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+
+*** START OF THE PROJECT GUTENBERG EBOOK 77076 ***
+
+
+
+
+
+ CLASSICS OF
+ MODERN SCIENCE
+
+
+ THERE is no grander nor more intellectually elevating spectacle than
+ that of the utterances of the fundamental investigators in their
+ gigantic power. Possessed as yet of no methods--for these were first
+ created by their labors and are only rendered comprehensible to us by
+ their performances--they grapple with and subjugate the object of their
+ inquiry and imprint upon it the forms of conceptual thought.
+
+ --ERNST MACH
+
+
+
+
+ CLASSICS
+ OF
+ MODERN SCIENCE
+
+ (COPERNICUS TO PASTEUR)
+
+
+
+
+ EDITED BY
+
+ WILLIAM S. KNICKERBOCKER, PH.D.
+
+ PROFESSOR OF ENGLISH IN THE UNIVERSITY
+ OF THE SOUTH · EDITOR, THE
+ SEWANEE REVIEW
+
+
+
+
+ ALFRED · A · KNOPF · NEW YORK
+
+ MCMXXVII
+
+
+
+
+ COPYRIGHT 1927, BY ALFRED · A · KNOPF, INC.
+
+
+ SET UP, ELECTROTYPED, PRINTED AND BOUND BY
+ THE VAIL-BALLOU PRESS, BINGHAMTON, N. Y.
+ PAPER FURNISHED BY W. F. ETHERINGTON & CO.,
+ NEW YORK
+
+
+ MANUFACTURED
+ IN THE UNITED STATES OF AMERICA
+
+
+
+
+ TO MY FORMER ASSOCIATES OF THE FACULTY,
+ AND THE STUDENTS OF THE NEW YORK
+ STATE COLLEGE OF FORESTRY AT SYRACUSE
+ UNIVERSITY.
+
+
+
+
+ PREFACE
+
+
+“The history of science,” wrote Du Bois-Reymond, “is the real history
+of mankind.” Gradually we are coming to realize the significance of
+that statement, and the sooner we realize it on a grand scale the more
+shall we hasten the happiness of man.
+
+Fortunately for education, science no longer has to fight for its
+inclusion among the courses offered for study in colleges and
+universities. As scientific knowledge increases and the technique
+of teaching science improves, the exact knowledge of the few more
+rapidly becomes the accepted knowledge of the many. More than that,
+the scientific attitude of mind produces many of the virtues which in
+old-fashioned courses in ethics were taught as objectively as a problem
+in geometry. Patience, endurance, humility, teachableness, honesty,
+accuracy--without these it is impossible for a scientist properly to
+work. And the history of science is as inspiring in its human values as
+are the legends of the saints. Contemplate the heroism of a Galileo,
+the patience of a Darwin, the humility of a Pasteur; a modern eleventh
+chapter of _Hebrews_ might be written listing the names of all
+those men of faith who by quiet work, unremitting in their zeal, one by
+one discovered facts which have made man’s lot easier and happier in
+what was otherwise to him a hostile and unhappy universe.
+
+Little by little, accretion upon accretion, man’s knowledge of
+the physical forces of his universe has been increased, but his
+progress has often been retarded by those who, with good intentions,
+superstitiously feared the power of the gods who, as in the story of
+Brunhilde, encircled their mysteries with a ring of fire. Periodically
+superstition re-arises, but it does not permanently halt the advance
+deploy of armed skirmishers, however much it may temporarily retard
+the advancement of knowledge. Since the seventeenth century, however,
+so remarkable has been the progress of science, so evident have been
+its beneficent achievements, that regardless of the present assault
+upon one phase of science, western civilization is committed to this
+way of discovery. But it is no easy way! “The rapid increase of
+natural knowledge,” wrote Thomas Henry Huxley, “which is the chief
+characteristic of our age, is affected in various ways. The main army
+of science moves to the conquest of the new worlds slowly and surely,
+nor ever cedes an inch of the territory gained. But the advance is
+covered and facilitated by the ceaseless activity of clouds of light
+troops provided with a weapon--always efficient, if not always an
+arm of precision--the scientific imagination. It is the business of
+these _enfants perdus_ of science to make raids into the realms
+of ignorance wherever they see, or think they see, a chance; and
+cheerfully to accept defeat, or it may be annihilation, as the reward
+of error. Unfortunately the public, which watches the progress of the
+campaign, too often mistakes a dashing incursion ... for a forward
+movement of the main body; fondly imagining that the strategic movement
+to the rear, which occasionally follows, indicates a battle lost by
+science.”
+
+It is regrettable that Huxley was compelled to use the metaphor of
+a battle in describing the general advance of scientific knowledge;
+how much better it would have been if he could have used a scientific
+word like _enzyme_ or _catalyst_ in referring to those courageous men
+of the laboratory and the field who went forth alone with instruments
+to discover things as they really are and changed fields of knowledge
+through their discoveries. But if he had employed these scientific
+terms, no one, apart from the select company of scientists themselves
+who have had to evolve a special language of their own to express
+new matters and new meanings, would understand him. People who use
+strange tongues are always suspect to the populace. If science is to
+be “understanded” by the people, the people’s language must be used.
+Fortunately, for the sake of science, scientists themselves are now
+keenly aware of the necessity of presenting their findings in language
+which may be understood by the ordinary man. Huxley himself made the
+_liaison_ in his age, an age in which battles were highly idealised.
+His grandson, however, speaking to our age, rephrases the idea in a
+mode more acceptable to us: “Each science or branch of science seems
+roughly to go through three main phases in its development. There is
+first a preliminary phase in which miscellaneous sporadic knowledge
+is amassed and is dated; theories are pursued, often to be proved
+valueless. There then comes a classic or heroic age, in which a general
+principle of firmly interrelated principles is gradually laid down,
+upon which in its turn a coherent architecture of theory can be built,
+and finally this passes over into a period of maturity, in which the
+position is consolidated, the scope of the principles widened, their
+bases more finally tested, and their consequences worked out in fullest
+detail. Naturally, each stage lasts for a considerable time, and in
+many cases a science which thought itself securely embarked upon the
+third phase is reminded by some fundamental discovery that it is still
+only in the second.”[1]
+
+These movements of science have produced a copious literature which
+has not enjoyed the same attention and reading as imaginative books,
+because, once the ideas are known and incorporated into the existing
+body of scientific knowledge, these scientific writings tend to acquire
+chiefly an historical interest. Yet they are monuments of the advance
+of civilization, and deserve a better fate. Many of them are still
+interesting to read as human documents because they illustrate how
+painfully and slowly man’s exact knowledge of verifiable phenomena has
+been accumulated. No one outside of the small company of highly trained
+scientists can read all of them through, yet most of them have sections
+which are as readable and as exciting as any modern novel. It is the
+purpose of this book to present to the young college student and to the
+general reader some of the more representative of these classics in the
+literature of science, bringing together in this convenient form at
+least some reminders of a vast field of reading where one may browse
+for a lifetime with interest and profit. If it be used in conjunction
+with a history of science it will readily supply a vivid sense of
+the movement of the mind of western civilization, increasing in us a
+respect for the effort of our ancestors, and inspire us to encourage
+and to forward the work of contemporary scientists, and restrain us at
+least from hindering them in their efforts.
+
+Although the selections may be used as a textbook in courses like
+Introduction to Modern Civilization, Philosophy, and The History of
+Science now given in the more progressive colleges and universities,
+it may also profitably be used as a text for freshman or sophomore
+readings in English courses given in colleges predominantly technical
+or scientific, like Engineering, Agricultural, and Forestry Colleges.
+In those English courses where emphasis upon ideas is made to provide
+the inspiration for writing, these selections will be found, as I
+found them in my own work, to stir up considerable discussion and
+to provide opportunities for reading modern scientific literature.
+Moreover, the literary style of science at its best will be found to be
+excellently illustrated in these straightforward, coherent sentences
+written by some of the world’s clearest thinkers. They illustrate
+concretely what Tyndall remarked in his closing words of the famous
+_Belfast Address_: “It has been said that science divorces itself
+from literature. The statement, like so many others, arises from
+lack of knowledge. A glance at the less technical writings of its
+leaders--of its Helmholtz, its Huxley, and its Du Bois-Reymond--would
+show what breadth of literary culture they command. Where among
+modern writers can you find their superiors in clearness and vigor
+of literary style? Science desires no isolation, but freely combines
+with every effort toward the bettering of man’s estate. Single-handed
+and supported not with outward sympathy, but by inward force, it has
+built at least one great wing of the many-mansioned home which man in
+his totality demands.... The world embraces not only a Newton, but a
+Shakespeare; not only a Boyle, but a Raphael; not only a Kant, but a
+Beethoven; not only a Darwin, but a Carlyle. Not in each of these, but
+in all, is human nature whole. They are not opposed, but supplementary;
+not mutually exclusive, but reconcilable.”
+
+ WILLIAM S. KNICKERBOCKER
+
+UNIVERSITY OF THE SOUTH
+SEWANEE, TENN.
+_April 5, 1927_
+
+
+
+
+FOOTNOTES:
+
+[Footnote 1: Julian Huxley, in _Harper’s Magazine_ for April,
+1926.]
+
+
+
+
+ CONTENTS
+
+
+ I FRANCIS BACON (1561-1626) 1
+
+ THE METHOD OF INDUCTIVE SCIENCE
+ ON THE INTERPRETATION OF NATURE, OR THE
+ REIGN OF MAN
+
+ II NICOLAUS COPERNICUS (1473-1543) 20
+
+ THE NEW IDEA OF THE UNIVERSE
+
+ III JOHANN KEPLER (1671-1630) 29
+
+ ON THE PRINCIPLES OF ASTRONOMY
+
+ IV GALILEO GALILEI (1564-1642) 36
+
+ THE COPERNICAN VERSUS THE PTOLEMAIC ASTRONOMIES
+
+ V WILLIAM HARVEY (1578-1667) 46
+
+ THE CIRCULATION OF BLOOD IN ANIMALS
+
+ VI ROBERT BOYLE (1627-1691) 49
+
+ THE DISCOVERY OF THE LAW OF THE COMPRESSIBILITY
+ OF GASSES
+
+ VII CHRISTIAN HUYGHENS (1629-1695) 52
+
+ THE WAVE THEORY OF LIGHT
+
+ VIII ANTHONY VON LEEUWENHOECK (1632-1723) 62
+
+ OBSERVATIONS ON ANIMALCULÆ
+
+ IX SIR ISAAC NEWTON (1642-1727) 67
+
+ THE THEORY OF GRAVITATION
+
+ X BENJAMIN FRANKLIN (1706-1790) 72
+
+ THE IDENTITY OF LIGHTNING AND ELECTRICITY
+
+ XI LINNAEUS (1707-1778) 76
+
+ THE SEX OF PLANTS
+
+ XII JOSEPH BLACK (1728-1799) 89
+
+ THE DISCOVERY OF CARBONIC ACID GAS
+
+ XIII JOSEPH PRIESTLEY (1733-1804) 96
+
+ THE DISCOVERY OF OXYGEN
+
+ XIV HENRY CAVENDISH (1731-1810) 102
+
+ THE COMBINATION OF HYDROGEN AND OXYGEN
+ INTO WATER
+
+ XV SIR WILLIAM HERSCHEL (1738-1822) 109
+
+ THE DISCOVERY OF URANUS
+ ON THE NAME OF THE NEW PLANET
+ ON NEBULOUS STARS
+
+ XVI KARL WILHELM SCHEELE (1742-1786) 122
+
+ THE CONSTITUENTS OF AIR
+
+ XVII ANTOINE LAURENT LAVOISIER (1743-1794) 129
+
+ THE NATURE OF COMBUSTION
+
+ XVIII ALESSANDRO VOLTA (1745-1827) 135
+
+ NEW GALVANIC INSTRUMENT
+
+ XIX PIERRE SIMON LAPLACE (1749-1827) 138
+
+ THE NEBULAR HYPOTHESIS
+
+ XX EDWARD JENNER (1749-1823) 148
+
+ THE THEORY OF VACCINATION
+
+ XXI COUNT RUMFORD (1753-1814) 157
+
+ THE NATURE OF HEAT
+
+ XXII JOHN DALTON (1766-1844) 166
+
+ THE ATOMIC THEORY
+
+ XXIII MARIE FRANÇOIS XAVIER BICHAT (1771-1802) 168
+
+ THE DOCTRINE OF TISSUES
+
+ XXIV AMADEO AVOGADRO (1776-1856) 177
+
+ THE MOLECULES IN GASES PROPORTIONAL TO
+ THE VOLUMES
+
+ XXV SIR HUMPHREY DAVY (1778-1829) 183
+
+ ON SOME NEW PHENOMENA OF CHEMICAL
+ CHANGES PRODUCED BY ELECTRICITY
+
+ XXVI MICHAEL FARADAY (1791-1867) 190
+
+ ON FLUID CHLORINE
+ ELECTRICITY FROM MAGNETISM
+
+ XXVII JOSEPH HENRY (1797-1878) 198
+
+ ON THE PRODUCTION OF CURRENTS AND SPARKS
+ OF ELECTRICITY FROM MAGNETISM
+
+ XXVIII SIR CHARLES LYELL (1797-1875) 206
+
+ UNIFORMITY IN THE SERIES OF PAST CHANGES
+ IN THE ANIMATE AND INANIMATE WORLD
+
+ XXIX CHARLES DARWIN (1809-1882) 226
+
+ NATURAL SELECTION
+
+ XXX THEODOR SCHWANN (1810-1882) 245
+
+ CELL THEORY
+
+ XXXI HERMANN VON HELMHOLTZ (1821-1894) 273
+
+ THE CONSERVATION OF ENERGY
+
+ XXXII LOUIS PASTEUR (1822-1895) 304
+
+ INOCULATION FOR HYDROPHOBIA
+
+ XXXIII JAMES CLERK MAXWELL (1831-1879) 320
+
+ THE MAXWELL AND HERZ THEORY OF ELECTRICITY
+ AND LIGHT
+
+ XXXIV AUGUST WEISMANN (1834-1914) 334
+
+ THE CONTINUITY OF THE GERM-PLASM AS THE
+ FOUNDATION OF A THEORY OF HEREDITY
+
+ XXXV SIR NORMAN LOCKYER (1836-1920) 360
+
+ THE CHEMISTRY OF THE STARS
+
+ XXXVI ROBERT KOCH (1843-1910) 374
+
+ THEORY OF BACTERIA
+
+
+
+
+ CLASSICS OF
+ MODERN SCIENCE
+
+
+
+
+ I
+
+ FRANCIS BACON
+
+ 1561-1626
+
+
+ _Francis Bacon, Lord Verulam, is distinguished in the history of
+ science for his criticism of the methods of knowledge of his day.
+ In his great writings, “The Advancement of Learning” (1605), “Novum
+ Organum” (1620), and “De Augmentis Scientiarum” (1623), he cumulatively
+ outlined a new method, named after him, whereby all knowledge was
+ referred to experience and corrected by experiment. His inductive
+ method was epoch-making in that it established the technique underlying
+ all modern science._
+
+ _He was born in London, January 22, 1561, the son of Sir Nicholas
+ Bacon, Lord Keeper of the Seals. In 1573, at the age of twelve, he
+ matriculated in Trinity College, Cambridge. After his father’s death,
+ in 1579, he led a precarious life, accumulated many debts, and ended
+ by accusing his intimate friend, Lord Essex, of treason. In 1607 King
+ James appointed him Solicitor. In 1613 he became Attorney General,
+ and in 1618 was made Lord Chancellor and knighted Baron Verulam. The
+ following year he was impeached for bribery, and imprisoned four days
+ for the offense. Thereafter, until his death on April 9, 1626, he gave
+ himself wholly to the development of his new scientific method._
+
+
+ THE METHOD OF INDUCTIVE SCIENCE[2]
+
+They who have presumed to dogmatize on nature, as on some well
+investigated subject, either from self-conceit or arrogance, and in the
+professorial style, have inflicted the greatest injury on philosophy
+and learning. For they have tended to stifle and interrupt inquiry
+exactly in proportion as they have prevailed in bringing others to
+their opinion; and their own activity has not counterbalanced the
+mischief they have occasioned by corrupting and destroying that of
+others. They again who have entered upon a contrary course, and
+asserted that nothing whatever can be known, whether they have fallen
+into this opinion from their hatred of the ancient sophists, or from
+the hesitation of their minds, or from an exuberance of learning, have
+certainly adduced reasons for it which are by no means contemptible.
+They have not, however, derived their opinion from true sources,
+and, hurried on by their zeal and some affectation, have certainly
+exceeded due moderation. But the more ancient Greeks (whose writings
+have perished), held a more prudent mean, between the arrogance of
+dogmatism, and the despair of scepticism; and though too frequently
+intermingling complaints and indignation at the difficulty of inquiry,
+and the obscurity of things, and champing, as it were, the bit, have
+still persisted in pressing their point, and pursuing their intercourse
+with nature; thinking, as it seems, that the better method was not to
+dispute upon the very point of the possibility of anything being known,
+but to put it to the test of experience. Yet they themselves, by only
+employing the power of the understanding, have not adopted a fixed
+rule, but have laid their whole stress upon intense meditation, and a
+continual exercise and perpetual agitation of the mind.
+
+Our method, though difficult in its operation, is easily explained.
+It consists in determining the degrees of certainty, whilst we, as it
+were, restore the senses to their former rank, but generally reject
+that operation of the mind which follows close upon the senses, and
+open and establish a new and certain course for the mind from the first
+actual perceptions of the senses themselves. This, no doubt, was the
+view taken by those who have assigned so much to logic; showing clearly
+thereby that they sought some support for the mind, and suspected its
+natural and spontaneous mode of action. But this is now employed too
+late as a remedy, when all is clearly lost, and after the mind, by
+the daily habit and intercourse of life, has come prepossessed with
+corrupted doctrines, and filled with the vainest idols. The art of
+logic, therefore, being (as we have mentioned) too late a precaution,
+and in no way remedying the matter, has tended more to confirm errors,
+than to disclose truth. Our only remaining hope and salvation is to
+begin the whole labor of the mind again; not leaving it to itself,
+but directing it perpetually from the very first, and attaining our
+end as it were by mechanical aid. If men, for instance, had attempted
+mechanical labors with their hands alone, and without the power and aid
+of instruments, as they have not hesitated to carry on the labors of
+their understanding with the unaided efforts of their mind, they would
+have been able to move and overcome but little, though they had exerted
+their utmost and united powers. And just to pause awhile on this
+comparison, and look into it as a mirror; let us ask, if any obelisk of
+a remarkable size were perchance required to be moved, for the purpose
+of gracing a triumph or any similar pageant, and men were to attempt it
+with their bare hands, would not any sober spectator avow it to be an
+act of the greatest madness? And if they should increase the number of
+workmen, and imagine that they could thus succeed, would he not think
+so still more? But if they chose to make a selection, and to remove
+the weak, and only employ the strong and vigorous, thinking by this
+means, at any rate, to achieve their object, would he not say that they
+were more fondly deranged? Nay, if not content with this, they were
+to determine on consulting the athletic art, and were to give orders
+for all to appear with their hands, arms, and muscles regularly oiled
+and prepared, would he not exclaim that they were taking pains to rave
+by method and design? Yet men are hurried on with the same senseless
+energy and useless combination in intellectual matters, as long as
+they expect great results either from the number and agreement, or the
+excellence and acuteness of their wits; or even strengthen their minds
+with logic, which may be considered as an athletic preparation, but yet
+do not desist (if we rightly consider the matter) from applying their
+own understandings merely with all this zeal and effort. Whilst nothing
+is more clear, than that in every great work executed by the hand of
+man without machines or implements, it is impossible for the strength
+of individuals to be increased, or that of the multitude to combine.
+
+Having premised so much, we lay down two points on which we would
+admonish mankind lest they should fail to see or to observe them. The
+first of these is, that it is our good fortune (as we consider it), for
+the sake of extinguishing and removing contradiction and irritation of
+mind, to leave the honor and reverence due to the ancients untouched
+and undiminished, so that we can perform our intended work, and yet
+enjoy the benefit of our respectful moderation. For if we profess
+to offer something better than the ancients, and yet should pursue
+the same course as they have done, we could never, by any artifice,
+contrive to avoid the imputation of having engaged in a contest or
+rivalry as to our respective wits, excellencies, or talents; which,
+though neither inadmissible nor new (for why should we not blame and
+point out anything that is imperfectly discovered or laid down by
+them, of our own right, a right common to all), yet however just and
+allowable, would perhaps be scarcely an equal match, on account of
+the disproportion of our strength. But since our present plan leads
+us to open an entirely different course to the understanding, and one
+unattempted and unknown to them, the case is altered. There is an end
+to party zeal, and we only take upon ourselves the character of a
+guide, which requires a moderate share of authority and good fortune,
+rather than talents and excellence. The first admonition relates to
+persons, the next to things.
+
+We make no attempt to disturb the system of philosophy that now
+prevails, or any other which may or will exist, either more correct or
+more complete. For we deny not that the received system of philosophy,
+and others of a similar nature, encourage discussion, embellish
+harangues, are employed, and are of service in the duties of the
+professor, and the affairs of civil life. Nay, we openly express and
+declare that the philosophy we offer will not be very useful in such
+respects. It is not obvious, or to be understood in a cursory view,
+nor does it flatter the mind in its preconceived notions, nor will
+it descend to the level of the generality of mankind unless by its
+advantages and effects.
+
+Let there exist, then (and may it be of advantage to both), two
+sources, and two distributions of learning, and in like manner
+two tribes, and as it were kindred families of contemplators or
+philosophers, without any hostility or alienation between them; but
+rather allied and united by mutual assistance. Let there be, in short,
+one method of cultivating the sciences, and another in discovering
+them. And as for those who prefer and more readily receive the former,
+on account of their haste or from motives arising from their ordinary
+life, or because they are unable from weakness of mind to comprehend
+and embrace the other (which must necessarily be the case with by
+far the greater number), let us wish that they may prosper as they
+desire in their undertaking, and attain what they pursue. But if any
+individual desire, and is anxious not merely to adhere to, and make
+use of present discoveries, but to penetrate still further, and not
+to overcome his adversaries in disputes, but nature by labor, not in
+short to give elegant and specious opinions, but to know to a certainty
+and demonstration, let him, as a true son of science (if such be his
+wish), join with us; that when he has left the antechambers of nature
+trodden by the multitude, an entrance may at last be discovered to her
+inner apartments. And in order to be better understood, and to render
+our meaning more familiar by assigning determinate names, we have
+accustomed ourselves to call the one method the anticipation of the
+mind, and the other the interpretation of nature.
+
+We have still one request left. We have at least reflected and taken
+pains, in order to render our propositions not only true, but of easy
+and familiar access to men’s minds, however wonderfully prepossessed
+and limited. Yet it is but just that we should obtain this favor from
+mankind (especially in so great a restoration of learning and the
+sciences), that whosoever may be desirous of forming any determination
+upon an opinion of this our work either from his own perceptions,
+or the crowd of authorities, or the forms of demonstrations, he
+will not expect to be able to do so in a cursory manner, and whilst
+attending to other matters; but in order to have a thorough knowledge
+of the subject, will himself, by degrees, attempt the course which we
+describe and maintain; will be accustomed to the subtlety of things
+which is manifested by experience; and will correct the depraved and
+deeply-rooted habits of his mind by a seasonable, and, as it were, just
+hesitation: and then, finally (if he will), use his judgment when he
+has begun to be master of himself.
+
+
+ ON THE INTERPRETATION OF NATURE, OR THE REIGN OF MAN[3]
+
+Man acts, then, upon natural bodies (besides merely bringing them
+together or removing them) by seven principal methods: I. By the
+exclusion of all that impedes and disturbs; II. by compression,
+extension, agitation, and the like; III. by heat and cold; IV. by
+detention in a suitable place; V. by checking or directing motion; VI.
+by peculiar harmonies; VII. by a seasonable and proper alternation,
+series, and succession of all these, or, at least, of some of them.
+
+I. With regard to the first--common air, which is always at hand, and
+forces its admission, as also the rays of the heavenly bodies, create
+much disturbance. Whatever, therefore, tends to exclude them may
+well be considered as generally useful. The substance and thickness
+of vessels in which bodies are placed when prepared for operations
+may be referred to this head. So also may the accurate methods of
+closing vessels by consolidation, or the _lutum sapientiæ_ as
+the chemists call it. The exclusion of air by means of liquids at
+the extremity is also very useful, as when they pour oil on wine,
+or the juices of herbs, which by spreading itself upon the top like
+a cover, preserves them uninjured from the air. Powders, also, are
+serviceable, for although they contain air mixed up in them, yet they
+ward off the power of the mass of circumambient air, which is seen in
+the preservation of grapes and other fruits in sand or flour. Wax,
+honey, pitch, and other resinous bodies, are well used in order to
+make the exclusion more perfect, and to remove the air and celestial
+influence. We have sometimes made an experiment by placing a vessel or
+other bodies in quicksilver, the most dense of all substances capable
+of being poured round others. Grottoes and subterraneous caves are of
+great use in keeping off the effects of the sun, and the predatory
+action of air, and in the north of Germany are used for granaries.
+The depositing of bodies at the bottom of water may be also mentioned
+here; and I remember having heard of some bottles of wine being let
+down into a deep well in order to cool them, but left there by chance,
+carelessness, and forgetfulness, for several years, and then taken
+out; by which means the wine not only escaped becoming flat or dead,
+but was much more excellent in flavor, arising (as it appears) from
+a more complete mixture of its parts. But if the case require that
+bodies should be sunk to the bottom of water, as in rivers or the sea,
+and yet should not touch the water, nor be enclosed in sealed vessels,
+but surrounded only by air, it would be right to use that vessel which
+has been sometimes employed under water above ships that have sunk, in
+order to enable the divers to remain below and breathe occasionally
+by turns. It was of the following nature:--A hollow tub of metal was
+formed, and sunk so as to have its bottom parallel with the surface of
+the water; it thus carried down with it to the bottom of the sea all
+the air contained in the tub. It stood upon three feet (like a tripod),
+being of rather less height than a man, so that, when the diver was
+in want of breath, he could put his head into the hollow of the tub,
+breathe, and then continue his work. We hear that some sort of boat or
+vessel has now been invented, capable of carrying men some distance
+under water. Any bodies, however, can easily be suspended under some
+such vessel as we have mentioned, which has occasioned our remarks upon
+the experiment.
+
+Another advantage of the careful and hermetical closing of bodies is
+this--not only the admission of external air is prevented (of which we
+have treated), but the spirit of bodies also is prevented from making
+its escape, which is an internal operation. For anyone operating on
+natural bodies must be certain as to their quantity, and that nothing
+has evaporated or escaped, since profound alterations take place in
+bodies, when art prevents the loss or escape of any portion, whilst
+nature prevents their annihilation. With regard to this circumstance,
+a false idea has prevailed (which if true would make us despair of
+preserving quantity without diminution), namely, that the spirit of
+bodies, and air when rarefied by a great degree of heat, cannot be so
+kept in by being enclosed in any vessel as not to escape by the small
+pores. Men are led into this idea by the common experiments of a cup
+inverted over water, with a candle or piece of lighted paper in it,
+by which the water is drawn up, and of those cups which, when heated,
+draw up the flesh. For they think that in each experiment the rarefied
+air escapes, and that its quantity is therefore diminished, by which
+means the water or flesh rises by the motion of connection. This is,
+however, most incorrect. For the air is not diminished in quantity,
+but contracted in dimensions, nor does this motion of the rising of
+the water begin till the flame is extinguished, or the air cooled, so
+that physicians place cold sponges, moistened with water, on the cups,
+in order to increase their attraction. There is, therefore, no reason
+why men should fear much from the ready escape of air: for although it
+be true that the most solid bodies have their pores, yet neither air,
+nor spirit, readily suffers itself to be rarefied to such an extreme
+degree; just as water will not escape by a small chink.
+
+II. With regard to the second of the seven above-mentioned methods, we
+must especially observe, that compression and similar violence have a
+most powerful effect either in producing locomotion, and other motions
+of the same nature, as may be observed in engines and projectiles, or
+in destroying the organic body, and those qualities, which consist
+entirely in motion (for all life, and every description of flame and
+ignition are destroyed by compression, which also injures and deranges
+every machine); or in destroying those qualities which consist in
+position and a coarse difference of parts, as in colors; for the color
+of a flower when whole, differs from that it presents when bruised, and
+the same may be observed of whole and powdered amber; or in tastes,
+for the taste of a pear before it is ripe, and of the same pear when
+bruised and softened, is different, since it becomes perceptibly
+more sweet. But such violence is of little avail in the more noble
+transformations and changes of homogeneous bodies, for they do not,
+by such means, acquire any constantly and permanently new state, but
+one that is transitory, and always struggling to return to its former
+habit and freedom. It would not, however, be useless to make some more
+diligent experiments with regard to this; whether, for instance, the
+condensation of a perfectly homogeneous body (such as air, water, oil,
+and the like) or their rarefaction, when effected by violence, can
+become permanent, fixed, and, as it were, so changed, as to become
+a nature. This might at first be tried by simple perseverance, and
+then by means of helps and harmonies. It might readily have been
+attempted (if we had but thought of it), when we condensed water (as
+was mentioned above), by hammering and compression, until it burst out.
+For we ought to have left the flattened globe untouched for some days,
+and then to have drawn off the water, in order to try whether it would
+have immediately occupied the same dimensions as it did before the
+condensation. If it had not been done so, either immediately, or soon
+afterwards, the condensation would have appeared to have been rendered
+constant; if not, it would have appeared that a restitution took place,
+and that the condensation had been transitory. Something of the same
+kind might have been tried with the glass eggs; the egg should have
+been sealed up suddenly and firmly, after a complete exhaustion of
+the air, and should have been allowed to remain so for some days, and
+it might then have been tried whether, on opening the aperture, the
+air would be drawn in with a hissing noise, or whether as much water
+would be drawn into it when immersed, as would have been drawn into it
+at first, if it had not continued sealed. For it is probable (or, at
+least, worth making the experiment) that this might have happened, or
+might happen, because perseverance has a similar effect upon bodies
+which are a little less homogeneous. A stick bent together for some
+time does not rebound, which is not owing to any loss of quantity in
+the wood during the time, for the same would occur (after a larger
+time) in a plate of steel, which does not evaporate. If the experiment
+of simple perseverance should fail, the matter should not be given up,
+but other means should be employed. For it would be no small advantage,
+if bodies could be endued with fixed and constant natures by violence.
+Air could then be converted into water by condensation, with other
+similar effects; for man is more the master of violent motions than of
+any other means.
+
+III. The third of our seven methods is referred to that great practical
+engine of nature as well as of art, cold and heat. Here, man’s power
+limps, as it were, with one leg. For we possess the heat of fire, which
+is infinitely more powerful and intense than that of the sun (as it
+reaches us), and that of animals. But we want cold, except such as we
+can obtain in winter, in caverns, or by surrounding objects with snow
+and ice, which, perhaps, may be compared in degree with the noontide
+heat of the sun in tropical countries, increased by the reflection of
+mountains and walls. For this degree of heat and cold can be borne
+for a short period only by animals, yet it is nothing compared with
+the heat of a burning furnace, or the corresponding degree of cold.
+Everything with us has a tendency to become rarefied, dry, and wasted,
+and nothing to become condensed or soft, except by mixtures, and,
+as it were, spurious methods. Instances of cold, therefore, should
+be searched for most diligently, such as may be found by exposing
+bodies upon buildings in a hard frost, in subterraneous caverns, by
+surrounding bodies with snow and ice in deep places excavated for
+that purpose, by letting bodies down into wells, by burying bodies in
+quicksilver and metals, by immersing them in streams which petrify
+wood, by burying them in the earth (which the Chinese are reported to
+do with their china, masses of which, made for that purpose, are said
+to remain in the ground for forty or fifty years, and to be transmitted
+to their heirs as a sort of artificial mine), and the like. The
+condensations which take place in nature, by means of cold, should also
+be investigated, that by learning their causes, they may be introduced
+into the arts; such as are observed in the exudation of marble and
+stones, in the dew upon the panes of glass in a room towards morning
+after a frosty night, in the formation and the gathering of vapors
+under the earth into water, whence spring fountains, and the like.
+
+Besides the substances which are cold to the touch, there are others
+which have also the effect of cold, and condense; they appear, however,
+to act only upon the bodies of animals, and scarcely any further. Of
+these we have many instances, in medicines and plasters. Some condense
+the flesh and tangible parts, such as astringent and inspissating
+medicines, others the spirits, such as soporifics. There are two modes
+of condensing the spirits, by soporifics or provocatives to sleep;
+the one by calming the motion, the other by expelling the spirit. The
+violet, dried roses, lettuces, and other benign or mild remedies,
+by their friendly and gently cooling vapors, invite the spirits to
+unite, and restrain their violent and perturbed motion. Rosewater, for
+instance, applied to the nostrils in fainting fits, causes the resolved
+and relaxed spirits to recover themselves, and, as it were, cherishes
+them. But opiates, and the like, banish the spirits by their malignant
+and hostile quality. If they be applied, therefore, externally, the
+spirits immediately quit the part and no longer readily flow into it;
+but if they be taken internally, their vapor, mounting to the head,
+expels, in all directions, the spirits contained in the ventricles of
+the brain, and since these spirits retreat, but cannot escape, they
+consequently meet and are condensed, and are sometimes completely
+extinguished and suffocated; although the same opiates, when taken in
+moderation, by a secondary accident (the condensation which succeeds
+their union), strengthen the spirits, render them more robust, and
+check their useless and inflammatory motion, by which means they
+contribute not a little to the cure of diseases, and the prolongation
+of life.
+
+The preparations of bodies, also, for the reception of cold should not
+be omitted, such as that water a little warmed is more easily frozen
+than that which is quite cold, and the like.
+
+Moreover, since nature supplies cold so sparingly, we must act like
+the apothecaries, who, when they cannot obtain any simple ingredient,
+take a succedaneum, or quid pro quo, as they term it, such as aloes for
+xylobalsamum, cassia for cinnamon. In the same manner we should look
+diligently about us, to ascertain whether there may be any substitutes
+for cold, that is to say, in what other manner condensation can be
+effected, which is the peculiar operation of cold. Such condensations
+appear hitherto to be of four kinds only. 1. By simple compression,
+which is of little avail towards permanent condensation, on account
+of the elasticity of substances, but may still however be of some
+assistance. 2. By the contraction of the coarser, after the escape
+or departure of the finer parts of a given body; as is exemplified
+in induration by fire, and the repeated heating and extinguishing of
+metals, and the like. 3. By the cohesion of the most solid homogeneous
+parts of a given body, which were previously separated, and mixed with
+others less solid, as in the return of sublimated mercury to its simple
+state, in which it occupies much less space than it did in powder, and
+the same may be observed of the cleansing of all metals from their
+dross. 4. By harmony or the application of substances which condense by
+some latent power. These harmonies are as yet but rarely observed, at
+which we cannot be surprised, since there is little to hope for from
+their investigation, unless the discovery of forms and conformation
+be attained. With regard to animal bodies, it is not to be questioned
+that there are many internal and external medicines which condense
+by harmony, as we have before observed, but this action is rare in
+inanimate bodies. Written accounts, as well as report, have certainly
+spoken of a tree in one of the Tercera or Canary Islands (for I do not
+exactly recollect which) that drips perpetually, so as to supply the
+inhabitants, in some degree, with water; and Paracelsus says that the
+herb called _ros solis_ is filled with dew at noon, whilst the sun
+gives out its greatest heat, and all other herbs around it are dry. We
+treat both these accounts as fables; they would, however, if true, be
+of the most important service, and most worthy of examination. As to
+the honey-dew, resembling manna, which is found in May on the leaves
+of the oak, we are of opinion that it is not condensed by any harmony
+or peculiarity of the oak-leaf, but that whilst it falls equally upon
+other leaves it is retained and continues on those of the oak, because
+their texture is closer, and not so porous as that of most of the other
+leaves.
+
+With regard to heat, man possesses abundant means and power; but his
+observation and inquiry are defective in some respects, and those of
+the greatest importance, notwithstanding the boasting of quacks. For
+the effects of intense heat are examined and observed, whilst those of
+a more gentle degree of heat, being of the most frequent occurrence
+in the paths of nature, are, on that very account, least known. We
+see, therefore, the furnaces, which are most esteemed, employed in
+increasing the spirits of bodies to a great extent, as in the strong
+acids, and some chemical oils; whilst the tangible parts are hardened,
+and, when the volatile part has escaped, become sometimes fixed; the
+homogeneous parts are separated, and the heterogeneous incorporated and
+agglomerated in a coarse lump; and (what is chiefly worthy of remark)
+the junction of compound bodies, and the more delicate conformations
+are destroyed and confounded. But the operation of a less violent heat
+should be tried and investigated, by which more delicate mixtures, and
+regular conformations may be produced and elicited, according to the
+example of nature, and in imitation of the effect of the sun, which we
+have alluded to in the aphorism on the instances of alliance. For the
+works of nature are carried on in much smaller portions, and in more
+delicate and varied positions than those of fire, as we now employ
+it. But man will then appear to have really augmented his power, when
+the works of nature can be imitated in species, perfected in power,
+and varied in quantity; to which should be added the acceleration in
+point of time. Rust, for instance, is the result of a long process,
+but _crocus martis_ is obtained immediately; and the same may be
+observed of natural verdigris and ceruse. Crystal is formed slowly,
+whilst glass is blown immediately: stones increase slowly, whilst
+bricks are baked immediately, etc. In the mean time (with regard to
+our present subject) every different species of heat should, with its
+peculiar effects, be diligently collected and inquired into; that
+of the heavenly bodies, whether their rays be direct, reflected, or
+refracted, or condensed by a burning-glass; that of lightning, flame,
+and ignited charcoal; that of fire of different materials, either open
+or confined, straitened or overflowing, qualified by the different
+forms of the furnaces, excited by the bellows, or quiescent, removed to
+a greater or less distance, or passing through different media; moist
+heats, such as the _balneum Mariæ_, and the dunghill; the external
+and internal heat of animals; dry heats, such as the heat of ashes,
+lime, warm sand; in short, the nature of every kind of heat, and its
+degrees.
+
+We should, however, particularly attend to the investigation and
+discovery of the effects and operations of heat, when made to approach
+and retire by degrees, regularly, periodically, and by proper intervals
+of space and time. For this systematical inequality is in truth the
+daughter of heaven and mother of generation, nor can any great result
+be expected from a vehement, precipitate, or desultory heat. For this
+is not only most evident in vegetables, but in the wombs of animals
+also there arises a great inequality of heat, from the motion, sleep,
+food, and passions of the female. The same inequality prevails in
+those subterraneous beds where metals and fossils are perpetually
+forming, which renders yet more remarkable the ignorance of some of the
+reformed alchemists, who imagined they could attain their object by the
+equable heat of lamps, or the like, burning uniformly. Let this suffice
+concerning the operation and effects of heat; nor is it time for us
+to investigate them thoroughly before the forms and conformations
+of bodies have been further examined and brought to light. When we
+have determined upon our models, we may seek, apply, and arrange our
+instruments.
+
+IV. The fourth mode of action is by continuance, the very steward and
+almoner, as it were, of nature. We apply the term continuance to the
+abandonment of a body to itself for an observable time, guarded and
+protected in the mean while from all external force. For the internal
+motion then commences to betray and exert itself when the external and
+adventitious is removed. The effects of time, however, are far more
+delicate than those of fire. Wine, for instance, cannot be clarified
+by fire as it is by continuance. Nor are the ashes produced by
+combustion so fine as the particles dissolved or wasted by the lapse
+of ages. The incorporations and mixtures, which are hurried by fire,
+are very inferior to those obtained by continuance; and the various
+conformations assumed by bodies left to themselves, such as mouldiness,
+etc., are put a stop to by fire or a strong heat. It is not, in the
+mean time, unimportant to remark that there is a certain degree of
+violence in the motion of bodies entirely confined; for the confinement
+impedes the proper motion of the body. Continuance in an open vessel,
+therefore, is useful for separations, and in one hermetically sealed
+for mixtures, that in a vessel partly closed, but admitting the
+air, for putrefaction. But instances of the operation and effect of
+continuance must be collected diligently from every quarter.
+
+V. The direction of motion (which is the fifth method of action) is
+of no small use. We adopt this term, when speaking of a body which,
+meeting with another, either arrests, repels, allows, or directs
+its original motion. This is the case principally in the figure and
+position of vessels. An upright cone, for instance, promotes the
+condensation of vapor in alembics, but when reversed, as in inverted
+vessels, it assists the refining of sugar. Sometimes a curved form,
+or one alternately contracted and dilated, is required. Strainers may
+be ranged under this head, where the opposed body opens a way for
+one portion of another substance and impedes the rest. Nor is this
+process or any other direction of motion carried on externally only,
+but sometimes by one body within another. Thus, pebbles are thrown
+into water to collect the muddy particles, and syrups are refined by
+the white of an egg, which glues the grosser particles together so as
+to facilitate their removal. Telesius, indeed, rashly and ignorantly
+enough attributes the formation of animals to this cause, by means of
+the channels and folds of the womb. He ought to have observed a similar
+formation of the young in eggs which have no wrinkles or inequalities.
+One may observe a real result of this direction of motion in casting
+and modelling.
+
+VI. The effects produced by harmony and aversion (which is the
+sixth method) are frequently buried in obscurity; for these occult
+and specific properties (as they are termed), the sympathies and
+antipathies, are for the most part but a corruption of philosophy. Nor
+can we form any great expectation of the discovery of the harmony which
+exists between natural objects, before that of their forms and simple
+conformations, for it is nothing more than the symmetry between these
+forms and conformations.
+
+The greater and more universal species of harmony are not, however,
+so wholly obscure, and with them, therefore, we must commence. The
+first and principal distinction between them is this; that some bodies
+differ considerably in the abundance and rarity of their substance, but
+correspond in their conformation; others, on the contrary, correspond
+in the former and differ in the latter. Thus the chemists have well
+observed, that in their trial of first principles sulphur and mercury,
+as it were, pervade the universe; their reasoning about salt, however,
+is absurd, and merely introduced to compromise earthy dry fixed bodies.
+In the other two, indeed, one of the most universal species of natural
+harmony manifests itself. Thus there is a correspondence between
+sulphur, oil, greasy exhalations, flame, and, perhaps, the substance of
+the stars. On the other hand, there is a like correspondence between
+mercury, water, aqueous vapor, air, and perhaps pure inter-sidereal
+ether. Yet do these two quarternions, or great natural tribes (each
+within its own limits), differ immensely in quantity and density of
+substance, whilst they generally agree in conformation, as is manifest
+in many instances. On the other hand, the metals agree in such quantity
+and density (especially when compared with vegetables, etc.), but
+differ in many respects in conformation. Animals and vegetables, in
+like manner, vary in their almost infinite modes of conformation, but
+range within very limited degrees of quantity and density of substance.
+
+The next most general correspondence is that between individual bodies
+and those which supply them by way of menstruum or support. Inquiry,
+therefore, must be made as to the climate, soil, and depth at which
+each metal is generated, and the same of gems, whether produced in
+rocks or mines, also as to the soil in which particular trees, shrubs,
+and herbs, mostly grow and, as it were, delight; and as to the best
+species of manure, whether dung, chalk, sea sand, or ashes, etc., and
+their different propriety and advantage according to the variety of
+soils. So also the grafting and setting of trees and plants (as regards
+the readiness of grafting one particular species on another) depends
+very much upon harmony, and it would be amusing to try an experiment
+I have lately heard of, in grafting forest trees (garden trees alone
+having hitherto been adopted), by which means the leaves and fruit
+are enlarged, and the trees produce more shade. The specific food of
+animals again should be observed, as well as that which cannot be used.
+Thus the carnivorous cannot be fed on herbs, for which reason the order
+of _feuilletans_, the experiment having been made, has nearly
+vanished; human nature being incapable of supporting their regimen,
+although the human will has more power over the bodily frame than
+that of other animals. The different kinds of putrefaction from which
+animals are generated should be noted.
+
+The harmony of principal bodies with those subordinate to them (such
+indeed may be deemed those we have alluded to above) are sufficiently
+manifest, to which may be added those that exist between different
+bodies and their objects, and, since these latter are more apparent,
+they may throw great light when well observed and diligently examined
+upon those which are more latent.
+
+The more internal harmony and aversion, or friendship and enmity
+(for superstition and folly have rendered the terms of sympathy and
+antipathy almost disgusting) have been either falsely assigned, or
+mixed with fable, or most rarely discovered from neglect. For if
+one were to allege that there is an enmity between the vine and the
+cabbage, because they will not come up well sown together, there is
+a sufficient reason for it in the succulent and absorbent nature of
+each plant, so that the one defrauds the other. Again, if one were
+to say that there is a harmony and friendship between the corn and
+the corn-flower, or the wild poppy, because the latter seldom grow
+anywhere but in cultivated soils, he ought rather to say, there is an
+enmity between them, for the poppy and the corn-flower are produced and
+created by those juices which the corn has left and rejected, so that
+the sowing of the corn prepares the ground for their production. And
+there are a vast number of similar false assertions. As for fables,
+they must be totally exterminated. There remains, then, but a scanty
+supply of such species of harmony as has borne the test of experiment,
+such as that between the magnet and iron, gold and quicksilver, and
+the like. In chemical experiments on metals, however, there are some
+others worthy of notice, but the greatest abundance (where the whole
+are so few in numbers) is discovered in certain medicines, which,
+from their occult and specific qualities (as they are termed), affect
+particular limbs, humors, diseases, or constitutions. Nor should we
+omit the harmony between the motion and phenomena of the moon, and
+their effects on lower bodies, which may be brought together by an
+accurate and honest selection from the experiments of agriculture,
+navigation, and medicine, or of other sciences. By as much as these
+general instances, however, of more latent harmony, are rare, with
+so much the more diligence are they to be inquired after, through
+tradition, and faithful and honest reports, but without rashness and
+credulity, with an anxious and, as it were, hesitating degree of
+reliance. There remains one species of harmony which, though simple
+in its mode of action, is yet most valuable in its use, and must
+by no means be omitted, but rather diligently investigated. It is
+the ready or difficult coition or union of bodies in composition, or
+simple juxtaposition. For some bodies readily and willingly mix, and
+are incorporated, others tardily and perversely; thus powders mix best
+with water, chalk, and ashes with oils, and the like. Nor are these
+instances of readiness and aversion to mixture to be alone collected,
+but others, also, of the collocation, distribution, and digestion of
+the parts when mingled, and the predominance after the mixture is
+complete.
+
+VII. Lastly, there remains the seventh, and last of the seven, modes
+of action; namely that by the alternation and interchange of the
+other six; but of this, it will not be the right time to offer any
+examples, until some deeper investigation shall have taken place of
+each of the others. The series, or chain of this alternation, in its
+mode of application to separate effects, is no less powerful in its
+operation, than difficult to be traced. But men are possessed with the
+most extreme impatience, both of such inquiries, and their practical
+application, although it be the clue of the labyrinth in all greater
+works.
+
+
+But it must be noted, that in this our organ, we treat of logic, and
+not of philosophy. Seeing, however, that our logic instructs and
+informs the understanding, in order that it may not, with the small
+hooks, as it were, of the mind, catch at, and grasp mere abstractions,
+but rather actually penetrate nature, and discover the properties and
+effects of bodies, and the determinate laws of their substance (so that
+this science of ours springs from the nature of things, as well as
+from that of the mind); it is not to be wondered at, if it have been
+continually interspersed and illustrated with natural observations and
+experiments, as instances of our method. The prerogative instances are,
+as appears from what has preceded, twenty-seven in number, and are
+termed: solitary instances, migrating instances, conspicuous instances,
+clandestine instances, constitutive, instances, similar instances,
+singular instances, deviating instances, bordering instances,
+instances of power, accompanying and hostile instances, subjunctive
+instances, instances of alliance, instances of the cross, instances
+of divorce, instances of the gate, citing instances, instances of the
+road, supplementary instances, lancing instances, instances of the
+rod, instances of the course, doses of nature, wrestling instances,
+suggesting instances, generally useful instances, and magical
+instances. The advantage, by which these instances excel the more
+ordinary, regards specifically either theory or practice, or both. With
+regard to theory, they assist either the senses or the understanding;
+the senses, as in the five instances of the lamp; the understanding,
+either by expediting the exclusive mode of arriving at the form, as in
+solitary instances, or by confining, and more immediately indicating
+the affirmative, as in the migrating, conspicuous, accompanying, and
+subjunctive instances; or by elevating the understanding, and leading
+it to general and common natures, and that either immediately, as in
+the clandestine and singular instances, and those of alliance; or very
+nearly so, as in the constitutive; or still less so, as in the similar
+instances; or by correcting the understanding of its habits, as in
+the deviating instances; or by leading to the grand form or fabric of
+the universe, as in the bordering instances; or by guarding it from
+false forms and causes, as in those of the cross and of divorce. With
+regard to practice, they either point it out, or measure, or elevate
+it. They point it out, either by showing where we must commence in
+order not to repeat the labors of others, as in the instances of power;
+or by inducing us to aspire to that which may be possible, as in the
+suggesting instances; the four mathematical instances measure it. The
+generally useful and the magical elevate it.
+
+Again, out of these twenty-seven instances, some must be collected
+immediately, without waiting for a particular investigation of
+properties. Such are the similar, singular, deviating, and bordering
+instances, those of power, and of the gate, and suggesting, generally
+useful, and magical instances; for these either assist and cure
+the understanding and senses, or furnish our general practice. The
+remainder are to be collected when we furnish our synoptical tables
+for the work of the interpreter, upon any particular nature; for these
+instances, honored and gifted with such prerogatives, are like the
+soul amid the vulgar crowd of instances, and (as we from the first
+observed) a few of them are worth a multitude of the others. When,
+therefore, we are forming our tables they must be searched out with the
+greatest zeal, and placed in the table. And, since mention must be made
+of them in what follows, a treatise upon their nature has necessarily
+been prefixed. We must next, however, proceed to the supports and
+corrections of induction, and thence to concretes, the latent process,
+and latent conformations, and the other matters, which we have
+enumerated in their order in the twenty-first aphorism, in order that,
+like good and faithful guardians, we may yield up their fortune to
+mankind upon the emancipation and majority of their understanding; from
+which must necessarily follow an improvement of their estate, and an
+increase of their power over nature. For man, by the fall, lost at once
+his state of innocence, and his empire over creation, both of which can
+be partially recovered even in this life, the first by religion and
+faith, the second by the arts and sciences. For creation did not become
+entirely and utterly rebellious by the curse, but in consequence of the
+Divine decree, “in the sweat of thy brow shalt thou eat bread,” she
+is compelled by our labors (not assuredly by our disputes or magical
+ceremonies), at length, to afford mankind in some degree his bread,
+that is to say, to supply man’s daily wants.
+
+
+FOOTNOTES:
+
+[Footnote 2: Selection from the Preface to the _Novum Organum_.]
+
+[Footnote 3: Part II, Conclusion of the _Novum Organum_.]
+
+
+
+
+ II
+
+ NICOLAUS COPERNICUS
+
+ 1473-1543
+
+
+ _One of the first and most striking contributions to modern science
+ was the substitution of the Copernican for the Ptolemaic conception of
+ the universe._
+
+ _Nicolaus Copernicus was born in the Prussian village of Thorn,
+ located on the Vistula River, February 19, 1473. Although destined for
+ the Church, he became interested in medicine, which he studied at the
+ University of Cracow. Later, he turned to mathematics and continued
+ his studies at the Universities of Vienna, Bologna, Padua, Ferrara,
+ and Rome. Although he settled down as canon at Frauenberg, Poland, and
+ gratuitously practised medicine in conjunction with his ecclesiastical
+ duties, he found considerable time for other intellectual pursuits.
+ Reading widely in the Greek philosophers, he came across a statement
+ that the earth moved in its own orbit. This idea deeply appealed to
+ him. “Occasioned by this,” he wrote, “I also began to think of a
+ motion of the earth, and although the idea seemed absurd, still, as
+ others before me had been permitted to assume certain circles in order
+ to explain the motions of the stars, I believed it would be readily
+ permitted me to try whether on the assumption of some motion of the
+ earth better explanations of the revolutions of the heavenly bodies
+ might not be found. And thus I have, assuming the motions which I in
+ the following work attribute to the earth, after long and careful
+ investigation, finally found that when the motions of the other planets
+ are referred to the circulation of the earth and are computed for the
+ revolution of each star, not only do the phenomena necessarily follow
+ therefrom, but the order and magnitude of the stars and all their orbs
+ and the heaven itself are so connected that in no part can anything be
+ transposed without confusion to the rest and to the whole universe.”_
+
+ _In 1530 he issue a “Commentariolus” which outlined his theory, but
+ his prudence prompted him to withhold the publication of his great
+ work, “De Orbium Caelestium Revolutionibus,” until 1543. In May of that
+ year the first printed copy was laid on his death-bed._
+
+
+ THE NEW IDEA OF THE UNIVERSE[4]
+
+I can well believe, most holy father, that certain people, when they
+hear of my attributing motion to the earth in these books of mine, will
+at once declare that such an opinion ought to be rejected. Now, my own
+theories do not please me so much as not to consider what others may
+judge of them. Accordingly, when I began to reflect upon what those
+persons who accept the stability of the earth, as confirmed by the
+opinion of many centuries, would say when I claimed that the earth
+moves, I hesitated for a long time as to whether I should publish that
+which I have written to demonstrate its motion, or whether it would
+not be better to follow the example of the Pythagoreans, who used to
+hand down the secrets of philosophy to their relatives and friends only
+in oral form. As I well considered all this, I was almost impelled to
+put the finished work wholly aside, through the scorn I had reason to
+anticipate on account of the newness and apparent contrariness of my
+theory to reason.
+
+My friends, however, dissuaded me from such a course and admonished
+me that I ought to publish my book, which had lain concealed in my
+possession not only nine years, but already into four times the ninth
+year. Not a few other distinguished and very learned men asked me to do
+the same thing, and told me that I ought not, on account of my anxiety,
+to delay any longer in consecrating my work to the general service of
+mathematicians.
+
+But your holiness will perhaps not so much wonder that I have dared to
+bring the results of my night labors to the light of day, after having
+taken so much care in elaborating them, but is waiting instead to
+hear how it entered my mind to imagine that the earth moved, contrary
+to the accepted opinion of mathematicians--nay, almost contrary to
+ordinary human understanding. Therefore I will not conceal from your
+holiness that what moved me to consider another way of reckoning the
+motions of the heavenly bodies was nothing else than the fact that the
+mathematicians do not agree with one another in their investigations.
+In the first place, they are so uncertain about the motions of the sun
+and moon that they cannot find out the length of a full year. In the
+second place, they apply neither the same laws of cause and effect, in
+determining the motions of the sun and moon and of the five planets,
+nor the same proofs. Some employ only concentric circles, others use
+eccentric and epicyclic ones, with which, however, they do not fully
+attain the desired end. They could not even discover nor compute the
+main thing--namely, the form of the universe and the symmetry of its
+parts. It was with them as if some should, from different places, take
+hands, feet, head, and other parts of the body, which, although very
+beautiful, were not drawn in their proper relations, and, without
+making them in any way correspond, should construct a monster instead
+of a human being.
+
+Accordingly, when I had long reflected, on this uncertainty of
+mathematical tradition, I took the trouble to read again the books of
+all the philosophers I could get hold of, to see if some one of them
+had not once believed that there were other motions of the heavenly
+bodies. First I found in Cicero that Niceties had believed in the
+motion of the earth. Afterwards I found in Plutarch, likewise, that
+some others had held the same opinion. This induced me also to begin to
+consider the movability of the earth, and, although the theory appeared
+contrary to reason, I did so because I knew that others before me had
+been allowed to assume rotary movements at will, in order to explain
+the phenomena of these celestial bodies. I was of the opinion that I,
+too, might be permitted to see whether, by presupposing motion in the
+earth, more reliable conclusions than hitherto reached could not be
+discovered for the rotary motions of the spheres. And thus, acting on
+the hypothesis of the motion which, in the following book, I ascribe
+to the earth, and by long and continued observations, I have finally
+discovered that if the motion of the other planets be carried over to
+the relation of the earth and this is made the basis for the rotation
+of every star, not only will the phenomena of the planets be explained
+thereby, but also the laws and the size of the stars; all their spheres
+and the heavens themselves will appear so harmoniously connected that
+nothing could be changed in any part of them without confusion in the
+remaining parts and in the whole universe.
+
+
+ THAT THE UNIVERSE IS SPHERICAL
+
+First we must remark that the universe is spherical in form, partly
+because this form being a perfect whole requiring no joints, is the
+most complete of all, partly because it makes the most capacious
+form, which is best suited to contain and preserve everything; or
+again because all the constituent parts of the universe, that is the
+sun, moon, and the planets appear in this form; or because everything
+strives to attain this form, as appears in the case of drops of water
+and other fluid bodies if they attempt to define themselves. So no one
+will doubt that this form belongs to the heavenly bodies.
+
+
+ THAT THE EARTH IS ALSO SPHERICAL
+
+That the earth is also spherical is therefore beyond question, because
+it presses from all sides upon its center. Although by reason of
+the elevations of the mountains and the depressions of the valleys
+a perfect circle cannot be understood, yet this does not affect the
+general spherical nature of the earth. This appears in the following
+manner. To those who journey towards the North the north pole of the
+daily revolution of the heavenly sphere seems gradually to rise, while
+the opposite seems to sink. Most of the stars in the region of the Bear
+seem not to set, while some of the southern stars seem not to rise at
+all. So Italy does not see Canopes which is visible to the Egyptians.
+And Italy sees the outermost star of the Stream, which our region of a
+colder zone does not know. On the other hand to those who go towards
+the South the others seem to rise and those to sink which are high in
+our region. Moreover, the inclination of the Poles to the diameter
+of the earth bears always the same relation, which could happen only
+in the case of a sphere. So it is evident that the earth is included
+between the two poles, and is therefore spherical in form. Let us add
+that the inhabitants of the East do not observe the eclipse of the sun
+or of the moon which occurs in the evening, and the inhabitants of the
+West those which occur in the morning, while those who dwell between
+see those later and these earlier. That the water also has the same
+form can be observed from ships, in that the land which cannot be seen
+from the deck, is visible from the mast-tree. And conversely if a light
+be placed at the mast-head it seems to those who remain on the shores
+gradually to sink and at last still sinking to disappear. It is clear
+that the water also according to its nature continually presses like
+the earth downward, and does not rise above its banks higher than its
+convexity permits. So the land extends above the ocean as much as the
+land happens to be higher.
+
+
+WHETHER THE EARTH HAS A CIRCULAR MOTION, AND CONCERNING THE LOCATION OF
+ THE EARTH
+
+As it has been already shown that the earth has the form of a sphere,
+we must consider whether a movement also coincides with this form, and
+what place the earth holds in the universe. Without this there will be
+no secure results to be obtained in regard to the heavenly phenomena.
+The great majority of authors of course agree that the earth stands
+still in the center of the universe, and consider it inconceivable and
+ridiculous to suppose the opposite. But if the matter is carefully
+weighed it will be seen that the question is not yet settled and
+therefore by no means to be regarded lightly. Every change of place
+which is observed is due, namely, to a movement of the observed object
+or of the observer, or to movements of both, naturally in different
+directions, for if the observed object and the observer move in the
+same manner and in the same direction no movement will be seen. Now it
+is from the earth that the revolution of the heavens is observed and it
+is produced for our eyes. Therefore if the earth undergoes no movement
+this movement must take place in everything outside of the earth, but
+in the opposite direction than if everything on the earth moved, and
+of this kind is the daily revolution. So this appears to affect the
+whole universe, that is, everything outside the earth with the single
+exception of the earth itself. If, however, one should admit that this
+movement was not peculiar to the heavens, but that the earth revolved
+from west to east, and if this was carefully considered in regard to
+the apparent rising and setting of the sun, the moon and the stars,
+it would be discovered that this was the real situation. Since the
+sky, which contains and shelters all things, is the common seat of all
+things, it is not easy to understand why motion should not be ascribed
+rather to the thing contained than to the containing, to the located
+rather than to the location. From this supposition follows another
+question of no less importance, concerning the place of the earth,
+although it has been accepted and believed by almost all, that the
+earth occupies the middle of the universe. But if one should suppose
+that the earth is not at the center of the universe, that, however,
+the distance between the two is not great enough to be measured on the
+orbits of the fixed stars, but would be noticeable and perceptible on
+the orbit of the sun or of the planets: and if one was further of the
+opinion that the movements of the planets appeared to be irregular
+as if they were governed by a center other than the earth, then such
+an one could perhaps have given the true reasons for the apparently
+irregular movement. For since the planets appear now nearer and now
+farther from the earth, this shows necessarily that the center of their
+revolutions is not the center of the earth: although it does not settle
+whether the earth increases and decreases the distance from them or
+they their distance from the earth.
+
+
+REFUTATION OF THE ARGUMENT OF THE ANCIENTS THAT THE EARTH REMAINS STILL
+ IN THE MIDDLE OF THE UNIVERSE, AS IF IT WERE ITS CENTER
+
+From this and similar reasons it is supposed that the earth rests at
+the center of the universe and that there is no doubt of the fact.
+But if one believed that the earth revolved, he would certainly be
+of the opinion that this movement was natural and not arbitrary. For
+whatever is in accord with nature produces results which are the
+opposite of those produced by force. Things upon which force or an
+outside power has acted, must be injured and cannot long endure: what
+happens by nature, however, preserves itself well and exists in the
+best condition. So Ptolemy feared without good reason that the earth
+and all earthly objects subject to the revolution would be destroyed
+by the act of nature, since this latter is opposed to artificial acts,
+or to what is produced by the human spirit. But why did not he fear
+the same, and in a much higher degree, of the universe, whose motion
+must be as much more rapid as the heavens are greater than the earth?
+Or has the heaven become so immense because it has been driven outward
+from the center by the inconceivable power of the revolution; while if
+it stood still, on the contrary, it would collapse and fall together?
+But surely if this is the case the extent of the heavens would increase
+infinitely. For the more it is driven higher by the outward force of
+the movement, so much the more rapid will the movement become, because
+of the ever increasing circle which must be traversed in 24 hours; and
+conversely if the movement grows the immensity of the heavens grows. So
+the velocity would increase the size and the size would increase the
+velocity unendingly. According to the physical law that the endless
+cannot wear away nor in any way move, the heavens must necessarily
+stand still.
+
+But it is said that beyond the sky no body, no place, no vacant space,
+in fact nothing at all exists; then it is strange that some thing
+should be enclosed by nothing. But if the heaven is endless and is
+bounded only by the inner hollow, perhaps this establishes all the more
+clearly the fact that there is nothing outside the heavens, because
+everything is within it, but the heaven must then remain unmoved.
+The highest proof on which one supports the finite character of the
+universe is its movement. But whether the universe is endless or
+limited we will leave to the physiologues; this remains sure for us
+that the earth enclosed between the poles, is bounded by a spherical
+surface. Why therefore should we not take the position of ascribing
+to a movement conformable to its nature and corresponding to its
+form, rather than suppose that the whole universe whose limits are
+not and cannot be known moves? and why will we not recognize that
+the appearance of a daily revolution belongs to the heavens, but the
+actuality to the earth; and that the relation is similar to that of
+which one says: “We run out of the harbor, the lands and cities retreat
+from us.” Because if a ship sails along quietly, everything outside
+of it appears to those on board as if it moved with the motion of
+the boat, and the boatman thinks that the boat with all on board is
+standing still, this same thing may hold without doubt of the motion
+of the earth, and it may seem as if the whole universe revolved. What
+shall we say, however, of the clouds and other things floating, falling
+or raising in the air--except that not only does the earth move with
+the watery elements belonging with it, but also a large part of the
+atmosphere, and whatever else is in any way connected with the earth;
+whether it is because the air immediately touching the earth has the
+same nature as the earth, or that the motion has become imparted to the
+atmosphere. A like astonishment must be felt if that highest region
+of the air be supposed to follow the heavenly motion, as shown by
+those suddenly appearing stars which the Greeks call comets or bearded
+stars, which belong to that region and which rise and set like other
+stars. We may suppose that part of the atmosphere, because of its great
+distance from the earth, has become free from the earthly motion. So
+the atmosphere which lies close to the earth and all things floating in
+it would appear to remain still, unless driven here and there by the
+wind or some other outside force, which chance may bring into play;
+for how is the wind in the air different from the current in the sea?
+We must admit that the motion of things rising and falling in the air
+is in relation to the universe a double one, being always made up of a
+rectilinear and a circular movement. Since that which seeks of its own
+weight to fall is essentially earthy, so there is no doubt that these
+follow the same natural law as their whole; and it results from the
+same principle that those things which pertain to fire are forcibly
+driven on high. Earthly fire is nourished with earthly stuff, and it
+is said that the flame is only burning smoke. But the peculiarity of
+the fire consists in this that it expands whatever it seizes upon,
+and it carries this out so consistently that it can in no way and
+by no machinery be prevented from breaking its bonds and completing
+its work. The expanding motion, however, is directed from the center
+outward; therefore if any earthly material is ignited it moves upward.
+So to each single body belongs a single motion, and this is evinced
+preferably in a circular direction as long as the single body remains
+in its natural place and its entirety. In this position the movement
+is the circular movement which as far as the body itself is concerned
+is as if it did not occur. The rectilinear motion, however, seizes
+upon those bodies which have wandered or have been driven from their
+natural position or have been in any way disturbed. Nothing is so much
+opposed to the order and form of the world as the displacement of one
+of its parts. Rectilinear motion takes place only when objects are
+not properly related, and are not complete according to their nature
+because they have separated from their whole and have lost their unity.
+Moreover, objects which have been driven outward or away, leaving out
+of consideration the circular motion, do not obey a single, simple
+and regular motion, since they cannot be controlled simply by their
+lightness or by the force of their weight, and if in falling they have
+at first a slow movement the rapidity of the motion increases as they
+fall, while in the case of earthly fire which is forced upwards--and
+we have no means of knowing any other kind of fire--we will see that
+its motion is slow as if its earthly origin thereby showed itself.
+The circular motion, on the other hand, is always regular, because it
+is not subject to an intermittent cause. Those other objects, however,
+would cease to be either light or heavy in respect to their natural
+movement if they reached their own place, and thus they would fit into
+that movement. Therefore if the circular movement is to be ascribed
+to the universe as a whole and the rectilinear to the parts, we might
+say that the revolution is to the straight line as the natural state
+is to sickness. That Aristotle divided motion into three sorts, that
+from the center out, that inward toward the center, and that around
+about the center, appears to be merely a logical convenience, just
+as we distinguish point, line and surface, although one cannot exist
+without the others, and none of them are found apart from bodies. This
+fact is also to be considered, that the condition of immovability is
+held to be nobler and more divine than that of change and inconstancy,
+which latter therefore should be ascribed rather to the earth than
+to the universe, and I would add also that it seems inconsistent to
+attribute motion to the containing and locating element rather than to
+the contained and located object, which the earth is. Finally since the
+planets plainly are at one time nearer and at another time farther from
+the earth, it would follow, on the theory that the universe revolves,
+that the movement of the one and same body which is known to take place
+about a center, that is the center of the earth, must also be directed
+toward the center from without and from the center outward. The
+movement about the center must therefore be made more general, and it
+suffices if that single movement be about its own center. So it appears
+from all these considerations that the movement of the earth is more
+probable than its fixity, especially in regard to the daily revolution,
+which is most peculiar to the earth.
+
+
+FOOTNOTES:
+
+[Footnote 4: Selections from the Introduction to _De Orbium
+Caelestium Revolutionibus_.]
+
+
+
+
+ III
+
+ JOHANN KEPLER
+
+ 1571-1630
+
+
+ _Tycho Brahe (1546-1601), nobleman of Denmark, studied law at
+ the University of Copenhagen and became attracted to astronomical
+ studies by the occurrence of a predicted eclipse. Constructing his
+ own instruments, he made observations of the stars at Augsburg
+ and Wittenberg, and in 1576 established the first observatory at
+ Huen, where he continued his work for twenty years. Banished from
+ Germany, he was invited by Emperor Rudolph to Prague, where he began
+ his compilation of the Rudolphin Tables which listed many of his
+ observations on the locations of the planets. Hearing of Kepler’s
+ interest in astronomy, he secured the young German’s assistance and
+ assigned to him the study of the planet Mars, which study Kepler
+ continued after Tycho Brahe’s death in 1601._
+
+ _Johann Kepler, the son of an innkeeper, was born December 27, 1571,
+ in Württemberg and sent to a local school, from which he was removed
+ when he was nine years old because of his father’s impoverishment.
+ After three years of work in the tavern, he was sent to a monastic
+ school and thence to the University of Tübingen. Although he was very
+ frail in physique, he was a good student and attained high scholarly
+ standing. Becoming interested in the Copernican theory, in 1599 he was
+ invited by Tycho Brahe to become his assistant at Prague._
+
+ _Kepler found his master’s tables sufficiently accurate in his
+ efforts to discover some recognizable motion of the planet Mars which
+ would account for its apparent positions. In the course of this work
+ he corrected some of the Ptolemaic ideas which Copernicus had not
+ completely abandoned. The latter retained the epicycle motion of the
+ planets within their larger revolutions in cycles. In comparing this
+ theory with his tables, Kepler found that it would not satisfactorily
+ account for the positions of Mars; and he was therefore led to the
+ long studies and mathematical computations which finally resulted
+ in his discovery of the orbit of Mars, and to the establishment of
+ the first two of his three famous laws: “1. the planet describes an
+ ellipse, the sun being in one focus; 2. the straight line joining the
+ planet to the sun sweeps out equal areas in equal intervals of time.”
+ (Sedgwick and Tyler, pp. 211-213). He published these laws in 1609 in
+ his “Commentaries on the Motions of Mars.”_
+
+ _In 1611, when his patron, Emperor Rudolph, was compelled to
+ abdicate, Kepler was left penniless, but he moved to Linz where he was
+ appointed to a professorship. In 1619 he published his “Harmony of
+ the World,” which contained his third law: “The squares of the times
+ of revolution of any two planets (including the earth) about the sun
+ are proportional to the cubes of their mean distances from the sun.”
+ (Sedgwick and Tyler, p. 213). This was the triumph about which he wrote
+ in the year of its discovery, 1618: “What I prophesied twenty-two years
+ ago, as soon as I found the heavenly orbits were of the same number
+ as the five (regular) solids, what I fully believed long before I
+ had seen Ptolemy’s Harmonies, what I promised my friends in the name
+ of this book, which I christened before I was sixteen years old, I
+ urged as an end to be sought, that for which I joined Tycho Brahe, for
+ which I settled at Prague, for which I have spent most of my life at
+ astronomical calculations--at last I have brought to light, and seen to
+ be true beyond my fondest hopes. It is not eighteen months since I saw
+ the first ray of light, three months since the unclouded sun-glorious
+ sight! burst upon me. Let nothing confine me: I will indulge my sacred
+ ecstasy. I will triumph over mankind by the honest confession that I
+ have stolen the golden vases of the Egyptians to raise a tabernacle for
+ my God far away from the lands of Egypt. If you forgive me, I rejoice;
+ if you are angry, I cannot help it. The book is written; the die is
+ cast. Let it be read now or by posterity, I care not which. It may well
+ wait a century for a reader, as God had waited six thousand years for
+ an observer.” Kepler died at Ratisbon, November 15, 1630._
+
+
+ ON THE PRINCIPLES OF ASTRONOMY[5]
+
+What is _astronomy_? It is the science of treating of the causes
+of those celestial appearances which we who live on the earth observe
+and which mark the changes of times and seasons; by the studying of
+which we are able to predict for the future the face of the heavens,
+that is, the stellar phenomena, and to assign fixed dates for those
+which have occurred in the past.
+
+_Why is it called astronomy?_ From the law (νουος) or governance
+of the stars (ἀστρα), that is, of the motions in which the stars move,
+just as economy is named from the law of domestic affairs (οἰκονουία)
+and paedonomy (παιδονουία) from the ruling of youths.
+
+_What is the relation of this science to the other sciences?_ 1)
+It is a branch of physics because it investigates the causes of natural
+objects and events, and because among its subjects are the motions of
+the heavenly bodies, and because it has the same end as physics, to
+inquire into the conformation of the world and its parts.
+
+2) Astronomy is the soul of geography and hydrography, for the various
+appearances of the sky in various districts and regions of the earth
+and sea are known only by astronomy.
+
+3) Chronology is dependent upon it, because the movements of the
+heavenly bodies prescribe seasons and years and date the histories.
+
+4) Meteorology is also its subordinate, for the stars move and
+influence this sublunary nature and even men themselves.
+
+5) It includes a large part of optics, because it has a subject in
+common with that; that is, the light of the heavenly bodies, and
+because it corrects many errors of sight in regard to the character of
+the earth and its motions.
+
+6) It is, however, subordinate to the general subject of mathematics
+and uses arithmetic and geometry as its two wings, studying the extent
+and form of the bodies and motions of the universe and computing the
+periods, by these means expediting its demonstrations and reducing them
+to use and practical value.
+
+_How many, then, are the branches of astronomical study?_ The
+departments of the study of astronomy are five; historical, in the
+matter of observations, optical as to the hypothesis, physical as
+to the causes of the hypotheses, arithmetical as to the tables and
+calculations, mechanical as to its instruments.
+
+ * * * * *
+
+_Since we must begin with appearances, explain how the world seems to
+be made up._ The world is commonly thought, accepting the testimony
+of the eyes, to be an immense structure consisting of two parts, the
+earth and the sky.
+
+_What do men imagine concerning the figure of the earth?_ The
+earth seems to be a broad plane extending in a circle in every
+direction around the spectator. And from this appearance of a plane
+bounded by a great circle the appellation, _orbis terrarum_,
+the circle of the earth, has arisen, and has been taken over by the
+Scripture and among other nations.
+
+_What do men imagine to be the center of the earth?_ Each nation,
+unless it has become familiar with the notion of the circle, thinks by
+the instinct of nature and the error of vision that its country is in
+the center or middle of this plane circle. So the common people among
+the Jews believe still that Jerusalem, the earliest home of their race,
+is situated at the center of the world.
+
+_What do men think about the waters?_ Since men proceeding as far
+as possible in any direction finally came upon the ocean, some have
+thought that the earth is like a disc swimming in the waters, and that
+the waters are held up by the lower part of the sky, whence poets have
+called the ocean, the father of all things. Others believe that a strip
+of land surrounds the ocean which keeps the water from flowing away,
+and these suppose there is land under the water, saying that the water
+is held up by the earth. Besides these there are still others who,
+since the ocean seems higher than the land if it is looked at from the
+edge of the shore, believe that the earth is, as it were, sunk in the
+waters and supernaturally guarded by the omnipotence of God lest the
+waters rushing in from the deep should overwhelm it.
+
+_What do men imagine to be under both the land and the waters?_
+There has been great discussion among men marveling concerning the
+foundation which could bear up the great mass of the earth so that
+it should remain for so many centuries firm and immovable and should
+not sink; and Heraclitus among the early philosophers, and Lactantius
+among the ecclesiastics said that it reached down to the lowest root of
+things.
+
+_How about the other part of the world, the sky and its extent?_
+Men have thought that the sky was not much larger than the earth, and
+indeed was connected with the earth and the ocean at the circumference
+of the circle, so that it bounded the earth; and that anyone going
+that far, if it could be done, would run up against the sky, blocking
+further progress. With this idea of men the Scriptures also agreed.
+
+So also the poets said that Mt. Atlas, a lofty mountain on the
+farthest shore of Africa, bore up the sky on his shoulders, and Homer
+placed the Aethiopeans at the extremities of the rising and setting
+sun, thinking that because of the contiguity of the earth and sky
+there, the sun was so close to them that it burned their skin.
+
+_What form do they ascribe to the sky?_ The eyes ascribe to the
+sky the shape of a tent, extending over our heads and beyond the
+sun, moon and stars, or rather the shape of an arch overspanning the
+terrestrial plane, with a long curve, so that the part of the sky just
+over the head of the spectator is much nearer to him than the part that
+touches the mountains.
+
+_What have men conceived in regard to the motion of the sky?_
+Whether the sky moves or stands still is not apparent to the sight
+because the tenuity of its substance escapes the eyes, unless indeed
+those things appear to stand still in which the eye can perceive no
+variation. But the changing positions of the sun, moon and stars in
+relation to the ends of the earth was apparent to the eyes. For the
+sun seems to emerge from an opening between the sky and the immovable
+mountains and ocean, as if coming out of a chamber, and having
+traversed the vault of the sky seems to sink again in the opposite
+region; so also the moon, and the planets, and the whole host of stars
+proceed as if strictly marshalled and drawn up in line, first one and
+then the other marching along, each in his order and place.
+
+And so, since the ocean lies beyond the extreme lands, the mass of men
+have thought that the sun plunges into the ocean and is extinguished,
+and from the opposite region a new sun issues forth daily from the
+ocean. The poets have used this figure in their creations. But,
+indeed, there have been even philosophers who have declared that on
+the farthest shores of Lusitania could be heard the roar of the ocean
+extinguishing the flames of the sun, as Strabo recounts.
+
+ * * * * *
+
+_I understand the forms of the sky and the earth and the atmosphere
+surrounding the earth, also the place of the earth in the universe; now
+I would ask what causes the stars to seem to rise daily from the one
+part of the horizon and to sink in the opposite part; the motion of the
+sky or of the earth?_ The astronomy of Copernicus shows that our
+sight has led us astray in regard to this motion; for the stars do not
+actually come up from beyond the mountains and climb toward the zenith,
+but rather the mountains which surround us and which are a part of the
+surface of the earth are revolved along with the whole globe about its
+axis from west to east and by this revolution the immovable stars of
+the east are disclosed to us one after the other, and those of the west
+are obscured, so the stars are not passing over us, but the vertical
+point is moving through the fixed stars.
+
+_You say that by this marvelous hypothesis may be explained
+satisfactorily all the phenomena of the first motion and the spherical
+theory._ Just so, and that is the scope of this section, to
+demonstrate in fact what has been suggested in words.
+
+_How do you expect to be able to prove this absurd hypothesis,
+and by what arguments?_ It is possible to demonstrate that this
+first motion results from the revolution of the earth about its axis,
+while the heavenly bodies are at rest (as far as this first motion is
+concerned), by seven kinds of arguments: 1) from the subject of the
+motion; 2) from the velocity of the motion; 3) from the equableness of
+the motion; 4) from the cause of the motion, or the moving principle;
+5) from the motive instruments, that is, the axis and the poles; 6)
+from the object of the first motion; and 7) from the indications or
+results.
+
+_Demonstrate it then from the subject of the motion._ Nature does
+not seek difficult means when she can use simple ones. Now, by the
+rotation of the earth, a very small body, about its axis, toward the
+east, the same thing is accomplished as by the rotation of the immense
+universe about its axis toward the west. Just as it is more likely that
+a man’s head turns in the auditorium than that the auditorium is turned
+about his head, so it is more credible that the earth is rotating from
+west to east, than that the rest of the machine of the universe is
+revolved from east to west, since in both cases the same thing results.
+
+If the first motion is in the heavenly bodies, then they are subject
+to two motions, one common to the whole universe, the other particular
+to each sphere; but it is much more probable that the two motions
+should be distinct in regard to their subjects, so that the second set
+of motions, which is multifold, should belong to each sphere, and the
+first, which is single, should belong to the single body of the earth,
+and to it alone.
+
+_Why cannot the whole machinery of the universe be moved?_ The
+universe is either infinite or finite. Suppose it to be the former,
+according to the opinion of William Gilbert, who thinks that the
+omnipotence of God is illustrated in this that the universe extends
+outward infinitely, so that the infinite power of the creator would be
+recognized from the infinite extent of the creation. Although this may
+be refuted by metaphysical arguments, no argument on either side can be
+drawn from astronomy, in which trust is placed rather in the evidence
+of the senses than in abstract reasonings not dependent on observation.
+But supposing this universe to be infinite, Aristotle has shown that
+the whole universe should not be moved about in a revolution since it
+is the whole.
+
+But let the universe be finite; then there is nothing outside the
+universe which would locate the universe but should remain quiet
+itself. Where there is nothing that rests there is no motion. For 1)
+motion is the separation of a movable thing from its place and its
+transfer to another place: 2) the motion of a machine about an axis and
+quiescent poles cannot be grasped by the mind where there is nothing in
+respect to which the poles remain still.
+
+
+FOOTNOTES:
+
+[Footnote 5: From _The Epitome of Astronomy_.]
+
+
+
+
+ IV
+
+ GALILEO GALILEI
+
+ 1564-1642
+
+
+ _Galileo Galilei, born at Pisa, February 15, 1564, was the son of
+ a mathematician who, seeing no future in that profession, had him
+ educated for the practice of medicine. But when Galileo was about
+ eighteen years of age, while observing a large lamp swinging in
+ the Pisa cathedral, he noticed that, regardless of the length of
+ the oscillation, the time did not vary. In spite of his father’s
+ discouragements, therefore, he became absorbed in mathematics and
+ abandoned the study of medicine. Applying himself to the study of
+ motion, he performed his famous experiment of letting bodies of
+ different weights fall from the leaning tower of Pisa, proving that
+ things of unequal weight, if heavier than the resistance of air, fall
+ with the same speed. The doctrine of inertia which he deduced from
+ this and similar experiments decisively answered the opponents of
+ Copernicus; for the principle stated that bodies would continue to
+ move in the same direction forever unless their course was disturbed
+ or opposed by another force, and that the motion of bodies resulted
+ from independent forces operating upon them. His treatise on the center
+ of gravity in solids earned him a lectureship at the University of
+ Pisa._
+
+ _Meeting malignant opposition at Pisa, he secured the chair of
+ mathematics at Padua (which he held from 1592 to 1610) and there
+ continued his observations and experiments in physics and chemistry.
+ He succeeded in making a crude thermometer in 1600. In 1609 he learned
+ that Hans Lippershey, an optician of Middleburg, had succeeded in
+ making a telescope. He thereupon made one of his own and improved it
+ until it had a power of magnifying thirty-two times, enabling him to
+ discover the mountainous surface of the moon, the moons of the planet
+ Jupiter, the fact that Venus showed different sides like the moon, and
+ that many small stars made up the Milky Way._
+
+ _In 1610 he left Padua for Florence, and by 1613 openly declared
+ his acceptance of Copernican ideas. Immediately he was opposed by
+ theologians, and after being given an opportunity to renounce his
+ adherence to the new system of astronomy, was sentenced in 1616 not to
+ hold, teach, or defend it. In 1623, when his friend Maffeo was made
+ Pope Urban VIII, he wrote his dialogues on the system of the world. He
+ had much difficulty in getting them published and succeeded only when
+ he assured the authorities that they were not heretical. It was quite
+ evident, however, that the dialogues were slightly concealed arguments
+ for the acceptance of the Copernican system and consequently in 1633
+ he was summoned before the Inquisition and compelled to renounce his
+ heresy. In 1637, a few months after he had discovered the librations
+ of the moon, he lost his sight. He died five years later, January 8,
+ 1642._
+
+
+ THE COPERNICAN VERSUS THE PTOLEMAIC ASTRONOMIES[6]
+
+Formerly I used frequently to visit the marvelous city of Venice
+and to meet there Signore Giovan Francesco Sagredo, a man of most
+distinguished ancestry and remarkable intelligence. Thither also came
+from Florence, Signore Filippo Salviati, whose least claim to renown
+was his noble blood and great wealth; a noble mind, that held no
+enjoyment of greater price than that of study and thought. With both
+of these men I often discussed these questions, in the presence of
+a Peripatetic philosopher, who apparently valued the acquisition of
+knowledge in no way in so high a degree, as he did the renown which his
+interpretations of Aristotle had gained for him.
+
+Now that cruel death has robbed the cities of Venice and Florence
+of these two enlightened men in the bloom of their years, I have
+endeavored, as far as my weak powers may permit, to perpetuate their
+fame in these pages by making them the speakers in this dialogue.
+The valiant Peripatetic also shall not fail to appear; because of
+his over-weaning love for the commentary of Simplicius, it seemed
+permissible to omit his own name and let him pass under that of his
+favorite author. May the souls of these two great men accept this
+public testimony of my undying love; may the recollection of their
+eloquence aid me in setting down for posterity the spoken discussions.
+
+
+ SECOND DAY
+
+SALVIATI: We departed yesterday so often and so far from the
+direct path of our discussion, that I can scarcely return to the right
+point and proceed without your help.
+
+SAGREDO: I find it quite intelligible that you are somewhat at
+a loss, since you have had your head so full of both the things already
+brought forward and things still to be discussed. I, however, who as
+merely a listener have in mind only the things already discussed, may
+I hope set our investigation straight by a brief summary of what has
+been gone over. So, if my memory fails not, the chief result of our
+yesterday’s conversation was that we tested thoroughly which of the
+two theories was the more probable and better grounded; that according
+to which the substance of the heavenly bodies is unproducible,
+indestructible, unchangeable, intangible, in brief not subject to
+any variation aside from change of location, and so presents a fifth
+element which is entirely distinct from our elementary, producible,
+destructible, changeable bodies; or the other view, according to which
+an incongruity between parts of the universe is rejected, our earth
+rather enjoys the same privileges as the rest of the constituent
+bodies of the universe, in a word, is a freely moving ball just as
+the moon, Jupiter, Venus, or any other planet. Finally we noticed the
+many similarities in particular between the earth and the moon, and of
+course with the moon more than any other planet because of the closer
+and more definite knowledge which we possess of it by reason of its
+less distance. Since we agreed that this second opinion possessed the
+greater probability, the logical consequence, it seems to me, is that
+we should investigate the question whether we should hold the world
+immovable, as has been formerly believed in general, or movable as some
+ancient philosophers believed and as some recent ones suppose: and if
+movable, how its movement could have been produced.
+
+SALV.: Let us begin our discussion with the admission
+that whatever sort of motion may be ascribed the earth, we, as its
+inhabitants and therefore partakers in the movement, would be
+unconscious of it, as if it did not occur, since we can only take into
+consideration earthly things. Therefore it is necessary that this
+movement should seem to belong to all the other bodies and visible
+objects in common which, separated from the earth, have no share in its
+movement. The correct method of determining whether movement is to be
+attributed to the earth, and what movement, is that one should inquire
+and observe whether an apparent movement can be ascribed to the bodies
+outside of the earth, which belongs to all of them in the same degree.
+So a movement which, for example, can be supposed of the moon, and not
+of Venus or Jupiter or other stars, cannot be peculiar to the earth.
+Now there is such a general movement governing all other objects,
+namely that which the sun, moon, planets, fixed stars, in a word the
+whole universe with the single exception of the earth, seems to follow
+from east to west within the space of twenty-four hours. This, at least
+at first glance, may be just as well attributed to the earth alone, as
+to the rest of the entire universe except the earth.
+
+SAGR.: I understand clearly that your suggestion is correct.
+An objection, however, forces itself upon me that I cannot solve. That
+is, since Copernicus ascribes to the earth a further movement aside
+from the daily one, according to the above mentioned principle this
+should be apparently un-noticeable on the earth, but should be visible
+in the rest of the universe. I come then to the conclusion that either
+he plainly erred when he ascribed to the earth a movement to which
+no counterpart is apparent in the firmament, or else such a movement
+exists, and then Ptolemaus is guilty of a second error in that he did
+not refute with arguments this movement as well as that daily rotation.
+
+SALV.: Your objection is very just. If we take up this
+other movement, you shall see how much superior in intelligence was
+Copernicus to Ptolemaus, in that he saw what this one did not, namely
+how wonderfully this second motion is reflected in the rest of the
+heavenly bodies. For the present, however, we will leave this aside and
+return to our first consideration. Proceeding from the most general
+suppositions, I will present the arguments which seem to favor the
+motion of the earth, in order then to hear the opposing arguments
+of Signore Simplicio. First, then, when we consider the immense
+circumference of the stellar sphere in comparison with the smallness
+of the earth, which is contained in that several million times, and
+therefore regard the velocity of motion which would be necessary for
+an entire revolution in the course of a day and night, I am unable to
+understand how any one could hold it more reasonable and credible that
+it is this whole stellar sphere that moves and that the earth remains
+still.
+
+SAGR.: Even if universal phenomena which depend upon these
+movements could be explained as readily by the one hypothesis as by
+the other, yet by the first general impression I would regard as more
+unreasonable the view that the whole universe moves; just as if any
+one should climb to the top of your dome for the purpose of getting
+a view of the city and its environs and then should demand that the
+whole region be made to move around him to save him the trouble of
+turning his head. In any event, there would have to be great advantages
+connected with this theory, which were lacking in the other, in
+order that such an absurdity should be balanced and outweighed and
+should appear more credible than the opposite opinion. But Aristotle,
+Ptolemaus, and Signore Simplicio must find such advantages in their
+theory, and I should be glad if we might hear these advantages if they
+exist, or if they do not, that some one would explain to me why they do
+not and cannot exist.
+
+SALV.: If, in spite of every sort of investigation, I am
+able to find no such differences, I believe I have thereby discovered
+that such difference does not exist. So in my opinion it is useless
+to pursue this further: rather let us proceed. Motion is only so far
+motion and acts as such, if it stands in relation to things which lack
+motion. In relation to things that are all in the same degree affected
+by it, it is as much without effect as if it did not take place. The
+wares with which a ship is loaded move, when they depart from Venice
+and arrive at Aleppo, passing Korfu, Candia, Cyprus etc; since Venice,
+Korfu and Candia remain fixed and do not move with the ship. But in
+respect to the bales, chests, and other pieces of baggage which are
+on the ship as cargo or ballast, the movement of the ship itself from
+Venice to Syria is as good as non-existent, since their position in
+relation to one another does not change; and this is due to the fact
+that the movement is a common one in which they all take part. If of
+the wares on the ship one bale moves only an inch away from the chest,
+this is for it a greater movement in relation to the chest, than the
+whole journey of 2,000 miles which they undergo in common.
+
+Therefore, since plainly the motion which many movable bodies undergo
+in common is without effect and, with regard to their mutual position
+toward one another, it is as if it did not exist, for there is no
+change among them; and since it only affects the relative position
+of such bodies as do not share in the movement, for in this case the
+mutual relation is changed; since we have divided the universe into
+two parts, of which one must be movable and the other immovable; then
+for all purposes this movement will be of the same effect whether it
+is ascribed to the earth alone or to all the rest of the universe. For
+the working of such a motion is on nothing but the relative position in
+which the earth and the heavenly bodies stand to one another, and aside
+from this relative position nothing changes. If now it is indifferent
+for accomplishing this result whether the earth alone moves and the
+whole universe rests, or the earth rests and the whole universe is
+subject to one common movement, who can believe that Nature--who by
+common agreement does not employ great means when she can obtain the
+same result by smaller ones--would have undertaken to set in motion
+an immeasurable number of mighty bodies, and that with incredible
+velocity, to accomplish what could be obtained by the moderate motion
+of one single body around the center?
