided certain colours, "and -likewise varnishes and whatever produces a shining surface.[7] When -this second painting was dry, they proceeded to scumble over this or -that figure with a low tint to make the one next it come forward, -giving another, at the same time, an additional light--for example, on -a head, a hand, or a foot, thus detaching them, so to speak, from the -canvas." (Tintoret's _Prigionia di S. Rocco_ is here quoted.) "By thus -still multiplying these well-understood retouchings where required, on -the dry surface, _(à secco)_ they reduced the whole to harmony. In this -operation they took care not to cover entire figures, but rather went -on gemming them _(gioielandole)_ with vigorous touches. In the shadows, -too, they infused vigour frequently by glazing with asphaltum, always -leaving great masses in middle-tint, with many darks, in addition to -the partial glazings, and few lights." - -The introduction to the subject of Venetian colouring, in the poem by -the same author, is also worth transcribing, but as the style is quaint -and very concise, a translation is necessarily a paraphrase.[8] - -"The art of colouring has the imitation of qualities for its object; -not all qualities, but those secondary ones which are appreciable by -the sense of sight. The eye especially sees colours, the imitation -of nature in painting is therefore justly called colouring; but the -painter arrives at his end by indirect means. He gives the varieties -of tone in masses;[9] he smartly impinges lights, he clothes his -preparation with more delicate local hues, he unites, he glazes: thus -everything depends on the method, on the process. For if we look -at colour abstractedly, the most positive may be called the most -beautiful, but if we keep the end of imitation in view, this shallow -conclusion falls to the ground. The refined Venetian manner is very -different from mere direct, sedulous imitation. Every one who has -a good eye may arrive at such results, but to attain the manner of -Paolo, of Bassan, of Palma, Tintoret, or Titian, is a very different -undertaking."[10] - -The effects of semi-transparent mediums in some natural productions -seem alluded to in the following passage--"Nature sometimes -accidentally imitates figures in stones and other substances, and -although they are necessarily incomplete in form, yet the principle -of effect (depth) resembles the Venetian practice." In a passage that -follows there appears to be an allusion to the production of the -atmospheric colours by semi-transparent mediums.[11] - - -[1] "Dialogo della Pittura, intitolato l'Aretino." It was first -published at Venice in 1557; about twenty years before Titian's death. -In the dedication to the senator Loredano, Lodovico Dolce eulogises -the work, which he would hardly have done if it had been entirely his -own: again, the supposition that it may have been suggested by Aretino, -would be equally conclusive, coupled with internal evidence, as to the -original source. - -[2] Introduction to the "Ricche Minere della Pittura Veneziana," -Venezia, 1674. The Italian annotators on older works on painting are -sometimes at a loss to find modern terms equivalent to the obsolete -names of pigments. (See "Antologia dell 'Arte Pittorica.") The colours -now in use corresponding with Boschini's list, are probably yellow -lakes, smalt, verditer, and Naples yellow. Boschini often censures the -practice of other schools, and in this emphatic condemnation he seems -to have had an eye to certain precepts in Lomazzo, and perhaps, even -in Leonardo da Vinci, who, on one occasion, recommends Naples yellow, -lake, and white for flesh. The Venetian writer often speaks, too, in -no measured terms of certain Flemish pictures, probably because they -appeared to him too tinted. - -[3] "La Carta del Navegar Pitoresco," p. 338. - -[4] Ib. p. 341. In describing Titian's actual practice ("Ricche -Minere"), he, however, adds yellow (ochre). The red is also -particularised, viz., the common terra rossa. - -[5] High examples here again prove that the opposite system may attain -results quite as successful. - -[6] Introduction to the "Ricche Minere." - -[7] See Note to Par. 555. Here again, assuming the description to be -correct, high authorities might be opposed to the Venetians. - -[8] The following quatrain may serve as a specimen; the author is -speaking of the importance of the colour of flesh as conducive to -picturesque effect:-- - - "Importa el nudo; e come ben l'importa! - Un quadro senta nudo è come aponto - Un disnar senza pan, se ben ghe zonto, - Per più delicia, confetura e torta."--p. 346. - -In his preface he anticipates, and thus answers the objections to his -Venetian dialect--"Mi, che son Venetian in Venetia e che parlo de' -Pitori Venetiani hò da andarme a stravestir? Guarda el Cielo." - -[9] The word _Macchia_, literally a blot, is generally used by Italian -writers, by Vasari for instance, for the local colour. Boschini -understands by it the relative depth of tones rather than the mere -difference of hue. "By macchia," he says, "I understand that treatment -by which the figures are distinguished from each other by different -tones lighter or darker."--_La Carta del Navegar_, p. 328. Elsewhere, -"Colouring (as practised by the Venetians) comprehends both the macchia -and drawing;" (p. 300) that is, comprehends the gradations of light -and dark in objects, and the parts of objects, and consequently, their -essential form. "The macchia," he adds, "is the effect of practice, and -is dictated by the knowledge of what is requisite for effect." - -[10] - - "Ma l'arivar a la maniera, al trato - (Verbi gratia) de Paulo, del Bassan, - Del Vechio, Tentoreto, e di Tician, - Per Dio, l'è cosa da deventar mato."--p. 294, 297. - - -[11] The traces of the Aristotelian theory are quite as apparent in -Boschini as in the other Italian writers on art; but as he wrote in the -seventeenth century, his authority in this respect is only important as -an indication of the earlier prevalence of the doctrine. - - - -NOTE Y.--Par. 672. - -The author's conclusion here is unsatisfactory, for the colour of -the black races may be considered at least quite as negative as that -of Europeans. It would be safer to say that the white skin is more -beautiful than the black, because it is more capable of indications -of life, and indications of emotion. A degree of light which would -fail to exhibit the finer varieties of form on a dark surface, would -be sufficient to display them on a light one; and the delicate -mantlings of colour, whether the result of action or emotion, are more -perceptible for the same reason. - - - -NOTE Z.--Par. 690. - -The author appears to mean that a degree of brightness which the organ -can bear at all, must of necessity be removed from dazzling, white -light. The slightest tinge of colour to this brightness, implies that -it is seen through a medium, and thus, in painting, the lightest, -whitest surface should partake of the quality of depth. Goethe's view -here again accords, it must be admitted, with the practice of the best -colourists, and with the precepts of the highest authorities.--See Note -C. - - - -NOTE A A.--Par. 732. - -Ample details respecting the opinions of Louis Bertrand Castel, a -Jesuit, are given in the historical part. The coincidence of some -of his views with those of Goethe is often apparent: he objects, -for instance, to the arbitrary selection of the Newtonian spectrum; -observing that the colours change with every change of distance between -the prism and the recipient surface.--_Farbenl._ vol. ii. p. 527. -Jeremias Friedrich Gülich was a dyer in the neighbourhood of Stutgardt: -he published an elaborate work on the technical details of his own -pursuit.--_Farbenl._ vol. ii. p. 630. - - - -NOTE B B.--Par. 748. - -Goethe, in his account of Castel, suppresses the learned Jesuit's -attempt at colorific music (the claveçin oculaire), founded on the -Newtonian doctrine. Castel was complimented, perhaps ironically, on -having been the first to remark that there were but three principal -colours. In asserting his claim to the discovery, he admits that there -is nothing new. In fact, the notion of three colours is to be found in -Aristotle; for that philosopher enumerates no more in speaking of the -rainbow,[1] and Seneca calls them by their right names.[2] Compare with -Dante, Parad. c. 33. The relation between colours and sounds is in like -manner adverted to by Aristotle; he says--"It is possible that colours -may stand in relation to each other in the same manner as concords -in music, for the colours which are (to each other) in proportions -corresponding with the musical concords, are those which appear to -be the most agreeable."[3] In the latter part of the 16th century, -Arcimboldo, a Milanese painter, invented a colorific music; an account -of his principles and method will be found in a treatise on painting -which appeared about the same time. "Ammaestrato dal quai ordine Mauro -Cremonese dalla viola, musico dell' Imperadore Ridolfo II. trovò sul -gravicembalo tutte quelle consonanze che dall' Arcimboldo erano segnate -coi colori sopra una carta."[4] - -[1] "De Meteor.," lib. 3, c. ii. and iv. He observes that this is the -only effect of colour which painters cannot imitate. - -[2] "De Ignib. cœlest." The description of the prism by Seneca is -another instance of the truth of Castel's admission. The Roman -philosopher's words are--"Virgula solet fieri vitrea, stricta vel -pluribus angulis in modo clavæ tortuosæ; hæc si ex transverso solem -accipit colorem talem qualis in arcu videri solet, reddit," &c. - -[3] "De Sensu et sensili." - -[4] "Il Figino, overo del Fine della Pittura," Mantova, 1591, p. 249. -An account of the absurd invention of the same painter in composing -figures of flowers and animals, and even painting portraits in this -way, to the great delight of the emperor, will be found in the same -work. - - - -NOTE C C.--Par. 758. - -The moral associations of colours have always been a more favourite -subject with poets than with painters. This is to be traced to the -materials and means of description as distinguished from those of -representation. An image is more distinct for the mind when it is -compared with something that resembles it. An object is more distinct -for the eye when it is compared with something that differs from it. -Association is the auxiliary in the one case, contrast in the other. -The poet, of necessity, succeeds best in conveying the impression -of external things by the aid of analogous rather than of opposite -qualities: so far from losing their effect by this means, the images -gain in distinctness. Comparisons that are utterly false and groundless -never strike us as such if the great end is accomplished of placing -the thing described more vividly before the imagination. In the common -language of laudatory description the colour of flesh is like snow -mixed with vermilion: these are the words used by Aretino in one of -his letters in speaking of a figure of St. John, by Titian. Similar -instances without end might be quoted from poets: even a contrast can -only be strongly conveyed in description by another contrast that -resembles it.[1] On the other hand it would be easy to show that -whenever poets have attempted the painter's method of direct contrast, -the image has failed to be striking, for the mind's eye cannot see the -relation between two colours. - -Under the same category of effect produced by association may be -classed the moral qualities in which poets have judiciously taken -refuge when describing visible forms and colours, to avoid competition -with the painters' elements, or rather to attain their end more -completely. But a little examination would show that very pleasing -moral associations may be connected with colours which would be far -from agreeable to the eye. All light, positive colours, light-green, -light-purple, white, are pleasing to the mind's eye, and no degree -of dazzling splendour is offensive. The moment, however, we have to -do with the actual sense of vision, the susceptibility of the eye -itself is to be considered, the law of comparison is reversed, colours -become striking by being opposed to what they are not, and their moral -associations are not owing to the colours themselves, but to the -modifications such colours undergo in consequence of what surrounds -them. This view, so naturally consequent on the principles the author -has himself arrived at, appears to be overlooked in the chapter under -consideration, the remarks in which, in other respects, are acute and -ingenious. - - -[1] Such as-- - - "Her beauty hangs upon the cheek of night, - Like a rich jewel in an Ethiop's ear." - _Romeo and Juliet_. - - - - -NOTE D D.--Par. 849. - -According to the usual acceptation of the term chiaro-scuro in the -artist world, it means not only the mutable effects produced by light -and shade, but also the permanent differences in brightness and -darkness which are owing to the varieties of local colour. - - - -NOTE E E.--Par. 855. - -The mannered treatment of light and shade here alluded to by the -author is very seldom to be met with in the works of the colourists; -the taste may have first arisen from the use of plaster-casts, and -was most prevalent in France and Italy in the early part of the last -century. Piazzetta represented it in Venice, Subleyras in Rome. In -France "Restout taught his pupils that a globe ought to be represented -as a polyhedron. Greuze most implicitly adopted the doctrine, and in -practice showed that he considered the round cheeks of a young girl or -an infant as bodies cut into facettes."[1] - - -[1] See Taylor's translation of Merimée on oil-painting, p. 27. -Barry, in a letter from Paris, speaks of Restout as the only painter -who resembled the earlier French masters: the manner in question is -undoubtedly sometimes very observable in Poussin. The English artist -elsewhere speaks of the "broad, happy manner of Subleyras."--_Works_, -London, 1809. - - - -NOTE F F.--Par. 859. - -All this was no doubt suggested by Heinrich Meyer, whose chief -occupation in Rome, at one time, was making sepia drawings from -sculpture (see Goethe's Italiänische Reise). It is hardly necessary to -say that the observation respecting the treatment of the surface in the -antique statues is very fanciful. - - - -NOTE G G.--Par. 863. - -This observation might have been suggested by the drawings of Claude, -which, with the slightest means, exhibit an harmonious balance of warm -and cold. - - - -NOTE H H.--Par. 865. - -The colouring of Paolo Uccello, according to Vasari's account of him, -was occasionally so remarkable that he might perhaps have been fairly -included among the instances of defective vision given by the author. -His skill in perspective, indicating an eye for gradation, may be also -reckoned among the points of resemblance (see Par. 105). - - - -NOTE I I.--Par. 902. - -The quotation before given from Boschini shows that the method -described by the author, and which is true with regard to some of the -Florentine painters, was not practised by the Venetians, for their -first painting was very solid. It agrees, however, with the manner -of Rubens, many of whose works sufficiently corroborate the account -of his process given by Descamps. "In the early state of Rubens's -pictures," says that writer,[1] "everything appeared like a thin wash; -but although he often made use of the ground in producing his tones, -the canvas was entirely covered more or less with colour." In this -system of leaving the shadows transparent from the first, with the -ground shining through them, it would have been obviously destructive -of richness to use white mixed with the darks, the brightness, in -fact, already existed underneath. Hence the well-known precept of -Rubens to avoid white in the shadows, a precept, like many others, -belonging to a particular practice, and involving all the conditions of -that practice.[2] Scarmiglione, whose Aristotelian treatise on colour -was published in Germany when Rubens was three-and-twenty, observes, -"Painters, with consummate art, lock up the bright colours with dark -ones, and, on the other hand, employ white, the poison of a picture, -very sparingly." (Artificiosissimè pictores claros obscuris obsepiant -et contra candido picturarum veneno summè parcentes, &c.) - - -[1] "La Vie des Peintres Flamands," vol. i. - -[2] The method he recommended for keeping the colours pure in the -lights, viz. to place the tints next each other unmixed, and then -slightly to unite them, may have degenerated to a methodical manner -in the hands of his followers. Boschini, who speaks of Rubens himself -with due reverence, and is far from confounding him with his imitators, -contrasts such a system with that of the Venetians, and adds that -Titian used to say, "Chi de imbratar colori teme, imbrata e machia -si medemi."--_Carta del Navegar_, p. 341. The poem of Boschini is in -many respects polemical. He wrote at a time when the Flemish painters, -having adopted and modified the Venetian principles, threatened to -supersede the Italian masters in the opinion of the world. Their -excellence, too, had all the charm of novelty, for in the seventeenth -century Venice produced no remarkable talent, and it was precisely -the age for her to boast of past glories. The contemptuous manner in -which Boschini speaks of the Flemish varnishes, of the fear of mixing -tints, &c., is thus always to be considered with reference to the time -and circumstances. So also his boasting that the Venetian masters -painted without nature, which may be an exaggeration, is pointed at -the _Naturalisti_, Caravaggio and his followers, who copied nature -literally. - - - -NOTE K K.--Par. 903. - -The practice here alluded to is more frequently observable in slight -works by Paul Veronese. His ground was often pure white, and in some -of his works it is left as such. Titian's white ground was covered -with a light warm colour, probably at first, and appears to have -been similar to that to which Armenini gives the preference, namely, -"quella che tira al color di carne chiarissima con un non so che di -fiammeggiante."[1] - - -[1] "Veri Precetti della Pittura," p. 123. - - -NOTE L L.--Par. 919. - -The notion which the author has here ventured to express may have -been suggested by the remarkable passage in the last canto of Dante's -"Paradiso"-- - - "Nella profonda e chiara sussistenza, - Dell' alto lume parremi tre giri - Di tre colori e d'una continenza," &c. - -After the concluding paragraph the author inserts a letter from a -landscape-painter, Philipp Otto Runge, which is intended to show that -those who imitate nature may arrive at principles analogous to those of -the "Farbenlehre." - - -THE END. - - - - - -End of the Project Gutenberg EBook of Goethe's Theory of Colours, by -Johann, Wolfgang von Goethe - -*** END OF THIS PROJECT GUTENBERG EBOOK GOETHE'S THEORY OF COLOURS *** - -***** This file should be named 50572-0.txt or 50572-0.zip ***** -This and all associated files of various formats will be found in: - http://www.gutenberg.org/5/0/5/7/50572/ - -Produced by Annemie Arnst, Clare Graham & Marc D'Hooghe -at http://.freeliterature.org (Images generously made -available by the Internet Archive.) - -Updated editions will replace the previous one--the old editions will -be renamed. - -Creating the works from print editions not protected by U.S. copyright -law means that no one owns a United States copyright in these works, -so the Foundation (and you!) can copy and distribute it in the United -States without permission and without paying copyright -royalties. 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If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: Goethe's Theory of Colours - -Author: Johann, Wolfgang von Goethe - -Translator: Charles Lock Eastlake - -Release Date: November 29, 2015 [EBook #50572] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK GOETHE'S THEORY OF COLOURS *** - - - - -Produced by Annemie Arnst, Clare Graham & Marc D'Hooghe -at http://.freeliterature.org (Images generously made -available by the Internet Archive.) - - - - - - -</pre> - -<div class="figcenter" style="width: 500px;"> -<img src="images/cover.jpg" width="500" alt="" /> -</div> - -<h2>GOETHE'S</h2> - -<h1>THEORY OF COLOURS;</h1> - -<h4>TRANSLATED FROM THE GERMAN:</h4> - -<h4>WITH NOTES BY</h4> - -<h4>CHARLES LOCK EASTLAKE, R.A., F.R.S.</h4> - -<hr class="r5" /> -<blockquote> - -<p>"Cicero varietatem propriè in coloribus nasci, hinc in -alienum migrare existimavit. Certè non alibi natura -copiosius aut majore lasciviâ opes suas commendavit. -Metalla, gemmas, marmora, flores, astra, omnia denique quæ -progenuit suis etiam coloribus distinxit; ut venia debeatur -si quis in tam numerosâ rerum sylvâ caligaverit."</p> - -<p style="margin-left: 65%; font-size: 0.8em;">CELIO CALCAGNINI.</p></blockquote> -<hr class="r5" /> -<h5>LONDON:</h5> - -<h5>JOHN MURRAY, ALBEMARLE STREET.</h5> - -<h5>1840</h5> - - - - -<hr class="chap" /> -<h5><a name="TO" id="TO">TO</a></h5> - -<h4>JEREMIAH HARMAN, Esq.</h4> - -<blockquote> - -<p style="margin-left: 10%;">Dear Sir,</p> - -<p style="margin-left: 10%;">I dedicate to you the following translation as a testimony -of my sincere gratitude and respect; in doing so, I but -follow the example of Portius, an Italian writer, who -inscribed his translation of Aristotle's Treatise on Colours -to one of the Medici.</p> - -<p style="margin-left: 40%;">I have the honour to be,</p> - -<p style="margin-left: 45%;">Dear Sir,</p> - -<p style="margin-left: 30%;">Your most obliged and obedient Servant,</p> - -<p style="margin-left: 65%; font-size: 0.8em;">C. L. EASTLAKE.</p></blockquote> - - - -<hr class="chap" /> -<h4><a name="THE_TRANSLATORS_PREFACE" id="THE_TRANSLATORS_PREFACE">THE TRANSLATOR'S PREFACE.</a></h4> - - -<p>English writers who have spoken of Goethe's "Doctrine of Colours,"<a name="FNanchor_1_1" id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">[1]</a> -have generally confined their remarks to those parts of the work in -which he has undertaken to account for the colours of the prismatic -spectrum, and of refraction altogether, on principles different -from the received theory of Newton. The less questionable merits -of the treatise consisting of a well-arranged mass of observations -and experiments, many of which are important and interesting, have -thus been in a great measure overlooked. The translator, aware of -the opposition which the theoretical views alluded to have met with, -intended at first to make a selection of such of the experiments as -seem more directly applicable to the theory and practice of painting. -Finding, however, that the alterations this would have involved would -have been incompatible with a clear and connected view of the author's -statements, he preferred giving the theory itself entire, reflecting, -at the same time, that some scientific readers may be curious to hear -the author speak for himself even on the points at issue.</p> - -<p>In reviewing the history and progress of his opinions and researches, -Goethe tells us that he first submitted his views to the public -in two short essays entitled "Contributions to Optics." Among the -circumstances which he supposes were unfavourable to him on that -occasion, he mentions the choice of his title, observing that by a -reference to optics he must have appeared to make pretensions to a -knowledge of mathematics, a science with which he admits he was very -imperfectly acquainted. Another cause to which he attributes the severe -treatment he experienced, was his having ventured so openly to question -the truth of the established theory: but this last provocation could -not be owing to mere inadvertence on his part; indeed the larger work, -in which he alludes to these circumstances,<span class="pagenum"><a name="Page_ix" id="Page_ix">[Pg ix]</a></span> is still more remarkable -for the violence of his objections to the Newtonian doctrine.</p> - -<p>There can be no doubt, however, that much of the opposition Goethe met -with was to be attributed to the manner as well as to the substance -of his statements. Had he contented himself with merely detailing his -experiments and showing their application to the laws of chromatic -harmony, leaving it to others to reconcile them as they could with the -pre-established system, or even to doubt in consequence, the truth of -some of the Newtonian conclusions, he would have enjoyed the credit -he deserved for the accuracy and the utility of his investigations. -As it was, the uncompromising expression of his convictions only -exposed him to the resentment or silent neglect of a great portion -of the scientific world, so that for a time he could not even obtain -a fair hearing for the less objectionable or rather highly valuable -communications contained in his book. A specimen of his manner of -alluding to the Newtonian theory will be seen in the preface.</p> - -<p>It was quite natural that this spirit should call forth a somewhat -vindictive feeling, and with it not a little uncandid as well as -unsparing criticism. "The Doctrine of Colours" met<span class="pagenum"><a name="Page_x" id="Page_x">[Pg x]</a></span> with this reception -in Germany long before it was noticed in England, where a milder and -fairer treatment could hardly be expected, especially at a time when, -owing perhaps to the limited intercourse with the continent, German -literature was far less popular than it is at present. This last fact, -it is true, can be of little importance in the present instance, -for although the change of opinion with regard to the genius of an -enlightened nation must be acknowledged to be beneficial, it is to be -hoped there is no fashion in science, and the translator begs to state -once for all, that in advocating the neglected merits of the "Doctrine -of Colours," he is far from undertaking to defend its imputed errors. -Sufficient time has, however, now elapsed since the publication of this -work (in 1810) to allow a calmer and more candid examination of its -claims. In this more pleasing task Germany has again for some time led -the way, and many scientific investigators have followed up the hints -and observations of Goethe with a due acknowledgment of the acuteness -of his views.<a name="FNanchor_2_2" id="FNanchor_2_2"></a><a href="#Footnote_2_2" class="fnanchor">[2]</a></p> - -<p><span class="pagenum"><a name="Page_xi" id="Page_xi">[Pg xi]</a></span></p> - -<p>It may require more magnanimity in English scientific readers to do -justice to the merits of one who was so open and, in many respects, it -is believed, so mistaken an opponent of Newton; but it must be admitted -that the statements of Goethe contain more useful principles in all -that relates to harmony of colour than any that have been derived from -the established doctrine. It is no derogation of the more important -truths of the Newtonian theory to say, that the views it contains -seldom appear in a form calculated for direct application to the arts. -The principle of contrast, so universally exhibited in nature, so -apparent in the action and re-action of the eye itself, is scarcely -hinted at. The equal pretensions of seven colours, as<span class="pagenum"><a name="Page_xii" id="Page_xii">[Pg xii]</a></span> such, and the -fanciful analogies which their assumed proportions could suggest, have -rarely found favour with the votaries of taste,—indeed they have -long been abandoned even by scientific authorities.<a name="FNanchor_3_3" id="FNanchor_3_3"></a><a href="#Footnote_3_3" class="fnanchor">[3]</a> And here the -translator stops: he is quite aware that the defects which make the -Newtonian theory so little available for æsthetic application, are -far from invalidating its more important conclusions in the opinion -of most scientific men. In carefully abstaining therefore from any -comparison between the two theories in these latter respects, he may -still be permitted to advocate the clearness and fulness of Goethe's -experiments. The German philosopher reduces the colours to their<span class="pagenum"><a name="Page_xiii" id="Page_xiii">[Pg xiii]</a></span> -origin and simplest elements; he sees and constantly bears in mind, and -sometimes ably elucidates, the phenomena of contrast and gradation, -two principles which may be said to make up the artist's world, and to -constitute the chief elements of beauty. These hints occur mostly in -what may be called the scientific part of the work. On the other hand, -in the portion expressly devoted to the æsthetic application of the -doctrine, the author seems to have made but an inadequate use of his -own principles.</p> - -<p>In that part of the chapter on chemical colours which relates to the -colours of plants and animals, the same genius and originality which -are displayed in the Essays on Morphology, and which have secured -to Goethe undisputed rank among the investigators of nature, are -frequently apparent.</p> - -<p>But one of the most interesting features of Goethe's theory, although -it cannot be a recommendation in a scientific point of view, is, that -it contains, undoubtedly with very great improvements, the general -doctrine of the ancients and of the Italians at the revival of letters. -The translator has endeavoured, in some notes, to point out the -connexion between this theory and the practice of the Italian painters.</p> - -<p><span class="pagenum"><a name="Page_xiv" id="Page_xiv">[Pg xiv]</a></span></p> - -<p>The "Doctrine of Colours," as first published in 1810, consists of -two volumes in 8vo., and sixteen plates, with descriptions, in 4to. -It is divided into three parts, a didactic, a controversial, and an -historical part; the present translation is confined to the first of -these, with such extracts from the other two as seemed necessary, -in fairness to the author, to explain some of his statements. The -polemical and historical parts are frequently alluded to in the -preface and elsewhere in the present work, but it has not been thought -advisable to omit these allusions. No alterations whatever seem to -have been made by Goethe in the didactic portion in later editions, -but he subsequently wrote an additional chapter on entoptic colours, -expressing his wish that it might be inserted in the theory itself at -a particular place which he points out. The form of this additional -essay is, however, very different from that of the rest of the work, -and the translator has therefore merely given some extracts from it in -the appendix. The polemical portion has been more than once omitted in -later editions.</p> - -<p>In the two first parts the author's statements are arranged -numerically, in the style of Bacon's Natural History. This, we are -told, was for the<span class="pagenum"><a name="Page_xv" id="Page_xv">[Pg xv]</a></span> convenience of reference; but many passages are -thus separately numbered which hardly seem to have required it. The -same arrangement is, however, strictly followed in the translation to -facilitate a comparison with the original where it may be desired; and -here the translator observes, that although he has sometimes permitted -himself to make slight alterations, in order to avoid unnecessary -repetition, or to make the author's meaning clearer, he feels that an -apology may rather be expected from him for having omitted so little. -He was scrupulous on this point, having once determined to translate -the whole treatise, partly, as before stated, from a wish to deal -fairly with a controversial writer, and partly because many passages, -not directly bearing on the scientific views, are still characteristic -of Goethe. The observations which the translator has ventured to add -are inserted in the appendix: these observations are chiefly confined -to such of the author's opinions and conclusions as have direct -reference to the arts; they seldom interfere with the scientific -propositions, even where these have been considered most vulnerable.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">[1]</span></a> "Farbenlehre"—in the present translation generally -rendered "Theory of Colours."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_2" id="Footnote_2_2"></a><a href="#FNanchor_2_2"><span class="label">[2]</span></a> Sixteen years after the appearance of the Farbenlehre, -Dr. Johannes Müller devoted a portion of his work, "Zur vergleichenden -Physiologie des Gesichtssinnes des Menschen und der Thiere," to the -critical examination of Goethe's theory. In his introductory remarks he -expresses himself as follows—"For my own part I readily acknowledge -that I have been greatly indebted to Goethe's treatise, and can truly -say that without having studied it for some years in connexion with the -actual phenomena, the present work would hardly have been undertaken. -I have no hesitation in confessing more particularly that I have full -faith in Goethe's statements, where they are merely descriptive of -the phenomena, and where the author does not enter into explanations -involving a decision on the great points of controversy." The names of -Hegel, Schelling, Seebeck, Steffens, may also be mentioned, and many -others might be added, as authorities more or less favourable to the -Farbenlehre.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_3" id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">[3]</span></a> "When Newton attempted to reckon up the rays of light -decomposed by the prism," says Sir John Leslie, "and ventured to assign -the famous number <i>seven</i>, he was apparently influenced by some lurking -disposition towards mysticism. If any unprejudiced person will fairly -repeat the experiment, he must soon be convinced that the various -coloured spaces which paint the spectrum slide into each other by -indefinite shadings: he may name four or five principal colours, but -the subordinate spaces are evidently so multiplied as to be incapable -of enumeration. The same illustrious mathematician, we can hardly -doubt, was betrayed by a passion for analogy, when he imagined that the -primary colours are distributed over the spectrum after the proportions -of the diatonic scale of music, since those intermediate spaces have -really no precise and defined limits."—<i>Treatises on Various Subjects -of Natural and Chemical Philosophy</i>, p. 59.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_xvii" id="Page_xvii">[Pg xvii]</a></span></p></div> - - - - -<h4><a name="PREFACE_TO_THE_FIRST_EDITION_OF_1810" id="PREFACE_TO_THE_FIRST_EDITION_OF_1810">PREFACE TO THE FIRST EDITION OF 1810.</a></h4> - - -<p>It may naturally be asked whether, in proposing to treat of colours, -light itself should not first engage our attention: to this we briefly -and frankly answer that since so much has already been said on the -subject of light, it can hardly be desirable to multiply repetitions by -again going over the same ground.</p> - -<p>Indeed, strictly speaking, it is useless to attempt to express the -nature of a thing abstractedly. Effects we can perceive, and a complete -history of those effects would, in fact, sufficiently define the -nature of the thing itself. We should try in vain to describe a man's -character, but let his acts be collected and an idea of the character -will be presented to us.</p> - -<p>The colours are acts of light; its active and passive modifications: -thus considered we may expect from them some explanation respecting -light itself. Colours and light, it is true, stand in the most intimate -relation to each other, but<span class="pagenum"><a name="Page_xviii" id="Page_xviii">[Pg xviii]</a></span> we should think of both as belonging to -nature as a whole, for it is nature as a whole which manifests itself -by their means in an especial manner to the sense of sight.</p> - -<p>The completeness of nature displays itself to another sense in a -similar way. Let the eye be closed, let the sense of hearing be -excited, and from the lightest breath to the wildest din, from the -simplest sound to the highest harmony, from the most vehement and -impassioned cry to the gentlest word of reason, still it is Nature that -speaks and manifests her presence, her power, her pervading life and -the vastness of her relations; so that a blind man to whom the infinite -visible is denied, can still comprehend an infinite vitality by means -of another organ.</p> - -<p>And thus as we descend the scale of being, Nature speaks to other -senses—to known, misunderstood, and unknown senses: so speaks she with -herself and to us in a thousand modes. To the attentive observer she -is nowhere dead nor silent; she has even a secret agent in inflexible -matter, in a metal, the smallest portions of which tell us what -is passing in the entire mass. However manifold, complicated, and -unintelligible this language may often seem to us, yet its elements -remain ever the same. With light poise<span class="pagenum"><a name="Page_xix" id="Page_xix">[Pg xix]</a></span> and counterpoise, Nature -oscillates within her prescribed limits, yet thus arise all the -varieties and conditions of the phenomena which are presented to us in -space and time.</p> - -<p>Infinitely various are the means by which we become acquainted with -these general movements and tendencies: now as a simple repulsion and -attraction, now as an upsparkling and vanishing light, as undulation -in the air, as commotion in matter, as oxydation and de-oxydation; but -always, uniting or separating, the great purpose is found to be to -excite and promote existence in some form or other.</p> - -<p>The observers of nature finding, however, that this poise and -counterpoise are respectively unequal in effect, have endeavoured to -represent such a relation in terms. They have everywhere remarked and -spoken of a greater and lesser principle, an action and resistance, -a doing and suffering, an advancing and retiring, a violent and -moderating power; and thus a symbolical language has arisen, which, -from its close analogy, may be employed as equivalent to a direct and -appropriate terminology.</p> - -<p>To apply these designations, this language of Nature to the subject -we have undertaken: to enrich and amplify this language by means of<span class="pagenum"><a name="Page_xx" id="Page_xx">[Pg xx]</a></span> -the theory of colours and the variety of their phenomena, and thus -facilitate the communication of higher theoretical views, was the -principal aim of the present treatise.</p> - -<p>The work itself is divided into three parts. The first contains the -outline of a theory of colours. In this, the innumerable cases which -present themselves to the observer are collected under certain leading -phenomena, according to an arrangement which will be explained in -the Introduction; and here it may be remarked, that although we have -adhered throughout to experiment, and throughout considered it as our -basis, yet the theoretical views which led to the arrangement alluded -to, could not but be stated. It is sometimes unreasonably required by -persons who do not even themselves attend to such a condition, that -experimental information should be submitted without any connecting -theory to the reader or scholar, who is himself to form his conclusions -as he may list. Surely the mere inspection of a subject can profit us -but little. Every act of seeing leads to consideration, consideration -to reflection, reflection to combination, and thus it may be said that -in every attentive look on nature we already theorise. But in order to -guard against the possible<span class="pagenum"><a name="Page_xxi" id="Page_xxi">[Pg xxi]</a></span> abuse of this abstract view, in order that -the practical deductions we look to should be really useful, we should -theorise without forgetting that we are so doing, we should theorise -with mental self-possession, and, to use a bold word, with irony.</p> - -<p>In the second part<a name="FNanchor_1_4" id="FNanchor_1_4"></a><a href="#Footnote_1_4" class="fnanchor">[1]</a> we examine the Newtonian theory; a theory which -by its ascendancy and consideration has hitherto impeded a free inquiry -into the phenomena of colours. We combat that hypothesis, for although -it is no longer found available, it still retains a traditional -authority in the world. Its real relations to its subject will require -to be plainly pointed out; the old errors must be cleared away, if the -theory of colours is not still to remain in the rear of so many other -better investigated departments of natural science. Since, however, -this second part of our work may appear somewhat dry as regards its -matter, and perhaps too vehement and excited in its manner, we may here -be permitted to introduce a sort of allegory in a lighter style, as a -prelude to that graver portion, and as some excuse for the earnestness -alluded to.</p> - -<p>We compare the Newtonian theory of colours<span class="pagenum"><a name="Page_xxii" id="Page_xxii">[Pg xxii]</a></span> to an old castle, which -was at first constructed by its architect with youthful precipitation; -it was, however, gradually enlarged and equipped by him according -to the exigencies of time and circumstances, and moreover was still -further fortified and secured in consequence of feuds and hostile -demonstrations.</p> - -<p>The same system was pursued by his successors and heirs: their -increased wants within, the harassing vigilance of their opponents -without, and various accidents compelled them in some places to build -near, in others in connexion with the fabric, and thus to extend the -original plan.</p> - -<p>It became necessary to connect all these incongruous parts and -additions by the strangest galleries, halls and passages. All damages, -whether inflicted by the hand of the enemy or the power of time, were -quickly made good. As occasion required, they deepened the moats, -raised the walls, and took care there should be no lack of towers, -battlements, and embrasures. This care and these exertions gave rise -to a prejudice in favour of the great importance of the fortress, -and still upheld that prejudice, although the arts of building and -fortification were by this time very much advanced, and people had<span class="pagenum"><a name="Page_xxiii" id="Page_xxiii">[Pg xxiii]</a></span> -learnt to construct much better dwellings and defences in other cases. -But the old castle was chiefly held in honour because it had never -been taken, because it had repulsed so many assaults, had baffled so -many hostile operations, and had always preserved its virgin renown. -This renown, this influence lasts even now: it occurs to no one that -the old castle is become uninhabitable. Its great duration, its costly -construction, are still constantly spoken of. Pilgrims wend their -way to it; hasty sketches of it are shown in all schools, and it is -thus recommended to the reverence of susceptible youth. Meanwhile, -the building itself is already abandoned; its only inmates are a few -invalids, who in simple seriousness imagine that they are prepared for -war.</p> - -<p>Thus there is no question here respecting a tedious siege or a -doubtful war; so far from it we find this eighth wonder of the world -already nodding to its fall as a deserted piece of antiquity, and -begin at once, without further ceremony, to dismantle it from gable -and roof downwards; that the sun may at last shine into the old nest -of rats and owls, and exhibit to the eye of the wondering traveller -that labyrinthine, incongruous style of building, with its scanty,<span class="pagenum"><a name="Page_xxiv" id="Page_xxiv">[Pg xxiv]</a></span> -make-shift contrivances, the result of accident and emergency, its -intentional artifice and clumsy repairs. Such an inspection will, -however, only be possible when wall after wall, arch after arch, is -demolished, the rubbish being at once cleared away as well as it can be.</p> - -<p>To effect this, and to level the site where it is possible to do -so, to arrange the materials thus acquired, so that they can be -hereafter again employed for a new building, is the arduous duty -we have undertaken in this Second Part. Should we succeed, by a -cheerful application of all possible ability and dexterity, in razing -this Bastille, and in gaining a free space, it is thus by no means -intended at once to cover the site again and to encumber it with a new -structure; we propose rather to make use of this area for the purpose -of passing in review a pleasing and varied series of illustrative -figures.</p> - -<p>The third part is thus devoted to the historical account of early -inquirers and investigators. As we before expressed the opinion that -the history of an individual displays his character, so it may here be -well affirmed that the history of science is science itself. We cannot -clearly be aware of what we possess till we have the means of knowing -what others possessed<span class="pagenum"><a name="Page_xxv" id="Page_xxv">[Pg xxv]</a></span> before us. We cannot really and honestly rejoice -in the advantages of our own time if we know not how to appreciate -the advantages of former periods. But it was impossible to write, or -even to prepare the way for a history of the theory of colours while -the Newtonian theory existed; for no aristocratic presumption has ever -looked down on those who were not of its order, with such intolerable -arrogance as that betrayed by the Newtonian school in deciding on -all that had been done in earlier times and all that was done around -it. With disgust and indignation we find Priestley, in his History -of Optics, like many before and after him, dating the success of all -researches into the world of colours from the epoch of a decomposed ray -of light, or what pretended to be so; looking down with a supercilious -air on the ancient and less modern inquirers, who, after all, had -proceeded quietly in the right road, and who have transmitted to us -observations and thoughts in detail which we can neither arrange better -nor conceive more justly.</p> - -<p>We have a right to expect from one who proposes to give the history of -any science, that he inform us how the phenomena of which it treats -were gradually known, and what was imagined,<span class="pagenum"><a name="Page_xxvi" id="Page_xxvi">[Pg xxvi]</a></span> conjectured, assumed, -or thought respecting them. To state all this in due connexion is by -no means an easy task; need we say that to write a history at all is -always a hazardous affair; with the most honest intention there is -always a danger of being dishonest; for in such an undertaking, a -writer tacitly announces at the outset that he means to place some -things in light, others in shade. The author has, nevertheless, long -derived pleasure from the prosecution of his task: but as it is the -intention only that presents itself to the mind as a whole, while the -execution is generally accomplished portion by portion, he is compelled -to admit that instead of a history he furnishes only materials for -one. These materials consist in translations, extracts, original and -borrowed comments, hints, and notes; a collection, in short, which, if -not answering all that is required, has at least the merit of having -been made with earnestness and interest. Lastly, such materials,—not -altogether untouched it is true, but still not exhausted,—may be more -satisfactory to the reflecting reader in the state in which they are, -as he can easily combine them according to his own judgment.</p> - -<p>This third part, containing the history of the<span class="pagenum"><a name="Page_xxvii" id="Page_xxvii">[Pg xxvii]</a></span> science, does not, -however, thus conclude the subject: a fourth supplementary portion<a name="FNanchor_2_5" id="FNanchor_2_5"></a><a href="#Footnote_2_5" class="fnanchor">[2]</a> -is added. This contains a recapitulation or revision; with a view -to which, chiefly, the paragraphs are headed numerically. In the -execution of a work of this kind some things may be forgotten, some -are of necessity omitted, so as not to distract the attention, some -can only be arrived at as corollaries, and others may require to be -exemplified and verified: on all these accounts, postscripts, additions -and corrections are indispensable. This part contains, besides, some -detached essays; for example, that on the atmospheric colours; for as -these are introduced in the theory itself without any classification, -they are here presented to the mind's eye at one view. Again, if this -essay invites the reader to consult Nature herself, another is intended -to recommend the artificial aids of science by circumstantially -describing the apparatus which will in future be necessary to assist -researches into the theory of colours.</p> - -<p>In conclusion, it only remains to speak of the<span class="pagenum"><a name="Page_xxviii" id="Page_xxviii">[Pg xxviii]</a></span> plates which are added -at the end of the work;<a name="FNanchor_3_6" id="FNanchor_3_6"></a><a href="#Footnote_3_6" class="fnanchor">[3]</a> and here we confess we are reminded of that -incompleteness and imperfection which the present undertaking has, -in common with all others of its class; for as a good play can be in -fact only half transmitted to writing, a great part of its effect -depending on the scene, the personal qualities of the actor, the powers -of his voice, the peculiarities of his gestures, and even the spirit -and favourable humour of the spectators; so it is, in a still greater -degree, with a book which treats of the appearances of nature. To be -enjoyed, to be turned to account, Nature herself must be present to -the reader, either really, or by the help of a lively imagination. -Indeed, the author should in such cases communicate his observations -orally, exhibiting the phenomena he describes—as a text, in the -first instance,—partly as they appear to us unsought, partly as they -may be presented by contrivance to serve in particular illustration. -Explanation and description could not then fail to produce a lively -impression.</p> - -<p>The plates which generally accompany works like the present are thus -a most inadequate substitute<span class="pagenum"><a name="Page_xxix" id="Page_xxix">[Pg xxix]</a></span> for all this; a physical phenomenon -exhibiting its effects on all sides is not to be arrested in lines -nor denoted by a section. No one ever dreams of explaining chemical -experiments with figures; yet it is customary in physical researches -nearly allied to these, because the object is thus found to be in -some degree answered. In many cases, however, such diagrams represent -mere notions; they are symbolical resources, hieroglyphic modes of -communication, which by degrees assume the place of the phenomena and -of Nature herself, and thus rather hinder than promote true knowledge. -In the present instance we could not dispense with plates, but we have -endeavoured so to construct them that they may be confidently referred -to for the explanation of the didactic and polemical portions. Some of -these may even be considered as forming part of the apparatus before -mentioned.</p> - -<p>We now therefore refer the reader to the work itself; first, only -repeating a request which many an author has already made in vain, and -which the modern German reader, especially, so seldom grants:—</p> - -<p style="margin-left: 20%;"> -<span style="margin-left: 6em;">Si quid novisti rectius istis</span><br /> -Candidus imperti; si non, his utere mecum.<br /> -</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_4" id="Footnote_1_4"></a><a href="#FNanchor_1_4"><span class="label">[1]</span></a> The Polemical part.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_5" id="Footnote_2_5"></a><a href="#FNanchor_2_5"><span class="label">[2]</span></a> This preface must have been written before the work was -finished, for at the conclusion of the historical part there is only an -apology for the non-appearance of the supplement here alluded to.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_6" id="Footnote_3_6"></a><a href="#FNanchor_3_6"><span class="label">[3]</span></a> In the present translation the necessary plates accompany -the text.</p></div> - -<hr class="chap" /> - - - - -<p><span class="pagenum"><a name="Page_xxxi" id="Page_xxxi">[Pg xxxi]</a></span></p> -<h5><a name="CONTENTS" id="CONTENTS">CONTENTS</a></h5> - - - -<table border="0" cellpadding="3" cellspacing="0" summary=""> -<tr><th style="font-size: 0.8em;" colspan="3">INTRODUCTION</th><td align="right">xxxvii</td></tr> -<tr><th style="font-size: 0.8em;" colspan="3">PART I.<br />PHYSIOLOGICAL COLOURS.</th></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">I.</span></td><td align="left">Effects of Light and Darkness on the Eye</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_2">2</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">II.</span></td><td align="left">Effects of Black and White Objects on the Eye</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_5">5</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">III</span>.</td><td align="left">Grey Surfaces and Objects</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_14">14</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">IV</span>.</td><td align="left">Dazzling Colourless Objects</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_16">16</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">V</span>.</td><td align="left">Coloured Objects</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_20">20</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">VI</span>.</td><td align="left">Coloured Shadows</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_29">29</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">VII</span>.</td><td align="left">Faint Lights</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_38">38</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">VIII</span>.</td><td align="left">Subjective Halos</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_40">40</a></span></td></tr> -<tr><td align="left"></td><td align="right"></td><td align="left">Pathological Colours—Appendix</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_45">45</a></span></td></tr> -<tr><th style="font-size: 0.8em;" colspan="3">PART II.<br />PHYSICAL COLOURS.</th></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">IX.</span></td><td align="left">Dioptrical Colours</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_59">59</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">X.</span></td><td align="left">Dioptrical Colours of the First Class</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_60">60</a></span></td></tr> -<tr><td align="left"></td><td align="right" valign="top"><span style="font-size: 0.8em;">XI</span>.</td><td align="left">Dioptrical Colours of the Second Class<br /> -—Refraction</td><td align="right"><span style="font-size: 0.8em;"><a href="#Pg_74">74</a></span></td></tr> -<tr><td align="left"></td><td align="left"></td><td align="left">Subjective Experiments</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_80">80</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XII.</span></td><td align="left">Refraction without the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_80">80</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XIII.</span></td><td align="left">Conditions of the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_81">81</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XIV.</span></td><td align="left">Conditions under which the Appearance of</td></tr> -<tr><td align="left"></td><td align="left"></td><td align="left">Colour increases</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_86">86</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XV.</span></td><td align="left">Explanation of the foregoing Phenomena</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_90">90</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XVI.</span></td><td align="left">Decrease of the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_100">100</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XVII.</span></td><td align="left">Grey Objects displaced by Refraction</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_103">103</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XVIII.</span></td><td align="left">Coloured Objects displaced by Refraction</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_106">106</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XIX.</span></td><td align="left">Achromatism and Hyperchromatism</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_118">118</a></span> -<span class="pagenum"><a name="Page_xxxii" id="Page_xxxii">[Pg xxxii]</a></span></td></tr> -<tr><td align="left"></td><td align="right" valign="top"><span style="font-size: 0.8em;">XX.</span></td><td align="left">Advantages of Subjective Experiments<br /> -—Transition to the Objective</td><td align="right" valign="bottom"><span style="font-size: 0.8em;"><a href="#Page_123">123</a></span></td></tr> -<tr><td align="left"></td><td align="left"></td><td align="left">Objective Experiments</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_125">125</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXI</span>.</td><td align="left">Refraction without the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_121">121</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXII</span>.</td><td align="left">Conditions of the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_128">128</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXIII</span>.</td><td align="left">Conditions of the Increase of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_134">134</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXIV</span>.</td><td align="left">Explanation of the foregoing Phenomena</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_139">139</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXV</span>.</td><td align="left">Decrease of the Appearance of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_141">141</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXVI</span>.</td><td align="left">Grey Objects</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_142">142</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXVII</span>.</td><td align="left">Coloured Objects</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_143">143</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXVIII</span>.</td><td align="left">Achromatism and Hyperchromatism</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_145">145</a></span></td></tr> -<tr><td align="left"></td><td align="right" valign="top"><span style="font-size: 0.8em;">XXIX</span>.</td><td align="left">Combination of Subjective and Objective<br /> -Experiments</td><td align="right" valign="bottom"><span style="font-size: 0.8em;"><a href="#Page_147">147</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXX</span>.</td><td align="left">Transition</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_150">150</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXI</span>.</td><td align="left">Catoptrical Colours</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_154">154</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXII</span>.</td><td align="left">Paroptical Colours</td><td align="right"><span style="font-size: 0.8em;"><a href="#a163">163</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXIII</span>.</td><td align="left">Epoptical Colours</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_177">177</a></span></td></tr> -<tr><th style="font-size: 0.8em;" colspan="3">PART III.<br />CHEMICAL COLOURS.</th></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXIV</span>.</td><td align="left">Chemical Contrast</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_202">202</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXV</span>.</td><td align="left">White</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_203">203</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXVI</span>.</td><td align="left">Black</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_205">205</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXVII</span>.</td><td align="left">First Excitation of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_206">206</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXVIII</span>.</td><td align="left">Augmentation of Colour</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_212">212</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XXXIX</span>.</td><td align="left">Culmination</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_214">214</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XL</span>.</td><td align="left">Fluctuation</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_217">217</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLI</span>.</td><td align="left">Passage through the Whole Scale</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_218">218</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLII</span>.</td><td align="left">Inversion</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_220">220</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLIII</span>.</td><td align="left">Fixation</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_221">221</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLIV</span>.</td><td align="left">Intermixture, Real</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_223">223</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLV</span>.</td><td align="left">Intermixture, Apparent</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_226">226</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLVI</span>.</td><td align="left">Communication, Actual</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_230">230</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLVII</span>.</td><td align="left">Communication, Apparent</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_235">235</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLVIII</span>.</td><td align="left">Extraction</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_237">237</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">XLIX</span>.</td><td align="left">Nomenclature</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_242">242</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">L</span>.</td><td align="left">Minerals</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_245">245</a></span> -<span class="pagenum"><a name="Page_xxxiii" id="Page_xxxiii">[Pg xxxiii]</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">LI</span>.</td><td align="left">Plants</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_247">247</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">LII</span>.</td><td align="left">Worms, Insects, Fishes</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_252">252</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">LIII</span>.</td><td align="left">Birds</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_259">259</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">LIV</span>.</td><td align="left">Mammalia and Human Beings</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_262">262</a></span></td></tr> -<tr><td align="left"></td><td align="right" valign="top"><span style="font-size: 0.8em;">LV</span>.</td><td align="left">Physical and Chemical Effects of the -Transmission<br /> of Light through Coloured Mediums</td><td align="right" valign="bottom"><span style="font-size: 0.8em;"><a href="#Page_266">266</a></span></td></tr> -<tr><td align="left"></td><td align="right"><span style="font-size: 0.8em;">LVI</span>.</td><td align="left">Chemical Effect in Dioptrical Achromatism</td><td align="right"><span style="font-size: 0.8em;"><a href="#Page_270">270</a></span></td></tr> -</table> - -<p class="caption">PART IV.<br /> -GENERAL CHARACTERISTICS.</p> - -<p style="margin-left: 15%;"> -The Facility with which Colour appears <span class="tabnum"><a href="#Page_274">274</a></span><br /> -The Definite Nature of Colour <span class="tabnum"><a href="#Page_276">276</a></span><br /> -Combination of the Two Principles <span class="tabnum"><a href="#Page_277">277</a></span><br /> -Augmentation to Red <span class="tabnum"><a href="#Page_277">277</a></span><br /> -Junction of the Two Augmented Extremes <span class="tabnum"><a href="#Page_278">278</a></span><br /> -Completeness the Result of Variety in Colour <span class="tabnum"><a href="#Page_279">279</a></span><br /> -Harmony of the Complete State <span class="tabnum"><a href="#Page_280">280</a></span><br /> -Facility with which Colour may be made to tend either to<br /> -the Plus or Minus side <span class="tabnum"><a href="#Page_281">281</a></span><br /> -Evanescence of Colour <span class="tabnum"><a href="#Page_281">281</a></span><br /> -Permanence of Colour <span class="tabnum"><a href="#Page_282">282</a></span><br /> -</p> - - -<p class="caption">PART V.<br /> -RELATION TO OTHER PURSUITS.</p> - -<p style="margin-left: 15%;">Relation to Philosophy <span class="tabnum"><a href="#Page_283">283</a></span><br /> -Relation to Mathematics <span class="tabnum"><a href="#Page_286">286</a></span><br /> -Relation to the Technical Operations of the Dyer <span class="tabnum"><a href="#Page_289">289</a></span><br /> -Relation to Physiology and Pathology <span class="tabnum"><a href="#Page_291">291</a></span><br /> -Relation to Natural History <span class="tabnum"><a href="#Page_292">292</a></span><br /> -Relation to General Physics <span class="tabnum"><a href="#Page_293">293</a></span><br /> -Relation to the Theory of Music <span class="tabnum"><a href="#Page_298">298</a></span><br /> -Concluding Observations on Terminology <span class="tabnum"><a href="#Page_300">300</a></span><br /> -</p> - - -<p class="caption">PART VI.<br /> -EFFECT OF COLOUR WITH REFERENCE<br /> TO MORAL ASSOCIATIONS.</p> -<p class="pagenum"><a name="Page_xxxiv" id="Page_xxxiv">[Pg xxxiv]</a></p> -<p style="margin-left: 15%;"> -Yellow <span class="tabnum"><a href="#Page_306">306</a></span><br /> -Red-Yellow <span class="tabnum"><a href="#Page_308">308</a></span><br /> -Yellow-Red <span class="tabnum"><a href="#Page_309">309</a></span><br /> -Blue <span class="tabnum"><a href="#Page_310">310</a></span><br /> -Red-Blue <span class="tabnum"><a href="#Page_312">312</a></span><br /> -Blue-Red <span class="tabnum"><a href="#Page_313">313</a></span><br /> -Red <span class="tabnum"><a href="#Page_313">313</a></span><br /> -Green <span class="tabnum"><a href="#Page_316">316</a></span><br /> -Completeness and Harmony <span class="tabnum"><a href="#Page_316">316</a></span><br /> -Characteristic Combinations <span class="tabnum"><a href="#Page_321">321</a></span><br /> -Yellow and Blue <span class="tabnum"><a href="#Page_322">322</a></span><br /> -Yellow and Red <span class="tabnum"><a href="#Page_322">322</a></span><br /> -Blue and Red <span class="tabnum"><a href="#Page_322">322</a></span><br /> -Yellow-Red and Blue-Red <span class="tabnum"><a href="#Page_323">323</a></span><br /> -Combinations Non-Characteristic <span class="tabnum"><a href="#Page_324">324</a></span><br /> -Relation of the Combinations to Light and Dark <span class="tabnum"><a href="#Page_325">325</a></span><br /> -Considerations derived from the Evidence of Experience<br /> -and History <span class="tabnum"><a href="#Page_326">326</a></span><br /> -Æsthetic Influence <span class="tabnum"><a href="#Page_330">330</a></span><br /> -Chiaro-Scuro <span class="tabnum"><a href="#Page_331">331</a></span><br /> -Tendency to Colour <span class="tabnum"><a href="#Page_334">334</a></span><br /> -Keeping <span class="tabnum"><a href="#Page_335">335</a></span><br /> -Colouring <span class="tabnum"><a href="#Page_337">337</a></span><br /> -Colour in General Nature <span class="tabnum"><a href="#Page_337">337</a></span><br /> -Colour of Particular Objects <span class="tabnum"><a href="#Page_338">338</a></span><br /> -Characteristic Colouring <span class="tabnum"><a href="#Page_339">339</a></span><br /> -Harmonious Colouring <span class="tabnum"><a href="#Page_341">341</a></span><br /> -Genuine Tone <span class="tabnum"><a href="#Page_342">342</a></span><br /> -False Tone <span class="tabnum"><a href="#Page_342">342</a></span><br /> -Weak Colouring <span class="tabnum"><a href="#Page_343">343</a></span><br /> -The Motley <span class="tabnum"><a href="#Page_344">344</a></span><br /> -Dread of Theory <span class="tabnum"><a href="#Page_344">344</a></span><br /> -Ultimate Aim <span class="tabnum"><a href="#Page_345">345</a></span><br /> -Grounds <span class="tabnum"><a href="#Page_345">345</a></span><br /> -Pigments <span class="tabnum"><a href="#Page_348">348</a></span><br /> -Allegorical, Symbolical, Mystical Application of Colour <span class="tabnum"><a href="#Page_350">350</a></span><br /> -Concluding Observations <span class="tabnum"><a href="#Page_352">352</a></span><br /> -</p> -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_xxxv" id="Page_xxxv">[Pg xxxv]</a></span></p> - -<h3><a name="OUTLINE_OF_A_THEORY_OF_COLOURS" id="OUTLINE_OF_A_THEORY_OF_COLOURS">OUTLINE OF A THEORY OF COLOURS.</a></h3> - - -<blockquote> - -<p>"Si vera nostra sunt aut falsa, erunt talia, licet nostra -per vitam defendimus. Post fata nostra pueri qui nunc ludunt -nostri judices erunt."</p></blockquote> - -<hr class="tb" /> - -<p><span class="pagenum"><a name="Page_xxxvii" id="Page_xxxvii">[Pg xxxvii]</a></span></p> - - - - -<h4><a name="INTRODUCTION" id="INTRODUCTION">INTRODUCTION.</a></h4> - - -<p>The desire of knowledge is first stimulated in us when remarkable -phenomena attract our attention. In order that this attention be -continued, it is necessary that we should feel some interest in -exercising it, and thus by degrees we become better acquainted with the -object of our curiosity. During this process of observation we remark -at first only a vast variety which presses indiscriminately on our -view; we are forced to separate, to distinguish, and again to combine; -by which means at last a certain order arises which admits of being -surveyed with more or less satisfaction.</p> - -<p>To accomplish this, only in a certain degree, in any department, -requires an unremitting and close application; and we find, for this -reason, that men prefer substituting a general theoretical view, or -some system of explanation, for the facts themselves, instead of taking -the trouble to make themselves first acquainted with cases in detail -and then constructing a whole.</p> - -<p>The attempt to describe and class the phenomena of colours has been -only twice made: first by Theophrastus,<a name="FNanchor_1_7" id="FNanchor_1_7"></a><a href="#Footnote_1_7" class="fnanchor">[1]</a> and in modern times by<span class="pagenum"><a name="Page_xxxviii" id="Page_xxxviii">[Pg xxxviii]</a></span> -Boyle. The pretensions of the present essay to the third place will -hardly be disputed.</p> - -<p>Our historical survey enters into further details. Here we merely -observe that in the last century such a classification was not to be -thought of, because Newton had based his hypothesis on a phenomenon -exhibited in a complicated and secondary state; and to this the other -cases that forced themselves on the attention were contrived to be -referred, when they could not be passed over in silence; just as an -astronomer would do, if from whim he were to place the moon in the -centre of our system; he would be compelled to make the earth, sun, and -planets revolve round the lesser body, and be forced to disguise and -gloss over the error of his first assumption by ingenious calculations -and plausible statements.</p> - -<p>In our prefatory observations we assumed the reader to be acquainted -with what was known respecting light; here we assume the same with -regard to the eye. We observed that all nature manifests itself by -means of colours to the sense of sight. We now assert, extraordinary as -it may in some degree appear, that the eye sees no form, inasmuch as -light, shade, and colour together constitute that which to our vision -distinguishes object from object, and the parts of an object from each -other. From these three, light, shade, and colour, we construct the -visible<span class="pagenum"><a name="Page_xxxix" id="Page_xxxix">[Pg xxxix]</a></span> world, and thus, at the same time, make painting possible, -an art which has the power of producing on a flat surface a much more -perfect visible world than the actual one can be.</p> - -<p>The eye may be said to owe its existence to light, which calls forth, -as it were, a sense that is akin to itself; the eye, in short, is -formed with reference to light, to be fit for the action of light; the -light it contains corresponding with the light without.</p> - -<p>We are here reminded of a significant adage in constant use with the -ancient Ionian school—"Like is only known by Like;" and again, of the -words of an old mystic writer, which may be thus rendered, "If the eye -were not sunny, how could we perceive light? If God's own strength -lived not in us, how could we delight in Divine things?" This immediate -affinity between light and the eye will be denied by none; to consider -them as identical in substance is less easy to comprehend. It will be -more intelligible to assert that a dormant light resides in the eye, -and that it may be excited by the slightest cause from within or from -without. In darkness we can, by an effort of imagination, call up the -brightest images; in dreams objects appear to us as in broad daylight; -awake, the slightest external action of light is perceptible, and if -the organ suffers an actual shock, light and colours spring forth.<span class="pagenum"><a name="Page_xl" id="Page_xl">[Pg xl]</a></span> -Here, however, those who are wont to proceed according to a certain -method, may perhaps observe that as yet we have not decidedly explained -what colour is. This question, like the definition of light and the -eye, we would for the present evade, and would appeal to our inquiry -itself, where we have circumstantially shown how colour is produced. -We have only therefore to repeat that colour is a law of nature in -relation with the sense of sight. We must assume, too, that every one -has this sense, that every one knows the operation of nature on it, for -to a blind man it would be impossible to speak of colours.</p> - -<p>That we may not, however, appear too anxious to shun such an -explanation, we would restate what has been said as follows: colour is -an elementary phenomenon in nature adapted to the sense of vision; a -phenomenon which, like all others, exhibits itself by separation and -contrast, by commixture and union, by augmentation and neutralization, -by communication and dissolution: under these general terms its nature -may be best comprehended.</p> - -<p>We do not press this mode of stating the subject on any one. Those -who, like ourselves, find it convenient, will readily adopt it; but we -have no desire to enter the lists hereafter in its defence. From time -immemorial it has been dangerous to treat of colour; so much so, that<span class="pagenum"><a name="Page_xli" id="Page_xli">[Pg xli]</a></span> -one of our predecessors ventured on a certain occasion to say, "The ox -becomes furious if a red cloth is shown to him; but the philosopher, -who speaks of colour only in a general way, begins to rave."</p> - -<p>Nevertheless, if we are to proceed to give some account of our work, to -which we have appealed, we must begin by explaining how we have classed -the different conditions under which colour is produced. We found three -modes in which it appears; three classes of colours, or rather three -exhibitions of them all. The distinctions of these classes are easily -expressed.</p> - -<p>Thus, in the first instance, we considered colours, as far as they -may be said to belong to the eye itself, and to depend on an action -and re-action of the organ; next, they attracted our attention as -perceived in, or by means of, colourless mediums; and lastly, where -we could consider them as belonging to particular substances. We have -denominated the first, physiological, the second, physical, the third, -chemical colours. The first are fleeting and not to be arrested; the -next are passing, but still for a while enduring; the last may be made -permanent for any length of time.</p> - -<p>Having separated these classes and kept them as distinct as possible, -with a view to a clear, didactic exposition, we have been enabled at<span class="pagenum"><a name="Page_xlii" id="Page_xlii">[Pg xlii]</a></span> -the same time to exhibit them in an unbroken series, to connect the -fleeting with the somewhat more enduring, and these again with the -permanent hues; and thus, after having carefully attended to a distinct -classification in the first instance, to do away with it again when a -larger view was desirable.</p> - -<p>In a fourth division of our work we have therefore treated generally -what was previously detailed under various particular conditions, and -have thus, in fact, given a sketch for a future theory of colours. We -will here only anticipate our statements so far as to observe, that -light and darkness, brightness and obscurity, or if a more general -expression is preferred, light and its absence, are necessary to the -production of colour. Next to the light, a colour appears which we call -yellow; another appears next to the darkness, which we name blue. When -these, in their purest state, are so mixed that they are exactly equal, -they produce a third colour called green. Each of the two first-named -colours can however of itself produce a new tint by being condensed or -darkened. They thus acquire a reddish appearance which can be increased -to so great a degree that the original blue or yellow is hardly to -be recognised in it: but the intensest and purest red, especially in -physical cases, is produced when the two extremes of the yellow-red -and blue-red are<span class="pagenum"><a name="Page_xliii" id="Page_xliii">[Pg xliii]</a></span> united. This is the actual state of the appearance -and generation of colours. But we can also assume an existing red in -addition to the definite existing blue and yellow, and we can produce -contrariwise, by mixing, what we directly produced by augmentation or -deepening. With these three or six colours, which may be conveniently -included in a circle, the elementary doctrine of colours is alone -concerned. All other modifications, which may be extended to infinity, -have reference more to the application,—have reference to the -technical operations of the painter and dyer, and the various purposes -of artificial life. To point out another general quality, we may -observe that colours throughout are to be considered as half-lights, as -half-shadows, on which account if they are so mixed as reciprocally to -destroy their specific hues, a shadowy tint, a grey, is produced.</p> - -<p>In the fifth division of our inquiry we had proposed to point out -the relations in which we should wish our doctrine of colours to -stand to other pursuits. Important as this part of our work is, it -is perhaps on this very account not so successful as we could wish. -Yet when we reflect that strictly speaking these relations cannot be -described before they exist, we may console ourselves if we have in -some degree failed in endeavouring for the first time to define them. -For undoubtedly we should first<span class="pagenum"><a name="Page_xliv" id="Page_xliv">[Pg xliv]</a></span> wait to see how those whom we have -endeavoured to serve, to whom we have intended to make an agreeable and -useful offering, how such persons, we say, will accept the result of -our utmost exertion: whether they will adopt it, whether they will make -use of it and follow it up, or whether they will repel, reject, and -suffer it to remain unassisted and neglected.</p> - -<p>Meanwhile, we venture to express what we believe and hope. From the -philosopher we believe we merit thanks for having traced the phenomena -of colours to their first sources, to the circumstances under which -they simply appear and are, and beyond which no further explanation -respecting them is possible. It will, besides, be gratifying to him -that we have arranged the appearances described in a form that admits -of being easily surveyed, even should he not altogether approve of the -arrangement itself.</p> - -<p>The medical practitioner, especially him whose study it is to watch -over the organ of sight, to preserve it, to assist its defects and to -cure its disorders, we reckon to make especially our friend. In the -chapter on the physiological colours, in the Appendix relating to those -that are more strictly pathological, he will find himself quite in his -own province. We are not without hopes of seeing the physiological -phenomena,—a hitherto neglected, and, we may add, most important -branch of the theory of<span class="pagenum"><a name="Page_xlv" id="Page_xlv">[Pg xlv]</a></span> colours,—completely investigated through the -exertions of those individuals who in our own times are treating this -department with success.</p> - -<p>The investigator of nature should receive us cordially, since we -enable him to exhibit the doctrine of colours in the series of other -elementary phenomena, and at the same time enable him to make use of a -corresponding nomenclature, nay, almost the same words and designations -as under the other rubrics. It is true we give him rather more trouble -as a teacher, for the chapter of colours is not now to be dismissed -as heretofore with a few paragraphs and experiments; nor will the -scholar submit to be so scantily entertained as he has hitherto been, -without murmuring. On the other hand, an advantage will afterwards -arise out of this: for if the Newtonian doctrine was easily learnt, -insurmountable difficulties presented themselves in its application. -Our theory is perhaps more difficult to comprehend, but once known, all -is accomplished, for it carries its application along with it.</p> - -<p>The chemist who looks upon colours as indications by which he may -detect the more secret properties of material things, has hitherto -found much inconvenience in the denomination and description of -colours; nay, some have been induced after closer and nicer examination -to look upon colour as an uncertain and fallacious criterion<span class="pagenum"><a name="Page_xlvi" id="Page_xlvi">[Pg xlvi]</a></span> in -chemical operations. Yet we hope by means of our arrangement and the -nomenclature before alluded to, to bring colour again into credit, -and to awaken the conviction that a progressive, augmenting, mutable -quality, a quality which admits of alteration even to inversion, is not -fallacious, but rather calculated to bring to light the most delicate -operations of nature.</p> - -<p>In looking a little further round us, we are not without fears -that we may fail to satisfy another class of scientific men. By an -extraordinary combination of circumstances the theory of colours -has been drawn into the province and before the tribunal of the -mathematician, a tribunal to which it cannot be said to be amenable. -This was owing to its affinity with the other laws of vision which the -mathematician was legitimately called upon to treat. It was owing, -again, to another circumstance: a great mathematician had investigated -the theory of colours, and having been mistaken in his observations as -an experimentalist, he employed the whole force of his talent to give -consistency to this mistake. Were both these circumstances considered, -all misunderstanding would presently be removed, and the mathematician -would willingly co-operate with us, especially in the physical -department of the theory.</p> - -<p>To the practical man, to the dyer, on the other hand, our labour must -be altogether acceptable;<span class="pagenum"><a name="Page_xlvii" id="Page_xlvii">[Pg xlvii]</a></span> for it was precisely those who reflected on -the facts resulting from the operations of dyeing who were the least -satisfied with the old theory: they were the first who perceived the -insufficiency of the Newtonian doctrine. The conclusions of men are -very different according to the mode in which they approach a science -or branch of knowledge; from which side, through which door they -enter. The literally practical man, the manufacturer, whose attention -is constantly and forcibly called to the facts which occur under his -eye, who experiences benefit or detriment from the application of his -convictions, to whom loss of time and money is not indifferent, who -is desirous of advancing, who aims at equalling or surpassing what -others have accomplished,—such a person feels the unsoundness and -erroneousness of a theory much sooner than the man of letters, in whose -eyes words consecrated by authority are at last equivalent to solid -coin; than the mathematician, whose formula always remains infallible, -even although the foundation on which it is constructed may not square -with it. Again, to carry on the figure before employed, in entering -this theory from the side of painting, from the side of æsthetic<a name="FNanchor_2_8" id="FNanchor_2_8"></a><a href="#Footnote_2_8" class="fnanchor">[2]</a> -colouring generally, we shall be<span class="pagenum"><a name="Page_xlviii" id="Page_xlviii">[Pg xlviii]</a></span> found to have accomplished a -most thank-worthy office for the artist. In the sixth part we have -endeavoured to define the effects of colour as addressed at once to -the eye and mind, with a view to making them more available for the -purposes of art. Although much in this portion, and indeed throughout, -has been suffered to remain as a sketch, it should be remembered that -all theory can in strictness only point out leading principles, under -the guidance of which, practice may proceed with vigour and be enabled -to attain legitimate results.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_7" id="Footnote_1_7"></a><a href="#FNanchor_1_7"><span class="label">[1]</span></a> The treatise to which the author alludes in more generally -ascribed to Aristotle.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_8" id="Footnote_2_8"></a><a href="#FNanchor_2_8"><span class="label">[2]</span></a> Æsthetic—belonging to taste as mere internal sense, from -αἰσθάνομαι, to feel; the word was first used by Wolf.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_1" id="Page_1">[Pg 1]</a></span></p></div> - - - - -<h5><a name="PART_I" id="PART_I">PART I.</a></h5> - - -<h4>PHYSIOLOGICAL COLOURS.</h4> - - -<p class="para"><a id="a1"></a>1.</p> - -<p>We naturally place these colours first, because they belong altogether, -or in a great degree, to the <i>subject</i><a name="FNanchor_1_9" id="FNanchor_1_9"></a><a href="#Footnote_1_9" class="fnanchor">[1]</a>—to the eye itself. They -are the foundation of the whole doctrine, and open to our view the -chromatic harmony on which so much difference of opinion has existed. -They have been hitherto looked upon as extrinsic and casual, as -illusion and infirmity: their appearances have been known from ancient -date; but, as they were too evanescent to be arrested, they were -banished into the region of phantoms, and under this idea have been -very variously described.</p> - -<p class="para"><a id="a2">2.</a></p> - -<p>Thus they are called <i>colores adventicii</i> by Boyle; <i>imaginarii</i> and -<i>phantastici</i> by Rizetti; by Buffon, <i>couleurs accidentelles</i>; by -Scherfer, <i>scheinfarben</i> (apparent colours); <i>ocular illusions</i> and -<i>deceptions of sight</i><span class="pagenum"><a name="Page_2" id="Page_2">[Pg 2]</a></span> by many; by Hamberger, <i>vitia fugitiva</i>; by -Darwin, <i>ocular spectra</i>.</p> - -<p class="para"><a id="a3">3.</a></p> - -<p>We have called them physiological because they belong to the eye in a -healthy state; because we consider them as the necessary conditions -of vision; the lively alternating action of which, with reference to -external objects and a principle within it, is thus plainly indicated.</p> - -<p class="para"><a id="a4">4.</a></p> - -<p>To these we subjoin the pathological colours, which, like all -deviations from a constant law, afford a more complete insight into the -nature of the physiological colours.</p> - -<hr class="r5" /> - -<h5>I</h5> -<h5>EFFECTS OF LIGHT AND DARKNESS ON THE EYE.</h5> - - -<p class="para"><a id="a5">5.</a></p> - -<p>The retina, after being acted upon by light or darkness, is found to be -in two different states, which are entirely opposed to each other.</p> - -<p class="para"><a id="a6">6.</a></p> - -<p>If we keep the eyes open in a totally dark place, a certain sense of -privation is experienced. The organ is abandoned to itself; it retires -into itself. That stimulating and grateful contact is wanting by means -of which it is connected with the external world, and becomes part of a -whole.</p> - -<p><span class="pagenum"><a name="Page_3" id="Page_3">[Pg 3]</a></span></p> - -<p class="para"><a id="a7">7.</a></p> - -<p>If we look on a white, strongly illumined surface, the eye is dazzled, -and for a time is incapable of distinguishing objects moderately -lighted.</p> - -<p class="para"><a id="a8">8.</a></p> - -<p>The whole of the retina is acted on in each of these extreme states, -and thus we can only experience one of these effects at a time. In -the one case (6) we found the organ in the utmost relaxation and -susceptibility; in the other (7) in an overstrained state, and scarcely -susceptible at all.</p> - -<p class="para"><a id="a9">9.</a></p> - -<p>If we pass suddenly from the one state to the other, even without -supposing these to be the extremes, but only, perhaps, a change from -bright to dusky, the difference is remarkable, and we find that the -effects last for some time.</p> - -<p class="para"><a id="a10">10.</a></p> - -<p>In passing from bright daylight to a dusky place we distinguish nothing -at first: by degrees the eye recovers its susceptibility; strong eyes -sooner than weak ones; the former in a minute, while the latter may -require seven or eight minutes.</p> - -<p class="para"><a id="a11">11.</a></p> - -<p>The fact that the eye is not susceptible to faint<span class="pagenum"><a name="Page_4" id="Page_4">[Pg 4]</a></span> impressions of -light, if we pass from light to comparative darkness, has led to -curious mistakes in scientific observations. Thus an observer, whose -eyes required some time to recover their tone, was long under the -impression that rotten wood did not emit light at noon-day, even in a -dark room. The fact was, he did not see the faint light, because he was -in the habit of passing from bright sunshine to the dark room, and only -subsequently remained so long there that the eye had time to recover -itself.</p> - -<p>The same may have happened to Doctor Wall, who, in the daytime, even in -a dark room, could hardly perceive the electric light of amber.</p> - -<p>Our not seeing the stars by day, as well as the improved appearance of -pictures seen through a double tube, is also to be attributed to the -same cause.</p> - -<p class="para"><a id="a12">12.</a></p> - -<p>If we pass from a totally dark place to one illumined by the sun, we -are dazzled. In coming from a lesser degree of darkness to light that -is not dazzling, we perceive all objects clearer and better: hence eyes -that have been in a state of repose are in all cases better able to -perceive moderately distinct appearances.</p> - -<p>Prisoners who have been long confined in darkness acquire so great -a susceptibility of the retina, that even in the dark (probably a -darkness<span class="pagenum"><a name="Page_5" id="Page_5">[Pg 5]</a></span> very slightly illumined) they can still distinguish objects.</p> - -<p class="para"><a id="a13">13.</a></p> - -<p>In the act which we call seeing, the retina is at one and the same time -in different and even opposite states. The greatest brightness, short -of dazzling, acts near the greatest darkness. In this state we at once -perceive all the intermediate gradations of <i>chiaro-scuro</i>, and all the -varieties of hues.</p> - -<p class="para"><a id="a14">14.</a></p> - -<p>We will proceed in due order to consider and examine these elements of -the visible world, as well as the relation in which the organ itself -stands to them, and for this purpose we take the simplest objects.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_9" id="Footnote_1_9"></a><a href="#FNanchor_1_9"><span class="label">[1]</span></a> The German distinction between <i>subject</i> and <i>object</i> -is so generally understood and adopted, that it is hardly necessary -to explain that the subject is the <i>individual</i>, in this case the -<i>beholder</i>; the object, <i>all that is without him</i>.—T.</p></div> - - -<hr class="chap" /> - -<h5><a name="II" id="II">II.</a></h5> - - -<h5>EFFECTS OF BLACK AND WHITE OBJECTS ON THE EYE.</h5> - - -<p class="para"><a id="a15">15.</a></p> - -<p>In the same manner as the retina generally is affected by brightness -and darkness, so it is affected by single bright or dark objects. -If light and dark produce different results on the whole retina, so -black and white objects seen at<span class="pagenum"><a name="Page_6" id="Page_6">[Pg 6]</a></span> the same time produce the same states -together which light and dark occasioned in succession.</p> - -<p class="para"><a id="a16">16.</a></p> - -<p>A dark object appears smaller than a bright one of the same size. Let -a white disk be placed on a black ground, and a black disk on a white -ground, both being exactly similar in size; let them be seen together -at some distance, and we shall pronounce the last to be about a fifth -part smaller than the other. If the black circle be made larger by so -much, they will appear equal.<a name="FNanchor_1_10" id="FNanchor_1_10"></a><a href="#Footnote_1_10" class="fnanchor">[1]</a></p> - -<p class="para"><a id="a17">17.</a></p> - -<p>Thus Tycho de Brahe remarked that the moon in conjunction (the darker -state) appears about a fifth part smaller than when in opposition -(the bright full state). The first crescent appears to belong to a -larger disk than the remaining dark portion, which can sometimes be -distinguished at the period of the new moon. Black dresses make people -appear smaller than light ones. Lights seen behind an edge make an -apparent notch in it. A ruler, behind which the flame of a light just -appears, seems to us indented. The rising or setting sun appears to -make a notch in the horizon.</p> - -<div class="figcenter" style="width: 500px;"> -<a id="col000"></a> -<img src="images/col_000.jpg" width="500" alt="" /> -<p style="text-align: center; font-weight: bold;">Plate 1.</p> -</div> - -<p class="para"><a id="a18">18.</a></p> - -<p>Black, as the equivalent of darkness, leaves<span class="pagenum"><a name="Page_7" id="Page_7">[Pg 7]</a></span> the organ in a state of -repose; white, as the representative of light, excites it. We may, -perhaps, conclude from the above experiment (16) that the unexcited -retina, if left to itself, is drawn together, and occupies a less space -than in its active state, produced by the excitement of light.</p> - -<p>Hence Kepler says very beautifully: "Certum est vel in retinâ caussâ -picturæ, vel in spiritibus caussâ impressionis, exsistere dilatationem -lucidorum."—<i>Paralip. in Vitellionem</i>, p. 220. Scherfer expresses a -similar conjecture.—<a href="#NOTE_A">Note A</a>.</p> - -<p class="para"><a id="a19">19.</a></p> - -<p>However this may be, both impressions derived from such objects remain -in the organ itself, and last for some time, even when the external -cause is removed. In ordinary experience we scarcely notice this, for -objects are seldom presented to us which are very strongly relieved -from each other, and we avoid looking at those appearances that dazzle -the sight. In glancing from one object to another, the succession of -images appears to us distinct; we are not aware that some portion of -the impression derived from the object first contemplated passes to -that which is next looked at.</p> - -<p class="para"><a id="a20">20.</a></p> - -<p>If in the morning, on waking, when the eye is very susceptible, we look -intently at the bars<span class="pagenum"><a name="Page_8" id="Page_8">[Pg 8]</a></span> of a window relieved against the dawning sky, and -then shut our eyes or look towards a totally dark place, we shall see a -dark cross on a light ground before us for some time.</p> - -<p class="para"><a id="a21">21.</a></p> - -<p>Every image occupies a certain space on the retina, and of course a -greater or less space in proportion as the object is seen near or at a -distance. If we shut the eyes immediately after looking at the sun we -shall be surprised to find how small the image it leaves appears.</p> - -<p class="para"><a id="a22">22.</a></p> - -<p>If, on the other hand, we turn the open eye towards the side of a -room, and consider the visionary image in relation to other objects, -we shall always see it larger in proportion to the distance of the -surface on which it is thrown. This is easily explained by the laws of -perspective, according to which a small object near covers a great one -at a distance.</p> - -<p class="para"><a id="a23">23.</a></p> - -<p>The duration of these visionary impressions varies with the powers -or structure of the eye in different individuals, just as the time -necessary for the recovery of the tone of the retina varies in passing -from brightness to darkness (10): it can be measured by minutes and -seconds,<span class="pagenum"><a name="Page_9" id="Page_9">[Pg 9]</a></span> indeed much more exactly than it could formerly have been -by causing a lighted linstock to revolve rapidly, so as to appear a -circle.—<a href="#NOTE_B">Note B</a>.</p> - -<p class="para"><a id="a24">24.</a></p> - -<p>But the force with which an impinging light impresses the eye is -especially worthy of attention. The image of the sun lasts longest; -other objects, of various degrees of brightness, leave the traces of -their appearance on the eye for a proportionate time.</p> - -<p class="para"><a id="a25">25.</a></p> - -<p>These images disappear by degrees, and diminish at once in distinctness -and in size.</p> - -<p class="para"><a id="a26">26.</a></p> - -<p>They are reduced from the contour inwards, and the impression on some -persons has been that in square images the angles become gradually -blunted till at last a diminished round image floats before the eye.</p> - -<p class="para"><a id="a27">27.</a></p> - -<p>Such an image, when its impression is no more observable, can, -immediately after, be again revived on the retina by opening and -shutting the eye, thus alternately exciting and resting it.</p> - -<p><span class="pagenum"><a name="Page_10" id="Page_10">[Pg 10]</a></span></p> - -<p class="para"><a id="a28">28.</a></p> - -<p>Images may remain on the retina in morbid affections of the eye for -fourteen, seventeen minutes, or even longer. This indicates extreme -weakness of the organ, its inability to recover itself; while visions -of persons or things which are the objects of love or aversion indicate -the connexion between sense and thought.</p> - -<p class="para"><a id="a29">29.</a></p> - -<p>If, while the image of the window-bars before mentioned lasts, we -look upon a light grey surface, the cross will then appear light -and the panes dark. In the first case (20) the image was like the -original picture, so that the visionary impression also could continue -unchanged; but in the present instance our attention is excited by a -contrary effect being produced. Various examples have been given by -observers of nature.</p> - -<p class="para"><a id="a30">30.</a></p> - -<p>The scientific men who made observations in the Cordilleras saw a -bright appearance round the shadows of their heads on some clouds. This -example is a case in point; for, while they fixed their eyes on the -dark shadow, and at the same time moved from the spot, the compensatory -light image appeared to float round the<span class="pagenum"><a name="Page_11" id="Page_11">[Pg 11]</a></span> real dark one. If we look at -a black disk on a light grey surface, we shall presently, by changing -the direction of the eyes in the slightest degree, see a bright halo -floating round the dark circle.</p> - -<p>A similar circumstance happened to myself: for while, as I sat in the -open air, I was talking to a man who stood at a little distance from me -relieved on a grey sky, it appeared to me, as I slightly altered the -direction of my eyes, after having for some time looked fixedly at him, -that his head was encircled with a dazzling light.</p> - -<p>In the same way probably might be explained the circumstance that -persons crossing dewy meadows at sunrise see a brightness round each -other's heads<a name="FNanchor_2_11" id="FNanchor_2_11"></a><a href="#Footnote_2_11" class="fnanchor">[2]</a>; the brightness in this case may be also iridescent, -as the phenomena of refraction come into the account.</p> - -<p>Thus again it has been asserted that the shadows of a balloon thrown on -clouds were bordered with bright and somewhat variegated circles.</p> - -<p>Beccaria made use of a paper kite in some experiments on electricity. -Round this kite appeared a small shining cloud varying in size; the -same brightness was even observed round part of the string. Sometimes -it disappeared,<span class="pagenum"><a name="Page_12" id="Page_12">[Pg 12]</a></span> and if the kite moved faster the light appeared to -float to and fro for a few moments on the place before occupied. This -appearance, which could not be explained by those who observed it at -the time, was the image which the eye retained of the kite relieved as -a dark mass on a bright sky; that image being changed into a light mass -on a comparatively dark background.</p> - -<p>In optical and especially in chromatic experiments, where the observer -has to do with bright lights whether colourless or coloured, great care -should be taken that the spectrum which the eye retains in consequence -of a previous observation does not mix with the succeeding one, and -thus affect the distinctness and purity of the impression.</p> - -<p class="para"><a id="a31">31.</a></p> - -<p>These appearances have been explained as follows: That portion of the -retina on which the dark cross (29) was impressed is to be considered -in a state of repose and susceptibility. On this portion therefore the -moderately light surface acted in a more lively manner than on the rest -of the retina, which had just been impressed with the light through -the panes, and which, having thus been excited by a much stronger -brightness, could only view the grey surface as a dark.</p> - -<p><span class="pagenum"><a name="Page_13" id="Page_13">[Pg 13]</a></span></p> - -<p class="para"><a id="a32">32.</a></p> - -<p>This mode of explanation appears sufficient for the cases in question, -but, in the consideration of phenomena hereafter to be adduced, we are -forced to trace the effects to higher sources.</p> - -<p class="para"><a id="a33">33.</a></p> - -<p>The eye after sleep exhibits its vital elasticity more especially by -its tendency to alternate its impressions, which in the simplest form -change from dark to light, and from light to dark. The eye cannot for a -moment remain in a particular state determined by the object it looks -upon. On the contrary, it is forced to a sort of opposition, which, in -contrasting extreme with extreme, intermediate degree with intermediate -degree, at the same time combines these opposite impressions, and thus -ever tends to a whole, whether the impressions are successive, or -simultaneous and confined to one image.</p> - -<p class="para"><a id="a34">34.</a></p> - -<p>Perhaps the peculiarly grateful sensation which we experience in -looking at the skilfully treated chiaro-scuro of colourless pictures -and similar works of art arises chiefly from the <i>simultaneous</i> -impression of a whole, which by the organ itself is sought, rather than -arrived at, in <i>succession</i>, and which, whatever may be the result, can -never be arrested.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_10" id="Footnote_1_10"></a><a href="#FNanchor_1_10"><span class="label">[1]</span></a> <a href="#col000">Plate 1</a>. fig. 1.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_11" id="Footnote_2_11"></a><a href="#FNanchor_2_11"><span class="label">[2]</span></a> See the Life of Benvenuto Cellini, vol. i. p. 453. Milan -edition, 1806.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_14" id="Page_14">[Pg 14]</a></span></p></div> - - - - -<h5><a name="III" id="III">III.</a></h5> - - -<h5>GREY SURFACES AND OBJECTS.</h5> - - -<p class="para"><a id="a35">35.</a></p> - -<p>A moderate light is essential to many chromatic experiments. This can -be presently obtained by surfaces more or less grey, and thus we have -at once to make ourselves acquainted with this simplest kind of middle -tint, with regard to which it is hardly necessary to observe, that -in many cases a white surface in shadow, or in a low light, may be -considered equivalent to a grey.</p> - -<p class="para"><a id="a36">36.</a></p> - -<p>Since a grey surface is intermediate between brightness and darkness, -it admits of our illustrating a phenomenon before described (29) by an -easy experiment.</p> - -<p class="para"><a id="a37">37.</a></p> - -<p>Let a black object be held before a grey surface, and let the -spectator, after looking steadfastly at it, keep his eyes unmoved while -it is taken away: the space it occupied appears much lighter. Let a -white object be held up in the same manner: on taking it away the space -it occupied will appear much darker than the<span class="pagenum"><a name="Page_15" id="Page_15">[Pg 15]</a></span> rest of the surface. Let -the spectator in both cases turn his eyes this way and that on the -surface, the visionary images will move in like manner.</p> - -<p class="para"><a id="a38">38.</a></p> - -<p>A grey object on a black ground appears much brighter than the same -object on a white ground. If both comparisons are seen together the -spectator can hardly persuade himself that the two greys are identical. -We believe this again to be a proof of the great excitability of the -retina, and of the silent resistance which every vital principle is -forced to exhibit when any definite or immutable state is presented to -it. Thus inspiration already presupposes expiration; thus every systole -its diastole. It is the universal formula of life which manifests -itself in this as in all other cases. When darkness is presented to -the eye it demands brightness, and <i>vice versâ</i>: it shows its vital -energy, its fitness to receive the impression of the object, precisely -by spontaneously tending to an opposite state.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_16" id="Page_16">[Pg 16]</a></span></p> - - - - -<h5><a name="IV" id="IV">IV.</a></h5> - - -<h5>DAZZLING COLOURLESS OBJECTS.</h5> - - -<p class="para"><a id="a39">39.</a></p> - -<p>If we look at a dazzling, altogether colourless object, it makes a -strong lasting impression, and its after-vision is accompanied by an -appearance of colour.</p> - -<p class="para"><a id="a40">40.</a></p> - -<p>Let a room be made as dark as possible; let there be a circular opening -in the window-shutter about three inches in diameter, which may be -closed or not at pleasure. The sun being suffered to shine through this -on a white surface, let the spectator from some little distance fix his -eyes on the bright circle thus admitted. The hole being then closed, -let him look towards the darkest part of the room; a circular image -will now be seen to float before him. The middle of this circle will -appear bright, colourless, or somewhat yellow, but the border will at -the same moment appear red.</p> - -<p>After a time this red, increasing towards the centre, covers the whole -circle, and at last the bright central point. No sooner, however, is -the whole circle red than the edge begins to be blue, and the blue -gradually encroaches inwards<span class="pagenum"><a name="Page_17" id="Page_17">[Pg 17]</a></span> on the red. When the whole is blue -the edge becomes dark and colourless. This darker edge again slowly -encroaches on the blue till the whole circle appears colourless. The -image then becomes gradually fainter, and at the same time diminishes -in size. Here again we see how the retina recovers itself by a -succession of vibrations after the powerful external impression it -received. (<a href="#a25">25</a>, <a href="#a26">26</a>.)</p> - -<p class="para"><a id="a41">41.</a></p> - -<p>By several repetitions similar in result, I found the comparative -duration of these appearances in my own case to be as follows:—</p> - -<p>I looked on the bright circle five seconds, and then, having closed -the aperture, saw the coloured visionary circle floating before me. -After thirteen seconds it was altogether red; twenty-nine seconds -next elapsed till the whole was blue, and forty-eight seconds till -it appeared colourless. By shutting and opening the eye I constantly -revived the image, so that it did not quite disappear till seven -minutes had elapsed.</p> - -<p>Future observers may find these periods shorter or longer as their -eyes may be stronger or weaker (<a href="#a23">23</a>), but it would be very remarkable -if, notwithstanding such variations, a corresponding proportion as to -relative duration should be found to exist.</p> - -<p><span class="pagenum"><a name="Page_18" id="Page_18">[Pg 18]</a></span></p> - -<p class="para"><a id="a42">42.</a></p> - -<p>But this remarkable phenomenon no sooner excites our attention than we -observe a new modification of it.</p> - -<p>If we receive the impression of the bright circle as before, and then -look on a light grey surface in a moderately lighted room, an image -again floats before us; but in this instance a dark one: by degrees it -is encircled by a green border that gradually spreads inwards over the -whole circle, as the red did in the former instance. As soon as this -has taken place a dingy yellow appears, and, filling the space as the -blue did before, is finally lost in a negative shade.</p> - -<p class="para"><a id="a43">43.</a></p> - -<p>These two experiments may be combined by placing a black and a white -plane surface next each other in a moderately lighted room, and then -looking alternately on one and the other as long as the impression of -the light circle lasts: the spectator will then perceive at first a red -and green image alternately, and afterwards the other changes. After a -little practice the two opposite colours may be perceived at once, by -causing the floating image to fall on the junction of the two planes. -This can be more conveniently done if the planes are at some distance, -for the spectrum then appears larger.</p> - -<p><span class="pagenum"><a name="Page_19" id="Page_19">[Pg 19]</a></span></p> - -<p class="para"><a id="a44">44.</a></p> - -<p>I happened to be in a forge towards evening at the moment when a -glowing mass of iron was placed on the anvil; I had fixed my eyes -steadfastly on it, and, turning round, I looked accidentally into an -open coal-shed: a large red image now floated before my eyes, and, as I -turned them from the dark opening to the light boards of which the shed -was constructed, the image appeared half green, half red, according as -it had a lighter or darker ground behind it. I did not at that time -take notice of the subsequent changes of this appearance.</p> - -<p class="para"><a id="a45">45.</a></p> - -<p>The after-vision occasioned by a total dazzling of the retina -corresponds with that of a circumscribed bright object. The red colour -seen by persons who are dazzled with snow belongs to this class of -phenomena, as well as the singularly beautiful green colour which dark -objects seem to wear after looking long on white paper in the sun. The -details of such experiments may be investigated hereafter by those -whose young eyes are capable of enduring such trials further for the -sake of science.</p> - -<p class="para"><a id="a46">46.</a></p> - -<p>With these examples we may also class the black letters which in the -evening light appear<span class="pagenum"><a name="Page_20" id="Page_20">[Pg 20]</a></span> red. Perhaps we might insert under the same -category the story that drops of blood appeared on the table at which -Henry IV. of France had seated himself with the Duc de Guise to play at -dice.</p> - - - -<hr class="chap" /> -<h5><a name="V" id="V">V.</a></h5> - - -<h5>COLOURED OBJECTS.</h5> - - -<p class="para"><a id="a47">47.</a></p> - -<p>We have hitherto seen the physiological colours displayed in the -after-vision of colourless bright objects, and also in the after-vision -of general colourless brightness; we shall now find analogous -appearances if a given colour be presented to the eye: in considering -this, all that has been hitherto detailed must be present to our -recollection.</p> - -<p class="para"><a id="a48">48.</a></p> - -<p>The impression of coloured objects remains in the eye like that of -colourless ones, but in this case the energy of the retina, stimulated -as it is to produce the opposite colour, will be more apparent.</p> - -<p class="para"><a id="a49">49.</a></p> - -<p>Let a small piece of bright-coloured paper or silk stuff be held before -a moderately lighted white surface; let the observer look steadfastly<span class="pagenum"><a name="Page_21" id="Page_21">[Pg 21]</a></span> -on the small coloured object, and let it be taken away after a time -while his eyes remain unmoved; the spectrum of another colour will then -be visible on the white plane. The coloured paper may be also left in -its place while the eye is directed to another part of the white plane; -the same spectrum will be visible there too, for it arises from an -image which now belongs to the eye.</p> - -<p class="para"><a id="a50">50.</a></p> - -<p>In order at once to see what colour will be evoked by this contrast, -the chromatic circle<a name="FNanchor_1_12" id="FNanchor_1_12"></a><a href="#Footnote_1_12" class="fnanchor">[1]</a> may be referred to. The colours are here -arranged in a general way according to the natural order, and the -arrangement will be found to be directly applicable in the present -case; for the colours diametrically opposed to each other in this -diagram are those which reciprocally evoke each other in the eye. Thus, -yellow demands purple; orange, blue; red, green; and <i>vice versâ</i>: thus -again all intermediate gradations reciprocally evoke each other; the -simpler colour demanding the compound, and <i>vice versâ</i>.—<a href="#NOTE_C">Note C</a>.</p> - -<p class="para"><a id="a51">51.</a></p> - -<p>The cases here under consideration occur oftener than we are aware in -ordinary life; indeed,<span class="pagenum"><a name="Page_22" id="Page_22">[Pg 22]</a></span> an attentive observer sees these appearances -everywhere, while, on the other hand, the uninstructed, like our -predecessors, consider them as temporary visual defects, sometimes -even as symptoms of disorders in the eye, thus exciting serious -apprehensions. A few remarkable instances may here be inserted.</p> - -<p class="para"><a id="a52">52.</a></p> - -<p>I had entered an inn towards evening, and, as a well-favoured girl, -with a brilliantly fair complexion, black hair, and a scarlet bodice, -came into the room, I looked attentively at her as she stood before me -at some distance in half shadow. As she presently afterwards turned -away, I saw on the white wall, which was now before me, a black face -surrounded with a bright light, while the dress of the perfectly -distinct figure appeared of a beautiful sea-green.</p> - -<p class="para"><a id="a53">53.</a></p> - -<p>Among the materials for optical experiments, there are portraits with -colours and shadows exactly opposite to the appearance of nature. The -spectator, after having looked at one of these for a time, will see the -visionary figure tolerably true to nature. This is conformable to the -same principles, and consistent with experience, for, in the former -instance, a negress with a white head-dress would have given me a -white face surrounded with black. In the case<span class="pagenum"><a name="Page_23" id="Page_23">[Pg 23]</a></span> of the painted figures, -however, which are commonly small, the parts are not distinguishable by -every one in the after-image.</p> - -<p class="para"><a id="a54">54.</a></p> - -<p>A phenomenon which has before excited attention among the observers of -nature is to be attributed, I am persuaded, to the same cause.</p> - -<p>It has been stated that certain flowers, towards evening in summer, -coruscate, become phosphorescent, or emit a momentary light. Some -persons have described their observation of this minutely. I had often -endeavoured to witness it myself, and had even resorted to artificial -contrivances to produce it.</p> - -<p>On the 19th of June, 1799, late in the evening, when the twilight was -deepening into a clear night, as I was walking up and down the garden -with a friend, we very distinctly observed a flame-like appearance -near the oriental poppy, the flowers of which are remarkable for their -powerful red colour. We approached the place and looked attentively -at the flowers, but could perceive nothing further, till at last, by -passing and repassing repeatedly, while we looked sideways on them, we -succeeded in renewing the appearance as often as we pleased. It proved -to be a physiological phenomenon, such as others we have described, and -the apparent<span class="pagenum"><a name="Page_24" id="Page_24">[Pg 24]</a></span> coruscation was nothing but the spectrum of the flower in -the compensatory blue-green colour.</p> - -<p>In looking directly at a flower the image is not produced, but it -appears immediately as the direction of the eye is altered. Again, by -looking sideways on the object, a double image is seen for a moment, -for the spectrum then appears near and on the real object.</p> - -<p>The twilight accounts for the eye being in a perfect state of repose, -and thus very susceptible, and the colour of the poppy is sufficiently -powerful in the summer twilight of the longest days to act with -full effect and produce a compensatory image. I have no doubt these -appearances might be reduced to experiment, and the same effect -produced by pieces of coloured paper. Those who wish to take the most -effectual means for observing the appearance in nature—suppose in a -garden—should fix the eyes on the bright flowers selected for the -purpose, and, immediately after, look on the gravel path. This will -be seen studded with spots of the opposite colour. The experiment is -practicable on a cloudy day, and even in the brightest sunshine, for -the sun-light, by enhancing the brilliancy of the flower, renders it -fit to produce the compensatory colour sufficiently distinct to be -perceptible even in a bright light. Thus, peonies produce beautiful -green, marigolds vivid blue spectra.</p> - -<p><span class="pagenum"><a name="Page_25" id="Page_25">[Pg 25]</a></span></p> - -<p class="para"><a id="a55">55.</a></p> - -<p>As the opposite colour is produced by a constant law in experiments -with coloured objects on portions of the retina, so the same effect -takes place when the whole retina is impressed with a single colour. We -may convince ourselves of this by means of coloured glasses. If we look -long through a blue pane of glass, everything will afterwards appear -in sunshine to the naked eye, even if the sky is grey and the scene -colourless. In like manner, in taking off green spectacles, we see all -objects in a red light. Every decided colour does a certain violence to -the eye, and forces the organ to opposition.</p> - -<p class="para"><a id="a56">56.</a></p> - -<p>We have hitherto seen the opposite colours producing each other -successively on the retina: it now remains to show by experiment -that the same effects can exist simultaneously. If a coloured object -impinges on one part of the retina, the remaining portion at the same -moment has a tendency to produce the compensatory colour. To pursue -a former experiment, if we look on a yellow piece of paper placed -on a white surface, the remaining part of the organ has already a -tendency to produce a purple hue on the colourless surface: in this -case the small portion of yellow is not powerful enough to produce<span class="pagenum"><a name="Page_26" id="Page_26">[Pg 26]</a></span> -this appearance distinctly, but, if a white paper is placed on a yellow -wall, we shall see the white tinged with a purple hue.</p> - -<p class="para"><a id="a57">57.</a></p> - -<p>Although this experiment may be made with any colours, yet red and -green are particularly recommended for it, because these colours seem -powerfully to evoke each other. Numerous instances occur in daily -experience. If a green paper is seen through striped or flowered -muslin, the stripes or flowers will appear reddish. A grey building -seen through green pallisades appears in like manner reddish. A -modification of this tint in the agitated sea is also a compensatory -colour: the light side of the waves appears green in its own colour, -and the shadowed side is tinged with the opposite hue. The different -direction of the waves with reference to the eye produces the same -effect. Objects seen through an opening in a red or green curtain -appear to wear the opposite hue. These appearances will present -themselves to the attentive observer on all occasions, even to an -unpleasant degree.</p> - -<p class="para"><a id="a58">58.</a></p> - -<p>Having made ourselves acquainted with the simultaneous exhibition of -these effects in direct cases, we shall find that we can also observe -them by indirect means. If we place a piece of<span class="pagenum"><a name="Page_27" id="Page_27">[Pg 27]</a></span> paper of a bright -orange colour on the white surface, we shall, after looking intently -at it, scarcely perceive the compensatory colour on the rest of the -surface: but when we take the orange paper away, and when the blue -spectrum appears in its place, immediately as this spectrum becomes -fully apparent, the rest of the surface will be overspread, as if by a -flash, with a reddish-yellow light, thus exhibiting to the spectator -in a lively manner the productive energy of the organ, in constant -conformity with the same law.</p> - -<p class="para"><a id="a59">59.</a></p> - -<p>As the compensatory colours easily appear, where they do not exist in -nature, near and after the original opposite ones, so they are rendered -more intense where they happen to mix with a similar real hue. In a -court which was paved with grey limestone flags, between which grass -had grown, the grass appeared of an extremely beautiful green when -the evening clouds threw a scarcely perceptible reddish light on the -pavement. In an opposite case we find, in walking through meadows, -where we see scarcely anything but green, the stems of trees and the -roads often gleam with a reddish hue. This tone is not uncommon in -the works of landscape painters, especially those who practice in -water-colours: they probably see it in<span class="pagenum"><a name="Page_28" id="Page_28">[Pg 28]</a></span> nature, and thus, unconsciously -imitating it, their colouring is criticised as unnatural.</p> - -<p class="para"><a id="a60">60.</a></p> - -<p>These phenomena are of the greatest importance, since they direct our -attention to the laws of vision, and are a necessary preparation for -future observations on colours. They show that the eye especially -demands completeness, and seeks to eke out the colorific circle in -itself. The purple or violet colour suggested by yellow contains red -and blue; orange, which responds to blue, is composed of yellow and -red; green, uniting blue and yellow, demands red; and so through all -gradations of the most complicated combinations. That we are compelled -in this case to assume three leading colours has been already remarked -by other observers.</p> - -<p class="para"><a id="a61">61.</a></p> - -<p>When in this completeness the elements of which it is composed are -still appreciable by the eye, the result is justly called harmony. We -shall subsequently endeavour to show how the theory of the harmony of -colours may be deduced from these phenomena, and how, simply through -these qualities, colours may be capable of being applied to æsthetic -purposes. This will be shown when we have gone through the whole circle -of our observations, returning to the point from which we started.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_12" id="Footnote_1_12"></a><a href="#FNanchor_1_12"><span class="label">[1]</span></a> <a href="#col000">Plate 1</a>, fig. 3.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_29" id="Page_29">[Pg 29]</a></span></p></div> - - - - -<h5><a name="VI" id="VI">VI.</a></h5> - - -<h5>COLOURED SHADOWS.</h5> - - -<p class="para"><a id="a62">62.</a></p> - -<p>Before, however, we proceed further, we have yet to observe some very -remarkable cases of the vivacity with which the suggested colours -appear in the neighbourhood of others: we allude to coloured shadows. -To arrive at these we first turn our attention to shadows that are -colourless or negative.</p> - -<p class="para"><a id="a63">63.</a></p> - -<p>A shadow cast by the sun, in its full brightness, on a white surface, -gives us no impression of colour; it appears black, or, if a contrary -light (here assumed to differ only in degree) can act upon it, it is -only weaker, half-lighted, grey.</p> - -<p class="para"><a id="a64">64.</a></p> - -<p>Two conditions are necessary for the existence of coloured shadows: -first, that the principal light tinge the white surface with some hue; -secondly, that a contrary light illumine to a certain extent the cast -shadow.</p> - -<p class="para"><a id="a65">65.</a></p> - -<p>Let a short, lighted candle be placed at twilight on a sheet of white -paper. Between it and the declining daylight let a pencil be placed<span class="pagenum"><a name="Page_30" id="Page_30">[Pg 30]</a></span> -upright, so that its shadow thrown by the candle may be lighted, but -not overcome, by the weak daylight: the shadow will appear of the most -beautiful blue.</p> - -<p class="para"><a id="a66">66.</a></p> - -<p>That this shadow is blue is immediately evident; but we can only -persuade ourselves by some attention that the white paper acts as a -reddish yellow, by means of which the complemental blue is excited in -the eye.—<a href="#NOTE_D">Note D</a>.</p> - -<p class="para"><a id="a67">67.</a></p> - -<p>In all coloured shadows, therefore, we must presuppose a colour excited -or suggested by the hue of the surface on which the shadow is thrown. -This may be easily found to be the case by attentive consideration, but -we may convince ourselves at once by the following experiment.</p> - -<p class="para"><a id="a68">68.</a></p> - -<p>Place two candles at night opposite each other on a white surface; hold -a thin rod between them upright, so that two shadows be cast by it; -take a coloured glass and hold it before one of the lights, so that -the white paper appear coloured; at the same moment the shadow cast by -the coloured light and slightly illumined by the colourless one will -exhibit the complemental hue.</p> - -<p><span class="pagenum"><a name="Page_31" id="Page_31">[Pg 31]</a></span></p> - -<p class="para"><a id="a69">69.</a></p> - -<p>An important consideration suggests itself here, to which we shall -frequently have occasion to return. Colour itself is a degree of -darkness <i>σκιερόν</i>; hence Kircher is perfectly right in calling it -<i>lumen opacatum</i>. As it is allied to shadow, so it combines readily -with it; it appears to us readily in and by means of shadow the -moment a suggesting cause presents itself. We could not refrain from -adverting at once to a fact which we propose to trace and develop -hereafter.—<a href="#NOTE_E">Note E</a>.</p> - -<p class="para"><a id="a70">70.</a></p> - -<p>Select the moment in twilight when the light of the sky is still -powerful enough to cast a shadow which cannot be entirely effaced by -the light of a candle. The candle may be so placed that a double shadow -shall be visible, one from the candle towards the daylight, and another -from the daylight towards the candle. If the former is blue the latter -will appear orange-yellow: this orange-yellow is in fact, however, only -the yellow-red light of the candle diffused over the whole paper, and -which <i>becomes visible in shadow</i>.</p> - -<p class="para"><a id="a71">71.</a></p> - -<p>This is best exemplified by the former experiment with two candles and -coloured glasses.</p> - -<p><span class="pagenum"><a name="Page_32" id="Page_32">[Pg 32]</a></span></p> - -<p>The surprising readiness with which shadow assumes a colour will again -invite our attention in the further consideration of reflections and -elsewhere.</p> - -<p class="para"><a id="a72">72.</a></p> - -<p>Thus the phenomena of coloured shadows may be traced to their cause -without difficulty. Henceforth let any one who sees an instance of -the kind observe only with what hue the light surface on which they -are thrown is tinged. Nay, the colour of the shadow may be considered -as a chromatoscope of the illumined surface, for the spectator may -always assume the colour of the light to be the opposite of that of the -shadow, and by an attentive examination may ascertain this to be the -fact in every instance.</p> - -<p class="para"><a id="a73">73.</a></p> - -<p>These appearances have been a source of great perplexity to former -observers: for, as they were remarked chiefly in the open air, where -they commonly appeared blue, they were attributed to a certain inherent -blue or blue colouring quality in the air. The inquirer can, however, -convince himself, by the experiment with the candle in a room, that no -kind of blue light or reflection is necessary to produce the effect -in question. The experiment may be made on a cloudy day with white -curtains drawn<span class="pagenum"><a name="Page_33" id="Page_33">[Pg 33]</a></span> before the light, and in a room where no trace of blue -exists, and the blue shadow will be only so much the more beautiful.</p> - -<p class="para"><a id="a74">74.</a></p> - -<p>De Saussure, in the description of his ascent of Mont Blanc, says, "A -second remark, which may not be uninteresting, relates to the colour of -the shadows. These, notwithstanding the most attentive observation, we -never found dark blue, although this had been frequently the case in -the plain. On the contrary, in fifty-nine instances we saw them once -yellowish, six times pale bluish, eighteen times colourless or black, -and thirty-four times pale violet. Some natural philosophers suppose -that these colours arise from accidental vapours diffused in the air, -which communicate their own hues to the shadows; not that the colours -of the shadows are occasioned by the reflection of any given sky colour -or interposition of any given air colour: the above observations seem -to favour this opinion." The instances given by De Saussure may be now -explained and classed with analogous examples without difficulty.</p> - -<p>At a great elevation the sky was generally free from vapours, the sun -shone in full force on the snow, so that it appeared perfectly white -to the eye: in this case they saw the shadows quite colourless. If the -air was charged with a<span class="pagenum"><a name="Page_34" id="Page_34">[Pg 34]</a></span> certain degree of vapour, in consequence of -which the light snow would assume a yellowish tone, the shadows were -violet-coloured, and this effect, it appears, occurred oftenest. They -saw also bluish shadows, but this happened less frequently; and that -the blue and violet were pale was owing to the surrounding brightness, -by which the strength of the shadows was mitigated. Once only they -saw the shadow yellowish: in this case, as we have already seen (<a href="#a70">70</a>), -the shadow is cast by a colourless light, and slightly illumined by a -coloured one.</p> - -<p class="para"><a id="a75">75.</a></p> - -<p>In travelling over the Harz in winter, I happened to descend from the -Brocken towards evening; the wide slopes extending above and below me, -the heath, every insulated tree and projecting rock, and all masses of -both, were covered with snow or hoar-frost. The sun was sinking towards -the Oder ponds<a name="FNanchor_1_13" id="FNanchor_1_13"></a><a href="#Footnote_1_13" class="fnanchor">[1]</a>. During the day, owing to the yellowish hue of the -snow, shadows tending to violet had already been observable; these -might now be pronounced to be decidedly blue, as the illumined parts -exhibited a yellow deepening to orange.</p> - -<p>But as the sun at last was about to set, and its rays, greatly -mitigated by the thicker vapours,<span class="pagenum"><a name="Page_35" id="Page_35">[Pg 35]</a></span> began to diffuse a most beautiful -red colour over the whole scene around me, the shadow colour changed -to a green, in lightness to be compared to a sea-green, in beauty to -the green of the emerald. The appearance became more and more vivid: -one might have imagined oneself in a fairy world, for every object had -clothed itself in the two vivid and so beautifully harmonising colours, -till at last, as the sun went down, the magnificent spectacle was lost -in a grey twilight, and by degrees in a clear moon-and-starlight night.</p> - -<p class="para"><a id="a76">76.</a></p> - -<p>One of the most beautiful instances of coloured shadows may be -observed during the full moon. The candle-light and moon-light may be -contrived to be exactly equal in force; both shadows may be exhibited -with equal strength and clearness, so that both colours balance each -other perfectly. A white surface being placed opposite the full moon, -and the candle being placed a little on one side at a due distance, -an opaque body is held before the white plane, A double shadow will -then be seen: that cast by the moon and illumined by the candle-light -will be a powerful red-yellow; and contrariwise, that cast by the -candle and illumined by the moon will appear of the most beautiful -blue. The shadow, composed of the union of the two shadows, where<span class="pagenum"><a name="Page_36" id="Page_36">[Pg 36]</a></span> -they cross each other, is black. The yellow shadow (<a href="#a74">74</a>) cannot perhaps -be exhibited in a more striking manner. The immediate vicinity of -the blue and the interposing black shadow make the appearance the -more agreeable. It will even be found, if the eye dwells long on -these colours, that they mutually evoke and enhance each other, the -increasing red in the one still producing its contrast, viz. a kind of -sea-green.</p> - -<p class="para"><a id="a77">77.</a></p> - -<p>We are here led to remark that in this, and in all cases, a moment or -two may perhaps be necessary to produce the complemental colour. The -retina must be first thoroughly impressed with the demanding hue before -the responding one can be distinctly observable.</p> - -<p class="para"><a id="a78">78.</a></p> - -<p>When divers are under water, and the sunlight shines into the -diving-bell, everything is seen in a red light (the cause of which -will be explained hereafter), while the shadows appear green. The very -same phenomenon which I observed on a high mountain (<a href="#a75">75</a>) is presented -to others in the depths of the sea, and thus Nature throughout is in -harmony with herself.</p> - -<p class="para"><a id="a79">79.</a></p> - -<p>Some observations and experiments which equally illustrate what has -been stated with regard<span class="pagenum"><a name="Page_37" id="Page_37">[Pg 37]</a></span> to coloured objects and coloured shadows may -be here added. Let a white paper blind be fastened inside the window -on a winter evening; in this blind let there be an opening, through -which the snow of some neighbouring roof can be seen. Towards dusk let -a candle be brought into the room; the snow seen through the opening -will then appear perfectly blue, because the paper is tinged with warm -yellow by the candle-light. The snow seen through the aperture is here -equivalent to a shadow illumined by a contrary light (<a href="#a76">76</a>), and may also -represent a grey disk on a coloured surface (<a href="#a56">56</a>).</p> - -<p class="para"><a id="a80">80.</a></p> - -<p>Another very interesting experiment may conclude these examples. If we -take a piece of green glass of some thickness, and hold it so that the -window bars be reflected in it, they will appear double owing to the -thickness of the glass. The image which is reflected from the under -surface of the glass will be green; the image which is reflected from -the upper surface, and which should be colourless, will appear red.</p> - -<p>The experiment may be very satisfactorily made by pouring water into -a vessel, the inner surface of which can act as a mirror; for both -reflections may first be seen colourless while the water is pure, and -then by tinging it, they will exhibit two opposite hues.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_13" id="Footnote_1_13"></a><a href="#FNanchor_1_13"><span class="label">[1]</span></a> Reservoirs in which water is collected from various small -streams, to work the mines.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_38" id="Page_38">[Pg 38]</a></span></p></div> - - - - -<h5><a name="VII" id="VII">VII.</a></h5> - - -<h5>FAINT LIGHTS.</h5> - - -<p class="para"><a id="a81">81.</a></p> - -<p>Light, in its full force, appears purely white, and it gives this -impression also in its highest degree of dazzling splendour. Light, -which is not so powerful, can also, under various conditions, remain -colourless. Several naturalists and mathematicians have endeavoured to -measure its degrees—Lambert, Bouguer, Rumford.</p> - -<p class="para"><a id="a82">82.</a></p> - -<p>Yet an appearance of colour presently manifests itself in fainter -lights, for in their relation to absolute light they resemble the -coloured spectra of dazzling objects (<a href="#a39">39</a>).</p> - -<p class="para"><a id="a83">83.</a></p> - -<p>A light of any kind becomes weaker, either when its own force, from -whatever cause, is diminished, or when the eye is so circumstanced or -placed, that it cannot be sufficiently impressed by the action of the -light. Those appearances which may be called objective, come under the -head of physical colours. We will only advert here to the transition -from white to red heat in glowing iron. We may also observe<span class="pagenum"><a name="Page_39" id="Page_39">[Pg 39]</a></span> that the -flames of lights at night appear redder in proportion to their distance -from the eye.—<a href="#NOTE_F">Note F</a>.</p> - -<p class="para"><a id="a84">84.</a></p> - -<p>Candle-light at night acts as yellow when seen near; we can perceive -this by the effect it produces on other colours. At night a pale yellow -is hardly to be distinguished from white; blue approaches to green, and -rose-colour to orange.</p> - -<p class="para"><a id="a85">85.</a></p> - -<p>Candle-light at twilight acts powerfully as a yellow light: this -is best proved by the purple blue shadows which, under these -circumstances, are evoked by the eye.</p> - -<p class="para"><a id="a86">86.</a></p> - -<p>The retina may be so excited by a strong light that it cannot perceive -fainter lights (<a href="#a11">11</a>): if it perceive these they appear coloured: hence -candle-light by day appears reddish, thus resembling, in its relation -to fuller light, the spectrum of a dazzling object; nay, if at night we -look long and intently on the flame of a light, it appears to increase -in redness.</p> - -<p class="para"><a id="a87">87.</a></p> - -<p>There are faint lights which, notwithstanding their moderate lustre, -give an impression of a<span class="pagenum"><a name="Page_40" id="Page_40">[Pg 40]</a></span> white, or, at the most, of a light yellow -appearance on the retina; such as the moon in its full splendour. -Rotten wood has even a kind of bluish light. All this will hereafter be -the subject of further remarks.</p> - -<p class="para"><a id="a88">88.</a></p> - -<p>If at night we place a light near a white or greyish wall so that the -surface be illumined from this central point to some extent, we find, -on observing the spreading light at some distance, that the boundary of -the illumined surface appears to be surrounded with a yellow circle, -which on the outside tends to red-yellow. We thus observe that when -light direct or reflected does not act in its full force, it gives an -impression of yellow, of reddish, and lastly even of red. Here we find -the transition to halos which we are accustomed to see in some mode or -other round luminous points.</p> - - - -<hr class="chap" /> -<h5><a name="VIII" id="VIII">VIII.</a></h5> - - -<h5>SUBJECTIVE HALOS.</h5> - - -<p class="para"><a id="a89">89.</a></p> - -<p>Halos may be divided into subjective and objective. The latter will -be considered under the physical colours; the first only belong here. -These are distinguished from the objective<span class="pagenum"><a name="Page_41" id="Page_41">[Pg 41]</a></span> halos by the circumstance -of their vanishing when the point of light which produces them on the -retina is covered.</p> - -<p class="para"><a id="a90">90.</a></p> - -<p>We have before noticed the impression of a luminous object on the -retina, and seen that it appears larger: but the effect is not at -an end here, it is not confined to the impression of the image; an -expansive action also takes place, spreading from the centre.</p> - -<p class="para"><a id="a91">91.</a></p> - -<p>That a nimbus of this kind is produced round the luminous image in the -eye may be best seen in a dark room, if we look towards a moderately -large opening in the window-shutter. In this case the bright image is -surrounded by a circular misty light. I saw such a halo bounded by a -yellow and yellow-red circle on opening my eyes at dawn, on an occasion -when I passed several nights in a bed-carriage.</p> - -<p class="para"><a id="a92">92.</a></p> - -<p>Halos appear most vivid when the eye is susceptible from having been in -a state of repose. A dark background also heightens their appearance. -Both causes account for our seeing them so strong if a light is -presented to the eyes<span class="pagenum"><a name="Page_42" id="Page_42">[Pg 42]</a></span> on waking at night. These conditions were -combined when Descartes after sleeping, as he sat in a ship, remarked -such a vividly-coloured halo round the light.</p> - -<p class="para"><a id="a93">93.</a></p> - -<p>A light must shine moderately, not dazzle, in order to produce the -impression of a halo in the eye; at all events the halos of dazzling -lights cannot be observed. We see a splendour of this kind round the -image of the sun reflected from the surface of water.</p> - -<p class="para"><a id="a94">94.</a></p> - -<p>A halo of this description, attentively observed, is found to be -encircled towards its edge with a yellow border: but even here the -expansive action, before alluded to, is not at an end, but appears -still to extend in varied circles.</p> - -<p class="para"><a id="a95">95.</a></p> - -<p>Several cases seem to indicate a circular action of the retina, whether -owing to the round form of the eye itself and its different parts, or -to some other cause.</p> - -<p class="para"><a id="a96">96.</a></p> - -<p>If the eye is pressed only in a slight degree from the inner corner, -darker or lighter circles<span class="pagenum"><a name="Page_43" id="Page_43">[Pg 43]</a></span> appear. At night, even without pressure, we -can sometimes perceive a succession of such circles emerging from, or -spreading over, each other.</p> - -<p class="para"><a id="a97">97.</a></p> - -<p>We have already seen that a yellow border is apparent round the white -space illumined by a light placed near it. This may be a kind of -objective halo. (<a href="#a88">88</a>.)</p> - -<p class="para"><a id="a98">98.</a></p> - -<p>Subjective halos may be considered as the result of a conflict between -the light and a living surface. From the conflict between the exciting -principle and the excited, an undulating motion arises, which may be -illustrated by a comparison with the circles on water. The stone thrown -in drives the water in all directions; the effect attains a maximum, -it reacts, and being opposed, continues under the surface. The effect -goes on, culminates again, and thus the circles are repeated. If we -have ever remarked the concentric rings which appear in a glass of -water on trying to produce a tone by rubbing the edge; if we call to -mind the intermitting pulsations in the reverberations of bells, we -shall approach a conception of what may take place on the retina when -the image of a luminous object impinges on it, not to mention<span class="pagenum"><a name="Page_44" id="Page_44">[Pg 44]</a></span> that as -a living and elastic structure, it has already a circular principle in -its organisation.—<a href="#NOTE_G">Note G</a>.</p> - -<p class="para"><a id="a99">99.</a></p> - -<p>The bright circular space which appears round the shining object -is yellow, ending in red: then follows a greenish circle, which is -terminated by a red border. This appears to be the usual phenomenon -where the luminous body is somewhat considerable in size. These halos -become greater the more distant we are from the luminous object.</p> - -<p class="para"><a id="a100">100.</a></p> - -<p>Halos may, however, appear extremely small and numerous when the -impinging image is minute, yet powerful, in its effect. The experiment -is best made with a piece of gold-leaf placed on the ground and -illumined by the sun. In these cases the halos appear in variegated -rays. The iridescent appearance produced in the eye when the sun -pierces through the leaves of trees seems also to belong to the same -class of phenomena.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_45" id="Page_45">[Pg 45]</a></span></p> - - - - -<h5><a name="PATHOLOGICAL_COLOURS" id="PATHOLOGICAL_COLOURS">PATHOLOGICAL COLOURS.</a></h5> - - -<h5>APPENDIX.</h5> - - -<p class="para"><a id="a101">101.</a></p> - -<p>We are now sufficiently acquainted with the physiological colours to -distinguish them from the pathological. We know what appearances belong -to the eye in a healthy state, and are necessary to enable the organ to -exert its complete vitality and activity.</p> - -<p class="para"><a id="a102">102.</a></p> - -<p>Morbid phenomena indicate in like manner the existence of organic -and physical laws: for if a living being deviates from those rules -with reference to which it is constructed, it still seeks to agree -with the general vitality of nature in conformity with general laws, -and throughout its whole course still proves the constancy of those -principles on which the universe has existed, and by which it is held -together.</p> - -<p class="para"><a id="a103">103.</a></p> - -<p>We will here first advert to a very remarkable state in which the -vision of many persons is found to be. As it presents a deviation -from the ordinary mode of seeing colours, it might be fairly classed -under morbid impressions; but as it is consistent in itself, as it -often occurs,<span class="pagenum"><a name="Page_46" id="Page_46">[Pg 46]</a></span> may extend to several members of a family, and probably -does not admit of cure, we may consider it as bordering only on the -nosological cases, and therefore place it first.</p> - -<p class="para"><a id="a104">104.</a></p> - -<p>I was acquainted with two individuals not more than twenty years of -age, who were thus affected: both had bluish-grey eyes, an acute sight -for near and distant objects, by day-light and candle-light, and their -mode of seeing colours was in the main quite similar.</p> - -<p class="para"><a id="a105">105.</a></p> - -<p>They agreed with the rest of the world in denominating white, black, -and grey in the usual manner. Both saw white untinged with any hue. One -saw a somewhat brownish appearance in black, and in grey a somewhat -reddish tinge. In general they appeared to have a very delicate -perception of the gradations of light and dark.</p> - -<p class="para"><a id="a106">106.</a></p> - -<p>They appeared to see yellow, red-yellow, and yellow-red,<a name="FNanchor_1_14" id="FNanchor_1_14"></a><a href="#Footnote_1_14" class="fnanchor">[1]</a> like -others: in the last case they said they saw the yellow passing as it -were over the red as if glazed: some thickly-ground carmine, which had -dried in a saucer, they called red.</p> - -<p><span class="pagenum"><a name="Page_47" id="Page_47">[Pg 47]</a></span></p> - -<p class="para"><a id="a107">107.</a></p> - -<p>But now a striking difference presented itself. If the carmine was -passed thinly over the white saucer, they would compare the light -colour thus produced to the colour of the sky, and call it blue. If -a rose was shown them beside it, they would, in like manner, call it -blue; and in all the trials which were made, it appeared that they -could not distinguish light blue from rose-colour. They confounded -rose-colour, blue, and violet on all occasions: these colours only -appeared to them to be distinguished from each other by delicate shades -of lighter, darker, intenser, or fainter appearance.</p> - -<p class="para"><a id="a108">108.</a></p> - -<p>Again they could not distinguish green from dark orange, nor, more -especially, from a red brown.</p> - -<p class="para"><a id="a109">109.</a></p> - -<p>If any one, accidentally conversing with these individuals, happened -to question them about surrounding objects, their answers occasioned -the greatest perplexity, and the interrogator began to fancy his own -wits were out of order. With some method we may, however, approach to a -nearer knowledge of the law of this deviation from the general law.</p> - -<p><span class="pagenum"><a name="Page_48" id="Page_48">[Pg 48]</a></span></p> - -<p class="para"><a id="a110">110.</a></p> - -<p>These persons, as may be gathered from what has been stated, saw fewer -colours than other people: hence arose the confusion of different -colours. They called the sky rose-colour, and the rose blue, or -<i>vice versâ</i>. The question now is: did they see both blue or both -rose-colour? did they see green orange, or orange green?</p> - -<p class="para"><a id="a111">111.</a></p> - -<p>This singular enigma appears to solve itself, if we assume that they -saw no blue, but, instead of it, a light pure red, a rose-colour. -We can comprehend what would be the result of this by means of the -chromatic diagram.</p> - -<p class="para"><a id="a112">112.</a></p> - -<p>If we take away blue from the chromatic circle we shall miss violet and -green as well. Pure red occupies the place of blue and violet, and in -again mixing with yellow the red produces orange where green should be.</p> - -<p class="para"><a id="a113">113.</a></p> - -<p>Professing to be satisfied with this mode of explanation, we have named -this remarkable deviation from ordinary vision "Acyanoblepsia."<a name="FNanchor_2_15" id="FNanchor_2_15"></a><a href="#Footnote_2_15" class="fnanchor">[2]</a> -We have prepared some coloured figures for<span class="pagenum"><a name="Page_49" id="Page_49">[Pg 49]</a></span> its further elucidation, -and in explaining these we shall add some further details. Among the -examples will be found a landscape, coloured in the mode in which the -individuals alluded to appeared to see nature: the sky rose-colour, and -all that should be green varying from yellow to brown red, nearly as -foliage appears to us in autumn<a name="FNanchor_3_16" id="FNanchor_3_16"></a><a href="#Footnote_3_16" class="fnanchor">[3]</a>.—<a href="#NOTE_H">Note H</a>.</p> - -<p class="para"><a id="a114">114.</a></p> - -<p>We now proceed to speak of morbid and other extraordinary affections -of the retina, by which the eye may be susceptible of an appearance -of light without external light, reserving for a future occasion the -consideration of galvanic light.</p> - -<p class="para"><a id="a115">115.</a></p> - -<p>If the eye receives a blow, sparks seem to spread from it. In some -states of body, again, when the blood is heated, and the system much -excited, if the eye is pressed first gently, and then more and more -strongly, a dazzling and intolerable light may be excited.</p> - -<p class="para"><a id="a116">116.</a></p> - -<p>If those who have been recently couched experience pain and heat in the -eye, they frequently<span class="pagenum"><a name="Page_50" id="Page_50">[Pg 50]</a></span> see fiery flashes and sparks: these symptoms last -sometimes for a week or fortnight, or till the pain and heat diminish.</p> - -<p class="para"><a id="a117">117.</a></p> - -<p>A person suffering from ear-ache saw sparks and balls of light in the -eye during each attack, as long as the pain lasted.</p> - -<p class="para"><a id="a118">118.</a></p> - -<p>Persons suffering from worms often experience extraordinary appearances -in the eye, sometimes sparks of fire, sometimes spectres of light, -sometimes frightful figures, which they cannot by an effort of the will -cease to see: sometimes these appearances are double.</p> - -<p class="para"><a id="a119">119.</a></p> - -<p>Hypochondriacs frequently see dark objects, such as threads, hairs, -spiders, flies, wasps. These appearances also exhibit themselves in the -incipient hard cataract. Many see semi-transparent small tubes, forms -like wings of insects, bubbles of water of various sizes, which fall -slowly down, if the eye is raised: sometimes these congregate together -so as to resemble the spawn of frogs; sometimes they appear as complete -spheres, sometimes in the form of lenses.</p> - -<p class="para"><a id="a120">120.</a></p> - -<p>As light appeared, in the former instances,<span class="pagenum"><a name="Page_51" id="Page_51">[Pg 51]</a></span> without external light, -so also these images appear without corresponding external objects. -The images are sometimes transient, sometimes they last during -the patient's life. Colour, again, frequently accompanies these -impressions: for hypochondriacs often see yellow-red stripes in the -eye: these are generally more vivid and numerous in the morning, or -when lasting.</p> - -<p class="para"><a id="a121">121.</a></p> - -<p>We have before seen that the impression of any object may remain for a -time in the eye: this we have found to be a physiological phenomenon -(<a href="#a23">23</a>): the excessive duration of such an impression, on the other band, -may be considered as morbid.</p> - -<p class="para"><a id="a122">122.</a></p> - -<p>The weaker the organ the longer the impression of the image lasts. -The retina does not so soon recover itself; and the effect may be -considered as a kind of paralysis (<a href="#a28">28</a>).</p> - -<p class="para"><a id="a123">123.</a></p> - -<p>This is not to be wondered at in the case of dazzling lights. If any -one looks at the sun, he may retain the image in his eyes for several -days. Boyle relates an instance of ten years.</p> - -<p class="para"><a id="a124">124.</a></p> - -<p>The same takes place, in a certain degree, with<span class="pagenum"><a name="Page_52" id="Page_52">[Pg 52]</a></span> regard to objects -that are not dazzling. Büsch relates of himself that the image of an -engraving, complete in all its parts, was impressed on his eye for -seventeen minutes.</p> - -<p class="para"><a id="a125">125.</a></p> - -<p>A person inclined to fulness of blood retained the image of a bright -red calico, with white spots, many minutes in the eye, and saw it float -before everything like a veil. It only disappeared by rubbing the eye -for some time.</p> - -<p class="para"><a id="a126">126.</a></p> - -<p>Scherfer observes that the red colour, which is the consequence of a -powerful impression of light, may last for some hours.</p> - -<p class="para"><a id="a127">127.</a></p> - -<p>As we can produce an appearance of light on the retina by pressure -on the eyeball, so by a gentle pressure a red colour appears, thus -corresponding with the after-image of an impression of light.</p> - -<p class="para"><a id="a128">128.</a></p> - -<p>Many sick persons, on awaking, see everything in the colour of the -morning sky, as if through a red veil: so, if in the evening they doze -and wake again, the same appearance presents itself. It remains for -some minutes, and<span class="pagenum"><a name="Page_53" id="Page_53">[Pg 53]</a></span> always disappears if the eye is rubbed a little. Red -stars and balls sometimes accompany the impression. This state may last -for a considerable time.</p> - -<p class="para"><a id="a129">129.</a></p> - -<p>The aëronauts, particularly Zambeccari and his companions, relate -that they saw the moon blood-red at the highest elevation. As they -had ascended above the vapours of the earth, through which we see the -moon and sun naturally of such a colour, it may be suspected that this -appearance may be classed with the pathological colours. The senses, -namely, may be so influenced by an unusual state, that the whole -nervous system, and particularly the retina, may sink into a kind of -inertness and inexcitability. Hence it is not impossible that the moon -might act as a very subdued light, and thus produce the impression of -the red colour. The sun even appeared blood-red to the aëronauts of -Hamburgh.</p> - -<p>If those who are at some elevation in a balloon scarcely hear each -other speak, may not this, too, be attributed to the inexcitable state -of the nerves as well as to the thinness of the air?</p> - -<p class="para"><a id="a130">130.</a></p> - -<p>Objects are often seen by sick persons in variegated colours. Boyle -relates an instance<span class="pagenum"><a name="Page_54" id="Page_54">[Pg 54]</a></span> of a lady, who, after a fall by which an eye was -bruised, saw all objects, but especially white objects, glittering in -colours, even to an intolerable degree.</p> - -<p class="para"><a id="a131">131.</a></p> - -<p>Physicians give the name of "Chrupsia" to an affection of the sight, -occurring in typhoid maladies. In these cases the patients state that -they see the boundaries of objects coloured where light and dark meet. -A change probably takes place in the humours of the eye, through which -their achromatism is affected.</p> - -<p class="para"><a id="a132">132.</a></p> - -<p>In cases of milky cataract, a very turbid crystalline lens causes -the patient to see a red light. In a case of this kind, which was -treated by the application of electricity, the red light changed by -degrees to yellow, and at last to white, when the patient again began -to distinguish objects. These changes of themselves warranted the -conclusion that the turbid state of the lens was gradually approaching -the transparent state. We shall be enabled easily to trace this effect -to its source as soon as we become better acquainted with the physical -colours.</p> - -<p class="para"><a id="a133">133.</a></p> - -<p>If again it may be assumed that a jaundiced<span class="pagenum"><a name="Page_55" id="Page_55">[Pg 55]</a></span> patient sees through -an actually yellow-coloured humour, we are at once referred to the -department of chemical colours, and it is thus evident that we can only -thoroughly investigate the chapter of pathological colours when we -have made ourselves acquainted with the whole range of the remaining -phenomena. What has been adduced may therefore suffice for the present, -till we resume the further consideration of this portion of our subject.</p> - -<p class="para"><a id="a134">134.</a></p> - -<p>In conclusion we may, however, at once advert to some peculiar states -or dispositions of the organ.</p> - -<p>There are painters who, instead of rendering the colours of nature, -diffuse a general tone, a warm or cold hue, over the picture. In some, -again, a predilection for certain colours displays itself; in others a -want of feeling for harmony.</p> - -<p class="para"><a id="a135">135.</a></p> - -<p>Lastly, it is also worthy of remark, that savage nations, uneducated -people, and children have a great predilection for vivid colours; -that animals are excited to rage by certain colours; that people of -refinement avoid vivid colours in their dress and the objects that are -about them, and seem inclined to banish them altogether from their -presence.—<a href="#NOTE_I">Note I</a>.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_14" id="Footnote_1_14"></a><a href="#FNanchor_1_14"><span class="label">[1]</span></a> It has been found necessary to follow the author's -nomenclature throughout—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_15" id="Footnote_2_15"></a><a href="#FNanchor_2_15"><span class="label">[2]</span></a> Non-perception of blue.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_16" id="Footnote_3_16"></a><a href="#FNanchor_3_16"><span class="label">[3]</span></a> It has not been thought necessary to copy the plates here -referred to.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_56" id="Page_56">[Pg 56]</a></span></p></div> - - - - -<h5><a name="PART_II" id="PART_II">PART II.</a></h5> - - -<h4>PHYSICAL COLOURS.</h4> - - -<p class="para"><a id="a136">136.</a></p> - -<p>We give this designation to colours which are produced by certain -material mediums: these mediums, however, have no colour themselves, -and may be either transparent, semi-transparent yet transmitting light, -or altogether opaque. The colours in question are thus produced in the -eye through such external given causes, or are merely reflected to -the eye when by whatever means they are already produced without us. -Although we thus ascribe to them a certain objective character, their -distinctive quality still consists in their being transient, and not to -be arrested.</p> - -<p class="para"><a id="a137">137.</a></p> - -<p>They are called by former investigators <i>colores apparentes, fluxi, -fugitivi, phantastici, falsi, variantes</i>. They are also called -<i>speciosi</i> and <i>emphatici</i>, on account of their striking splendour. -They are immediately connected with the physiological colours, and -appear to have but little more reality: for, while in the production<span class="pagenum"><a name="Page_57" id="Page_57">[Pg 57]</a></span> -of the physiological colours the eye itself was chiefly efficient, and -we could only perceive the phenomena thus evoked within ourselves, -but not without us, we have now to consider the fact that colours are -produced in the eye by means of colourless objects; that we thus too -have a colourless surface before us which is acted upon as the retina -itself is, and that we can perceive the appearance produced upon it -without us. In such a process, however, every observation will convince -us that we have to do with colours in a progressive and mutable, but -not in a final or complete, state.</p> - -<p class="para"><a id="a138">138.</a></p> - -<p>Hence, in directing our attention to these physical colours, we find -it quite possible to place an objective phenomenon beside a subjective -one, and often by means of the union of the two successfully to -penetrate farther into the nature of the appearance.</p> - -<p class="para"><a id="a139">139.</a></p> - -<p>Thus, in the observations by which we become acquainted with the -physical colours, the eye is not to be considered as acting alone; nor -is the light ever to be considered in immediate relation with the eye: -but we direct our attention especially to the various effects produced -by mediums, those mediums being themselves colourless.</p> - -<p><span class="pagenum"><a name="Page_58" id="Page_58">[Pg 58]</a></span></p> - -<p class="para"><a id="a140">140.</a></p> - -<p>Light under these circumstances may be affected by three conditions. -First, when it flashes back from the surface of a medium; in -considering which <i>catoptrical</i> experiments invite our attention. -Secondly, when it passes by the edge of a medium: the phenomena -thus produced were formerly called <i>perioptical</i>; we prefer the -term <i>paroptical</i>. Thirdly, when it passes through either a merely -light-transmitting or an actually transparent body; thus constituting -a class of appearances on which <i>dioptrical</i> experiments are founded. -We have called a fourth class of physical colours <i>epoptical</i>, as the -phenomena exhibit themselves on the colourless surface of bodies under -various conditions, without previous or actual dye (βαφή).—<a href="#NOTE_K">Note K</a>.</p> - -<p class="para"><a id="a141">141.</a></p> - -<p>In examining these categories with reference to our three leading -divisions, according to which we consider the phenomena of colours in a -physiological, physical, or chemical view, we find that the catoptrical -colours are closely connected with the physiological; the paroptical -are already somewhat more distinct and independent; the dioptrical -exhibit themselves as entirely and strictly physical, and as having -a decidedly objective character; the epoptical, although still only -apparent, may be considered as the transition to the chemical colours.</p> - -<p><span class="pagenum"><a name="Page_59" id="Page_59">[Pg 59]</a></span></p> - -<p class="para"><a id="a142">142.</a></p> - -<p>If we were desirous of prosecuting our investigation strictly in the -order of nature, we ought to proceed according to the classification -which has just been made; but in didactic treatises it is not of -so much consequence to connect as to duly distinguish the various -divisions of a subject, in order that at last, when every single -class and case has been presented to the mind, the whole may be -embraced in one comprehensive view. We therefore turn our attention -forthwith to the dioptrical class, in order at once to give the reader -the full impression of the physical colours, and to exhibit their -characteristics the more strikingly.</p> - - - -<hr class="chap" /> -<h5><a name="IX" id="IX">IX.</a></h5> - - -<h5>DIOPTRICAL COLOURS.</h5> - - -<p class="para"><a id="a143">143.</a></p> - -<p>Colours are called dioptrical when a colourless medium is necessary -to produce them; the medium must be such that light and darkness can -act through it either on the eye or on opposite surfaces. It is thus -required that the medium should be transparent, or at least capable, to -a certain degree, of transmitting light.</p> - -<p><span class="pagenum"><a name="Page_60" id="Page_60">[Pg 60]</a></span></p> - -<p class="para"><a id="a144">144.</a></p> - -<p>According to these conditions we divide the dioptrical phenomena into -two classes, placing in the first those which are produced by means of -imperfectly transparent, yet light-transmitting mediums; and in the -second such as are exhibited when the medium is in the highest degree -transparent.</p> - - - -<hr class="chap" /> -<h5><a name="X" id="X">X.</a></h5> - -<h5>DIOPTRICAL COLOURS OF THE FIRST CLASS.</h5> - - -<p class="para"><a id="a145">145.</a></p> - -<p>Space, if we assume it to be empty, would have the quality of absolute -transparency to our vision. If this space is filled so that the eye -cannot perceive that it is so, there exists a more or less material -transparent medium, which may be of the nature of air and gas, may be -fluid or even solid.</p> - -<p class="para"><a id="a146">146.</a></p> - -<p>The pure and light-transmitting semi-transparent medium is only an -accumulated form of the transparent medium. It may therefore be -presented to us in three modes.</p> - -<p><span class="pagenum"><a name="Page_61" id="Page_61">[Pg 61]</a></span></p> - -<p class="para"><a id="a147">147.</a></p> - -<p>The extreme degree of this accumulation is white; the simplest, -brightest, first, opaque occupation of space.</p> - -<p class="para"><a id="a148">148.</a></p> - -<p>Transparency itself, empirically considered, is already the first -degree of the opposite state. The intermediate degrees from this point -to opaque white are infinite.</p> - -<p class="para"><a id="a149">149.</a></p> - -<p>At whatever point short of opacity we arrest the thickening medium, it -exhibits simple and remarkable phenomena when placed in relation with -light and darkness.</p> - -<p class="para"><a id="a150">150.</a></p> - -<p>The highest degree of light, such as that of the sun, of phosphorus -burning in oxygen, is dazzling and colourless: so the light of the -fixed stars is for the most part colourless. This light, however, seen -through a medium but very slightly thickened, appears to us yellow. -If the density of such a medium be increased, or if its volume become -greater, we shall see the light gradually assume a yellow-red hue, -which at last deepens to a ruby-colour.—<a href="#NOTE_L">Note L</a>.</p> - -<p><span class="pagenum"><a name="Page_62" id="Page_62">[Pg 62]</a></span></p> - -<p class="para"><a id="a151">151.</a></p> - -<p>If on the other hand darkness is seen through a semi-transparent -medium, which is itself illumined by a light striking on it, a blue -colour appears: this becomes lighter and paler as the density of the -medium is increased, but on the contrary appears darker and deeper the -more transparent the medium becomes: in the least degree of dimness -short of absolute transparence, always supposing a perfectly colourless -medium, this deep blue approaches the most beautiful violet.</p> - -<p class="para"><a id="a152">152.</a></p> - -<p>If this effect takes place in the eye as here described, and may -thus be pronounced to be subjective, it remains further to convince -ourselves of this by objective phenomena. For a light thus mitigated -and subdued illumines all objects in like manner with a yellow, -yellow-red, or red hue; and, although the effect of darkness through -the non-transparent medium does not exhibit itself so powerfully, yet -the blue sky displays itself in the camera obscura very distinctly on -white paper, as well as every other material colour.</p> - -<p class="para"><a id="a153">153.</a></p> - -<p>In examining the cases in which this important<span class="pagenum"><a name="Page_63" id="Page_63">[Pg 63]</a></span> leading phenomenon -appears, we naturally mention the atmospheric colours first: most of -these may be here introduced in order.</p> - -<p class="para"><a id="a154">154.</a></p> - -<p>The sun seen through a certain degree of vapour appears with a yellow -disk; the centre is often dazzlingly yellow when the edges are already -red. The orb seen through a thick yellow mist appears ruby-red (as was -the case in 1794, even in the north); the same appearance is still -more decided, owing to the state of the atmosphere, when the scirocco -prevails in southern climates: the clouds generally surrounding the sun -in the latter case are of the same colour, which is reflected again on -all objects.</p> - -<p>The red hues of morning and evening are owing to the same cause. The -sun is announced by a red light, in shining through a greater mass -of vapours. The higher he rises, the yellower and brighter the light -becomes.</p> - -<p class="para"><a id="a155">155.</a></p> - -<p>If the darkness of infinite space is seen through atmospheric vapours -illumined by the day-light, the blue colour appears. On high mountains -the sky appears by day intensely blue, owing to the few thin vapours -that float before the endless dark space: as soon as we descend in the<span class="pagenum"><a name="Page_64" id="Page_64">[Pg 64]</a></span> -valleys, the blue becomes lighter; till at last, in certain regions, -and in consequence of increasing vapours, it altogether changes to a -very pale blue.</p> - -<p class="para"><a id="a156">156.</a></p> - -<p>The mountains, in like manner, appear to us blue; for, as we see them -at so great a distance that we no longer distinguish the local tints, -and as no light reflected from their surface acts on our vision, they -are equivalent to mere dark objects, which, owing to the interposed -vapours, appear blue.</p> - -<p class="para"><a id="a157">157.</a></p> - -<p>So we find the shadowed parts of nearer objects are blue when the air -is charged with thin vapours.</p> - -<p class="para"><a id="a158">158.</a></p> - -<p>The snow-mountains, on the other hand, at a great distance, still -appear white, or approaching to a yellowish hue, because they act on -our eyes as brightness seen through atmospheric vapour.</p> - -<p class="para"><a id="a159">159.</a></p> - -<p>The blue appearance at the lower part of the flame of a candle belongs -to the same class of phenomena. If the flame be held before a white -ground, no blue will be seen, but this colour will immediately appear -if the flame is opposed<span class="pagenum"><a name="Page_65" id="Page_65">[Pg 65]</a></span> to a black ground. This phenomenon may be -exhibited most strikingly with a spoonful of lighted spirits of wine. -We may thus consider the lower part of the flame as equivalent to the -vapour which, although infinitely thin, is still apparent before the -dark surface; it is so thin, that one may easily see to read through -it: on the other hand, the point of the flame which conceals objects -from our sight is to be considered as a self-illuminating body.</p> - -<p class="para"><a id="a160">160.</a></p> - -<p>Lastly, smoke is also to be considered as a semi-transparent medium, -which appears to us yellow or reddish before a light ground, but blue -before a dark one.</p> - -<p class="para"><a id="a161">161.</a></p> - -<p>If we now turn our attention to fluid mediums, we find that water, -deprived in a very slight degree of its transparency, produces the same -effects.</p> - -<p class="para"><a id="a162">162.</a></p> - -<p>The infusion of the lignum nephriticum (guilandina Linnæi), which -formerly excited so much attention, is only a semi-transparent liquor, -which in dark wooden cups must appear blue, but held towards the sun in -a transparent glass must exhibit a yellow appearance.</p> - -<p><span class="pagenum"><a name="Page_66" id="Page_66">[Pg 66]</a></span></p> - -<p class="para"><a id="a163">163.</a></p> - -<p>A drop of scented water, of spirit varnish, of several metallic -solutions, may be employed to give various degrees of opacity to water -for such experiments. Spirit of soap perhaps answers best.</p> - -<p class="para"><a id="a164">164.</a></p> - -<p>The bottom of the sea appears to divers of a red colour in bright -sunshine: in this case the water, owing to its depth, acts as a -semi-transparent medium. Under these circumstances, they find the -shadows green, which is the complemental colour.</p> - -<p class="para"><a id="a165">165.</a></p> - -<p>Among solid mediums the opal attracts our attention first: its colours -are, at least, partly to be explained by the circumstance that it is, -in fact, a semi-transparent medium, through which sometimes light, -sometimes dark, substrata are visible.</p> - -<p class="para"><a id="a166">166.</a></p> - -<p>For these experiments, however, the opal-glass (vitrum astroides, -girasole) is the most desirable material. It is prepared in various -ways, and its semi-opacity is produced by metallic oxydes. The same -effect is produced also by melting pulverised and calcined bones -together<span class="pagenum"><a name="Page_67" id="Page_67">[Pg 67]</a></span> with the glass, on which account it is also known by the name -of <i>beinglas</i>; but, prepared in this mode, it easily becomes too opaque.</p> - -<p class="para"><a id="a167">167.</a></p> - -<p>This glass may be adapted for experiments in various ways: it may -either be made in a very slight degree non-transparent, in which case -the light seen through various layers placed one upon the other may -be deepened from the lightest yellow to the deepest red, or, if made -originally more opaque, it may be employed in thinner or thicker -laminæ. The experiments may be successfully made in both ways: in -order, however, to see the bright blue colour, the glass should neither -be too opaque nor too thick. For, as it is quite natural that darkness -must act weakly through the semi-transparent medium, so this medium, if -too thick, soon approaches whiteness.</p> - -<p class="para"><a id="a168">168.</a></p> - -<p>Panes of glass throw a yellow light on objects through those parts -where they happen to be semi-opaque, and these same parts appear blue -if we look at a dark object through them.</p> - -<p class="para"><a id="a169">169.</a></p> - -<p>Smoked glass may be also mentioned here, and is, in like manner, to be -considered as a semi-opaque medium. It exhibits the sun more<span class="pagenum"><a name="Page_68" id="Page_68">[Pg 68]</a></span> or less -ruby-coloured; and, although this appearance may be attributed to the -black-brown colour of the soot, we may still convince ourselves that a -semi-transparent medium here acts if we hold such a glass moderately -smoked, and lit by the sun on the unsmoked side, before a dark object, -for we shall then perceive a bluish appearance.</p> - -<p class="para"><a id="a170">170.</a></p> - -<p>A striking experiment may be made in a dark room with sheets of -parchment. If we fasten a piece of parchment before the opening in the -window-shutter when the sun shines, it will appear nearly white; by -adding a second, a yellowish colour appears, which still increases as -more leaves are added, till at last it changes to red.</p> - -<p class="para"><a id="a171">171.</a></p> - -<p>A similar effect, owing to the state of the crystalline lens in milky -cataract, has been already adverted to (131).</p> - -<p class="para"><a id="a172">172.</a></p> - -<p>Having now, in tracing these phenomena, arrived at the effect of a -degree of opacity scarcely capable of transmitting light, we may here -mention a singular appearance which was owing to a momentary state of -this kind.</p> - -<p><span class="pagenum"><a name="Page_69" id="Page_69">[Pg 69]</a></span></p> - -<p>A portrait of a celebrated theologian had been painted some years -before the circumstance to which we allude, by an artist who was known -to have considerable skill in the management of his materials. The -very reverend individual was represented in a rich velvet dress, which -was not a little admired, and which attracted the eye of the spectator -almost more than the face. The picture, however, from the effect of the -smoke of lamps and dust, had lost much of its original vivacity. It -was, therefore, placed in the hands of a painter, who was to clean it, -and give it a fresh coat of varnish. This person began his operations -by carefully washing the picture with a sponge: no sooner, however, -had he gone over the surface once or twice, and wiped away the first -dirt, than to his amazement the black velvet dress changed suddenly to -a light blue plush, which gave the ecclesiastic a very secular, though -somewhat old-fashioned, appearance. The painter did not venture to go -on with his washing: he could not comprehend how a light blue should be -the ground of the deepest black, still less how he could so suddenly -have removed a glazing colour capable of converting the one tint to the -other.</p> - -<p>At all events, he was not a little disconcerted at having spoilt the -picture to such an extent. Nothing to characterize the ecclesiastic -remained<span class="pagenum"><a name="Page_70" id="Page_70">[Pg 70]</a></span> but the richly-curled round wig, which made the exchange -of a faded plush for a handsome new velvet dress far from desirable. -Meanwhile, the mischief appeared irreparable, and the good artist, -having turned the picture to the wall, retired to rest with a mind ill -at ease. But what was his joy the next morning, when, on examining the -picture, he beheld the black velvet dress again in its full splendour. -He could not refrain from again wetting a corner, upon which the blue -colour again appeared, and after a time vanished. On hearing of this -phenomenon, I went at once to see the miraculous picture. A wet sponge -was passed over it in my presence, and the change quickly took place. I -saw a somewhat faded, but decidedly light blue plush dress, the folds -under the arm being indicated by some brown strokes.</p> - -<p>I explained this appearance to myself by the doctrine of the -semi-opaque medium. The painter, in order to give additional depth -to his black, may have passed some particular varnish over it: on -being washed, this varnish imbibed some moisture, and hence became -semi-opaque, in consequence of which the black underneath immediately -appeared blue. Perhaps those who are practically acquainted with the -effect of varnishes may, through accident or contrivance, arrive at -some means of exhibiting this singular appearance, as an experiment, to -those<span class="pagenum"><a name="Page_71" id="Page_71">[Pg 71]</a></span> who are fond of investigating natural phenomena. Notwithstanding -many attempts, I could not myself succeed in re-producing it.</p> - -<p class="para"><a id="a173">173.</a></p> - -<p>Having now traced the most splendid instances of atmospheric -appearances, as well as other less striking yet sufficiently remarkable -cases, to the leading examples of semi-transparent mediums, we have no -doubt that attentive observers of nature will carry such researches -further, and accustom themselves to trace and explain the various -appearances which present themselves in every-day experience on the -same principle: we may also hope that such investigators will provide -themselves with an adequate apparatus in order to place remarkable -facts before the eyes of others who may be desirous of information.</p> - -<p class="para"><a id="a174">174.</a></p> - -<p>We venture, once for all, to call the leading appearance in question, -as generally described in the foregoing pages, a primordial and -elementary phenomenon; and we may here be permitted at once to state -what we understand by the term.</p> - -<p class="para"><a id="a175">175.</a></p> - -<p>The circumstances which come under our notice in ordinary observation -are, for the most part, insulated cases, which, with some attention, -admit<span class="pagenum"><a name="Page_72" id="Page_72">[Pg 72]</a></span> of being classed under general leading facts. These again range -themselves under theoretical rubrics which are more comprehensive, and -through which we become better acquainted with certain indispensable -conditions of appearances in detail. From henceforth everything is -gradually arranged under higher rules and laws, which, however, are not -to be made intelligible by words and hypotheses to the understanding -merely, but, at the same time, by real phenomena to the senses. We -call these primordial phenomena, because nothing appreciable by the -senses lies beyond them, on the contrary, they are perfectly fit to be -considered as a fixed point to which we first ascended, step by step, -and from which we may, in like manner, descend to the commonest case -of every-day experience. Such an original phenomenon is that which has -lately engaged our attention. We see on the one side light, brightness; -on the other darkness, obscurity: we bring the semi-transparent medium -between the two, and from these contrasts and this medium the colours -develop themselves, contrasted, in like manner, but soon, through a -reciprocal relation, directly tending again to a point of union.<a name="FNanchor_1_17" id="FNanchor_1_17"></a><a href="#Footnote_1_17" class="fnanchor">[1]</a></p> - -<p><span class="pagenum"><a name="Page_73" id="Page_73">[Pg 73]</a></span></p> - -<p class="para"><a id="a176">176.</a></p> - -<p>With this conviction we look upon the mistake that has been committed -in the investigation of this subject to be a very serious one, inasmuch -as a secondary phenomenon has been thus placed higher in order—the -primordial phenomenon has been degraded to an inferior place; nay, the -secondary phenomenon has been placed at the head, a compound effect has -been treated as simple, a simple appearance as compound: owing to this -contradiction, the most capricious complication and perplexity have -been introduced into physical inquiries, the effects of which are still -apparent.</p> - -<p class="para"><a id="a177">177.</a></p> - -<p>But when even such a primordial phenomenon is arrived at, the evil -still is that we refuse to recognise it as such, that we still aim at -something beyond, although it would become us to confess that we are -arrived at the limits of experimental knowledge. Let the observer of -nature suffer the primordial phenomenon to remain undisturbed in its -beauty; let the philosopher admit it into his department, and he will -find that important elementary facts are a worthier basis for further -operations than insulated cases, opinions, and hypotheses.—<a href="#NOTE_M">Note M</a>.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_17" id="Footnote_1_17"></a><a href="#FNanchor_1_17"><span class="label">[1]</span></a> That is (according to the author's statement 150. 151.) -both tend to red; the yellow deepening to orange as the comparatively -dark medium is thickened before brightness; the blue deepening to -violet as the light medium is thinned before darkness.—T.</p></div> - - - -<hr class="chap" /> - -<p class="pagenum"><a name="Pg_74" id="Pg_74">[Pg 74]</a></p> - - - -<h5>XI.</h5> - -<h5>DIOPTRICAL COLOURS OF THE SECOND CLASS.—REFRACTION.</h5> - - -<p class="para"><a id="a178">178.</a></p> - -<p>Dioptrical colours of both classes are closely connected, as will -presently appear on a little examination. Those of the first class -appeared through semi-transparent mediums, those of the second class -will now appear through transparent mediums. But since every substance, -however transparent, may be already considered to partake of the -opposite quality (as every accumulation of a medium called transparent -proves), so the near affinity of the two classes is sufficiently -manifest.</p> - -<p class="para"><a id="a179">179.</a></p> - -<p>We will, however, first consider transparent mediums abstractedly as -such, as entirely free from any degree of opacity, and direct our whole -attention to a phenomenon which here presents itself, and which is -known by the name of refraction.</p> - -<p class="para"><a id="a180">180.</a></p> - -<p>In treating of the physiological colours, we have already had occasion -to vindicate what<span class="pagenum"><a name="Pg_75" id="Pg_75">[Pg 75]</a></span> were formerly called illusions of sight, as -the active energies of the healthy and duly efficient eye (<a href="#a2">2</a>), and we -are now again invited to consider similar instances confirming the -constancy of the laws of vision.</p> - -<p class="para"><a id="a181">181.</a></p> - -<p>Throughout nature, as presented to the senses, everything depends on -the relation which things bear to each other, but especially on the -relation which man, the most important of these, bears to the rest. -Hence the world divides itself into two parts, and the human being -as <i>subject</i>, stands opposed to the <i>object</i>. Thus the practical -man exhausts himself in the accumulation of facts, the thinker in -speculation; each being called upon to sustain a conflict which admits -of no peace and no decision.</p> - -<p class="para"><a id="a182">182.</a></p> - -<p>But still the main point always is, whether the relations are truly -seen. As our senses, if healthy, are the surest witnesses of external -relations, so we may be convinced that, in all instances where they -appear to contradict reality, they lay the greater and surer stress -on true relations. Thus a distant object appears to us smaller; and -precisely by this means we are aware of distance. We produced coloured -appearances on colourless objects, through colourless mediums, and at -the same moment our<span class="pagenum"><a name="Page_76" id="Page_76">[Pg 76]</a></span> attention was called to the degree of opacity in -the medium.</p> - -<p class="para"><a id="a183">183.</a></p> - -<p>Thus the different degrees of opacity in so-called transparent mediums, -nay, even other physical and chemical properties belonging to them, -are known to our vision by means of refraction, and invite us to make -further trials in order to penetrate more completely by physical and -chemical means into those secrets which are already opened to our view -on one side.</p> - -<p class="para"><a id="a184">184.</a></p> - -<p>Objects seen through mediums more or less transparent do not appear -to us in the place which they should occupy according to the laws of -perspective. On this fact the dioptrical colours of the second class -depend.</p> - -<p class="para"><a id="a185">185.