+
+SIMPL.: I do not agree that that mighty movement would be as
+if it did not happen in regard to the sun, the moon, the innumerable
+host of fixed stars. Do you call it nothing that the sun goes from
+one meridian to another, rises from one horizon, sinks under another,
+brings now day, now night; that the moon goes through similar changes
+and likewise the other planets, as well as the fixed stars?
+
+SALV.: All the changes mentioned by you are such only with
+respect to the earth. To demonstrate this, only imagine yourself away
+from the earth; there is then no rising or setting of the sun, no
+horizons, no meridians, no day, no night; in a word, by the movement
+mentioned no change in the relation of the moon to the sun or to any
+other star is evoked. All these changes have reference to the earth;
+they are supposed only because the sun is first visible in China, then
+Egypt, Greece, France, Spain, America, and so on, and so also for the
+moon and the other heavenly bodies. The same process would occur in
+the same way, if, without disturbing so vast a part of the universe,
+the earth alone should be revolved.
+
+The difficulty is however doubled since a second very important one is
+added. That is, if one attributes to the firmament this mighty motion,
+one must regard it as necessarily opposed to the particular movements
+of all the planets, all of which indisputably have their own movements
+from west to east, and in comparison very moderate movements at that.
+One is then forced to the conclusion that they depart from that
+rapid daily motion, namely from east to west, to go in the opposite
+direction. But, if we suppose that the earth moves, the opposition of
+motions disappears and the single movement from west to east fits in
+with all the facts and explains them most satisfactorily.
+
+SIMPL.: As far as this opposition of motions is concerned that
+has little importance, since Aristotle proves that the circular motions
+are not opposed to one another and that the apparent opposition cannot
+actually be called so.
+
+SALV.: Does Aristotle prove that or merely suppose it,
+because it aids him for a certain purpose? If, according to his own
+declaration, those things are opposed which mutually destroy one
+another I do not see how two moving bodies which meet one another in a
+circular motion should do one another less harm than if they meet on a
+straight line.
+
+SAGR.: Wait a moment, I pray. Tell me, Signore Simplicio, if
+two knights run into one another with leveled lances on the open field,
+if two squadrons or two streams on their way to the sea break through
+and unite with one another, would you call such collisions opposed
+movements?
+
+SIMPL.: Of course we would call them opposed.
+
+SAGR.: How then is there no opposition in circular motions?
+For the movements mentioned take place upon the surface of the earth
+or water, both of which are recognized to be circular in form and so
+the motions must be circular. Do you understand, Signore Simplicio,
+what circular motions are not opposed to one another? Two circles which
+touch each other on the outside and of which the revolution of one is
+in a reverse direction from that of the other. If, however, one circle
+is within the other, then motions in different directions must be
+opposed to one another.
+
+SALV.: Whether opposed or not opposed is merely a strife of
+words. I know that in fact it is simpler and more natural to accomplish
+everything with one motion than to call in two. If you do not wish to
+call them opposite, then call them reverse. Moreover, I mention this
+introduction of a double movement not as something impossible, and in
+no way propose to deduce from it a strong proof for the motion of the
+earth, but merely a high degree of probability for it.
+
+The improbability of the movement of the universe about the earth is
+tripled, however, by the complete upsetting of that arrangement which
+governs all the heavenly bodies whose circular motion is accepted not
+doubtfully but with full assurance. That is, that in such cases the
+larger the orbit the longer the time required for its completion,
+and the smaller, the shorter. Saturn, whose course surpasses all the
+planets in extent, completes it in thirty years. Jupiter revolves in a
+smaller circle in twelve years. Mars in two, the moon in a month. We
+see clearly in the case of the Medicean stars [the moons of Jupiter]
+that the one nearest Jupiter goes through its orbit in a very short
+time, namely, forty-two hours, the next nearest in three and a half
+days, the third in seven days, and the farthest removed in sixteen
+days. This thoroughly constant rule remains unchanged if we ascribe
+the twenty-four hour movement to the revolution of the earth, but if
+we suppose the earth to remain unmoved, we must proceed from the short
+period of the moon to increasingly greater periods, to the two year
+period of Mars, the twelve year period of Jupiter, the thirty year
+period of Saturn, and then abruptly to a disproportionately larger
+orbit, to which must also be ascribed the revolution in twenty-four
+hours. And these suppositions entail the smallest part of the
+disturbance of the otherwise constant law. For when one passes from
+the orbit of Saturn to those of the fixed stars and attributes to them
+even greater orbits, which correspond to the period of revolution
+of many thousands of years, one must pass from this by a much more
+disproportionate transition to that other movement and ascribe to them
+a period of revolution about the earth of twenty-four hours. But if
+the movement of the earth is supposed, the regularity of the period is
+accounted for in the best possible way; from the slow period of Saturn
+we arrive at the immovable fixed star.
+
+A fourth difficulty also is encountered which must be added if
+we suppose the motion of the smaller sphere. I mean the great
+dissimilarity in movements of these stars, some of which must revolve
+at a tremendous rate in immense circles, others slowly in smaller
+circles, according as they are placed at greater or smaller distances
+from the pole. And not only the size of the different circles and so
+the velocity of movement varies greatly in different fixed stars, but
+also the same stars change their courses and their velocity; herein
+is the fifth difficulty. That is, those stars which 2,000 years ago
+stood on the equator of the stellar sphere and thereafter moved in
+the greatest circles, must now, since to-day they have moved several
+degrees from it, move more slowly and in smaller circles. Within a
+conceivable time it will happen that one of those which have been
+continually moving will eventually reach the pole and cease to revolve,
+then later, after a period of rest, begin to move again. The other
+stars, however, which undoubtedly move, all have, as has been said, as
+orbit an immense circle and move in it without change.
+
+The improbability is increased (and this may be called a sixth
+difficulty) for him who investigates basic principles, by the fact that
+one cannot imagine the firmness which that immense sphere must possess,
+in whose depths so many stars are so solidly fixed that in spite of
+such varieties of motions they are held together in the revolution
+without in any way changing their relative positions. But if according
+to the most probable view the heavens are fluid, so that each star may
+describe its own orbit, by what law and according to what principles
+are their orbits governed, so that seen from the earth they appear as
+if held in one sphere? To accomplish this it seems to me it would be
+easier and more convenient to make them stationary instead of movable,
+just as the paving stones in the market place are kept in order more
+easily than the troops of children who race over them.
+
+Finally the seventh objection; if we ascribe the daily revolution to
+the highest heavens we must suppose this to be of such power and force
+that it bears along the innumerable crowd of fixed stars, every one a
+body of immense mass and much larger than the earth, further, all the
+planets, although these by their nature move in an opposite direction.
+Moreover, we must suppose that the element of fire and the greater
+portion of the air is also borne along; therefore, singly and alone the
+little earth ball withstands stubbornly and independently this mighty
+force: a supposition that seems to me to have much against it. I cannot
+explain how the earth, a body freely suspended and balanced on its
+axis, inclined by nature as much toward motion as the rest, surrounded
+by a fluid medium, is not seized on by this general revolution. We do
+not encounter this difficulty, however, if we suppose the earth to
+move, a body so small, so inconsiderable in comparison with the whole
+universe that it could have no effect at all upon this.
+
+
+FOOTNOTES:
+
+[Footnote 6: Translated from the _Dialogo dei due Massima Systemi del
+Mondo_ (1632).]
+
+
+
+
+ V
+
+ WILLIAM HARVEY
+
+ 1578-1657
+
+
+ _In 1615 William Harvey stated his theory of the circulation of the
+ blood, which he derived from patient observations, in his lectures
+ on anatomy. The theory was epoch-making in the history of physiology
+ because it initiated the study of the chemical constituency of the
+ blood and of its function in nutrition._
+
+ _Harvey, born April 1, 1578, in the south of England, attended the
+ University of Cambridge, and took his degree in 1597. The following
+ four years he studied at Padua under Fabricius. In 1602, when he
+ returned to England, he began the practice of medicine, and in 1609
+ became connected with St. Bartholomew’s Hospital. He published his
+ “Excercitatio” in 1628, served for several years as physician to
+ Charles I, and retired in 1646 to private life. He died June 3,
+ 1657._
+
+ _He described the process of his discovery as follows: “I frequently
+ and seriously bethought me, and long revolved in my mind, what might be
+ the quantity of blood which was transmitted, in how short a time its
+ passage might be effected, and the like; and not finding it possible
+ that this could be supplied by the juices of the ingested aliment
+ without the veins on the one hand being drained, and the arteries on
+ the other hand becoming ruptured through the excessive charge of blood,
+ unless the blood should somehow find its way from the arteries into
+ the veins, and so return to the right side of the heart; I began to
+ think whether there might not be a motion, as it were, in a circle. Now
+ this I afterwards found to be true; and I finally saw that the blood,
+ forced by the action of the left ventricle into the arteries, was
+ distributed to the body at large, and its several parts, in the same
+ manner as it is sent through the lungs, impelled by the right ventricle
+ into the pulmonary artery, and that it then passed through the veins
+ and along the vena cava, and so round to the left ventricle in the
+ manner already indicated,--which motion we may be allowed to call
+ circular._”
+
+
+ THE CIRCULATION OF BLOOD IN ANIMALS[7]
+
+Thus far I have spoken of the passages of the blood from the veins
+into the arteries, and of the manner in which it is transmitted and
+distributed by the action of the heart; points to which some, moved
+either by the authority of Galen or Columbus, or the reasonings of
+others, will give in their adhesion. But what remains to be said upon
+the quantity and source of the blood which thus passes, is of so novel
+and unheard-of character, that I not only fear injury to myself from
+the envy of the few, but I tremble lest I have mankind at large for my
+enemies, so much doth wont and custom, that become as another nature,
+and doctrine once sown and that hath struck deep root, and respect
+for antiquity influence all men: Still the die is cast, and my trust
+is in my love of truth, and the candour that inheres in cultivated
+minds. And sooth to say, when I surveyed my mass of evidence, whether
+derived from vivisections, and my various reflections on them, or from
+the ventricles of the heart and the vessels that enter into and issue
+from them, the symmetry and size of these conduits,--for nature doing
+nothing in vain, would never have given them so large a relative size
+without a purpose,--or from the arrangement and intimate structure
+of the valves in particular, and of the other parts of the heart in
+general, with many other things besides, I frequently and seriously
+bethought me, and long revolved in my mind, what might be the quantity
+of blood that was transmitted, in how short a time its passage might
+be effected, and the like; and not finding it possible that this could
+be supplied by the juices of the ingested aliment without the veins on
+the one hand becoming drained, and the arteries on the other getting
+ruptured, through the excessive charge of blood, unless the blood
+should somehow find its way from the arteries into the veins, and so
+return to the right side of the heart; I began to think whether there
+might not be _A Motion, As It Were, In A Circle_. Now this I
+afterward found to be true; and I finally saw that the blood, forced
+by the action of the left ventricle into the arteries, was distributed
+to the body at large, and its several parts, in the same manner as it
+is sent through the lungs, impelled by the right ventricle into the
+pulmonary artery, and that it then passes through the veins and along
+the vena cava, and so round to the left ventricle in the manner already
+indicated. Which motions we may be allowed to call circular, in the
+same way as Aristotle says that the air and rain emulate the circular
+motion of the superior bodies; for the moist earth, warmed by the sun,
+evaporates; the vapours drawn upwards are condensed, and descending
+in the form of rain, moisten the earth again; and by this arrangement
+are generations of living things produced; and in like manner too are
+tempests and meteors engendered by the circular motion, and by the
+approach and recession of the sun.
+
+And so, in all likelihood, does it come to pass in the body, through
+the motion of the blood; the various parts are nourished, cherished,
+quickened by the warmer, more perfect, vaporous, spiritous, and, as
+I may say, alimentive blood; which, on the contrary, in contact with
+these parts becomes cooled, coagulated, and, so to speak, effete;
+whence it returns to its sovereign the heart, as if to its source,
+or to the inmost home of the body, there to recover its state of
+excellence, or perfection.
+
+Here it resumes its due fluidity and receives an infusion of natural
+heat--powerful, fervid, a kind of treasury of life, and is impregnated
+with spirits, and it might be said with balsam; and thence it is again
+dispersed; and all this depends on the motion and action of the heart.
+
+The heart, consequently, is the beginning of life; the sun of the
+microcosm, even as the sun in his turn might well be designated the
+heart of the world; for it is the heart by whose virtue and pulse
+the blood is moved, perfected, made apt to nourish, and is preserved
+from corruption and coagulation; it is the household divinity which,
+discharging its function, nourishes, cherishes, quickens the whole
+body, and is indeed the foundation of life, the source of all action.
+
+
+FOOTNOTES:
+
+[Footnote 7: From _An Anatomical Disquisition on the Motion of the
+Heart-Blood in Animals_.]
+
+
+
+
+ VI
+
+ ROBERT BOYLE
+
+ 1627-1691
+
+
+ _Robert Boyle, fourteenth child of the Earl of Cork, was born
+ January 25, 1627, in Munster, Ireland. He went to Eton, studied under
+ the rector of Stalbridge, and later traveled on the Continent under
+ private tutors. On the death of his father in 1644, he inherited the
+ manor at Stalbridge. At the age of eighteen he became associated with
+ the English scientific investigators at Oxford who later founded
+ the Royal Society, and engaged actively in physical experiments and
+ researches. The greatest of his achievements was his discovery of the
+ law of the compressibility of gases. He died December 30, 1691._
+
+
+ THE DISCOVERY OF THE LAW OF THE COMPRESSIBILITY OF GASES[8]
+
+We took a long glass tube, which, by a dexterous hand and the help of a
+lamp, was in such a manner crooked at the bottom, that the part turned
+up was almost parallel to the rest of the tube, and the orifice of
+this shorter leg of the syphon (if I may so call the whole instrument)
+being hermetically sealed, the length of it was divided into inches
+(each of which was subdivided into eight parts) by a straight list of
+paper, which, containing those divisions, was carefully pasted all
+along it. Then putting in as much quicksilver as served to fill the
+arch or bended part of the syphon, that the mercury standing in a level
+might reach in one leg to the bottom of the divided paper, and just
+to the same height or horizontal line in the other, we took care, by
+frequently inclining the tube, so that the air might freely pass from
+one leg into the other by the sides of the mercury (we took, I say,
+care), that the air at last included in the shorter cylinder should be
+the same laxity with the rest of the air about it. This done, we began
+to pour quicksilver into the longer leg of the syphon, which, by its
+weight pressing up that in the shorter leg, did by degrees straighten
+the included air; and continuing this pouring in of quicksilver till
+the air in the shorter leg was by condensation reduced to take up but
+half the space it possessed (I say possessed, not filled) before, we
+cast our eyes upon the longer leg of the glass, upon which we likewise
+pasted a slip of paper carefully divided into inches and parts, and we
+observed, not without delight and satisfaction, that the quicksilver
+in that longer part of the tube was 29 inches higher than the other.
+Now that this observation does both very well agree with and confirm
+our hypothesis, will be easily discerned by him that takes notice what
+we teach: and Monsieur Pascal and our English friend’s [Mr. Townley’s]
+experiments prove, that the greater the weight is that leans upon the
+air, the more forcible is its endeavor of dilation, and consequently
+its power of resistance (as other springs are stronger when bent by
+greater weights). For this being considered, it will appear to agree
+rarely well with the hypothesis, that as according to it the air in
+that degree of density, and correspondent measure of resistance, to
+which the weight of the incumbent atmosphere had brought it, was unable
+to counterbalance and resist the pressure of a mercurial cylinder of
+about 29 inches, as we are taught by the Torricellian experiment; so
+here the same air being brought to a degree of density about twice
+as great as that it had before, obtains a spring twice as strong as
+formerly. As may appear by its being able to sustain or resist a
+cylinder of 29 inches in the longer tube, together with the weight of
+the atmospherical cylinder that leaned upon those 29 inches of mercury;
+and, as we just now inferred from the Torricellian experiment, was
+equivalent to them.
+
+(_The tube broke at this point and, unable to proceed after several
+similar efforts, Boyle tried the converse experiment--to determine the
+spring of rarefied air. A tube, about 6 feet in length, and sealed at
+one end, was nearly filled with mercury, and into it was placed_)--
+
+A slender glass pipe of about the bigness of a swan’s quill, and open
+at both ends; all along of which was pasted a narrow list of paper,
+divided into inches and half-quarters. This slender pipe being thrust
+down into the greater tube almost filled with quicksilver, the glass
+helped to make it swell to the top of the tube; and the quicksilver
+getting in at the lower orifice of the pipe filled it up till the
+mercury included in that was near about a level with the surface of
+the surrounding mercury in the tube. There being, as near as we could
+guess, little more than an inch of the slender pipe left above the
+surface of the restagnant mercury, and consequently unfilled therewith,
+the prominent orifice was carefully closed with sealing-wax melted;
+after which the pipe was let alone for a while that the air, dilated a
+little by the heat of the wax, might, upon refrigeration, be reduced
+to its wonted density. And then we observed, by the help of the
+above-mentioned list of paper, whether we had not included somewhat
+more or somewhat less than an inch of air; and in either case we were
+fain to rectify the error by a small hole made (with a heated pin) in
+the wax, and afterward closed up again. Having thus included a just
+inch of air, we lifted up the slender pipe by degrees, till the air
+was dilated to an inch, an inch and a half, two inches, etc., and
+observed in inches and eighths the length of the mercurial cylinder,
+which, at each degree of the air’s expansion, was impelled above the
+surface of the restagnant mercury in the tube. The observations being
+ended, we presently made the Torricellian experiment with the above
+mentioned great tube of 6 feet long, that we might know the height of
+the mercurial cylinder for that particular day and hour, which height
+we found to be 29-3/4 inches.
+
+
+FOOTNOTES:
+
+[Footnote 8: From Thorpe, _Essays on Historical Chemistry_.]
+
+
+
+
+ VII
+
+ CHRISTIAN HUYGHENS
+
+ 1629-1695
+
+
+ _Christian Huyghens was born at The Hague, April 14, 1629. He
+ studied law in Breda, but becoming attracted to the study of
+ mathematics he neglected his legal practice for it. In 1655 he
+ improved the method of grinding telescopic lenses, and, assisted
+ by his brother, discovered the sixth satellite of Saturn and the
+ fact that it was belted with rings. In 1657 he presented to the
+ States-General the first pendulum clock. In 1678 he evolved his wave
+ theory of light, and published it at Leyden in 1690. He died at The
+ Hague, June 8, 1695._
+
+
+ THE WAVE THEORY OF LIGHT[9]
+
+Proofs in optics, as in every science in which mathematics is applied
+to matter, are founded upon facts from experience--as for example,
+that light moves in straight lines, that the angles of incidence and
+reflection are equal, and that light rays are refracted in accordance
+with the law of sines [i. e., that the ratio between the sines of the
+incident and refracted ray is constant for the same substance.] For
+this last law is now as generally and surely known as either of the
+others.
+
+Most writers in optics have been content to assume these facts, but
+others more curious have attempted to discover the source and reason of
+these phenomena, looking upon them as being in themselves interesting
+data. Yet although they have propounded some ingenious theories,
+intelligent readers still require a fuller explanation before being
+entirely satisfied. Therefore I herein offer some considerations on the
+matter with the hope of making clearer this branch of physics which has
+not improperly gained the reputation of being very obscure.
+
+I feel myself particularly indebted to those that first began to study
+these profound subjects, and to lead us to hope them capable of orderly
+explanation. Yet I have been surprised to find these very investigators
+accepting arguments far from clear as if proof conclusive. No one has
+yet offered even a probable explanation of the first two remarkable
+phenomena of light,--why it moves in straight lines, and why rays from
+any and all directions can cross one another without interference.
+
+I shall attempt in this treatise to submit clearer and more probable
+reasons, along the lines of modern philosophy, first for the
+transmission of light, and, second, for its reflection when it meets
+certain bodies.
+
+Further, I shall explain the fact of rays said to undergo refraction in
+passing through various transparent bodies. Here I shall consider also,
+the refractions due to the differing densities of the atmosphere. Later
+I shall investigate the remarkable refraction occurring in Icelandic
+crystals. Finally, I shall study the different shapes necessary in
+transparent and reflecting bodies in order to bring together rays upon
+a single point or to deflect them in different ways. Here we shall see
+how easy it is by our new theory to determine not alone the ellipses,
+hyperbolas, and other curves which M. Descartes has so shrewdly
+constructed for this end, but as well the curve that one surface of a
+lens must have when the other surface is known, as spherical, plane, or
+any other figure.
+
+We cannot but believe that light is the motion of a certain material.
+Thus when we reflect on its production, we discover that here on
+the earth it is usually emitted from fire and flame, and that these
+unquestionably contain bodies in rapid motion, since they can soften
+and melt many other more solid substances. If we note its effects, we
+see that when light is brought to a point, as, for example, by concave
+mirrors, it can cause combustion the same as fire: that is, it can
+force bodies apart, a power that certainly argues motion, at least in
+that true science where one believes all natural phenomena to result
+from mechanical causes. Moreover, in my mind we must either admit this
+or give up all hope of ever understanding anything in natural science.
+
+Since, according to this philosophy, it is believed certain that the
+sensation of sight is produced only by the impulse of some form of
+matter against the nerves at the base of the eye, we have yet another
+reason for believing light to be a motion in the substance lying
+between us and the body producing the light.
+
+As soon as we consider, moreover, the enormous speed with which light
+travels in every direction, and the fact that when rays come from
+different directions, even from those exactly opposite, they cross
+without interference, it must be plain that we do not see luminous
+objects by means of particles transmitted from the objects to us, as a
+shot or an arrow moves through the air. For surely this would not allow
+for the two qualities of light just mentioned, particularly the latter
+(that of speed). Light, then, is transmitted in some other way, a
+comprehension of which we may get from our knowledge of how sound moves
+through the air.
+
+We know that sound is sent out in all directions through the medium of
+the air, a substance invisible and impalpable, by means of a motion
+that is communicated successively from one part of the air to the next;
+and as this movement has the same speed in all directions, it must form
+spherical surfaces that keep enlarging until at last they strike the
+ear. Now there can be no doubt that light likewise reaches us from a
+luminous substance through some motion caused in the matter lying in
+the intervening space,--for we have seen above that this cannot take
+place through transmission of matter from one place to another.
+
+If, moreover, light requires time for its passage--a matter we shall
+discuss in a moment--it will then follow that this movement is caused
+in the substance gradually, and therefore is transmitted, like sound,
+by surfaces and spherical waves. I call these _waves_ because of
+their likeness to those formed when one throws a pebble into water,
+which are examples of gradual propagation in circles, although from a
+different cause and on a plane surface.
+
+In regard to the question of light requiring time for its transmission,
+let us consider whether there is any experimental evidence against it.
+
+What experiments we can make here on the earth with sources of light
+placed at great distances (although indicating that it does not take a
+sensible time for light to pass over these distances) are subject to
+the objection that these distances are yet too small, and that we can
+only argue that the movement of light is enormously fast. M. Descartes
+thought it to be instantaneous and based his opinion upon much better
+reasons taken from the eclipse of the moon. Yet as I shall make clear,
+even this evidence is not decisive. I shall state the matter in a
+somewhat different way from his in order more easily to exhibit all the
+consequences.
+
+Suppose S to be the position of the sun, E A part of the orbit of the
+earth, S E M a straight line intersecting in M, the orbit of the moon,
+represented by the circle A M.
+
+Now if light requires time--say an hour--to move the distance between
+the earth and the moon, then [at the time of an eclipse] it follows
+that when the earth has come to E its shadow, or the stoppage of the
+light of the sun, will not yet have reached M [the moon], and will
+not for an hour. Counting from the instant the earth reaches E, it
+will be an hour before it will reach M if it is to be obscured there.
+This eclipse will not be seen from the earth for yet another hour.
+Suppose that during these two hours the earth has moved to X, the moon
+appearing eclipsed at M, the sun still being seen at S. For I assume as
+does Copernicus that the sun is fixed and since light moves in straight
+lines, is always seen in its true position.
+
+But as a matter of fact, we are assured that the eclipsed moon always
+appears directly opposite the sun; while on the above supposition [that
+light takes an hour in passing between the moon and the earth], its
+position ought to be back of the straight line by the angle Y X M, the
+supplement of the angle S X M. But this is not the case, for this angle
+Y X M would be very easily noticed, it being about 33 degrees. For by
+our analysis (found in the essay on the causes of the phenomena of
+Saturn), the distance from the sun to the earth, S E, is about 12,000
+times the diameter of the earth, and hence 400 times the distance of
+the moon, which is 30 diameters. The angle X M E then will be nearly
+400 times as great as E S X, which is 5 minutes, i. e., the angular
+distance travelled by the earth in two hours [the earth traversing
+almost a degree in a day]. Thus the angle E M X is almost 33 degrees,
+and likewise the angle M X Y, being 5 minutes greater [than E M X].
+
+Now it must be remembered that in this computation it is assumed that
+the speed of light is such as to consume an hour in passing from here
+to the moon. But if we assume it to take only a minute of time, then
+the angle Y X M would amount to only 33 minutes, and if it only takes
+ten seconds, this angle will be less than six minutes. Now so small
+an angle is not observable in a lunar eclipse and hence it is not
+permissible to argue that light is absolutely instantaneous.
+
+It is rather unusual, we admit, to take for granted a speed 100,000
+times as great as that of sound, which (following my experiments)
+travels about 180 toises [about 1150 feet] in a second, or during a
+pulse-beat. Yet this supposition is not at all impossible, for it is
+not necessary to carry a body at such speed but only for motion to
+traverse successively from one point to another.
+
+Hence I do not hesitate in this matter to assume that the passage
+of light takes time, for on this assumption all phenomena can be
+explained, while on the contrary supposition none of them can be
+explained. In fact, it seems to me and to many others as well, that
+M. Descartes, whose purpose has been to discuss all physical matters
+clearly, and who has certainly succeeded in this better than any one
+before him, has written nothing on light and its qualities that is not
+either hard to understand or even incomprehensible.
+
+Moreover, this idea that I have propounded as an hypothesis has lately
+been made a well nigh established fact by that keen calculation of
+Roemer, whose method I will here take occasion to describe, on the
+expectation that he will himself in the future fully confirm this
+theory.
+
+His method, the same as the one we have just discussed, is
+astronomical. He shows not only that light takes time for its passage,
+but calculates also its speed and that this must be at least six times
+as much as the rate I have just given as an estimate.
+
+In his demonstration he uses the eclipses of the small satellites that
+revolve around Jupiter, and very frequently pass into his shadow.
+Roemer’s reasoning is this:
+
+Let S be the sun, B C D E the yearly orbit of the earth, J Jupiter and
+G H the orbit of his nearest satellite, for this one because of its
+short period is better suited to this investigation than any one of the
+other three. Suppose G to be the point where the satellite enters, and
+H where it leaves, Jupiter’s shadow.
+
+Suppose that when the earth is at B, the satellite is seen to emerge
+[at G], at some time before the last quarter. Were the earth to remain
+stationary there, 42-1/2 hours would elapse before the next emergence
+would take place, for this much time is taken by the satellite in
+making one revolution in its orbit and returning to opposition to the
+sun. For example, if the earth remained at B during 30 revolutions,
+then after 30 times 42-1/2 hours, the satellite would again be seen
+to emerge. If in the meantime the earth has moved to C, farther from
+Jupiter, it is clear that if light requires time for its passage, the
+emergence of the satellite will be seen later when the earth is at C
+than when at B. For we must add to the 30 times 42-1/2 hours, the time
+occupied by light in passing over the difference between the distances
+[of the earth from Jupiter] G B and G C, i. e., M C. So in the other
+quarter, when the earth travels from D to E, approaching Jupiter, the
+eclipses will occur earlier when the earth is at E than when at D.
+
+Now by many observations of these eclipses throughout ten years, it is
+shown that these inequalities are actually of some moment, amounting to
+as much as ten minutes or more: whence it is argued that in traversing
+the whole diameter of the earth’s orbit, K L, double the distance from
+the earth to the sun, light takes about 22 minutes.
+
+The motion of Jupiter in its orbit while the earth passes from B
+to C or from D to E has been taken into consideration in Roemer’s
+calculation, where it is also proved that these inequalities cannot
+be caused by any irregularity or eccentricity in the movement of the
+satellite.
+
+Now if we consider the enormous size of this diameter K L [the earth’s
+orbit] which I have estimated to be about 24,000 times that of the
+earth, we get some comprehension of the extraordinary speed of light.
+
+Even if K L were only 22,000 diameters of the earth, a speed traversing
+this distance in 22 minutes would be equal to the rate of a thousand
+diameters a minute, i. e., 16 2-3 diameters a second (or a pulse-beat)
+which makes more than 1,100 times 100,000 toises, since one diameter of
+the earth equals 2,865 leagues, of which there are 25 to the degree,
+and since in accordance with the very precise calculation made by M.
+Picard in 1609 under orders from the king, each league contains 2,282
+toises.
+
+As I stated before sound moves only 180 toises per second. Hence
+the speed of light is over 600,000 times as great as that of sound,
+which, however, is very different from being instantaneous,--it is the
+difference between any finite number and infinity. The theory that
+light movements are propagated from point to point in time being thus
+demonstrated, it follows that light moves in spherical waves, as does
+sound.
+
+But if they are alike in this regard, they are unlike in others, as
+in the original cause of the motion that transmits them, the medium
+through which they move, and the manner in which they are transmitted
+in it.
+
+We know that sound is caused by the rapid vibration of some body
+(either as a whole or in part), this vibration setting in motion the
+adjoining air. But light movements must arise at every point of the
+luminous body, otherwise all the various parts of the body would not be
+visible. This fact will be clearer from what follows.
+
+In my judgment, this movement of light-giving bodies cannot be more
+satisfactorily explained than by supposing that those that are fluid,
+e. g., a flame, and probably the sun and stars, consist of particles
+that float about in a much rarer medium, that sets them in violent
+motion, causing them to strike against the still more minute particles
+of the surrounding ether. In the case of light-giving solids such as
+red-hot metal or carbon we may suppose this movement to be caused by
+the rapid motions of the metal or wood, the particles on the surface
+exciting the ether. Hence the vibration producing light must be much
+shorter and faster than that causing sound, since we do not find that
+sound disturbances give rise to light any more than the wave of the
+hand through the air causes sound.
+
+The next question is in regard to the nature of the medium through
+which the vibration produced by light-giving bodies moves. I have
+named it _ether_, but it plainly differs from the medium through
+which sound moves. The latter is simply the air we feel and breathe,
+and when it is removed from any space, the medium which carries light
+still remains. This is shown by surrounding the sounding body in a
+glass vessel, and exhausting the air by means of the air-pump that Mr.
+Boyle has devised, and with which he has performed so many striking
+experiments. In trying this experiment, however, it is best to set the
+sounder on cotton or feathers so that it cannot communicate vibrations
+to the glass receiver or the air-pump, a point hitherto neglected.
+Then, when all the air has been exhausted, one catches no sound from
+the metal when it is struck.
+
+Hence we conclude not only that our atmosphere which cannot penetrate
+glass is the medium through which sound acts, but that the medium
+carrying light-vibrations is something different: for after the vessel
+is exhausted of air, light passes through it as easily as before.
+
+The last point is proven even more conclusively by the famous
+experiment of Torricelli. [Fill a long closed glass tube with mercury,
+then invert it.] The top of the glass tube not filled by the mercury
+contains a high vacuum, but transmits light as well as when filled
+with air. This demonstrates that there is within the tube some form
+of matter different from air, and which penetrates either glass or
+mercury, or both, though both are impenetrable to air. And if a like
+experiment is tried with a little water on top of the mercury, it
+becomes equally clear that the substance in question traverses either
+glass or water or both.
+
+In regard to the different methods of transmission of sound and light,
+in the case of sound it is easy to see what happens when one remembers
+that air can be compressed and reduced to a much smaller volume than
+usual, and that it tends with the same force to expand to its original
+volume. This quality, considered along with its penetrability retained
+in spite of such condensation seems to show that it consists of small
+particles that float about in rapid vibration in an ether consisting
+of still more minute particles. Sound, then, is caused by the struggle
+of these particles to escape when at any point in the course of a wave
+they are more crowded together than at some other point.
+
+Now the wonderful speed of light considered with its other qualities,
+does not permit us to believe it to be transmitted in the same manner.
+Therefore I shall try to explain the way in which I think it must
+take place. I must first, however, describe that quality of hard
+substances through which they transmit motion one to another. If one
+take a number of balls of the same size of any hard substance, and
+place them touching one another in one line, he will find that on
+letting a ball of the same size strike against one end of the line,
+the motion is transmitted in an instant to the other end of the line.
+The last ball is driven from the line while the others are apparently
+undisturbed, the ball that struck the line coming to a dead stop.
+This is an illustration of a transmission of motion at great speed,
+varying directly as the hardness of the balls. Yet it is certain that
+this transmission is not instantaneous, but requires time. For if the
+movement, or if you wish, the tendency to move, did not pass from one
+ball to another in succession, they would all be set in motion at the
+same instant and would all move forward at the same time. Now this is
+so far from the case that only the last one leaves the row, and it has
+the speed of the ball that first struck the line.
+
+There are other experiments, also demonstrating that all bodies, even
+those thought hardest, such as steel, glass and agate, are really
+elastic, and bend a little, no matter whether they are in rods, balls,
+or bodies of any other shape,--that is, they give slightly at the
+point where struck, and at once regain their former shape. Thus I have
+discovered that in letting a glass or agate ball strike on a large,
+thick, flat piece of the same substance the surface of which has been
+roughened by the breath, the place where it strikes is shown by a
+circular indentation that varies in size directly as the force of the
+blow. This indicates that the materials give when struck and then fly
+back,--an event that necessarily takes time.
+
+Now to apply such a motion to the explanation of light, there is
+nothing in the way of our imagining the particles of ether to have
+an almost complete hardness, and an elasticity as perfect as we need
+wish. We need not here discuss the cause of either this hardness or
+elasticity, as this would lead us too far from the question at issue.
+I will remark, however, by the way, that these particles of ether,
+in spite of their minuteness, are also composed of parts and that
+their elasticity depends on a very rapid motion of a subtle substance
+traversing them in all directions and making them take a structure
+that offers a ready passage to this fluid. This agrees with the idea
+of M. Descartes, except that I would not, like him, give the pores the
+shape of round, hollow canals. This is so far from being at all absurd
+or incomprehensible that it is easily credible that nature uses an
+infinite series of different-sized molecules in order to produce her
+marvelous effects.
+
+Moreover, although we do not know the cause of elasticity, we cannot
+have failed to notice that most bodies possess this characteristic;
+hence it is not unreasonable to suppose that it is a quality of the
+minute, invisible particles of the ether. And it is a fact that if one
+looks for some other method of accounting for the gradual transmission
+of light, he will have a hard time finding any supposition better
+suited than elasticity to explain the fact of uniform speed. This
+[uniform speed] seems to be a necessary assumption, for if the motion
+slowed down when distributed over a great mass of matter at a far
+distance from its source, then this great speed would at last be lost.
+On the other hand, we suppose ether to have the property of elasticity
+so that its particles regain their shape with equal activity whether
+struck a hard or gentle blow. Thus the rate at which light would move
+would remain constant.
+
+
+FOOTNOTES:
+
+[Footnote 9: Translated from _Traité de la Lumière_.]
+
+
+
+
+ VIII
+
+ ANTHONY VAN LEEUWENHOECK
+
+ 1632-1723
+
+
+ _Born in Delft, Holland, October 24, 1632, Anthony Van Leeuwenhoeck,
+ a lens-maker for microscopes, made several important biological
+ discoveries. In 1673 he noticed the red globules in the blood; in
+ 1675 he discovered animalculæ in water; in 1677 he described the
+ spermatozoa; in 1690 he traced the passage of blood from the arteries
+ into the veins. Among his other achievements were his investigations
+ of the tubules of teeth, the solidity of hair, the structure of the
+ epidermis, and his descriptions of insect anatomies. He announced most
+ of his findings to the Royal Society of London. Against the generally
+ accepted idea of spontaneous generation, he held that all things
+ generated their kind. He died at Delft, August 26, 1723._
+
+
+ OBSERVATIONS ON ANIMALCULÆ[10]
+
+In the year 1675, I discovered very small living creatures in rain
+water, which had stood but few days in a new earthen pot glazed blue
+within. This invited me to view this water with great attention,
+especially those little animals appearing to me ten thousand times less
+than those represented by M. Swammerdam, and by him called water-fleas,
+or water-lice, which may be perceived in the water with the naked eye.
+
+The first sort I several times observed to consist of 5, 6, 7, or 8
+clear globules without being able to discern any film that held them
+together, or contained them. When these animalcula or living atoms
+moved, they put forth two little horns, continually moving. The space
+between these two horns was flat, though the rest of the body was
+roundish, sharpening a little towards the end, where they had a tail,
+near four times the length of the whole body, of the thickness, by my
+microscope, of a spider’s web; at the end of which appeared a globule
+of the size of one of those which made up the body. These little
+creatures, if they chanced to light on the least filament or string,
+or other particle, were entangled therein, extending their body in a
+long round, and endeavoring to disentangle their tail. Their motion of
+extension and contraction continued a while; and I have seen several
+thousands of these poor little creatures, within the space of a grain
+of gross sand, lie fast clustered together in a few filaments.
+
+I also discovered a second sort, of an oval figure; and I imagined
+their head to stand on a sharp end. These were a little longer than
+the former. The inferior part of their body is flat, furnished with
+several extremely thin feet, which moved very nimbly. The upper part of
+the body was round, and had within 8, 10, or 12 globules, where they
+were very clear. These little animals sometimes changed their figure
+into a perfect round, especially when they came to lie on a dry place.
+Their body was also very flexible; for as soon as they struck against
+the smallest fibre or string, their body was bent in, which bending
+presently jerked out again. When I put any of them on a dry place, I
+observed that, changing themselves into a round, their body was raised
+pyramidal-wise, with an extant point in the middle; and having laid
+thus a little while, with a motion of their feet, they burst asunder,
+and the globules were presently diffused and dissipated, so that I
+could not discern the least thing of any film, in which the globules
+had doubtless been enclosed; and at this time of their bursting
+asunder, I was able to discover more globules than when they were alive.
+
+I observed a third sort of little animals, that were twice as long as
+broad, and to my eye eight times smaller than the first. Yet I thought
+I discerned little feet, whereby they moved very briskly, both in round
+and straight line.
+
+There was a fourth sort, which were so small that I was not able to
+give them any figure at all. These were a thousand times smaller than
+the eye of a large louse. These exceeded all the former in celerity. I
+have often observed them to stand still as it were on a point, and then
+turn themselves about with that swiftness, as we see a top turn round,
+the circumference they made being no larger than that of a grain of
+small sand, and then extending themselves straight forward, and by and
+by lying in a bending posture. I discovered also several other sorts
+of animals; these were generally made up of such soft parts, as the
+former, that they burst asunder as soon as they came to want water.
+
+May 26, it rained hard; the rain growing less, I caused some of that
+rain-water running down from the house top, to be gathered in a clean
+glass, after it had been washed two or three times with water. And in
+this I observed some few very small living creatures, and seeing them,
+I thought they might have been produced in the leaded gutters in some
+water that had remained there before.
+
+I perceived in pure water, after some days, more of those animals, as
+also some that were somewhat larger. And I imagine, that many thousands
+of these little creatures do not equal an ordinary grain of sand in
+bulk; and comparing them with a cheese-mite, which may be seen to
+move with the naked eye, I make the proportion of one of these small
+water-creatures to a cheese-mite to be like that of a bee to a horse;
+for, the circumference of one of these little animals in water is not
+so large as the thickness of a hair in a cheese-mite.
+
+In another quantity of rain-water, exposed for some days to the air,
+I observed some thousands of them in a drop of water, which were of
+the smallest sort that I had seen hitherto. And in some time after I
+observed, besides the animals already noted, a sort of creatures that
+were eight times as large, of almost a round figure; and as those very
+small animalcula swam gently among each other, moving as gnats do in
+the air, so did these larger ones move far more swiftly, tumbling round
+as it were, and then making a sudden downfall.
+
+In the waters of the river Maese I saw very small creatures of
+different kinds and colours, and so small, that I could very hardly
+discern their figures; but the number of them was far less than those
+found in rain-water. In the water of a very cold well in the autumn, I
+discovered a very great number of living animals very small, that were
+exceedingly clear, and a little larger than the smallest I ever saw.
+In sea-water I observed at first, a little blackish animal, looking as
+if it had been made up of two globules. This creature had a peculiar
+motion, resembling the skipping of a flea on white paper, so that it
+might very well be called a water-flea; but it was far less than the
+eye of that little animal, which Dr. Swammerdam calls the water-flea. I
+also discovered little creatures therein that were clear, of the same
+size with the former animal, but of an oval figure, having a serpentine
+motion. I further noticed a third sort, which were very slow in their
+motion; their body was of a mouse colour, clear toward the oval point;
+and before the head and behind the body there stood out a sharp little
+point angle-wise. This sort was a little larger. But there was yet a
+fourth somewhat longer than oval. Yet of all these sorts there were
+but a few of each. Some days after viewing this water, I saw 100 where
+before I had seen but one; but these were of another figure, and not
+only less, but they were also very clear, and of an oblong oval figure,
+only with this difference, that their heads ended sharper; and although
+they were a thousand times smaller than a small grain of sand, yet when
+they lay out of the water in a dry place, they burst in pieces and
+spread into three or four very little globules, and into some aqueous
+matter, without any other parts appearing in them.
+
+Having put about one-third of an ounce of whole pepper in water, and
+it having lain about three weeks in the water, to which I had twice
+added some snow-water, the other water being in great part exhaled;
+I discerned in it with great surprise an incredible number of little
+animals, of divers kinds, and among the rest, some that were three
+or four times as long as broad; but their whole thickness did not
+much exceed the hair of a louse. They had a very pretty motion, often
+tumbling about and sideways; and when the water was let to run off from
+them, they turned round like a top; at first their body changed into an
+oval, and afterwards, when the circular motion ceased, they returned to
+their former length. The second sort of creatures discovered in this
+water, were of a perfect oval figure, and they had no less pleasing or
+nimble a motion than the former; and these were in far greater numbers.
+There was a third sort, which exceeded the two former in number, and
+these had tails like those I had formerly observed in rain-water.
+The fourth sort, which moved through the three former sorts, were
+incredibly small, so that I judged, that if 100 of them lay one by
+another, they would not equal the length of a grain of coarse sand;
+and according to this estimate, 1,000,000 of them could not equal the
+dimensions of a grain of such coarse sand. There was discovered a fifth
+sort, which had near the thickness of the former, but almost twice the
+length.
+
+In snow-water, which had been about three years in a glass bottle
+well stopped, I could discover no living creatures; and having poured
+some of it into a porcelain tea-cup, and put therein half an ounce of
+whole pepper, after some days I observed some animalcula, and those
+exceedingly small ones, whose body seemed to me twice as long as broad,
+but they moved very slowly, and often circularly. I observed also a
+vast multitude of oval-figured animalcula, to the number of 8,000 in a
+single drop.
+
+
+FOOTNOTES:
+
+[Footnote 10: From the _Transactions of the Royal Society of
+London_.]
+
+
+
+
+ IX
+
+ SIR ISAAC NEWTON
+
+ 1642-1727
+
+
+ _Sir Isaac Newton, whose researches in light, gravitation, and
+ mathematics are outstanding in the history of modern science, was born
+ in Woolsthorpe, Lincolnshire, December 25, 1642. He was the son of an
+ English farmer who died before Newton was born. His early education
+ was interrupted by his mother’s poverty, but his ingenuity in making
+ mechanical toys soon provided a means whereby he was enabled to return
+ to school. He entered Cambridge University in 1661 and took his degree
+ in 1665; two years later he was made a fellow of the university, and
+ in 1669 became professor of mathematics._
+
+ _In 1665 he discovered his method of fluxions, not greatly unlike
+ Leibnitz’s Differential Calculus. In 1672 he was elected a fellow of
+ the Royal Society and shortly afterwards sent them a paper describing
+ how he had broken up light by means of a prism, demonstrating by that
+ means the compound nature of the sun’s rays._
+
+ _In 1687 elaborated his theory of gravitation in “Philosophiæ
+ Naturalis Principia Mathematica.” This was the result of his
+ reflections and researches dating from 1666, when he attempted to
+ explain the moon’s motion by the hypothesis of the assumed influence
+ of gravitation. In the meantime, through the use of telescopic
+ instruments, French geographers had tested the spherical shape of the
+ earth and had made a new and more accurate triangulation. Using the
+ data which they supplied, Newton perceived that these data agreed
+ with his theory that the force varied inversely as the square of the
+ distance. Overcome with the emotion incident to the solution of a
+ great problem, he begged a friend to complete his calculations, with
+ the result that the new astronomy begun by Copernicus, and continued
+ by Brahe, Kepler, and Galileo, was formulated and mathematically
+ interpreted by a single mechanical principle._
+
+ _Although he later made some chemical investigations, his papers
+ were accidentally destroyed, and it is said that he never recovered
+ from the shock of losing them. In 1695 he was made warden, and in 1699
+ promoted to the mastership of the mint, which office he retained at a
+ munificent salary until his death on March 20, 1727._
+
+
+ THE THEORY OF GRAVITATION[11]
+
+ BOOK III. PROPOSITION V. THEOREM V. SCHOLIUM
+
+The force which retains the celestial bodies in their orbits has been
+hitherto called centripetal force; but it being now made plain that it
+can be no other than a gravitating force, we shall hereafter call it
+gravity. For the cause of that centripetal force which retains the moon
+in its orbit will extend itself to all the planets.
+
+
+ BOOK III. PROPOSITION VI. THEOREM VI.
+
+_That all bodies gravitate towards every planet; and that the weights
+of bodies towards any the same planet, at equal distances from the
+centre of the planet, are proportional to the quantities of matter
+which they severally contain._
+
+It has been, now of a long time, observed by others, that all sorts of
+heavy bodies (allowance being made for the inequality of retardation
+which they suffer from a small power of resistance in the air) descend
+to the earth _from equal heights_ in equal times; and that
+equality of times we may distinguish to a great accuracy, by the help
+of pendulums. I tried the things in gold, silver, lead, glass, sand,
+common salt, wood, water, and wheat. I provided two wooden boxes,
+round and equal; I filled the one with wood, and suspended an equal
+weight of gold (as exactly as I could) in the centre of oscillation
+of the other. The boxes hanging by equal threads of 11 feet made a
+couple of pendulums perfectly equal in weight and figure, and equally
+receiving the resistance of the air. And, placing the one by the
+other, I observed them to play together forwards and backwards, for
+a long time, with equal vibrations ... and the like happened in the
+other bodies. By these experiments, in bodies of the same weight, I
+could manifestly have discovered a difference of matter less than
+the thousandth part of the whole, had any such been. But, without
+all doubt, the nature of gravity towards the planets is the same
+as towards the earth.... Moreover, since the satellites of Jupiter
+perform their revolutions in times which observe the sesquiplicate
+proportion of their distances from Jupiter’s centre--that is, equal
+at equal distances. And, therefore, these satellites, if supposed
+to fall _towards Jupiter_ from equal heights, would describe
+equal spaces in equal times, in like manner as heavy bodies do on
+our earth.... If, at equal distances from the sun, any satellite, in
+proportion to the quantity of its matter, did gravitate towards the
+sun with a force greater than Jupiter in proportion to his, according
+to any given proportion, suppose of _d_ to _e_; then the
+distance between the centres of the sun and of the satellite’s orbit
+would be always greater than the distance between the centres of the
+sun and of Jupiter nearly in the sub-duplicate of that proportion; as
+by some computations I have found. And if the satellite did gravitate
+towards the sun with a force, lesser in the proportion of _e_ to
+_d_, the distance of the centre of the satellite’s orbit from
+the sun would be less than the distance of the centre of Jupiter from
+the sun in the sub-duplicate of the same proportion. Therefore if, at
+equal distances from the sun, the accelerative gravity of any satellite
+towards the sun were greater or less than the accelerative gravity of
+Jupiter towards the sun but one 1-1000 part of the whole gravity, the
+distance of the centre of the satellite’s orbit from the sun would be
+greater or less than the distance of Jupiter from the sun by one 1-2000
+part of the whole distance--that is, by a fifth part of the distance
+of the utmost satellite from the centre of Jupiter; an eccentricity of
+the orbit which would be very sensible. But the orbits of the satellite
+are concentric to Jupiter, and therefore the accelerative gravities of
+Jupiter, and of all its satellites towards the sun, are equal among
+themselves....
+
+But further; the weights of all the parts of every planet towards
+any other planet are one to another as the matter in the several
+parts; for if some parts did gravitate more, others less, than for
+the quantity of their matter, then the whole planet, according to the
+sort of parts with which it most abounds, would gravitate more or less
+than in proportion to the quantity of matter in the whole. Nor is it
+of any moment whether these parts are external or internal; for if,
+for example, we should imagine the terrestrial bodies with us to be
+raised up to the orb of the moon, to be there compared with its body;
+if the weights of such bodies were to the weights of the external parts
+of the moon as the quantities of matter in the one and in the other
+respectively; but to the weights of the internal parts in a greater or
+less proportion, then likewise the weights of those bodies would be to
+the weight of the whole moon in a greater or less proportion; against
+what we have showed above.
+
+Cor. 1. Hence the weights of bodies do not depend upon their forms and
+textures; for if the weights could be altered with the forms, they
+would be greater or less, according to the variety of forms in equal
+matter; altogether against experience.
+
+Cor. 2. Universally, all bodies about the earth gravitate towards the
+earth; and the weights of all, at equal distances from the earth’s
+centre, are as the quantities of matter which they severally contain.
+This is the quality of all bodies within the reach of our experiments;
+and therefore (by rule 3) to be affirmed of all bodies whatsoever....
+
+Cor. 5. The power of gravity is of a different nature from the power of
+magnetism; for the magnetic attraction is not as the matter attracted.
+Some bodies are attracted more by the magnet; others less; most bodies
+not at all. The power of magnetism in one and the same body may be
+increased and diminished; and is sometimes far stronger, for the
+quantity of matter, than the power of gravity; and in receding from
+the magnet decreases not in the duplicate but almost in the triplicate
+proportion of the distance, as nearly as I could judge from some rude
+observations.
+
+
+ BOOK III. PROPOSITION VII. THEOREM VII.
+
+_That there is a power of gravity tending to all bodies, proportional
+to the several quantities of matter which they contain._
+
+That all the planets mutually gravitate one towards another, we have
+proved before; as well as that the force of gravity towards every
+one of them, considered apart, is reciprocally as the square of the
+distance of places from the centre of the planet. And thence (by prop.
+69, book I, and its corollaries) it follows, that the gravity tending
+towards all the planets is proportional to the matter which they
+contain.
+
+Moreover, since all the parts of any planet A gravitate towards any
+other planet B; and the gravity of every part is to the gravity of the
+whole as the matter of the part to the matter of the whole; and (by law
+3) to every action corresponds an equal reaction; therefore the planet
+B will, on the other hand, gravitate towards all the parts of the
+planet A; and its gravity towards any one part will be to the gravity
+towards the whole as the matter of the part to the matter of the whole.
+Q. E. D.
+
+Cor. 1. Therefore the force of gravity towards any whole planet arises
+from, and is compounded of, the forces of gravity towards all its
+parts. Magnetic and electric attractions afford us examples of this;
+for all attraction towards the whole arises from the attractions
+towards the several parts. The thing may be easily understood in
+gravity, if we consider a greater planet as formed of a number of
+lesser planets meeting together in one globe, for _hence it would
+appear_ that the force of the whole must arise from the forces of
+the component parts. If it is objected that, according to this law, all
+bodies with us must mutually gravitate one towards another, I answer,
+that since the gravitation towards these bodies is to the gravitation
+towards the whole earth as these bodies are to the whole earth, the
+gravitation towards them must be far less than to fall under the
+observation of our senses.
+
+Cor. 2. The force of gravity towards the several particles of any body
+is reciprocally as the square of the distance from the particles; as
+appears from cor. 3, prop. 74, book I.
+
+
+FOOTNOTES:
+
+[Footnote 11: Translated from the _Philosophiæ Naturalis Principia
+Mathematica_.]
+
+
+
+
+ X
+
+ BENJAMIN FRANKLIN
+
+ 1706-1790
+
+
+ _Benjamin Franklin, representative of the rationalist tendencies
+ of the eighteenth century, was born in Boston, January 17, 1706.
+ His early life and political missions are intimately related in his
+ “Autobiography,” a classic in American literature. Apart from his
+ political services to the cause of American independence, he attained
+ distinction in the field of scientific researches and experiments. In
+ 1746 he began the experiments in electricity which resulted in his
+ identification of electricity with lightning. He died in Philadelphia,
+ April 17, 1790._
+
+
+ THE IDENTITY OF LIGHTNING AND ELECTRICITY[12]
+
+But points have a property, by which they draw on as well as throw
+off the electrical fluid, at greater distances than blunt bodies can.
+That is, as the pointed part of an electrified body will discharge the
+atmosphere of that body, or communicate it farthest to another body,
+so the point of an unelectrified body will draw off the electrical
+atmosphere from an electrified body, farther than a blunter part of
+the same unelectrified body will do. Thus, a pin held by the head,
+and the point presented to an electrified body, will draw off its
+atmosphere at a foot distance; where, if the head were presented
+instead of the point, no such effect would follow. To understand
+this, we may consider, that, if a person standing on the floor would
+draw off the electrical atmosphere from an electrified body, an iron
+crow and a blunt knitting-needle, held alternately in his hand, and
+presented for that purpose, do not draw with different forces in
+proportion to their different masses. For the man, and what he holds in
+his hand, be it large or small, are connected with the common mass of
+unelectrified matter; and the force with which he draws is the same in
+both cases, it consisting in the different proportion of electricity
+in the electrified body, and that common mass. But the force, with
+which the electrified body retains its atmosphere by attracting it, is
+proportioned to the surface over which the particles are placed; that
+is, four square inches of that surface retain their atmosphere with
+four times the force that one square inch retains its atmosphere. And,
+as in plucking the hairs from the horse’s tail, a degree of strength
+not sufficient to pull away a handful at once, could yet easily strip
+it hair by hair, so a blunt body presented cannot draw off a number of
+particles at once, but a pointed one, with no greater force, takes them
+away easily, particle by particle.
+
+These explanations of the power and operation of points, when they
+first occurred to me, and while they first floated in my mind, appeared
+perfectly satisfactory; but now I have written them, and considered
+them more closely, I must own I have some doubts about them; yet, as I
+have at present nothing better to offer in their stead, I do not cross
+them out; for, even a bad solution read, and its faults discovered, has
+often given rise to a good one, in the mind of an ingenious reader.
+
+Nor is it of much importance to us to know the manner in which nature
+executes her laws; it is enough if we know the laws themselves. It is
+of real use to know that China left in the air unsupported, will fall
+and break; but how it comes to fall, and why it breaks, are matters of
+speculation. It is a pleasure indeed to know them, but we can preserve
+our China without it.
+
+Thus, in the present case, to know this power of points may possibly
+be of some use to mankind, though we should never be able to explain
+it. The following experiments, as well as those in my first paper, show
+this power. I have a large prime conductor, made of several thin sheets
+of clothier’s pasteboard, formed into a tube, near ten feet long and a
+foot diameter. It is covered with Dutch embossed paper, almost totally
+gilt. This large metallic surface supports a much greater electrical
+atmosphere than a rod of iron of fifty times the weight would do. It
+is suspended by silk lines, and when charged will strike, at near two
+inches distance, a pretty hard stroke, so as to make one’s knuckles
+ache. Let a person standing on the floor present the point of a needle,
+at twelve or more inches distance from it, and while the needle is
+so presented, the conductor cannot be charged, the point drawing off
+the fire as fast as it is thrown on by the electrical globe. Let it
+be charged, and then present the point at the same distance, and it
+will suddenly be discharged. In the dark you may see the light on the
+point, when the experiment is made. And if the person holding the point
+stands upon wax, he will be electrified by receiving the fire at that
+distance. Attempt to draw off the electricity with a blunt body, as
+a bolt of iron round at the end, and smooth, (a silversmith’s iron
+punch, inch thick, is what I use,) and you must bring it within the
+distance of three inches before you can do it, and then it is done
+with a stroke and crack. As the pasteboard tube hangs loose on silk
+lines, when you approach it with the punch-iron, it likewise will move
+towards the punch, being attracted while it is charged, but if, at the
+same instant, a point be presented as before, it retires again, for the
+point discharges it. Take a pair of large brass scales, of two or more
+feet beam, the cords of the scales being silk. Suspend the beam by a
+pack-thread from the ceiling, so that the bottom of the scales may be
+about a foot from the floor; the scales will move round in a circle
+by the untwisting of the pack-thread. Set the iron punch on the end
+upon the floor, in such a place as that the scales may pass over it
+in making their circle; then electrify one scale by applying the wire
+of a charged phial to it. As they move round, you see that scale draw
+nigher to the floor, and dip more when it comes over the punch; and, if
+that be placed at a proper distance, the scale will snap and discharge
+its fire into it. But, if a needle be stuck on the end of the punch,
+its point upward, the scale, instead of drawing nigh to the punch, and
+snapping, discharges its fire silently through the point, and rises
+higher from the punch. Nay, even if the needle be placed upon the floor
+near the punch, its point upward, the end of the punch, though so much
+higher than the needle, will not attract the scale and receive its
+fire, for the needle will get it and convey it away, before it comes
+nigh enough for the punch to act. And this is constantly observable
+in these experiments, that the greater quantity of electricity on the
+pasteboard tube, the farther it strikes or discharges its fire, and the
+point likewise will draw it off at a still greater distance.
+
+Now if the fire of electricity and that of lightning be the same,
+as I have endeavoured to show at large in a former paper, this
+pasteboard tube and these scales may represent electrified clouds. If
+a tube of only ten feet long will strike and discharge its fire on
+the punch at two or three inches distance, an electrified cloud of
+perhaps ten thousand acres may strike and discharge on the earth at a
+proportionately greater distance. The horizontal motion of the scales
+over the floor, may represent the motion of the clouds over the earth;
+and the erect iron punch, a hill or high building; and then we see how
+electrified clouds, passing over hills or high buildings at too great
+a height to strike, may be attracted lower till within their striking
+distance, And, lastly, if a needle fixed on the punch with its point
+upright, or even on the floor below the punch, will draw the fire from
+the scale silently at a much greater than the striking distance, and so
+prevent its descending towards the punch; or if in its course it would
+have come nigh enough to strike, yet being first deprived of its fire
+it cannot, and the punch is thereby secured from the stroke; I say, if
+these things are so, may not the knowledge of this power of points be
+of use to mankind, in preserving houses, churches, ships, &c., from
+the stroke of lightning, by directing us to fix, on the highest parts
+of those edifices, upright rods of iron made sharp as a needle, and
+gilt to prevent rusting, and from the foot of those rods a wire down
+the outside of the building into the ground, or down round one of the
+shrouds of a ship, and down her side till it reaches the water? Would
+not these pointed rods probably draw the electrical fire silently out
+of a cloud before it came nigh enough to strike, and thereby secure us
+from that most sudden and terrible mischief?
+
+To determine the question, whether the clouds that contain lightning
+are electrified or not, I would propose an experiment to be tried where
+it may be done conveniently. On the top of some high tower or steeple,
+place a kind of sentry-box, ... big enough to contain a man and an
+electrical stand. From the middle of the stand let an iron rod rise
+and pass bending out of the door, and then upright twenty or thirty
+feet, pointed very sharp at the end. If the electrical stand be kept
+clean and dry, a man standing on it, when such clouds are passing low,
+might be electrified and afford sparks, the rod drawing fire to him
+from a cloud. If any danger to the man should be apprehended (though I
+think there would be none), let him stand on the floor of his box, and
+now and then bring near to the rod the loop of wire that has one end
+fastened to the leads, he holding it by a wax handle, so the sparks, if
+the rod is electrified, will strike from the rod to the wire, and not
+affect him.
+
+
+FOOTNOTES:
+
+[Footnote 12: From Franklin’s correspondence with Peter Collinson, July
+29, 1750. _Works of Benjamin Franklin_, Philadelphia, 1809, Vol.
+III, pp. 45-49.]
+
+
+
+
+ XI
+
+ LINNAEUS
+
+ 1707-1778
+
+
+ _Carl von Linné [Linnaeus] was born May 13, 1707, at Rashult in
+ Smaland, Sweden. At the age of four he showed a precocious interest
+ in plants, an interest which seriously interfered with his studies
+ when he went to school. When his father was about to remove him, a
+ friend urged that the boy be fitted for the profession of medicine.
+ Linnaeus entered the university at Lund in 1727, but in the following
+ year transferred to Upsala. In 1732, at the expense of the Academy
+ of Sciences, he explored Lapland. Later he made pilgrimages to many
+ of the most eminent professors of Europe, returning to Stockholm in
+ 1738. After his marriage, in 1739, he was appointed professor at
+ Upsala, where he continued his work in botany and established it on a
+ rational basis. He died January 10, 1778, noted as one of the foremost
+ botanists of his time, having discovered sex in plants and given his
+ name to a famous botanical system of classification._
+
+
+ THE SEX OF PLANTS[13]
+
+The organs common in general to all plants are: 1st. The root, with its
+capillary vessels, extracting nourishment from the ground. 2nd. The
+leaves, which may be called the limbs, and which, like the feet and
+wings of animals, are organs of motion; for being themselves shaken by
+the external air, they shake and exercise the plant. 3rd. The trunk,
+containing the medullary substance, which is nourished by the bark, and
+for the most part multiplied into several compound plants. 4th. The
+fructification, which is the true body of the plant, set at liberty by
+a metamorphosis, and consists only of the organs of generation; it is
+often defended by a calyx, and furnished with petals, by means of which
+it in a manner flutters in the air.
+
+Many flowers have no calyx, as several of the lily tribe, the
+Hippuris, etc., many want the corolla, as grasses, and the plants
+called apetalous; but there are none more destitute of stamina and
+pistilla, those important organs destined to the formation of fruit.
+We therefore infer from experience that the stamina are the male
+organs of generation, and the pistilla of the female; and as many
+flowers are furnished with both at once, it follows that such flowers
+are hermaphrodites. Nor is this so wonderful, as that there should be
+any plants in which the different sexes are distinct individuals; for
+plants being immovably fixed to one spot, cannot like animals, travel
+in search of a mate. There exists, however, in some plants a real
+difference of sex. From seeds of the same mother, some individuals
+shall be produced, whose flowers exhibit stamina without pistilla, and
+may therefore properly be called male; while the rest being furnished
+with pistilla without stamina are therefore denominated females; and
+so uniformly does this take place, that no vegetable was ever found to
+produce female flowers without flowers furnished with stamina being
+produced, either on the same individual or on another plant of the same
+species, and _vice versa_.
+
+As all seed vessels are destined to produce seeds, so are the stamina
+to bear the pollen, or fecundating powder. All seeds contain within
+their membranes a certain medullary substance, which swells when dipped
+into warm water. All pollen, likewise, contains in its membrane an
+elastic substance, which, although very subtle, and almost invisible,
+by means of warm water often explodes with great vehemence. While
+plants are in flower, the pollen falls from their antheræ, and is
+dispersed abroad, as seeds are dislodged from their situation when
+the fruit is ripe. At the same time that the pollen is scattered, the
+pistillum presents its stigma, which is then in its highest vigour,
+and, for a portion of the day at least, is moistened with a fine dew.
+The stamina either surround this stigma, or if the flowers are of the
+drooping kind, they are bent towards one side, so that the pollen can
+easily find access to the stigma, where it not only adheres by means of
+the dew of that part, but the moisture occasions its bursting, by which
+means its contents are discharged. That issued from it being mixed with
+the fluid of the stigma, is conveyed to rudiments of the seed. Many
+evident instances of this present themselves to our notice; but I have
+nowhere seen it more manifest than in the Jacobean Lily (_Amarylis
+formosissima_), the pistillum of which, when sufficient heat is
+given the plant to make it flower in perfection, is bent downwards and
+from its stigma issues a drop of limpid fluid, so large that one would
+think it in danger of falling to the ground. It is, however, gradually
+reabsorbed into the style about three or four o’clock and becomes
+invisible until about ten the next morning, when it appears again; by
+noon it attains its largest dimensions; and in the afternoon, by a
+gentle and scarcely perceptible decrease it returns to its source. If
+we shake the antheræ over the stigma, so that the pollen may fall on
+this limpid drop, we see the fluid soon after become turbid and assume
+a yellow color; and we perceive little rivulets, or opaque streaks
+running from the stigma towards the rudiments of the seed. Some time
+afterwards, when the drop has totally disappeared, the pollen may be
+observed adhering to the stigma, but of an irregular figure, having
+lost its original form. No one, therefore, can assent to what Morland
+and others have asserted, that the pollen passes into the stigma,
+pervades the style and enters the tender rudiments of the seed, as
+Leeuwenhoeck supposed his worms to enter the ova. A most evident proof
+of the falsehood of this opinion may be obtained from any species of
+_Mirabilis_ (Marvel of Peru), whose pollen is so very large that
+it almost exceeds the style itself in thickness, and, falling on the
+stigma, adheres firmly to it; that organ sucking and exhausting the
+pollen, as a cuttle fish devours everything that comes within its
+grasp. One evening in the month of August, I removed all the stamina
+from three flowers of the _Mirabilis Longiflora_, at the same time
+destroying all the rest of the flowers which were expanded; I sprinkled
+these three flowers with the pollen of _Mirabilis Jalappa_; the
+seed-buds swelled, but did not ripen. Another evening I performed a
+similar experiment, only sprinkling the flowers with the pollen of the
+same species; all these flowers produced ripe seeds.
+
+Some writers have believed that the stamina are parts of the
+fructification, which serve only to discharge an impure or
+excrementitious matter, and by no means formed for so important a work
+as generation. But it is very evident that these authors have not
+sufficiently examined the subject; for, as in many vegetables, some
+flowers are furnished with stamina only, and others only with pistilla;
+it is altogether impossible that stamina situated at so very great a
+distance from the fruit, as on a different branch, or perhaps on a
+separate plant, should serve to convey any impurities from the embryo.
+
+No physiologist could demonstrate, _a priori_, the necessity of
+the masculine fluid to the rendering the eggs of animals prolific, but
+experience has established it beyond a doubt. We therefore judge _a
+posteriori_ principally, of the same effect in plants.
+
+In the month of January, 1760, the _Antholyza Cunonia_ flowered
+in a pot in my parlour, but produced no fruit, the air of the room not
+being sufficiently agitated to waft the pollen to the stigma. One day,
+about noon, feeling the stigma very moist, I plucked off one of the
+antheræ, by means of a fine pair of forceps, and gently rubbed it on
+one part of the expanded stigmata. The spike of flowers remained eight
+or ten days longer; when I observed, in gathering the branch for my
+herbarium, that the fruit of that flower only on which the experiment
+had been made, had swelled to the size of a bean. I then dissected this
+fruit and discovered that one of the three cells contained seeds in
+considerable number, the other two being entirely withered.
+
+In the month of April I sowed the seeds of hemp (_Cannabis_) in
+two different pots. The young plants came up so plentifully, that each
+pot contained thirty or forty. I placed each by the light of a window,
+but in different and remote apartments. The hemp grew extremely well
+in both pots. In one of them I permitted the male and female plants
+to remain together, to flower and bear fruit, which ripened in July,
+being macerated in water, and committed to the earth, sprung up in
+twelve days. From the other, however, I removed all the male plants,
+as soon as they were old enough for me to distinguish them from the
+females. The remaining females grew very well, and presented their long
+pistilla in great abundance, these flowers continuing a very long time,
+as if in expectation of their mates; while the plants in the other pot
+had already ripened their fruit, their pistilla having, quite in a
+different manner, faded as soon as the males had discharged all their
+pollen. It was truly a beautiful and truly admirable spectacle to see
+the unimpregnated females preserve their pistilla so long green and
+flourishing, not permitting them to begin to fade till they had been
+for a very considerable time exposed in vain, to the access of the
+male pollen.
+
+Afterwards, when these virgin plants began to decay through age, I
+examined all their calyces in the presence of several botanists and
+found them large and flourishing, although every one of the seed-buds
+was brown, compressed, membranaceous, and dry, not exhibiting any
+appearance of cotyledons or pulp. Hence I am perfectly convinced that
+the circumstance which authors have recorded, of the female hemp having
+produced seeds, although deprived of the male, could only have happened
+by means of pollen brought by the wind from some distant place. No
+experiment can be more easily performed than the above; none more
+satisfactory in demonstrating the generation of plants.
+
+The _Clutia tenella_ was in like manner kept growing in my window
+during the months of June and July. The male plant was in one pot,
+the female in another. The latter abounded with fruit, not one of its
+flowers proving abortive. I removed the two pots into different windows
+of the same apartment; still all the female flowers continued to become
+fruitful. At length I took away the male entirely, leaving the female
+alone, and cutting off all the flowers which it had already borne.
+Every day new ones appeared from the axila of every leaf; each remained
+eight or ten days, after which their foot stalks turning yellow, they
+fell barren to the ground. A botanical friend, who had amused himself
+with observing this phenomenon with me, persuaded me to bring, from the
+stove in the garden, a single male flower, which he placed over one of
+the female ones, then in perfection, tying a piece of red silk around
+its pistillum. The next day the male flower was taken away, and this
+single seed-bud remained, and bore fruit. Afterwards I took another
+male flower out of the same stove, and with a pair of slender forceps
+pinched off one of its antheræ, which I afterwards gently scratched
+with a feather, so that a very small portion of its pollen was
+discharged upon one of the three stigmata of a female flower, the other
+two stigmata being covered with paper. This fruit likewise attained its
+due size, and on being cut transversely, exhibited one cell filled with
+a large seed, and the other two empty. The rest of the flowers, being
+unimpregnated, faded and fell off. This experiment may be performed
+with as little trouble as the former.
+
+The _Datisca cannabina_ came up in my garden from seed ten years
+ago, and has every year been plentifully increased by means of its
+perennial root. Flowers in great number have been produced by it; but,
+being all female, they proved abortive. Being desirous of producing
+male plants, I obtained more seeds from Paris. Some more plants were
+raised; but these likewise to my great mortification, all proved
+females, and bore flowers, but no fruit. In the year 1757 I received
+another parcel of seeds. From these I obtained a few male plants, which
+flowered in 1758. These were planted at a great distance from the
+females; and when their flowers were just ready to emit their pollen,
+holding a paper under them, I gently shook the spike of panicle with
+my finger, till the paper was almost covered with the yellow powder. I
+carried this to the females, which were flowering in another part of
+the garden, and placed it over them. The cold nights of the year in
+which this experiment was made, destroyed these Datiscas, with many
+other plants, much earlier than usual. Nevertheless, when I examined
+the flowers of those plants, which I had sprinkled with the fertilizing
+powder, I found the seeds of their due magnitude; while in the more
+remote Datiscas, which had not been impregnated with pollen, no traces
+of seeds were visible.
+
+Several species of Momordica, cultivated by us, like other Indian
+vegetables, in close stoves, have frequently borne female flowers;
+which, although at first very vigorous, after a short time have
+constantly faded and turned yellow, without perfecting any seed, till
+I instructed the gardener, as soon as he observed a female flower, to
+gather a male one, and place it above the female. By this contrivance
+we are so certain of obtaining fruit that we dare pledge ourselves to
+make any female flowers fertile that shall be fixed on.
+
+The _Jatropha urens_ has flowered every year in my hot-house; but
+the female flowers coming before the males, in a week’s time dropped
+their petals and faded before the latter were opened; from which cause
+no fruit has been produced, but the _germina_ themselves have
+fallen off. We have therefore never had any fruit of the Jatropha till
+the year 1752, when the male flowers were in vigour on a tall tree,
+at the same time that the females began to appear on a small Jatropha
+which was growing in a garden-pot. I placed this pot under the other
+tree, by which means the female flowers bore seeds, which grew on being
+sown. I have frequently amused myself with taking the male flowers from
+one plant, and scattering them over the female flowers of another, and
+have always found the seeds of the latter impregnated by it.
+
+Two years ago I placed a piece of paper under some of these male
+flowers and afterwards folded up the pollen which had fallen upon it,
+preserving it so folded up, if I remember right, four or six weeks,
+at the end of which time another branch of the same Jatropha was in
+flower. I then took the pollen, which I had so long preserved in paper,
+and strewed it over three female flowers, the only ones at that time
+expanded. The three females proved fruitful, while all the rest, which
+grew in the same bunch, fell off abortive.
+
+The interior petals of the _Ornithogalum_, commonly but improperly
+called _Canadense_, cohere so closely together that they only just
+admit the air to the germen and will scarcely permit the pollen of
+another flower to pass; this plant produced every day new flowers and
+fruit, the fructification never failing in any instance; I therefore,
+with the utmost care, extracted the antheræ from one of the flowers
+with a hooked needle, and as I hoped, this single flower proved barren.
+This experiment was repeated about a week after with the same success.
+
+I removed all of the antheræ out of a flower of _Chelidonium
+corniculatum_ (scarlet-horned poppy), which was growing in a remote
+part of the garden, upon the first opening of its petals, and stripped
+off all the rest of the flowers; another day I treated another flower
+of the same plant in a similar manner, but sprinkled the pistillum of
+this with the pollen borrowed from another plant of the same species;
+the result was, that the first flower produced no fruit, but the second
+afforded very perfect seed. My design in this experiment was to prove
+that the mere removal of the antheræ from a flower is not in itself
+sufficient to render the germen abortive.
+
+Having the _Nicotiana fruticosa_ growing in a garden-pot, and
+producing plenty of flowers and seed, I extracted the antheræ from the
+newly expanded flowers before they had burst, at the same time cutting
+away all the other flowers; this germen produced no fruit, nor did it
+even swell.
+
+I removed an urn, in which the _Asphodelus fistulosus_ was
+growing, to one corner of the garden, and from one of the flowers
+which had lately opened, I extracted its antheræ; this caused the
+impregnation to fail. Another day I treated another flower in the same
+manner; but, bringing a flower from a plant in a different part of the
+garden, with which I sprinkled the pistillum of the mutilated one, its
+germen became by that means fruitful.
+
+_Ixia chinensis_, flowering in my stove, the windows of which
+were shut, all its flowers proved abortive. I therefore took one of
+its antheræ in a pair of pincers, and with them sprinkled the stigmata
+of two flowers, and the next day one stigma only of a third flower;
+the seed-buds of these flowers remained, grew to a large size and bore
+seed, the fruit of the third, however, contained ripe seed only in one
+of its cells.
+
+To relate more experiments would only be to fatigue the reader
+unnecessarily. All nature proclaims the truth I have endeavored to
+inculcate, and every flower bears witness to it. Any person may make
+the experiment for himself with any plant he pleases, only taking
+care to place the pot in which it is growing, in the window of a room
+sufficiently out of reach of other flowers; and I will venture to
+promise him that he will obtain no perfect fruit unless pollen has
+access to the pistillum.
+
+Logan’s experiments on the Mays are perfectly satisfactory, and
+manifestly show that the pollen does not enter the style, or arrive
+at the germen, but that it is exhausted by the genital fluid of the
+pistillum. And as in animals no conception can take place, unless the
+genital fluid of the female be discharged at the same moment as the
+impregnating liquor of the male; so in plants, generation fails, unless
+the stigma be moist with prolific dew.
+
+Husbandmen know, by long experience, that if rain falls while rye is
+in flower, by coagulating the pollen of its antheræ, it occasions the
+emptiness of many husks in the ear.
+
+Gardeners remark the same thing every year in fruit trees. Their
+blossoms produce no fruit if they have unfortunately been exposed to
+long-continued rains.
+
+Aquatic plants rise above the water at the time of flowering, and
+afterwards again subside, for no other reason, than that the pollen may
+safely reach the stigma.
+
+The white water-lily (_Nymphaea alba_) raises itself every morning
+out of the water and opens its flowers, so that by noon at least three
+inches of its flower-stalk may be seen above the surface. In the
+evening it is closely shut up, and withdrawn again; for about four
+o’clock in the afternoon the flower closes, and remains all night under
+water; which was observed full two thousand years since, even as long
+ago as the time of Theophrastus, who has described this circumstance
+in the _Nymphaea Lotus_, a plant so much resembling our white
+water-lily that they are only distinguished from each other by the
+leaves of the Lotus being indented. Theophrastus gives the following
+account of this vegetable, in his _History of Plants_, book IV.,
+chap. 10: “It is said to withdraw its flowers into the Euphrates,
+which continue to descend till midnight, to so great a depth that at
+daybreak they are out of reach of the hand; after which it rises again,
+and in the course of the morning appears above the water, and expands
+its flowers, rising higher and higher, till it is a considerable
+height above the surface.” The very same thing may be observed in the
+_Nymphaea alba_.
+
+Many flowers close themselves in the evening and before rain, lest the
+pollen should be coagulated; but after the discharge of the pollen
+they always remain open. Such of them as do not shut up, incline their
+flowers downward in those circumstances, and several flowers, which
+come forth in the moisture of spring, droop perpetually. The manner in
+which the Parnassia and Saxifrage move their antheræ to the stigma is
+well known. The common Rue, a plant everywhere to be met with, moves
+one of its antheræ every day to the stigma, till all of them in their
+turns have deposited their pollen there.
+
+The Neapolitan star flower (_Ornithogalum nutans_) has six broad
+stamina, which stand close together in the form of a bell, the three
+external ones being but half the length of the others; so that it seems
+impossible for their antheræ ever to convey their pollen to the stigma;
+but nature, by an admirable contrivance, bends the summits of these
+external stamina inwards between the other filaments, so that they are
+enabled to accomplish their purpose.
+
+The Plaintain tree (_Musa_) bears two kinds of hermaphrodite
+flowers; some have imperfect antheræ, others only the rudiments of
+stigmata; as the last mentioned kind appear after the others, they
+cannot impregnate them, consequently no seeds are produced in our
+gardens, and scarcely ever on the plants cultivated in India. An event
+happened this year, which I have long wished for; two plaintain-trees
+flowering with me so fortunately that one of them brought forth its
+first female blossoms at the time that male ones began to appear on the
+other. I eagerly ran to collect antheræ from the first plant, in order
+to scatter them over the newly-expanded females, in hopes of obtaining
+seed from them, which no botanist has yet been able to do. But when I
+came to examine the antheræ I found even the largest of them absolutely
+empty and void of pollen, consequently unfit for impregnating the
+females; the seeds of this plant, therefore, can never be perfected in
+our gardens. I do not doubt, however, that real male plants of this
+species may be found in its native country, bearing flowers without
+fruit, which the gardeners have neglected; while the females in this
+country produce imperfect fruit, without seeds, like the female fig;
+and, like that tree, are increased easily by suckers. The fruit,
+therefore, of the plaintain-tree scarcely attains anything like its due
+size, the larger seed-buds only ripening, without containing anything
+in them.
+
+The day would sooner fail me than examples. A female date-bearing palm
+flowered many years at Berlin, without producing any seeds. But the
+Berlin people taking care to have some of the blossoms of the male
+tree, which was then flowering at Leipsic, sent them by the post, they
+obtained fruit by that means; and some dates, the offspring of this
+impregnation, being planted in my garden, sprung up, and to this day
+continue to grow vigorously. Kœmpfer formerly told us how necessary
+it was found by the oriental people, who live upon the produce of
+palm-trees, and are the true Lotophagi, to plant some male trees among
+the females, if they hoped for any fruit; hence, it is the practice of
+those who make war in that part of the world to cut down all the male
+palms, that a famine may afflict their proprietors; sometimes even
+the inhabitants themselves destroy the male trees, when they dread an
+invasion, that their enemies may find no sustenance in the country.
+
+Leaving these instances, and innumerable others, which are so well
+known to botanists that they would by no means bear the appearance of
+novelty, and can only be doubted by those persons who neither have
+observed nature, nor will they take the trouble to study her, I pass
+to a fresh subject, concerning which much new light is wanted; I mean
+hybrid, or mule vegetables, the existence and origin of which we shall
+now consider.
+
+I shall enumerate three or four real mule plants, to whose origin I
+have been an eye-witness.
+
+1. _Veronica spuria_, described in Amœnitates Acad. vol. III. p.
+35, came from the impregnation of _Veronic maratima_ by _Verbena
+officinalis_; it is easily propagated by cuttings, and agrees
+perfectly with its mother in fructification, and with its father in
+leaves.
+
+2. _Delphinium hybridum_, sprung up in a part of the garden where
+_Delphinium clatum_ and _Aconitum Napellus_ grew together;
+it resembles its mother as much in its internal parts, that is, in
+fructification as it does its father (the _Aconitum_) in outward
+structure, or leaves; and, owing its origin to plants so nearly allied
+to each other, it propagates itself by seed; some of which I now send
+with this Dissertation.
+
+3. _Hieracium Taraxici_, gathered in 1753 upon our mountains by
+Dr. Solander, in its thick, brown, woolly calyx; in its stem being
+hairy towards the top, and in its bracteæ, as well as in every part of
+its fructification, resembles so perfectly its mother, _Hieracium
+alpinum_, that an inexperienced person might mistake one for the
+other; but in the smoothness of its leaves, in their indentations and
+whole structure, it so manifestly agrees with its father, _Leontodon
+Taraxacum_ (Dandelion), that there can be no doubt of its origin.
+
+4. _Tragopogon hybridum_ attracted my notice the autumn before
+last, in a part of the garden where I had planted _Tragopogon
+pratense_, and _Tragopogon porrifolium_; but winter coming on,
+destroyed its seeds. Last year, while the _Tragopogon pratense_
+was in flower I rubbed off its pollen early in the morning, and
+about eight o’clock sprinkled its stigmata with some pollen of the
+_Tragopogon porrifolium_, marking the calyces by tying a thread
+round them. I afterwards gathered the seeds when ripe, and sowed them
+that autumn in another place; they grew, and produced this year, 1759,
+purple flowers yellow at the base, seeds of which I now send. I doubt
+whether any experiment demonstrates the generation of plants more
+certainly than this.
+
+There can be no doubt that these are all new species produced by
+hybrid generation. And hence we learn, that a mule offspring is
+the exact image of its mother in its medullary substance, internal
+nature, or fructification, but resembles its father in leaves. This
+is a foundation upon which naturalists may build much. For it seems
+probable that many plants, which now appear different species of
+the same _genus_, may in the beginning have been but one plant,
+having arisen merely from hybrid generation. Many of those Geraniums
+which grow at the Cape of Good Hope, and have never been found wild
+anywhere but in the south parts of Africa, and which, as they are
+distinguished from all other Geraniums by their single-leaved calyx,
+many-flowered foot-stalk, irregular corolla, seven fertile stamina,
+and three mutilated ones, and by their naked seeds furnished with
+downy awns; so they agree together in all these characters, although
+very various in their roots, stems and leaves; these Geraniums, I say,
+would almost induce a botanist to believe that the species of one
+_genus_ in vegetables are only so many different plants as there
+have been different associations with the flowers of one species, and
+consequently a _genus_ is nothing else than a number of plants
+sprung from the same mother by different fathers. But whether all
+these species be the offspring of time; whether, in the beginning
+of all things, the Creator limited the number of future species, I
+dare not presume to determine. I am, however, convinced this mode of
+multiplying plants does not interfere with the system or general scheme
+of nature; as I daily observe that insects, which live upon one species
+of a particular _genus_, are contented with another of the same
+_genus_.
+
+A person who has once seen the _Achyranthes aspera_, and remarked
+its spike, the parts of its flower, its small and peculiarly formed
+nectaria, as well as its calyces bent backwards as the fruit ripens,
+would think it very easy at any time to distinguish these flowers
+from all others in the universe; but when he finds the flowers of
+_Achyranthes indica_ agreeing with them even in their minutest
+parts, and at the same time observes the large, thick, obtuse,
+undulated leaves of the last-mentioned plant, he will think he sees
+_Achyranthes aspera_ masked in the foliage of _Xanthium
+strumarium_. But I forbear to mention any more instances.
+
+Here is a new employment for botanists, to attempt the production of
+new species of vegetables by scattering the pollen of various plants
+over various widowed females. And if these remarks should meet with
+a favourable reception, I shall be the more induced to dedicate what
+remains of my life to such experiments, which recommend themselves by
+being at the same time agreeable and useful. I am persuaded by many
+considerations that those numerous and most valuable varieties of
+plants which are used for culinary purposes, have been produced in
+this manner, as the several kinds of cabbages, lettuces, etc.; and I
+apprehend this is the reason of their not being changed by a difference
+of soil. Hence I cannot give my assent to the opinion of those who
+imagine all varieties to have been occasioned by change of soil; for,
+if this were the case, the plants would return to their original form,
+if removed again to their original situation.
+
+
+FOOTNOTES:
+
+[Footnote 13: From the _Publications of the Linnaean Society_.]
+
+
+
+
+ XII
+
+ JOSEPH BLACK
+
+ 1728-1799
+
+
+ _Joseph Black, born in 1728 at Bordeaux, France, was educated in
+ Belfast and at the University of Glasgow. Before he took his M.D.
+ degree he showed that alkalies were formed, not by their absorbing
+ “phlogiston,” but by their having carbonic acid gas, or “fixed air,”
+ as a component. In 1753 he was appointed lecturer on chemistry at
+ Glasgow, and in 1776 became professor of chemistry at Edinburgh. In
+ 1763 he announced his discovery of latent heat, a principle which
+ has been of great practical value. He died in Edinburgh, December 6,
+ 1799._
+
+
+ THE DISCOVERY OF CARBONIC ACID GAS[14]
+
+Hoffman, in one of his observations, gives the history of a powder
+called _Magnesia Alba_, which has been long used, and esteemed as
+a mild and tasteless purgative; but the method of preparing it was not
+generally known before he made it public.
+
+It was originally obtained from a liquor called the _Mother of
+nitre_, which is produced in the following manner:
+
+Salt-petre is separated from the brine which first affords it, or from
+the water with which it is washed out of nitrous earths, by the process
+commonly used in crystallizing salts. In this process, the brine is
+gradually diminished, and at length reduced to a small quantity of
+an unctuous bitter saline liquor, affording no more salt-petre by
+evaporation, but, if urged with a brisk fire, drying up into a confused
+mass, which attracts water strongly, and becomes fluid again when
+exposed to the open air.
+
+To this liquor the workmen have given the name of the _Mother of
+nitre_; and Hoffman, finding it composed of the magnesia united
+to an acid, obtained a separation of these, either by exposing the
+compound to a strong fire, in which the acid was dissipated, and the
+magnesia remained behind, or by the addition of an alkali, which
+attracted the acid to itself: and this last method he recommends as
+the best. He likewise makes an inquiry into the nature and virtues
+of the powder thus prepared; and observes, that it is an absorbent
+earth, which joins readily with all acids, and must necessarily destroy
+any acidity it meets in the stomach; but that its purgative power is
+uncertain, for sometimes it has not the least effect of that kind.
+As it is a mere insipid earth, he rationally concludes it to be a
+purgative only when converted into a sort of neutral salt by an acid
+in the stomach, and that its effect is therefore proportional to the
+quantity of this acid.
+
+Although magnesia appears from this history of it, to be a very
+innocent medicine; yet, having observed that some hypochondriacs,
+who used it frequently, were subject to flatulencies and spasms, he
+seems to have suspected it of some noxious quality. The circumstances,
+however, which gave rise to his suspicion, may very possibly have
+proceeded from the imprudence of his patients; who, trusting too much
+to magnesia (which is properly a palliative in that disease) and
+neglecting the assistance of other remedies, allowed their disorder
+to increase upon them. It may, indeed, be alleged that magnesia, as a
+purgative, is not the most eligible medicine for such constitutions, as
+they agree best with those that strengthen, stimulate, and warm; which
+the saline purges, commonly used, are not observed to do. But there
+seems at last to be no objection to its use, when children are troubled
+with an acid in their stomach: for, gentle purging, in this case, is
+very proper; and it is often more conveniently procured by means of
+magnesia, than of any other medicine, on account of its being entirely
+insipid.
+
+The above-mentioned Author, observing, some time after, that a bitter
+saline liquor, similar to that obtained from the brine of salt-petre,
+was likewise produced by the evaporation of those waters which contain
+common salt, had the curiosity to try if this would also yield a
+magnesia. The experiment succeeded: And he thus found out another
+process for obtaining this powder; and at the same time assured
+himself, by experiments, that the product from both was exactly the
+same.
+
+My curiosity led me, some time ago, to inquire more particularly into
+the nature of magnesia, and especially to compare its properties with
+those of the other absorbent earths, of which there plainly appeared to
+me to be very different kinds, although commonly confounded together
+under one name. I was indeed led to this examination of the absorbent
+earths, partly by the hope of discovering a new sort of lime and
+lime-water, which might possibly be a more powerful solvent of the
+stone, than that commonly used; but was disappointed in my expectations.
+
+I have had no opportunity of seeing Hoffman’s first magnesia, or the
+liquor from which it is prepared, and have therefore been obliged to
+make my experiments upon the second.
+
+In order to prepare it, I at first employed the bitter saline liquor
+called _bittern_, which remains in the pans after the evaporation
+of sea-water. But as that liquor is not always easily procured, I
+afterwards made use of a salt called Epsom salt, which is separated
+from the bittern by crystallization, and is evidently composed of
+magnesia and the vitriolic acid.
+
+There is likewise a spurious kind of Glauber salt, which yields plenty
+of magnesia, and seems to be no other than Epsom salt, of sea-water
+reduced to crystals of a larger size. And common salt also affords
+a small quantity of this powder; because, being separated from the
+bittern by one hasty crystallization only, it necessarily contains a
+portion of that liquor.
+
+Those who would prepare a magnesia from Epsom salt, may use the
+following process:
+
+Dissolve equal quantities of Epsom salt, and of pearl ashes,
+separately, in a sufficient quantity of water; purify each solution
+from its dregs, and mix them accurately together by violent agitation.
+Then make them just to boil over a brisk fire.
+
+Add now to the mixture, three or four times its quantity of hot water;
+after a little agitation, allow the magnesia to settle to the bottom,
+and decant off as much of the water as possible. Pour on the same
+quantity of cold water; and, after settling, decant it off in the
+same manner. Repeat this washing with the cold water ten or twelve
+times, or even oftener, if the magnesia be required perfectly pure for
+chemical experiments.
+
+When it is sufficiently washed, the water may be strained and squeezed
+from it in a linen cloth; for very little of the magnesia passes
+through.
+
+The alkali in the mixture, uniting with the acid, separates it from
+the magnesia; which, not being of itself soluble in water, must
+consequently appear immediately under a solid form. But the powder
+which thus appears is not entirely magnesia; part of it is the neutral
+salt formed from the union of the acid and alkali. This neutral salt
+is found, upon examination, to agree in all respects with vitriolated
+tartar, and requires a large quantity of hot water to dissolve it. As
+much of it is therefore dissolved as the water can take up; the rest
+is dispersed through the mixture, in the form of a powder. Hence the
+necessity of washing the magnesia with so much trouble; for the first
+effusion of hot water is intended to dissolve the whole of the salt,
+and the subsequent additions of cold water to wash away this solution.
+
+The caution given, of boiling the mixture, is not unnecessary: if it
+be neglected, the whole of the magnesia is not accurately separated at
+once; and, by allowing it to rest for some time, that powder concretes
+into minute grains, which, when viewed with the microscope, appear to
+be assemblages of needles diverging from a point. This happens more
+especially when the solutions of the Epsom salt, and of the alkali,
+are diluted with too much water before they are mixed together. Thus,
+if a dram of Epsom salt, and of salt of tartar, be dissolved each in
+four ounces of water, and be mixed, and then allowed to rest three or
+four days, the whole of the magnesia will be formed into these grains.
+Or, if we filtrate the mixture soon after it is made, and heat the
+clear liquor which passes through, it will become turbid, and deposit a
+magnesia.
+
+
+An ounce of magnesia was exposed in a crucible, for about an hour, to
+such a heat as is sufficient to melt copper. When taken out, it weighed
+three drams and one scruple, or had lost 7-12 of its former weight.
+
+I repeated, with the magnesia prepared in this manner, most of those
+experiments I had already made upon it before calcination, and the
+result was as follows:--
+
+It dissolves in all the acids, and with these composes salts exactly
+similar to those described in the first set of experiments: But, what
+is particularly to be remarked, it is dissolved without any the least
+degree of effervescence.
+
+It slowly precipitates the corrosive sublimate of mercury, in the form
+of a black powder.
+
+It separates the volatile alkali in salt-ammoniac from the acid, when
+it is mixed with a warm solution of that salt. But it does not separate
+an acid from a calcareous earth, nor does it introduce the least change
+upon lime-water.
+
+Lastly, when a dram of it is digested with an ounce of water in a
+bottle for some hours, it does not make any the least change in the
+water. The magnesia, when dried, is found to have gained ten grains;
+but it neither effervesces with acids, nor does it sensibly affect
+lime-water.
+
+Observing magnesia to lose such a remarkable proportion of its weight
+in the fire, my next attempts were directed to the investigation of
+this volatile part; and, among other experiments, the following seemed
+to throw some light upon it:--
+
+Three ounces of magnesia were distilled in a glass retort and receiver,
+the fire being gradually increased until the magnesia was obscurely red
+hot. When all was cool, I found only five drams of a whitish water in
+the receiver, which had a faint smell of the spirit of hartshorn, gave
+a green colour to the juice of violets, and rendered the solutions of
+corrosive sublimate, and of silver, very slightly turbid. But it did
+not sensibly effervesce with acids.
+
+The magnesia, when taken out of the retort, weighed an ounce, three
+drams, and thirty grains, or had lost more than half of its weight. It
+still effervesced pretty briskly with acids, though not so strongly as
+before this operation.
+
+The fire should have been raised here to the degree requisite for
+the perfect calcination of magnesia. But, even from this imperfect
+experiment, it is evident, that, of the volatile parts contained in
+that powder, a small proportion only is water; the rest cannot, it
+seems, be retained in vessels, under a visible form. Chemists have
+often observed in their distillations that part of a body has vanished
+from their senses notwithstanding the utmost care to retain it; and
+they have always found, upon further inquiry, that subtle part to be
+air, which having been imprisoned in the body, under a solid form, was
+set free, and rendered fluid and elastic by the fire. We may therefore
+safely conclude, that the volatile matter lost in the calcination of
+magnesia, is mostly air; and hence the calcined magnesia does not emit
+air, or make an effervescence when mixed with acids.
+
+The water, from its properties, seems to contain a small portion of
+volatile alkali, which was probably formed from the earth, air and
+water, from some of these combined together; and perhaps also from a
+small quantity of inflammable matter, which adhered accidently to the
+magnesia. Whenever chemists meet with this salt, they are inclined to
+ascribe its origin to some animal or putrid vegetable substance; and
+this they have always done, when they obtained it from the calcareous
+earths, all of which afford a small quantity of it. There is, however,
+no doubt, that it can sometimes be produced independently of any such
+mixture, since many fresh vegetables, and tartar, afford a considerable
+quantity of it. And how can it, in the present instance, be supposed,
+that any animal or vegetable matter adhered to the magnesia, while it
+was dissolved by an acid, separated from this by an alkali, and washed
+with so much water?
+
+Two drams of magnesia were calcined in a crucible, in the manner
+described above, and thus reduced to two scruples and twelve grains.
+This calcined magnesia was dissolved in a sufficient quantity of spirit
+of vitriol, and then again separated from the acid by the addition of
+an alkali, of which a large quantity is necessary for this purpose. The
+magnesia being very well washed and dried, weighed one dram and fifty
+grains. It effervesced violently, or emitted a large quantity of air,
+when thrown into acids; formed a red powder, when mixed with a solution
+of sublimate; separated the calcareous earths from an acid, and
+sweetened lime-water; and had thus recovered all those properties which
+it had but just now lost by calcination. Nor had it only recovered
+its original properties, but acquired besides an addition of weight,
+nearly equal to what had been lost in the fire; and as it is found to
+effervesce with acids, part of the addition must certainly be air.
+
+This air seems to have been furnished by the alkali, from which it
+was separated by the acid; for Dr. Hales has clearly proved, that
+alkaline salts contain a large quantity of fixed air, which they emit
+in great abundance when joined to a pure acid. In the present case, the
+alkali is really joined to an acid, but without any visible emission
+of air; and yet the air is not retained in it; for the neutral salt,
+into which it is converted, is the same in quantity, and in every other
+respect, as if the acid employed had not been previously saturated with
+magnesia, but offered to the alkali in its pure state, and had driven
+the air out of it in their conflict. It seems therefore evident, that
+the air was forced from the alkali by the acid, and lodged itself in
+the magnesia.
+
+These considerations led me to try a few experiments, whereby I might
+know what quantity of air is expelled from an alkali, or from magnesia,
+by acids.
+
+Two drams of a pure fixed alkaline salt, and an ounce of water, were
+put into a Florentine flask, which, together with its contents, weighed
+two ounces and two drams. Some oil of vitriol diluted with water was
+dropped in, until the salt was exactly saturated; which it was found to
+be, when two drams, two scruples and three grains of this acid had been
+added. The phial with its contents now weighed two ounces, four drams
+and fifteen grains. One scruple, therefore, and eight grains, were lost
+during the ebullition; of which a trifling portion may be water, or
+something of the same kind; the rest is air.
+
+
+FOOTNOTES:
+
+[Footnote 14: From _Experiments upon Magnesia, Quicklime, and some
+other Alkaline Substances_ (1775).]
+
+
+
+
+ XIII
+
+ JOSEPH PRIESTLEY
+
+ 1733-1804
+
+
+ _Joseph Priestley, born in Yorkshire, England, March 13, 1733, was
+ a Unitarian minister. In 1774 he discovered oxygen, which he called
+ “dephlogisticated air.” Because of his liberal political ideas he was
+ persecuted by his countrymen, and in 1794 emigrated to Northumberland,
+ Pennsylvania, where he lived until his death, February 6, 1804._
+
+
+ THE DISCOVERY OF OXYGEN[15]
+
+Presently, after my return from abroad, I went to work upon the
+_mercurius calcinatus_, which I had procured from Mr. Cadet; and,
+with a very moderate degree of heat, I got from about one-fourth of
+an ounce of it, an ounce-measure of air, which I observed to be not
+readily imbibed, either by the substance itself from which it had
+been expelled (for I suffered them to continue a long time together
+before I transferred the air to any other place) or by water, in which
+I suffered this air to stand a considerable time before I made any
+experiment upon it.
+
+In this air, as I had expected, a candle burned with a vivid flame; but
+what I observed new at this time (November 19), and which surprised me
+no less than the fact I had discovered before, was, that, whereas a
+few moments agitation in water will deprive the modified nitrous air
+of its property of admitting a candle to burn in it; yet, after more
+than ten times as much agitation as would be sufficient to produce this
+alteration in the nitrous air, no sensible change was produced in this.
+A candle still burned in it with a strong flame; and it did not, in
+the least, diminish common air, which I have observed that nitrous air,
+in this state, in some measure does.
+
+But I was much more surprised, when, after two days, in which this air
+had continued in contact with water (by which it was diminished about
+one-twentieth of its bulk) I agitated it violently in water about five
+minutes, and found that a candle still burned in it as well as in
+common air. The same degree of agitation would have made phlogisticated
+nitrous air fit for respiration indeed, but it would certainly have
+extinguished a candle.
+
+These facts fully convinced me, that there must be a very material
+difference between the constitution of air from _mercurius
+calcinatus_, and that of phlogisticated nitrous air, notwithstanding
+their resemblance in some particulars. But though I did not doubt that
+the air from _mercurius calcinatus_ was fit for respiration, after
+being agitated in water, as every kind of air without exception, on
+which I have tried the experiment, had been, I still did not suspect
+that it was respirable in the first instance; so far was I from having
+any idea of this air being, what it really was, much superior, in this
+respect, to the air of the atmosphere.
+
+In this ignorance of the real nature of this kind of air, I continued
+from this time (November) to the 1st of March following; having, in the
+meantime, been intent upon my experiments on the vitriolic acid air
+above recited, and the various modifications of air produced by spirit
+of nitre, an account of which will follow. But in the course of this
+month, I not only ascertained the nature of this kind of air, though
+very gradually, but was led to it by the complete discovery of the
+constitution of the air we breathe.
+
+Till this 1st of March, 1775, I had so little suspicion of the air from
+_mercurius calcinatus_, &c., being wholesome, that I had not even
+thought of applying it to the test of nitrous air; but thinking (as my
+reader must imagine I frequently must have done) on the candle burning
+in it after long agitation in water, it occurred to me at last to make
+the experiment; and putting one measure of nitrous air to two measures
+of this air, I found, not only that it was diminished, but that it was
+diminished quite as much as common air, and that the redness of the
+mixture was likewise equal to that of a similar mixture of nitrous and
+common air.
+
+After this I had no doubt but that the air from _mercurius
+calcinatus_ was fit for respiration, and that it had all the other
+properties of genuine common air. But I did not take notice of what I
+might have observed, if I had not been so fully possessed by the notion
+of there being no air better than common air, that the redness was
+really deeper, and the diminution something greater than common air
+would have admitted.
+
+Moreover, this advance in the way of truth, in reality, threw me back
+into error, making me give up the hypothesis I had first formed, viz.
+that the _mercurius calcinatus_ had extracted spirit of nitre
+from the air; for I now concluded, that all the constituent parts of
+the air were equally, and in their proper proportion, imbibed in the
+preparation of this substance, and also in the process of making red
+lead. For at the same time that I made the above mentioned experiment
+on the air from _mercurius calcinatus_, I likewise observed that
+the air which I had extracted from red lead, after the fixed air was
+washed out of it, was of the same nature, being diminished by nitrous
+air like common air: but, at the same time, I was puzzled to find that
+air from the red precipitate was diminished in the same manner, though
+the process for making this substance is quite different from that of
+making the two others. But to this circumstance I happened not to give
+much attention.
+
+I wish my reader be not quite tired with the frequent repetition of the
+word surprise, and others of similar import; but I must go on in that
+style a little longer. For the next day I was more surprised than ever
+I had been before, with finding that, after the above-mentioned mixture
+of nitrous air and the air from _mercurius calcinatus_, had stood
+all night, (in which time the whole diminution must have taken place;
+and, consequently, had it been common air, it must have been made
+perfectly noxious, and entirely unfit for respiration or inflammation)
+a candle burned in it, and even better than in common air.
+
+I cannot, at this distance of time, recollect what it was that I had in
+view in making this experiment; but I know I had no expectation of the
+real issue of it. Having acquired a considerable degree of readiness in
+making experiments of this kind, a very slight and evanescent motive
+would be sufficient to induce me to do it. If, however, I had not
+happened, for some other purpose, to have had a lighted candle before
+me I should probably never have made the trial; and the whole train
+of my future experiments relating to this kind of air might have been
+prevented.
+
+Still, however, having no conception of the real cause of this
+phenomenon, I considered it as something very extraordinary; but as
+a property that was peculiar to air that was extracted from these
+substances, and adventitious; and I always spoke of the air to my
+acquaintance as being substantially the same thing with common air.
+
+I particularly remember my telling Dr. Price, that I was myself
+perfectly satisfied of its being common air, as it appeared to be so
+by the test of nitrous air; though, for the satisfaction of others, I
+wanted a mouse to make the proof quite complete.
+
+On the 8th of this month I procured a mouse, and put it into a glass
+vessel, containing two ounce-measures of the air from _mercuris
+calcinatus_. Had it been common air, a full-grown mouse, as this
+was, would have lived in it about a quarter of an hour. In this air,
+however, my mouse lived a full half hour; and though it was taken out
+seemingly dead, it appeared to have been only exceedingly chilled; for,
+upon being held to fire, it presently revived, and appeared not to have
+received any harm from the experiment.
+
+By this I was confirmed in my conclusion, that the air extracted
+from _mercurius calcinates_, &c., was, at least, as good as
+common air; but I did not certainly conclude that it was any better;
+because, though one mouse would live only a quarter of an hour in a
+given quantity of air, I knew it was not impossible but that another
+mouse might have lived in it half an hour; so little accuracy is
+there in this method of ascertaining the goodness of air; and indeed
+I have never had recourse to it for my own satisfaction, since the
+discovery of that most ready, accurate, and elegant test that nitrous
+air furnishes. But in this case I had a view to publishing the most
+generally satisfactory account of my experiments that the nature of the
+thing would admit of.
+
+This experiment with the mouse, when I had reflected upon it some time,
+gave me so much suspicion that the air into which I had put it was
+better than common air, that I was induced, the day after, to apply
+the test of nitrous air to a small part of that very quantity of air
+which the mouse had breathed so long; so that, had it been common air,
+I was satisfied it must have been very nearly, if not altogether, as
+noxious as possible, so as not to be affected by nitrous air; when,
+to my surprise again, I found that though it had been breathed so
+long, it was still better than common air. For after mixing it with
+nitrous air, in the usual proportion of two to one, it was diminished
+in the proportion of four and one-half to three and one-half; that
+is, the nitrous air had made it two-ninths less than before, and this
+in a very short space of time; whereas I had never found that, in the
+longest time, any common air was reduced more than one-fifth of its
+bulk by any proportion of nitrous air, nor more than one-fourth by any
+phlogistic process whatever. Thinking of this extraordinary fact upon
+my pillow, the next morning I put another measure of nitrous air to the
+same mixture, and, to my utter astonishment, found that it was farther
+diminished to almost one-half of its original quantity. I then put a
+third measure to it; but this did not diminish it any farther; but,
+however, left it one measure less than it was even after the mouse had
+been taken out of it.
+
+Being now fully satisfied that this air, even after the mouse had
+breathed it half an hour, was much better than common air; and having
+a quantity of it still left, sufficient for the experiment, viz. an
+ounce-measure and a half, I put the mouse into it; when I observed that
+it seemed to feel no shock upon being put into it, evident signs of
+which would have been visible, if the air had not been very wholesome;
+but that it remained perfectly at its ease another full half hour, when
+I took it out quite lively and vigorous. Measuring the air the next
+day, I found it to be reduced from one and one-half to two-thirds of an
+ounce-measure. And after this, if I remember well (for in my register
+of the day I only find it noted, that it was considerably diminished
+by nitrous air), it was nearly as good as common air. It was evident,
+indeed, from the mouse having been taken out quite vigorous, that the
+air could not have been rendered very noxious.
+
+For my farther satisfaction I procured another mouse, and putting it
+into less than two ounce-measures of air extracted from _mercurius
+calcinatus_ and air from red precipitate (which, having found
+them to be of the same quality, I had mixed together) it lived
+three-quarters of an hour. But not having had the precaution to set the
+vessel in a warm place, I suspect that the mouse died of cold. However,
+as it had lived three times as long as it could probably have lived in
+the same quantity of common air, and I did not expect much accuracy
+from this kind of a test, I did not think it necessary to make any more
+experiments with mice.
+
+Being now fully satisfied of the superior goodness of this kind of air,
+I proceeded to measure that degree of purity, with as much accuracy
+as I could, by the test of nitrous air; and I began with putting one
+measure of nitrous air to two measures of this air, as if I had been
+examining common air; and now I observed that the diminution was
+evidently greater than common air would have suffered by the same
+treatment. A second measure of nitrous air reduced it to two-thirds
+of its original quantity, and a third measure to one-half. Suspecting
+that the diminution could not proceed much farther, I then added only
+half a measure of nitrous air, by which it was diminished still more;
+but not much, and another half-measure made it more than half of its
+original quantity; so that, in this case, two measures of this air took
+more than two measures of nitrous air, and yet remained less than half
+of what it was. Five measures brought it pretty exactly to its original
+dimensions.
+
+At the same time, air from the red precipitate was diminished in
+the same proportion as that from _mercurius calcinatus_, five
+measures of nitrous air being received by two measures of this without
+any increase of dimensions. Now as common air takes about one-half
+of its bulk of nitrous air, before it begins to receive any addition
+to its dimensions from more nitrous air, and this air took more than
+four half-measures before it ceased to be diminished by more nitrous
+air, and even five half-measures made no addition to its original
+dimensions, I conclude that it was between four and five times as good
+as common air. It will be seen that I have since procured air better
+than this, even between five and six times as good as the best common
+air that I have ever met with.
+
+
+FOOTNOTES:
+
+[Footnote 15: From _Experiments and Observations on Different Kinds
+of Air_, Vol. II, (1775).]
+
+
+
+
+ XIV
+
+ HENRY CAVENDISH
+
+ 1731-1810
+
+
+ _Henry Cavendish, the discoverer of hydrogen, was born of English
+ parents in Nice, October 10, 1731. He studied at Cambridge University,
+ England, and in 1760 joined the Royal Society, devoting his great
+ fortune to the advancement of science. He discovered hydrogen in 1766,
+ and later, using Priestley’s discovery of oxygen, found that the two
+ gases combined under certain physical conditions to produce water.
+ Besides his studies in chemistry, he made some interesting discoveries
+ in physics. In 1783 he proposed the theory that heat was a motion
+ rather than a substance; and in 1798 he computed the density of the
+ earth to be about five and a half times that of water. He died at
+ Clapham, February 24, 1810._
+
+
+ THE COMBINATION OF HYDROGEN AND OXYGEN INTO WATER[16]
+
+In Dr. Priestley’s last volume of experiments is related an experiment
+of Mr. Warltire’s, in which it is said that, on firing a mixture of
+common and inflammable air by electricity in a close copper vessel
+holding about three pints, a loss of weight was always perceived, on
+an average about two grains, though the vessel was stopped in such a
+manner that no air could escape by the explosion. It is also related,
+that on repeating the experiment in glass vessels, the inside of the
+glass, though clean and dry before, immediately became dewy; which
+confirmed an opinion he had long entertained, that common air deposits
+its moisture by phlogistication. As the latter experiment seemed likely
+to throw great light on the subject I had in view, I thought it well
+worth examining more closely. The first experiment also, if there was
+no mistake in it, would be very extraordinary and curious; but it did
+not succeed with me; for though the vessel I used held more than Mr.
+Warltire’s, namely, 24,000 grains of water, and though the experiment
+was repeated several times with different proportions of common and
+inflammable air, I could never perceive a loss of weight of more than
+one-fifth of a grain, and commonly none at all. It must be observed,
+however, that though there were some of the experiments in which it
+seemed to diminish a little in weight, there were none in which it
+increased.
+
+In all the experiments, the inside of the glass globe became dewy,
+as observed by Mr. Warltire; but not the least sooty matter could be
+perceived. Care was taken in all of them to find how much the air was
+diminished by the explosion, and to observe its test. The result is as
+follows, the bulk of the inflammable air being expressed in decimals of
+the common air:
+
+------+-----------+----------+-------------+------------+--------
+ | | |Air Remaining|Test of this|
+Common|Inflammable|Diminution| after the | Air in the |Standard
+ Air | Air | | Explosion |First Method|
+------+-----------+----------+-------------+------------+--------
+ 1 | 1.241 | .686 | 1.555 | .055 | .0
+ | 1.955 | .642 | 1.423 | .063 | .0
+ | .706 | .647 | 1.059 | .066 | .0
+ | .423 | .612 | .811 | .097 | .03
+ | .331 | .476 | .855 | .339 | .27
+ | .206 | .294 | .912 | .648 | .58
+------+-----------+----------+-------------+------------+---------
+
+In these experiments the inflammable air was procured from zinc, as it
+was in all my experiments, except where otherwise expressed: but I made
+two more experiments, to try whether there was any difference between
+the air from zinc and that from iron, the quantity of inflammable air
+being the same in both, namely, 0.331 of the common; but I could not
+find any difference to be depended on between the two kinds of air,
+either in the diminution which they suffered by the explosion, or the
+test of the burnt air.
+
+From the fourth experiment it appears, that 423 measures of inflammable
+air are nearly sufficient to phlogisticate completely 1000 of common
+air; and that the bulk of the remaining air after the explosion is then
+very little more than four-fifths of the common air employed; so that
+as common air cannot be reduced to a much less bulk than that by any
+method of phlogistication, we may safely conclude, that when they are
+mixed in this proportion, and exploded, almost all the inflammable air,
+and about one-fifth part of the common air, lose their elasticity, and
+are condensed into the dew which lines the glass.
+
+The better to examine the nature of this dew, 500,000 grain measures
+of inflammable air were burnt with about two and one-half times the
+quantity of common air, and the burnt air made to pass through a glass
+cylinder eight feet long and three-quarters of an inch in diameter,
+in order to deposit the dew. The two airs were conveyed slowly into
+this cylinder by separate copper pipes, passing through a brass plate
+which stopped up the end of the cylinder; and as neither inflammable
+nor common air can burn by themselves, there was no danger of the flame
+spreading into the magazines from which they were conveyed. Each of
+these magazines consisted of a large tin vessel, inverted into another
+vessel just big enough to receive it. The inner vessel communicated
+with the copper pipe, and the air was forced out of it by pouring water
+into the outer vessel; and in order that the quantity of common air
+expelled should be two and one-half times that of the inflammable, the
+water was let into the outer vessels by two holes in the bottom of the
+same tin pan, the hole which conveyed the water into that vessel in
+which the common air was confined being two and one-half times as big
+as the other.
+
+In trying the experiment, the magazines being first filled with their
+respective airs, the glass cylinder was taken off, and water let, by
+the two holes, into the outer vessel, till the airs began to issue from
+the ends of the copper pipes; they were then set on fire by a candle,
+and the cylinder put on again in its place. By this means upwards of
+135 grains of water were condensed in the cylinder, which had no taste
+nor smell, and which left no sensible sediment when evaporated to
+dryness; neither did it yield any pungent smell during evaporation; in
+short, it seemed pure water.
+
+In my first experiment, the cylinder near that part where the air
+was fired was a little tinged with sooty matter, but very slightly
+so; and that little seemed to proceed from the putty with which the
+apparatus was luted, and which was heated by the flame; for in another
+experiment, in which it is contrived so that the luting should not be
+much heated, scarce any sooty tinge could be perceived.
+
+By the experiments with the globe it appeared, that when inflammable
+and common air are exploded in a proper proportion, almost all the
+inflammable air, and nearly one-fifth of the common air, lose their
+elasticity, and are condensed into dew. And by this experiment it
+appears, that this dew is plain water, and consequently that almost all
+the inflammable air and about one-fifth of the common air, are turned
+into pure water.
+
+In order to examine the nature of the matter condensed on firing a
+mixture of dephlogisticated and inflammable air, I took a glass globe
+holding 8,800 grain measures, furnished with a brass cock and an
+apparatus for firing air by electricity. This globe was well exhausted
+by an air-pump, and then filled with a mixture of inflammable and
+dephlogisticated air, by shutting the cock, fastening a bent glass tube
+to its mouth, and letting up the end of it into a glass jar inverted
+into water, and containing a mixture of 19,500 grain measures of
+dephlogisticated air, and 37,000 of inflammable; so that, upon opening
+the cock, some of this mixed air rushed through the bent tube, and
+filled the globe. The cock was then shut, and the included air fired by
+electricity, by which means almost all of it lost its elasticity. The
+cock was then again opened, so as to let in more of the same air, to
+supply the place of that destroyed by the explosion, which was again
+fired, and the operation continued till almost the whole of the mixture
+was let into the globe and exploded. By this means, though the globe
+held not more than the sixth part of the mixture, almost the whole of
+it was exploded therein, without any fresh exhaustion of the globe.
+
+As I was desirous to try the quantity and test of this burnt air,
+without letting any water into the globe, which would have prevented my
+examining the nature of the condensed matter, I took a larger globe,
+furnished also with a stop cock, exhausted it by an air-pump, and
+screwed it on upon the cock of the former globe; upon which, by opening
+both cocks, the air rushed out of the smaller globe into the larger,
+till it became of equal density in both; then, by shutting the cock of
+the larger globe, unscrewing it again from the former, and opening it
+under water, I was enabled to find the quantity of the burnt air in
+it; and consequently, as the proportion which the contents of the two
+globes bore to each other was known, could tell the quantity of burnt
+air in the small globe before the communication was made between them.
+By this means the whole quantity of the burnt air was found to be 2,950
+grain measures; its standard was 1.85.
+
+The liquor condensed in the globe, in weight about thirty grains, was
+sensibly acid to the taste, and by saturation with fixed alkali, and
+evaporation, yielded near two grains of nitre; so that it consisted
+of water united to a small quantity of nitrous acid. No sooty matter
+was deposited in the globe. The dephlogisticated air used in this
+experiment was procured from red precipitate, that is, from a solution
+of quicksilver in spirit of nitre distilled till it acquires a red
+colour.
+
+As it was suspected, that the acid contained in the condensed liquor
+was no essential part of the dephlogisticated air, but was owing to
+some acid vapour which came over in making it and had not been absorbed
+by the water, the experiment was repeated in the same manner, with some
+more of the same air, which had been previously washed with water, by
+keeping it a day or two in a bottle with some water, and shaking it
+frequently; whereas that used in the preceding experiment had never
+passed through water, except in preparing it. The condensed liquor was
+still acid.
+
+The experiment was also repeated with dephlogisticated air, procured
+from red lead by means of oil of vitriol; the liquor condensed was
+acid, but by an accident I was prevented from determining the nature of
+the acid.
+
+I also procured some dephlogisticated air from the leaves of plants, in
+the manner of Doctors Ingenhousz and Priestley, and exploded it with
+inflammable air as before; the condensed liquor still continued acid,
+and of the nitrous kind.
+
+In all these experiments the proportion of inflammable air was such,
+that the burnt air was not much phlogisticated; and it was observed,
+that the less phlogisticated it was, the more acid was the condensed
+liquor. I therefore made another experiment, with some more of the
+same air from plants, in which the proportion of inflammable air was
+greater, so that the burnt air was almost completely phlogisticated,
+its standard being 1-10. The condensed liquor was then not at all acid,
+but seemed pure water; so that it appears, that with this kind of
+dephlogisticated air, the condensed liquor is not at all acid, when the
+two airs are mixed in such a proportion that the burnt air is almost
+completely phlogisticated, but is considerably so when it is not much
+phlogisticated.
+
+In order to see whether the same thing would obtain with air procured
+from red precipitate, I made two more experiments with that kind
+of air, the air in both being taken from the same bottle, and the
+experiment tried in the same manner, except that the proportions of
+inflammable air were different. In the first, in which the burnt air
+was almost completely phlogisticated, the condensed liquor was not at
+all acid. In the second, in which its standard was 1.86, that is, not
+much phlogisticated, it was considerably acid; so that with this air,
+as well as with that from plants, the condensed liquor contains, or is
+entirely free from, acid, according as the burnt air is less or more
+phlogisticated; and there can be little doubt but that the same rule
+obtains with any other kind of dephlogisticated air.
+
+In order to see whether the acid, formed by the explosion of
+dephlogisticated air obtained by means of the vitriolic acid, would
+also be of the nitrous kind, I procured some air from turbith mineral,
+and exploded it with inflammable air, the proportion being such that
+the burnt air was not much phlogisticated. The condensed liquor
+manifested an acidity, which appeared, by saturation with a solution
+of salt of tartar, to be of the nitrous kind; and it was found, by the
+addition of some _terra ponderosa salita_, to contain little or no
+vitriolic acid.
+
+When inflammable air was exploded with common air, in such a proportion
+that the standard of the burnt air was about 4-10, the condensed
+liquor was not in the least acid. There is no difference, however, in
+this respect between common air, and dephlogisticated air mixed with
+phlogisticated in such a proportion as to reduce it to the standard of
+common air; for some dephlogisticated air from red precipitate, being
+reduced to this standard by the addition of perfectly phlogisticated
+air, and then exploded with the same proportion of inflammable air as
+the common air was in the foregoing experiment, the condensed liquor
+was not in the least acid.
+
+From the foregoing experiments it appears, that when a mixture of
+inflammable and dephlogisticated air is exploded in such proportion
+that the burnt air is not much phlogisticated, the condensed liquor
+contains a little acid, which is always of the nitrous kind,
+whatever substance the dephlogisticated air is procured from; but
+if the proportion be such that the burnt air is almost entirely
+phlogisticated, the condensed liquor is not at all acid, but seems
+pure water, without any addition whatever; and as, when they are mixed
+in that proportion, very little air remains after the explosion,
+almost the whole being condensed, it follows that almost the whole
+of the inflammable and dephlogisticated air is converted into pure
+water. It is not easy, indeed, to determine from these experiments
+what proportion the burnt air, remaining after the explosions, bore to
+the dephlogisticated air employed, as neither the small nor the large
+globe could be perfectly exhausted of air, and there was no saying
+with exactness what quantity was left in them; but in most of them,
+after allowing for this uncertainty, the true quantity of burnt air
+seemed not more than 1-17 of the dephlogisticated air employed, or
+1-50 of the mixture. It seems, however, unnecessary to determine this
+point exactly, as the quantity is so small, that there can be little
+doubt but that it proceeds only from the impurities mixed with the
+dephlogisticated and inflammable air, and consequently that, if those
+airs could be obtained perfectly pure, the whole would be condensed.
+
+With respect to common air, and dephlogisticated air reduced by the
+addition of phlogisticated air to the standard of common air, the
+case is different; as the liquor condensed in exploding them with
+inflammable air, I believe I may say in any proportion, is not at all
+acid; perhaps because if they are mixed in such a proportion as that
+the burnt air is not much phlogisticated, the explosion is too weak,
+and not accompanied with sufficient heat.
+
+All the foregoing experiments, on the explosion of inflammable air
+with common and dephlogisticated airs, except those which relate to
+the cause of the acid found in the water, were made in the summer
+of the year 1781, and were mentioned by me to Dr. Priestley, who
+in consequence of it made some experiments of the same kind, as he
+relates in a paper printed in the preceding volume of the Transactions.
+During the last summer also, a friend of mine gave some account of
+them to M. Lavoisier, as well as of the conclusion drawn from them
+that dephlogisticated air is only water deprived of phlogiston; but
+at that time so far was M. Lavoisier from thinking any such opinion
+warranted, that, till he was prevailed upon to repeat the experiment
+himself, he found some difficulty in believing that nearly the whole
+of the two airs could be converted into water. It is remarkable, that
+neither of these gentlemen found any acid in the water produced by the
+combustion; which might proceed from the latter having burnt two airs
+in a different manner from what I did; and from the former having used
+a different kind of inflammable air, namely, that from charcoal, and
+perhaps having used a greater proportion of it.
+
+
+FOOTNOTES:
+
+[Footnote 16: From _Experiments with Airs--Transactions of Royal
+Society of London_ (1784).]
+
+
+
+
+ XV
+
+ SIR WILLIAM HERSCHEL
+
+ 1738-1822
+
+
+ _Sir William Herschel was born in Hanover, Germany, November 15,
+ 1738, the son of a bandmaster. At an early age he was compelled to
+ earn his own living by playing in the band of the Hanoverian Guards.
+ In 1766, after some years of financial straits, he found work as
+ an organist at Bath. Studying languages and mathematics without
+ assistance from tutors, he became interested in “the music of the
+ spheres” which developed into a scientific attitude in astronomy. He
+ managed, in spite of his poverty, to construct specula for a telescope
+ and in 1781, with one of his own instruments, he discovered the
+ planet Uranus, one of the most romantic discoveries in the history of
+ science. Among his other discoveries were two of the satellites of
+ Uranus, two more of Saturn, and the fact that the moon was without
+ atmosphere; he also described many of the binary stars, discovered
+ many nebulous stars (which prepared the way for the nebular theory of
+ the universe), and made the inference from the movements of the stars
+ that the whole solar system was rushing towards the constellation
+ of Hercules. After his death, August 25, 1822, his son, Sir John
+ Herschel, continued his work in astronomy._
+
+
+ I
+
+ THE DISCOVERY OF URANUS[17]
+
+ ACCOUNT OF A COMET
+
+On Tuesday, the 13th of March, 1781, between 10 and 11 in the evening,
+while examining the small stars in the neighborhood of H Geminorum, I
+perceived one that appeared visibly larger than the rest: being struck
+with its uncommon magnitude, I compared it to H Geminorum and the
+small star in the quartile between Auriga and Gemini, and finding it
+so much larger than either of them, suspected it to be a comet. I was
+then engaged in a series of observations on the parallax of the fixed
+stars, which I hope soon to have the honour of laying before the R.S.,
+and those observations requiring very high powers, I had ready at hand
+several magnifiers of 227, 460, 932, 1536, 2010, &c., all of which I
+have successfully used on that occasion. The power I had on when I
+first saw the comet was 227. From experience I knew that the diameters
+of the fixed stars are not proportionally magnified with higher powers,
+as the planets are; I therefore now put on the powers of 460 and 932,
+and found the diameter of the comet increased in proportion to the
+power, as it ought to be, on the supposition of its not being a fixed
+star, while the diameters of the stars to which I compared it, were not
+increased in the same ratio. Also, that the comet being magnified much
+beyond what its light would admit of, appeared hazy and ill-defined
+with these great powers, while the stars preserved that lustre and
+distinctness which from many thousand observations I knew they would
+retain. The sequel has shown that my surmises were well founded, this
+proving to be the comet we have lately observed.
+
+
+ II
+
+ ON THE NAME OF THE NEW PLANET
+
+By the observations of the most eminent astronomers in Europe it
+appears that the new star, which I had the honour of pointing out
+to them in March, 1781, is a primary planet of our solar system. A
+body so nearly related to us by its similar condition and situation,
+in the unbounded expanse of the starry heavens, must often be the
+subject of conversation, not only of astronomers, but of every lover
+of science in general. This consideration, then, makes it necessary
+to give it a name, by which it may be distinguished from the rest of
+the planets and fixed stars. In the fabulous ages of ancient times
+the appellations of Mercury, Venus, Mars, Jupiter, and Saturn, were
+given to the planets, as being the names of their principal heroes
+and divinities. In the present more philosophical era, it would
+hardly be allowable to have recourse to the same method, and call
+on Juno, Apollo, Pallas or Minerva, for a name to our new heavenly
+body. The first consideration in any particular event, or remarkable
+incident, seems to be its chronology; if in any future age it should be
+asked, when this last-found planet was discovered it would be a very
+satisfactory answer to say, “In the reign of King George the Third.” As
+a philosopher, then, the name of Georgium Sidus presents itself to me,
+as an appellation which will conveniently convey the information of the
+time and country where and when it was brought to view.
+
+
+ III
+
+ ON NEBULOUS STARS, PROPERLY SO CALLED
+
+In one of his late examinations of a space in the heavens, which
+he had not reviewed before, Dr. H. discovered a star of about the
+eighth magnitude, surrounded with a faintly luminous atmosphere, of a
+considerable extent. The phenomenon was so striking that he could not
+help reflecting on the circumstance that attended it, which appeared to
+be of a very instructive nature, and such as might lead to inferences
+which will throw a considerable light on some points relating to the
+construction of the heavens.
+
+Cloudy or nebulous stars have been mentioned by several astronomers;
+but this name ought not to be applied to the objects which they have
+pointed out as such; for, on examination, they proved to be either
+mere clusters of stars, plainly to be distinguished with his large
+instruments, or such nebulous appearances as might be reasonably
+supposed to be occasioned by a multitude of stars at a vast distance.
+The milky way itself consists entirely of stars, and by imperceptible
+degrees he was led on from most evident congeries of stars to other
+groups in which the lucid points were smaller, but still very plainly
+to be seen; and from them to such wherein they could but barely be
+suspected, till he arrived at last to spots in which no trace of a star
+was to be discerned. But then the gradations to these later were by
+such well-connected steps as left no room for doubt but that all these
+phenomena were equally occasioned by stars, variously dispersed in the
+immense expanse of the universe.
+
+When Dr. H. pursued these researches, he was in the situation of a
+natural philosopher who follows the various species of animals and
+insects from the height of their perfection down to the lowest ebb of
+life; when, arriving at the vegetable kingdom, he can scarcely point
+out to us the precise boundary where the animal ceases and the plant
+begins; and may even go so far as to suspect them not to be essentially
+different. But recollecting himself, he compares, for instance, one
+of the human species to a tree, and all doubt of the subject vanishes
+before him. In the same manner we pass through gentle steps from a
+coarse cluster of stars, such as the Pleiades, the Præserpe, the milky
+way, the cluster in the Crab, the nebula in Hercules, that near the
+preceding hip of Bootis, the 17th, 38th, 41st of the 7th class of his
+catalogues, the 10th, 20th, 35th of the 6th class, the 33d, 48th, 213th
+of the 1st, the 12th, 150th, 756th of the 2d, and the 18th, 140th,
+725th of the 3d, without any hesitation, till we find ourselves brought
+to an object such as the nebula in Orion, where we are still inclined
+to remain in the once adopted idea, of stars exceedingly remote,
+and inconceivably crowded, as being the occasion of that remarkable
+appearance. It seems, therefore, to require a more dissimilar object
+to set us right again. A glance like that of the naturalist, who casts
+his eye from the perfect animal to the perfect vegetable, is wanting to
+remove the veil from the mind of the astronomer. The object mentioned
+above is the phenomenon that was wanting for this purpose. View, for
+instance, the 19th cluster of the 6th class, and afterwards cast your
+eye on this cloudy star, and the result will be no less decisive than
+that of the naturalist alluded to. Our judgment will be, that the
+nebulosity about the star is not of a starry nature.
+
+But that we may not be too precipitate in these new decisions, let us
+enter more at large into the various grounds which induced us formerly
+to surmise, that every visible object, in the extended and distant
+heavens, was of the starry kind, and collate them with those which now
+offer themselves for the contrary opinion. It has been observed, on a
+former occasion, that all the smaller parts of other great systems,
+such as the planets, their rings and satellites, the comets, and such
+other bodies of the like nature as may belong to them, can never be
+perceived by us, on account of the faintness of light reflected from
+small opaque objects: in the present remarks, therefore, all these are
+to be entirely set aside.
+
+A well connected series of objects, such as mentioned above, has led
+us to infer that all nebulæ consist of stars. This being admitted, we
+were authorized to extend our analogical way of reasoning a little
+further. Many of the nebulæ had no other appearance than that whitish
+cloudiness, on the blue ground on which they seemed to be projected;
+and why the same cause should not be assigned to explain the most
+extensive nebulosities, as well as those that amounted only to a
+few minutes of a degree in size, did not appear. It could not be
+inconsistent to call up a telescopic milky way, at an immense distance,
+to account for such a phenomenon; and if any part of the nebulosity
+seemed detached from the rest, or contained a visible star or two,
+the probability of seeing a few near stars, apparently scattered over
+the far distant regions of myriads of sidereal collections, rendered
+nebulous by their distance, would also clear up these singularities.
+
+In order to be more easily understood in his remarks on the comparative
+disposition of the heavenly bodies, Dr. H. mentions some of the
+particulars which introduced the ideas of connection and disjunction:
+for these, being properly founded on an examination of objects that
+may be reviewed at any time, will be of considerable importance to the
+validity of what we may advance with regard to the lately discovered
+nebulous stars. On June 27, 1786, he saw a beautiful cluster of very
+small stars of various sizes, about 15' in diameter, and very rich
+of stars. On viewing this object, it is impossible to withhold our
+assent to the idea which occurs, that these stars are connected so far
+with one another as to be gathered together, within a certain space,
+of little extent when compared to the vast expanse of the heavens.
+As this phenomenon has been repeatedly seen in a thousand cases, Dr.
+H. thinks he may justly lay great stress on the idea of such stars
+being connected. On September 9, 1779, he discovered a very small star
+near _ε_ Bootis. The question here occurring, whether it had any
+connection with _ε_ or not, was determined in the negative; for,
+considering the number of stars scattered in a variety of places, it is
+very far from being uncommon, that a star at a great distance should
+happen to be nearly in a line drawn from the sun through _ε_, and
+thus constitute the observed double star. September 7, 1782, when Dr.
+H. first saw the planetary nebula near υ Aquarii, he pronounced it to
+be a system whose parts were connected together. Without entering
+into any kind of calculation, it is evident that a certain degree of
+light within a very small space, joined to the particular shape this
+object presents to us, which is nearly round, and even in its deviation
+consistent with regularity, being a little elliptical, ought naturally
+to give us the idea of a conjunction in the things that produce it.
+And a considerable addition to this argument may be derived from a
+repetition of the same phenomenon, in nine or ten more of a similar
+construction.
+
+When Dr. H. examined the cluster of stars, following the head of the
+Great Dog, he found on March 19, 1786, that there was within this
+cluster a round, resolvable nebula, of about 2' in diameter, and nearly
+an equal degree of light throughout. Here, considering that the cluster
+was free from nebulosity in other parts, and that many such clusters,
+as well as such nebulæ, exist in divers parts of the heavens, it seemed
+very probable that the nebula was unconnected with the cluster; and
+that a similar reason would as easily account for this appearance as
+it had resolved the phenomenon of the double star near e Bootis; that
+is, a casual situation of our sun and the two other objects nearly in
+a line. And though it may be rather more remarkable, that this should
+happen with two compound systems, which are not by far so numerous
+as single stars, we have, to make up for this singularity, a much
+larger space in which it may take place, the cluster being of a very
+considerable extent.
+
+On February 15, 1786, Dr. H. discovered that one of his planetary
+nebulæ had a spot in the centre, which was more luminous than the rest,
+and with long attention, a very bright, round, well-defined centre
+became visible. He remained not a single moment in doubt, but that
+the bright centre was connected with the rest of the apparent disc.
+October 6, 1785, he found a very bright, round nebula, of about 1-1/2'
+in diameter. It has a large, bright nucleus in the middle, which is
+undoubtedly connected with the luminous parts about it. And though
+we must confess, that if this phenomenon, and many more of the same
+nature, recorded in the catalogues of nebulæ, consist of clustering
+stars, we find ourselves involved in some difficulty to account for the
+extraordinary condensation of them about the centre; yet the idea of
+a connection between the outward parts and these very condensed ones
+within, is by no means lessened on that account.
+
+There is a telescopic milky way, which Dr. H. has traced out in the
+heavens in many sweeps made from the year 1783 to 1789. It takes up
+a space of more than 60 square degrees of the heavens, and there are
+thousands of stars scattered over it: among others, four that form a
+trapezium, and are situated in the well known nebula of Orion, which
+is included in the above extent. All these stars, as well as the four
+mentioned, he takes to be entirely unconnected with the nebulosity
+which involves them in appearance. Among them is also _δ_ Orionis,
+a cloudy star, improperly so called by former astronomers; but it does
+not seem to be connected with the milkiness any more than the rest.
+
+Dr. H. now comes to some other phenomena, that, from their singularity,
+merit undoubtedly a very full discussion. Among the reasons which
+induced us to embrace the opinion that all very faint milky nebulosity
+ought to be ascribed to an assemblage of stars is, that we could
+not easily assign any other cause of sufficient importance for such
+luminous appearances, to reach us at the immense distance we must
+suppose ourselves to be from them. But if an argument of considerable
+force should now be brought forward, to show the existence of luminous
+matter, in a state of modification very different from the construction
+of a sun or star, all objections, drawn from our incapacity of
+accounting for new phenomena on old principles, he thinks, will lose
+their validity.
+
+Hitherto Dr. H. has been showing, by various instances in objects whose
+places are given, in what manner we may form ideas of connection, and
+its contrary, by an attentive inspection of them only; he now relates
+a series of observations, with remarks on them as they are delivered,
+from which he afterwards draws a few simple conclusions, that seem to
+be of considerable importance.
+
+October 16, 1784. A star of about the ninth magnitude, surrounded by a
+milky nebulosity, or chevelure, of about 3' in diameter. The nebulosity
+is very faint, and a little extended or elliptical, the extent being
+not far from the meridian, or a little from north preceding to south
+following. The chevelure involves a small star, which is about 1-1/2'
+north of the cloudy star; other stars of equal magnitude are perfectly
+free from this appearance. (R.A. 5h 57m 4s. P.D. 96° 22'). His present
+judgment concerning this remarkable object is, that the nebulosity
+belongs to the star which is situated in its centre. The small one, on
+the contrary, which is mentioned as involved, being one of many that
+are profusely scattered over this rich neighbourhood, he supposes to
+be quite unconnected with this phenomenon. A circle of 3' in diameter
+is sufficiently large to admit another small star, without any bias to
+the judgment he formed concerning the one in question. It might appear
+singular, that such an object should not have immediately suggested
+all the remarks contained in this paper; but about things that appear
+new we ought not to form opinions too hastily, and his observations
+on the construction of the heavens were then but entered on. In this
+case, therefore, it was the safest way to lay down a rule not to reason
+on the phenomena that might offer themselves, till he should be in
+possession of a sufficient stock of materials to guide his researches.
+
+October 16, 1784. A small star of about the 11th or 12th magnitude,
+very faintly affected with milky nebulosity; other stars of the same
+magnitude were perfectly free from this appearance. Another observation
+mentions five or six small stars within the space of 3 or 4', all very
+faintly affected in the same manner, and the nebulosity suspected to
+be a little stronger about each star. But a third observation rather
+opposes this increase of the faintly luminous appearance. (R. A. 6h
+Om 33s. P. D. 96° 13'). Here the connection between the stars and the
+nebulosity is not so evident as to amount to conviction; for which
+reason we shall pass on to the next.
+
+ * * * * *
+
+November 25, 1788. A star of about the 9th magnitude, surrounded with
+very faint milky nebulosity; other stars of the same size are perfectly
+free from that appearance. Less than 1' in diameter. The star is either
+not round or double (a).
+
+March 23, 1789. A bright, considerably well-defined nucleus, with a
+very faint, small, round chevelure (b). The connection admits of no
+doubt; but the object is not perhaps of the same nature with those
+called cloudy stars.
+
+April 14, 1789. A considerable, bright, round nebula; having a large
+place in the middle of nearly an equal brightness; but less bright
+towards the margin (c). This seems rather to approach the planetary
+sort.
+
+March 5, 1790. A pretty considerable star of the 9th or 10th
+magnitude, visibly affected with a very faint nebulosity of little
+extent, all around. A power of 300 showed the nebulosity of greater
+extent (d). The connection is not to be doubted.
+
+March 19, 1790. A very bright nucleus, with a small, very faint
+chevelure, exactly round. In a low situation, where the chevelure
+could hardly be seen, this object would put on the appearance of an
+ill-defined, planetary nebula, of 6, 8 or 10" diameter (e).
+
+November 13, 1790. A most singular phenomenon! A star of about the 8th
+magnitude, with a faint luminous atmosphere, of a circular form, and
+of about 3' in diameter. The star is perfectly in the centre, and the
+atmosphere is so diluted, faint, and equal throughout, that there can
+be no surmise of its consisting of stars; nor can there be a doubt of
+the evident connection between the atmosphere and the star. Another
+star not much less in brightness, and in the same field with the above,
+was perfectly free from any such appearance. This last object is so
+decisive in every particular, Dr. H. says, that we need not hesitate
+to admit it as a pattern, from which we are authorised to draw the
+following important consequences:
+
+Supposing the connection between the star and its surrounding
+nebulosity to be allowed, we argue, that one of the two following cases
+must necessarily be admitted: In the first place, if the nebulosity
+consist of stars that are very remote, which appear nebulous on account
+of the small angles their mutual distances subtend at the eye, by which
+they will not only, as it were, run into each other, but also appear
+extremely faint and diluted; then, what must be the enormous size of
+the central point, which outshines all the rest in so superlative a
+degree as to admit of no comparison! In the next place, if the star be
+larger than common, how very small and compressed must be those other
+luminous points that are the occasion of the nebulosity which surrounds
+the central one! As, by the former supposition, the luminous central
+point must far exceed the standard of what we call a star, so, in the
+latter, the shining matter about the centre will be much too small to
+come under the same denomination; we therefore either have a central
+body which is not a star, or have a star which is involved in a shining
+fluid, of a nature totally unknown to us. Dr. H. can adopt no other
+sentiment than the latter, since the probability is certainly not for
+the existence of so enormous a body as would be required to shine like
+a star of the eighth magnitude, at a distance sufficiently great to
+cause a vast system of stars to put on the appearance of a very diluted
+milky nebulosity.
+
+But what a field of novelty is here opened to our conceptions! A
+shining fluid, of a brightness sufficient to reach us from the remote
+regions of a star of the 8th, 9th, 10th, or 12th magnitude, and of an
+extent so considerable as to take up 3, 4, 5, or 6 minutes in diameter!
+Can we compare it to the coruscation of the electric fluid in the
+aurora borealis? Or to the more magnificent cone of the zodiacal light
+as we see it in the spring or autumn? The latter, notwithstanding Dr.
+H. has observed it to reach at least 90° from the sun, is yet of so
+little extent and brightness, as probably not to be perceived even by
+the inhabitants of Saturn or the Georgian planet, and must be utterly
+invisible at the remoteness of the nearest fixed star.
+
+More extensive views may be derived from this proof of the existence
+of a shining matter. Perhaps it has been too hastily surmised that
+all milky nebulosity, of which there is so much in the heavens, is
+owing to starlight only. These nebulous stars may serve as a clue to
+unravel other mysterious phenomena. If the shining fluid that surrounds
+them is not so essentially connected with these nebulous stars, but
+that it can also exist without them, which seems to be sufficiently
+probable, and will be examined hereafter, we may with great facility
+explain that very extensive, telescopic nebulosity, which, as before
+mentioned, is expanded over more than 60° of the heavens, about the
+constellation of Orion; a luminous matter accounting much better for it
+than clustering stars at a distance. In this case we may also pretty
+nearly guess at its situation, which must commence somewhere about the
+range of the stars of the 7th magnitude, or a little farther from us,
+and extend unequally in some places perhaps to the regions of those
+of the 9th, 10th, 11th, and 12th. The foundation for this surmise is,
+that not unlikely some of the stars that happen to be situated in a
+more condensed part of it, or that perhaps by their own attraction
+draw together some quantity of this fluid greater than what they are
+entitled to by their situation in it, will, of course, assume the
+appearance of cloudy stars; and many of those named are either in this
+stratum of luminous matter, or very near it.
+
+It has been said above, that in nebulous stars the existence of the
+shining fluid does not seem to be so essentially connected with the
+central points that it might not also exist without them. For this
+opinion we may assign several reasons. One of them is the greater
+resemblance of the chevelure of these stars and the diffused extensive
+nebulosity mentioned before, which renders it highly probable that
+they are of the same nature. Now, if this be admitted, the separate
+existence of the luminous matter, or its independence of a central
+star, is fully proved. We may also judge, very confidently, that the
+light of this shining fluid is no kind of reflection from the star in
+the centre; for, as we have already observed, reflected light could
+never reach us at the great distance we are from such objects. Besides,
+how impenetrable would be an atmosphere of a sufficient density to
+reflect so great a quantity of light! And yet we observe, that the
+outward parts of the chevelure are nearly as bright as those that are
+close to the star; so that this supposed atmosphere ought to give no
+obstruction to the passage of the central rays. If therefore this
+matter is self-luminous, it seems more fit to produce a star by its
+condensation than to depend on the star for its existence.
+
+Many other diffused nebulosities, besides that about the constellation
+of Orion, have been observed or suspected; but some of them are
+probably very distant, and run far out into space. For instance, about
+5m in time preceding _x_ Cygni, Dr. H. suspects as much of it
+as covers near 4 square degrees; and much about the same quantity
+44m preceding the 125 Tauri. A space of almost 8 square degrees, 6m
+preceding _α_ Trianguli, seems to be tinged with milky nebulosity.
+Three minutes preceding the 46 Eridani, strong, milky nebulosity is
+expanded over more than 2 square degrees. Fifty-four minutes preceding
+the 13th _Canum venaticorum_, and again 48m preceding the same
+star, the field of view affected with whitish nebulosity throughout
+the whole breadth of the sweep, which was 2° 39'. Four minutes
+following the 57 Cygni a considerable space is filled with faint,
+milky nebulosity, which is pretty bright in some places, and contains
+the 37th nebula of the 5th class, in the brightest part of it. In the
+neighbourhood of the 44th Piscium, very faint nebulosity appears to
+be diffused over more than 9 square degrees of the heavens. Now all
+these phenomena, as we have already seen, will admit of a much easier
+explanation by a luminous fluid than by stars at an immense distance.
+
+The nature of planetary nebulæ, which has hitherto been involved in
+much darkness, may now be explained with some degree of satisfaction,
+since the uniform and very considerable brightness of their apparent
+disc accords remarkably well with a much condensed, luminous fluid;
+whereas, to suppose them to consist of clustering stars, will not so
+completely account for the milkiness or soft tint of their light, to
+produce which it would be required that the condensation of the stars
+should be carried to an almost inconceivable degree of accumulation.
+The surmise of the regeneration of stars, by means of planetary nebulæ,
+expressed in a former paper, will become more probable, as all the
+luminous matter contained in one of them, when gathered together into a
+body of the size of a star, would have nearly such a quantity of light
+as we find the planetary nebulæ to give. To prove this experimentally,
+we may view them with a telescope that does not magnify sufficiently
+to show their extent, by which means we shall gather all their light
+together into a point, when they will be found to assume the appearance
+of small stars; that is, of stars at the distance of those which we
+call of the 8th, 9th, or 10th magnitude. Indeed this idea is greatly
+supported by the discovery of a well-defined, lucid point, resembling
+a star, in the centre of one of them; for the argument which has been
+used, in the case of nebulous stars, to show the probability of the
+existence of luminous matter, which rested on the disparity between a
+bright point and its surrounding shining fluid, may here be alleged
+with equal justice. If the point be a generating star, the further
+accumulation of the already much condensed, luminous matter may
+complete it in time.
+
+How far the light that is perpetually emitted from millions of suns may
+be concerned in this shining fluid, it might be presumptuous to attempt
+to determine; but, notwithstanding the inconceivable subtilty of the
+particles of light, when the number of the emitting bodies is almost
+infinitely great, and the time of the continual emission indefinitely
+long, the quantity of emitted particles may well become adequate to the
+constitution of a shining fluid, or luminous matter, provided a cause
+can be found that may retain them from flying off, or reunite them. But
+such a cause cannot be difficult to guess at, when we know that light
+is so easily reflected, refracted, inflected and deflected; and that,
+in the immense range of its course, it must pass through innumerable
+systems, where it cannot but frequently meet with many obstacles to
+its rectilinear progression not to mention the great counteraction
+of the united attractive force of whole sidereal systems, which must
+be continually exerting their power on the particles while they are
+endeavouring to fly off. However, we shall lay no stress on a surmise
+of this kind, as the means of verifying it are wanting; nor is it of
+any immediate consequence to us to know the origin of the luminous
+matter. Let it suffice, that its existence is rendered evident, by
+means of nebulous stars.
+
+
+FOOTNOTES:
+
+[Footnote 17: This excerpt and the one following are from the report
+by Herschel in the _Transactions of the Royal Society of London_;
+the third is an abstract from the same report, the conclusion, however,
+being by Herschel.]
+
+
+
+
+ XVI
+
+ KARL WILHELM SCHEELE
+
+ 1742-1786
+
+
+ _Karl Wilhelm Scheele, who discovered independently of the English
+ chemists the double constitution of air, was born in Stralsund,
+ Pomerania, December 19, 1742. At an early age he manifested interest
+ in pharmacy, and during his career as an apothecary engaged in various
+ experiments in chemistry. He published his “Treatise on Air and Fire”
+ in 1777. He died at Köping, May 21, 1786._
+
+
+ THE CONSTITUENTS OF AIR[18]
+
+1. It is the object and chief business of chemistry to separate
+skilfully substances into their constituents, to discover their
+properties, and to compound them in different ways. How difficult it
+is, however, to carry out such operations with the greatest accuracy,
+can only be unknown to one who either has never undertaken this
+occupation, or at least has not done so with sufficient attention.
+
+2. Hitherto chemical investigators are not agreed as to how many
+elements or fundamental materials compose all substances. In fact this
+is one of the most difficult problems; some indeed hold that there
+remains no further hope of searching out the elements of substances.
+Poor comfort for those who feel their greatest pleasure in the
+investigation of natural things! Far is he mistaken, who endeavours
+to confine chemistry, this noble science, within such narrow bounds!
+Others believe that earth and phlogiston are the things from which all
+material nature has derived its origin. The majority seem completely
+attached to the peripatetic elements.
+
+3. I must admit that I have bestowed no little trouble upon this
+matter in order to obtain a clear conception of it. One may reasonably
+be amazed at the ideas and conjectures which authors have recorded
+on the subject, especially when they give a decision respecting the
+phenomenon of fire; and this very matter was of the greatest importance
+to me. I perceived the necessity of a knowledge of fire, because
+without this it is not possible to make any experiment; and without
+fire and heat it is not possible to make use of the action of any
+solvent. I began accordingly to put aside all explanations of fire; I
+undertook a multitude of experiments in order to fathom this beautiful
+phenomenon as fully as possible. I soon found, however, that one could
+not form any true judgment regarding the phenomena which fire presents,
+without a knowledge of the air. I saw, after carrying out a series of
+experiments, that air really enters into the mixture of fire, and with
+it forms a constituent of flame and of sparks. I learned accordingly
+that a treatise like this, on fire, could not be drawn up with proper
+completeness without taking the air also into consideration.
+
+4. Air is that fluid invisible substance which we continually breathe,
+which surrounds the whole surface of the earth, is very elastic, and
+possesses weight. It is always filled with an astonishing quantity
+of all kinds of exhalations, which are so finely subdivided in it
+that they are scarcely visible even in the sun’s rays. Water vapours
+always have the preponderance amongst these foreign particles. The
+air, however, is also mixed with another elastic substance resembling
+air, which differs from it in numerous properties, and is, with good
+reason, called aerial acid by Professor Bergman. It owes its presence
+to organised bodies, destroyed by putrefaction or combustion.
+
+5. Nothing has given philosophers more trouble for some years than just
+this delicate acid or so-called fixed air. Indeed it is not surprising
+that the conclusions which one draws from the properties of this
+elastic acid are not favourable to all who are prejudiced by previously
+conceived opinions. These defenders of the Paracelsian doctrine believe
+that the air is in itself unalterable; and, with Hales, that it really
+unites with substances thereby losing its elasticity; but that it
+regains its original nature as soon as it is driven out of these by
+fire or fermentation. But since they see that the air so produced is
+endowed with properties quite different from common air, they conclude,
+without experimental proofs, that this air has united with foreign
+materials, and that it must be purified from these admixed foreign
+particles by agitation and filtration with various liquids. I believe
+that there would be no hesitation in accepting this opinion, if one
+could only demonstrate clearly by experiments that a given quantity
+of air is capable of being completely converted into fixed or other
+kind of air by the admixture of foreign materials; but since this has
+not been done, I hope I do not err if I assume as many kinds of air as
+experiment reveals to me. For when I have collected an elastic fluid,
+and observe concerning it that its expansive power is increased by heat
+and diminished by cold, while it still uniformly retains its elastic
+fluidity, but also discover in it properties and behavior different
+from those of common air, then I consider myself justified in believing
+that this is a peculiar kind of air. I say that air thus collected must
+retain its elasticity even in the greatest cold, because otherwise an
+innumerable multitude of varieties of air would have to be assumed,
+since it is very probable that all substances can be converted by
+excessive heat into a vapour resembling air.
+
+6. Substances which are subjected to putrefaction or to destruction by
+means of fire diminish, and at the same time consume, a part of the
+air; sometimes it happens that they perceptibly increase the bulk of
+the air, and sometimes finally that they neither increase nor diminish
+a given quantity of air--phenomena which are certainly remarkable.
+Conjectures can here determine nothing with certainty, at least they
+can only bring small satisfaction to a chemical philosopher, who must
+have his proofs in his hands. Who does not see the necessity of making
+experiments in this case, in order to obtain light concerning this
+secret of nature?
+
+7. General properties of ordinary air.
+
+(1.) Fire must burn for a certain time in a given quantity of air.
+(2.) If, so far as can be seen, this fire does not produce during
+combustion any fluid resembling air, then, after the fire has gone
+out of itself, the quantity of air must be diminished between a third
+and a fourth part. (3.) It must not unite with common water. (4.) All
+kinds of animals must live for a certain time in a confined quantity of
+air. (5.) Seeds, as for example peas, in a given quantity of similarly
+confined air, must strike roots and attain a certain height with the
+aid of some water and of a moderate heat.
+
+Consequently, when I have a fluid resembling air in its external
+appearance, and find that it has not the properties mentioned, even
+when only one of them is wanting, I feel convinced that it is not
+ordinary air.
+
+8. Air must be composed of elastic fluids of two kinds.
+
+First Experiment.--I dissolved one ounce of alkaline liver of sulphur
+in eight ounces of water; I poured four ounces of this solution into an
+empty bottle capable of holding 24 ounces of water, and closed it most
+securely with a cork; I then inverted the bottle and placed the neck
+in a small vessel with water; in this position I allowed it to stand
+for fourteen days. During this time the solution had lost a part of its
+red colour and had also deposited some sulphur: afterwards I took the
+bottle and held it in the same position in a larger vessel with water,
+so that the mouth was under and the bottom above the water-level, and
+withdrew the cork under the water; immediately water rose with violence
+into the bottle. I closed the bottle again, removed it from the water,
+and weighed the fluid which it contained. There were 10 ounces. After
+substracting from this the four ounces of solution of sulphur there
+remain six ounces, consequently it is apparent from this experiment
+that of 20 parts of air six parts have been lost in 14 days.
+
+9. Second Experiment.--(a) I repeated the preceding experiment with the
+same quantity of liver of sulphur, but with this difference that I only
+allowed the bottle to stand a week tightly closed. I then found that of
+20 parts of air only 4 had been lost. (b) On another occasion I allowed
+the very same bottle to stand four months; the solution still possessed
+a somewhat dark yellow colour. But no more air had been lost than in
+the first experiment, that is to say six parts.
+
+10. Third Experiment.--I mixed two ounces of caustic ley, which
+was prepared from alkali of tartar and unslaked lime and did not
+precipitate lime-water, with half an ounce of the preceding solution of
+sulphur, which likewise did not precipitate lime-water. This mixture
+had a yellow colour. I poured it into the same bottle, and after this
+had stood fourteen days, well closed, I found the mixture entirely
+without colour and also without precipitate. I was enabled to conclude
+that the air in this bottle had likewise diminished, from the fact that
+air rushed into the bottle with a hissing sound after I had made a
+small hole in the cork.
+
+11. Fourth Experiment.--(a) I took four ounces of a solution of
+sulphur in lime-water; I poured this solution into a bottle and closed
+it tightly. After 14 days the yellow colour had disappeared, and of 20
+parts of air 4 parts had been lost. The solution contained no sulphur,
+but had allowed a precipitate to fall which was chiefly gypsum. (b.)
+Volatile liver of sulphur likewise diminishes the bulk of air. (c.)
+Sulphur, however, and volatile spirit of sulphur, undergo no alteration
+in it.
+
+12. Fifth Experiment.--I hung up over burning sulphur, linen rags which
+were dipped in a solution of alkali of tartar. After the alkali was
+saturated with the volatile acid, I placed the rags in a flask, and
+closed the mouth most carefully with a wet bladder. After three weeks
+had elapsed I found the bladder strongly pressed down; I inverted
+the flask, held its mouth in water and made a hole in the bladder;
+thereupon water rose with violence into the flask and filled the fourth
+part.
+
+13. Sixth Experiment.--I collected in the bladder the nitrous acid
+which arises on the dissolution of the metals in nitrous acid, and
+after I had tied the bladder tightly I laid it in a flask and secured
+the mouth very carefully with a wet bladder. The nitrous air gradually
+lost its elasticity, the bladder collapsed, and became yellow as if
+corroded by _aqua fortis_. After 14 days I made a hole in the
+bladder tied over the flask, having previously held it, inverted, under
+water; the water rose rapidly into the flask, and it remained only
+two-thirds empty.
+
+14. Seventh Experiment.--(a.) I immersed the mouth of a flask in a
+vessel with oil of turpentine. The oil rose in the flask a few lines
+every day. After the lapse of 14 days the fourth part of the flask
+was filled with it. I allowed it to stand for three weeks longer, but
+the oil did not rise higher. All those oils which dry in the air, and
+become converted into resinous substances, possess this property. Oil
+of turpentine, however, and linseed oil rise up sooner if the flask is
+previously rinsed out with a concentrated sharp ley. (b.) I poured two
+ounces of colourless and transparent animal oil of Dippel into a bottle
+and closed it very tightly; after the expiration of two months the oil
+was thick and black. I then held the bottle, inverted, under water and
+drew out the cork; the bottle immediately became one-fourth filled with
+water.
+
+15. Eighth Experiment.--(a.) I dissolved two ounces of vitriol of iron
+in thirty-two ounces of water, and precipitated this solution with
+a caustic ley. After the precipitate had settled, I poured away the
+clear fluid and put the dark green precipitate of iron so obtained,
+together with the remaining water, into the before-mentioned bottle (§
+8), and closed it tightly. After 14 days (during which time I shook the
+bottle frequently) this green calx of iron had acquired the colour of
+crocus of iron, and of 40 parts of air 12 had been lost. (b.) When iron
+filings are moistened with some water and preserved for a few weeks
+in a well closed bottle, a portion of the air is likewise lost. (c.)
+The solution of iron in vinegar has the same effect upon air. In this
+case the vinegar permits the dissolved iron to fall out in the form of
+a yellow crocus, and becomes completely deprived of this metal. (d.)
+The solution of copper prepared in closed vessels with spirit of salt
+likewise diminishes air. In none of the foregoing kinds of air can
+either a candle burn or the smallest spark glow.
+
+16. It is seen from these experiments that phlogiston, the simple
+inflammable principle, is present in each of them. It is known that the
+air strongly attracts to itself the inflammable part of substances and
+deprives them of it: not only this may be seen from the experiments
+cited, but it is at the same time evident that on the transference of
+the inflammable substance to the air a considerable part of the air
+is lost. But that inflammable substance alone is the cause of this
+action, is plain from this, that, according to the tenth paragraph,
+not the least trace of sulphur remains over, since, according to my
+experiments this colourless ley contains only some vitriolated tartar.
+The eleventh paragraph likewise shows this. But since sulphur alone,
+and also the volatile spirit of sulphur, have no effect upon the air (§
+11. c), it is clear that the decomposition of liver of sulphur takes
+place according to the laws of double affinity--that is to say, that
+the alkalies and lime attract the vitriolic acid, and the air attracts
+the phlogiston.
+
+It may also be seen from the above experiments, that a given quantity
+of air can only unite with, and at the same time saturate, a certain
+quantity of the inflammable substance: this is evident from the ninth
+paragraph, letter b. But whether the phlogiston which was lost by the
+substances was still present in the air left behind in the bottle,
+or whether the air which was lost had united and fixed itself with
+the materials such as liver of sulphur, oils, &c., are questions of
+importance.
+
+From the first view, it would necessarily follow that the inflammable
+substance possessed the property of depriving the air of part of its
+elasticity, and that in consequence of this it becomes more closely
+compressed by the external air. In order now to help myself out of
+these uncertainties, I formed the opinion that any such air must
+be specifically heavier than ordinary air, both on account of its
+containing phlogiston and also of its greater condensation. But how
+perplexed was I when I saw that a very thin flask which was filled with
+this air, and most accurately weighed, not only did not counterpoise
+an equal quantity of ordinary air, but was even somewhat lighter. I
+then thought that the latter view might be admissible; but in that case
+it would necessarily follow also that the lost air could be separated
+again from the materials employed. None of the experiments cited seemed
+to me capable of showing this more clearly than that according to the
+tenth paragraph, because this residuum, as already mentioned, consists
+of vitriolated tartar and alkali. In order therefore to see whether the
+lost air had been converted into fixed air, I tried whether the latter
+shewed itself when some of the caustic ley was poured into lime-water;
+but in vain--no precipitation took place. Indeed, I tried in several
+ways to obtain the lost air from this alkaline mixture, but as the
+results were similar to the foregoing, in order to avoid prolixity I
+shall not cite these experiments. Thus much I see from the experiments
+mentioned, that the air consists of two fluids, differing from each
+other, the one of which does not manifest in the least the property
+of attracting phlogiston, while the other, which composes between the
+third and the fourth part of the whole mass of the air, is peculiarly
+disposed to such attraction. But where this latter kind of air has gone
+to after it has united with the inflammable substance, is a question
+which must be decided by further experiments, and not by conjectures.
+
+
+FOOTNOTES:
+
+[Footnote 18: Translated from _Treatise on Air and Fire_ (1777).]
+
+
+
+
+ XVII
+
+ ANTOINE LAURENT LAVOISIER
+
+ 1743-1794
+
+
+ _Antoine Laurent Lavoisier was born in Paris, August 26, 1743.
+ After an early life spent in diligent study, in 1766 he was awarded
+ a prize for his essay on the best method of lighting Paris. His
+ attention having been called to the English experiments on gases
+ made by Priestley and Cavendish, he attacked the current phlogiston
+ conception of combustion and stated that Priestley’s “dephlogisticated
+ air” was the universal acidifying gas, and gave it the name of
+ “oxygen.” Systematizing chemistry and renaming the elements and their
+ compounds, he came to believe that chemical reactions had the certainty
+ of mathematical equations. From this he derived the idea of the
+ persistence of matter, regardless of changes, now established as one of
+ the basic concepts of modern science. During the French Revolution a
+ charge was brought against him and he was sent to the guillotine on May
+ 8, 1794._
+
+
+ THE NATURE OF COMBUSTION[19]
+
+I venture to submit to the Academy to-day a new theory of combustion,
+or rather, to speak with that reserve to whose law I submit myself,
+an hypothesis, by the aid of which all the phenomena of combustion,
+calcination, and even to some extent those accompanying the respiration
+of animals are explained in a very satisfactory manner. I had already
+laid the foundations of this hypothesis p. 279-280 of vol. I. of my
+_Opuscules physiques et chimiques_; but I admit that trusting
+little to my own knowledge, I did not then dare to put forward an
+opinion which might seem singular, and which was directly opposed to
+the theory of Stahl and of many celebrated men who have followed him.
+
+Though perhaps some of the reasons which then checked me still remain
+to-day, nevertheless, the facts which have multiplied since that
+time, and which seem to me favorable to my views, have confirmed
+me in my opinion: though not, perhaps, any stronger, I have become
+more confident, and I think I have sufficient proofs, or at least
+probabilities, so that even those who may not be of my opinion cannot
+blame me for having written.
+
+In general in the combustion of bodies four constant phenomena are
+observable, which seem to be laws from which nature never departs.
+Though these phenomena may be found implicitly stated in other memoirs,
+yet I cannot dispense with recalling them here in a few words.
+
+
+ FIRST PHENOMENON
+
+All combustion sets free matter either of fire or light.
+
+
+ SECOND PHENOMENON
+
+Bodies can burn only in a very small number of kinds of gases (airs),
+or rather there can be combustion only in one kind of air, that which
+Mr. Priestley has named dephlogisticated air, and which I should call
+pure air. Not only will the bodies which we call combustibles not burn
+in a vacuum or in any other kind of air, they are, on the contrary,
+extinguished there as promptly as if they had been plunged into water
+or any other liquid.
+
+
+ THIRD PHENOMENON
+
+In all combustion there is destruction or decomposition of the pure
+air in which the combustion takes place, and the body burned increases
+in weight exactly in proportion to the quantity of air destroyed or
+decomposed.
+
+
+ FOURTH PHENOMENON
+
+In all combustion the body burned changes to an acid by the addition
+of the substance which has increased its weight: thus, for example,
+if sulphur is burned under a receiver the product of the combustion is
+vitriolic acid; if phosphorus be burned the product is phosphoric acid;
+if a carboniferous substance, the product is fixed air, otherwise known
+as acid of lime (carbonic acid, etc.).
+
+(Note: I would remark in passing that the number of acids is infinitely
+greater than has been supposed.)
+
+The calcination of metals is subject to exactly the same laws, and it
+is with very great reason that Mr. Macquer has treated it as a slow
+combustion; thus, 1°, in all metallic combustion there is a liberating
+of fire matter (_matière du feu_); 2°, veritable calcination can
+take place only in pure air; 3°, there is a combination of the air with
+the substance calcined, but with this difference, that in place of
+forming an acid with it there results from it a particular combination
+known as metallic calx.
+
+This is not the place to point out the analogy which exists between the
+respiration of animals, combustion and calcination; I shall return to
+that in the sequel to this memoir.
+
+These different phenomena of the calcination of metals and of
+combustion are explained in a very happy manner by Stahl’s hypothesis;
+but it is necessary with him to suppose the existence of fire matter
+(_matière du feu_) or of fixed phlogiston in the metals, in
+sulphur and in all bodies which he regards as combustibles; yet if the
+partisans of Stahl’s doctrine are asked to prove the existence of fire
+matter in combustible bodies, they fall necessarily into a vicious
+circle and are obliged to reply that combustible bodies contain fire
+matter because they burn, and that they burn because they contain fire
+matter. It is easy to see that in the last analysis this is explaining
+combustion by combustion.
+
+The existence of fire matter, or phlogiston, in metals, in sulphur,
+etc., is then really only an hypothesis, a supposition which, once
+admitted, explains, it is true, some of the phenomena of calcination
+and combustion; but if I show that these very phenomena may be
+explained in quite as natural a way by the opposite hypothesis, that
+is to say, without supposing the existence of either fire matter or
+phlogiston in the substances called combustible, Stahl’s system will be
+shaken to its foundations.
+
+No doubt you will not fail to ask me first what I understand by fire
+matter. I reply with Franklin, Boerhaave and some of the philosophers
+of old, that the matter of fire or of light is a very subtle, very
+elastic fluid, which surrounds every part of the planet we live
+on, which penetrates with more or less ease the substances which
+compose that, and which tends, when it is free, to come to a state of
+equilibrium in all.
+
+I will add, borrowing the chemical phraseology, that this fluid is the
+solvent of a large number of substances; that it combines with them
+in the same way that water does with salt, and the acids with metals,
+and that the bodies thus combined and dissolved by the igneous fluid
+lose in part the properties which they had before the combination and
+acquire new ones which bring them nearer (make them more like) the fire
+matter.
+
+It is thus, as I have shown in a memoir deposited with the secretary
+of this Academy, that every aeriform fluid, every kind of air, is a
+resultant of the combination of some substance, solid or fluid, with
+the matter of fire or of light; and it is to this combination that
+aeriform fluids owe their elasticity, their specific volatility, their
+rarity, and all the other properties which ally (_rapprochent_)
+them to the igneous fluid.
+
+Pure air, according to this, what Mr. Priestley calls dephlogisticated
+air, is an igneous compound into which the matter of fire or of light
+enters as solvent, and into which some other substance enters as a
+base; but if, in any solution whatever, a substance is presented to
+the base with which that has greater affinity, it unites with this
+instantly and the solvent which it leaves is set free.
+
+The same thing happens with the air in combustion; the substance
+which burns steals away the base; then the fire matter which served
+as its solvent becomes free, regains its rights and escapes with the
+characteristics by which we know it; that is to say, with flame, heat
+and light.
+
+To elucidate whatever may seem obscure in this theory let us apply it
+to some examples: when a metal is calcined in pure air, the base of the
+air, which has less affinity for its own solvent than for the metal,
+unites with the latter as it melts and converts it into metallic calx.
+This combination of the base of the air with the metal is proved 1st,
+by the increase in weight which the latter undergoes in calcination;
+2nd, by the almost total using up of the air under the receiving bell.
+But, if the base of the air was held in solution by the fire matter,
+in proportion as this base combined with the metal, the fire matter
+should become free and produce, in freeing itself, flame and light. You
+understand that the more speedy the calcination of the metal, that is
+to say, the more fixation of the air takes place in a given time, the
+more fire matter will be liberated, and, consequently, the more marked
+and obvious the combustion will be.
+
+
+I might apply this theory successively to all combustions, but as
+I shall have frequent occasion to return to this subject, I will
+content myself at this time with these general illustrations. So, to
+resume, the air is composed, according to my idea, of fire matter as
+a dissolvent combined with a substance which serves it as a base,
+and which in some way neutralizes it; whenever a substance for which
+it has a greater affinity is brought into contact with this base, it
+leaves its solvent; then the fire-substance regains its rights, its
+properties, and appears to our eyes with heat, flame and light.
+
+Pure air, the dephlogisticated air of Mr. Priestley, is then, according
+to this opinion, the real combustible body, and perhaps the only one of
+that nature, and it is seen that it is no longer necessary, in order
+to explain the phenomena of combustion, to suppose that there exists
+a large quantity of fire fixed in all the substances which we call
+combustible, but that it is very probable, on the contrary, that very
+little of it exists in metals, in sulphur, phosphorus, and in most of
+the very solid, heavy and compact bodies, and, perhaps even that there
+exists in these substances only free fire matter, in virtue of the
+property which this matter has of putting itself in equilibrium with
+all surrounding bodies.
+
+Another striking reflection which comes to the support of the preceding
+ones, is that almost all substances may exist in three different
+states: under a solid form, under a liquid form, that is to say
+melted, or in the state of air or vapor. These three states depend
+solely on the quantity, more or less, of fire matter with which these
+substances are interpenetrated and with which they are combined.
+Fluidity, vaporization, elasticity, are then properties characteristic
+of the presence of fire and of a great abundance of fire; solidity,
+compactness, on the contrary, are evidences of its absence. By so much
+then as it is demonstrated that aeriform substances and air itself
+contain a large quantity of fire in combination, by so much it is
+probable that solid bodies contain little of it.
+
+For the rest, I repeat, in attacking here the doctrine of Stahl, it was
+not my purpose to substitute for it a rigorously demonstrated theory,
+but only an hypothesis which seemed to me more probable, more in
+conformity with the laws of nature, and one which appeared to involve
+less forced explanations and fewer contradictions.
+
+
+FOOTNOTES:
+
+[Footnote 19: _On Combustion_, Vol. II, p. 225.]
+
+
+
+
+ XVIII
+
+ ALESSANDRO VOLTA
+
+ 1745-1827
+
+
+ _Alessandro Volta, born at Como, Italy, February 18, 1745, became
+ teacher of physics at Como in 1774, and five years later accepted a
+ professorship at Pavia. Becoming interested in Galvani’s experiments
+ with electricity on the muscles of a frog, he applied them in his
+ attempts to confirm his own theory that the frog’s muscles were a
+ sensitive electrometer. In doing this he conceived the voltaic pile,
+ which produced the first constant electrical current--a discovery which
+ had immense effects in later studies in electricity. He died at Como,
+ March 5, 1827._
+
+
+ NEW GALVANIC INSTRUMENT[20]
+
+ON THE ELECTRICITY EXCITED BY THE MERE CONTACT OF CONDUCTING SUBSTANCES
+ OF DIFFERENT KINDS
+
+The chief of these results, and which comprehends nearly all the
+others, is the construction of an apparatus which resembles in its
+effects, viz. (such as giving shocks to the arms, &c.,) the Leyden
+phial, and still better, electric batteries weakly charged; acting
+continually, or whose charge, after each explosion, recharges itself
+again; which in short becomes perpetual, from one infallible charge,
+from one action or impulse on the electric fluid; but which besides
+differs essentially from the other, by this continual action which
+is proper to it, and because that instead of consisting, like the
+ordinary phials and electric batteries, in one or more isolated plates,
+or thin layers of those bodies deemed the only electrics, and armed
+with conductors or bodies called non-electrics, this new apparatus is
+formed only of a number of these last bodies, chosen even among the
+best conductors, and so the farthest removed, according to the usual
+opinion, from the electric principle. This astonishing apparatus is
+nothing but an assemblage of a number of good conductors of a different
+kind, arranged in a certain manner. Thus, 30, 40, 60, or more pieces
+of copper, or better of silver, each applied to a piece of tin or
+still better of zinc, and an equal number of layers of water, or of
+some other liquid which may be a better conductor than simple water,
+as salt water, lye, &c., or of bits of card or leather, &c., soaked
+in such liquids. Of such layers interposed between each couple or
+combination of two different metals, one such alternate series, and
+always in the same order, of these three kinds of conductors, is all
+that constitutes M. Volta’s new instrument; which imitates so well
+the effects of the Leyden phial or electric batteries; not indeed
+with the force and explosions of these, when highly charged; but only
+equalling the effects of a battery charged to a very weak degree, of
+a battery, however, having an immense capacity, but which besides
+infinitely surpasses the virtue and the power of these same batteries;
+as it has no need, like them, of being charged beforehand, by means
+of a foreign electricity; and as it is capable of giving the usual
+commotion as often as ever it is properly touched. This apparatus, as
+it resembles more the natural electric organ of the torpedo, or of the
+electric eel than the Leyden phial and the ordinary electric batteries,
+M. Volta calls the artificial electric organ. For the construction of
+this instrument, M. Volta provides some dozens of small round metal
+plates of copper, or tin, or best of silver, about an inch in diameter,
+like shillings or half-crowns, and an equal number of plates of tin,
+or much better of zinc, of the same shape and size. These pieces he
+places exactly one upon another, forming a column, pillar or pile. He
+provides also as many round pieces of card, or leather, or such like
+spongy matter, capable of imbibing and retaining much of the water, or
+other liquid, when soaked in it. These soaked roullets or circles are
+to be a little less in diameter than the small metal discs or plates,
+that they may not jut out beyond them. All these discs are then placed
+horizontally on a table, one over another continually alternating, in a
+pile as high as will well support itself without tottering and falling
+down: beginning with a plate of either of the metals, as for instance,
+the silver, then upon that one of zinc, over which is to be put the
+soaked card; then other three discs, over these in the same order, viz.
+a silver, next a zinc, and then another moistened card, &c.
+
+After having raised the pile to about 20 of these stages or triads of
+plates, it will be already capable, not only of affecting Cavallo’s
+electrometer, assisted by the condenser, so as to raise it 10 or 15°,
+charging it by a simple touching, so as to cause it to give a spark,
+&c., as also to strike the fingers with which we touch the top or
+bottom of the column, with several small snaps, the fingers being
+wetted with water. But if to the 20 sets of triplets of the plates be
+added 20 or 30 more, disposed in the same order, the actions of the
+extended pile will be much stronger, and be felt through the arms up to
+the shoulders; and by continuing the touchings, the pains in the hands
+become insupportable.
+
+M. Volta constructs and combines his apparatus in various ways and
+forms, more or less powerful, convenient or amusing. One is as follows
+(Fig. 1, pl. 13,), which he calls a _couronne de tasses_. He
+disposes in a row a number of cups of wood, or earth, or glass, or
+any thing but metal, half filled with pure water, or salt water or
+lye; these are all made to communicate in a kind of chain, by several
+metallic arcs of which one arm or link, Aa, or only the extremity A,
+immersed in one of the cups, is of copper, or of copper silvered,
+and the other Z, immersed in the following cup, is of tin, or rather
+of zinc, the other two being soldered together near the crown of
+the arch. It is evident that a series of these cups, thus connected
+together, either in a straight or curved line, by the two metals and
+the intermediate liquid, is similar to the pillar or pile before
+described, and consequently will exhibit similar effects. Thus, to
+produce commotion or sensation in the hands and arms, we need only dip
+one hand into one of the cups and the finger of the other hand into
+another cup, sufficiently far from the former; and the action will be
+so much the stronger as the two cups are farther asunder, or have the
+more intermediate cups; and consequently the greatest by touching the
+first and the last in the chain.
+
+ * * * * *
+
+M. Volta concludes with various remarks and cautions in using this
+instrument; showing that it is perpetual in its virtue, renewing its
+charge spontaneously, and serving most of the purposes of the ordinary
+electrical machines, and even affecting and manifesting its power by
+most of the human senses, viz. feeling, tasting, hearing, and seeing.
+
+
+FOOTNOTES:
+
+[Footnote 20: From the _Transactions of the Royal Society of
+London_.]
+
+
+
+
+ XIX
+
+ PIERRE SIMON LAPLACE
+
+ 1749-1827
+
+
+ _Pierre Simon Laplace, born at Beaumont-en-Auge, Normandy, March
+ 28, 1749, became a teacher of mathematics at Beaufort before he was
+ eighteen years old. He gained d’Alembert’s attention by a letter
+ which he wrote to him on the principles of mathematics. After 1770
+ he engaged with Lagrange in determining the permanency of the solar
+ system by studying its perturbations and interactions, and finally
+ suggested how these changes were periodic. His monumental work, in five
+ volumes, “Mechanics of the Heavens” (1799-1825), gave a comprehensive
+ description of the movements of the solar system, and his “System of
+ the World” proposed the nebular theory of the origin of the universe.
+ His researches were important in the development of modern astronomy
+ because he substituted a dynamic for the descriptive point of view. He
+ died at Arcueil, March 5, 1827._
+
+
+ THE NEBULAR HYPOTHESIS[21]
+
+Buffon is the only individual that I know of, who, since the discovery
+of the true system of the world, endeavoured to investigate the origin
+of the planets and satellites. He supposed that a comet, by impinging
+on the Sun, carried away a torrent of matter, which was reunited far
+off, into globes of different magnitudes and at different distances
+from this star. These globes, when they cool and become hardened,
+are the planets and their satellites. This hypothesis satisfies the
+first of the five preceding phenomena[22]; for it is evident that all
+bodies thus formed should move very nearly in the plane which passes
+through the centre of the Sun, and through the direction of the torrent
+of matter which has produced them: but the four remaining phenomena
+appear to me inexplicable on this supposition. Indeed, the absolute
+motion of the molecules of a planet ought to be in the same direction
+as the motion of the centre of gravity; but it by no means follows
+from this, that the motion of rotation of a planet should be also in
+the same direction. Thus the Earth may revolve from east to west, and
+yet the absolute motion of each of its molecules may be directed from
+west to east. This observation applies also to the revolution of the
+satellites, of which the direction in the same hypothesis, is not
+necessarily the same as that of the motion of projection of the planets.
+
+The small eccentricity of the planetary orbits is a phenomenon,
+not only difficult to explain on this hypothesis, but altogether
+inconsistent with it. We know from the theory of central forces, that
+if a body which moves in a re-entrant orbit about the Sun, passes
+very near the body of the Sun, it will return constantly to it, at
+the end of each revolution. Hence it follows that if the planets were
+originally detached from the Sun, they would touch it, at each return
+to this star; and their orbits, instead of being nearly circular,
+would be very eccentric. Indeed it must be admitted that a torrent
+of matter detached from the Sun, cannot be compared to a globe which
+just skims by its surface; from the impulsions which the parts of this
+torrent receive from each other, combined with their mutual attraction,
+they may, by changing the direction of their motions, increase the
+distances of their perihelions from the Sun. But their orbits should
+be extremely eccentric, or at least all the orbits would not be q. p.
+circular, except by the most extraordinary chance. Finally, no reason
+can be assigned on the hypothesis of Buffon, why the orbits of more
+than one hundred comets, which have been already observed, should be
+all very eccentric. The hypothesis, therefore, is far from satisfying
+the preceding phenomena. Let us consider whether we can assign the true
+cause.
+
+Whatever may be its nature, since it has produced or influenced the
+direction of the planetary motions, it must have embraced them all
+within the sphere of its action; and considering the immense distance
+which intervenes between them, nothing could have effected this but
+a fluid of almost indefinite extent. In order to have impressed on
+them all a motion q. p. circular and in the same direction about the
+Sun, this fluid must environ this star, like an atmosphere. From a
+consideration of the planetary motions, we are therefore brought to
+the conclusion, that in consequence of an excessive heat, the solar
+atmosphere originally extended beyond the orbits of all the planets,
+and that it has successively contracted itself within its present
+limits.
+
+In the primitive state in which we have supposed the Sun to be, it
+resembles those substances which are termed nebulæ, which, when seen
+through telescopes, appear to be composed of a nucleus, more or less
+brilliant, surrounded by a nebulosity, which, by condensing on its
+surface, transforms it into a star. If all the stars are conceived to
+be similarly formed, we can suppose their anterior state of nebulosity
+to be preceded by other states, in which the nebulous matter was more
+or less diffuse, the nucleus being at the same time more or less
+brilliant. By going back in this manner, we shall arrive at a state
+of nebulosity so diffuse, that its existence can with difficulty be
+conceived.
+
+For a considerable time back, the particular arrangement of some stars
+visible to the naked eye, has engaged the attention of philosophers.
+Mitchel remarked long since how extremely improbable it was that the
+stars composing the constellation called the Pleiades, for example,
+should be confined within the narrow space which contains them, by the
+sole chance of hazard; from which he inferred that this group of stars,
+and the similar groups which the heavens present to us, are the effects
+of a primitive law of nature. These groups are a general result of the
+condensation of nebulæ of several nuclei; for it is evident that the
+nebulous matter being perpetually attracted by these different nuclei,
+ought at length to form a group of stars, like to that of the Pleiades.
+The condensation of nebulæ consisting of two nuclei, will in like
+manner form stars very near to each other, revolving the one about the
+other like to the double stars, whose respective motions have been
+already recognized.
+
+But in what manner has the solar atmosphere determined the motions of
+rotation and revolution of the planets and satellites? If these bodies
+had penetrated deeply into this atmosphere, its resistance would cause
+them to fall on the Sun. We may therefore suppose that the planets
+were formed at its successive limits, by the condensation of zones of
+vapours, which it must, while it was cooling, have abandoned in the
+plane of its equator.