</a></p> - -<p>Those laws of vision which admit of being expressed in mathematical -formulæ are based on the principle that, as light proceeds in straight -lines, it must be possible to draw a straight line from the eye to any -given object in order that it be seen. If, therefore, a case arises in -which the light arrives to us in a bent or broken line, that we see the -object by means of a bent or broken line, we are at once informed that -the<span class="pagenum"><a name="Page_77" id="Page_77">[Pg 77]</a></span> medium between the eye and the object is denser, or that it has -assumed this or that foreign nature.</p> - -<p class="para"><a id="a186">186.</a></p> - -<p>This deviation from the law of right-lined vision is known by the -general term of refraction; and, although we may take it for granted -that our readers are sufficiently acquainted with its effects, yet we -will here once more briefly exhibit it in its objective and subjective -point of view.</p> - -<p class="para"><a id="a187">187.</a></p> - -<p>Let the sun shine diagonally into an empty cubical vessel, so that -the opposite side be illumined, but not the bottom: let water be -then poured into this vessel, and the direction of the light will -be immediately altered; for a part of the bottom is shone upon. At -the point where the light enters the thicker medium it deviates from -its rectilinear direction, and appears broken: hence the phenomenon -is called the breaking (<i>brechung</i>) or refraction. Thus much of the -objective experiment.</p> - -<p class="para"><a id="a188">188.</a></p> - -<p>We arrive at the subjective fact in the following mode:—Let the eye -be substituted for the sun: let the sight be directed in like manner -<span class="pagenum"><a name="Page_78" id="Page_78">[Pg 78]</a></span> diagonally over one side, so that the opposite inner side be -entirely seen, while no part of the bottom is visible. On pouring in -water the eye will perceive a part of the bottom; and this takes place -without our being aware that we do not see in a straight line; for -the bottom appears to us raised, and hence we give the term elevation -(<i>hebung</i>) to the subjective phenomenon. Some points, which are -particularly remarkable with reference to this, will be adverted to -hereafter.</p> - -<p class="para"><a id="a189">189.</a></p> - -<p>Were we now to express this phenomenon generally, we might here repeat, -in conformity with the view lately taken, that the relation of the -objects is changed or deranged.</p> - -<p class="para"><a id="a190">190.</a></p> - -<p>But as it is our intention at present to separate the objective from -the subjective appearances, we first express the phenomenon in a -subjective form, and say,—a derangement or displacement of the object -seen, or to be seen, takes place.</p> - -<p class="para"><a id="a191">191.</a></p> - -<p>But that which is seen without a limiting outline may be thus affected -without our perceiving the change. On the other hand, if what we look -at has a visible termination, we have an evident indication that a -displacement occurs. If, therefore,<span class="pagenum"><a name="Page_79" id="Page_79">[Pg 79]</a></span> we wish to ascertain the -relation or degree of such a displacement, we must chiefly confine -ourselves to the alteration of surfaces with visible boundaries; in -other words, to the displacement of circumscribed objects.</p> - -<p class="para"><a id="a192">192.</a></p> - -<p>The general effect may take place through parallel mediums, for every -parallel medium displaces the object by bringing it perpendicularly -towards the eye. The apparent change of position is, however, more -observable through mediums that are not parallel.</p> - -<p class="para"><a id="a193">193.</a></p> - -<p>These latter may be perfectly spherical, or may be employed in the -form of convex or concave lenses. We shall make use of all these as -occasion may require in our experiments. But as they not only displace -the object from its position, but alter it in various ways, we shall, -in most cases, prefer employing mediums with surfaces, not, indeed, -parallel with reference to each other, but still altogether plane, -namely, prisms. These have a triangle for their base, and may, it is -true, be considered as portions of a lens, but they are particularly -available for our experiments, inasmuch as they very perceptibly -displace the object from its position, without producing a remarkable -distortion.</p> - -<p><span class="pagenum"><a name="Page_80" id="Page_80">[Pg 80]</a></span></p> - -<p class="para"><a id="a194">194.</a></p> - -<p>And now, in order to conduct our observations with as much exactness -as possible, and to avoid all confusion and ambiguity, we confine -ourselves at first to</p> - - -<h5>SUBJECTIVE EXPERIMENTS,</h5> - - -<p>in which, namely, the object is seen by the observer through a -refracting medium. As soon as we have treated these in due series, the -objective experiments will follow in similar order.</p> - - - -<hr class="chap" /> -<h5><a name="XII" id="XII">XII.</a></h5> - - -<h5>REFRACTION WITHOUT THE APPEARANCE OF COLOUR.</h5> - - -<p class="para"><a id="a195">195.</a></p> - -<p>Refraction can visibly take place without our perceiving an appearance -of colour. To whatever extent a colourless or uniformly coloured -surface may be altered as to its position by refraction, no colour -consequent upon refraction appears within it, provided it has no -outline or boundary. We may convince ourselves of this in various ways.</p> - -<p><span class="pagenum"><a name="Page_81" id="Page_81">[Pg 81]</a></span></p> - -<p class="para"><a id="a196">196.</a></p> - -<p>Place a glass cube on any larger surface, and look through the glass -perpendicularly or obliquely, the unbroken surface opposite the eye -appears altogether raised, but no colour exhibits itself. If we look at -a pure grey or blue sky or a uniformly white or coloured wall through a -prism, the portion of the surface which the eye thus embraces will be -altogether changed as to its position, without our therefore observing -the smallest appearance of colour.</p> - - - -<hr class="chap" /> -<h5><a name="XIII" id="XIII">XIII.</a></h5> - - -<h5>CONDITIONS OF THE APPEARANCE OF COLOUR.</h5> - - -<p class="para"><a id="a197">197.</a></p> - -<p>Although in the foregoing experiments we have found all unbroken -surfaces, large or small, colourless, yet at the outlines or -boundaries, where the surface is relieved upon a darker or lighter -object, we observe a coloured appearance.</p> - -<p class="para"><a id="a198">198.</a></p> - -<p>Outline, as well as surface, is necessary to constitute a figure or -circumscribed object. We therefore express the leading fact thus: -circumscribed objects must be displaced by refraction in order to the -exhibition of an appearance of colour.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_82" id="Page_82">[Pg 82]</a></span></p> - -<p class="para"><a id="a199">199.</a></p> - -<p>We place before us the simplest object, a light disk on a dark ground -(A).<a name="FNanchor_1_18" id="FNanchor_1_18"></a><a href="#Footnote_1_18" class="fnanchor">[1]</a> A displacement occurs with regard to this object, if we -apparently extend its outline from the centre by magnifying it. This -may be done with any convex glass, and in this case we see a blue edge -(B).</p> - -<p class="para"><a id="a200">200.</a></p> - -<p>We can, to appearance, contract the circumference of the same light -disk towards the centre by diminishing the object; the edge will then -appear yellow (C). This may be done with a concave glass, which, -however, should not be ground thin like common eye-glasses, but must -have some substance. In order, however, to make this experiment at once -with the convex glass, let a smaller black disk be inserted within -the light disk on a black ground. If we magnify the black disk on a -white ground with a convex glass, the same result takes place as if we -diminished the white disk; for we extend the black outline upon the -white, and we thus perceive the yellow edge together with the blue edge -(D).</p> - -<p class="para"><a id="a201">201.</a></p> - -<p>These two appearances, the blue and yellow, exhibit themselves in and -upon the white: they<span class="pagenum"><a name="Page_83" id="Page_83">[Pg 83]</a></span> both assume a reddish hue, in proportion as they -mingle with the black.<a name="FNanchor_2_19" id="FNanchor_2_19"></a><a href="#Footnote_2_19" class="fnanchor">[2]</a></p> - -<div class="figcenter" style="width: 500px;"> -<a id="col001"></a> -<img src="images/col_001.jpg" width="500" alt="" /> -<p style="text-align: center; font-weight: bold;">Plate 2.</p> -</div> - -<p class="para"><a id="a202">202.</a></p> - -<p>In this short statement we have described the primordial phenomena of -all appearance of colour occasioned by refraction. These undoubtedly -may be repeated, varied, and rendered more striking; may be combined, -complicated, confused; but, after all, may be still restored to their -original simplicity.</p> - -<p class="para"><a id="a203">203.</a></p> - -<p>In examining the process of the experiment just given, we find that -in the one case we have, to appearance, extended the white edge upon -the dark surface; in the other we have extended the dark edge upon -the white surface, supplanting one by the other, pushing one over -the other. We will now endeavour, step by step, to analyse these and -similar cases.</p> - -<p class="para"><a id="a204">204.</a></p> - -<p>If we cause the white disk to move, in appearance, entirely from its -place, which can be done<span class="pagenum"><a name="Page_84" id="Page_84">[Pg 84]</a></span> effectually by prisms, it will be coloured -according to the direction in which it apparently moves, in conformity -with the above laws. If we look at the disk <i>a</i><a name="FNanchor_3_20" id="FNanchor_3_20"></a><a href="#Footnote_3_20" class="fnanchor">[3]</a> through a prism, -so that it appear moved to <i>b</i>, the outer edge will appear blue and -blue-red, according to the law of the figure B (fig. 1), the other -edge being yellow, and yellow-red, according to the law of the figure -C (fig. 1). For in the first case the white figure is, as it were, -extended over the dark boundary, and in the other case the dark -boundary is passed over the white figure. The same happens if the disk -is, to appearance, moved from <i>a</i> to <i>c</i>, from <i>a</i> to <i>d</i>, and so -throughout the circle.</p> - -<p class="para"><a id="a205">205.</a></p> - -<p>As it is with the simple effect, so it is with more complicated -appearances. If we look through a horizontal prism (<i>a b</i><a name="FNanchor_4_21" id="FNanchor_4_21"></a><a href="#Footnote_4_21" class="fnanchor">[4]</a>) at a -white disk placed at some distance behind it at <i>e</i>, the disk will -be raised to <i>f</i>, and coloured according to the above law. If we -remove this prism, and look through a vertical one (<i>c d</i>) at the same -disk, it will appear at <i>h</i>, and coloured according to the same law. -If we place the two prisms one upon the other, the disk will appear -displaced diagonally, in conformity with a general law of nature, and -will be coloured as<span class="pagenum"><a name="Page_85" id="Page_85">[Pg 85]</a></span> before; that is, according to its movement in the -direction, <i>e.g.</i>:<a name="FNanchor_5_22" id="FNanchor_5_22"></a><a href="#Footnote_5_22" class="fnanchor">[5]</a></p> - -<p class="para"><a id="a206">206.</a></p> - -<p>If we attentively examine these opposite coloured edges, we find that -they only appear in the direction of the apparent change of place. -A round figure leaves us in some degree uncertain as to this: a -quadrangular figure removes all doubt.</p> - -<p class="para"><a id="a207">207.</a></p> - -<p>The quadrangular figure <i>a</i>,<a name="FNanchor_6_23" id="FNanchor_6_23"></a><a href="#Footnote_6_23" class="fnanchor">[6]</a> moved in the direction <i>a b</i> or <i>a d</i> -exhibits no colour on the sides which are parallel with the direction -in which it moves: on the other hand, if moved in the direction <i>a -c</i>, parallel with its diagonal, all the edges of the figure appear -coloured.<a name="FNanchor_7_24" id="FNanchor_7_24"></a><a href="#Footnote_7_24" class="fnanchor">[7]</a></p> - -<p class="para"><a id="a208">208.</a></p> - -<p>Thus, a former position (203) is here confirmed; viz. to produce -colour, an object must be so displaced that the light edges be -apparently carried over a dark surface, the dark edges over a light -surface, the figure over its boundary, the boundary over the figure. -But<span class="pagenum"><a name="Page_86" id="Page_86">[Pg 86]</a></span> if the rectilinear boundaries of a figure could be indefinitely -extended by refraction, so that figure and background might only pursue -their course next, but not over each other, no colour would appear, not -even if they were prolonged to infinity.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_18" id="Footnote_1_18"></a><a href="#FNanchor_1_18"><span class="label">[1]</span></a> <a href="#col001">Plate 2</a>, fig. 1.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_19" id="Footnote_2_19"></a><a href="#FNanchor_2_19"><span class="label">[2]</span></a> The author has omitted the orange and purple in the -coloured diagrams which illustrate these first experiments, from a wish -probably to present the elementary contrast, on which he lays a stress, -in greater simplicity. The reddish tinge would be apparent, as stated -above, where the blue and yellow are in contact with the black.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_20" id="Footnote_3_20"></a><a href="#FNanchor_3_20"><span class="label">[3]</span></a> <a href="#col001">Plate 2</a>, fig. 2</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_21" id="Footnote_4_21"></a><a href="#FNanchor_4_21"><span class="label">[4]</span></a> <a href="#col001">Plate 2</a>, fig. 4</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_22" id="Footnote_5_22"></a><a href="#FNanchor_5_22"><span class="label">[5]</span></a> In this case, according to the author, the refracting -medium being increased in mass, the appearance of colour is increased, -and the displacement is greater.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_23" id="Footnote_6_23"></a><a href="#FNanchor_6_23"><span class="label">[6]</span></a> <a href="#col001">Plate 2</a>, fig. 3.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_24" id="Footnote_7_24"></a><a href="#FNanchor_7_24"><span class="label">[7]</span></a> Fig. 2, <a href="#col000">plate 1</a>, contains a variety of forms, which, when -viewed through a prism, are intended to illustrate the statement in -this and the following paragraph.</p></div> - - -<hr class="chap" /> - -<h5><a name="XIV" id="XIV">XIV.</a></h5> - - -<h5>CONDITIONS UNDER WHICH THE APPEARANCE OF COLOUR INCREASES.</h5> - - -<p class="para"><a id="a209">209.</a></p> - -<p>We have seen in the foregoing experiments that all appearance of colour -occasioned by refraction depends on the condition that the boundary or -edge be moved in upon the object itself, or the object itself over the -ground, that the figure should be, as it were, carried over itself, or -over the ground. And we shall now find that, by increased displacement -of the object, the appearance of colour exhibits itself in a greater -degree. This takes place in subjective experiments, to which, for the -present, we confine ourselves, under the following conditions.</p> - -<p class="para"><a id="a210">210.</a></p> - -<p>First, if, in looking through parallel mediums, the eye is directed -more obliquely.</p> - -<p>Secondly, if the surfaces of the medium are no longer parallel, but -form a more or less acute angle.</p> - -<p><span class="pagenum"><a name="Page_87" id="Page_87">[Pg 87]</a></span></p> - -<p>Thirdly, owing to the increased proportion of the medium, whether -parallel mediums be increased in size, or whether the angle be -increased, provided it does not attain a right angle.</p> - -<p>Fourthly, owing to the distance of the eye armed with a refracting -medium from the object to be displaced.</p> - -<p>Fifthly, owing to a chemical property that may be communicated to the -glass, and which may be afterwards increased in effect.</p> - -<p class="para"><a id="a211">211.</a></p> - -<p>The greatest change of place, short of considerable distortion of the -object, is produced by means of prisms, and this is the reason why the -appearance of colour can be exhibited most powerfully through glasses -of this form. Yet we will not, in employing them, suffer ourselves to -be dazzled by the splendid appearances they exhibit, but keep the above -well-established, simple principles calmly in view.</p> - -<p class="para"><a id="a212">212.</a></p> - -<p>The colour which is outside, or foremost, in the apparent change of an -object by refraction, is always the broader, and we will henceforth -call this a <i>border</i>: the colour that remains next the outline is the -narrower, and this we will call an <i>edge</i>.</p> - -<p><span class="pagenum"><a name="Page_88" id="Page_88">[Pg 88]</a></span></p> - -<p class="para"><a id="a213">213.</a></p> - -<p>If we move a dark boundary towards a light surface, the yellow broader -border is foremost, and the narrower yellow-red edge follows close to -the outline. If we move a light boundary towards a dark surface, the -broader violet border is foremost, and the narrower blue edge follows.</p> - -<p class="para"><a id="a214">214.</a></p> - -<p>If the object is large, its centre remains uncoloured. Its inner -surface is then to be considered as unlimited (195): it is displaced, -but not otherwise altered: but if the object is so narrow, that under -the above conditions the yellow border can reach the blue edge, the -space between the outlines will be entirely covered with colour. If we -make this experiment with a white stripe on a black ground,<a name="FNanchor_1_25" id="FNanchor_1_25"></a><a href="#Footnote_1_25" class="fnanchor">[1]</a> the two -extremes will presently meet, and thus produce green. We shall then see -the following series of colours:—</p> - -<p style="margin-left: 20%;"> -Yellow-red.<br /> -Yellow.<br /> -Green.<br /> -Blue.<br /> -Blue-red.<br /> -</p> - -<p class="para"><a id="a215">215.</a></p> - -<p>If we place a black band, or stripe, on white paper,<a name="FNanchor_2_26" id="FNanchor_2_26"></a><a href="#Footnote_2_26" class="fnanchor">[2]</a> the violet -border will spread till it meets<span class="pagenum"><a name="Page_89" id="Page_89">[Pg 89]</a></span> the yellow-red edge. In this case the -intermediate black is effaced (as the intermediate white was in the -last experiment), and in its stead a splendid pure red will appear.<a name="FNanchor_3_27" id="FNanchor_3_27"></a><a href="#Footnote_3_27" class="fnanchor">[3]</a> -The series of colours will now be as follows:—</p> - -<p style="margin-left: 20%;"> -Blue.<br /> -Blue-red.<br /> -Red.<br /> -Yellow-red.<br /> -Yellow.<br /> -</p> - -<p class="para"><a id="a216">216.</a></p> - -<p>The yellow and blue, in the first case (214), can by degrees meet so -fully, that the two colours blend entirely in green, and the order will -then be,</p> - -<p style="margin-left: 20%;"> -Yellow-red.<br /> -Green.<br /> -Blue-red.<br /> -</p> - -<p>In the second case (215), under similar circumstances, we see only</p> - -<p style="margin-left: 20%;"> -Blue.<br /> -Red.<br /> -Yellow.<br /> -</p> - -<p>This appearance is best exhibited by refracting the bars of a window -when they are relieved on a grey sky.<a name="FNanchor_4_28" id="FNanchor_4_28"></a><a href="#Footnote_4_28" class="fnanchor">[4]</a></p> - -<p><span class="pagenum"><a name="Page_90" id="Page_90">[Pg 90]</a></span></p> - -<p class="para"><a id="a217">217.</a></p> - -<p>In all this we are never to forget that this appearance is not to be -considered as a complete or final state, but always as a progressive, -increasing, and, in many senses, controllable appearance. Thus we -find that, by the negation of the above five conditions, it gradually -decreases, and at last disappears altogether.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_25" id="Footnote_1_25"></a><a href="#FNanchor_1_25"><span class="label">[1]</span></a> <a href="#col001">Plate 2</a>, fig. 5, <i>left</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_26" id="Footnote_2_26"></a><a href="#FNanchor_2_26"><span class="label">[2]</span></a> <a href="#col001">Plate 2</a>, fig. 5, <i>right</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_27" id="Footnote_3_27"></a><a href="#FNanchor_3_27"><span class="label">[3]</span></a> This pure red, the union of orange and violet, is -considered by the author the maximum of the coloured appearance: he -has appropriated the term <i>purpur</i> to it. See paragraph <a href="#a703">703</a>, and -<i>note</i>.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_28" id="Footnote_4_28"></a><a href="#FNanchor_4_28"><span class="label">[4]</span></a> The bands or stripes in fig. 4, <a href="#col000">plate 1</a>, when viewed -through a prism, exhibit the colours represented in <a href="#col001">plate 2</a>, fig. 5.</p></div> - - -<hr class="chap" /> - -<h5><a name="XV" id="XV">XV.</a></h5> - - -<h5>EXPLANATION OF THE FOREGOING PHENOMENA.</h5> - - -<p class="para"><a id="a218">218.</a></p> - -<p>Before we proceed further, it is incumbent on us to explain the first -tolerably simple phenomenon, and to show its connexion with the -principles first laid down, in order that the observer of nature may -be enabled clearly to comprehend the more complicated appearances that -follow.</p> - -<p class="para"><a id="a219">219.</a></p> - -<p>In the first place, it is necessary to remember that we have to do -with circumscribed objects. In the act of seeing, generally, it is -the circumscribed visible which chiefly invites our observation; and -in the present instance, in speaking of the appearance of colour, as -occasioned by refraction, the circumscribed visible, the detached -object solely occupies our attention.</p> - -<p><span class="pagenum"><a name="Page_91" id="Page_91">[Pg 91]</a></span></p> - -<p class="para"><a id="a220">220.</a></p> - -<p>For our chromatic exhibitions we can, however, divide objects generally -into <i>primary</i> and <i>secondary</i>. The expressions of themselves denote -what we understand by them, but our meaning will be rendered still more -plain by what follows.</p> - -<p class="para"><a id="a221">221.</a></p> - -<p>Primary objects may be considered firstly as <i>original</i>, as images -which are impressed on the eye by things before it, and which assure -us of their reality. To these the secondary images may be opposed -as <i>derived</i> images, which remain in the organ when the object -itself is taken away; those apparent after-images, which have been -circumstantially treated of in the doctrine of physiological colours.</p> - -<p class="para"><a id="a222">222.</a></p> - -<p>The primary images, again, may be considered as <i>direct</i> images, which, -like the original impressions, are conveyed immediately from the object -to the eye. In contradistinction to these, the secondary images may -be considered as <i>indirect</i>, being only conveyed to us, as it were, -at second-hand from a reflecting surface. These are the mirrored, or -catoptrical, images, which in certain cases can also become double -images:</p> - -<p class="para"><a id="a223">223.</a></p> - -<p>When, namely, the reflecting body is transparent,<span class="pagenum"><a name="Page_92" id="Page_92">[Pg 92]</a></span> and has two parallel -surfaces, one behind the other: in such a case, an image may be -reflected to the eye from both surfaces, and thus arise double images, -inasmuch as the upper image does not quite cover the under one: this -may take place in various ways.</p> - -<p>Let a playing-card be held before a mirror. We shall at first see the -distinct image of the card, but the edge of the whole card, as well -as that of every spot upon it, will be bounded on one side with a -border, which is the beginning of the second reflection. This effect -varies in different mirrors, according to the different thickness of -the glass, and the accidents of polishing. If a person wearing a white -waistcoat, with the remaining part of his dress dark, stands before -certain mirrors, the border appears very distinctly, and in like manner -the metal buttons on dark cloth exhibit the double reflection very -evidently.</p> - -<p class="para"><a id="a224">224.</a></p> - -<p>The reader who has made himself acquainted with our former descriptions -of experiments (<a href="#a80">80</a>) will the more readily follow the present statement. -The window-bars reflected by plates of glass appear double, and -by increased thickness of the glass, and a due adaptation of the -angle of reflection, the two reflections may be entirely separated -from each other. So a vase full of<span class="pagenum"><a name="Page_93" id="Page_93">[Pg 93]</a></span> water, with a plane mirror-like -bottom, reflects any object twice, the two reflections being more or -less separated under the same conditions. In these cases it is to be -observed that, where the two reflections cover each other, the perfect -vivid image is reflected, but where they are separated they exhibit -only weak, transparent, and shadowy images.</p> - -<p class="para"><a id="a225">225.</a></p> - -<p>If we wish to know which is the under and which the upper image, we -have only to take a coloured medium, for then a light object reflected -from the under surface is of the colour of the medium, while that -reflected from the upper surface presents the complemental colour. With -dark objects it is the reverse; hence black and white surfaces may be -here also conveniently employed. How easily the double images assume -and evoke colours will here again be striking.</p> - -<p class="para"><a id="a226">226.</a></p> - -<p>Thirdly, the primary images may be considered as <i>principal</i> images, -while the secondary can be, as it were, annexed to these as <i>accessory</i> -images. Such an accessory image produces a sort of double form; except -that it does not separate itself from the principal object, although it -may be said to be always endeavouring to do so. It is<span class="pagenum"><a name="Page_94" id="Page_94">[Pg 94]</a></span> with secondary -images of this last description that we have to do in prismatic -appearances.</p> - -<p class="para"><a id="a227">227.</a></p> - -<p>A surface without a boundary exhibits no appearance of colour when -refracted (<a href="#a195">195</a>). Whatever is seen must be circumscribed by an -outline to produce this effect. In other words a figure, an object, -is required; this object undergoes an apparent change of place by -refraction: the change is however not complete, not clean, not sharp; -but incomplete, inasmuch as an accessory image only is produced.</p> - -<p class="para"><a id="a228">228.</a></p> - -<p>In examining every appearance of nature, but especially in examining -an important and striking one, we should not remain in one spot, we -should not confine ourselves to the insulated fact, nor dwell on it -exclusively, but look round through all nature to see where something -similar, something that has affinity to it, appears: for it is only by -combining analogies that we gradually arrive at a whole which speaks -for itself, and requires no further explanation.</p> - -<p class="para"><a id="a229">229.</a></p> - -<p>Thus we here call to mind that in certain cases refraction -unquestionably produces double images, as is the case in Iceland spar: -similar<span class="pagenum"><a name="Page_95" id="Page_95">[Pg 95]</a></span> double images are also apparent in cases of refraction through -large rock crystals, and in other instances; phenomena which have not -hitherto been sufficiently observed.<a name="FNanchor_1_29" id="FNanchor_1_29"></a><a href="#Footnote_1_29" class="fnanchor">[1]</a></p> - -<p class="para"><a id="a230">230.</a></p> - -<p>But since in the case under consideration (227) the question relates -not to double but to accessory images, we refer to a phenomenon already -adverted to, but not yet thoroughly investigated. We allude to an -earlier experiment, in which it appeared that a sort of conflict took -place in regard to the retina between a light object and its dark -ground, and between a dark object and its light ground (<a href="#a16">16</a>). The light -object in this case appeared larger, the dark one smaller.</p> - -<p class="para"><a id="a231">231.</a></p> - -<p>By a more exact observation of this phenomenon we may remark that the -forms are not sharply distinguished from the ground, but that they -appear with a kind of grey, in some degree, coloured edge; in short, -with an accessory image. If, then, objects seen only with the naked -eye produce such effects, what may not take place when a dense medium -is interposed? It is not that alone which presents itself to us<span class="pagenum"><a name="Page_96" id="Page_96">[Pg 96]</a></span> in -obvious operation which produces and suffers effects, but likewise all -principles that have a mutual relation only of some sort are efficient -accordingly, and indeed often in a very high degree.</p> - -<p class="para"><a id="a232">232.</a></p> - -<p>Thus when refraction produces its effect on an object there appears an -accessory image next the object itself: the real form thus refracted -seems even to linger behind, as if resisting the change of place; but -the accessory image seems to advance, and extends itself more or less -in the mode already shown (<a href="#a212">212</a>-<a href="#a216">216</a>).</p> - -<p class="para"><a id="a233">233.</a></p> - -<p>We also remarked (<a href="#a224">224</a>) that in double images the fainter appear only -half substantial, having a kind of transparent, evanescent character, -just as the fainter shades of double shadows must always appear as -half-shadows. These latter assume colours easily, and produce them -readily (<a href="#a69">69</a>), the former also (80); and the same takes place in the -instance of accessory images, which, it is true, do not altogether -quit the real object, but still advance or extend from it as -half-substantial images, and hence can appear coloured so quickly and -so powerfully.</p> - -<p class="para"><a id="a234">234.</a></p> - -<p>That the prismatic appearance is in fact an<span class="pagenum"><a name="Page_97" id="Page_97">[Pg 97]</a></span> accessory image we may -convince ourselves in more than one mode. It corresponds exactly with -the form of the object itself. Whether the object be bounded by a -straight line or a curve, indented or waving, the form of the accessory -image corresponds throughout exactly with the form of the object.<a name="FNanchor_2_30" id="FNanchor_2_30"></a><a href="#Footnote_2_30" class="fnanchor">[2]</a></p> - -<p class="para"><a id="a235">235.</a></p> - -<p>Again, not only the form but other qualities of the object are -communicated to the accessory image. If the object is sharply relieved -from its ground, like white on black, the coloured accessory image in -like manner appears in its greatest force. It is vivid, distinct, and -powerful; but it is most especially powerful when a luminous object is -shown on a dark ground, which may be contrived in various ways.</p> - -<p class="para"><a id="a236">236.</a></p> - -<p>But if the object is but faintly distinguished from the ground, like -grey objects on black or white, or even on each other, the accessory -image is also faint, and, when the original difference of tint or force -is slight, becomes hardly discernible.</p> - -<p><span class="pagenum"><a name="Page_98" id="Page_98">[Pg 98]</a></span></p> - -<p class="para"><a id="a237">237.</a></p> - -<p>The appearances which are observable when coloured objects are relieved -on light, dark, or coloured grounds are, moreover, well worthy of -attention. In this case a union takes place between the apparent colour -of the accessory image and the real colour of the object; a compound -colour is the result, which is either assisted and enhanced by the -accordance, or neutralised by the opposition of its ingredients.</p> - -<p class="para"><a id="a238">238.</a></p> - -<p>But the common and general characteristic both of the double and -accessory image is semi-transparence. The tendency of a transparent -medium to become only half transparent, or merely light-transmitting, -has been before adverted to (<a href="#a147">147</a>, <a href="#a148">148</a>). Let the reader assume that he -sees within or through such a medium a visionary image, and he will at -once pronounce this latter to be a semi-transparent image.</p> - -<p class="para"><a id="a239">239.</a></p> - -<p>Thus the colours produced by refraction may be fitly explained by the -doctrine of the semi-transparent mediums. For where dark passes over -light, as the border of the semi-transparent accessory image advances, -yellow appears; and, on the other hand, where a light outline passes -over the dark background, blue appears (<a href="#a150">150</a>, <a href="#a151">151</a>).</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_99" id="Page_99">[Pg 99]</a></span></p> - -<p class="para"><a id="a240">240.</a></p> - -<p>The advancing foremost colour is always the broader. Thus the yellow -spreads over the light with a broad border, but the yellow-red appears -as a narrower stripe and is next the dark, according to the doctrine of -augmentation, as an effect of shade.<a name="FNanchor_3_31" id="FNanchor_3_31"></a><a href="#Footnote_3_31" class="fnanchor">[3]</a></p> - -<p class="para"><a id="a241">241.</a></p> - -<p>On the opposite side the condensed blue is next the edge, while the -advancing border, spreading as a thinner veil over the black, produces -the violet colour, precisely on the principles before explained in -treating of semi-transparent mediums, principles which will hereafter -be found equally efficient in many other cases.</p> - -<p class="para"><a id="a242">242.</a></p> - -<p>Since an analysis like the present requires to be confirmed by ocular -demonstration, we beg every reader to make himself acquainted with the -experiments hitherto adduced, not in a superficial manner, but fairly -and thoroughly. We have not placed arbitrary signs before him instead -of the appearances themselves; no modes of expression are here proposed -for his<span class="pagenum"><a name="Page_100" id="Page_100">[Pg 100]</a></span> adoption which may be repeated for ever without the exercise -of thought and without leading any one to think; but we invite him to -examine intelligible appearances, which must be present to the eye and -mind, in order to enable him clearly to trace these appearances to -their origin, and to explain them to himself and to others.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_29" id="Footnote_1_29"></a><a href="#FNanchor_1_29"><span class="label">[1]</span></a> The date of the publication, 1810, is sometimes to be -remembered.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_30" id="Footnote_2_30"></a><a href="#FNanchor_2_30"><span class="label">[2]</span></a> The forms in fig. 2, <a href="#col000">plate 1</a>, when seen through a prism, -are again intended to exemplify this. In the plates to the original -work curvilinear figures are added, but the circles, fig. 1, in the -same plate, may answer the same end.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_31" id="Footnote_3_31"></a><a href="#FNanchor_3_31"><span class="label">[3]</span></a> The author has before observed that colour is a degree -of darkness, and he here means that increase of darkness, produced by -transparent mediums, is, to a certain extent, increase of colour.—T.</p></div> - - - -<hr class="r5" /> -<h5><a name="XVI" id="XVI">XVI.</a></h5> - - -<h5>DECREASE OF THE APPEARANCE OF COLOUR.</h5> - - -<p class="para"><a id="a243">243.</a></p> - -<p>We need only take the five conditions (<a href="#a210">210</a>) under which the appearance -of colour increases in the contrary order, to produce the contrary or -decreasing state; it may be as well, however, briefly to describe and -review the corresponding modifications which are presented to the eye.</p> - -<p class="para"><a id="a244">244.</a></p> - -<p>At the highest point of complete junction of the opposite edges, the -colours appear as follows (<a href="#a216">216</a>):—</p> - -<table border="0" cellpadding="2" cellspacing="0" summary=""> -<tr><td align="left">Yellow-red. </td><td align="left">Blue.</td></tr> -<tr><td align="left">Green.</td><td align="left">Red.</td></tr> -<tr><td align="left">Blue-red.</td><td align="left">Yellow.</td></tr> -</table> - -<p><span class="pagenum"><a name="Page_101" id="Page_101">[Pg 101]</a></span></p> - -<p class="para"><a id="a245">245.</a></p> - -<p>Where the junction is less complete, the appearance is as follows (<a href="#a214">214</a>, -<a href="#a215">215</a>):—</p> - -<table border="0" cellpadding="2" cellspacing="0" summary=""> -<tr><td align="left">Yellow-red. </td><td align="left">Blue.</td></tr> -<tr><td align="left">Yellow.</td><td align="left">Blue-red.</td></tr> -<tr><td align="left">Green.</td><td align="left">Red.</td></tr> -<tr><td align="left">Blue.</td><td align="left">Yellow-red.</td></tr> -<tr><td align="left">Blue-red.</td><td align="left">Yellow.</td></tr> -</table> - -<p>Here, therefore, the surface still appears completely coloured, but -neither series is to be considered as an elementary series, always -developing itself in the same manner and in the same degrees; on the -contrary, they can and should be resolved into their elements; and, in -doing this, we become better acquainted with their nature and character.</p> - -<p class="para"><a id="a246">246.</a></p> - -<p>These elements then are (<a href="#a199">199</a>, <a href="#a200">200</a>, <a href="#a201">201</a>)—</p> - -<table border="0" cellpadding="4" cellspacing="0" summary=""> -<tr><td align="left">Yellow-red. </td><td align="left">Blue.</td></tr> -<tr><td align="left">Yellow.</td><td align="left">Blue-red.</td></tr> -<tr><td align="left">White.</td><td align="left">Black.</td></tr> -<tr><td align="left">Blue.</td><td align="left">Yellow-red.</td></tr> -<tr><td align="left">Blue-red.</td><td align="left">Yellow.</td></tr> -</table> - -<p>Here the surface itself, the original object, which has been hitherto -completely covered, and as it were lost, again appears in the centre of -the colours, asserts its right, and enables us<span class="pagenum"><a name="Page_102" id="Page_102">[Pg 102]</a></span> fully to recognise the -secondary nature of the accessory images which exhibit themselves as -"edges" and "borders."—<a href="#NOTE_N">Note N.</a></p> - -<p class="para"><a id="a247">247.</a></p> - -<p>We can make these edges and borders as narrow as we please; nay, we -can still have refraction in reserve after having done away with all -appearance of colour at the boundary of the object.</p> - -<p>Having now sufficiently investigated the exhibition of colour in this -phenomenon, we repeat that we cannot admit it to be an elementary -phenomenon. On the contrary, we have traced it to an antecedent and -a simpler one; we have derived it, in connexion with the theory of -secondary images, from the primordial phenomenon of light and darkness, -as affected or acted upon by semi-transparent mediums. Thus prepared, -we proceed to describe the appearances which refraction produces on -grey and coloured objects, and this will complete the section of -subjective phenomena.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_103" id="Page_103">[Pg 103]</a></span></p> - - - - -<h5><a name="XVII" id="XVII">XVII.</a></h5> - -<h5>GREY OBJECTS DISPLACED BY REFRACTION.</h5> - - -<p class="para"><a id="a248">248.</a></p> - -<p>Hitherto we have confined our attention to black and white objects -relieved on respectively opposite grounds, as seen through the prism, -because the coloured edges and borders are most clearly displayed in -such cases. We now repeat these experiments with grey objects, and -again find similar results.</p> - -<p class="para"><a id="a249">249.</a></p> - -<p>As we called black the equivalent of darkness, and white the -representative of light (<a href="#a18">18</a>), so we now venture to say that grey -represents half-shadow, which partakes more or less of light and -darkness, and thus stands between the two. We invite the reader to call -to mind the following facts as bearing on our present view.</p> - -<p class="para"><a id="a250">250.</a></p> - -<p>Grey objects appear lighter on a black than on a white ground (<a href="#a33">33</a>); -they appear as a light on a black ground, and larger; as a dark on the -white ground, and smaller. (<a href="#a16">16</a>.)</p> - -<p><span class="pagenum"><a name="Page_104" id="Page_104">[Pg 104]</a></span></p> - -<p class="para"><a id="a251">251.</a></p> - -<p>The darker the grey the more it appears as a faint light on black, as a -strong dark on white, and <i>vice versâ</i>; hence the accessory images of -dark-grey on black are faint, on white strong: so the accessory images -of light-grey on white are faint, on black strong.</p> - -<p class="para"><a id="a252">252.</a></p> - -<p>Grey on black, seen through the prism, will exhibit the same -appearances as white on black; the edges are coloured according to the -same law, only the borders appear fainter. If we relieve grey on white, -we have the same edges and borders which would be produced if we saw -black on white through the prism.—<a href="#NOTE_O">Note O.</a></p> - -<p class="para"><a id="a253">253.</a></p> - -<p>Various shades of grey placed next each other in gradation will exhibit -at their edges, either blue and violet only, or red and yellow only, -according as the darker grey is placed over or under.</p> - -<p class="para"><a id="a254">254.</a></p> - -<p>A series of such shades of grey placed horizontally next each other -will be coloured conformably to the same law according as the whole -series is relieved, on a black or white ground above or below.</p> - -<p><span class="pagenum"><a name="Page_105" id="Page_105">[Pg 105]</a></span></p> - -<p class="para"><a id="a255">255.</a></p> - -<p>The observer may see the phenomena exhibited by the prism at one -glance, by enlarging the plate intended to illustrate this section.<a name="FNanchor_1_32" id="FNanchor_1_32"></a><a href="#Footnote_1_32" class="fnanchor">[1]</a></p> - -<p class="para"><a id="a256">256.</a></p> - -<p>It is of great importance duly to examine and consider another -experiment in which a grey object is placed partly on a black and -partly on a white surface, so that the line of division passes -vertically through the object.</p> - -<p class="para"><a id="a257">257.</a></p> - -<p>The colours will appear on this grey object in conformity with the -usual law, but according to the opposite relation of the light to the -dark, and will be contrasted in a line. For as the grey is as a light -to the black, so it exhibits the red and yellow above the blue and -violet below: again, as the grey is as a dark to the white, the blue -and violet appear above the red and yellow below. This experiment will -be found of great importance with reference to the next chapter.</p> - - -<div class="footnote"> - -<p><a name="Footnote_1_32" id="Footnote_1_32"></a><a href="#FNanchor_1_32"><span class="label">[1]</span></a> It has been thought unnecessary to give all the examples -in the plate alluded to, but the leading instance referred to in the -next paragraph will be found in <a href="#col002">plate 3</a>, fig. 1. The grey square -when seen through a prism will exhibit the effects described in par. -<a href="#a257">257</a>.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_106" id="Page_106">[Pg 106]</a></span></p></div> - - - - -<h5><a name="XVIII" id="XVIII">XVIII.</a></h5> - - -<h5>COLOURED OBJECTS DISPLACED BY REFRACTION.</h5> - - -<p class="para"><a id="a258">258.</a></p> - -<p>An unlimited coloured surface exhibits no prismatic colour in addition -to its own hue, thus not at all differing from a black, white, or -grey surface. To produce the appearance of colour, light and dark -boundaries must act on it either accidentally or by contrivance. Hence -experiments and observations on coloured surfaces, as seen through the -prism, can only be made when such surfaces are separated by an outline -from another differently tinted surface, in short when <i>circumscribed -objects</i> are coloured.</p> - -<p class="para"><a id="a259">259.</a></p> - -<p>All colours, whatever they may be, correspond so far with grey, that -they appear darker than white and lighter than black. This shade-like -quality of colour (σκιέρον) has been already alluded to (<a href="#a69">69</a>), and will -become more and more evident. If then we begin by placing coloured -objects on black and white surfaces, and examine them through the -prism, we shall again have all that we have seen exhibited with grey -surfaces.</p> - - -<div class="figcenter" style="width: 500px;"> -<a id="col002"></a> -<img src="images/col_002.jpg" width="500" alt="" /> -<p style="text-align: center; font-weight: bold;">Plate 3.</p> -</div> - -<p><span class="pagenum"><a name="Page_107" id="Page_107">[Pg 107]</a></span></p> - -<p class="para"><a id="a260">260.</a></p> - -<p>If we displace a coloured object by refraction, there appears, as -in the case of colourless objects and according to the same laws, -an accessory image. This accessory image retains, as far as colour -is concerned, its usual nature, and acts on one side as a blue and -blue-red, on the opposite side as a yellow and yellow-red. Hence the -apparent colour of the edge and border will be either homogeneous -with the real colour of the object, or not so. In the first case the -apparent image identifies itself with the real one, and appears to -increase it, while, in the second case, the real image may be vitiated, -rendered indistinct, and reduced in size by the apparent image. We -proceed to review the cases in which these effects are most strikingly -exhibited.</p> - -<p class="para"><a id="a261">261.</a></p> - -<p>If we take a coloured drawing enlarged from the plate, which -illustrates this experiment<a name="FNanchor_1_33" id="FNanchor_1_33"></a><a href="#Footnote_1_33" class="fnanchor">[1]</a>, and examine the red and blue squares -placed next each other on a black ground, through the prism as usual, -we shall find that as both colours are lighter than the ground, -similarly coloured edges and borders will appear above and below,<span class="pagenum"><a name="Page_108" id="Page_108">[Pg 108]</a></span> at -the outlines of both, only they will not appear equally distinct to the -eye.</p> - -<p class="para"><a id="a262">262.</a></p> - -<p>Red is proportionally much lighter on black than blue is. The colours -of the edges will therefore appear stronger on the red than on the -blue, which here acts as a dark-grey, but little different from black. -(<a href="#a251">251</a>.)</p> - -<p class="para"><a id="a263">263.</a></p> - -<p>The extreme red edge will identify itself with the vermilion colour -of the square, which will thus appear a little elongated in this -direction; while the yellow border immediately underneath it only gives -the red surface a more brilliant appearance, and is not distinguished -without attentive observation.</p> - -<p class="para"><a id="a264">264.</a></p> - -<p>On the other hand the red edge and yellow border are heterogeneous -with the blue square; a dull red appears at the edge, and a dull green -mingles with the figure, and thus the blue square seems, at a hasty -glance, to be comparatively diminished on this side.</p> - -<p class="para"><a id="a265">265.</a></p> - -<p>At the lower outline of the two squares a blue edge and a violet border -will appear, and will<span class="pagenum"><a name="Page_109" id="Page_109">[Pg 109]</a></span> produce the contrary effect; for the blue edge, -which is heterogeneous with the warm red surface, will vitiate it -and produce a neutral colour, so that the red on this side appears -comparatively reduced and driven upwards, and the violet border on the -black is scarcely perceptible.</p> - -<p class="para"><a id="a266">266.</a></p> - -<p>On the other hand, the blue apparent edge will identify itself with the -blue square, and not only not reduce, but extend it. The blue edge and -even the violet border next it have the apparent effect of increasing -the surface, and elongating it in that direction.</p> - -<p class="para"><a id="a267">267.</a></p> - -<p>The effect of homogeneous and heterogeneous edges, as I have now -minutely described it, is so powerful and singular that the two squares -at the first glance seem pushed out of their relative horizontal -position and moved in opposite directions, the red upwards, the blue -downwards. But no one who is accustomed to observe experiments in a -certain succession, and respectively to connect and trace them, will -suffer himself to be deceived by such an unreal effect.</p> - -<p class="para"><a id="a268">268.</a></p> - -<p>A just impression with regard to this important<span class="pagenum"><a name="Page_110" id="Page_110">[Pg 110]</a></span> phenomenon will, -however, much depend on some nice and even troublesome conditions, -which are necessary to produce the illusion in question. Paper should -be tinged with vermilion or the best minium for the red square, and -with deep indigo for the blue square. The blue and red prismatic edges -will then unite imperceptibly with the real surfaces where they are -respectively homogeneous; where they are not, they vitiate the colours -of the squares without producing a very distinct middle tint. The real -red should not incline too much to yellow, otherwise the apparent deep -red edge above will be too distinct; at the same time it should be -somewhat yellow, otherwise the transition to the yellow border will be -too observable. The blue must not be light, otherwise the red edge will -be visible, and the yellow border will produce a too decided green, -while the violet border underneath would not give us the impression of -being part of an elongated light blue square.</p> - -<p class="para"><a id="a269">269.</a></p> - -<p>All this will be treated more circumstantially hereafter, when we speak -of the apparatus intended to facilitate the experiments connected with -this part of our subject.<a name="FNanchor_2_34" id="FNanchor_2_34"></a><a href="#Footnote_2_34" class="fnanchor">[2]</a> Every inquirer<span class="pagenum"><a name="Page_111" id="Page_111">[Pg 111]</a></span> should prepare the figures -himself, in order fairly to exhibit this specimen of ocular deception, -and at the same time to convince himself that the coloured edges, even -in this case, cannot escape accurate examination.</p> - -<p class="para"><a id="a270">270.</a></p> - -<p>Meanwhile various other combinations, as exhibited in the plate, are -fully calculated to remove all doubt on this point in the mind of every -attentive observer.</p> - -<p class="para"><a id="a271">271.</a></p> - -<p>If, for instance, we look at a white square, next the blue one, on a -black ground, the prismatic hues of the opposite edges of the white, -which here occupies the place of the red in the former experiment, will -exhibit themselves in their utmost force. The red edge extends itself -above the level of the blue almost in a greater degree than was the -case with the red square itself in the former experiment. The lower -blue edge, again, is visible in its full force next the white, while, -on the other hand, it cannot be distinguished next the blue square. The -violet border underneath is also much more apparent on the white than -on the blue.</p> - -<p class="para"><a id="a272">272.</a></p> - -<p>If the observer now compares these double<span class="pagenum"><a name="Page_112" id="Page_112">[Pg 112]</a></span> squares, carefully prepared -and arranged one above the other, the red with the white, the two blue -squares together, the blue with the red, the blue with the white, he -will clearly perceive the relations of these surfaces to their coloured -edges and borders.</p> - -<p class="para"><a id="a273">273.</a></p> - -<p>The edges and their relations to the coloured surfaces appear still -more striking if we look at the coloured squares and a black square -on a white ground; for in this case the illusion before mentioned -ceases altogether, and the effect of the edges is as visible as in -any case that has come under our observation. Let the blue and red -squares be first examined through the prism. In both the blue edge now -appears above; this edge, homogeneous with the blue surface, unites -with it, and appears to extend it upwards, only the blue edge, owing -to its lightness, is somewhat too distinct in its upper portion; the -violet border underneath it is also sufficiently evident on the blue. -The apparent blue edge is, on the other hand, heterogeneous with the -red square; it is neutralised by contrast, and is scarcely visible; -meanwhile the violet border, uniting with the real red, produces a hue -resembling that of the peach-blossom.</p> - -<p class="para"><a id="a274">274.</a></p> - -<p>If thus, owing to the above causes, the upper<span class="pagenum"><a name="Page_113" id="Page_113">[Pg 113]</a></span> outlines of these -squares do not appear level with each other, the correspondence of the -under outlines is the more observable; for since both colours, the red -and the blue, are darks compared with the white (as in the former case -they were light compared with the black), the red edge with its yellow -border appears very distinctly under both. It exhibits itself under the -warm red surface in its full force, and under the dark blue nearly as -it appears under the black: as may be seen if we compare the edges and -borders of the figures placed one above the other on the white ground.</p> - -<p class="para"><a id="a275">275.</a></p> - -<p>In order to present these experiments with the greatest variety and -perspicuity, squares of various colours are so arranged<a name="FNanchor_3_35" id="FNanchor_3_35"></a><a href="#Footnote_3_35" class="fnanchor">[3]</a> that the -boundary of the black and white passes through them vertically. -According to the laws now known to us, especially in their application -to coloured objects, we shall find the squares as usual doubly coloured -at each edge; each square will appear to be split in two, and to be -elongated upwards or downwards. We may here call to mind the experiment -with the grey figure seen in like manner on the line of division -between black and white (257).<a name="FNanchor_4_36" id="FNanchor_4_36"></a><a href="#Footnote_4_36" class="fnanchor">[4]</a></p> - -<p><span class="pagenum"><a name="Page_114" id="Page_114">[Pg 114]</a></span></p> - -<p class="para"><a id="a276">276.</a></p> - -<p>A phenomenon was before exhibited, even to illusion, in the instance of -a red and blue square on a black ground; in the present experiment the -elongation upwards and downwards of two differently coloured figures -is apparent in the two halves of one and the same figure of one and -the same colour. Thus we are still referred to the coloured edges and -borders, and to the effects of their homogeneous and heterogeneous -relations with respect to the real colours of the objects.</p> - -<p class="para"><a id="a277">277.</a></p> - -<p>I leave it to observers themselves to compare the various gradations -of coloured squares, placed half on black half on white, only inviting -their attention to the apparent alteration which takes place in -contrary directions; for red and yellow appear elongated upwards if -on a black ground, downwards if on a white; blue, downwards if on a -black ground, upwards if on a white. All which, however, is quite in -accordance with the diffusely detailed examples above given.</p> - -<p class="para"><a id="a278">278.</a></p> - -<p>Let the observer now turn the figures so that the before-mentioned -squares placed on the line of division between black and white may -be in a horizontal series; the black above, the white underneath. On -looking at these squares<span class="pagenum"><a name="Page_115" id="Page_115">[Pg 115]</a></span> through the prism, he will observe that the -red square gains by the addition of two red edges; on more accurate -examination he will observe the yellow border on the red figure, and -the lower yellow border upon the white will be perfectly apparent.</p> - -<p class="para"><a id="a279">279.</a></p> - -<p>The upper red edge on the blue square is on the other hand hardly -visible; the yellow border next it produces a dull green by mingling -with the figure; the lower red edge and the yellow border are displayed -in lively colours.</p> - -<p class="para"><a id="a280">280.</a></p> - -<p>After observing that the red figure in these cases appears to gain by -an addition on both sides, while the dark blue, on one side at least, -loses something; we shall see the contrary effect produced by turning -the same figures upside down, so that the white ground be above, the -black below.</p> - -<p class="para"><a id="a281">281.</a></p> - -<p>For as the homogeneous edges and borders now appear above and below -the blue square, this appears elongated, and a portion of the surface -itself seems even more brilliantly coloured: it is only by attentive -observation that we can distinguish the edges and borders from the -colour of the figure itself.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_116" id="Page_116">[Pg 116]</a></span></p> - -<p class="para"><a id="a282">282.</a></p> - -<p>The yellow and red squares, on the other hand, are comparatively -reduced by the heterogeneous edges in this position of the figures, -and their colours are, to a certain extent, vitiated. The blue edge -in both is almost invisible. The violet border appears as a beautiful -peach-blossom hue on the red, as a very pale colour of the same kind on -the yellow; both the lower edges are green; dull on the red, vivid on -the yellow; the violet border is but faintly perceptible under the red, -but is more apparent under the yellow.</p> - -<p class="para"><a id="a283">283.</a></p> - -<p>Every inquirer should make it a point to be thoroughly acquainted with -all the appearances here adduced, and not consider it irksome to follow -out a single phenomenon through so many modifying circumstances. These -experiments, it is true, may be multiplied to infinity by differently -coloured figures, upon and between differently coloured grounds. Under -all such circumstances, however, it will be evident to every attentive -observer that coloured squares only appear relatively altered, or -elongated, or reduced by the prism, because an addition of homogeneous -or heterogeneous edges produces an illusion. The inquirer will now -be enabled to do away with this illusion if he has the<span class="pagenum"><a name="Page_117" id="Page_117">[Pg 117]</a></span> patience to -go through the experiments one after the other, always comparing the -effects together, and satisfying himself of their correspondence.</p> - -<p>Experiments with coloured objects might have been contrived in various -ways: why they have been exhibited precisely in the above mode, and -with so much minuteness, will be seen hereafter. The phenomena, -although formerly not unknown, were much misunderstood; and it was -necessary to investigate them thoroughly to render some portions of our -intended historical view clearer.</p> - -<p class="para"><a id="a284">284.</a></p> - -<p>In conclusion, we will mention a contrivance by means of which our -scientific readers may be enabled to see these appearances distinctly -at one view, and even in their greatest splendour. Cut in a piece of -pasteboard five perfectly similar square openings of about an inch, -next each other, exactly in a horizontal line: behind these openings -place five coloured glasses in the natural order, orange, yellow, -green, blue, violet. Let the series thus adjusted be fastened in an -opening of the camera obscura, so that the bright sky may be seen -through the squares, or that the sun may shine on them; they will thus -appear very powerfully coloured. Let the spectator now examine them -through the prism, and observe the appearances, already<span class="pagenum"><a name="Page_118" id="Page_118">[Pg 118]</a></span> familiar by -the foregoing experiments, with coloured objects, namely, the partly -assisting, partly neutralising effects of the edges and borders, and -the consequent apparent elongation or reduction of the coloured squares -with reference to the horizontal line. The results witnessed by the -observer in this case, entirely correspond with those in the cases -before analysed; we do not, therefore, go through them again in detail, -especially as we shall find frequent occasions hereafter to return to -the subject.—<a href="#NOTE_P">Note P.</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_33" id="Footnote_1_33"></a><a href="#FNanchor_1_33"><span class="label">[1]</span></a> <a href="#col002">Plate 3</a>, fig. 1. The author always recommends making -the experiments on an increased scale, in order to see the prismatic -effects distinctly.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_34" id="Footnote_2_34"></a><a href="#FNanchor_2_34"><span class="label">[2]</span></a> Neither the description of the apparatus nor the -recapitulation of the whole theory, so often alluded to by the author, -were ever given.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_35" id="Footnote_3_35"></a><a href="#FNanchor_3_35"><span class="label">[3]</span></a> <a href="#col002">Plate 3</a>. fig. 1.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_36" id="Footnote_4_36"></a><a href="#FNanchor_4_36"><span class="label">[4]</span></a> The grey square is introduced in the same <a href="#col002">plate</a>, fig. 1, -above the coloured squares.</p></div> - - -<hr class="chap" /> - -<h5><a name="XIX" id="XIX">XIX.</a></h5> - - -<h5>ACHROMATISM AND HYPERCHROMATISM.</h5> - - -<p class="para"><a id="a285">285.</a></p> - -<p>Formerly when much that is regular and constant in nature was -considered as mere aberration and accident, the colours arising from -refraction were but little attended to, and were looked upon as an -appearance attributable to particular local circumstances.</p> - -<p class="para"><a id="a286">286.</a></p> - -<p>But after it had been assumed that this appearance of colour -accompanies refraction at all times, it was natural that it should -be considered as intimately and exclusively connected with that -phenomenon; the belief obtaining that the<span class="pagenum"><a name="Page_119" id="Page_119">[Pg 119]</a></span> measure of the coloured -appearance was in proportion to the measure of the refraction, and that -they must advance <i>pari passu</i> with each other.</p> - -<p class="para"><a id="a287">287.</a></p> - -<p>If, again, philosophers ascribed the phenomenon of a stronger or weaker -refraction, not indeed wholly, but in some degree, to the different -density of the medium, (as purer atmospheric air, air charged with -vapours, water, glass, according to their increasing density, increase -the so-called refraction, or displacement of the object;) so they -could hardly doubt that the appearance of colour must increase in the -same proportion; and hence took it for granted, in combining different -mediums which were to counteract refraction, that as long as refraction -existed, the appearance of colour must take place, and that as soon as -the colour disappeared, the refraction also must cease.</p> - -<p class="para"><a id="a288">288.</a></p> - -<p>Afterwards it was, however, discovered that this relation which was -assumed to correspond, was, in fact, dissimilar; that two mediums can -refract an object with equal power, and yet produce very dissimilar -coloured borders.</p> - -<p class="para"><a id="a289">289.</a></p> - -<p>It was found that, in addition to the physical principle to which -refraction was ascribed, a<span class="pagenum"><a name="Page_120" id="Page_120">[Pg 120]</a></span> chemical one was also to be taken into the -account. We propose to pursue this subject hereafter, in the chemical -division of our inquiry, and we shall have to describe the particulars -of this important discovery in our history of the doctrine of colours. -What follows may suffice for the present.</p> - -<p class="para"><a id="a290">290.</a></p> - -<p>In mediums of similar or nearly similar refracting power, we find -the remarkable circumstance that a greater and lesser appearance of -colour can be produced by a chemical treatment; the greater effect is -owing, namely, to acids, the lesser to alkalis. If metallic oxydes are -introduced into a common mass of glass, the coloured appearance through -such glasses becomes greatly increased without any perceptible change -of refracting power. That the lesser effect, again, is produced by -alkalis, may be easily supposed.</p> - -<p class="para"><a id="a291">291.</a></p> - -<p>Those kinds of glass which were first employed after the discovery, -are called flint and crown glass; the first produces the stronger, the -second the fainter appearance of colour.</p> - -<p class="para"><a id="a292">292.</a></p> - -<p>We shall make use of both these denominations as technical terms in our -present statement,<span class="pagenum"><a name="Page_121" id="Page_121">[Pg 121]</a></span> and assume that the refractive power of both is -the same, but that flint-glass produces the coloured appearance more -strongly by one-third than the crown-glass. The diagram (<a href="#col002">Plate 3</a>, fig. -2,) may serve in illustration.</p> - -<p class="para"><a id="a293">293.</a></p> - -<p>A black surface is here divided into compartments for more convenient -demonstration: let the spectator imagine five white squares between the -parallel lines <i>a, b,</i> and <i>c, d</i>. The square No. 1, is presented to -the naked eye unmoved from its place.</p> - -<p class="para"><a id="a294">294.</a></p> - -<p>But let the square No. 2, seen through a crown-glass prism <i>g</i>, be -supposed to be displaced by refraction three compartments, exhibiting -the coloured borders to a certain extent; again, let the square No. 3, -seen through a flint glass prism <i>h</i>, in like manner be moved downwards -three compartments, when it will exhibit the coloured borders by about -a third wider than No. 2.</p> - -<p class="para"><a id="a295">295.</a></p> - -<p>Again, let us suppose that the square No. 4, has, like No. 2, been -moved downwards three compartments by a prism of crown-glass, and that -then by an oppositely placed prism <i>h</i>, of<span class="pagenum"><a name="Page_122" id="Page_122">[Pg 122]</a></span> flint-glass, it has been -again raised to its former situation, where it now stands.</p> - -<p class="para"><a id="a296">296.</a></p> - -<p>Here, it is true, the refraction is done away with by the opposition of -the two; but as the prism <i>h</i>, in displacing the square by refraction -through three compartments, produces coloured borders wider by a -third than those produced by the prism <i>g</i>, so, notwithstanding the -refraction is neutralised, there must be an excess of coloured border -remaining. (The position of this colour, as usual, depends on the -direction of the apparent motion (<a href="#a204">204</a>) communicated to the square by -the prism <i>h</i>, and, consequently, it is the reverse of the appearance -in the two squares 2 and 3, which have been moved in an opposite -direction.) This excess of colour we have called Hyperchromatism, and -from this the achromatic state may be immediately arrived at.</p> - -<p class="para"><a id="a297">297.</a></p> - -<p>For assuming that it was the square No. 5 which was removed three -compartments from its first supposed place, like No. 2, by a prism of -crown-glass <i>g</i>, it would only be necessary to reduce the angle of a -prism of flint-glass <i>h</i>, and to connect it, reversed, to the prism -<i>g</i>, in order to raise the square No. 5 two degrees or compartments; -by which means the Hyperchromatism<span class="pagenum"><a name="Page_123" id="Page_123">[Pg 123]</a></span> of the first case would cease, the -figure would not quite return to its first position, and yet be already -colourless. The prolonged lines of the united prisms, under No. 5, show -that a single complete prism remains: again, we have only to suppose -the lines curved, and an object-glass presents itself. Such is the -principle of the achromatic telescopes.</p> - -<p class="para"><a id="a298">298.</a></p> - -<p>For these experiments, a small prism composed of three different -prisms, as prepared in England, is extremely well adapted. It is to be -hoped our own opticians will in future enable every friend of science -to provide himself with this necessary instrument.</p> - - - -<hr class="chap" /> -<h5><a name="XX" id="XX">XX.</a></h5> - - -<h5>ADVANTAGES OF SUBJECTIVE EXPERIMENTS.—TRANSITION TO THE OBJECTIVE.</h5> - - -<p class="para"><a id="a299">299.</a></p> - -<p>We have presented the appearances of colour as exhibited by refraction, -first, by means of subjective experiments; and we have so far arrived -at a definite result, that we have been enabled to deduce the phenomena -in question<span class="pagenum"><a name="Page_124" id="Page_124">[Pg 124]</a></span> from the doctrine of semi-transparent mediums and double -images.</p> - -<p class="para"><a id="a300">300.</a></p> - -<p>In statements which have reference to nature, everything depends on -ocular inspection, and these experiments are the more satisfactory as -they may be easily and conveniently made. Every amateur can procure -his apparatus without much trouble or cost, and if he is a tolerable -adept in pasteboard contrivances, he may even prepare a great part of -his machinery himself. A few plain surfaces, on which black, white, -grey, and coloured objects may be exhibited alternately on a light and -dark ground, are all that is necessary. The spectator fixes them before -him, examines the appearances at the edge of the figures conveniently, -and as long as he pleases; he retires to a greater distance, again -approaches, and accurately observes the progressive states of the -phenomena.</p> - -<p class="para"><a id="a301">301.</a></p> - -<p>Besides this, the appearances may be observed with sufficient exactness -through small prisms, which need not be of the purest glass. The other -desirable requisites in these glass instruments will, however, be -pointed out in the section which treats of the apparatus.<a name="FNanchor_1_37" id="FNanchor_1_37"></a><a href="#Footnote_1_37" class="fnanchor">[1]</a></p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_125" id="Page_125">[Pg 125]</a></span></p> - -<p class="para"><a id="a302">302.</a></p> - -<p>A great advantage in these experiments, again, is, that they can be -made at any hour of the day in any room, whatever aspect it may have. -We have no need to wait for sunshine, which in general is not very -propitious to northern observers.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_37" id="Footnote_1_37"></a><a href="#FNanchor_1_37"><span class="label">[1]</span></a> This description of the apparatus was never given.</p></div> - - - - -<h5><a name="OBJECTIVE_EXPERIMENTS" id="OBJECTIVE_EXPERIMENTS">OBJECTIVE EXPERIMENTS.</a></h5> - - -<p class="para"><a id="a303">303.</a></p> - -<p>The objective experiments, on the contrary, necessarily require the -sun-light which, even when it is to be had, may not always have the -most desirable relation with the apparatus placed opposite to it. -Sometimes the sun is too high, sometimes too low, and withal only a -short time in the meridian of the best situated room. It changes its -direction during the observation, the observer is forced to alter -his own position and that of his apparatus, in consequence of which -the experiments in many cases become uncertain. If the sun shines -through the prism it exhibits all inequalities, lines, and bubbles -in the glass, and thus the appearance is rendered confused, dim, and -discoloured.</p> - -<p class="para"><a id="a304">304.</a></p> - -<p>Yet both kinds of experiments must be investigated with equal accuracy. -They appear to<span class="pagenum"><a name="Page_126" id="Page_126">[Pg 126]</a></span> be opposed to each other, and yet are always parallel. -What one order of experiments exhibits the other exhibits likewise, -and yet each has its peculiar capabilities, by means of which certain -effects of nature are made known to us in more than one way.</p> - -<p class="para"><a id="a305">305.</a></p> - -<p>In the next place there are important phenomena which may be exhibited -by the union of subjective and objective experiments. The latter -experiments again have this advantage, that we can in most cases -represent them by diagrams, and present to view the component relations -of the phenomena. In proceeding, therefore, to describe the objective -experiments, we shall so arrange them that they may always correspond -with the analogous subjective examples; for this reason, too, we annex -to the number of each paragraph the number of the former corresponding -one. But we set out by observing generally that the reader must consult -the plates, that the scientific investigator must be familiar with the -apparatus in order that the twin-phenomena in one mode or the other may -be placed before them.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_127" id="Page_127">[Pg 127]</a></span></p> - - - - -<h5><a name="XXI" id="XXI">XXI.</a></h5> - - -<h5>REFRACTION WITHOUT THE APPEARANCE OF COLOUR.</h5> - -<p class="para"><a id="a306">306</a> (<a href="#a195">195</a>, <a href="#a196">196</a>).</p> - -<p>That refraction may exhibit its effects without producing an appearance -of colour, is not to be demonstrated so perfectly in objective as -in subjective experiments. We have, it is true, unlimited spaces -which we can look at through the prism, and thus convince ourselves -that no colour appears where there is no boundary; but we have no -unlimited source of light which we can cause to act through the prism. -Our light comes to us from circumscribed bodies; and the sun, which -chiefly produces our prismatic appearances, is itself only a small, -circumscribed, luminous object.</p> - -<p class="para"><a id="a307">307.</a></p> - -<p>We may, however, consider every larger opening through which the sun -shines, every larger medium through which the sun-light is transmitted -and made to deviate from its course, as so far unlimited that we can -confine our attention to the centre of the surface without considering -its boundaries.</p> - -<p class="para"><a id="a308">308</a> (<a href="#a197">197</a>).</p> - -<p>If we place a large water-prism in the sun, a<span class="pagenum"><a name="Page_128" id="Page_128">[Pg 128]</a></span> large bright space is -refracted upwards by it on the plane intended to receive the image, and -the middle of this illumined space will be colourless. The same effect -may be produced if we make the experiment with glass prisms having -angles of few degrees: the appearance may be produced even through -glass prisms, whose refracting angle is sixty degrees, provided we -place the recipient surface near enough.</p> - - - -<hr class="chap" /> -<h5><a name="XXII" id="XXII">XXII.</a></h5> - - -<h5>CONDITIONS OF THE APPEARANCE OF COLOUR.</h5> - - -<p class="para"><a id="a309">309</a> (<a href="#a198">198</a>).</p> - -<p>Although, then, the illumined space before mentioned appears indeed -refracted and moved from its place, but not coloured, yet on the -horizontal edges of this space we observe a coloured appearance. -That here again the colour is solely owing to the displacement of a -circumscribed object may require to be more fully proved.</p> - -<p>The luminous body which here acts is circumscribed: the sun, while it -shines and diffuses light, is still an insulated object. However small -the opening in the lid of a camera obscura be made, still the whole -image of the sun will<span class="pagenum"><a name="Page_129" id="Page_129">[Pg 129]</a></span> penetrate it. The light which streams from all -parts of the sun's disk, will cross itself in the smallest opening, and -form the angle which corresponds with the sun's apparent diameter. On -the outside we have a cone narrowing to the orifice; within, this apex -spreads again, producing on an opposite surface a round image, which -still increases in size in proportion to the distance of the recipient -surface from the apex. This image, together with all other objects -of the external landscape, appears reversed on the white surface in -question in a dark room.</p> - -<p class="para"><a id="a310">310.</a></p> - -<p>How little therefore we have here to do with single sun-rays, bundles -or fasces of rays, cylinders of rays, pencils, or whatever else of the -kind may be imagined, is strikingly evident. For the convenience of -certain diagrams the sun-light may be assumed to arrive in parallel -lines, but it is known that this is only a fiction; a fiction quite -allowable where the difference between the assumption and the true -appearance is unimportant; but we should take care not to suffer such a -postulate to be equivalent to a fact, and proceed to further operations -on such a fictitious basis.</p> - -<p class="para"><a id="a311">311.</a></p> - -<p>Let the aperture in the window-shutter be now enlarged at pleasure, let -it be made round<span class="pagenum"><a name="Page_130" id="Page_130">[Pg 130]</a></span> or square, nay, let the whole shutter be opened, and -let the sun shine into the room through the whole window; the space -which the sun illumines will always be larger according to the angle -which its diameter makes; and thus even the whole space illumined by -the sun through the largest window is only the image of the sun <i>plus</i> -the size of the opening. We shall hereafter have occasion to return to -this.</p> - -<p class="para"><a id="a312">312</a> (<a href="#a199">199</a>).</p> - -<p>If we transmit the image of the sun through convex glasses we contract -it towards the focus. In this case, according to the laws before -explained, a yellow border and a yellow-red edge must appear when the -spectrum is thrown on white paper. But as this experiment is dazzling -and inconvenient, it may be made more agreeably with the image of the -full moon. On contracting this orb by means of a convex glass, the -coloured edge appears in the greatest splendour; for the moon transmits -a mitigated light in the first instance, and can thus the more readily -produce colour which to a certain extent accompanies the subduing of -light: at the same time the eye of the observer is only gently and -agreeably excited.</p> - -<p class="para"><a id="a313">313</a> (<a href="#a200">200</a>).</p> - -<p>If we transmit a luminous image through concave<span class="pagenum"><a name="Page_131" id="Page_131">[Pg 131]</a></span> glasses, it is -dilated. Here the image appears edged with blue.</p> - -<p class="para"><a id="a314">314.</a></p> - -<p>The two opposite appearances may be produced by a convex glass, -simultaneously or in succession; simultaneously by fastening an opaque -disk in the centre of the convex glass, and then transmitting the sun's -image. In this case the luminous image and the black disk within it are -both contracted, and, consequently, the opposite colours must appear. -Again, we can present this contrast in succession by first contracting -the luminous image towards the focus, and then suffering it to expand -again beyond the focus, when it will immediately exhibit a blue edge.</p> - -<p class="para"><a id="a315">315</a> (<a href="#a201">201</a>).</p> - -<p>Here too what was observed in the subjective experiments is again to be -remarked, namely, that blue and yellow appear in and upon the white, -and that both assume a reddish appearance in proportion as they mingle -with the black.</p> - -<p class="para"><a id="a316">316</a> (<a href="#a202">202</a>, <a href="#a203">203</a>).</p> - -<p>These elementary phenomena occur in all subsequent objective -experiments, as they constituted the groundwork of the subjective -ones.<span class="pagenum"><a name="Page_132" id="Page_132">[Pg 132]</a></span> The process too which takes place is the same; a light boundary -is carried over a dark surface, a dark surface is carried over a light -boundary. The edges must advance, and as it were push over each other -in these experiments as in the former ones.</p> - -<p class="para"><a id="a317">317</a> (<a href="#a204">204</a>).</p> - -<p>If we admit the sun's image through a larger or smaller opening into -the dark room, if we transmit it through a prism so placed that its -refracting angle, as usual, is underneath; the luminous image, instead -of proceeding in a straight line to the floor, is refracted upwards on -a vertical surface placed to receive it. This is the moment to take -notice of the opposite modes in which the subjective and objective -refractions of the object appear.</p> - -<p class="para"><a id="a318">318.</a></p> - -<p>If we <i>look</i> through a prism, held with its refracting angle -underneath, at an object above us, the object is moved downwards; -whereas a luminous image refracted through the same prism is moved -upwards. This, which we here merely mention as a matter of fact for -the sake of brevity, is easily explained by the laws of refraction and -elevation.</p> - -<p><span class="pagenum"><a name="Page_133" id="Page_133">[Pg 133]</a></span></p> - -<p class="para"><a id="a319">319.</a></p> - -<p>The luminous object being moved from its place in this manner, the -coloured borders appear in the order, and according to the laws before -explained. The violet border is always foremost, and thus in objective -cases proceeds upwards, in subjective cases downwards.</p> - -<p class="para"><a id="a320">320</a> (<a href="#a205">205</a>).</p> - -<p>The observer may convince himself in like manner of the mode in which -the appearance of colour takes place in the diagonal direction when the -displacement is effected by means of two prisms, as has been plainly -enough shown in the subjective example; for this experiment, however, -prisms should be procured of few degrees, say about fifteen.</p> - -<p class="para"><a id="a321">321</a> (<a href="#a206">206</a>, <a href="#a207">207</a>).</p> - -<p>That the colouring of the image takes place here too, according to the -direction in which it moves, will be apparent if we make a <i>square</i> -opening of moderate size in a shutter, and cause the luminous image -to pass through a water-prism; the spectrum being moved first in the -horizontal and vertical directions, then diagonally, the coloured edges -will change their position accordingly.</p> - -<p><span class="pagenum"><a name="Page_134" id="Page_134">[Pg 134]</a></span></p> - -<p class="para"><a id="a322">322</a> (<a href="#a208">208</a>).</p> - -<p>Whence it is again evident that to produce colour the boundaries must -be carried over each other, not merely move side by side.</p> - - - -<hr class="chap" /> -<h5><a name="XXIII" id="XXIII">XXIII.</a></h5> - -<h5>CONDITIONS OF THE INCREASE OF COLOUR.</h5> - - -<p class="para"><a id="a323">323</a> (<a href="#a209">209</a>).</p> - -<p>Here too an increased displacement of the object produces a greater -appearance of colour.</p> - -<p class="para"><a id="a324">324</a> (<a href="#a210">210</a>).</p> - -<p>This increased displacement occurs,</p> - -<p>1. By a more oblique direction of the impinging luminous object through -mediums with parallel surfaces.</p> - -<p>2. By changing the parallel form for one more or less acute angled.</p> - -<p>3. By increased proportion of the medium, whether parallel or acute -angled; partly because the object is by this means more powerfully -displaced, partly because an effect depending on the mere mass -co-operates.</p> - -<p>4. By the distance of the recipient surface from the refracting medium -so that the coloured <span class="pagenum"><a name="Page_135" id="Page_135">[Pg 135]</a></span> spectrum emerging from the prism may be said to -have a longer way to travel.</p> - -<p>5. When a chemical property produces its effects under all these -circumstances: this we have already entered into more fully under the -head of achromatism and hyperchromatism.</p> - -<p class="para"><a id="a325">325</a> (<a href="#a211">211</a>).</p> - -<p>The objective experiments have this advantage that the progressive -states of the phenomenon may be arrested and clearly represented by -diagrams, which is not the case with the subjective experiments.</p> - -<p class="para"><a id="a326">326.</a></p> - -<p>We can observe the luminous image after it has emerged from the prism, -step by step, and mark its increasing colour by receiving it on a -plane at different distances, thus exhibiting before our eyes various -sections of this cone, with an elliptical base: again, the phenomenon -may at once be rendered beautifully visible throughout its whole course -in the following manner:—Let a cloud of fine white dust be excited -along the line in which the image passes through the dark space; the -cloud is best produced by fine, perfectly dry, hair-powder. The more or -less coloured appearance will now be painted on the white atoms, and -presented in<span class="pagenum"><a name="Page_136" id="Page_136">[Pg 136]</a></span> its whole length and breadth to the eye of the spectator.</p> - -<p class="para"><a id="a327">327.</a></p> - -<p>By this means we have prepared some diagrams, which will be found among -the plates. In these the appearance is exhibited from its first origin, -and by these the spectator can clearly comprehend why the luminous -image is so much more powerfully coloured through prisms than through -parallel mediums.</p> - -<p class="para"><a id="a328">328</a> (<a href="#a212">212</a>).</p> - -<p>At the two opposite outlines of the image an opposite appearance -presents itself, beginning from an acute angle;<a name="FNanchor_1_38" id="FNanchor_1_38"></a><a href="#Footnote_1_38" class="fnanchor">[1]</a> the appearance -spreads as it proceeds further in space, according to this angle. On -one side, in the direction in which the luminous image is moved, a -violet border advances on the dark, a narrower blue edge remains next -the outline of the image. On the opposite side a yellow border advances -into the light of the image itself, and a yellow-red edge remains at -the outline.</p> - -<p class="para"><a id="a329">329</a> (<a href="#a213">213</a>).</p> - -<p>Here, therefore, the movement of the dark against the light, of the -light against the dark, may be clearly observed.</p> - -<div class="figcenter" style="width: 500px;"> -<a id="col003"></a> -<img src="images/col_003.jpg" width="500" alt="" /> -<p style="text-align: center; font-weight: bold;">Plate 4.</p> -</div> - -<p><span class="pagenum"><a name="Page_137" id="Page_137">[Pg 137]</a></span></p> - -<p class="para"><a id="a330">330</a> (<a href="#a214">214</a>).</p> - -<p>The centre of a large object remains long uncoloured, especially with -mediums of less density and smaller angles; but at last the opposite -borders and edges touch each other, upon which a green appears in the -centre of the luminous image.</p> - -<p class="para"><a id="a331">331</a> (<a href="#a215">215</a>).</p> - -<p>Objective experiments have been usually made with the sun's image: an -objective experiment with a dark object has hitherto scarcely been -thought of. We have, however, prepared a convenient contrivance for -this also. Let the large water-prism before alluded to be placed in -the sun, and let a round pasteboard disk be fastened either inside or -outside. The coloured appearance will again take place at the outline, -beginning according to the usual law; the edges will appear, they will -spread in the same proportion, and when they meet, red will appear in -the centre<a name="FNanchor_2_39" id="FNanchor_2_39"></a><a href="#Footnote_2_39" class="fnanchor">[2]</a>. An intercepting square may be added near the round disk, -and placed in any direction <i>ad libitum</i>, and the spectator can again -convince himself of what has been before so often described.</p> - -<p class="para"><a id="a332">332</a> (<a href="#a216">216</a>).</p> - -<p>If we take away these dark objects from the<span class="pagenum"><a name="Page_138" id="Page_138">[Pg 138]</a></span> prism, in which case, -however, the glass is to be carefully cleaned, and hold a rod or a -large pencil before the centre of the horizontal prism, we shall -then accomplish the complete immixture of the violet border and the -yellow-red edge, and see only the three colours, the external blue, and -yellow, and the central red.</p> - -<p class="para"><a id="a333">333.</a></p> - -<p>If again we cut a long horizontal opening in the middle of a piece of -pasteboard, fastened on the prism, and then cause the sun-light to pass -through it, we shall accomplish the complete union of the yellow border -with the blue edge upon the light, and only see yellow-red, green and -violet. The details of this are further entered into in the description -of the plates.</p> - -<p class="para"><a id="a334">334</a> (<a href="#a217">217</a>).</p> - -<p>The prismatic appearance is thus by no means complete and final when -the luminous image emerges from the prism. It is then only that -we perceive its elements in contrast; for as it increases these -contrasting elements unite, and are at last intimately joined. The -section of this phenomenon arrested on a plane surface is different -at every degree of distance from the prism; so that the notion of an -immutable series of colours, or of a pervading similar proportion -between them, cannot be a question for a moment.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_38" id="Footnote_1_38"></a><a href="#FNanchor_1_38"><span class="label">[1]</span></a> <a href="#col003">Plate 4</a>. fig. 1.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_39" id="Footnote_2_39"></a><a href="#FNanchor_2_39"><span class="label">[2]</span></a> <a href="#col003">Plate 4</a>. fig. 2.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_139" id="Page_139">[Pg 139]</a></span></p></div> - - - - -<h5><a name="XXIV" id="XXIV">XXIV.</a></h5> - - -<h5>EXPLANATION OF THE FOREGOING PHENOMENA.</h5> - - -<p class="para"><a id="a335">335</a> (<a href="#a218">218</a>).</p> - -<p>As we have already entered into this analysis circumstantially while -treating of the subjective experiments, as all that was of force there -is equally valid here, it will require no long details in addition to -show that the phenomena, which are entirely parallel in the two cases, -may also be traced precisely to the same sources.</p> - -<p class="para"><a id="a336">336</a> (<a href="#a219">219</a>).</p> - -<p>That in objective experiments also we have to do with circumscribed -images, has been already demonstrated at large. The sun may shine -through the smallest opening, yet the image of the whole disk -penetrates beyond. The largest prism may be placed in the open -sun-light, yet it is still the sun's image that is bounded by the -edges of the refracting surfaces, and produces the accessory images -of this boundary. We may fasten pasteboard, with many openings cut in -it, before the water-prism, yet we still merely see multiplied images -which, after having been moved from their place by refraction, exhibit -coloured edges and borders, and in these mere accessory images.</p> - -<p><span class="pagenum"><a name="Page_140" id="Page_140">[Pg 140]</a></span></p> - -<p class="para"><a id="a337">337</a> (<a href="#a235">235</a>).</p> - -<p>In subjective experiments we have seen that objects strongly relieved -from each other produce a very lively appearance of colour, and this -will be the case in objective experiments in a much more vivid and -splendid degree. The sun's image is the most powerful brightness we -know; hence its accessory image will be energetic in proportion, and -notwithstanding its really secondary dimmed and darkened character, -must be still very brilliant. The colours thrown by the sun-light -through the prism on any object, carry a powerful light with them, for -they have the highest and most intense source of light, as it were, for -their ground.</p> - -<p class="para"><a id="a338">338.</a></p> - -<p>That we are warranted in calling even these accessory images -semi-transparent, thus deducing the appearances from the doctrine -of the semi-transparent mediums, will be clear to every one who has -followed us thus far, but particularly to those who have supplied -themselves with the necessary apparatus, so as to be enabled at all -times to witness the precision and vivacity with which semi-transparent -mediums act.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_141" id="Page_141">[Pg 141]</a></span></p> - - - - -<h5><a name="XXV" id="XXV">XXV.</a></h5> - - -<h5>DECREASE OF THE APPEARANCE OF COLOUR.</h5> - - -<p class="para"><a id="a339">339</a> (243).</p> - -<p>If we could afford to be concise in the description of the decreasing -coloured appearance in subjective cases, we may here be permitted -to proceed with still greater brevity while we refer to the former -distinct statement. One circumstance, only on account of its great -importance, may be here recommended to the reader's especial attention -as a leading point of our whole thesis.</p> - -<p class="para"><a id="a340">340</a> (<a href="#a244">244</a>, <a href="#a247">247</a>).</p> - -<p>The decline of the prismatic appearance must be preceded by its -separation, by its resolution into its elements. At a due distance from -the prism, the image of the sun being entirely coloured, the blue and -yellow at length mix completely, and we see only yellow-red, green, and -blue-red. If we bring the recipient surface nearer to the refracting -medium, yellow and blue appear again, and we see the five colours with -their gradations. At a still shorter distance the yellow and blue -separate from each other entirely, the green vanishes, and the image -itself appears, colourless, between the coloured edges and borders. The -nearer we bring the recipient surface to the prism, the<span class="pagenum"><a name="Page_142" id="Page_142">[Pg 142]</a></span> narrower the -edges and borders become, till at last, when in contact with the prism, -they are reduced to nothing.</p> - - - -<hr class="chap" /> -<h5><a name="XXVI" id="XXVI">XXVI.