+
+Let us resume the results which we have given in the tenth chapter of
+the preceding book. The Sun’s atmosphere cannot extend indefinitely;
+its limit is the point where the centrifugal force arising from the
+motion of rotation balances the gravity; but according as the cooling
+contracts the atmosphere, and condenses the molecules which are near
+to it, on the surface of the star, the motion of rotation increases;
+for, in virtue of the principle of areas, the sum of the areas
+described by the _radius vector_ of each particle of the Sun and
+its atmosphere, and projected on the plane of its equator, is always
+the same. Consequently the rotation ought to be quicker, when these
+particles approach to the centre of the Sun. The centrifugal force
+arising from this motion becoming thus greater; the point where the
+gravity is equal to it, is nearer to the centre of the Sun. Supposing,
+therefore, what is natural to admit, that the atmosphere extended at
+any epoch as far as this limit, it ought, according as it cooled,
+to abandon the molecules, which are situated at this limit, and at
+the successive limits produced by the increased rotation of the Sun.
+These particles, after being abandoned, have continued to circulate
+about this star, because their centrifugal force was balanced by their
+gravity. But as this equality does not obtain for these molecules
+of the atmosphere which are situated on the parallels to the Sun’s
+equator, these have come nearer by their gravity to the atmosphere
+according as it condensed, and they have not ceased to belong to it
+inasmuch as by their motion, they have approached to the plane of this
+equator.
+
+Let us now consider the zones of vapours, which have been successively
+abandoned. These zones ought, according to all probability, to form by
+their condensation, and by the mutual attraction of their particles,
+several concentrical rings of vapours circulating about the Sun. But
+mutual friction of the molecules of each ring ought to accelerate
+some and retard others, until they all had acquired the same angular
+motion. Consequently the real velocities of the molecules which are
+farther from the Sun, ought to be greatest. The following cause ought
+likewise to contribute to this difference of velocities: The most
+distant particles of the Sun, and which, by the effects of cooling
+and condensation, have collected so as to constitute the superior
+part of the ring, have always described areas proportional to the
+times, because the central force by which they are actuated has been
+constantly directed to this star; but this constancy of areas requires
+an increase of velocity, according as they approach more to each other.
+It appears that the same cause ought to diminish the velocity of the
+particles, which, situated near the ring, constitute its inferior part.
+
+If all the particles of a ring of vapours continued to condense without
+separating, they would at length constitute a solid or a liquid ring.
+But the regularity which this formation requires in all the parts of
+the ring, and in their cooling, ought to make this phenomenon very
+rare. Thus the solar system presents but one example of it; that of the
+rings of Saturn. Almost always each ring of vapours ought to be divided
+into several masses, which, being moved with velocities which differ
+little from each other, should continue to revolve at the same distance
+about the Sun. These masses should assume a spheroidical form, with a
+rotatory motion in the direction of that of their revolution, because
+their inferior particles have a less real velocity than the superior;
+they have therefore constituted so many planets in a state of vapour.
+But if one of them was sufficiently powerful, to unite successively by
+its attraction, all the others about its centre, the ring of vapours
+would be changed into one sole spheroidical mass, circulating about
+the Sun, with a motion of rotation in the same direction with that
+of revolution. This last case has been the most common; however, the
+solar system presents to us the first case, in the four small planets
+which revolve between Mars and Jupiter, at least unless we suppose
+with Olbers, that they originally formed one planet only, which was
+divided by an explosion into several parts, and actuated by different
+velocities. Now if we trace the changes which a further cooling ought
+to produce in the planets formed of vapours, and of which we have
+suggested the formation, we shall see to arise in the centre of each
+of them, a nucleus increasing continually, by the condensation of the
+atmosphere which environs it. In this state, the planet resembles the
+Sun in the nebulous state, in which we have first supposed it to be;
+the cooling should therefore produce at the different limits of its
+atmosphere, phenomena similar to those which have been described,
+namely, rings and satellites circulating about its centre in the
+direction of its motion of rotation, and revolving in the same
+direction on their axes. The regular distribution of the mass of rings
+of Saturn about its centre and in the plane of its equator, results
+naturally from this hypothesis, and, without it, is inexplicable. Those
+rings appear to me to be existing proofs of the primitive extension of
+the atmosphere of Saturn, and of its successive condensations. Thus,
+the singular phenomena of the small eccentricities of the orbits of the
+planets and satellites, of the small inclination of these orbits to the
+solar equator, and of the identity in the direction of the motions of
+rotation and revolution of all those bodies with that of the rotation
+of the Sun, follow the hypothesis which has been suggested, and render
+it extremely probable. If the solar system was formed with perfect
+regularity, the orbits of the bodies which compose it would be circles,
+of which the planes, as well as those of the various equators and
+rings, would coincide with the plane of the solar equator. But we may
+suppose that the innumerable varieties which must necessarily exist in
+the temperature and density of different parts of these great masses,
+ought to produce the eccentricities of their orbits, and the deviations
+of their motions, from the plane of this equator.
+
+In the preceding hypothesis, the comets do not belong to the solar
+system. If they be considered, as we have done, as small nebulæ,
+wandering from one solar system to another, and formed by the
+condensation of the nebulous matter, which is diffused so profusely
+throughout the universe, we may conceive that when they arrive in
+that part of space where the attraction of the Sun predominates, it
+should force them to describe elliptic or hyperbolic orbits. But
+as their velocities are equally possible in every direction, they
+must move indifferently in all directions, and at every possible
+inclination to the elliptic; which is conformable to observation. Thus
+the condensation of the nebulous matter, which explains the motions
+of rotation and revolution of the planets and satellites in the same
+direction, and in orbits very little inclined to each other, likewise
+explains why the motions of the comets deviate from this general law.
+
+The great eccentricity of the orbits of the comets, is also a result of
+our hypothesis. If those orbits are elliptic, they are very elongated,
+since their greater axes are at least equal to the radius of the sphere
+of activity of the Sun. But these orbits may be hyperbolic; and if the
+axes of these hyperbolæ are not very great with respect to the mean
+distance of the Sun from the Earth, the motion of the comets which
+describe them will appear to be sensibly hyperbolic. However, with
+respect to the hundred comets, of which the elements are known, not
+one appears to move in a hyperbola; hence the chances which assign
+a sensible hyperbola are extremely rare relatively to the contrary
+chances. The comets are so small, that they only become sensible when
+their perihelion distance is inconsiderable. Hitherto this distance
+has not surpassed twice the diameter of the Earth’s orbit, and most
+frequently, it has been less than the radius of this orbit. We may
+conceive, that in order to approach so near to the Sun, their velocity
+at the moment of their ingress within its sphere of activity, must have
+an intensity and direction confined within very narrow limits. If we
+determine by the analysis of probabilities, the ratio of the chances
+which in these limits, assign a sensible hyperbola to the chances which
+assign an orbit, which may without sensible error be confounded with a
+parabola, it will be found that there is at least six thousand to unity
+that a nebula which penetrates within the sphere of the Sun’s activity
+so as to be observed, will either describe a very elongated ellipse,
+or an hyperbola, which, in consequence of the magnitude of its axis
+will be as to sense confounded with a parabola in the part of its orbit
+which is observed. It is not therefore surprising that hitherto no
+hyperbolic motions have been recognized.
+
+The attraction of the planets, and perhaps also the resistance of the
+ethereal media, ought to change several cometary orbits into ellipses,
+of which the greater axes are much less than the radius of the sphere
+of the solar activity. It is probable that such a change was produced
+in the orbit of the comet of 1759, the greater axis of which was not
+more than thirty-five times the distance of the Sun from the Earth. A
+still greater change was produced in the orbits of the comets of 1770
+and of 1805.
+
+If in the zones abandoned by the atmosphere of the Sun, there are any
+molecules too volatile to be united to each other, or to the planets,
+they ought in their circulation about this star to exhibit all the
+appearances of the zodiacal light, without opposing any sensible
+resistance to the different bodies of the planetary system, both on
+account of their great rarity and also because their motion is very
+nearly the same as that of the planets which they meet.
+
+An attentive examination of all the circumstances of this system
+renders our hypothesis still more probable. The primitive fluidity of
+the planets is clearly indicated by the compression of their figure,
+conformably to the laws of the mutual attraction of their molecules; it
+is moreover demonstrated by the regular diminution of gravity, as we
+proceed from the equator to the poles. This state of primitive fluidity
+to which we are conducted by astronomical phenomena, is also apparent
+from those which natural history points out. But in order fully to
+estimate them, we should take into account the immense variety of
+combinations formed by all the terrestial substances which were mixed
+together in a state of vapour, when the depression of their temperature
+enabled their elements to unite; it is necessary likewise to consider
+the wonderful changes which this depression ought to cause in the
+interior and at the surface of the earth, in all its productions, in
+the constitution and pressure of the atmosphere, in the ocean, and in
+all substances which it held in a state of solution. Finally, we should
+take into account the sudden changes, such as great volcanic eruptions,
+which must at different epochs have deranged the regularity of these
+changes. Geology, thus studied under the point of view which connects
+it with astronomy, may, with respect to several objects, acquire both
+precision and certainty.
+
+One of the most remarkable phenomena of the solar system is the
+rigorous equality which is observed to subsist between the angular
+motions of rotation and revolution of each satellite. It is infinity to
+unity that this is not the effect of hazard. The theory of universal
+gravitation makes infinity to disappear from this improbability, by
+shewing that it is sufficient for the existence of this phenomenon,
+that at the commencement these motions did not differ much. Then,
+the attraction of the planet would establish between them a perfect
+equality; but at the same time it has given rise to a periodic
+oscillation in the axis of the satellite directed to the planet, of
+which oscillation the extent depends on the primitive difference
+between these motions. As the observations of Mayer on the libration
+of the Moon, and those which Bouvard and Nicollet made for the
+same purpose, at my request, did not enable us to recognize this
+oscillation; the difference on which it depends must be extremely
+small, which indicates with every appearance of probability the
+existence of a particular cause, which has confined this difference
+within very narrow limits, in which the attraction of the planet might
+establish between the mean motions of rotation and revolution a rigid
+equality, which at length terminated by annihilating the oscillation
+which arose from this equality. Both these effects result from our
+hypothesis; for we may conceive that the Moon, in a state of vapour,
+assumed in consequence of the powerful attraction of the earth the
+form of an elongated spheroid, of which the greater axis would be
+constantly directed towards this planet, from the facility with which
+the vapours yield to the slightest force impressed upon them. The
+terrestrial attraction continuing to act in the same manner, while
+the Moon is in a state of fluidity, ought at length, by making the
+two motions of this satellite to approach each other, to cause their
+difference to fall within the limits, at which their rigorous equality
+commences to establish itself. Then this attraction should annihilate,
+by little and little, the oscillation which this equality produced on
+the greater axis of the spheroid directed towards the earth. It is in
+this manner that the fluids which cover this planet, have destroyed by
+their friction and resistance the primitive oscillations of its axis
+of rotation, which is only now subject to the nutation resulting from
+the actions of the Sun and Moon. It is easy to be assured that the
+equality of the motions of rotation and revolution of the satellites
+ought to oppose the formation of rings and secondary satellites, by the
+atmospheres of these bodies. Consequently observation has not hitherto
+indicated the existence of any such. The motions of the three first
+satellites of Jupiter present a phenomenon still more extraordinary
+than the preceding; which consists in this, that the mean longitude of
+the first, minus three times that of the second, plus twice that of
+the third, is constantly equal to two right angles. There is the ratio
+of infinity to one, that this equality is not the effect of chance.
+But we have seen, that in order to produce it, it is sufficient if at
+the commencement, the mean motions of these three bodies approached
+very near to the relation which renders the mean motion of the first,
+minus three times that of the second, plus twice that of the third,
+equal to nothing. Then their mutual attraction rendered this ratio
+rigorously exact, and it has moreover made the mean longitude of the
+first minus three times that of the second, plus twice that of the
+third, equal to a semicircumference. At the same time, it gave rise to
+a periodic inequality, which depends on the small quantity, by which
+the mean motions originally deviated from the relation which we have
+just announced. Notwithstanding all the care Delambre took in his
+observations, he could not recognize this inequality, which, while it
+evinces its extreme smallness, also indicates, with a high degree of
+probability, the existence of a cause which makes it to disappear. In
+our hypothesis, the satellites of Jupiter, immediately after their
+formation, did not move in a perfect vacuo; the less condensable
+molecules of the primitive atmospheres of the Sun and planet would
+then constitute a rare medium, the resistance of which being different
+for each of the stars, might make the mean motions to approach by
+degrees to the ratio in question; and when these movements had thus
+attained the conditions requisite, in order that the mutual attraction
+of the three satellites might render this relation accurately true, it
+perpetually diminished the inequality which this relation originated,
+and eventually rendered it insensible. We cannot better illustrate
+these effects than by comparing them to the motion of a pendulum,
+which, actuated by a great velocity, moves in a medium, the resistance
+of which is inconsiderable. It will first describe a great number of
+circumstances; but at length its motion of circulation perpetually
+decreasing, it will be converted into an oscillatory motion, which
+itself diminishing more and more, by the resistance of the medium, will
+eventually be totally destroyed, and then the pendulum, having attained
+a state of repose, will remain at rest for ever.
+
+
+FOOTNOTES:
+
+[Footnote 21: Translated from _Exposition du Système du Monde_,
+(Paris, 1796).]
+
+[Footnote 22: viz: “The motions of the planets in the same direction,
+and very nearly in the same plane; the motions of the satellites
+in the same direction as those of the planets; the motions of the
+rotation of these different bodies and also of the sun, in the same
+direction as their motions of projection, and in planes very little
+inclined to each other; the small eccentricity of the orbits of the
+comets and satellites; finally, the great eccentricity of the orbits
+of the comets, their inclinations being at the same time entirely
+indeterminate.”]
+
+
+
+
+ XX
+
+ EDWARD JENNER
+
+ 1749-1823
+
+
+ _Edward Jenner, born May 17, 1749, at Berkeley, Gloucestershire,
+ England, studied surgery under John Hunter at London, and returned
+ to his native town to practise. Having learned, about 1796, that
+ milk-maids who had caught the cow-pox were immune from small-pox, he
+ began at once to make investigations and to conduct experiments. This
+ led to his “Inquiry,” published in 1798, in which he made public his
+ theory of vaccination. His discovery created widespread interest, but
+ although the theory at once met with the most virulent criticism,
+ vaccination was soon widely accepted. By 1801, ten thousand persons
+ were vaccinated in England, and the beneficent results justified its
+ wide adoption. He died of apoplexy, January 26, 1823._
+
+
+ THE THEORY OF VACCINATION[23]
+
+The deviation of Man from the state in which he was originally placed
+by Nature seems to have proved to him a prolific source of Diseases.
+From the love of splendour, from the indulgences of luxury, and from
+his fondness for amusement, he has familiarised himself with a great
+number of animals, which may not originally have been intended for his
+associates.
+
+The Wolf, disarmed of ferocity, is now pillowed in the lady’s lap. The
+Cat, the little Tyger of our island, whose natural home is the forest,
+is equally domesticated and caressed. The Cow, the Hog, the Sheep, and
+the Horse, are all, for a variety of purposes, brought under his care
+and dominion.
+
+There is a disease to which the Horse, from his state of
+domestication, is frequently subject. The Farriers have termed it the
+Grease. It is an inflammation and swelling in the heel, from which
+issues matter possessing properties of a very peculiar kind, which
+seems capable of generating a disease in the Human Body (after it has
+undergone the modification which I shall presently speak of), which
+bears so strong a resemblance to the Small-pox that I think it highly
+probable it may be the source of that disease.
+
+In this Dairy Country a great number of Cows are kept, and the office
+of milking is performed indiscriminately by Men and Maid Servants. One
+of the former having been appointed to apply dressings to the heels
+of a Horse affected with the Grease, and not paying due attention to
+cleanliness, incautiously bears his part in milking the Cows, with some
+particles of the infectious matter adhering to his fingers. When this
+is the case, it commonly happens that a disease is communicated to
+the Cows, and from the Cows to the Dairy-maids, which spreads through
+the farm until most of the cattle and domestics feel its unpleasant
+consequences. This disease has obtained the name of the Cow-pox. It
+appears on the nipples of the Cows in the form of irregular pustules.
+At their first appearance they are commonly of a palish blue, or
+rather of a colour somewhat approaching to livid, and are surrounded
+by an erysipelatous inflammation. These pustules, unless a timely
+remedy be applied, frequently degenerate into phagedenic ulcers, which
+prove extremely troublesome. The animals become indisposed, and the
+secretion of milk is much lessened. Inflamed spots now begin to appear
+on different parts of the hands of the domestics employed in milking,
+and sometimes on the wrists, which quickly run on to suppuration, first
+assuming the appearance of the small vesications produced by a burn.
+Most commonly they appear about the joints of the fingers, and at their
+extremities; but whatever parts are affected, if the situation will
+admit, these superficial suppurations put on a circular form, with
+their edges more elevated than their centre, and of a colour distantly
+approaching to blue. Absorption takes place, and tumours appear in
+each axilla. The system becomes affected--the pulse is quickened; and
+shiverings, with general lassitude and pains about the loins and limbs,
+with vomiting, come on. The head is painful, and the patient is now
+and then even affected with delirium. These symptoms, varying in their
+degrees of violence, generally continue from one day to three or four,
+leaving ulcerated sores about the hands, which, from the sensibility of
+the parts, are very troublesome, and commonly heal slowly, frequently
+becoming phagedenic, like those from whence they sprung. The lips,
+nostrils, eyelids, and other parts of the body, are sometimes affected
+with sores; but these evidently arise from their being needlessly
+rubbed or scratched with the patient’s infected fingers. No eruptions
+on the skin have followed the decline of the feverish symptoms in any
+instance that has come under my inspection, one only excepted, and in
+this case a very few appeared on the arms: they were very minute, of a
+vivid red colour, and soon died away without advancing to maturation;
+so that I cannot determine whether they had any connection with the
+preceding symptoms.
+
+Thus the disease makes its progress from the Horse to the nipple of the
+Cow, and from the Cow to the Human Subject.
+
+Morbid matter of various kinds, when absorbed into the system, may
+produce effects in some degree similar; but what renders the Cow-pox
+virus so extremely singular is, that the person who has been thus
+affected is forever after secure from the infection of the Small-pox;
+neither exposure to the _variolous effluvia_, nor the insertion of
+the matter into the skin producing this distemper.
+
+ [I shall now conclude this Inquiry with some general observations on
+ the subject, and on some others which are interwoven with it.]
+
+Although I presume it may be unnecessary to produce further testimony
+in support of my assertion “that Cow-pox protects the human
+constitution from the infection of the Small-pox,” yet it affords me
+considerable satisfaction to say that Lord Somerville, the president of
+the Board of Agriculture, to whom this paper was shown by Sir Joseph
+Banks, has found upon inquiry that the statements were confirmed by
+the concurring testimony of Mr. Dolland, a surgeon, who resides in a
+dairy country remote from this, in which these observations were made.
+With respect to the opinion adduced “that the source of the infection
+is a peculiar morbid matter arising in the horse,” although I have not
+been able to prove it from actual experiments conducted immediately
+under my own eye, yet the evidence I have adduced appears sufficient to
+establish it.
+
+They who are not in the habit of conducting experiments may not be
+aware of the coincidence of circumstances necessary for their being
+managed so as to prove perfectly decisive; nor how often men engaged in
+professional pursuits are liable to interruptions which disappoint them
+almost at the instant of their being accomplished.
+
+ [However, I feel no room for hesitation respecting the common origin
+ of the disease, being well convinced that it never appears among the
+ cows (except it can be traced to a cow introduced among the general
+ herd which has been previously infected, or to an infected servant),
+ unless they have been milked by someone who, at the same time, has the
+ care of a horse affected with diseased heels.
+
+ The spring of 1797, which I intended particularly to have devoted
+ to the completion of this investigation, proved, from its dryness,
+ remarkably adverse to my wishes; for it frequently happens, while
+ the farmers’ horses are exposed to the cold rains which fall at that
+ season that their heels become diseased, and no Cow-pox then appeared
+ in the neighbourhood.]
+
+The active quality of the virus from the horses’ heels is greatly
+increased after it has acted on the nipples of the cow, as it rarely
+happens that the horse affects his dresser with sores, and as rarely
+that a milk-maid escapes the infection when she milks infected cows.
+It is most active at the commencement of the disease, even before it
+has acquired a pus-like appearance; indeed I am not confident whether
+this property in the matter does not entirely cease as soon as it is
+secreted in the form of pus. I am induced to think it does cease,
+and that it is the thin darkish-looking fluid only, oozing from the
+newly-formed cracks in the heels, similar to what sometimes appears
+from erysipelatous blisters, which gives the disease. Nor am I certain
+that the nipples of the cows are at all times in a state to receive
+the infection. The appearance of the disease in the spring and the
+early part of the summer, when they are disposed to be affected with
+spontaneous eruptions so much more frequently than at other seasons,
+induces me to think that the virus from the horse must be received
+upon them when they are in this state, in order to produce effects;
+experiments, however, must determine these points. But it is clear that
+when the Cow-pox virus is once generated, that the cows cannot resist
+the contagion, in whatever state their nipples may chance to be, if
+they are milked with an infected hand.
+
+Whether the matter, either from the cow or the horse, will affect the
+sound skin of the human body, I cannot positively determine; probably
+it will not, unless on those parts where the cuticle is extremely thin,
+as on the lips for example. I have known an instance of a poor girl
+who produced an ulceration on her lip by frequently holding her finger
+to her mouth to cool the raging of a Cow-pox sore by blowing upon it.
+The hands of the farmers’ servants here, from the nature of their
+employments, are constantly exposed to those injuries which occasion
+abrasions of the cuticle, to punctures from thorns and such like
+accidents; so that they are always in a state to feel the consequences
+of exposure to infectious matter.
+
+ [It is singular to observe that the Cow-pox virus, although it renders
+ the constitution unsusceptible of the variolous, should, nevertheless,
+ leave it unchanged with respect to its own action. I have already
+ produced an instance to point out this, and shall now corroborate it
+ with another.
+
+ Elizabeth Wynne, who had the Cow-pox in the year 1759, was inoculated
+ with variolous matter, without effect, in the year 1797, and again
+ caught the Cow-pox in the year 1798. When I saw her, which was on the
+ 8th day after she received the infection, I found her infected with
+ general lassitude, shiverings, alternating with heat, coldness of the
+ extremities, and a quick and irregular pulse. These symptoms were
+ preceded by a pain in the axilla.]
+
+It is curious also to observe that the virus, which with respect to
+its effects is undetermined and uncertain previously to its passing
+from the horse through the medium of the cow, should then not only
+become more active, but should invariably and completely possess those
+specific properties which induce in the human constitution symptoms
+similar to those of the variolous fever, and effect in it that peculiar
+change which forever renders it unsusceptible of the variolous
+contagion.
+
+May it not then be reasonably conjectured that the source of the
+Small-pox is morbid matter of a peculiar kind, generated by a disease
+in the horse, and that accidental circumstances may have again and
+again arisen, still working new changes upon it, until it has acquired
+the contagious and malignant form under which we now commonly see it
+making its devastations amongst us? And, from a consideration of the
+change which the infectious matter undergoes from producing a disease
+on the cow, may we not conceive that many contagious diseases, now
+prevalent among us, may owe their present appearance not to a simple,
+but to a compound origin? For example, is it difficult to imagine that
+the measles, scarlet fever, and the ulcerous sore throat with a spotted
+skin, have all sprung from the same source, assuming some variety in
+their forms according to the nature of their new combinations? The same
+question will apply respecting the origin of many other contagious
+diseases, which bear a strong analogy to each other.
+
+There are certainly more forms than one, without considering the common
+variation between the confluent and distinct, in which the Small-pox
+appears in what is called the natural way. About seven years ago a
+species of Small-pox spread through many of the towns and villages of
+this part of Gloucestershire: it was of so mild a nature that a fatal
+instance was scarcely ever heard of, and consequently so little dreaded
+by the lower orders of the community that they scrupled not to hold the
+same intercourse with each other as if no infectious disease had been
+present among them. I never saw nor heard of an instance of its being
+confluent. The most accurate manner, perhaps, in which I can convey
+an idea of it, is, by saying that had fifty individuals been taken
+promiscuously and infected by exposure to this contagion, they would
+have had as mild and light a disease as if they had been inoculated
+with variolous matter in the usual way. The harmless manner in which it
+showed itself could not arise from any peculiarity either in the season
+or the weather, for I watched its progress upwards of a year without
+perceiving any variation in its general appearance. I consider it then
+as a variety of the Small-pox.
+
+ [In some of the preceding cases I have noticed the attention that was
+ paid to the state of the variolous matter previous to the experiment
+ of inserting it into the arms of those who had gone through the
+ Cow-pox. This I conceived to be of great importance in conducting
+ these experiments, and were it always properly attended to by those
+ who inoculate for the Small-pox, it might prevent much subsequent
+ mischief and confusion. With the view of enforcing so necessary a
+ precaution, I shall take the liberty of digressing so far as to
+ point out some unpleasant facts relative to mismanagement in this
+ particular, which have fallen under my own observation.]
+
+A medical gentleman (now no more), who for many years inoculated
+in this neighbourhood, frequently preserved the variolous matter
+intended for his use, on a piece of lint or cotton, which, in its
+fluid state, was put into a vial, corked, and conveyed into a warm
+pocket; a situation certainly favourable for speedily producing
+putrefaction in it. In this state (not infrequently after it had been
+taken several days from the pustules) it was inserted into the arms
+of his patients, and brought on inflammation of the incised parts,
+swellings of the axillary glands, fever, and sometimes eruptions. But
+what was this disease? Certainly not the Small-pox; for the matter
+having from putrefaction lost, or suffered a derangement in its
+specific properties, was no longer capable of producing that malady,
+those who had been inoculated in this manner being as much subject
+to the contagion of the Small-pox, as if they had never been under
+the influence of this artificial disease; and many, unfortunately,
+fell victims to it, who thought themselves in perfect security. The
+same unfortunate circumstance of giving a disease, supposed to be the
+Small-pox, with inefficacious variolous matter, having occurred under
+the direction of some other practitioners within my knowledge, and
+probably from the same incautious method of securing the variolous
+matter, I avail myself of this opportunity of mentioning what I
+conceive to be of great importance; and, as a further cautionary hint,
+I shall again digress so far as to add another observation on the
+subject of Inoculation.
+
+Whether it be yet ascertained by experiment, that the quantity of
+variolous matter inserted into the skin makes any difference with
+respect to the subsequent mildness or violence of the disease, I know
+not; but I have the strongest reason for supposing that if either the
+punctures or incisions be made so deep as to go through it, and wound
+the adipose membrane, that the risk of bringing on a violent disease is
+greatly increased. I have known an inoculator, whose practice was “to
+cut deep enough (to use his own expression) to see a bit of fat,” and
+there to lodge the matter. The great number of bad cases, independent
+of inflammations and abscesses on the arms, and the fatality which
+attended this practice was almost inconceivable; and I cannot account
+for it on any other principle than that of the matter being placed in
+this situation instead of the skin.
+
+At what period the Cow-pox was first noticed here is not upon record.
+Our oldest farmers were not unacquainted with it in their earliest
+days, when it appeared among their farms without any deviation from
+the phenomena which it now exhibits. Its connection with the Small-pox
+seems to have been unknown to them. Probably the general introduction
+of inoculation first occasioned the discovery.
+
+Its rise in this country may not have been of very remote date, as the
+practice of milking cows might formerly have been in the hands of women
+only; which I believe is the case now in some other dairy countries,
+and consequently that the cows might not in former times have been
+exposed to the contagious matter brought by the men servants from the
+heels of horses. Indeed a knowledge of the source of the infection is
+new in the minds of most of the farmers in this neighbourhood, but it
+has at length produced good consequences; and it seems probable from
+the precautions they are now disposed to adopt, that the appearance
+of the Cow-pox here may either be entirely extinguished or become
+extremely rare.
+
+Should it be asked whether this investigation is a matter of mere
+curiosity, or whether it tends to any beneficial purpose, I should
+answer that, notwithstanding the happy effects of inoculation, with
+all the improvements which the practice has received since its first
+introduction into this country, it not very infrequently produces
+deformity of the skin, and sometimes, under the best management, proves
+fatal.
+
+These circumstances must naturally create in every instance some degree
+of painful solicitude for its consequences. But as I have never known
+fatal effects arise from the Cow-pox, even when impressed in the most
+unfavourable manner, producing extensive inflammations and suppurations
+on the hands; and as it clearly appears that this disease leaves the
+constitution in a state of perfect security from the infection of
+the Small-pox, may we not infer that a mode of inoculation may be
+introduced preferable to that at present adopted, especially among
+those families which, from previous circumstances, we may judge to be
+predisposed to have the disease unfavourably? It is an excess in the
+number of pustules which we chiefly dread in the Small-pox; but, in
+the Cow-pox, no pustules appear, nor does it seem possible for the
+contagious matter to produce the disease from effluvia, or by any other
+means than contact, and that probably not simply between the virus and
+the cuticle; so that a single individual in a family might at any time
+receive it without the risk of infecting the rest, or of spreading a
+distemper that fills a country with terror.
+
+ [Several instances have come under my observation which justify the
+ assertion that the disease cannot be propagated by effluvia. The first
+ boy whom I inoculated with the matter of Cow-pox slept in a bed while
+ the experiment was going forward, with two children who had never gone
+ through either that disease or the Small-pox, without infecting either
+ of them.
+
+ A young woman who had the Cow-pox to a great extent, several sores
+ which maturated having appeared on the hands and wrists, slept in the
+ same bed with a fellow-dairymaid, who never had been infected with
+ either the Cow-pox or the Small-pox, but no indisposition followed.
+
+ Another instance has occurred of a young woman on whose hands were
+ several large suppurations from the Cow-pox, who was at the same time
+ a daily nurse to an infant, but the complaint was not communicated to
+ the child.]
+
+In some other points of view the inoculation of this disease appears
+preferable to the variolous inoculation.
+
+In constitutions predisposed to scrofula, how frequently we see the
+inoculated Small-pox rouse into activity that distressful malady.
+This circumstance does not seem to depend on the manner in which the
+distemper has shown itself, for it has as frequently happened among
+those who have had it mildly, as when it has appeared in the contrary
+way. There are many, who from some peculiarity in the habit resist the
+common effects of variolous matter inserted into the skin, and who
+are in consequence haunted through life with the distressing idea of
+being insecure from subsequent infection. A ready mode of dissipating
+anxiety originating from such a cause must now appear obvious. And, as
+we have seen that the constitution may at any time be made to feel the
+fertile attack of Cow-pox, might it not, in many chronic diseases, be
+introduced into the system, with the probability of affording relief,
+upon well-known physiological principles?
+
+Although I say the system may at any time be made to feel the febrile
+attack of Cow-pox, yet I have a single instance before me where the
+virus acted locally only, but it is not in the least probable that
+the same person would resist the action both of Cow-pox virus and the
+variolous.
+
+
+FOOTNOTES:
+
+[Footnote 23: From _An Inquiry into the Cause and Effects of the
+Variolae Vaccinae_.]
+
+
+
+
+ XXI
+
+ COUNT RUMFORD
+
+ 1753-1814
+
+
+ _Sir Benjamin Thompson, Count Rumford, was born in Woburn,
+ Massachusetts, March 26, 1753, a member of an old New England family.
+ After a very romantic youth and early manhood in which he underwent
+ many exciting adventures as a British loyalist at the time of the
+ American Revolution, he was sent to England with despatches by the
+ British expeditionary authorities and there found employment in the
+ office of the Secretary of State. After the close of the Revolution
+ he went to Bavaria, where he became Minister of War and Grand
+ Chamberlain. In 1791 he was made a count of the Holy Roman Empire. In
+ 1796 President Adams invited him to return to America to become an
+ inspector of artillery, but he declined; and at about the same time he
+ became interested in problems of heat, light, and fuel. His suggestions
+ ultimately became the basis for the doctrine of the conservation of
+ energy. He died at Auteuil, August 25, 1814._
+
+
+ THE NATURE OF HEAT[24]
+
+After I had long meditated upon a way of putting this interesting
+problem entirely out of doubt by a perfectly conclusive experiment, I
+thought finally that I had discovered it, and I think so still.
+
+I argued that if the existence of caloric was a fact, it must be
+absolutely impossible for a body or for several individual bodies,
+which together made one whole, to communicate this substance
+continuously to various other bodies by which they were surrounded,
+without this substance gradually being entirely exhausted.
+
+A sponge filled with water, and hung by a thread in the middle of a
+room filled with dry air, communicates its moisture to the air, it is
+true, but soon the water evaporates and the sponge can no longer give
+out moisture. On the contrary, a bell sounds without interruption when
+it is struck, and gives out its sound as often as we please without the
+slightest perceptible loss. Moisture is a substance; sound is not.
+
+It is well known that two hard bodies, if rubbed together, produce
+much heat. Can they continue to produce it without finally becoming
+exhausted? Let the result of experiment decide this question.
+
+It would be too tedious to describe here in detail all the experiments
+which I undertook with a view of answering in a decisive manner this
+important and disputed question. They may be found in my memoir, “On
+the Source of Heat excited by Friction.” I have had it printed in
+the _Philosophical Transactions_ for the year 1798; still these
+experiments bear too close a relation to my later researches on heat
+for me to omit attempting at least to give the reader a clear idea of
+the experiments and of their results.
+
+The apparatus which I used in these investigations is too complicated
+to be represented in this place; still it will not be difficult for
+the reader to form a conception of the principal experiments and their
+results.
+
+Let A be the vertical section of a brass rod which is an inch in
+diameter and is fastened in an upright position on a stout block,
+B; it is provided at its upper end with a massive hemisphere of the
+same metal, three and a half inches in diameter. C is a similar rod,
+likewise vertical, to the lower end of which is fastened a similar
+hemisphere. Both hemispheres must fit each other in such a way that
+both the rods stand in a perfectly straight vertical line.
+
+D is the vertical section of a globular metallic vessel twelve inches
+in diameter, which is provided with a cylindrical neck three inches
+long and three and three-quarter inches in diameter. The rod A goes
+through a hole in the bottom of the vessel, is soldered into the
+vessel, and serves as a support to keep it in its proper position.
+
+The centre of the ball, made up of the two hemispheres which lie the
+one upon the other, is in the centre of the globular vessel, so that,
+if the vessel is filled with water, the water covers the ball as well
+as a part of each of the brass rods.
+
+If now the hemispheres be pressed strongly together, and at the same
+time the rod C be turned, by some means or other, about its axis,
+a very considerable quantity of heat is generated by means of the
+friction which takes place between the flat surfaces of the two
+hemispheres.
+
+The quantity of the heat excited in this manner is exactly proportional
+to the force with which the two surfaces are pressed together, and to
+the rapidity of the friction. When this force was equal to the pressure
+of ten thousand pounds, and when the rod was turned with such rapidity
+about its axis that it revolved thirty-two times a minute, the quantity
+of heat generated by the continual rubbing of the two surfaces together
+was extraordinarily great. It was equal to the quantity given off by
+the flame of nine wax-candles of moderate size all burning together.
+
+The quantity of heat generated in this manner during a given time is
+manifestly the same, whether the globular vessel D is filled with
+water, and the surfaces of the two hemispheres rub on each other in
+this liquid, or whether there is no water in the vessel, and the
+apparatus by which the friction is produced is simply surrounded by air.
+
+The source of the heat which is generated by this apparatus is
+inexhaustible. As long as the rod C is turned about its axis, so long
+will heat be produced by the apparatus, and always to the same amount.
+
+If the globe-shaped vessel D is filled with water, this water becomes
+hotter and hotter, and finally begins to boil. I have myself in this
+way boiled a considerable quantity of water.
+
+If this experiment is performed in winter when the temperature of the
+air is but little above the freezing-point, and if the vessel D is
+filled with a mixture of water and pounded ice, the quantity of heat
+caused in a given time by the rubbing together of the two surfaces can
+be expressed very exactly by the amount of ice melted by this heat.
+
+Since the apparatus affords heat continuously, and always to the same
+amount, we can melt in this way as much ice as we please.
+
+But whence comes this heat? This is the contested point, to determine
+which was the real aim of the experiment.
+
+It is certain that it comes neither from the decomposition of the
+water nor from the decomposition of the air. Various experiments
+on this point, which I have described at length in my memoir in
+the _Philosophical Transactions_, are more than sufficient to
+establish this fact beyond doubt.
+
+Just as little does it come from a change in the capacity for heat
+brought about by friction in the metal of which the hemispheres are
+composed. This is shown, first, by the continuance and uniformity of
+the production of the heat; and, secondly, by an experiment bearing
+directly on this point, by which I am convinced that not the slightest
+change had taken place in the capacity of the metal for heat.
+
+Just as little does it come from the rods which are attached to
+the hemispheres, for these rods were always warm, the hemispheres
+communicating heat to them.
+
+Much less could this heat come from the air of the water immediately
+surrounding the hemispheres, for the apparatus communicated heat to
+both these fluids without cessation.
+
+Whence, then, came this heat? and what is heat actually?
+
+I must confess that it has always been impossible for me to explain
+the results of such experiments except by taking refuge in the very
+old doctrine which rests on the supposition that heat is nothing but a
+vibratory motion taking place among the particles of bodies.
+
+A bell, on being struck, immediately gives forth a sound, and the
+oscillations of the air produced by these vibrations forthwith cause a
+quivering motion in those bodies with which they come in contact. On
+the other hand, a sponge filled with water cannot give off its moisture
+to the bodies in its vicinity for any length of time without itself
+losing moisture.
+
+A very illustrious philosopher, for whom I have always entertained the
+greatest respect, and whom, moreover, I have the good fortune to count
+among my most intimate friends, M. Bertholet, has, in his admirable
+_Essai de Statique Chimique_, attempted to explain the results
+of this investigation, and to reconcile them with that theory of heat
+which is founded upon the hypothesis of caloric.
+
+If a man as learned, as honest, as worthy, and as renowned as is
+M. Bertholet spares no pains in opposing the errors of a natural
+philosopher or chemist, one cannot and dare not keep silence unless he
+wishes to acknowledge himself vanquished. If, however, one can produce
+proofs--a fortunate thing for all those who find themselves driven to
+similar self-vindication--that the objections of M. Bertholet have no
+foundation, he has done very much towards establishing beyond doubt the
+opinions and facts in question.
+
+I will now endeavor to answer the objections which M. Bertholet has
+offered to my explanation of the above-mentioned experiments; and, that
+the reader may be in a position to give to these objections their just
+value, I will insert them here in the writer’s own words.
+
+ “Count Rumford has made a curious experiment with regard to the heat
+ which may be excited by friction. He causes a blunt borer to revolve
+ very rapidly (this borer revolved about its axis only thirty-two times
+ a minute) in a brass cylinder weighing thirteen pounds, English weight
+ (the cylinder weighed one hundred and thirteen pounds and somewhat
+ more), and says that he observed that this borer in the course of
+ two (one and a half) hours, and under a pressure equal to 100 cwt.,
+ reduced to powder 4145 grains (8-1/2 ounces Troy) of brass, and that
+ an amount of heat was generated during this operation sufficient
+ to bring to boil 26.38 pounds of water, previously cooled to the
+ freezing-point. He asserts that he did not discover the slightest
+ difference between the specific heat of the metallic dust and that of
+ the brass which had not experienced the friction. Hence he supposes
+ that the heat was excited by the pressure alone, and was not at all
+ due to caloric, as is the opinion of most chemists.
+
+ “I will for the present satisfy myself with simply inquiring whether
+ it necessarily follows from this experiment that we must renounce
+ entirely the received theory of caloric, according to which it is
+ regarded as a substance which enters into combination with bodies, or
+ whether this result cannot be explained in a satisfactory manner by
+ applying to the case in question those laws of nature in accordance
+ with which the operations of heat are manifested under other
+ conditions.
+
+ “If the evolution of heat be regarded as a consequence of the decrease
+ of volume caused by the pressure, then not only the metallic powder,
+ but also all the rest of the brass cylinder must have contributed,
+ though not in an equal manner, to this evolution, by the powerful
+ expansive effort of that portion which experienced the greatest
+ pressure, and consequently acquired the greatest temperature, without
+ being able to assume the dimensions proper to this same temperature on
+ account of the less heated and less expanded parts; consequently there
+ must have arisen, necessarily, a certain condensation of the metal
+ in respect of its natural dimensions, which condensation gradually
+ decreased from the point where the pressure was greatest to the
+ surface. We may suppose that this operation took place in a similar
+ manner in all parts of the cylinder.
+
+ “As a consequence of this decrease of volume, an amount of caloric was
+ given out equal to that which would have caused a similar increase
+ of volume, on the supposition, that is, that the specific heat of
+ the metal does not change through this range of the scale of the
+ thermometer, and that the expansions are equal; and this, considering
+ the range of temperatures and the consequent expansions, is probably
+ not far from the truth. The entire amount of heat disengaged would
+ have raised the cylinder to about 180° of Reaumur’s scale; and if
+ the expansion of brass by heat is equal to that of iron, which has
+ been found to be 1-75000 for each degree of the thermometer, the 180
+ degrees would have caused an expansion of 18-75000 in each direction,
+ and the decrease of volume must have brought about the same degree of
+ heat if we suppose that the pressure stood in equal relation to this
+ expansion.
+
+ “Now there is a change, and sometimes a very considerable one, wrought
+ in the specific gravity of a metal, by percussion, by the action of
+ a fly-wheel, or by the compression of a wire-drawing machine. It
+ appears, for example, that the specific gravity of platina and of
+ iron, on being forged, is thus increased by a twentieth part.
+
+ “Hence it appears that the experiment of Count Rumford is far from
+ explaining satisfactorily a property which is well known, and called
+ in question by no one.
+
+ “It is easy, it is true, to arrange side by side in an imposing manner
+ the phenomena of heat; if, however, you were to say to one who has
+ little or no knowledge of chemical speculations, ‘Count Rumford’s
+ cylinder has, in the course of two hours, by means of a violent
+ friction, afforded all the heat required to dissolve in water, without
+ changing its temperature, 15 kilogrammes of ice, or as much as 2
+ hectogrammes (6-1/2 ounces) of oxygen would require [_sic_] in
+ its combination with phosphorus,’ I do not know at which of these
+ phenomena he would be most astonished.
+
+ “The slight changes which can take place in the amount of combined
+ caloric have so inconsiderable an influence on the capacity for work
+ of the caloric within the narrow limits of the thermometric scale,
+ that it cannot be computed. Moreover, we have not, as yet, adequate
+ data for determining the nature of the changes in this respect which
+ take place in a solid body in consequence of the particular condition
+ of condensation into which it has been brought by means of certain
+ mechanical force, and by degrees of heat differing greatly from each
+ other.
+
+ “Besides, Rumford, in the experiment to determine the specific heat
+ of the filings of bell-metal thus obtained, heated them to the
+ temperature of boiling water. But this extremely elastic heat would
+ very naturally as soon as left to itself, and especially during the
+ operation just mentioned, resume that state of expansion and that
+ capacity for heat which is proper to it at a given temperature, so
+ that the effect of the pressure to which it has been subjected partly
+ disappears again, just as a piece of metal which has been hammered
+ resumes its natural properties on being annealed.”
+
+In reply to these remarks, I will call to mind what follows.
+
+1st. The discovery which I made, that no considerable change had
+taken place in the specific heat of the metallic dust produced by the
+friction, led me in no way to the supposition that the heat excited
+in the experiment could not come from the caloric set free. I only
+found that the source of this heat was inexhaustible. To explain this
+phenomenon, which has never yet been explained, is the point now in
+question, and I do not see how it can be explained except by giving up
+altogether the hypothesis adopted in regard to caloric.
+
+2d. If we actually suppose (and it is far from having been proved)
+that the simple pressing together of a metal is sufficient to expel
+the caloric contained in it; still the explanation of such a natural
+phenomenon would be advanced little or none; for since the action of
+the force which causes the pressure is continuous, the condensation
+of the metal brought about by this force would in a short time reach
+its maximum; and if really in this operation ever so much caloric had
+been disengaged from the metal, still it would very soon disperse. The
+rubbing surfaces, on the contrary, continue to give forth heat, and
+that always to the same amount.
+
+3d. In regard to the objection made to the experiment which was
+undertaken with a view of determining whether a change had taken place
+in the capacity of the metallic dust for heat, this can very readily be
+answered, and in such a way that nothing, it seems to me, can be said
+against it. If the temperature of boiling water were really sufficient
+to give to these small, forcibly condensed particles of metal the
+quantity of heat necessary to bring them back to their original
+condition as far as their capacity for heat is concerned, then, as the
+water by which the apparatus was surrounded finally began to boil,
+they must, without doubt, have taken the necessary amount of heat from
+this water. If, now, these particles of metal received finally from
+the water the caloric which in the beginning they imparted to it,
+the question arises, whence came the caloric which served to heat,
+not only the water, but also the metal and the objects immediately
+surrounding it?
+
+I am far from desiring to deceive anyone by an imposing arrangement
+of facts; but the facts in my experiments were so very striking that
+it was altogether impossible for me to help instituting comparisons
+and making calculations with regard to them which would make them
+clear, especially to those not yet sufficiently acquainted with such
+investigations.
+
+I will now close my remarks with an entirely new computation. I will
+show whether it is probable that the metal could supply all the heat
+which was produced by friction in the experiment in question. If we are
+to make this supposition, we must, in the first place, allow that all
+the heat came directly from the particles of metal which were separated
+from the solid mass of metal by the friction; for, since the mass
+remained in the same condition throughout the entire experiment, it is
+evident that it could contribute in no measure to the effect produced.
+
+We will now inquire how much heat would have been developed if the
+experiment had been carried on without cessation, until the whole mass
+of metal had been reduced to powder by the friction.
+
+After the experiment had lasted an hour and a half, there were 4145
+grains (Troy) of the metallic dust, and during that time an amount of
+heat was produced by the friction sufficient to raise 26.58 pounds of
+ice-cold water to the boiling point.
+
+Since the mass of metal weighed 113.13 pounds, or 791,190 grains, all
+this metal would have been reduced to powder if the experiment had
+lasted uninterruptedly, day and night, for 477-1/2 hours, or for 19
+days 21-1/2 hours, and during this time an amount of heat would have
+been produced sufficient to have raised 5078 pounds of water to the
+boiling-point.
+
+Since the metal used in this experiment showed a capacity for heat
+which was to that of water as 0.11 to 1, it is evident that this amount
+of heat would have been sufficient to raise a mass of the same metal
+46,165 pounds in weight through 180 degrees of Fahrenheit’s scale, or
+from the temperature of melting ice to that of boiling water.
+
+This amount of heat would be sufficient to melt a mass of metal sixteen
+times heavier than that which I used in the experiment.
+
+Is it at all conceivable that such an enormous quantity of caloric
+could really be present in this body? But even this supposition would
+be by no means sufficient for the explanation of the fact in question,
+as I have shown by a decisive experiment that the capacity of the metal
+for heat has not sensibly altered.
+
+Whence, then, came the caloric which the apparatus furnished in such
+abundance?
+
+I leave this question to be answered by those persons who believe in
+the actual existence of caloric.
+
+In my opinion, I have made it sufficiently evident that it was
+impossible for it to come from the metallic bodies which were rubbed
+together, and I am absolutely unable to imagine how it can have come
+from any other object in the neighborhood of the apparatus, for all
+these objects received their heat constantly from the apparatus itself.
+
+
+FOOTNOTES:
+
+[Footnote 24: From _An Enquiry Concerning the Source of Heat Excited
+by Friction_ (1798)--_Transactions of the Royal Society of
+London_.]
+
+
+
+
+ XXII
+
+ JOHN DALTON
+
+ 1766-1844
+
+
+ _John Dalton, son of a weaver, was born in Cumberland,
+ England, September 5, 1766. After an early life spent in teaching in
+ elementary schools, in 1793 he became a teacher of mathematics and
+ philosophy at New College, Manchester. He began his researches into the
+ combination of gases in 1800 and discovered that gases expanded equally
+ with the same pressure and heat. He announced his discovery in a paper
+ read before the Manchester Society in 1801. From further experiments
+ he derived his theory that gases combined with one another in definite
+ proportions, and evolved his atomic theory to explain the results.
+ Awarded the King’s medal in 1822, he was further honored by a pension
+ granted in 1833. He died May 27, 1844._
+
+
+ THE ATOMIC THEORY[25]
+
+There are three distinctions in the kinds of bodies, or three states,
+which have more especially claimed the attention of philosophical
+chemists; namely, those which are marked by the terms elastic fluids,
+liquids, and solids. A very familiar instance is exhibited to us
+in water, of a body which, in certain circumstances, is capable of
+assuming all the three states. In steam we recognize a perfectly
+elastic fluid, in water a perfect liquid, and in ice a complete solid.
+These observations have tacitly led to the conclusion which seems
+universally adopted, that all bodies of sensible magnitude, whether
+liquid or solid, are constituted of a vast number of extremely small
+particles, or atoms of matter bound together by a force of attraction,
+which is more or less powerful according to circumstances, and which
+as it endeavours to prevent their separation, is very properly called
+in that view, attraction of cohesion; but as it collects them from a
+dispersed state (as from steam into water) it is called attraction of
+aggregation, or more simply, affinity. Whatever names it may go by,
+they will signify one and the same power. It is not my design to call
+in question this conclusion, which appears completely satisfactory;
+but to show that we have hitherto made no use of it, and that the
+consequence of the neglect has been a very obscure view of chemical
+agency, which is daily growing more so in proportion to the new lights
+attempted to be thrown upon it.
+
+The opinions I more particularly allude to, are those of Bertholet
+on the Laws of chemical affinity; such as that chemical agency is
+proportional to the mass, and that in all chemical unions there exist
+insensible gradations in the proportions of the constituent principles.
+The inconsistence of these opinions, both with reason and observation,
+cannot, I think, fail to strike every one who takes a proper view of
+the phenomena.
+
+Whether the ultimate particles of a body, such as water, are all
+alike, that is, of the same figure, weight, etc., is a question of
+some importance. From what is known, we have no reason to apprehend
+a diversity in these particulars: if it does exist in water, it must
+equally exist in the elements constituting water, namely, hydrogen and
+oxygen. Now it is scarcely possible to conceive how the aggregates
+of dissimilar particles should be so uniformly the same. If some of
+the particles of water were heavier than others, if a parcel of the
+liquid on any occasion were constituted principally of these heavier
+particles, it must be supposed to affect the specific gravity of the
+mass, a circumstance not known. Similar observations may be made on
+other substances. Therefore we may conclude that the ultimate particles
+of all homogeneous bodies are perfectly alike in weight, figure, etc.
+In other words, every particle of water is like every other particle
+of water; every particle of hydrogen is like every other particle of
+hydrogen, etc.
+
+
+FOOTNOTES:
+
+[Footnote 25: From a note entitled _On the Constitution of Bodies_
+which Dalton wrote and had incorporated in Thomas Thompson’s _System
+of Chemistry_ (3d edition, 1807).]
+
+
+
+
+ XXIII
+
+ MARIE FRANÇOIS XAVIER BICHAT
+
+ 1771-1802
+
+
+ _Bichat was born in the French town of Thoirette (Department of
+ Ain), November 14, 1771. At the University of Lyons he was especially
+ interested in anatomy, surgery, and natural history. In 1793, because
+ of the Revolution, he fled to Paris, where he studied under the eminent
+ surgeon Desault. In 1800 he distinguished between animal and organic
+ functions and after many dissections he developed, in 1801, his famous
+ doctrine of tissues. He died July 22, 1802, from injuries received in a
+ fall._
+
+
+ THE DOCTRINE OF TISSUES[26]
+
+ OBJECT OF THE WORK
+
+The general doctrine of this work has not precisely the character of
+any of those which have prevailed in medicine. Opposed to that of
+Boerhaave, it differs from that of Stahl and those authors who, like
+him, refer everything in the living economy to a single principle,
+purely speculative, ideal, and imaginary, whether designated by the
+name of soul, vital principle, or archeus. The general doctrine of this
+work consists in analyzing with precision the properties of living
+bodies, in showing that every physiological phenomenon is ultimately
+referable to these properties considered in their natural state;
+that every pathological phenomenon derives from their augmentation,
+diminution, or alteration; that every therapeutic phenomenon has for
+its principle the restoration of that part of the natural type, from
+which it has been changed; in determining with precision the cases
+in which each property is brought into action; in distinguishing
+accurately in physiology as well as in medicine, that which is
+derived from one, and that which flows from others; in ascertaining by
+rigorous induction the natural and morbific phenomena which the animal
+properties produce, and those which are derived from the organic;
+and in pointing out when the animal sensibility and contractility
+are brought into action, and when the organic sensibility and the
+sensible or insensible contractility. We shall be easily convinced upon
+reflection, that we cannot precisely estimate the immense influence
+of the vital properties in the physiological sciences, before we have
+considered these properties in the point of view in which I have
+presented them. It will be said, perhaps, that this manner of viewing
+them is still a theory; I will answer that it is a theory like that
+which shows in the physical sciences, gravity, elasticity, affinity,
+etc., as the primitive principles of the facts observed in these
+sciences. The relation of these properties as causes to the phenomena
+as effects, is an axiom so well known in physics, chemistry, astronomy,
+etc., at the present day, that it is unnecessary to repeat it. If this
+work establishes an analogous axiom in the physiological sciences, its
+object will be attained.
+
+
+ OBSERVATIONS UPON THE ORGANIZATION OF ANIMALS
+
+The properties, whose influence we have just analyzed, are not
+absolutely inherent in the particles of matter that are the seat of
+them. They disappear when these scattered particles have lost their
+organic arrangement. It is to this arrangement that they exclusively
+belong; let us treat of it here in a general way.
+
+All animals are an assemblage of different organs, which, executing
+each a function, concur in their own manner, to the preservation of
+the whole. It is several separate machines in a general one, that
+constitutes the individual. Now these separate machines are themselves
+formed by many textures of a very different nature, and which really
+compose the elements of these organs. Chemistry has its simple bodies,
+which form, by the combination of which they are susceptible, the
+compound bodies; such are caloric, light, hydrogen, oxygen, carbon
+azote, phosphorus, etc. In the same way anatomy has its simple
+textures, which, by their combinations four with four, six with six,
+eight with eight, etc., make the organs. These textures, are, 1st,
+the cellular; 2d, the nervous of animal life; 3d, the nervous of
+organic life; 4th, the arterial; 5th, the venous; 6th, the texture
+of the exhalants; 7th, that of the absorbents and their glands; 8th,
+the osseous; 9th, the medullary; 10th, the cartilaginous; 11th, the
+fibrous; 12th, the fibro-cartilaginous; 13th, the muscular of animal
+life; 14th, the muscular of organic life; 15th, the mucous; 16th, the
+serous; 17th, the synovial; 18th, the glandular; 19th, the dermoid;
+20th, the epidermoid; 21st, the pilous.
+
+These are the true organized elements of our bodies. Their nature is
+constantly the same, wherever they are met with. As in chemistry, the
+simple bodies do not alter, notwithstanding the different compound ones
+they form. The organized elements of man form the particular object of
+this work.
+
+The idea of thus considering abstractly the different simple textures
+of our bodies, is not the work of the imagination; it rests upon the
+most substantial foundation, and I think it will have a powerful
+influence upon physiology as well as practical medicine. Under whatever
+point of view we examine them, it will be found that they do not
+resemble each other; it is nature and not science that has drawn the
+line of distinction between them.
+
+1st. Their forms are everywhere different; here they are flat, there
+round. We see the simple textures arranged as membranes, canals,
+fibrous fasciæs, etc. No one has the same external character with
+another, considered as to their attributes of thickness or size.
+These differences of form, however, can only be accidental, and the
+same texture is sometimes seen under many different appearances; for
+example, the nervous appears as a membrane in the retina, and as cords
+in the nerves. This has nothing to do with their nature; it is then
+from the organization of the properties that the principal differences
+should be drawn.
+
+2dly. There is no analogy in the organization of the simple textures.
+We shall see that this organization results from parts that are common
+to all, and from those that are peculiar to each; but the common parts
+are all differently arranged in each texture. Some unite in abundance
+the cellular texture, the blood vessels and the nerves; in others, one
+or two of these three common parts are scarcely evident or entirely
+wanting. Here there are only the exhalants and absorbents of nutrition;
+there the vessels are more numerous for other purposes. The capillary
+network, wonderfully multiplied, exists in certain textures; in
+others this network can hardly be demonstrated. As to the peculiar
+part, which essentially distinguishes the texture, the differences
+are striking. Color, thickness, hardness, density, resistance, etc.,
+nothing is similar. More inspection is sufficient to show a number of
+characteristic attributes of each clearly different from the others.
+Here is a fibrous arrangement, there a granulated one; here it is
+lamellated, there circular. Notwithstanding these differences, authors
+are not agreed as to the limits of the different textures. I have had
+recourse, in order to leave no doubt upon this point, to the action
+of different re-agents. I have examined every texture, submitted them
+to the action of caloric, air, water, the acids, the alkalies, the
+neutral salts, etc., drying, putrefaction, maceration, boiling, etc.;
+the products of many of these actions have altered in a different
+manner each kind of texture. Now it will be seen that the results have
+almost all been different, that in these various changes each acts in
+a particular way, each gives results of its own, no one resembling
+another.
+
+There has been considerable inquiry to ascertain whether the arterial
+coats are fleshy, whether the veins are of an analogous nature, etc. By
+comparing the results of my experiments upon the different textures,
+the question is easily resolved. It would seem at first view that all
+these experiments upon the intimate texture of systems answer but
+little purpose; I think, however, that they have effected a useful
+object, in fixing with precision the limits of each organized texture;
+for the nature of these textures being unknown, their differences can
+be ascertained only by the different results they furnish.
+
+3rdly. In giving to each system a different organic arrangement,
+nature has also endowed them with different properties. You will
+see in the subsequent part of this work, that what we call texture
+presents degrees indefinitely varying, from the muscles, the skin,
+the cellular membrane, etc., which enjoy it in the highest degree,
+to the cartilages, the tendons, the bones, etc., which are almost
+destitute of it. Shall I speak of the vital properties? See the
+animal sensibly predominant in the nerves, contractility of the same
+kind particularly marked in the voluntary muscles, sensible organic
+contractility, forming the peculiar property of the involuntary,
+insensible contractility and sensibility of the same nature, which is
+not separated from it more than from the preceding, characterizing
+especially the glands, the skin, the serous surfaces, etc., etc. See
+each of these simple textures combining, in different degrees, more or
+less of these properties, and consequently living with more or less
+energy.
+
+There is but little difference arising from the number of vital
+properties they have in common; when these properties exist in many,
+they take in each a distinctive and peculiar character. This character
+is chronic, if I may so express myself, in the bones, the cartilages,
+the tendons, etc.; it is acute in the muscles, the skin, the glands,
+etc.
+
+Independently of this general difference, each texture has a particular
+kind of force, of sensibility, etc. Upon this principle rests the whole
+theory of secretion, of exhalation, of absorption, and of nutrition.
+The blood is a common reservoir, from which each texture chooses that
+which is adapted to its sensibility, to appropriate and keep it, and
+afterwards reject it.
+
+Much has been said since the time of Bordeu, of the peculiar life of
+each organ, which is nothing else than that particular character which
+distinguishes the combination of the vital properties of one organ
+from those of another. Before these properties had been analyzed with
+exactness and precision, it was clearly impossible to form a correct
+idea of this peculiar life. From the recount I have just given of it,
+it is evident that the greatest part of the organs being composed of
+very different simple textures, the idea of a peculiar life can only
+apply to these simple textures, and not to the organs themselves.
+
+Some examples will render the point of doctrine which is important,
+more evident. The stomach is composed of the serous, organic muscular,
+mucous, and of almost all the common textures, as the arterial, the
+venous, etc., which we can consider separately. Now if you should
+attempt to describe in a general manner, the peculiar life of the
+stomach, it is evidently impossible that you could give a very precise
+and exact idea of it. In fact the mucous surface is so different
+from the serous, and both so different from the muscular, that by
+associating them together, the whole would be confused. The same is
+true of the intestines, the bladder, the womb, etc.; if you do not
+distinguish what belongs to each of the textures that form the compound
+organs, the term peculiar life will offer nothing but vagueness and
+uncertainty. This is so true, that oftentimes the same textures
+alternately belong or are foreign to their organs. The same portion of
+the peritoneum, for example, enters or does not enter, into the gastric
+viscera, according to their fulness or vacuity.
+
+Shall I speak of the pectoral organs? What has the life of the
+fleshy texture of the heart in common with that of the membrane that
+surrounds it? Is not the pleura independent of the pulmonary texture?
+Has this texture nothing in common with the membrane that surrounds
+the bronchia? Is it not the same with the brain with relation to its
+membranes, of the different parts of the eye, the ear, etc.?
+
+When we study a function it is necessary carefully to consider in a
+general manner, the compound organ that performs it; but when you
+wish to know the properties and life of this organ, it is absolutely
+necessary to decompose it. In the same way, if you seek only general
+notions of anatomy, you can study each organ as a whole; but it is
+essential to separate the textures, if you have a desire to analyze
+with accuracy its intimate structure.
+
+
+ CONSEQUENCES OF THE PRECEDING PRINCIPLES RELATIVE TO DISEASE
+
+What I have been saying leads to important consequences, as it respects
+those acute or chronic diseases that are local; for those which, like
+most fevers, affect almost simultaneously every part, cannot be much
+elucidated by the anatomy of systems. The first then will engage our
+attention.
+
+Since diseases are only alterations of the vital properties, and each
+texture differs from the others in its properties, it is evident that
+there must be a difference also in the diseases. In every organ, then,
+composed of different textures, one may be diseased, while the others
+remain sound; now this happens in a great many cases; let us take the
+principal organs, for example.
+
+1st. Nothing is more rare than affections of the mass of the
+brain; nothing is more common than inflammation of the _tunica
+arachnoides_ that covers it. 2d. Oftentimes one membrane of the
+eye only is affected, the others preserving their ordinary degree of
+vitality. 3d. In convulsions or paralysis of the muscles of the larynx,
+the mucous surface is unaffected; and on the other hand, the muscles
+perform their functions as usual in catarrhs of this surface. Both
+these affections are foreign to the cartilages, and _vice versa_.
+4th. We observe a variety of different alterations in the texture
+of the pericardium, but hardly ever in that of the heart itself; it
+remains sound while the other is inflamed. The ossification of the
+common membrane of the red blood does not extend to the neighboring
+textures. 5th. When the membrane of the bronchia is the seat of
+catarrh, the pleura is hardly affected at all, and reciprocally in
+pleurisy the first is scarcely ever altered. In peripneumonia, when an
+enormous infiltration in the dead body shows the excessive inflammation
+that has existed during life in the pulmonary texture, the serous and
+mucous surfaces often appear not to have been affected. Those who open
+dead know that they are frequently healthy in incipient phthisis.
+6th. We speak of a bad stomach, a weak stomach; this most commonly
+should be understood as applying to the mucous surface only. Whilst
+this secretes with difficulty the nutritive juices, without which
+digestion is impaired, the serous surface exhales as usual its fluid,
+the muscular coat continues to contract, etc. In ascites, in which
+the serous surface exhales more lymph than in a natural state, the
+mucous oftentimes performs its functions perfectly well, etc. 7th.
+All authors have said much of the inflammation of the stomach, the
+intestines, the bladder, etc. For myself, I believe that this disease
+rarely ever affects at first the whole of any of these organs, except
+in the case where poison or some other deleterious substance acts upon
+them. There are for the mucous surface of the stomach and intestines,
+acute and chronic catarrhs; for the peritoneum serous inflammations;
+perhaps even for the layer of organic muscles that separates the two
+membranes, there is a particular kind of inflammation, though we have
+as yet hardly anything certain upon this point; but the stomach, the
+intestines, and the bladder are not suddenly affected with these
+three diseases. A diseased texture can affect those near it, but the
+primitive affection seizes only upon one. I have examined a great
+number of bodies in which the peritoneum was inflamed either upon the
+intestines, the stomach, the pelvis, or universally; now very often
+when this affection is chronic, and almost always when it is acute,
+the subjacent organs remain sound. I have never seen this membrane
+exclusively diseased upon one organ, while that of neighboring ones
+remain untouched; its affection is propagated more or less remotely.
+I know not why authors have hardly ever spoken of its inflammation,
+and have placed to the account of the subjacent viscera that which
+most often belongs only to this. There are almost as many cases
+of peritonitis as of pleurisy, and yet while these last have been
+particularly noticed the others are almost entirely overlooked.
+Oftentimes that part of the peritoneum corresponding to an organ,
+is much inflamed; we see it in the case of the stomach; we observe
+especially after the suppression of the lochia or the menses, that it
+is the portion that lines the pelvis that is first affected. But soon
+the affection becomes more or less general; at least examinations after
+death prove it satisfactorily. 8th. Certainly the acute or chronic
+catarrh of the bladder, or womb even, has nothing in common with the
+inflammation of that portion of the peritoneum corresponding with
+these organs. 9th. Every one knows that diseases of the periosteum
+have oftentimes no connection with the bone, and _vice versa_,
+that frequently the marrow is for a long time affected, while both the
+others remain sound. There is no doubt that the osseous, medullary
+and fibrous textures have their peculiar affections which we shall
+not confound with the idea we may form of the diseases of the bones.
+The same can be said of the intestines, of the stomach, etc., in
+relation to their mucous, serous, muscular textures, etc. 10th. Though
+the muscular and tendinous textures are combined in a muscle, their
+diseases are very different. 11th. You must not think that the synovial
+is subject to the same diseases as the ligaments that surround it, etc.
+
+I think the more we observe diseases, and the more we examine bodies,
+the more we shall be convinced of the necessity of considering local
+diseases, not under the relations of the compound organs, which are
+rarely ever affected as a whole, but under that of their different
+textures, which are almost always attacked separately.
+
+When the phenomena of disease are sympathetic, they follow the same
+laws as when they arise from a direct affection. Much has been said
+of the sympathies of the stomach, the intestines, the bladder, the
+lungs, etc. But it is impossible to form an idea of them, if they
+are referred to the organ as a whole, separate from the different
+textures. 1st. When in the stomach, the fleshy fibres contract by the
+influence of another organ and produce vomiting, they alone receive
+the influence, which is not extended either to the serous or mucous
+surfaces; if it were, they would be the seat, the one of exhalation,
+the other of sympathetic exhalation and secretion. 2d. It is certain
+that when the action of the liver is sympathetically increased, so
+that it pours out more bile, the portion of peritoneum that covers it
+does not throw out more serum, because it is not affected by it. It
+is the same of the kidney, the pancreas, etc. 3d. For the same reason
+the gastric organs upon which the peritoneum is spread do not partake
+of the sympathetic influences that it experiences. I shall say as much
+of the lungs in relation to the pleura, the brain in relation to the
+_tunica arachnoides_, the heart to the pericardium, etc. 4th. It
+is undeniable that in all sympathetic convulsions, the fleshy texture
+alone is affected, and that the tendinous is not so at all. 5th. What
+has the fibrous membrane of the testicles in common with the sympathies
+of its peculiar texture? 6th. No doubt a number of sympathetic pains
+that we refer to the bones, are seated exclusively in the marrow.
+
+I could cite many other examples to prove, that it is not this or that
+organ that sympathizes as a whole, but only this or that texture in
+the organs; besides, this an immediate consequence of the nature of
+sympathies. In fact the sympathies are but aberrations of the vital
+properties; now these properties vary according to each texture; the
+sympathies of these textures then would do the same.
+
+
+FOOTNOTES:
+
+[Footnote 26: Translated from _Traité sur les Membranes_ (1800).]
+
+
+
+
+ XXIV
+
+ AMADEO AVOGADRO
+
+ 1776-1856
+
+
+ _Avogadro, who continued the researches of Dalton and Gay-Lussac,
+ was born in Turin, Italy, June 9, 1776. In 1796, after receiving the
+ doctor’s degree in law from the University of Turin, he was employed
+ by the government for the following ten years. He began his work in
+ science in 1806 and three years later was made professor of physics at
+ Vercelli. In 1811 he announced his famous law. According to Merz, since
+ the time of Boyle “it had been known that equal volumes of different
+ gases under equal pressure change their volumes equally if the
+ pressure is varied equally, and it was also known that equal volumes
+ of different gases under equal pressure change their volumes equally
+ with equal rise of temperature. These facts suggested to Avogadro, and
+ almost simultaneously to Ampère, the very simple assumption that this
+ is owing to the fact that equal volumes of different gases contain an
+ equal number of the smallest independent particles of matter. This is
+ Avogadro’s celebrated hypothesis. It was the first step in the direct
+ physical verification of the atomic view of matter.”_
+
+ _In 1820 Avogadro became professor of physics at Turin University,
+ where he remained for many years. He died July 9, 1856._
+
+
+ THE MOLECULES IN GASES PROPORTIONAL TO THE VOLUMES[27]
+
+ I.
+
+M. Gay-Lussac has shown in an interesting Memoir (_Mémoires de la
+Société d’Arcueil_, Tome II.) that gases always unite in a very
+simple proportion by volume, and that when the result of the union is a
+gas, its volume also is very simply related to those of its components.
+But the quantitative proportions of substances in compounds seem only
+to depend on the relative number of molecules which combine, and on the
+number of composite molecules which result. It must then be admitted
+that very simple relations also exist between the volumes of gaseous
+substances and the numbers of simple or compound molecules which form
+them. The first hypothesis to present itself in this connection, and
+apparently even the only admissible one, is the supposition that the
+number of integral molecules in any gases is always the same for equal
+volumes, or always proportional to the volumes. Indeed, if we were
+to suppose that the number of molecules contained in a given volume
+were different for different gases, it would scarcely be possible
+to conceive that the law regulating the distance of molecules could
+give in all cases relations so simple as those which the facts just
+detailed compel us to acknowledge between the volume and the number
+of molecules. On the other hand, it is very well conceivable that
+the molecules of gases being at such a distance that their mutual
+attraction cannot be exercised, their varying attraction for caloric
+may be limited to condensing a greater or smaller quantity around
+them, without the atmosphere formed by this fluid having any greater
+extent in the one case than in the other, and, consequently, without
+the distance between the molecules varying; or, in other words, without
+the number of molecules contained in a given volume being different.
+Dalton, it is true, has proposed a hypothesis directly opposed to
+this, namely, that the quantity of caloric is always the same for the
+molecules of all bodies whatsoever in the gaseous state, and that the
+greater or less attraction for caloric only results in producing a
+greater or less condensation of this quantity around the molecules,
+and thus varying the distance between the molecules themselves. But
+in our present ignorance of the manner in which this attraction of
+the molecules for caloric is exerted, there is nothing to decide
+us _a priori_ in favour of the one of these hypotheses rather
+than the other; and we should rather be inclined to adopt a neutral
+hypothesis, which would make the distance between the molecules and
+the quantities of caloric vary according to unknown laws, were it not
+that the hypothesis we have just proposed is based on that simplicity
+of relation between the volumes of gases on combination, which would
+appear to be otherwise inexplicable.
+
+Setting out from this hypothesis, it is apparent that we have the means
+of determining very easily the relative masses of the molecules of
+substances obtainable in the gaseous state, and the relative number
+of these molecules in compounds; for the ratios of the masses of the
+molecules are then the same as those of the densities of the different
+gases at equal temperature and pressure, and the relative number of
+molecules in a compound is given at once by the ratio of the volumes
+of the gases that form it. For example, since the numbers 1.10359 and
+0.07321 express the densities of the two gases oxygen and hydrogen
+compared to that of atmospheric air as unity, and the ratio of the two
+numbers consequently represents the ratio between the masses of equal
+volumes of these two gases, it will also represent on our hypothesis
+the ratio of the masses of their molecules. Thus the mass of the
+molecule of oxygen will be about 15 times that of the molecule of
+hydrogen, or, more exactly, as 15.074 to 1. In the same way the mass
+of the molecule of nitrogen will be to that of hydrogen as 0.96913 to
+0.07321, that is, as 13, or more exactly 13.238, to 1. On the other
+hand, since we know that the ratio of the volumes of hydrogen and
+oxygen in the formation of water is 2 to 1, it follows that water
+results from the union of each molecule of oxygen with two molecules of
+hydrogen. Similarly, according to the proportions by volume established
+by M. Gay-Lussac for the elements of ammonia, nitrous oxide, nitrous
+gas, and nitric acid, ammonia will result from the union of one
+molecule of nitrogen with three of hydrogen, nitrous oxide from one
+molecule of oxygen with two of nitrogen, nitrous gas from one molecule
+of nitrogen with one of oxygen, and nitric acid from one of nitrogen
+with two of oxygen.
+
+
+ II.
+
+There is a consideration which appears at first sight to be opposed to
+the admission of our hypothesis with respect to compound substances.
+It seems that a molecule composed of two or more elementary molecules
+should have its mass equal to the sum of the masses of these molecules;
+and that in particular, if in a compound one molecule of one substance
+unites with two or more molecules of another substance, the number
+of compound molecules should remain the same as the number of
+molecules of the first substance. Accordingly, on our hypothesis when
+a gas combines with two or more times its volume of another gas, the
+resulting compound, if gaseous, must have a volume equal to that of
+the first of these gases. Now, in general, this is not actually the
+case. For instance, the volume of water in the gaseous state is, as
+M. Gay-Lussac has shown, twice as great as the volume of oxygen which
+enters into it, or, what comes to the same thing, equal to that of the
+hydrogen instead of being equal to that of the oxygen. But a means
+of explaining facts of this type in conformity with our hypothesis
+presents itself naturally enough: we suppose, namely, that the
+constituent molecules of any simple gas whatever (i. e., the molecules
+which are at such a distance from each other that they cannot exercise
+their mutual action) are not formed of a solitary elementary molecule,
+but are made up of a certain number of these molecules united by
+attraction to form a single one; and further, that when molecules of
+another substance unite with the former to form a compound molecule,
+the integral molecule which should result splits up into two or more
+parts (or integral molecules) composed of half, quarter, &c., the
+number of elementary molecules going to form the constituent molecule
+of the first substance, combined with half, quarter, &c., the number of
+constituent molecules of the second substance that ought to enter into
+combination with one constituent molecule of the first substance (or,
+what comes to the same thing, combined with a number equal to this last
+of half-molecules, quarter-molecules, &c., of the second substance);
+so that the number of integral molecules of the compound becomes
+double, quadruple, &c., what it would have been if there had been no
+splitting-up, and exactly what is necessary to satisfy the volume of
+the resulting gas.
+
+On reviewing the various compound gases most generally known, I only
+find examples of duplication of the volume relatively to the volume of
+that one of the constituents which combines with one or more volumes
+of the other. We have already seen this for water. In the same way,
+we know that the volume of ammonia gas is twice that of the nitrogen
+which enters into it. M. Gay-Lussac has also shown that the volume of
+nitrous oxide is equal to that of the nitrogen which forms part of
+it, and consequently is twice that of the oxygen. Finally, nitrous
+gas, which contains equal volumes of nitrogen and oxygen, has a
+volume equal to the sum of the two constituent gases, that is to say,
+double that of each of them. Thus in all these cases there must be a
+division of the molecule into two; but it is possible that in other
+cases the division might be into four, eight, &c. The possibility of
+this division of compound molecules might have been conjectured _a
+priori_; for otherwise the integral molecules of bodies composed
+of several substances with a relatively large number of molecules,
+would come to have a mass excessive in comparison with the molecules
+of simple substances. We might therefore imagine that nature had some
+means of bringing them back to the order of the latter, and the facts
+have pointed out to us the existence of such means. Besides, there
+is another consideration which would seem to make us admit in some
+cases the division in question; for how could one otherwise conceive
+a real combination between two gaseous substances uniting in equal
+volumes without condensation, such as takes place in the formation of
+nitrous gas? Supposing the molecules to remain at such a distance that
+the mutual attraction of those of each gas could not be exercised,
+we cannot imagine that a new attraction could take place between the
+molecules of one gas and those of the other. But on the hypothesis
+of division of the molecule, it is easy to see that the combination
+really reduces two different molecules to one, and that there would be
+contraction by the whole volume of one of the gases if each compound
+molecule did not split up into two molecules of the same nature. M.
+Gay-Lussac clearly saw that, according to the facts, the diminution of
+volume on the combination of gases cannot represent the approximation
+of their elementary molecules. The division of molecules on combination
+explains to us how these two things may be made independent of each
+other.
+
+
+ III.
+
+Dalton, on arbitrary suppositions as to the most likely relative number
+of molecules in compounds, has endeavoured to fix ratios between the
+masses of the molecules of simple substances. Our hypothesis, supposing
+it well founded, puts us in a position to confirm or rectify his
+results from precise data, and, above all, to assign the magnitude of
+compound molecules according to the volumes of the gaseous compounds,
+which depend partly on the division of molecules entirely unsuspected
+by this physicist.
+
+Thus Dalton supposes that water is formed by the union of hydrogen and
+oxygen, molecule to molecule. From this, and from the ratio by weight
+of the two components, it would follow that the mass of the molecule of
+oxygen would be to that of hydrogen as 7-1/2 to 1 nearly, or, according
+to Dalton’s evaluation, as 6 to 1. This ratio on our hypothesis is,
+as we saw, twice as great, namely, as 15 to 1. As for the molecule of
+water, its mass ought to be roughly expressed by 15 + 2 = 17 (taking
+for unity that of hydrogen), if there were no division of the molecule
+into two; but on account of this division it is reduced to half, 8-1/2,
+or more exactly 8.537, as may also be found directly by dividing the
+density of aqueous vapour 0.625 (Gay-Lussac) by the density of hydrogen
+0.0732. This mass only differs from 7, that assigned to it by Dalton,
+by the difference in the values for the composition of water; so that
+in this respect Dalton’s result is approximately correct from the
+combination of two compensating errors,--the error in the mass of the
+molecule of oxygen, and his neglect of the division of the molecule.
+
+
+FOOTNOTES:
+
+[Footnote 27: Translated from _Essai d’une manière de déterminer
+les masses relatives des molécules élémentaires des corps,
+et les proportions selon lesquelles elles entrent dans les
+combinaisons_--_Journal de Physique_, (1811).]
+
+
+
+
+ XXV
+
+ SIR HUMPHREY DAVY
+
+ 1778-1829
+
+
+ _Born December 17, 1778, in Cornwall, Sir Humphrey Davy was
+ apprenticed in 1794 to a surgeon-apothecary at Penzance in whose
+ service he became interested in chemistry. Made superintendent of a
+ hospital in 1798, he had opportunities for gaining acquaintance with
+ influential men who in turn recommended him to Count Rumford. Through
+ the latter’s assistance he was appointed lecturer on chemistry at the
+ newly-founded Royal Institution where, in spite of his unattractive
+ appearance, he gained considerable reputation. In 1807 he advanced a
+ theory which partly explained electrolysis; in the following year he
+ discovered strontium and magnesium; and in 1809, chlorine. In 1812 he
+ was knighted; and shortly after his marriage, in the same year, he
+ injured an eye while experimenting and was compelled to interrupt his
+ work for a short time. In 1815 he invented the safety-lamp used by
+ miners. In 1818 he was created a baronet, and was elected President
+ of the Royal Society in 1820. He died May 29, 1829, at Geneva,
+ Switzerland, at the age of fifty-one._
+
+
+ ON SOME NEW PHENOMENA OF CHEMICAL CHANGES PRODUCED BY ELECTRICITY[28]
+
+ _Read November 19, 1807._
+
+ INTRODUCTION.
+
+In the Bakerian Lecture which I had the honour of presenting to the
+Royal Society last year, I described a number of decompositions
+and chemical changes produced in substances of known composition by
+electricity, and I ventured to conclude from the general principles
+on which the phenomena were capable of being explained, that the new
+methods of investigation promised to lead to a more intimate knowledge
+than had hitherto been obtained, concerning the true elements of bodies.
+
+This conjecture, then sanctioned only by strong analogies, I am now
+happy to be able to support by some conclusive facts. In the course of
+a laborious experimental application of the powers of electro-chemical
+analysis, to bodies which have appeared simple when examined by common
+chemical agents, or which at least have never been decomposed, it has
+been my good fortune to obtain new and singular results.
+
+Such of the series of experiments as are in a tolerably mature state,
+and capable of being arranged in a connected order, I shall detail
+in the following sections, particularly those which demonstrate the
+decomposition and composition of the fixed alkalies, and the production
+of the new and extraordinary bodies which constitute their bases.
+
+In speaking of novel methods of investigation, I shall not fear to be
+minute. When the common means of chemical research have been employed,
+I shall mention only results. A historical detail of the progress
+of the investigation, of all the difficulties that occurred, and of
+the manner in which they were overcome, and of all the manipulations
+employed, would far exceed the limits assigned to this Lecture. It is
+proper to state, however, that when general facts are mentioned, they
+are such only as have been deduced from processes carefully performed
+and often repeated.
+
+
+ ON THE METHODS USED FOR THE DECOMPOSITION OF THE FIXED ALKALIES
+
+The researches I had made on the decomposition of acids, and of
+alkaline and earthy neutral compounds, proved that the powers of
+electrical decomposition were proportional to the strength of the
+opposite electricities in the circuit, and to the conducting power and
+degree of concentration of the materials employed.
+
+In the first attempts, that I made on the decomposition of the fixed
+alkalies, I acted upon aqueous solutions of potash and soda, saturated
+at common temperatures, by the highest electrical power I could
+command, and which was produced by a combination of Voltaic batteries
+belonging to the Royal Institution, containing 24 plates of copper and
+zinc of 12 inches square, 100 plates of 6 inches, and 150 of 4 inches
+square, charged with solutions of alum and nitrous acid; but in these
+cases, though there was a high intensity of action, the water of the
+solutions alone was affected, and hydrogen and oxygen disengaged with
+the production of much heat and violent effervescence.
+
+The presence of water appearing thus to prevent any decomposition, I
+used potash in igneous fusion. By means of a stream of oxygen gas from
+a gasometer applied to the flame of a spirit lamp, which was thrown
+on a platina spoon containing potash, this alkali was kept for some
+minutes in a strong red heat, and in a state of perfect fluidity.
+The spoon was preserved in communication with the positive side of
+the battery of the power of 100 of 6 inches, highly charged; and the
+connection from the negative side was made by a platina wire.
+
+By this arrangement some brilliant phenomena were produced. The potash
+appeared a conductor in a high degree, and as long as the communication
+was preserved, a most intense light was exhibited at the negative wire,
+and a column of flame, which seemed to be owing to the development of
+combustible matter, arose from the point of contact.
+
+When the order was changed, so that the platina spoon was made
+negative, a vivid and constant light appeared at the opposite point:
+there was no effect of inflammation round it; but aeriform globules,
+which inflamed in the atmosphere, rose through the potash.
+
+The platina, as might have been expected, was considerably acted upon;
+and in the cases when it had been negative, in the highest degree.
+
+The alkali was apparently dry in this experiment; and it seemed
+probable that the inflammable matter arose from its decomposition.
+The residual potash was unaltered; it contained indeed a number of
+dark grey metallic particles, but these proved to be derived from the
+platina.
+
+I tried several experiments on the electrization of potash rendered
+fluid by heat, with the hopes of being able to collect the combustible
+matter, but without success; and I only attained my object by employing
+electricity as the common agent for fusion and decomposition.
+
+Though potash, perfectly dried by ignition, is a non-conductor, yet it
+is rendered a conductor by a very slight addition of moisture, which
+does not perceptibly destroy its aggregation; and in this state it
+readily fuses and decomposes by strong electrical powers.
+
+A small piece of pure potash, which had been exposed for a few seconds
+to the atmosphere, so as to give conducting power to the surface, was
+placed upon an insulated disc of platina, connected with the negative
+side of the battery of the power of 250 of 6 and 4, in a state of
+intense activity; and a platina wire, communicating with the positive
+side, was brought in contact with the upper surface of the alkali. The
+whole apparatus was in the open atmosphere.
+
+Under these circumstances a vivid action was soon observed to take
+place. The potash began to fuse at both its points of electrization.
+There was a violent effervescence at the upper surface; at the lower,
+or negative surface, there was no liberation of elastic fluid; but
+small globules having a high metallic lustre, and being precisely
+similar in visible characters to quicksilver, appeared, some of which
+burnt with explosion and bright flame, as soon as they were formed, and
+others remained, and were merely tarnished, and finally covered by a
+white film which formed on their surfaces.
+
+These globules, numerous experiments soon showed to be the substance
+I was in search of, and a peculiar inflammable principle the basis
+of potash. I found that the platina was in no way connected with the
+result, except as the medium for exhibiting the electrical powers of
+decomposition; and a substance of the same kind was produced when
+pieces of copper, silver, gold, plumbago, or even charcoal were
+employed for completing the circuit.
+
+The phenomenon was independent of the presence of air; I found that it
+took place when the alkali was in the vacuum of an exhausted receiver.
+
+The substance was likewise produced from potash fused by means of
+a lamp, in glass tubes confined by mercury, and furnished with
+hermetically inserted platina wires by which the electrical action
+was transmitted. But this operation could not be carried on for any
+considerable time; the glass was rapidly dissolved by the action of
+the alkali, and this substance soon penetrated through the body of the
+tube.
+
+Soda, when acted upon in the same manner as potash, exhibited an
+analogous result; but the decomposition demanded greater intensity
+of action in the batteries, or the alkali was required to be in much
+thinner and smaller pieces. With the battery of 100 of 6 inches in full
+activity I obtained good results from pieces of potash weighing from
+40 to 70 grains, and of a thickness which made the distance of the
+electrified metallic surfaces nearly a quarter of an inch; but with a
+similar power it was impossible to produce the effects of decomposition
+on pieces of soda of more than 15 or 20 grains in weight, and that only
+when the distance between the wires was about 1/8 or 1/10 of an inch.
+
+The substance produced from potash remained fluid at the temperature of
+the atmosphere at the time of its production; that from soda, which was
+fluid in the degree of heat of the alkali during its formation, became
+solid on cooling, and appeared having the lustre of silver.
+
+When the power of 250 was used, with a very high charge for the
+decomposition of soda, the globules often burnt at the moment of their
+formation, and sometimes violently exploded and separated into smaller
+globules, which flew with great velocity through the air in a state of
+vivid combustion, producing a beautiful effect of continued jets of
+fire.
+
+
+ THEORY OF THE DECOMPOSITION OF THE FIXED ALKALIES; THEIR COMPOSITION
+ AND PRODUCTION
+
+As in all decompositions of compound substances which I had previously
+examined, at the same time that combustible bases were developed at
+the negative surface in the electrical circuit, oxygen was produced,
+and evolved or carried into combination at the positive surface, it
+was reasonable to conclude that this substance was generated in a
+similar manner by the electrical action upon the alkalies; and a number
+of experiments made above mercury, with the apparatus for excluding
+external air, proved that this was the case.
+
+When solid potash, or soda in its conducting state, was included
+in glass tubes furnished with electrified platina wires, the new
+substances were generated at the negative surfaces; the gas given out
+at the other surface proved by the most delicate examination to be pure
+oxygen; and unless an excess of water was present, no gas was evolved
+from the negative surface.
+
+In the synthetical experiments, a perfect coincidence likewise will be
+found.
+
+I mentioned that the metallic lustre of the substance from potash
+immediately became destroyed in the atmosphere, and that a white crust
+formed upon it. This crust I soon found to be pure potash, which
+immediately deliquesced, and new quantities were formed, which in their
+turn attracted moisture from the atmosphere till the whole globule
+disappeared, and assumed the form of a saturated solution of potash.
+
+When globules were placed in appropriate tubes containing common air
+or oxygen gas confined by mercury, an absorption of oxygen took place;
+a crust of alkali instantly formed upon the globule; but from the want
+of moisture for its solution, the process stopped, the interior being
+defended from the action of the gas.
+
+With the substance from soda, the appearances and effects were
+analogous.
+
+When the substances were strongly heated, confined in given proportions
+of oxygen, a rapid combustion with a brilliant white flame was
+produced, and the metallic globules were found converted into a white
+and solid mass, which in the case of the substance from potash was
+found to be potash, and in the case of that from soda, soda.
+
+Oxygen gas was absorbed in this operation, and nothing emitted which
+affected the purity of the residual air.
+
+The alkalies produced were apparently dry, or at least contained no
+more moisture than might well be conceived to exist in the oxygen
+gas absorbed; and their weights considerably exceeded those of the
+combustible matters consumed.
+
+The processes on which these conclusions are founded will be fully
+described hereafter, when the minute details which are necessary will
+be explained, and the proportions of oxygen, and of the respective
+inflammable substances which enter into union to form the fixed
+alkalies, will be given.
+
+It appears, then, that in these facts there is the same evidence
+for the decomposition of potash and soda into oxygen and two
+peculiar substances, as there is for the decomposition of sulphuric
+and phosphoric acids and the metallic oxides into oxygen and their
+respective combustible bases.
+
+In the analytical experiments, no substances capable of decomposition
+are present but the alkalies and a minute portion of moisture; which
+seems in no other way essential to the result, than in rendering them
+conductors at the surface: for the new substances are not generated
+till the interior, which is dry, begins to be fused; they explode when
+in rising through the fused alkali they come in contact with the heated
+moistened surface; they cannot be produced from crystallised alkalies,
+which contain much water; and the effect produced by the electrization
+of ignited potash, which contains no sensible quantity of water,
+confirms the opinion of their formation independently of the presence
+of this substance.
+
+The combustible bases of the fixed alkalies seem to be repelled as
+other combustible substances, by positively electrified surfaces, and
+attracted by negatively electrified surfaces, and the oxygen follows
+the contrary order; or the oxygen being naturally possessed of the
+negative energy, and the bases of the positive, do not remain in
+combination when either of them is brought into an electrical state
+opposite to its natural one. In the synthesis, on the contrary, the
+natural energies or attractions come in equilibrium with each other;
+and when these are in a low state at common temperatures, a slow
+combination is effected; but when they are exalted by heat, a rapid
+motion is the result; and as in other like cases with the production of
+fire.
+
+
+FOOTNOTES:
+
+[Footnote 28: From the _Transactions of the Royal Society of
+London_.]
+
+
+
+
+ XXVI
+
+ MICHAEL FARADAY
+
+ 1791-1867
+
+
+ _Born on September 22, 1791, at Newington, Surrey, England,
+ Michael Faraday was the son of a blacksmith. After an early and very
+ elementary education, he was apprenticed in 1805 to a book-binder in
+ whose service he read widely and thus educated himself. Developing an
+ interest in physics, he attended the evening lectures of Sir Humphrey
+ Davy who, in 1813, engaged him as an assistant. Seven years later he
+ wrote a history of electro-magnetism and succeeded, in the same year,
+ in getting a needle to rotate fully around a live wire. In 1823 he
+ liquefied chlorine, an experiment which destroyed the old notion of the
+ permanent distinction between gases and liquids. In 1831 he discovered
+ magneto-electric induction and advanced the conception of “lines of
+ magnetic force.” In 1845, in trying to send polarized rays of light
+ through heavy magnetized glass, he found that the magnet’s action
+ interrupted the passage of the light and that magnetization caused the
+ plane of polarization to rotate. He died August 25, 1867._
+
+
+ ON FLUID CHLORINE[29]
+
+ _Read March 13, 1823._
+
+It is well known that before the year 1810, the solid substance
+obtained by exposing chlorine, as usually procured, to a low
+temperature, was considered as the gas itself reduced into that form;
+and that Sir Humphrey Davy first showed it to be a hydrate, the pure
+dry gas not being considerable even at a temperature of 40° F.
+
+I took advantage of the late cold weather to procure crystals of this
+substance for the purpose of analysis. The results are contained
+in a short paper in the Quarterly Journal of Science, Vol. XV. Its
+composition is very nearly 27.7 chlorine, 72.3 water, or 1 proportional
+of chlorine, and 10 of water.
+
+The President of the Royal Society having honoured me by looking at
+these conclusions, suggested, that an exposure of the substance to
+heat under pressure, would probably lead to interesting results; the
+following experiments were commenced at his request. Some hydrate
+of chlorine was prepared, and being dried as well as could be by
+pressure in bibulous paper, was introduced into a sealed glass tube,
+the upper end of which was then hermetically closed. Being placed
+in water at 60°, it underwent no change; but when put into water
+at 100°, the substance fused, the tube became filled with a bright
+yellow atmosphere, and, on examination, was found to contain two
+fluid substances: the one, about three-fourths of the whole, was of
+a faint yellow colour, having very much the appearance of water; the
+remaining fourth was a heavy bright yellow fluid, lying at the bottom
+of the former, without any apparent tendency to mix with it. As the
+tube cooled, the yellow atmosphere condensed into more of the yellow
+fluid, which floated in a film on the pale fluid, looking very like
+chloride of nitrogen; and at 70° the pale portion congealed, although
+even at 32° the yellow portion did not solidify. Heated up to 100° the
+yellow fluid appeared to boil, and again produced the bright coloured
+atmosphere.
+
+By putting the hydrate into a bent tube, afterwards hermetically
+sealed, I found it easy, after decomposing it by a heat of 100°, to
+distil the yellow fluid to one end of the tube, and so separate it from
+the remaining portion. In this way a more complete decomposition of the
+hydrate was effected, and, when the whole was allowed to cool, neither
+of the fluids solidified at temperatures above 34°, and the yellow
+portion not even at 0°. When the two were mixed together they gradually
+combined at temperatures below 60°, and formed the same solid substance
+as that first introduced. If, when the fluids were separated, the tube
+was cut in the middle, the parts flew asunder as if with an explosion,
+the whole of the yellow portion disappeared, and there was a powerful
+atmosphere of chlorine produced; the pale portion on the contrary
+remained, and when examined, proved to be a weak solution of chlorine
+in water, with a little muriatic acid, probably from the impurity of
+the hydrate used. When that end of the tube in which the yellow fluid
+lay was broken under a jar of water, there was an immediate production
+of chlorine gas.
+
+I at first thought that muriatic acid and euchlorine had been formed;
+then, that two new hydrates of chlorine had been produced; but at
+last I suspected that the chlorine had been entirely separated from
+the water by the heat and condensed into a dry fluid by the mere
+pressure of its own abundant vapour. If that were true, it followed,
+that chlorine gas, when compressed, should be condensed into the
+same fluid, and, as the atmosphere in the tube in which the fluid
+lay was not very yellow at 50° or 60°, it seemed probable that the
+pressure required was not beyond what could readily be obtained by a
+condensing syringe. A long tube was therefore furnished with a cap and
+stop-cock, then exhausted of air and filled with chlorine, and being
+held vertically with the syringe upwards, air was forced in, which
+thrust the chlorine to the bottom of the tube, and gave a pressure of
+about 4 atmospheres. Being now cooled, there was an immediate deposit
+in films, which appeared to be hydrate, formed by water contained in
+the gas and vessels, but some of the yellow fluid was also produced.
+As this however might also contain a portion of the water present,
+a perfectly dry tub and apparatus were taken, and the chlorine left
+for some time over a bath of sulphuric acid before it was introduced.
+Upon throwing in air and giving pressure, there was now no solid film
+formed, but the clear yellow fluid was deposited, and more abundantly
+still upon cooling. After remaining some time it disappeared, having
+gradually mixed with the atmosphere above it, but every repetition of
+the experiment produced the same results.
+
+Presuming that I had now a right to consider the yellow fluid as pure
+chlorine in the liquid state, I proceeded to examine its properties,
+as well as I could when obtained by heat from the hydrate. However
+obtained, it always appears very limpid and fluid, and excessively
+volatile at common pressure. A portion was cooled in its tube to 0°;
+it remained fluid. The tube was then opened, when a part immediately
+flew off, leaving the rest so cooled by the evaporation as to remain a
+fluid under the atmospheric pressure. The temperature could not have
+been higher than 40° in this case; as Sir Humphrey Davy has shown
+that dry chlorine does not condense at that temperature under common
+pressure. Another tube was opened at a temperature of 50°; a part of
+the chlorine volatilised, and cooled the tube so much as to condense
+the atmospheric vapour on it as ice.
+
+A tube having the water at one end and the chlorine at the other was
+weighed, and then cut in two; the chlorine immediately flew off, and
+the loss being ascertained was found to be 1.6 grains: the water
+left was examined and found to contain some chlorine: its weight was
+ascertained to be 5.4 grains. These proportions, however, must not
+be considered as indicative of the true composition of hydrate of
+chlorine; for, from the mildness of the weather during the time when
+these experiments were made, it was impossible to collect the crystals
+of hydrate, press, and transfer them, without losing much chlorine; and
+it is also impossible to separate the chlorine and water in the tube
+perfectly, or keep them separate, as the atmosphere within will combine
+with the water, and gradually reform the hydrate.
+
+Before cutting the tube, another tube had been prepared exactly like it
+in form and size, and a portion of water introduced into it, as near as
+the eye could judge, of the same bulk as the fluid chlorine: this water
+was found to weigh 1.2 grains; a result, which, if it may be trusted,
+would give the specific gravity of fluid chlorine as 1.33; and from its
+appearance in, and on water, this cannot be far wrong.
+
+
+ ELECTRICITY FROM MAGNETISM
+
+ _Read November 24, 1831._
+
+1. The power which electricity of tension possesses of causing an
+opposite electrical state in its vicinity has been expressed by the
+general term Induction; which, as it has been received into scientific
+language, may also, with propriety, be used in the same general sense
+to express the power which electrical currents may possess of inducing
+any particular state upon matter in their immediate neighborhood,
+otherwise indifferent. It is with this meaning that I purpose using it
+in the present paper.
+
+2. Certain effects of the induction of electrical currents have already
+been recognized and described: as those of magnetization; Ampère’s
+experiments of bringing a copper disc near to a flat spiral; his
+repetition with electro-magnets of Arago’s extraordinary experiments,
+and perhaps a few others. Still it appeared unlikely that these
+could be all the effects which induction by currents could produce;
+especially as, upon dispensing with iron, almost the whole of them
+disappear, whilst yet an infinity of bodies, exhibiting definite
+phenomena of induction with electricity of tension still remain to be
+acted upon by the induction of electricity in motion.
+
+3. Further: whether Ampère’s beautiful theory were adopted, or any
+other, or whatever reservation were mentally made, still it appeared
+very extraordinary, that, as every electric current was accompanied by
+a corresponding intensity of magnetic action at right angles to the
+current, good conductors of electricity, when placed within the sphere
+of this action, should not have any current induced through them, or
+some sensible effect produced equivalent in force to such a current.
+
+4. These considerations, with their consequence, the hope of obtaining
+electricity from ordinary magnetism, have stimulated me at various
+times to investigate experimentally the inductive effect of electric
+currents. I lately arrived at positive results; and not only had my
+hopes fulfilled, but obtained a key which appeared to me to open out a
+full explanation of Arago’s magnetic phenomena, and also to discover a
+new state, which may probably have great influence in some of the most
+important effects of electric currents.
+
+5. These results I purpose describing, not as they were obtained, but
+in such a manner as to give the most concise view of the whole.
+
+
+ EVOLUTION OF ELECTRICITY FROM MAGNETISM
+
+27. A welded ring was made of soft round bar-iron, the metal being
+seven-eighths of an inch in thickness, and the ring six inches in
+external diameter. Three helices were put round one part of this ring,
+each containing about twenty-four feet of copper wire one-twentieth
+of an inch thick; they were insulated from the iron and each other,
+and superposed in the manner before described (6), occupying about
+nine inches in length upon the ring. They could be used separately or
+conjointly; the group may be distinguished by the letter A. On the
+other part of the ring about sixty feet of similar copper wire in two
+pieces were applied in the same manner, forming a helix B, which had
+the same common direction with the helices of A, but being separated
+from it at each extremity by about half an inch of the uncovered iron.
+
+28. The helix B, was connected by copper wires with a galvanometer
+three feet from the ring. The helices of A were connected end to
+end so as to form one common helix, the extremities of which were
+connected with a battery of ten pairs of plates four inches square. The
+galvanometer was immediately affected, and to a degree far beyond what
+has been described when with a battery of tenfold power helices without
+iron were used (10); but though the contact was continued, the effect
+was not permanent, for the needle soon came to rest in its natural
+position, as if quite indifferent to the attached electro-magnetic
+arrangement. Upon breaking the contact with the battery, the needle
+was again powerfully deflected, but in the contrary direction to that
+induced in the first instance.
+
+29. Upon arranging the apparatus so that B should be out of use, the
+galvanometer be connected with one of the three wires of A (27), and
+the other two made into a helix through which the current from the
+trough (28) was passed, similar but rather more powerful effects were
+produced.
+
+30. When the battery contact was made in one direction, the
+galvanometer-needle was deflected on the one side; if made in the other
+direction, the deflection was on the other side. The deflection on
+breaking the battery contact was always the reverse of that produced
+by completing it. The deflection on making a battery contact always
+indicated an induced current in the opposite direction to that from
+the battery; but on breaking the contact the deflection indicated
+an induced current in the same direction as that of the battery.
+No making or breaking of the contact at B side, or in any part of
+the galvanometer circuit, produced any effect at the galvanometer.
+No continuance of the battery current caused any deflection of the
+galvanometer-needle. As the above results are common to all these
+experiments, and to similar ones with ordinary magnets to be hereafter
+detailed, they need not be again particularly described.
+
+31. Upon using the power of 100 pairs of plates (10) with this ring,
+the impulse at the galvanometer, when contact was completed or broken,
+was so great as to make the needle spin round rapidly four or five
+times, before the air and terrestrial magnetism could reduce its motion
+to mere oscillation.
+
+39. But as might be supposed that in all the preceding experiments of
+this section, it was by some peculiar effect taking place during the
+formation of the magnet, and not by its mere virtual approximation,
+that the momentary induced current was excited, the following
+experiment was made. All the similar ends of the compound hollow
+helix (34) were bound together by copper wire, forming two general
+terminations, and these were connected with the galvanometer. The soft
+iron cylinder (34) was removed, and a cylindrical magnet three-quarters
+of an inch in diameter and eight inches and a half in length, used
+instead. One end of this magnet was introduced into the axis of the
+helix and then, the galvanometer-needle being stationary, the magnet
+was suddenly thrust in; immediately the needle was deflected in the
+same direction as if the magnet had been formed by either of the two
+preceding processes (34, 36). Being left in, the needle resumed its
+first position, and then the magnet being withdrawn the needle was
+deflected in the opposite direction. These effects were not great; but
+by introducing and withdrawing the magnet, so that the impulse each
+time should be added to those previously communicated to the needle,
+the latter could be made to vibrate through an arc of 180° or more.
+
+40. In this experiment the magnet must not be passed entirely through
+the helix, for then a second action occurs. When the magnet is
+introduced the needle at the galvanometer is deflected in a certain
+direction; but being in, whether it be pushed quite through or
+withdrawn, the needle is deflected in a direction the reverse of that
+previously produced. When the magnet is passed in and through at one
+continuous motion, the needle moves one way, is then suddenly stopped,
+and finally moves the other way.
+
+41. If such a hollow helix as that described (34) be laid east and west
+(or in any other constant position), and a magnet be retained east and
+west, its marked pole always being one way; then whichever end of the
+helix the magnet goes in at, and consequently whichever pole of the
+magnet enters first, still the needle is deflected the same way: on the
+other hand, whichever direction is followed in withdrawing the magnet,
+the deflection is constant, but contrary to that due to its entrance.
+
+57. The various experiments of this section prove, I think, most
+completely the production of electricity from ordinary magnetism.
+That its intensity should be very feeble and quantity small,
+cannot be considered wonderful, when it is remembered that like
+thermo-electricity it is evolved entirely within the substance of
+metals retaining all their conducting power. But an agent which is
+conducted along the metallic wires in the manner described; which,
+whilst so passing possesses the peculiar magnetic actions and force
+of a current of electricity; which can agitate and convulse the limbs
+of a frog; and which, finally, can produce a spark by its discharge
+through charcoal (32), can only be electricity. As all the effects can
+be produced by ferruginous electro-magnets (34), there is no doubt that
+arrangements like the magnets of Professors Moll, Henry, Ten Eyke, and
+others, in which as many as two thousand pounds have been lifted, may
+be used for these experiments; in which case not only a brighter spark
+may be obtained, but wires also ignited, and, as the current can pass
+liquids (23), chemical action be produced. These effects are still
+more likely to be obtained when the magneto-electric arrangements to
+be explained in the fourth section are excited by the powers of such
+apparatus.
+
+58. The similarity of action, almost amounting to identity, between
+common magnets and either electro-magnets or volta-electric currents,
+is strikingly in accordance with and confirmatory of M. Ampère’s
+theory, and furnishes powerful reasons for believing that the action
+is the same in both cases; but, as a distinction in language is still
+necessary, I propose to call the agency thus exerted by ordinary
+magnets, magneto-electric or magnelectric induction (26).
+
+59. The only difference which powerfully strikes the attention as
+existing between volta-electric and magneto-electric induction, is the
+suddenness of the former, and the sensible time required by the latter:
+but even in this early state of investigation there are circumstances
+which seem to indicate, that upon further inquiry this difference will,
+as a philosophical distinction, disappear (68).
+
+
+FOOTNOTES:
+
+[Footnote 29: This excerpt and the one following are from the
+_Transactions of the Royal Society of London_.]
+
+
+
+
+ XXVII
+
+ JOSEPH HENRY
+
+ 1797-1878
+
+
+ _Born at Albany, New York, December 17, 1797, Joseph Henry prepared
+ for the profession of medicine, but an appointment as an assistant
+ engineer on the state road diverted his interests toward mechanics.
+ In 1826 he was appointed instructor of physics at Albany Institute,
+ now the Albany Boys Academy, where he conducted his first experiments
+ in electricity. In 1828 he first produced a strong electro-magnet by
+ winding fine insulated wire around a piece of soft iron, and soon
+ succeeded in exciting his electro-magnet at a distance by the use of
+ high intensity batteries made up of many cells. Demonstrating that
+ the number of coils of fine wire about a magnet had as much influence
+ as the intensity of the current and that after winding many coils
+ around the soft iron magnet it could still be made magnetic, he
+ suggested the principle which Morse later used in the telegraph. In
+ 1832 he discovered that in a long conductor the primary current, by an
+ induction upon itself, produced a number of secondary currents that
+ greatly increased the intensity of the discharge._
+
+ _He was appointed professor of natural philosophy at Princeton
+ University in 1832 and became secretary of the Smithsonian Institution
+ in 1846. He died in Washington, May 13, 1878._
+
+
+ ON THE PRODUCTION OF CURRENTS AND SPARKS OF ELECTRICITY FROM
+ MAGNETISM[30]
+
+Although the discoveries of Oersted, Arago, Faraday, and others, have
+placed the intimate connection of electricity and magnetism in a most
+striking point of view, and although the theory of Ampère has referred
+all the phenomena of both these departments of science to the same
+general laws, yet until lately one thing remained to be proved by
+experiment, in order more fully to establish their identity; namely,
+the possibility of producing electrical effects from magnetism.
+It is well known that surprising magnetic results can readily be
+obtained from electricity, and at first sight it might be supposed
+that electrical effects could with equal facility be produced from
+magnetism; but such has not been found to be the case, for although the
+experiment has often been attempted, it has nearly as often failed.
+
+It early occurred to me that if galvanic magnets on my plan were
+substituted for ordinary magnets, in researches of this kind, more
+success might be expected. Besides their great powers these magnets
+possess other properties, which render them important instruments in
+the hands of the experimenter; their polarity can be instantaneously
+reversed, and their magnetism suddenly destroyed or called into full
+action, according as the occasion may require. With this view, I
+commenced, last August, the construction of a much larger galvanic
+magnet than, to my knowledge, had before been attempted, and also made
+preparations for a series of experiments with it on a large scale,
+in reference to the production of electricity from magnetism. I was,
+however, at that time accidentally interrupted in the prosecution of
+these experiments, and have not been able since to resume them until
+within the last few weeks, and then on a much smaller scale than was
+at first intended. In the meantime, it has been announced in the 117th
+number of the _Library of Useful Knowledge_, that the result
+so much sought after has at length been found by Mr. Faraday of the
+Royal Institution. It states that he has established the general fact,
+that when a piece of metal is moved in any direction, in front of a
+magnetic pole, electrical currents are developed in the metal, which
+pass in a direction at right angles to its own motion, and also that
+the application of this principle affords a complete and satisfactory
+explanation of the phenomena of magnetic rotation. No detail is given
+of the experiments, and it is somewhat surprising that results so
+interesting, and which certainly form a new era in the history of
+electricity and magnetism, should not have been more fully described
+before this time in some of the English publications; the only mention
+I have found of them is the following short account from the _Annals
+of Philosophy_ for April, under the head of Proceedings of the Royal
+Institution:
+
+ “Feb. 17.--Mr. Faraday gave an account of the first two parts of
+ his researches in electricity; namely, Volta-electric induction and
+ magneto-electric induction. If two wires, A and B, be placed side by
+ side, but not in contact, and a Voltaic current be passed through
+ A, there is instantly a current produced by induction in B, in the
+ opposite direction. Although the principal current in A be continued,
+ still the secondary current in B is not found to accompany it, for
+ it ceases after the first moment, but when the principal current is
+ stopped, then there is a second current produced in B, in the opposite
+ direction to that of the first produced by the inductive action, or in
+ the same direction as that of the principal current.
+
+ “If a wire, connected at both extremities with a galvanometer,
+ be coiled in the form of a helix around a magnet, no current of
+ electricity takes place in it. This is an experiment which has been
+ made by various persons hundreds of times, in the hope of evolving
+ electricity from magnetism, and in other cases in which the wishes of
+ the experimenter and the facts are opposed to each other, has given
+ rise to very conflicting conclusions. But if the magnet be withdrawn
+ from or introduced into such a helix, a current of electricity is
+ produced whilst the magnet is in motion, and is rendered evident by
+ the deflection of the galvanometer. If a single wire be passed by a
+ magnetic pole, a current of electricity is induced through it which
+ can be rendered sensible.”
+
+Before having any knowledge of the method given in the above account, I
+had succeeded in producing electrical effects in the following manner,
+which differs from that employed by Mr. Faraday, and which appears to
+me to develop some new and interesting facts. A piece of copper wire,
+about thirty feet long and covered with elastic varnish, was closely
+coiled around the middle of the soft iron armature of the galvanic
+magnet described in Vol. XIX of the _American Journal of Science_,
+and which, when excited, will readily sustain between six hundred and
+seven hundred pounds. The wire was wound upon itself so as to occupy
+only about one inch of the length of the armature which is seven inches
+in all. The armature, thus furnished with the wire, was placed in its
+proper position across the ends of the galvanic magnet, and there
+fastened so that no motion could take place. The two protecting ends
+of the helix were dipped into two cups of mercury, and there connected
+with a distant galvanometer by means of two copper wires, each about
+forty feet long. This arrangement being completed, I stationed myself
+near the galvanometer and directed an assistant at a given word to
+immerse suddenly, in a vessel of dilute acid, the galvanic battery
+attached to the magnet. At the instant of immersion, the north end
+of the needle was deflected 30° to the west, indicating a current
+of electricity from the helix surrounding the armature. The effect,
+however, appeared only as a single impulse, for the needle, after a few
+oscillations, resumed its former undisturbed position in the magnetic
+meridian, although the galvanic action of the battery, and consequently
+the magnetic power, was still continued. I was, however, much surprised
+to see the needle suddenly deflected from a state of rest to about 20°
+to the east, or in a contrary direction when the battery was withdrawn
+from the acid, and again deflected to the west when it was re-immersed.
+This operation was repeated many times in succession, and uniformly
+with the same result, the armature the whole time remaining immovably
+attached to the poles of the magnet, no motion being required to
+produce the effect, as it appeared to take place only in consequence of
+the instantaneous development of the magnetic action in one, and the
+sudden cessation of it in the other.
+
+This experiment illustrates most strikingly the reciprocal action of
+the two principles of electricity and magnetism, if indeed it does not
+establish their absolute identity. In the first place, magnetism is
+developed in the soft iron of the galvanic magnet by the action of the
+currents of electricity from the battery, and secondly, the armature,
+rendered magnetic by contact with the poles of the magnet, induces in
+its turn currents of electricity in the helix which surrounds it; we
+have thus, as it were, electricity converted into magnetism and this
+magnetism again into electricity.
+
+Another fact was observed which is somewhat interesting, inasmuch as it
+serves in some respects to generalize the phenomena. After the battery
+had been withdrawn from the acid, and the needle of the galvanometer
+suffered to come to a state of rest after the resulting deflection, it
+was again deflected in the same direction by partially detaching the
+armature from the poles of the magnet to which it continued to adhere
+from the action of the residual magnetism, and in this way, a series of
+deflections, all in the same direction, was produced by merely slipping
+off the armature by degrees until the contact was entirely broken. The
+following extract from the register of the experiments exhibits the
+relative deflections observed in one experiment of this kind.
+
+At the instant of immersion of the battery, deflection 40° west.
+
+At the instant of emersion of the battery, deflection 18° east.
+
+Armature partially detached, deflection 7° east.
+
+Armature entirely detached, deflection 12° west.
+
+The effect was reversed in another experiment, in which the needle was
+turned to the west in a series of deflections by dipping the battery
+but a small distance into the acid at first and afterwards immersing it
+by degrees.
+
+From the foregoing facts it appears that a current of electricity is
+produced, for an instant, in a helix of copper wire surrounding a piece
+of soft iron whenever magnetism is induced in the iron; and a current
+in an opposite direction when the magnetic action ceases; also that an
+instantaneous current in one or the other direction accompanies every
+change in the magnetic intensity of the iron.
+
+Since reading the account before given of Mr. Faraday’s method of
+producing electrical currents I have attempted to combine the effects
+of motion and induction; for this purpose a rod of soft iron ten inches
+long and one inch and a quarter in diameter, was attached to a common
+turning lathe, and surrounded with four helices of copper wire in such
+a manner that it could be suddenly and powerfully magnetized, while
+in rapid motion, by transmitting galvanic currents through three of
+the helices; the fourth being connected with the distant galvanometer
+was intended to transmit the current of induced electricity; all the
+helices were stationary while the iron rod revolved on its axis within
+them. From a number of trials in succession, first with the rod in one
+direction, then in the opposite, and next in a state of rest, it was
+concluded that no perceptible effect was produced on the intensity of
+the magneto-electric current by a rotary motion of the iron combined
+with its sudden magnetization.
+
+The same apparatus, however, furnished the means of measuring
+separately the relative power of motion and induction in producing
+electrical currents. The iron rod was first magnetized by currents
+through the helices attached to the battery and while in this state
+one of its ends was quickly introduced into the helix connected with
+the galvanometer; the deflection of the needle in this case was
+seven degrees. The end of the rod was next introduced into the same
+helix while in its natural state and then suddenly magnetized; the
+deflection in this instance amounted to thirty degrees, showing a great
+superiority in the method of induction.
+
+The next attempt was to increase the magneto-electric effect while the
+magnetic power remained the same, and in this I was more successful.
+Two iron rods six inches long and one inch in diameter were each
+surrounded by two helices and then placed perpendicularly on the
+face of the armature, and between it and the poles of the magnet,
+so that each rod formed, as it were, a prolongation of the poles,
+and to these the armature adhered when the magnet was excited. With
+this arrangement, a current from one helix produced a deflection of
+thirty-seven degrees; from two helices both on the same rod, fifty-two
+degrees, and from three fifty-nine degrees; but when four helices
+were used, the deflection was only fifty-five degrees, and when to
+these were added the helix of smaller wire around the armature, the
+deflection was no more than thirty degrees. This result may perhaps
+have been somewhat affected by the want of proper insulation in the
+several spires of the helices; it, however, establishes the fact that
+an increase in the electric current is produced by using at least
+two or three helices instead of one. The same principle was applied
+to another arrangement which seems to afford the maximum of electric
+development from a given magnetic power; in place of the two pieces of
+iron and the armature used in the last experiments, the poles of the
+magnet were connected by a single rod of iron, bent into the form of a
+horse-shoe, and its extremities filed perfectly flat so as to come in
+perfect contact with the faces of the poles; around the middle of the
+arch of this horse-shoe, two strands of copper wire were tightly coiled
+one over the other. A current from one of these helices deflected the
+needle one hundred degrees, and when both were used the needle was
+deflected with such force as to make a complete circuit. But the most
+surprising effect was produced when, instead of passing the current
+through the long wires to the galvanometer, the opposite ends of the
+helices were held nearly in contact with each other, and the magnet
+suddenly excited; in this case a small but vivid spark was seen to pass
+between the ends of the wires, and this effect was repeated as often as
+the state of intensity of the magnet was changed.
+
+In these experiments the connection of the battery with the wires from
+the magnet was not formed by soldering, but by two cups of mercury,
+which permitted the galvanic action on the magnet to be instantaneously
+suspended and the polarity to be changed and rechanged without removing
+the battery from the acid; a succession of vivid sparks was obtained
+by rapidly interrupting and forming the communication by means of one
+of these cups; but the greatest effect was produced when the magnetism
+was entirely destroyed and instantaneously reproduced by a change of
+polarity.
+
+It appears from the May number of the _Annals of Philosophy_ that
+I have been anticipated in this experiment of drawing sparks from the
+magnet by Mr. James D. Forbes of Edinburgh, who obtained a spark on the
+30th of March; my experiment being made during the last two weeks of
+June. A simple notification of his result is given, without any account
+of the experiment, which is reserved for a communication to the Royal
+Society of Edinburgh; my result is therefore entirely independent of
+his and was undoubtedly obtained by a different process.
+
+
+ ELECTRICAL SELF-INDUCTION IN A LONG HELICAL WIRE
+
+I have made several other experiments in relation to the same subject,
+but which more important duties will not permit me to verify in time
+for this paper. I may, however, mention one fact which I have not seen
+noticed in any work, and which appears to me to belong to the same
+class of phenomena as those before described; it is this: when a small
+battery is moderately excited by diluted acid, and its poles, which
+should be terminated by cups of mercury, are connected by a copper
+wire not more than a foot in length, no spark is perceived when the
+connection is either formed or broken; but if a wire thirty or forty
+feet long be used instead of the short wire, though no spark will be
+perceptible when the connection is made, yet when it is broken by
+drawing one end of the wire from its cup of mercury, a vivid spark
+is produced. If the action of the battery be very intense, a spark
+will be given by the short wire; in this case it is only necessary to
+wait a few minutes until the action partially subsides, and until no
+more sparks are given from the short wire; if the long wire be now
+substituted a spark will again be obtained. The effect appears somewhat
+increased by coiling the wire into a helix; it seems also to depend in
+some measure on the length and thickness of the wire. I can account for
+these phenomena only by supposing the long wire to become charged with
+electricity, which by its reaction on itself projects a spark when the
+connection is broken.
+
+
+FOOTNOTES:
+
+[Footnote 30: Silliman’s _American Journal of Science_, July,
+1832, Vol. XXII, pp. 403-408; _Scientific Writings_, Vol. I., p.
+73.]
+
+
+
+
+ XXVIII
+
+ SIR CHARLES LYELL
+
+ 1797-1875
+
+
+ _Sir Charles Lyell, the son of a Scottish botanist of literary
+ tastes, was born at Kinnordy, Scotland, November 14, 1797. He went to
+ Oxford University, from which he graduated in 1819. He was admitted to
+ the bar in 1825. In 1827 he abandoned law for geology, and published
+ his “Principles of Geology” in 1830-1833. Lyell’s thesis was that
+ all the past changes of the earth were explainable by forces now
+ operative--an idea which underlies modern geology. He published his
+ “Antiquity of Man” in 1863, providing proofs of man’s long existence
+ on earth and thus contributing to the establishment of the Darwinian
+ theory. He died February 22, 1875._
+
+
+ UNIFORMITY IN THE SERIES OF PAST CHANGES IN THE ANIMATE AND INANIMATE
+ WORLD[31]
+
+
+_Origin of the doctrine of alternate periods of repose and
+disorder._--It has been truly observed that when we arrange the
+fossiliferous formations in chronological order, they constitute
+a broken and defective series of monuments; we pass without any
+intermediate gradations from systems of strata which are horizontal, to
+other systems which are highly inclined--from rocks of peculiar mineral
+composition to others which have a character wholly distinct--from one
+assemblage of organic remains to another, in which frequently nearly
+all the species, and a large part of the genera, are different. These
+violations of continuity are so common as to constitute in most regions
+the rule rather than the exception, and they have been considered by
+many geologists as conclusive in favour of sudden revolutions in the
+inanimate and animate world. We have already seen that according to
+the speculations of some writers, there have been in the past history
+of the planet alternate periods of tranquility and convulsion, the
+former enduring for ages, and resembling the state of things now
+experienced by man; the other brief, transient, and paroxysmal, giving
+rise to new mountains, seas, and valleys, annihilating one set of
+organic beings and ushering in the creation of another.
+
+It will be the object of the present chapter to demonstrate that
+these theoretical views are not borne out by a fair interpretation of
+geological monuments. It is true that in the solid framework of the
+globe we have a chronological chain of natural records, many links of
+which are wanting: but a careful consideration of all the phenomena
+leads to the opinion that the series was originally defective--that
+it has been rendered still more so by time--that a great part of what
+remains is inaccessible to man, and even of that fraction which is
+accessible nine-tenths or more are to this day unexplored.
+
+The readiest way, perhaps, of persuading the reader that we may
+dispense with great and sudden revolutions in the geological order
+of events is by showing him how a regular and uninterrupted series
+of changes in the animate and inanimate world must give rise to such
+breaks in the sequence, and such unconformability of stratified rocks,
+as are usually thought to imply convulsions and catastrophes. It is
+scarcely necessary to state that the order of events thus assumed to
+occur, for the sake of illustration, should be in harmony with all
+the conclusions legitimately drawn by geologists from the structure
+of the earth, and must be equally in accordance with the changes
+observed by man to be now going on in the living as well as in the
+inorganic creation. It may be necessary in the present state of science
+to supply some part of the assumed course of nature hypothetically;
+but if so, this must be done without any violation of probability,
+and always consistently with the analogy of what is known both of the
+past and present economy of our system. Although the discussion of so
+comprehensive a subject must carry the beginner far beyond his depth,
+it will also, it is hoped, stimulate his curiosity, and prepare him to
+read some elementary treatises on geology with advantage, and teach
+him the bearing on that science of the changes now in progress on the
+earth. At the same time it may enable him the better to understand the
+intimate connection between the Second and Third Books of this work,
+one of which is occupied with the changes of the inorganic, the latter
+with those of the organic creation.
+
+In pursuance, then, of the plan above proposed, I will consider
+in this chapter, first, the laws which regulate the denudation of
+strata and the deposition of sediment; secondly, those which govern
+the fluctuation in the animate world; and thirdly, the mode in which
+subterranean movements affect the earth’s crust.
+
+
+_Uniformity of change considered, first, in reference to denudation
+and sedimentary deposition._--First, in regard to the laws governing
+the deposition of new strata. If we survey the surface of the globe,
+we immediately perceive that it is divisible into areas of deposition
+and non-deposition; or, in other words, at any given time there are
+spaces which are the recipients, others which are not the recipients,
+of sedimentary matter. No new strata, for example, are thrown down on
+dry land, which remains the same from year to year; whereas, in many
+parts of the bottom of seas and lakes, mud, sand, and pebbles are
+annually spread out by rivers and currents. There are also great masses
+of limestone growing in some seas, chiefly composed of corals and
+shells, or, as in the depths of the Atlantic, of chalky mud made up of
+foraminifera and diatomaceæ.
+
+As to the dry land, so far from being the receptacle of fresh
+accessions of matter, it is exposed almost everywhere to waste away.
+Forests may be as dense and lofty as those of Brazil, and may swarm
+with quadrupeds, birds, and insects, yet at the end of thousands of
+years one layer of black mould a few inches thick may be the sole
+representative of those myriads of trees, leaves, flowers, and fruits,
+those innumerable bones and skeletons of birds, quadrupeds, and
+reptiles, which tenanted the fertile region. Should this land be at
+length submerged, the waves of the sea may wash away in a few hours
+the scanty covering of mould, and it may merely import a darker shade
+of colour to the next stratum of marl, sand, or other matter newly
+thrown down. So also at the bottom of the ocean where no sediment is
+accumulating, seaweed, zoophytes, fish, and even shells, may multiply
+for ages and decompose, leaving no vestige of their form or substance
+behind. Their decay, in water, although more slow, is as certain and
+eventually as complete as in the open air. Nor can they be perpetuated
+for indefinite periods in a fossil state, unless imbedded in some
+matrix which is impervious to water, or which at least does not allow
+a free percolation of that fluid, impregnated as it usually is, with
+a slight quantity of carbonic or other acid. Such a free percolation
+may be prevented either by the mineral nature of the matrix itself,
+or by the superposition of an impermeable stratum; but if unimpeded,
+the fossil shell or bone will be dissolved and removed, particle after
+particle, and thus entirely effaced, unless petrification or the
+substitution of some mineral for the organic matter happen to take
+place.
+
+That there has been land as well as sea at all former geological
+periods, we know from the fact that fossil trees and terrestrial plants
+are imbedded in rocks of every age, except those which are so ancient
+as to be very imperfectly known to us. Occasionally lacrustine and
+fluviatile shells, or the bones of amphibious or land reptiles, point
+to the same conclusion. The existence of dry land at all periods of the
+past implies, as before mentioned, the partial deposition of sediment,
+or its limitation to certain areas; and the next point to which I shall
+call the reader’s attention is the shifting of these areas from one
+region to another.
+
+First, then, variations in the site of sedimentary deposition are
+brought about independently of subterranean movements. There is always
+a slight change from year to year, or from century to century. The
+sediment of the Rhone, for example, thrown in the Lake of Geneva, is
+now conveyed to a spot a mile and a half distant from that where it
+accumulated in the tenth century, and six miles from the point where
+the delta began originally to form. We may look forward to the period
+when this lake will be filled up, and then the distribution of the
+transported matter will be suddenly altered, for the mud and sand
+brought down from the Alps will thenceforth, instead of being deposited
+near Geneva, be carried nearly 200 miles southwards, where the Rhone
+enters the Mediterranean.
+
+In the deltas of large rivers, such as those of the Ganges and Indus,
+the mud is first carried down for many centuries through one arm,
+and on this being stopped up it is discharged by another, and may
+then enter the sea at a point 50 or 100 miles distant from its first
+receptacle. The direction of marine currents is also liable to be
+changed by various accidents, as by the heaping up of new sandbanks, or
+the wearing away of cliffs and promontories.
+
+But, secondly, all these causes of fluctuation in the sedimentary areas
+are entirely subordinate to those great upward or downward movements
+of lands, which will be presently spoken of, as prevailing over large
+tracts of the globe. By such elevation or subsidence certain spaces
+are gradually submerged, or made gradually to emerge: in the one case
+sedimentary deposition may be suddenly renewed after having been
+suspended for one or more geological periods, in the other as suddenly
+made to cease after having continued for ages.
+
+If deposition be renewed after a long interval, the new strata will
+usually differ greatly from the sedimentary rocks previously formed
+in the same place, and especially if the older rocks have suffered
+derangement, which implies a change in the physical geography of the
+district since the previous conveyance of sediment to the same spot. It
+may happen, however, that, even where the two groups, the superior and
+the inferior, are horizontal and conformable to each other, they may
+still differ entirely in mineral character, because, since the origin
+of the older formation, the geography of some distant country has
+been altered. In that country rocks before concealed may have become
+exposed by denudation; volcanoes may have burst out and covered the
+surface with scoriæ and lava; or new lakes, intercepting the sediment
+previously conveyed from the upper country, may have been formed by
+subsidence; and other fluctuations may have occurred, by which the
+materials brought down from thence by rivers to the sea have acquired a
+distinct mineral character.
+
+It is well known that the stream of the Mississippi is charged with
+sediment of a different colour from that of the Arkansas and Red
+Rivers, which are tinged with red mud, derived from rocks of porphyry
+and red gypseous clays in “the far west.” The waters of the Uruguay,
+says Darwin, draining a granitic country, are clear and black, those
+of the Parana, red. The mud with which the Indus is loaded, says
+Burnes, is of a clayey hue, that of the Chenab, on the other hand, is
+reddish, that of the Sutlej is more pale. The same causes which make
+these several rivers, sometimes situated at no great distance the one
+from the other, to differ greatly in the character of their sediment,
+will make the waters draining the same country at different epochs,
+especially before and after great revolutions in physical geography,
+to be entirely dissimilar. It is scarcely necessary to add that marine
+currents will be affected in an analogous manner in consequence of the
+formation of new shoals, the emergence of new islands, the subsidence
+of others, the gradual waste of neighbouring coasts, the growth of
+new deltas, the increase of coral reefs, volcanic eruptions, and other
+changes.
+
+
+_Uniformity of change considered, secondly, in reference to the
+living creation._--Secondly, in regard to the vicissitudes of
+the living creation, all are agreed that the successive groups of
+sedimentary strata found in the earth’s new crust are not only
+dissimilar in mineral composition for reasons above alluded to, but are
+likewise distinguishable from each other by their organic remains. The
+general inference drawn from the study and comparison of the various
+groups, arranged in chronological order, is this: that at successive
+periods distinct tribes of animals and plants have inhabited the land
+and waters, and that the organic types of the newer formations are more
+analogous to species now existing than those of more ancient rocks. If
+we then turn to the present state of the animate creation, and inquire
+whether it has now become fixed and stationary, we discover that, on
+the contrary, it is in a state of continual flux--that there are many
+causes in action which tend to the extinction of species, and which are
+conclusive against the doctrine of their unlimited durability.
+
+There are also causes which give rise to new varieties and races in
+plants and animals, and new forms are continually supplanting others
+which had endured for ages. But natural history has been successfully
+cultivated for so short a period, that a few examples only of local,
+and perhaps but one or two of absolute, extirpation of species can as
+yet be proved, and these only where the interference of man has been
+conspicuous. It will nevertheless appear evident, from the facts and
+arguments detailed in the chapters which treat of the geographical
+distribution of species in the next volume, that man is not the only
+exterminating agent; and that, independently of his intervention, the
+annihilation of species is promoted by the multiplication and gradual
+diffusion of every animal or plant. It will also appear that every
+alteration in the physical geography and climate of the globe cannot
+fail to have the same tendency. If we proceed still farther, and
+inquire whether new species are substituted from time to time for those
+which die out, we find that the successive introduction of new forms
+appears to have been a constant part of the economy of the terrestrial
+system, and if we have no direct proof of the fact it is because the
+changes take place so slowly as not to come within the period of exact
+scientific observation. To enable the reader to appreciate the gradual
+manner in which a passage may have taken place from an extinct fauna to
+that now living, I shall say a few words on the fossils of successive
+Tertiary periods. When we trace the series of formations from the more
+ancient to the more modern, it is in these Tertiary deposits that we
+first meet with assemblages of organic remains having a near analogy to
+the fauna of certain parts of the globe in our own time. In the Eocene,
+or oldest subdivisions, some few of the testacea belong to existing
+species, although almost all of them, and apparently all the associated
+vertebrata, are now extinct. These Eocene strata are succeeded by a
+great number of more modern deposits, which depart gradually in the
+character of their fossils from the Eocene type, and approach more and
+more to that of the living creation. In the present state of science,
+it is chiefly by the aid of shells, that we are enabled to arrive at
+these results, for of all classes the testacea are the most generally
+diffused in a fossil state, and may be called the medals principally
+employed by nature in recording the chronology of past events. In the
+Upper Miocene rocks (No. 5 of the table, p. 135) we begin to find a
+considerable number, although still a minority, of recent species,
+intermixed with some fossils common to the preceding, or Eocene,
+epoch. We then arrive at the Pliocene strata, in which species now
+contemporary with man begin to preponderate, and in the newest of
+which nine-tenths of the fossils agree with species still inhabiting
+the neighbouring sea. It is in the Post-Tertiary strata, where all
+the shells agree with species now living, that we have discovered the
+first or earliest known remains of man associated with the bones of
+quadrupeds, some of which are of extinct species.
+
+In thus passing from the older to the newer members of the Tertiary
+system, we meet with many chasms, but none which separate entirely,
+by a broad line of demarcation, one state of the organic world from
+another. There are no signs of an abrupt termination of one fauna and
+flora, and the starting into life of new and wholly distinct forms.
+Although we are far from being able to demonstrate geologically an
+insensible transition from the Eocene to the Miocene, or even from the
+latter to the recent fauna, yet the more we enlarge and perfect our
+general survey, the more nearly do we approximate to such a continuous
+series, and the more gradually are we conducted from times when many of
+the genera and nearly all the species were extinct, to those in which
+scarcely a single species flourished, which we do not know to exist
+at present. Dr. A. Philippi, indeed, after an elaborate comparison
+of the fossil tertiary shells of Sicily with those now living in the
+Mediterranean, announced, as the result of his examination, that there
+are strata in that island which attest a very gradual passage from a
+period when only thirteen in a hundred of the shells were like the
+species now living in the sea, to an era when the recent species had
+attained a proportion of ninety-five in a hundred. There is, therefore,
+evidence, he says, in Sicily of this revolution in the animate world
+having been effected “without the intervention of any convulsion
+or abrupt changes, certain species having from time died out, and
+others having been introduced, until at length the existing fauna was
+elaborated.”
+
+In no part of Europe is the absence of all signs of man or his works,
+in strata of comparatively modern date, more striking than in Sicily.
+In the central parts of that island we observe a lofty table-land and
+hills, sometimes rising to the height of 3,000 feet, capped with a
+limestone, in which from 70 to 85 per cent of the fossil testacea are
+specifically identical with those now inhabiting the Mediterranean.
+These calcareous and other argillaceous strata of the same age are
+intersected by deep valleys which appear to have been gradually formed
+by denudation, but have not varied materially in width or depth since
+Sicily was first colonized by the Greeks. The limestone, moreover,
+which is of so late a date in geological chronology, was quarried for
+building those ancient temples of Girgenti and Syracuse, of which the
+ruins carry us back to a remote era in human history. If we are lost
+in conjectures when speculating on the ages required to lift up these
+formations to the height of several thousand feet above the sea, and
+to excavate the valleys, how much more remote must be the era when the
+same rocks were gradually formed beneath the waters!
+
+The intense cold of the Glacial period was spoken of in the tenth
+chapter. Although we have not yet succeeded in detecting proofs of the
+origin of man antecedently to that epoch, we have yet found evidence
+that most of the testacea, and not a few of the quadrupeds, which
+preceded, were of the same species as those which followed the extreme
+cold. To whatever local disturbances this cold may have given rise in
+the distribution of species, it seems to have done little in effecting
+their annihilation. We may conclude, therefore, from a survey of
+the tertiary and modern strata, which constitute a more complete and
+unbroken series than rocks of older date, that the extinction and
+creation of species have been, and are, the result of a slow and
+gradual change in the organic world.
+
+
+_Uniformity of change considered, thirdly, in reference to
+subterranean movements._--Thirdly, to pass on to the last of the
+three topics before proposed for discussion, the reader will find, in
+the account given in the Second Book, Vol. II., of the earthquakes
+recorded in history, that certain countries have, from time immemorial,
+been rudely shaken again and again; while others, comprising by
+far the largest part of the globe, have remained to all appearance
+motionless. In the regions of convulsion rocks have been rent asunder,
+the surface has been forced up into ridges, chasms have opened, or the
+ground throughout large spaces has been permanently lifted up above
+or let down below its former level. In the regions of tranquillity
+some areas have remained at rest, but others have been ascertained,
+by a comparison of measurements made at different periods, to have
+arisen by an insensible motion, as in Sweden, or to have subsided very
+slowly, as in Greenland. That these same movements, whether ascending
+or descending, have continued for ages in the same direction has been
+established by historical or geological evidence. Thus we find on the
+opposite coasts of Sweden that brackish water deposits, like those
+now forming in the Baltic, occur on the eastern side, and upraised
+strata filled with purely marine shells, now proper to the ocean, on
+the western coast. Both of these have been lifted up to an elevation
+of several hundred feet above high-water mark. The rise within the
+historical period has not amounted to many yards, but the greater
+extent of antecedent upheaval is proved by the occurrence in inland
+spots, several hundred feet high, of deposits filled with fossil shells
+of species now living either in the ocean or the Baltic.
+
+It must in general be more difficult to detect proofs of slow and
+gradual subsidence than of elevation, but the theory which accounts for
+the form of circular coral reefs and lagoon islands, and which will
+be explained in the concluding chapter of this work, will satisfy the
+reader that there are spaces on the globe, several thousand miles in
+circumference, throughout which the downward movement has predominated
+for ages, and yet the land has never, in a single instance, gone down
+suddenly for several hundred feet at once. Yet geology demonstrates
+that the persistency of subterranean movements in one direction has
+not been perpetual throughout all past time. There have been great
+oscillations of level, by which a surface of dry land has been
+submerged to a depth of several thousand feet, and then at a period
+long subsequent raised again and made to emerge. Nor have the regions
+now motionless been always at rest; and some of those which are at
+present the theatres of reiterated earthquakes have formerly enjoyed
+a long continuance of tranquillity. But, although disturbances have
+ceased after having long prevailed, or have recommenced after a
+suspension of ages, there has been no universal disruption of the
+earth’s crust or desolation of the surface since times the most
+remote. The non-occurrence of such a general convulsion is proved by
+the perfect horizontality now retained by some of the most ancient
+fossiliferous strata throughout wide areas.
+
+That the subterranean forces have visited different parts of the globe
+at successive periods is inferred chiefly from the unconformability of
+strata belonging to groups of different ages. Thus, for example, on the
+borders of Wales and Shropshire, we find the slaty beds of the ancient
+Silurian system inclined and vertical, while the beds of the overlying
+carboniferous shale and sandstone are horizontal. All are agreed that
+in such a case the older set of strata had suffered great disturbance
+before the deposition of the newer or carboniferous beds, and that
+these last have never since been violently fractured, nor have ever
+been bent into folds, whether by sudden or continuous lateral pressure.
+On the other hand, the more ancient or Silurian group suffered only a
+local derangement, and neither in Wales nor elsewhere are all the rocks
+of that age found to be curved or vertical.
+
+In various parts of Europe, for example, and particularly near Lake
+Wener in the south of Sweden, and in many parts of Russia, the
+Silurian strata maintain the most perfect horizontality; and a similar
+observation may be made respecting limestones and shales of like
+antiquity in the great lake district of Canada and the United States.
+These older rocks are still as flat and horizontal as when first
+formed; yet, since their origin, not only have most of the actual
+mountain-chains been uplifted, but some of the very rocks of which
+those mountains are composed have been formed, some of them by igneous
+and others by aqueous action.
+
+It would be easy to multiply instances of similar unconformability
+in formations of other ages; but a few more will suffice. The
+carboniferous rocks before alluded to as horizontal on the borders
+of Wales are vertical in the Mendip hills in Somersetshire, where
+the overlying beds of the New Red Sandstone are horizontal. Again,
+in the Wolds of Yorkshire the last-mentioned sandstone supports on
+its curved and inclined beds the horizontal Chalk. The Chalk again is
+vertical on the flanks of the Pyrenees, and the tertiary strata repose
+unconformably upon it.
+
+As almost every country supplies illustrations of the same phenomena,
+they who advocate the doctrine of alternate periods of disorder and
+repose may appeal to the facts above described, as proving that every
+district has been by turns convulsed by earthquakes and then respited
+for ages from convulsions. But so it might with equal truth be affirmed
+that every part of Europe has been visited alternately by winter and
+summer, although it has always been winter and always summer in some
+part of the planet, and neither of these seasons has ever reigned
+simultaneously over the entire globe. They have been always shifting
+from place to place; but the vicissitudes which recur thus annually
+in a single spot are never allowed to interfere with the invariable
+uniformity of seasons throughout the whole planet.
+
+So, in regard to subterranean movements, the theory of the perpetual
+uniformity of the force which they exert on the earth’s crust is quite
+consistent with the admission of their alternate development and
+suspension for long and indefinite periods within limited geographical
+areas.
+
+If, for reasons before stated, we assume a continual extinction of
+species and appearance of others on the globe, it will then follow
+that the fossils of strata formed at two distant periods on the same
+spot will differ even more certainly than the mineral composition of
+those strata. For rocks of the same kind have sometimes been reproduced
+in the same district after a long interval of time; whereas all the
+evidence derived from fossil remains is in favour of the opinion that
+species which have once died out have never been reproduced. The
+submergence, then, of land must be often attended by the commencement
+of a new class of sedimentary deposits, characterized by a new set of
+fossil animals and plants, while the reconversion of the bed of the sea
+into land may arrest at once and for an indefinite time the formation
+of geological monuments. Should the land again sink, strata will again
+be formed; but one or many entire revolutions in animal or vegetable
+life may have been completed in the interval.
+
+As to the want of completeness in the fossiliferous series, which
+may be said to be almost universal, we have only to reflect on what
+has been already said of the laws governing sedimentary deposition,
+and those which give rise to fluctuations in the animate world, to
+be convinced that a very rare combination of circumstances can alone
+give rise to such a superposition and preservation of strata as will
+bear testimony to the gradual passage from one state of organic life
+to another. To produce such strata nothing less will be requisite
+than the fortunate coincidence of the following conditions: first, a
+never-failing supply of sediment in the same region throughout a period
+of vast duration; secondly, the fitness of the deposit in every part
+for the permanent preservation of imbedded fossils; and, thirdly, a
+gradual subsidence to prevent the sea or lake from being filled up and
+converted into land.
+
+It will appear in the chapter on coral reefs, that, in certain parts
+of the Pacific and Indian Oceans, most of these conditions, if not
+all, are complied with, and the constant growth of coral, keeping
+pace with the sinking of the bottom of the sea, seems to have gone on
+so slowly, for such indefinite periods, that the signs of a gradual
+change in organic life might probably be detected in that quarter of
+the globe if we could explore its submarine geology. Instead of the
+growth of coralline limestone, let us suppose, in some other place,
+the continuous deposition of fluviatile mud and sand, such as the
+Ganges and Brahmapootra have poured for thousands of years into the
+Bay of Bengal. Part of this bay, although of considerable depth,
+might at length be filled up before an appreciable amount of change
+was effected in the fish, mollusca, and other inhabitants of the sea
+and neighbouring land. But if the bottom be lowered by sinking at
+the same rate that it is raised by fluviatile mud, the bay can never
+be turned into dry land. In that case one new layer of matter may be
+superimposed upon another for a thickness of many thousand feet, and
+the fossils of the inferior beds may differ greatly from those entombed
+in the uppermost, yet every intermediate gradation may be indicated in
+the passage from an older to a newer assemblage of species. Granting,
+however, that such an unbroken sequence of monuments may thus be
+elaborated in certain parts of the sea, and that the strata happen
+to be all of them well adapted to preserve the included fossils from
+decomposition, how many accidents must still concur before these
+submarine formations will be laid open to our investigation! The whole
+deposit must first be raised several thousand feet, in order to bring
+into view the very foundation; and during the process of exposure the
+superior beds must not be entirely swept away by denudation.
+
+In the first place, the chances are nearly as three to one against
+the mere emergence of the mass above the waters, because nearly
+three-fourths of the globe are covered by the ocean. But if it be
+upheaved and made to constitute part of the dry land, it must also,
+before it can be available for our instruction, become part of that
+area already surveyed by geologists. In this small fraction of land
+already explored, and still very imperfectly known, we are required to
+find a set of strata deposited under peculiar conditions, and which,
+having been originally of limited extent, would have been probably much
+lessened by subsequent denudation.
+
+Yet it is precisely because we do not encounter at every step the
+evidence of such gradations from one state of the organic world to
+another, that so many geologists have embraced the doctrine of great
+and sudden revolutions in the history of the animate world. Not content
+with simply availing themselves, for the convenience of classification,
+of those gaps and chasms which here and there interrupt the continuity
+of the chronological series, as at present known, they deduce, from the
+frequency of these breaks in the chain of records, an irregular mode of
+succession in the events themselves, both in the organic and inorganic
+world. But, besides that some links of the chain which once existed are
+now entirely lost and others concealed from view, we have good reason
+to suspect that it was never complete originally. It may undoubtedly be
+said that strata have been always forming somewhere, and therefore at
+every moment of past time Nature has added a page to her archives; but,
+in reference to this subject, it should be remembered that we can never
+hope to compile a consecutive history by gathering together monuments
+which were originally detached and scattered over the globe. For, as
+the species of organic beings contemporaneously inhabiting remote
+regions are distinct, the fossils of the first of several periods which
+may be preserved in any one country, as in America for example, will
+have no connection with those of a second period found in India, and
+will therefore no more enable us to trace the signs of a gradual change
+in the living creation, than a fragment of Chinese history will fill up
+a blank in the political annals of Europe.
+
+The absence of any deposits of importance containing recent shells in
+Chili, or anywhere on the western shore of South America, naturally led
+Mr. Darwin to the conclusion that “where the bed of the sea is either
+stationary or rising, circumstances are far less favourable than where
+the level is sinking to the accumulation of conchiferous strata of
+sufficient thickness and extension to resist the average vast amount
+of denudation.” In like manner the beds of superficial sand, clay, and
+gravel, with recent shells, on the coasts of Norway and Sweden, where
+the land has risen in Post-tertiary times, are so thin and scanty as to
+incline us to admit a similar proposition. We may in fact assume that
+in all cases where the bottom of the sea has been undergoing continuous
+elevation, the total thickness of sedimentary matter accumulating
+at depths suited to the habitation of most of the species of shells
+can never be great, nor can the deposits be thickly covered with
+superincumbent matter, so as to be consolidated by pressure. When they
+are upheaved, therefore, the waves on the beach will bear down and
+disperse the loose materials; whereas, if the bed of the sea subsides
+slowly, a mass of strata containing abundance of such species as live
+at moderate depths, may be formed and may increase in thickness to any
+amount. It may also extend horizontally over a broad area, as the water
+gradually encroaches on the subsiding land.
+
+Hence it will follow that great violations of continuity in the
+chronological series of fossiliferous rocks will always exist, and the
+imperfection of the record, though lessened, will never be removed by
+future discoveries. For not only will no deposits originate on the
+dry land, but those formed in the sea near land, which is undergoing
+constant upheaval, will usually be too slight in thickness to endure
+for ages.
+
+In proportion as we become acquainted with larger geographical
+areas, many of the gaps, by which a chronological table is rendered
+defective, will be removed. We were enabled by aid of the labours of
+Prof. Sedgwick and Sir Roderick Murchison, to intercalate, in 1838,
+the marine strata of the Devonian period, with their fossil shells,
+corals, and fish, between the Silurian and Carboniferous rocks.
+Previously the marine fauna of these last-mentioned formations wanted
+the connecting links which now render the passage from the one to
+the other much less abrupt. In like manner the Upper Miocene has no
+representative in England, but in France, Germany, and Switzerland it
+constitutes a most instructive link between the living creation and the
+middle of the great Tertiary period. Still we must expect, for reasons
+before stated, that chasms will forever continue to occur, in some
+parts of our sedimentary series.
+
+
+_Concluding remarks on the consistency of the theory of gradual
+change with the existence of great breaks in the series._--To
+return to the general argument pursued in this chapter, it is assumed,
+for reasons above explained, that a slow change of species is in
+simultaneous operation everywhere throughout the habitable surface
+of sea and land; whereas the fossilization of plants and animals is
+confined to those areas where new strata are produced. These areas,
+as we have seen, are always shifting their position, so that the
+fossilizing process, by means of which the commemoration of the
+particular state of the organic world, at any given time, is effected,
+may be said to move about, visiting and revisiting different tracts in
+succession.
+
+To make still more clear the supposed working of this machinery, I
+shall compare it to a somewhat analogous case that might be imagined
+to occur in the history of human affairs. Let the mortality of the
+population of a large country represent the successive extinction
+of species, and the births of new individuals the introduction of
+new species. While these fluctuations are gradually taking place
+everywhere, suppose commissioners to be appointed to visit each
+province of the country in succession, taking an exact account of the
+number, names and individual peculiarities of all the inhabitants,
+and leaving in each district a register containing a record of this
+information. If, after the completion of one census, another is
+immediately made on the same plan, and then another, there will at
+last be a series of statistical documents in each province. When
+those belonging to any one province are arranged in chronological
+order, the contents of such as stand next to each other will differ
+according to the length of the intervals of time between the taking of
+each census. If, for example, there are sixty provinces, and all the
+registers are made in a single year and renewed annually, the number
+of births and deaths will be so small, in proportion to the whole
+of the inhabitants, during the interval between the compiling of two
+consecutive documents, that the individuals described in such documents
+will be nearly identical; whereas, if the survey of each of the sixty
+provinces occupies all the commissioners for a whole year, so that they
+are unable to revisit the same place until the expiration of sixty
+years, there will then be an almost entire discordance between the
+persons enumerated in two consecutive registers in the same province.
+There are, undoubtedly, other causes, besides the mere quantity of
+time, which may augment or diminish the amount of discrepancy. Thus,
+at some periods, a pestilential disease may have lessened the average
+duration of human life; or a variety of circumstances may have caused
+the births to be unusually numerous, and the population to multiply;
+or a province may be suddenly colonized by persons migrating from
+surrounding districts.
+
+These exceptions may be compared to the accelerated rate of
+fluctuations in the fauna and flora of a particular region, in which
+the climate and physical geography may be undergoing an extraordinary
+degree of alteration.
+
+But I must remind the reader that the case above proposed has no
+pretensions to be regarded as an exact parallel to the geological
+phenomena which I desire to illustrate; for the commissioners are
+supposed to visit the different provinces in rotation; whereas the
+commemorating processes by which organic remains become fossilized,
+although they are always shifting from one area to the other, are yet
+very irregular in their movements. They may abandon and revisit many
+spaces again and again, before they once approach another district;
+and, besides this source of irregularity, it may often happen that,
+while the depositing process is suspended, denudation may take place,
+which may be compared to the occasional destruction by fire or other
+causes of some of the statistical documents before mentioned. It is
+evident that where such accidents occur the want of continuity in the
+series may become indefinitely great, and that the monuments which
+follow next in succession will by no means be equidistant from each
+other in point of time.
+
+If this train of reasoning be admitted, the occasional distinctness of
+the fossil remains, in formations immediately in contact, would be a
+necessary consequence of the existing laws of sedimentary deposition
+and subterranean movement, accompanied by a constant dying-out and
+renovation of species.
+
+As all the conclusions above insisted on are directly opposed to
+opinions still popular, I shall add another comparison, in the hope of
+preventing any possible misapprehension of the argument. Suppose we
+had discovered two buried cities at the foot of Vesuvius, immediately
+superimposed upon each other, with a great mass of tuff and lava
+intervening, just as Portici and Resina, if now covered with ashes,
+would overlie Herculaneum. An antiquary might possibly be entitled to
+infer, from the inscriptions on public edifices, that the inhabitants
+of the inferior and older city were Greeks, and those of the modern
+town Italians. But he would reason very hastily if he also concluded
+from these data, that there had been a sudden change from the Greek
+to the Italian language in Campania. But if he afterwards found three
+buried cities, one above the other, the intermediate one being Roman,
+while, as in the former example, the lowest was Greek and the uppermost
+Italian, he would then perceive the fallacy of his former opinion and
+would begin to suspect that the catastrophes, by which the cities
+were inhumed, might have no relation whatever to the fluctuations in
+the language of the inhabitants; and that, as the Roman tongue had
+evidently intervened between the Greek and Italian, so many other
+dialects may have been spoken in succession, and the passage from the
+Greek to the Italian may have been very gradual, some terms growing
+obsolete, while others were introduced from time to time.
+
+If this antiquary could have shown that the volcanic paroxysms of
+Vesuvius were so governed as that cities should be buried one above the
+other, just as often as any variation occurred in the language of the
+inhabitants, then, indeed, the abrupt passage from a Greek to a Roman,
+and from a Roman to an Italian city, would afford proof of fluctuations
+no less sudden in the language of the people.
+
+So, in Geology, if we could assume that it is part of the plan of
+Nature to preserve, in every region of the globe, an unbroken series
+of monuments to commemorate the vicissitudes of the organic creation,
+we might infer the sudden extirpation of species, and the simultaneous
+introduction of others, as often as two formations in contact are found
+to include dissimilar organic fossils. But we must shut our eyes to the
+whole economy of the existing causes, aqueous, igneous, and organic,
+if we fail to perceive that such is not the plan of Nature.
+
+I shall now conclude the discussion of a question with which we have
+been occupied since the beginning of the fifth chapter--namely, whether
+there has been any interruption, from the remotest periods, of one
+uniform and continuous system of change in the animate and inanimate
+world. We were induced to enter into that inquiry by reflecting how
+much the progress of opinion in Geology had been influenced by the
+assumption that the analogy was slight in kind, and still more slight
+in degree, between the causes which produced the former revolutions
+of the globe, and those now in every-day operation. It appeared clear
+that the earlier geologists had not only a scanty acquaintance with
+existing changes, but were singularly unconscious of the amount of
+their ignorance. With the presumption naturally inspired by this
+unconsciousness, they had no hesitation in deciding at once that time
+could never enable the existing powers of nature to work out changes
+of great magnitude, still less such important revolutions as those
+which are brought to light by Geology. They therefore felt themselves
+at liberty to indulge their imaginations in guessing at what might be,
+rather than inquiring what is; in other words, they employed themselves
+in conjecturing what might have been the course of Nature at a remote
+period, rather than in the investigation of what was the course of
+Nature in their own times.
+
+It appeared to them far more philosophical to speculate on the
+possibilities of the past, than patiently to explore the realities of
+the present; and having invented theories under the influences of such
+maxims, they were consistently unwilling to test their validity by the
+criterion of their accordance with the ordinary operations of Nature.
+On the contrary, the claims of each new hypothesis to credibility
+appeared enhanced by the great contrast, in kind or intensity, of the
+causes referred to and those now in operation.
+
+Never was there a dogma more calculated to foster indolence, and
+to blunt the keen edge of curiosity, than this assumption of the
+discordance between the ancient and existing causes of change. It
+produced a state of mind unfavourable in the highest degree to the
+candid reception of the evidence of those minute but incessant
+alterations which every part of the earth’s surface is undergoing,
+and by which the condition of its living inhabitants is continually
+made to vary. The student, instead of being encouraged with the
+hope of interpreting the enigmas presented to him in the earth’s
+structure--instead of being prompted to undertake laborious inquiries
+into the natural history of the organic world, and the complicated
+effects of the igneous and aqueous causes now in operation--was taught
+to despond from the first. Geology, it was affirmed, could never rise
+to the rank of an exact science; the greater number of phenomena
+must forever remain inexplicable, or only be partially elucidated by
+ingenious conjectures. Even the mystery which invested the subject was
+said to constitute one of its principal charms, affording, as it did,
+full scope to the fancy to indulge in a boundless field of speculation.
+
+The course directly opposed to this method of philosophizing consists
+in an earnest and patient inquiry, how far geological appearances are
+reconcilable with the effect of changes now in progress, or which
+may be in progress in regions inaccessible to us, but of which the
+reality is attested by volcanoes and subterranean movements. It also
+endeavours to estimate the aggregate result of ordinary operations
+multiplied by time, and cherishes a sanguine hope that the resources
+to be derived from observation and experiment, or from the study of
+Nature such as she now is, are very far from being exhausted. For this
+reason all theories are rejected which involve the assumption of sudden
+and violent catastrophes and revolutions of the whole earth, and its
+inhabitants--theories which are restrained by no reference to existing
+analogies, and in which a desire is manifested to cut, rather than
+patiently to untie, the Gordian knot.
+
+We have now, at least, the advantage of knowing, from experience, that
+an opposite method has always put geologists on the road that leads
+to truth--suggesting views which, although imperfect at first, have
+been found capable of improvement, until at last adopted by universal
+consent; while the method of speculating on a former distinct state of
+things and causes has led invariably to a multitude of contradictory
+systems, which have been overthrown one after the other--have been
+found incapable of modification--and which have often required to be
+precisely reversed.
+
+The remainder of this work will be devoted to an investigation of the
+changes now going on in the crust of the earth and its inhabitants.
+The importance which the student will attach to such researches will
+mainly depend on the degree of confidence which he feels in the
+principles above expounded. If he firmly believes in the resemblance
+or identity of the ancient and present system of terrestrial changes,
+he will regard every fact collected respecting the causes in diurnal
+action as affording him a key to the interpretation of some mystery in
+the past. Events which have occurred at the most distant periods in
+the animate and inanimate world will be acknowledged to throw light
+on each other, and the deficiency of our information respecting some
+of the most obscure parts of the present creation will be removed.
+For as, by studying the external configuration of the existing land
+and its inhabitants, we may restore in imagination the appearance of
+the ancient continents which have passed away, so may we obtain from
+the deposits of ancient seas and lakes an insight into the nature
+of the subaqueous processes now in operation, and of many forms of
+organic life which, though now existing, are veiled from sight. Rocks,
+also, produced by subterranean fire in former ages, at great depths
+in the bowels of the earth, present us, when upraised by gradual
+movements, and exposed to the light of heaven, with an image of those
+changes which the deep-seated volcano may now occasion in the nether
+regions. Thus, although we are mere sojourners on the surface of the
+planet, chained to a mere point in space, enduring but for a moment of
+time, the human mind is not only enabled to number worlds beyond the
+unassisted ken of mortal eye, but to trace the events of indefinite
+ages before the creation of our race, and is not even withheld from
+penetrating into the dark secrets of the ocean, or the interior of
+the solid globe; free, like the spirit which the poet described as
+animating the universe,
+
+ --_ire per omnes_
+ _Terrasque, tractusque maris, coelumque profundum_.
+
+
+FOOTNOTES:
+
+[Footnote 31: From the _Principles of Geology_, Bk. I, Ch. XIII.]
+
+
+
+
+ XXIX
+
+ CHARLES DARWIN
+
+ 1809-1882
+
+
+ _Charles Robert Darwin, the grandson of Erasmus Darwin, was born at
+ Shrewsbury, England, February 12, 1809. He studied at both Edinburgh
+ and Cambridge, and graduated from the latter in 1831. From 1831 to 1836
+ he served as a naturalist on the “Beagle,” which made a trip around the
+ world in the interests of science. The voyage served as a post-graduate
+ course for Darwin, who then first adopted his evolutionary ideas and
+ developed as an original investigator. Reading Malthus, in 1838, on
+ the problem of population and the food supply, he integrated Malthus’
+ ideas into his own views of biology. In 1844 be began his “Origin of
+ Species,” which he completed in 1859. In 1858 he received a paper
+ from Alfred Russell Wallace, then in the Malay Archipelago, which
+ proposed the same theory of natural selection. Darwin believed that
+ when organisms increased much faster than the means of subsistence,
+ the ratios varied, and in the conditions produced by these natural
+ causes only those organisms survived which were best fitted to their
+ environment. He applied his concept to human evolution in his “Descent
+ of Man,” published in 1871. He died April 19, 1882, and was buried in
+ Westminster Abbey._
+
+
+ NATURAL SELECTION[32]
+
+How will the struggle for existence, briefly discussed in the last
+chapter, act in regard to variation? Can the principle of selection,
+which we have seen is so potent in the hands of man, apply under
+nature? I think we shall see that it can act most efficiently. Let
+the endless number of slight variations and individual differences
+occurring in our domestic productions, and, in a lesser degree, in
+those under nature, be borne in mind; as well as the strength of the
+hereditary tendency. Under domestication, it may be truly said that the
+whole organization becomes in some degree plastic. But the variability,
+which we almost universally meet with in our domestic production, is
+not directly produced, as Hooker and Asa Gray have well remarked, by
+man; he can neither originate varieties, nor prevent their occurrence;
+he can only preserve and accumulate such as do occur. Unintentionally
+he exposes organic beings to new and changing conditions of life, and
+variability ensues; but similar changes of conditions might and do
+occur under nature. Let it also be borne in mind how infinitely complex
+and close-fitting are the mutual relations of all organic beings to
+each other and to their physical conditions of life; and consequently
+what infinitely varied diversities of structure might be of use to
+each being under changing conditions of life. Can it then be thought
+improbable, seeing that variations useful to man have undoubtedly
+occurred, that other variations useful in some way to each being in the
+great and complex battle of life, should occur in the course of many
+successive generations? If such do occur, can we doubt (remembering
+that many more individuals are born than can possibly survive) that
+individuals having any advantage, however slight, over others, would
+have the best chance of surviving and of procreating their kind? On the
+other hand, we may feel sure that any variation in the least degree
+injurious would be rigidly destroyed. This preservation of favourable
+individual differences and variations, and the destruction of those
+which are injurious, I have called Natural Selection, or the Survival
+of the Fittest. Variations neither useful nor injurious would not be
+affected by natural selection, and would be left either a fluctuating
+element, as perhaps we see in certain polymorphic species, or would
+ultimately become fixed, owing to the nature of the organism and the
+nature of the conditions.
+
+Several writers have misapprehended or objected to the term Natural
+Selection. Some have even imagined that natural selection induces
+variability, whereas it implies only the preservation of such
+variations as arise and are beneficial to the being under its
+conditions of life. No one objects to agriculturists speaking of the
+potent effects of man’s selection; and in this case the individual
+differences given by nature, which man for some object selects, must of
+necessity first occur. Others have objected that the term selection
+implies conscious choice in the animals which become modified; and it
+has even been urged that, as plants have no volition, natural selection
+is not applicable to them! In the literal sense of the word, no doubt,
+natural selection is a false term; but who ever objected to chemists
+speaking of the elective affinities of the various elements?--and yet
+an acid cannot strictly be said to elect the base with which it in
+preference combines. It has been said that I speak of natural selection
+as an active power or Deity; but who objects to an author speaking
+of the attraction of gravity as ruling the movements of the planets?
+Everyone knows what is meant and is implied by such metaphorical
+expressions; and they are almost necessary for brevity. So again it is
+difficult to avoid personifying the word Nature; but I mean by Nature,
+only the aggregate action and product of many natural laws, and by laws
+the sequence of events as ascertained by us. With a little familiarity
+such superficial objections will be forgotten.
+
+We shall best understand the probable course of natural selection by
+taking the case of a country undergoing some slight physical change,
+for instance, of climate. The proportional numbers of its inhabitants
+will almost immediately undergo a change, and some species will
+probably become extinct. We may conclude, from what we have seen of the
+intimate and complex manner in which the inhabitants of each country
+are bound together, that any change in the numerical proportions of
+the inhabitants, independently of the change of climate itself, would
+seriously affect the others. If the country were open on its borders,
+new forms would certainly immigrate, and this would likewise seriously
+disturb the relations of some of the former inhabitants. Let it be
+remembered how powerful the influence of a single introduced tree
+or mammal has been shown to be. But in the case of an island, or of
+a country partly surrounded by barriers, into which new and better
+adapted forms could not freely enter, we should then have places in the
+economy of nature which would assuredly be better filled up, if some
+of the original inhabitants were in some manner modified; for, had the
+area been open to immigration, these same places would have been seized
+on by intruders. In such cases, slight modifications, which in any
+way favoured the individuals of any species, by better adapting them
+to their altered conditions, would tend to be preserved; and natural
+selection would have free scope for the work of improvement.
+
+We have good reason to believe, as shown in the first chapter, that
+changes in the conditions of life give a tendency to increased
+variability; and in the foregoing cases the conditions have changed,
+and this would manifestly be favourable to natural selection, by
+affording a better chance of the occurrence of profitable variations.
+Unless such occur, natural selection can do nothing. Under the term
+of “variations,” it must never be forgotten that mere individual
+differences are included. As man can produce a great result with
+his domestic animals and plants by adding up in any given direction
+individual differences, so could natural selection, but far more easily
+from having incomparably longer time for action. Nor do I believe
+that any great physical change, as of climate, or any unusual degree
+of isolation to check immigration, is necessary in order that new and
+unoccupied places should be left for natural selection to fill up by
+improving some of the varying inhabitants. For as all the inhabitants
+of each country are struggling together with nicely balanced forces,
+extremely slight modifications in the structure or habits of one
+species would often give it an advantage over others; and still further
+modifications of the same kind would often still further increase the
+advantage, as long as the species continued under the same conditions
+of life and profited by similar means of subsistence and defense. No
+country can be named in which all the native inhabitants are now so
+perfectly adapted to each other and to the physical conditions under
+which they live, that none of them could be still better adapted or
+improved; for in all countries, the natives have been so far conquered
+by naturalized productions, that they have allowed some foreigners to
+take firm possession of the land. And as foreigners have thus in every
+country beaten some of the natives, we may safely conclude that the
+natives might have been modified with advantage, so as to have better
+resisted the intruders.
+
+As man can produce, and certainly has produced, a great result by his
+methodical and unconscious means of selection, what may not natural
+selection effect? Man can act only on external and visible characters:
+Nature, if I may be allowed to personify the natural preservation or
+survival of the fittest, cares nothing for appearances, except in so
+far as they are useful to any being. She can act on every internal
+organ, on every shade of constitutional difference, on the whole
+machinery of life. Man selects only for his own good: Nature only for
+that of the being which she tends. Every selected character is fully
+exercised by her, as is implied by the fact of their selection. Man
+keeps the natives of many climates in the same country; he seldom
+exercises each selected character in some peculiar and fitting manner;
+he feeds a long and a short-beaked pigeon on the same food; he does
+not exercise a long-backed or long-legged quadruped in any peculiar
+manner; he exposes sheep with long and short wool to the same climate.
+He does not allow the most vigorous males to struggle for the females.
+He does not rigidly destroy all inferior animals, but protects during
+each varying season, as far as lies in his power, all his productions.
+He often begins his selection by some half-monstrous form; or at
+least by some modification prominent enough to catch the eye or to
+be plainly useful to him. Under nature, the slightest differences of
+structure or constitution may well turn the nicely-balanced scale in
+the struggle for life, and so be preserved. How fleeting are the wishes
+and efforts of man! how short his time! and consequently how poor will
+be his results, compared with those accumulated by Nature during whole
+geological periods! Can we wonder, then, that Nature’s productions
+should be far “truer” in character than man’s productions; that they
+should be infinitely better adapted to the most complex conditions of
+life, and should plainly bear the stamp of far higher workmanship?
+
+It may metaphorically be said that natural selection is daily and
+hourly scrutinizing, throughout the world, the slightest variations;
+rejecting those that are bad, preserving and adding up all that are
+good; silently and sensibly working, whenever and wherever opportunity
+offers, at the improvement of each organic being in relation to its
+organic and inorganic conditions of life. We see nothing of these slow
+changes in progress, until the hand of time has marked the lapse of
+ages, and then so imperfect is our view into long-past geological ages,
+that we see only that the forms of life are now different from what
+they formerly were.
+
+In order that any great amount of modification should be effected in
+a species, a variety when once formed must again, perhaps after a
+long interval of time, vary or present individual differences of the
+same favourable nature as before; and these must be again preserved,
+and so onwards step by step. Seeing that individual differences of
+the same kind perpetually recur, this can hardly be considered as an
+unwarrantable assumption. But whether it is true, we can judge only by
+seeing how far the hypothesis accords with and explains the general
+phenomena of nature. On the other hand, the ordinary belief that the
+amount of possible variation is a strictly limited quantity is likewise
+a simple assumption.
+
+Although natural selection can act only through and for the good of
+each being, yet characters and structures, which we are apt to consider
+as of very trifling importance, may thus be acted on. When we see
+leaf-eating insects green, and bark-feeders mottled gray; the Alpine
+ptarmigan white in winter, the red-grouse the colour of heather,
+we must believe that these tints are of service to these birds and
+insects in preserving them from danger. Grouse, if not destroyed at
+some period of their lives, would increase in countless numbers;
+they are known to suffer largely from birds of prey; and hawks are
+guided by eyesight to their prey--so much so, that on parts of the
+Continent persons are warned not to keep white pigeons, as being the
+most liable to destruction. Hence natural selection might be effective
+in giving the proper colour to each kind of grouse, and in keeping
+that colour, when once acquired, true and constant. Nor ought we to
+think that the occasional destruction of an animal of any particular
+colour would produce little effect: we should remember how essential
+it is in a flock of white sheep to destroy a lamb with the faintest
+trace of black. We have seen how the colour of the hogs, which feed on
+the “paint-root” in Virginia, determines whether they shall live or
+die. In plants, the down on the fruit and the colour of the flesh are
+considered by botanists as characters of the most trifling importance:
+yet we hear from an excellent horticulturist, Downing, that in the
+United States smooth-skinned fruits suffer far more from a beetle, a
+Curculio, than those with down; that purple plums suffer far more from
+a certain disease than yellow plums; whereas another disease attacks
+yellow-fleshed peaches far more than those with other coloured flesh.
+If, with all the aids of arts, these slight differences make a great
+difference in cultivating the several varieties, assuredly, in a state
+of nature, where the trees would have to struggle with other trees and
+with a host of enemies, such differences would effectually settle which
+variety, whether a smooth or downy, a yellow or purple-fleshed fruit,
+should succeed.
+
+In looking at many small points of difference between species, which,
+as far as our ignorance permits us to judge, seem quite unimportant,
+we must not forget that climate, food, etc., have no doubt produced
+some direct effect. It is also necessary to bear in mind that, owing to
+the law of correlation, when one part varies, and the variations are
+accumulated through natural selection, other modifications, often of
+the most unexpected nature, will ensue.
+
+As we see that those variations which, under domestication, appear at
+any particular period of life, tend to reappear in the offspring at the
+same period; for instance, in the shape, size, and flavour of the seeds
+of the many varieties of our culinary and agricultural plants; in the
+caterpillar and cocoon stages of the varieties of the silkworm; in the
+eggs of poultry, and in the colour of the down of their chickens; in
+the horns of our sheep and cattle when nearly adult; so in a state of
+nature natural selection will be enabled to act on and modify organic
+beings at any age, by the accumulation of variations profitable at that
+age, and by their inheritance at a corresponding age. If it profit
+a plant to have its seeds more and more widely disseminated by the
+wind, I can see no greater difficulty in this being effected through
+natural selection, than in the cotton planter increasing and improving
+by selection the down in the pods on his cotton trees. Natural
+selection may modify and adapt the larva of an insect to a score of
+contingencies, wholly different from those which concern the mature
+insect; and these modifications may effect, through correlation, the
+structure of the adult. So, conversely, modifications in the adult may
+affect the structure of the larva; but in all cases natural selection
+will insure that they shall not be injurious: for if they were so, the
+species would become extinct.
+
+Natural selection will modify the structure of the young in relation
+to the parent, and of the parent in relation to the young. In social
+animals it will adapt the structure of each individual for the benefit
+of the whole community; if the community profits by the selected
+change. What natural selection cannot do, is to modify the structure
+of one species; without giving it any advantage, for the good of
+another species; and though statements to this effect may be found
+in works of natural history, I cannot find one case which will bear
+investigation. A structure used only once in an animal’s life, if
+of high importance to it, might be modified to any extent by natural
+selection; for instance, the great jaws possessed by certain insects,
+used exclusively for opening the cocoon--or the hard tip of the beak of
+unhatched birds, used for breaking the egg. It has been asserted, that
+of the best short-beaked tumbler-pigeons a greater number perish in the
+egg than are able to get out of it; so that fanciers assist in the act
+of hatching. Now if nature had to make the beak of a full-grown pigeon
+very short for the bird’s own advantage, the process of modification
+would be very slow, and there would be simultaneously the most rigorous
+selection of all the young birds within the egg, which had the most
+powerful and hardest beaks, for all with weak beaks would inevitably
+perish; or, more delicate and more easily broken shells might be
+selected, the thickness of the shell being known to vary like every
+other structure.
+
+It may be well here to remark that with all beings there must be much
+fortuitous destruction, which can have little or no influence on
+the course of natural selection. For instance a vast number of eggs
+or seeds are annually devoured, and these could be modified through
+natural selection only if they varied in some manner which protected
+them from their enemies. Yet many of these eggs or seeds would perhaps,
+if not destroyed, have yielded individuals better adapted to their
+conditions of life than any of those which happened to survive. So
+again a vast number of mature animals and plants, whether or not they
+be the best adapted to their conditions, must be annually destroyed by
+accidental causes, which would not be in the least degree mitigated
+by certain changes of structure or constitution which would in other
+ways be beneficial to the species. But let the destruction of the
+adults be ever so heavy, if the number which can exist in any district
+be not wholly kept down by such causes,--or again let the destruction
+of eggs or seeds be so great that only a hundredth or a thousandth
+part are developed,--yet of those which do survive, the best adapted
+individuals, supposing that there is any variability in a favourable
+direction, will tend to propagate their kind in larger numbers than the
+less well adapted. If the numbers be wholly kept down by the causes
+just indicated, as will often have been the case, natural selection
+will be powerless in certain beneficial directions; but this is no
+valid objection to its efficiency at other times and in other ways; for
+we are far from having any reason to suppose that many species ever
+undergo modification and improvement at the same time in the same area.
+
+
+ SEXUAL SELECTION
+
+Inasmuch as peculiarities often appear under domestication in one sex
+and become hereditarily attached to that sex, so no doubt it will be
+under nature. Thus it is rendered possible for the two sexes to be
+modified through natural selection in relation to different habits
+of life, as is sometimes the case; or for one sex to be modified in
+relation to the other sex, as commonly occurs. This leads me to say
+a few words on what I have called Sexual Selection. This form of
+selection depends, not on a struggle for existence in relation to other
+organic beings or to external conditions, but on a struggle between the
+individuals of one sex, generally the males, for the possession of the
+other sex. The result is not death to the unsuccessful competitor, but
+few or no offspring. Sexual selection is, therefore, less rigorous than
+natural selection. Generally, the most vigorous males, those which are
+best fitted for their places in nature, will leave most progeny. But in
+many cases, victory depends not so much on general vigour, as on having
+special weapons, confined to the male sex. A hornless stag or spurless
+cock would have a poor chance of leaving numerous offspring. Sexual
+selection, by always allowing the victor to breed, might surely give
+indomitable courage, length to the spur, and strength to the wing to
+strike in the spurred leg, in nearly the same manner as does the brutal
+cockfighter by the careful selection of his best cocks. How low in the
+scale of nature the law of battle descends, I know not; male alligators
+have been described as fighting, bellowing, and whirling round, like
+Indians in a war-dance, for the possession of the females; male
+salmons have been observed fighting all day long; male stag-beetles
+sometimes bear wounds from the huge mandibles of other males; the
+males of certain hymenopterous insects have been frequently seen by
+that inimitable observer, M. Fabre, fighting for a particular female
+who sits by, an apparently unconcerned beholder of the struggle, and
+then retires with the conquerer. The war is, perhaps, severest between
+the males of polygamous animals, and these seem oftenest provided with
+special weapons. The males of carnivorous animals are already well
+armed; though to them and to others, special means of defence may be
+given through means of sexual selection, as the mane of the lion, and
+the hooked jaw to the male salmon; for the shield may be as important
+for victory as the sword or spear.
+
+Amongst birds, the contest is often of a more peaceful character.
+All those who have attended to the subject believe that there is the
+severest rivalry between the males of many species to attract, by
+singing, the females. The rock-thrush of Guiana, birds of paradise,
+and some others, congregate; and successive males display with the
+most elaborate care, and show off in the best manner, their gorgeous
+plumage; they likewise perform strange antics before the females,
+which, standing by as spectators, at last choose the most attractive
+partner. Those who have closely attended to birds in confinement well
+know that they often take individual preferences and dislikes: thus
+Sir R. Heron has described how a pied peacock was eminently attractive
+to all his hen birds. I cannot here enter on the necessary details;
+but if man can in a short time give beauty and an elegant carriage to
+his bantams, according to his standard of beauty, I can see no good
+reason to doubt that female birds, by selecting, during thousands
+of generations, the most melodious or beautiful males, according
+to their standard of beauty, might produce a marked effect. Some
+well-known laws, with respect to the plumage of male and female birds,
+in comparison with the plumage of the young, can partly be explained
+through the action of sexual selection on variations occuring at
+different ages, and transmitted to the males alone or to both sexes at
+corresponding ages; but I have not space here to enter on this subject.
+
+Thus it is, as I believe, that when the males and females of any
+animal have the same general habits of life, but differ in structure,
+colour, or ornament, such differences have been mainly caused by sexual
+selection: that is, by individual males having had, in successive
+generations, some slight advantage over other males, in their weapons,
+means of defence, or charms, which they have transmitted to their
+male offspring alone. Yet, I would not wish to attribute all sexual
+differences to this agency: for we see in our domestic animals
+peculiarities arising and becoming attached to the male sex, which
+apparently have not been augmented through selection by man. The tuft
+of hair on the breast of the wild turkey-cock cannot be of any use, and
+it is doubtful whether it can be ornamental in the eyes of the female
+bird;--indeed, had the tuft appeared under domestication, it would have
+been called a monstrosity.
+
+
+ ON THE DEGREE TO WHICH ORGANISATION TENDS TO ADVANCE
+
+Natural Selection acts exclusively by the preservation and accumulation
+of variations, which are beneficial under the organic and inorganic
+conditions to which each nature is exposed at all periods of life. The
+ultimate result is that each creature tends to become more and more
+improved in relation to its conditions. This improvement inevitably
+leads to the gradual advancement of the organisation of the greater
+number of living beings throughout the world. But here we enter on
+a very intricate subject, for naturalists have not defined to each
+other’s satisfaction what is meant by an advance in organisation.
+Amongst the vertebrata the degree of intellect and an approach in
+structure to man clearly come into play. It might be thought that
+the amount of change which the various parts and organs pass through
+in their development from the embryo to maturity would suffice as a
+standard of comparison; but there are cases, as with certain parasitic
+crustaceans, in which several parts of the structure become less
+perfect, so that the mature animal cannot be called higher than its
+larva. Von Bar’s standard seems the most widely applicable and the
+best, namely, the amount of differentiation of the parts of the same
+organic being, in the adult state as I should be inclined to add, and
+their specialisation for different functions; or, as Milne Edwards
+would express it, the completeness of the division of physiological
+labour. But we shall see how obscure this subject is if we look,
+for instance, to fishes, amongst which some naturalists rank those
+as highest which, like the sharks, approach nearest to amphibians;
+whilst other naturalists rank the common bony or teleostean fishes as
+the highest, inasmuch as they are most strictly fishlike, and differ
+most from the other vertebrate classes. We see still more plainly
+the obscurity of the subject by turning to plants, amongst which the
+standard of intellect is of course quite excluded; and here some
+botanists rank those plants as highest which have every organ, as
+sepals, petals, stamens, and pistils, fully developed in each flower;
+whereas other botanists, probably with more truth, look at the plants
+which have their several organs much modified and reduced in number as
+the highest.
+
+If we take as the standard of high organisation, the amount of
+differentiation and specialisation of the several organs in each
+being when adult (and this will include the advancement of the brain
+for intellectual purposes), natural selection clearly leads towards
+this standard; for all physiologists admit that the specialisation
+of organs, inasmuch as in this state they perform their functions
+better, is an advantage to each being; and hence the accumulation
+of variations tending towards specialisation is within the scope of
+natural selection. On the other hand, we can see, bearing in mind that
+all organic beings are striving to increase at a high ratio and to
+seize on every unoccupied or less well occupied place in the economy of
+nature, that it is quite possible for natural selection gradually to
+fit a being to a situation in which several organs would be superfluous
+or useless: in such cases there would be retrogression in the scale of
+organisation. Whether organisation on the whole has actually advanced
+from the remotest geological periods to the present day will be more
+conveniently discussed in our chapter on Geological Succession.
+
+But it may be objected that if all organic beings thus tend to rise
+in the scale, how is it that throughout the world a multitude of the
+lowest forms still exist; and how is it that in each great class some
+forms are far more highly developed than others? Why have not the
+more highly developed forms everywhere supplanted and exterminated
+the lower? Lamarck, who believed in an innate and inevitable tendency
+towards perfection in all organic beings, seems to have felt this
+difficulty so strongly, that he was led to suppose that new and simple
+forms are continually being produced by spontaneous generation. Science
+has not as yet proved the truth of this belief, whatever the future
+may reveal. On our theory the continued existence of lowly organisms
+offers no difficulty; for natural selection, or the survival of the
+fittest, does not necessarily include progressive development--it only
+takes advantage of such variations as arise and are beneficial to each
+creature under its complex relations of life. And it may be asked
+what advantage, as far as we can see, would it be to an infusorian
+animalcule--to an intestinal worm--or even to an earth-worm, to be
+highly organised. If it were no advantage, these forms would be left,
+by natural selection, unimproved or but little improved, and might
+remain for indefinite ages in their present lowly condition. And
+geology tells us that some of the lowest forms, as the infusoria and
+rhizopods, have remained for an enormous period in nearly their present
+state. But to suppose that most of the many now existing low forms
+have not in the least advanced since the first dawn of life would be
+extremely rash; for every naturalist who has dissected some of the
+beings now ranked as very low in the scale, must have been struck with
+their really wondrous and beautiful organisation.