</a></h5> - - -<h5>GREY OBJECTS.</h5> - - -<p class="para"><a id="a341">341</a> (<a href="#a218">218</a>).</p> - -<p>We have exhibited grey objects as very important to our inquiry in the -subjective experiments. They show, by the faintness of the accessory -images, that these same images are in all cases derived from the -principal object. If we wish here, too, to carry on the objective -experiments parallel with the others, we may conveniently do this by -placing a more or less dull ground glass before the opening through -which the sun's image enters. By this means a subdued image would be -produced, which on being refracted would exhibit much duller colours on -the recipient plane than those immediately derived from the sun's disk; -and thus, even from the intense sun-image, only a faint accessory image -would appear, proportioned to the mitigation of the light by the glass. -This experiment, it is true, will only again and again confirm what is -already sufficiently familiar to us.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_143" id="Page_143">[Pg 143]</a></span></p> - - - - -<h5><a name="XXVII" id="XXVII">XXVII.</a></h5> - - -<h5>COLOURED OBJECTS.</h5> - - -<p class="para"><a id="a342">342</a> (<a href="#a260">260</a>).</p> - -<p>There are various modes of producing coloured images in objective -experiments. In the first place, we can fix coloured glass before the -opening, by which means a coloured image is at once produced; secondly, -we can fill the water-prism with coloured fluids; thirdly, we can cause -the colours, already produced in their full vivacity by the prism, to -pass through proportionate small openings in a tin plate, and thus -prepare small circumscribed colours for a second operation. This last -mode is the most difficult; for owing to the continual progress of the -sun, the image cannot be arrested in any direction at will. The second -method has also its inconveniences, since not all coloured liquids can -be prepared perfectly bright and clear. On these accounts the first is -to be preferred, and deserves the more to be adopted because natural -philosophers have hitherto chosen to consider the colours produced -from the sun-light through the prism, those produced through liquids -and glasses, and those which are already fixed on paper or cloth, as -exhibiting effects equally to be depended on, and equally available in -demonstration.</p> - -<p class="para"><a id="a343">343.</a></p> - -<p>As it is thus merely necessary that the image<span class="pagenum"><a name="Page_144" id="Page_144">[Pg 144]</a></span> should be coloured, so -the large water-prism before alluded to affords us the best means of -effecting this. A pasteboard screen may be contrived to slide before -the large surfaces of the prism, through which, in the first instance, -the light passes uncoloured. In this screen openings of various forms -may be cut, in order to produce different images, and consequently -different accessory images. This being done, we need only fix coloured -glasses before the openings, in order to observe what effect refraction -produces on coloured images in an objective sense.</p> - -<p class="para"><a id="a344">344.</a></p> - -<p>A series of glasses may be prepared in a mode similar to that before -described (<a href="#a284">284</a>); these should be accurately contrived to slide in the -grooves of the large water-prism. Let the sun then shine through them, -and the coloured images refracted upwards will appear bordered and -edged, and will vary accordingly: for these borders and edges will be -exhibited quite distinctly on some images, and on others will be mixed -with the specific colour of the glass, which they will either enhance -or neutralize. Every observer will be enabled to convince himself -here again that we have only to do with the same simple phenomenon so -circumstantially described subjectively and objectively.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_145" id="Page_145">[Pg 145]</a></span></p> - - - - -<h5><a name="XXVIII" id="XXVIII">XXVIII.</a></h5> - - -<h5>ACHROMATISM AND HYPERCHROMATISM.</h5> - - -<p class="para"><a id="a345">345</a> (<a href="#a285">285</a>, <a href="#a290">290</a>).</p> - -<p>It is possible to make the hyperchromatic and achromatic experiments -objectively as well as subjectively. After what has been already -stated, a short description of the method will suffice, especially as -we take it for granted that the compound prism before mentioned is in -the hands of the observer.</p> - -<p class="para"><a id="a346">346.</a></p> - -<p>Let the sun's image pass through an acute-angled prism of few degrees, -prepared from crown-glass, so that the spectrum be refracted upwards on -an opposite surface; the edges will appear coloured, according to the -constant law, namely, the violet and blue above and outside, the yellow -and yellow-red below and within the image. As the refracting angle of -this prism is undermost, let another proportionate prism of flint-glass -be placed against it, with its refracting angle uppermost. The sun's -image will by this means be again moved to its place, where, owing to -the excess of the colouring power of the prism of flint-glass, it will -still appear a little coloured, and, in consequence of the direction -in which it has been moved, the blue and violet<span class="pagenum"><a name="Page_146" id="Page_146">[Pg 146]</a></span> will now appear -underneath and outside, the yellow and yellow-red above and inside.</p> - -<p class="para"><a id="a347">347.</a></p> - -<p>If the whole image be now moved a little upwards by a proportionate -prism of crown-glass, the hyperchromatism will disappear, the sun's -image will be moved from its place, and yet will appear colourless.</p> - -<p class="para"><a id="a348">348.</a></p> - -<p>With an achromatic object-glass composed of three glasses, this -experiment may be made step by step, if we do not mind taking out the -glasses from their setting. The two convex glasses of crown-glass in -contracting the sun's image towards the focus, the concave glass of -flint-glass in dilating the image beyond it, exhibit at the edges the -usual colours. A convex glass united with a concave one exhibits the -colours according to the law of the latter. If all three glasses are -placed together, whether we contract the sun's image towards the focus, -or suffer it to dilate beyond the focus, coloured edges never appear, -and the achromatic effect intended by the optician is, in this case, -again attained.</p> - -<p class="para"><a id="a349">349.</a></p> - -<p>But as the crown-glass has always a greenish tint, and as a tendency -to this hue may be more<span class="pagenum"><a name="Page_147" id="Page_147">[Pg 147]</a></span> decided in large and strong object-glasses, -and under certain circumstances produce the compensatory red, -(which, however, in repeated experiments with several instruments of -this kind did not occur to us,) philosophers have resorted to the -most extraordinary modes of explaining such a result; and having -been compelled, in support of their system, theoretically to prove -the impossibility of achromatic telescopes, have felt a kind of -satisfaction in having some apparent ground for denying so great an -improvement. Of this, however, we can only treat circumstantially in -our historical account of these discoveries.</p> - - - -<hr class="chap" /> -<h5><a name="XXIX" id="XXIX">XXIX.</a></h5> - - -<h5>COMBINATION OF SUBJECTIVE AND OBJECTIVE EXPERIMENTS.</h5> - - -<p class="para"><a id="a350">350.</a></p> - -<p>Having shown above (<a href="#a318">318</a>) that refraction, considered objectively and -subjectively, must act in opposite directions, it will follow that if -we combine the experiments, the effects will reciprocally destroy each -other.</p> - -<p class="para"><a id="a351">351.</a></p> - -<p>Let the sun's image be thrown upwards on a<span class="pagenum"><a name="Page_148" id="Page_148">[Pg 148]</a></span> vertical plane, through -a horizontally-placed prism. If the prism is long enough to admit of -the spectator also looking through it, he will see the image elevated -by the objective refraction again depressed, and in the same place in -which it appeared without refraction.</p> - -<p class="para"><a id="a352">352.</a></p> - -<p>Here a remarkable case presents itself, but at the same time a natural -result of a general law. For since, as often before stated, the -objective sun's image thrown on the vertical plane is not an ultimate -or unchangeable state of the phenomenon, so in the above operation the -image is not only depressed when seen through the prism, but its edges -and borders are entirely robbed of their hues, and the spectrum is -reduced to a colourless circular form.</p> - -<p class="para"><a id="a353">353.</a></p> - -<p>By employing two perfectly similar prisms placed next each other, for -this experiment, we can transmit the sun's image through one, and look -through the other.</p> - -<p class="para"><a id="a354">354.</a></p> - -<p>If the spectator advances nearer with the prism through which he looks, -the image is again elevated, and by degrees becomes coloured according -to the law of the first prism. If he<span class="pagenum"><a name="Page_149" id="Page_149">[Pg 149]</a></span> again retires till he has brought -the image to the neutralized point, and then retires still farther -away, the image, which had become round and colourless, moves still -more downwards and becomes coloured in the opposite sense, so that -if we look through the prism and upon the refracted spectrum at the -same time, we see the same image coloured according to subjective and -objective laws.</p> - -<p class="para"><a id="a355">355.</a></p> - -<p>The modes in which this experiment may be varied are obvious. If the -refracting angle of the prism, through which the sun's image was -objectively elevated, is greater than that of the prism through which -the observer looks, he must retire to a much greater distance, in order -to depress the coloured image so low on the vertical plane that it -shall appear colourless, and <i>vice versâ</i>.</p> - -<p class="para"><a id="a356">356.</a></p> - -<p>It will be easily seen that we may exhibit achromatic and -hyperchromatic effects in a similar manner, and we leave it to the -amateur to follow out such researches more fully. Other complicated -experiments in which prisms and lenses are employed together, others -again, in which objective and subjective experiments are variously -intermixed, we reserve for a future<span class="pagenum"><a name="Page_150" id="Page_150">[Pg 150]</a></span> occasion, when it will be our -object to trace such effects to the simple phenomena with which we are -now sufficiently familiar.</p> - - - -<hr class="chap" /> -<h5><a name="XXX" id="XXX">XXX.</a></h5> - - -<h5>TRANSITION.</h5> - - -<p class="para"><a id="a357">357.</a></p> - -<p>In looking back on the description and analysis of dioptrical colours, -we do not repent either that we have treated them so circumstantially, -or that we have taken them into consideration before the other physical -colours, out of the order we ourselves laid down. Yet, before we quit -this branch of our inquiry, it may be as well to state the reasons that -have weighed with us.</p> - -<p class="para"><a id="a358">358.</a></p> - -<p>If some apology is necessary for having treated the theory of the -dioptrical colours, particularly those of the second class, so -diffusely, we should observe, that the exposition of any branch of -knowledge is to be considered partly with reference to the intrinsic -importance of the subject, and partly with reference to the particular -necessities of the time in which the<span class="pagenum"><a name="Page_151" id="Page_151">[Pg 151]</a></span> inquiry is undertaken. In our -own case we were forced to keep both these considerations constantly -in view. In the first place we had to state a mass of experiments with -our consequent convictions; next, it was our especial aim to exhibit -certain phenomena (known, it is true, but misunderstood, and above -all, exhibited in false connection,) in that natural and progressive -development which is strictly and truly conformable to observation; in -order that hereafter, in our polemical or historical investigations, -we might be enabled to bring a complete preparatory analysis to bear -on, and elucidate, our general view. The details we have entered into -were on this account unavoidable; they may be considered as a reluctant -consequence of the occasion. Hereafter, when philosophers will look -upon a simple principle as simple, a combined effect as combined; when -they will acknowledge the first elementary, and the second complicated -states, for what they are; then, indeed, all this statement may be -abridged to a narrower form; a labour which, should we ourselves -not be able to accomplish it, we bequeath to the active interest of -contemporaries and posterity.</p> - -<p class="para"><a id="a359">359.</a></p> - -<p>With respect to the order of the chapters, it should be remembered -that natural phenomena,<span class="pagenum"><a name="Page_152" id="Page_152">[Pg 152]</a></span> which are even allied to each other, are -not connected in any particular sequence or constant series; their -efficient causes act in a narrow circle, so that it is in some sort -indifferent what phenomenon is first or last considered; the main point -is, that all should be as far as possible present to us, in order that -we may embrace them at last from one point of view, partly according to -their nature, partly according to generally received methods.</p> - -<p class="para"><a id="a360">360.</a></p> - -<p>Yet, in the present particular instance, it may be asserted that the -dioptrical colours are justly placed at the head of the physical -colours; not only on account of their striking splendour and their -importance in other respects, but because, in tracing these to their -source, much was necessarily entered into which will assist our -subsequent enquiries.</p> - -<p class="para"><a id="a361">361.</a></p> - -<p>For, hitherto, light has been considered as a kind of abstract -principle, existing and acting independently; to a certain extent -self-modified, and on the slightest cause, producing colours out of -itself. To divert the votaries of physical science from this mode -of viewing the subject; to make them attentive to the fact, that in -prismatic and other appearances we have not to do<span class="pagenum"><a name="Page_153" id="Page_153">[Pg 153]</a></span> with light as an -uncircumscribed and modifying principle, but as circumscribed and -modified; that we have to do with a luminous image; with images or -circumscribed objects generally, whether light or dark: this was the -purpose we had in view, and such is the problem to be solved.</p> - -<p class="para"><a id="a362">362.</a></p> - -<p>All that takes place in dioptrical cases,—especially those of the -second class which are connected with the phenomena of refraction,—is -now sufficiently familiar to us, and will serve as an introduction to -what follows.</p> - -<p class="para"><a id="a363">363.</a></p> - -<p>Catoptrical appearances remind us of the physiological phenomena, but -as we ascribe a more objective character to the former, we thought -ourselves justified in classing them with the physical examples. It is -of importance, however, to remember that here again it is not light, in -an abstract sense, but a luminous image that we have to consider.</p> - -<p class="para"><a id="a364">364.</a></p> - -<p>In proceeding onwards to the paroptrical class, the reader, if duly -acquainted with the foregoing facts, will be pleased to find himself -once more in the region of circumscribed forms. The shadows of bodies, -especially, as secondary<span class="pagenum"><a name="Page_154" id="Page_154">[Pg 154]</a></span> images, so exactly accompanying the object, -will serve greatly to elucidate analogous appearances.</p> - -<p class="para"><a id="a365">365.</a></p> - -<p>We will not, however, anticipate these statements, but proceed as -heretofore in what we consider the regular course.</p> - - - -<hr class="chap" /> -<h5><a name="XXXI" id="XXXI">XXXI.</a></h5> - - -<h5>CATOPTRICAL COLOURS.</h5> - - -<p class="para"><a id="a366">366.</a></p> - -<p>Catoptrical colours are such as appear in consequence of a mirror-like -reflection. We assume, in the first place, that the light itself -as well as the surface from which it is reflected, is perfectly -colourless. In this sense the appearances in question come under the -head of physical colours. They arise in consequence of reflection, as -we found the dioptrical colours of the second class appear by means of -refraction. Without further general definitions, we turn our attention -at once to particular cases, and to the conditions which are essential -to the exhibition of these phenomena.</p> - -<p><span class="pagenum"><a name="Page_155" id="Page_155">[Pg 155]</a></span></p> - -<p class="para"><a id="a367">367.</a></p> - -<p>If we unroll a coil of bright steel-wire, and after suffering it to -spring confusedly together again, place it at a window in the light, -we shall see the prominent parts of the circles and convolutions -illumined, but neither resplendent nor iridescent. But if the sun -shines on the wire, this light will be condensed into a point, and we -perceive a small resplendent image of the sun, which, when seen near, -exhibits no colour. On retiring a little, however, and fixing the eyes -on this refulgent appearance, we discern several small mirrored suns, -coloured in the most varied manner; and although the impression is that -green and red predominate, yet, on a more accurate inspection, we find -that the other colours are also present.</p> - -<p class="para"><a id="a368">368.</a></p> - -<p>If we take an eye-glass, and examine the appearance through it, we -find the colours have vanished, as well as the radiating splendour in -which they were seen, and we perceive only the small luminous points, -the repeated images of the sun. We thus find that the impression is -subjective in its nature, and that the appearance is allied to those -which we have adverted to under the name of radiating halos (<a href="#a100">100</a>).</p> - -<p><span class="pagenum"><a name="Page_156" id="Page_156">[Pg 156]</a></span></p> - -<p class="para"><a id="a369">369.</a></p> - -<p>We can, however, exhibit this phenomenon objectively. Let a piece -of white paper be fastened beneath a small aperture in the lid of a -camera-obscura, and when the sun shines through this aperture, let -the confusedly-rolled steel-wire be held in the light, so that it be -opposite to the paper. The sun-light will impinge on and in the circles -of the wire, and will not, as in the concentrating lens of the eye, -display itself in a point; but, as the paper can receive the reflection -of the light in every part of its surface will be seen in hair-like -lines, which are also iridescent.</p> - -<p class="para"><a id="a370">370.</a></p> - -<p>This experiment is purely catoptrical; for as we cannot imagine that -the light penetrates the surface of the steel, and thus undergoes a -change, we are soon convinced that we have here a mere reflection -which, in its subjective character, is connected with the theory of -faintly acting lights, and the after-image of dazzling lights, and as -far as it can be considered objective, announces even in the minutest -appearances, a real effect, independent of the action and reaction of -the eye.</p> - -<p class="para"><a id="a371">371.</a></p> - -<p>We have seen that to produce these effects<span class="pagenum"><a name="Page_157" id="Page_157">[Pg 157]</a></span> not merely light but a -powerful light is necessary; that this powerful light again is not an -abstract and general quality, but a circumscribed light, a luminous -image. We can convince ourselves still further of this by analogous -cases.</p> - -<p class="para"><a id="a372">372.</a></p> - -<p>A polished surface of silver placed in the sun reflects a dazzling -light, but in this case no colour is seen. If, however, we slightly -scratch the surface, an iridescent appearance, in which green and red -are conspicuous, will be exhibited at a certain angle. In chased and -carved metals the effect is striking: yet it may be remarked throughout -that, in order to its appearance, some form, some alternation of light -and dark must co-operate with the reflection; thus a window-bar, -the stem of a tree, an accidentally or purposely interposed object -produces a perceptible effect. This appearance, too, may be exhibited -objectively in the camera-obscura.</p> - -<p class="para"><a id="a373">373.</a></p> - -<p>If we cause a polished plated surface to be so acted on by aqua fortis -that the copper within is touched, and the surface itself thus rendered -rough, and if the sun's image be then reflected from it, the splendour -will be reverberated from every minutest prominence, and the surface -will appear iridescent. So, if we hold a sheet of<span class="pagenum"><a name="Page_158" id="Page_158">[Pg 158]</a></span> black unglazed paper -in the sun, and look at it attentively, it will be seen to glisten in -its minutest points with the most vivid colours.</p> - -<p class="para"><a id="a374">374.</a></p> - -<p>All these examples are referable to the same conditions. In the first -case the luminous image is reflected from a thin line; in the second -probably from sharp edges; in the third from very small points. In all -a very powerful and circumscribed light is requisite. For all these -appearances of colour again it is necessary that the eye should be at a -due distance from the reflecting points.</p> - -<p class="para"><a id="a375">375.</a></p> - -<p>If these observations are made with the microscope, the appearance -will be greatly increased in force and splendour, for we then see the -smallest portion of the surfaces, lit by the sun, glittering in these -colours of reflection, which, allied to the hues of refraction, now -attain their highest degree of brilliancy. In such cases we may observe -a vermiform iridescence on the surface of organic bodies, the further -description of which will be given hereafter.</p> - -<p class="para"><a id="a376">376.</a></p> - -<p>Lastly, the colours which are chiefly exhibited<span class="pagenum"><a name="Page_159" id="Page_159">[Pg 159]</a></span> in reflection are red -and green, whence we may infer that the linear appearance especially -consists of a thin line of red, bounded by blue on one side and yellow -on the other. If these triple lines approach very near together, the -intermediate space must appear green; a phenomenon which will often -occur to us as we proceed.</p> - -<p class="para"><a id="a377">377.</a></p> - -<p>We frequently meet with these colours in nature. The colours of the -spider's web might be considered exactly of the same class with those -reflected from the steel wire, except that the non-translucent quality -of the former is not so certain as in the case of steel; on which -account some have been inclined to class the colours of the spider's -web with the phenomena of refraction.</p> - -<p class="para"><a id="a378">378.</a></p> - -<p>In mother-of-pearl we perceive infinitely fine organic fibres and -lamellæ in juxta-position, from which, as from the scratched silver -before alluded to, varied colours, but especially red and green, may -arise.</p> - -<p class="para"><a id="a379">379.</a></p> - -<p>The changing colours of the plumage of birds may also be mentioned -here, although in all organic<span class="pagenum"><a name="Page_160" id="Page_160">[Pg 160]</a></span> instances a chemical principle -and an adaptation of the colour to the structure may be assumed; -considerations to which we shall return in treating of chemical colours.</p> - -<p class="para"><a id="a380">380.</a></p> - -<p>That the appearances of objective halos also approximate catoptrical -phenomena will be readily admitted, while we again do not deny that -refraction as well may here come into the account. For the present -we restrict ourselves to one or two observations; hereafter we may -be enabled to make a fuller application of general principles to -particular examples.</p> - -<p class="para"><a id="a381">381.</a></p> - -<p>We first call to mind the yellow and red circles produced on a white or -grey wall by a light placed near it (<a href="#a88">88</a>). Light when reflected appears -subdued, and a subdued light excites the impression of yellow, and -subsequently of red.</p> - -<p class="para"><a id="a382">382.</a></p> - -<p>Let the wall be illumined by a candle placed quite close to it. The -farther the light is diffused the fainter it becomes; but it is still -the effect of the flame, the continuation of its action, the dilated -effect of its image. We might, therefore, very fairly call these -circles<span class="pagenum"><a name="Page_161" id="Page_161">[Pg 161]</a></span> reiterated images, because they constitute the successive -boundaries of the action of the light, and yet at the same time only -present an extended image of the flame.</p> - -<p class="para"><a id="a383">383.</a></p> - -<p>If the sky is white and luminous round the sun owing to the atmosphere -being filled with light vapours; if mists or clouds pass before the -moon, the reflection of the disk mirrors itself in them; the halos we -then perceive are single or double, smaller or greater, sometimes very -large, often colourless, sometimes coloured.</p> - -<p class="para"><a id="a384">384.</a></p> - -<p>I witnessed a very beautiful halo round the moon the 15th of November, -1799, when the barometer stood high; the sky was cloudy and vapoury. -The halo was completely coloured, and the circles were concentric round -the light as in subjective halos. That this halo was objective I was -presently convinced by covering the moon's disk, when the same circles -were nevertheless perfectly visible.</p> - -<p class="para"><a id="a385">385.</a></p> - -<p>The different extent of the halos appears to have a relation with the -proximity or distance of the vapour from the eye of the observer.</p> - -<p><span class="pagenum"><a name="Page_162" id="Page_162">[Pg 162]</a></span></p> - -<p class="para"><a id="a386">386.</a></p> - -<p>As window-panes lightly breathed upon increase the brilliancy of -subjective halos, and in some degree give them an objective character, -so, perhaps, with a simple contrivance in winter, during a quickly -freezing temperature, a more exact definition of this might be arrived -at.</p> - -<p class="para"><a id="a387">387.</a></p> - -<p>How much reason we have in considering these circles to insist on the -<i>image</i> and its effects, is apparent in the phenomenon of the so-called -double suns. Similar double images always occur in certain points -of halos and circles, and only present in a circumscribed form what -takes place in a more general way in the whole circle. All this will -be more conveniently treated in connexion with the appearance of the -rainbow.—<a href="#NOTE_Q">Note Q</a>.</p> - -<p class="para"><a id="a388">388.</a></p> - -<p>In conclusion it is only necessary to point out the affinity between -the catoptrical and paroptical colours.</p> - -<p>We call those paroptical colours which appear when the light passes -by the edge of an opaque colourless body. How nearly these are allied -to the dioptrical colours of the second class will be easily seen by -those who are convinced with us that the colours of refraction<span class="pagenum"><a name="Page_163" id="Page_163">[Pg 163]</a></span> -take place only at the edges of objects. The affinity again between the -catoptrical and paroptical colours will be evident in the following -chapter.</p> - - - -<hr class="chap" /> -<h5><a name="XXXII" id="XXXII">XXXII.</a></h5> - -<h5> -PAROPTICAL COLOURS.</h5> - - -<p class="para"><a id="a389">389.</a></p> - -<p>The paroptical colours have been hitherto called peri-optical, because -a peculiar effect of light was supposed to take place as it were round -the object, and was ascribed to a certain flexibility of the light to -and from the object.</p> - -<p class="para"><a id="a390">390.</a></p> - -<p>These colours again may be divided into subjective and objective, -because they appear partly without us, as it were, painted on surfaces, -and partly within us, immediately on the retina. In this chapter we -shall find it more to our purpose to take the objective cases first, -since the subjective are so closely connected with other appearances -already known to us, that it is hardly possible to separate them.</p> - -<p class="para"><a id="a391">391.</a></p> - -<p>The paroptical colours then are so called because<span class="pagenum"><a name="Page_164" id="Page_164">[Pg 164]</a></span> the light must pass -by an outline or edge to produce them. They do not, however, always -appear in this case; to produce the effect very particular conditions -are necessary besides.</p> - -<p class="para"><a id="a392">392.</a></p> - -<p>It is also to be observed that in this instance again light does not -act as an abstract diffusion (361), the sun shines towards an edge. -The volume of light poured from the sun-image passes by the edge of -a substance, and occasions shadows. Within these shadows we shall -presently find colours appear.</p> - -<p class="para"><a id="a393">393.</a></p> - -<p>But, above all, we should make the experiments and observations that -bear upon our present inquiry in the fullest light. We, therefore, -place the observer in the open air before we conduct him to the limits -of a dark room.</p> - -<p class="para"><a id="a394">394.</a></p> - -<p>A person walking in sun-shine in a garden, or on any level path, may -observe that his shadow only appears sharply defined next the foot on -which he rests; farther from this point, especially round the head, it -melts away into the bright ground. For as the sun-light proceeds not -only from the middle of the sun, but also acts cross-wise from the two -extremes of every<span class="pagenum"><a name="Page_165" id="Page_165">[Pg 165]</a></span> diameter, an objective parallax takes place which -produces a half-shadow on both sides of the object.</p> - -<p class="para"><a id="a395">395.</a></p> - -<p>If the person walking raises and spreads his hand, he distinctly sees -in the shadow of each finger the diverging separation of the two -half-shadows outwards, and the diminution of the principal shadow -inwards, both being effects of the cross action of the light.</p> - -<p class="para"><a id="a396">396.</a></p> - -<p>This experiment may be repeated and varied before a smooth wall, -with rods of different thicknesses, and again with balls; we shall -always find that the farther the object is removed from the surface of -the wall, the more the weak double shadow spreads, and the more the -forcible main shadow diminishes, till at last the main shadow appears -quite effaced, and even the double shadows become so faint, that they -almost disappear; at a still greater distance they are, in fact, -imperceptible.</p> - -<p class="para"><a id="a397">397.</a></p> - -<p>That this is caused by the cross-action of the light we may easily -convince ourselves; for the shadow of a pointed object plainly exhibits -two points. We must thus never lose sight of the<span class="pagenum"><a name="Page_166" id="Page_166">[Pg 166]</a></span> fact that in this -case the whole sun-image acts, produces shadows, changes them to double -shadows, and finally obliterates them.</p> - -<p class="para"><a id="a398">398.</a></p> - -<p>Instead of solid bodies let us now take openings cut of various given -sizes next each other, and let the sun shine through them on a plane -surface at some little distance; we shall find that the bright image -produced by the sun on the surface, is larger than the opening; this -is because one edge of the sun shines towards the opposite edge of the -opening, while the other edge of the disk is excluded on that side. -Hence the bright image is more weakly lighted towards the edges.</p> - -<p class="para"><a id="a399">399.</a></p> - -<p>If we take square openings of any size we please, we shall find that -the bright image on a surface nine feet from the opening, is on every -side about an inch larger than the opening; thus nearly corresponding -with the angle of the apparent diameter of the sun.</p> - -<p class="para"><a id="a400">400.</a></p> - -<p>That the brightness should gradually diminish towards the edges of the -image is quite natural, for at last only a minimum of the light can -act cross-wise from the sun's circumference through the edge of the -aperture.</p> - -<p><span class="pagenum"><a name="Page_167" id="Page_167">[Pg 167]</a></span></p> - -<p class="para"><a id="a401">401.</a></p> - -<p>Thus we here again see how much reason we have in actual observation to -guard against the assumption of parallel rays, bundles and fasces of -rays, and the like hypothetical notions.</p> - -<p class="para"><a id="a402">402.</a></p> - -<p>We might rather consider the splendour of the sun, or of any light, -as an infinite specular multiplication of the circumscribed luminous -image, whence it may be explained that all square openings through -which the sun shines, at certain distances, according as the apertures -are greater or smaller, must give a round image of light.</p> - -<p class="para"><a id="a403">403.</a></p> - -<p>The above experiments may be repeated through openings of various -shapes and sizes, and the same effect will always take place at -proportionate distances. In all these cases, however, we may still -observe that in a full light and while the sun merely shines past an -edge, no colour is apparent.</p> - -<p class="para"><a id="a404">404.</a></p> - -<p>We therefore proceed to experiments with a subdued light, which is -essential to the appearance of colour. Let a small opening be made in -the window-shutter of a dark room; let the<span class="pagenum"><a name="Page_168" id="Page_168">[Pg 168]</a></span> crossing sun-light which -enters, be received on a surface of white paper, and we shall find that -the smaller the opening is, the dimmer the light image will be. This is -quite obvious, because the paper does not receive light from the whole -sun, but partially from single points of its disk.</p> - -<p class="para"><a id="a405">405.</a></p> - -<p>If we look attentively at this dim image of the sun, we find it still -dimmer towards the outlines where a yellow border is perceptible. The -colour is still more apparent if a vapour or a transparent cloud passes -before the sun, thus subduing and dimming its brightness. The halo on -the wall, the effect of the decreasing brightness of a light placed -near it, is here forced on our recollection. (<a href="#a88">88</a>.)</p> - -<p class="para"><a id="a406">406.</a></p> - -<p>If we examine the image more accurately, we perceive that this yellow -border is not the only appearance of colour; we can see, besides, a -bluish circle, if not even a halo-like repetition of the coloured -border. If the room is quite dark, we discern that the sky next the -sun also has its effect: we see the blue sky, nay, even the whole -landscape, on the paper, and are thus again convinced that as far as -regards the sun, we have here only to do with a luminous image.</p> - -<p><span class="pagenum"><a name="Page_169" id="Page_169">[Pg 169]</a></span></p> - -<p class="para"><a id="a407">407.</a></p> - -<p>If we take a somewhat larger square opening, so large that the image -of the sun shining through it does not immediately become round, we -may distinctly observe the half-shadows of every edge or side, the -junction of these in the corners, and their colours; just as in the -above-mentioned appearance with the round opening.</p> - -<p class="para"><a id="a408">408.</a></p> - -<p>We have now subdued a parallactic light by causing it to shine through -small apertures, but we have not taken from it its parallactic -character; so that it can produce double shadows of bodies, although -with diminished power. These double shadows which we have hitherto -been describing, follow each other in light and dark, coloured and -colourless circles, and produce repeated, nay, almost innumerable -halos. These effects have been often represented in drawings and -engravings. By placing needles, hairs, and other small bodies, in the -subdued light, the numerous halo-like double shadows may be increased; -thus observed, they have been ascribed to an alternating flexile action -of the light, and the same assumption has been employed to explain the -obliteration of the central shadow, and the appearance of a light in -the place of the dark.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_170" id="Page_170">[Pg 170]</a></span></p> - -<p class="para"><a id="a409">409.</a></p> - -<p>For ourselves, we maintain that these again are parallactic double -shadows, which appear edged with coloured borders and halos.</p> - -<p class="para"><a id="a410">410.</a></p> - -<p>After having seen and investigated the foregoing phenomena, we -can proceed to the experiments with knife-blades,<a name="FNanchor_1_40" id="FNanchor_1_40"></a><a href="#Footnote_1_40" class="fnanchor">[1]</a> exhibiting -effects which may be referred to the contact and parallactic mutual -intersection of the half-shadows and halos already familiar to us.</p> - -<p class="para"><a id="a411">411.</a></p> - -<p>Lastly, the observer may follow out the experiments with hairs, -needles, and wires, in the half-light produced as before described by -the sun, as well as in that derived from the blue sky, and indicated on -the white paper. He will thus make himself still better acquainted with -the true nature of this phenomenon.</p> - -<p class="para"><a id="a412">412.</a></p> - -<p>But since in these experiments everything depends on our being -persuaded of the parallactic action of the light, we can make this more -evident by means of two sources of light, the two shadows from which -intersect each other, and may be altogether separated. By day this may -be contrived with two small<span class="pagenum"><a name="Page_171" id="Page_171">[Pg 171]</a></span> openings in a window-shutter; by night, -with two candles. There are even accidental effects in interiors, on -opening and closing shutters, by means of which we can better observe -these appearances than with the most careful apparatus. But still, -all and each of these may be reduced to experiment by preparing a box -which the observer can look into from above, and gradually diminishing -the openings after having caused a double light to shine in. In this -case, as might be expected, the coloured shadow, considered under the -physiological colours, appears very easily.</p> - -<p class="para"><a id="a413">413.</a></p> - -<p>It is necessary to remember, generally, what has been before stated -with regard to the nature of double shadows, half-lights, and the like. -Experiments also should especially be made with different shades of -grey placed next each other, where every stripe will appear light by a -darker, and dark by a lighter stripe next it. If at night, with three -or more lights, we produce shadows which cross each other successively, -we can observe this phenomenon very distinctly, and we shall be -convinced that the physiological case before more fully treated, here -comes into the account (<a href="#a38">38</a>).</p> - -<p class="para"><a id="a414">414.</a></p> - -<p>To what extent the appearances that accompany<span class="pagenum"><a name="Page_172" id="Page_172">[Pg 172]</a></span> the paroptical colours, -may be derived from the doctrine of subdued lights, from half-shadows, -and from the physiological disposition of the retina, or whether we -shall be forced to take refuge in certain intrinsic qualities of light, -as has hitherto been done, time may teach. Suffice it here to have -pointed out the conditions under which the paroptical colours appear, -and we may hope that our allusion to their connexion with the facts -before adduced by us will not remain unnoticed by the observers of -nature.</p> - -<p class="para"><a id="a415">415.</a></p> - -<p>The affinity of the paroptical colours with the dioptrical of the -second class will also be readily seen and followed up by every -reflecting investigator. Here, as in those instances, we have to do -with edges or boundaries; here, as in those instances, with a light, -which appears at the outline. How natural, therefore, it is to conclude -that the paroptical effects may be heightened, strengthened, and -enriched by the dioptrical. Since, however, the luminous image actually -shines through the medium, we can here only have to do with objective -cases of refraction: it is these which are strictly allied to the -paroptical cases. The subjective cases of refraction, where we see -objects through the medium, are quite distinct from the paroptical.<span class="pagenum"><a name="Page_173" id="Page_173">[Pg 173]</a></span> -We have already recommended them on account of their clearness and -simplicity.</p> - -<p class="para"><a id="a416">416.</a></p> - -<p>The connexion between the paroptical colours and the catoptrical may -be already inferred from what has been said: for as the catoptrical -colours only appear on scratches, points, steel-wire, and delicate -threads, so it is nearly the same case as if the light shone past an -edge. The light must always be reflected from an edge in order to -produce colour. Here again, as before pointed out, the partial action -of the luminous image and the subduing of the light are both to be -taken into the account.</p> - -<p class="para"><a id="a417">417.</a></p> - -<p>We add but few observations on the subjective paroptical colours, -because these may be classed partly with the physiological colours, -partly with the dioptrical of the second order. The greater part hardly -seem to belong here, but, when attentively considered, they still -diffuse a satisfactory light over the whole doctrine, and establish its -connexion.</p> - -<p class="para"><a id="a418">418.</a></p> - -<p>If we hold a ruler before the eyes so that the flame of a light just -appears above it, we see the ruler as it were indented and notched -at the<span class="pagenum"><a name="Page_174" id="Page_174">[Pg 174]</a></span> place where the light appears. This seems deducible from the -expansive power of light acting on the retina (<a href="#a18">18</a>).</p> - -<p class="para"><a id="a419">419.</a></p> - -<p>The same phenomenon on a large scale is exhibited at sun-rise; for when -the orb appears distinctly, but not too powerfully, so that we can -still look at it, it always makes a sharp indentation in the horizon.</p> - -<p class="para"><a id="a420">420.</a></p> - -<p>If, when the sky is grey, we approach a window, so that the dark cross -of the window-bars be relieved on the sky; if after fixing the eyes on -the horizontal bar we bend the head a little forward; on half closing -the eyes as we look up, we shall presently perceive a bright yellow-red -border under the bar, and a bright light-blue one above it. The duller -and more monotonous the grey of the sky, the more dusky the room, and, -consequently, the more previously unexcited the eye, the livelier the -appearance will be; but it may be seen by an attentive observer even in -bright daylight.</p> - -<p class="para"><a id="a421">421.</a></p> - -<p>If we move the head backwards while half closing the eyes, so that the -horizontal bar be seen below, the phenomenon will appear reversed.<span class="pagenum"><a name="Page_175" id="Page_175">[Pg 175]</a></span> The -upper edge will appear yellow, the under edge blue.</p> - -<p class="para"><a id="a422">422.</a></p> - -<p>Such observations are best made in a dark room. If white paper is -spread before the opening where the solar microscope is commonly -fastened, the lower edge of the circle will appear blue, the upper -yellow, even while the eyes are quite open, or only by half-closing -them so far that a halo no longer appears round the white. If the head -is moved backwards the colours are reversed.</p> - -<p class="para"><a id="a423">423.</a></p> - -<p>These phenomena seem to prove that the humours of the eye are in fact -only really achromatic in the centre where vision takes place, but that -towards the circumference, and in unusual motions of the eyes, as in -looking horizontally when the head is bent backwards or forwards, a -chromatic tendency remains, especially when distinctly relieved objects -are thus looked at. Hence such phenomena may be considered as allied to -the dioptrical colours of the second class.</p> - -<p class="para"><a id="a424">424.</a></p> - -<p>Similar colours appear if we look on black and white objects, through a -pin-hole in a card.<span class="pagenum"><a name="Page_176" id="Page_176">[Pg 176]</a></span> Instead of a white object we may take the minute -light aperture in the tin plate of a camera obscura, as prepared for -paroptical experiments.</p> - -<p class="para"><a id="a425">425.</a></p> - -<p>If we look through a tube, the farther end of which is contracted or -variously indented, the same colours appear.</p> - -<p class="para"><a id="a426">426.</a></p> - -<p>The following phenomena appear to me to be more nearly allied to the -paroptical appearances. If we hold up a needle near the eye, the point -appears double. A particularly remarkable effect again is produced if -we look towards a grey sky through the blades of knives prepared for -paroptical experiments. We seem to look through a gauze; a multitude of -threads appear to the eye; these are in fact only the reiterated images -of the sharp edges, each of which is successively modified by the next, -or perhaps modified in a parallactic sense by the oppositely acting -one, the whole mass being thus changed to a thread-like appearance.</p> - -<p class="para"><a id="a427">427.</a></p> - -<p>Lastly, it is to be remarked that if we look through the blades towards -a minute light in<span class="pagenum"><a name="Page_177" id="Page_177">[Pg 177]</a></span> the window-shutter, coloured stripes and halos -appear on the retina as on the paper.</p> - -<p class="para"><a id="a428">428.</a></p> - -<p>The present chapter may be here terminated, the less reluctantly, -as a friend has undertaken to investigate this subject by further -experiments. In our recapitulation, in the description of the -plates and apparatus, we hope hereafter to give an account of his -observations.<a name="FNanchor_2_41" id="FNanchor_2_41"></a><a href="#Footnote_2_41" class="fnanchor">[2]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_40" id="Footnote_1_40"></a><a href="#FNanchor_1_40"><span class="label">[1]</span></a> See Newton's Optics, book iii.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_41" id="Footnote_2_41"></a><a href="#FNanchor_2_41"><span class="label">[2]</span></a> The observations here alluded to never appeared.</p></div> - - -<hr class="chap" /> - -<h5><a name="XXXIII" id="XXXIII">XXXIII.</a></h5> - - -<h5>EPOPTICAL COLOURS.</h5> - - -<p class="para"><a id="a429">429.</a></p> - -<p>We have hitherto had to do with colours which appear with vivacity, but -which immediately vanish again when certain conditions cease. We have -now to become acquainted with others, which it is true are still to be -considered as transient, but which, under certain circumstances, become -so fixed that, even after the conditions which first occasioned their -appearance cease, they still remain, and thus constitute<span class="pagenum"><a name="Page_178" id="Page_178">[Pg 178]</a></span> the link -between the physical and the chemical colours.</p> - -<p class="para"><a id="a430">430.</a></p> - -<p>They appear from various causes on the surface of a colourless body, -originally, without communication, die or immersion (βαφή); and we now -proceed to trace them, from their faintest indication to their most -permanent state, through the different conditions of their appearance, -which for easier survey we here at once summarily state.</p> - -<p class="para"><a id="a431">431.</a></p> - -<p>First condition.—The contact of two smooth surfaces of hard -transparent bodies.</p> - -<p>First case: if masses or plates of glass, or if lenses are pressed -against each other.</p> - -<p>Second case: if a crack takes place in a solid mass of glass, chrystal, -or ice.</p> - -<p>Third case: if lamellæ of transparent stones become separated.</p> - -<p>Second condition.—If a surface of glass or a polished stone is -breathed upon.</p> - -<p>Third condition.—The combination of the two last; first, breathing on -the glass, then placing another plate of glass upon it, thus exciting -the colours by pressure; then removing the upper glass, upon which the -colours begin to fade and vanish with the breath.</p> - -<p><span class="pagenum"><a name="Page_179" id="Page_179">[Pg 179]</a></span></p> - -<p>Fourth condition.—Bubbles of various liquids, soap, chocolate, beer, -wine, fine glass bubbles.</p> - -<p>Fifth condition.—Very fine pellicles and lamellæ, produced by the -decomposition of minerals and metals. The pellicles of lime, the -surface of stagnant water, especially if impregnated with iron, and -again pellicles of oil on water, especially of varnish on aqua fortis.</p> - -<p>Sixth condition.—If metals are heated; the operation of imparting -tints to steel and other metals.</p> - -<p>Seventh condition.—If the surface of glass is beginning to decompose.</p> - -<p class="para"><a id="a432">432.</a></p> - -<p>First condition, first case. If two convex glasses, or a convex and -plane glass, or, best of all, a convex and concave glass come in -contact, concentric coloured circles appear. The phenomenon exhibits -itself immediately on the slightest pressure, and may then be gradually -carried through various successive states. We will describe the -complete appearance at once, as we shall then be better enabled to -follow the different states through which it passes.</p> - -<p class="para"><a id="a433">433.</a></p> - -<p>The centre is colourless; where the glasses are, so to speak, united -in one by the strongest pressure, a dark grey point appears with a -silver<span class="pagenum"><a name="Page_180" id="Page_180">[Pg 180]</a></span> white space round it: then follow, in decreasing distances, -various insulated rings, all consisting of three colours, which are -in immediate contact with each other. Each of these rings, of which -perhaps three or four might be counted, is yellow on the inner side, -blue on the outer, and red in the centre. Between two rings there -appears a silver white interval. The rings which are farthest from the -centre are always nearer together: they are composed of red and green -without a perceptible white space between them.</p> - -<p class="para"><a id="a434">434.</a></p> - -<p>We will now observe the appearances in their gradual formation, -beginning from the slightest pressure.</p> - -<p class="para"><a id="a435">435.</a></p> - -<p>On the slightest pressure the centre itself appears of a green colour. -Then follow as far as the concentric circles extend, red and green -rings. They are wide, accordingly, and no trace of a silver white -space is to be seen between them. The green is produced by the blue of -an imperfectly developed circle, mixing with the yellow of the first -circle. All the remaining circles are, in this slight contact, broad; -their yellow and blue edges mix together, thus producing a beautiful -green. The red, however, of<span class="pagenum"><a name="Page_181" id="Page_181">[Pg 181]</a></span> each circle, remains pure and untouched; -hence the whole series is composed of these two colours.</p> - -<p class="para"><a id="a436">436.</a></p> - -<p>A somewhat stronger pressure separates the first circle by a slight -interval from the imperfectly developed one: it is thus detached, and -may be said to appear in a complete state. The centre is now a blue -point; for the yellow of the first circle is now separated from this -central point by a silver white space. From the centre of the blue a -red appears, which is thus, in all cases, bounded on the outside by -its blue edge. The second and third rings from the centre are quite -detached. Where deviations from this order present themselves, the -observer will be enabled to account for them, from what has been or -remains to be stated.</p> - -<p class="para"><a id="a437">437.</a></p> - -<p>On a stronger pressure the centre becomes yellow; this yellow is -surrounded by a red and blue edge: at last, the yellow also retires -from the centre; the innermost circle is formed and is bounded with -yellow. The whole centre itself now appears silver white, till at last, -on the strongest pressure, the dark point appears, and the phenomenon, -as described at first, is complete.</p> - -<p><span class="pagenum"><a name="Page_182" id="Page_182">[Pg 182]</a></span></p> - -<p class="para"><a id="a438">438.</a></p> - -<p>The relative size of the concentric circles and their intervals depends -on the form of the glasses which are pressed together.</p> - -<p class="para"><a id="a439">439.</a></p> - -<p>We remarked above, that the coloured centre is, in fact, an undeveloped -circle. It is, however, often found, on the slightest pressure, that -several undeveloped circles exist there, as it were, in the germ; these -can be successively developed before the eye of the observer.</p> - -<p class="para"><a id="a440">440.</a></p> - -<p>The regularity of these rings is owing to the form of the convex -glasses, and the diameter of the coloured appearance depends on the -greater or lesser section of a circle on which a lens is polished. We -easily conclude from this, that by pressing plane glasses together, -irregular appearances only will be produced; the colours, in fact, -undulate like watered silks, and spread from the point of pressure in -all directions. Yet, the phenomenon as thus exhibited is much more -splendid than in the former instance, and cannot fail to strike every -spectator. If we make the experiment in this mode, we shall distinctly -see, as in the other case, that, on a slight pressure, the green and -red waves appear; on a stronger, stripes of blue, red, and yellow, -become detached.<span class="pagenum"><a name="Page_183" id="Page_183">[Pg 183]</a></span> At first, the outer sides of these stripes touch; on -increased pressure they are separated by a silver white space.</p> - -<p class="para"><a id="a441">441.</a></p> - -<p>Before we proceed to a further description of this phenomenon, we may -point out the most convenient mode of exhibiting it. Place a large -convex glass on a table near the window; upon this glass lay a plate -of well-polished mirror-glass, about the size of a playing-card, and -the mere weight of the plate will press sufficiently to produce one -or other of the phenomena above described. So, also, by the different -weight of plates of glass, by other accidental circumstances, for -instance, by slipping the plate on the side of the convex glass where -the pressure cannot be so strong as in the centre, all the gradations -above described can be produced in succession.</p> - -<p class="para"><a id="a442">442.</a></p> - -<p>In order to observe the phenomenon it is necessary to look obliquely -on the surface where it appears. But, above all, it is to be remarked -that by stooping still more, and looking at the appearance under a more -acute angle, the circles not only grow larger but other circles are -developed from the centre, of which no trace is to be discovered when -we look perpendicularly, even through the strongest magnifiers.</p> - -<p><span class="pagenum"><a name="Page_184" id="Page_184">[Pg 184]</a></span></p> - -<p class="para"><a id="a443">443.</a></p> - -<p>In order to exhibit the phenomenon in its greatest beauty, the utmost -attention should be paid to the cleanness of the glasses. If the -experiment is made with plate-glass adapted for mirrors, the glass -should be handled with gloves. The inner surfaces, which must come in -contact with the utmost nicety, may be most conveniently cleaned before -the experiment, and the outer surfaces should be kept clean while the -pressure is increased.</p> - -<p class="para"><a id="a444">444.</a></p> - -<p>From what has been said it will be seen that an exact contact of two -smooth surfaces is necessary. Polished glasses are best adapted for the -purpose. Plates of glass exhibit the most brilliant colours when they -fit closely together, and for this reason the phenomenon will increase -in beauty if exhibited under an air-pump, by exhausting the air.</p> - -<p class="para"><a id="a445">445.</a></p> - -<p>The appearance of the coloured rings may be produced in the greatest -perfection by placing a convex and concave glass together which have -been ground on similar segments of circles. I have never seen the -effect more brilliant than with the object-glass of an achromatic -telescope,<span class="pagenum"><a name="Page_185" id="Page_185">[Pg 185]</a></span> in which the crown-glass and flint-glass were necessarily -in the closest contact.</p> - -<p class="para"><a id="a446">446.</a></p> - -<p>A remarkable appearance takes place when dissimilar surfaces are -pressed together; for example, a polished crystal and a plate of -glass. The appearance does not at all exhibit itself in large flowing -waves, as in the combination of glass with glass, but it is small and -angular, and, as it were, disjointed: thus it appears that the surface -of the polished crystal, which consists of infinitely small sections of -lamellæ, does not come so uninterruptedly in contact with the glass as -another glass-plate would.</p> - -<p class="para"><a id="a447">447.</a></p> - -<p>The appearance of colour vanishes on the strongest pressure, which so -intimately unites the two surfaces that they appear to make but one -substance. It is this which occasions the dark centre, because the -pressed lens no longer reflects any light from this point, for the -very same point, when seen against the light, is perfectly clear and -transparent. On relaxing the pressure, the colours, in like manner, -gradually diminish, and disappear entirely when the surfaces are -separated.</p> - -<p><span class="pagenum"><a name="Page_186" id="Page_186">[Pg 186]</a></span></p> - -<p class="para"><a id="a448">448.</a></p> - -<p>These same appearances occur in two similar cases. If entirely -transparent masses become partially separated, the surfaces of their -parts being still sufficiently in contact, we see the same circles and -waves more or less. They may be produced in great beauty by plunging a -hot mass of glass in water; the different fissures and cracks enabling -us to observe the colours in various forms. Nature often exhibits the -same phenomena in split rock crystals.</p> - -<p class="para"><a id="a449">449.</a></p> - -<p>This appearance, again, frequently displays itself in the mineral world -in those kinds of stone which by nature have a tendency to exfoliate. -These original lamellæ are, it is true, so intimately united, that -stones of this kind appear altogether transparent and colourless, yet, -the internal layers become separated, from various accidental causes, -without altogether destroying the contact: thus the appearance, which -is now familiar to us by the foregoing description, often occurs in -nature, particularly in calcareous spars; the specularis, adularia, and -other minerals of similar structure. Hence it shows an ignorance of the -proximate causes of an appearance so often accidentally produced, to -consider it so important in mineralogy, and to attach especial value to -the specimens exhibiting it.</p> - -<p><span class="pagenum"><a name="Page_187" id="Page_187">[Pg 187]</a></span></p> - -<p class="para"><a id="a450">450.</a></p> - -<p>We have yet to speak of the very remarkable inversion of this -appearance, as related by men of science. If, namely, instead of -looking at the colours by a reflected light, we examine them by a -transmitted light, the opposite colours are said to appear, and in -a mode corresponding with that which we have before described as -physiological; the colours evoking each other. Instead of blue, we -should thus see red-yellow; instead of red, green, &c., and <i>vice -versâ</i>. We reserve experiments in detail, the rather as we have -ourselves still some doubts on this point.</p> - -<p class="para"><a id="a451">451.</a></p> - -<p>If we were now called upon to give some general explanation of these -epoptical colours, as they appear under the first condition, and to -show their connexion with the previously detailed physical phenomena, -we might proceed to do so as follows:—</p> - -<p class="para"><a id="a452">452.</a></p> - -<p>The glasses employed for the experiments are to be regarded as the -utmost possible practical approach to transparence. By the intimate -contact, however, occasioned by the pressure applied to them, their -surfaces, we are persuaded, immediately become in a very slight -degree dimmed. Within this semi-transparence<span class="pagenum"><a name="Page_188" id="Page_188">[Pg 188]</a></span> the colours immediately -appear, and every circle comprehends the whole scale; for when the two -opposites, yellow and blue, are united by their red extremities, pure -red appears: the green, on the other hand, as in prismatic experiments, -when yellow and blue touch.</p> - -<p class="para"><a id="a453">453.</a></p> - -<p>We have already repeatedly found that where colour exists at all, the -whole scale is soon called into existence; a similar principle may be -said to lurk in the nature of every physical phenomenon; it already -follows, from the idea of polar opposition, from which an elementary -unity or completeness results.</p> - -<p class="para"><a id="a454">454.</a></p> - -<p>The fact that a colour exhibited by transmitted light is different -from that displayed by reflected light, reminds us of those dioptrical -colours of the first class which we found were produced precisely in -the same way through semi-opacity. That here, too, a diminution of -transparency exists there can scarcely be a doubt; for the adhesion -of the perfectly smooth plates of glass (an adhesion so strong that -they remain hanging to each other) produces a degree of union which -deprives each of the two surfaces, in some degree, of its smoothness -and transparence. The fullest proof may, however,<span class="pagenum"><a name="Page_189" id="Page_189">[Pg 189]</a></span> be found in the -fact that in the centre, where the lens is most strongly pressed on -the other glass, and where a perfect union is accomplished, a complete -transparence takes place, in which we no longer perceive any colour. -All this may be hereafter confirmed in a recapitulation of the whole.</p> - -<p class="para"><a id="a455">455.</a></p> - -<p>Second condition.—If after breathing on a plate of glass, the breath -is merely wiped away with the finger, and if we then again immediately -breathe on the glass, we see very vivid colours gliding through each -other; these, as the moisture evaporates, change their place, and at -last vanish altogether. If this operation is repeated, the colours are -more vivid and beautiful, and remain longer than they did the first -time.</p> - -<p class="para"><a id="a456">456.</a></p> - -<p>Quickly as this appearance passes, and confused as it appears to be, I -have yet remarked the following effects:—At first all the principal -colours appear with their combinations; on breathing more strongly, the -appearance may be perceived in some order. In this succession it may be -remarked, that when the breath in evaporating becomes contracted from -all sides<span class="pagenum"><a name="Page_190" id="Page_190">[Pg 190]</a></span> towards the centre, the blue colour vanishes last.</p> - -<p class="para"><a id="a457">457.</a></p> - -<p>The phenomenon appears most readily between the minute lines, which the -action of passing the fingers leaves on the clear surface; a somewhat -rough state of the surface of the glass is otherwise requisite. On -some glass the appearance may be produced by merely breathing; in -other cases the wiping with the fingers is necessary: I have even met -with polished mirror-glasses, one side of which immediately showed the -colours vividly; the other not. To judge from some remaining pieces, -the former was originally the front of the glass, the latter the side -which was covered with quicksilver.</p> - -<p class="para"><a id="a458">458.</a></p> - -<p>These experiments may be best made in cold weather, because the glass -may be more quickly and distinctly breathed upon, and the breath -evaporates more suddenly. In severe frost the phenomenon may be -observed on a large scale while travelling in a carriage; the glasses -being well cleaned, and all closed. The breath of the persons within is -very gently diffused over the glass, and immediately produces the most -vivid play of colours. How far they may present a regular succession I -have not been able to remark;<span class="pagenum"><a name="Page_191" id="Page_191">[Pg 191]</a></span> but they appear particularly vivid when -they have a dark object as a background. This alternation of colours -does not, however, last long; for as soon as the breath gathers in -drops, or freezes to points of ice, the appearance is at once at an end.</p> - -<p class="para"><a id="a459">459.</a></p> - -<p>Third condition.—The two foregoing experiments of the pressure and -breathing may be united; namely, by breathing on a plate of glass, and -immediately after pressing the other upon it. The colours then appear -as in the case of two glasses unbreathed upon, with this difference, -that the moisture occasions here and there an interruption of the -undulations. On pushing one glass away from the other the moisture -appears iridescent as it evaporates.</p> - -<p class="para"><a id="a460">460.</a></p> - -<p>It might, however, be asserted that this combined experiment exhibits -no more than each single experiment; for it appears the colours excited -by pressure disappear in proportion as the glasses are less in contact, -and the moisture then evaporates with its own colours.</p> - -<p class="para"><a id="a461">461.</a></p> - -<p>Fourth condition.—Iridescent appearances are observable in almost all -bubbles; soap-bubbles<span class="pagenum"><a name="Page_192" id="Page_192">[Pg 192]</a></span> are the most commonly known, and the effect in -question is thus exhibited in the easiest mode; but it may be observed -in wine, beer, in pure spirit, and again, especially, in the froth of -chocolate.</p> - -<p class="para"><a id="a462">462.</a></p> - -<p>As in the above cases we required an infinitely narrow space between -two surfaces which are in contact, so we can consider the pellicle -of the soap-bubble as an infinitely thin lamina between two elastic -bodies; for the appearance in fact takes place between the air within, -which distends the bubble, and the atmospheric air.</p> - -<p class="para"><a id="a463">463.</a></p> - -<p>The bubble when first produced is colourless; then coloured stripes, -like those in marble paper, begin to appear: these at length spread -over the whole surface, or rather are driven round it as it is -distended.</p> - -<p class="para"><a id="a464">464.</a></p> - -<p>In a single bubble, suffered to hang from the straw or tube, the -appearance of colour is difficult to observe, for the quick rotation -prevents any accurate observation, and all the colours seem to mix -together; yet we can perceive that the colours begin at the orifice of -the tube. The solution itself may, however, be blown into carefully,<span class="pagenum"><a name="Page_193" id="Page_193">[Pg 193]</a></span> -so that only one bubble shall appear. This remains white (colourless) -if not much agitated; but if the solution is not too watery, circles -appear round the perpendicular axis of the bubble; these being near -each other, are commonly composed alternately of green and red. Lastly, -several bubbles may be produced together by the same means; in this -case the colours appear on the sides where two bubbles have pressed -each other flat.</p> - -<p class="para"><a id="a465">465.</a></p> - -<p>The bubbles of chocolate-froth may perhaps be even more conveniently -observed than those of soap; though smaller, they remain longer. In -these, owing to the heat, an impulse, a movement, is produced and -sustained, which appears necessary to the development and succession of -the appearances.</p> - -<p class="para"><a id="a466">466.</a></p> - -<p>If the bubble is small, or shut in between others, coloured lines -chase each other over the surface, resembling marbled paper; all the -colours of the scale are seen to pass through each other; the pure, the -augmented, the combined, all distinctly clear and beautiful. In small -bubbles the appearance lasts for a considerable time.</p> - -<p><span class="pagenum"><a name="Page_194" id="Page_194">[Pg 194]</a></span></p> - -<p class="para"><a id="a467">467.</a></p> - -<p>If the bubble is larger, or if it becomes by degrees detached, owing -to the bursting of others near, we perceive that this impulsion and -attraction of the colours has, as it were, an end in view; for on -the highest point of the bubble we see a small circle appear, which -is yellow in the centre; the other remaining coloured lines move -constantly round this with a vermicular action.</p> - -<p class="para"><a id="a468">468.</a></p> - -<p>In a short time the circle enlarges and sinks downwards on all sides; -in the centre the yellow remains; below and on the outside it becomes -red, and soon blue; below this again appears a new circle of the -same series of colours: if they approximate sufficiently, a green is -produced by the union of the border-colours.</p> - -<p class="para"><a id="a469">469.</a></p> - -<p>When I could count three such leading circles, the centre was -colourless, and this space became by degrees larger as the circles sank -lower, till at last the bubble burst.</p> - -<p class="para"><a id="a470">470.</a></p> - -<p>Fifth condition.—Very delicate pellicles may be formed in various -ways: on these films we discover a very lively play of colours, either -in the usual order, or more confusedly passing through each other. The -water in which lime<span class="pagenum"><a name="Page_195" id="Page_195">[Pg 195]</a></span> has been slaked soon skims over with a coloured -pellicle: the same happens on the surface of stagnant water, especially -if impregnated with iron. The lamellæ of the fine tartar which adheres -to bottles, especially in red French wine, exhibit the most brilliant -colours, on being exposed to the light, if carefully detached. Drops of -oil on water, brandy, and other fluids, produce also similar circles -and brilliant effects: but the most beautiful experiment that can be -made is the following:—Let aqua fortis, not too strong, be poured into -a flat saucer, and then with a brush drop on it some of the varnish -used by engravers to cover certain portions during the process of -biting their plates. After quick commotion there presently appears a -film which spreads itself out in circles, and immediately produces the -most vivid appearances of colour.</p> - -<p class="para"><a id="a471">471.</a></p> - -<p>Sixth condition.—When metals are heated, colours rapidly succeeding -each other appear on the surface: these colours can, however, be -arrested at will.</p> - -<p class="para"><a id="a472">472.</a></p> - -<p>If a piece of polished steel is heated, it will, at a certain degree -of warmth, be overspread with yellow. If taken suddenly away from the -fire, this yellow remains.</p> - -<p><span class="pagenum"><a name="Page_196" id="Page_196">[Pg 196]</a></span></p> - -<p class="para"><a id="a473">473.</a></p> - -<p>As the steel becomes hotter, the yellow appears darker, intenser, and -presently passes into red. This is difficult to arrest, for it hastens -very quickly to bright blue.</p> - -<p class="para"><a id="a474">474.</a></p> - -<p>This beautiful blue is to be arrested if the steel is suddenly taken -out of the heat and buried in ashes. The blue steel works are produced -in this way. If, again, the steel is held longer over the fire, it soon -becomes a light blue, and so it remains.</p> - -<p class="para"><a id="a475">475.</a></p> - -<p>These colours pass like a breath over the plate of steel; each seems -to fly before the other, but, in reality, each successive hue is -constantly developed from the preceding one.</p> - -<p class="para"><a id="a476">476.</a></p> - -<p>If we hold a penknife in the flame of a light, a coloured stripe will -appear across the blade. The portion of the stripe which was nearest to -the flame is light blue; this melts into blue-red; the red is in the -centre; then follow yellow-red and yellow.</p> - -<p class="para"><a id="a477">477.</a></p> - -<p>This phenomenon is deducible from the preceding<span class="pagenum"><a name="Page_197" id="Page_197">[Pg 197]</a></span> ones; for the portion -of the blade next the handle is less heated than the end which is in -the flame, and thus all the colours which in other cases exhibited -themselves in succession, must here appear at once, and may thus be -permanently preserved.</p> - -<p class="para"><a id="a478">478.</a></p> - -<p>Robert Boyle gives this succession of colours as follows:—"A florido -flavo ad flavum saturum et rubescentem (quem artifices sanguineum -vocant) inde ad languidum, postea ad saturiorem cyaneum." This would be -quite correct if the words "languidus" and "saturior" were to change -places. How far the observation is correct, that the different colours -have a relation to the degree of temper which the metal afterwards -acquires, we leave to others to decide. The colours are here only -indications of the different degrees of heat.—<a href="#NOTE_R">Note R</a>.</p> - -<p class="para"><a id="a479">479.</a></p> - -<p>When lead is calcined, the surface is first greyish. This greyish -powder, with greater heat, becomes yellow, and then orange. Silver, -too, exhibits colours when heated; the fracture of silver in the -process of refining belongs to the same class of examples. When -metallic glasses melt, colours in like manner appear on the surface.</p> - -<p><span class="pagenum"><a name="Page_198" id="Page_198">[Pg 198]</a></span></p> - -<p class="para"><a id="a480">480.</a></p> - -<p>Seventh condition.—When the surface of glass becomes decomposed. The -accidental opacity (blindwerden) of glass has been already noticed: the -term (blindwerden) is employed to denote that the surface of the glass -is so affected as to appear dim to us.</p> - -<p class="para"><a id="a481">481.</a></p> - -<p>White glass becomes "blind" soonest; cast, and afterwards polished -glass is also liable to be so affected; the bluish less, the green -least.</p> - -<p class="para"><a id="a482">482.</a></p> - -<p>Of the two sides of a plate of glass one is called the mirror side; -it is that which in the oven lies uppermost, on which one may observe -roundish elevations: it is smoother than the other, which is undermost -in the oven, and on which scratches may be sometimes observed. On this -account the mirror side is placed facing the interior of rooms, because -it is less affected by the moisture adhering to it from within, than -the other would be, and the glass is thus less liable to become "blind."</p> - -<p class="para"><a id="a483">483.</a></p> - -<p>This half-opacity or dimness of the glass assumes by degrees an -appearance of colour which may become very vivid, and in which<span class="pagenum"><a name="Page_199" id="Page_199">[Pg 199]</a></span> perhaps -a certain succession, or otherwise regular order, might be discovered.</p> - -<p class="para"><a id="a484">484.</a></p> - -<p>Having thus traced the physical colours from their simplest effects to -the present instances, where these fleeting appearances are found to -be fixed in bodies, we are, in fact, arrived at the point where the -chemical colours begin; nay, we have in some sort already passed those -limits; a circumstance which may excite a favourable prejudice for the -consistency of our statement. By way of conclusion to this part of our -inquiry, we subjoin a general observation, which may not be without its -bearing on the common connecting principle of the phenomena that have -been adduced.</p> - -<p class="para"><a id="a485">485.</a></p> - -<p>The colouring of steel and the appearances analogous to it, might -perhaps be easily deduced from the doctrine of the semi-opaque mediums. -Polished steel reflects light powerfully: we may consider the colour -produced by the heat as a slight degree of dimness: hence a bright -yellow must immediately appear; this, as the dimness increases, must -still appear deeper, more condensed, and redder, and at last pure and -ruby-red. The colour has now reached the extreme point of depth, and -if we suppose the same degree<span class="pagenum"><a name="Page_200" id="Page_200">[Pg 200]</a></span> of semi-opacity still to continue, the -dimness would now spread itself over a dark ground, first producing a -violet, then a dark-blue, and at last a light-blue, and thus complete -the series of the appearances.</p> - -<p>We will not assert that this mode of explanation will suffice in -all cases; our object is rather to point out the road by which the -all-comprehensive formula, the very key of the enigma, may be at last -discovered.—<a href="#NOTE_S">Note S</a>.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_201" id="Page_201">[Pg 201]</a></span></p> - - - - -<h5><a name="PART_III" id="PART_III">PART III.</a></h5> - - -<h5>CHEMICAL COLOURS.</h5> - - -<p class="para"><a id="a486">486.</a></p> - -<p>We give this denomination to colours which we can produce, and more -or less fix, in certain bodies; which we can render more intense, -which we can again take away and communicate to other bodies, and to -which, therefore, we ascribe a certain permanency: duration is their -prevailing characteristic.</p> - -<p class="para"><a id="a487">487.</a></p> - -<p>In this view the chemical colours were formerly distinguished with -various epithets; they were called <i>colores proprii, corporei, -materiales, veri, permanentes, fixi</i>.</p> - -<p class="para"><a id="a488">488.</a></p> - -<p>In the preceding chapter we observed how the fluctuating and transient -nature of the physical colours becomes gradually fixed, thus forming -the natural transition to our present subject.</p> - -<p class="para"><a id="a489">489.</a></p> - -<p>Colour becomes fixed in bodies more or less permanently; superficially, -or thoroughly.</p> - -<p class="para"><a id="a490">490.</a></p> - -<p>All bodies are susceptible of colour; it can<span class="pagenum"><a name="Page_202" id="Page_202">[Pg 202]</a></span> either be excited, -rendered intense, and gradually fixed in them, or at least communicated -to them.</p> - - - -<hr class="chap" /> -<h5><a name="XXXIV" id="XXXIV">XXXIV.</a></h5> - - -<h5>CHEMICAL CONTRAST.</h5> - - -<p class="para"><a id="a491">491.</a></p> - -<p>In the examination of coloured appearances we had occasion everywhere -to take notice of a principle of contrast: so again, in approaching the -precincts of chemistry, we find a chemical contrast of a remarkable -nature. We speak here, with reference to our present purpose, only of -that which is comprehended under the general names of acid and alkali.</p> - -<p class="para"><a id="a492">492.</a></p> - -<p>We characterised the chromatic contrast, in conformity with all other -physical contrasts as a <i>more</i> and <i>less</i>; ascribing the <i>plus</i> to -the yellow side, the <i>minus</i> to the blue; and we now find that these -two divisions correspond with the chemical contrasts. The yellow and -yellow-red affect the acids, the blue and blue-red the alkalis; thus -the phenomena of chemical colours, although still necessarily mixed -up with<span class="pagenum"><a name="Page_203" id="Page_203">[Pg 203]</a></span> other considerations, admit of being traced with sufficient -simplicity.</p> - -<p class="para"><a id="a493">493.</a></p> - -<p>The principal phenomena in chemical colours are produced by the -oxydation of metals, and it will be seen how important this -consideration is at the outset. Other facts which come into the -account, and which are worthy of attention, will be examined under -separate heads; in doing this we, however, expressly state that we only -propose to offer some preparatory suggestions to the chemist in a very -general way, without entering into the nicer chemical problems and -questions, or presuming to decide on them. Our object is only to give a -sketch of the mode in which, according to our conviction, the chemical -theory of colours may be connected with general physics.</p> - - - -<hr class="chap" /> -<h5><a name="XXXV" id="XXXV">XXXV.</a></h5> - - -<h5>WHITE.</h5> - - -<p class="para"><a id="a494">494.</a></p> - -<p>In treating of the dioptrical colours of the first class (155) we -have already in some degree anticipated this subject. Transparent -substances<span class="pagenum"><a name="Page_204" id="Page_204">[Pg 204]</a></span> may be said to be in the highest class of inorganic matter. -With these, colourless semi-transparence is closely connected, and -white may be considered the last opaque degree of this.</p> - -<p class="para"><a id="a495">495.</a></p> - -<p>Pure water crystallised to snow appears white, for the transparence of -the separate parts makes no transparent whole. Various crystallised -salts, when deprived to a certain extent of moisture, appear as a white -powder. The accidentally opaque state of a pure transparent substance -might be called white; thus pounded glass appears as a white powder. -The cessation of a combining power, and the exhibition of the atomic -quality of the substance might at the same time be taken into the -account.</p> - -<p class="para"><a id="a496">496.</a></p> - -<p>The known undecomposed earths are, in their pure state, all white. -They pass to a state of transparence by natural crystallization. Silex -becomes rock-crystal; argile, mica; magnesia, talc; calcareous earth -and barytes appear transparent in various spars.—<a href="#NOTE_T">Note T</a>.</p> - -<p class="para"><a id="a497">497.</a></p> - -<p>As in the colouring of mineral bodies the<span class="pagenum"><a name="Page_205" id="Page_205">[Pg 205]</a></span> metallic oxydes will often -invite our attention, we observe, in conclusion, that metals, when -slightly oxydated, at first appear white, as lead is converted to white -lead by vegetable acid.</p> - - - -<hr class="chap" /> -<h5><a name="XXXVI" id="XXXVI">XXXVI.</a></h5> - - -<h5>BLACK.</h5> - - -<p class="para"><a id="a498">498.</a></p> - -<p>Black is not exhibited in so elementary a state as white. We meet -with it in the vegetable kingdom in semi-combustion; and charcoal, a -substance especially worthy of attention on other accounts, exhibits -a black colour. Again, if woods—for example, boards, owing to the -action of light, air, and moisture, are deprived in part of their -combustibility, there appears first the grey then the black colour. So -again, we can convert even portions of animal substance to charcoal by -semi-combustion.</p> - -<p class="para"><a id="a499">499.</a></p> - -<p>In the same manner we often find that a sub-oxydation takes place -in metals when the black colour is to be produced. Various metals, -particularly iron, become black by slight oxydation,<span class="pagenum"><a name="Page_206" id="Page_206">[Pg 206]</a></span> by vinegar, by -mild acid fermentations; for example, a decoction of rice, &c.</p> - -<p class="para"><a id="a500">500.</a></p> - -<p>Again, it may be inferred that a de-oxydation may produce black. This -occurs in the preparation of ink, which becomes yellow by the solution -of iron in strong sulphuric acid, but when partly de-oxydised by the -infusion of gall-nuts, appears black.</p> - - - -<hr class="chap" /> -<h5><a name="XXXVII" id="XXXVII">XXXVII.</a></h5> - - -<h5>FIRST EXCITATION OF COLOUR.</h5> - - -<p class="para"><a id="a501">501.</a></p> - -<p>In the division of physical colours, where semi-transparent mediums -were considered, we saw colours antecedently to white and black. In the -present case we assume a white and black already produced and fixed; -and the question is, how colour can be excited in them?</p> - -<p class="para"><a id="a502">502.</a></p> - -<p>Here, too, we can say, white that becomes darkened or dimmed inclines -to yellow; black, as it becomes lighter, inclines to blue.—<a href="#NOTE_U">Note U</a>.</p> - -<p><span class="pagenum"><a name="Page_207" id="Page_207">[Pg 207]</a></span></p> - -<p class="para"><a id="a503">503.</a></p> - -<p>Yellow appears on the active (plus) side, immediately in the light, the -bright, the white. All white surfaces easily assume a yellow tinge; -paper, linen, wool, silk, wax: transparent fluids again, which have -a tendency to combustion, easily become yellow; in other words they -easily pass into a very slight state of semi-transparence.</p> - -<p class="para"><a id="a504">504.</a></p> - -<p>So again the excitement on the passive side, the tendency to obscure, -dark, black, is immediately accompanied with blue, or rather with a -reddish-blue. Iron dissolved in sulphuric acid, and much diluted with -water, if held to the light in a glass, exhibits a beautiful violet -colour as soon as a few drops only of the infusion of gall-nuts are -added. This colour presents the peculiar hues of the dark topaz, the -<i>orphninon</i> of a burnt-red, as the ancients expressed it.</p> - -<p class="para"><a id="a505">505.</a></p> - -<p>Whether any colour can be excited in the pure earths by the chemical -operations of nature and art, without the admixture of metallic oxydes, -is an important question, generally, indeed, answered in the negative. -It is perhaps connected with the question—to what extent<span class="pagenum"><a name="Page_208" id="Page_208">[Pg 208]</a></span> changes may -be produced in the earths through oxydation?</p> - -<p class="para"><a id="a506">506.</a></p> - -<p>Undoubtedly the negation of the above question is confirmed by the -circumstance that wherever mineral colours are found, some trace of -metal, especially of iron, shows itself; we are thus naturally led -to consider how easily iron becomes oxydised, how easily the oxyde -of iron assumes different colours, how infinitely divisible it is, -and how quickly it communicates its colour. It were to be wished, -notwithstanding, that new experiments could be made in regard to the -above point, so as either to confirm or remove any doubt.</p> - -<p class="para"><a id="a507">507.</a></p> - -<p>However this may be, the susceptibility of the earths with regard -to colours already existing is very great; aluminous earth is thus -particularly distinguished.</p> - -<p class="para"><a id="a508">508.</a></p> - -<p>In proceeding to consider the metals, which in the inorganic world -have the almost exclusive prerogative of appearing coloured, we find -that, in their pure, independent, natural state, they are already -distinguished from the<span class="pagenum"><a name="Page_209" id="Page_209">[Pg 209]</a></span> pure earths by a tendency to some one colour or -other.</p> - -<p class="para"><a id="a509">509.</a></p> - -<p>While silver approximates most to pure white,—nay, really represents -pure white, heightened by metallic splendour,—steel, tin, lead, and so -forth, incline towards pale blue-grey; gold, on the other hand, deepens -to pure yellow, copper approaches a red hue, which, under certain -circumstances, increases almost to bright red, but which again returns -to a yellow golden colour when combined with zinc.</p> - -<p class="para"><a id="a510">510.</a></p> - -<p>But if metals in their pure state have so specific a determination -towards this or that exhibition of colour, they are, through the effect -of oxydation, in some degree reduced to a common character; for the -elementary colours now come forth in their purity, and although this -or that metal appears to have a particular tendency to this or that -colour, we find some that can go through the whole circle of hues, -others, that are capable of exhibiting more than one colour; tin, -however, is distinguished by its comparative inaptitude to become -coloured. We propose to give a table hereafter, showing how far the -different metals can be more or less made to exhibit the different -colours.</p> - - -<p><span class="pagenum"><a name="Page_210" id="Page_210">[Pg 210]</a></span></p> - -<p class="para"><a id="a511">511.</a></p> - -<p>When the clean, smooth surface of a pure metal, on being heated, -becomes overspread with a mantling colour, which passes through a -series of appearances as the heat increases, this, we are persuaded, -indicates the aptitude of the metal to pass through the whole range of -colours. We find this phenomenon most beautifully exhibited in polished -steel; but silver, copper, brass, lead, and tin, easily present similar -appearances. A superficial oxydation is probably here taking place, -as may be inferred from the effects of the operation when continued, -especially in the more easily oxydizable metals.</p> - -<p class="para"><a id="a512">512.</a></p> - -<p>The same conclusion may be drawn from the fact that iron is more -easily oxydizable by acid liquids when it is red hot, for in this -case the two effects concur with each other. We observe, again, that -steel, accordingly as it is hardened in different stages of its -colorification, may exhibit a difference of elasticity: this is quite -natural, for the various appearances of colour indicate various degrees -of heat.<a name="FNanchor_1_42" id="FNanchor_1_42"></a><a href="#Footnote_1_42" class="fnanchor">[1]</a></p> - -<p class="para"><a id="a513">513.</a></p> - -<p>If we look beyond this superficial mantling,<span class="pagenum"><a name="Page_211" id="Page_211">[Pg 211]</a></span> this pellicle of colour, -we observe that as metals are oxydized throughout their masses, white -or black appears with the first degree of heat, as may be seen in white -lead, iron, and quicksilver.</p> - -<p class="para"><a id="a514">514.</a></p> - -<p>If we examine further, and look for the actual exhibition of colour, -we find it most frequently on the <i>plus</i> side. The mantling, so often -mentioned, of smooth metallic surfaces begins with yellow. Iron -passes presently into yellow ochre, lead from white lead to massicot, -quicksilver from æthiops to yellow turbith. The solutions of gold and -platinum in acids are yellow.</p> - -<p class="para"><a id="a515">515.</a></p> - -<p>The exhibitions on the <i>minus</i> side are less frequent. Copper slightly -oxydized appears blue. In the preparation of Prussian-blue, alkalis are -employed.</p> - -<p class="para"><a id="a516">516.</a></p> - -<p>Generally, however, these appearances of colour are of so mutable a -nature that chemists look upon them as deceptive tests, at least in the -nicer gradations. For ourselves, as we can only treat of these matters -in a general way, we merely observe that the appearances of colour in -metals may be classed according to their<span class="pagenum"><a name="Page_212" id="Page_212">[Pg 212]</a></span> origin, manifold appearance, -and cessation, as various results of oxydation, hyper-oxydation, -ab-oxydation, and de-oxydation.<a name="FNanchor_2_43" id="FNanchor_2_43"></a><a href="#Footnote_2_43" class="fnanchor">[2]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_42" id="Footnote_1_42"></a><a href="#FNanchor_1_42"><span class="label">[1]</span></a> See par. <a href="#a478">478</a>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_43" id="Footnote_2_43"></a><a href="#FNanchor_2_43"><span class="label">[2]</span></a> As these terms are afterwards referred to (par. <a href="#a525">525</a>), it -was necessary to preserve them.</p></div> - -<hr class="chap" /> - - -<h5><a name="XXXVIII" id="XXXVIII">XXXVIII.</a></h5> - - -<h5>AUGMENTATION OF COLOUR.<a name="FNanchor_1_44" id="FNanchor_1_44"></a><a href="#Footnote_1_44" class="fnanchor">[1]</a></h5> - - -<p class="para"><a id="a517">517.</a></p> - -<p>The augmentation of colour exhibits itself as a condensation, a -fulness, a darkening of the hue. We have before seen, in treating of -colourless mediums, that by increasing the degree of opacity in the -medium, we can deepen a bright object from the lightest yellow to the -intensest ruby-red. Blue, on the other hand, increases to the most -beautiful violet, if we rarefy and diminish a semi-opaque medium, -itself lighted, but through which we see darkness (150, 151).</p> - -<p class="para"><a id="a518">518.</a></p> - -<p>If the colour is positive, a similar colour appears in the intenser -state. Thus if we fill a white porcelain cup with a pure yellow -liquor, the fluid will appear to become gradually redder<span class="pagenum"><a name="Page_213" id="Page_213">[Pg 213]</a></span> towards the -bottom, and at last appears orange. If we pour a pure blue solution -into another cup, the upper portion will exhibit a sky-blue, that -towards the bottom, a beautiful violet. If the cup is placed in the -sun, the shadowed side, even of the upper portion, is already violet. -If we throw a shadow with the hand, or any other substance, over the -illumined portion, the shadow in like manner appears reddish.</p> - -<p class="para"><a id="a519">519.</a></p> - -<p>This is one of the most important appearances connected with the -doctrine of colours, for we here manifestly find that a difference of -quantity produces a corresponding qualified impression on our senses. -In speaking of the last class of epoptical colours (<a href="#a452">452</a>, <a href="#a485">485</a>), we -stated our conjecture that the colouring of steel might perhaps be -traced to the doctrine of the semi-transparent mediums, and we would -here again recall this to the reader's recollection.</p> - -<p class="para"><a id="a520">520.</a></p> - -<p>All chemical augmentation of colour, again, is the immediate -consequence of continued excitation. The augmentation advances -constantly and unremittingly, and it is to be observed that the -increase of intenseness is most common on the <i>plus</i> side. Yellow iron -ochre increases, as well by fire as by other operations, to a very<span class="pagenum"><a name="Page_214" id="Page_214">[Pg 214]</a></span> -strong red: massicot is increased to red lead, turbith to vermilion, -which last attains a very high degree of the yellow-red. An intimate -saturation of the metal by the acid, and its separation to infinity, -take place together with the above effects.