+
+Nearly the same remarks are applicable if we look to the different
+grades of organisation within the same great group; for instance,
+in the vertebrata, to the co-existence of mammals and fish--amongst
+mammalia, to the co-existence of man and the ornithorhynchus--amongst
+fishes, to the co-existence of the shark and the lancelet
+(_Amphioxus_), which latter fish in the extreme simplicity of
+its structure approaches the invertebrate classes. But mammals and
+fish hardly come into competition with each other; the advancement
+of the whole class of mammals, or of certain members in this class,
+to the highest grade would not lead to their taking the place of
+fishes. Physiologists believe that the brain must be bathed by warm
+blood to be highly active, and this requires aërial respiration;
+so that warm-blooded mammals when inhabiting the water lie under a
+disadvantage in having to come continually to the surface to breathe.
+With fishes, members of the shark family would not tend to supplant the
+lancelet; for the lancelet, as I hear from Fritz Müller, has as sole
+companion and competitor on the barren, sandy shore of South Brazil,
+an anomalous annelid. The three lowest orders of mammals, namely,
+marsupials, edentata, and rodents, co-exist in South America in the
+same region with numerous monkeys, and probably interfere little with
+each other. Although organisation, on the whole, may have advanced and
+be still advancing throughout the world, yet the scale will always
+present many degrees of perfection; for the high advancement of certain
+whole classes, or of certain members of each class, does not at all
+necessarily lead to the extinction of those groups with which they do
+not enter into close competition. In some cases, as we shall hereafter
+see, lowly organised forms appear to have been preserved to the present
+day, from inhabiting confined or peculiar stations, where they have
+been subjected to less severe competition, and where their scanty
+numbers have retarded the chance of favourable variations arising.
+
+Finally, I believe that many lowly organised forms now exist
+throughout the world, from various causes. In some cases variations or
+individual differences of a favourable nature may never have arisen
+for natural selection to act on and accumulate. In no case, probably,
+has time sufficed for the utmost possible amount of development.
+In some few cases there has been what we must call retrogression
+of organisation. But the main cause lies in the fact that under
+very simple conditions of life a high organisation would be of no
+service,--possibly would be of actual disservice, as being of a more
+delicate nature, and more liable to be put out of order and injured.
+
+Looking to the first dawn of life, when all organic beings, as we may
+believe, presented the simplest structure, how, it has been asked,
+could the first steps in the advancement of differentiation of parts
+have arisen? Mr. Herbert Spencer would probably answer that, as soon as
+simple unicellular organism came by growth or division to be compounded
+of several cells, or became attached to any supporting surface, his law
+“that homologous units of any order become differentiated in proportion
+as their relations to incident forces become different” would come into
+action. But as we have no facts to guide us, speculation on the subject
+is almost useless. It is, however, an error to suppose that there would
+be no struggle for existence, and, consequently, no natural selection,
+until many forms had been produced; variations in a single species
+inhabiting an isolated station might be beneficial, and thus the whole
+mass of individuals might be modified, or two distinct forms might
+arise. But, as I remarked towards the close of the Introduction, no
+one ought to feel surprise at much remaining as yet unexplained on the
+origin of species, if we make due allowance for our profound ignorance
+on the mutual relations of the inhabitants of the world at the present
+time, and still more so during past ages.
+
+
+ CONVERGENCE OF CHARACTER
+
+Mr. H. C. Watson thinks that I have overrated the importance of
+divergence of character (in which, however, he apparently believes),
+and that convergence, as it may be called, has likewise played a
+part. If two species, belonging to two distinct though allied genera,
+had both produced a large number of new and divergent forms, it is
+conceivable that these might approach each other so closely that they
+would have all to be classed under the same genus; and thus the
+descendants of two distinct genera would converge into one. But it
+would in most cases be extremely rash to attribute to convergence a
+close and general similarity of structure in the modified descendants
+of widely distinct forms. The shape of a crystal is determined solely
+by the molecular forces, and it is not surprising that dissimilar
+substances should sometimes assume the same form; but with organic
+beings we should bear in mind that the form of each depends on an
+infinitude of complex relations, namely, on the variations which have
+arisen, those being due to causes far too intricate to be followed
+out,--on the nature of the variations which have been preserved or
+selected, and this depends on the surrounding physical conditions, and
+in a still higher degree on the surrounding organisms with which each
+being has come into competition,--and lastly, on inheritance (in itself
+a fluctuating element) from innumerable progenitors, all of which have
+had their forms determined through equally complex relations. It is
+incredible that the descendants of two organisms, which had originally
+differed in a marked manner, should ever afterwards converge so closely
+as to lead to a near approach to identity throughout their whole
+organisation. If this had occurred, we should meet with the same form,
+independently of genetic connection, recurring in widely separated
+geological formations; and the balance of evidence is opposed to any
+such an admission.
+
+Mr. Watson has also objected that the continued action of natural
+selection, together with divergence of character, would tend to make
+an indefinite number of specific forms. As far as mere inorganic
+conditions are concerned, it seems probable that a sufficient number
+of species would soon become adapted to all considerable diversities
+of heat, moisture, &c.; but I fully admit that the mutual relations
+of organic beings are more important; and as the number of species in
+any country goes on increasing, the organic conditions of life must
+become more and more complex. Consequently there seems at first sight
+no limit to the amount of profitable diversification of structure, and
+therefore no limit to the number of species which might be produced.
+We do not know that even the most prolific area is fully stocked with
+specific forms: at the Cape of Good Hope and in Australia, which
+support such an astonishing number of species, many European plants
+have become naturalised. But geology shows us, that from an early part
+of the tertiary period the number of species of shells, and that from
+the middle part of this same period the number of mammals, has not
+greatly or at all increased. What then checks an indefinite increase
+in the number of species? The amount of life (I do not mean the number
+of specific forms) supported on an area must have a limit, depending
+so largely as it does on physical conditions; therefore, if an area
+be inhabited by very many species, each or nearly each species will
+be represented by few individuals; and such species will be liable to
+exterminate from accidental fluctuations in the nature of the seasons
+or in the number of their enemies. The process of extermination in
+such cases would be rapid, whereas the production of new species
+must always be slow. Imagine the extreme case of as many species as
+individuals in England, and the first severe winter or very dry summer
+would exterminate thousands on thousands of species. Rare species, and
+each species will become rare if the number of species in any country
+becomes indefinitely increased, will, on the principle often explained,
+present within a given period few favourable variations; consequently,
+the process of giving birth to new specific forms would thus be
+retarded. When any species becomes very rare, close interbreeding will
+help to exterminate it; authors have thought that this comes into play
+in accounting for the deterioration of the Aurochs in Lithuania, of Red
+Deer in Scotland, and of Bears in Norway, &c. Lastly, and this I am
+inclined to think is the most important element, a dominant species,
+which has already beaten many competitors in its own home, will tend to
+spread and supplant many others. Alph. de Candolle has shown that those
+species which spread widely, tend generally to spread very widely;
+consequently, they will tend to supplant and exterminate several
+species in several areas, and thus check the inordinate increase of
+specific forms throughout the world. Dr. Hooker has recently shown that
+in the S. E. corner of Australia, where, apparently, there are many
+invaders from different quarters of the globe, the endemic Australian
+species have been greatly reduced in number. How much weight to
+attribute to these several considerations I will not pretend to say;
+but conjointly they must limit in each country the tendency to an
+indefinite augmentation of specific forms.
+
+
+ SUMMARY OF CHAPTER
+
+If under changing conditions of life organic beings present individual
+differences in almost every part of their structure, and this cannot
+be disputed; if there be, owing to their geometrical rate of increase,
+a severe struggle for life at some age, season, or year, and this
+certainly cannot be disputed; then, considering the infinite complexity
+of the relations of all organic beings to each other and to their
+conditions of life, causing an infinite diversity in structure,
+constitution, and habits, to be advantageous to them, it would be a
+most extraordinary fact if no variations had ever occurred useful to
+each being’s own welfare, in the same manner as so many variations
+have occurred useful to man. But if variations useful to any organic
+being ever do occur, assuredly individuals thus characterised will
+have the best chance of being preserved in the struggle for life; and
+from the strong principle of inheritance, these will tend to produce
+offspring similarly characterised. This principle of preservation,
+or the survival of the fittest, I have called Natural Selection. It
+leads to the improvement of each creature in relation to its organic
+and inorganic conditions of life; and consequently, in most cases, to
+what must be regarded as an advance in organisation. Nevertheless,
+low and simple forms will long endure if well fitted for their simple
+conditions of life.
+
+Natural selection, on the principle of qualities being inherited at
+corresponding ages, can modify the egg, seed, or young, as easily as
+the adult. Amongst many animals, sexual selection will have given its
+aid to ordinary selection, by assuring to the most vigorous and best
+adapted males the greatest number of offspring. Sexual selection will
+also give characters useful to the males alone, in their struggles or
+rivalry with other males; and these characters will be transmitted to
+one sex or to both sexes, according to the form of inheritance which
+prevails.
+
+Whether natural selection has really thus acted in adapting the
+various forms of life to their several conditions and stations, must
+be judged by the general tenor and balance of evidence given in the
+following chapters. But we have already seen how it entails extinction;
+and how largely extinction has acted in the world’s history, geology
+plainly declares. Natural selection, also, leads to divergence of
+character; for the more organic beings diverge in structure, habits,
+and constitution, by so much the more can a large number be supported
+on the area,--of which we see proof by looking to the inhabitants of
+any small spot, and to the productions naturalised in foreign lands.
+Therefore, during the modification of the descendants of any one
+species, and during the incessant struggle of all species to increase
+in numbers, the more diversified the descendants become, the better
+will be their chance of success in the battle for life. Thus the small
+differences distinguishing varieties of the same species, steadily tend
+to increase, till they equal the greater differences between species of
+the same genus, or even of distinct genera.
+
+We have seen that it is the common, the widely diffused and widely
+ranging species, belonging to the larger genera within each class,
+which vary most; and these tend to transmit to their modified offspring
+that superiority which now makes them dominant in their own countries.
+Natural selection, as has just been remarked, leads to divergence of
+character and to much extinction of the less improved and intermediate
+forms of life. On these principles, the nature of the affinities, and
+the generally well-defined distinctions between the innumerable organic
+beings in each class throughout the world, may be explained. It is
+a truly wonderful fact--the wonder of which we are apt to overlook
+from familiarity--that all animals and all plants throughout all time
+and space should be related to each other in groups, subordinate to
+groups, in the manner which we everywhere behold--namely, varieties of
+the same species most closely related, species of the same genus less
+closely and unequally related, forming sections and sub-genera, species
+of distinct genera much less closely related, and genera related in
+different degrees, forming sub-families, families, orders, sub-classes
+and classes. The several subordinate groups in any class cannot be
+ranked in a single file, but seem clustered round points, and these
+round other points, and so on in almost endless cycles. If species had
+been independently created, no explanation would have been possible of
+this kind of classification; but it is explained through inheritance
+and the complex action of natural selection, entailing extinction and
+divergence of character....
+
+The affinities of all the beings of the same class have sometimes been
+represented by a great tree. I believe this simile largely speaks the
+truth. The green and budding twigs may represent existing species; and
+those produced during former years may represent the long succession
+of extinct species. At each period of growth all the growing twigs
+have tried to branch out on all sides, and to overtop and kill the
+surrounding twigs and branches, in the same manner as species and
+groups of species have at all times overmastered other species in the
+great battle for life. The limbs divided into great branches, and these
+into lesser and lesser branches, were themselves once, when the tree
+was young, budding twigs; and this connection of the former and present
+buds by ramifying branches may well represent the classification of
+all extinct and living species in groups subordinate to groups. Of the
+many twigs which flourished when the tree was a mere bush, only two or
+three, now grown into great branches, yet survive and bear the other
+branches; so with the species which lived during long-past geological
+periods, very few have left living and modified descendants. From
+the first growth of the tree, many a limb and branch has decayed and
+dropped off; and these fallen branches of various sizes may represent
+those whole orders, families, and genera which have now no living
+representatives, and which are known to us only in a fossil state. As
+we here and there see a thin straggling branch springing from a fork
+low down in a tree, and which by some chance has been favoured and is
+still alive on its summit, so we occasionally see an animal like the
+Ornithorhynchus or Lepidosiren, which in some small degree connects by
+its affinities two large branches of life, and which has apparently
+been saved from fatal competition by having inhabited a protected
+station. As buds give rise by growth to fresh buds, and these, if
+vigorous, branch out and overtop on all sides many a feebler branch, so
+by generation I believe it has been with the great Tree of Life, which
+fills with its dead and broken branches the crust of the earth, and
+covers the surface with its ever-branching and beautiful ramifications.
+
+
+FOOTNOTES:
+
+[Footnote 32: From the _Origin of Species_. Ch. IV.]
+
+
+
+
+ XXX
+
+ THEODOR SCHWANN
+
+ 1810-1882
+
+
+ _Theodor Schwann, the son of a Prussian printer, was born at Neuss,
+ Prussia, December 7, 1810. He first studied medicine, but was persuaded
+ to devote himself to science by Johannes Mueller, who appointed him
+ assistant in the anatomical museum. In 1838 he was called to the
+ Catholic University of Louvain, and later removed to Liège. One of
+ the first to suggest the chemical explanation of life, he discovered
+ the presence and function of pepsin as a ferment in digestion. In
+ 1839 he established his great theory that all life is composed of
+ inter-connected cellular units--a conception which revolutionized
+ biology. He died at Liège on January 11, 1882._
+
+
+ CELL THEORY[33]
+
+The various opinions entertained with respect to the fundamental powers
+of an organized body may be reduced to two, which are essentially
+different from one another. The first is, that every organism
+originates with an inherent power, which models it into conformity
+with a predominant idea, arranging the molecules in the relation
+necessary for accomplishing certain purposes held forth by this idea.
+Here, therefore, that which arranges and combines the molecules is a
+power acting with a definite purpose. A power of this kind would be
+essentially different from all the powers of inorganic nature, because
+action goes on in the latter quite blindly. A certain impression is
+followed of necessity by a certain change of quality and quantity,
+without regard to any purpose. In this view, however, the fundamental
+power of the organism (or the soul, in the sense employed by Stahl)
+would, inasmuch as it works with a definite individual purpose, be
+much more nearly allied to the immaterial principle, endued with
+consciousness which we must admit operates in man.
+
+The other view is, that the fundamental powers of organized bodies
+agree essentially with those of inorganic nature, that they work
+altogether blindly according to laws of necessity and irrespective
+of any purpose, that they are powers which are as much established
+with the existence of matter as the physical powers are. It might be
+assumed that the powers which form organized bodies do not appear at
+all in inorganic nature, because this or that particular combination
+of molecules, by which the powers are elicited, does not occur in
+inorganic nature, and yet they might not be essentially distinct
+from physical and chemical powers. It cannot, indeed, be denied that
+adaptation to a particular purpose, in some individuals even in a
+high degree, is characteristic of every organism; but, according to
+this view, the source of this adaptation does not depend upon each
+organism being developed by the operation of its own power in obedience
+to that purpose, but it originates as in inorganic nature, in the
+creation of the matter with its blind powers by a rational Being. We
+know, for instance, the powers which operate in our planetary system.
+They operate, like all physical powers, in accordance with blind laws
+of necessity, and yet is the planetary system remarkable for its
+adaptation to a purpose. The ground of this adaptation does not lie in
+the powers, but in Him, who has so constituted matter with its powers,
+that in blindly obeying its laws it produces a whole suited to fulfil
+an intended purpose. We may even assume that the planetary system
+has an individual adaptation to a purpose. Some external influence,
+such as a comet, may occasion disturbances of motion, without thereby
+bringing the whole into collision; derangements may occur on single
+planets, such as a high tide, &c., which are yet balanced entirely by
+physical laws. As respects their adaptation to a purpose, organized
+bodies differ from these in degree only; and by this second view we are
+just as little compelled to conclude that the fundamental powers of
+organization operate according to laws of adaptation to a purpose, as
+we are in inorganic nature.
+
+The first view of the fundamental powers of organized bodies may be
+called the teleological, the second the physical view. An example will
+show at once, how important for physiology is the solution of the
+question as to which is to be followed. If, for instance, we define
+inflammation and suppuration to be the effort of the organism to remove
+a foreign body that has been introduced into it; or fever to be the
+effort of the organism to eliminate diseased matter, and both as the
+result of the “autocracy of the organism,” then these explanations
+accord with the teleological view. For, since by these processes the
+obnoxious matter is actually removed, the process which effects them
+is one adapted to an end; and as the fundamental power of the organism
+operates in accordance with definite purposes, it may either set these
+processes in action primarily, or may also summon further powers of
+matter to its aid, always, however, remaining itself the “primum
+movens.” On the other hand, according to the physical view, this is
+just as little an explanation as it would be to say, that the motion of
+the earth around the sun is an effort of the fundamental power of the
+planetary system to produce a change of seasons on the planets, or to
+say, that ebb and flood are the reaction of the organism of the earth
+upon the moon.
+
+In physics, all those explanations which were suggested by a
+teleological view of nature, as “horror vacui,” and the like, have
+long been discarded. But in animated nature, adaptation--individual
+adaptation--to a purpose is so prominently marked, that it is
+difficult to reject all teleological explanations. Meanwhile it must
+be remembered that those explanations, which explain at once all
+and nothing, can be but the last resources, when no other view can
+possibly be adopted; and there is no such necessity for admitting the
+teleological view in the case of organized bodies. The adaptation of
+a purpose which is characteristic of organized bodies differs only in
+degree from what is apparent also in the inorganic part of nature;
+and the explanation that organized bodies are developed, like all the
+phenomena of inorganic nature, by the operation of blind laws framed
+with the matter, cannot be rejected as impossible. Reason certainly
+requires some ground for such adaptation, but for her it is sufficient
+to assume that matter with the powers inherent in it owes its existence
+to a rational Being. Once established and preserved in their integrity,
+these powers may, in accordance with their immutable laws of blind
+necessity, very well produce combinations, which manifest, even in
+a high degree, individual adaptation to a purpose. If, however,
+rational power interpose after creation merely to sustain, and not
+as an immediately active agent, it may, so far as natural science is
+concerned, be entirely excluded from the consideration of the creation.
+
+But the teleological view leads to further difficulties in the
+explanation, and especially with respect to generation. If we assume
+each organism to be formed by a power which acts according to a certain
+predominant idea, a portion of this power may certainly reside in the
+ovum during generation; but then we must ascribe to this subdivision
+of the original power, at the separation of the ovum from the body of
+the mother, the capability of producing an organism similar to that
+which the power, of which it is but a portion, produced: that is, we
+must assume that this power is infinitely divisible, and yet that each
+part may perform the same actions as the whole power. If, on the other
+hand, the power of organized bodies reside, like the physical powers,
+in matter as such, and be set free only by a certain combination of the
+molecules, as, for instance, electricity is set free by the combination
+of a zinc and copper plate, then also by the conjunction of molecules
+to form an ovum the power may be set free, by which the ovum is capable
+of appropriating to itself fresh molecules, and these newly-conjoined
+molecules again by this very mode of combination acquire the same
+power to assimilate fresh molecules. The first development of the
+many forms of organized bodies--the progressive formation of organic
+nature indicated by geology--is also much more difficult to understand
+according to the teleological than the physical view.
+
+Another objection to the teleological view may be drawn from the
+foregoing investigation. The molecules, as we have seen, are not
+immediately combined in various ways, as the purpose of the organism
+requires, but the formation of the elementary parts of organic
+bodies is regulated by laws which are essentially the same for all
+elementary parts. One can see no reason why this should be the case,
+if each organism be endued with a special power to frame the parts
+according to the purpose which they have to fulfil: it might much
+rather be expected that the formative principle, although identical
+for organs physiologically the same, would yet in different tissues
+be correspondingly varied. This resemblance of the elementary parts
+has, in the instance of plants, already led to the conjecture that
+the cells are really the organisms, and that the whole plant is an
+aggregrate of these organisms arranged according to certain laws.
+But since the elementary parts of animals bear exactly similar
+relations, the individuality of an entire animal would thus be lost;
+and yet precisely upon the individuality of the whole animal does the
+assumption rest, that it possesses a single fundamental power operating
+in accordance with a definite idea.
+
+Meanwhile, we cannot altogether lay aside teleological views if all
+phenomena are not clearly explicable by the physical view. It is,
+however, unnecessary to do so, because an explanation, according to
+the teleological view, is only admissible when the physical can be
+shown to be impossible. In any case it conduces much more to the object
+of science to strive, at least, to adopt the physical explanation.
+And I would repeat that, when speaking of a physical explanation of
+organic phenomena, it is not necessary to understand an explanation by
+known physical powers, such, for instance, as that universal refuge
+electricity, and the like; but an explanation by means of powers which
+operate like the physical powers, in accordance with strict laws of
+blind necessity, whether they be also to be found in inorganic nature
+or not.
+
+We set out, therefore, with the supposition that an organized body
+is not produced by a fundamental power which is guided in its
+operation by a definite idea, but is developed, according to blind
+laws of necessity, by powers which, like those of inorganic nature,
+are established by the very existence of matter. As the elementary
+materials of organic nature are not different from those of the
+inorganic kingdom, the source of the organic phenomena can only
+reside in another combination of these materials, whether it be in a
+peculiar mode of union of the elementary atoms to form atoms of the
+second order, or in the arrangement of these conglomerate molecules
+when forming either the separate morphological elementary parts of
+organisms, or an entire organism. We have here to do with the latter
+question solely, whether the cause of organic phenomena lies in the
+whole organism, or in its separate elementary parts. If this question
+can be answered, a further inquiry still remains as to whether the
+organism or its elementary parts possess this power through the
+peculiar mode of combination of the conglomerate molecules, or through
+the mode in which the elementary atoms are united into conglomerate
+molecules.
+
+We may, then, form the two following ideas of the cause of organic
+phenomena, such as growth, &c. First, that the cause resides in the
+totality of the organism. By the combination of the molecules into
+a systematic whole, such as the organism is in every stage of its
+development, a power is engendered, which enables such an organism to
+take up fresh material from without, and appropriate it either to the
+formation of new elementary parts, or to the growth of those already
+present. Here, therefore, the cause of the growth of the elementary
+parts resides in the totality of the organism. The other mode of
+explanation is, that growth does not ensue from a power resident in the
+entire organism, but that each separate elementary part is possessed of
+an independent power, an independent life, so to speak; in other words,
+the molecules in each separate elementary part are so combined as to
+set free a power by which it is capable of attracting new molecules,
+and so increasing, and the whole organism subsists only by means of
+the reciprocal action of the single elementary parts. So that here the
+single elementary parts only exert an active influence on nutrition,
+and totality of the organism may indeed be a condition, but is not in
+this view a cause.
+
+In order to determine which of these two views is the correct one,
+we must summon to our aid the results of the previous investigation.
+We have seen that all organized bodies are composed of essentially
+similar parts, namely, of cells; that these cells are formed and grow
+in accordance with essentially similar laws; and, therefore, that these
+processes must, in every instance, be produced by the same powers. Now,
+if we find that some of these elementary parts, not differing from the
+others, are capable of separating themselves from the organism, and
+pursuing an independent growth, we may thence conclude that each of
+the other elementary parts, each cell, is already possessed of power
+to take up fresh molecules and growth; and that, therefore, every
+elementary part possesses a power of its own, an independent life, by
+means of which it would be enabled to develop itself independently,
+if the relations which it bore to external parts were but similar to
+those in which it stands in the organism. The ova of animals afford us
+example of such independent cells, growing apart from the organism.
+It may, indeed, be said of the ova of higher animals, that after
+impregnation the ovum is essentially different from the other cells of
+the organism; that by impregnation there is a something conveyed to the
+ovum, which is more to it than an external condition for vitality, more
+than nutrient matter; and that it might thereby have first received
+its peculiar vitality, and therefore that nothing can be inferred from
+it with respect to the other cells. But this fails in application to
+those classes which consist only of female individuals, as well as
+with the spores of the lower plants; and, besides, in the inferior
+plants any given cell may be separated from the plant, and then grow
+alone. So that here are whole plants consisting of cells, which can
+be positively proved to have independent vitality. Now, as all cells
+grow according to the same laws, and consequently the cause of growth
+cannot in one case lie in the cell, and in another in the whole
+organism; and since it may be further proved that some cells, which
+do not differ from the rest in their mode of growth, are developed
+independently, we must ascribe to all cells an independent vitality,
+that is, such combinations of molecules as occur in any single cell,
+are capable of setting free the power by which it is enabled to take
+up fresh molecules. The cause of nutrition and growth resides not in
+the organism as a whole, but in the separate elementary parts--the
+cells. The failure of growth in the case of any particular cell, when
+separated from an organized body, is as slight an objection to this
+theory as it is an objection against the independent vitality of a bee,
+that it cannot continue long in existence after being separated from
+its swarm. The manifestation of the power which resides in the cell
+depends upon conditions to which it is subject only when in connexion
+with the whole (organism).
+
+The question, then, as to the fundamental power of organized bodies
+resolves itself into that of the fundamental powers of the individual
+cells. We must now consider the general phenomena attending the
+formation of cells, in order to discover what powers may be presumed
+to exist in the cells to explain them. These phenomena may be arranged
+in two natural groups: first, those which relate to the combination of
+the molecules to form a cell, and which may be denominated the plastic
+phenomena of the cells; secondly, those which result from chemical
+changes either in the component particles of the cell itself, or in the
+surrounding cytoblastema, and which may be called metabolic phenomena
+(_to metabolikon_, implying that which is liable to occasion or to
+suffer change).
+
+The general plastic appearances in the cells are, as we have seen,
+the following: at first a minute corpuscle is formed (the nucleolus);
+a layer of substance (the nucleus) is then precipitated around it,
+which becomes more thickened and expanded by the continual deposition
+of fresh molecules between those already present. Deposition goes on
+more vigorously at the outer part of this layer than at the inner.
+Frequently the entire layer, or in other instances the outer part of
+it only, becomes condensed to a membrane, which may continue to take
+up new molecules in such a manner that it increases more rapidly in
+superficial extent than in thickness, and thus an intervening cavity is
+necessarily formed between it and the nucleolus. A second layer (cell)
+is next precipitated around this first, in which precisely the same
+phenomena are repeated, with merely the difference that in this case
+the processes, especially the growth of the layer and the formation of
+the space intervening between it and the first layer (the cell-cavity),
+go on more rapidly and more completely. Such were the phenomena in
+the formation of most cells; in some, however, there appeared to be
+only a single layer formed, while in others (those especially in which
+the nucleolus was hollow) there were three. The other varieties in
+the development of the elementary parts were (as we saw) reduced to
+these--that if two neighbouring cells commence their formation so near
+to one another that the boundaries of the layers forming around each
+of them meet at any spot, a common layer may be formed enclosing the
+two incipient cells. So at least the origin of nuclei, with two or
+more nucleoli, seemed explicable, by a coalescence of the first layers
+(corresponding to the nucleus), and the union of many primary cells
+into one secondary cell by a similar coalescence of the second layers
+(which correspond to the cell). But the further development of these
+common layers proceeds as though they were only an ordinary single
+layer. Lastly, there were some varieties in the progressive development
+of the cells, which were referable to an unequal deposition of the new
+molecules between those already present in the separate layers. In this
+way modifications of form and division of the cells were explained.
+And among the number of the plastic phenomena in the cells we may
+mention, lastly, the formation of secondary deposits; for instances
+occur in which one or more new layers, each on the inner surface of
+the previous one, are deposited on the inner surface of a simple or of
+a secondary cell.
+
+These are the most important phenomena observed in the formation and
+development of cells. The unknown cause, presumed to be capable of
+explaining these processes in the cells, may be called the plastic
+power of the cells. We will, in the next place, proceed to determine
+how far a more accurate definition of this power may be deduced from
+these phenomena.
+
+In the first place, there is a power of attraction exerted in the
+very commencement of the cell, in the nucleolus, which occasions the
+addition of new molecules to those already present. We may imagine
+the nucleolus itself to be first formed by a sort of crystallization
+from out of a concentrated fluid. For if a fluid be so concentrated
+that the molecules of the substance in solution exert a more powerful
+mutual attraction than is exerted between them and the molecules of
+the fluid in which they are dissolved, a part of the solid substance
+must be precipitated. One can readily understand that the fluid must be
+more concentrated when new cells are being formed in it than when those
+already present have merely to grow. For if the cell is already partly
+formed, it exerts an attractive force upon the substance still in
+solution. There is then a cause for the deposition of this substance,
+which does not co-operate when no part of the cell is yet formed.
+Therefore, the greater the attractive force of the cell is, the less
+concentration of the fluid is required; while, at the commencement of
+the formation of a cell, the fluid must be more than concentrated. But
+the conclusion which may be thus directly drawn, as to the attractive
+power of the cell, may also be verified by observation. Wherever the
+nutrient fluid is not equally distributed in a tissue, the new cells
+are formed in that part into which the fluid penetrates first, and
+where, consequently, it is most concentrated. Upon this fact, as we
+have seen, depended the difference between the growth of organized and
+unorganized tissues. And this confirmation of the foregoing conclusion
+by experience speaks also for the correctness of the reasoning itself.
+
+The attractive power of the cells operates so as to effect the addition
+of new molecules in two ways,--first, in layers, and secondly, in such
+a manner in each layer that the new molecules are deposited between
+those already present. This is only an expression of the fact; the
+more simple law, by which several layers are formed and the molecules
+are not all deposited between those already present, cannot yet be
+explained. The formation of layers may be repeated once, twice, or
+thrice. The growth of the separate layers is regulated by a law,
+that the deposition of new molecules should be greatest at the part
+where the nutrient fluid is most concentrated. Hence the outer part
+particularly becomes condensed into a membrance both in the layer
+corresponding to the nucleus and in that answering to the cell, because
+the nutrient fluid penetrates from without, and consequently is more
+concentrated at the outer than at the inner part of each layer. For
+the same reason the nucleus grows rapidly, so long as the layer of the
+cell is not formed around it, but it either stops growing altogether,
+or at least grows much more slowly as soon as the cell-layer has
+surrounded it; because then the latter receives the nutrient matter
+first, and, therefore, in a more concentrated form. And hence the cell
+becomes, in a general sense, much more completely developed, while
+the nucleus-layer usually remains at a stage of development, in which
+the cell-layer had been in its earlier period. The addition of new
+molecules is so arranged that the layers increase more considerably in
+superficial extent than in thickness; and thus an intervening space
+is formed between each layer and the one preceding it, by which cells
+and nuclei are formed into actual hollow vesicles. From this it may be
+inferred that the deposition of new molecules is more active between
+those which lie side by side along the surface of the membrane, than
+between those which lie one upon the other in its thickness. Were it
+otherwise, each layer would increase in thickness, but there would be
+no intervening cavity between it and the previous one, there would be
+no vesicles, but a solid body composed of layers.
+
+Attractive power is exerted in all the solid parts of the cell. This
+follows, not only from the fact that new molecules may be deposited
+everywhere between those already present, but also from the formation
+of secondary deposits. When the cavity of a cell is once formed,
+material may be also attracted from its contents and deposited in
+layers; and as this deposition takes place upon the inner surface
+of the membrane of the cell, it is probably that which exerts the
+attractive influence. This formation of layers on the inner surface of
+the cell-membrane is, perhaps, merely a repetition of the same process
+by which, at an earlier period, nucleus and cell were precipitated as
+layers around the nucleolus. It must, however, be remarked that the
+identity of these two processes cannot be so clearly proved as that of
+the processes by which nucleus and cell are formed; more especially
+as there is a variety in the phenomena, for the secondary deposits in
+plants occur in spiral forms, while this has at least not yet been
+demonstrated in the formation of the cell-membrane and the nucleus,
+although by some botanical writers the cell-membrane itself is supposed
+to consist of spirals.
+
+The power of attraction may be uniform throughout the whole cell,
+but it may also be confined to single spots; the deposition of new
+molecules is then more vigorous at these spots, and the consequence of
+this uneven growth of the cell-membrane is a change in the form of the
+cell.
+
+The attractive power of the cells manifest a certain form of election
+in its operation. It does not take up all the substances contained in
+the surrounding cytoblastema, but only particular ones, either those
+which are analogous with the substance already present in the cell
+(assimilation), or such as differ from it in chemical properties. The
+several layers grow by assimilation, but when a new layer is being
+formed, different material from that of the previously-formed layer
+is attracted: for the nucleolus, the nucleus and cell-membrane are
+composed of materials which differ in their chemical properties.
+
+Such are the peculiarities of the plastic power of the cells, so far as
+they can as yet be drawn from observation. But the manifestations of
+this power presuppose another faculty of the cells. The cytoblastema,
+in which the cells are formed, contains the elements of the materials
+of which the cell is composed, but in other combinations; it is
+not a mere solution of cell-material, but it contains only certain
+organic substances in solution. The cells, therefore, not only attract
+materials from out of the cytoblastema, but they must have the faculty
+of producing chemical changes in its constituent particles. Besides
+which, all the parts of the cell itself may be chemically altered
+during the process of its vegetation. The unknown cause of all these
+phenomena, which we comprise under the term metabolic phenomena of the
+cells, we will denominate the metabolic power.
+
+The next point which can be proved is, that this power is an attribute
+of the cells themselves, and that the cytoblastema is passive under
+it. We may mention vinous fermentation as an instance of this. A
+decoction of malt will remain for a long time unchanged; but as soon as
+some yeast is added to it, which consists partly of entire fungi and
+partly of a number of single cells, the chemical change immediately
+ensues. Here the decoction of malt is the cytoblastema; the cells
+clearly exhibit activity, the cytoblastema, in this instance even a
+boiled fluid, being quite passive during the change. The same occurs
+when any simple cells, as the spores of the lower plants, are sown in
+boiled substances.
+
+In the cells themselves again, it appears to be the solid parts, the
+cell-membrane and the nucleus, which produce the change. The contents
+of the cell undergo similar and even more various changes than the
+external the cytoblastema, and it is at least probable that these
+changes originate with the solid parts composing the cells, especially
+the cell-membrane, because the secondary deposits are formed on
+the inner surface of the cell-membrane, and other precipitates are
+generally formed in the first instance around the nucleus. It may
+therefore, on the whole, be said that the solid component particles of
+the cells possess the power of chemically altering the substances in
+contact with them.
+
+The substances which result from the transformation of the contents
+of the cell are different from those which are produced by change
+in the external cytoblastema. What is the cause of this difference,
+if the metamorphosing power of the cell-membrane be limited to its
+immediate neighbourhood merely? Might we not much rather expect that
+converted substance would be found without distinction on the inner
+as on the outer surface of the cell-membrane? It might be said that
+the cell-membrane converts the substance in contact with it without
+distinction, and that the variety in the products of this conversion
+depends only upon a difference between the convertible substance
+contained in the cell and the external cytoblastema. But the question
+then arises, as to how it happens that the contents of the cell differ
+from the external cytoblastema. If it be true that the cell-membrane,
+which at first closely surrounds the nucleus, expands in the course of
+its growth, so as to leave an interspace between it and the cell, and
+that the contents of the cell consist of fluid which has entered this
+space merely by imbibition, they cannot differ essentially from the
+external cytoblastema. I think therefore that, in order to explain the
+distinction between the cell-contents and the external cytoblastema,
+we must ascribe to the cell-membrane not only the power in general of
+chemically altering the substances which it is either in contact with,
+or has imbibed, but also of so separating them that certain substances
+appear on its inner, and others on its outer surface. The secretion of
+substances already present in the blood, as, for instance, of urea, by
+the cells with which the urinary tubes are lined, cannot be explained
+without such a faculty of the cells. There is, however, nothing so
+very hazardous in it, since it is a fact that different substances are
+separated in the decompositions produced by the galvanic pile. It might
+perhaps be conjectured from this peculiarity of the metabolic phenomena
+in the cells, that a particular position of the axes of the atoms
+composing the cell-membrane is essential for the production of these
+appearances.
+
+Chemical changes occur, however, not only in the cytoblastema and the
+cell-contents, but also in the solid parts of which the cells are
+composed, particularly the cell-membrane. Without wishing to assert
+that there is any intimate connexion between the metabolic power
+of the cells and galvanism, I may yet, for the sake of making the
+representation of the process more clear, remark that the chemical
+changes produced by a galvanic pile are accompanied by corresponding
+changes in the pile itself.
+
+The more obscure the cause of the metabolic phenomena in the cells
+is, the more accurately we must mark the circumstances and phenomena
+under which they occur. One condition to them is a certain temperature,
+which has a maximum and a minimum. The phenomena are not produced in
+a temperature below 0° or above 80° R.; boiling heat destroys this
+faculty of the cells permanently; but the most favorable temperature is
+one between 10° and 32° R. Heat is evolved by the process itself.
+
+Oxygen, or carbonic acid, in a gaseous form or lightly confined, is
+essentially necessary to the metabolic phenomena of the cells. The
+oxygen disappears and carbonic acid is formed, or _vice versa_,
+carbonic acid disappears, and oxygen is formed. The universality of
+respiration is based entirely upon this fundamental condition to the
+metabolic phenomena of the cells. It is so important that, as we shall
+see further on, even the principal varieties of form in organized
+bodies are occasioned by this peculiarity of the metabolic process in
+the cells.
+
+Each cell is not capable of producing chemical changes in every organic
+substance contained in solution, but only in particular ones. The fungi
+of fermentation, for instance, effect no changes in any other solutions
+than sugar; and the spores of certain plants do not become developed in
+all substances. In the same manner it is probable that each cell in the
+animal body converts only particular constituents of the blood.
+
+The metabolic power of the cells is arrested not only by powerful
+chemical actions, such as destroy organic substances in general, but
+also by matters which chemically are less uncongenial; for instance,
+concentrated solutions of neutral salts. Other substances, as arsenic,
+do so in less quantity. The metabolic phenomena may be altered in
+quality by other substances, both organic and inorganic, and a change
+of this kind may result even from mechanical impressions on the cells.
+
+Such are the most essential characteristics of the fundamental powers
+of the cell, so far as they can as yet be deduced from the phenomena.
+And now, in order to comprehend distinctly in what the peculiarity of
+the formative process of a cell, and therefore in what the peculiarity
+of the essential phenomenon in the formation of organized bodies
+consist, we will compare this process with a phenomenon of inorganic
+nature as nearly as possible similar to it. Disregarding all that
+is specially peculiar to the formation of cells, in order to find a
+more general definition in which it may be included with a process
+occurring in inorganic nature, we may view it as a process in which a
+solid body of definite and regular shape is formed in a fluid at the
+expense of a substance held in solution by that fluid. The process of
+crystallization in inorganic nature comes also within this definition,
+and is, therefore, the nearest analogue to the formation of cells.
+
+Let us now compare the two processes, that the difference of the
+organic process may be clearly manifest. First, with reference to the
+plastic phenomena, the forms of cells and crystals are very different.
+The primary forms of crystals are simple, always angular, and bounded
+by plane surfaces; they are regular, or at least symmetrical, and
+even the very varied secondary forms of crystals are almost, without
+exception, bounded by plane surfaces. But manifold as is the form of
+cells, they have very little resemblance to crystals; round surfaces
+predominate, and where angles occur, they are never quite sharp, and
+the polyhedral crystal-like form of many cells results only from
+mechanical causes. The structure too of cells and of crystals is
+different. Crystals are solid bodies, composed merely of layers placed
+one upon another; cells are hollow vesicles, either single, or several
+inclosed one within another. And if we regard the membranes of these
+vesicles as layers, there will still remain marks of difference between
+them and crystals; these layers are not in contact, but contain fluid
+between them, which is not the case with crystals; the layers in the
+cells are few, from one to three only; and they differ from each
+other in chemical properties, while those of crystals consist of the
+same chemical substance. Lastly, there is also a great difference
+between crystals and cells in their mode of growth. Crystals grow by
+apposition, the new molecules are set only upon the surface of those
+already deposited, but cells increase also by intussusception, that
+is to say, the new molecules are deposited also between those already
+present.
+
+But greatly as these plastic phenomena differ in cells and in crystals,
+the metabolic are yet more different, or rather they are quite peculiar
+to cells. For a crystal to grow, it must be already present as such in
+the solution, and some extraneous cause must interpose to diminish its
+solubility. Cells, on the contrary, are capable of producing a chemical
+change in the surrounding fluid, of generating matters which had not
+previously existed in it as such, but of which only the elements were
+present in another combination. They therefore require no extraneous
+influence to effect a change of solubility; for if they can produce
+chemical changes in the surrounding fluid, they may also produce
+such substances as could not be held in solution under the existing
+circumstances, and therefore need no external cause of growth. If a
+crystal be laid in a pretty strong solution, of a substance similar
+even to itself, nothing ensues without our interference, or the crystal
+dissolves completely: the fluid must be evaporated for the crystal
+to increase. If a cell be laid in a solution of a substance, even
+different from itself, it grows and converts this substance without
+our aid. And this it is from which the process going on in the cells
+(so long as we do not separate it into its several acts) obtains that
+magical character, to which attaches the idea of Life.
+
+From this we perceive how very different are the phenomena in the
+formation of cells and of crystals. Meanwhile, however, the points
+of resemblance between them should not be overlooked. They agree in
+this important point, that solid bodies of a certain regular shape are
+formed in obedience to definite laws at the expense of a substance
+contained in solution in a fluid; and the crystal, like the cell, is
+so far an active and positive agent as to cause the substances which
+are precipitated to be deposited on itself, and nowhere else. We
+must, therefore, attribute to it as well as to the cell a power to
+attract the substance held in solution in the surrounding fluid. It
+does not indeed follow that these two attractive powers, the power of
+crystallization--to give it a brief title--and the plastic power of the
+cells, are essentially the same. This could only be admitted, if it
+were proved that both powers acted according to the same laws. But this
+is seen at the first glance to be by no means the case: the phenomena
+in the formation of cells and crystals, are, as we have observed, very
+different, even if we regard merely the plastic phenomena of the cells,
+and leave their metabolic power (which may possibly arise from some
+other peculiarity of organic substance) for a time entirely out of the
+question.
+
+Is it, however, possible that these distinctions are only secondary,
+that the power of crystallization and the plastic power of the cells
+are identical, and that an original difference can be demonstrated
+between the substance of cells and that of crystals, by which we
+may perceive that the substance of cells must crystallize as cells
+according to the laws by which crystals are formed, rather than in the
+shape of the ordinary crystals? It may be worth while to institute such
+an inquiry.
+
+In seeking such a distinction between the substance of cells and that
+of crystals, we may say at once that it cannot consist in anything
+which the substance of cells has in common with those organic
+substances which crystallize in the ordinary form. Accordingly, the
+more complicated arrangement of the atoms of the second order in
+organic bodies cannot give rise to this difference; for we see in
+sugar, for instance, that the mode of crystallization is not altered by
+this chemical composition.
+
+Another point of difference by which inorganic bodies are distinguished
+from at least some of the organic bodies, is the faculty of imbibition.
+Most organic bodies are capable of being infiltrated by water, and
+in such a manner that it penetrates not so much into the interspaces
+between the elementary tissues of the body, as into the simple
+structureless tissues, such as areolar tissue, &c.; so that they form
+an homogeneous mixture, and we can neither distinguish particles
+of organic matter, nor interspaces filled with water. The water
+occupies the infiltrated organic substances, just as it is present in
+a solution, and there is as much difference between the capacity for
+imbibition and capillary permeation, as there is between a solution and
+the phenomena of capillary permeation. When water soaks through a layer
+of glue, we do not imagine it to pass through pores, in the common
+sense of the term; and this is just the condition of all substances
+capable of imbibition. They possess, therefore, a double nature,
+they have a definite form like solid bodies; but like fluids, on the
+other hand, they are also permeable by anything held in solution. As
+a specifically lighter fluid poured on one specifically heavier so
+carefully as not to mix with it, yet gradually penetrates it, so also,
+every solution, when brought into contact with a membrane already
+infiltrated with water, bears the same relations to the membrane, as
+though it were a solution. And crystallization being the transition
+from the fluid to the solid state, we may conceive it possible, or
+even probable, that if bodies, capable of existing in an intermediate
+state between solid and fluid could be made to crystallize, a
+considerable difference would be exhibited from the ordinary mode of
+crystallization. In fact, there is nothing, which we call a crystal,
+composed of substance capable of imbibition; and even among organized
+substances, crystallization takes place only in those which are capable
+of imbibition, as fat, sugar, tartaric acid, &c. The bodies capable of
+imbibition, therefore, either do not crystallize at all, or they do so
+under a form so different from the crystal that they are not recognized
+as such.
+
+Let us inquire what would most probably ensue if material capable of
+imbibition crystallized according to the ordinary laws, what varieties
+from the common crystals would be most likely to show themselves,
+assuming only that the solution has permeated through the parts of
+the crystal already formed, and that new molecules can therefore
+be deposited between them. The ordinary crystals increase only by
+apposition; but there may be an important difference in the mode of
+this apposition. If the molecules were all deposited symmetrically
+one upon another, we might indeed have a body of a certain external
+form like a crystal; but it would not have the structure of one,
+it would not consist of layers. The existence of this laminated
+structure in crystals presupposes a double kind of apposition of their
+molecules; for in each layer the newly-deposited molecules coalesce,
+and become continuous with those of the same layer already present;
+but those molecules which form the adjacent surfaces of two layers
+do not coalesce. This is a remarkable peculiarity in the formation
+of crystals, and we are quite ignorant of its cause. We cannot yet
+perceive why the new molecules, which are being deposited on the
+surface of a crystal (already formed up to a certain point), do not
+coalesce and become continuous with those already deposited, like the
+molecules in each separate layer, instead of forming, as they do, a
+new layer; and why this new layer does not constantly increase in
+thickness, instead of producing a second layer around the crystal, and
+so on. In the meantime we can do no more than express the fact in the
+form of a law, that the coalescing molecules are deposited rather along
+the surface beside each other, than in the thickness upon one another,
+and thus, as the breadth of the layer depends upon the size of the
+crystal, so also the layer can attain only a certain thickness, and
+beyond this, the molecules which are being deposited cannot coalesce
+with it, but must form a new layer.
+
+If we now assume that bodies capable of imbibition could also
+crystallize, the two modes of junction of the molecules should be
+shown also by them. Their structure should also be laminated, at least
+there is no perceptible reason for a difference in this particular,
+as the very fact of layers being formed in common crystals shows that
+the molecules need not be all joined together in the most exact manner
+possible. The closest possible conjunction of the molecules takes place
+only in the separate layers. In the common crystals this occurs by
+apposition of the new molecules on the surface of those present and
+coalescence with them. In bodies capable of imbibition, a much closer
+union is possible, because in them the new molecules may be deposited
+by intussusception between those already present. It is scarcely,
+therefore, too bold an hypothesis to assume, that when bodies capable
+of imbibition crystallize, their separate layers would increase by
+intussusception; and that this does not happen in ordinary crystals,
+simply because it is impossible.
+
+Let us then imagine a portion of the crystal to be formed: new
+molecules continue to be deposited, but do not coalesce with the
+portion of the crystal already formed; they unite with one another
+only, and form a new layer, which, according to analogy with the common
+crystals, may invest either the whole or a part of the crystal. We
+will assume that it invests the entire crystal. Now, although this
+layer be formed by the deposition of new molecules between those
+already present instead of by apposition, yet this does not involve
+any change in the law, in obedience to which the deposition of the
+coalescing molecules goes on more vigorously in two directions,
+that is, along the surface, than it does in the third direction
+corresponding to the thickness of the layer; that is to say, the
+molecules which are deposited by intussusception between those already
+present, must be deposited much more vigorously between those lying
+together along the surface of the layer than between those which lie
+over one another in its thickness. This deposition of molecules side
+by side is limited in common crystals by the size of the crystal, or
+by that of the surface on which the layer is formed; the coalescence
+of molecules therefore ceases as regards that layer, and a new one
+begins. But if the layers grow by intussusception in crystals capable
+of imbibition, there is nothing to prevent the deposition of more
+molecules between those which lie side by side upon the surface, even
+after the lamina has invested the whole crystal; it may continue to
+grow without the law by which the new molecules coalesce requiring to
+be altered. But the consequence is, that the layer becomes, in the
+first instance more condensed, that is, more solid substance is taken
+into the same space; and afterwards it will expand and separate from
+the completed part of the crystal so as to leave a hollow space between
+itself and the crystal; this space fills with fluid by imbibition,
+and the first-formed portion of the crystal adheres to a spot on its
+inner surface. Thus, in bodies capable of imbibition, instead of a new
+layer attached to the part of the crystal already formed, we obtain a
+hollow vesicle. At first this must have the shape of the body of the
+crystal around which it is formed, and must, therefore, be angular,
+if the crystal is angular. If, however, we imagine this layer to be
+composed of soft substance capable of imbibition, we may readily
+comprehend how such a vesicle must very soon become round or oval. But
+the first-formed part of the crystal also consists of substance capable
+of imbibition, so that it is very doubtful whether it must have an
+angular form at all. In common crystals atoms of some one particular
+substance are deposited together, and we can understand how a certain
+angular form of the crystal may result if these atoms have a certain
+form, or if in certain axes they attract each other differently. But in
+bodies capable of imbibition, an atom of one substance is not set upon
+another atom of the same substance, but atoms of water come between;
+atoms of water, which are not united with an atom of solid substance,
+so as to form a compound atom, as in the water of crystallization, but
+which exist in some other unknown manner between the atoms of solid
+substance. It is not possible, therefore, to determine whether that
+part of the crystal which is first formed must have an angular figure
+or not.
+
+An ordinary crystal consists of a number of laminæ; when so small as
+to be but just discernible, it has the form which the whole crystal
+afterwards exhibits, at least as far as regards the angles; we must
+therefore suppose that the first layer is formed around a very small
+corpuscle, which is of the same shape as the subsequent crystal. We
+will call this the primitive corpuscle. It is doubtful what may be
+the shape of this corpuscle in the crystals which are capable of
+imbibition. The first layer, then, is formed around the corpuscle
+in the way mentioned; it grows by intussusception, and thus forms
+a hollow, round or oval vesicle, to the inner surface of which the
+primitive corpuscle adheres. As all the new molecules that are being
+deposited may be placed in this layer without any alteration being
+required in the law which regulates the coalescence of the molecules
+during crystallization, we must conclude that it remains the only
+layer, and becomes greatly expanded, so as to represent all the
+layers of an ordinary crystal. It is, however, a question whether
+there may not exist some reasons why several layers can be formed.
+We can certainly conceive such to be the case. The quantity of the
+solid substance that must crystallize in a given time, depends upon
+the concentration of the fluid; the number of molecules that may,
+in accordance with the law already mentioned, be deposited in the
+layer in a given time depends upon the quantity of the solution
+which can penetrate the membrane by imbibition during that time. If
+in consequence of the concentration of the fluid there must be more
+precipitated in the time than can penetrate the membrane, it can only
+be deposited as a new layer on the outer surface of the vesicle. When
+this second layer is formed, the new molecules are deposited in it, and
+it rapidly becomes expanded into a vesicle, on the inner surface of
+which the first vesicle lies with its primitive corpuscle. The first
+vesicle now either does not grow at all, or at any rate much more
+slowly, and then only when the endosmosis into the cavity of the second
+vesicle proceeds so rapidly that all that might be precipitated while
+passing through it, is not deposited. The second vesicle, when it is
+developed at all, must needs be developed relatively with more rapidity
+than the first; for as the solution is in the most concentrated state
+at the beginning, the necessity for the formation of a second layer
+then occurs sooner; but when it is formed, the concentration of the
+fluid is diminished, and this necessity occurs either later or not at
+all. It is possible, however, that even a third, or fourth, and more,
+may be formed; but the outermost layer must always be relatively the
+most vigorously developed; for when the concentration of the solution
+is only so strong, that all that must be deposited in a certain time,
+can be deposited in the outermost layer, it is all applied to the
+increase of this layer.
+
+Such, then, would be the phenomena under which substances capable of
+imbibition would probably crystallize, if they did so at all. I say
+probably, for our incomplete knowledge of crystallization and the
+faculty of imbibition, does not as yet admit of our saying anything
+positively _a priori_. It is, however, obvious that these are the
+principal phenomena attending the formation of cells. They consist
+always of substance capable of imbibition; the first part formed is
+a small corpuscle, not angular (nucleolus), around this a lamina is
+deposited (nucleus), which advances rapidly in its growth, until a
+second lamina (cell) is formed around it. This second now grows more
+quickly and expands into a vesicle, as indeed often happens with
+the first layer. In some rarer instances only one layer is formed;
+in others, again, there are three. The only other difference in the
+formation of cells is, that the separate layers do not consist of the
+same chemical substance, while a common crystal is always composed
+of one material. In instituting a comparison, therefore, between the
+formation of cells and crystallization, the above-mentioned differences
+in form, structure, and mode of growth fall altogether to the ground.
+If crystals were formed from the same substance as cells, they would
+probably, in these respects, be subject to the same conditions as the
+cells. Meanwhile the metabolic phenomena, which are entirely absent in
+crystals, still indicate essential distinctions.
+
+Should this important difference between the mode of formation of
+cells and crystals lead us to deny all intimate connexion of the two
+processes, the comparison of the two may serve at least to give a clear
+representation of the cell-life. The following may be conceived to be
+the state of the matter: the material of which the cells are composed
+is capable of producing chemical changes in the substance with which it
+is in contact, just as the well-known preparation of platinum converts
+alcohol into acetic acid. This power is possessed by every part of the
+cell. Now, if the cytoblastema be so changed by a cell already formed,
+that a substance is produced which cannot become attached to that cell,
+it immediately crystallizes as the central nucleolus of a new cell. And
+then this converts the cytoblastema in the same manner. A portion of
+that which is converted may remain in the cytoblastema in solution,
+or may crystallize as the commencement of new cells; another portion,
+the cell-substance, crystallizes around the central corpuscle. The
+cell-substance is either soluble in the cytoblastema, and crystallizes
+from it, so soon as the latter becomes saturated with it; or else it is
+insoluble, and crystallizes at the time of its formation, according to
+the laws of crystallization of bodies capable of imbibition mentioned
+above, forming in this manner one or more layers around the central
+corpuscle, and so on. If we conceive the above to represent the mode
+of formation of cells, we regard the plastic power of the cells as
+identical with the power by which crystals grow. According to the
+foregoing description of the crystallization of bodies capable of
+imbibition, the most important plastic phenomena of the cells are
+certainly satisfactorily explained. But let us see if this comparison
+agrees with all the characteristics of the plastic power of the cells.
+
+The attractive power of the cells does not always operate
+symmetrically; the deposition of new molecules may be more vigorous in
+particular spots, and thus produce a change in the form of the cell.
+This is quite analogous to what happens in crystals; for although
+in them an angle is never altered, there may be much more material
+deposited on some surfaces than on others; and thus, for instance,
+a quadrilateral prism may be formed out of a cube. In this case new
+layers are deposited on one, or on two opposite sides of a cube. Now,
+if one layer in cells represent a number of layers in a common crystal,
+it may be easily perceived that instead of several new layers being
+formed on two opposite surfaces of a cell, the one layer would grow
+more at those spots, and thus a round cell would be elongated into a
+fibre; and so with the other changes of form. Division of the cells
+can have no analogue in common crystals, because that which is once
+deposited is incapable of any further change. But this phenomenon
+may be made to accord with the representation of crystals capable
+of imbibition.... And if we ascribe to a layer of a crystal capable
+of imbibition the power of producing chemical changes in organic
+substances, we can very well understand also the origin of secondary
+deposits on its inner surface as they occur in cells. For if, in
+accordance with the laws of crystallization, the lamina has become
+expanded into a vesicle, and its cavity has become filled by imbibition
+with a solution of organic substance, there may be materials formed
+by means of the converting influence of the lamina, which cannot any
+longer be held in solution. These may, then, either crystallize within
+the vesicle, as new crystals capable of imbibition under the form of
+cells; or if they are allied to the substance of the vesicle, they may
+so crystallize as to form part of the system of the vesicle itself:
+the latter may occur in two ways, the new matters may be applied to
+the increase of the vesicle, or they may form new layers on its inner
+surface from the same cause which led to the first formation of the
+vesicle itself as a layer. In the cells of plants these secondary
+deposits have a spiral arrangement. This is a very important fact,
+though the laws of crystallization do not seem to account for the
+absolute necessity of it. If, however, it could be mathematically
+proved from the laws of the crystallization of inorganic bodies, that
+under the altered circumstances in which bodies capable of imbibition
+are placed, these deposits must be arranged in spiral forms, it might
+be asserted without hesitation that the plastic power of cells and the
+fundamental powers of crystals are identical.
+
+We come now, however, to some peculiarities in the plastic power of
+cells, to which we might, at first sight, scarcely expect to find
+anything analogous in crystals. The attractive power of the cells
+manifests a certain degree of election in its operation; it does
+not attract every substance present in the cytoblastema, but only
+particular ones; and here a muscle-cell, there a fat-cell, is generated
+from the same fluid, the blood. Yet crystals afford us an example
+of a precisely similar phenomenon, and one which has already been
+frequently adduced as analogous to assimilation. If a crystal of nitre
+be placed in a solution of nitre and sulphate of soda, only the nitre
+crystallizes; when a crystal of sulphate of soda is put in, only the
+sulphate of soda crystallizes. Here, therefore, there occurs just the
+same selection of the substance to be attracted.
+
+We observed another law attending the development of the plastic
+phenomena in the cells, viz. that a more concentrated solution is
+requisite for the first formation of a cell than for its growth when
+already formed, a law upon which the difference between organized and
+unorganized tissues is based. In ordinary crystallization the solution
+must be more than saturated for the process to begin. But when it is
+over, there remains a mother lye, according to Thénard, which is no
+longer saturated at the same temperature. This phenomenon accords
+precisely with the cells; it shows that a more concentrated solution is
+requisite for the commencement of crystallization than for the increase
+of a crystal already formed. The fact has indeed been disputed by
+Thomson; but if, in the undisputed experiment quoted above, the crystal
+of sulphate of soda attracts the dissolved sulphate of soda rather
+than the dissolved nitre, and _vice versa_, the crystal of nitre
+attracts the dissolved nitre more than the dissolved sulphate of soda,
+it follows that a crystal does attract a salt held in solution, because
+the experiment proves that there are degrees of this attraction. But if
+there be such an attraction exerted by a crystal, then the introduction
+of a crystal into a solution of a salt, affords an efficient cause for
+the deposition of this salt, which does not exist when no crystal is
+introduced. The solution must therefore be more concentrated in the
+latter case than in the former, though the difference be so slight
+as not to be demonstrable by experiment. It would not, however, be
+superfluous to repeat the experiments. In the instance of crystals
+capable of imbibition, this difference may be considerably augmented,
+since the attraction of molecules may increase perhaps considerably by
+the penetrating of the solution between those already deposited.
+
+We see then how all the plastic phenomena in the cells may be compared
+with phenomena which, in accordance with the ordinary laws of
+crystallization, would probably appear if bodies capable of imbibition
+could be brought to crystallize. So long as the object of such a
+comparison were merely to render the representation of the process
+by which cells are formed more clear, there could not be much urged
+against it; it involves nothing hypothetical, since it contains no
+explanation; no assertion is made that the fundamental power of the
+cells really has something in common with the power by which crystals
+are formed. We have, indeed, compared the growth of organisms with
+crystallization, in so far as in both cases solid substances are
+deposited from a fluid, but we have not therefore asserted the
+identity of the fundamental powers. So far we have not advanced beyond
+the data, beyond a certain simple mode of representing the facts.
+
+The question is, however, whether the exact accordance of the phenomena
+would not authorize us to go further. If the formation and growth of
+the elementary particles of organisms have nothing more in common with
+crystallization than merely the deposition of solid substances from out
+of a fluid, there is certainly no reason for assuming any more intimate
+connexion of the two processes. But we have seen, first, that the laws
+which regulate the deposition of the molecules forming the elementary
+particles of organisms are the same for all elementary parts; that
+there is a common principle in the development of all elementary parts,
+namely, that of the formation of cells; it was then shown that the
+power which induced the attachment of the new molecules did not reside
+in the entire organism, but in the separated elementary particles (this
+we called the plastic power of the cells); lastly, it was shown that
+the laws, according to which the new molecules combine to form cells,
+are (so far as our incomplete knowledge of the laws of crystallization
+admits of our anticipating their probability) the same as those by
+which substances capable of imbibition would crystallize. Now the
+cells do, in fact, consist only of material capable of imbibition;
+should we not then be justified in putting forth the proposition, that
+the formation of the elementary parts of organisms is nothing but a
+crystallization of substance, capable of imbibition, and the organism
+nothing but an aggregate of such crystals capable of imbibition?
+
+To advance so important a point as absolutely true, would certainly
+need the clearest proof; but it cannot be said that even the premises
+which have been set forth have in all points the requisite force. For
+too little is still known of the cause of crystallization to predict
+with safety (as was attempted above) what would follow if a substance
+capable of imbibition were to crystallize. And if these premises were
+allowed, there are two other points which must be proved in order to
+establish the proposition in question: 1. That the metabolic phenomena
+of the cells, which have not been referred to in the foregoing
+argument, are as much the necessary consequence of the faculty of
+imbibition, or of some other peculiarity of the substance of cells, as
+the plastic phenomena are. 2. That if a number of crystals capable of
+imbibition are formed, they must combine according to certain laws
+so as to form a systematic whole, similar to an organism. Both these
+points must be clearly proved, in order to establish the truth of the
+foregoing view. But it is otherwise if this view be adduced merely as
+an hypothesis, which may serve as a guide for new investigations. In
+such case the inferences are sufficiently probable to justify such
+an hypothesis, if only the two points just mentioned can be shown to
+accord with it.
+
+With reference to the first of these points, it would certainly be
+impossible, in our ignorance as to the cause of chemical phenomena in
+general, to prove that a crystal capable of imbibition must produce
+chemical changes in substances surrounding it; but then we could not
+infer, from the manner in which spongy platinum is formed, that it
+would act so peculiarly upon oxygen and hydrogen. But in order to
+render this view tenable as a possible hypothesis, it is only necessary
+to see that it may be a consequence. It cannot be denied that it may:
+there are several reasons for it, though they certainly are but weak.
+For instance, since all cells possess this metabolic power, it is more
+likely to depend on a certain position of the molecules, which in all
+probability is essentially the same in all cells, than on the chemical
+combination of the molecules, which is very different in different
+cells. The presence, too, of different substances on the inner and
+outer surface of the cell-membrane in some measure implies that a
+certain direction of the axes of the atoms may be essential to the
+metabolic phenomena of the cells. I think, therefore, that the cause of
+the metabolic phenomena resides in that definite mode of arrangement
+of the molecules which occurs in crystals, combined with the capacity
+which the solution has to penetrate between these regularly deposited
+molecules (by means of which, presuming the molecules to possess
+polarity, a sort of galvanic pile will be formed), and that the same
+phenomena would be observed in an ordinary crystal, if it could be
+rendered capable of imbibition. And then perhaps the differences
+of quality in the metabolic phenomena depend upon their chemical
+composition.
+
+In order to render tenable the hypothesis contained in the second
+point, it is merely necessary to show that crystals capable of
+imbibition can unite with one another according to certain laws. If
+at their first formation all crystals were isolated, if they held
+no relation whatever to each other, the view would leave entirely
+unexplained how the elementary parts of organisms, that is, the
+crystals in question, become united to form a whole. It is therefore
+necessary to show that crystals do unite with each other according
+to certain laws, in order to perceive, at least, the possibility
+of their uniting also to form an organism, without the need of any
+further combining power. But there are many crystals in which a union
+of this kind, according to certain laws, is indisputable; indeed they
+often form a whole, so like an organism in its entire form, that
+groups of crystals are known in common life by the names of flowers,
+trees, etc. I need only refer to the ice-flowers on the windows, or
+to the lead-tree, etc. In such instances a number of crystals arrange
+themselves in groups around others, which form an axis. If we consider
+the contact of each crystal with the surrounding fluid to be an
+indispensable condition to the growth of crystals which are not capable
+of imbibition, but that those which are capable of imbibition, in which
+the solution can penetrate whole layers of crystals, do not require
+this condition, we perceive that the similarity between organisms and
+these aggregations of crystals is as great as could be expected with
+such difference of substance. As most cells require for the production
+of their metabolic phenomena, not only their peculiar nutrient fluid,
+but also the access of oxygen and the power of exhaling carbonic acid,
+or _vice versa_; so, on the other hand, organisms in which there
+is no circulation of respiratory fluid, or in which at least it is not
+sufficient, must be developed in such a way as to present as extensive
+a surface as possible to the atmospheric air. This is the condition of
+plants, which require for their growth that the individual cells should
+come into contact with the surrounding medium in a similar manner,
+if not in the same degree as occurs in a crystal tree, and in them
+indeed the cells unite into a whole organism in a form much resembling
+a crystal tree. But in animals the circulation renders the contact of
+the individual cells with the surrounding medium superfluous, and they
+may have more compact forms, even though the laws by which the cells
+arrange themselves are essentially the same.
+
+The view then that organisms are nothing but the form under which
+substances capable of imbibition crystallize, appears to be compatible
+with the most important phenomena of organic life, and may be so
+far admitted, that it is a possible hypothesis; or attempt towards
+an explanation of these phenomena. It involves very much that is
+uncertain and paradoxical, but I have developed it in detail, because
+it may serve as a guide for new investigations. For even if no relation
+between crystallization and the growth of organisms be admitted
+in principle, this view has the advantage of affording a distinct
+representation of the organic processes; an indispensable requisite for
+the institution of new inquiries in a systematic manner, or for testing
+by the discovery of new facts a mode of explanation which harmonizes
+with phenomena already known.
+
+
+FOOTNOTES:
+
+[Footnote 33: Translated from _Mikroskopische Untersuchungen über die
+Wachstum der Tiere und der Pflanzen_ (Berlin, 1839) by Henry Smith
+in the _Publications of the Sydenham Society_ (1847).]
+
+
+
+
+ XXXI
+
+ HERMANN VON HELMHOLTZ
+
+ 1821-1894
+
+
+ _Hermann von Helmholtz, born at Potsdam, Prussia, August 31, 1821,
+ studied medicine at the University of Berlin, from which he received
+ his degree in 1842. He then entered the German Army as surgeon and
+ in 1847 published his paper on “The Conservation of Energy,” which
+ summarized historically the development of the idea. In 1849 he was
+ appointed professor of physiology and general pathology at Königsberg.
+ In 1855 he was called to Bonn, and in 1858 was elected to the chair of
+ physiology at Heidelberg._
+
+ _In 1851 he invented the ophthalmoscope and later at Heidelberg he
+ continued his researches in the subject of sight, and also cleared up
+ the problem of the mechanical causes of sound. In 1871 he was appointed
+ professor of physics at the University of Berlin, where he remained
+ until his death, September 8, 1894._
+
+
+ THE CONSERVATION OF ENERGY[34]
+
+A new conquest of very general interest has been recently made by
+natural philosophy. In the following pages I will endeavour to give a
+notion of the nature of this conquest. It has reference to a new and
+universal natural law, which rules the action of natural forces in
+their mutual relations towards each other, and is as influential on
+our theoretic views of natural processes as it is important in their
+technical applications.
+
+Among the practical arts which owe their progress to the development of
+the natural sciences, from the conclusion of the middle ages downwards,
+practical mechanics, aided by the mathematical science which bears the
+same name, was one of the most prominent. The character of the art
+was, at the time referred to, naturally very different from its present
+one. Surprised and stimulated by its own success, it thought no problem
+beyond its power, and immediately attacked some of the most difficult
+and complicated. Thus it was attempted to build automaton figures which
+should perform the functions of men and animals. The wonder of the last
+century was Vaucanson’s duck, which fed and digested its food; the
+flute player of the same artist, which moved all its fingers correctly;
+the writing boy of the older, and the pianoforte player of the younger
+Droz: which latter, when performing, followed its hands with its eyes,
+and at the conclusion of the piece bowed courteously to the audience.
+That men like those mentioned, whose talent might bear comparison with
+the most inventive heads of the present age, should spend so much
+time in the construction of these figures, which we at present regard
+as the merest trifles, would be incomprehensible, if they had not
+hoped in solemn earnest to solve a great problem. The writing boy of
+the elder Droz was publicly exhibited in Germany some years ago. Its
+wheel-work is so complicated, that no ordinary head would be sufficient
+to decipher its manner of action. When, however, we are informed that
+this boy and its constructor, being suspected of the black art, lay
+for a time in the Spanish Inquisition, and with difficulty obtained
+their freedom, we may infer that in those days even such a toy appeared
+great enough to excite doubts as to its natural origin. And though
+these artists may not have hoped to breathe into the creature of
+their ingenuity a soul gifted with moral completeness, still there
+were many who would be willing to dispense with the moral qualities
+of their servants if, at the same time, their immoral qualities could
+also be got rid of; and accept, instead of the mutability of flesh
+and bones, services which should combine the regularity of a machine
+with the durability of brass and steel. The object, therefore, which
+the inventive genius of the past century placed before it with the
+fullest earnestness, and not as a piece of amusement merely, was boldly
+chosen, and was followed up with an expenditure of sagacity which has
+contributed not a little to enrich the mechanical experience which a
+later time knew how to take advantage of. We no longer seek to build
+machines which shall fulfil the thousand services required of one man,
+but desire, on the contrary, that a machine shall perform one service,
+but shall occupy in doing it the place of a thousand men.
+
+From these efforts to imitate living creatures, another idea, also by
+a misunderstanding, seems to have developed itself, which, as it were,
+formed the new philosopher’s stone of the seventeenth and eighteenth
+centuries. It was now the endeavour to construct a perpetual motion
+machine. Under this term was understood a machine which, without being
+wound up, without consuming in the working of it, falling water, wind
+or any other natural force, should still continue in motion, the motive
+power being perpetually supplied by the machine itself. Beasts and
+human beings seemed to correspond to the idea of such an apparatus, for
+they moved themselves energetically and incessantly as long as they
+lived, were never wound up, and nobody set them in motion. A connection
+between the taking in of nourishment and the development of force did
+not make itself apparent. The nourishment seemed only necessary to
+grease, as it were, the wheel-work of the animal machine, to replace
+what was used up, and to renew the old. The development of force out of
+itself seemed to be the essential peculiarity, the real quintessence of
+organic life. If, therefore, men were to be constructed, a perpetual
+motion must first be found.
+
+Another hope also seemed to take up incidentally the second place,
+which, in our wiser age, would certainly have claimed the first rank
+in the thoughts of men. The perpetual motion was to produce work
+inexhaustibly without corresponding consumption, that is to say, out
+of nothing. Work, however, is money. Here, therefore, the practical
+problem which the cunning heads of all centuries have followed in the
+most diverse ways, namely, to fabricate money out of nothing, invited
+solution. The similarity with the philosopher’s stone sought by the
+ancient chemists was complete. That also was thought to contain the
+quintessence of organic life, and to be capable of producing gold.
+
+The spur which drove men to inquiry was sharp, and the talent of some
+of the seekers must not be estimated as small. The nature of the
+problem was quite calculated to entice poring brains, to lead them
+round a circle for years, deceiving ever with new expectations, which
+vanished upon nearer approach, and finally reducing these dupes of
+hope to open insanity. The phantom could not be grasped. It would be
+impossible to give a history of these efforts, as the clearer heads,
+among whom the elder Droz must be ranked, convinced themselves of the
+futility of their experiments, and were naturally not inclined to
+speak much about them. Bewildered intellects, however, proclaimed
+often enough that they had discovered the grand secret; and as the
+incorrectness of their proceedings was always speedily manifest, the
+matter fell into bad repute, and the opinion strengthened itself more
+and more that the problem was not capable of solution; one difficulty
+after another was brought under the dominion of mathematical mechanics,
+and finally a point was reached where it could be proved that, at least
+by the use of pure mechanical forces, no perpetual motion could be
+generated.
+
+We have here arrived at the idea of the driving force or power of
+a machine, and shall have much to do with it in future. I must,
+therefore, give an explanation of it. The idea of work is evidently
+transferred to machines by comparing their arrangements with those of
+men and animals to replace which they were applied. We still reckon
+the work of steam engines according to horse-power. The value of
+manual labor is determined partly by the force which is expended in
+it (a strong laborer is valued more highly than a weak one), partly,
+however, by the skill which is brought into action. A machine, on the
+contrary, which executes work skilfully, can always be multiplied to
+any extent; hence its skill has not the high value of human skill in
+domains where the latter cannot be supplied by machines. Thus the idea
+of the quantity of work in the case of machines has been limited to the
+consideration of the expenditure of force; this was the more important,
+as indeed most machines are constructed for the express purpose of
+exceeding, by the magnitude of their effects, the powers of men and
+animals. Hence, in a mechanical sense, the idea of work is become
+identical with that of the expenditure of force, and in this way I will
+apply it.
+
+How, then, can we measure this expenditure, and compare it in the case
+of different machines?
+
+I must here conduct you a portion of the way--as short a portion
+as possible--over the uninviting field of mathematico-mechanical
+ideas, in order to bring you to a point of view from which a more
+rewarding prospect will open. And though the example which I shall
+here choose, namely, that of a water-mill with iron hammer, appears
+to be tolerably romantic, still, alas, I must leave the dark forest
+valley, the spark-emitting anvil, and the black Cyclops wholly out of
+sight, and beg a moment’s attention to the less poetic side of the
+question, namely, the machinery. This is driven by a water-wheel, which
+in its turn is set in motion by the falling water. The axle of the
+water-wheel has at certain places small projections, thumbs, which,
+during the rotation, lift the heavy hammer and permit it to fall again.
+The falling hammer belabors the mass of metal, which is introduced
+beneath it. The work therefore done by the machine consists, in this
+case, in the lifting of the hammer, to do which the gravity of the
+latter must be overcome. The expenditure of force will, in the first
+place, other circumstances being equal, be proportioned to the weight
+of the hammer; it will, for example, be double when the weight of the
+hammer is doubled. But the action of the hammer depends not upon its
+weight alone, but also upon the height from which it falls. If it falls
+through two feet, it will produce a greater effect than if it falls
+through only one foot. It is, however, clear that if the machine, with
+a certain expenditure of force, lifts the hammer a foot in height, the
+same amount of force must be expended to raise it a second foot in
+height. The work is therefore not only doubled when the weight of the
+hammer is increased twofold, but also when the space through which it
+falls is doubled. From this it is easy to see that the work must be
+measured by the product of the weight into the space through which it
+ascends. And in this way, indeed, do we measure in mechanics.
+
+The unit of work is a foot-pound, that is, a pound weight, raised to
+the height of one foot.
+
+While the work in this case consists in the raising of the heavy
+hammer-head, the driving force which sets the latter in motion is
+generated by falling water. It is not necessary that the water should
+fall vertically, it can also flow in a moderately inclined bed; but
+it must always, where it has water-mills to set in motion, move from
+a higher to a lower position. Experiment and theory coincided in
+teaching, that when a hammer of a hundred weight is to be raised one
+foot, to accomplish this at least a hundred weight of water must fall
+through the space of one foot; or what is equivalent to this, two
+hundred weight must fall full half a foot, or four hundred weight a
+quarter of a foot, etc. In short, if we multiply the weight of the
+falling water by the height through which it falls, and regard, as
+before, the product as the measure of the work, then the work performed
+by the machine in raising the hammer can, in the most favourable case,
+be only equal to the number of foot-pounds of water which have fallen
+in the same time. In practice, indeed, this ratio is by no means
+attained; a great portion of the work of the falling water escapes
+unused, inasmuch as part of the force is unwillingly sacrificed for the
+sake of obtaining greater speed.
+
+I will further remark, that this relation remains unchanged whether
+the hammer is driven immediately by the axle of the wheel, or
+whether--by the intervention of wheel-work, endless screws, pulleys,
+ropes--the motion is transferred to the hammer. We may, indeed, by
+such arrangements, succeed in raising a hammer of ten hundred weight,
+when by the first simple arrangement, the elevation of a hammer of one
+hundred weight might alone be possible; but either this heavier hammer
+is raised to only one-tenth of the height, or tenfold the time is
+required to raise it to the same height; so that, however we may alter,
+by the interposition of machinery, the intensity of the acting force,
+still in a certain time, during which the mill-stream furnishes us with
+a definite quantity of water, a certain definite quantity of work, and
+no more, can be performed.
+
+Our machinery, therefore, has, in the first place, done nothing more
+than make use of the gravity of the falling water in order to overpower
+the gravity of the hammer, and to raise the latter. When it has lifted
+the hammer to the necessary height, it again liberates it, and the
+hammer falls upon the metal mass which is pushed beneath it. But why
+does the falling hammer here exercise a greater force than when it is
+permitted simply to press with its own weight on the mass of metal? Why
+is its power greater as the height from which it falls is increased?
+We find, in fact, that the work performed by the hammer is determined
+by its velocity. In other cases, also, the velocity of moving masses
+is a means of producing great effects. I only remind you of the
+destructive effects of musket-bullets, which, in a state of rest, are
+the most harmless things in the world. I remind you of the windmill,
+which derives its force from the moving air. It may appear surprising
+that motion, which we are accustomed to regard as a non-essential and
+transitory endowment of bodies, can produce such great effects. But
+the fact is, that motion appears to us, under ordinary circumstances,
+transitory, because the movement of all terrestrial bodies is resisted
+perpetually by other forces, friction, resistance of the air, etc.,
+so that motion is incessantly weakened and finally neutralized. A
+body, however, which is opposed by no resisting force, when once set
+in motion, moves onward eternally with undiminished velocity. Thus
+we know that the planetary bodies have moved without change, through
+space, for thousands of years. Only by resisting forces can motion
+be diminished or destroyed. A moving body, such as the hammer or the
+musket-ball, when it strikes against another, presses the latter
+together, or penetrates it, until the sum of the resisting forces which
+the body struck presents to its pressure, or to the separation of its
+particles, is sufficiently great to destroy the motion of the hammer
+or of the bullet. The motion of a mass regarded as taking the place of
+working force is called the living force (_vis viva_) of the mass.
+The word “living” has of course here no reference whatever to living
+beings, but is intended to represent solely the force of the motion as
+distinguished from the state of unchanged rest--from the gravity of
+a motionless body, for example, which produces an incessant pressure
+against the surface which supports it, but does not produce any motion.
+
+In the case before us, therefore, we had first power in the form of
+a falling mass of water, then in the form of a lifted hammer, and,
+thirdly, in the form of the living force of the fallen hammer. We
+should transform the third form into the second, if we, for example,
+permitted the hammer to fall upon a highly elastic steel beam strong
+enough to resist the shock. The hammer would rebound, and in the most
+favourable case would reach a height equal to that from which it
+fell, but would never rise higher. In this way its mass would ascend:
+and at the moment when its highest point has been attained, it would
+represent the same number of raised foot-pounds as before it fell,
+never a greater number; that is to say, living force can generate the
+same amount of work as that expended in its production. It is therefore
+equivalent to this quantity of work.
+
+Our clocks are driven by means of sinking weights, and our watches by
+means of the tension of springs. A weight which lies on the ground, an
+elastic spring which is without tension, can produce no effects; to
+obtain such we must first raise the weight or impart tension to the
+spring, which is accomplished when we wind up our clocks and watches.
+The man who winds the clock or watch communicates to the weight or
+to the spring a certain amount of power, and exactly so much as is
+thus communicated is gradually given out again during the following
+twenty-four hours, the original force being thus slowly consumed
+to overcome the friction of the wheels and the resistance which the
+pendulum encounters from the air. The wheel-work of the clock therefore
+exhibits no working force which was not previously communicated to it,
+but simply distributes the force given to it uniformly over a longer
+time.
+
+Into the chamber of an air-gun we squeeze, by means of a condensing
+air-pump, a great quantity of air. When we afterwards open the cock of
+a gun and admit the compressed air into the barrel, the ball is driven
+out of the latter with a force similar to that exerted by ignited
+powder. Now we may determine the work consumed in the pumping-in of the
+air, and the living force which, upon firing, is communicated to the
+ball, but we shall never find the latter greater than the former. The
+compressed air has generated no working force, but simply gives to the
+bullet that which has been previously communicated to it. And while we
+have pumped for perhaps a quarter of an hour to charge the gun, the
+force is expended in a few seconds when the bullet is discharged; but
+because the action is compressed into so short a time, a much greater
+velocity is imparted to the ball than would be possible to communicate
+to it by the unaided effort of the arm in throwing it.
+
+From these examples you observe, and the mathematical theory has
+corroborated this for all purely mechanical, that is to say, for
+moving forces, that all our machinery and apparatus generate no
+force, but simply yield up the power communicated to them by
+natural forces--falling water, moving wind, or by the muscles of
+men and animals. After this law had been established by the great
+mathematicians of the last century, a perpetual motion, which should
+make only use of pure mechanical forces, such as gravity, elasticity,
+pressure of liquids and gases, could only be sought after by bewildered
+and ill-instructed people. But there are still other natural forces
+which are not reckoned among the purely moving forces--heat,
+electricity, magnetism, light, chemical forces, all of which
+nevertheless stand in manifold relation to mechanical processes. There
+is hardly a natural process to be found which is not accompanied by
+mechanical actions, or from which mechanical work may not be derived.
+Here the question of a perpetual motion remained open; the decision of
+this question marks the progress of modern physics.
+
+In the case of the air-gun, the work to be accomplished in the
+propulsion of the ball was given by the arm of the man who pumped in
+the air. In ordinary firearms, the condensed mass of air which propels
+the bullet is obtained in a totally different manner, namely, by the
+combustion of the powder. Gunpowder is transformed by combustion for
+the most part into gaseous products, which endeavor to occupy a much
+larger space than that previously taken by the volume of the powder.
+Thus, you see, that, by the use of gunpowder, the work which the human
+arm must accomplish in the case of the air-gun is spared.
+
+In the mightiest of our machines, the steam engine, it is a strongly
+compressed aeriform body, water, vapour, which, by its effort to
+expand, sets the machine in motion. Here, also, we do not condense the
+steam by means of an external mechanical force, but by communicating
+heat to a mass of water in a closed boiler, we change this water
+into steam, which, in consequence of the limits of the space, is
+developed under strong pressure. In this case, therefore, it is the
+heat communicated which generates the mechanical force. The heat thus
+necessary for the machine we might obtain in many ways; the ordinary
+method is to procure it from the combustion of coal.
+
+Combustion is a chemical process. A particular constituent of our
+atmosphere, oxygen, possesses a strong force of attraction, or, as
+it is named in chemistry, a strong affinity for the constituents of
+the combustible body, which affinity, however, in most cases, can
+only exert itself at high temperatures. As soon as a portion of the
+combustible body, for example, the coal, is sufficiently heated,
+the carbon unites itself with great violence to the oxygen of the
+atmosphere and forms a peculiar gas, carbonic acid, the same which we
+see foaming from beer and champagne. By this combination, light and
+heat are generated; heat is generally developed by any combination
+of two bodies of strong affinity for each other; and when the heat
+is intense enough, light appears. Hence, in the steam engine, it is
+chemical processes and chemical forces which produce the astonishing
+work of these machines. In like manner the combustion of gunpowder is a
+chemical process which, in the barrel of the gun, communicates living
+force to the bullet.
+
+While now the steam engine develops for us mechanical work out of
+heat, we can conversely generate heat by mechanical forces. A skilful
+blacksmith can render an iron wedge red hot by hammering. The axes of
+our carriages must be protected, by careful greasing, from ignition
+through friction. Even lately this property has been applied on a large
+scale. In some factories, where a surplus of water power is at hand,
+this surplus is applied to cause a strong iron plate to rotate swiftly
+upon another, so that they become strongly heated by friction. The heat
+so obtained warms the room, and thus a stove without fuel is provided.
+Now, could not the heat generated by the plates be applied to a small
+steam engine, which in its turn should be able to keep the rubbing
+plates in motion? The perpetual motion would thus be at length found.
+This question might be asked, and could not be decided by the older
+mathematico-mechanical investigations. I will remark, beforehand, that
+the general law which I will lay before you answers the question in the
+negative.
+
+By a similar plan, however, a speculative American set some time ago
+the industrial world of Europe in excitement. The magneto-electric
+machines often made use of in the case of rheumatic disorders are well
+known to the public. By imparting a swift rotation to the magnet of
+such a machine, we obtain powerful currents of electricity. If those
+be conducted through water, the latter will be reduced into its two
+components, oxygen and hydrogen. By the combustion of hydrogen, water
+is again generated. If this combustion takes place, not in atmospheric
+air, of which oxygen only constitutes a fifth part, but in pure oxygen,
+and if a bit of chalk be placed in the flame, the chalk will be raised
+to a white heat, and give us the sun-like Drummond’s light. At the same
+time, the flame develops a considerable quantity of heat. Our American
+proposed to utilize in this way the gases obtained from electrolytic
+decomposition, and asserted that by the combustion a sufficient amount
+of heat was generated to keep a small steam engine in action, which
+again drove his magneto-electric machine, decomposed the water, and
+thus continually prepared its own fuel. This would certainly have been
+the most splendid of all discoveries; a perpetual motion which, besides
+the force which kept it going, generated light like the sun, and
+warmed all around it. The matter was by no means badly cogitated. Each
+practical step in the affair was known to be possible; but those who at
+that time were acquainted with the physical investigations which bear
+upon this subject could have affirmed, on first hearing the report,
+that the matter was to be numbered among the numerous stories of the
+fable-rich America; and indeed a fable it remained.
+
+It is not necessary to multiply examples further. You will infer from
+those given, in what immediate connection heat, electricity, magnetism,
+light, and chemical affinity, stand with mechanical forces.
+
+Starting from each of these different manifestations of natural forces
+we can set every other in motion, for the most part not in one way
+merely, but in many ways. It is here as with the weaver’s web--
+
+ Where a step stirs a thousand threads
+ The shuttles shoot from side to side,
+ The fibres flow unseen,
+ And one shock strikes a thousand combinations.
+
+Now it is clear that if by any means we could succeed, as the above
+American professed to have done, by mechanical forces, to excite
+chemical, electrical, or other natural processes, which, by any circuit
+whatever, and without altering permanently the active masses in the
+machine, could produce mechanical force in greater quantity than that
+at first applied, a portion of the work thus gained might be made use
+of to keep the machine in motion, while the rest of the work might be
+applied to any other purpose whatever. The problem was, to find in
+the complicated net of reciprocal actions, a track through chemical,
+electrical, magnetical, and thermic processes, back to mechanical
+actions, which might be followed with a final gain of mechanical work;
+thus would the perpetual motion be found.
+
+But, warned by the futility of former experiments, the public had
+become wiser. On the whole, people did not seek much after combinations
+which promised to furnish a perpetual motion, but the question was
+inverted. It was no more asked, how can I make use of the known and
+unknown relations of natural forces so as to construct a perpetual
+motion? but it was asked, if a perpetual motion be impossible, what are
+the relations which must subsist between natural forces? Everything
+was gained by this inversion of the question. The relations of natural
+forces rendered necessary by the above assumption, might be easily
+and completely stated. It was found that all known relations of force
+harmonize with the consequences of that assumption, and a series of
+unknown relations were discovered at the same time, the correctness of
+which remained to be proved. If a single one of them could be proved
+false, then a perpetual motion would be possible.
+
+The first who endeavoured to travel this way was a Frenchman, named
+Carnot, in the year 1824. In spite of a too limited conception of
+his subject, and an incorrect view as to the nature of heat, which
+led him to some erroneous conclusions, his experiment was not quite
+unsuccessful. He discovered a law which now bears his name, and to
+which I will return further on.
+
+His labors remained for a long time without notice, and it was not
+till eighteen years afterwards, that is, in 1842, that different
+investigators in different countries, and independent of Carnot, laid
+hold of the same thought.
+
+The first who saw truly the general law here referred to, and expressed
+it correctly, was a German physician, J. R. Mayer, of Heilbronn,
+in the year 1842. A little later, in 1843, a Dane, named Colding,
+presented a memoir to the Academy of Copenhagen, in which the same law
+found utterance, and some experiments were described for its further
+corroboration. In England, Joule began about the same time to make
+experiments having reference to the same subject. We often find, in the
+case of questions to the solution of which the development of science
+points, that several heads, quite independent of each other, generate
+exactly the same series of reflections.
+
+I myself, without being acquainted with either Mayer or Colding, and
+having first made the acquaintance of Joule’s experiments at the end of
+my investigation, followed the same path. I endeavoured to ascertain
+all the relations between the different natural processes, which
+followed from our regarding them from the above point of view. My
+inquiry was made public in 1847, in a small pamphlet bearing the title,
+“On the Conservation of Force.”
+
+Since that time the interest of the scientific public for this subject
+has gradually augmented. A great number of the essential consequences
+of the above manner of viewing the subject, the proof of which was
+wanting when the first theoretic notions were published, have since
+been confirmed by experiment, particularly by those of Joule; and
+during the last year the most eminent physicist of France, Regnault,
+has adopted the new mode regarding the question, and by fresh
+investigations on the specific heat of gases has contributed much to
+its support. For some important consequences the experimental proof
+is still wanting, but the number of confirmations is so predominant,
+that I have not deemed it too early to bring the subject before even a
+non-scientific audience.
+
+How the question has been decided you may already infer from what has
+been stated. In the series of natural processes there is no circuit
+to be found, by which mechanical force can be gained without a
+corresponding consumption. The perpetual motion remains impossible. Our
+reflections, however, gain thereby a higher interest.
+
+We have thus far regarded the development of force by natural
+processes, only in its relation to its usefulness to man, as mechanical
+force. You now see that we have arrived at a general law, which holds
+good wholly independent of the application which man makes of natural
+forces; we must therefore make the expression of our new law correspond
+to this more general significance. It is in the first place clear, that
+the work which, by any natural process whatever, is performed under
+favourable conditions by a machine, and which may be measured in the
+way already indicated, may be used as a measure of force common to
+all. Further, the important question arises, “If the quantity of force
+cannot be augmented except by corresponding consumption, can it be
+diminished or lost?” For the purpose of our machines it certainly can,
+if we neglect the opportunity to convert natural processes to use, but
+as investigation has proved, not for a nature as a whole.
+
+In the collision and friction of bodies against each other, the
+mechanics of former years assumed simply that living force was lost.
+But I have already stated that each collision and each act of friction
+generates heat; and, moreover, Joule has established by experiment
+the important law that for every foot-pound of force which is lost a
+definite quantity of heat is always generated, and that when work is
+performed by the consumption of heat, for each foot-pound thus gained
+a definite quantity of heat disappears. The quantity of heat necessary
+to raise the temperature of a pound of water a degree of the centigrade
+thermometer, corresponds to a mechanical force by which a pound weight
+would be raised to the height of 1350 feet; we name this quantity the
+mechanical equivalent of heat. I may mention here that these facts
+conduct of necessity to the conclusion, that the heat is not, as was
+formerly imagined, a fine imponderable substance, but that, like
+light, it is a peculiar shivering motion of the ultimate particles of
+bodies. In collision and friction, according to this manner of viewing
+the subject, the motion of the mass of a body which is apparently lost
+is converted into a motion of the ultimate particles of the body; and
+conversely, when mechanical force is generated by heat, the motion of
+the ultimate particles is converted into a motion of the mass.