</p> - -<p class="para"><a id="a521">521.</a></p> - -<p>The augmentation on the <i>minus</i> side is less frequent; but we observe -that the more pure and condensed the Prussian-blue or cobalt glass is -prepared, the more readily it assumes a reddish hue and inclines to the -violet.</p> - -<p class="para"><a id="a522">522.</a></p> - -<p>The French have a happy expression for the less perceptible tendency of -yellow and blue towards red: they say the colour has "un œil de rouge," -which we might perhaps express by a reddish glance (einen röthlichen -blick).</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_44" id="Footnote_1_44"></a><a href="#FNanchor_1_44"><span class="label">[1]</span></a> Steigerung, literally <i>gradual ascent</i>. See the note to -par. 523.</p></div> - - -<hr class="chap" /> - -<h5><a name="XXXIX" id="XXXIX">XXXIX.</a></h5> - - -<h5>CULMINATION<a name="FNanchor_1_45" id="FNanchor_1_45"></a><a href="#Footnote_1_45" class="fnanchor">[1]</a></h5> - - -<p class="para"><a id="a523">523.</a></p> - -<p>This is the consequence of still progressing augmentation. Red, in -which neither yellow nor<span class="pagenum"><a name="Page_215" id="Page_215">[Pg 215]</a></span> blue is to be detected, here constitutes the -acme.</p> - -<p class="para"><a id="a524">524.</a></p> - -<p>If we wish to select a striking example of a culmination on the <i>plus</i> -side, we again find it in the coloured steel, which attains the bright -red acme, and can be arrested at this point.</p> - -<p class="para"><a id="a525">525.</a></p> - -<p>Were we here to employ the terminology before proposed, we should -say that the first oxydation produces yellow, the hyper-oxydation -yellow-red; that here a kind of maximum exists, and that then an -ab-oxydation, and lastly a de-oxydation takes place.</p> - -<p class="para"><a id="a526">526.</a></p> - -<p>High degrees of oxydation produce a bright red. Gold in solution, -precipitated by a solution of tin, appears bright red: oxyde of -arsenic, in combination, with sulphur, produces a ruby colour.</p> - -<p class="para"><a id="a527">527.</a></p> - -<p>How far, however, a kind of sub-oxydation may co-operate in some -culminations, is matter for inquiry; for an influence of alkalis on<span class="pagenum"><a name="Page_216" id="Page_216">[Pg 216]</a></span> -yellow-red also appears to produce the culmination; the colour reaching -the acme by being forced towards the <i>minus</i> side.</p> - -<p class="para"><a id="a528">528.</a></p> - -<p>The Dutch prepare a colour known by the name of vermilion, from the -best Hungarian cinnabar, which exhibits the brightest yellow-red. This -vermilion is still only a cinnabar, which, however, approximates the -pure red, and it may be conjectured that alkalis are used to bring it -nearer to the culminating point.</p> - -<p class="para"><a id="a529">529.</a></p> - -<p>Vegetable juices, treated in this way, offer very striking examples of -the above effects. The colouring-matter of turmeric, annotto, dyer's -saffron,<a name="FNanchor_2_46" id="FNanchor_2_46"></a><a href="#Footnote_2_46" class="fnanchor">[2]</a> and other vegetables, being extracted with spirits of wine, -exhibits tints of yellow, yellow-red, and hyacinth-red; these, by the -admixture of alkalis, pass to the culminating point, and even beyond it -to blue-red.</p> - -<p class="para"><a id="a530">530.</a></p> - -<p>No instance of a culmination on the <i>minus</i> side has come to my -knowledge in the mineral and vegetable kingdoms. In the animal -kingdom the juice of the murex is remarkable; of its augmentation and -culmination on the <i>minus</i> side, we shall hereafter have occasion to -speak.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_45" id="Footnote_1_45"></a><a href="#FNanchor_1_45"><span class="label">[1]</span></a> <i>Culmination</i>, the original word. It might have been -rendered <i>maximum of colour</i>, but as the author supposes an <i>ascent</i> -through yellow and blue to red, his meaning is better expressed by his -own term.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_46" id="Footnote_2_46"></a><a href="#FNanchor_2_46"><span class="label">[2]</span></a> Curcuma, Bixa Orellana, Carthamus Tinctorius.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_217" id="Page_217">[Pg 217]</a></span></p></div> - - - - -<h5><a name="XL" id="XL">XL.</a></h5> - - -<h5>FLUCTUATION.</h5> - - -<p class="para"><a id="a531">531.</a></p> - -<p>The mutability of colour is so great, that even those pigments, which -may have been considered to be defined and arrested, still admit of -slight variations on one side or the other. This mutability is most -remarkable near the culminating point, and is effected in a very -striking manner by the alternate employment of acids and alkalis.</p> - -<p class="para"><a id="a532">532.</a></p> - -<p>To express this appearance in dyeing, the French make use of the word -"virer," to turn from one side to the other; they thus very adroitly -convey an idea which others attempt to express by terms indicating the -component hues.</p> - -<p class="para"><a id="a533">533.</a></p> - -<p>The effect produced with litmus is one of the most known and striking -of this kind. This colouring substance is tendered red-blue by means of -alkalis. The red-blue is very readily changed to red-yellow by means -of acids, and again returns to its first state by again employing -alkalis. The question whether a culminating point is to be discovered -and arrested by<span class="pagenum"><a name="Page_218" id="Page_218">[Pg 218]</a></span> nice experiments, is left to those who are practised -in these operations. Dyeing, especially scarlet-dyeing, might afford a -variety of examples of this fluctuation.</p> - - - -<hr class="chap" /> -<h5><a name="XLI" id="XLI">XLI.</a></h5> - - -<h5>PASSAGE THROUGH THE WHOLE SCALE.</h5> - - -<p class="para"><a id="a534">534.</a></p> - -<p>The first excitation and gradual increase of colour take place more on -the <i>plus</i> than on the <i>minus</i> side. So, also, in passing through the -whole scale, colour exhibits itself most on the <i>plus</i> side.</p> - -<p class="para"><a id="a535">535.</a></p> - -<p>A passage of this kind, regular and evident to the senses, from yellow -through red to blue, is apparent in the colouring of steel.</p> - -<p class="para"><a id="a536">536.</a></p> - -<p>The metals may be arrested at various points of the colorific circle by -various degrees and kinds of oxydation.</p> - -<p class="para"><a id="a537">537.</a></p> - -<p>As they also appear green, a question arises whether chemists know any -instance in the<span class="pagenum"><a name="Page_219" id="Page_219">[Pg 219]</a></span> mineral kingdom of a constant transition from yellow, -through green, to blue, and <i>vice versâ</i>. Oxyde of iron, melted with -glass, produces first a green, and with a more powerful heat, a blue -colour.</p> - -<p class="para"><a id="a538">538.</a></p> - -<p>We may here observe of green generally, that it appears, especially -in an atomic sense, and certainly in a pure state, when we mix blue -and yellow: but, again, an impure and dirty yellow soon gives us the -impression of green; yellow and black already produce green; this, -however, is owing to the affinity between black and blue. An imperfect -yellow, such as that of sulphur, gives us the impression of a greenish -hue: thus, again, an imperfect blue appears green. The green of wine -bottles arises, it appears, from an imperfect union of the oxyde of -iron with the glass. If we produce a more complete union by greater -heat, a beautiful blue-glass is the result.</p> - -<p class="para"><a id="a539">539.</a></p> - -<p>From all this it appears that a certain chasm exists in nature between -yellow and blue, the opposite characters of which, it is true, may be -done away atomically by due immixture, and, thus combined, to green; -but the true reconciliation between yellow and blue, it seems, only -takes place by means of red.</p> - -<p><span class="pagenum"><a name="Page_220" id="Page_220">[Pg 220]</a></span></p> - -<p class="para"><a id="a540">540.</a></p> - -<p>The process, however, which appears unattainable in inorganic -substances, we shall find to be possible when we turn our attention to -organic productions; for in these, the passage through the whole circle -from yellow, through green and blue, to red, really takes place.</p> - - - -<hr class="chap" /> -<h5><a name="XLII" id="XLII">XLII.</a></h5> - - -<h5>INVERSION.</h5> - - -<p class="para"><a id="a541">541.</a></p> - -<p>Again, an immediate inversion or change to the totally opposite hue, is -a very remarkable appearance which sometimes occurs; at present, we are -merely enabled to adduce what follows.</p> - -<p class="para"><a id="a542">542.</a></p> - -<p>The mineral chameleon, a name which has been given to an oxyde of -manganese, may be considered, in its perfectly dry state, as a green -powder. If we strew it in water, the green colour displays itself very -beautifully in the first moment of solution, but it changes presently -to the bright red opposite to green, without any apparent intermediate -state.</p> - -<p><span class="pagenum"><a name="Page_221" id="Page_221">[Pg 221]</a></span></p> - -<p class="para"><a id="a543">543.</a></p> - -<p>The same occurs with the sympathetic ink, which may be considered a -reddish liquid, but which, when dried by warmth, appears as a green -colour on paper.</p> - -<p class="para"><a id="a544">544.</a></p> - -<p>In fact, this phenomenon appears to be owing to the conflict between -a dry and moist state, as has been already observed, if we are not -mistaken, by the chemists. We may look to the improvements of time to -point out what may further be deduced from these phenomena, and to show -what other facts they may be connected with.</p> - - - -<hr class="chap" /> -<h5><a name="XLIII" id="XLIII">XLIII.</a></h5> - - -<h5>FIXATION.</h5> - - -<p class="para"><a id="a545">545.</a></p> - -<p>Mutable as we have hitherto found colour to be, even as a substance, -yet under certain circumstances it may at last be fixed.</p> - -<p class="para"><a id="a546">546.</a></p> - -<p>There are bodies capable of being entirely converted into colouring -matter: here it may be said that the colour fixes itself in its own -substance,<span class="pagenum"><a name="Page_222" id="Page_222">[Pg 222]</a></span> stops at a certain point, and is there defined. Such -colouring substances are found throughout nature; the vegetable world -affords a great quantity of examples, among which some are particularly -distinguished, and may be considered as the representatives of the -rest; such as, on the active side, madder, on the passive side, indigo.</p> - -<p class="para"><a id="a547">547.</a></p> - -<p>In order to make these materials available in use, it is necessary -that the colouring quality in them should be intimately condensed, and -the tinging substance refined, practically speaking, to an infinite -divisibility. This is accomplished in various ways, and particularly by -the well-known means of fermentation and decomposition.</p> - -<p class="para"><a id="a548">548.</a></p> - -<p>These colouring substances now attach themselves again to other bodies. -Thus, in the mineral kingdom they adhere to earths and metallic oxydes; -they unite in melting with glasses; and in this case, as the light is -transmitted through them, they appear in the greatest beauty, while an -eternal duration may be ascribed to them.</p> - -<p class="para"><a id="a549">549.</a></p> - -<p>They fasten on vegetable and animal bodies with more or less power, and -remain more or less<span class="pagenum"><a name="Page_223" id="Page_223">[Pg 223]</a></span> permanently; partly owing to their nature,—as -yellow, for instance, is more evanescent than blue,—or owing to -the nature of the substance on which they appear. They last less in -vegetable than in animal substances, and even within this latter -kingdom there are again varieties. Hemp or cotton threads, silk or -wool, exhibit very different relations to colouring substances.</p> - -<p class="para"><a id="a550">550.</a></p> - -<p>Here comes into the account the important operation of employing -mordants, which may be considered as the intermediate agents between -the colour and the recipient substance; various works on dyeing speak -of this circumstantially. Suffice it to have alluded to processes by -means of which the colour retains a permanency only to be destroyed -with the substance, and which may even increase in brightness and -beauty by use.</p> - - - -<hr class="chap" /> -<h5><a name="XLIV" id="XLIV">XLIV.</a></h5> - - -<h5>INTERMIXTURE, REAL.</h5> - - -<p class="para"><a id="a551">551.</a></p> - -<p>Every intermixture pre-supposes a specific state of colour; and thus -when we speak of intermixture, we here understand it in an atomic<span class="pagenum"><a name="Page_224" id="Page_224">[Pg 224]</a></span> -sense. We must first have before us certain bodies arrested at any -given point of the colorific circle, before we can produce gradations -by their union.</p> - -<p class="para"><a id="a552">552.</a></p> - -<p>Yellow, blue, and red, may be assumed as pure elementary colours, -already existing; from these, violet, orange, and green, are the -simplest combined results.</p> - -<p class="para"><a id="a553">553.</a></p> - -<p>Some persons have taken much pains to define these intermixtures more -accurately, by relations of number, measure, and weight, but nothing -very profitable has been thus accomplished.</p> - -<p class="para"><a id="a554">554.</a></p> - -<p>Painting consists, strictly speaking, in the intermixture of -such specific colouring bodies and their infinite possible -combinations—combinations which can only be appreciated by the nicest, -most practised eye, and only accomplished under its influence.</p> - -<p class="para"><a id="a555">555.</a></p> - -<p>The intimate combination of these ingredients is effected, in the first -instance, through the most perfect comminution of the material by means -of grinding, washing, &c., as well as by vehicles<span class="pagenum"><a name="Page_225" id="Page_225">[Pg 225]</a></span> or liquid mediums -which hold together the pulverized substance, and combine organically, -as it were, the unorganic; such are the oils, resins, &c.—<a href="#NOTE_V">Note V</a>.</p> - -<p class="para"><a id="a556">556.</a></p> - -<p>If all the colours are mixed together they retain their general -character as σκιερόν, and as they are no longer seen next each other, -no completeness, no harmony, is experienced; the result is grey, which, -like apparent colour, always appears somewhat darker than white, and -somewhat lighter than black.</p> - -<p class="para"><a id="a557">557.</a></p> - -<p>This grey may be produced in various ways. By mixing yellow and blue to -an emerald green, and then adding pure red, till all three neutralize -each other; or, by placing the primitive and intermediate colours next -each other in a certain proportion, and afterwards mixing them.</p> - -<p class="para"><a id="a558">558.</a></p> - -<p>That all the colours mixed together produce white, is an absurdity -which people have credulously been accustomed to repeat for a century, -in opposition to the evidence of their senses.</p> - -<p class="para"><a id="a559">559.</a></p> - -<p>Colours when mixed together retain their<span class="pagenum"><a name="Page_226" id="Page_226">[Pg 226]</a></span> original darkness. The darker -the colours, the darker will be the grey resulting from their union, -till at last this grey approaches black. The lighter the colours the -lighter will be the grey, which at last approaches white.</p> - - - -<hr class="chap" /> -<h5><a name="XLV" id="XLV">XLV.</a></h5> - - -<h5>INTERMIXTURE, APPARENT.</h5> - - -<p class="para"><a id="a560">560.</a></p> - -<p>The intermixture, which is only apparent, naturally invites our -attention in connexion with the foregoing; it is in many respects -important, and, indeed, the intermixture which we have distinguished as -real, might be considered as merely apparent. For the elements of which -the combined colour consists are only too small to be considered as -distinct parts. Yellow and blue powders mingled together appear green -to the naked eye, but through a magnifying glass we can still perceive -yellow and blue distinct from each other. Thus yellow and blue stripes -seen at a distance, present a green mass; the same observation is -applicable with regard to the intermixture of other specific colours.</p> - -<p class="para"><a id="a561">561.</a></p> - -<p>In the description of our apparatus we shall<span class="pagenum"><a name="Page_227" id="Page_227">[Pg 227]</a></span> have occasion to mention -the wheel by means of which the apparent intermixture is produced by -rapid movement. Various colours are arranged near each other round -the edge of a disk, which is made to revolve with velocity, and thus -by having several such disks ready, every possible intermixture can -be presented to the eye, as well as the mixture of all colours to -grey, darker or lighter, according to the depth of the tints as above -explained.</p> - -<p class="para"><a id="a562">562.</a></p> - -<p>Physiological colours admit, in like manner, of being mixed with -others. If, for example, we produce the blue shadow (<a href="#a65">65</a>) on a light -yellow paper, the surface will appear green. The same happens with -regard to the other colours if the necessary preparations are attended -to.</p> - -<p class="para"><a id="a563">563.</a></p> - -<p>If, when the eye is impressed with visionary images that last for a -while, we look on coloured surfaces, an intermixture also takes place; -the spectrum is determined to a new colour which is composed of the two.</p> - -<p class="para"><a id="a564">564.</a></p> - -<p>Physical colours also admit of combination. Here might be adduced the -experiments in<span class="pagenum"><a name="Page_228" id="Page_228">[Pg 228]</a></span> which many-coloured images are seen through the prism, -as we have before shown in detail (<a href="#a258">258</a>, <a href="#a284">284</a>).</p> - -<p class="para"><a id="a565">565.</a></p> - -<p>Those who have prosecuted these inquiries have, however, paid most -attention to the appearances which take place when the prismatic -colours are thrown on coloured surfaces.</p> - -<p class="para"><a id="a566">566.</a></p> - -<p>What is seen under these circumstances is quite simple. In the first -place it must be remembered that the prismatic colours are much more -vivid than the colours of the surface on which they are thrown. -Secondly, we have to consider that the prismatic colours may be either -homogeneous or heterogeneous, with the recipient surface. In the former -case the surface deepens and enhances them, and is itself enhanced in -return, as a coloured stone is displayed by a similarly coloured foil. -In the opposite case each vitiates, disturbs, and destroys the other.</p> - -<p class="para"><a id="a567">567.</a></p> - -<p>These experiments may be repeated with coloured glasses, by causing the -sun-light to shine through them on coloured surfaces. In every instance -similar results will appear.</p> - -<p><span class="pagenum"><a name="Page_229" id="Page_229">[Pg 229]</a></span></p> - -<p class="para"><a id="a568">568.</a></p> - -<p>The same effect takes place when we look on coloured objects through -coloured glasses; the colours being thus according to the same -conditions enhanced, subdued, or neutralized.</p> - -<p class="para"><a id="a569">569.</a></p> - -<p>If the prismatic colours are suffered to pass through coloured glasses, -the appearances that take place are perfectly analogous; in these cases -more or less force, more or less light and dark, the clearness and -cleanness of the glass are all to be allowed for, as they produce many -delicate varieties of effect: these will not escape the notice of every -accurate observer who takes sufficient interest in the inquiry to go -through the experiments.</p> - -<p class="para"><a id="a570">570.</a></p> - -<p>It is scarcely necessary to mention that several coloured glasses, as -well as oiled or transparent papers, placed over each other, may be -made to produce and exhibit every kind of intermixture at pleasure.</p> - -<p class="para"><a id="a571">571.</a></p> - -<p>Lastly, the operation of glazing in painting belongs to this kind of -intermixture; by this means a much more refined union may be produced -than that arising from the mechanical, atomic mixture which is commonly -employed.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_230" id="Page_230">[Pg 230]</a></span></p> - - - - -<h5><a name="XLVI" id="XLVI">XLVI.</a></h5> - - -<h5>COMMUNICATION, ACTUAL.</h5> - - -<p class="para"><a id="a572">572.</a></p> - -<p>Having now provided the colouring materials, as before shown, a further -question arises how to communicate these to colourless substances: -the answer is of the greatest importance from the connexion of the -object with the ordinary wants of men, with useful purposes, and with -commercial and technical interests.</p> - -<p class="para"><a id="a573">573.</a></p> - -<p>Here, again, the dark quality of every colour again comes into the -account. From a yellow, that is very near to white, through orange, -and the hue of minium to pure red and carmine, through all gradations -of violet to the deepest blue which is almost identified with black, -colour still increases in darkness. Blue once defined, admits of -being diluted, made light, united with yellow, and then, as green, -it approaches the light side of the scale: but this is by no means -according to its own nature.</p> - -<p class="para"><a id="a574">574.</a></p> - -<p>In the physiological colours we have already seen that they are less -than the light, inasmuch<span class="pagenum"><a name="Page_231" id="Page_231">[Pg 231]</a></span> as they are a repetition of an impression -of light, nay, at last they leave this impression quite as a dark. In -physical experiments the employment of semi-transparent mediums, the -effect of semi-transparent accessory images, taught us that in such -cases we have to do with a subdued light, with a transition to darkness.</p> - -<p class="para"><a id="a575">575.</a></p> - -<p>In treating of the chemical origin of pigments we found that the same -effect was produced on the very first excitement. The yellow tinge -which mantles over the steel, already darkens the shining surface. In -changing white lead to massicot it is evident that the yellow is darker -than white.</p> - -<p class="para"><a id="a576">576.</a></p> - -<p>This process is in the highest degree delicate; the growing -intenseness, as it still increases, tinges the substance more and more -intimately and powerfully, and thus indicates the extreme fineness, and -the infinite divisibility of the coloured atoms.</p> - -<p class="para"><a id="a577">577.</a></p> - -<p>The colours which approach the dark side, and consequently, blue in -particular, can be made to approximate to black; in fact, a very -perfect Prussian blue, or an indigo acted on by vitriolic acid appears -almost as a black.</p> - -<p><span class="pagenum"><a name="Page_232" id="Page_232">[Pg 232]</a></span></p> - -<p class="para"><a id="a578">578.</a></p> - -<p>A remarkable appearance may be here adverted to; pigments, in their -deepest and most condensed state, especially those produced from -the vegetable kingdom, such as the indigo just mentioned, or madder -carried to its intensest hue, no longer show their own colour; on the -contrary, a decided metallic shine is seen on their surface, in which -the physiological compensatory colour appears.</p> - -<p class="para"><a id="a579">579.</a></p> - -<p>All good indigo exhibits a copper-colour in its fracture, a -circumstance attended to, as a known characteristic, in trade. Again, -the indigo which has been acted on by sulphuric acid, if thickly laid -on, or suffered to dry so that neither white paper nor the porcelain -can appear through, exhibits a colour approaching to orange.</p> - -<p class="para"><a id="a580">580.</a></p> - -<p>The bright red Spanish rouge, probably prepared from madder, exhibits -on its surface a perfectly green, metallic shine. If this colour, or -the blue before mentioned, is washed with a pencil on porcelain or -paper, it is seen in its real state owing to the bright ground shining -through.</p> - -<p class="para"><a id="a581">581.</a></p> - -<p>Coloured liquids appear black when no light<span class="pagenum"><a name="Page_233" id="Page_233">[Pg 233]</a></span> is transmitted through -them, as we may easily see in cubic tin vessels with glass bottoms. -In these every transparent-coloured infusion will appear black and -colourless if we place a black surface under them.</p> - -<p class="para"><a id="a582">582.</a></p> - -<p>If we contrive that the image of a flame be reflected from the bottom, -the image will appear coloured. If we lift up the vessel and suffer the -transmitted light to fall on white paper under it, the colour of the -liquid appears on the paper. Every light ground seen through such a -coloured medium exhibits the colour of the medium.</p> - -<p class="para"><a id="a583">583.</a></p> - -<p>Thus every colour, in order to be seen, must have a light within or -behind it. Hence the lighter and brighter the grounds are, the more -brilliant the colours appear. If we pass lac-varnish over a shining -white metal surface, as the so-called foils are prepared, the splendour -of the colour is displayed by this internally reflected light as -powerfully as in any prismatic experiment; nay, the force of the -physical colours is owing principally to the circumstance that light is -always acting with and behind them.</p> - -<p class="para"><a id="a584">584.</a></p> - -<p>Lichtenberg, who of necessity followed the<span class="pagenum"><a name="Page_234" id="Page_234">[Pg 234]</a></span> received theory, owing -to the time and circumstances in which he lived, was yet too good an -observer, and too acute not to explain and classify, after his fashion, -what was evident to his senses. He says, in the preface to Delaval, -"It appears to me also, on other grounds, probable, that our organ, in -order to be impressed by a colour, must at the same time be impressed -by all light (white)."</p> - -<p class="para"><a id="a585">585.</a></p> - -<p>To procure white as a ground is the chief business of the dyer. Every -colour may be easily communicated to colourless earths, especially -to alum: but the dyer has especially to do with animal and vegetable -products as the ground of his operations.</p> - -<p class="para"><a id="a586">586.</a></p> - -<p>Everything living tends to colour—to local, specific colour, to -effect, to opacity—pervading the minutest atoms. Everything in which -life is extinct approximates to white (<a href="#a494">494</a>), to the abstract, the -general state, to clearness<a name="FNanchor_1_47" id="FNanchor_1_47"></a><a href="#Footnote_1_47" class="fnanchor">[1]</a>, to transparence.</p> - -<p class="para"><a id="a587">587.</a></p> - -<p>How this is put in practice in technical operations remains to be -adverted to in the chapter on the privation of colour. With regard -to the<span class="pagenum"><a name="Page_235" id="Page_235">[Pg 235]</a></span> communication of colour, we have especially to bear in mind -that animals and vegetables, in a living state, produce colours, and -hence their substances, if deprived of colours, can the more readily -re-assume them.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_47" id="Footnote_1_47"></a><a href="#FNanchor_1_47"><span class="label">[1]</span></a> Verklärung, literally <i>clarification</i>.</p></div> - - - -<hr class="chap" /> -<h5><a name="XLVII" id="XLVII">XLVII.</a></h5> - - -<h5>COMMUNICATION, APPARENT.</h5> - - -<p class="para"><a id="a588">588.</a></p> - -<p>The communication of colours, real as well as apparent, corresponds, as -may easily be seen, with their intermixture: we need not, therefore, -repeat what has been already sufficiently entered into.</p> - -<p class="para"><a id="a589">589.</a></p> - -<p>Yet we may here point out more circumstantially the importance of an -apparent communication which takes place by means of reflection. This -phenomenon is well known, but still it is pregnant with inferences, and -is of the greatest importance both to the investigator of nature and to -the painter.</p> - -<p class="para"><a id="a590">590.</a></p> - -<p>Let a surface coloured with any one of the positive colours be placed -in the sun, and let its<span class="pagenum"><a name="Page_236" id="Page_236">[Pg 236]</a></span> reflection be thrown on other colourless -objects. This reflection is a kind of subdued light, a half-light, -a half-shadow, which, in a subdued state, reflects the colours in -question.</p> - -<p class="para"><a id="a591">591.</a></p> - -<p>If this reflection acts on light surfaces, it is so far overpowered -that we can scarcely perceive the colour which accompanies it; but if -it acts on shadowed portions, a sort of magical union takes place with -the σκιερῷ. Shadow is the proper element of colour, and in this case -a subdued colour approaches it, lighting up, tinging, and enlivening -it. And thus arises an appearance, as powerful as agreeable, which may -render the most pleasing service to the painter who knows how to make -use of it. These are the types of the so-called reflexes, which were -only noticed late in the history of art, and which have been too seldom -employed in their full variety.</p> - -<p class="para"><a id="a592">592.</a></p> - -<p>The schoolmen called these colours <i>colores notionales</i> and -<i>intentionales</i>, and the history of the doctrine of colours will -generally show that the old inquirers already observed the phenomena -well enough, and knew how to distinguish them properly, although the -whole method of treating such subjects is very different from ours.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_237" id="Page_237">[Pg 237]</a></span></p> - - - - -<h5><a name="XLVIII" id="XLVIII">XLVIII.</a></h5> - - -<h5>EXTRACTION.</h5> - - -<p class="para"><a id="a593">593.</a></p> - -<p>Colour may be extracted from substances, whether they possess it -naturally or by communication, in various ways. We have thus the power -to remove it intentionally for a useful purpose, but, on the other -hand, it often flies contrary to our wish.</p> - -<p class="para"><a id="a594">594.</a></p> - -<p>Not only are the elementary earths in their natural state white, but -vegetable and animal substances can be reduced to a white state without -disturbing their texture. A pure white is very desirable for various -uses, as in the instance of our preferring to use linen and cotton -stuffs uncoloured. In like manner some silk stuffs, paper, and other -substances, are the more agreeable the whiter they can be. Again, -the chief basis of all dyeing consists in white grounds. For these -reasons manufacturers, aided by accident and contrivance, have devoted -themselves assiduously to discover means of extracting colour: infinite -experiments have been made in connexion with this object, and many -important facts have been arrived at.</p> - -<p><span class="pagenum"><a name="Page_238" id="Page_238">[Pg 238]</a></span></p> - -<p class="para"><a id="a595">595.</a></p> - -<p>It is in accomplishing this entire extraction of colour that the -operation of bleaching consists, which is very generally practised -empirically or methodically. We will here shortly state the leading -principles.</p> - -<p class="para"><a id="a596">596.</a></p> - -<p>Light is considered as one of the first means of extracting colour -from substances, and not only the sun-light, but the mere powerless -day-light: for as both lights—the direct light of the sun, as well as -the derived light of the sky—kindle Bologna phosphorus, so both act on -coloured surfaces. Whether the light attacks the colour allied to it, -and, as it were, kindles and consumes it, thus reducing the definite -quality to a general state, or whether some other operation, unknown -to us, takes place, it is clear that light exercises a great power on -coloured surfaces, and bleaches them more or less. Here, however, the -different colours exhibit a different degree of durability; yellow, -especially if prepared from certain materials, is, in this case, the -first to fly.</p> - -<p class="para"><a id="a597">597.</a></p> - -<p>Not only light, but air, and especially water, act strongly in -destroying colour. It has been even asserted that thread, well soaked -and<span class="pagenum"><a name="Page_239" id="Page_239">[Pg 239]</a></span> spread on the grass at night, bleaches better than that which is -exposed, after soaking, to the sun-light. Thus, in this case, water -proves to be a solving and conducting agent, removing the accidental -quality, and restoring the substance to a general or colourless state.</p> - -<p class="para"><a id="a598">598.</a></p> - -<p>The extraction of colour is also effected by re-agents. Spirits of wine -has a peculiar tendency to attract the juice which tinges plants, and -becomes coloured with it often in a very permanent manner. Sulphuric -acid is very efficient in removing colour, especially from wool and -silk, and every one is acquainted with the use of sulphur vapours in -bleaching.</p> - -<p class="para"><a id="a599">599.</a></p> - -<p>The strongest acids have been recommended more recently as more -expeditious agents in bleaching.</p> - -<p class="para"><a id="a600">600.</a></p> - -<p>The alkaline re-agents produce the same effects by contrary -means—lixiviums alone, oils and fat combined with lixiviums to soap, -and so forth.</p> - -<p class="para"><a id="a601">601.</a></p> - -<p>Before we dismiss this subject, we observe [Pg 240] that it may be -well worth while to make certain delicate experiments as to how far -light and air exhibit their action in the removal of colour. It might -be possible to expose coloured substances to the light under glass -bells, without air, or filled with common or particular kinds of air. -The colours might be those of known fugacity, and it might be observed -whether any of the volatilized colour attached itself to the glass or -was otherwise perceptible as a deposit or precipitate; whether, again, -in such a case, this appearance would be perfectly like that which had -gradually ceased to be visible, or whether it had suffered any change. -Skilful experimentalists might devise various contrivances with a view -to such researches.</p> - -<p class="para"><a id="a602">602.</a></p> - -<p>Having thus first considered the operations of nature as subservient to -our proposes, we add a few observations on the modes in which they act -against us.</p> - -<p class="para"><a id="a603">603.</a></p> - -<p>The art of painting is so circumstanced that the most beautiful results -of mind and labour are altered and destroyed in various ways by time. -Hence great pains have been always taken to find durable pigments, and -so to unite them with each other and with their ground, that their<span class="pagenum"><a name="Page_241" id="Page_241">[Pg 241]</a></span> -permanency might be further insured. The technical history of the -schools of painting affords sufficient information on this point.</p> - -<p class="para"><a id="a604">604.</a></p> - -<p>We may here, too, mention a minor art, to which, in relation to -dyeing, we are much indebted, namely, the weaving of tapestry. As the -manufacturers were enabled to imitate the most delicate shades of -pictures, and hence often brought the most variously coloured materials -together, it was soon observed that the colours were not all equally -durable, but that some faded from the tapestry more quickly than -others. Hence the most diligent efforts were made to ensure an equal -permanency to all the colours and their gradations. This object was -especially promoted in France, under Colbert, whose regulations to this -effect constitute an epoch in the history of dyeing. The gay dye which -only aimed at a transient beauty, was practised by a particular guild. -On the other hand, great pains were taken to define the technical -processes which promised durability.</p> - -<p>And thus, after considering the artificial extraction, the evanescence, -and the perishable nature of brilliant appearances of colour, we are -again returned to the desideratum of permanency.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_242" id="Page_242">[Pg 242]</a></span></p> - - - - -<h5><a name="XLIX" id="XLIX">XLIX.</a></h5> - - -<h5>NOMENCLATURE.</h5> - - -<p class="para"><a id="a605">605.</a></p> - -<p>After what has been adduced respecting the origin, the increase, -and the affinity of colours, we may be better enabled to judge what -nomenclature would be desirable in future, and what might be retained -of that hitherto in use.</p> - -<p class="para"><a id="a606">606.</a></p> - -<p>The nomenclature of colours, like all other modes of designation, -but especially those employed to distinguish the objects of sense, -proceeded in the first instance from particular to general, and from -general back again to particular terms. The name of the species became -a generic name to which the individual was again referred.</p> - -<p class="para"><a id="a607">607.</a></p> - -<p>This method might have been followed in consequence of the mutability -and uncertainty of ancient modes of expression, especially since, in -the early ages, more reliance may be supposed to have been placed on -the vivid impressions of sense. The qualities of objects were described -indistinctly, because they were impressed clearly on every imagination.</p> - -<p><span class="pagenum"><a name="Page_243" id="Page_243">[Pg 243]</a></span></p> - -<p class="para"><a id="a608">608.</a></p> - -<p>The pure chromatic circle was limited, it is true; but, specific as it -was, it appears to have been applied to innumerable objects, while it -was circumscribed by qualifying characteristics. If we take a glance -at the copiousness of the Greek and Roman terms, we shall perceive how -mutable the words were, and how easily each was adapted to almost every -point in the colorific circle.—<a href="#NOTE_W">Note W</a>.</p> - -<p class="para"><a id="a609">609.</a></p> - -<p>In modern ages terms for many new gradations were introduced in -consequence of the various operations of dyeing. Even the colours -of fashion and their designations, represented an endless series of -specific hues. We shall, on occasion, employ the chromatic terminology -of modern languages, whence it will appear that the aim has gradually -been to introduce more exact definitions, and to individualise and -arrest a fixed and specific state by language equally distinct.</p> - -<p class="para"><a id="a610">610.</a></p> - -<p>With regard to the German terminology, it has the advantage of -possessing four monosyllabic names no longer to be traced to their -origin, viz., yellow (Gelb), blue, red, green. They represent the most -general idea of colour to the imagination, without reference to any -very specific modification.</p> - -<p><span class="pagenum"><a name="Page_244" id="Page_244">[Pg 244]</a></span></p> - -<p class="para"><a id="a611">611.</a></p> - -<p>If we were to add two other qualifying terms to each of these four, as -thus—red-yellow, and yellow-red, red-blue and blue-red, yellow-green -and green-yellow, blue-green and green-blue,<a name="FNanchor_1_48" id="FNanchor_1_48"></a><a href="#Footnote_1_48" class="fnanchor">[1]</a> we should express the -gradations of the chromatic circle with sufficient distinctness; and if -we were to add the designations of light and dark, and again define, in -some measure, the degree of purity or its opposite by the monosyllables -black, white, grey, brown, we should have a tolerably sufficient range -of expressions to describe the ordinary appearances presented to us, -without troubling ourselves whether they were produced dynamically or -atomically.</p> - -<p class="para"><a id="a612">612.</a></p> - -<p>The specific and proper terms in use might, however, still be -conveniently employed, and we have thus made use of the words orange -and violet. We have in like manner employed the word "<i>purpur</i>" to -designate a pure central red, because the secretion of the murex or -"<i>purpura</i>" is to be carried to the highest point of culmination by the -action of the sun-light on fine linen saturated with the juice.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_48" id="Footnote_1_48"></a><a href="#FNanchor_1_48"><span class="label">[1]</span></a> This description is suffered to remain because it accounts -for the terminology employed throughout.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_245" id="Page_245">[Pg 245]</a></span></p></div> - - - - -<h5><a name="L" id="L">L.</a></h5> - - -<h5>MINERALS.</h5> - - -<p class="para"><a id="a613">613.</a></p> - -<p>The colours of minerals are all of a chemical nature, and thus the -modes in which they are produced may be explained in a general way by -what has been said on the subject of chemical colours.</p> - -<p class="para"><a id="a614">614.</a></p> - -<p>Among the external characteristics of minerals, the description of -their colours occupies the first place; and great pains have been -taken, in the spirit of modern times, to define and arrest every -such appearance exactly: by this means, however, new difficulties, -it appears to us, have been created, which occasion no little -inconvenience in practice.</p> - -<p class="para"><a id="a615">615.</a></p> - -<p>It is true, this precision, when we reflect how it arose, carries with -it its own excuse. The painter has at all times been privileged in -the use of colours. The few specific hues, in themselves, admitted of -no change; but from these, innumerable gradations were artificially -produced which imitated the surface of natural objects. It was, -therefore, not to be wondered<span class="pagenum"><a name="Page_246" id="Page_246">[Pg 246]</a></span> at that these gradations should also be -adopted as criterions, and that the artist should be invited to produce -tinted patterns with which the objects of nature might be compared, and -according to which they were to receive their designations.</p> - -<p class="para"><a id="a616">616.</a></p> - -<p>But, after all, the terminology of colours which has been introduced in -mineralogy, is open to many objections. The terms, for instance, have -not been borrowed from the mineral kingdom, as was possible enough in -most cases, but from all kinds of visible objects. Too many specific -terms have been adopted; and in seeking to establish new definitions -by combining these, the nomenclators have not reflected that they thus -altogether efface the image from the imagination, and the idea from -the understanding. Lastly, these individual designations of colours, -employed to a certain extent as elementary definitions, are not -arranged in the best manner as regards their respective derivation from -each other: hence, the scholar must learn every single designation, -and impress an almost lifeless but positive language on his memory. -The further consideration of this would be too foreign to our present -subject.<a name="FNanchor_1_49" id="FNanchor_1_49"></a><a href="#Footnote_1_49" class="fnanchor">[1]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_49" id="Footnote_1_49"></a><a href="#FNanchor_1_49"><span class="label">[1]</span></a> These remarks have reference to the German mineralogical -terminology.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_247" id="Page_247">[Pg 247]</a></span></p></div> - - - - -<h5><a name="LI" id="LI">LI.</a></h5> - - -<h5>PLANTS.</h5> - - -<p class="para"><a id="a617">617.</a></p> - -<p>The colours of organic bodies in general may be considered as a higher -kind of chemical operation, for which reason the ancients employed the -word concoction, πέψις, to designate the process. All the elementary -colours, as well as the combined and secondary hues, appear on the -surface of organic productions, while on the other hand, the interior, -if not colourless, appears, strictly speaking, negative when brought to -the light. As we propose to communicate our views respecting organic -nature, to a certain extent, in another place, we only insert here -what has been before connected with the doctrine of colours, while it -may serve as an introduction to the further consideration of the views -alluded to: and first, of plants.</p> - -<p class="para"><a id="a618">618.</a></p> - -<p>Seeds, bulbs, roots, and what is generally shut out from the light, or -immediately surrounded by the earth, appear, for the most part, white.</p> - -<p class="para"><a id="a619">619.</a></p> - -<p>Plants reared from seed, in darkness, are white, or approaching to -yellow. Light, on the<span class="pagenum"><a name="Page_248" id="Page_248">[Pg 248]</a></span> other hand, in acting on their colours, acts at -the same time on their form.</p> - -<p class="para"><a id="a620">620.</a></p> - -<p>Plants which grow in darkness make, it is true, long shoots from joint -to joint: but the stems between two joints are thus longer than they -should be; no side stems are produced, and the metamorphosis of the -plant does not take place.</p> - -<p class="para"><a id="a621">621.</a></p> - -<p>Light, on the other hand, places it at once in an active state; the -plant appears green, and the course of the metamorphosis proceeds -uninterruptedly to the period of reproduction.</p> - -<p class="para"><a id="a622">622.</a></p> - -<p>We know that the leaves of the stem are only preparations and -pre-significations of the instruments of florification and -fructification, and accordingly we can already see colours in the -leaves of the stem which, as it were, announce the flower from afar, as -is the case in the amaranthus.</p> - -<p class="para"><a id="a623">623.</a></p> - -<p>There are white flowers whose petals have wrought or refined themselves -to the greatest purity; there are coloured ones, in which the<span class="pagenum"><a name="Page_249" id="Page_249">[Pg 249]</a></span> -elementary hues may be said to fluctuate to and fro. There are some -which, in tending to the higher state, have only partially emancipated -themselves from the green of the plant.</p> - -<p class="para"><a id="a624">624.</a></p> - -<p>Flowers of the same genus, and even of the same kind, are found of all -colours. Roses, and particularly mallows, for example, vary through -a great portion of the colorific circle from white to yellow, then -through red-yellow to bright red, and from thence to the darkest hue it -can exhibit as it approaches blue.</p> - -<p class="para"><a id="a625">625.</a></p> - -<p>Others already begin from a higher degree in the scale, as, for -example, the poppy, which is yellow-red in the first instance, and -which afterwards approaches a violet hue.</p> - -<p class="para"><a id="a626">626.</a></p> - -<p>Yet the same colours in species, varieties, and even in families and -classes, if not constant, are still predominant, especially the yellow -colour: blue is throughout rarer.</p> - -<p class="para"><a id="a627">627.</a></p> - -<p>A process somewhat similar takes place in the juicy capsule of -the fruit, for it increases in colour from the green, through the -yellowish<span class="pagenum"><a name="Page_250" id="Page_250">[Pg 250]</a></span> and yellow, up to the highest red, the colour of the rind -thus indicating the degree of ripeness. Some are coloured all round, -some only on the sunny side, in which last case the augmentation of the -yellow into red,—the gradations crowding in and upon each other,—may -be very well observed.</p> - -<p class="para"><a id="a628">628.</a></p> - -<p>Many fruits, too, are coloured internally; pure red juices, especially, -are common.</p> - -<p class="para"><a id="a629">629.</a></p> - -<p>The colour which is found superficially in the flower and penetratingly -in the fruit, spreads itself through all the remaining parts, colouring -the roots and the juices of the stem, and this with a very rich and -powerful hue.</p> - -<p class="para"><a id="a630">630.</a></p> - -<p>So, again, the colour of the wood passes from yellow through the -different degrees of red up to pure red and on to brown. Blue woods are -unknown to me; and thus in this degree of organisation the active side -exhibits itself powerfully, although both principles appear balanced in -the general green of the plant.</p> - -<p class="para"><a id="a631">631.</a></p> - -<p>We have seen above that the germ pushing<span class="pagenum"><a name="Page_251" id="Page_251">[Pg 251]</a></span> from the earth is generally -white and yellowish, but that by means of the action of light and air -it acquires a green colour. The same happens with young leaves of -trees, as may be seen, for example, in the birch, the young leaves of -which are yellowish, and if boiled, yield a beautiful yellow juice: -afterwards they become greener, while the leaves of other trees become -gradually blue-green.</p> - -<p class="para"><a id="a632">632.</a></p> - -<p>Thus a yellow ingredient appears to belong more essentially to leaves -than a blue one; for this last vanishes in the autumn, and the yellow -of the leaf appears changed to a brown colour. Still more remarkable, -however, are the particular cases where leaves in autumn again become -pure yellow, and others increase to the brightest red.</p> - -<p class="para"><a id="a633">633.</a></p> - -<p>Other plants, again, may, by artificial treatment be entirely converted -to a colouring matter, which is as fine, active, and infinitely -divisible as any other. Indigo and madder, with which so much is -effected, are examples: lichens are also used for dyes.</p> - -<p class="para"><a id="a634">634.</a></p> - -<p>To this fact another stands immediately opposed;<span class="pagenum"><a name="Page_252" id="Page_252">[Pg 252]</a></span> we can, namely, -extract the colouring part of plants, and, as it were, exhibit it -apart, while the organisation does not on this account appear to suffer -at all. The colours of flowers may be extracted by spirits of wine, and -tinge it; the petals meanwhile becoming white.</p> - -<p class="para"><a id="a635">635.</a></p> - -<p>There are various modes of acting on flowers and their juices by -re-agents. This has been done by Boyle in many experiments. Roses are -bleached by sulphur, and may be restored to their first state by other -acids; roses are turned green by the smoke of tobacco.</p> - - - -<hr class="chap" /> -<h5><a name="LII" id="LII">LII.</a></h5> - - -<h5>WORMS, INSECTS, FISHES.</h5> - - -<p class="para"><a id="a636">636.</a></p> - -<p>With regard to creatures belonging to the lower degrees of -organisation, we may first observe that worms, which live in the earth -and remain in darkness and cold moisture, are imperfectly negatively -coloured; worms bred in warm moisture and darkness are colourless; -light seems expressly necessary to the definite exhibition of colour.</p> - -<p><span class="pagenum"><a name="Page_253" id="Page_253">[Pg 253]</a></span></p> - -<p class="para"><a id="a637">637.</a></p> - -<p>Creatures which live in water, which, although a very dense medium, -suffers sufficient light to pass through it, appear more or less -coloured. Zoophytes, which appear to animate the purest calcareous -earth, are mostly white; yet we find corals deepened into the most -beautiful yellow-red: in other cells of worms this colour increases -nearly to bright red.</p> - -<p class="para"><a id="a638">638.</a></p> - -<p>The shells of the crustaceous tribe are beautifully designed and -coloured, yet it is to be remarked that neither land-snails nor the -shells of crustacea of fresh water, are adorned with such bright -colours as those of the sea.</p> - -<p class="para"><a id="a639">639.</a></p> - -<p>In examining shells, particularly such as are spiral, we find that -a series of animal organs, similar to each other, must have moved -increasingly forward, and in turning on an axis produced the shell in -a series of chambers, divisions, tubes, and prominences, according to -a plan for ever growing larger. We remark, however, that a tinging -juice must have accompanied the development of these organs, a juice -which marked the surface of the shell, probably through the immediate -co-operation of the sea-water, with coloured lines, points, spots, and -shadings:<span class="pagenum"><a name="Page_254" id="Page_254">[Pg 254]</a></span> this must have taken place at regular intervals, and thus -left the indications of increasing growth lastingly on the exterior; -meanwhile the interior is generally found white or only faintly -coloured.</p> - -<p class="para"><a id="a640">640.</a></p> - -<p>That such a juice is to be found in shell-fish is, besides, -sufficiently proved by experience; for the creatures furnish it in its -liquid and colouring state: the juice of the ink-fish is an example. -But a much stronger is exhibited in the red juice found in many -shell-fish, which was so famous in ancient times, and has been employed -with advantage by the moderns. There is, it appears, in the entrails of -many of the crustaceous tribe a certain vessel which is filled with a -red juice; this contains a very strong and durable colouring substance, -so much so that the entire creature may be crushed and boiled, and -yet out of this broth a sufficiently strong tinging liquid may be -extracted. But the little vessel filled with colour may be separated -from the animal, by which means of course a concentrated juice is -gained.</p> - -<p class="para"><a id="a641">641.</a></p> - -<p>This juice has the property that when exposed to light and air it -appears first yellowish, then greenish; it then passes to blue, then to -a<span class="pagenum"><a name="Page_255" id="Page_255">[Pg 255]</a></span> violet, gradually growing redder; and lastly, by the action of the -sun, and especially if transferred to cambric, it assumes a pure bright -red colour.</p> - -<p class="para"><a id="a642">642.</a></p> - -<p>Thus we should here have an augmentation, even to culmination, on the -<i>minus</i> side, which we cannot easily meet with in inorganic cases; -indeed, we might almost call this example a passage through the -whole scale, and we are persuaded that by due experiments the entire -revolution of the circle might really be effected, for there is no -doubt that by acids duly employed, the pure red may be pushed beyond -the culminating point towards scarlet.</p> - -<p class="para"><a id="a643">643.</a></p> - -<p>This juice appears on the one hand to be connected with the phenomena -of reproduction, eggs being found, the embryos of future shell-fish, -which contain a similar colouring principle. On the other hand, in -animals ranking higher in the scale of being, the secretion appears to -bear some relation to the development of the blood. The blood exhibits -similar properties in regard to colour; in its thinnest state it -appears yellow; thickened, as it is found in the veins, it appears red; -while the arterial blood exhibits a brighter red, probably owing to the -oxydation<span class="pagenum"><a name="Page_256" id="Page_256">[Pg 256]</a></span> which takes place by means of breathing. The venous blood -approaches more to violet, and by this mutability denotes the tendency -to that augmentation and progression which are now familiar to us.</p> - -<p class="para"><a id="a644">644.</a></p> - -<p>Before we quit the element whence we derived the foregoing examples, -we may add a few observations on fishes, whose scaly surface is -coloured either altogether in stripes, or in spots, and still oftener -exhibits a certain iridescent appearance, indicating the affinity of -the scales with the coats of shell-fish, mother-of-pearl, and even -the pearl itself. At the same time it should not be forgotten that -warmer climates, the influence of which extends to the watery regions, -produce, embellish, and enhance these colours in fishes in a still -greater degree.</p> - -<p class="para"><a id="a645">645.</a></p> - -<p>In Otaheite, Forster observed fishes with beautifully iridescent -surfaces, and this effect was especially apparent at the moment when -the fish died. We may here call to mind the hues of the chameleon, -and other similar appearances; for when similar facts are presented -together, we are better enabled to trace them.</p> - -<p class="para"><a id="a646">646.</a></p> - -<p>Lastly, although not strictly in the same<span class="pagenum"><a name="Page_257" id="Page_257">[Pg 257]</a></span> class, the iridescent -appearance of certain molluscæ may be mentioned, as well as the -phosphorescence which, in some marine creatures, it is said becomes -iridescent just before it vanishes.</p> - -<p class="para"><a id="a647">647.</a></p> - -<p>We now turn our attention to those creatures which belong to light, -air and dry warmth, and it is here that we first find ourselves in -the living region of colours. Here, in exquisitely organised parts, -the elementary colours present themselves in their greatest purity -and beauty. They indicate, however, that the creatures they adorn, -are still low in the scale of organisation, precisely because these -colours can thus appear, as it were, unwrought. Here, too, heat seems -to contribute much to their development.</p> - -<p class="para"><a id="a648">648.</a></p> - -<p>We find insects which may be considered altogether as concentrated -colouring matter; among these, the cochineals especially are -celebrated; with regard to these we observe that their mode of settling -on vegetables, and even nestling in them, at the same time produces -those excrescences which are so useful as mordants in fixing colours.</p> - -<p><span class="pagenum"><a name="Page_258" id="Page_258">[Pg 258]</a></span></p> - -<p class="para"><a id="a649">649.</a></p> - -<p>But the power of colour, accompanied by regular organisation, exhibits -itself in the most striking manner in those insects which require a -perfect metamorphosis for their development—in scarabæ, and especially -in butterflies.</p> - -<p class="para"><a id="a650">650.</a></p> - -<p>These last, which might be called true productions of light and air, -often exhibit the most beautiful colours, even in their chrysalis -state, indicating the future colours of the butterfly; a consideration -which, if pursued further hereafter, must undoubtedly afford a -satisfactory insight into many a secret of organised being.</p> - -<p class="para"><a id="a651">651.</a></p> - -<p>If, again, we examine the wings of the butterfly more accurately, and -in its net-like web discover the rudiments of an arm, and observe -further the mode in which this, as it were, flattened arm is covered -with tender plumage and constituted an organ of flying; we believe -we recognise a law according to which the great variety of tints is -regulated. This will be a subject for further investigation hereafter.</p> - -<p class="para"><a id="a652">652.</a></p> - -<p>That, again, heat generally has an influence<span class="pagenum"><a name="Page_259" id="Page_259">[Pg 259]</a></span> on the size of the -creature, on the accomplishment of the form, and on the greater beauty -of the colours, hardly needs to be remarked.</p> - - - -<hr class="chap" /> -<h5><a name="LIII" id="LIII">LIII.</a></h5> - -<h5>BIRDS.</h5> - - -<p class="para"><a id="a653">653.</a></p> - -<p>The more we approach the higher organisations, the more it becomes -necessary to limit ourselves to a few passing observations; for all the -natural conditions of such organised beings are the result of so many -premises, that, without having at least hinted at these, our remarks -would only appear daring, and at the same time insufficient.</p> - -<p class="para"><a id="a654">654.</a></p> - -<p>We find in plants, that the consummate flower and fruit are, as it -were, rooted in the stem, and that they are nourished by more perfect -juices than the original roots first afforded; we remark, too, -that parasitical plants which derive their support from organised -structures, exhibit themselves especially endowed as to their energies -and qualities. We might in some sense compare the feathers of birds -with plants of this description; the feathers spring up as a last -structural result from the surface of a body<span class="pagenum"><a name="Page_260" id="Page_260">[Pg 260]</a></span> which has yet much in -reserve for the completion of the external economy, and thus are very -richly endowed organs.</p> - -<p class="para"><a id="a655">655.</a></p> - -<p>The quills not only grow proportionally to a considerable size, but are -throughout branched, by which means they properly become feathers, and -many of these feathered branches are again subdivided; thus, again, -recalling the structure of plants.</p> - -<p class="para"><a id="a656">656.</a></p> - -<p>The feathers are very different in shape and size, but each still -remains the same organ, forming and transforming itself according to -the constitution of the part of the body from which it springs.</p> - -<p class="para"><a id="a657">657.</a></p> - -<p>With the form, the colour also becomes changed, and a certain law -regulates the general order of hues as well as that particular -distribution by which a single feather becomes party coloured, It -is from this that all combination of variegated plumage arises, and -whence, at last, the eyes in the peacock's tail are produced. It is -a result similar to that which we have already unfolded in treating -of the metamorphosis of plants, and which we shall take an early -opportunity to prove.</p> - -<p><span class="pagenum"><a name="Page_261" id="Page_261">[Pg 261]</a></span></p> - -<p class="para"><a id="a658">658.</a></p> - -<p>Although time and circumstances compel us here to pass by this organic -law, yet we are bound to refer to the chemical operations which -commonly exhibit themselves in the tinting of feathers in a mode now -sufficiently known to us.</p> - -<p class="para"><a id="a659">659.</a></p> - -<p>Plumage is of all colours, yet, on the whole, yellow deepening to red -is commoner than blue.</p> - -<p class="para"><a id="a660">660.</a></p> - -<p>The operation of light on the feathers and their colours, is to be -remarked in all cases. Thus, for example, the feathers on the breast of -certain parrots, are strictly yellow; the scale-like anterior portion, -which is acted on by the light, is deepened from yellow to red. The -breast of such a bird appears bright-red, but if we blow into the -feathers the yellow appears.</p> - -<p class="para"><a id="a661">661.</a></p> - -<p>The exposed portion of the feathers is in all cases very different -from that which, in a quiet state, is covered; it is only the exposed -portion, for instance, in ravens, which exhibits the iridescent -appearance; the covered portion does not: from which indication, the -feathers of the tail when ruffled together, may be at once placed in -the natural order again.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_262" id="Page_262">[Pg 262]</a></span></p> - - - - -<h5><a name="LIV" id="LIV">LIV.</a></h5> - - -<h5>MAMMALIA AND HUMAN BEINGS.</h5> - - -<p class="para"><a id="a662">662.</a></p> - -<p>Here the elementary colours begin to leave us altogether. We are -arrived at the highest degree of the scale, and shall not dwell on its -characteristics long.</p> - -<p class="para"><a id="a663">663.</a></p> - -<p>An animal of this class is distinguished among the examples of -organised being. Every thing that exhibits itself about him is living. -Of the internal structure we do not speak, but confine ourselves -briefly to the surface. The hairs are already distinguished from -feathers, inasmuch as they belong more to the skin, inasmuch as they -are simple, thread-like, not branched. They are however, like feathers, -shorter, longer, softer, and firmer, colourless or coloured, and all -this in conformity to laws which might be defined.</p> - -<p class="para"><a id="a664">664.</a></p> - -<p>White and black, yellow, yellow-red and brown, alternate in various -modifications, but they never appear in such a state as to remind us -of the elementary hues. On the contrary,<span class="pagenum"><a name="Page_263" id="Page_263">[Pg 263]</a></span> they are all broken colours -subdued by organic concoction, and thus denote, more or less, the -perfection of life in the being they belong to.</p> - -<p class="para"><a id="a665">665.</a></p> - -<p>One of the most important considerations connected with morphology, -so far as it relates to surfaces, is this, that even in quadrupeds -the spots of the skin have a relation with the parts underneath -them. Capriciously as nature here appears, on a hasty examination, -to operate, she nevertheless consistently observes a secret law. The -development and application of this, it is true, are reserved only for -accurate and careful investigation and sincere co-operation.</p> - -<p class="para"><a id="a666">666.</a></p> - -<p>If in some animals portions appear variegated with positive colours, -this of itself shows how far such creatures are removed from a perfect -organisation; for, it may be said, the nobler a creature is, the more -all the mere material of which he is composed, is disguised by being -wrought together; the more essentially his surface corresponds with the -internal organisation, the less can it exhibit the elementary colours. -Where all tends to make up a perfect whole, any detached specific -developments cannot take place.</p> - -<p class="para"><a id="a667">667.</a></p> - -<p>Of man we have little to say, for he is entirely<span class="pagenum"><a name="Page_264" id="Page_264">[Pg 264]</a></span> distinct from the -general physiological results of which we now treat. So much in this -case is in affinity with the internal structure, that the surface can -only be sparingly endowed.</p> - -<p class="para"><a id="a668">668.</a></p> - -<p>When we consider that brutes are rather encumbered than advantageously -provided with intercutaneous muscles; when we see that much that is -superfluous tends to the surface, as, for instance, large ears and -tails, as well as hair, manes, tufts; we see that nature, in such -cases, had much to give away and to lavish.</p> - -<p class="para"><a id="a669">669.</a></p> - -<p>On the contrary, the general surface of the human form is smooth and -clean, and thus in the most perfect examples, the beautiful forms are -apparent; for it may be remarked in passing, that a superfluity of -hair on the chest, arms, and lower limbs, rather indicates weakness -than strength. Poets only have sometimes been induced, probably by the -example of the ferine nature, so strong in other respects, to extol -similar attributes in their rough heroes.</p> - -<p class="para"><a id="a670">670.</a></p> - -<p>But we have here chiefly to speak of colour, and observe that the -colour of the human skin, in all its varieties, is never an elementary -colour,<span class="pagenum"><a name="Page_265" id="Page_265">[Pg 265]</a></span> but presents, by means of organic concoction, a highly -complicated result.—<a href="#NOTE_X">Note X</a>.</p> - -<p class="para"><a id="a671">671.</a></p> - -<p>That the colour of the skin and hair has relation with the differences -of character, is beyond question; and we are led to conjecture that the -circumstance of one or other organic system predominating, produces -the varieties we see. A similar hypothesis may be applied to nations, -in which case it might perhaps be observed, that certain colours -correspond with certain confirmations, which has always been observed -of the negro physiognomy.</p> - -<p class="para"><a id="a672">672.</a></p> - -<p>Lastly, we might here consider the problematical question, whether all -human forms and hues are not equally beautiful, and whether custom -and self-conceit are not the causes why one is preferred to another? -We venture, however, after what has been adduced, to assert that the -white man, that is, he whose surface varies from white to reddish, -yellowish, brownish, in short, whose surface appears most neutral in -hue and least inclines to any particular or positive colour, is the -most beautiful. On the same principle a similar point of perfection in -human conformation may be defined hereafter, when the question relates -to form. We do not<span class="pagenum"><a name="Page_266" id="Page_266">[Pg 266]</a></span> imagine that this long-disputed question is to be -thus, once for all, settled, for there are persons enough who have -reason to leave this significancy of the exterior in doubt; but we thus -express a conclusion, derived from observation and reflection, such -as might suggest itself to a mind aiming at a satisfactory decision. -We subjoin a few observations connected with the elementary chemical -doctrine of colours.—<a href="#NOTE_Y">Note Y</a>.</p> - - - -<hr class="chap" /> -<h5><a name="LV" id="LV">LV.</a></h5> - - -<h5>PHYSICAL AND CHEMICAL EFFECTS OF THE TRANSMISSION OF LIGHT THROUGH -COLOURED MEDIUMS.</h5> - - -<p class="para"><a id="a673">673.</a></p> - -<p>The physical and chemical effects of colourless light are known, so -that it is unnecessary here to describe them at length. Colourless -light exhibits itself under various conditions as exciting warmth, as -imparting a luminous quality to certain bodies, as promoting oxydation -and de-oxydation. In the modes and degrees of these effects many -varieties take place, but no difference is found indicating a principle -of contrast such as we find in the transmission of coloured light. We -proceed briefly to advert to this.</p> - -<p><span class="pagenum"><a name="Page_267" id="Page_267">[Pg 267]</a></span></p> - -<p class="para"><a id="a674">674.</a></p> - -<p>Let the temperature of a dark room be observed by means of a very -sensible air-thermometer; if the bulb is then brought to the direct sun -light as it shines into the room, nothing is more natural than that the -fluid should indicate a much higher degree of warmth. If upon this we -interpose coloured glasses, it follows again quite naturally that the -degree of warmth must be lowered; first, because the operation of the -direct light is already somewhat impeded by the glass, and again, more -especially, because a coloured glass, as a dark medium, admits less -light through it.</p> - -<p class="para"><a id="a675">675.</a></p> - -<p>But here a difference in the excitation of warmth exhibits itself to -the attentive observer, according to the colour of the glass. The -yellow and the yellow-red glasses produce a higher temperature than the -blue and blue-red, the difference being considerable.</p> - -<p class="para"><a id="a676">676.</a></p> - -<p>This experiment may be made with the prismatic spectrum. The -temperature of the room being first remarked on the thermometer, the -blue coloured light is made to fall on the bulb, when a somewhat higher -degree of warmth is exhibited, which still increases as the other -colours<span class="pagenum"><a name="Page_268" id="Page_268">[Pg 268]</a></span> are gradually brought to act on the mercury. If the experiment -is made with the water-prism, so that the white light can be retained -in the centre, this, refracted indeed, but not yet coloured light, is -the warmest; the other colours, stand in relation to each other as -before.</p> - -<p class="para"><a id="a677">677.</a></p> - -<p>As we here merely describe, without undertaking to deduce or explain -this phenomenon, we only remark in passing, that the pure light is by -no means abruptly and entirely at an end with the red division in the -spectrum, but that a refracted light is still to be observed deviating -from its course and, as it were, insinuating itself beyond the -prismatic image, so that on closer examination it will hardly be found -necessary to take refuge in invisible rays and their refraction.</p> - -<p class="para"><a id="a678">678.</a></p> - -<p>The communication of light by means of coloured mediums exhibits the -same difference. The light communicates itself to Bologna phosphorus -through blue and violet glasses, but by no means through yellow and -yellow-red glasses. It has been even remarked that the phosphori which -have been rendered luminous under violet and blue glasses, become -sooner extinguished when afterwards placed under yellow and yellow-red -glasses than those which have been<span class="pagenum"><a name="Page_269" id="Page_269">[Pg 269]</a></span> suffered to remain in a dark room -without any further influence.</p> - -<p class="para"><a id="a679">679.</a></p> - -<p>These experiments, like the foregoing, may also be made by means of the -prismatic spectrum, when the same results take place.</p> - -<p class="para"><a id="a680">680.</a></p> - -<p>To ascertain the effect of coloured light on oxydation and -de-oxydation, the following means may be employed:—Let moist, -perfectly white muriate of silver<a name="FNanchor_1_50" id="FNanchor_1_50"></a><a href="#Footnote_1_50" class="fnanchor">[1]</a> be spread on a strip of paper; -place it in the light, so that it may become to a certain degree grey, -and then cut it in three portions. Of these, one may be preserved -in a book, as a specimen of this state; let another be placed under -a yellow-red, and the third under a blue-red glass. The last will -become a darker grey, and exhibit a de-oxydation; the other, under the -yellow-red glass, will, on the contrary, become a lighter grey, and -thus approach nearer to the original state of more perfect oxydation. -The change in both may be ascertained by a comparison with the -unaltered specimen.</p> - -<p class="para"><a id="a681">681.</a></p> - -<p>An excellent apparatus has been contrived to<span class="pagenum"><a name="Page_270" id="Page_270">[Pg 270]</a></span> perform these experiments -with the prismatic image. The results are analogous to those already -mentioned, and we shall hereafter give the particulars, making use -of the labours of an accurate observer, who has been for some time -carefully prosecuting these experiments.<a name="FNanchor_2_51" id="FNanchor_2_51"></a><a href="#Footnote_2_51" class="fnanchor">[2]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_50" id="Footnote_1_50"></a><a href="#FNanchor_1_50"><span class="label">[1]</span></a> Now generally called chloride of silver: the term in the -original is Hornsilber.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_51" id="Footnote_2_51"></a><a href="#FNanchor_2_51"><span class="label">[2]</span></a> The individual alluded to was Seebeck: the result of his -experiments was published in the second volume.—T.</p></div> - - -<hr class="chap" /> - -<h5><a name="LVI" id="LVI">LVI.</a></h5> - - -<h5>CHEMICAL EFFECT IN DIOPTRICAL ACHROMATISM.</h5> - - -<p class="para"><a id="a682">682.</a></p> - -<p>We first invite our readers to turn to what has been before observed on -this subject (<a href="#a285">285</a>, <a href="#a298">298</a>), to avoid unnecessary repetition here.</p> - -<p class="para"><a id="a683">683.</a></p> - -<p>We can thus give a glass the property of producing much wider coloured -edges without refracting more strongly than before, that is, without -displacing the object much more perceptibly.</p> - -<p class="para"><a id="a684">684.</a></p> - -<p>This property is communicated to the glass by means of metallic oxydes. -Minium, melted and thoroughly united with a pure glass, produces<span class="pagenum"><a name="Page_271" id="Page_271">[Pg 271]</a></span> this -effect, and thus flint-glass (<a href="#a291">291</a>) is prepared with oxyde of lead. -Experiments of this kind have been carried farther, and the so-called -butter of antimony, which, according to a new preparation, may be -exhibited as a pure fluid, has been made use of in hollow lenses and -prisms, producing a very strong appearance of colour with a very -moderate refraction, and presenting the effect which we have called -hyperchromatism in a very vivid manner.</p> - -<p class="para"><a id="a685">685.</a></p> - -<p>In common glass, the alkaline nature obviously preponderates, since -it is chiefly composed of sand and alkaline salts; hence a series of -experiments, exhibiting the relation of perfectly alkaline fluids to -perfect acids, might lead to useful results.</p> - -<p class="para"><a id="a686">686.</a></p> - -<p>For, could the maximum and minimum be found, it would be a question -whether a refracting medium could not be discovered, in which the -increasing and diminishing appearance of colour, (an effect almost -independent of refraction,) could not be done away with altogether, -while the displacement of the object would be unaltered.</p> - -<p class="para"><a id="a687">687.</a></p> - -<p>How desirable, therefore, it would be with<span class="pagenum"><a name="Page_272" id="Page_272">[Pg 272]</a></span> regard to this last point, -as well as for the elucidation of the whole of this third division of -our work, and, indeed, for the elucidation of the doctrine of colours -generally, that those who are occupied in chemical researches, with new -views ever opening to them, should take this subject in hand, pursuing -into more delicate combinations what we have only roughly hinted at, -and prosecuting their inquiries with reference to science as a whole.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_273" id="Page_273">[Pg 273]</a></span></p> - - - - -<h5><a name="PART_IV" id="PART_IV">PART IV.</a></h5> - - -<h5>GENERAL CHARACTERISTICS.</h5> - - -<p class="para"><a id="a688">688.</a></p> - -<p>We have hitherto, in a manner forcibly, kept phenomena asunder, -which, partly from their nature, partly in accordance with our mental -habits, have, as it were, constantly sought to be reunited. We have -exhibited them in three divisions. We have considered colours, first, -as transient, the result of an action and re-action in the eye -itself; next, as passing effects of colourless, light-transmitting, -transparent, or opaque mediums on light; especially on the luminous -image; lastly, we arrived at the point where we could securely -pronounce them as permanent, and actually inherent in bodies.</p> - -<p class="para"><a id="a689">689.</a></p> - -<p>In following this order we have as far as possible endeavoured to -define, to separate, and to class the appearances. But now that we -need no longer be apprehensive of mixing or confounding them, we may -proceed, first, to state the general nature of these appearances -considered abstractedly, as an independent circle of facts, and, in the -next place, to show how this particular circle is connected with other -classes of analogous phenomena in nature.</p> -<hr class="tb" /> -<p><span class="pagenum"><a name="Page_274" id="Page_274">[Pg 274]</a></span></p> - - -<h5>THE FACILITY WITH WHICH COLOUR APPEARS.</h5> - - -<p class="para"><a id="a690">690.</a></p> - -<p>We have observed that colour under many conditions appears very easily. -The susceptibility of the eye with regard to light, the constant -re-action of the retina against it, produce instantaneously a slight -iridescence. Every subdued light may be considered as coloured, nay, we -ought to call any light coloured, inasmuch as it is seen. Colourless -light, colourless surfaces, are, in some sort, abstract ideas; in -actual experience we can hardly be said to be aware of them.—<a href="#NOTE_Z">Note Z</a>.</p> - -<p class="para"><a id="a691">691.</a></p> - -<p>If light impinges on a colourless body, is reflected from it or passes -through it, colour immediately appears; but it is necessary here to -remember what has been so often urged by us, namely, that the leading -conditions of refraction, reflection, &c., are not of themselves -sufficient to produce the appearance. Sometimes, it is true, light acts -with these merely as light, but oftener as a defined, circumscribed -appearance, as a luminous image. The semi-opacity of the medium is -often a necessary condition; while half, and double shadows, are -required for many coloured appearances. In all cases, however, colour -appears instantaneously. We find, again, that by means of pressure, -breathing heat (<a href="#a432">432</a>, <a href="#a471">471</a>), by various kinds of motion and<span class="pagenum"><a name="Page_275" id="Page_275">[Pg 275]</a></span> alteration -on smooth clean surfaces (<a href="#a461">461</a>), as well as on colourless fluids (<a href="#a470">470</a>), -colour is immediately produced.</p> - -<p class="para"><a id="a692">692.</a></p> - -<p>The slightest change has only to take place in the component parts -of bodies, whether by immixture with other particles or other such -effects, and colour either makes its appearance or becomes changed.</p> - -<hr class="tb" /> -<h5>THE FORCE OF COLOUR.</h5> - - -<p class="para"><a id="a693">693.</a></p> - -<p>The physical colours, and especially those of the prism, were formerly -called "<i>colores emphatici</i>," on account of their extraordinary beauty -and force. Strictly speaking, however, a high degree of effect may be -ascribed to all appearances of colour, assuming that they are exhibited -under the purest and most perfect conditions.</p> - -<p class="para"><a id="a694">694.</a></p> - -<p>The dark nature of colour, its full rich quality, is what produces -the grave, and at the same time fascinating impression we sometimes -experience, and as colour is to be considered a condition of light, -so it cannot dispense with light as the co-operating cause of its -appearance, as its basis or ground; as a power thus displaying and -manifesting colour.</p> - -<p><span class="pagenum"><a name="Page_276" id="Page_276">[Pg 276]</a></span></p> - -<hr class="tb" /> -<h5>THE DEFINITE NATURE OF COLOUR.</h5> - - -<p class="para"><a id="a695">695.</a></p> - -<p>The existence and the relatively definite character of colour are one -and the same thing. Light displays itself and the face of nature, as -it were, with a general indifference, informing us as to surrounding -objects perhaps devoid of interest or importance; but colour is at all -times specific, characteristic, significant.</p> - -<p class="para"><a id="a696">696.</a></p> - -<p>Considered in a general point of view, colour is determined towards one -of two sides. It thus presents a contrast which we call a polarity, and -which we may fitly designate by the expressions <i>plus</i> and <i>minus</i>.</p> - -<table border="0" cellpadding="2" cellspacing="0" summary=""> -<tr><th align="left" colspan="1"><i>Plus</i>.</th><th align="left" colspan="1"><i>Minus</i>.</th></tr> -<tr><td align="left">Yellow.</td><td align="left">Blue.</td></tr> -<tr><td align="left">Action.</td><td align="left">Negation.<a name="FNanchor_1_52" id="FNanchor_1_52"></a><a href="#Footnote_1_52" class="fnanchor">[1]</a></td></tr> -<tr><td align="left">Light.</td><td align="left">Shadow.</td></tr> -<tr><td align="left">Brightness.</td><td align="left">Darkness.</td></tr> -<tr><td align="left">Force.</td><td align="left">Weakness.</td></tr> -<tr><td align="left">Warmth.</td><td align="left">Coldness.</td></tr> -<tr><td align="left">Proximity.</td><td align="left">Distance.</td></tr> -<tr><td align="left">Repulsion</td><td align="left">Attraction.</td></tr> -<tr><td align="left">Affinity with acids. </td><td align="left">Affinity with alkalis.</td></tr> -</table> - -<p><span class="pagenum"><a name="Page_277" id="Page_277">[Pg 277]</a></span></p> - - -<hr class="tb" /> -<h5>COMBINATION OF THE TWO PRINCIPLES.</h5> - - -<p class="para"><a id="a697">697.</a></p> - -<p>If these specific, contrasted principles are combined, the respective -qualities do not therefore destroy each other: for if in this -intermixture the ingredients are so perfectly balanced that neither -is to be distinctly recognised, the union again acquires a specific -character; it appears as a quality by itself in which we no longer -think of combination. This union we call green.</p> - -<p class="para"><a id="a698">698.</a></p> - -<p>Thus, if two opposite phenomena springing from the same source do not -destroy each other when combined, but in their union present a third -appreciable and pleasing appearance, this result at once indicates -their harmonious relation. The more perfect result yet remains to be -adverted to.</p> - -<hr class="tb" /> -<h5>AUGMENTATION TO RED.</h5> - - -<p class="para"><a id="a699">699.</a></p> - -<p>Blue and yellow do not admit of increased intensity without presently -exhibiting a new appearance in addition to their own. Each colour, in -its lightest state, is a dark; if condensed it must become darker, but -this effect no sooner takes place than the hue assumes an appearance -which we designate by the word reddish.</p> - -<p><span class="pagenum"><a name="Page_278" id="Page_278">[Pg 278]</a></span></p> - -<p class="para"><a id="a700">700.</a></p> - -<p>This appearance still increases, so that when the highest degree of -intensity is attained it predominates over the original hue. A powerful -impression of light leaves the sensation of red on the retina. In the -prismatic yellow-red which springs directly from the yellow, we hardly -recognise the yellow.</p> - -<p class="para"><a id="a701">701.</a></p> - -<p>This deepening takes place again by means of colourless -semi-transparent mediums, and here we see the effect in its utmost -purity and extent. Transparent fluids, coloured with any given hues, in -a series of glass-vessels, exhibit it very strikingly. The augmentation -is unremittingly rapid and constant; it is universal, and obtains in -physiological as well as in physical and chemical colours.</p> - -<hr class="tb" /> -<h5>JUNCTION OF THE TWO AUGMENTED EXTREMES.</h5> - - -<p class="para"><a id="a702">702.</a></p> - -<p>As the extremes of the simple contrast produce a beautiful and -agreeable appearance by their union, so the deepened extremes on being -united, will present a still more fascinating colour; indeed, it might -naturally be expected that we should here find the acme of the whole -phenomenon.</p> - -<p><span class="pagenum"><a name="Page_279" id="Page_279">[Pg 279]</a></span></p> -<hr class="tb" /> -<h5>COMPLETENESS THE RESULT OF VARIETY.</h5> - - -<p class="para"><a id="a703">703.</a></p> - -<p>And such is the fact, for pure red appears; a colour to which, from its -excellence, we have appropriated the term "purpur."<a name="FNanchor_2_53" id="FNanchor_2_53"></a><a href="#Footnote_2_53" class="fnanchor">[2]</a></p> - -<p class="para"><a id="a704">704.</a></p> - -<p>There are various modes in which pure red may appear. By bringing -together the violet edge and yellow-red border in prismatic -experiments, by continued augmentation in chemical operations, and by -the organic contrast in physiological effects.</p> - -<p class="para"><a id="a705">705.</a></p> - -<p>As a pigment it cannot be produced by intermixture or union, but -only by arresting the hue in substances chemically acted on, at the -high culminating point. Hence the painter is justified in assuming -that there are <i>three</i> primitive colours from which he combines all -the others. The natural philosopher, on the other hand, assumes only -<i>two</i> elementary colours, from which he, in like manner, developes and -combines the rest.</p> - -<hr class="tb" /> -<h5>COMPLETENESS THE RESULT OF VARIETY IN COLOUR.</h5> - - -<p class="para"><a id="a706">706.</a></p> - -<p>The various appearances of colour arrested in<span class="pagenum"><a name="Page_280" id="Page_280">[Pg 280]</a></span> their different degrees, -and seen in juxtaposition, produce a whole. This totality is harmony to -the eye.</p> - -<p class="para"><a id="a707">707.</a></p> - -<p>The chromatic circle has been gradually presented to us; the -various relations of its progression are apparent to us. Two pure -original principles in contrast, are the foundation of the whole; -an augmentation manifests itself by means of which both approach a -third state; hence there exists on both sides a lowest and highest, -a simplest and most qualified state. Again, two combinations present -themselves; first that of the simple primitive contrasts, then that of -the deepened contrasts.</p> - -<hr class="tb" /> -<h5>HARMONY OF THE COMPLETE STATE.</h5> - - -<p class="para"><a id="a708">708.</a></p> - -<p>The whole ingredients of the chromatic scale, seen in juxtaposition, -produce an harmonious impression on the eye. The difference between the -physical contrast and harmonious opposition in all its extent should -not be overlooked. The first resides in the pure restricted original -dualism, considered in its antagonizing elements; the other results -from the fully developed effects of the complete state.</p> - -<p class="para"><a id="a709">709.</a></p> - -<p>Every single opposition in order to be harmonious must comprehend the -whole. The<span class="pagenum"><a name="Page_281" id="Page_281">[Pg 281]</a></span> physiological experiments are sufficiently convincing -on this point. A development of all the possible contrasts of the -chromatic scale will be shortly given.<a name="FNanchor_3_54" id="FNanchor_3_54"></a><a href="#Footnote_3_54" class="fnanchor">[3]</a></p> - -<hr class="tb" /> -<h5>FACILITY WITH WHICH COLOUR MAY BE MADE TO TEND EITHER TO THE PLUS OR -MINUS SIDE.</h5> - - -<p class="para"><a id="a710">710.</a></p> - -<p>We have already had occasion to take notice of the mutability of colour -in considering its so-called augmentation and progressive variations -round the whole circle; but the hues even pass and repass from one side -to the other, rapidly and of necessity.</p> - -<p class="para"><a id="a711">711.</a></p> - -<p>Physiological colours are different in appearance as they happen -to fall on a dark or on a light ground. In physical colours the -combination of the objective and subjective experiments is very -remarkable. The epoptical colours, it appears, are contrasted according -as the light shines through or upon them. To what extent the chemical -colours may be changed by fire and alkalis, has been sufficiently shown -in its proper place.</p> - -<hr class="tb" /> -<h5>EVANESCENCE OF COLOUR.</h5> - - -<p class="para"><a id="a712">712.</a></p> - -<p>All that has been adverted to as subsequent<span class="pagenum"><a name="Page_282" id="Page_282">[Pg 282]</a></span> to the rapid excitation -and definition of colour, immixture, augmentation, combination, -separation, not forgetting the law of compensatory harmony, all takes -place with the greatest rapidity and facility; but with equal quickness -colour again altogether disappears.</p> - -<p class="para"><a id="a713">713.</a></p> - -<p>The physiological appearances are in no wise to be arrested; the -physical last only as long as the external condition lasts; even the -chemical colours have great mutability, they may be made to pass and -repass from one side to the other by means of opposite re-agents, and -may even be annihilated altogether.</p> - -<hr class="tb" /> -<h5>PERMANENCE OF COLOUR.</h5> - - -<p class="para"><a id="a714">714.</a></p> - -<p>The chemical colours afford evidence of very great duration. Colours -fixed in glass by fusion, and by nature in gems, defy all time and -re-action.</p> - -<p class="para"><a id="a715">715.</a></p> - -<p>The art of dyeing again fixes colour very powerfully. The hues of -pigments which might otherwise be easily rendered mutable by re-agents, -may be communicated to substances in the greatest permanency by means -of mordants.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_52" id="Footnote_1_52"></a><a href="#FNanchor_1_52"><span class="label">[1]</span></a> Wirkung, Beraubung; the last would be more literally -rendered <i>privation</i>. The author has already frequently made use of the -terms <i>active</i> and <i>passive</i> as equivalent to <i>plus</i> and <i>minus</i>.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_53" id="Footnote_2_53"></a><a href="#FNanchor_2_53"><span class="label">[2]</span></a> Wherever this word occurs incidentally it is translated -<i>pure red</i>, the English word <i>purple</i> being generally employed to -denote a colour similar to violet.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_54" id="Footnote_3_54"></a><a href="#FNanchor_3_54"><span class="label">[3]</span></a> No diagram or table of this kind was ever given by the -author.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_283" id="Page_283">[Pg 283]</a></span></p></div> - - - - -<h5><a name="PART_V" id="PART_V">PART V.</a></h5> - - -<h5>RELATION TO OTHER PURSUITS—RELATION TO PHILOSOPHY.</h5> - - -<p class="para"><a id="a716">716.</a></p> - -<p>The investigator of nature cannot be required to be a philosopher, -but it is expected that he should so far have attained the habit of -philosophizing, as to distinguish himself essentially from the world, -in order to associate himself with it again in a higher sense. He -should form to himself a method in accordance with observation, but -he should take heed not to reduce observation to mere notion, to -substitute words for this notion, and to use and deal with these words -as if they were things. He should be acquainted with the labours of -philosophers, in order to follow up the phenomena which have been the -subject of his observation, into the philosophic region.</p> - -<p class="para"><a id="a717">717.</a></p> - -<p>It cannot be required that the philosopher should be a naturalist, and -yet his co-operation in physical researches is as necessary as it is -desirable. He needs not an acquaintance with details for this, but only -a clear view of those conclusions where insulated facts meet.</p> - -<p><span class="pagenum"><a name="Page_284" id="Page_284">[Pg 284]</a></span></p> - -<p class="para"><a id="a718">718.</a></p> - -<p>We have before (<a href="#a175">175</a>) alluded to this important consideration, and -repeat it here where it is in its place. The worst that can happen -to physical science as well as to many other kinds of knowledge is, -that men should treat a secondary phenomenon as a primordial one, and -(since it is impossible to derive the original fact from the secondary -state), seek to explain what is in reality the cause by an effect made -to usurp its place. Hence arises an endless confusion, a mere verbiage, -a constant endeavour to seek and to find subterfuges whenever truth -presents itself and threatens to be overpowering.