+
+Chemical combinations generate heat, and the quantity of this heat is
+totally independent of the time and steps through which the combination
+has been effected, provided that other actions are not at the same
+time brought into play. If, however, mechanical work is at the same
+time accomplished, as in the case of the steam engine, we obtain as
+much less heat as is equivalent to this work. The quantity of work
+produced by chemical force is in general very great. A pound of the
+purest coal gives when burnt, sufficient heat to raise the temperature
+of 8086 pounds of water one degree of the centigrade thermometer; from
+this we can calculate that the magnitude of the chemical force of
+attraction between the particles of a pound of coal and the quantity
+of oxygen that corresponds to it is capable of lifting a weight of one
+hundred pounds to a height of twenty miles. Unfortunately, in our steam
+engines, we have hitherto been able to gain only the smallest portion
+of this work; the greater part is lost in the shape of heat. The best
+expansive engines give back as mechanical work only eighteen per cent.
+of the heat generated by the fuel.
+
+From a similar investigation of all the other known physical and
+chemical processes, we arrive at the conclusion that Nature as a whole
+possesses a store of force which cannot in any way be either increased
+or diminished. And that, therefore, the quantity of force in Nature is
+just as eternal and unalterable as the quantity of matter. Expressed
+in this form, I have named the general law “The Principle of the
+Conservation of Force.”
+
+We cannot create mechanical force, but we may help ourselves from the
+general store-house of Nature. The brook and the wind, which drive our
+mills, the forest and the coal-bed, which supply our steam engines and
+warm our rooms, are to us the bearers of a small portion of the great
+natural supply which we draw upon for our purposes, and the actions of
+which we can apply as we think fit. The possessor of a mill claims the
+gravity of the descending rivulet, or the living force of the moving
+wind, as his possession. These portions of the store of Nature are what
+give his property its chief value.
+
+Further, from the fact that no portion of force can be absolutely lost,
+it does not follow that a portion may not be inapplicable to human
+purposes. In this respect the inferences drawn by William Thomson from
+the law of Carnot are of importance. This law, which was discovered
+by Carnot during his endeavours to ascertain the relations between
+heat and mechanical force, which, however, by no means belongs to the
+necessary consequences of the conservation of force, and which Clausius
+was the first to modify in such a manner that it no longer contradicted
+the above general law, expresses a certain relation between the
+compressibility, the capacity for heat, and the expansion by heat of
+all bodies. It is not yet considered as actually proved, but some
+remarkable deductions having been drawn from it, and afterwards proved
+to be facts by experiment, it has attained thereby a great degree
+of probability. Besides the mathematical form in which the law was
+first expressed by Carnot, we can give it the following more general
+expression:--“Only, when heat passes from a warmer to a colder body,
+and even then only partially, can it be converted into mechanical work.”
+
+The heat of a body which we cannot cool further, cannot be changed
+into another form of force; into the electric or chemical force, for
+example. Thus, in our steam engines, we convert a portion of the heat
+of the glowing coal into work, by permitting it to pass to the less
+warm water of the boiler. If, however, all the bodies in nature had
+the same temperature, it would be impossible to convert any portion of
+their heat into mechanical work. According to this, we can divide the
+total force store of the universe into two parts, one of which is heat,
+and must continue to be such; the other, to which a portion of the heat
+of the warmer bodies, and the total supply of chemical, mechanical,
+electrical, and magnetical forces belong, is capable of the most varied
+changes of form, and constitutes the whole wealth of change which takes
+place in nature.
+
+But the heat of the warmer bodies strives perpetually to pass to
+bodies less warm by radiation and conduction, and thus to establish
+an equilibrium of temperature. At each motion of a terrestrial body,
+a portion of mechanical force passes by friction or collision into
+heat, of which only a part can be converted back again into mechanical
+force. This is also generally the case in every electrical and chemical
+process. From this, it follows that the first portion of the store of
+force, the unchangeable heat, is augmented by every natural process,
+while the second portion, mechanical, electrical, and chemical force,
+must be diminished; so that if the universe be delivered over to
+the undisturbed action of its physical processes, all force will
+finally pass into the form of heat, and all heat come into a state of
+equilibrium. Then all possibility of a further change would be at an
+end, and the complete cessation of all natural processes must set in.
+The life of men, animals, and plants, could not of course continue if
+the sun had lost its high temperature, and with it his light,--if all
+the components of the earth’s surface had closed those combinations
+which their affinities demand. In short, the universe from that time
+forward would be condemned to a state of eternal rest.
+
+These consequences of the law of Carnot are, of course, only valid,
+provided that the law, when sufficiently tested, proves to be
+universally correct. In the mean time there is little prospect of the
+law being proved incorrect. At all events we must admire the sagacity
+of Thomson, who, in the letters of a long known little mathematical
+formula, which only speaks of the heat, volume, and pressure of bodies,
+was able to discern consequences which threatened the universe, though
+certainly after an infinite period of time, with eternal death.
+
+I have already given you notice that our path lay through a thorny and
+unrefreshing field of mathematico-mechanical developments. We have
+now left this portion of our road behind us. The general principle
+which I have sought to lay before you has conducted us to a point from
+which our view is a wide one, and aided by this principle, we can now
+at pleasure regard this or the other side of the surrounding world,
+according as our interest in the matter leads us. A glance into the
+narrow laboratory of the physicist, with its small appliances and
+complicated abstractions, will not be so attractive as a glance at the
+wide heaven above us, the clouds, the rivers, the woods, and the living
+beings around us. While regarding the laws which have been deduced
+from the physical processes of terrestrial bodies, as applicable also
+to the heavenly bodies, let me remind you that the same force which,
+acting at the earth’s surface, we call gravity (_Schwere_), acts
+as gravitation in the celestial spaces, and also manifests its power in
+the motion of the immeasurably distant double stars which are governed
+by exactly the same laws as those subsisting between the earth and
+moon; that, therefore, the light and heat of terrestrial bodies do not
+in any way differ essentially from those of the sun, or of the most
+distant fixed star; that the meteoric stones which sometimes fall from
+external space upon the earth are composed of exactly the same simple
+chemical substances as those with which we are acquainted. We need,
+therefore, feel no scruple in granting that general laws to which all
+terrestrial natural processes are subject, are also valid for other
+bodies than the earth. We will, therefore, make use of our law to
+glance over the household of the universe with respect to the store of
+force, capable of action, which it possesses.
+
+A number of singular peculiarities in the structure of our planetary
+system indicate that it was once a connected mass with a uniform
+motion of rotation. Without such an assumption, it is impossible to
+explain why all the planets move in the same direction round the sun,
+why they all rotate in the same direction round their axes, why the
+planes of their orbits, and those of their satellites and rings all
+nearly coincide, why all their orbits differ but little from circles;
+and much besides. From these remaining indications of a former state,
+astronomers have shaped an hypothesis regarding the formation of our
+planetary system, which, although from the nature of the case it must
+ever remain an hypothesis, still in its special traits is so well
+supported by analogy, that it certainly deserves our attention. It
+was Kant who, feeling great interest in the physical description of
+the earth and the planetary system, undertook the labour of studying
+the works of Newton, and as an evidence of the depth to which he had
+penetrated into the fundamental ideas of Newton, seized the notion
+that the same attractive force of all ponderable matter which now
+supports the motion of the planets, must also aforetime have been able
+to form from matter loosely scattered in space the planetary system.
+Afterwards, and independent of Kant, Laplace, the great author of the
+_Mecanique Celeste_, laid hold of the same thought, and introduced
+it among astronomers.
+
+The commencement of our planetary system, including the sun, must,
+according to this, be regarded as an immense nebulous mass which filled
+the portion of space which is now occupied by our system, far beyond
+the limits of Neptune, our most distant planet. Even now we perhaps
+see similar masses in the distant regions of the firmament, as patches
+of nebulæ, and nebulous stars; within our system also, comets, the
+zodiacal light, the corona of the sun during a total eclipse, exhibit
+remnants of a nebulous substance, which is so thin that the light
+of the stars passes through it unenfeebled and unrefracted. If we
+calculate the density of the mass of our planetary system, according to
+the above assumption, for the time when it was a nebulous sphere, which
+reached to the path of the outmost planet, we should find that it would
+require several cubic miles of such matter to weigh a single grain.
+
+The general attractive force of all matter must, however, impel these
+masses to each other, and to condense, so that the nebulous sphere
+became incessantly smaller, by which, according to mechanical laws, a
+motion of rotation originally slow, and the existence of which must be
+assumed, would gradually become quicker and quicker. By the centrifugal
+force which must act most energetically in the neighbourhood of the
+equator of the nebulous sphere, masses could from time to time be torn
+away, which afterwards would continue their courses separate from the
+main mass, forming themselves into single planets, or, similar to the
+great original sphere, into planets with satellites and rings, until
+finally the principal mass condensed itself into the sun. With regard
+to the origin of heat and light, this view gives us no information.
+
+When the nebulous chaos first separated itself from other fixed star
+masses, it must not only have contained all kinds of matter which was
+to constitute the future planetary system, but also, in accordance
+with our new law, the whole store of force which at one time must
+unfold therein its wealth of actions. Indeed in this respect an immense
+dower was bestowed in the shape of the general attraction of all the
+particles for each other. This force, which on the earth exerts itself
+as gravity, acts in the heavenly spaces as gravitation. As terrestrial
+gravity when it draws a weight downwards performs work and generates
+_vis viva_, so also the heavenly bodies do the same when they draw
+two portions of matter from distant regions of space towards each other.
+
+The chemical forces must have been also present, ready to act; but as
+these forces can only come into operation by the most intimate contact
+of the different masses, condensation must have taken place before the
+play of chemical forces began.
+
+Whether a still further supply of force in the shape of heat was
+present at the commencement we do not know. At all events, by aid of
+the law of the equivalence of heat and work, we find in the mechanical
+forces, existing at the time to which we refer, such a rich source of
+heat and light, that there is no necessity whatever to take refuge in
+the idea of a store of these forces originally existing. When through
+condensation of the masses their particles came into collision,
+and clung to each other, the _vis viva_ of their motion would
+be thereby annihilated, and must reappear as heat. Already in old
+theories, it has been calculated that cosmical masses must generate
+heat by their collision, but it was far from anybody’s thought to make
+even a guess at the amount of heat to be generated in this way. At
+present we can give definite numerical values with certainty.
+
+Let us make this addition to our assumption; that, at the commencement,
+the density of the nebulous matter was a vanishing quantity, as
+compared with the present density of the sun and planets; we can then
+calculate how much work has been performed by the condensation; we can
+further calculate how much of this work still exists in the form of
+mechanical force, as attraction of the planets towards the sun, and as
+_vis viva_ of their motion, and find by this how much of the force
+has been converted into heat.
+
+The result of this calculation is, that only about the 454th part
+of the original mechanical force remains as such, and that the
+remainder, converted into heat, would be sufficient to raise a mass
+of water equal to the sun and planets taken together, not less than
+twenty-eight millions of degrees of the centigrade scale. For the
+sake of comparison, I will mention that the highest temperature which
+we can produce by the oxyhydrogen blowpipe, which is sufficient to
+fuse and vaporize even platina, and which but few bodies can endure,
+is estimated at about two thousand centigrade degrees. Of the action
+of a temperature of twenty-eight millions of such degrees we can
+form no notion. If the mass of our entire system were pure coal,
+by the combustion of the whole of it only the 3500th part of the
+above quantity would be generated. This is also clear, that such a
+development of heat must have presented the greatest obstacle to the
+speedy union of the masses, that the larger part of the heat must have
+been diffused by radiation into space, before the masses could form
+bodies possessing the present density of the sun and planets, and that
+these bodies must once have been in a state of fiery fluidity. This
+notion is corroborated by the geological phenomena of our planet; and
+with regard to the other planetary bodies, the flattened form of the
+sphere, which is the form of equilibrium of a fluid mass, is indicative
+of a former state of fluidity. If I thus permit an immense quantity of
+heat to disappear without compensation from our system, the principle
+of the conservation of force is not thereby invaded. Certainly for our
+planet it is lost, but not for the universe. It has proceeded outwards,
+and daily proceeds outwards into infinite space; and we know not
+whether the medium which transmits the undulations of light and heat
+possesses an end where the rays must return, or whether they eternally
+pursue their way through infinitude.
+
+The store of force at present possessed by our system, is also
+equivalent to immense quantities of heat. If our earth were by a sudden
+shock brought to rest on her orbit--which is not to be feared in the
+existing arrangements of our system--by such a shock a quantity of heat
+would be generated equal to that produced by the combustion of fourteen
+such earths of solid coal. Making the most unfavourable assumption as
+to its capacity for heat, that is, placing it equal to that of water,
+the mass of the earth would thereby be heated 11,200 degrees; it would
+therefore be quite fused and for the most part reduced to vapour. If,
+then, the earth, after having been thus brought to rest, should fall
+into the sun, which of course would be the case, the quantity of heat
+developed by the shock would be four hundred times greater.
+
+Even now, from time to time, such a process is repeated on a small
+scale. There can hardly be a doubt that meteors, fire-balls, and
+meteoric stones are masses which belong to the universe, and before
+coming into the domain of our earth, moved like the planets round the
+sun. Only when they enter our atmosphere do they become visible and
+fall sometimes to the earth. In order to explain the emission of light
+by these bodies, and the fact that for some time after their descent
+they are very hot, the friction was long ago thought of which they
+experience in passing through the air. We can now calculate that a
+velocity of 3,000 feet a second, supposing the whole of the friction
+to be expended in heating the solid mass, would raise a piece of
+meteoric iron 1,000° C. in temperature, or, in other words, to a vivid
+red heat. Now the average velocity of the meteors seems to be thirty or
+forty times the above amount. To compensate this, however, the greater
+portion of the heat is, doubtless, carried away by the condensed mass
+of air which the meteor drives before it. It is known that bright
+meteors generally leave a luminous trail behind them, which probably
+consists of several portions of the red-hot surfaces. Meteoric masses
+which fall to the earth often burst with a violent explosion, which
+may be regarded as a result of the quick heating. The newly-fallen
+pieces have been for the most part found hot, but not red-hot, which
+is easily explainable by the circumstances, that during the short time
+occupied by the meteor in passing through the atmosphere, only a thin,
+superficial layer is heated to redness, while but a small quantity of
+heat has been able to penetrate to the interior of the mass. For this
+reason the red heat can speedily disappear.
+
+Thus has the falling of the meteoric stone, the minute remnant of
+processes which seems to have played an important part in the formation
+of the heavenly bodies, conducted us to the present time, where we
+pass from the darkness of hypothetical views to the brightness of
+knowledge. In what we have said, however, all that is hypothetical is
+the assumption of Kant and Laplace, that the masses of our system were
+once distributed as nebulæ in space.
+
+On account of the rarity of the case, we will still further remark,
+in what close coincidence the results of science here stand with the
+earlier legends of the human family, and the forebodings of poetic
+fancy. The cosmogony of ancient nations generally commences with chaos
+and darkness.
+
+Neither is the Mosaic tradition very divergent, particularly when we
+remember that that which Moses names heaven is different from the blue
+dome above us, and is synonymous with space, and that the unformed
+earth, and the waters of the great deep, which were afterwards divided
+into waters above the firmament, and waters below the firmament,
+resembled the chaotic components of the world.
+
+Our earth bears still the unmistakable traces of its old fiery fluid
+condition. The granite formations of her mountains exhibit a structure,
+which can only be produced by the crystallization of fused masses.
+Investigation still shows that the temperature in mines, and borings,
+increases as we descend; and if this increase is uniform, at the depth
+of fifty miles, a heat exists sufficient to fuse all our minerals. Even
+now our volcanoes project, from time to time, mighty masses of fused
+rocks from their interior, as a testimony of the heat which exists
+there. But the cooled crust of the earth has already become so thick,
+that, as may be shown by calculations of its conductive power, the heat
+coming to the surface from within, in comparison with that reaching the
+earth from the sun, is exceedingly small, and increases the temperature
+of the surface only about one-thirtieth of a degree centigrade; so that
+the remnant of the old store of force which is enclosed as heat within
+the bowels of the earth, has a sensible influence upon the processes
+at the earth’s surface, only through the instrumentality of volcanic
+phenomena. These processes owe their power almost wholly to the action
+of other heavenly bodies, particularly to the light and heat of the
+sun, and partly also, in the case of the tides, to the attraction of
+the sun and moon.
+
+Most varied and numerous are the changes which we owe to the light
+and heat of the sun. The sun heats our atmosphere irregularly, the
+warm rarefied air ascends, while fresh cool air flows from the sides
+to supply its place: in this way winds are generated. This action is
+most powerful at the equator, the warm air of which incessantly flows
+in the upper regions of the atmosphere towards the poles: while just
+as persistently, at the earth’s surface, the trade wind carries new
+and cool air to the equator. Without the heat of the sun all winds
+must, of necessity, cease. Similar currents are produced by the same
+cause in the waters of the sea. Their power may be inferred from the
+influence which in some cases they exert upon climate. By them the warm
+water of the Antilles is carried to the British Isles, and confers upon
+them a mild, uniform warmth and rich moisture; while, through similar
+causes, the floating ice of the North Pole is carried to the coast
+of Newfoundland, and produces cold. Further, by the heat of the sun,
+a portion of the water is converted into vapour which rises in the
+atmosphere, is condensed to clouds, or falls in rain and snow upon the
+earth, collects in the form of springs, brooks, and rivers, and finally
+reaches the sea again, after having gnawed the rocks, carried away the
+light earth, and thus performed its part in the geologic changes of the
+earth; perhaps, besides all this it has driven our water-mill upon its
+way. If the heat of the sun were withdrawn, there would remain only a
+single motion of water, namely, the tides, which are produced by the
+attraction of the sun and moon.
+
+How is it now, with the motions and the work of organic beings? To
+the builders of the automata of the last century, men and animals
+appeared as clockwork which was never wound up, and created the force
+which they exerted out of nothing. They did not know how to establish
+a connection between the nutriment consumed and the work generated.
+Since, however, we have learned to discern in the steam-engine this
+origin of mechanical force, we must inquire whether something similar
+does not hold good with regard to men. Indeed, the continuation of
+life is dependent on the consumption of nutritive materials: these
+are combustible substances, which, after digestion and being passed
+into the blood, actually undergo a slow combustion, and finally enter
+into almost the same combinations with the oxygen of the atmosphere
+that are produced in an open fire. As the quantity of heat generated
+by combustion is independent of the duration of the combustion and
+the steps in which it occurs, we can calculate from the mass of the
+consumed material how much heat, or its equivalent work is thereby
+generated in an animal body. Unfortunately, the difficulty of the
+experiments is still very great; but within those limits of accuracy
+which have been as yet attainable, the experiments show that the heat
+generated in the animal body corresponds to the amount which would be
+generated by the chemical processes. The animal body therefore does not
+differ from the steam-engine, as regards the manner in which it obtains
+heat and force, but does differ from it in the manner in which the
+force gained is to be made use of. The body is, besides, more limited
+than the machine in the choice of its fuel; the latter could be heated
+with sugar, with starch-flour, and butter, just as well as with coal
+or wood; the animal body must dissolve its materials artificially, and
+distribute them through its system; it must, further, perpetually renew
+the used-up materials of its organs, and as it cannot itself create
+the matter necessary for this, the matter must come from without.
+Liebig was the first to point out these various uses of the consumed
+nutriment. As material for the perpetual renewal of the body, it seems
+that certain definite albuminous substances which appear in plants, and
+form the chief mass of the animal body, can alone be used. They form
+only a portion of the mass of nutriment taken daily; the remainder,
+sugar, starch, fat, are really only materials for warming, and are
+perhaps not to be superseded by coal, simply because the latter does
+not permit itself to be dissolved.
+
+If, then, the processes in the animal body are not in this respect to
+be distinguished from inorganic processes, the question arises, whence
+comes the nutriment which constitutes the source of the body’s force?
+The answer is, from the vegetable kingdom; for only the material of
+plants, or the flesh of plant-eating animals, can be made use of for
+food. The animals which live on plants occupy a mean position between
+carnivorous animals, in which we reckon man, and vegetables, which
+the former could not make use of immediately as nutriment. In hay and
+grass the same nutritive substances are present as in meal and flour,
+but in less quantity. As, however, the digestive organs of man are not
+in a condition to extract the small quantity of the useful from the
+great excess of the insoluble, we submit, in the first place, these
+substances to the powerful digestion of the ox, permit the nourishment
+to store itself in the animal’s body, in order in the end to gain it
+for ourselves in a more agreeable and useful form. In answer to our
+question, therefore, we are referred to the vegetable world. Now when
+what plants take in and what they give out are made the subjects of
+investigation, we find that the principal part of the former consists
+in the products of combustion which are generated by the animal.
+They take the consumed carbon given off in respiration, as carbonic
+acid, from the air, the consumed hydrogen as water, the nitrogen in
+its simplest and closest combinations as ammonia; and from these
+materials, with the assistance of small ingredients which they take
+from the soil, they generate anew the compound combustible substances,
+albumen, sugar, oil, on which the animal subsists. Here, therefore,
+is a circuit which appears to be a perpetual store of force. Plants
+prepare fuel and nutriment, animals consume these, burn them slowly
+in their lungs, and from the products of combustion the plants again
+derive their nutriment. The latter is an eternal source of chemical,
+the former of mechanical forces. Would not the combination of both
+organic kingdoms produce the perpetual motion? We must not conclude
+hastily: further inquiry shows, that plants are capable of producing
+combustible substances only when they are under the influence of the
+sun. A portion of the sun’s rays exhibits a remarkable relation to
+chemical forces,--it can produce and destroy chemical combinations;
+and these rays, which for the most part are blue or violet, are called
+therefore chemical rays. We make use of their action in the production
+of photographs. Here compounds of silver are decomposed at the place
+where the sun’s rays strike them. The same rays overpower in the green
+leaves of plants the strong chemical affinity of the carbon of the
+carbonic acid for oxygen, give back the latter free to the atmosphere,
+and accumulate the other, in combination with other bodies, as woody
+fibre, starch, oil, or resin. These chemically active rays of the sun
+disappear completely as soon as they encounter the green portions of
+the plants, and hence it is that in daguerreotype images the green
+leaves of plants appear uniformly black. Inasmuch as the light coming
+from them does not contain the chemical rays, it is unable to act upon
+the silver compounds.
+
+Hence a certain portion of force disappears from the sunlight, while
+combustible substances are generated and accumulated in plants; and
+we can assume it as very probable, that the former is the cause of
+the latter. I must indeed remark, that we are in possession of no
+experiments from which we might determine whether the vis viva of the
+sun’s rays which have disappeared, corresponds to the chemical forces
+accumulated during the same time; and as long as these experiments are
+wanting, we cannot regard the stated relation as a certainty. If this
+view should prove correct, we derive from it the flattering result,
+that all force, by means of which our bodies live and move, finds
+its source in the purest sunlight; and hence we are all, in point
+of nobility, not behind the race of the great monarch of China, who
+heretofore alone called himself Son of the Sun. But it must also be
+conceded that our lower fellow-beings, the frog and leech, share the
+same ethereal origin, as also the whole vegetable world, and even the
+fuel which comes to us from the ages past, as well as the youngest
+offspring of the forest with which we heat our stoves and set our
+machines in motion.
+
+You see, then, that the immense wealth of ever-changing meteorological,
+climatic, geological, and organic processes of our earth are almost
+wholly preserved in action by the light and heat-giving rays of the
+sun; and you see in this a remarkable example, how Proteus-like the
+effects of a single cause, under altered external conditions, may
+exhibit itself in nature. Besides these, the earth experiences an
+action of another kind from its central luminary, as well as from its
+satellite the moon, which exhibits itself in the remarkable phenomenon
+of the ebb and flow of the tide.
+
+Each of these bodies excites, by its attraction upon the waters of the
+sea, two gigantic waves, which flow in the same direction round the
+world, as the attracting bodies themselves apparently do. The two waves
+of the moon, on account of her greater nearness, are about three and a
+half times as large as those excited by the sun. One of these waves has
+its crest on the quarter of the earth’s surface which is turned towards
+the moon, the other is at the opposite side. Both these quarters
+possess the flow of the tide, while the regions which lie between have
+the ebb. Although in the open sea the height of the tide amounts to
+only about three feet, and only in certain narrow channels, where the
+moving water is squeezed together, rises to thirty feet, the might of
+the phenomena is nevertheless manifest from the calculation of Bessel,
+according to which a quarter of the earth covered by the sea possesses,
+during the flow of the tide, about 25,000 cubic miles of water more
+than during the ebb, and that therefore such a mass of water must, in
+six and a quarter hours, flow from one quarter of the earth to the
+other.
+
+The phenomena of the ebb and flow, as already recognized by Mayer,
+combined with the law of the conservation of force, stand in remarkable
+connection with the question of the stability of our planetary system.
+The mechanical theory of the planetary motions discovered by Newton
+teaches, that if a solid body in absolute vacuo, attracted by the sun,
+move around him in the same manner as the planets, this motion will
+endure unchanged through all eternity.
+
+Now we have actually not only one, but several such planets, which
+move around the sun, and by their mutual attraction create little
+changes and disturbances in each other’s paths. Nevertheless Laplace,
+in his great work, the _Mecanique Celeste_, has proved that in
+our planetary system all these disturbances increase and diminish
+periodically, and can never exceed certain limits, so that by this
+cause the external existence of the planetary system is unendangered.
+
+But I have already named two assumptions which must be made: first,
+that the celestial spaces must be absolutely empty; and secondly, that
+the sun and planets must be solid bodies. The first is at least the
+case as far as astronomical observations reach, for they have never
+been able to detect any retardation of the planets, such as would
+occur if they moved in a resisting medium. But on a body of less mass,
+the comet of Encke, changes are observed of such a nature: this comet
+describes ellipses round the sun which are becoming gradually smaller.
+If this kind of motion, which certainly corresponds to that through a
+resisting medium, be actually due to the existence of such a medium,
+a time will come when the comet will strike the sun; and a similar
+end threatens all the planets, although after a time, the length of
+which baffles our imagination to conceive of it. But even should the
+existence of a resisting medium appear doubtful to us, there is no
+doubt that the planets are not wholly composed of solid materials which
+are inseparably bound together. Signs of the existence of an atmosphere
+are observed on the Sun, on Venus, Mars, Jupiter, and Saturn. Signs
+of water and ice upon Mars; and our earth has undoubtedly a fluid
+portion on its surface, and perhaps a still greater portion of fluid
+within it. The motions of the tides, however, produce friction, all
+friction destroys _vis viva_, and the loss in this case can only
+affect the _vis viva_ of the planetary system. We come thereby to
+the unavoidable conclusion, that every tide, although with infinite
+slowness, still with certainty, diminishes the store of mechanical
+force of the system; and as a consequence of this, the rotation of
+the planets in question round their axes must become more slow; they
+must therefore approach the sun, or their satellites must approach
+them. What length of time must pass before the length of our day is
+diminished one second by the action of the tide cannot be calculated,
+until the height and time of the tide in all portions of the ocean are
+known. This alteration, however, takes place with extreme slowness,
+as is known by the consequences which Laplace has deduced from the
+observations of Hipparchus, according to which, during a period of
+2000 years, the duration of the day has not been shortened by the
+one-three-hundredth part of a second. The final consequence would be,
+but after millions of years, if in the mean time the ocean did not
+become frozen, that one side of the earth would be constantly turned
+towards the sun, and enjoy a perpetual day, whereas the opposite side
+would be involved in eternal night. Such a position we observe in our
+moon with regard to the earth, and also in the case of the satellites
+as regards their planets; it is, perhaps, due to the action of the
+mighty ebb and flow to which these bodies, in the time of their fiery
+fluid condition, were subjected.
+
+I would not have brought forward these conclusions, which again
+plunge us in the most distant future, if they were not unavoidable.
+Physico-mechanical laws are, as it were, the telescopes of our
+spiritual eye, which can penetrate into the deepest night of time, past
+and to come.
+
+Another essential question as regards the future of our planetary
+system has reference to its future temperature and illumination.
+As the internal heat of the earth has but little influence on the
+temperature of the surface, the heat of the sun is the only thing which
+essentially affects the question. The quantity of heat falling from the
+sun during a given time upon a given portion of the earth’s surface
+may be measured, and from this it can be calculated how much heat in a
+given time is sent out from the entire sun. Such measurements have been
+made by the French physicist Pouillet, and it has been found that the
+sun gives out a quantity of heat per hour equal to that which a layer
+of the densest coal ten feet thick would give out by its combustion;
+and hence in a year a quantity equal to the combustion of a layer of
+seventeen miles. If this heat were drawn uniformly from the entire mass
+of the sun, its temperature would only be diminished thereby one and
+one-third of a degree centigrade per year, assuming its capacity for
+heat to be equal to that of water. These results can give us an idea of
+the magnitude of the emission, in relation to the surface and mass of
+the sun; but they cannot inform us whether the sun radiates heat as a
+glowing body, which since its formation has its heat accumulated within
+it, or whether a new generation of heat by chemical processes takes
+place at the sun’s surface. At all events the law of the conservation
+of force teaches us that no process analogous to those known at the
+surface of the earth, can supply for eternity an inexhaustible amount
+of light and heat to the sun. But the same law also teaches that the
+store of force at present existing, as heat, or as what may become
+heat, is sufficient for an immeasurable time. With regard to the store
+of chemical force in the sun, we can form no conjecture, and the
+store of heat there existing can only be determined by very uncertain
+estimations. If, however, we adopt the very probable view, that the
+remarkably small density of so large a body is caused by its high
+temperature, and may become greater in time, it may be calculated that
+if the diameter of the sun were diminished only the ten-thousandth
+part of its present length, by this act a sufficient quantity of heat
+would be generated to cover the total emission for 2100 years. Such a
+small change besides it would be difficult to detect even by the finest
+astronomical observations.
+
+Indeed, from the commencement of the period during which we possess
+historic accounts, that is, for a period of about 4000 years, the
+temperature of the earth has not sensibly diminished. From these old
+ages we have certainly no thermometric observations, but we have
+information regarding the distribution of certain cultivated plants,
+the vine, the olive tree, which are very sensitive to changes of the
+mean annual temperature, and we find that these plants at the present
+moment have the same limits of distribution that they had in the times
+of Abraham and Homer; from which we may infer backwards the constancy
+of the climate.
+
+In opposition to this it has been urged, that here in Prussia the
+German knights in former times cultivated the vine, cellared their
+own wine and drank it, which is no longer possible. From this the
+conclusion has been drawn, that the heat of our climate has diminished
+since the time referred to. Against this, however, Dove has cited the
+reports of ancient chroniclers, according to which, in some peculiarly
+hot years, the Prussian grape possessed somewhat less than its usual
+quantity of acid. The fact also speaks not so much for the climate of
+the country as for the throats of the German drinkers.
+
+But even though the force store of our planetary system is so immensely
+great, that by the incessant emission which has occurred during the
+period of human history it has not been sensibly diminished, even
+though the length of the time which must flow by, before a sensible
+change in the state of our planetary system occurs, is totally
+incapable of measurement, still the inexorable laws of mechanics
+indicate that this store of force, which can only suffer loss and not
+gain, must be finally exhausted. Shall we terrify ourselves by this
+thought? Men are in the habit of measuring the greatness and the wisdom
+of the universe by the duration and the profit which it promises to
+their own race; but the past history of the earth already shows what
+an insignificant moment the duration of the existence of our race
+upon it constitutes. A Nineveh vessel, a Roman sword awakes in us the
+conception of grey antiquity. What the museums of Europe show us of the
+remains of Egypt and Assyria we gaze upon with silent astonishment, and
+despair of being able to carry our thoughts back to a period so remote.
+Still must the human race have existed for ages, and multiplied itself
+before the pyramids of Nineveh could have been erected. We estimate the
+duration of human history at 6000 years; but immeasurable as this time
+may appear to us, what is it in comparison with the time during which
+the earth carried successive series of rank plants and mighty animals,
+and no men; during which in our neighbourhood the amber-tree bloomed,
+and dropped its costly gum on the earth and in the sea; when in
+Siberia, Europe and North America groves of tropical palms flourished;
+where gigantic lizards, and after them elephants, whose mighty remains
+we still find buried in the earth, found a home? Different geologists,
+proceeding from different premises, have sought to estimate the
+duration of the above creative period, and vary from a million to nine
+million years. And the time during which the earth generated organic
+beings is again small when we compare it with the ages during which the
+world was a ball of fused rocks. For the duration of its cooling from
+2000° to 200° centigrade, the experiments of Bishop upon basalt show
+that about 350 millions of years would be necessary. And with regard
+to the time during which the first nebulous mass condensed into our
+planetary system, our most daring conjectures must cease. The history
+of man, therefore, is but a short ripple in the ocean of time. For a
+much longer series of years than that during which man has already
+occupied this world, the existence of the present state of inorganic
+nature favourable to the duration of man seems to be secured, so that
+for ourselves and for long generations after us, we have nothing
+to fear. But the same forces of air and water, and of the volcanic
+interior, which produced former geological revolutions, and buried one
+series of living forms after another, act still upon the earth’s crust.
+They more probably will bring about the last day of the human race than
+those distant cosmical alterations of which we have spoken, and perhaps
+force us to make way for new and more complete living forms, as the
+lizards and the mammoth have given place to us and our fellow-creatures
+which now exist.
+
+Thus the thread which was spun in darkness by those who sought a
+perpetual motion has conducted us to a universal law of nature, which
+radiates light into the distant nights of the beginning and of the
+end of the history of the universe. To our own race it permits a long
+but not an endless existence; it threatens it with a day of judgment,
+the dawn of which is still happily obscured. As each of us singly
+must endure the thought of his death, the race must endure the same.
+But above the forms of life gone by, the human race has higher moral
+problems before it, the bearer of which it is, and in the completion of
+which it fulfils its destiny.
+
+
+FOOTNOTES:
+
+[Footnote 34: Translated from _Über die Erhaltung der Kraft_
+(Berlin, 1847).]
+
+
+
+
+ XXXII
+
+ LOUIS PASTEUR
+
+ 1822-1895
+
+
+ _Louis Pasteur was born at Dôle, France, December 27, 1822, the son
+ of a tanner. Educated at Arbois, Besançon, and the École Normale,
+ he was appointed assistant professor of chemistry at the last-named
+ institution. His first important work was in demonstrating the
+ asymmetry of molecules. In 1863 he investigated fermentation and showed
+ that it was caused by the growth of bacteria and later proved that it
+ was also the cause of putrefaction, a suggestion which Lister employed
+ in developing antiseptic surgery. In 1865 Pasteur discovered the
+ bacillus which caused the silkworm disease. Taking up the principle of
+ inoculation he applied it to small-pox and later extended it to other
+ infectious diseases. He died September 28, 1895._
+
+
+ INOCULATION FOR HYDROPHOBIA[35]
+
+Gentlemen:--Your Congress meetings are the place for the discussion
+of the gravest problems of medicine; they serve also to point out the
+great landmarks of the future. Three years ago, on the eve of the
+London Congress, the doctrine of micro-organisms, the ætiological cause
+of transmissible maladies, was still the subject of sharp criticisms.
+Certain refractory minds continued to uphold the idea that “disease is
+in us, from us, by us.”
+
+It was expected that the decided supporters of the theory of the
+spontaneity of diseases would make a bold stand in London; but no
+opposition was made to the doctrine of “exteriority,” or external
+causes, the first cause of contagious diseases, and those questions
+were not discussed at all.
+
+It was there seen, once again, that when all is ready for the final
+triumph of truth, the united conscience of a great assembly feels it
+instinctively and recognises it.
+
+All clear-sighted minds had already foreseen that the theory of the
+spontaneity of diseases received its death-blow on the day when it
+became possible reasonably to consider the spontaneous generation of
+microscopic organisms as a myth, and when, on the other hand, the
+life-activity of those same beings was shown to be the main cause of
+organic decomposition and of all fermentation.
+
+From the London Congress, also, dates the recognition of another very
+hopeful progress; we refer to the attenuation of different viruses,
+to the production of varying degrees of virulence for each virus, and
+their preservation by suitable methods of cultivation; to the practical
+application, finally, of those new facts in animal medicine.
+
+New microbic prophylactic viruses have been added to those of
+fowl-cholera and of splenic fever. The animals saved from death by
+contagious diseases are now counted by hundreds of thousands, and the
+sharp opposition which those scientific novelties met with at the
+beginning was soon swept away by the rapidity of their onward progress.
+
+Will the circle of practical applications of those new notions be
+limited in future to the prophylaxis of animal distempers? We must
+never think little of a new discovery, nor despair of its fecundity;
+but more than that, in the present instance, it may be asserted that
+the question is already solved in principle. Thus, splenic fever is
+common to animals and man, and we make bold to declare that, were it
+necessary to do so, nothing could be easier than to render man also
+proof against that affection. The process which is employed for animals
+might, almost without a change, be applied to him also. It would simply
+become advisable to act with an amount of prudence which the value of
+the life of an ox or a sheep does not call for. Thus, we should use
+three or four vaccine-viruses instead of two, of progressive intensity
+of virulence, and choose the first ones so weak that the patient
+should never be exposed to the slightest morbid complication, however
+susceptible to the disease he might be by his constitution.
+
+The difficulty, then, in the case of human diseases, does not lie in
+the application of the new method of prophylaxis, but rather in the
+knowledge of the physiological properties of their viruses. All our
+experiments must tend to discover the proper degree of attenuation
+for each virus. But experimentation, if allowable on animals, is
+criminal on man. Such is the principal cause of the complication of
+researches bearing on diseases exclusively human. Let us keep in mind,
+nevertheless, that the studies of which we are speaking were born
+yesterday only, that they have already yielded valuable results, and
+that new ones may be fairly expected when we shall have gone deeper
+into the knowledge of animal maladies, and of those in particular which
+affect animals in common with man.
+
+The desire to penetrate farther forward in that double study led me to
+choose rabies as the subject of my researches, in spite of the darkness
+in which it was veiled.
+
+The study of rabies was begun in my laboratory four years ago, and
+pursued since then without other interruption than what was inherent
+to the nature of the researches themselves, which present certain
+unfavourable conditions. The incubation of the disease is always
+protracted, the space disposed of is never sufficient, and it thus
+becomes impossible at a given moment to multiply the experiments as
+one would like. Notwithstanding those material obstacles, lessened by
+the interest taken by the French Government in all questions of great
+scientific interest, we now no longer count the experiments which we
+have made, my fellow workers and myself. I shall limit myself to-day to
+an exposition of our latest acquisitions.
+
+The name alone of a disease, and of rabies above all others, at once
+suggests to the mind the notion of a remedy.
+
+But it will, in the majority of cases, be labour lost to aim in the
+first instance at discovering a mode of cure. It is, in a manner,
+leaving all progress to chance. Far better to endeavour to acquaint
+oneself, first of all, with the nature, the cause, and the evolution of
+the disease, with a glimmering hope, perhaps, of finally arriving at
+its prophylaxis.
+
+To this last method we are indebted for the result that rabies is no
+longer to-day to be considered as an insoluble riddle.
+
+We have found that the virus of rabies develops itself invariably in
+the nervous system, brain, and spinal cord, in the nerves, and in the
+salivary glands; but it is not present at the same moment in every
+one of those parts. It may, for example, develop itself at the lower
+extremity of the spinal cord, and only after a time reach the brain.
+It may be met with at one or at several points of the encephalon whilst
+being absent at certain other points of the same region.
+
+If an animal is killed whilst in the power of rabies, it may require
+a pretty long search to discover the presence here or there in the
+nervous system, or in the glands, of the virus of rabies. We have been
+fortunate enough to ascertain that in all cases, when death has been
+allowed to supervene naturally, the swelled-out portion, or bulb, of
+the medulla oblongata nearest to the brain, and uniting the spinal
+cord with it, is always rabid. When an animal has died of rabies (and
+the disease always ends in death), rabid matter can with certainty be
+obtained from its bulb, capable of reproducing the disease in other
+animals when inoculated into them, after trephining, in the arachnoid
+space of the cerebral meninges.
+
+Any street dog whatsoever, inoculated in the manner described with
+portions of the bulb of an animal which has died of rabies, will
+certainly develop the same disease. We have thus inoculated several
+hundreds of dogs brought without any choice from the pound. Never once
+was the inoculation a failure. Similarly also, with uniform success,
+several hundred guinea-pigs, and rabbits more numerous still.
+
+Those two great results, the constant presence of the virus in the
+bulb at the time of death, and the certainty of the reproduction
+of the disease by inoculation into the arachnoid space, stand out
+like experimental axioms, and their importance is paramount. Thanks
+to the precision of their application, and to the well-known daily
+repetition of those two criteria of our experiments, we have been
+able to move forward steadily and surely in that arduous study. But,
+however solid those experimental bases, they were, nevertheless,
+incapable in themselves of giving us the faintest notion as to some
+method of vaccination against rabies. In the present state of science
+the discovery of a method of vaccination against some virulent malady
+presupposes:
+
+1. That we have to deal with a virus capable of assuming diverse
+intensities, of which the weaker ones can be put to vaccinal or
+protective uses.
+
+2. That we are in possession of a method enabling us to reproduce those
+diverse degrees of virulence at will.
+
+At the present time, however, science is acquainted with one sort of
+rabies only--viz., dog rabies.
+
+Rabies, whether in dog, man, horse, ox, wolf, fox, etc., comes
+originally from the bite of a mad dog. It is never spontaneous,
+neither in the dog nor in any other animal. There are none seriously
+authenticated among the alleged cases of so-called spontaneous rabies,
+and I add that it is idle to argue that the first case of rabies of
+all must have been spontaneous. Such an argument does not solve the
+difficulty, and wantonly calls into question the as yet inscrutable
+problem of the origin of life. It would be quite as well, against the
+assertion that an oak tree always proceeded from another oak tree, to
+argue that the first of all oak trees that ever grew must have been
+produced spontaneously. Science, which knows itself, is well aware that
+it would be useless for her to discuss about the origin of things;
+she is aware that, for the present at any rate, that origin is placed
+beyond the ken of her investigations.
+
+In fine, then, the first question to be solved on our way towards the
+prophylaxis of rabies is that of knowing whether the virus of that
+malady is susceptible of taking on varying intensities, after the
+manner of the virus of fowl-cholera or of splenic fever.
+
+But in what way shall we ascertain the possible existence of varying
+intensities in the virus of rabies? By what standard shall we measure
+the strength of a virus which either fails completely or kills? Shall
+we have recourse to the visible symptoms of rabies? But those symptoms
+are extremely variable, and depend essentially on the particular point
+of the encephalon or of the spinal cord where the virus has in the
+first instance fixed and developed itself. The most caressing rabies,
+for such do exist, when inoculated into another animal of the same
+species, give rise to furious rabies of the intensest type.
+
+Might we then perhaps make use of the duration of incubation as a
+means of estimating the intensity of our virus? But what can be more
+changeful than the incubative period? Suppose a mad dog were to bite
+several sound dogs: one of them will take rabies in one month or six
+weeks, another after two or three months or more. Nothing, too, is more
+changeful than the length of incubation according to the different
+modes of inoculation. Thus, other circumstances the same, after bites
+or hypodermic inoculation rabies occasionally develops itself, and at
+other times aborts completely; but inoculations on the brain are never
+sterile, and give the disease after a relatively short incubation.
+
+It is possible, nevertheless, to gauge with sufficient accuracy the
+degree of intensity of our virus by means of the time of incubation,
+on condition that we make use exclusively of the intra-cranial mode
+of inoculation; and secondly, that we do away with one of the great
+disturbing influences inherent to the results of inoculation made
+by bites, under the skin or in the veins, by injecting the right
+proportion of material.
+
+The duration of incubation, as a matter of fact, may depend largely
+on the quantity of efficient virus--that is to say, on the quantity
+of virus which reaches the nervous system without diminution or
+modification. Although the quantity of virus capable of giving rabies
+may be, so to speak, infinitely small, as seen in the common fact of
+the disease developing itself after rabid bites which, as a rule,
+introduce into the system a barely appreciable weight of virus, it
+is easy to double the length of incubation by simply changing the
+proportion of those very small quantities of inoculated matter. I may
+quote the following examples:--
+
+On May 10, 1882, we injected into the popliteal vein of a dog ten drops
+of a liquid prepared by crushing a portion of the bulb of a dog, which
+had died of ordinary canine madness, in three or four times its volume
+of sterilised broth.
+
+Into a second dog we injected 1/100th of that quantity, into a third
+1/200th. Rabies showed itself in the first dog on the eighteenth day
+after the injection, on the thirty-fifth day in the second dog, whilst
+the third one did not take the disease at all, which means that, for
+the last animal, with the particular mode of inoculation employed, the
+quantity of virus injected was not sufficient to give rabies. And yet
+that dog, like all dogs, was susceptible of taking the disease, for it
+actually took it twenty-two days after a second inoculation, performed
+on September 3, 1882.
+
+I now take another example bearing on rabbits, and by a different mode
+of inoculation. This time, after trephining, the bulb of a rabbit
+which had died of rabies after inoculation of an extremely powerful
+virus is triturated and mixed with two or three times its volume of
+sterilised broth. The mixture is allowed to stand a little, and then
+two drops of the supernatant liquid are injected after trephining into
+a first rabbit, into a second rabbit one-fourth of that quantity, and
+in succession into other rabbits, 1/16th, 1/64th, 1/128th, and 1/152nd
+of that same quantity. All those rabbits died of rabies, the incubation
+having been eight days, nine and ten days for the third and fourth,
+twelve and sixteen days for the last ones.
+
+Those variations in the length of incubation were not the result of
+any weakening or diminution of the intrinsic virulence of the virus
+brought on possibly by its dilution, for the incubation of eight days
+was at once recovered when the nervous matter of all those rabbits was
+inoculated into new animals.
+
+Those examples show that, whenever rabies follows upon bites or
+hypodermic inoculations, the differences in respect of length of
+incubation must be chiefly ascribed to the variations, at times within
+considerable limits, of the ever-undeterminate proportions of the
+inoculated viruses which reach the central nervous system.
+
+If, therefore, we desire to make use of the length of incubation as a
+measure of the intensity of the virulence, it will be indispensable
+to have recourse to inoculation on the surface of the brain, after
+trephining, a process the action of which is absolutely certain,
+coupled with the use of a larger quantity of virus than what is
+strictly sufficient to give rise to rabies. By those means the
+irregularities in the length of incubation for the same virus tend to
+disappear completely, because we always have the maximum effect which
+that virus can produce; that maximum coincides with a minimum length of
+incubation.
+
+We have thus, finally, become possessed of a method enabling us to
+investigate the possible existence of different degrees of virulence,
+and to compare them with one another. The whole secret of the method,
+I repeat, consists in inoculating on the brain, after trephining, a
+quantity of virus which, although small in itself, is still greater
+than what is simply necessary to reproduce rabies. We thus disengage
+the incubation from all disturbing influences and render its duration
+dependent exclusively on the activity of the particular virus used,
+that activity being in each case estimated by the minimum incubation
+determined by it.
+
+This method was applied in the first instance to the study of canine
+madness, and in particular to the question of knowing whether
+dog-madness was always one and the same, with perhaps the slight
+variations which might be due to the differences of race in diverse
+dogs.
+
+We accordingly got hold of a number of dogs affected with ordinary
+street rabies, at all times of the year, at all seasons of the same
+year or of different years, and belonging to the most dissimilar canine
+races. In each case the bulbar portion of the medulla oblongata was
+taken out from the recently dead animal, triturated and suspended in
+two or three times its volume of sterilised liquid, making use all
+along of every precaution to keep our materials pure, and two drops
+of this liquid injected after trephining into one or two rabbits.
+The inoculation is made with a Pravaz syringe, the needle of which,
+slightly curved at its extremity, is inserted through the dura-mater
+into the arachnoid space. The results were as follows: all the rabbits,
+from whatever sort of dog inoculated, showed a period of incubation
+which ranged between twelve and fifteen days, without almost a single
+exception. Never did they show an incubation of eleven, ten, nine, or
+eight days, never an incubation of several weeks or of several months.
+
+Dog-rabies, the ordinary rabies, the only known rabies, is thus
+sensibly one in its virulence, and its modifications, which are very
+limited, appear to depend solely on the varying aptitude for rabies
+of the different known races. But we are going now to witness a deep
+change in the virulence of dog-rabies.
+
+Let us take one, any one, of our numerous rabbits, inoculated with the
+virus of an ordinary mad dog, and, after it has died, extract its bulb,
+prepare it just as described, and inject two drops of the bulb-emulsion
+into the arachnoid space of a second rabbit, whose bulb will in turn
+and in time be injected into a third rabbit, the bulb of which again
+will serve for a fourth rabbit, and so on.
+
+There will be evidence, even from the first few passages, of a marked
+tendency towards a lessening of the period of incubation in the
+succeeding rabbits. Just one example:
+
+Towards the end of the year 1882 fifteen cows and one bull died of
+rabies on a farm situated in the neighbourhood of the town of Melun.
+They had been bitten on October 2 by the farm dog, which had become
+mad. The head of one of the cows, which had died on November 15, was
+sent to my laboratory by M. Rossignol, a veterinary surgeon in Melun.
+A number of experiments were made on dogs and rabbits, and showed that
+the following parts, the only encephalic (or those pertaining to the
+brain) ones tested, were rabid: the bulb, the cerebellum, the frontal
+lobe, the sphenoidal lobe. The rabbits trephined and inoculated with
+those different parts showed the first symptoms of rabies on the
+seventeenth and eighteenth days after inoculation. With the bulb of
+one of those rabbits two more were inoculated, of which one took rabies
+on the fifteenth day, the other on the twenty-third day.
+
+We may notice, once for all, that when rabies is transferred from one
+animal to another of a different species, the period of incubation is
+always very irregular at first in the individuals of the second species
+if the virus had not yet become fixed in its maximum virulence for the
+first species. We have just seen an example of that phenomenon, since
+one of the rabbits had an incubation of fifteen days, the other of
+twenty-three days, both having received the same virus and all other
+circumstances remaining apparently the same for them.
+
+The bulb of the first one of those last rabbits which died was
+injected into two more rabbits, still after trephining. One of them
+took rabies on the tenth day, the other on the fourteenth day. The
+bulb of the first one that died was again injected into a couple of
+new rabbits, which developed the disease in ten days and twelve days
+respectively. A fifth time two new animals were inoculated from the
+first one that died, and they both took the disease on the eleventh day
+after inoculation: similarly, a sixth passage was made, and gave an
+incubation of eleven days, twelve days for the seventh passage, ten and
+eleven for the eighth, ten days for the ninth and tenth passages, nine
+days for the eleventh, eight and nine days for the twelfth, and so on,
+with differences of twenty-four hours at the most, until we got to the
+twenty-first passage, when rabies declared itself in eight days, and
+subsequently to that always in eight days up to the fiftieth passage,
+which was only effected a few days ago. That long experimental series
+which is still going on was begun on November 15, 1882, and will be
+kept up for the purpose of preserving in our rabies virus that maximum
+virulence which it has come to now for some considerable time, as it is
+easy to calculate.
+
+Allow me to call your attention to the ease and safety of the
+operations for trephining and then inoculating the virus. Throughout
+the last twenty months we have been able without a single interruption
+in the course of the series to carry the one initial virus through a
+succession of rabbits which were all trephined and inoculated every
+twelfth day or so.
+
+Guinea-pigs reach more rapidly the maximum virulence of which they are
+susceptible. The period of incubation is in them also variable and
+irregular at the beginning of the series of successive passages, but
+it soon enough fixes itself at a minimum of five days. The maximum
+virulence in guinea-pigs is reached after seven or eight passages only.
+It is worth noting that the number of passages required before reaching
+the maximum virulence, both in guinea-pigs and in rabbits, varies with
+the origin of the first virus with which the series is begun.
+
+If now this rabies with maximum virulence be transferred again into the
+dog from guinea-pig or rabbit, there is produced a dog-virus which in
+point of virulence goes far beyond that of ordinary canine madness.
+
+But, a natural query--of what use can be that discovery as to the
+existence and artificial production of diverse varieties of rabies,
+every one of them more violent and more rapidly fatal than the habitual
+madness of the dog? The man of science is thankful for the smallest
+find he can make in the field of pure science, but the many, terrified
+at the very name of hydrophobia, claim something more than mere
+scientific curiosities. How much more interesting it would be to become
+acquainted with a set of rabies viruses which should, on the contrary,
+be possessed of attenuated degrees of virulence! Then, indeed, might
+there be some hope of creating a number of vaccinal rabies viruses
+such as we have done for the virus of fowl-cholera, of the microbe of
+saliva, of the red evil of swine (swine-plague), and even of acute
+septicæmia. Unfortunately, however, the methods which had served for
+those different viruses showed themselves to be either inapplicable
+or inefficient in the case of rabies. It therefore became necessary
+to find out new and independent methods, such, for example, as the
+cultivation _in vitro_ of the mortal rabies virus.
+
+Jenner was the first to introduce into current science the opinion that
+the virus which he called the grease of the horse, and which we call
+now more exactly horse-pox, probably softened its virulence, so to
+speak, in passing through the cow and before it could be transferred
+to man without danger. It was therefore natural to think of a possible
+diminution of the virulence of rabies by a number of passages through
+the organisms of some animal or other, and the experiment was worth
+trying. A large number of attempts were made, but the majority of the
+animal species experimented on exalted the virulence after the manner
+of rabbits and guinea-pigs; fortunately, however, it was not so with
+monkey.
+
+On December 6, 1883, a monkey was trephined and inoculated with the
+bulb of a dog, which had itself been similarly inoculated from a child
+who had died of rabies. The monkey took rabies eleven days later, and
+when dead served for inoculation into a second monkey, which also took
+the disease on the eleventh day. A third monkey, similarly inoculated
+from the second one, showed the first symptoms on the twenty-third
+day, etc. The bulb of each one of the monkeys was inoculated, after
+trephining, into two rabbits each time. The rabbits inoculated from the
+first monkey developed rabies between thirteen and sixteen days, those
+from the second monkey between fourteen and twenty days, those from
+the third monkey between twenty-six and thirty days, those from the
+fourth monkey both of them after the twenty-eighth day, those from the
+fifth monkey after twenty-seven days, those from the sixth monkey after
+thirty days.
+
+It cannot be doubted after that, that successive passages through
+monkeys, and from the several monkeys to rabbits, do diminish the
+virulence of the virus for the latter animals; they diminish it for
+dogs also. The dog inoculated with the bulb of the fifth monkey gave
+an incubation of no less than fifty-eight days, although it had been
+inoculated in the arachnoid space.
+
+The experiments were renewed with fresh sets of monkeys and led
+to similar results. We were therefore actually in possession of a
+method by means of which we could attenuate the virulence of rabies.
+Successive inoculations from monkey to monkey elaborate viruses which,
+when transferred to rabbits, reproduce rabies in them, but with a
+progressively lengthening period of incubation. Nevertheless, if one of
+those rabbits be taken as the first for inoculations through a series
+of rabbits, the rabies thus cultivated obeys the law which we have seen
+before, and has its virulence increased at each passage.
+
+The practical application of those facts gives us a method for the
+vaccination of dogs against rabies. As a starting point, make use of
+one of the rabbits inoculated from a monkey sufficiently removed from
+the first animal of the monkey series for the inoculation--hypodermic
+or intra-venous--of that rabbit’s bulb not to be mortal for a new
+rabbit. The next vaccinal inoculations are made with the bulbs of
+rabbits derived by successive passages from that first rabbit.
+
+In the course of our experiments we made use, as a rule, for
+inoculation, of the virus of rabbits which had died after an incubation
+of four weeks, repeating three or four times each the vaccinal
+inoculations made with the bulbs of rabbits derived in succession
+from one another and from the first one of the series, itself coming
+directly from the monkey. I abstain from giving more details, because
+certain experiments which are actually going on allow me to expect that
+the process will be greatly simplified.
+
+You must be feeling, gentlemen, that there is a great blank in my
+communication; I do not speak of the micro-organism of rabies. We have
+not got it. The process for isolating it is still imperfect, and the
+difficulties of its cultivation outside the bodies of animals have not
+yet been got rid of, even by the use, as pabulum, of fresh nervous
+matter. The methods which we employed in our study of rabies ought all
+the more perhaps, on that account, to fix attention. Long still will
+the art of preventing diseases have to grapple with virulent maladies
+the micro-organic germs of which will escape our investigations. It is,
+therefore, a capital scientific fact that we should be able, after all,
+to discover the vaccination process for a virulent disease without yet
+having at our disposal its special virus and whilst yet ignorant of how
+to isolate or to cultivate its microbe.
+
+As soon as the method for the vaccination of dogs was firmly
+established, and we had in our possession a large number of dogs which
+had been rendered refractory to rabies, I had the idea of submitting
+to a competent committee those of the facts which appeared destined in
+future to serve as a basis for the vaccination of dogs against rabies.
+That course was suggested to me in prevision of the later practical
+application of the method, by the recollection of the opposition with
+which Jenner’s discovery met at its beginning.
+
+I spoke of my project to M. Fallières, the Minister of Public
+Instruction, who was pleased to approve of it and gave commission to
+the following gentlemen to control the facts which I had summarily
+communicated to the Academy of Sciences in its sitting of May 19 last:
+Messrs. Béclard, Paul Bert, Bouley, Aimeraud, Villemin, Vulpian. M.
+Bouley was appointed president, Dr. Villemin, secretary, and the
+commission at once set to work. I have the pleasure of informing
+you that it has just sent in a first report to the Minister. I was
+acquainted with it here, and the following are in a few words, the
+facts related in that first report on rabies. I had given to the
+commission nineteen vaccinated dogs in succession--that is to say,
+dogs which had been rendered refractory by preventive inoculations.
+Thirteen only of them had after their vaccination been already
+submitted to the test-inoculation on the brain.
+
+The nineteen dogs were, for the sake of comparison, divided into
+sets along with nineteen more control dogs brought from the pound
+without any sort of selection. To begin with, two refractory dogs
+and two control dogs were on June 1 trephined and inoculated under
+the dura-mater, on the surface of the brain, with the bulb of a dog
+affected with ordinary street rabies.
+
+On June 3 another refractory dog and another control dog were bitten by
+a furious street mad dog.
+
+The same furious mad dog was on June 4 made to bite still another
+refractory and another control dog. On June 6 the furious dog which
+had been utilised on June 3 and 4 died. The bulb was taken out and
+inoculated, after trephining, into three refractory dogs and three
+control dogs. On June 10 another street mad dog, having been secured,
+was, by the commission, made to bite one refractory and one control
+dog. On June 16 the commission had two new dogs, a refractory one and
+a control one, bitten by one of the control dogs of June 1, which had
+been seized with rabies on June 14 in consequence of the inoculation
+after trephining which it had received on June 1.
+
+On June 19 the commission got three refractory and three control dogs
+inoculated before their own eyes in the popliteal vein with the bulb
+of an ordinary street mad dog. On June 20 they had inoculated in
+their presence, and still in a vein, ten dogs altogether, six of them
+refractory and four just brought from the pound.
+
+On June 28, the Commission hearing that M. Paul Simon, a veterinary
+surgeon, had a furious biting mad dog, had four of their dogs, two
+refractory and two control dogs, taken to his place and bitten by the
+mad dog.
+
+The Rabies Commission have, therefore, experimented on thirty-eight
+dogs altogether--namely, nineteen refractory dogs and nineteen control
+dogs susceptible of taking the disease. Those of the dogs which have
+not died in consequence of the operations themselves are still under
+observation, and will long continue to be. The commission, reporting
+up to the present moment on their observations as to the state of the
+animals tried and tested by them, find that out of the nineteen control
+dogs six were bitten, of which six three have taken rabies. Seven
+received intra-venous inoculations, of which five have died of rabies.
+Five were trephined and inoculated on the brain; the five have died of
+rabies.
+
+On the other hand, not one of the nineteen vaccinated dogs has taken
+rabies.
+
+In the course of the experiments, on July 13, one of the refractory
+dogs died in consequence of a black diarrhœa which had begun in the
+first days of July. In order to ascertain whether rabies had anything
+to do with it as the cause of death, its bulb was at once inoculated,
+after trephining, into three rabbits and one guinea-pig. All four
+animals are still to-day in perfect health, a certain proof that the
+dog died of some common malady, and not of rabies.
+
+The second report of the Commission will be concerned with the
+experiments made as to the refractoriness to rabies of twenty dogs to
+be vaccinated by the Commission themselves.
+
+(_M. Pasteur then announced that he had just received that same
+morning the first report addressed to M. Fallières by the Official
+Commission on Rabies. It states that twenty-three refractory dogs were
+bitten by ordinary mad dogs, and that not one of them had taken rabies.
+On the other hand, within two months after the bites, 66 per cent. of
+the normal dogs similarly bitten had already taken the disease._)
+
+
+_November 1, 1886.--New Communication on Rabies._--On October 26,
+1885, I acquainted the Academy with a method of prophylaxis of rabies
+after bites. Numerous applications on dogs had justified me in trying
+it on man. As early as March 1, 350 persons bitten by dogs undoubtedly
+mad, and several more by dogs simply suspected of rabies, had already
+been treated at my laboratory by Dr. Grancher. And in consideration
+of the happy results obtained it appeared to me that it had become
+necessary to found an establishment for anti-rabic vaccinations.
+
+To-day, October 31, 1886, 2,490 persons have received the preventive
+inoculations in Paris alone. The treatment was in the first instance
+uniform for the great majority of the patients, notwithstanding the
+different conditions presented by them as to age, sex, the number of
+bites received, their seat, their depth, and the time which had elapsed
+since the occurrence of the accident. It lasted ten days, the patient
+receiving every day an injection prepared from the spinal marrow of a
+rabbit, beginning with that of fourteen days’ and ending with that of
+five days’ desiccation.
+
+Those 2,490 cases are subdivided according to nationality in the
+following manner:
+
+ Russia 191
+ Italy 165
+ Spain 107
+ England 80
+ Belgium 57
+ Austria 52
+ Portugal 25
+ Roumania 22
+ United States 18
+ Holland 14
+ Greece 10
+ Germany 9
+ Turkey 7
+ Brazil 3
+ India 2
+ Switzerland 2
+ France and Algeria 1,726
+
+The number of French persons has been considerable, amounting to 1,726,
+and it will be enough to confine ourselves to the category formed by
+them as a basis for discussing the degree of efficacy of the method.
+
+Out of the total 1,726 cases treated, the treatment has failed ten
+times--namely, in the following cases:
+
+The children: Lagut, Peytel, Clédière, Moulis, Astier, Videau.
+
+The woman: Leduc, seventy years old.
+
+The men: Marius Bouvier (thirty years), Clergot (thirty), and Norbert
+Magnevon (eighteen).
+
+I leave out of count two other persons, Louise Pelletier and Moermann,
+whose deaths must be attributed to their tardy arrival at the
+laboratory, Louise Pelletier thirty-six days, and Moermann forty-three
+days after they had been bitten.
+
+We have therefore ten deaths for 1,726 cases, or 1 in 170; such are,
+for France and Algeria, the results of the first year’s application of
+the method.
+
+Those statistics, taken as a whole, demonstrate the efficacy of the
+treatment, as proved further by the relatively large number of deaths
+which occurred amongst bitten persons who had not been vaccinated.
+
+
+FOOTNOTES:
+
+[Footnote 35: From Address delivered August 10, 1884 at the Copenhagen
+meeting of the International Medical Congress.]
+
+
+
+
+ XXXIII
+
+ JAMES CLERK MAXWELL
+
+ 1831-1879
+
+
+ _James Clerk Maxwell, born November 13, 1831, attended Edinburgh
+ University 1847-1850. Entering Cambridge, he graduated second wrangler
+ in 1854. He then taught for four years in Marischal College, Aberdeen,
+ and in 1860 was called to King’s College, London, where he remained for
+ the following eight years. He early revealed his mathematical genius
+ and before he was nineteen had the honor of reading several pages
+ before the Royal Society of Edinburgh. He developed by mathematics the
+ theory that electricity was a condition of stress or strain in the
+ ether, a wave moving in the same medium as light and traveling at the
+ same rate of speed. The theory was substantiated by the experiments of
+ Hertz, a pupil of Helmholtz, who in 1887 proved the existence of the
+ waves which now bear his name. Maxwell died at Cambridge, November 5,
+ 1879._
+
+
+ THE MAXWELL AND HERTZ THEORY OF ELECTRICITY AND LIGHT[36]
+
+It was at the moment when the experiments of Fresnel were forcing
+the scientific world to admit that light consists of the vibrations
+of a highly attenuated fluid filling interplanetary spaces that the
+researches of Ampère were making known the laws of the mutual action
+of currents and were so enunciating the fundamental principles of
+electro-dynamics.
+
+It needed but one step to the supposition that that same fluid, the
+ether, which is the medium of luminous phenomena, is at the same
+time the vehicle of electrical action. In imagination Ampère made
+this stride; but the illustrious physicist could not foresee that the
+seducing hypothesis with which he was toying, a mere dream for him, was
+ere long to take a precise form and become one of the vital concerns of
+exact science.
+
+A dream it remained for many years, till one day, after electrical
+measurements had become extremely exact, some physicist, turning over
+the numerical data, much as a resting pedestrian might idly turn over
+a stone, brought to light an odd coincidence. It was that the factor
+of transformation between the system of electro-statical units and the
+system of electro-dynamical units was equal to the velocity of light.
+Soon the observations directed to this strange coincidence became so
+exact that no sane head could longer hold it a mere coincidence. No
+longer could it be doubted that some occult affinity existed between
+optical and electrical phenomena. Perhaps, however, we might be
+wondering to this day what this affinity could be were it not for the
+genius of Clerk Maxwell.
+
+
+ DISPLACEMENT CURRENTS
+
+The reader is aware that solid bodies are divided into two classes,
+conductors through which electricity can move in the form of a galvanic
+current, and nonconductors, or dielectrics. The electricians of former
+days regarded dielectrics as quite inert, having no part to play but
+that of obstinately refusing passage to electricity. Had that been so,
+any one non-conductor might be replaced by any other without making
+any difference in the phenomena; but Faraday found that that was not
+the case. Two condensers of the same form and dimensions put into
+connection with the same source of electricity do not take the same
+charge, though the thickness of the isolating plate be the same, unless
+the matter of that plate be chemically the same. Now Clerk Maxwell had
+too deeply studied the researches of Faraday not to comprehend the
+importance of dielectrics and the imperative obligation to recognize
+their active part.
+
+Besides, if light is but an electric phenomenon, when it traverses a
+thickness of glass electrical events must take place in that glass. And
+what can be the nature of those events? Maxwell boldly answers, they
+are, and must be, currents.
+
+All the experience of his day seemed to contradict this. Never had
+currents been observed except in conductors. How was Maxwell to
+reconcile his audacious hypothesis with a fact so well established
+as that? Why is it that under certain circumstances those supposed
+currents produce manifest effects, while under ordinary conditions they
+can not be observed at all?
+
+The answer was that dielectrics resist the passage of electricity not
+so much more than conductors do, but in a different manner. Maxwell’s
+idea will best be understood by a comparison.
+
+If we bend a spring, we meet a resistance which increases the more
+the spring is bended. So, if we can only dispose of a finite force, a
+moment will come when the motion will cease, equilibrium being reached.
+Finally, when the force ceases the spring will in flying back restore
+the whole of the energy which has been expended in bending it.
+
+Suppose, on the other hand, that we wish to displace a body plunged
+into water. Here again a resistance will be experienced, but it will
+not go on increasing in proportion as the body advances, supposing it
+to be maintained at a constant velocity. So long as the motive force
+acts, equilibrium will never, then, be attained; nor when the force
+is removed will the body in the least tend to return, nor can any
+portion of the energy expended be restored. It will, in fact, have been
+converted into heat by the viscosity of the water.
+
+The contrast is plain; and we ought to distinguish elastic resistance
+from viscous resistance. Using these terms, we may express Maxwell’s
+idea by saying that dielectrics offer an elastic resistance, conductors
+a viscous resistance, to the movements of electricity. Hence, there
+are two kinds of currents; currents of displacement which traverse
+dielectrics and ordinary currents of conduction which circulate in
+conductors.
+
+Currents of the first kind, having to overcome an elastic resistance
+which continually increases, naturally can last but a very short time,
+since a state of equilibrium will quickly be reached.
+
+Currents of conduction, on the other hand, having only a viscous
+resistance to overcome, must continue so long as there is any
+electromotive force.
+
+Let us return to the simile used by M. Cornu in his notice in the
+Annuaire du Bureau des Longitudes for 1893. Suppose we have in a
+reservoir water under pressure. Lead a tube plumb downward into the
+reservoir. The water will rise in the tube, but the rise will stop
+when hydrostatic equilibrium is attained--that is, when the downward
+pressure of the water in the tube above the point of application of the
+first pressure on the reservoir, and due to the weight of the water,
+balances that first pressure. If the pipe is large, there will be no
+friction or loss of head, and the water so raised can be used to do
+work. That represents a current of displacement.
+
+If, on the other hand, the water flows out of the reservoir by a
+horizontal pipe, the motion will go on till the reservoir is emptied;
+but if the tube is small and long there will be a great loss of energy
+and considerable production of heat by friction. That represents a
+current of conduction.
+
+Though it would be vain, not to say idle, to attempt to represent all
+details, it may be said that everything happens just as if the currents
+of displacement were acting to bend a multitude of little springs.
+When the currents cease, electrostatic equilibrium is established,
+and the springs are bent the more, the more intense is the electric
+field. The accumulated work of the springs--that is, the electrostatic
+energy--can be entirely restored as soon as they can unbend, and so it
+is that we obtain mechanical work when we leave the conductors to obey
+the electrostatic attractions. Those attractions must be due to the
+pressure exercised on the conductors by the bent springs. Finally, to
+pursue the image to the death, the disruptive discharge may be compared
+to the breaking of the springs when they are bent too much.
+
+On the other hand, the energy employed to produce conduction currents
+is lost, being wholly converted into heat, like that spent in
+overcoming the viscosity of fluids. Hence it is that the conducting
+wires become heated.
+
+From Maxwell’s point of view it seems that all currents are in closed
+circuits. The older electricians did not so opine. They regarded the
+current circulating in a wire joining the two poles of a pile as
+closed; but if in place of directly uniting the two poles we place them
+in communication with the two armatures of a condenser, the momentary
+current which lasts while the condenser is getting charged was not
+considered as a current round a closed circuit. It went, they thought,
+from one armature through the wire, the battery, the other wire, to
+the other armature, and there it stopped. Maxwell, on the contrary,
+supposed that in the form of a current of displacement it passes
+through the nonconducting plate of the condenser, and that precisely
+what brings it to cessation is the opposite electromotive force set up
+by the displacement of electricity in this dielectric.
+
+Currents become sensible in three ways--by their heating effects, by
+their actions on other currents and on magnets, and by the induced
+currents to which they give rise. We have seen why currents of
+conduction develop heat and why currents of displacement do not.
+But Maxwell’s hypothetical currents ought at any rate to produce
+electro-magnetic and inductive effects. Why do these effects not
+appear? The answer is, that it is because a current of displacement
+can not last long enough. That is to say, they can not last long in
+one direction. Consequently in a dielectric no current can long exist
+without alteration. But the effects ought to and will become observable
+if the current is continually reversed at sufficiently short intervals.
+
+
+ THE NATURE OF LIGHT
+
+Such, according to Maxwell, is the origin of light. A luminiferous wave
+is a series of alternating currents produced in dielectrics, in air, or
+even in the interplanetary void, and reversed in direction a million
+of million of times per second. The enormous induction due to these
+frequent alternations sets up other currents in the neighboring parts
+of the dielectric, and so the waves are propagated.
+
+Calculation shows that the velocity of propagation would be equal to
+the ratio of the units, which we know is the velocity of light.
+
+Those alternative currents are a sort of electrical oscillation. Are
+they longitudinal, like those of sound, or are they transversal, like
+those of Fresnal’s ether? In the case of sound the air undergoes
+alternative condensations and rarefactions. The ether of Fresnal, on
+the other hand, behaves as if it were composed of incompressible layers
+capable only of slipping over one another. Were these currents in open
+paths, the electricity carried from one end to the other would become
+accumulated at one extremity. It would thus be condensed and rarefied
+like air, and its vibrations would be longitudinal. But Maxwell only
+admits currents in closed circuits; accumulation is impossible, and
+electricity behaves like the incomprehensible ether of Fresnel, with
+its transversal vibrations.
+
+
+ EXPERIMENTAL VERIFICATION
+
+We thus obtain all the results of the theory of waves. Yet this was not
+enough to decide the physicists to adopt the ideas of Maxwell. It was a
+seductive hypothesis; but physicists consider hypotheses which lead to
+no distinct observational consequences as beyond the borders of their
+province. That province, so defined, no experimental confirmation of
+Maxwell’s theory invaded for twenty-five years.
+
+What was wanted was some issue between the two theories not too
+delicate for our coarse methods of observation to decide. There was but
+one line of research along which any _experimentum crucis_ was to
+be met with.
+
+The old electro-dynamics makes electro-magnetic induction take place
+instantaneously; but according to Maxwell’s doctrine it propagates
+itself with the velocity of light.
+
+The point was then to measure, or at least to make certain, a velocity
+of propagation of inductive effects. This is what the illustrious
+German physicist Hertz has done by the method of interferences.
+
+The method is well known in its application to optical phenomena. Two
+luminous rays from one identical center interfere when they reach the
+same point after pursuing paths of different lengths. If the difference
+is one, two, or any whole number of wave lengths, the two lights
+re-enforce one another so that if their intensities are equal, that of
+their combination is four times as great. But if the difference is an
+odd number of half wave lengths, the two lights extinguish one another.
+
+Luminiferous waves are not peculiar in showing this phenomenon;
+it belongs to every periodic change which is propagated with
+definite velocity. Sound interferes just as light does, and so must
+electro-dynamic induction if it is strictly periodic and has a definite
+velocity of propagation. But if the propagation is instantaneous there
+can be no interference, since in that case there is no finite wave
+length.
+
+The phenomenon, however, could not be observed were the wave length
+greater than the distance within which induction is sensible. It is
+therefore requisite to make the period of alternation as short as
+possible.
+
+
+ ELECTRICAL EXCITERS
+
+We can obtain such currents by means of an apparatus which constitutes
+a veritable electrical pendulum. Let two conductors be united by a
+wire. If they have not the same electric potential the electrical
+equilibrium is disturbed and tends to restore itself, just as the molar
+equilibrium is disturbed when a pendulum is carried away from the
+position of repose.
+
+A current is set up in the wire, tending to equalize the potential,
+just as the pendulum begins to move so as to be carried back to the
+position of repose. But the pendulum does not stop when it reaches that
+position. Its inertia carries it farther. Nor, when the two electrical
+conductors reach the same potential, does the current in the wire
+cease. The equilibrium instantaneously existing is at once destroyed by
+a cause analogous to inertia, namely self-induction. We know that when
+a current is interrupted it gives rise in parallel wires to an induced
+current in the same direction. The same effect is produced in the
+circuit itself, if that is not broken. In other words, a current will
+persist after the cessation of its causes, just as a moving body does
+not stop the instant it is no longer driven forward.
+
+When, then, the two potentials become equal, the current will go on and
+give the two conductors relative charges opposite to those they had
+at first. In this case, as in that of the pendulum, the position of
+equilibrium is passed, and a return motion is inevitable. Equilibrium,
+again instantaneously attained, is at once again broken for the same
+reason; and so the oscillations pursue one another unceasingly.
+
+Calculation shows that the period depends on the capacity of the
+conductors in such a way that it is only necessary to diminish that
+capacity sufficiently (which is easily done) to have an electric
+pendulum capable of producing an alternating current of extremely short
+period.
+
+All that was well enough known by the theoretical researches of Lord
+Kelvin and by the experimentation of Federson on the oscillatory
+discharge of the Leyden jar. It was not that which constituted the
+originality of Hertz.
+
+But it is not enough to construct a pendulum; it is further requisite
+to set it into oscillation. For that, it is necessary to carry it off
+from equilibrium and to let it go suddenly, that is to say, to release
+it in a time short as compared to the period of its oscillation.
+
+For if, having pulled a pendulum to one side by a string, we were to
+let go of the string more slowly than the pendulum would have descended
+of itself, it would reach the vertical without momentum, and no
+oscillation would be set up.
+
+In like manner, with an electric pendulum whose natural period is, say,
+a hundred-millionth of a second, no mechanical mode of release would
+answer the purpose at all, sudden as it might seem to us with our more
+than sluggish conceptions of promptitude. How, then, did Hertz solve
+the problem?
+
+To return to our electric pendulum, a gap of a few millimeters is
+made in the wire which joins the two conductors. This gap divides our
+apparatus into two symmetrical parts, which are connected to the two
+poles of a Ruhmkorff coil. The induced current begins to charge the
+two conductors, and the difference of their potential increases with
+relative slowness.
+
+At first the gap prevents a discharge from the conductors; the air in
+it plays the rôle of insulator and maintains our pendulum in a position
+diverted from that of equilibrium.
+
+But when the difference of potential becomes great enough, a spark will
+jump across. If the self-induction is great enough and the capacity
+and resistance small enough, there will be an oscillatory discharge
+whose period can be brought down to a hundred-millionth of a second.
+The oscillatory discharge would not, it is true, last long by itself;
+but it is kept up by the Ruhmkorff coil, whose current is itself
+oscillatory with a period of about a hundred-thousandth of a second,
+and thus the pendulum gets a new impulse as often as that.
+
+The instrument just described is called a resonance exciter. It
+produces oscillations which are reversed from a hundred million to a
+thousand million times per second. Thanks to this extreme frequency,
+they can produce inductive effects at great distances. To make these
+effects sensible another electric pendulum is used, called a resonator.
+In this the coil is suppressed. It consists simply of two little
+metallic spheres very near to one another, with a long wire connecting
+them in a roundabout way.
+
+The induction due to the exciter will set the resonator in vibration
+the more intensely the more nearly the natural periods of vibration
+are the same. At certain phases of the vibration the difference of
+potential of the two spheres will be just great enough to cause the
+sparks to leap across.
+
+
+ PRODUCTION OF THE INTERFERENCES
+
+Thus we have an instrument which reveals the inductive waves which
+radiate from the exciter. We can study them in two ways. We may either
+expose the resonator to the direct induction of the exciter at a great
+distance, or else make this induction act at a small distance on a long
+conducting wire which the electric wave will follow and which in its
+turn will act at a small distance on the resonator.
+
+Whether the wave is propagated along a wire or across the air,
+interferences can be produced by reflection. In the first case it
+will be reflected at the extremity of the wire, which it will again
+pass through in the opposite direction. In the second case it can be
+reflected on a metallic leaf which will act as a mirror. In either case
+the reflected ray will interfere with the direct ray, and positions
+will be found in which the spark of the resonator will be extinguished.
+
+Experiments with a long wire are the easier and furnish much valuable
+information, but they cannot furnish an _experimentum crucis_,
+since in the old theory, as in the new, the velocity of the electric
+wave in a wire should be equal to that of light. But experiments on
+direct induction at great distances are decisive. They not only show
+that the velocity of propagation of induction across air is finite,
+but also that it is equal to the velocity of the wave propagated along
+a wire, conformably to the ideas of Maxwell.
+
+
+ SYNTHESIS OF LIGHT
+
+I shall insist less on other experiments of Hertz, more brilliant
+but less instructive. Concentrating with a parabolic mirror the wave
+of induction that emanates from the exciter, the German physicist
+obtained a true pencil of rays of electric force, susceptible of
+regular reflection and refraction. These rays, were the period but
+one-millionth of what it is, would not differ from rays of light.
+We know that the sun sends us several varieties of radiations, some
+luminiferous, since they act on the retina, others dark, infra-red, or
+ultraviolet, which reveal themselves in chemical and calorific effects.
+The first owe the qualities which render them sensible to us to a
+physiological chance. For the physicist, the infra-red differs from red
+only as red differs from green; it simply has a greater wave length.
+That of the Hertzian radiations is far greater still, but they are mere
+differences of degree, and if the ideas of Clerk Maxwell are true, the
+illustrious professor of Bonn has effected a genuine synthesis of light.
+
+
+ CONCLUSION
+
+Nevertheless, our admiration for such unhoped-for successes must not
+let us forget what remains to be accomplished. Let us endeavor to take
+exact account of the results definitely acquired.
+
+In the first place, the velocity of direct induction through air is
+finite; for otherwise interferences could not exist. Thus the old
+electro-dynamics is condemned. But what is to be set up in its place?
+Is it to be the doctrine of Maxwell, or rather some approximation to
+that, for it would be too much to suppose that he had foreseen the
+truth in all its details? Though the probabilities are accumulating, no
+complete demonstration of that doctrine has ever attained.
+
+We can measure the wave length of the Hertzian oscillations. That
+length is the product of the period into the velocity of propagation.
+We should know the velocity if we knew the period; but this last is
+so minute that we cannot measure it; we can only calculate it by a
+formula due to Lord Kelvin. That calculation leads to figures agreeable
+to the theory of Maxwell; but the last doubts will only be dissipated
+when the velocity of propagation has been directly measured. (See Note
+I.)
+
+But this is not all. Matters are far from being as simple as this
+brief account of the matter would lead one to think. There are various
+complications.
+
+In the first place, there is around the exciter a true radiation of
+induction. The energy of the apparatus radiates abroad, and if no
+source feeds it, it quickly dissipates itself and the oscillations
+are rapidly extinguished. Hence arises the phenomenon of multiple
+resonance, discovered by Messrs. Sarasin and De la Rive, which at first
+seemed irreconcilable with the theory.
+
+On the other hand, we know that light does not exactly follow the
+laws of geometrical optics, and the discrepancy, due to diffraction,
+increases proportionately to the wave length. With the great waves
+of the Hertzian undulations these phenomena must assume enormous
+importance and derange everything. It is doubtless fortunate, for the
+moment at least, that our means of observation are as coarse as they
+are, for otherwise the simplicity which struck us would give place to
+a dedalian complexity in which we should lose our way. No doubt a good
+many perplexing anomalies have been due to this. For the same reason
+the experiments to prove a refraction of the electrical waves can
+hardly be considered as demonstrative.
+
+It remains to speak of a difficulty still more grave, though doubtless
+not insurmountable. According to Maxwell, the coefficient of
+electrostatic induction of a transparent body ought to be equal to the
+square of its index of refraction. Now this is not so. The few bodies
+which follow Maxwell’s law are exceptions. The phenomena are plainly
+far more complex than was at first thought. But we have not yet been
+able to make out how matters stand, and the experiments conflict with
+one another.
+
+Much, then, remains to be done. The identity of light with a vibratory
+motion in electricity is henceforth something more than a seductive
+hypothesis; it is a probable truth. But it is not yet quite proved.
+
+NOTE I.--Since the above was written another great step
+has been taken. M. Blondlot has virtually succeeded, by ingenious
+experimental contrivances, in directly measuring the velocity of a
+disturbance along a wire. The number found differs little from the
+ratio of the units; that is, from the velocity of light, which is
+300,000 kilometers per second. Since the interference experiments made
+at Geneva by Messrs. Sarasin and De la Rive have shown, as I said
+above, that induction is propagated in air with the same velocity as an
+electric disturbance which follows a conducting wire, we must conclude
+that the velocity of the induction is the same as that of light, which
+is a confirmation of the ideas of Maxwell.
+
+M. Fizeau had formerly found for the velocity of electricity a number
+far smaller, about 180,000 kilometers. But there is no contradiction.
+The currents used by M. Fizeau, though intermittent, were of small
+frequency and penetrated to the axis of the wire, while the currents of
+M. Blondlot, oscillatory and of very short period, remained superficial
+and were confined to a layer of less than a hundredth of a millimeter
+in thickness. One may readily suppose the laws of propagation are not
+the same in the two cases.
+
+NOTE II.--I have endeavored above to render the explanation
+of the electrostatic attractions and of the phenomena of induction
+comprehensible by means of a simile. Now let us see what Maxwell’s idea
+is of the cause which produces the mutual attractions of currents.
+
+While the electrostatic attractions are taken to be due to a multitude
+of little springs--that is to say, to the elasticity of the ether--it
+is supposed to be the living force and inertia of the same fluid which
+produce the phenomena of induction and electro-dynamical effects.
+
+The complete calculation is far too extended for these pages, and I
+shall again content myself with a simile. I shall borrow it from a well
+known instrument--the centrifugal governor.
+
+The living force of this apparatus is proportional to the square of the
+angular velocity and to the square of the distance of the balls.
+
+According to the hypothesis of Maxwell, the ether is in motion in
+galvanic currents, and its living force is proportional to the square
+of the intensity of the current, which thus correspond, in the parallel
+I am endeavoring to establish, to the angular velocity of rotation.
+
+If we consider two currents in the same direction, the living force,
+with equal intensity, will be greater the nearer the currents are to
+one another. If the currents have opposite directions, the living force
+will be greater the farther they are apart.
+
+In order to increase the angular velocity of the regulator and
+consequently its living force, it is necessary to supply it with
+energy and consequently to overcome a resistance which we call its
+inertia.
+
+In the same way, in order to increase the intensity of a current, we
+must augment the living force of the ether, and it will be necessary to
+supply it with energy and to overcome a resistance which is nothing but
+the inertia of the ether and which we call the induction.
+
+The living force will be greater if the currents are in the same
+direction and near together. The energy to be furnished the counter
+electromotive force of induction will be greater. This is what we
+express when we say that the mutual action of two currents is to be
+added to their self-induction. The contrary is the case when their
+directions are opposite.
+
+If we separate the balls of the regulator, it will be necessary, in
+order to maintain the angular velocity, to furnish energy, because with
+equal angular velocity the living force is greater the more the balls
+are separated.
+
+In the same way, if two currents have the same direction and are
+brought toward one another, it will be necessary, in order to maintain
+the intensity to supply energy, because the living force will be
+augmented. We shall, therefore, have to overcome an electromotive
+force of induction which will tend to diminish the intensity of the
+currents. It would tend on the contrary to augment it, if the currents
+had the same direction and were carried apart, or if they had opposite
+directions and were brought together.
+
+Finally, the centrifugal force tends to increase the distance between
+the balls, which would augment the living force were the angular
+velocity to be maintained.
+
+In like manner, when the currents have the same direction, they attract
+each other--that is to say, they tend to approach each other, which
+would increase the living force if the intensity were maintained.
+If their directions are opposed they repel one another and tend to
+separate, which would again tend to increase the living force were the
+intensity kept constant.
+
+Thus the electrostatic effects would be due to the elasticity of the
+ether and the electro-dynamical phenomena to the living force. Now,
+ought this elasticity itself to be explained, as Lord Kelvin thinks, by
+rotations of small parts of the fluid? Different reasons may render
+this hypothesis attractive; but it plays no essential part in the
+theory of Maxwell, which is quite independent of it.
+
+In the same way, I have made comparisons with divers mechanisms. But
+they are only similes, and pretty rough ones. A complete mechanical
+explanation of electrical phenomena is not to be sought in the volumes
+of Maxwell, but only a statement of the conditions which any such
+explanation has to satisfy. Precisely what will confer long life on the
+work of Maxwell is its being unentangled with any special mechanical
+hypothesis.
+
+
+FOOTNOTES:
+
+[Footnote 36: Translated from a paper by M. Henri Poincaré.]
+
+
+
+
+ XXXIV
+
+ AUGUST WEISMANN
+
+ 1834-1914
+
+
+ _August Weismann was born at Frankfort-on-Main, January 17, 1834,
+ and studied medicine at Göttingen, 1852-1856. He was physician to the
+ Austrian Archduke for two years (1860-62), but was compelled to retire
+ because of his poor eyesight. He was called to the chair of zoology
+ at Freiburg University. After a close study of Darwin’s theory, he
+ published in 1876 his “Studies in the Theories of Descent,” a book
+ which at once attracted much attention among scientists, for it
+ proposed the theory of the germ-plasm as the basis of heredity, and
+ denied the theory of the transmissibility of acquired characteristics.
+ He died at Freiburg-in-Baden, November 6, 1914._
+
+
+ THE CONTINUITY OF THE GERM-PLASM AS THE FOUNDATION OF A THEORY OF
+ HEREDITY[37]
+
+ INTRODUCTION
+
+When we see that, in the higher organisms, the smallest structural
+details, and the most minute peculiarities of bodily and mental
+disposition, are transmitted from one generation to another; when we
+find in all species of plants and animals a thousand characteristic
+peculiarities of structure continued unchanged through long series of
+generations; when we even see them in many cases unchanged throughout
+whole geological periods; we very naturally ask for the causes of
+such a striking phenomenon: and inquire how it is that such facts
+become possible, how it is that the individual is able to transmit its
+structural features to its offspring with such precision. And the
+immediate answer to such a question must be given in the following
+terms:--“A single cell out of the millions of diversely differentiated
+cells which compose the body, becomes specialized as a sexual cell; it
+is thrown off from the organism and is capable of reproducing all the
+peculiarities of the parent body, in the new individual which springs
+from it by cell-division and the complex process of differentiation.”
+Then the more precise question follows: “How is it that such a single
+cell can reproduce the _tout ensemble_ of the parent with all the
+faithfulness of a portrait?”
+
+The answer is extremely difficult; and no one of the many attempts
+to solve the problem can be looked upon as satisfactory; no one of
+them can be regarded as even the beginning of a solution or as a
+secure foundation from which a complete solution may be expected in
+the future. Neither Häeckel’s “Perigenesis of the Plastidule,” nor
+Darwin’s “Pangenesis,” can be regarded as such a beginning. The former
+hypothesis does not really treat of that part of the problem which
+is here placed in the foreground, viz., the explanation of the fact
+that the tendencies of heredity are present in single cells, but it
+is rather concerned with the question as to the manner in which it
+is possible to conceive the transmission of a certain tendency of
+development into the sexual cell, and ultimately into the organism
+arising from it. The same may be said of the hypothesis of His, who,
+like Häeckel regards heredity as the transmission of certain kinds of
+motion. On the other hand, it must be conceded that Darwin’s hypothesis
+goes to the very root of the question, but he is content to give, as
+it were, a provisional or purely formal solution, which, as he himself
+says, does not claim to afford insight into the real phenomena, but
+only to give us the opportunity of looking at all the facts of heredity
+from a common standpoint. It has achieved this end, and I believe it
+has unconsciously done more, in that the thoroughly logical application
+of its principles has shown that the real causes of heredity cannot
+lie in the formation of gemmules or in any allied phenomena. The
+improbabilities to which any such theory would lead are so great that
+we can affirm with certainty that its details cannot accord with
+existing facts. Furthermore, Brooks’ well-considered and brilliant
+attempt to modify the theory of Pangenesis cannot escape the reproach
+that it is based upon possibilities, which one might certainly describe
+as improbabilities. But although I am of the opinion that the whole
+foundation of the theory of Pangenesis, however it may be modified,
+must be abandoned, I think, nevertheless, its author deserves great
+credit, and that its production has been one of those indirect roads
+along which science has been compelled to travel in order to arrive
+at the truth. Pangenesis is a modern revival of the oldest theory of
+heredity, that of Democritus, according to which the sperm is secreted
+from all parts of the body of both sexes during copulation, and is
+animated by a bodily force; according to this theory also, the sperm
+from each part of the body reproduces the same part.