</p> - -<p class="para"><a id="a719">719.</a></p> - -<p>While the observer, the investigator of nature, is thus dissatisfied -in finding that the appearances he sees still contradict a received -theory, the philosopher can calmly continue to operate in his abstract -department on a false result, for no result is so false but that it can -be made to appear valid, as form without substance, by some means or -other.</p> - -<p class="para"><a id="a720">720.</a></p> - -<p>If, on the other hand, the investigator of nature can attain to the -knowledge of that which we have called a primordial phenomenon, he is -safe; and the philosopher with him. The investigator<span class="pagenum"><a name="Page_285" id="Page_285">[Pg 285]</a></span> of nature is -safe, since he is persuaded that he has here arrived at the limits -of his science, that he finds himself at the height of experimental -research; a height whence he can look back upon the details of -observation in all its steps, and forwards into, if he cannot enter, -the regions of theory. The philosopher is safe, for he receives -from the experimentalist an ultimate fact, which, in his hands, now -becomes an elementary one. He now justly pays little attention to -appearances which are understood to be secondary, whether he already -finds them scientifically arranged, or whether they present themselves -to his casual observation scattered and confused. Should he even be -inclined to go over this experimental ground himself, and not be -averse to examination in detail, he does this conveniently, instead of -lingering too long in the consideration of secondary and intermediate -circumstances, or hastily passing them over without becoming accurately -acquainted with them.</p> - -<p class="para"><a id="a721">721.</a></p> - -<p>To place the doctrine of colours nearer, in this sense, within the -philosopher's reach, was the author's wish; and although the execution -of his purpose, from various causes, does not correspond with his -intention, he will still keep this object in view in an intended -recapitulation,<span class="pagenum"><a name="Page_286" id="Page_286">[Pg 286]</a></span> as well as in the polemical and historical portions of -his work; for he will have to return to the consideration of this point -hereafter, on an occasion where it will be necessary to speak with less -reserve.</p> - -<hr class="tb" /> -<h5>RELATION TO MATHEMATICS.</h5> - - -<p class="para"><a id="a722">722.</a></p> - -<p>It may be expected that the investigator of nature, who proposes to -treat the science of natural philosophy in its entire range, should be -a mathematician. In the middle ages, mathematics was the chief organ by -means of which men hoped to master the secrets of nature, and even now, -geometry in certain departments of physics, is justly considered of -first importance.</p> - -<p class="para"><a id="a723">723.</a></p> - -<p>The author can boast of no attainments of this kind, and on this -account confines himself to departments of science which are -independent of geometry; departments which in modern times have been -opened up far and wide.</p> - -<p class="para"><a id="a724">724.</a></p> - -<p>It will be universally allowed that mathematics, one of the noblest -auxiliaries which can be employed by man, has, in one point of view, -been of the greatest use to the physical sciences; but that, by a -false application of its methods,<span class="pagenum"><a name="Page_287" id="Page_287">[Pg 287]</a></span> it has, in many respects, been -prejudicial to them, is also not to be denied; we find it here and -there reluctantly admitted.</p> - -<p class="para"><a id="a725">725.</a></p> - -<p>The theory of colours, in particular, has suffered much, and its -progress has been incalculably retarded by having been mixed up with -optics generally, a science which cannot dispense with mathematics; -whereas the theory of colours, in strictness, may be investigated quite -independently of optics.</p> - -<p class="para"><a id="a726">726.</a></p> - -<p>But besides this there was an additional evil. A great mathematician -was possessed with an entirely false notion on the physical origin of -colours; yet, owing to his great authority as a geometer, the mistakes -which he committed as an experimentalist long became sanctioned in the -eyes of a world ever fettered in prejudices.</p> - -<p class="para"><a id="a727">727.</a></p> - -<p>The author of the present inquiry has endeavoured throughout to keep -the theory of colours distinct from the mathematics, although there -are evidently certain points where the assistance of geometry would be -desirable. Had not the unprejudiced mathematicians, with whom he has -had, or still has, the good fortune to be acquainted,<span class="pagenum"><a name="Page_288" id="Page_288">[Pg 288]</a></span> been prevented -by other occupations from making common cause with him, his work would -not have wanted some merit in this respect. But this very want may be -in the end advantageous, since it may now become the object of the -enlightened mathematician to ascertain where the doctrine of colours is -in need of his aid, and how he can contribute the means at his command -with a view to the complete elucidation of this branch of physics.</p> - -<p class="para"><a id="a728">728.</a></p> - -<p>In general it were to be wished that the Germans, who render such -good service to science, while they adopt all that is good from other -nations, could by degrees accustom themselves to work in concert. We -live, it must be confessed, in an age, the habits of which are directly -opposed to such a wish. Every one seeks, not only to be original in -his views, but to be independent of the labours of others, or at least -to persuade himself that he is so, even in the course of his life -and occupation. It is very often remarked that men who undoubtedly -have accomplished much, quote themselves only, their own writings, -journals, and compendiums; whereas it would be far more advantageous -for the individual, and for the world, if many were devoted to a common -pursuit. The conduct of our neighbours the French is, in this respect, -worthy<span class="pagenum"><a name="Page_289" id="Page_289">[Pg 289]</a></span> of imitation; we have a pleasing instance in Cuvier's preface -to his "Tableau Élémentaire de l'Histoire Naturelle des Animaux."</p> - -<p class="para"><a id="a729">729.</a></p> - -<p>He who has observed science and its progress with an unprejudiced eye, -might even ask whether it is desirable that so many occupations and -aims, though allied to each other, should be united in one person, and -whether it would not be more suitable for the limited powers of the -human mind to distinguish, for example, the investigator and inventor, -from him who employs and applies the result of experiment? Astronomers, -who devote themselves to the observation of the heavens and the -discovery or enumeration of stars, have in modern times formed, to a -certain extent, a distinct class from those who calculate the orbits, -consider the universe in its connexion, and more accurately define its -laws. The history of the doctrine of colours will often lead us back to -these considerations.</p> - -<hr class="tb" /> -<h5>RELATION TO THE TECHNICAL OPERATIONS OF THE DYER.</h5> - - -<p class="para"><a id="a730">730.</a></p> - -<p>If in our labours we have gone out of the province of the -mathematician, we have, on the other hand, endeavoured to meet the -practical<span class="pagenum"><a name="Page_290" id="Page_290">[Pg 290]</a></span> views of the dyer; and although the chapter which treats -of colour in a chemical point of view is not the most complete and -circumstantial, yet in that portion, as well as in our general -observations respecting colour, the dyer will find his views assisted -far more than by the theory hitherto in vogue, which failed to afford -him any assistance.</p> - -<p class="para"><a id="a731">731.</a></p> - -<p>It is curious, in this view, to take a glance at the works containing -directions on the art of dyeing. As the Catholic, on entering his -temple, sprinkles himself with holy water, and after bending the knee, -proceeds perhaps to converse with his friends on his affairs, without -any especial devotion; so all the treatises on dyeing begin with a -respectful allusion to the accredited theory, without afterwards -exhibiting a single trace of any principle deduced from this theory, -or showing that it has thrown light on any part of the art, or that it -offers any useful hints in furtherance of practical methods.</p> - -<p class="para"><a id="a732">732.</a></p> - -<p>On the other hand, there are men who, after having become thoroughly -and experimentally acquainted with the nature of dyes, have not been -able to reconcile their observations with the received theory; who -have, in short, discovered<span class="pagenum"><a name="Page_291" id="Page_291">[Pg 291]</a></span> its weak points, and sought for a general -view more consonant to nature and experience. When we come to the names -of Castel and Gülich, in our historical review, we shall have occasion -to enter into this more fully, and an opportunity will then present -itself to show that an assiduous experience in taking advantage of -every accident may, in fact, be said almost to exhaust the knowledge -of the province to which it is confined. The high and complete result -is then submitted to the theorist, who, if he examines facts with -accuracy, and reasons with candour, will find such materials eminently -useful as a basis for his conclusions.—<a href="#NOTE_AA">Note AA</a>.</p> - -<hr class="tb" /> -<h5>RELATION TO PHYSIOLOGY AND PATHOLOGY.</h5> - - -<p class="para"><a id="a733">733.</a></p> - -<p>If the phenomena adduced in the chapter where colours were considered -in a physiological and pathological view are for the most part -generally known, still some new views, mixed up with them, will not be -unacceptable to the physiologist. We especially hope to have given him -cause to be satisfied by classing certain phenomena which stood alone, -under analogous facts, and thus, in some measure, to have prepared the -way for his further investigations.</p> - -<p class="para"><a id="a734">734.</a></p> - -<p>The appendix on pathological colours, again,<span class="pagenum"><a name="Page_292" id="Page_292">[Pg 292]</a></span> is admitted to be scanty -and unconnected. We reflect, however, that Germany can boast of men who -are not only highly experienced in this department, but are likewise so -distinguished for general cultivation, that it can cost them but little -to revise this portion, to complete what has been sketched, and at the -same time to connect it with the higher facts of organisation.</p> - -<hr class="tb" /> -<h5>RELATION TO NATURAL HISTORY.</h5> - - -<p class="para"><a id="a735">735.</a></p> - -<p>If we may at all hope that natural history will gradually be modified -by the principle of deducing the ordinary appearances of nature from -higher phenomena, the author believes he may have given some hints -and introductory views bearing on this object also. As colour, in its -infinite variety, exhibits itself on the surface of living beings, it -becomes an important part of the outward indications, by means of which -we can discover what passes underneath.</p> - -<p class="para"><a id="a736">736.</a></p> - -<p>In one point of view it is certainly not to be too much relied on, on -account of its indefinite and mutable nature; yet even this mutability, -inasmuch as it exhibits itself as a constant quality, again becomes -a criterion of a mutable vitality; and the author wishes nothing -more<span class="pagenum"><a name="Page_293" id="Page_293">[Pg 293]</a></span> than that time may be granted him to develop the results of his -observations on this subject more fully; here they would not be in -their place.</p> - -<hr class="tb" /> -<h5>RELATION TO GENERAL PHYSICS.</h5> - - -<p class="para"><a id="a737">737.</a></p> - -<p>The state in which general physics now is, appears, again, particularly -favourable to our labours; for natural philosophy, owing to -indefatigable and variously directed research, has gradually attained -such eminence, that it appears not impossible to refer a boundless -empiricism to one centre.</p> - -<p class="para"><a id="a738">738.</a></p> - -<p>Without referring to subjects which are too far removed from our own -province, we observe that the formulæ under which the elementary -appearances of nature are expressed, altogether tend in this direction; -and it is easy to see that through this correspondence of expression, a -correspondence in meaning will necessarily be soon arrived at.</p> - -<p class="para"><a id="a739">739.</a></p> - -<p>True observers of nature, however they may differ in opinion in other -respects, will agree that all which presents itself as appearance, all -that we meet with as phenomenon, must either<span class="pagenum"><a name="Page_294" id="Page_294">[Pg 294]</a></span> indicate an original -division which is capable of union, or an original unity which admits -of division, and that the phenomenon will present itself accordingly. -To divide the united, to unite the divided, is the life of nature; -this is the eternal systole and diastole, the eternal collapsion and -expansion, the inspiration and expiration of the world in which we live -and move.</p> - -<p class="para"><a id="a740">740.</a></p> - -<p>It is hardly necessary to observe that what we here express as number -and restrict to dualism is to be understood in a higher sense; the -appearance of a third, a fourth order of facts progressively developing -themselves is to be similarly understood; but actual observation -should, above all, be the basis of all these expressions.</p> - -<p class="para"><a id="a741">741.</a></p> - -<p>Iron is known to us as a peculiar substance, different from other -substances: in its ordinary state we look upon it as a mere material -remarkable only on account of its fitness for various uses and -applications. How little, however, is necessary to do away with the -comparative insignificancy of this substance. A two-fold power is -called forth,<a name="FNanchor_1_55" id="FNanchor_1_55"></a><a href="#Footnote_1_55" class="fnanchor">[1]</a> which, while it tends again to a<span class="pagenum"><a name="Page_295" id="Page_295">[Pg 295]</a></span> state of union, and, -as it were, seeks itself, acquires a kind of magical relation with -its like, and propagates this double property, which is in fact but a -principle of reunion, throughout all bodies of the same kind. We here -first observe the mere substance, iron; we see the division that takes -place in it propagate itself and disappear, and again easily become -re-excited. This, according to our mode of thinking, is a primordial -phenomenon in immediate relation with its idea, and which acknowledges -nothing earthly beyond it.</p> - -<p class="para"><a id="a742">742.</a></p> - -<p>Electricity is again peculiarly characterised. As a mere quality we are -unacquainted with it; for us it is a nothing, a zero, a mere point, -which, however, dwells in all apparent existences, and at the same time -is the point of origin whence, on the slightest stimulus, a double -appearance presents itself, an appearance which only manifests itself -to vanish. The conditions under which this manifestation is excited -are infinitely varied, according to the nature of particular bodies. -From the rudest mechanical friction of very different substances with -one another, to the mere contiguity of two entirely similar bodies, -the phenomenon is present and stirring, nay, striking and powerful, -and so decided and specific, that when we employ the terms or formulæ<span class="pagenum"><a name="Page_296" id="Page_296">[Pg 296]</a></span> -polarity, plus and minus, for north and south, for glass and resin, we -do so justifiably and in conformity with nature.</p> - -<p class="para"><a id="a743">743.</a></p> - -<p>This phenomenon, although it especially affects the surface, is yet by -no means superficial. It influences the tendency or determination of -material qualities, and connects itself in immediate co-operation with -the important double phenomenon which takes place so universally in -chemistry,—oxydation, and de-oxydation.</p> - -<p class="para"><a id="a744">744.</a></p> - -<p>To introduce and include the appearances of colour in this series, -this circle of phenomena was the object of our labours. What we have -not succeeded in others will accomplish. We found a primordial vast -contrast between light and darkness, which may be more generally -expressed by light and its absence. We looked for the intermediate -state, and sought by means of it to compose the visible world of light, -shade, and colour. In the prosecution of this we employed various terms -applicable to the development of the phenomena, terms which we adopted -from the theories of magnetism, of electricity, and of chemistry. It -was necessary, however, to extend this terminology, since we found -ourselves in an abstract region, and had to express more complicated -relations.</p> - -<p><span class="pagenum"><a name="Page_297" id="Page_297">[Pg 297]</a></span></p> - -<p class="para"><a id="a745">745.</a></p> - -<p>If electricity and galvanism, in their general character, are -distinguished as superior to the more limited exhibition of magnetic -phenomena, it may be said that colour, although coming under similar -laws, is still superior; for since it addresses itself to the noble -sense of vision, its perfections are more generally displayed. Compare -the varied effects which result from the augmentation of yellow and -blue to red, from the combination of these two higher extremes to pure -red, and the union of the two inferior extremes to green. What a far -more varied scheme is apparent here than that in which magnetism and -electricity are comprehended. These last phenomena may be said to be -inferior again on another account; for though they penetrate and give -life to the universe, they cannot address themselves to man in a higher -sense in order to his employing them æsthetically. The general, simple, -physical law must first be elevated and diversified itself in order to -be available for elevated uses.</p> - -<p class="para"><a id="a746">746.</a></p> - -<p>If the reader, in this spirit, recalls what has been stated by us -throughout, generally and in detail, with regard to colour, he will -himself pursue and unfold what has been here only lightly hinted at. -He will augur well for<span class="pagenum"><a name="Page_298" id="Page_298">[Pg 298]</a></span> science, technical processes, and art, if it -should prove possible to rescue the attractive subject of the doctrine -of colours from the atomic restriction and isolation in which it has -been banished, in order to restore it to the general dynamic flow of -life and action which the present age loves to recognise in nature. -These considerations will press upon us more strongly when, in the -historical portion, we shall have to speak of many an enterprising -and intelligent man who failed to possess his contemporaries with his -convictions.</p> - -<hr class="tb" /> -<h5>RELATION TO THE THEORY OF MUSIC.</h5> - - -<p class="para"><a id="a747">747.</a></p> - -<p>Before we proceed to the moral associations of colour, and the æsthetic -influences arising from them, we have here to say a few words on its -relation to melody. That a certain relation exists between the two, -has been always felt; this is proved by the frequent comparisons we -meet with, sometimes as passing allusions, sometimes as circumstantial -parallels. The error which writers have fallen into in trying to -establish this analogy we would thus define:</p> - -<p class="para"><a id="a748">748.</a></p> - -<p>Colour and sound do not admit of being directly compared together -in any way, but both are referable to a higher formula, both are -derivable,<span class="pagenum"><a name="Page_299" id="Page_299">[Pg 299]</a></span> although each for itself, from this higher law. They are -like two rivers which have their source in one and the same mountain, -but subsequently pursue their way under totally different conditions -in two totally different regions, so that throughout the whole course -of both no two points can be compared. Both are general, elementary -effects acting according to the general law of separation and tendency -to union, of undulation and oscillation, yet acting thus in wholly -different provinces, in different modes, on different elementary -mediums, for different senses.—<a href="#NOTE_BB">Note BB</a>.</p> - -<p class="para"><a id="a749">749.</a></p> - -<p>Could some investigator rightly adopt the method in which we have -connected the doctrine of colours with natural philosophy generally, -and happily supply what has escaped or been missed by us, the theory -of sound, we are persuaded, might be perfectly connected with general -physics: at present it stands, as it were, isolated within the circle -of science.</p> - -<p class="para"><a id="a750">750.</a></p> - -<p>It is true it would be an undertaking of the greatest difficulty -to do away with the positive character which we are now accustomed -to attribute to music—a character resulting from the achievements -of practical skill, from accidental,<span class="pagenum"><a name="Page_300" id="Page_300">[Pg 300]</a></span> mathematical, æsthetical -influences—and to substitute for all this a merely physical inquiry -tending to resolve the science into its first elements. Yet considering -the point at which science and art are now arrived, considering the -many excellent preparatory investigations that have been made relative -to this subject, we may perhaps still see it accomplished.</p> - -<hr class="tb" /> -<h5>CONCLUDING OBSERVATIONS ON TERMINOLOGY.</h5> - - -<p class="para"><a id="a751">751.</a></p> - -<p>We never sufficiently reflect that a language, strictly speaking, can -only be symbolical and figurative, that it can never express things -directly, but only, as it were, reflectedly. This is especially the -case in speaking of qualities which are only imperfectly presented -to observation, which might rather be called powers than objects, -and which are ever in movement throughout nature. They are not to be -arrested, and yet we find it necessary to describe them; hence we look -for all kinds of formulæ in order, figuratively at least, to define -them.</p> - -<p class="para"><a id="a752">752.</a></p> - -<p>Metaphysical formulæ have breadth as well as depth, but on this -very account they require a corresponding import; the danger -here is vagueness. Mathematical expressions may in many cases be -very conveniently and happily<span class="pagenum"><a name="Page_301" id="Page_301">[Pg 301]</a></span> employed, but there is always an -inflexibility in them, and we presently feel their inadequacy; for even -in elementary cases we are very soon conscious of an incommensurable -idea; they are, besides, only intelligible to those who are especially -conversant in the sciences to which such formulæ are appropriated. The -terms of the science of mechanics are more addressed to the ordinary -mind, but they are ordinary in other senses, and always have something -unpolished; they destroy the inward life to offer from without an -insufficient substitute for it. The formulæ of the corpuscular theories -are nearly allied to the last; through them the mutable becomes rigid, -description and expression uncouth: while, again, moral terms, which -undoubtedly can express nicer relations, have the effect of mere -symbols in the end, and are in danger of being lost in a play of wit.</p> - -<p class="para"><a id="a753">753.</a></p> - -<p>If, however, a writer could use all these modes of description and -expression with perfect command, and thus give forth the result of his -observations on the phenomena of nature in a diversified language; -if he could preserve himself from predilections, still embodying a -lively meaning in as animated an expression, we might look for much -instruction communicated in the most agreeable of forms.</p> - -<p><span class="pagenum"><a name="Page_302" id="Page_302">[Pg 302]</a></span></p> - -<p class="para"><a id="a754">754.</a></p> - -<p>Yet, how difficult it is to avoid substituting the sign for the thing; -how difficult to keep the essential quality still living before us, -and not to kill it with the word. With all this, we are exposed in -modern times to a still greater danger by adopting expressions and -terminologies from all branches of knowledge and science to embody our -views of simple nature. Astronomy, cosmology, geology, natural history, -nay religion and mysticism, are called in in aid; and how often do -we not find a general idea and an elementary state rather hidden and -obscured than elucidated and brought nearer to us by the employment of -terms, the application of which is strictly specific and secondary. -We are quite aware of the necessity which led to the introduction and -general adoption of such a language, we also know that it has become in -a certain sense indispensable; but it is only a moderate, unpretending -recourse to it, with an internal conviction of its fitness, that can -recommend it.</p> - -<p class="para"><a id="a755">755.</a></p> - -<p>After all, the most desirable principle would be that writers should -borrow the expressions employed to describe the details of a given -province of investigation from the province itself; treating the -simplest phenomenon as an elementary<span class="pagenum"><a name="Page_303" id="Page_303">[Pg 303]</a></span> formula, and deriving and -developing the more complicated designations from this.</p> - -<p class="para"><a id="a756">756.</a></p> - -<p>The necessity and suitableness of such a conventional language where -the elementary sign expresses the appearance itself, has been duly -appreciated by extending, for instance, the application of the term -polarity, which is borrowed from the magnet to electricity, &c. The -<i>plus</i> and <i>minus</i> which may be substituted for this, have found as -suitable an application to many phenomena; even the musician, probably -without troubling himself about these other departments, has been -naturally led to express the leading difference in the modes of melody -by <i>major</i> and <i>minor</i>.</p> - -<p class="para"><a id="a757">757.</a></p> - -<p>For ourselves we have long wished to introduce the term polarity into -the doctrine of colours; with what right and in what sense, the present -work may show. Perhaps we may hereafter find room to connect the -elementary phenomena together according to our mode, by a similar use -of symbolical terms, terms which must at all times convey the directly -corresponding idea; we shall thus render more explicit what has been -here only alluded to generally, and perhaps too vaguely expressed.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_55" id="Footnote_1_55"></a><a href="#FNanchor_1_55"><span class="label">[1]</span></a> Eine Entzweyung geht vor; literally, <i>a division takes -place</i>. According to some, the two magnetic powers are previously in -the bar, and are then separated at the ends.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_304" id="Page_304">[Pg 304]</a></span></p></div> - - - - -<h5><a name="PART_VI" id="PART_VI">PART VI.</a></h5> - - -<h5>EFFECT OF COLOUR WITH REFERENCE TO MORAL ASSOCIATIONS.</h5> - - -<p class="para"><a id="a758">758.</a></p> - -<p>Since colour occupies so important a place in the series of elementary -phenomena, filling as it does the limited circle assigned to it with -fullest variety, we shall not be surprised to find that its effects are -at all times decided and significant, and that they are immediately -associated with the emotions of the mind. We shall not be surprised -to find that these appearances presented singly, are specific, that -in combination they may produce an harmonious, characteristic, often -even an inharmonious effect on the eye, by means of which they act on -the mind; producing this impression in their most general elementary -character, without relation to the nature or form of the object on -whose surface they are apparent. Hence, colour considered as an element -of art, may be made subservient to the highest æsthetical ends.—<a href="#NOTE_CC">Note CC</a>.</p> - -<p class="para"><a id="a759">759.</a></p> - -<p>People experience a great delight in colour, generally. The eye -requires it as much as it requires light. We have only to remember -the<span class="pagenum"><a name="Page_305" id="Page_305">[Pg 305]</a></span> refreshing sensation we experience, if on a cloudy day the sun -illumines a single portion of the scene before us and displays its -colours. That healing powers were ascribed to coloured gems, may have -arisen from the experience of this indefinable pleasure.</p> - -<p class="para"><a id="a760">760.</a></p> - -<p>The colours which we see on objects are not qualities entirely -strange to the eye; the organ is not thus merely habituated to the -impression; no, it is always predisposed to produce colour of itself, -and experiences a sensation of delight if something analogous to its -own nature is offered to it from without; if its susceptibility is -distinctly determined towards a given state.</p> - -<p class="para"><a id="a761">761.</a></p> - -<p>From some of our earlier observations we can conclude, that general -impressions produced by single colours cannot be changed, that they act -specifically, and must produce definite, specific states in the living -organ.</p> - -<p class="para"><a id="a762">762.</a></p> - -<p>They likewise produce a corresponding influence on the mind. Experience -teaches us that particular colours excite particular states of feeling. -It is related of a witty Frenchman, "Il prétendoit que son ton de -conversation avec<span class="pagenum"><a name="Page_306" id="Page_306">[Pg 306]</a></span> Madame étoit changé depuis qu'elle avoit changé en -cramoisi le meuble de son cabinet, qui étoit bleu."</p> - -<p class="para"><a id="a763">763.</a></p> - -<p>In order to experience these influences completely, the eye should be -entirely surrounded with one colour; we should be in a room of one -colour, or look through a coloured glass. We are then identified with -the hue, it attunes the eye and mind in mere unison with itself.</p> - -<p class="para"><a id="a764">764.</a></p> - -<p>The colours on the <i>plus</i> side are yellow, red-yellow (orange), -yellow-red (minium, cinnabar). The feelings they excite are quick, -lively, aspiring.</p> - -<hr class="r5" /> -<h5>YELLOW.</h5> - - -<p class="para"><a id="a765">765.</a></p> - -<p>This is the colour nearest the light. It appears on the slightest -mitigation of light, whether by semi-transparent mediums or faint -reflection from white surfaces. In prismatic experiments it extends -itself alone and widely in the light space, and while the two poles -remain separated from each other, before it mixes with blue to -produce green it is to be seen in its utmost purity and beauty. How -the chemical yellow developes itself in and upon the white, has been -circumstantially described in its proper place.</p> - -<p><span class="pagenum"><a name="Page_307" id="Page_307">[Pg 307]</a></span></p> - -<p class="para"><a id="a766">766.</a></p> - -<p>In its highest purity it always carries with it the nature of -brightness, and has a serene, gay, softly exciting character.</p> - -<p class="para"><a id="a767">767.</a></p> - -<p>In this state, applied to dress, hangings, carpeting, &c., it is -agreeable. Gold in its perfectly unmixed state, especially when the -effect of polish is superadded, gives us a new and high idea of this -colour; in like manner, a strong yellow, as it appears on satin, has a -magnificent and noble effect.</p> - -<p class="para"><a id="a768">768.</a></p> - -<p>We find from experience, again, that yellow excites a warm and -agreeable impression. Hence in painting it belongs to the illumined and -emphatic side.</p> - -<p class="para"><a id="a769">769.</a></p> - -<p>This impression of warmth may be experienced in a very lively manner if -we look at a landscape through a yellow glass, particularly on a grey -winter's day. The eye is gladdened, the heart expanded and cheered, a -glow seems at once to breathe towards us.</p> - -<p class="para"><a id="a770">770.</a></p> - -<p>If, however, this colour in its pure and bright<span class="pagenum"><a name="Page_308" id="Page_308">[Pg 308]</a></span> state is agreeable -and gladdening, and in its utmost power is serene and noble, it is, on -the other hand, extremely liable to contamination, and produces a very -disagreeable effect if it is sullied, or in some degree tends to the -<i>minus</i> side. Thus, the colour of sulphur, which inclines to green, has -a something unpleasant in it.</p> - -<p class="para"><a id="a771">771.</a></p> - -<p>When a yellow colour is communicated to dull and coarse surfaces, -such as common cloth, felt, or the like, on which it does not appear -with full energy, the disagreeable effect alluded to is apparent. By -a slight and scarcely perceptible change, the beautiful impression -of fire and gold is transformed into one not undeserving the epithet -foul; and the colour of honour and joy reversed to that of ignominy -and aversion. To this impression the yellow hats of bankrupts and the -yellow circles on the mantles of Jews, may have owed their origin.</p> - -<hr class="r5" /> -<h5>RED-YELLOW.</h5> - - -<p class="para"><a id="a772">772.</a></p> - -<p>As no colour can be considered as stationary, so we can very easily -augment yellow into reddish by condensing or darkening it. The colour -increases in energy, and appears in red-yellow more powerful and -splendid.</p> - -<p><span class="pagenum"><a name="Page_309" id="Page_309">[Pg 309]</a></span></p> - -<p class="para"><a id="a773">773.</a></p> - -<p>All that we have said of yellow is applicable here in a higher -degree. The red-yellow gives an impression of warmth and gladness, -since it represents the hue of the intenser glow of fire, and of the -milder radiance of the setting sun. Hence it is agreeable around us, -and again, as clothing, in greater or less degrees is cheerful and -magnificent. A slight tendency to red immediately gives a new character -to yellow, and while the English and Germans content themselves -with bright pale yellow colours in leather, the French, as Castel -has remarked, prefer a yellow enhanced to red; indeed, in general, -everything in colour is agreeable to them which belongs to the active -side.</p> - -<hr class="r5" /> -<h5>YELLOW-RED.</h5> - - -<p class="para"><a id="a774">774.</a></p> - -<p>As pure yellow passes very easily to red-yellow, so the deepening of -this last to yellow-red is not to be arrested. The agreeable, cheerful -sensation which red-yellow excites, increases to an intolerably -powerful impression in bright yellow-red.</p> - -<p class="para"><a id="a775">775.</a></p> - -<p>The active side is here in its highest energy, and it is not to -be wondered at that impetuous, robust, uneducated men, should be -especially<span class="pagenum"><a name="Page_310" id="Page_310">[Pg 310]</a></span> pleased with this colour. Among savage nations the -inclination for it has been universally remarked, and when children, -left to themselves, begin to use tints, they never spare vermilion and -minium.</p> - -<p class="para"><a id="a776">776.</a></p> - -<p>In looking steadfastly at a perfectly yellow-red surface, the colour -seems actually to penetrate the organ. It produces an extreme -excitement, and still acts thus when somewhat darkened. A yellow-red -cloth disturbs and enrages animals. I have known men of education to -whom its effect was intolerable if they chanced to see a person dressed -in a scarlet cloak on a grey, cloudy day.</p> - -<p class="para"><a id="a777">777.</a></p> - -<p>The colours on the <i>minus</i> side are blue, red-blue, and blue-red. They -produce a restless, susceptible, anxious impression.</p> - -<hr class="r5" /> -<h5>BLUE.</h5> - - -<p class="para"><a id="a778">778.</a></p> - -<p>As yellow is always accompanied with light, so it may be said that blue -still brings a principle of darkness with it.</p> - -<p class="para"><a id="a779">779.</a></p> - -<p>This colour has a peculiar and almost indescribable<span class="pagenum"><a name="Page_311" id="Page_311">[Pg 311]</a></span> effect on the eye. -As a hue it is powerful, but it is on the negative side, and in its -highest purity is, as it were, a stimulating negation. Its appearance, -then, is a kind of contradiction between excitement and repose.</p> - -<p class="para"><a id="a780">780.</a></p> - -<p>As the upper sky and distant mountains appear blue, so a blue surface -seems to retire from us.</p> - -<p class="para"><a id="a781">781.</a></p> - -<p>But as we readily follow an agreeable object that flies from us, so we -love to contemplate blue, not because it advances to us, but because it -draws us after it.</p> - -<p class="para"><a id="a782">782.</a></p> - -<p>Blue gives us an impression of cold, and thus, again, reminds us of -shade. We have before spoken of its affinity with black.</p> - -<p class="para"><a id="a783">783.</a></p> - -<p>Rooms which are hung with pure blue, appear in some degree larger, but -at the same time empty and cold.</p> - -<p class="para"><a id="a784">784.</a></p> - -<p>The appearance of objects seen through a blue glass is gloomy and -melancholy.</p> - -<p><span class="pagenum"><a name="Page_312" id="Page_312">[Pg 312]</a></span></p> - -<p class="para"><a id="a785">785.</a></p> - -<p>When blue partakes in some degree of the <i>plus</i> side, the effect is not -disagreeable. Sea-green is rather a pleasing colour.</p> - -<hr class="r5" /> -<h5>RED-BLUE.</h5> - - -<p class="para"><a id="a786">786.</a></p> - -<p>We found yellow very soon tending to the intense state, and we observe -the same progression in blue.</p> - -<p class="para"><a id="a787">787.</a></p> - -<p>Blue deepens very mildly into red, and thus acquires a somewhat active -character, although it is on the passive side. Its exciting power is, -however, of a very different kind from that of the red-yellow. It may -be said to disturb rather than enliven.</p> - -<p class="para"><a id="a788">788.</a></p> - -<p>As augmentation itself is not to be arrested, so we feel an inclination -to follow the progress of the colour, not, however, as in the case of -the red-yellow, to see it still increase in the active sense, but to -find a point to rest in.</p> - -<p class="para"><a id="a789">789.</a></p> - -<p>In a very attenuated state, this colour is known to us under the name -of lilac; but even in this degree it has a something lively without -gladness.</p> - -<p><span class="pagenum"><a name="Page_313" id="Page_313">[Pg 313]</a></span></p> - -<p class="para"><a id="a790">790.</a></p> - -<p>This unquiet feeling increases as the hue progresses, and it may be -safely assumed, that a carpet of a perfectly pure deep blue-red would -be intolerable. On this account, when it is used for dress, ribbons, or -other ornaments, it is employed in a very attenuated and light state, -and thus displays its character as above defined, in a peculiarly -attractive manner.</p> - -<p class="para"><a id="a791">791.</a></p> - -<p>As the higher dignitaries of the church have appropriated this unquiet -colour to themselves, we may venture to say that it unceasingly aspires -to the cardinal's red through the restless degrees of a still impatient -progression.</p> - -<hr class="r5" /> -<h5>RED.</h5> - - -<p class="para"><a id="a792">792.</a></p> - -<p>We are here to forget everything that borders on yellow or blue. We -are to imagine an absolutely pure red, like fine carmine suffered to -dry on white porcelain. We have called this colour "purpur" by way -of distinction, although we are quite aware that the purple of the -ancients inclined more to blue.</p> - -<p class="para"><a id="a793">793.</a></p> - -<p>Whoever is acquainted with the prismatic<span class="pagenum"><a name="Page_314" id="Page_314">[Pg 314]</a></span> origin of red, will not think -it paradoxical if we assert that this colour partly <i>actu</i>, partly -<i>potentiâ</i>, includes all the other colours.</p> - -<p class="para"><a id="a794">794.</a></p> - -<p>We have remarked a constant progress or augmentation in yellow and -blue, and seen what impressions were produced by the various states; -hence it may naturally be inferred that now, in the junction of the -deepened extremes, a feeling of satisfaction must succeed; and thus, in -physical phenomena, this highest of all appearances of colour arises -from the junction of two contrasted extremes which have gradually -prepared themselves for a union.</p> - -<p class="para"><a id="a795">795.</a></p> - -<p>As a pigment, on the other hand, it presents itself to us already -formed, and is most perfect as a hue in cochineal; a substance which, -however, by chemical action may be made to tend to the <i>plus</i> or the -<i>minus</i> side, and may be considered to have attained the central point -in the best carmine.</p> - -<p class="para"><a id="a796">796.</a></p> - -<p>The effect of this colour is as peculiar as its nature. It conveys an -impression of gravity and dignity, and at the same time of grace and -attractiveness. The first in its dark deep state,<span class="pagenum"><a name="Page_315" id="Page_315">[Pg 315]</a></span> the latter in its -light attenuated tint; and thus the dignity of age and the amiableness -of youth may adorn itself with degrees of the same hue.</p> - -<p class="para"><a id="a797">797.</a></p> - -<p>History relates many instances of the jealousy of sovereigns with -regard to the quality of red. Surrounding accompaniments of this colour -have always a grave and magnificent effect.</p> - -<p class="para"><a id="a798">798.</a></p> - -<p>The red glass exhibits a bright landscape in so dreadful a hue as to -inspire sentiments of awe.</p> - -<p class="para"><a id="a799">799.</a></p> - -<p>Kermes and cochineal, the two materials chiefly employed in dyeing to -produce this colour, incline more or less to the <i>plus</i> or <i>minus</i> -state, and may be made to pass and repass the culminating point by -the action of acids and alkalis: it is to be observed that the French -arrest their operations on the active side, as is proved by the French -scarlet, which inclines to yellow. The Italians, on the other hand, -remain on the passive side, for their scarlet has a tinge of blue.</p> - -<p class="para"><a id="a800">800.</a></p> - -<p>By means of a similar alkaline treatment, the so-called crimson is -produced; a colour which the French must be particularly prejudiced<span class="pagenum"><a name="Page_316" id="Page_316">[Pg 316]</a></span> -against, since they employ the expressions—"Sot en cramoisi, méchant -en cramoisi," to mark the extreme of the silly and the reprehensible.</p> - -<hr class="r5" /> -<h5>GREEN.</h5> - - -<p class="para"><a id="a801">801.</a></p> - -<p>If yellow and blue, which we consider as the most fundamental and -simple colours, are united as they first appear, in the first state of -their action, the colour which we call green is the result.</p> - -<p class="para"><a id="a802">802.</a></p> - -<p>The eye experiences a distinctly grateful impression from this colour. -If the two elementary colours are mixed in perfect equality so that -neither predominates, the eye and the mind repose on the result of this -junction as upon a simple colour. The beholder has neither the wish -nor the power to imagine a state beyond it. Hence for rooms to live in -constantly, the green colour is most generally selected.</p> - -<hr class="r5" /> -<h5>COMPLETENESS AND HARMONY.</h5> - - -<p class="para"><a id="a803">803.</a></p> - -<p>We have hitherto assumed, for the sake of clearer explanation, that the -eye can be compelled to assimilate or identify itself with a single -colour; but this can only be possible for an instant.</p> - -<p><span class="pagenum"><a name="Page_317" id="Page_317">[Pg 317]</a></span></p> - -<p class="para"><a id="a804">804.</a></p> - -<p>For when we find ourselves surrounded by a given colour which excites -its corresponding sensation on the eye, and compels us by its presence -to remain in a state identical with it, this state is soon found to be -forced, and the organ unwillingly remains in it.</p> - -<p class="para"><a id="a805">805.</a></p> - -<p>When the eye sees a colour it is immediately excited, and it is its -nature, spontaneously and of necessity, at once to produce another, -which with the original colour comprehends the whole chromatic scale. -A single colour excites, by a specific sensation, the tendency to -universality.</p> - -<p class="para"><a id="a806">806.</a></p> - -<p>To experience this completeness, to satisfy itself, the eye seeks for -a colourless space next every hue in order to produce the complemental -hue upon it.</p> - -<p class="para"><a id="a807">807.</a></p> - -<p>In this resides the fundamental law of all harmony of colours, of which -every one may convince himself by making himself accurately acquainted -with the experiments which we have described in the chapter on the -physiological colours.</p> - -<p><span class="pagenum"><a name="Page_318" id="Page_318">[Pg 318]</a></span></p> - -<p class="para"><a id="a808">808.</a></p> - -<p>If, again, the entire scale is presented to the eye externally, the -impression is gladdening, since the result of its own operation is -presented to it in reality. We turn our attention therefore, in the -first place, to this harmonious juxtaposition.</p> - -<p class="para"><a id="a809">809.</a></p> - -<p>As a very simple means of comprehending the principle of this, the -reader has only to imagine a moveable diametrical index in the -colorific circle.<a name="FNanchor_1_56" id="FNanchor_1_56"></a><a href="#Footnote_1_56" class="fnanchor">[1]</a> The index, as it revolves round the whole circle, -indicates at its two extremes the complemental colours, which, after -all, may be reduced to three contrasts.</p> - -<p class="para"><a id="a810">810.</a></p> - -<p style="margin-left: 10%;"> -Yellow demands Red-blue,<br /> -Blue demands Red-yellow,<br /> -Red demands Green,<br /> -and contrariwise.<br /> -</p> - -<p class="para"><a id="a811">811.</a></p> - -<p>In proportion as one end of the supposed index deviates from the -central intensity of the colours, arranged as they are in the natural -order, so the opposite end changes its place in the contrasted -gradation, and by such a simple<span class="pagenum"><a name="Page_319" id="Page_319">[Pg 319]</a></span> contrivance the complemental colours -may be indicated at any given point. A chromatic circle might be made -for this purpose, not confined, like our own, to the leading colours, -but exhibiting them with their transitions in an unbroken series. -This would not be without its use, for we are here considering a very -important point which deserves all our attention.<a name="FNanchor_2_57" id="FNanchor_2_57"></a><a href="#Footnote_2_57" class="fnanchor">[2]</a></p> - -<p class="para"><a id="a812">812.</a></p> - -<p>We before stated that the eye could be in some degree pathologically -affected by being long confined to a single colour; that, again, -definite moral impressions were thus produced, at one time lively and -aspiring, at another susceptible and anxious—now exalted to grand -associations, now reduced to ordinary ones. We now observe that the -demand for completeness, which is inherent in the organ, frees us from -this restraint; the eye relieves itself by producing the opposite -of the single colour forced upon it, and thus attains the entire -impression which is so satisfactory to it.</p> - -<p class="para"><a id="a813">813.</a></p> - -<p>Simple, therefore, as these strictly harmonious contrasts are, as -presented to us in the narrow circle, the hint is important, that -nature tends to emancipate the sense from confined<span class="pagenum"><a name="Page_320" id="Page_320">[Pg 320]</a></span> impressions by -suggesting and producing the whole, and that in this instance we have a -natural phenomenon immediately applicable to æsthetic purposes.</p> - -<p class="para"><a id="a814">814.</a></p> - -<p>While, therefore, we may assert that the chromatic scale, as given by -us, produces an agreeable impression by its ingredient hues, we may -here remark that those have been mistaken who have hitherto adduced -the rainbow as an example of the entire scale; for the chief colour, -pure red, is deficient in it, and cannot be produced, since in this -phenomenon, as well as in the ordinary prismatic series, the yellow-red -and blue-red cannot attain to a union.</p> - -<p class="para"><a id="a815">815.</a></p> - -<p>Nature perhaps exhibits no general phenomenon where the scale is in -complete combination. By artificial experiments such an appearance may -be produced in its perfect splendour. The mode, however, in which the -entire series is connected in a circle, is rendered most intelligible -by tints on paper, till after much experience and practice, aided by -due susceptibility of the organ, we become penetrated with the idea of -this harmony, and feel it present in our minds.</p> - -<p><span class="pagenum"><a name="Page_321" id="Page_321">[Pg 321]</a></span></p> - -<p class="para"><a id="a816">816.</a></p> - -<p>Besides these pure, harmonious, self-developed combinations, which -always carry the conditions of completeness with them, there are -others which may be arbitrarily produced, and which may be most easily -described by observing that they are to be found in the colorific -circle, not by diameters, but by chords, in such a manner that an -intermediate colour is passed over.</p> - -<p class="para"><a id="a817">817.</a></p> - -<p>We call these combinations characteristic because they have all a -certain significancy and tend to excite a definite impression; an -impression, however, which does not altogether satisfy, inasmuch as -every characteristic quality of necessity presents itself only as a -part of a whole, with which it has a relation, but into which it cannot -be resolved.</p> - -<p class="para"><a id="a818">818.</a></p> - -<p>As we are acquainted with the impressions produced by the colours -singly as well as in their harmonious relations, we may at once -conclude that the character of the arbitrary combinations will be very -different from each other as regards their significancy. We proceed to -review them separately.</p> - -<p><span class="pagenum"><a name="Page_322" id="Page_322">[Pg 322]</a></span></p> - -<hr class="r5" /> -<h5>YELLOW AND BLUE.</h5> - - -<p class="para"><a id="a819">819.</a></p> - -<p>This is the simplest of such combinations. It may be said that it -contains too little, for since every trace of red is wanting in it, -it is defective as compared with the whole scale. In this view it -may be called poor, and as the two contrasting elements are in their -lowest state, may be said to be ordinary; yet it is recommended by -its proximity to green—in short, by containing the ingredients of an -ultimate state.</p> - -<hr class="r5" /> -<h5>YELLOW AND RED.</h5> - - -<p class="para"><a id="a820">820.</a></p> - -<p>This is a somewhat preponderating combination, but it has a serene -and magnificent effect. The two extremes of the active side are seen -together without conveying any idea of progression from one to the -other. As the result of their combination in pigments is yellow-red, so -they in some degree represent this colour.</p> - -<hr class="r5" /> -<h5>BLUE AND RED.</h5> - - -<p class="para"><a id="a821">821.</a></p> - -<p>The two ends of the passive side, with the excess of the upper end of -the active side. The effect of this juxtaposition approaches that of -the blue-red produced by their union.</p> - -<p><span class="pagenum"><a name="Page_323" id="Page_323">[Pg 323]</a></span></p> - -<hr class="r5" /> -<h5>YELLOW-RED AND BLUE-RED.</h5> - - -<p class="para"><a id="a822">822.</a></p> - -<p>These, when placed together, as the deepened extremes of both sides, -have something exciting, elevated: they give us a presentiment of red, -which in physical experiments is produced by their union.</p> - -<p class="para"><a id="a823">823.</a></p> - -<p>These four combinations have also the common quality of producing the -intermediate colour of our colorific circle by their union, a union -which actually takes place if they are opposed to each other in small -quantities and seen from a distance. A surface covered with narrow blue -and yellow stripes appears green at a certain distance.</p> - -<p class="para"><a id="a824">824.</a></p> - -<p>If, again, the eye sees blue and yellow next each other, it finds -itself in a peculiar disposition to produce green without accomplishing -it, while it neither experiences a satisfactory sensation in -contemplating the detached colours, nor an impression of completeness -in the two.</p> - -<p class="para"><a id="a825">825.</a></p> - -<p>Thus it will be seen that it was not without reason we called these -combinations characteristic; the more so, since the character of each<span class="pagenum"><a name="Page_324" id="Page_324">[Pg 324]</a></span> -combination must have a relation to that of the single colours of which -it consists.</p> - -<hr class="r5" /> -<h5>COMBINATIONS NON-CHARACTERISTIC.</h5> - - -<p class="para"><a id="a826">826.</a></p> - -<p>We now turn our attention to the last kind of combinations. These are -easily found in the circle; they are indicated by shorter chords, for -in this case we do not pass over an entire intermediate colour, but -only the transition from one to the other.</p> - -<p class="para"><a id="a827">827.</a></p> - -<p>These combinations may justly be called non-characteristic, inasmuch -as the colours are too nearly alike for their impression to be -significant. Yet most of these recommend themselves to a certain -degree, since they indicate a progressive state, though its relations -can hardly be appreciable.</p> - -<p class="para"><a id="a828">828.</a></p> - -<p>Thus yellow and yellow-red, yellow-red and red, blue and blue-red, -blue-red and red, represent the nearest degrees of augmentation and -culmination, and in certain relations as to quantity may produce no -unpleasant effect.</p> - -<p class="para"><a id="a829">829.</a></p> - -<p>The juxtaposition of yellow and green has<span class="pagenum"><a name="Page_325" id="Page_325">[Pg 325]</a></span> always something ordinary, -but in a cheerful sense; blue and green, on the other hand, is ordinary -in a repulsive sense. Our good forefathers called these last fool's -colours.</p> - -<hr class="r5" /> -<h5>RELATION OF THE COMBINATIONS TO LIGHT AND DARK.</h5> - - -<p class="para"><a id="a830">830.</a></p> - -<p>These combinations may be very much varied by making both colours light -or both dark, or one light and the other dark; in which modifications, -however, all that has been found true in a general sense is applicable -to each particular case. With regard to the infinite variety thus -produced, we merely observe:</p> - -<p class="para"><a id="a831">831.</a></p> - -<p>The colours of the active side placed next to black gain in energy, -those of the passive side lose. The active conjoined with white and -brightness lose in strength, the passive gain in cheerfulness. Red and -green with black appear dark and grave; with white they appear gay.</p> - -<p class="para"><a id="a832">832.</a></p> - -<p>To this we may add that all colours may be more or less broken or -neutralised, may to a certain degree be rendered nameless, and thus -combined partly together and partly with pure colours; but although the -relations may thus<span class="pagenum"><a name="Page_326" id="Page_326">[Pg 326]</a></span> be varied to infinity, still all that is applicable -with regard to the pure colours will be applicable in these cases.</p> - -<hr class="r5" /> -<h5>CONSIDERATIONS DERIVED FROM THE EVIDENCE OF EXPERIENCE AND HISTORY.</h5> - - -<p class="para"><a id="a833">833.</a></p> - -<p>The principles of the harmony of colours having been thus far defined, -it may not be irrelevant to review what has been adduced in connexion -with experience and historical examples.</p> - -<p class="para"><a id="a834">834.</a></p> - -<p>The principles in question have been derived from the constitution of -our nature and the constant relations which are found to obtain in -chromatic phenomena. In experience we find much that is in conformity -with these principles, and much that is opposed to them.</p> - -<p class="para"><a id="a835">835.</a></p> - -<p>Men in a state of nature, uncivilised nations, children, have a great -fondness for colours in their utmost brightness, and especially for -yellow-red: they are also pleased with the motley. By this expression -we understand the juxtaposition of vivid colours without an harmonious -balance; but if this balance is observed, through instinct or accident, -an agreeable effect may be produced. I remember a Hessian officer, -returned<span class="pagenum"><a name="Page_327" id="Page_327">[Pg 327]</a></span> from America, who had painted his face with the positive -colours, in the manner of the Indians; a kind of completeness or due -balance was thus produced, the effect of which was not disagreeable.</p> - -<p class="para"><a id="a836">836.</a></p> - -<p>The inhabitants of the south of Europe make use of very brilliant -colours for their dresses. The circumstance of their procuring silk -stuffs at a cheap rate is favourable to this propensity. The women, -especially, with their bright-coloured bodices and ribbons, are always -in harmony with the scenery, since they cannot possibly surpass the -splendour of the sky and landscape.</p> - -<p class="para"><a id="a837">837.</a></p> - -<p>The history of dyeing teaches us that certain technical conveniences -and advantages have had great influence on the costume of nations. -We find that the Germans wear blue very generally because it is a -permanent colour in cloth; so in many districts all the country people -wear green twill, because that material takes a green dye well. If -a traveller were to pay attention to these circumstances, he might -collect some amusing and curious facts.</p> - -<p class="para"><a id="a838">838.</a></p> - -<p>Colours, as connected with particular frames<span class="pagenum"><a name="Page_328" id="Page_328">[Pg 328]</a></span> of mind, are again a -consequence of peculiar character and circumstances. Lively nations, -the French for instance, love intense colours, especially on the active -side; sedate nations, like the English and Germans, wear straw-coloured -or leather-coloured yellow accompanied with dark blue. Nations aiming -at dignity of appearance, the Spaniards and Italians for instance, -suffer the red colour of their mantles to incline to the passive side.</p> - -<p class="para"><a id="a839">839.</a></p> - -<p>In dress we associate the character of the colour with the character of -the person. We may thus observe the relation of colours singly, and in -combination, to the colour of the complexion, age, and station.</p> - -<p class="para"><a id="a840">840.</a></p> - -<p>The female sex in youth is attached to rose-colour and sea-green, in -age to violet and dark-green. The fair-haired prefer violet, as opposed -to light yellow, the brunettes, blue, as opposed to yellow-red, and -all on good grounds. The Roman emperors were extremely jealous with -regard to their purple. The robe of the Chinese Emperor is orange -embroidered with red; his attendants and the ministers of religion wear -citron-yellow.</p> - -<p><span class="pagenum"><a name="Page_329" id="Page_329">[Pg 329]</a></span></p> - -<p class="para"><a id="a841">841.</a></p> - -<p>People of refinement have a disinclination to colours. This may be -owing partly to weakness of sight, partly to the uncertainty of taste, -which readily takes refuge in absolute negation. Women now appear -almost universally in white and men in black.</p> - -<p class="para"><a id="a842">842.</a></p> - -<p>An observation, very generally applicable, may not be out of place -here, namely, that man, desirous as he is of being distinguished, is -quite as willing to be lost among his fellows.</p> - -<p class="para"><a id="a843">843.</a></p> - -<p>Black was intended to remind the Venetian noblemen of republican -equality.</p> - -<p class="para"><a id="a844">844.</a></p> - -<p>To what degree the cloudy sky of northern climates may have gradually -banished colour may also admit of explanation.</p> - -<p class="para"><a id="a845">845.</a></p> - -<p>The scale of positive colours is obviously soon exhausted; on the -other hand, the neutral, subdued, so-called fashionable colours -present infinitely varying degrees and shades, most of which are not -unpleasing.</p> - -<p><span class="pagenum"><a name="Page_330" id="Page_330">[Pg 330]</a></span></p> - -<p class="para"><a id="a846">846.</a></p> - -<p>It is also to be remarked that ladies, in wearing positive colours, -are in danger of making a complexion which may not be very bright -still less so, and thus to preserve a due balance with such brilliant -accompaniments, they are induced to heighten their complexions -artificially.</p> - -<p class="para"><a id="a847">847.</a></p> - -<p>An amusing inquiry might be made which would lead to a critique of -uniforms, liveries, cockades, and other distinctions, according to the -principles above hinted at. It might be observed, generally, that such -dresses and insignia should not be composed of harmonious colours. -Uniforms should be characteristic and dignified; liveries might be -ordinary and striking to the eye. Examples both good and bad would -not be wanting, since the scale of colours usually employed for such -purposes is limited, and its varieties have been often enough tried.<a name="FNanchor_3_58" id="FNanchor_3_58"></a><a href="#Footnote_3_58" class="fnanchor">[3]</a></p> - -<hr class="r5" /> -<h5>ÆSTHETIC INFLUENCE.</h5> - - -<p class="para"><a id="a848">848.</a></p> - -<p>From the moral associations connected with the appearance of colours, -single or combined, their æsthetic influence may now be deduced<span class="pagenum"><a name="Page_331" id="Page_331">[Pg 331]</a></span> for -the artist. We shall touch the most essential points to be attended -to after first considering the general condition of pictorial -representation, light and shade, with which the appearance of colour is -immediately connected.</p> - -<hr class="r5" /> -<h5>CHIARO-SCURO.</h5> - - -<p class="para"><a id="a849">849.</a></p> - -<p>We apply the term chiaro-scuro (Helldunkel) to the appearance of -material objects when the mere effect produced on them by light and -shade is considered.—<a href="#NOTE_DD">Note DD</a>.</p> - -<p class="para"><a id="a850">850.</a></p> - -<p>In a narrower sense a mass of shadow lighted by reflexes is often -thus designated; but we here use the expression in its first and more -general sense.</p> - -<p class="para"><a id="a851">851.</a></p> - -<p>The separation of light and dark from all appearance of colour is -possible and necessary. The artist will solve the mystery of imitation -sooner by first considering light and dark independently of colour, and -making himself acquainted with it in its whole extent.</p> - -<p class="para"><a id="a852">852.</a></p> - -<p>Chiaro-scuro exhibits the substance as substance, inasmuch as light and -shade inform us as to degrees of density.</p> - -<p><span class="pagenum"><a name="Page_332" id="Page_332">[Pg 332]</a></span></p> - -<p class="para"><a id="a853">853.</a></p> - -<p>We have here to consider the highest light, the middle tint, and the -shadow, and in the last the shadow of the object itself, the shadow it -casts on other objects, and the illumined shadow or reflexion.</p> - -<p class="para"><a id="a854">854.</a></p> - -<p>The globe is well adapted for the general exemplification of the nature -of chiaro-scuro, but it is not altogether sufficient. The softened -unity of such complete rotundity tends to the vapoury, and in order to -serve as a principle for effects of art, it should be composed of plane -surfaces, so as to define the gradations more.</p> - -<p class="para"><a id="a855">855.</a></p> - -<p>The Italians call this manner "il piazzoso;" in German it might -be called "das Flächenhafte."<a name="FNanchor_4_59" id="FNanchor_4_59"></a><a href="#Footnote_4_59" class="fnanchor">[4]</a> If, therefore, the sphere is a -perfect example of natural chiaro-scuro, a polygon would exhibit the -artist-like treatment in which all kinds of lights, half-lights, -shadows, and reflexions, would be appreciable.—<a href="#NOTE_EE">Note EE</a>.</p> - -<p class="para"><a id="a856">856.</a></p> - -<p>The bunch of grapes is recognised as a good example of a picturesque -completeness in chiaro-scuro, the more so as it is fitted, from its -form, to represent a principal group; but it is only<span class="pagenum"><a name="Page_333" id="Page_333">[Pg 333]</a></span> available for the -master who can see in it what he has the power of producing.</p> - -<p class="para"><a id="a857">857.</a></p> - -<p>In order to make the first idea intelligible to the beginner, (for -it is difficult to consider it abstractedly even in a polygon,) we -may take a cube, the three sides of which that are seen represent the -light, the middle tint, and the shadow in distinct order.</p> - -<p class="para"><a id="a858">858.</a></p> - -<p>To proceed again to the chiaro-scuro of a more complicated figure, we -might select the example of an open book, which presents a greater -diversity.</p> - -<p class="para"><a id="a859">859.</a></p> - -<p>We find the antique statues of the best time treated very much with -reference to these effects. The parts intended to receive the light -are wrought with simplicity, the portion originally in shade is, on -the other hand, in more distinct surfaces to make them susceptible -of a variety of reflexions; here the example of the polygon will be -remembered.—<a href="#NOTE_FF">Note FF</a>.</p> - -<p class="para"><a id="a860">860.</a></p> - -<p>The pictures of Herculaneum and the Aldobrandini marriage are examples -of antique painting in the same style.</p> - -<p><span class="pagenum"><a name="Page_334" id="Page_334">[Pg 334]</a></span></p> - -<p class="para"><a id="a861">861.</a></p> - -<p>Modern examples may be found in single figures by Raphael, in entire -works by Correggio, and also by the Flemish masters, especially Rubens.</p> - -<hr class="r5" /> -<h5>TENDENCY TO COLOUR.</h5> - - -<p class="para"><a id="a862">862.</a></p> - -<p>A picture in black and white seldom makes its appearance; some works -of Polidoro are examples of this kind of art. Such works, inasmuch as -they can attain form and keeping, are estimable, but they have little -attraction for the eye, since their very existence supposes a violent -abstraction.</p> - -<p class="para"><a id="a863">863.</a></p> - -<p>If the artist abandons himself to his feeling, colour presently -announces itself. Black no sooner inclines to blue than the eye demands -yellow, which the artist instinctively modifies, and introduces partly -pure in the light, partly reddened and subdued as brown, in the -reflexes, thus enlivening the whole.—<a href="#NOTE_GG">Note GG</a>.</p> - -<p class="para"><a id="a864">864.</a></p> - -<p>All kinds of <i>camayeu</i>, or colour on similar colour, end in the -introduction either of a complemental contrast, or some variety of hue. -Thus, Polidoro in his black and white frescoes<span class="pagenum"><a name="Page_335" id="Page_335">[Pg 335]</a></span> sometimes introduced a -yellow vase, or something of the kind.</p> - -<p class="para"><a id="a865">865.</a></p> - -<p>In general it may be observed that men have at all times instinctively -striven after colour in the practice of the art. We need only observe -daily, how soon amateurs proceed from colourless to coloured materials. -Paolo Uccello painted coloured landscapes to colourless figures.—<a href="#NOTE_HH">Note HH</a>.</p> - -<p class="para"><a id="a866">866.</a></p> - -<p>Even the sculpture of the ancients could not be exempt from the -influence of this propensity. The Egyptians painted their bas-reliefs; -statues had eyes of coloured stones. Porphyry draperies were added to -marble heads and extremities, and variegated stalactites were used -for the pedestals of busts. The Jesuits did not fail to compose the -statue of their S. Luigi, in Rome, in this manner, and the most modern -sculpture distinguishes the flesh from the drapery by staining the -latter.</p> - -<hr class="r5" /> -<h5>KEEPING.</h5> - - -<p class="para"><a id="a867">867.</a></p> - -<p>If linear perspective displays the gradation of objects in their -apparent size as affected by distance, aërial perspective shows us -their gradation<span class="pagenum"><a name="Page_336" id="Page_336">[Pg 336]</a></span> in greater or less distinctness, as affected by the -same cause.</p> - -<p class="para"><a id="a868">868.</a></p> - -<p>Although from the nature of the organ of sight, we cannot see distant -objects so distinctly as nearer ones, yet aërial perspective is -grounded strictly on the important fact that all mediums called -transparent are in some degree dim.</p> - -<p class="para"><a id="a869">869.</a></p> - -<p>The atmosphere is thus always, more or less, semi-transparent. This -quality is remarkable in southern climates, even when the barometer is -high, the weather dry, and the sky cloudless, for a very pronounced -gradation is observable between objects but little removed from each -other.</p> - -<p class="para"><a id="a870">870.</a></p> - -<p>The appearance on a large scale is known to every one; the painter, -however, sees or believes he sees, the gradation in the slightest -varieties of distance. He exemplifies it practically by making a -distinction, for instance, in the features of a face according to their -relative position as regards the plane of the picture. The direction of -the light is attended to in like manner. This is considered to produce -a gradation from side to side, while keeping has reference to depth, to -the comparative distinctness of near and distant things.</p> - -<p><span class="pagenum"><a name="Page_337" id="Page_337">[Pg 337]</a></span></p> - -<p class="para"><a id="a871">871.</a></p> - -<p>In proceeding to consider this subject, we assume that the painter is -generally acquainted with our sketch of the theory of colours, and that -he has made himself well acquainted with certain chapters and rubrics -which especially concern him. He will thus be enabled to make use of -theory as well as practice in recognising the principles of effect in -nature, and in employing the means of art.</p> - -<hr class="r5" /> -<h5>COLOUR IN GENERAL NATURE.</h5> - - -<p class="para"><a id="a872">872.</a></p> - -<p>The first indication of colour announces itself in nature together -with the gradations of aërial perspective; for aërial perspective is -intimately connected with the doctrine of semi-transparent mediums. We -see the sky, distant objects and even comparatively near shadows, blue. -At the same moment, the illuminating and illuminated objects appear -yellow, gradually deepening to red. In many cases the physiological -suggestion of contrasts comes into the account, and an entirely -colourless landscape, by means of these assisting and counteracting -tendencies, appears to our eyes completely coloured.</p> - -<p><span class="pagenum"><a name="Page_338" id="Page_338">[Pg 338]</a></span></p> - -<p class="para"><a id="a873">873.</a></p> - -<p>Local colours are composed of the general elementary colours; but these -are determined or specified according to the properties of substances -and surfaces on which they appear: this specification is infinite.</p> - -<p class="para"><a id="a874">874.</a></p> - -<p>Thus, there is at once a great difference between silk and wool -similarly dyed. Every kind of preparation and texture produces -corresponding modifications. Roughness, smoothness, polish, all are to -be considered.</p> - -<p class="para"><a id="a875">875.</a></p> - -<p>It is therefore one of the pernicious prejudices of art that the -skilful painter must never attend to the material of draperies, -but always represent, as it were, only abstract folds. Is not all -characteristic variety thus done away with, and is the portrait of Leo -X. less excellent because velvet, satin, and moreen, are imitated in -their relative effect?</p> - -<p class="para"><a id="a876">876.</a></p> - -<p>In the productions of nature, colours appear more or less modified, -specified, even individualised: this may be readily observed in -minerals<span class="pagenum"><a name="Page_339" id="Page_339">[Pg 339]</a></span> and plants, in the feathers of birds and the skins of beasts.</p> - -<p class="para"><a id="a877">877.</a></p> - -<p>The chief art of the painter is always to imitate the actual appearance -of the definite hue, doing away with the recollection of the elementary -ingredients of colour. This difficulty is in no instance greater than -in the imitation of the surface of the human figure.</p> - -<p class="para"><a id="a878">878.</a></p> - -<p>The colour of flesh, as a whole, belongs to the active side, yet the -bluish of the passive side mingles with it. The colour is altogether -removed from the elementary state and neutralised by organisation.</p> - -<p class="para"><a id="a879">879.</a></p> - -<p>To bring the colouring of general nature into harmony with the -colouring of a given object, will perhaps be more attainable for the -judicious artist after the consideration of what has been pointed out -in the foregoing theory. For the most fancifully beautiful and varied -appearances may still be made true to the principles of nature.</p> - -<hr class="r5" /> -<h5>CHARACTERISTIC COLOURING.</h5> - - -<p class="para"><a id="a880">880.</a></p> - -<p>The combination of coloured objects, as well as the colour of -their ground, should depend on<span class="pagenum"><a name="Page_340" id="Page_340">[Pg 340]</a></span> considerations which the artist -pre-establishes for himself. Here a reference to the effect of colours -singly or combined, on the feelings, is especially necessary. On this -account the painter should possess himself with the idea of the general -dualism, as well as of particular contrasts, not forgetting what has -been adverted to with regard to the qualities of colours.</p> - -<p class="para"><a id="a881">881.</a></p> - -<p>The characteristic in colour may be comprehended under three leading -rubrics, which we here define as the powerful, the soft, and the -splendid.</p> - -<p class="para"><a id="a882">882.</a></p> - -<p>The first is produced by the preponderance of the active side, the -second by that of the passive side, and the third by completeness, by -the exhibition of the whole chromatic scale in due balance.</p> - -<p class="para"><a id="a883">883.</a></p> - -<p>The powerful impression is attained by yellow, yellow-red, and red, -which last colour is to be arrested on the plus side. But little violet -and blue, still less green, are admissible. The soft effect is produced -by blue, violet, and red, which in this case is arrested on the minus -side; a moderate addition of yellow and yellow-red, but much green may -be admitted.</p> - -<p><span class="pagenum"><a name="Page_341" id="Page_341">[Pg 341]</a></span></p> - -<p class="para"><a id="a884">884.</a></p> - -<p>If it is proposed to produce both these effects in their full -significancy, the complemental colours may be excluded to a minimum, -and only so much of them may be suffered to appear as is indispensable -to convey an impression of completeness.</p> - -<hr class="r5" /> -<h5>HARMONIOUS COLOURING.</h5> - - -<p class="para"><a id="a885">885.</a></p> - -<p>Although the two characteristic divisions as above defined may in some -sense be also called harmonious, the harmonious effect, properly so -called, only takes place when all the colours are exhibited together in -due balance.</p> - -<p class="para"><a id="a886">886.</a></p> - -<p>In this way the splendid as well as the agreeable may be produced; both -of these, however, have of necessity a certain generalised effect, and -in this sense may be considered the reverse of the characteristic.</p> - -<p class="para"><a id="a887">887.</a></p> - -<p>This is the reason why the colouring of most modern painters is without -character, for, while they follow their general instinctive feeling -only, the last result of such a tendency must be mere completeness; -this, they more or less attain, but thus at the same time neglect the -characteristic<span class="pagenum"><a name="Page_342" id="Page_342">[Pg 342]</a></span> impression which the subject might demand.</p> - -<p class="para"><a id="a888">888.</a></p> - -<p>But if the principles before alluded to are kept in view, it must be -apparent that a distinct style of colour may be adopted on safe grounds -for every subject. The application requires, it is true, infinite -modifications, which can only succeed in the hands of genius.</p> - -<hr class="r5" /> -<h5>GENUINE TONE.</h5> - - -<p class="para"><a id="a889">889.</a></p> - -<p>If the word tone, or rather tune, is to be still borrowed in future -from music, and applied to colouring, it might be used in a better -sense than heretofore.</p> - -<p class="para"><a id="a890">890.</a></p> - -<p>For it would not be unreasonable to compare a painting of powerful -effect, with a piece of music in a sharp key; a painting of soft effect -with a piece of music in a flat key, while other equivalents might be -found for the modifications of these two leading modes.</p> - -<hr class="r5" /> -<h5>FALSE TONE.</h5> - - -<p class="para"><a id="a891">891.</a></p> - -<p>The word tone has been hitherto understood to mean a veil of a -particular colour spread over<span class="pagenum"><a name="Page_343" id="Page_343">[Pg 343]</a></span> the whole picture; it was generally -yellow, for the painter instinctively pushed the effect towards the -powerful side.</p> - -<p class="para"><a id="a892">892.</a></p> - -<p>If we look at a picture through a yellow glass it will appear in this -tone. It is worth while to make this experiment again and again, in -order to observe what takes place in such an operation. It is a sort of -artificial light, deepening, and at the same time darkening the <i>plus</i> -side, and neutralising the <i>minus</i> side.</p> - -<p class="para"><a id="a893">893.</a></p> - -<p>This spurious tone is produced instinctively through uncertainty -as to the means of attaining a genuine effect; so that instead of -completeness, monotony is the result.</p> - -<hr class="r5" /> -<h5>WEAK COLOURING.</h5> - - -<p class="para"><a id="a894">894.</a></p> - -<p>It is owing to the same uncertainty that the colours are sometimes so -much broken as to have the effect of a grey camayeu, the handling being -at the same time as delicate as possible.</p> - -<p class="para"><a id="a895">895.</a></p> - -<p>The harmonious contrasts are often found to be very happily felt in -such pictures, but without spirit, owing to a dread of the motley.</p> - -<p><span class="pagenum"><a name="Page_344" id="Page_344">[Pg 344]</a></span></p> - -<hr class="r5" /> -<h5>THE MOTLEY.</h5> - - -<p class="para"><a id="a896">896.</a></p> - -<p>A picture may easily become party-coloured or motley, when the colours -are placed next each other in their full force, as it were only -mechanically and according to uncertain impressions.</p> - -<p class="para"><a id="a897">897.</a></p> - -<p>If, on the other hand, weak colours are combined, even although they -may be dissonant, the effect, as a matter of course, is not striking. -The uncertainty of the artist is communicated to the spectator, who, on -his side, can neither praise nor censure.</p> - -<p class="para"><a id="a898">898.</a></p> - -<p>It is also important to observe that the colours may be disposed -rightly in themselves, but that a work may still appear motley, if they -are falsely arranged in relation to light and shade.</p> - -<p class="para"><a id="a899">899.</a></p> - -<p>This may the more easily occur as light and shade are already defined -in the drawing, and are, as it were, comprehended in it, while the -colour still remains open to selection.</p> - -<hr class="r5" /> -<h5>DREAD OF THEORY.</h5> - - -<p class="para"><a id="a900">900.</a></p> - -<p>A dread of, nay, a decided aversion for all<span class="pagenum"><a name="Page_345" id="Page_345">[Pg 345]</a></span> theoretical views -respecting colour and everything belonging to it, has been hitherto -found to exist among painters; a prejudice for which, after all, they -were not to be blamed; for what has been hitherto called theory was -groundless, vacillating, and akin to empiricism. We hope that our -labours may tend to diminish this prejudice, and stimulate the artist -practically to prove and embody the principles that have been explained.</p> - -<hr class="r5" /> -<h5>ULTIMATE AIM.</h5> - - -<p class="para"><a id="a901">901.</a></p> - -<p>But without a comprehensive view of the whole of our theory, the -ultimate object will not be attained. Let the artist penetrate himself -with all that we have stated. It is only by means of harmonious -relations in light and shade, in keeping, in true and characteristic -colouring, that a picture can be considered complete, in the sense we -have now learnt to attach to the term.</p> - -<hr class="r5" /> -<h5>GROUNDS.</h5> - - -<p class="para"><a id="a902">902.</a></p> - -<p>It was the practice of the earlier artists to paint on light grounds. -This ground consisted of gypsum, and was thickly spread on linen or -panel, and then levigated. After the outline was drawn, the subject was -washed in with a<span class="pagenum"><a name="Page_346" id="Page_346">[Pg 346]</a></span> blackish or brownish colour. Pictures prepared in -this manner for colouring are still in existence, by Leonardo da Vinci, -and Fra Bartolomeo; there are also several by Guido.—<a href="#NOTE_II">Note II</a>.</p> - -<p class="para"><a id="a903">903.</a></p> - -<p>When the artist proceeded to colour, and had to represent white -draperies, he sometimes suffered the ground to remain untouched. -Titian did this latterly when he had attained the greatest certainty -in practice, and could accomplish much with little labour. The whitish -ground was left as a middle tint, the shadows painted in, and the high -lights touched on.—<a href="#NOTE_KK">Note KK</a>.</p> - -<p class="para"><a id="a904">904.</a></p> - -<p>In the process of colouring, the preparation merely washed as it were -underneath, was always effective. A drapery, for example, was painted -with a transparent colour, the white ground shone through it and gave -the colour life, so the parts previously prepared for shadows exhibited -the colour subdued, without being mixed or sullied.</p> - -<p class="para"><a id="a905">905.</a></p> - -<p>This method had many advantages; for the painter had a light ground -for the light portions of his work and a dark ground for the shadowed -portions. The whole picture was prepared; the<span class="pagenum"><a name="Page_347" id="Page_347">[Pg 347]</a></span> artist could work with -thin colours in the shadows, and had always an internal light to give -value to his tints. In our own time painting in water colours depends -on the same principles.</p> - -<p class="para"><a id="a906">906.</a></p> - -<p>Indeed a light ground is now generally employed in oil-painting, -because middle tints are thus found to be more transparent, and are in -some degree enlivened by a bright ground; the shadows, again, do not so -easily become black.</p> - -<p class="para"><a id="a907">907.</a></p> - -<p>It was the practice for a time to paint on dark grounds. Tintoret -probably introduced them. Titian's best pictures are not painted on a -dark ground.</p> - -<p class="para"><a id="a908">908.</a></p> - -<p>The ground in question was red-brown, and when the subject was drawn -upon it, the strongest shadows were laid in; the colours of the lights -impasted very thickly in the bright parts, and scumbled towards the -shadows, so that the dark ground appeared through the thin colour as a -middle tint. Effect was attained in finishing by frequently going over -the bright parts and touching on the high lights.</p> - -<p><span class="pagenum"><a name="Page_348" id="Page_348">[Pg 348]</a></span></p> - -<p class="para"><a id="a909">909.</a></p> - -<p>If this method especially recommended itself in practice on account -of the rapidity it allowed of, yet it had pernicious consequences. -The strong ground increased and became darker, and the light colours -losing their brightness by degrees, gave the shadowed portions more -and more preponderance. The middle tints became darker and darker, and -the shadows at last quite obscure. The strongly impasted lights alone -remained bright, and we now see only light spots on the painting. The -pictures of the Bolognese school, and of Caravaggio, afford sufficient -examples of these results.</p> - -<p class="para"><a id="a910">910.</a></p> - -<p>We may here in conclusion observe, that glazing derives its effect -from treating the prepared colour underneath as a light ground. By -this operation colours may have the effect of being mixed to the eye, -may be enhanced, and may acquire what is called tone; but they thus -necessarily become darker.</p> - -<hr class="r5" /> -<h5>PIGMENTS.</h5> - - -<p class="para"><a id="a911">911.</a></p> - -<p>We receive these from the hands of the chemist and the investigator of -nature. Much has been recorded respecting colouring substances,<span class="pagenum"><a name="Page_349" id="Page_349">[Pg 349]</a></span> which -is familiar to all by means of the press. But such directions require -to be revised from time to time. The master meanwhile communicates his -experience in these matters to his scholar, and artists generally to -each other.</p> - -<p class="para"><a id="a912">912.</a></p> - -<p>Those pigments which according to their nature are the most permanent, -are naturally much sought after, but the mode of employing them also -contributes much to the duration of a picture. The fewest possible -colouring materials are to be employed, and the simplest methods of -using them cannot be sufficiently recommended.</p> - -<p class="para"><a id="a913">913.</a></p> - -<p>For from the multitude of pigments colouring has suffered much. Every -pigment has its peculiar nature as regards its effect on the eye; -besides this it has its peculiar quality, requiring a corresponding -technical method in its application. The former circumstance is a -reason why harmony is more difficult of attainment with many materials -than with few, the latter, why chemical action and re-action may take -place among the colouring substances.</p> - -<p class="para"><a id="a914">914.</a></p> - -<p>We may refer, besides, to some false tendencies<span class="pagenum"><a name="Page_350" id="Page_350">[Pg 350]</a></span> which the artists -suffer themselves to be led away with. Painters are always looking -for new colouring substances, and believe when such a substance is -discovered that they have made an advance in the art. They have a -great curiosity to know the practical methods of the old masters, and -lose much time in the search. Towards the end of the last century -we were thus long tormented with wax-painting. Others turn their -attention to the discovery of new methods, through which nothing new is -accomplished; for, after all, it is the feeling of the artist only that -informs every kind of technical process.</p> - -<hr class="r5" /> -<h5>ALLEGORICAL, SYMBOLICAL, MYSTICAL APPLICATION OF COLOUR.</h5> - - -<p class="para"><a id="a915">915.</a></p> - -<p>It has been circumstantially shown above, that every colour produces -a distinct impression on the mind, and thus addresses at once the eye -and feelings. Hence it follows that colour may be employed for certain -moral and æsthetic ends.</p> - -<p class="para"><a id="a916">916.</a></p> - -<p>Such an application, coinciding entirely with nature, might be called -symbolical, since the colour would be employed in conformity with its -effect, and would at once express its meaning. If, for example, pure -red were assumed to<span class="pagenum"><a name="Page_351" id="Page_351">[Pg 351]</a></span> designate majesty, there can be no doubt that this -would be admitted to be a just and expressive symbol. All this has been -already sufficiently entered into.</p> - -<p class="para"><a id="a917">917.</a></p> - -<p>Another application is nearly allied to this; it might be called the -allegorical application. In this there is more of accident and caprice, -inasmuch as the meaning of the sign must be first communicated to us -before we know what it is to signify; what idea, for instance, is -attached to the green colour, which has been appropriated to hope?</p> - -<p class="para"><a id="a918">918.</a></p> - -<p>That, lastly, colour may have a mystical allusion, may be readily -surmised, for since every diagram in which the variety of colours may -be represented points to those primordial relations which belong both -to nature and the organ of vision, there can be no doubt that these may -be made use of as a language, in cases where it is proposed to express -similar primordial relations which do not present themselves to the -senses in so powerful and varied a manner. The mathematician extols -the value and applicability of the triangle; the triangle is revered -by the mystic; much admits of being expressed in it by diagrams, and, -among other things, the law<span class="pagenum"><a name="Page_352" id="Page_352">[Pg 352]</a></span> of the phenomena of colours; in this case, -indeed, we presently arrive at the ancient mysterious hexagon.</p> - -<p class="para"><a id="a919">919.</a></p> - -<p>When the distinction of yellow and blue is duly comprehended, and -especially the augmentation into red, by means of which the opposite -qualities tend towards each other and become united in a third; then, -certainly, an especially mysterious interpretation will suggest itself, -since a spiritual meaning may be connected with these facts; and when -we find the two separate principles producing green on the one hand and -red in their intenser state, we can hardly refrain from thinking in the -first case on the earthly, in the last on the heavenly, generation of -the Elohim.—<a href="#NOTE_LL">Note LL</a>.</p> - -<p class="para"><a id="a920">920.</a></p> - -<p>But we shall do better not to expose ourselves, in conclusion, to -the suspicion of enthusiasm; since, if our doctrine of colours finds -favour, applications and allusions, allegorical, symbolical, and -mystical, will not fail to be made, in conformity with the spirit of -the age.</p> - -<hr class="r5" /> -<h5>CONCLUDING OBSERVATIONS.</h5> - - -<p>In reviewing this labour, which has occupied me long, and which at -last I give but as a<span class="pagenum"><a name="Page_353" id="Page_353">[Pg 353]</a></span> sketch, I am reminded of a wish once expressed -by a careful writer, who observed that he would gladly see his works -printed at once as he conceived them, in order then to go to the task -with a fresh eye; since everything defective presents itself to us more -obviously in print than even in the cleanest manuscript. This feeling -may be imagined to be stronger in my case, since I had not even an -opportunity of going through a fair transcript of my work before its -publication, these pages having been put together at a time when a -quiet, collected state of mind was out of the question.<a name="FNanchor_5_60" id="FNanchor_5_60"></a><a href="#Footnote_5_60" class="fnanchor">[5]</a></p> - -<p>Some of the explanations I was desirous of giving are to be found in -the introduction, but in the portion of my work to be devoted to the -history of the doctrine of colours, I hope to give a more detailed -account of my investigations and the vicissitudes they underwent. One -inquiry, however, may not be out of place here; the consideration, -namely, of the question, what can a man accomplish who cannot devote -his whole life to scientific pursuits? what can he perform as a -temporary guest on an estate not his own, for the advantage of the -proprietor?</p> - -<p>When we consider art in its higher character, we might wish that -masters only had to do with<span class="pagenum"><a name="Page_354" id="Page_354">[Pg 354]</a></span> it, that scholars should be trained by -the severest study, that amateurs might feel themselves happy in -reverentially approaching its precincts. For a work of art should be -the effusion of genius, the artist should evoke its substance and form -from his inmost being, treat his materials with sovereign command, and -make use of external influences only to accomplish his powers.</p> - -<p>But if the professor in this case has many reasons for respecting -the dilettante, the man of science has every motive to be still more -indulgent, since the amateur here is capable of contributing what may -be satisfactory and useful. The sciences depend much more on experiment -than art, and for mere experiment many a votary is qualified. -Scientific results are arrived at by many means, and cannot dispense -with many hands, many heads. Science may be communicated, the treasure -may be inherited, and what is acquired by one may be appropriated -by many. Hence no one perhaps ought to be reluctant to offer his -contributions. How much do we not owe to accident, to mere practice, -to momentary observation. All who are endowed only with habits of -attention, women, children, are capable of communicating striking and -true remarks.</p> - -<p>In science it cannot therefore be required, that he who endeavours -to furnish something in<span class="pagenum"><a name="Page_355" id="Page_355">[Pg 355]</a></span> its aid should devote his whole life to it, -should survey and investigate it in all its extent; for this, in most -cases, would be a severe condition even for the initiated. But if we -look through the history of science in general, especially the history -of physics, we shall find that many important acquisitions have been -made by single inquirers, in single departments, and very often by -unprofessional observers.</p> - -<p>To whatever direction a man may be determined by inclination or -accident, whatever class of phenomena especially strike him, excite -his interest, fix his attention, and occupy him, the result will still -be for the advantage of science: for every new relation that comes to -light, every new mode of investigation, even the imperfect attempt, -even error itself is available; it may stimulate other observers and is -never without its use as influencing future inquiry.</p> - -<p>With this feeling the author himself may look back without regret -on his endeavours. From this consideration he can derive some -encouragement for the prosecution of the remainder of his task; and -although not satisfied with the result of his efforts, yet re-assured -by the sincerity of his intentions, he ventures to recommend his past -and future labours to the interest of his contemporaries and posterity.</p> - -<p style="margin-left: 20%;"> -Multi pertransibunt et augebitur scientia.<br /> -</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_56" id="Footnote_1_56"></a><a href="#FNanchor_1_56"><span class="label">[1]</span></a> <a href="#col000">Plate 1</a>, fig. 3.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_57" id="Footnote_2_57"></a><a href="#FNanchor_2_57"><span class="label">[2]</span></a> See <a href="#NOTE_C">Note C</a>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_58" id="Footnote_3_58"></a><a href="#FNanchor_3_58"><span class="label">[3]</span></a> Some early Italian writers, Sicillo, Occolti, Rinaldi, -and others, have treated this subject in connexion with the supposed -signification of colours.—T.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_59" id="Footnote_4_59"></a><a href="#FNanchor_4_59"><span class="label">[4]</span></a> The English technical expressions "flat" and "square" have -an association of mannerism.—T</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_60" id="Footnote_5_60"></a><a href="#FNanchor_5_60"><span class="label">[5]</span></a> Towards the close of 1806, when Weimar was occupied by -Napoleon after the battle of Jena.—T.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_357" id="Page_357">[Pg 357]</a></span></p></div> - - - - -<h4><a name="NOTES" id="NOTES">NOTES.</a></h4> - - -<p class="para"><a id="NOTE_A"></a>NOTE A.—<a href="#a18">Par. 18.</a></p> - -<p>Leonardo da Vinci observes that "a light object relieved on a dark -ground appears magnified;" and again, "Objects seen at a distance -appear out of proportion; this is because the light parts transmit -their rays to the eye more powerfully than the dark. A woman's white -head-dress once appeared to me much wider than her shoulders, owing -to their being dressed in black."<a name="FNanchor_1_61" id="FNanchor_1_61"></a><a href="#Footnote_1_61" class="fnanchor">[1]</a> "It is now generally admitted -that the excitation produced by light is propagated on the retina a -little beyond the outline of the image. Professor Plateau, of Ghent, -has devoted a very interesting special memoir to the description -and explanation of phenomena of this nature. See his 'Mémoire sur -l'Irradiation,' published in the 11th vol. of the Transactions of the -Royal Academy of Sciences at Brussels."<a name="FNanchor_2_62" id="FNanchor_2_62"></a><a href="#Footnote_2_62" class="fnanchor">[2]</a>—S. F.</p> - - -<p class="para"><a id="NOTE_B"></a>NOTE B.—<a href="#a23">Par. 23.</a></p> - -<p>"The duration of ocular spectra produced by strongly exciting the -retina, may be conveniently measured by minutes and seconds; but to -ascertain the duration of more evanescent phenomena, recourse must be -had to other means. The Chevalier d'Arcy (Mém. de l'Acad. des Sc.<span class="pagenum"><a name="Page_358" id="Page_358">[Pg 358]</a></span> -1765,) endeavoured to ascertain the duration of the impression produced -by a glowing coal in the following manner. He attached it to the -circumference of a wheel, the velocity of which was gradually increased -until the apparent trace of the object formed a complete circle, and -then measured the duration of a revolution, which was obviously that -of the impression. To ascertain the duration of a revolution it is -sufficient merely to know the number of revolutions described in a -given time. Recently more refined experiments of the same kind have -been made by Professors Plateau and Wheatstone."—S. F.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_61" id="Footnote_1_61"></a><a href="#FNanchor_1_61"><span class="label">[1]</span></a> "Trattato della Pittura, Roma, 1817," p. 143-223. This -edition, published from a Vatican MS., contains many observations not -included in former editions.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_62" id="Footnote_2_62"></a><a href="#FNanchor_2_62"><span class="label">[2]</span></a> A few notes (marked with inverted commas and with the -signature S. F.) have been kindly furnished by a scientific friend.</p></div> - - -<p class="para"><a id="NOTE_C"></a>NOTE C.—<a href="#a50">Par. 50.</a></p> - -<p>Every treatise on the harmonious combination of colours contains the -diagram of the chromatic circle more or less elaborately constructed. -These diagrams, if intended to exhibit the contrasts produced by -the action and re-action of the retina, have one common defect. The -opposite colours are made equal in intensity; whereas the complemental -colour pictured on the retina is always less vivid, and always darker -or lighter than the original colour. This variety undoubtedly accords -more with harmonious effects in painting.</p> - -<p>The opposition of two pure hues of equal intensity, differing only in -the abstract quality of colour, would immediately be pronounced crude -and inharmonious. It would not, however, be strictly correct to say -that such a contrast is too violent; on the contrary, it appears the -contrast is not carried far enough, for though differing in colour, -the two hues may be exactly similar in purity and intensity. Complete -contrast, on the other hand, supposes dissimilarity in all respects.</p> - -<p>In addition to the mere difference of hue, the eye, it seems, requires -difference in the lightness or darkness of the hue. The spectrum of a -colour relieved as a dark on a light ground, is a light colour on a -dark ground, and <i>vice versâ</i>. Thus, if we look at a bright red wafer -on the whitest<span class="pagenum"><a name="Page_359" id="Page_359">[Pg 359]</a></span> surface, the complemental image will be still lighter -than the white surface; if the same wafer is placed on a black surface, -the complemental image will be still darker. The colour of both these -spectra may be called greenish, but it is evident that a colour must be -scarcely appreciable as such, if it is lighter than white and darker -than black. It is, however, to be remarked, that the white surface -round the light greenish image seems tinged with a reddish hue, and -the black surface round the dark image becomes slightly illuminated -with the same colour, thus in both cases assisting to render the image -apparent (<a href="#a58">58</a>).</p> - -<p>The difficulty or impossibility of describing degrees of colour in -words, has also had a tendency to mislead, by conveying the idea of -more positive hues than the physiological contrast warrants. Thus, -supposing scarlet to be relieved as a dark, the complemental colour is -so light in degree and so faint in colour, that it should be called a -pearly grey; whereas the theorists, looking at the quality of colour -abstractedly, would call it a green-blue, and the diagram would falsely -present such a hue equal in intensity to scarlet, or as nearly equal as -possible.</p> - -<p>Even the difference of mass which good taste requires may be suggested -by the physiological phenomena, for unless the complemental image is -suffered to fall on a surface precisely as near to the eye as that on -which the original colour was displayed, it appears larger or smaller -than the original object (<a href="#a22">22</a>), and this in a rapidly increasing -proportion. Lastly, the shape itself soon becomes changed (26).</p> - -<p>That vivid colour demands the comparative absence of colour, either -on a lighter or darker scale, as its contrast, may be inferred again -from the fact that bright colourless objects produce strongly coloured -spectra. In darkness, the spectrum which is first white, or nearly -white, is followed by red: in light, the spectrum which is first black, -is followed by green (<a href="#Page_39">39</a>-<a href="#a44">44</a>). All colour, as the author observes -(<a href="#a259">259</a>), is to be considered as half-light, inasmuch as it<span class="pagenum"><a name="Page_360" id="Page_360">[Pg 360]</a></span> is in every -case lighter than black and darker than white. Hence no contrast of -colour with colour, or even of colour with black or white, can be so -great (as regards lightness or darkness) as the contrast of black and -white, or light and dark abstractedly. This distinction between the -differences of degree and the differences of kind is important, since a -just application of contrast in colour may be counteracted by an undue -difference in lightness or darkness. The mere contrast of colour is -happily employed in some of Guido's lighter pictures, but if intense -darks had been opposed to his delicate carnations, their comparative -whiteness would have been unpleasantly apparent. On the other hand, the -flesh-colour in Giorgione, Sebastian del Piombo (his best imitator), -and Titian, was sometimes so extremely glowing<a name="FNanchor_1_63" id="FNanchor_1_63"></a><a href="#Footnote_1_63" class="fnanchor">[1]</a> that the deepest -colours, and black, were indispensable accompaniments. The manner of -Titian as distinguished from his imitation of Giorgione, is golden -rather than fiery, and his biographers are quite correct in saying -that he was fond of opposing red (lake) and blue to his flesh<a name="FNanchor_2_64" id="FNanchor_2_64"></a><a href="#Footnote_2_64" class="fnanchor">[2]</a>. The -correspondence of these contrasts with the physiological phenomena will -be immediately apparent, while the occasional practice of Rubens in -opposing bright red to a still cooler flesh-colour, will be seen to be -equally consistent.</p> - -<p>The effect of white drapery (the comparative absence of colour) in -enhancing the glow of Titian's flesh-colour, has been frequently -pointed out:<a name="FNanchor_3_65" id="FNanchor_3_65"></a><a href="#Footnote_3_65" class="fnanchor">[3]</a> the shadows of white thus opposed to flesh, often -present, again, the physiological contrast, however delicately, -according to the hue of the carnation.<span class="pagenum"><a name="Page_361" id="Page_361">[Pg 361]</a></span> The lights, on the other hand, -are not, and probably never were, quite white, but from the first, -partook of the quality of depth, a quality assumed by the colourists to -pervade every part of a picture more or less.<a name="FNanchor_4_66" id="FNanchor_4_66"></a><a href="#Footnote_4_66" class="fnanchor">[4]</a></p> - -<p>It was before observed that the description of colours in words may -often convey ideas of too positive a nature, and it may be remarked -generally that the colours employed by the great masters are, in their -ultimate effect, more or less subdued or broken. The physiological -contrasts are, however, still applicable in the most comparatively -neutral scale.</p> - -<p>Again, the works of the colourists show that these oppositions are -not confined to large masses (except perhaps in works to be seen only -at a great distance); on the contrary, they are more or less apparent -in every part, and when at last the direct and intentional operations -of the artist may have been insufficient to produce them in their -minuter degrees, the accidental results of glazing and other methods -may be said to extend the contrasts to infinity. In such productions, -where every smallest portion is an epitome of the whole, the eye -still appreciates the fascinating effect of contrast, and the work is -pronounced to be true and complete, in the best sense of the words.</p> - -<p>The Venetian method of scumbling and glazing exhibits these minuter -contrasts within each other, and is thus generally considered more -refined than the system of breaking the colours, since it ensures a -fuller gradation of hues, and produces another class of contrasts, -those, namely, which result from degrees of transparence and opacity. -In some of the Flemish and Dutch masters, and sometimes in Reynolds, -the two methods are combined in great perfection.</p> - -<p><span class="pagenum"><a name="Page_362" id="Page_362">[Pg 362]</a></span></p> - -<p>The chromatic diagram does not appear to be older than the last -century. It is one of those happy adaptations of exacter principles to -the objects of taste which might have been expected from Leonardo da -Vinci. That its true principle was duly felt is abundantly evident from -the works of the colourists, as well as from the general observations -of early writers.<a name="FNanchor_5_67" id="FNanchor_5_67"></a><a href="#Footnote_5_67" class="fnanchor">[5]</a> The more practical directions occasionally to be -met with in the treatises of Leon Battista Alberti, Leonardo da Vinci -and others, are conformable to the same system. Some Italian works, -not written by painters, which pretend to describe this harmony, are, -however, very imperfect.<a name="FNanchor_6_68" id="FNanchor_6_68"></a><a href="#Footnote_6_68" class="fnanchor">[6]</a> A passage in Lodovico Dolce's Dialogue on -Colours is perhaps the only one worth quoting. "He," says that writer, -"who wishes to combine colours that are agreeable to the eye, will -put grey next dusky orange; yellow-green next rose-colour; blue next -orange; dark purple, black, next dark-green; white next black, and -white next flesh-colour."<a name="FNanchor_7_69" id="FNanchor_7_69"></a><a href="#Footnote_7_69" class="fnanchor">[7]</a> The Dialogue on Painting, by the same -author, has the reputation of containing some of Titian's precepts: -if the above passage may be traced to the same source, it must be -confessed that it is almost the only one of the kind in the treatise -from which it is taken.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_63" id="Footnote_1_63"></a><a href="#FNanchor_1_63"><span class="label">[1]</span></a> "Ardito veramente alquanto, sanguigno, e quasi -fiammeggiante."—<i>Zanetti della Pittura Veneziana</i>, Ven. 1771, p. -90. Warm as the flesh colour of the colourists is, it still never -approaches a positive hue, if we except some examples in frescoes and -other works intended to be seen at a great distance. Zanetti, speaking -of a fresco by Giorgione, now almost obliterated, compares the colour -to "un vivo raggio di cocente sole."—-<i>Varie Pitture a fresco dei -Principali Maestri Veneziani</i>. Ven. 1760.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_64" id="Footnote_2_64"></a><a href="#FNanchor_2_64"><span class="label">[2]</span></a> Ridolfi.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_65" id="Footnote_3_65"></a><a href="#FNanchor_3_65"><span class="label">[3]</span></a> Zanetti, I. ii.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_66" id="Footnote_4_66"></a><a href="#FNanchor_4_66"><span class="label">[4]</span></a> Two great authorities, divided by more than three -centuries, Leon Battista Alberti and Reynolds, have recommended this -subdued treatment of white. "It is to be remembered," says the first, -"that no surface should be made so white that it cannot be made more -so. In white dresses again, it is necessary to stop far short of the -last degree of whiteness."—<i>Della Pittura</i>, I. ii., compare with -Reynolds, vol. i. dis. 8.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_67" id="Footnote_5_67"></a><a href="#FNanchor_5_67"><span class="label">[5]</span></a> Vasari observes, "L'unione nella pittura è una discordanza -dicolori diversi accordati insième."—Vol. i. c. 18. This observation -is repeated by various writers on art in nearly the same words, and -at last appears in Sandrart: "Concordia, potissimum picturæ decus, -in discordiâ consistit, et quasi litigio colorum."—P. i. c. 5. The -source, perhaps, is Aristotle: he observes, "We are delighted with -harmony, because it is the union of contrary principles having a ratio -to each other."—<i>Problem.</i></p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_68" id="Footnote_6_68"></a><a href="#FNanchor_6_68"><span class="label">[6]</span></a> See "Occolti Trattato de' Colori." Parma, 1568.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_69" id="Footnote_7_69"></a><a href="#FNanchor_7_69"><span class="label">[7]</span></a> "Volendo l'uomo accoppiare insième colori che all'occhio -dilettino—porrà insième il berrettino col leonato; il verde-giallo con -l'incarnato e rosso; il turchino con l'arangi; il morello col verde -oscuro; il nero col bianco; il bianco con l'incarnato."—<i>Dialogo di -M. Lodovico Dolce nel quale si ragiona della qualità, diversità, e -proprietà de' colori</i>. Venezia, 1565.</p></div> - - - -<p class="para"><a id="NOTE_D"></a>NOTE D.—<a href="#a66">Par. 66.</a></p> - -<p>In some of these cases there can be no doubt that Goethe<span class="pagenum"><a name="Page_363" id="Page_363">[Pg 363]</a></span> attributes -the contrast too exclusively to the physiological cause, without -making sufficient allowance for the actual difference in the colour of -the lights. The purely physical nature of some coloured shadows was -pointed out by Pohlmann; and Dr. Eckermann took some pains to convince -Goethe of the necessity of making such a distinction. Goethe at first -adhered to his extreme view, but some time afterwards confessed to -Dr. Eckermann, that in the case of the blue shadows of snow (<a href="#a74">74</a>), the -reflection of the sky was undoubtedly to be taken into the account. -"Both causes may, however, operate together," he observed, "and the -contrast which a warm yellow light demands may heighten the effect of -the blue." This was all his opponent contended.<a name="FNanchor_1_70" id="FNanchor_1_70"></a><a href="#Footnote_1_70" class="fnanchor">[1]</a></p> - -<p>With a few such exceptions, the general theory of Goethe with regard -to coloured shadows is undoubtedly correct; the experiments with two -candles (68), and with coloured glass and fluids (80), as well as the -observations on the shadows of snow (75), are conclusive, for in all -these cases only one light is actually changed in colour, while the -other still assumes the complemental hue. "Coloured shadows," Dr. J. -Müller observes, "are usually ascribed to the physiological influence -of contrast; the complementary colour presented by the shadow being -regarded as the effect of internal causes acting on that part of the -retina, and not of the impression of coloured rays from without. This -explanation is the one adopted by Rumford, Goethe, Grotthuss, Brandes, -Tourtual, Pohlmann, and most authors who have studied the subject."<a name="FNanchor_2_71" id="FNanchor_2_71"></a><a href="#Footnote_2_71" class="fnanchor">[2]</a></p> - -<p>In the Historical Part the author gives an account of a scarce French -work, "Observations sur les Ombres Colorées," Paris, 1782. The -writer<a name="FNanchor_3_72" id="FNanchor_3_72"></a><a href="#Footnote_3_72" class="fnanchor">[3]</a> concludes that "the colour<span class="pagenum"><a name="Page_364" id="Page_364">[Pg 364]</a></span> of shadows is as much owing to -the light that causes them as to that which (more faintly) illumines -them."</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_70" id="Footnote_1_70"></a><a href="#FNanchor_1_70"><span class="label">[1]</span></a> Eckermann's "Gespräche mit Goethe," vol. ii. p. 76 and -280.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_71" id="Footnote_2_71"></a><a href="#FNanchor_2_71"><span class="label">[2]</span></a> "Elements of Physiology," by J. Müller, M. D., translated -from the German by William Baly, M.D. London, 1839.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_72" id="Footnote_3_72"></a><a href="#FNanchor_3_72"><span class="label">[3]</span></a> Anonymous, having only given the initials H. F. T.</p></div> - - - -<p class="para"><a id="NOTE_E"></a>NOTE E.—<a href="#a69">Par. 69.</a></p> - -<p>This opinion of the author is frequently repeated (<a href="#a201">201</a>, <a href="#a312">312</a>, <a href="#a591">591</a>), and -as it seems at first sight to be at variance with a received principle -of art, it may be as well at once to examine it.</p> - -<p>In order to see the general proposition in its true point of view, -it will be necessary to forget the arbitrary distinctions of light -and shade, and to consider all such modifications between highest -brightness and absolute darkness only as so many lesser degrees of -light.<a name="FNanchor_1_73" id="FNanchor_1_73"></a><a href="#Footnote_1_73" class="fnanchor">[1]</a> The author, indeed, by the word shadow, always understands a -lesser light.</p> - -<p>The received notion, as stated by Du Fresnoy,<a name="FNanchor_2_74" id="FNanchor_2_74"></a><a href="#Footnote_2_74" class="fnanchor">[2]</a> is much too positive -and unconditional, and is only true when we understand the "displaying" -light to comprehend certain degrees of half or reflected light, and the -"destroying" shade to mean the intensest degree of obscurity.</p> - -<p>There are degrees of brightness which destroy colour as well as -degrees of darkness.<a name="FNanchor_3_75" id="FNanchor_3_75"></a><a href="#Footnote_3_75" class="fnanchor">[3]</a> In general, colour resides in a mitigated -light, but a very little observation shows us that different colours -require different degrees of light to display them. Leonardo da Vinci -frequently inculcates the general principle above alluded to, but he -as frequently qualifies it; for he not only remarks that the highest -light may be comparative<span class="pagenum"><a name="Page_365" id="Page_365">[Pg 365]</a></span> privation of colour, but observes, with great -truth, that some hues are best displayed in their fully illumined -parts, some in their reflections, and some in their half-lights; and -again, that every colour is most beautiful when lit by reflections from -its own surface, or from a hue similar to its own.<a name="FNanchor_4_76" id="FNanchor_4_76"></a><a href="#Footnote_4_76" class="fnanchor">[4]</a></p> - -<p>The Venetians went further than Leonardo in this view and practice; -and he seems to allude to them when he criticises certain painters, -who, in aiming at clearness and fulness of colour, neglected what, in -his eyes, was of superior importance, namely, gradation and force of -chiaro-scuro.<a name="FNanchor_5_77" id="FNanchor_5_77"></a><a href="#Footnote_5_77" class="fnanchor">[5]</a></p> - -<p>That increase of colour supposes increase of darkness, as so often -stated by Goethe, may be granted without difficulty. To what extent, on -the other hand, increase of darkness, or rather diminution of light, -is accompanied by increase of colour, is a question which has been -variously answered by various schools. Examples of the total negation -of the principle are not wanting, nor are they confined to the infancy -of the art. Instances, again, of the opposite tendency are frequent -in Venetian and early Flemish pictures resembling the augmenting -richness of gems or of stained glass:<a name="FNanchor_6_78" id="FNanchor_6_78"></a><a href="#Footnote_6_78" class="fnanchor">[6]</a><span class="pagenum"><a name="Page_366" id="Page_366">[Pg 366]</a></span> indeed, it is not impossible -that the increase of colour in shade, which is so remarkable in the -pictures alluded to, may have been originally suggested by the rich -and fascinating effect of stained glass; and the Venetians, in this as -in many other respects, may have improved on a hint borrowed from the -early German painters, many of whom painted on glass.<a name="FNanchor_7_79" id="FNanchor_7_79"></a><a href="#Footnote_7_79" class="fnanchor">[7]</a></p> - -<p>At all events, the principle of still increasing in colour in certain -hues seems to have been adopted in Flanders and in Venice at an early -period;<a name="FNanchor_8_80" id="FNanchor_8_80"></a><a href="#Footnote_8_80" class="fnanchor">[8]</a> while Giorgione, in carrying the style to the most daring -extent, still recommended it by corresponding grandeur of treatment in -other respects.</p> - -<p>The same general tendency, except that the technical methods are -less transparent, is, however, very striking in some of the painters -of the school of Umbria, the instructors or early companions of -Raphael.<a name="FNanchor_9_81" id="FNanchor_9_81"></a><a href="#Footnote_9_81" class="fnanchor">[9]</a> The influence of<span class="pagenum"><a name="Page_367" id="Page_367">[Pg 367]</a></span> these examples, as well as that of Fra -Bartolommeo, in Florence, is distinctly to be traced in the works of -the great artist just named, but neither is so marked as the effect -of his emulation of a Venetian painter at a later period. The glowing -colour, sometimes bordering on exaggeration, which Raphael adopted -in Rome, is undoubtedly to be attributed to the rivalry of Sebastian -del Piombo. This painter, the best of Giorgione's imitators, arrived -in Rome, invited by Agostini Chigi, in 1511, and the most powerful of -Raphael's frescoes, the Heliodorus and Mass of Bolsena, as well as -some portraits in the same style, were painted in the two following -years. In the hands of some of Raphael's scholars, again, this extreme -warmth was occasionally carried to excess, particularly by Pierino del -Vaga, with whom it often degenerated into redness. The representative -of the glowing manner in Florence was Fra Bartolommeo, and, in the -same quality, considered abstractedly, some painters of the school of -Ferrara were second to none.</p> - -<p>In another Note (par. <a href="#a177">177</a>) some further considerations<span class="pagenum"><a name="Page_368" id="Page_368">[Pg 368]</a></span> are offered, -which may partly explain the prevalence of this style in the beginning -of the sixteenth century; here we merely add, that the conditions under -which the appearance itself is most apparent in nature are perhaps more -obvious in Venice than elsewhere. The colour of general nature may be -observed in all places with almost equal convenience, but with regard -to an important quality in living nature, namely, the colour of flesh, -perhaps there are no circumstances in which its effects at different -distances can be so conveniently compared as when the observer and the -observed gradually approach and glide past each other on so smooth an -element and in so undisturbed a manner as on the canals and in the -gondolas of Venice;<a name="FNanchor_10_82" id="FNanchor_10_82"></a><a href="#Footnote_10_82" class="fnanchor">[10]</a> the complexions, from the peculiar mellow -carnations of the Italian women to the sun-burnt features and limbs -of the mariners, presenting at the same time the fullest variety in -another sense.</p> - -<p>At a certain distance—the colour being always assumed to be unimpaired -by interposed atmosphere—the reflections appear kindled to intenser -warmth; the fiery glow of Giorgione is strikingly apparent; the colour -is seen in its largest relation; the <i>macchia</i>,<a name="FNanchor_11_83" id="FNanchor_11_83"></a><a href="#Footnote_11_83" class="fnanchor">[11]</a> an expression so -emphatically used by Italian writers, appears in all its quantity, and -the reflections being the focus of warmth, the hue seems to deepen in -shade.</p> - -<p>A nearer view gives the detail of cooler tints more perceptibly,<a name="FNanchor_12_84" id="FNanchor_12_84"></a><a href="#Footnote_12_84" class="fnanchor">[12]</a> -and the forms are at the same time more distinct. Hence Lanzi is quite -correct when, in distinguishing the style of Titian from that of -Giorgione, he says that Titian's<span class="pagenum"><a name="Page_369" id="Page_369">[Pg 369]</a></span> was at once more defined and less -fiery.<a name="FNanchor_13_85" id="FNanchor_13_85"></a><a href="#Footnote_13_85" class="fnanchor">[13]</a> In a still nearer observation the eye detects the minute -lights which Leonardo da Vinci says are incompatible with effects such -as those we have described<a name="FNanchor_14_86" id="FNanchor_14_86"></a><a href="#Footnote_14_86" class="fnanchor">[14]</a> and which, accordingly, we never find -in Giorgione and Titian. This large impression of colour, which seems -to require the condition of comparative distance for its full effect, -was most fitly employed by the same great artists in works painted in -the open air or for large altar-pieces. Their celebrated frescoes on -the exterior of the Fondaco de' Tedeschi at Venice, to judge from their -faint remains and the descriptions of earlier writers, were remarkable -for extreme warmth in the shadows. The old frescoes in the open air -throughout Friuli have often the same character, and, owing to the -fulness of effect which this treatment ensures, are conspicuous at a -very great distance.<a name="FNanchor_15_87" id="FNanchor_15_87"></a><a href="#Footnote_15_87" class="fnanchor">[15]</a></p> - -<p>In assuming that the Venetian painters may have acquired a taste for -this breadth<a name="FNanchor_16_88" id="FNanchor_16_88"></a><a href="#Footnote_16_88" class="fnanchor">[16]</a> of colour under the circumstances above alluded to, -it is moreover to be remembered that the time for this agreeable -study was the evening; when the sun had already set behind the hills -of Bassano; when the light was glowing but diffused; when shadows<span class="pagenum"><a name="Page_370" id="Page_370">[Pg 370]</a></span> -were soft—conditions all agreeing with the character of their -colouring:<a name="FNanchor_17_89" id="FNanchor_17_89"></a><a href="#Footnote_17_89" class="fnanchor">[17]</a> above all, when the hour invited the fairer portion of -the population to betake themselves in their gondolas to the lagunes. -The scene of this "promenade" was to the north of Venice, the quarter -in which Titian at one time lived. A letter exists written by Francesco -Priscianese, giving an account of his supping with the great painter in -company with Jacopo Nardi, Pietro Aretino, the sculptor Sansovino, and -others. The writer speaks of the beauty of the garden, where the table -was prepared, looking over the lagunes towards Murano, "which part of -the sea," he continues, "as soon as the sun was down, was covered with -a thousand gondolas, graced with beautiful women, and enlivened by the -harmony of voices and instruments, which lasted till midnight, forming -a pleasing accompaniment to our cheerful repast."<a name="FNanchor_18_90" id="FNanchor_18_90"></a><a href="#Footnote_18_90" class="fnanchor">[18]</a></p> - -<p>To return to Goethe: perhaps the foregoing remarks may warrant the -conclusion that his idea of colour in shadow is not irreconcileable -with the occasional practice of the best painters. The highest examples -of the style thus defined are, or were, to be found in the works of -Giorgione<a name="FNanchor_19_91" id="FNanchor_19_91"></a><a href="#Footnote_19_91" class="fnanchor">[19]</a> and Titian, and hence the style itself, though "within -that circle"<span class="pagenum"><a name="Page_371" id="Page_371">[Pg 371]</a></span> few "dare walk" is to be considered the grandest and -most perfect. Its possible defects or abuse are not to be dissembled: -in addition to the danger of exaggeration<a name="FNanchor_20_92" id="FNanchor_20_92"></a><a href="#Footnote_20_92" class="fnanchor">[20]</a> it is seldom united -with the plenitude of light and shade, or with roundness; yet, where -fine examples of both modes of treatment may be compared, the charm -of colour has perhaps the advantage.<a name="FNanchor_21_93" id="FNanchor_21_93"></a><a href="#Footnote_21_93" class="fnanchor">[21]</a> The difficulty of uniting -qualities so different in their nature, is proved by the very rare -instances in which it has been accomplished. Tintoret in endeavouring -to add chiaro-scuro to Venetian colour, in almost every instance fell -short of the glowing richness of Titian.<a name="FNanchor_22_94" id="FNanchor_22_94"></a><a href="#Footnote_22_94" class="fnanchor">[22]</a></p> - -<p><span class="pagenum"><a name="Page_372" id="Page_372">[Pg 372]</a></span></p> - -<p>Giacomo Bassan and his imitators, even in their dark effects, still had -the principle of the gem in view: their light, in certain hues, is the -minimum of colour, their lower tones are rich, their darks intense, -and all is sparkling.<a name="FNanchor_23_95" id="FNanchor_23_95"></a><a href="#Footnote_23_95" class="fnanchor">[23]</a> Of the great painters who, beginning, on -the other hand, with chiaro-scuro, sought to combine with it the full -richness of colour, Correggio, in the opinion of many, approached -perfection nearest; but we may perhaps conclude with greater justice -that the desired excellence was more completely attained by Rembrandt -than by any of the Italians.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_73" id="Footnote_1_73"></a><a href="#FNanchor_1_73"><span class="label">[1]</span></a> Leonardo da Vinci observes: "L'ombra è diminuzione di -luce, tenebre è privazione di luce." And again: "Sempre il minor lume è -ombra del lume maggiore."—<i>Trattato della Pittura</i>, pp. 274-299. -</p> -<p> -N. B. The same edition before described has been consulted throughout.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_74" id="Footnote_2_74"></a><a href="#FNanchor_2_74"><span class="label">[2]</span></a> -</p> -<p> -"Lux varium vivumque dabit, nullum umbra colorem."<br /> -<span style="margin-left: 20.5em;"><i>De Arte Graphicá</i>.</span><br /> -</p> -<p> -"Know first that light displays and shade destroys<br /> -Refulgent nature's variegated dies."—Mason's <i>Translation</i>.<br /> -</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_75" id="Footnote_3_75"></a><a href="#FNanchor_3_75"><span class="label">[3]</span></a> A Spanish writer, Diego de Carvalho e Sampayo, quoted -by Goethe ("Farbenlehre," vol. ii.), has a similar observation. This -destroying effect of light is striking in climates where the sun is -powerful, and was not likely to escape the notice of a Spaniard.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_76" id="Footnote_4_76"></a><a href="#FNanchor_4_76"><span class="label">[4]</span></a> Trattato, pp. 103, 121, 123, 324, &c.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_77" id="Footnote_5_77"></a><a href="#FNanchor_5_77"><span class="label">[5]</span></a> Ib. pp. 85, 134.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_78" id="Footnote_6_78"></a><a href="#FNanchor_6_78"><span class="label">[6]</span></a> Absolute opacity, to judge from the older specimens -of stained glass, seems to have been considered inadmissible. The -window was to admit light, however modified and varied, in the form -prescribed by the architect, and that form was to be preserved. This -has been unfortunately lost sight of in some modern glass-painting, -which, by excluding the light in large masses, and adopting the -opacity of pictures (the reverse of the influence above alluded to), -has interfered with the architectural symmetry in a manner far from -desirable. On the other hand, if we suppose painting at any period -to have aimed at the imitation of stained glass, such an imitation -must of necessity have led to extreme force; for the painter sets -out by substituting a mere white ground for the real light of the -sky, and would thus be compelled to subdue every tone accordingly. -In such an imitation his colour would soon deepen to its intensest -state; indeed, considerable portions of the darker hues would be lost -in obscurity. The early Flemish pictures seldom err on the side of -a gay superabundance of colour; on the contrary, they are generally -remarkable for comparatively cool lights, for extreme depth, and a -certain subdued splendour, qualities which would necessarily result -from the imitation or influence in question.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_79" id="Footnote_7_79"></a><a href="#FNanchor_7_79"><span class="label">[7]</span></a> See Langlois, "Peinture sur Verre." Rouen, 1832; -Descamps, "La Vie des Peintres Flamands;" and Gessert, "Geschichte der -Glasmalerei." Stutgard, 1839. The antiquity of the glass manufactory -of Murano (Venice) is also not to be forgotten. Vasari objects to the -Venetian glass, because it was darker in colour than that of Flanders, -France, and England; but this very quality was more likely to have an -advantageous influence on the style of the early oil-painters. The use -of stained glass was, however, at no period very general in Italy.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_8_80" id="Footnote_8_80"></a><a href="#FNanchor_8_80"><span class="label">[8]</span></a> Zanetti, "Della Pittura Veneziana," marks the progress of -the early Venetian painters by the gradual use of the warm outline. -There are some mosaics in St. Mark's which have the effect of -flesh-colour, but on examination, the only red colour used is found -to be in the outlines and markings. Many of the drawings of the old -masters, heightened with red in the shadows, have the same effect. In -these drawings the artists judiciously avoided colouring the lips and -cheeks much, for this would only have betrayed the want of general -colour, as is observable when statues are so treated.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_9_81" id="Footnote_9_81"></a><a href="#FNanchor_9_81"><span class="label">[9]</span></a> Andrea di Luigi, called L'Ingegno, and Niccolo di Fuligno, -are cited as the most prominent examples. See Rumohr, "Italienische -Forschungen." Perogino himself occasionally adopted a very glowing -colour. -</p> -<p> -The early Italian schools which adhered most to the Byzantine types -appear to have been also the most remarkable for depth, or rather -darkness, of colour. This fidelity to customary representation was -sometimes, as in the schools of Umbria, and to a certain extent in -those of Siena and Bologna, the result of a religious veneration for -the ancient examples; in others, as in Venice, the circumstance of -frequent intercourse with the Levant is also to be taken into the -account. The Greek pictures of the Madonna, not to mention other -representations, were extremely dark, in exaggerated conformity, -it is supposed, with the tradition respecting her real complexion -(see D'Agincourt, vol. iv. p. 1); a belief which obtained so late as -Lomazzo's time, for, speaking of the Madonna, he observes, "Leggesi -però che fu alquanto bruna." Giotto, who with the independence of -genius betrayed a certain contempt for these traditions, failed perhaps -to unite improvement with novelty when he substituted a pale white -flesh-colour for the traditional brown. Some specimens of his works, -still existing at Padua, present a remarkable contrast in this respect -with the earliest productions of the Venetian and Paduan artists. His -works at Florence differ as widely from those of the earlier painters -of Tuscany. This peculiarity was inherited by his imitators, and at -one time almost characterised the Florentine school. Leon Battista -Alberti was not perhaps the first who objected to it ("Vorrei io -che dai pittori fosse comperato il color bianco assai più caro che -le presiosissime gemme."—<i>Della Pittura</i>, I. ii.) The attachment -of Fra Bartolommeo to the grave character of the Christian types is -exemplified in his deep colouring, as well as in other respects.</p></div> -<hr class="r5" /> -<div class="footnote"> - -<p><a name="Footnote_10_82" id="Footnote_10_82"></a><a href="#FNanchor_10_82"><span class="label">[10]</span></a> Holland might be excepted, and in Holland similar causes -may have had a similar influence.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_11_83" id="Footnote_11_83"></a><a href="#FNanchor_11_83"><span class="label">[11]</span></a> Local colour; literally, the <i>blot</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_12_84" id="Footnote_12_84"></a><a href="#FNanchor_12_84"><span class="label">[12]</span></a> Zanetti ventures to single out the picture of Tobit and -the Angel in S. Marziale as the first example of Titian's own manner, -and in which a direct imitation of Giorgione is no longer apparent. In -this picture the lights are cool and the blood-tint very effective.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_13_85" id="Footnote_13_85"></a><a href="#FNanchor_13_85"><span class="label">[13]</span></a> "Meno sfumato, men focoso."—<i>Storia Pittorica</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_14_86" id="Footnote_14_86"></a><a href="#FNanchor_14_86"><span class="label">[14]</span></a> "La prima cosa che de' colori si perde nelle distante è -il lustro, loro minima parte."—<i>Trattato</i>, p. 213; and elsewhere, "I -lumi principali in picciol luogo son quelli che in picciola distanza -sono i primi che si perdono all' occhio."—p. 128.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_15_87" id="Footnote_15_87"></a><a href="#FNanchor_15_87"><span class="label">[15]</span></a> A colossal St. Christopher, the usual subject, is -frequently seen occupying the whole height of the external wall of a -church. We have here an example of the influence of religion, such -as it was, even on the style of colouring and practical methods of -the art. The mere sight of the image of St. Christopher, the type of -strength, was considered sufficient to reinvigorate those who were -exhausted by the labours of husbandry. The following is a specimen of -the inscriptions inculcating this belief:— -</p> -<p style="margin-left: 20%;"> -"Christophori Sancti speciem quicumque tuetur,<br /> -Illo namque die nullo languore tenetur."<br /> -</p> -<p> -Hence the practice of painting the figure on the outside of churches, -hence its colossal size, and hence the powerful qualities in colour -above described. See Maniago, "Storia delle Belle Arti Friulane."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_16_88" id="Footnote_16_88"></a><a href="#FNanchor_16_88"><span class="label">[16]</span></a> The authority of Fuseli sufficiently warrants the -application of the term breadth to colour; he speaks of Titian's -"breadth of local tint."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_17_89" id="Footnote_17_89"></a><a href="#FNanchor_17_89"><span class="label">[17]</span></a> Zanetti quotes an opinion of the painters of his time -to the same effect:—"Teneano essi (alcuni maestri) per cosa certa, -che in molte opere Tiziano volesse fingere il lume—quale si vede -nell' inclinarsi del sole verso la sera. Gli orizzonti assai luminosi -dietro le montagne, le ombre incerte e più le carnagioni brunette e -rosseggianti delle figure, gl'induceano a creder questo."—Lib. ii. -Leonardo da Vinci observes, "Quel corpo che si troverà in mediocre lume -fia in lui poca differenza da' lumi all' ombre. E questo accade sul far -della sera—e queste opere sono dolci ed hacci grazia ogni qualità di -volto," &c.—p. 336. Elsewhere, "Le ombre fatte dal sole od altri lumi -particolari sono senza grazia."—p. 357; see also p. 247.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_18_90" id="Footnote_18_90"></a><a href="#FNanchor_18_90"><span class="label">[18]</span></a> See "Francesco Priscianese De' Primi Principii della -Lingua Latina," Venice, 1550. The letter is at the end of the work. It -is quoted in Ticozzi's "Vite de' Pittori Vecelli," Milan, 1817.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_19_91" id="Footnote_19_91"></a><a href="#FNanchor_19_91"><span class="label">[19]</span></a> The works of Giorgione are extremely rare. The pictures -best calculated to give an idea of the glowing manner for which -he is celebrated, are the somewhat early works and several of the -altar-pieces of Titian, the best specimens of Palma Vecchio, and the -portraits of Sebastian del Piombo.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_20_92" id="Footnote_20_92"></a><a href="#FNanchor_20_92"><span class="label">[20]</span></a> Zanetti and Lodovico Dolce mention Lorenzo Lotto as an -instance of the excess of Giorgione's style. Titian himself sometimes -overstepped the mark, as his biographers confess, and as appears, -among other instances, from the head of St. Peter in the picture (now -in the Vatican) in which the celebrated St. Sebastian is introduced. -Raphael was criticised by some cardinals for a similar defect. See -"Castiglione, Il Cortigiano," 1. ii. -</p> -<p> -In the same paragraph to which the present observations refer, the -authority of Kircher is quoted; his treatise, "Ars magna lucis et -umbrae," was published in Rome in 1646. In a portrait of Nicholas -Poussin, engraved by Clouet, the painter is represented holding a book, -which, from the title and the circumstance of Poussin having lived in -Rome in Kircher's time, Goethe supposes to be the work in question. The -abuse of the principle above alluded to, is perhaps exemplified in the -red half-tints observable in some of Poussin's figures. -</p> -<p> -The augmentation of colour in subdued light was still more directly -taught by Lomazzo. He composes the half-tints of flesh merely by -diminishing the quantity of white, the proportions of the other colours -employed (for he enters into minute details) remaining unaltered. See -his "Trattato della arte della Pittura," Milan, 1584, p. 301.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_21_93" id="Footnote_21_93"></a><a href="#FNanchor_21_93"><span class="label">[21]</span></a> In the Dresden Gallery, a picture attributed to -Titian—at all events a lucid Venetian picture—hangs next the St. -George of Correggio. After looking at the latter, the Venetian work -appears glassy and unsubstantial, but on reversing the order of -comparison, the Correggio may be said to suffer more, and for a moment -its fine transitions of light and shade seem changed to heaviness.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_22_94" id="Footnote_22_94"></a><a href="#FNanchor_22_94"><span class="label">[22]</span></a> The finest works of Tintoret—-the Crucifixion and the -Miracolo del Servo (considered here merely with reference to their -colour,) may be said to combine the excellences of Titian and Giacomo -Bassan, on a grand scale; the sparkling clearness of the latter is -one of the prominent characteristics of these pictures. Tintoret is -reported to have once said that a union of his own knowledge of form -with Bassan's colour would be the perfection of painting. See "Verei -Notizie de' Pittori di Bassano;" Ven. 1775, p. 61.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_23_95" id="Footnote_23_95"></a><a href="#FNanchor_23_95"><span class="label">[23]</span></a> That this last quality, the characteristic of Bassan's -best pictures, was held in high estimation by Paul Veronese, is not -only evident from that painter's own works, but from the circumstance -of his preferring to place his sons with Bassan rather than with any -other painter. (See "Boschini Carta del Navegar," p. 280.) The Baptism -of Sta. Lucilla, in Boschini's time considered the finest of Giacomo's -works, is still in the church of S. Valentino, at Bassano, and may be -considered the type of the lucid and sparkling manner.</p></div> - - - -<p class="para"><a id="NOTE_F"></a>NOTE F.—<a href="#a83">Par. 83.</a></p> - -<p>The author, in these instances, seems to be anticipating his -subsequent explanations on the effect of semi-transparent mediums. -For an explanation of the general view contained in these paragraphs -respecting the gradual increase of colour from high light, see the last -Note.</p> - -<p>The anonymous French work before alluded to, among other interesting -examples, contains a chapter on shadows cast by the upper light of the -sky and coloured by the setting sun. The effect of this remarkable -combination is, that the light on a wall is most coloured immediately -under a projecting roof, and becomes comparatively neutralised in -proportion to its distance from the edge of the darkest shade.</p> - - -<p class="para"><a id="NOTE_G"></a>NOTE G.—<a href="#a98">Par. 98.</a></p> - -<p>"The simplest case of the phenomenon, which Goethe calls a subjective -halo, and one which at once explains its cause, is the following. -Regard a red wafer on a sheet of white paper, keeping the eye -stedfastly fixed on a point at<span class="pagenum"><a name="Page_373" id="Page_373">[Pg 373]</a></span> its center. When the retina is -fatigued, withdraw the head a little from the paper, and a green halo -will appear to surround the wafer. By this slight increase of distance -the image of the wafer itself on the retina becomes smaller, and the -ocular spectrum which before coincided with the direct image, being -now relatively larger, is seen as a surrounding ring."—S. F. Goethe -mentions cases of this kind, but does not class them with subjective -halos. See Par. 30.</p> - - -<p class="para"><a id="NOTE_H"></a>NOTE H.—<a href="#a113">Par. 113.</a></p> - -<p>"Cases of this kind are by no means uncommon. Several interesting -ones are related in Sir John Herschell's article on Light in the -Encyclopædia Metropolitana. Careful investigation has, however, shown -that this defect of vision arises in most, if not in all cases, from -an inability to perceive the red, not the blue rays. The terms are so -confounded by the individuals thus affected, that the comparison of -colours in their presence is the only criterion."—S. F.</p> - - -<p class="para"><a id="NOTE_I"></a>NOTE I.—<a href="#a135">Par. 135.</a></p> - -<p>The author more than once admits that this chapter on "Pathological -Colours" is very incomplete, and expresses a wish (Par. 734) that some -medical physiologists would investigate the subject further. This was -afterwards in a great degree accomplished by Dr. Johannes Müller, in -his memoir "Über die Phantastischen Gesichtserscheinungen." Coblentz, -1826. Similar phenomena have been also investigated with great labour -and success by Purkinje. For a collection of extraordinary facts of the -kind recorded by these writers, the reader may consult Scott's Letters -on Demonology and Witchcraft.<a name="FNanchor_1_96" id="FNanchor_1_96"></a><a href="#Footnote_1_96" class="fnanchor">[1]</a> The instances adduced by Müller and -others are, however, intended to prove the inherent capacity of the -organ of vision to produce light and colours. In some maladies of the -eye, the patient, it seems,<span class="pagenum"><a name="Page_374" id="Page_374">[Pg 374]</a></span> suffers the constant presence of light -without external light. The exciting principle in this case is thus -proved to be within, and the conclusion of the physiologists is that -external light is only one of the causes which produce luminous and -coloured impressions. That this view was anticipated by Newton may be -gathered from the concluding "query" in the third book of his Optics. -</p> -<hr class="r5" /> -<div class="footnote"> - -<p><a name="Footnote_1_96" id="Footnote_1_96"></a><a href="#FNanchor_1_96"><span class="label">[1]</span></a> See also a curious passage on the beatific vision of the -monks of Mount Athos, in Gibbon, chap. 63.</p></div> - - - -<p class="para"><a id="NOTE_K"></a>NOTE K.—<a href="#a140">Par. 140.</a></p> - -<p>"Catoptrical colours. The colours included under this head are -principally those of fibres and grooved surfaces; they can be produced -artificially by cutting parallel grooves on a surface of metal from -2000 to 10,000 in the inch. See 'Brewster's Optics,' p. 120. The -colours called by Goethe <i>paroptical</i>, correspond with those produced -by the diffraction or inflection of light in the received theory.—See -Brewster, p. 95. The phenomena included under the title 'Epoptical -Colours,' are generally known as the colours of thin plates. They vary -with the thickness of the film, and the colour seen by reflection -always differs from that seen by transmission. The laws of these -phenomena have been thoroughly investigated. See Nobili, and Brewster, -p. 100."—S. F.</p> - -<p>The colours produced by the transmission of polarised light through -chrystalised mediums, were described by Goethe, in his mode, -subsequently to the publication of his general theory, under the name -of Entoptic Colours. See note to Par. 485.</p> - - -<p class="para"><a id="NOTE_L"></a>NOTE L.—<a href="#a150">Par. 150.</a></p> - -<p>We have in this and the next paragraph the outline of Goethe's system. -The examples that follow seem to establish the doctrine here laid -down, but there are many cases which it appears cannot be explained on -such principles: hence, philosophers generally prefer the theory of -absorption, according to which it appears that certain mediums "have -the property of absorbing some of the component<span class="pagenum"><a name="Page_375" id="Page_375">[Pg 375]</a></span> rays of white light, -while they allow the passage of others."<a name="FNanchor_1_97" id="FNanchor_1_97"></a><a href="#Footnote_1_97" class="fnanchor">[1]</a></p> - -<p>Whether all the facts adduced by Goethe—for instance, that recorded -in Par. <a href="#a172">172</a>, are to be explained by this doctrine, we leave to the -investigators of nature to determine. Dr. Eckermann, in conversing with -Goethe, thus described the two leading phenomena (156, 158) as seen by -him in the Alps. "At a distance of eighteen or twenty miles at mid-day -in bright sunshine, the snow appeared yellow or even reddish, while the -dark parts of the mountain, free from snow, were of the most decided -blue. The appearances did not surprise me, for I could have predicted -that the mass of the interposed medium would give a deep yellow tone -to the white snow, but I was pleased to witness the effect, since it -so entirely contradicted the erroneous views of some philosophers, -who assert that the air has a blue-tinging quality. The observation, -said Goethe, is of importance, and contradicts the error you allude to -completely."<a name="FNanchor_2_98" id="FNanchor_2_98"></a><a href="#Footnote_2_98" class="fnanchor">[2]</a></p> - -<p>The same writer has some observations to the same effect on the colour -of the Rhone at Geneva. A circumstance of an amusing nature which he -relates in confirmation of Goethe's theory, deserves to be inserted. -"Here (at Strasburg), passing by a shop, I saw a little glass bust -of Napoleon, which, relieved as it was against the dark interior<span class="pagenum"><a name="Page_376" id="Page_376">[Pg 376]</a></span> of -the room, exhibited every gradation of blue, from milky light blue -to deep violet. I foresaw that the bust seen from within the shop -with the light behind it, would present every degree of yellow, and I -could not resist walking in and addressing the owner, though perfectly -unknown to me. My first glance was directed to the bust, in which, to -my great joy, I saw at once the most brilliant colours of the warmer -kind, from the palest yellow to dark ruby red. I eagerly asked if I -might be allowed to purchase the bust; the owner replied that he had -only lately brought it with him from Paris, from a similar attachment -to the emperor to that which I appeared to feel, but, as my ardour -seemed far to surpass his, I deserved to possess it. So invaluable -did this treasure seem in my eyes, that I could not help looking at -the good man with wonder as he put the bust into my hands for a few -franks. I sent it, together with a curious medal which I had bought -in Milan, as a present to Goethe, and when at Frankfort received the -following letter from him." The letter, which Dr. Eckermann gives -entire, thus concludes—"When you return to Weimar you shall see the -bust in bright sunshine, and while the transparent countenance exhibits -a quiet blue,<a name="FNanchor_3_99" id="FNanchor_3_99"></a><a href="#Footnote_3_99" class="fnanchor">[3]</a> the thick mass of the breast and epaulettes glows with -every gradation of warmth, from the most powerful ruby-red downwards; -and as the granite statue of Memnon uttered harmonious sounds, so the -dim glass image displays itself in the pomp of colours. The hero is -victorious still in supporting the Farbenlehre."<a name="FNanchor_4_100" id="FNanchor_4_100"></a><a href="#Footnote_4_100" class="fnanchor">[4]</a></p> - -<p>One effect of Goethe's theory has been to invite the attention of -scientific men to facts and appearances which had before been unnoticed -or unexplained. To the above cases may be added the very common, but -very important, fact in painting, that a light warm colour, passed in -a semi-transparent<span class="pagenum"><a name="Page_377" id="Page_377">[Pg 377]</a></span> state over a dark one, produces a cold, bluish -hue, while the operation reversed, produces extreme warmth. On the -judicious application of both these effects, but especially of the -latter, the richness and brilliancy of the best-coloured pictures -greatly depends. The principle is to be recognised in the productions -of schools apparently opposite in their methods. Thus the practice -of leaving the ground, through which a light colour is apparent, as -a means of ensuring warmth and depth, is very common among the Dutch -and Flemish painters. The Italians, again, who preferred a solid -under-painting, speak of internal light as the most fascinating quality -in colour. When the ground is entirely covered by solid painting, as -in the works of some colourists, the warmest tints in shadows and -reflections have been found necessary to represent it. This was the -practice of Rembrandt frequently, and of Reynolds universally, but the -glow of their general colour is still owing to its being repeatedly -or ultimately enriched on the above principle. Lastly, the works of -those masters who were accustomed to paint on dark grounds are often -heavy and opaque; and even where this influence of the ground was -overcome, the effects of time must be constantly diminishing the warmth -of their colouring as the surface becomes rubbed and the dark ground -more apparent through it. The practice of painting on dark grounds was -intended by the Carracci to compel the students of their school to -aim at the direct imitation of the model, and to acquire the use of -the brush; for the dark ground could only be overcome by very solid -painting. The result answered their expectations as far as dexterity of -pencil was concerned, but the method was fatal to brilliancy of colour. -An intelligent writer of the seventeenth century<a name="FNanchor_5_101" id="FNanchor_5_101"></a><a href="#Footnote_5_101" class="fnanchor">[5]</a> relates that Guido -adopted his extremely light style from seeing the rapid change in some -works of the Carracci soon after they were done. It<span class="pagenum"><a name="Page_378" id="Page_378">[Pg 378]</a></span> is important, -however, to remark, that Guido's remedy was external rather than -internal brilliancy; and it is evident that so powerless a brightness -as white paint can only acquire the splendour of light by great -contrast, and, above all, by being seen through external darkness. The -secret of Van Eyck and his contemporaries is always assumed to consist -in the vehicle (varnish or oils) he employed; but a far more important -condition of the splendour of colour in the works of those masters was -the careful preservation of internal light by painting thinly, but -ultimately with great force, on white grounds. In some of the early -Flemish pictures in the Royal Gallery at Munich, it may be observed, -that wherever an alteration was made by the painter, so that a light -colour is painted over a dark one, the colour is as opaque as in any -of the more modern pictures which are generally contrasted with such -works. No quality in the vehicle could prevent this opacity under such -circumstances; and on the other hand, provided the internal splendour -is by any means preserved, the vehicle is comparatively unimportant.</p> - -<p>It matters not (say the authorities on these points) whether the effect -in question is attained by painting thinly over the ground, in the -manner of the early Flemish painters and sometimes of Rubens, or by -painting a solid light preparation to be afterwards toned to richness -in the manner of the Venetians. Among the mechanical causes of the -clearness of colours superposed on a light preparation may be mentioned -that of careful grinding. All writers on art who have descended to -practical details have insisted on this. From the appearance of some -Venetian pictures it may be conjectured that the colours of the -solid under-painting were sometimes less perfectly ground than the -scumbling colours (the light having to pass through the one and to -be reflected from the other). The Flemish painters appear to have -used carefully-ground pigments universally. This is very evident in -Flemish copies from Raphael, which, though<span class="pagenum"><a name="Page_379" id="Page_379">[Pg 379]</a></span> equally impasted with -the originals, are to be detected, among other indications, by the -finely-ground colours employed.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_97" id="Footnote_1_97"></a><a href="#FNanchor_1_97"><span class="label">[1]</span></a> See "Müller's Elements of Physiology," translated from -the German by William Baly, M.D. "The laws of absorption," it has been -observed, "have not been studied with so much success as those of -other phenomena of physical optics, but some excellent observations -on the subject will be found in Herschell's Treatise on Light in the -Encyclopædia Metropolitana, § III."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_98" id="Footnote_2_98"></a><a href="#FNanchor_2_98"><span class="label">[2]</span></a> "Eckermann's Gespräche mit Goethe," vol. ii. p. 280. -Leonardo da Vinci had made precisely the same observation. "A distant -mountain will appear of a more beautiful blue in proportion as it is -dark in colour. The illumined air, interposed between the eye and the -dark mass, being thinner towards the summit of the mountain, will -exhibit the darkness as a deeper blue and <i>vice versâ</i>."—<i>Trattato -della Pittura</i>, p. 143. Elsewhere—"The air which intervenes between -the eye and dark mountains becomes blue; but it does not become blue in -(before) the light part, and much less in (before) the portion that is -covered with snow."—p. 244.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_99" id="Footnote_3_99"></a><a href="#FNanchor_3_99"><span class="label">[3]</span></a> This supposes either that the mass was considerably -thicker, or that there was a dark ground behind the head, and a light -ground behind the rest of the figure.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_100" id="Footnote_4_100"></a><a href="#FNanchor_4_100"><span class="label">[4]</span></a> "Eckermann's Gespräche mit Goethe," vol. ii. p. 242.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_101" id="Footnote_5_101"></a><a href="#FNanchor_5_101"><span class="label">[5]</span></a> Scanelli, "Microcosmo della Pittura," Cesena, 1657, p. -114.</p></div> - - - -<p class="para"><a id="NOTE_M"></a>NOTE M.—<a href="#a177">Par. 177.</a></p> - -<p>Without entering further into the scientific merits or demerits of -this chapter on the "First Class of Dioptrical Colours," it is to be -observed that several of the examples correspond with the observations -of Leonardo da Vinci, and again with those of a much older authority, -namely, Aristotle. Goethe himself admits, and it has been remarked by -others, that his theory, in many respects, closely resembles that of -Aristotle: indeed he confesses<a name="FNanchor_1_102" id="FNanchor_1_102"></a><a href="#Footnote_1_102" class="fnanchor">[1]</a> that at one time he had an intention -of merely paraphrasing that philosopher's Treatise on Colours.<a name="FNanchor_2_103" id="FNanchor_2_103"></a><a href="#Footnote_2_103" class="fnanchor">[2]</a></p> - -<p>We have already remarked (Note on par. <a href="#a150">150</a>) that Goethe's notion with -regard to the production of warm colours, by the interposition of dark -transparent mediums before a light ground, agrees with the practice of -the best schools in colouring; and it is not impossible that the same -reasons which may make this part of the doctrine generally acceptable -to artists now, may have recommended the very similar theory of -Aristotle to the painters of the fifteenth and sixteenth centuries: -at all events, it appears that the ancient theory was known to those -painters.</p> - -<p>It is unnecessary to dwell on the fact that the doctrines of Aristotle -were enthusiastically embraced and generally inculcated at the period -in question;<a name="FNanchor_3_104" id="FNanchor_3_104"></a><a href="#Footnote_3_104" class="fnanchor">[3]</a> but it has not been<span class="pagenum"><a name="Page_380" id="Page_380">[Pg 380]</a></span> observed that the Italian writers -who translated, paraphrased, and commented on Aristotle's Treatise -on Colours in particular, were in several instances the personal -friends of distinguished painters. Celio Calcagnini<a name="FNanchor_4_105" id="FNanchor_4_105"></a><a href="#Footnote_4_105" class="fnanchor">[4]</a> had the highest -admiration for Raphael; Lodovico Dolce<a name="FNanchor_5_106" id="FNanchor_5_106"></a><a href="#Footnote_5_106" class="fnanchor">[5]</a> was the eulogist of Titian; -Portius,<a name="FNanchor_6_107" id="FNanchor_6_107"></a><a href="#Footnote_6_107" class="fnanchor">[6]</a> whose amicable relations with the Florentine painters may -be inferred from various circumstances, lectured at Florence on the -Aristotelian doctrines early in the sixteenth century. The Italian -translations were later, but still prove that these studies were -undertaken with reference to the arts, for one of them is dedicated to -the painter Cigoli.<a name="FNanchor_7_108" id="FNanchor_7_108"></a><a href="#Footnote_7_108" class="fnanchor">[7]</a></p> - -<p><span class="pagenum"><a name="Page_381" id="Page_381">[Pg 381]</a></span></p> - -<p>The writers on art, from Leon Battista Alberti to Borghini, without -mentioning later authorities, either tacitly coincide with the -Aristotelian doctrine, or openly profess to explain it. It is true this -is not always done in the clearest manner, and some of these writers -might say with Lodovico Dolce, "I speak of colours, not as a painter, -for that would be the province of the divine Titian."</p> - -<p>Leonardo da Vinci in his writings, as in everything else, appears as -an original genius. He now and then alludes generally to opinions -of "philosophers," but he quotes no authority ancient or modern. -Nevertheless, a passage on the nature of colours, particularly where -he speaks of the colours of the elements, appears to be copied from -Leon Battista Alberti,<a name="FNanchor_8_109" id="FNanchor_8_109"></a><a href="#Footnote_8_109" class="fnanchor">[8]</a> and from the mode in which some of Leonardo's -propositions are stated, it has been supposed<a name="FNanchor_9_110" id="FNanchor_9_110"></a><a href="#Footnote_9_110" class="fnanchor">[9]</a> that he had been -accustomed at Florence to the form of the Aristotelian philosophy. At -all events, some of the most important of his observations respecting -light and colours, have a great analogy with those contained in the -treatise in question. The following examples will be sufficient to -prove this coincidence; the corresponding passages in Goethe are -indicated, as usual, by the numbers of the paragraphs; the references -to Leonardo's treatise are given at the bottom of the page.</p> - -<blockquote> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"A vivid and brilliant red appears when the weak rays of the -sun are tempered by subdued and shadowy white,"—154.</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO</p> - -<p>"The air which is between the sun and the earth at sun-rise<span class="pagenum"><a name="Page_382" id="Page_382">[Pg 382]</a></span> -or sun-set, always invests what is beyond it more than any -other (higher) portion of the air: this is because it is -whiter."<a name="FNanchor_10_111" id="FNanchor_10_111"></a><a href="#Footnote_10_111" class="fnanchor">[10]</a></p> - -<p>A bright object loses its whiteness in proportion to its -distance from the eye much more when it is illuminated by -the sun, for it partakes of the colour of the sun mingled -with the colour (tempered by the mass) of the air interposed -between the eye and the brightness.<a name="FNanchor_11_112" id="FNanchor_11_112"></a><a href="#Footnote_11_112" class="fnanchor">[11]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"If light is overspread with much obscurity, a red colour -appears; if the light is brilliant and vivid, this red -changes to a flame-colour."<a name="FNanchor_12_113" id="FNanchor_12_113"></a><a href="#Footnote_12_113" class="fnanchor">[12]</a>—150, 160.</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"This (the effect of transparent colours on various grounds) -is evident in smoke, which is blue when seen against black, -but when it is opposed to the (light) blue sky, it appears -brownish and reddening."<a name="FNanchor_13_114" id="FNanchor_13_114"></a><a href="#Footnote_13_114" class="fnanchor">[13]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"White surfaces as a ground for colours, have the effect of -making the pigments<a name="FNanchor_14_115" id="FNanchor_14_115"></a><a href="#Footnote_14_115" class="fnanchor">[14]</a> appear in greater splendour."—594, -902.</p> - -<p><span class="pagenum"><a name="Page_383" id="Page_383">[Pg 383]</a></span></p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"To exhibit colours in their beauty, the whitest ground -should be prepared. I speak of colours that are (more or -less) transparent."<a name="FNanchor_15_116" id="FNanchor_15_116"></a><a href="#Footnote_15_116" class="fnanchor">[15]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"The air near us appears colourless; but when seen in depth, -owing to its thinness it appears blue;<a name="FNanchor_16_117" id="FNanchor_16_117"></a><a href="#Footnote_16_117" class="fnanchor">[16]</a> for where the -light is deficient (beyond it), the air is affected by the -darkness and appears blue: in a very accumulated state, -however, it appears, as is the case with water, quite -white."—155, 158.</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"The blue of the atmosphere is owing to the mass of -illuminated air interposed between the darkness above and -the earth. The air in itself has no colour, but assumes -qualities according to the nature of the objects which are -beyond it. The blue of the atmosphere will be the more -intense in proportion to the degree of darkness beyond it:" -elsewhere—"if the air had not darkness beyond it, it would -be white."<a name="FNanchor_17_118" id="FNanchor_17_118"></a><a href="#Footnote_17_118" class="fnanchor">[17]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"We see no colour in its pure state, but every hue is -variously intermingled with others: even when it is -uninfluenced by other colours, the effect of light and -shade modifies it in various ways, so that it undergoes -alterations and appears unlike itself. Thus, bodies seen in -shade or in<span class="pagenum"><a name="Page_384" id="Page_384">[Pg 384]</a></span> light, in more pronounced or softer sun-shine, -with their surfaces inclined this way or that, with every -change exhibit a different colour."</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"No substance will ever exhibit its own hue unless the light -which illumines it is entirely similar in colour. It very -rarely happens that the shadows of opaque bodies are really -similar (in colour) to the illumined parts. The surface of -every substance partakes of as many hues as are reflected -from surrounding objects."<a name="FNanchor_18_119" id="FNanchor_18_119"></a><a href="#Footnote_18_119" class="fnanchor">[18]</a></p> - -<p>Aristotle.</p> - -<p>"So, again, with regard to the light of fire, of the moon, -or of lamps, each has a different colour, which is variously -combined with differently coloured objects."</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"We can scarcely ever say that the surface of illumined -bodies exhibits the real colour of those bodies. Take a -white band and place it in the dark, and let it receive -light by means of three apertures from the sun, from fire, -and from the sky: the white band will be tricoloured."<a name="FNanchor_19_120" id="FNanchor_19_120"></a><a href="#Footnote_19_120" class="fnanchor">[19]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"When the light falls on any object and assumes (for -example) a red or green tint, it is again reflected on other -substances, thus undergoing a new change. But this effect, -though it really takes place, is not appreciable by the -eye: though the light thus reflected to the eye is composed -of a variety of colours, the principal of these only are -distinguishable."</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"No colour reflected on the surface of another colour, -tinges that surface with its own colour (merely), but will -be<span class="pagenum"><a name="Page_385" id="Page_385">[Pg 385]</a></span> mixed with various other reflections impinging on the -same surface:" but such effects, he observes elsewhere, "are -scarcely, if at all, distinguishable in a very diffused -light."<a name="FNanchor_20_121" id="FNanchor_20_121"></a><a href="#Footnote_20_121" class="fnanchor">[20]</a></p> - -<p style="font-size: 0.8em; text-align: center;">ARISTOTLE.</p> - -<p>"Thus, all combinations of colours are owing to three -causes: the light, the medium through which the light -appears, such as water or air, and lastly the local colour -from which the light happens to be reflected."</p> - -<p style="font-size: 0.8em; text-align: center;">LEONARDO.</p> - -<p>"All illumined objects partake of the colour of the light -they receive.</p> - -<p>"Every opaque surface partakes of the colour of the -intervening transparent medium, according to the density of -such medium and the distance between the eye and the object.</p> - -<p>"The medium is of two kinds; either it has a surface, like -water, &c., or it is without a common surface, like the -air."<a name="FNanchor_21_122" id="FNanchor_21_122"></a><a href="#Footnote_21_122" class="fnanchor">[21]</a></p></blockquote> - -<hr class="r5" /> -<p>In the observations on trees and plants more points of resemblance -might be quoted; the passages corresponding with Goethe's views are -much more numerous.</p> - -<p>It is remarkable that Leonardo, in opposition, it seems to some -authorities,<a name="FNanchor_22_123" id="FNanchor_22_123"></a><a href="#Footnote_22_123" class="fnanchor">[22]</a> agrees with Aristotle in reckoning black and white -as colours, placing them at the beginning and end of the scale.<a name="FNanchor_23_124" id="FNanchor_23_124"></a><a href="#Footnote_23_124" class="fnanchor">[23]</a> -Like Aristotle, again, he frequently makes use of the term black, for -obscurity; he even goes further,<span class="pagenum"><a name="Page_386" id="Page_386">[Pg 386]</a></span> for he seems to consider that blue -may be produced by the actual mixture of black and white, provided they -are pure.<a name="FNanchor_24_125" id="FNanchor_24_125"></a><a href="#Footnote_24_125" class="fnanchor">[24]</a> The ancient author, however, explains himself on this -point as follows—"We must not attempt to make our observations on -these effects by mixing colours as painters mix them, but by remarking -the appearances as produced by the rays of light mingling with each -other."<a name="FNanchor_25_126" id="FNanchor_25_126"></a><a href="#Footnote_25_126" class="fnanchor">[25]</a></p> - -<p>When we consider that Leonardo's Treatise professes to embrace the -subject of imitation in painting, and that Aristotle's briefly examines -the physical nature and appearance of colours, it must be admitted -that the latter sustains the above comparison with advantage; and it -is somewhat extraordinary that observations indicating so refined a -knowledge of nature, as regards the picturesque, should not have been -taken into the account, for such appears to be the fact, in the various -opinions and conjectures that have been expressed from time to time on -the painting of the Greeks. The treatise in question must have been -written when Apelles painted, or immediately before; and as a proof<span class="pagenum"><a name="Page_387" id="Page_387">[Pg 387]</a></span> -that Aristotle's remarks on the effect of semi-transparent mediums were -not lost on the artists of his time, the following passage from Pliny -is subjoined, for, though it is well known, it acquires additional -interest from the foregoing extracts.</p> - -<p>"He (Apelles) passed a dark colour over his pictures when finished, so -thin that it increased the splendour of the tints, while it protected -the surface from dust and dirt: it could only be seen on looking into -the picture. The effect of this operation, judiciously managed, was to -prevent the colours from being too glaring, and to give the spectator -the impression of looking through a transparent crystal. At the same -time it seemed almost imperceptibly to add a certain dignity of tone to -colours that were too florid." "This," says Reynolds, "is a true and -artist-like description of glazing or scumbling, such as was practised -by Titian and the rest of the Venetian painters."</p> - -<p>The account of Pliny has, in this instance, internal evidence -of truth, but it is fully confirmed by the following passage in -Aristotle:—"Another mode in which the effect of colours is exhibited -is when they appear through each other, as painters employ them when -they glaze (ἐπαλειφοντες)<a name="FNanchor_26_127" id="FNanchor_26_127"></a><a href="#Footnote_26_127" class="fnanchor">[26]</a> a (dark) colour over a lighter one; just -as the sun, which is in itself white, assumes a red colour when seen -through darkness and smoke. This operation also ensures a variety of -colours, for there will be a certain ratio between those which are on -the surface and those which are in depth."—<i>De Sensu et Sensili</i>.</p> - -<p>Aristotle's notion respecting the derivation of colours from white and -black may perhaps be illustrated by the following opinion on the very -similar theory of Goethe.</p> - -<p>"Goethe and Seebeck regard colour as resulting from the mixture of -white and black, and ascribe to the different<span class="pagenum"><a name="Page_388" id="Page_388">[Pg 388]</a></span> colours a quality -of darkness (σκιερὸν), by the different degrees of which they are -distinguished, passing from white to black through the gradations -of yellow, orange, red, violet, and blue, while green appears to be -intermediate again between yellow and blue. This remark, though it has -no influence in weakening the theory of colours proposed by Newton, -is certainly correct, having been confirmed experimentally by the -researches of Herschell, who ascertained the relative intensity of the -different coloured rays by illuminating objects under the microscope by -their means, &c.</p> - -<p>"Another certain proof of the difference in brightness of the different -coloured rays is afforded by the phenomena of ocular spectra. If, after -gazing at the sun, the eyes are closed so as to exclude the light, the -image of the sun appears at first as a luminous or white spectrum upon -a dark ground, but it gradually passes through the series of colours to -black, that is to say, until it can no longer be distinguished from the -dark field of vision; and the colours which it assumes are successively -those intermediate between white and black in the order of their -illuminating power or brightness, namely, yellow, orange, red, violet, -and blue. If, on the other hand, after looking for some time at the -sun we turn our eyes towards a white surface, the image of the sun is -seen at first as a black spectrum upon the white surface, and gradually -passes through the different colours from the darkest to the lightest, -and at last becomes white, so that it can no longer be distinguished -from the white surface"<a name="FNanchor_27_128" id="FNanchor_27_128"></a><a href="#Footnote_27_128" class="fnanchor">[27]</a>—See par 40, 44.</p> - -<p>It is not impossible that Aristotle's enumeration of the colours may -have been derived from, or confirmed by, this very experiment. Speaking -of the after-image of colours he says, "The impression not only exists -in the sensorium in the act of perceiving, but remains when the organ -is at rest. Thus if we look long and intently on any object,<span class="pagenum"><a name="Page_389" id="Page_389">[Pg 389]</a></span> when -we change the direction of the eyes a responding colour follows. If -we look at the sun, or any other very bright object, and afterwards -shut our eyes, we shall, as if in ordinary vision, first see a colour -of the same kind; this will presently be changed to a red colour, -then to purple, and so on till it ends in black and disappears."—<i>De -Insomniis</i>.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_102" id="Footnote_1_102"></a><a href="#FNanchor_1_102"><span class="label">[1]</span></a> "Geschichte der Farbenlehre," in the "Nachgelassene -Werke." Cotta, 1833.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_103" id="Footnote_2_103"></a><a href="#FNanchor_2_103"><span class="label">[2]</span></a> The treatise in question is ascribed by Goethe to -Theophrastus, but it is included in most editions of Aristotle, and -even attributed to him in those which contain the works of both -philosophers; for instance, in the Aldine Princeps edition, 1496. -Calcagnini says, the treatise is made up of two separate works on the -subject, both by Aristotle.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_104" id="Footnote_3_104"></a><a href="#FNanchor_3_104"><span class="label">[3]</span></a> His authority seems to have been equally great on subjects -connected with the phenomena of vision; the Italian translator of -a Latin treatise, by Portius, on the structure and colours of the -eye, thus opens his dedication to the Cardinal Ercole Gonzaga, of -Mantua:—"Grande anzi quasi infinito è l'obligo che ha il mondo con -quel più divino che umano spirito di Aristotile."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_105" id="Footnote_4_105"></a><a href="#FNanchor_4_105"><span class="label">[4]</span></a> In a letter to Ziegler the mathematician, Calcagnini -speaks of Raphael as "the first of painters in the theory as well as -in the practice of his art." This expression may, however, have had -reference to a remarkable circumstance mentioned in the same letter, -namely, that Raphael entertained the learned Fabius of Ravenna as a -constant guest, and employed him to translate Vitruvius into Italian. -This MS. translation, with marginal notes, written by Raphael, is now -in the library at Munich. "Passavant, Rafael von Urbino."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_106" id="Footnote_5_106"></a><a href="#FNanchor_5_106"><span class="label">[5]</span></a> Lodovico Dolce's Treatise on Colours (1565) is in the form -of a dialogue, like his "Aretino." The abridged theory of Aristotle -is followed by a translation of the Treatise of Antonius Thylesius on -Colours; this is adapted to the same colloquial form, and the author is -not acknowledged: the book ends with an absurd catalogue of emblems. -The "Somma della Filosofia d'Aristotile," published earlier by the same -author, is a very careless performance.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_107" id="Footnote_6_107"></a><a href="#FNanchor_6_107"><span class="label">[6]</span></a> A Latin translation of Aristotle's Treatise on Colours, -with comments by Simon Portius, was first published, according to -Goethe, at Naples in 1537. In a later Florentine edition, 1548, -dedicated to Cosmo I., Portius alludes to his having lectured at an -earlier period in Florence on the doctrines of Aristotle, at which time -he translated the treatise in question. Another Latin translation, with -notes, was published later in the same century at Padua—"Emanuele -Marguino Interprete:" but by far the clearest view of the Aristotelian -theory is to be found in the treatise of Antonio Vidi Scarmiglione -of Fuligno ("De Coloribus," Marpurgi, 1591). It is dedicated to the -Emperor Rudolph II. Of all the paraphrases of the ancient doctrine -this comes nearest to the system of Goethe; but neither this nor any -other of the works alluded to throughout this Note are mentioned by -the author in his History of the Doctrine of Colours, except that of -Portius.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_108" id="Footnote_7_108"></a><a href="#FNanchor_7_108"><span class="label">[7]</span></a> An earlier Italian translation appeared in Rome, 1535. See -"Argelatus Biblioteca degli Volgarizzatori."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_8_109" id="Footnote_8_109"></a><a href="#FNanchor_8_109"><span class="label">[8]</span></a> "Della Pittura e della Statua," Lib. I, p. 16, Milan -edition, 1804. Compare with the "Trattato della Pittura," p. 141. Other -points of resemblance are to be met with. The notion of certain colours -appropriated to the four elements, occurs in Aristotle, and is indeed -attributed to older writers.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_9_110" id="Footnote_9_110"></a><a href="#FNanchor_9_110"><span class="label">[9]</span></a> See the notes to the Roman edition of the "Trattato della -Pittura."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_10_111" id="Footnote_10_111"></a><a href="#FNanchor_10_111"><span class="label">[10]</span></a> Page 237.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_11_112" id="Footnote_11_112"></a><a href="#FNanchor_11_112"><span class="label">[11]</span></a> Page 301.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_12_113" id="Footnote_12_113"></a><a href="#FNanchor_12_113"><span class="label">[12]</span></a> In the Treatise <i>De Igne</i>, by Theophrastus, we find -the same notion thus expressed: "Brightness (<i>τὸ λευκὸν</i>) seen -through a dark coloured medium (<i>διὰ του μέλανος</i>) appears red; as -the sun seen through smoke or soot: hence the coal is redder than -the flame." Scarmiglione, from whom Kircher seems to have copied, -observes:—"Itaque color realis est lux opaca; licet id e plurimis -apparentiis colligere. Luna enim in magnâ solis eclipsi rubra -conspicitur, quia tenebris lux præpeditur ac veluti tegitur."—<i>De -Coloribus</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_13_114" id="Footnote_13_114"></a><a href="#FNanchor_13_114"><span class="label">[13]</span></a> Page 122.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_14_115" id="Footnote_14_115"></a><a href="#FNanchor_14_115"><span class="label">[14]</span></a> <i>Τὰ ἂνθη</i>: translated <i>flores</i> by Calcagnini and the -rest, by Goethe, <i>die Blüthe</i>, the bloom. That the word sometimes -signified pigments is sufficiently apparent from the following -passage of Suidas (quoted by Emeric David, "Discours Historiques -sur la Peinture Moderne") <i>ἂνθεσι κεκοσμημέναι, οἶον ψιμμιωίῳ φύκει -καὶ τοῖς ὸμοίοις</i>. Variis pigmentis ornatæ, ut cerussâ, fuco, et -aliis similibus. (Suid. in voc. <i>Ἐξμηθισμένας</i>.) A panel prepared -for painting, with a white ground consolidated with wax, and perhaps -mastic, was found in Herculaneum.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_15_116" id="Footnote_15_116"></a><a href="#FNanchor_15_116"><span class="label">[15]</span></a> Page 114.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_16_117" id="Footnote_16_117"></a><a href="#FNanchor_16_117"><span class="label">[16]</span></a> <i>Ἐν βάθει δὲ θεωρουμίνου ιγγυτάτω φαίνεται τῶ χρώματι -κυανονοειδὴς διὰ τὴν ὰραιότητα.</i> "But when seen in depth, it appears -(even) in its nearest colour, blue, owing to its thinness." The Latin -interpretations vary very much throughout. The point which is chiefly -important is however plain enough, viz. that darkness seen through a -light medium is blue.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_17_118" id="Footnote_17_118"></a><a href="#FNanchor_17_118"><span class="label">[17]</span></a> Page 136-430.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_18_119" id="Footnote_18_119"></a><a href="#FNanchor_18_119"><span class="label">[18]</span></a> Page 121, 306, 326, 387.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_19_120" id="Footnote_19_120"></a><a href="#FNanchor_19_120"><span class="label">[19]</span></a> Page 306.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_20_121" id="Footnote_20_121"></a><a href="#FNanchor_20_121"><span class="label">[20]</span></a> Page 104, 369.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_21_122" id="Footnote_21_122"></a><a href="#FNanchor_21_122"><span class="label">[21]</span></a> Page 236, 260, 328.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_22_123" id="Footnote_22_123"></a><a href="#FNanchor_22_123"><span class="label">[22]</span></a> "De' semplici colori il primo è il bianco: beuchè -i filosofi non accettano nè il bianco nè il nero nel numero de' -colori."—p. 125, 141. Elsewhere, however, he sometimes adopts the -received opinion.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_23_124" id="Footnote_23_124"></a><a href="#FNanchor_23_124"><span class="label">[23]</span></a> Leon Battista Alberti, in like manner -observes:—"Affermano (i filosofi) che le spezie de' colori sono sette, -cioè, che il bianco ed il nero sono i duoi estremi, infra i quali ve -n'è uno nel mezzo (rosso) e che infra ciascuno di questi duoi estremi -e quel del mezzo, da ogni parte ve ne sono due altri." An absurd -statement of Lomazzo, p. 190, is copied verbatim from Lodovico Dolce -(Somma della Filos. d'Arist.); but elsewhere, p. 306, Lomazzo agrees -with Alberti. Aristotle seems to have misled the two first, for after -saying there are seven colours, he appears only to mention six: he -says—"There are seven colours, if brown is to be considered equivalent -to black, which seems reasonable. Yellow, again, may be said to be a -modification of white. Between these we find red, purple, green, and -blue."—<i>De Sensu et Sensili</i>. Perhaps it is in accordance with this -passage that Leonardo da Vinci reckons eight colours.—<i>Trattato</i>, p. -126.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_24_125" id="Footnote_24_125"></a><a href="#FNanchor_24_125"><span class="label">[24]</span></a> Page 122, 142, 237.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_25_126" id="Footnote_25_126"></a><a href="#FNanchor_25_126"><span class="label">[25]</span></a> On the authority of this explanation the word μιλάν -has sometimes been translated in the foregoing extracts <i>obscurity, -darkness</i>. -</p> -<p> -Raffaello Borghini, in his attempt to describe the doctrine of -Aristotle with a view to painting, observes—"There are two -principles which concur in the production of colour, namely, light -and transparence." But he soon loses this clue to the best part of -the ancient theory, and when he has to speak of the derivation of -colours from white and black, he evidently understands it in a mere -atomic sense, and adds—"I shall not at present pursue the opinion -of Aristotle, who assumes black and white as principal colours, and -considers all the rest as intermediate between them."—<i>Il Riposo</i>, 1. -ii. Accordingly, like Lodovico Dolce, he proceeds to a subject where he -was more at home, namely, the symbolical meaning of colours.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_26_127" id="Footnote_26_127"></a><a href="#FNanchor_26_127"><span class="label">[26]</span></a> This word is only strictly applied to unctuous -substances, and may confirm the views of those writers who have -conjectured that asphaltum was a chief ingredient in the <i>atramentum</i> -of the ancients.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_27_128" id="Footnote_27_128"></a><a href="#FNanchor_27_128"><span class="label">[27]</span></a> "Elements of Physiology," by J. Müller, M.D., translated -from the German by William Baly, M.D. London, 1839.</p></div> - - - -<p class="para"><a id="NOTE_N"></a>NOTE N.—Par. 246.</p> - -<p>"The appearance of white in the centre, according to the Newtonian -theory, arises from each line of rays forming its own spectrum. -These spectra, superposing each other on all the middle part, leave -uncorrected (unneutralised) colours only at the two edges."—S.F.<a name="FNanchor_1_129" id="FNanchor_1_129"></a><a href="#Footnote_1_129" class="fnanchor">[1]</a></p> - - -<div class="footnote"> - -<p><a name="Footnote_1_129" id="Footnote_1_129"></a><a href="#FNanchor_1_129"><span class="label">[1]</span></a> This was objected to Goethe when his "Beyträge sur Optik" -first appeared; he answered the objection by a coloured diagram in -the plates to the "Farbenlehre:" in this he undertakes to show that -the assumed gradual "correction" of the colours would produce results -different from the actual appearance in nature.</p></div> - - - -<p class="para"><a id="NOTE_O"></a>NOTE O.—<a href="#a252">Par. 252.</a></p> - -<p>These experiments with grey objects, which exhibit different colours -as they are on dark or light grounds, were suggested, Goethe tells -us, by an observation of Antonius Lucas, of Lüttich, one of Newton's -opponents, and, in the opinion of the author, one of the few who made -any well-founded objections. Lucas remarks, that the sun acts merely -as a circumscribed image in the prismatic experiments, and that if the -same sun had a lighter background than itself, the colours of the prism -would be reversed. Thus in Goethe's experiments, when the grey disk is -on a dark ground, it is edged with blue on being magnified; when on a -light ground it is edged with yellow. Goethe acknowledges that Lucas -had in some measure anticipated his own theory.—Vol. ii. p. 440.</p> - - - -<p class="para"><a id="NOTE_P"></a>NOTE P.—<a href="#a284">Par. 284.</a></p> - -<p>The earnestness and pertinacity with which Goethe insisted<span class="pagenum"><a name="Page_390" id="Page_390">[Pg 390]</a></span> that -the different colours are not subject to different degrees of -refrangibility are at least calculated to prove that he was himself -convinced on the subject, and, however extraordinary it may seem, his -conviction appears to have been the result of infinite experiments -and the fullest ocular evidence. He returns to the question in the -controversial division of his work, in the historical part, and again -in the description of the plates. In the first he endeavours to show -that Newton's experiment with the blue and red paper depends entirely -on the colours being so contrived as to appear elongated or curtailed -by the prismatic borders. "If," he says, "we take a light-blue instead -of a dark one, the illusion (in the latter case) is at once evident. -According to the Newtonian theory the yellow-red (red) is the least -refrangible colour, the violet the most refrangible. Why, then, does -Newton place a blue paper instead of a violet next the red? If the -fact were as he states it, the difference in the refrangibility of -the yellow-red and violet would be greater than in the case of the -yellow-red and blue. But here comes in the circumstance that a violet -paper conceals the prismatic borders less than a dark-blue paper, as -every observer may now easily convince himself," &c.—Polemischer -Theil, par. 45. Desaguliers, in repeating the experiment, confessed -that if the ground of the colours was not black, the effect did -not take place so well. Goethe adds, "not only not so well, but -not at all."—Historischer Theil, p. 459. Lucas of Lüttich, one of -Newton's first opponents, denied that two differently-coloured silks -are different in distinctness when seen in the microscope. Another -experiment proposed by him, to show the unsoundness of the doctrine of -various refrangibility, was the following:—Let a tin plate painted -with the prismatic colours in stripes be placed in an empty cubical -vessel, so that from the spectator's point of view the colours may be -just hidden by the rim. On pouring water into this vessel, all the -colours become visible in the same degree; whereas, it was contended, -if the Newtonian doctrine were true, some<span class="pagenum"><a name="Page_391" id="Page_391">[Pg 391]</a></span> colours would be apparent -before others.—Historischer Theil, p. 434.</p> - -<p>Such are the arguments and experiments adduced by Goethe on this -subject; they have all probably been answered. In his analysis of -Newton's celebrated <i>Experimentum Crucis</i>, he shows again that by -reversing the prismatic colours (refracting a dark instead of a -light object), the colours that are the most refrangible in Newton's -experiment become the least so, and <i>vice versâ</i>.</p> - -<p>Without reference to this objection, it is now admitted that "the -difference of colour is not a test of difference of refrangibility, and -the conclusion deduced by Newton is no longer admissible as a general -truth, that to the same degree of refrangibility ever belongs the -same colour, and to the same colour ever belongs the same degree of -refrangibility."—Brewster's Optics, p. 72.</p> - - - -<p class="para"><a id="NOTE_Q"></a>NOTE Q—<a href="#a387">Par. 387.</a></p> - -<p>With the exception of two very inconclusive letters to Sulpice -Boisserée, and some incidental observations in the conclusion of the -historical portion under the head of entoptic colours, Goethe never -returned to the rainbow. Among the plates he gave the diagram of -Antonius de Dominis. An interesting chapter on halos, parhelia, and -paraselenæ, will be found in Brewster's Optics, p. 270.</p> - - -<p class="para"><a id="NOTE_R"></a>NOTE R.—<a href="#a478">Par. 478.</a></p> - -<p>The most complete exhibition of the colouring or mantling of metals -was attained by the late Cav. Nobili, professor of physical science in -Florence. The general mode in which these colours are produced is thus -explained by him:<a name="FNanchor_1_130" id="FNanchor_1_130"></a><a href="#Footnote_1_130" class="fnanchor">[1]</a>—</p> - -<p>"A point of platinum is placed vertically at the distance of about -half a line above a lamina of the same metal laid<span class="pagenum"><a name="Page_392" id="Page_392">[Pg 392]</a></span> horizontally at the -bottom of a vessel of glass or porcelain. Into this vessel a solution -of acetate of lead is poured so as to cover not only the lamina of -platinum, but two or three lines of the point as well. Lastly, the -point is put in communication with the negative pole of a battery, and -the lamina with the positive pole. At the moment in which the circuit -is completed a series of coloured rings is produced on the lamina -under the point similar to those observed by Newton in lenses pressed -together."</p> - -<p>The scale of colours thus produced corresponds very nearly with that -observed by Newton and others in thin plates and films, but it is -fuller, for it extends to forty-four tints. The following list, as -given by Nobili, is divided by him into four series to agree with -those of Newton: the numbers in brackets are those of Newton's scale. -The Italian terms are untranslated, because the colours in some cases -present very delicate transitions.<a name="FNanchor_2_131" id="FNanchor_2_131"></a><a href="#Footnote_2_131" class="fnanchor">[2]</a></p> - - -<div class="p2"> -<table border="0" cellpadding="2" cellspacing="0" summary=""> -<tr><th colspan="4">First Series.</th></tr> -<tr><td align="left">1.</td><td align="left">Biondo argentino (4)<a name="FNanchor_3_132" id="FNanchor_3_132"></a><a href="#Footnote_3_132" class="fnanchor">[3]</a> -.</td><td align="left">6.</td><td align="left">Fulvo acceso.</td></tr> -<tr><td align="left">2.</td><td align="left">Biondo.</td><td align="left">7.</td><td align="left">Rosso di rame (6).</td></tr> -<tr><td align="left">3.</td><td align="left">Biondo d'oro.</td><td align="left">8.</td><td align="left">Ocria.</td></tr> -<tr><td align="left">4.</td><td align="left">Biondo acceso (5).</td><td align="left">9.</td><td align="left">Ocria violacea.</td></tr> -<tr><td align="left">5.</td><td align="left">Fulvo.</td><td align="left">10.</td><td align="left">Rosso violaceo (7).</td></tr> -<tr><th colspan="4">Second Series.</th></tr> -<tr><td align="left">11.</td><td align="left">Violetto (8).</td><td align="left">20.</td><td align="left">Giallo acceso.</td></tr> -<tr><td align="left">12.</td><td align="left">Indaco (10).</td><td align="left">21.</td><td align="left">Giallo-rancio.</td></tr> -<tr><td align="left">13.</td><td align="left">Blu carico.</td><td align="left">22.</td><td align="left">Rancio (13).</td></tr> -<tr><td align="left">14.</td><td align="left">Blu.</td><td align="left">23.</td><td align="left">Rancio-rossiccio.</td></tr> -<tr><td align="left">15.</td><td align="left">Blu chiaro (11)</td><td align="left">24.</td><td align="left">Rancio-rosso.</td></tr> -<tr><td align="left">16.</td><td align="left">Celeste.</td><td align="left">25.</td><td align="left">Rosso-rancio.</td></tr> -<tr><td align="left">17.</td><td align="left">Celeste giallognolo.</td><td align="left">26.</td><td align="left">Lacca-rancia (14).</td></tr> -<tr><td align="left">18.</td><td align="left">Giallo chiarissimo (12).</td><td align="left">27.</td><td align="left">Lacca.</td></tr> -<tr><td align="left">19.</td><td align="left">Giallo.</td><td align="left">28.</td><td align="left">Lacca accesa (15).</td></tr> -<tr><th colspan="4">Third Series.<span class="pagenum"><a name="Page_393" id="Page_393">[Pg 393]</a></span></th></tr> -<tr><td align="left">29.</td><td align="left">Lacca-purpurea (16).</td><td align="left">34.</td> <td align="left">Verde-giallo (20).</td></tr> -<tr><td align="left">30.</td><td align="left">Lacca-turchiniccia (17).</td><td align="left">35.</td> <td align="left">Verde-rancio.</td></tr> -<tr><td align="left">31.</td><td align="left">Porpora-verdognola (18).</td><td align="left">36.</td> <td align="left">Rancio-verde (21).</td></tr> -<tr><td align="left">32.</td><td align="left">Verde (19).</td><td align="left">37.</td> <td align="left">Rancio-roseo.</td></tr> -<tr><td align="left">33.</td><td align="left">Verde giallognolo.</td><td align="left">38.</td><td align="left">Lacca-rosea (22).</td></tr> -<tr><th colspan="4">Fourth Series.</th></tr> -<tr><td align="left">39.</td><td align="left">Lacca-violacea (24).</td><td align="left">43.</td><td align="left">Verde-giallo rossiccio (28).</td></tr> -<tr><td align="left">40.</td><td align="left">Violaceo-verdognolo (25). </td><td align="left">44.</td><td align="left">Lacca-rosea (30).</td></tr> -<tr><td align="left">41.</td><td align="left">Verde (26).</td></tr> -<tr><td align="left">42.</td><td align="left">Verde-giallo (27).</td></tr> -</table></div> - -<p class="p2">"These tints," Professor Nobili observes, "are disposed according to -the order of the thin mantlings which occasion them; the colour of -the thinnest film is numbered 1; then follow in order those produced -by a gradual thickening of the medium. I cannot deceive myself in -this arrangement, for the thin films which produce the colours are -all applied with the same electro-chemical process. The battery, the -solution, the distances, &c., are always the same; the only difference -is the time the effect is suffered to last. This is a mere instant for -the colour of No. 1, a little longer for No. 2, and so on, increasing -for the succeeding numbers. Other criterions, however, are not wanting -to ascertain the place to which each tint belongs."</p> - -<p>The scale differs from that of Newton, inasmuch as there is no blue in -Nobili's first series and no green in the second: green only appears in -the third and fourth series. "The first series," says the Professor, -"is remarkable for the fire and metallic appearance of its tints, the -second for clearness and brilliancy, the third and fourth for force and -richness." The fourth, he observes, has the qualities of the third in a -somewhat lesser degree, but the two greens are very nearly alike.</p> - -<p>It is to be observed, that red and green are the principal<span class="pagenum"><a name="Page_394" id="Page_394">[Pg 394]</a></span> ingredients -in the third and fourth series, blue and yellow in the second and first.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_130" id="Footnote_1_130"></a><a href="#FNanchor_1_130"><span class="label">[1]</span></a> See "Memorie ed Osservazioni, edite et inedite del Cav. -Professor Nobili," Firenze, 1834.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_131" id="Footnote_2_131"></a><a href="#FNanchor_2_131"><span class="label">[2]</span></a> The colours in some of the compound terms are in a manner -mutually neutralising; such terms might, no doubt, be amended.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_132" id="Footnote_3_132"></a><a href="#FNanchor_3_132"><span class="label">[3]</span></a> The three first numbers in Newton's scale are black, blue, -and white.</p></div> - - - -<p class="para"><a id="NOTE_S"></a>NOTE S.—<a href="#a485">Par. 485.</a></p> - -<p>A chapter on entoptic colours, contained in the supplement to Goethe's -works, was translated with the intention of inserting it among the -notes, but on the whole it was thought most advisable to omit it. Like -many other parts of the "Doctrine of Colours" it might have served as -a specimen of what may be achieved by accurate observation unassisted -by a mathematical foundation. The whole theory of the polarization of -light has, however, been so fully investigated since Goethe's time, -that the chapter in question would probably have been found to contain -very little to interest scientific readers, for whom it seems chiefly -to have been intended. One observation occurs in it which indeed has -more reference to the arts; in order to make this intelligible, the -leading experiment must be first described, and for this purpose the -following extracts may serve.</p> - -<p>3.<a name="FNanchor_1_133" id="FNanchor_1_133"></a><a href="#Footnote_1_133" class="fnanchor">[1]</a></p> - -<p>"The experiment, in its simplest form, is to be made as follows:—let -a tolerably thick piece of plate-glass be cut into several squares of -an inch and a half; let these be heated to a red heat and then suddenly -cooled. The squares of glass which do not split in this operation are -now fit to produce the entoptic colours.</p> - -<p>4.</p> - -<p>"In our mode of exhibiting the phenomenon, the observer is, above all, -to betake himself, with his apparatus to the open air. All dark rooms, -all small apertures<span class="pagenum"><a name="Page_395" id="Page_395">[Pg 395]</a></span> (foramina exigua),<a name="FNanchor_2_134" id="FNanchor_2_134"></a><a href="#Footnote_2_134" class="fnanchor">[2]</a> are again to be given up. A -pure, cloudless sky is the source whence we are derive a satisfactory -insight into the appearances.</p> - -<p>5.</p> - -<p>"The atmosphere being clear, let the observer lay the squares above -described on a black surface, so placing them that two sides may -be parallel with the plane of vision. When the sun is low, let him -hold the squares so as to reflect to the eye that portion of the sky -opposite to the sun, and he will then perceive four dark points in -the four corners of a light space. If, after this, he turn towards -the quarters of the sky at right angles with that where his first -observation was made, he will see four bright points on a dark ground: -between the two regions the figures appear to fluctuate.</p> - -<p>6.</p> - -<p>"From this simple reflection we now proceed to another, which, but -little more complicated, exhibits the appearance much more distinctly. -A solid cube of glass, or in its stead a cube composed of several -plates, is placed on a black mirror, or held a little inclined -above it, at sun-rise or sun-set. The reflection of the sky being -now suffered to fall through the cube on the mirror, the appearance -above described will appear more distinctly. The reflection of the -sky opposite to the sun presents four dark points on a light ground; -the two lateral portions of the sky present the contrary appearance, -namely, four light points on a dark ground. The space not occupied by -the corner points appears in the first case as a white cross, in the -other as a black cross, expressions hereafter employed in describing -the phenomena. Before sun-rise or after sun-set, in a very<span class="pagenum"><a name="Page_396" id="Page_396">[Pg 396]</a></span> subdued -light, the white cross appears on the side of the sun also.<a name="FNanchor_3_135" id="FNanchor_3_135"></a><a href="#Footnote_3_135" class="fnanchor">[3]</a></p> - -<p>"We thus conclude that the direct reflection of the sun produces a -light figure, which we call a white cross; the oblique reflection gives -a dark figure, which we call a black cross. If we make the experiment -all round the sky, we shall find that a fluctuation takes place in the -intermediate regions."</p> - -<p>We pass over a variety of observations on the modes of exhibiting this -phenomenon, the natural transparent substances which exhibit it best, -and the detail of the colours seen within<a name="FNanchor_4_136" id="FNanchor_4_136"></a><a href="#Footnote_4_136" class="fnanchor">[4]</a> them, and proceed to an -instance where the author was enabled to distinguish the "direct" from -the "oblique" reflection by means of the entoptic apparatus, in a -painter's study.</p> - -<p>40.</p> - -<p>"An excellent artist, unfortunately too soon taken from us, Ferdinand -Jagemann, who, with other qualifications, had a fine eye for light and -shade, colour and keeping, had built himself a painting-room for large -as well as small works. The single high window was to the north, facing -the most open sky, and it was thought that all necessary requisites had -been sufficiently attended to.</p> - -<p>"But after our friend had worked for some time, it appeared to him, -in painting portraits, that the faces he copied were not equally well -lighted at all hours of the day, and yet his sitters always occupied -the same place, and the serenity of the atmosphere was unaltered.</p> - -<p>"The variations of the favourable and unfavourable light had their -periods during the day. Early in the morning the light appeared most -unpleasantly grey and unsatisfactory;<span class="pagenum"><a name="Page_397" id="Page_397">[Pg 397]</a></span> it became better, till at last, -about an hour before noon, the objects had acquired a totally different -appearance. Everything presented itself to the eye of the artist in its -greatest perfection, as he would most wish to transfer it to canvas. -In the afternoon this beautiful appearance vanished—the light became -worse, even in the brightest day, without any change having taken place -in the atmosphere.</p> - -<p>"As soon as I heard of this circumstance, I at once connected it in -my own mind with the phenomena which I had been so long observing, -and hastened to prove, by a physical experiment, what a clear-sighted -artist had discovered entirely of himself, to his own surprise and -astonishment.</p> - -<p>"I had the second<a name="FNanchor_5_137" id="FNanchor_5_137"></a><a href="#Footnote_5_137" class="fnanchor">[5]</a> entoptic apparatus brought to the spot, and the -effect on this was what might be conjectured from the above statement. -At mid-day, when the artist saw his model best lighted, the north, -direct reflection gave the white cross; in the morning and evening, on -the other hand, when the unfavourable oblique light was so unpleasant -to him, the cube showed the black cross; in the intermediate hours the -state of transition was apparent."</p> - -<p>The author proceeds to recall to his memory instances where works of -art had struck him by the beauty of their appearance owing to the light -coming from the quarter opposite the sun, in "direct reflection," and -adds, "Since these decided effects are thus traceable to their cause, -the friends of art, in looking at and exhibiting pictures, may enhance -the enjoyment to themselves and others by attending to a fortunate -reflection."</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_133" id="Footnote_1_133"></a><a href="#FNanchor_1_133"><span class="label">[1]</span></a> The numbers, as usual, indicate the corresponding -paragraphs in the original.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_134" id="Footnote_2_134"></a><a href="#FNanchor_2_134"><span class="label">[2]</span></a> In the historical part, Goethe has to speak of so many -followers of Newton who begin their statements with "Si per foramen -exiguum," that the term is a sort of by-word with him.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_135" id="Footnote_3_135"></a><a href="#FNanchor_3_135"><span class="label">[3]</span></a> At mid-day on the 24th of June the author observed the -white cross reflected from every part of the horizon. At a certain -distance from the sun, corresponding, he supposes, with the extent of -halos, the black cross appeared.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_136" id="Footnote_4_136"></a><a href="#FNanchor_4_136"><span class="label">[4]</span></a> Whence the term <i>entoptic</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_137" id="Footnote_5_137"></a><a href="#FNanchor_5_137"><span class="label">[5]</span></a> Before described: the author describes several others more -or less complicated, and suggests a portable one. "Such plates, which -need only be an inch and a quarter square, placed on each other to form -a cube, might be set in a brass case, open above and below. At one end -of this case a black mirror with a hinge, acting like a cover, might be -fastened. We recommend this simple apparatus, with which the principal -and original experiment may be readily made. With this we could, in the -longest days, better define the circle round the sun where the black -cross appears," &c.</p> - -<p><span class="pagenum"><a name="Page_398" id="Page_398">[Pg 398]</a></span></p></div> - - -<p class="para"><a id="NOTE_T"></a>NOTE T.—<a href="#a496">Par. 496.</a></p> - -<p>"Since Goethe wrote, all the earths have been decomposed, and have -been shown to be metallic bases united with oxygen; but this does not -invalidate his statement."—S. F.</p> - - -<p class="para"><a id="NOTE_U"></a>NOTE U.—<a href="#a502">Par. 502.</a></p> - -<p>The cold nature of black and its affinity to blue are assumed by the -author throughout; if the quality is opaque, and consequently greyish, -such an affinity is obvious, but in many fine pictures, intense black -seems to be considered as the last effect of heat, and in accompanying -crimson and orange may be said rather to present a difference of -degree than a difference of kind. In looking at the great picture -of the globe, we find this last result produced in climates where -the sun has greatest power, as we find it the immediate effect of -fire. The light parts of black animals are often of a mellow colour; -the spots and stripes on skins and shells are generally surrounded -by a warm hue, and are brown before they are absolutely black. In -combustion, the blackness which announces the complete ignition, is -preceded always by the same mellow, orange colour. The representation -of this process was probably intended by the Greeks in the black and -subdued orange of their vases: indeed, the very colours may have been -first produced in the kiln. But without supposing that they were -retained merely from this accident, the fact that the combination -itself is extremely harmonious, would be sufficient to account for -its adoption. Many of the remarks of Aristotle<a name="FNanchor_1_138" id="FNanchor_1_138"></a><a href="#Footnote_1_138" class="fnanchor">[1]</a> and Theophrastus<a name="FNanchor_2_139" id="FNanchor_2_139"></a><a href="#Footnote_2_139" class="fnanchor">[2]</a> -on the production of black, are derived from the observation of the -action of fire, and on one occasion, the former distinctly alludes to -the terracotta kiln. That the above opinion as to the nature of black -was prevalent in the sixteenth century, may be inferred<span class="pagenum"><a name="Page_399" id="Page_399">[Pg 399]</a></span> from Lomazzo, -who observes,—"Quanto all' origine e generazione de' colori, la -frigidità è la madre della bianchezza: il calore è padre del nero."<a name="FNanchor_3_140" id="FNanchor_3_140"></a><a href="#Footnote_3_140" class="fnanchor">[3]</a> -The positive coldness of black may be said to begin when it approaches -grey. When Leonardo da Vinci says that black is most beautiful in -shade, he probably means to define its most intense and transparent -state, when it is furthest removed from grey.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_138" id="Footnote_1_138"></a><a href="#FNanchor_1_138"><span class="label">[1]</span></a> "De Coloribus."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_139" id="Footnote_2_139"></a><a href="#FNanchor_2_139"><span class="label">[2]</span></a> "De Igne."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_140" id="Footnote_3_140"></a><a href="#FNanchor_3_140"><span class="label">[3]</span></a> "Trattato," &c. p. 191, the rest of the passage, it must -be admitted, abounds with absurdities.</p></div> - - - -<p class="para"><a id="NOTE_V"></a>NOTE V.—<a href="#a555">Par. 555.</a></p> - -<p>The nature of vehicles or liquid mediums to combine with the substance -of colours, has been frequently discussed by modern writers on art, -and may perhaps be said to have received as much attention as it -deserves. Reynolds smiles at the notion of our not having materials -equal to those of former times, and indeed, although the methods of -individuals will always differ, there seems no reason to suppose that -any great technical secret has been lost. In these inquiries, however, -which relate merely to the mechanical causes of bright and durable -colouring, the skill of the painter in the adequate employment of the -higher resources of his art is, as if by common consent, left out of -the account, and without departing from this mode of considering the -question, we would merely repeat a conviction before expressed, viz. -that the preservation of internal brightness, a quality compatible with -various methods, has had more to do with the splendour and durability -of finely coloured pictures than any vehicle. The observations that -follow are therefore merely intended to show how far the older -written authorities on this subject agree with the results of modern -investigation, without at all assuming that the old methods, if known, -need be implicitly followed.</p> - -<p>On a careful examination of the earlier pictures, it is said<span class="pagenum"><a name="Page_400" id="Page_400">[Pg 400]</a></span> that -a resinous substance appears to have been mingled with the colours -together with the oil; that the fracture of the indurated pigment is -shining, and that the surface resists the ordinary solvents.<a name="FNanchor_1_141" id="FNanchor_1_141"></a><a href="#Footnote_1_141" class="fnanchor">[1]</a> This -admixture of resinous solutions or varnishes with the solid is not -alluded to, as far as we have seen, by any of the writers on Italian -practice, but as the method corresponds with that now prevalent in -England, the above hypothesis is not likely to be objected to for the -present.</p> - -<p>Various local circumstances and relations might seem to warrant the -supposition that the Venetian painters used resinous substances. An -important branch of commerce between the mountains of Friuli and Venice -still consists in the turpentine or fir-resin.<a name="FNanchor_2_142" id="FNanchor_2_142"></a><a href="#Footnote_2_142" class="fnanchor">[2]</a> Similar substances -produced from various trees, and known under the common name of -balsams,<a name="FNanchor_3_143" id="FNanchor_3_143"></a><a href="#Footnote_3_143" class="fnanchor">[3]</a> were imported from the East through Venice, for general -use, before the American balsams<a name="FNanchor_4_144" id="FNanchor_4_144"></a><a href="#Footnote_4_144" class="fnanchor">[4]</a> in some degree superseded them; -and a Venetian painter, Marco Boschini, in his description of the -Archipelago, does not omit to speak of the abundance of mastic produced -in the island of Scio.<a name="FNanchor_5_145" id="FNanchor_5_145"></a><a href="#Footnote_5_145" class="fnanchor">[5]</a></p> - -<p>The testimonies, direct or indirect, against the employment<span class="pagenum"><a name="Page_401" id="Page_401">[Pg 401]</a></span> of any -such substances by the Venetian painters, in the solid part of their -work, seem, notwithstanding, very conclusive; we begin with the writer -just named. In his principal composition, a poem<a name="FNanchor_6_146" id="FNanchor_6_146"></a><a href="#Footnote_6_146" class="fnanchor">[6]</a> describing the -practice and the productions of the Venetian painters, Boschini speaks -of certain colours which they shunned, and adds:—"In like manner -(they avoided) shining liquids and varnishes, which I should rather -call lackers;<a name="FNanchor_7_147" id="FNanchor_7_147"></a><a href="#Footnote_7_147" class="fnanchor">[7]</a> for the surface of flesh, if natural and unadorned, -assuredly does not shine, nature speaks as to this plainly." After -alluding to the possible alteration of this natural appearance by -means of cosmetics, he continues: "Foreign artists set such great -store by these varnishes, that a shining surface seems to them the -only desirable quality in art. What trash it is they prize! fir-resin, -mastic, and sandarach, and larch-resin (not to say treacle), stuff fit -to polish boots.<a name="FNanchor_8_148" id="FNanchor_8_148"></a><a href="#Footnote_8_148" class="fnanchor">[8]</a> If those great painters of ours had to represent -armour, a gold vase, a mirror, or anything of the kind, they made it -shine with (simple) colours."<a name="FNanchor_9_149" id="FNanchor_9_149"></a><a href="#Footnote_9_149" class="fnanchor">[9]</a></p> - -<p>This writer so frequently alludes to the Flemish painters, of whose -great reputation he sometimes seems jealous, that the above strong -expression of opinion may have been pointed at them. On the other hand -it is to be observed that the term <i>forestieri</i>, strangers, does not -necessarily mean transalpine foreigners, but includes those Italians -who were<span class="pagenum"><a name="Page_402" id="Page_402">[Pg 402]</a></span> not of the Venetian state.<a name="FNanchor_10_150" id="FNanchor_10_150"></a><a href="#Footnote_10_150" class="fnanchor">[10]</a> The directions given by -Raphael Borghini,<a name="FNanchor_11_151" id="FNanchor_11_151"></a><a href="#Footnote_11_151" class="fnanchor">[11]</a> and after him by Armenini,<a name="FNanchor_12_152" id="FNanchor_12_152"></a><a href="#Footnote_12_152" class="fnanchor">[12]</a> respecting the use -and preparation of varnishes made from the very materials in question, -may thus have been comprehended in the censure, especially as some of -these recipes were copied and republished in Venice by Bisagno,<a name="FNanchor_13_153" id="FNanchor_13_153"></a><a href="#Footnote_13_153" class="fnanchor">[13]</a> in -1642—that is, only six years before Boschini's poem appeared.</p> - -<p>Ridolfi's Lives of the Venetian Painters<a name="FNanchor_14_154" id="FNanchor_14_154"></a><a href="#Footnote_14_154" class="fnanchor">[14]</a> (1648) may be mentioned -with the two last. His only observation respecting the vehicle is, that -Giovanni Bellini, after introducing himself by an artifice into the -painting-room of Antonello da Messina, saw that painter dip his brush -from time to time in linseed oil. This story, related about two hundred -years after the supposed event, is certainly not to be adduced as very -striking evidence in any way.<a name="FNanchor_15_155" id="FNanchor_15_155"></a><a href="#Footnote_15_155" class="fnanchor">[15]</a></p> - -<p>Among the next writers, in order of time prior to Bisagno, may be -mentioned Canepario<a name="FNanchor_16_156" id="FNanchor_16_156"></a><a href="#Footnote_16_156" class="fnanchor">[16]</a> (1619). His work, "De Atramentis" contains -a variety of recipes for different purposes: one chapter, <i>De -atramentis diversicoloribus</i>, has a more direct reference to painting. -His observations under this head are by no means confined to the -preparation of transparent colours, but he says little on the subject -of<span class="pagenum"><a name="Page_403" id="Page_403">[Pg 403]</a></span> varnishes. After describing a mode of preserving white of egg, -he says, "Others are accustomed to mix colours in liquid varnish and -linseed, or nut-oil; for a liquid and oily varnish binds the (different -layers of) colours better together, and thus forms a very fit glazing -material."<a name="FNanchor_17_157" id="FNanchor_17_157"></a><a href="#Footnote_17_157" class="fnanchor">[17]</a> On the subject of oils he observes, that linseed oil was -in great request among painters; who, however, were of opinion that -nut-oil-excelled it "in giving brilliancy to pictures, in preserving -them better, and in rendering the colours more vivid."<a name="FNanchor_18_158" id="FNanchor_18_158"></a><a href="#Footnote_18_158" class="fnanchor">[18]</a></p> - -<p>Lomazzo (a Milanese) says nothing on the subject of vehicles in his -principal work, but in his "Idea del Tempio della Pittura,"<a name="FNanchor_19_159" id="FNanchor_19_159"></a><a href="#Footnote_19_159" class="fnanchor">[19]</a> he -speaks of grinding the colours "in nut-oil, and spike-oil, and other -things," the "and" here evidently means <i>or</i>, and by "other things" we -are perhaps to understand other oils, poppy oil, drying oils, &c.</p> - -<p>The directions of Raphael Borghini and Vasari<a name="FNanchor_20_160" id="FNanchor_20_160"></a><a href="#Footnote_20_160" class="fnanchor">[20]</a> cannot certainly be -considered conclusive as to the practice of the Venetians, but they are -very clear on the subject of varnish. These writers may be considered -the earliest Italian authorities who have entered much into practical -methods. In the few observations on the subject of vehicles in Leonardo -da Vinci's treatise, "there is nothing," as M. Merimée observes, "to -show that he was in the habit of mixing varnish with his colours." -Cennini says but little on the subject<span class="pagenum"><a name="Page_404" id="Page_404">[Pg 404]</a></span> of oil-painting; Leon Battista -Alberti is theoretical rather than practical, and the published -extracts of Lorenzo Ghiberti's MS. chiefly relate to sculpture.</p> - -<p>Borghini and Vasari agree in recommending nut-oil in preference to -linseed-oil; both recommend adding varnish to the colours in painting -on walls in oil, "because the work does not then require to be -varnished afterwards," but in the ordinary modes of painting on panel -or cloth, the varnish is omitted. Borghini expressly says, that oil -alone (senza più) is to be employed; he also recommends a very sparing -use of it.</p> - -<p>The treatise of Armenini (1587) was published at Ravenna, and he -himself was of Faenza, so that his authority, again, cannot be -considered decisive as to the Venetian practice. After all, he -recommends the addition of "common varnish" only for the ground or -preparation, as a consolidating medium, for the glazing colours, -and for those dark pigments which are slow in drying. Many of his -directions are copied from the writers last named; the recipes for -varnishes, in particular, are to be found in Borghini. Christoforo -Sorte<a name="FNanchor_21_161" id="FNanchor_21_161"></a><a href="#Footnote_21_161" class="fnanchor">[21]</a> (1580) briefly alludes to the subject in question. After -speaking of the methods of distemper, he observes that the same colours -may be used in oil, except that instead of mixing them with size, they -are mixed on the palette with nut-oil, or (if slow in drying) with -boiled linseed-oil: he does not mention varnish. The Italian writers -next in order are earlier than Vasari, and may therefore be considered -original, but they are all very concise.</p> - -<p><span class="pagenum"><a name="Page_405" id="Page_405">[Pg 405]</a></span></p> - -<p>The treatise of Michael Angelo Biondo<a name="FNanchor_22_162" id="FNanchor_22_162"></a><a href="#Footnote_22_162" class="fnanchor">[22]</a> (1549), remarkable for -its historical mistakes, is not without interest in other respects. -The list of colours he gives is, in all probability, a catalogue of -those in general use in Venice at the period he wrote. With regard -to the vehicle, he merely mentions oil and size as the mediums for -the two distinct methods of oil-painting and distemper, and does not -speak of varnish. The passages in the Dialogue of Doni<a name="FNanchor_23_163" id="FNanchor_23_163"></a><a href="#Footnote_23_163" class="fnanchor">[23]</a> (1549), -which relate to the subject in question, are to the same effect. "In -colouring in oil," he observes, "the most brilliant colours (that we -see in pictures) are prepared by merely mixing them with the end of a -knife on the palette." Speaking of the perishable nature of works in -oil-painting as compared with sculpture, he says, that the plaster of -Paris (gesso) and mastic, with other ingredients of which the ground -is prepared, are liable to decay, &c.; and elsewhere, in comparing -painting in general with mosaic, that in the former the colours "must -of necessity be mixed with various things, such as oils, gums, white -or yolk of egg, and juice of figs, all which tend to impair the beauty -of the tints." This catalogue of vehicles is derived from all kinds of -painting to enforce the argument, and is by no means to be understood -as belonging to one and the same method.</p> - -<p>An interesting little work,<a name="FNanchor_24_164" id="FNanchor_24_164"></a><a href="#Footnote_24_164" class="fnanchor">[24]</a> still in the form of a dialogue (Fabio -and Lauro), appeared a year earlier; the author, Paolo Pino, was a -Venetian painter. In speaking of the practical methods Fabio observes, -as usual, that oil-painting is of all modes of imitation the most -perfect, but his reasons for this opinion seem to have a reference -to the Venetian<span class="pagenum"><a name="Page_406" id="Page_406">[Pg 406]</a></span> practice of going over the work repeatedly. Lauro -asks whether it is not possible to paint in oil on the dry wall, as -Sebastian del Piombo did. Fabio answers, "the work cannot last, for the -solidity of the plaster is impenetrable, and the colours, whether in -oil or distemper, cannot pass the surface." This might seem to warrant -the inference that absorbent grounds were prepared for oil-painting, -but there are proofs enough that resins as well as oil were used with -the <i>gesso</i> to make the preparation compact. See Doni, Armenini, &c. -This writer, again, does not speak of varnish. These appear to be the -chief Venetian and Italian authorities<a name="FNanchor_25_165" id="FNanchor_25_165"></a><a href="#Footnote_25_165" class="fnanchor">[25]</a> of the sixteenth and part of -the following century; and although Boschini wrote latest, he appears -to have had his information from good sources, and more than once -distinctly quotes Palma Giovane.</p> - -<p>In all these instances it will be seen that there is no allusion to the -immixture of varnishes with the solid colours, except in painting on -walls in oil, and that the processes of distemper and oil are always -considered as separate arts.<a name="FNanchor_26_166" id="FNanchor_26_166"></a><a href="#Footnote_26_166" class="fnanchor">[26]</a><span class="pagenum"><a name="Page_407" id="Page_407">[Pg 407]</a></span> On the other hand, the prohibition -of Boschini cannot be understood to be universal, for it is quite -certain that the Venetians varnished their pictures when done.<a name="FNanchor_27_167" id="FNanchor_27_167"></a><a href="#Footnote_27_167" class="fnanchor">[27]</a> -After Titian had finished his whole-length portrait of Pope Paul III. -it was placed in the sun to be varnished.<a name="FNanchor_28_168" id="FNanchor_28_168"></a><a href="#Footnote_28_168" class="fnanchor">[28]</a> Again, in the archives of -the church of S. Niccolo at Treviso a sum is noted (Sept. 21, 1521 ), -"per far la vernise da invernisar la Pala dell' altar grando," and the -same day a second entry appears of a payment to a painter, "per esser -venuto a dar la vernise alla Pala," &c.<a name="FNanchor_29_169" id="FNanchor_29_169"></a><a href="#Footnote_29_169" class="fnanchor">[29]</a> It is to be observed that -in both these cases the pictures were varnished as soon as done;<a name="FNanchor_30_170" id="FNanchor_30_170"></a><a href="#Footnote_30_170" class="fnanchor">[30]</a> -the varnish employed was perhaps the thin compound of naphtha (oglio di -sasso) and melted turpentine (oglio d'abezzo), described by Borghini, -and after him by Armenini: the last-named writer remarks that he had -seen<span class="pagenum"><a name="Page_408" id="Page_408">[Pg 408]</a></span> this varnish used by the best painters in Lombardy, and had heard -that it was preferred by Correggio. The consequence of this immediate -varnishing may have been that the warm resinous liquid, whatever it -was, became united with the colours, and thus at a future time the -pigment may have acquired a consistency capable of resisting the -ordinary solvents. Not only was the surface of the picture required to -be warm, but the varnish was applied soon after it was taken from the -fire.<a name="FNanchor_31_171" id="FNanchor_31_171"></a><a href="#Footnote_31_171" class="fnanchor">[31]</a></p> - -<p>Many of the treatises above quoted contain directions for making the -colours dry:<a name="FNanchor_32_172" id="FNanchor_32_172"></a><a href="#Footnote_32_172" class="fnanchor">[32]</a> some of these recipes, and many in addition, are to be -found in Palomino, who, however defective as an historian,<a name="FNanchor_33_173" id="FNanchor_33_173"></a><a href="#Footnote_33_173" class="fnanchor">[33]</a> has left -very copious practical details, evidently of ancient date. His drying -recipes are numerous, and although sugar of lead does not appear, -cardenillo (verdigris), which is perhaps as objectionable, is admitted -to be the best of all dryers. It may excite some surprise that the -Spanish painters should have bestowed so much attention on this subject -in a climate like theirs, but the rapidity of their execution must have -often required such an assistance.<a name="FNanchor_34_174" id="FNanchor_34_174"></a><a href="#Footnote_34_174" class="fnanchor">[34]</a></p> - -<p>One circumstance alluded to by Palomino, in his very minute practical -directions, deserves to be mentioned. After<span class="pagenum"><a name="Page_409" id="Page_409">[Pg 409]</a></span> saying what colours should -be preserved in their saucers under water, and what colours should be -merely covered with oiled paper because the water injures them, he -proceeds to communicate "a curious mode of preserving oil-colours," and -of transporting them from place to place. The important secret is to -tie them in bladders, the mode of doing which he enters into with great -minuteness, as if the invention was recent. It is true, Christoforo -Sorte, in describing his practice in water-colour drawing, says he was -in the habit of preserving a certain vegetable green with gum-water in -a bladder; but as the method was obviously new to Palomino, there seems -sufficient reason to believe that oil-colours, when once ground, had, -up to his time, been kept in saucers and preserved under water.<a name="FNanchor_35_175" id="FNanchor_35_175"></a><a href="#Footnote_35_175" class="fnanchor">[35]</a> -Among the items of expense in the Treviso document before alluded to, -we find "a pan and saucers for the painters."<a name="FNanchor_36_176" id="FNanchor_36_176"></a><a href="#Footnote_36_176" class="fnanchor">[36]</a> This is in accordance -with Cennini's directions, and the same system appears to have been -followed till after 1700.<a name="FNanchor_37_177" id="FNanchor_37_177"></a><a href="#Footnote_37_177" class="fnanchor">[37]</a></p> - -<p>The Flemish accounts of the early practice of oil-painting are all -later than Vasari. Van Mander, in correcting the Italian historian in -his dates, still follows his narrative in other respects verbatim. If -Vasari's story is to be accepted as true, it might be inferred that -the Flemish secret consisted in an oil varnish like copal.<a name="FNanchor_38_178" id="FNanchor_38_178"></a><a href="#Footnote_38_178" class="fnanchor">[38]</a> Vasari -says, that Van<span class="pagenum"><a name="Page_410" id="Page_410">[Pg 410]</a></span> Eyck boiled the oils with other ingredients; that the -colours, when mixed with this kind of oil, had a very firm consistence; -that the surface of the pictures so executed had a lustre, so that they -needed no varnish when done; and that the colours were in no danger -from water.<a name="FNanchor_39_179" id="FNanchor_39_179"></a><a href="#Footnote_39_179" class="fnanchor">[39]</a></p> - -<p>Certain colours, as is well known, if mixed with oil alone, may be -washed off after a considerable time. Leonardo da Vinci remarks, that -verdigris may be thus removed. Carmine, Palomino observes, may be -washed off after six years. It is on this account the Italian writers -recommend the use of varnish with certain colours, and it appears the -Venetians, and perhaps the Italians generally, employed it solely in -such cases. But it is somewhat extraordinary that Vasari should teach -a mode of painting in oil so different in its results (inasmuch as the -work thus required varnish at last) from the Flemish method which he so -much extols—a method which he says the Italians long endeavoured to -find out in vain. If they knew it, it is evident, assuming his account -to be correct, that they did not practice it.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_141" id="Footnote_1_141"></a><a href="#FNanchor_1_141"><span class="label">[1]</span></a> See "Marcucci Saggio Analitico-chimico sopra i colori," -&c. Rome, 1816, and "Taylor's Translation of Merimée on Oil-painting," -London, 1839. The last-named work contains much useful information.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_142" id="Footnote_2_142"></a><a href="#FNanchor_2_142"><span class="label">[2]</span></a> Italian writers of the 16th century speak of three kinds. -Cardanus says, that of the <i>abies</i> was esteemed most, that of the -<i>larix</i> next, and that of the <i>picea</i> least. The resin extracted by -incision from the last (the pinus abies Linnæi) is known by the name -of Burgundy pitch; when extracted by fire it is black. The three -varieties occur in Italian treatises on art, under the names of <i>oglio -di abezzo</i>, <i>trementina</i> and <i>pece Greca</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_143" id="Footnote_3_143"></a><a href="#FNanchor_3_143"><span class="label">[3]</span></a> The concrete balsam <i>benzoe</i>, called by the Italians -<i>beluzino</i>, and <i>belzoino</i>, is sometimes spoken of as a varnish.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_144" id="Footnote_4_144"></a><a href="#FNanchor_4_144"><span class="label">[4]</span></a> Marcucci supposes that balsam of copaiba was mixed with -the pigments by the (later) Venetians.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_145" id="Footnote_5_145"></a><a href="#FNanchor_5_145"><span class="label">[5]</span></a> "L'Archipelago con tutte le Isole," Ven. 1658. The -incidental notices of the remains of antiquity in this work would be -curious and important if they could be relied on. In describing the -island of Samos, for instance, the author asserts that the temple of -Juno was in tolerable preservation, and that the statue was still -there.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_146" id="Footnote_6_146"></a><a href="#FNanchor_6_146"><span class="label">[6]</span></a> "La Carta del Navegar Pitoresco," Ven. 1660. It is in the -Venetian dialect.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_147" id="Footnote_7_147"></a><a href="#FNanchor_7_147"><span class="label">[7]</span></a> Inveriadure (invetriature), literally the glazing applied -to earthenware.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_8_148" id="Footnote_8_148"></a><a href="#FNanchor_8_148"><span class="label">[8]</span></a> -</p> -<p style="margin-left: 20%;"> -"O de che strazze se fan cavedal!<br /> -D'ogio d'avezzo, mastici e sandraca;<br /> -E trementina (per no'dir triaca)<br /> -Robe, che ilustrerave ogni stival."—p. 338.<br /> -</p> -<p> -The alliteration of the words <i>trementina</i> and <i>triaca</i> is of course -lost in a translation.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_9_149" id="Footnote_9_149"></a><a href="#FNanchor_9_149"><span class="label">[9]</span></a> "I li ha fati straluser co' i colori." Boschini was at -least constant in his opinion. In the second edition of his "Ricche -Minere della Pittura Veneziana," which appeared fourteen years after -the publication of his poem, he repeats that the Venetian painters -avoided some colours in flesh "e similmente i lustri e le vernici."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_10_150" id="Footnote_10_150"></a><a href="#FNanchor_10_150"><span class="label">[10]</span></a> Thus, in the introduction to the "Ricche Minere," -Boschini calls the Milanese, Florentine, Lombard, and Bolognese -painters, <i>forestieri</i>.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_11_151" id="Footnote_11_151"></a><a href="#FNanchor_11_151"><span class="label">[11]</span></a> "Il Riposo," Firenze, 1584.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_12_152" id="Footnote_12_152"></a><a href="#FNanchor_12_152"><span class="label">[12]</span></a> "De' Veri Precetti della Pittura," Ravenna, 1587.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_13_153" id="Footnote_13_153"></a><a href="#FNanchor_13_153"><span class="label">[13]</span></a> "Trattato della Pittura fondato nell' autorità di molti -eccellenti in questa professione." Venezia, 1642. Bisagno remarks in -his preface, that the books on art were few, and that painters were in -the habit of keeping them secret. He acknowledges that he has availed -himself of the labours of others, but without mentioning his sources: -some passages are copied from Lomazzo. He, however, lays claim to some -original observations, and says he had seen much and discoursed with -many excellent painters.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_14_154" id="Footnote_14_154"></a><a href="#FNanchor_14_154"><span class="label">[14]</span></a> "Le Meraviglie dell' Arte," Venezia, 1648.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_15_155" id="Footnote_15_155"></a><a href="#FNanchor_15_155"><span class="label">[15]</span></a> It has been conjectured by some that this story proved -the immixture of varnishes with the colours, and that the oil was only -used to dilute them. The epitaph on Antonello da Messina which existed -in Vasari's time, alludes to his having mixed the colours with oil.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_16_156" id="Footnote_16_156"></a><a href="#FNanchor_16_156"><span class="label">[16]</span></a> "Petri Mariæ Caneparii De Atramentis cujuscumque -generis," Venet. 1619. It was republished at Rotterdam in 1718.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_17_157" id="Footnote_17_157"></a><a href="#FNanchor_17_157"><span class="label">[17]</span></a> "Ita quod magis ex hiis evadit atramentum picturæ -summopere idoneum." Thus, if <i>atramentum</i> is to be understood, as -usual, to mean a glazing colour, the passage can only refer to the -immixture of varnish with the transparent colours applied last in -order.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_18_158" id="Footnote_18_158"></a><a href="#FNanchor_18_158"><span class="label">[18]</span></a> In a passage that follows respecting the mode of -extracting nut-oil, Caneparius appears to mistranslate Galen, c. -7—"De Simplicium Medicamentorum facultatibus." The observations of -Galen on this subject, and on the drying property of linseed, may have -given the first hint to the inventors of oil-painting. The custom of -dating the origin of this art from Van Eyck is like that of dating the -commencement of modern painting from Cimabue. The improver is often -assumed to be the inventor.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_19_159" id="Footnote_19_159"></a><a href="#FNanchor_19_159"><span class="label">[19]</span></a> Milan, 1590.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_20_160" id="Footnote_20_160"></a><a href="#FNanchor_20_160"><span class="label">[20]</span></a> The particulars here alluded to are to be found in the -first edition of Vasari (1550) as well as the second.—v. i. c. 21, &c.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_21_161" id="Footnote_21_161"></a><a href="#FNanchor_21_161"><span class="label">[21]</span></a> "Osservasioni nella Pittura." In Venezia, 1580. Sorte, -who, it appears, was a native of Verona, had worked in his youth -with Giulio Romano, at Mantua, and communicates the methods taught -him by that painter, for giving the true effects of perspective in -compositions of figures. He is, perhaps, the earliest who describes the -process of water-colour painting as distinguished from distemper and as -adapted to landscape, if the art he describes deserves the name.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_22_162" id="Footnote_22_162"></a><a href="#FNanchor_22_162"><span class="label">[22]</span></a> "Della nobilissima Pittura e sua Arte," Venezia, 1549. -Biondo is so ignorant as to attribute the Last Supper, by Leonardo da -Vinci, to Mantegna.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_23_163" id="Footnote_23_163"></a><a href="#FNanchor_23_163"><span class="label">[23]</span></a> "Disegno del Doni," in Venezia, 1549.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_24_164" id="Footnote_24_164"></a><a href="#FNanchor_24_164"><span class="label">[24]</span></a> "Dialogo di Pittura," Venezia, 1548. Pino, in enumerating -the celebrated contemporary artists, does not include Paul Veronese, -for a very obvious reason, that painter being at the time only about -17 years of age. Sorte, who wrote thirty years later, mentions -"l'eccellente Messer Paulino nostro," alone.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_25_165" id="Footnote_25_165"></a><a href="#FNanchor_25_165"><span class="label">[25]</span></a> The Dialogues of Lodovico Dolce, and various other works, -are not referred to here, as they contain nothing on the subject in -question. The latest authority at all connected with the traditions of -Venetian practice, is a certain Giambatista Volpato, of Bassano: he -died in 1706, and had been intimate with Ridolfi. The only circumstance -he has transmitted relating to practical details is that Giacomo -Bassan, in retouching on a dry surface, sometimes adopted a method -commonly practised, he says, by Paul Veronese (and commonly practised -still), namely, that of dipping his brush in spirits of turpentine; -at other times he oiled out the surface in the usual manner. Volpato -left a MS. which was announced for publication in Vicenza in 1685, -but it never appeared; it, however, afterwards formed the ground-work -of Verci's "Notizie intorno alla Vita e alle Opere de' Pittori di -Bassano." Venezia, 1775. See also "Lettera di Giambatista Roberti sopra -Giacomo da Ponte," Lugano, 1777. Another MS. by Natale Melchiori, of -about the same date, is preserved at Treviso and Castel Franco: it -abounds with historical mistakes; the author says, for instance, that -the Pietro Martyre was begun by Giorgione and finished by Titian. The -recipes for varnishes and colours are very numerous, but they are -mostly copied from earlier works.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_26_166" id="Footnote_26_166"></a><a href="#FNanchor_26_166"><span class="label">[26]</span></a> That distemper was not very highly esteemed by the -Venetians may be inferred from the following observation of Pino:—"Il -modo di colorir à guazzo è imperfetto et più fragile et à me non -diletta onde lasciamolo all' oltremontani i quali sono privi della vera -via." It is, however, certain that the Venetians sometimes painted in -this style, and Volpato mentions several works of the kind by Bassan, -but he never hints that he began his oil pictures in distemper.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_27_167" id="Footnote_27_167"></a><a href="#FNanchor_27_167"><span class="label">[27]</span></a> Boschini says, that the Venetians (he especially means -Titian) rendered their pictures sparkling by finally touching on a dry -surface (<i>à secco</i>). The absence of varnish in the solid colours, the -retouching with spirit of turpentine, and even <i>à secco</i>, all suppose a -dull surface, which would require varnish. The latter method, alluded -to by Boschini, was an exception to the general practice, and not -likely to be followed on account of its difficulty. Carlo Maratti, on -the authority of Palomino, used to say, "He must be a skilful painter -who can retouch without oiling out."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_28_168" id="Footnote_28_168"></a><a href="#FNanchor_28_168"><span class="label">[28]</span></a> See a letter by Francesco Bocchi, and another by Vasari, -in the "Lettere Pittoriche" of Bottari. The circumstance is mentioned -incidentally; the point chiefly dwelt on is, that some persons who -passed were deceived, and bowed to the picture, supposing it to be the -pope.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_29_169" id="Footnote_29_169"></a><a href="#FNanchor_29_169"><span class="label">[29]</span></a> Federici, "Memorie Trevigiane," Venezia, 1803. The -altar-piece of S. Niccolo at Treviso is attributed, in the document -alluded to, to Fra Marco Pensabene, a name unknown; the painting is so -excellent as to have been thought worthy of Sebastian del Piombo: for -this opinion, however, there are no historical grounds. It was begun -in 1520, but before it was quite finished the painter, whoever he was, -absconded: it was therefore completed by another.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_30_170" id="Footnote_30_170"></a><a href="#FNanchor_30_170"><span class="label">[30]</span></a> Titian's stay in Rome was short, and with respect to the -Treviso altar-piece, a week or two only, at most, can have elapsed -between the completion and the varnishing. Cennini, who recommends -delaying a year at least before varnishing, speaks of pictures in -distemper.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_31_171" id="Footnote_31_171"></a><a href="#FNanchor_31_171"><span class="label">[31]</span></a> See Borghini, Armenini, their Venetian copyist Bisagno, -and Palomino. The last-named writer, though of another school and much -more modern, was evidently well acquainted with the ancient methods: -he says, "Se advierte que siempre que se huviere de barnizar alguna -cosa conviene que la pintura y el barniz estèn calientes."—<i>El Museo -Pictorico</i>, v. ii.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_32_172" id="Footnote_32_172"></a><a href="#FNanchor_32_172"><span class="label">[32]</span></a> Burnt alum, one of the ingredients recommended, might -perhaps account for a shining fracture in the indurated pigment in some -old pictures.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_33_173" id="Footnote_33_173"></a><a href="#FNanchor_33_173"><span class="label">[33]</span></a> Of the earlier Spanish writers Pacheco may be mentioned -next to Palomino as containing most practical information. Carducho, De -Butron, and others, seldom descend to such details. Palomino contains -all the directions of Pacheco, and many in addition.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_34_174" id="Footnote_34_174"></a><a href="#FNanchor_34_174"><span class="label">[34]</span></a> See Cean Bermudez, "Sobre la Escuela Sevillana," Cadiz, -1806. The same reasons induced the later Venetian machinists to paint -on dark grounds, and to make use of (drying) oil in excess. See -Zanetti, <i>Della Pittura Veneziana</i>, 1. iv.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_35_175" id="Footnote_35_175"></a><a href="#FNanchor_35_175"><span class="label">[35]</span></a> Borghini, in describing the method of making a gold-size -(the same as Cennini's), speaks of boiling the "buccie de' colori" in -oil; this only means the skin or pellicle of the colour itself—in -fact, he proceeds to say that they dissolve in boiling. Vasari, in -describing the same process, uses the expression "colori seccaticci."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_36_176" id="Footnote_36_176"></a><a href="#FNanchor_36_176"><span class="label">[36]</span></a> "Maggio 4 (1520) Per un cadin (catino) per depentori. Per -scudellini per li depentori."—<i>Mem. Trev.</i>, vol. i. p. 131. Pungileoni -("Memorie Istoriche di Antonio Allegri") quotes a note of expenses -relating to two oil-pictures by Paolo Gianotti; among the items we find -"colori, telari, et brocchette."—vol. ii. p. 75.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_37_177" id="Footnote_37_177"></a><a href="#FNanchor_37_177"><span class="label">[37]</span></a> Salmon, in his "Polygraphice" (1701), gives the following -direction:—"Oyl colors, if not presently used, will have a skin grow -over them, to prevent which put them into a glass, and put the glass -three or four inches under water," &c.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_38_178" id="Footnote_38_178"></a><a href="#FNanchor_38_178"><span class="label">[38]</span></a> This varnish appears to have been known some centuries -before Van Eyck's time, but he may have been the first to mix it with -the colours.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_39_179" id="Footnote_39_179"></a><a href="#FNanchor_39_179"><span class="label">[39]</span></a> See Vasari, Life of Antonello da Messina.</p></div> - - - -<p class="para"><a id="NOTE_W"></a>NOTE W.—<a href="#a608">Par. 608.</a></p> - -<p>In the second volume Goethe gives the nomenclature of the Greeks and -Romans at some length. The general notions of the ancients with regard -to colours are thus described:—"The ancients derive all colours from -white and black, from light and darkness. They say, all colours are -between white and black, and are mixed out of these. We must not, -however, suppose that they understand by this a mere atomic mixture, -although they occasionally use the word μίξις;<a name="FNanchor_1_180" id="FNanchor_1_180"></a><a href="#Footnote_1_180" class="fnanchor">[1]</a> for in the remarkable -passages, where they wish to express a kind of reciprocal (dynamic) -action of the two contrasting principles, they employ the words κρᾶσις, -union, σύγκρισις, combination; thus, again, the mutual influence of -light and darkness, and of colours among each<span class="pagenum"><a name="Page_411" id="Page_411">[Pg 411]</a></span> other, is described by -the word κεράννυστας, an expression of similar import.</p> - -<p>"The varieties of colours are differently enumerated; some mention -seven, others twelve, but without giving the complete list. From a -consideration of the terminology both of the Greeks and Romans, it -appears that they sometimes employed general for specific terms, and -<i>vice versâ</i>.</p> - -<p>"Their denominations of colours are not permanently and precisely -defined, but mutable and fluctuating, for they are employed even with -regard to similar colours both on the <i>plus</i> and <i>minus</i> side. Their -yellow, on the one hand, inclines to red, on the other to blue; the -blue is sometimes green, sometimes red; the red is at one time yellow, -at another blue. Pure red (purpur) fluctuates between warm red and -blue, sometimes inclining to scarlet, sometimes to violet.</p> - -<p>"Thus the ancients not only seem to have looked upon colour as a -mutable and fleeting quality, but appear to have had a presentiment of -the (physical and chemical) effects of augmentation and re-action. In -speaking of colours they make use of expressions which indicate this -knowledge; they make yellow redden, because its augmentation tends to -red; they make red become yellow, for it often returns thus to its -origin.</p> - -<p>"The hues thus specified undergo new modifications. The colours -arrested at a given point are attenuated by a stronger light darkened -by a shadow, nay, deepened and condensed in themselves. For the -gradations which thus arise the name of the species only is often -given, but the more generic terms are also employed. Every colour, of -whatever kind, can, according to the same view, be multiplied into -itself, condensed, enriched, and will in consequence appear more or -less dark. The ancients called colour in this state," &c. Then follow -the designations of general states of colour and those of specific hues.</p> - -<p>Another essay on the notions of the ancients respecting<span class="pagenum"><a name="Page_412" id="Page_412">[Pg 412]</a></span> the origin -and nature of colour generally, shows how nearly Goethe himself has -followed in the same track. The dilating effect of light objects, -the action and reaction of the retina, the coloured after-image, the -general law of contrast, the effect of semi-transparent mediums in -producing warm or cold colours as they are interposed before a dark or -light background—all this is either distinctly expressed or hinted -at; "but," continues Goethe, "how a single element divides itself into -two, remained a secret for them. They knew the nature of the magnet, -in amber, only as attraction; polarity was not yet distinctly evident -to them. And in very modern times have we not found that scientific -men have still given their almost exclusive attention to attraction, -and considered the immediately excited repulsion only as a mere -after-action?"</p> - -<p>An essay on the Painting of the Ancients<a name="FNanchor_2_181" id="FNanchor_2_181"></a><a href="#Footnote_2_181" class="fnanchor">[2]</a> was contributed by Heinrich -Meyer.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_180" id="Footnote_1_180"></a><a href="#FNanchor_1_180"><span class="label">[1]</span></a> See Note on Par. 177.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_181" id="Footnote_2_181"></a><a href="#FNanchor_2_181"><span class="label">[2]</span></a> Vol. ii. p. 69, first edition.</p></div> - - - -<p class="para"><a id="NOTE_X"></a>NOTE X.—<a href="#a670">Par. 670.</a></p> - -<p>This agrees with the general recommendation so often given by high -authorities in art, to avoid a tinted look in the colour of flesh. The -great example of Rubens, whose practice was sometimes an exception -to this, may however show that no rule of art is to be blindly or -exclusively adhered to. Reynolds, nevertheless, in the midst of his -admiration for this great painter, considered the example dangerous, -and more than once expresses himself to this effect, observing on one -occasion that Rubens, like Baroccio, is sometimes open to the criticism -made on an ancient painter, namely, that his figures looked as if they -fed on roses.</p> - -<p>Lodovico Dolce, who is supposed to have given the <i>vivâ voce</i> precepts -of Titian in his Dialogue,<a name="FNanchor_1_182" id="FNanchor_1_182"></a><a href="#Footnote_1_182" class="fnanchor">[1]</a> makes Aretino<span class="pagenum"><a name="Page_413" id="Page_413">[Pg 413]</a></span> say: "I would generally -banish from my pictures those vermilion cheeks with coral lips; for -faces thus treated look like masks. Propertius, reproving his Cynthia -for using cosmetics, desires that her complexion might exhibit the -simplicity and purity of colour which is seen in the works of Apelles."</p> - -<p>Those who have written on the practice of painting have always -recommended the use of few colours for flesh. Reynolds and others quote -even ancient authorities as recorded by Pliny, and Boschini gives -several descriptions of the method of the Venetians, and particularly -of Titian, to the same effect. "They used," he says, "earths more than -any other colour, and at the utmost only added a little vermilion, -minium, and lake, abhorring as a pestilence <i>biadetti, gialli santi, -smaltini, verdi-azzurri, giallolini</i>."<a name="FNanchor_2_183" id="FNanchor_2_183"></a><a href="#Footnote_2_183" class="fnanchor">[2]</a> Elsewhere he says,<a name="FNanchor_3_184" id="FNanchor_3_184"></a><a href="#Footnote_3_184" class="fnanchor">[3]</a> "Earths -should be used rather than other colours:" after repeating the above -prohibited list he adds, "I speak of the imitation of flesh, for in -other things every colour is good;" again, "Our great Titian used to -say that he who wishes to be a painter should be acquainted with three -colours, white, black, and red."<a name="FNanchor_4_185" id="FNanchor_4_185"></a><a href="#Footnote_4_185" class="fnanchor">[4]</a> Assuming this<span class="pagenum"><a name="Page_414" id="Page_414">[Pg 414]</a></span> account to be a -little exaggerated, it is still to be observed that the monotony to -which the use of few colours would seem to tend, is prevented by the -nature of the Venetian process, which was sufficiently conformable to -Goethe's doctrine; the gradations being multiplied, and the effect -of the colours heightened by using them as semi-opaque mediums. -Immediately after the passage last quoted we read, "He also gave this -true precept, that to produce a lively colouring in flesh it is not -possible to finish at once."<a name="FNanchor_5_186" id="FNanchor_5_186"></a><a href="#Footnote_5_186" class="fnanchor">[5]</a> As these particulars may not be known -to all, we add some further abridged extracts explaining the order and -methods of these different operations.</p> - -<p>"The Venetian painters," says this writer,<a name="FNanchor_6_187" id="FNanchor_6_187"></a><a href="#Footnote_6_187" class="fnanchor">[6]</a> "after having drawn in -their subject, got in the masses with very solid colour, without making -use of nature or statues. Their great object in this stage of their -work was to distinguish the advancing and retiring portions, that the -figures might be relieved by means of chiaro-scuro—one of the most -important departments of colour and form, and indeed of invention. -Having decided on their scheme of effect, when this preparation was -dry, they consulted nature and the antique; not servilely, but with the -aid of a few lines on paper (<i>quattro segni in carta</i>) they corrected -their figures without any other model. Then returning to their brushes, -they began to paint smartly on this preparation, producing the colour -of flesh." The passage before quoted follows, stating that they used -earths chiefly, that they carefully avoided certain colours, "and -likewise varnishes and whatever produces a shining surface.<a name="FNanchor_7_188" id="FNanchor_7_188"></a><a href="#Footnote_7_188" class="fnanchor">[7]</a> When -this second painting was dry, they proceeded to scumble over this or -that figure with a low tint to make the one next it come forward, -giving another, at the same time, an additional light—for example,<span class="pagenum"><a name="Page_415" id="Page_415">[Pg 415]</a></span> on -a head, a hand, or a foot, thus detaching them, so to speak, from the -canvas." (Tintoret's <i>Prigionia di S. Rocco</i> is here quoted.) "By thus -still multiplying these well-understood retouchings where required, on -the dry surface, <i>(à secco)</i> they reduced the whole to harmony. In this -operation they took care not to cover entire figures, but rather went -on gemming them <i>(gioielandole)</i> with vigorous touches. In the shadows, -too, they infused vigour frequently by glazing with asphaltum, always -leaving great masses in middle-tint, with many darks, in addition to -the partial glazings, and few lights."</p> - -<p>The introduction to the subject of Venetian colouring, in the poem by -the same author, is also worth transcribing, but as the style is quaint -and very concise, a translation is necessarily a paraphrase.<a name="FNanchor_8_189" id="FNanchor_8_189"></a><a href="#Footnote_8_189" class="fnanchor">[8]</a></p> - -<p>"The art of colouring has the imitation of qualities for its object; -not all qualities, but those secondary ones which are appreciable by -the sense of sight. The eye especially sees colours, the imitation -of nature in painting is therefore justly called colouring; but the -painter arrives at his end by indirect means. He gives the varieties -of tone in masses;<a name="FNanchor_9_190" id="FNanchor_9_190"></a><a href="#Footnote_9_190" class="fnanchor">[9]</a><span class="pagenum"><a name="Page_416" id="Page_416">[Pg 416]</a></span> he smartly impinges lights, he clothes his -preparation with more delicate local hues, he unites, he glazes: thus -everything depends on the method, on the process. For if we look -at colour abstractedly, the most positive may be called the most -beautiful, but if we keep the end of imitation in view, this shallow -conclusion falls to the ground. The refined Venetian manner is very -different from mere direct, sedulous imitation. Every one who has -a good eye may arrive at such results, but to attain the manner of -Paolo, of Bassan, of Palma, Tintoret, or Titian, is a very different -undertaking."<a name="FNanchor_10_191" id="FNanchor_10_191"></a><a href="#Footnote_10_191" class="fnanchor">[10]</a></p> - -<p>The effects of semi-transparent mediums in some natural productions -seem alluded to in the following passage—"Nature sometimes -accidentally imitates figures in stones and other substances, and -although they are necessarily incomplete in form, yet the principle -of effect (depth) resembles the Venetian practice." In a passage that -follows there appears to be an allusion to the production of the -atmospheric colours by semi-transparent mediums.<a name="FNanchor_11_192" id="FNanchor_11_192"></a><a href="#Footnote_11_192" class="fnanchor">[11]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_182" id="Footnote_1_182"></a><a href="#FNanchor_1_182"><span class="label">[1]</span></a> "Dialogo della Pittura, intitolato l'Aretino." It -was first published at Venice in 1557; about twenty years before -Titian's death. In the dedication to the senator Loredano, Lodovico -Dolce eulogises the work, which he would hardly have done if it had -been entirely his own: again, the supposition that it may have been -suggested by Aretino, would be equally conclusive, coupled with -internal evidence, as to the original source.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_183" id="Footnote_2_183"></a><a href="#FNanchor_2_183"><span class="label">[2]</span></a> Introduction to the "Ricche Minere della Pittura -Veneziana," Venezia, 1674. The Italian annotators on older works on -painting are sometimes at a loss to find modern terms equivalent to the -obsolete names of pigments. (See "Antologia dell 'Arte Pittorica.") -The colours now in use corresponding with Boschini's list, are -probably yellow lakes, smalt, verditer, and Naples yellow. Boschini -often censures the practice of other schools, and in this emphatic -condemnation he seems to have had an eye to certain precepts in -Lomazzo, and perhaps, even in Leonardo da Vinci, who, on one occasion, -recommends Naples yellow, lake, and white for flesh. The Venetian -writer often speaks, too, in no measured terms of certain Flemish -pictures, probably because they appeared to him too tinted.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_184" id="Footnote_3_184"></a><a href="#FNanchor_3_184"><span class="label">[3]</span></a> "La Carta del Navegar Pitoresco," p. 338.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_185" id="Footnote_4_185"></a><a href="#FNanchor_4_185"><span class="label">[4]</span></a> Ib. p. 341. In describing Titian's actual practice -("Ricche Minere"), he, however, adds yellow (ochre). The red is also -particularised, viz., the common terra rossa.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_186" id="Footnote_5_186"></a><a href="#FNanchor_5_186"><span class="label">[5]</span></a> High examples here again prove that the opposite system -may attain results quite as successful.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_187" id="Footnote_6_187"></a><a href="#FNanchor_6_187"><span class="label">[6]</span></a> Introduction to the "Ricche Minere."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_188" id="Footnote_7_188"></a><a href="#FNanchor_7_188"><span class="label">[7]</span></a> See Note to Par. <a href="#a555">555</a>. Here again, assuming the description -to be correct, high authorities might be opposed to the Venetians.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_8_189" id="Footnote_8_189"></a><a href="#FNanchor_8_189"><span class="label">[8]</span></a> The following quatrain may serve as a specimen; the author -is speaking of the importance of the colour of flesh as conducive to -picturesque effect:— -</p> -<p style="margin-left: 20%;"> -"Importa el nudo; e come ben l'importa!<br /> -Un quadro senta nudo è come aponto<br /> -Un disnar senza pan, se ben ghe zonto,<br /> -Per più delicia, confetura e torta."—p. 346.<br /> -</p> -<p> -In his preface he anticipates, and thus answers the objections to his -Venetian dialect—"Mi, che son Venetian in Venetia e che parlo de' -Pitori Venetiani hò da andarme a stravestir? Guarda el Cielo."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_9_190" id="Footnote_9_190"></a><a href="#FNanchor_9_190"><span class="label">[9]</span></a> The word <i>Macchia</i>, literally a blot, is generally used by -Italian writers, by Vasari for instance, for the local colour. Boschini -understands by it the relative depth of tones rather than the mere -difference of hue. "By macchia," he says, "I understand that treatment -by which the figures are distinguished from each other by different -tones lighter or darker."—<i>La Carta del Navegar</i>, p. 328. Elsewhere, -"Colouring (as practised by the Venetians) comprehends both the macchia -and drawing;" (p. 300) that is, comprehends the gradations of light -and dark in objects, and the parts of objects, and consequently, their -essential form. "The macchia," he adds, "is the effect of practice, and -is dictated by the knowledge of what is requisite for effect."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_10_191" id="Footnote_10_191"></a><a href="#FNanchor_10_191"><span class="label">[10]</span></a> -</p> -<p style="margin-left: 20%;"> -"Ma l'arivar a la maniera, al trato<br /> -(Verbi gratia) de Paulo, del Bassan,<br /> -Del Vechio, Tentoreto, e di Tician,<br /> -Per Dio, l'è cosa da deventar mato."—p. 294, 297.<br /> -</p></div> - -<div class="footnote"> - -<p><a name="Footnote_11_192" id="Footnote_11_192"></a><a href="#FNanchor_11_192"><span class="label">[11]</span></a> The traces of the Aristotelian theory are quite as -apparent in Boschini as in the other Italian writers on art; but as he -wrote in the seventeenth century, his authority in this respect is only -important as an indication of the earlier prevalence of the doctrine.</p></div> - - - -<p class="para"><a id="NOTE_Y"></a>NOTE Y.—Par. 672.</p> - -<p>The author's conclusion here is unsatisfactory, for the colour of -the black races may be considered at least quite as negative as that -of Europeans. It would be safer to say that the white skin is more -beautiful than the black, because it is more capable of indications -of life, and indications of emotion. A degree of light which would -fail to exhibit the finer varieties of form on a dark surface, would -be sufficient to display them on a light one; and the delicate -mantlings<span class="pagenum"><a name="Page_417" id="Page_417">[Pg 417]</a></span> of colour, whether the result of action or emotion, are more -perceptible for the same reason.</p> - - - -<p class="para"><a id="NOTE_Z"></a>NOTE Z.—Par. 690.</p> - -<p>The author appears to mean that a degree of brightness which the organ -can bear at all, must of necessity be removed from dazzling, white -light. The slightest tinge of colour to this brightness, implies that -it is seen through a medium, and thus, in painting, the lightest, -whitest surface should partake of the quality of depth. Goethe's view -here again accords, it must be admitted, with the practice of the best -colourists, and with the precepts of the highest authorities.—See <a href="#NOTE_C">Note C</a>.</p> - - - -<p class="para"><a id="NOTE_AA"></a>NOTE AA.—<a href="#a732">Par. 732.</a></p> - -<p>Ample details respecting the opinions of Louis Bertrand Castel, a -Jesuit, are given in the historical part. The coincidence of some -of his views with those of Goethe is often apparent: he objects, -for instance, to the arbitrary selection of the Newtonian spectrum; -observing that the colours change with every change of distance between -the prism and the recipient surface.—<i>Farbenl.</i> vol. ii. p. 527. -Jeremias Friedrich Gülich was a dyer in the neighbourhood of Stutgardt: -he published an elaborate work on the technical details of his own -pursuit.—<i>Farbenl.</i> vol. ii. p. 630.</p> - - - -<p class="para"><a id="NOTE_BB"></a>NOTE BB.—<a href="#a748">Par. 748.</a></p> - -<p>Goethe, in his account of Castel, suppresses the learned Jesuit's -attempt at colorific music (the claveçin oculaire), founded on the -Newtonian doctrine. Castel was complimented, perhaps ironically, on -having been the first to remark that there were but three principal -colours. In asserting his claim to the discovery, he admits that there -is nothing new. In fact, the notion of three colours is to be found in -Aristotle; for that philosopher enumerates no<span class="pagenum"><a name="Page_418" id="Page_418">[Pg 418]</a></span> more in speaking of the -rainbow,<a name="FNanchor_1_193" id="FNanchor_1_193"></a><a href="#Footnote_1_193" class="fnanchor">[1]</a> and Seneca calls them by their right names.<a name="FNanchor_2_194" id="FNanchor_2_194"></a><a href="#Footnote_2_194" class="fnanchor">[2]</a> Compare with -Dante, Parad. c. 33. The relation between colours and sounds is in like -manner adverted to by Aristotle; he says—"It is possible that colours -may stand in relation to each other in the same manner as concords -in music, for the colours which are (to each other) in proportions -corresponding with the musical concords, are those which appear to -be the most agreeable."<a name="FNanchor_3_195" id="FNanchor_3_195"></a><a href="#Footnote_3_195" class="fnanchor">[3]</a> In the latter part of the 16th century, -Arcimboldo, a Milanese painter, invented a colorific music; an account -of his principles and method will be found in a treatise on painting -which appeared about the same time. "Ammaestrato dal quai ordine Mauro -Cremonese dalla viola, musico dell' Imperadore Ridolfo II. trovò sul -gravicembalo tutte quelle consonanze che dall' Arcimboldo erano segnate -coi colori sopra una carta."<a name="FNanchor_4_196" id="FNanchor_4_196"></a><a href="#Footnote_4_196" class="fnanchor">[4]</a></p> -<hr class="r5" /> -<div class="footnote"> - -<p><a name="Footnote_1_193" id="Footnote_1_193"></a><a href="#FNanchor_1_193"><span class="label">[1]</span></a> "De Meteor.," lib. 3, c. ii. and iv. He observes that this -is the only effect of colour which painters cannot imitate.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_194" id="Footnote_2_194"></a><a href="#FNanchor_2_194"><span class="label">[2]</span></a> "De Ignib. cœlest." The description of the prism by Seneca -is another instance of the truth of Castel's admission. The Roman -philosopher's words are—"Virgula solet fieri vitrea, stricta vel -pluribus angulis in modo clavæ tortuosæ; hæc si ex transverso solem -accipit colorem talem qualis in arcu videri solet, reddit," &c.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_195" id="Footnote_3_195"></a><a href="#FNanchor_3_195"><span class="label">[3]</span></a> "De Sensu et sensili."</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_196" id="Footnote_4_196"></a><a href="#FNanchor_4_196"><span class="label">[4]</span></a> "Il Figino, overo del Fine della Pittura," Mantova, 1591, -p. 249. An account of the absurd invention of the same painter in -composing figures of flowers and animals, and even painting portraits -in this way, to the great delight of the emperor, will be found in the -same work.</p></div> - - - -<p class="para"><a id="NOTE_CC"></a>NOTE CC.—<a href="#a758">Par. 758.</a></p> - -<p>The moral associations of colours have always been a more favourite -subject with poets than with painters. This is to be traced to the -materials and means of description as distinguished from those of -representation. An image is more distinct for the mind when it is -compared with something that resembles it. An object is more distinct -for the eye when it is compared with something that differs from it. -Association is the auxiliary in the one case, contrast in the<span class="pagenum"><a name="Page_419" id="Page_419">[Pg 419]</a></span> other. -The poet, of necessity, succeeds best in conveying the impression -of external things by the aid of analogous rather than of opposite -qualities: so far from losing their effect by this means, the images -gain in distinctness. Comparisons that are utterly false and groundless -never strike us as such if the great end is accomplished of placing -the thing described more vividly before the imagination. In the common -language of laudatory description the colour of flesh is like snow -mixed with vermilion: these are the words used by Aretino in one of -his letters in speaking of a figure of St. John, by Titian. Similar -instances without end might be quoted from poets: even a contrast can -only be strongly conveyed in description by another contrast that -resembles it.<a name="FNanchor_1_197" id="FNanchor_1_197"></a><a href="#Footnote_1_197" class="fnanchor">[1]</a> On the other hand it would be easy to show that -whenever poets have attempted the painter's method of direct contrast, -the image has failed to be striking, for the mind's eye cannot see the -relation between two colours.</p> - -<p>Under the same category of effect produced by association may be -classed the moral qualities in which poets have judiciously taken -refuge when describing visible forms and colours, to avoid competition -with the painters' elements, or rather to attain their end more -completely. But a little examination would show that very pleasing -moral associations may be connected with colours which would be far -from agreeable to the eye. All light, positive colours, light-green, -light-purple, white, are pleasing to the mind's eye, and no degree -of dazzling splendour is offensive. The moment, however, we have to -do with the actual sense of vision, the susceptibility of the eye -itself is to be considered, the law of comparison is reversed, colours -become striking by being opposed to what they are not, and their moral -associations are not owing to the colours themselves,<span class="pagenum"><a name="Page_420" id="Page_420">[Pg 420]</a></span> but to the -modifications such colours undergo in consequence of what surrounds -them. This view, so naturally consequent on the principles the author -has himself arrived at, appears to be overlooked in the chapter under -consideration, the remarks in which, in other respects, are acute and -ingenious.</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_197" id="Footnote_1_197"></a><a href="#FNanchor_1_197"><span class="label">[1]</span></a> Such as— -</p> -<p style="margin-left: 20%;"> -"Her beauty hangs upon the cheek of night,<br /> -Like a rich jewel in an Ethiop's ear."<br /> -<span style="margin-left: 11em;"><i>Romeo and Juliet</i>.</span><br /> -</p></div> - - - -<p class="para"><a id="NOTE_DD"></a>NOTE DD.—Par. 849.</p> - -<p>According to the usual acceptation of the term chiaro-scuro in the -artist world, it means not only the mutable effects produced by light -and shade, but also the permanent differences in brightness and -darkness which are owing to the varieties of local colour.</p> - - - -<p class="para"><a id="NOTE_EE"></a>NOTE EE.—Par. 855.</p> - -<p>The mannered treatment of light and shade here alluded to by the -author is very seldom to be met with in the works of the colourists; -the taste may have first arisen from the use of plaster-casts, and -was most prevalent in France and Italy in the early part of the last -century. Piazzetta represented it in Venice, Subleyras in Rome. In -France "Restout taught his pupils that a globe ought to be represented -as a polyhedron. Greuze most implicitly adopted the doctrine, and in -practice showed that he considered the round cheeks of a young girl or -an infant as bodies cut into facettes."<a name="FNanchor_1_198" id="FNanchor_1_198"></a><a href="#Footnote_1_198" class="fnanchor">[1]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_198" id="Footnote_1_198"></a><a href="#FNanchor_1_198"><span class="label">[1]</span></a> See Taylor's translation of Merimée on oil-painting, -p. 27. Barry, in a letter from Paris, speaks of Restout as the -only painter who resembled the earlier French masters: the manner -in question is undoubtedly sometimes very observable in Poussin. -The English artist elsewhere speaks of the "broad, happy manner of -Subleyras."—<i>Works</i>, London, 1809.</p></div> - - - -<p class="para"><a id="NOTE_FF"></a>NOTE FF.—<a href="#a859">Par. 859.</a></p> - -<p>All this was no doubt suggested by Heinrich Meyer, whose chief -occupation in Rome, at one time, was making<span class="pagenum"><a name="Page_421" id="Page_421">[Pg 421]</a></span> sepia drawings from -sculpture (see Goethe's Italiänische Reise). It is hardly necessary to -say that the observation respecting the treatment of the surface in the -antique statues is very fanciful.</p> - - - -<p class="para"><a id="NOTE_GG"></a>NOTE GG.—<a href="#a863">Par. 863.</a></p> - -<p>This observation might have been suggested by the drawings of Claude, -which, with the slightest means, exhibit an harmonious balance of warm -and cold.</p> - - - -<p class="para"><a id="NOTE_HH"></a>NOTE HH.—<a href="#a865">Par. 865.</a></p> - -<p>The colouring of Paolo Uccello, according to Vasari's account of him, -was occasionally so remarkable that he might perhaps have been fairly -included among the instances of defective vision given by the author. -His skill in perspective, indicating an eye for gradation, may be also -reckoned among the points of resemblance (see Par. 105).</p> - - - -<p class="para"><a id="NOTE_II"></a>NOTE II.—<a href="#a902">Par. 902.</a></p> - -<p>The quotation before given from Boschini shows that the method -described by the author, and which is true with regard to some of the -Florentine painters, was not practised by the Venetians, for their -first painting was very solid. It agrees, however, with the manner -of Rubens, many of whose works sufficiently corroborate the account -of his process given by Descamps. "In the early state of Rubens's -pictures," says that writer,<a name="FNanchor_1_199" id="FNanchor_1_199"></a><a href="#Footnote_1_199" class="fnanchor">[1]</a> "everything appeared like a thin wash; -but although he often made use of the ground in producing his tones, -the canvas was entirely covered more or less with colour." In this -system of leaving the shadows transparent from the first, with the -ground shining through them, it would have been obviously destructive -of richness to use white mixed with the darks, the brightness, in -fact, already existed underneath. Hence the<span class="pagenum"><a name="Page_422" id="Page_422">[Pg 422]</a></span> well-known precept of -Rubens to avoid white in the shadows, a precept, like many others, -belonging to a particular practice, and involving all the conditions of -that practice.<a name="FNanchor_2_200" id="FNanchor_2_200"></a><a href="#Footnote_2_200" class="fnanchor">[2]</a> Scarmiglione, whose Aristotelian treatise on colour -was published in Germany when Rubens was three-and-twenty, observes, -"Painters, with consummate art, lock up the bright colours with dark -ones, and, on the other hand, employ white, the poison of a picture, -very sparingly." (Artificiosissimè pictores claros obscuris obsepiant -et contra candido picturarum veneno summè parcentes, &c.)</p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_199" id="Footnote_1_199"></a><a href="#FNanchor_1_199"><span class="label">[1]</span></a> "La Vie des Peintres Flamands," vol. i.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_200" id="Footnote_2_200"></a><a href="#FNanchor_2_200"><span class="label">[2]</span></a> The method he recommended for keeping the colours pure in -the lights, viz. to place the tints next each other unmixed, and then -slightly to unite them, may have degenerated to a methodical manner -in the hands of his followers. Boschini, who speaks of Rubens himself -with due reverence, and is far from confounding him with his imitators, -contrasts such a system with that of the Venetians, and adds that -Titian used to say, "Chi de imbratar colori teme, imbrata e machia -si medemi."—<i>Carta del Navegar</i>, p. 341. The poem of Boschini is in -many respects polemical. He wrote at a time when the Flemish painters, -having adopted and modified the Venetian principles, threatened to -supersede the Italian masters in the opinion of the world. Their -excellence, too, had all the charm of novelty, for in the seventeenth -century Venice produced no remarkable talent, and it was precisely -the age for her to boast of past glories. The contemptuous manner in -which Boschini speaks of the Flemish varnishes, of the fear of mixing -tints, &c., is thus always to be considered with reference to the time -and circumstances. So also his boasting that the Venetian masters -painted without nature, which may be an exaggeration, is pointed at -the <i>Naturalisti</i>, Caravaggio and his followers, who copied nature -literally.</p></div> - - - -<p class="para"><span style="font-size: 0.8em;"><a id="NOTE_KK"></a>NOTE KK</span>.—Par. 903.</p> - -<p>The practice here alluded to is more frequently observable in slight -works by Paul Veronese. His ground was often pure white, and in some -of his works it is left as such. Titian's white ground was covered -with a light warm colour, probably at first, and appears to have -been similar to that to which Armenini gives the preference, namely, -"quella che tira al color di carne chiarissima con un non so che di -fiammeggiante."<a name="FNanchor_1_201" id="FNanchor_1_201"></a><a href="#Footnote_1_201" class="fnanchor">[1]</a></p> -<hr class="r5" /> - -<div class="footnote"> - -<p><a name="Footnote_1_201" id="Footnote_1_201"></a><a href="#FNanchor_1_201"><span class="label">[1]</span></a> "Veri Precetti della Pittura," p. 123.</p> - -<p><span class="pagenum"><a name="Page_423" id="Page_423">[Pg 423]</a></span></p></div> - - -<p class="para"><span style="font-size: 0.8em;"><a id="NOTE_LL"></a>NOTE LL.</span>—<a href="#a919">Par. 919.</a></p> - -<p>The notion which the author has here ventured to express may have -been suggested by the remarkable passage in the last canto of Dante's -"Paradiso"—</p> - -<p style="margin-left: 20%;"> -"Nella profonda e chiara sussistenza,<br /> -Dell' alto lume parremi tre giri<br /> -Di tre colori e d'una continenza," &c.<br /> -</p> - -<p>After the concluding paragraph the author inserts a letter from a -landscape-painter, Philipp Otto Runge, which is intended to show that -those who imitate nature may arrive at principles analogous to those of -the "Farbenlehre."</p> - - -<h4>THE END.</h4> - - - - - - - - -<pre> - - - - - -End of the Project Gutenberg EBook of Goethe's Theory of Colours, by -Johann, Wolfgang von Goethe - -*** END OF THIS PROJECT GUTENBERG EBOOK GOETHE'S THEORY OF COLOURS *** - -***** This file should be named 50572-h.htm or 50572-h.zip ***** -This and all associated files of various formats will be found in: - http://www.gutenberg.org/5/0/5/7/50572/ - -Produced by Annemie Arnst, Clare Graham & Marc D'Hooghe -at http://.freeliterature.org (Images generously made -available by the Internet Archive.) - -Updated editions will replace the previous one--the old editions will -be renamed. - -Creating the works from print editions not protected by U.S. copyright -law means that no one owns a United States copyright in these works, -so the Foundation (and you!) can copy and distribute it in the United -States without permission and without paying copyright -royalties. 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