+
+If, according to the received physiological and morphological ideas
+of the day, it is impossible to imagine that gemmules produced by
+each cell of the organism are at all times to be found in all parts
+of the body, and furthermore that these gemmules are collected in the
+sexual cells, which are then able to reproduce again in a certain
+order each separate cell of the organism, so that each sexual cell is
+capable of developing into the likeness of the parent body; if all
+this is inconceivable, we must inquire for some other way in which we
+can arrive at a foundation for the true understanding of heredity. My
+present task is not to deal with the whole question of heredity, but
+only with the single although fundamental question--“How is it that a
+single cell of the body can contain within itself all the hereditary
+tendencies of the whole organism?” I am here leaving out of account
+the further question as to the forces and the mechanism by which these
+tendencies are developed in the building-up of the organism. On this
+account I abstain from considering at present the views of Nägeli, for
+as will be shown later on, they only slightly touch this fundamental
+question, although they may certainly claim to be of the highest
+importance with respect to the further question alluded to above.
+
+Now if it is impossible for the germ-cell to be, as it were, an extract
+of the whole body, and for all the cells of the organism to dispatch
+small particles to the germ-cells, from which the latter derive their
+power of heredity; then there remain, as it seems to me, only two other
+possible, physiologically conceivable, theories as to the origin of
+germ-cells, manifesting such powers as we know they possess. Either
+the substance of the parent germ-cell is capable of undergoing a
+series of changes which, after the building-up of a new individual
+leads back again to identical germ-cells; or the germ-cells are not
+derived at all, as far as their essential and characteristic substance
+is concerned, from the body of the individual, but they are derived
+directly from the parent germ-cell.
+
+I believe that the latter view is the true one: I have expounded it
+for a number of years, and have attempted to defend it, and to work
+out its further details in various publications. I propose to call it
+the theory of “The Continuity of the Germ-plasm,” for it is founded
+upon the idea that heredity is brought about by the transference from
+one generation to another of a substance with a definite chemical,
+and above all, molecular constitution. I have called this substance
+“germ-plasm,” and have assumed that it possesses a highly complex
+structure, conferring upon it the power of developing into a complex
+organism. I have attempted to explain heredity by supposing that in
+each ontogeny a part of the specific germ-plasm contained in the
+parent egg-cell is not used up in the construction of the body of
+the offspring, but is reserved unchanged for the formation of the
+germ-cells of the following generation.
+
+It is clear that this view of the origin of germ-cells explains the
+phenomena of heredity very simply, inasmuch as heredity becomes thus
+a question of growth and of assimilation,--the most fundamental of
+all vital phenomena. If the germ-cells of successive generations are
+directly continuous, and thus only form, as it were, different parts
+of the same substance, it follows that these cells must, or at any
+rate may, possess the same molecular constitution, and that they
+would therefore pass through exactly the same stages under certain
+conditions of development, and would form the same final product. The
+hypothesis of the continuity of the germ-plasm gives an identical
+starting point to each successive generation, and thus explains how it
+is that an identical product arises from all of them. In other words,
+the hypothesis explains heredity as part of the underlying problems
+of assimilation and of the causes which act directly during ontogeny;
+it therefore builds a foundation from which the explanation of these
+phenomena can be attempted.
+
+It is true that this theory also meets with difficulties, for it seems
+to be unable to do justice to a certain class of phenomena, viz.,
+the transmission of so-called acquired characters. I therefore gave
+immediate and special attention to this point in my first publication
+on heredity, and I believe that I have shown that the hypothesis of
+the transmission of acquired characters--up to that time generally
+accepted--is, to say the least, very far from being proved, and
+that entire classes of facts which have been interpreted under this
+hypothesis may be quite as well interpreted otherwise, while in many
+cases they must be explained differently. I have shown that there is
+no ascertained fact which, at least up to the present time, remains
+in irrevocable conflict with the hypothesis of the continuity of
+the germ-plasm; and I do not know any reason why I should modify
+this opinion to-day, for I have not heard of any objection which
+appears to be feasible. E. Roth has objected that in pathology we
+everywhere meet with the fact that acquired local disease may be
+transmitted to the offspring as a predisposition; but all such cases
+are exposed to the serious criticism that the very point that first
+needs to be placed on a secure footing is incapable of proof, viz.,
+the hypothesis that the causes which in each particular case led to
+the predisposition were really acquired. It is not my intention, on
+the present occasion, to enter fully into the question of acquired
+characters; I hope to be able to consider the subject in greater detail
+at a future date. But in the meantime I should wish to point out that
+we ought, above all, to be clear as to what we really mean by the
+expression “acquired character.” An organism cannot acquire anything
+unless it already possesses the predisposition to acquire it: acquired
+characters are therefore no more than local or sometimes general
+variations which arise under the stimulus provided by certain external
+influences. If by the long-continued handling of a rifle, the so-called
+“_Exercierknochen_” (a bony growth caused by the pressure of
+the weapon in drilling) is developed, such a result depends upon
+the fact that the bone in question, like every other bone, contains
+within itself a predisposition to react upon certain mechanical
+stimuli, by growth in a certain direction and to a certain extent. The
+predisposition towards an “_Exercierknochen_” is therefore already
+present, or else the growth could not be formed; and the same reasoning
+applies to all other “acquired characters.”
+
+Nothing can arise in an organism unless the predisposition to it is
+pre-existent, for every acquired character is simply the reaction
+of the organism upon a certain stimulus. Hence I should never have
+thought of asserting that predispositions cannot be transmitted, as
+E. Roth appears to believe. For instance, I freely admit that the
+predisposition to an “_Exercierknochen_” varies, and that a
+strongly marked predisposition may be transmitted from father to son,
+in the form of bony tissue with a more susceptible constitution. But
+I should deny that the son could develop an “_Exercierknochen_”
+without having drilled, or that, after having drilled, he could
+develop it more easily than his father, on account of the drilling
+through which the latter first acquired it. I believe that this is as
+impossible as that the leaf of an oak should produce a gall without
+having been pierced by a gall-producing insect, as a result of the
+thousands of antecedent generations of oaks which have been pierced by
+such insects, and have thus “acquired” the power of producing galls. I
+am also far from asserting that the germ-plasm--which, as I hold, is
+transmitted as the basis of heredity from one generation to another--is
+absolutely unchangeable or totally uninfluenced by forces residing in
+the organism within which it is transformed into germ-cells. I am also
+compelled to admit that it is conceivable that organisms may exert a
+modifying influence upon their germ-cells, and even that such a process
+is to a certain extent inevitable. The nutrition and growth of the
+individual must exercise some influence upon its germ-cells; but in the
+first place this influence must be extremely slight, and in the second
+place it cannot act in the manner in which it is usually assumed that
+it takes place. A change of growth at the periphery of an organism,
+as in the case of an “_Exercierknochen_,” can never cause such a
+change in the molecular structure of the germ-plasm as would augment
+the predisposition to an “_Exercierknochen_,” so that the son
+would inherit an increased susceptibility of the bony tissue or even of
+the particular bone in question. But any change produced will result
+from the reaction of the germ-cell upon changes of nutrition caused by
+alteration in growth at the periphery, leading to some change in the
+size, number, or arrangement of its molecular units. In the present
+state of our knowledge there is reason for doubting whether such
+reaction can occur at all; but, if it can take place, at all events
+the quality of the change in the germ-plasm can have nothing to do
+with the quality of the acquired character, but only with the way in
+which the general nutrition is influenced by the latter. In the case of
+the “_Exercierknochen_” there would be practically no change in
+the general nutrition, but if such a bony growth could reach the size
+of a carcinoma, it is conceivable that a disturbance of the general
+nutrition of the body might ensue. Certain experiments on plants--on
+which Nägeli showed that they can be submitted to strongly varied
+conditions of nutrition for several generations, without the production
+of any visible hereditary change--show that the influence of nutrition
+upon the germ-cells must be very slight, and that it may possibly leave
+the molecular structure of the germ-plasm altogether untouched. This
+conclusion is also supported by comparing the uncertainty of these
+results with the remarkable precision with which heredity acts in the
+case of those characters which are known to be transmitted. In fact,
+up to the present time, it has never been proved that any changes in
+general nutrition can modify the molecular structure of the germ-plasm,
+and far less has it been rendered by any means probable that the
+germ-cells can be affected by acquired changes which have no influence
+on general nutrition. If we consider that each so-called predisposition
+(that is, a power of reacting upon a certain stimulus in a certain way,
+possessed by any organism or by one of its parts) must be innate, and
+further that each acquired character is only the predisposed reaction
+of some part of an organism upon some external influence; then we must
+admit that only one of the causes which produce any acquired character
+can be transmitted, the one which was present before the character
+itself appeared, viz., the predisposition; and we must further
+admit that the latter arises from the germ, and that it is quite
+immaterial to the following generation whether such predisposition
+comes into operation or not. The continuity of the germ-plasm is amply
+sufficient to account for such a phenomenon, and I do not believe that
+any objection to my hypothesis, founded upon the actually observed
+phenomena of heredity, will be found to hold. If it be accepted, many
+facts will appear in a light different from that which has been cast
+upon them by the hypothesis which has been hitherto received,--a
+hypothesis which assumes that the organism produces germ-cells afresh,
+again and again, and that it produces them entirely from its own
+substance. Under the former theory the germ-cells are no longer looked
+upon as the product of the parent’s body, at least as far as their
+essential part--the specific germ-plasm--is concerned: they are rather
+considered as something which is to be placed in contrast with the
+_tout ensemble_ of the cells which make up the parent’s body, and
+the germ-cells of succeeding generations stand in a similar relation
+to one another as a series of generations of unicellular organisms,
+arising by a continued process of cell-division. It is true that in
+most cases the generations of germ-cells do not arise immediately
+from one another as complete cells, but only as minute particles of
+germ-plasm. This latter substance, however forms the foundation of the
+germ-cells of the next generation, and stamps them with their specific
+character. Previous to the publication of my theory, C. Jäger, and
+later M. Nussbaum, have expressed ideas upon heredity which come very
+near to my own. Both of these writers started with the hypothesis that
+there must be a direct connection between the germ-cells of succeeding
+generations, and they tried to establish such a continuity by supposing
+that the germ-cells of the offspring are separated from the parent
+germ-cell before the beginning of embryonic development, or at least
+before any histological differentiation has taken place. In this form
+their suggestion cannot be maintained, for it is in conflict with
+numerous facts. A continuity of the germ-cells does not now take place,
+except in very rare instances; but this fact does not prevent us from
+adopting a theory of the continuity of the germ-plasm, in favour of
+which much weighty evidence can be brought forward. In the following
+pages I shall attempt to develop further the theory of which I have
+just given a short account, to defend it against any objections which
+have been brought forward, and to draw from it new conclusions which
+may perhaps enable us more thoroughly to appreciate facts which are
+known, but imperfectly understood. It seems to me that this theory of
+continuity of the germ-plasm deserves at least to be examined in all
+its details, for it is the simplest theory upon the subject, and the
+one which is most obviously suggested by the facts of the case, and we
+shall not be justified in forsaking it for a more complex theory until
+proof that it can be no longer maintained is forthcoming. It does not
+presuppose anything except facts which can be observed at any moment,
+although they may not be understood,--such as assimilation, or the
+development of like organisms from like germs; while every other theory
+of heredity is founded on hypotheses which cannot be proved. It is
+nevertheless possible that continuity of the germ-plasm does not exist
+in the manner in which I imagine that it takes place, for no one can at
+present decide whether all the ascertained facts agree with and can be
+explained by it. Moreover, the ceaseless activity of research brings to
+light new facts every day, and I am far from maintaining that my theory
+may not be disproved by some of these. But even if it should have to
+be abandoned at a later period, it seems to me that, at the present
+time, it is a necessary stage in the advancement of our knowledge, and
+one which must be brought forward and passed through, whether it prove
+right or wrong, in the future. In this spirit I offer the following
+considerations, and it is in this spirit that I should wish them to be
+received.
+
+
+ THE GERM-PLASM
+
+I entirely agree with Strasburger when he says, “The specific qualities
+of organisms are based upon nuclei”; and I further agree with him in
+many of his ideas as to the relation between the nucleus and cell-body:
+“Molecular stimuli proceed from the nucleus into the surrounding
+cytoplasm; stimuli which, on the one hand, control the phenomena of
+assimilation in the cell, and, on the other hand, give to the growth
+of the cytoplasm, which depends upon nutrition, a certain character
+peculiar to the species.” “The nutritive cytoplasm assimilates, while
+the nucleus controls the assimilation, and hence the substances
+assimilated possess a certain constitution and nourish in a certain
+manner the cyto-idioplasm and the nuclear idioplasm. In this way the
+cytoplasm takes part in the phenomena of construction, upon which the
+specific form of the organism depends. This constructive activity
+of the cyto-idioplasm depends upon the regulative influence of the
+nuclei.” The nuclei therefore “determine the specific direction in
+which an organism develops.”
+
+The opinion--derived from the recent study of the phenomena of
+fertilization--that the nucleus impresses its specific character
+upon the cell, has received conclusive and important confirmation
+in the experiments upon the regeneration of Infusoria, conducted
+simultaneously by M. Nussbaum at Bonn, and by A. Gruber at Freiburg.
+Nussbaum’s statement that an artificially separated portion of a
+_Paramaecium_, which does not contain any nuclear substance,
+immediately dies, must not be accepted as of general application, for
+Gruber has kept similar fragments of other Infusoria alive for several
+days. Moreover, Gruber had previously shown that individual Protozoa
+occur, which live in a normal manner, and are yet without a nucleus,
+although this structure is present in other individuals of the same
+species. But the meaning of the nucleus is made clear by the fact,
+published by Gruber, that such artificially separated fragments of
+Infusoria are incapable of regeneration, while on the other hand those
+fragments which contain nuclei always regenerate. It is therefore only
+under the influence of the nucleus that the cell substance re-develops
+into the full type of the species. In adopting the view that the
+nucleus is the factor which determines the specific nature of the cell,
+we stand on a firm foundation upon which we can build with security.
+
+If therefore the first segmentation nucleus contains, in its molecular
+structure, the whole of the inherited tendencies of development, it
+must follow that during segmentation and subsequent cell-division, the
+nucleoplasm will enter upon definite and varied changes which must
+cause the differences appearing in the cells which are produced; for
+identical cell-bodies depend, _ceteris paribus_, upon identical
+nucleoplasm, and conversely different cells depend upon differences
+in the nucleoplasm. The fact that the embryo grows more strongly in
+one direction than in another, that its cell-layers are of different
+nature and are ultimately differentiated into various organs and
+tissues,--forces us to accept the conclusion that the nuclear substance
+has also been changed in nature, and that such changes take place
+during ontogenetic development in a regular and definite manner.
+This view is also held by Strasburger, and it must be the opinion of
+all who seek to derive the development of inherited tendencies from
+the molecular structure of the germ-plasm, instead of from preformed
+gemmules.
+
+We are thus led to the important question as to the forces by which the
+determining substance or nucleoplasm is changed, and as to the manner
+in which it changes during the course of ontogeny, and on the answer
+to this question our further conclusions must depend. The simplest
+hypothesis would be to suppose that, at each division of the nucleus,
+its specific substance divides into two halves of unequal quality, so
+that the cell-bodies would also be transformed; for we have seen that
+the character of a cell is determined by that of its nucleus. Thus in
+any Metazoon the first two segmentation spheres would be transformed in
+such a manner that one only contained the hereditary tendencies of the
+endoderm and the other those of the ectoderm, and therefore, at a later
+stage, the cells of the endoderm would arise from the one and those of
+the ectoderm from the other; and this is actually known to occur. In
+the course of further division the nucleoplasm of the first ectoderm
+cell would again divide unequally, _e. g._, into the nucleoplasm
+containing the hereditary tendencies of the nervous system, and into
+that containing the tendencies of the external skin. But even then,
+the end of the unequal division of nuclei would not have been nearly
+reached; for, in the formation of the nervous system, the nuclear
+substance which contains the hereditary tendencies of the sense-organs
+would, in the course of further cell-division, be separated from that
+which contains the tendencies of the central organs, and the same
+process would continue in the formation of all single organs, and in
+the final development of the most minute histological elements. This
+process would take place in a definitely ordered course, exactly as
+it has taken place throughout a very long series of ancestors; and
+the determining and directing factor is simply and solely the nuclear
+substance, the nucleoplasm, which possesses such a molecular structure
+in the germ-cell that all such succeeding stages of its molecular
+structure in future nuclei must necessarily arise from it, as soon as
+the requisite external conditions are present. This is almost the same
+conception of ontogenetic development as that which has been held by
+embryologists who have not accepted the doctrine of evolution: for we
+have only to transfer the primary cause of development, from an unknown
+source within the organism, into the nuclear substance, in order to
+make the views identical.
+
+
+I believe I have shown that theoretically hardly any objection can be
+raised against the view that the nuclear substance of somatic cells
+may contain unchanged germ-plasm, or that this germ-plasm may be
+transmitted along certain lines. It is true that we might imagine _a
+priori_ that all somatic nuclei contain a small amount of unchanged
+germ-plasm. In Hydroids such an assumption cannot be made, because only
+certain cells in a certain succession possess the power of developing
+into germ-cells; but it might well be imagined that in some organisms
+it would be a great advantage if every part possessed the power of
+growing up into the whole organism and of producing sexual cells under
+appropriate circumstances. Such cases might exist if it were possible
+for all somatic nuclei to contain a minute fraction of unchanged
+germ-plasm. For this reason, Strasburger’s other objection against my
+theory also fails to hold; viz., that certain plants can be propagated
+by pieces of rhizomes, roots, or even by means of leaves, and that
+plants produced in this manner may finally give rise to flowers, fruit
+and seeds, from which new plants arise. “It is easy to grow new plants
+from the leaves of begonia which have been cut off and merely laid upon
+moist sand, and yet in the normal course of ontogeny the molecules of
+germ-plasm would not have been compelled to pass through the leaf; and
+they ought therefore to be absent from its tissue. Since it is possible
+to raise from the leaf a plant which produces flower and fruit, it is
+perfectly certain that special cells containing the germ-substance
+cannot exist in the plant.” But I think that this fact only proves
+that in begonia and similar plants all the cells of the leaves or
+perhaps only certain cells contain a small amount of germ-plasm, and
+that consequently these plants are specially adapted for propagation
+by leaves. How is it then that all plants cannot be reproduced in this
+way? No one has ever grown a tree from the leaf of the lime or oak,
+or a flowering plant from the leaf of the tulip or convolvulus. It
+is insufficient to reply that in the last mentioned cases the leaves
+are more strongly specialized, and have thus become unable to produce
+germ-substance; for the leaf-cells in these different plants have
+hardly undergone histological differentiation in different degrees.
+If, notwithstanding, the one can produce a flowering plant, while the
+others have not this power, it is of course clear that reasons other
+than the degree of histological differentiation must exist; and,
+according to my opinion, such a reason is to be found in the admixture
+of a minute quantity of unchanged germ-plasm with some of their nuclei.
+
+In Sach’s excellent lectures on the physiology of plants, we read on
+page 723--“In the true mosses almost any cell of the roots, leaves and
+shoot-axes, and even of the immature sporogonium, may grow out under
+favourable conditions, become rooted, form new shoots, and give rise to
+an independent living plant.” Since such plants produce germ-cells at
+a later period, we have here a case which requires the assumption that
+all or nearly all cells must contain germ-plasm.
+
+The theory of the continuity of the germ-plasm seems to me to be
+still less disproved or even rendered improbable by the facts of the
+alternation of generations. If the germ-plasm may pass on from the egg
+into certain somatic cells of an individual, and if it can be further
+transmitted along certain lines, there is no difficulty in supposing
+that it may be transmitted through a second, third, or through any
+number of individuals produced from the former by budding. In fact, in
+the Hydroids, on which my theory of the continuity of the germ-plasm
+has been chiefly based, alternation of generations is the most
+important means of propagation.
+
+
+ THE SIGNIFICANCE OF THE POLAR BODIES
+
+We have already seen that the specific nature of a cell depends upon
+the molecular structure of its nucleus; and it follows from this
+conclusion that my theory is further, and as I believe strongly,
+supported, by the phenomenon of the expulsion of polar bodies, which
+has remained inexplicable for so long a time.
+
+For if the specific molecular structure of a cell-body is caused
+and determined by the structure of the nucleoplasm, every kind of
+cell which is histologically differentiated must have a specific
+nucleoplasm. But the egg-cell of most animals, at any rate during
+the period of growth, is by no means an indifferent cell of the most
+primitive type. At such a period its cell-body has to perform quite
+peculiar and specific functions; it has to secrete nutritive substances
+of a certain chemical nature and physical constitution, and to store
+up this food material in such a manner that it may be at the disposal
+of the embryo during its development. In most cases the egg-cell
+also forms membranes which are often characteristic of particular
+species of animals. The growing egg-cell is therefore histologically
+differentiated: and in this respect resembles a somatic cell. It
+may perhaps be compared to a gland-cell, which does not expel its
+secretion, but deposits it within its own substance. To perform such
+specific functions it requires a specific cell-body, and the latter
+depends upon a specific nucleus. It therefore follows that the growing
+egg-cell must possess nucleoplasm of specific molecular structure,
+which directs the above mentioned secretory functions of the cell.
+The nucleoplasm of histologically differentiated cells may be called
+histogenetic nucleoplasm, and the growing egg-cell must contain such
+a substance, and even a certain specific modification of it. This
+nucleoplasm cannot possibly be the same as that which, at a later
+period, causes embryonic development. Such development can only be
+produced by the true germ-plasm of immensely complex constitution, such
+as I have previously attempted to describe. It therefore follows that
+the nucleus of the egg-cell contains two kinds of nucleoplasm:--germ
+and a peculiar modification of histogenetic nucleoplasm, which
+may be called ovogenetic nucleoplasm. This substance must greatly
+preponderate in the young egg-cell, for, as we have already seen, it
+controls the growth of the latter. The germ-plasm, on the other hand,
+can only be present in minute quantity at first, but it must undergo
+considerable increase during the growth of the cell. But in order
+that the germ-plasm may control the cell-body, or, in other words, in
+order that embryonic development may begin, the still preponderating
+ovogenetic nucleoplasm must be removed from the cell. This removal
+takes place in the same manner as that in which differing nuclear
+substances are separated during the ontogeny of the embryo: viz., by
+nuclear division, leading to cell-division. The expulsion of the polar
+bodies is nothing more than the removal of ovogenetic nucleoplasm from
+the egg-cell. That the ovogenetic nucleoplasm continues greatly to
+preponderate in the nucleus up to the very last, may be concluded from
+the fact that two successive divisions of the latter and the expulsion
+of two polar bodies appear to be the rule. If in this way a small part
+of the cell-body is expelled from the egg, the extrusion must in all
+probability be considered as an inevitable loss, without which the
+removal of the ovogenetic nucleoplasm cannot be effected.
+
+
+ ON THE NATURE OF PARTHENOGENESIS
+
+It is well known that the formation of polar bodies has been repeatedly
+connected with the sexuality of germ-cells, and that it has been
+employed to explain the phenomena of parthenogenesis. I may now perhaps
+be allowed to develop the views as to the nature of parthenogenesis at
+which I have arrived under the influence of my explanation of polar
+bodies.
+
+The theory of parthenogenesis adopted by Minot and Balfour is
+distinguished by its simplicity and clearness, among all other
+interpretations which had been hitherto offered. Indeed, their
+explanation follows naturally and almost as a matter of course, if the
+assumption made by these observers be correct, that the polar body is
+the male part of the hermaphrodite egg-cell. An egg which has lost its
+male part cannot develop into an embryo until it has received a new
+male part in fertilization. On the other hand, an egg which does not
+expel its male part may develop without fertilization, and thus we are
+led to the obvious conclusion that parthenogenesis is based upon the
+non-expulsion of polar bodies. Balfour distinctly states “that the
+function of forming polar cells has been acquired by the ovum for the
+express purpose of preventing parthenogenesis.”
+
+It is obvious that I cannot share this opinion, for I regard the
+expulsion of polar bodies as merely the removal of the ovogenetic
+nucleoplasm, on which depended the development of the specific
+histological structure of the egg-cell. I must assume that the
+phenomena of maturation in the parthenogenetic egg and in the sexual
+egg are precisely identical, and that in both, the ovogenetic
+nucleoplasm must in some way be removed before embryonic development
+can begin.
+
+Unfortunately the actual proof of this assumption is not so complete
+as might be desired. In the first place, we are as yet uncertain
+whether polar bodies are or are not expelled by parthenogenetic eggs;
+for in no single instance has such expulsion been established beyond
+doubt. It is true that this deficiency does not afford any support
+to the explanation of Minot and Balfour, for in all cases in which
+polar bodies have not been found in parthenogenetic eggs, these
+structures are also absent from the eggs which require fertilization
+in the same species. But although the expulsion of polar bodies in
+parthenogenesis has not yet been proved to occur, we must assume it to
+be nearly certain that the phenomena of maturation, whether connected
+or unconnected with the expulsion of polar bodies, are the same in the
+eggs which develop parthenogenetically and in those which are capable
+of fertilization, in one and the same species. This conclusion depends,
+above all, upon the phenomena of reproduction in bees, in which,
+as a matter of fact, the same egg may be fertilized or may develop
+parthenogenetically, as I shall have occasion to describe in greater
+detail at a later period.
+
+Hence when we see that the eggs of many animals are capable of
+developing without fertilization, while in other animals such
+development is impossible, the difference between the two kinds of eggs
+must rest upon something more than the mode of transformation of the
+nucleus of the germ-cell into the first segmentation nucleus. There
+are, indeed, facts which distinctly point to the conclusion that the
+difference is based upon quantitative and not qualitative relations.
+A large number of insects are exceptionally reproduced by the
+parthenogenetic method, _e. g._, in Lepidoptera. Such development
+does not take place in all the eggs laid by an unfertilized female,
+but only in part, and generally a small fraction of the whole, while
+the rest die. But among the latter there are some which enter upon
+embryonic development without being able to complete it, and the
+stage at which development may cease also varies. It is also known
+that the eggs of higher animals may pass through the first stages of
+segmentation without having been fertilized. This was shown to be
+the case in the egg of the frog by Leuckart, in that of the fowl by
+Oellacher, and even in the egg of mammals by Hensen.
+
+Hence in such cases it is not the impulse to development, but the power
+to complete it, which is absent. We know that force is always bound up
+with matter, and it seems to me that such instances are best explained
+by the supposition that too small an amount of that form of matter
+is present, which, by its controlling agency, effects the building
+up of the embryo by the transformation of mere nutritive material.
+This substance is the germ-plasm of the segmentation nucleus, and I
+have assumed above that it is altered in the course of ontogeny by
+changes which arise from within, so that when sufficient nourishment
+is afforded by the cell-body, each succeeding stage necessarily
+results from the preceding one. I believe that changes arise in the
+constitution of the nucleoplasm at each cell-division which takes place
+during the building up of the embryo, changes which either correspond
+or differ in the two halves of each nucleus. If, for the present, we
+neglect the minute amount of unchanged germ-plasm which is reserved
+for the formation of the germ-cells, it is clear that a great many
+different stages in the development of somatic nucleoplasm are thus
+formed, which may be denominated as stages 1, 2, 3, 4, etc., up to
+_n_. In each of these stages the cells differ more as development
+proceeds, and as the number by which the stage is denominated becomes
+higher. Thus, for instance, the two first segmentation spheres would
+represent the first stage of somatic nucleoplasm, a stage which may
+be considered as but slightly different in its molecular structure
+from the nucleoplasm of the segmentation nucleus; the first four
+segmentation spheres would represent the second stage; the succeeding
+eight spheres the third, and so on. It is clear that at each successive
+stage the molecular structure of the nucleoplasm must be further
+removed from that of the germ-plasm, and that, at the same time, the
+cells of each successive stage must also diverge more widely among
+themselves in the molecular structure of their nucleoplasm. Early in
+development each cell must possess its own peculiar nucleoplasm, for
+the further course of development is peculiar to each cell. It is
+only in the later stages that equivalent or nearly equivalent cells
+are formed in large numbers, cells in which we must also suppose the
+existence of equivalent nucleoplasm.
+
+If we may assume that a certain amount of germ-plasm must be contained
+in the segmentation nucleus in order to complete the whole process of
+the ontogenetic differentiation of this substance; if we may further
+assume that the quantity of germ-plasm in the segmentation nucleus
+varies in different cases; then we should be able to understand why
+one egg can only develop after fertilization, while another can
+begin its development without fertilization, but cannot finish it,
+and why a third is even able to complete its development. We should
+also understand why one egg only passes through the first stages of
+segmentation and is then arrested, while another reaches a few more
+stages in advance, and a third develops so far that the embryo is
+nearly completely formed. These differences would depend upon the
+extent to which the germ-plasm, originally present in the egg, was
+sufficient for the development of the latter; development will be
+arrested as soon as the nucleoplasm is no longer capable of producing
+the succeeding stage, and is thus unable to enter upon the following
+nuclear division.
+
+From a general point of view such a theory would explain many
+difficulties, and it would render possible an explanation of the
+phyletic origin of parthenogenesis, and an adequate understanding
+of the strange and often apparently abrupt and arbitrary manner
+of its occurrence. In my works on Daphnidae I have already laid
+especial stress upon the proposition that parthenogenesis in insects
+and Crustacea certainly cannot be an ancestral condition which has
+been transmitted by heredity, but that it has been derived from a
+sexual condition. In what other way can we explain the fact that
+parthenogenesis is present in certain species or genera, but absent
+in others closely allied to them; or the fact that males are entirely
+wanting in species of which the females possess a complete apparatus
+for fertilization? I will not repeat all the arguments with which I
+attempted to support this conclusion. Such a conclusion may be almost
+certainly accepted for the Daphnidae, because parthenogenesis does not
+occur in their still living ancestors, the Phyllopods, and especially
+the Estheridae. In Daphnidae the cause and object of the phyletic
+development of parthenogenesis may be traced more clearly than in any
+other group of animals. In Daphnidae we can accept the conclusion with
+greater certainty than in all other groups, except perhaps the Aphidae,
+that parthenogenesis is extremely advantageous to species in certain
+conditions of life; and that it has only been adopted when, and as far
+as, it has been beneficial; and further, that at least in this group
+parthenogenesis became possible and was adopted in each species as soon
+as it became useful. Such a result can be easily understood if it is
+only the presence of more or less germ-plasm which decides whether an
+egg is or is not capable of development without fertilization.
+
+If we now examine the foundations of this hypothesis we shall find that
+we may at once accept one of its assumptions, viz., that fluctuations
+occur in the quantity of germ-plasm in the segmentation nucleus; for
+there can never be absolute equality in any single part of different
+individuals. As soon therefore as these fluctuations become so great
+that parthenogenesis is produced, it may become, by the operation of
+natural selection, the chief mode of reproduction of the species or
+of certain generations of the species. In order to place this theory
+upon a firm basis, we have simply to decide whether the quantity of
+germ-plasm contained in the segmentation nucleus is the factor which
+determines development; although for the present it will be sufficient
+if we can render this view to some extent probable, and show that it is
+not a contradiction of established facts.
+
+At first sight this hypothesis seems to encounter serious difficulties.
+It will be objected that neither the beginning nor the end of embryonic
+development can possibly depend upon the quantity of nucleoplasm in the
+segmentation nucleus, since the amount may be continually increased
+by growth; for it is well known that during embryonic development
+the nuclear substance increases with astonishing rapidity. By an
+approximate calculation I found that in the egg of a Cynips the
+quantity of nuclear substance present at the time when the blastoderm
+was about to be formed, and when there were twenty-six nuclei, was even
+then seven times as great as the quantity which had been contained
+in the segmentation nucleus. How then can we imagine that embryonic
+development would ever be arrested from want of nuclear substance, and
+if such deficiency really acted as an arresting force, how then could
+development begin at all? We might suppose that when germ-plasm is
+present in sufficient quantity to start segmentation, it must also be
+sufficient to complete the development; for it grows continuously, and
+must presumably always possess a power equal to that which it possessed
+at the beginning, and which was just sufficient to start the process of
+segmentation. If at each ontogenetic stage the quantity of nucleoplasm
+is just sufficient to produce the following stage, we might well
+imagine that the whole ontogeny would necessarily be completed.
+
+The flaw in this argument lies in the erroneous assumption that the
+growth of nuclear substance is, when the quality of the nucleus and
+the conditions of nutrition are equal, unlimited and uncontrolled. The
+intensity of growth must depend upon the quantity of nuclear substance
+with which growth and the phenomena of segmentation commenced. There
+must be an optimum quantity of nucleoplasm with which the growth of
+the nucleus proceeds most favourably and rapidly, and this optimum
+will be represented in the normal size of the segmentation nucleus.
+Such a size is just sufficient to produce, in a certain time and
+under certain external conditions, the nuclear substance necessary
+for the construction of the embryo, and to start the long series
+of cell-divisions. When the segmentation nucleus is smaller, but
+large enough to enter upon segmentation, the nuclei of the two first
+embryonic cells will fall rather more below the normal size, because
+the growth of the segmentation nucleus, during and after division will
+be less rapid on account of its unusually small size. The succeeding
+generations of nuclei will depart more and more from the normal size in
+each respective stage, because they do not pass into a resting stage
+during embryonic development, but divide again immediately after their
+formation. Hence nuclear growth would become less vigorous as the
+nuclei fell more and more below the optimum size, and at last a moment
+would arrive when they would be unable to divide, or would be at least
+unable to control the cell-body in such a manner as to lead to its
+division.
+
+The first event of importance for embryonic development is the
+maturation of the egg, _i. e._, the transformation of the
+nucleus of the germ-cell into a nuclear spindle and the removal of
+the ovogenetic nucleoplasm by the separation of polar bodies, or by
+some analogous process. There must be some cause for this separation,
+and I have already tried to show that it may lie in the quantitative
+relations which obtain between the two kinds of nucleoplasm contained
+in the nucleus of the egg. I have suggested that the germ-plasm, at
+first small in quantity, undergoes a gradual increase, so that it
+can finally oppose the ovogenetic nucleoplasm. I will not further
+elaborate this suggestion, for the ascertained facts are insufficient
+for the purpose. But the appearances witnessed in nuclear division
+indicate that there are opposing forces, and that such a contest is
+the motive cause of division; and Roux may be right in referring the
+opposition to electrical forces. However this may be, it is perfectly
+certain that the development of this opposition is based upon internal
+conditions arising during growth in the nucleus itself. The quantity
+of nuclear thread cannot by itself determine whether the nucleus can
+or cannot enter upon division; if so, it would be impossible for two
+divisions to follow each other in rapid succession, as is actually
+the case in the separation of the two polar bodies, and also in their
+subsequent division. In addition to the effects of quantity, the
+internal conditions of the nucleus must also play an important part in
+these phenomena. Quantity alone does not necessarily produce nuclear
+division, or the nucleus of the egg would divide long before maturation
+is complete, for it contains much more nucleoplasm than the female
+pronucleus, which remains in the egg after the expulsion of the polar
+bodies, and which is in most cases capable of further division. But
+the fact that segmentation begins immediately after the conjugation of
+male and female pronuclei, also shows that quantity is an essential
+requisite. The effect of fertilization has been represented as
+analogous to that of the spark which kindles the gunpowder. In the
+latter case an explosion ensues, in the former segmentation begins.
+Even now many authorities are inclined to refer the polar repulsion
+manifested in the nuclear division which immediately follows
+fertilization, to the antagonism between male and female elements. But,
+according to the important discoveries of Flemming and van Beneden, the
+polar repulsion in each nuclear division is not based on the antagonism
+between male and female loops, but depends upon the antagonism and
+mutual repulsion between the two halves of the same loop. The loops of
+the father and those of the mother remain together and divide together
+throughout the whole ontogeny.
+
+What can be the explanation of the fact that nuclear division follows
+immediately after fertilization, but that without fertilization it
+does not occur in most cases? There is only one possible explanation,
+viz., the fact that the quantity of the nucleus has been suddenly
+doubled, as the result of conjugation. The difference between the male
+and female pronuclei cannot serve as an explanation, even though the
+nature of this difference is entirely unknown, because polar repulsion
+is not developed between the male and female halves of the nucleus, but
+within each male and each female half. We are thus forced to conclude
+that increase in the quantity of the nucleus affords an impulse for
+division, the disposition towards it being already present. It seems
+to me that this view does not encounter any theoretical difficulties,
+and that it is an entirely feasible hypothesis to suppose that, besides
+the internal conditions of the nucleus, its quantitative relation to
+the cell-body must be taken into especial account. It is imaginable, or
+perhaps even probable, that the nucleus enters upon division as soon
+as its idioplasm has attained a certain strength, quite apart from the
+supposition that certain internal conditions are necessary for this
+end. As above stated, such conditions may be present, but division may
+not occur because the right quantitative relation between nucleus and
+cell-body, or between the different kinds of nuclear idioplasm has not
+been established. I imagine that such a quantitative deficiency exists
+in an egg which, after the expulsion of the ovogenetic nucleoplasm
+in the polar bodies, requires fertilization in order to begin
+segmentation. The fact that the polar bodies were expelled proves that
+the quantity of the nucleus was sufficient to cause division, while
+afterwards it was no longer sufficient to produce such a result.
+
+This suggestion will be made still clearer by an example. In _Ascaris
+megalocephala_ the nuclear substance of the female pronucleus
+forms two loops, and the male pronucleus does the same; hence the
+segmentation nucleus contains four loops, and this is also the case
+with the first segmentation spheres. If we suppose that in embryonic
+development the first nuclear division requires such an amount of
+nuclear substance as is necessary for the formation of four loops,--it
+follows that an egg, which can only form two or three loops from its
+nuclear reticulum, would not be able to develop parthenogenetically,
+and that not even the first division would take place. If we further
+suppose that, while four loops are sufficient to start nuclear
+division, these loops must be of a certain size and quantity in order
+to complete the whole ontogeny (in a certain species), it follows
+that eggs possessing a reticulum which contains barely enough nuclear
+substance to divide into four segments, would be able to produce
+the first division and perhaps also the second and third, or some
+later division, but that at a certain point during ontogeny, the
+nuclear substance would become insufficient, and development would be
+arrested. This will occur in eggs which enter upon development without
+fertilization, but are arrested before its completion. One might
+compare this retardation leading to the final arrest of development,
+to a railway train which is intended to meet a number of other trains
+at various junctions, and which can only travel slowly because of some
+defect in the engine. It will be a little behind time at the first
+junction, but it may just catch the train, and it may also catch the
+second or even the third; but it will be later at each successive
+junction, and will finally arrive too late for a certain train; and
+after that it will miss all the trains at the remaining junctions. The
+nuclear substance grows continuously during development, but the rate
+at which it increases depends upon the nutritive conditions together
+with its initial quantity. The nutritive changes during the development
+of an egg depend upon the quantity of the cell-body which was present
+at the outset, and which cannot be increased. If the quantity of
+the nuclear substance is rather too small at the beginning, it will
+become more and more insufficient in succeeding stages, as its growth
+becomes less vigorous, and differs more from the standard it would
+have reached if the original quantity had been normal. Consequently it
+will gradually fall more and more short of the normal quantity, like
+the train which arrives later and later at each successive junction,
+because its engine, although with the full pressure of steam, is unable
+to attain the normal speed.
+
+It will be objected that four loops cannot be necessary for nuclear
+division in _Ascaris_, since such division takes place in the
+formation of the polar bodies, resulting in the appearance of the
+female pronucleus with only two loops. But this fact only shows that
+the quantity of nuclear substance necessary for the formation of four
+loops is not necessary for all nuclear divisions; it does not disprove
+the assumption that such a quantity is required for the division of
+the segmentation nucleus. In addition to these considerations we must
+not leave the substance of the cell-body altogether out of account,
+for, although it is not the bearer of the tendencies of heredity, it
+must be necessary for every change undergone by the nucleus, and it
+surely also possesses the power of influencing changes to a large
+extent. There must be some reason for the fact that in all animal eggs
+with which we are acquainted, the nucleus moves to the surface of the
+egg at the time of maturation, and there passes through its well known
+transformation. It is obvious that it is there subjected to different
+influences from those which would have acted upon it in the center of
+the cell-body, and it is clear that such an unequal cell-division as
+takes place in the separation of the polar bodies could not occur if
+the nucleus remained in the center of the egg.
+
+This explanation of the necessity for fertilization does not exclude
+the possibility that, under certain circumstances, the substance of the
+egg-nucleus may be larger, so that it is capable of forming four loops.
+Eggs which thus possess sufficient nucleoplasm, viz., germ-plasm, for
+the formation of the requisite four loops of normal size (namely, of
+the size which would have been produced by fertilization), can and must
+develop by the parthenogenetic method.
+
+Of course the assumption that four loops must be formed has only
+been made for the sake of illustration. We do not yet know whether
+there are always exactly four loops in the segmentation nucleus. I
+may add that, although the details by which these considerations are
+illustrated are based on arbitrary assumptions, the fundamental view
+that the development of the egg depends, _ceteris paribus_, upon
+the quantity of nuclear substance, is certainly right, and follows as
+a necessary conclusion from the ascertained facts. It is not unlikely
+that such a view may receive direct proof in the results of future
+investigations. Such proof might, for instance, be forthcoming if we
+were to ascertain, in the same species, the number of loops present
+in the segmentation nucleus of fertilization, as compared with those
+present in the segmentation nucleus of parthenogenesis.
+
+The reproductive process in bees will perhaps be used as an argument
+against my theory. In these insects the same egg will develop into a
+female or male individual, according as fertilization has or has not
+taken place, respectively. Hence one and the same egg is capable of
+fertilization, and also of parthenogenetic development, if it does
+not receive a spermatozoon. It is in the power of the queen-bee to
+produce male or female individuals: by an act of will she decides
+whether the egg she is laying is to be fertilized or unfertilized.
+She “knows beforehand” whether an egg will develop into a male or a
+female animal, and deposits the latter kind in the cells of queens and
+workers, the former in the cells of drones. It has been shown by the
+discoveries of Leuckart and von Siebold that all the eggs are capable
+of developing into male individuals, and that they are only transformed
+into “female eggs” by fertilization. This fact seems to be incompatible
+with my theory as to the cause of parthenogenesis, for if the same
+egg, possessing exactly the same contents, and above all the same
+segmentation nucleus, may develop sexually or parthenogenetically, it
+appears that the power of parthenogenetic development must depend on
+some factor other than the quantity of germ-plasm.
+
+Although this appears to be the case, I believe that my theory
+encounters no real difficulty. I have no doubt whatever that the same
+egg may develop with or without fertilization. From a careful study of
+the numerous excellent investigations upon this point which have been
+conducted in a particularly striking manner by Bessels (in addition
+to the observers quoted above), I have come to the conclusion that
+the fact is absolutely certain. It must be candidly admitted that
+the same egg will develop into a drone when not fertilized, or into
+a worker or queen when fertilized. One of Bessels’ experiments is
+sufficient to prove this assertion. He cut off the wings of a young
+queen and thus rendered her incapable of taking “the nuptial flight.”
+He then observed that all the eggs which she laid developed into
+male individuals. This experiment was made in order to prove that
+drones are produced by unfertilized eggs; but it also proves that the
+assertion mentioned above is correct, for the eggs which ripen first
+and are therefore first laid, would have been fertilized had the queen
+been impregnated. The supposition that, at certain times, the queen
+produces eggs requiring fertilization, while at other times her eggs
+develop parthenogenetically, is quite excluded by this experiment; for
+it follows from it that the eggs must all be of precisely the same
+kind, and that there is no difference between the eggs which require
+fertilization and those which do not.
+
+But does it therefore follow that the quantity of germ-plasm in
+the segmentation nucleus is not the factor which determines the
+beginning of embryonic development? I believe not. It can be very
+well imagined that the nucleus of the egg, having expelled the
+ovogenetic nucleoplasm, may be increased to the size requisite for the
+segmentation nucleus in one of two ways: either by conjugation with
+a sperm-nucleus, or by simply growing to double its size. There is
+nothing improbable in this latter assumption, and one is even inclined
+to inquire why such growth does not take place in all unfertilized
+eggs. The true answer to this question must be that nature pursues
+the sexual method of reproduction, and that the only way in which the
+general occurrence of parthenogenesis could be prevented was by the
+production of eggs which remained sterile unless they were fertilized.
+This was effected by a loss of the capability of growth on the part of
+the egg-nucleus after it had expelled the ovogenetic nucleoplasm.
+
+The case of the bee proves in a very striking manner that the
+difference between eggs which require fertilization, and those which
+do not, is not produced until after the maturation of the egg and the
+removal of the ovogenetic nucleoplasm. The increase in the quantity of
+the germ-plasm cannot have taken place at any earlier period, or else
+the nucleus of the egg would always start embryonic development by
+itself, and the egg would probably be incapable of fertilization. For
+the relation between egg-nucleus and sperm-nucleus is obviously based
+upon the fact that each of them is insufficient by itself, and requires
+completion. If such completion had taken place at an early stage the
+egg-nucleus would either cease to exercise any attractive force upon
+the sperm-nucleus, or else conjugation would be effected, as in Fol’s
+interesting experiments upon fertilization by many spermatozoa; and,
+as in these experiments, malformation of the embryo would result. In
+Daphnidae I believe I have shown that the summer eggs are not only
+developed parthenogenetically, but also that they are never fertilized;
+and the explanation of this incapacity for fertilization may perhaps be
+found in the fact that their segmentation nucleus is already formed.
+
+We may therefore conclude that, in bees, the nucleus of the egg, formed
+during maturation, may either conjugate with the sperm-nucleus, or
+else if no spermatozoon reaches it the egg may, under the stimulus of
+internal causes, grow to double its size, thus attaining the dimensions
+of the segmentation nucleus. For our present purpose we may leave
+out of consideration the fact that in the latter case the individual
+produced is a male, and in the former case a female.
+
+
+FOOTNOTES:
+
+[Footnote 37: From _Essays upon Heredity and Kindred Biological
+Problems_, Vol. I (1889).]
+
+
+
+
+ XXXV
+
+ SIR NORMAN LOCKYER
+
+ 1836-1920
+
+
+ _Sir Joseph Norman Lockyer, born at Rugby, England, May 17, 1836,
+ entered the War Office in 1857. Through his own exertions he educated
+ himself in science and was one of the first to suggest the hypothesis
+ that the earth and other spheres were the result of the aggregation
+ of meteorites. He was also the first to apply the spectroscope to
+ the corona of the sun, revealing the chemical composition of solar
+ prominences as chiefly hydrogen, calcium, and helium. He died at
+ Sidmouth, Devonshire, August 16, 1920._
+
+
+ THE CHEMISTRY OF THE STARS[38]
+
+The importance of practical work, the educational value of the seeking
+after truth by experiment and observation on the part of even young
+students, are now generally recognized. That battle has been fought
+and won. But there is a tendency in the official direction of seats of
+learning to consider what is known to be useful, because it is used,
+in the first place. The fact that the unknown, that is, the unstudied,
+is the mine from which all scientific knowledge with its million
+applications has been won is too often forgotten.
+
+Bacon, who was the first to point out the importance of experiment in
+the physical sciences, and who predicted the applications to which I
+have referred, warns us that “_lucifera experimenta non fructifera
+quaerenda_”; and surely we should highly prize those results which
+enlarge the domain of human thought and help us to understand the
+mechanism of the wonderful universe in which our lot is cast, as well
+as those which add to the comfort and the convenience of our lives.
+
+It would be also easy to show by many instances how researches,
+considered ideally useless at the time they were made, have been the
+origin of the most tremendous applications. One instance suffices.
+Faraday’s trifling with wires and magnets has already landed us in one
+of the greatest revolutions which civilization has witnessed; and where
+the triumphs of electrical science will stop no man can say.
+
+This is a case in which the useless has been rapidly sublimed into
+utility so far as our material wants are concerned.
+
+I propose to bring to your notice another “useless” observation
+suggesting a line of inquiry which I believe sooner or later is
+destined profoundly to influence human thought along many lines.
+
+Fraunhofer at the beginning of this century examined sunlight and
+starlight through a prism. He found that the light received from the
+sun differed from that of the stars. So useless did his work appear
+that we had to wait for half a century till any considerable advance
+was made. It was found at last that the strange “lines” seen and named
+by Fraunhofer were precious indications of the chemical substances
+present in worlds immeasurably remote. We had, after half a century’s
+neglect, the foundation of solar and stellar chemistry, an advance in
+knowledge equaling any other in its importance.
+
+In dealing with my subject I shall first refer to the work which
+has been done in more recent years with regard to this chemical
+conditioning of the atmospheres of stars, and afterwards very briefly
+show how this work carries us into still other new and wider fields of
+thought.
+
+The first important matter which lies on the surface of such a general
+inquiry as this is that if we deal with the chemical elements as judged
+by the lines in their spectra we know for certain of the existence of
+oxygen, of nitrogen, of argon, representing one class of gases, in no
+celestial body whatever; whereas, representing other gases, we have a
+tremendous demonstration of the existence of all the known lines of
+hydrogen and helium.
+
+We see, then, that the celestial sorting out of gases is quite
+different from the terrestrial one.
+
+Taking the substances classed by the chemist as non-metals, we find
+carbon and silicium--I prefer, on account of its stellar behavior, to
+call it silicium, though it is old fashioned--present in celestial
+phenomena. We have evidence of this in the fact that we have a
+considerable development of carbon in some stars and an indication
+of silicium in others. But these are the only non-metals observed.
+Now, with regard to the metallic substances which we find, we deal
+chiefly with calcium, strontium, iron, and magnesium. Others are not
+absolutely absent, but their percentage quantity is so small that they
+are negligible in a general statement.
+
+Now do these chemical elements exist indiscriminately in all the
+celestial bodies, so that practically, from a chemical point of view,
+the bodies appear to us of similar chemical constitution? No; it is not
+so.
+
+From the spectra of those stars which resemble the sun, in that they
+consist of an interior nucleus surrounded by an atmosphere which
+absorbs the light of the nucleus, and which, therefore, we study by
+means of this absorption, it is to be gathered that the atmospheres
+of some stars are chiefly gaseous--i. e., consisting of elements we
+recognize as gases here--of others chiefly metallic, of others again
+mainly composed of carbon or compounds of carbon.
+
+Here, then, we have spectroscopically revealed the fact that there is
+considerable variation in the chemical constituents which build up the
+stellar atmospheres.
+
+This, though a general, is still an isolated statement. Can we connect
+it with another? One of the laws formulated by Kirchhoff in the infancy
+of spectroscopic inquiry has to do with the kind of radiation given
+out by bodies at different temperatures. A poker placed in a fire
+first becomes red, and, as it gets hotter, white hot. Examined in a
+spectroscope, we find that the red condition comes from the absence of
+blue light; that the white condition comes from the gradual addition of
+blue as the temperature increases.
+
+The law affirms that the hotter a mass of matter is the farther its
+spectrum extends into the ultraviolet.
+
+Hence the hotter a star is the farther does its complete or continuous
+spectrum lengthen out toward the ultraviolet and the less it is
+absorbed by cooler vapors in its atmosphere.
+
+Now, to deal with three of the main groups of stars, we find the
+following very general result:
+
+Gaseous stars Longest spectrum.
+Metallic stars Medium spectrum.
+Carbon stars Shortest spectrum.
+
+We have now associated two different series of phenomena, and we are
+enabled to make the following statement:
+
+Gaseous stars Highest temperature.
+Metallic stars Medium temperature.
+Carbon stars Lowest temperature.
+
+Hence the differences in apparent chemical constitutions are associated
+with differences of temperature.
+
+Can we associate with the two to which I have already called attention
+still a third class of facts? Laboratory work enables us to do this.
+When I began my inquiries the idea was, one gas or vapor, one spectrum.
+We now know that this is not true; the systems of bright lines given
+out by radiating substances change with the temperature.
+
+We can get the spectrum of a well known compound substance--say
+carbonic oxide; it is one special to the compound; we increase the
+temperature so as to break up the compound, and we then get the spectra
+of its constituents, carbon and oxygen.
+
+But the important thing in the present connection is that the spectra
+of the chemical elements behave exactly in the same way as the spectra
+of known compounds do when we employ temperatures far higher than those
+which break up the compounds; and indeed in some cases the changes
+are more marked. For brevity I will take for purposes of illustration
+three substances, and deal with one increase of temperature only, a
+considerable one and obtainable by rendering a substance incandescent,
+first by a direct current of electricity, as happens in the so-called
+“arc lamps” employed in electric lighting, and next by the employment
+of a powerful induction coil and battery of Leyden jars. In laboratory
+parlance we pass thus from the arc to the jar-spark. In the case of
+magnesium, iron, and calcium, the changes observed on passing from
+the temperature of the arc to that of the spark have been minutely
+observed. In each, new lines are added or old ones are intensified at
+the higher temperature. Such lines have been termed “enhanced lines.”
+
+These enhanced lines are not seen alone; outside the region of high
+temperature in which they are produced, the cooling vapors give us the
+cool lines. Still we can conceive the enhanced lines to be seen alone
+at the highest temperature in a space sufficiently shielded from the
+action of all lower temperatures, but such a shielding is beyond our
+laboratory expedients.
+
+In watching the appearance of these special enhanced lines in stellar
+spectra we have a third series of phenomena available, and we find that
+the results are absolutely in harmony with what has gone before. Thus:
+
+Gaseous stars Highest temperature Strong helium and faint
+ enhanced lines.
+
+Metallic stars Feeble helium and strong
+ Medium temperature enhanced lines.
+
+Carbon stars No helium and strong arc lines.
+ Lowest temperature Faint arc lines.
+
+It is clear now, not only that the spectral changes in stars are
+associated with, or produced by, changes of temperature, but that
+the study of the enhanced spark and the arc lines lands us in the
+possibility of a rigorous stellar thermometry, such lines being more
+easy to observe than the relative lengths of spectrum.
+
+Accepting this, we can take a long stride forward and, by carefully
+studying the chemical revelations of the spectrum, classify the stars
+along a line of temperature. But which line? Were all the stars in
+popular phraseology created hot? If so, we should simply deal with
+the running down of temperature, and because all the hottest stars
+are chemically alike, all cooler stars would be alike. But there are
+two very distinct groups of coolest stars; and since there are two
+different kinds of coolest stars, and only one kind of hottest stars,
+it cannot be merely a question either of a running up or a running down
+of temperature.
+
+Many years of very detailed inquiry have convinced me that all stars
+save the hottest must be sorted out into two series--those getting
+hotter and those, like our sun, getting cooler, and that the hottest
+stage in the history of a star is reached near the middle of its life.
+
+The method of inquiry adopted has been to compare large-scale
+photographs of the spectra of the different stars taken by my
+assistants at South Kensington; the complete harmony of the results
+obtained along various lines of other work carries conviction with it.
+
+We find ourselves here in the presence of minute details exhibiting the
+workings of a chemical law, associated distinctly with temperature;
+and more than this, we are also in the presence of high temperature
+furnaces, entirely shielded by their vastness from the presence of
+those distracting phenomena which we are never free from in the most
+perfect conditions of experiment we can get here.
+
+What, then, is the chemical law? It is this: In the very hottest
+stars we deal with the gases hydrogen, helium, and doubtless others
+still unknown, almost exclusively. At the next lowest temperatures we
+find these gases being replaced by metals in the state in which they
+are observed in our laboratories when the most powerful jar-spark is
+employed. At a lower temperature still the gases almost disappear
+entirely, and the metals exist in the state produced by the electric
+arc. Certain typical stars showing these chemical changes may be
+arranged as follows:
+
+This, then, is the result of our first inquiry into the existence of
+the various chemical elements in the atmospheres of stars generally.
+We get a great diversity, and we know that this diversity accompanies
+changes of temperature. We have also found that the sun, which we
+independently know to be a cooling star, and Arcturus are identical
+chemically.
+
+We have now dealt with the presence of the various chemical elements
+generally in the atmospheres of stars. The next point we have to
+consider is, whether the absorption which the spectrum indicates for
+us takes place from top to bottom of the atmosphere or only in certain
+levels.
+
+In many of these stars the atmosphere may be millions of miles high. In
+each the chemical substances in the hottest and coldest portions may be
+vastly different. The region, therefore, in which this absorption takes
+place, which spectroscopically enables us to discriminate star from
+star, must be accurately known before we can obtain the greatest amount
+of information from our inquiries.
+
+Our next duty then, clearly, is to study the sun--a star so near us
+that we can examine the different parts of its atmosphere, which we
+cannot do in the case of the more distant stars. By doing this we
+may secure facts which will enable us to ascertain in what parts of
+the atmosphere the absorption takes place which produces the various
+phenomena on which the chemical classification has been based.
+
+It is obvious that the general spectrum of the sun, like that of stars
+generally, is built up of all the absorptions which can make themselves
+felt in every layer of its atmosphere from bottom to top; that is, from
+the photosphere to the outermost part of the corona. Let me remind you
+that this spectrum is changeless from year to year.
+
+Now, sun-spots are disturbances produced in the photosphere; and the
+chromosphere, with its disturbances, called prominences, lies directly
+above it. Here, then, we are dealing with the lowest part of the sun’s
+atmosphere. We find first of all that, in opposition to the changeless
+general spectrum, great changes occur with the sun-spot period, both in
+the spots and chromosphere.
+
+The spot spectrum is indicated, as was found in 1866, by the widening
+of certain lines; the chromospheric spectrum, as was found in 1868, by
+the appearance at the sun’s limb of certain bright lines. In both cases
+the lines affected, seen at any one time, are relatively few in number.
+
+In the spot spectrum, at a sun-spot minimum, we find iron lines chiefly
+affected; at a maximum they are chiefly of unknown or unfamiliar
+origin. At the present moment the affected lines are those recorded
+in the spectra of vanadium and scandium, with others never seen in
+a laboratory. That we are here far away from terrestrial chemical
+conditions is evidenced by the fact that there is not a gram of
+scandium available for laboratory use in the world at the present time.
+
+Then we have the spectrum of the prominences and the chromosphere. That
+spectrum we are enabled to observe every day when the sun shines, as
+conveniently as we can observe that of sun spots. The chromosphere is
+full of marvels. At first, when our knowledge of spectra was very much
+more restricted than now, almost all the lines observed were unknown.
+In 1868 I saw a line in the yellow, which I found behaved very much
+like hydrogen, though I could prove that it was not due to hydrogen;
+for laboratory use the substance which gave rise to it I called helium.
+Next year I saw a line in the green at 1474 of Kirchhoff’s scale. That
+was an unknown line, but in some subsequent researches I traced it to
+iron. From that day to this we have observed a large number of lines.
+They have gradually been dragged out from the region of the unknown,
+and many are now recognized as enhanced lines, to which I have already
+called attention as appearing in the spectra of metals at a very high
+temperature.
+
+But useful as the method of observing the chromosphere without an
+eclipse, which enables us
+
+ “... to feel from world to world,”
+
+as Tennyson has put it, has proved, we want an eclipse to see it face
+to face.
+
+A tremendous flood of light has been thrown upon it by the use of large
+instruments constructed on a plan devised by Respighi and myself in
+1871. These give us an image of the chromosphere painted in each one
+of its radiations, so that the exact locus of each chemical layer is
+revealed. One of the instruments employed during the Indian eclipse of
+this year is that used in photographing the spectra of stars, so that
+it is now easy to place photographs of the spectra of the chromosphere
+obtained during a total eclipse and of the various stars side by side.
+
+I have already pointed out that the chemical classification indicated
+that the stars next above the sun in temperature are represented by γ
+Cygni and Procyon, one on the ascending, the other on the descending
+branch of the temperature curve.
+
+Studying the spectra photographed during the eclipse of this year we
+see that practically the lower part of the sun’s atmosphere, if present
+by itself, would give us the lines which specialize the spectra of γ
+Cygni or Procyon.
+
+I recognize in this result a veritable Rosetta stone, which will enable
+us to read the celestial hieroglyphics presented to us in stellar
+spectra, and help us to study the spectra and to get at results much
+more distinctly and certainly than ever before.
+
+One of the most important conclusions we draw from the Indian eclipse
+is that, for some reason or other, the lowest, hottest part of the
+sun’s atmosphere does not write its record among the lines which build
+up the general spectrum so effectively as does a higher one.
+
+There was another point especially important on which we hoped for
+information, and that was this: Up to the employment of the prismatic
+camera insufficient attention had been directed to the fact that in
+observations made by an ordinary spectroscope no true measure of the
+height to which the vapors or gases extended above the sun could be
+obtained; early observations, in fact, showed the existence of glare
+between the observer and the dark moon; hence it must exist between us
+and the sun’s surroundings.
+
+The prismatic camera gets rid of the effects of this glare, and its
+results indicate that the effective absorbing layer--that, namely,
+which gives rise to the Fraunhofer lines--is much more restricted in
+thickness than was to be gathered from the early observations.
+
+We are justified in extending these general conclusions to all the
+stars that shine in the heavens.
+
+So much, then, in brief, for solar teachings in relation to the record
+of the absorption of the lower parts of stellar atmospheres.
+
+Let us next turn to the higher portions of the solar surroundings, to
+see if we can get any effective help from them.
+
+In this matter we are dependent absolutely upon eclipses, and I shall
+fulfill my task very badly if I do not show you that the phenomena
+then observable when the so-called corona is visible, full of awe and
+grandeur to all, are also full of precious teaching to the student
+of science. This also varies like the spots and prominences with the
+sun-spot period.
+
+It happened that I was the only person that saw both the eclipse of
+1871 at the maximum of the sun-spot period and that of 1878 at minimum;
+the corona of 1871 was as distinct from the corona of 1878 as anything
+could be. In 1871 we got nothing but bright lines, indicating the
+presence of gases; namely, hydrogen and another, since provisionally
+called coronium. In 1878 we got no bright lines at all, so I stated
+that probably the changes in the chemistry and appearance of the corona
+would be found to be dependent upon the sun-spot period, and recent
+work has borne out that suggestion.
+
+I have now specially to refer to the corona as observed and
+photographed this year in India by means of the prismatic camera,
+remarking that an important point in the use of the prismatic camera is
+that it enables us to separate the spectrum of the corona from that of
+the prominences.
+
+One of the chief results obtained is the determination of the position
+of several lines of probably more than one new gas, which, so far, have
+not been recognized as existing on the earth.
+
+Like the lowest hottest layer, for some reason or other, this upper
+layer does not write its record among the lines which build up the
+general spectrum.
+
+
+GENERAL RESULTS REGARDING THE LOCUS OF ABSORPTION IN STELLAR ATMOSPHERES
+
+We learn from the sun, then, that the absorption which defines the
+spectrum of a star is the absorption of a middle region, one shielded
+both from the highest temperature of the lowest reaches of the
+atmosphere, where most tremendous changes are continually going on and
+the external region where the temperature must be low, and where the
+metallic vapors must condense.
+
+If this is true for the sun it must be equally true for Arcturus,
+which exactly resembles it. I go further than this, and say that in
+the presence of such definite results as those I have brought before
+you it is not philosophical to assume that the absorption may take
+place at the bottom of the atmosphere of one star or at the top of the
+atmosphere of another. The _onus probandi_ rests upon those who
+hold such views.
+
+So far I have only dealt in detail with the hotter stars, but I have
+pointed out that we have two distinct kinds of coolest ones, the
+evidence of their much lower temperature being the shortness of their
+spectra. In one of these groups we deal with absorption alone, as in
+those already considered; we find an important break in the phenomena
+observed; helium, hydrogen, and metals have practically disappeared,
+and we deal with carbon absorption alone.
+
+But the other group of coolest stars presents us with quite new
+phenomena. We no longer deal with absorption alone, but accompanying
+it we have radiation, so that the spectra contain both dark lines and
+bright ones. Now, since such spectra are visible in the case of new
+stars, the ephemera of the skies, which may be said to exist only for
+an instant relatively, and when the disturbance which gives rise to
+their sudden appearance has ceased, we find their places occupied by
+nebulæ, we cannot be dealing here with stars like the sun, which has
+already taken some millions of years to slowly cool, and requires more
+millions to complete the process into invisibility.
+
+The bright lines seen in the large number of permanent stars which
+resemble these fleeting ones--new stars, as they are called--are those
+discerned in the once mysterious nebulæ which, so far from being stars,
+were supposed not many years ago to represent a special order of
+created things.
+
+Now the nebulæ differ from stars generally in the fact that in their
+spectra we have practically to deal with radiation alone; we study them
+by their bright lines; the conditions which produce the absorption by
+which we study the chemistry of the hottest stars are absent.
+
+
+ A NEW VIEW OF STARS
+
+Here, then, we are driven to the perfectly new idea that some of the
+cooler bodies in the heavens, the temperature of which is increasing
+and which appear to us as stars, are really disturbed nebulæ.
+
+What, then, is the chemistry of the nebulæ? It is mainly gaseous;
+the lines of helium and hydrogen and the flutings of carbon, already
+studied by their absorption in the groups of stars to which I have
+already referred, are present as bright ones.
+
+The presence of the lines of the metals iron, calcium, and probably
+magnesium, shows us that we are not dealing with gases merely.
+
+Of the enhanced metallic lines there are none; only the low temperature
+lines are present, so far as we yet know. The temperature, then, is
+low, and lowest of all in those nebulæ where carbon flutings are seen
+almost alone.
+
+
+ A NEW VIEW OF NEBULÆ
+
+Passing over the old views, among them one that the nebulæ were holes
+in something dark which enabled us to see something bright beyond, and
+another that they were composed of a fiery fluid, I may say that not
+long ago, they were supposed to be masses of gases only, existing at a
+very high temperature.
+
+Now, since gases may glow at a low temperature as well as at a high
+one, the temperature evidence must depend upon the presence of cool
+metallic lines and the absence of the enhanced ones.
+
+The nebulæ, then, are relatively cool collections of some of the
+permanent gases and of some cool metallic vapors, and both gases and
+metals are precisely those I have referred to as writing their records
+most visibly in stellar atmosphere.
+
+Now, can we get more information concerning this association of certain
+gases and metals? In laboratory work it is abundantly recognized that
+all meteorites (and many minerals) when slightly heated give out
+permanent gases, and under certain conditions the spectrum of the
+nebulæ may in this way be closely approximated to. I have not time to
+labor this point, but I may say that a discussion of all the available
+observations to my mind demonstrates the truth of the suggestion, made
+many years ago by Professor Tait before any spectroscopic facts were
+available, that the nebulæ are masses of meteorites rendered hot by
+collisions.
+
+Surely human knowledge is all the richer for this indication of the
+connection between the nebulæ, hitherto the most mysterious bodies in
+the skies, and the “stones that fall from heaven.”
+
+
+ CELESTIAL EVOLUTION
+
+But this is, after all, only a stepping stone, important though it be.
+It leads us to a vast generalization. If the nebulæ are thus composed,
+they are bound to condense to centers, however vast their initial
+proportions, however irregular the first distribution of the cosmic
+clouds which compose them. Each pair of meteorites in collision puts us
+in mental possession of what the final stage must be. We begin with a
+feeble absorption of metallic vapors round each meteorite in collision;
+the space between the meteorites is filled with the permanent gases
+driven out farther afield and having no power to condense. Hence
+dark metallic and bright gas lines. As time goes on the former must
+predominate, for the whole swarm of meteorites will then form a gaseous
+sphere with a strongly heated center, the light of which will be
+absorbed by the exterior vapor.
+
+The temperature order of the group of stars with bright lines as well
+as dark ones in their spectra has been traced, and typical stars
+indicating the chemical changes have been as carefully studied as those
+in which absorption phenomena are visible alone, so that now there are
+no breaks in the line connecting the nebulæ with the stars on the verge
+of extinction.
+
+Here we are brought to another tremendous outcome--that of the
+evolution of all cosmical bodies from meteorites, the various stages
+recorded by the spectra being brought about by the various conditions
+which follow from the conditions.
+
+These are, shortly, that at first collisions produce luminosity among
+the colliding particles of the swarm, and the permanent gases are given
+off and fill the interspaces. As condensation goes on, the temperature
+at the center of condensation always increasing, all the meteorites
+in time are driven into a state of gas. The meteoritic bombardment
+practically now ceases for lack of material, and the future history
+of the mass of gas is that of a cooling body, the violent motions in
+the atmosphere while condensation was going on now being replaced by a
+relative calm.
+
+The absorption phenomena in stellar spectra are not identical at
+the same mean temperature on the ascending and descending sides of
+the curve, on account of the tremendous difference in the physical
+conditions.
+
+In a condensing swarm, the center of which is undergoing meteoritic
+bombardment from all sides, there cannot be the equivalent of the
+solar chromosphere; the whole mass is made up of heterogeneous vapor
+at different temperatures and moving with different velocities in
+different regions.
+
+In a condensed swarm, of which we can take the sun as a type, all
+action produced from without has practically ceased; we get relatively
+a quiet atmosphere and an orderly assortment of the vapors from top to
+bottom, disturbed only by the fall of condensed metallic vapors. But
+still, on the view that the differences in the spectra of the heavenly
+bodies chiefly represent differences in degree of condensation and
+temperature, there can be _au fond_, no great chemical difference
+between bodies of increasing and bodies of decreasing temperature.
+Hence we find at equal mean temperatures on opposite sides of the
+temperature curve this chemical similarity of the absorbing vapors
+proved by many points of resemblance in the spectra, especially the
+identical behavior of the enhanced metallic and cleveite lines.
+
+
+ CELESTIAL DISSOCIATION
+
+The time you were good enough to put at my disposal is now exhausted,
+but I cannot conclude without stating that I have not yet exhausted
+all the conceptions of a high order to which Fraunhofer’s apparently
+useless observation has led us.
+
+The work which to my mind has demonstrated the evolution of the cosmos
+as we know it from swarms of meteorites, has also suggested a chemical
+evolution equally majestic in its simplicity.
+
+A quarter of a century ago I pointed out that all the facts then
+available suggested the hypothesis that in the atmospheres of the sun
+and stars various degrees of “celestial dissociation” were at work,
+a “dissociation” which prevented the coming together of the finest
+particles of matter which at the temperature of the earth and at all
+artificial temperature yet attained here compose the metals, the
+metalloids and compounds.
+
+On this hypothesis the so-called atoms of the chemist represent not the
+origins of things, but only early stages of the evolutionary process.
+
+At the present time we have tens of thousands of facts which were not
+available twenty-five years ago. All these go to the support of the
+hypothesis, and among them I must indicate the results obtained at the
+last eclipse, dealing with the atmosphere of the sun in relation to
+that of the various stars of higher temperature to which I called your
+attention. In this way we can easily explain the enhanced lines of iron
+existing practically alone in Alpha Cygni. I have yet to learn any
+other explanation.
+
+I have nothing to take back, either from what I then said or what I
+have said since on this subject, and although the view is not yet
+accepted, I am glad to know that many other lines of work which are now
+being prosecuted tend to favor it.
+
+I have no hesitation in expressing my conviction that in a not distant
+future the inorganic evolution to which we have been finally led by
+following up Fraunhofer’s useless experiment will take its natural
+place side by side with that organic evolution, the demonstration of
+which has been one of the glories of the nineteenth century.
+
+And finally now comes the moral of my address. If I have helped to show
+that observations having no immediate practical bearing may yet help
+on the thought of mankind, and that this is a thing worth the doing,
+let me express a hope that such work shall find no small place in the
+future University of Birmingham.
+
+
+FOOTNOTES:
+
+[Footnote 38: From an address delivered at the University of Birmingham
+(1900).]
+
+
+
+
+ XXXVI
+
+ ROBERT KOCH
+
+ 1843-1910
+
+
+ _Robert Koch, born at Klausthal, Hanover, Germany, December 11,
+ 1843, graduated from Göttingen in 1866. After a short period as
+ assistant surgeon in the General Hospital in Hamburg, he practised
+ medicine at Langenhagen, Kackwitz, and Wollstein from 1872 to 1880,
+ during which time he began his researches in bacteriology. By 1878 he
+ had placed bacteriology on a scientific basis. In 1880 he was called
+ to Berlin as chief of the Sanitary Institute, where he continued his
+ studies of tuberculosis and cholera. After inventing new microscopical
+ appliances and a new technique, in 1882 he stated his discovery of
+ the tubercle bacillus. In 1883, after publishing a method for the
+ prevention of anthrax by inoculation, he was sent by his government
+ to Egypt and India to investigate cholera. During that work he
+ discovered the cholera bacillus. In 1884 he returned to Germany and
+ in the following year went to France as cholera commissioner. In 1888
+ he published a paper on the prophylaxis of infectious diseases in the
+ army. In later years he investigated the bubonic plague, malaria, and
+ sleeping-sickness. He died at Baden-Baden, May 28, 1910._
+
+
+ THEORY OF BACTERIA[39]
+
+I am well aware that the investigations above described are very
+imperfect. It was necessary, in order to have time for those parts
+of the investigation which seemed the most important and essential,
+to omit the examination of many organs, such as the brain, heart,
+retina, etc., which ought not to pass unnoticed in researches on
+infective diseases. For the same reason no record was kept of the
+temperature, although this would undoubtedly have yielded most
+interesting results. I have intentionally refrained from entering into
+details of morbid anatomy, as only the etiology interested me, and as
+I did not feel qualified to undertake a study of the morbid anatomy of
+traumatic infective diseases. I must therefore leave this part of the
+investigation to those who are better able to undertake it.
+
+Nevertheless I consider that the results of my researches are
+sufficiently definite to enable me to deduce from them some well
+founded conclusions.
+
+In this summary I shall, however, confine myself to the most obvious
+conclusions. It has indeed of late become too common to draw the most
+sweeping conclusions as to infective diseases in general from the
+most unimportant observations on bacteria. I shall not follow this
+custom, although the material at my command would furnish rich food
+for meditation. For the longer I study infective diseases the more am
+I convinced that generalisations of new facts are here a mistake, and
+that every individual infective disease or group of closely allied
+diseases must be investigated for itself.
+
+As regards the artificial traumatic infective diseases observed by me,
+the conditions which must be established before their parasitic nature
+can be proved, we completely fulfilled in the case of the first five,
+but only partially in that of the sixth. For the infection was produced
+by such small quantities of fluid (blood, serum, pus, etc.) that the
+result cannot be attributed to a merely chemical poison.
+
+In the materials used for inoculation bacteria were without exception
+present, and in each disease a different and well marked form of
+organism could be demonstrated.
+
+At the same time, the bodies of those animals which died of the
+artificial traumatic infective diseases contained bacteria in
+such numbers that the symptoms and the death of the animals were
+sufficiently explained. Further, the bacteria found were identical
+with those which were present in the fluid used for inoculation, and a
+definite form of organisms corresponded in every instance to a distinct
+disease.
+
+These artificial traumatic infective diseases bear the greatest
+resemblance to human traumatic infective diseases, both as regards
+their origin from putrid substances, their course, and the result of
+post-mortem examination. Further, in the first case, just as in the
+last, the parasitic organisms could be only imperfectly demonstrated
+by the earlier methods of investigation; not till an improved method of
+procedure was introduced was it possible to obtain complete proof that
+they were parasitic diseases. We are therefore justified in assuming
+that human traumatic infective diseases will in all probability be
+proved to be parasitic when investigated by these improved methods.
+
+On the other hand, it follows from the fact that a definite pathogenic
+bacterium, e. g., the septicæmic bacillus, cannot be inoculated on
+every variety of animal (a similar fact is also true with regard to the
+bacillus anthracis); that the septicæmia of mice, rabbits, and man are
+not under all circumstances produced by the same bacterial form. It is
+of course possible that one or other of the bacteric forms found in
+animals also play a part in such diseases in the human subject. That,
+however, must be especially demonstrated for each case; _a priori_
+one need only expect that bacteria are present; as regards form, size
+and conditions of growth, they may be similar, but not always the same,
+even in what appear to be similar diseases in different animals.
+
+Besides the pathogenic bacteria already found in animals there are no
+doubt many others. My experiments refer only to those diseases which
+ended fatally. Even these are in all probability not exhausted in the
+six forms mentioned. Further experiments on many different species
+of animals, with the most putrid substances and with every possible
+modification in the method of application, will doubtless bring to
+light a number of other infective diseases, which will lead to further
+conclusions regarding infective diseases and pathogenic bacteria.
+
+But even in the small series of experiments which I was able to carry
+out, one fact was so prominent that I must regard it as constant,
+and, as it helps to remove most of the obstacles to the admission of
+the existence of a centagium vivum for traumatic infective diseases,
+I look on it as the most important result of my work. I refer to
+the differences which exist between pathogenic bacteria and to the
+constancy of their characters. A distinct bacteric form corresponds, as
+we have seen, to each disease, and this form always remains the same,
+however often the disease is transmitted from one animal to another.
+Further, when we succeed in reproducing the same disease _de novo_
+by the injection of putrid substances, only the same bacteric form
+occurs which was before found to be specific for that disease.
+
+Further, the differences between these bacteria are as great as could
+be expected between particles which border on the invisible. With
+regard to these differences, I refer not only to the size and form
+of the bacteria, but also to the conditions of their growth, which
+can be best recognized by observing their situation and grouping. I
+therefore study not only the individual alone, but the whole group of
+bacteria, and would, for example, consider a micrococcus which in one
+species of animal occurred only in masses (i. e., in a zooglæa form),
+as different from another which in the same variety of animal, under
+the same conditions of life, was only met with as isolated individuals.
+Attention must also be paid to the physiological effect, of which I
+scarcely know a more striking example than the case of the bacillus
+and the chain-like micrococcus growing together in the cellular tissue
+of the ear; the one passing into the blood and penetrating into the
+white blood corpuscles, the other spreading out slowly into the tissues
+in its vicinity and destroying everything around about; or again, the
+case of the septicæmic and pyæmic micrococci of the rabbit in their
+different relations to the blood; or lastly, the bacilli only extending
+over the surface of the aural cartilage in the erysipetalous disease,
+as contrasted with the bacillus anthracis, likewise inoculated on the
+rabbit’s ear, but quickly passing into the blood.
+
+As, however, there corresponds to each of the diseases investigated a
+form of bacterium distinctly characterized by its physiological action,
+by its conditions of growth, size, and form, which, however often the
+disease be transmitted from one animal to another, always remains the
+same and never passes over into another form, e. g., from the spherical
+to the rod shaped, we must in the meantime regard these different forms
+of pathogenic bacteria as distinct and constant species.
+
+This is, however, an assertion that will be much disputed by botanists,
+to whose special province this subject really belongs.
+
+Amongst those botanists who have written against the subdivision of
+bacteria into species, is Nägeli, who says, “I have for ten years
+examined thousands of different forms of bacteria, and I have not yet
+seen any absolute necessity for dividing them even into two distinct
+species.”
+
+Brefeld also states that he can only admit the existence of specific
+forms justifying the formation of distinct species when the whole
+history of development has been traced by cultivation from spore to
+spore in the most nutritive fluids.
+
+Although Brefeld’s demand is undoubtedly theoretically correct it
+cannot be made a _sine qua non_ in every investigation on
+pathogenic bacteria. We should otherwise be compelled to cease our
+investigations into the etiology of infective diseases till botanists
+have succeeded in finding out the different species of bacteria by
+cultivation and development from spore to spore. It might then very
+easily happen that the endless trouble of pure cultivation would be
+expended on some form of bacterium which would finally turn out to be
+scarcely worthy of attention. In practice only the opposite method can
+work. In the first place certain peculiarities of a particular form of
+bacterium different from those of other forms, and in the second place
+its constancy, compel us to separate it from other less known and less
+interesting, and provisionally to regard it as a species. And now, to
+verify this provisional supposition, the cultivation from spore to
+spore may be undertaken. If this succeeds under conditions which cut
+out all sources of fallacy, and if it furnishes a result corresponding
+to that obtained by the previous observations, then the conclusions
+which were drawn from these observations and which led to its being
+ranked as a distinct species must be regarded as valid.
+
+On this, which as it seems to me is the only correct practical method,
+I take my stand, and, till the cultivation of bacteria from spore to
+spore shows that I am wrong, I shall look on pathogenic bacteria as
+consisting of different species.
+
+In order, however, to show that I do not stand alone in this view, I
+shall here mention the opinion of some botanists who have already come
+to a similar conclusion.
+
+Cohn states that, in spite of the fact that many dispute the necessity
+of separating bacteria into genera or species, he must nevertheless
+adhere to the method as yet followed by him, and separate bacteria
+of a different form and fermenting power from each other, so long as
+complete proof of their identity is not given.
+
+From his investigations on the effects of different temperatures and
+of desiccation on the development of bacterium termo, Eidam came to
+the conclusion that different forms of bacteria require different
+conditions of nutriment, and that they behave differently towards
+physical and chemical influences. He regards these facts as a further
+proof of the necessity of dividing organisms into distinct species.
+
+I shall bring forward another reason to show the necessity of looking
+on the pathogenic bacteria which I have described as distinct species.
+The greatest stress, in investigations on bacteria, is justly laid on
+the so-called pure cultivations, in which only one definite form of
+bacterium is present. This evidently arises from the view that if, in a
+series of cultivations, the same form of bacterium is always obtained,
+a special significance must attach to this form: it must indeed be
+accepted as a constant form, or in a word as a species. Can, then,
+a series of pure cultivations be carried out without admixture of
+other bacteria? It can in truth be done, but only under very limited
+conditions. Only such bacteria can be cultivated pure, with the aids
+at present at command, which can always be known to be pure, either by
+their size and easily recognizable form, as the bacillus anthracis, or
+by the production of a characteristic coloring matter as the pigment
+bacteria. When, during a series of cultivations, a strange species of
+bacteria has by chance got in, as may occasionally happen under any
+circumstances, it will in these cases be at once observed, and the
+unsuccessful experiment will be thrown out of the series without the
+progress of investigation being thereby necessarily interfered with.
+
+But the case is quite different when attempts are made to carry
+out cultivations of very small bacteria, which, perhaps, cannot be
+distinguished at all without staining; how are we then to discover the
+occurrence of contamination? It is impossible to do so, and therefore
+all attempts at pure cultivation in apparatus, however skilfully
+planned and executed, must, as soon as small bacteria with but little
+characteristic appearances are dealt with, be considered as subject to
+unavoidable sources of fallacy, and in themselves inconclusive.
+
+But nevertheless a pure cultivation is possible, even in the case
+of the bacteria which are smallest and most difficult to recognise.
+This, however, is not conducted in cultivation apparatus, but in
+the animal body. My experiments demonstrate this. In all the cases
+of a distinct disease, e. g., of septicæmia of mice, only the small
+bacilli were present, and no other form of bacterium was ever found
+with it, unless in the case where that causing the tissue gangrene was
+intentionally inoculated at the same time. In fact, there exists no
+better cultivation apparatus for pathogenic bacteria than the animal
+body itself. Only a very limited number of bacteria can grow in the
+body, and the penetration of organisms into it is so difficult that
+the uninjured living body may be regarded as completely isolated
+with respect to other forms of bacteria than those intentionally
+introduced. It is quite evident, from a careful consideration of
+the two diseases produced in mice--septicæmia and gangrene of the
+tissue--that I have succeeded in my experiments in obtaining a pure
+cultivation. In the putrefying blood, which was the cause of these two
+diseases, the most different forms of bacteria were present, and yet
+only two of these found in the living mouse the conditions necessary
+for their existence. All the others died, and these two alone, a small
+bacillus and a chain-like micrococcus, remained and grew. These could
+be transferred from one animal to another as often as was desired,
+without suffering any alteration in their characteristic form, in
+their specific physiological action and without any other variety of
+bacteria at any time appearing. And further, as I have demonstrated, it
+is quite in the power of the experimenter to separate these two forms
+of bacteria from each other. When the blood in which only the bacilli
+are present is used, these alone are transmitted, and thenceforth are
+obtained quite pure; while on the other hand, when a field mouse is
+inoculated with both forms of bacteria, the bacilli disappear, and
+the micrococcus can be then cultivated pure. Doubtless an attempt to
+unite these two forms again in the same animal by inoculation would
+have been successful. In short, one has it completely in one’s power
+to cultivate several varieties of bacteria together, to separate them
+from each other, and eventually to combine them again. Greater demands
+can hardly be made on a pure cultivation, and I must therefore regard
+the successive transmission of artificial infective diseases as the
+best and surest method of pure cultivation. And it can further claim
+the same power of demonstrating the existence of specific forms of
+bacteria, as must be conceded to any faultless cultivation experiments.
+
+From the fact that the animal body is such an excellent apparatus for
+pure cultivation, and that, as we have seen, when the experiments are
+properly arranged and sufficient optical aids used, only one specific
+form of bacterium can be found in each distinct case of artificial
+traumatic infective disease, we may now further conclude that when, in
+examining a traumatic infective disease, several different varieties
+of bacteria are found, as e. g., chains of small granules, rods, and
+long, oscillating threads--such as were seen together by Coze and Feltz
+in the artificial septicæmia of rabbits--we have to do either with a
+combined infective disease,--that is, not a pure one,--or, what in the
+case cited is more probable, an inexact and inaccurate observation.
+When, therefore, several species of bacteria occur together in any
+morbid process, before definite conclusions are drawn as to the
+relations of the disease in question to the organisms, either proof
+must be furnished that they are all concerned in the morbid process,
+or an attempt must be made to isolate them and to obtain a true
+pure cultivation. Otherwise we cannot avoid the objection that the
+cultivation was not pure, and therefore not conclusive. I shall only
+briefly refer to a further necessary consequence of the admission of
+the existence of different species of pathogenic bacteria. The number
+of the species of these bacteria is limited; for, of the numerous
+diverse forms present in putrid fluids, one or but few can in the most
+favorable cases develop in the animal body. Those which disappear
+are, for that species of animal at least, not pathogenic bacteria.
+If, however, as follows from the foregoing, there exist hurtful and
+harmless bacteria, experiments performed on animals with the latter,
+e. g., with bacterium termo, prove absolutely nothing for or against
+the behavior of the former--the pathogenic--forms. But almost all the
+experiments of this nature have been carried out with the first mixture
+of different species of bacteria which came to hand without there being
+any certainty that pathogenic bacteria were in reality present in the
+mixture. It is therefore evident that none of these experiments can
+be regarded as furnishing evidence of any value for or against the
+parasitic nature of infective diseases.
+
+In all my experiments, not only have the form and size of the bacteria
+been constant, but the greatest uniformity in their actions on the
+animal organisms has been observed, though no increase of virulence, as
+described by Coze and Feltz, Davaine, and others. This leads me to make
+some remarks on the supposed law of the increasing virulence of blood
+when transmitted through successive animals, discovered or confirmed by
+the investigators just named.
+
+The discovery of this law has, as is well known, been received with
+great enthusiasm, and it has excited no little interest owing to its
+intimate bearing on the doctrine of natural selection (Anpassung and
+Vererbung). Some investigators, who are in other things very exact,
+have allowed themselves to be blinded by the seductive theory that
+the insignificant action of a single putrefactive bacterium may, by
+continued natural selection in passing from animal to animal, be
+increased in virulence till it becomes deadly though a drop of the
+infective liquid be diluted in a quadrillion times. They have founded
+thereon the most beautiful practical applications, not suspecting that
+the bacteria in question have never been certainly demonstrated.
+
+The original works of Coze and Feltz, as also that of Davaine, are
+not at my disposal for reference; and I cannot therefore enter into
+a complete criticism of them. So far, however, as I can gather from
+the references accessible to me, especially from the detailed notices
+in Virchow and Hirch’s “Jahnesbericht,” no complete proof that the
+virulence of septicæmic blood increases from generation to generation
+seems to have been furnished. Apparently blood more and more diluted
+was injected, and astonishment was felt when this always acted, the
+effect being then ascribed to its increasing virulence. But controlling
+experiments to ascertain whether the septicæmic blood were not already
+as virulent in the second and third generations as in the twenty-fifth,
+do not seem to have been made. My experiments so far support and are in
+accordance with those of Coze, Feltz, and Davaine in that for the first
+infection of an animal relatively large quantities of putrid fluid are
+necessary; but in the second generation, or at the latest in the third,
+the full virulence was attained, and afterwards remained constant.
+
+Of my artificial infective diseases the septicæmia of the mouse has
+the greatest correspondence with the artificial septicæmia described
+by Davaine. If we were to experiment with this disease in the same
+manner as Davaine experimented, we would, if no controlling experiments
+were employed, find the same increase in virulence of the disease. It
+would only be necessary to use blood in slowly decreasing quantities in
+order to obtain in this way any progressive increase of the virulence
+that might be desired. I, however, took from the second or third
+animal the smallest possible quantity of material for inoculation, and
+thus arrived more quickly at the greatest degree of virulence. Till,
+therefore, I am assured that, in the septicæmia observed by Davaine,
+such controlling experiments were made, I can only look on an increase
+in virulence as holding good for the earlier generations. In order
+to explain this we do not, however, require to have recourse to the
+magical wand of natural selection; a feasible explanation can be very
+naturally furnished. Let us take again the septicæmia of mice, as being
+the most suitable example.
+
+If two drops of putrefying blood be injected into such an animal
+there is introduced not only a number of totally distinct species
+of bacteria, but also a certain amount of dissolved putrid poison
+(sepsin), not sufficient to produce a fatal effect, but yet certainly
+not without influence on the health of the animal. Different factors
+must therefore be considered as affecting the health of the animal. On
+the one hand there is the dissolved poison, on the other the different
+species of bacteria, of which, however, perhaps only two, as in the
+example before us, can multiply in the body of the mouse and there
+exert a continuous noxious influence. Only one of these two species can
+penetrate into the blood, and if the blood alone be used for further
+inoculations, only this one variety will come victorious out of the
+battle for existence. The further development of the experiment depends
+entirely on the quantity of the putrid poison, and on the relation
+of the two forms of bacteria to each other in point of numbers. If
+one injects a large amount of septic poison and a large number of
+that variety of bacteria which increase locally (in this case the
+chain-like micrococci causing the gangrene of the tissue), but only a
+very small number of the bacteria which pass into the blood (here the
+bacilli), the first animal experimented on will die, as a result of the
+preponderation influence of the first two factors before many bacilli
+can have got into the blood and multiplied there. Of the blood of this
+first animal, containing, as it does, proportionately very few bacilli,
+one-fifth to one-tenth of a drop must be inoculated in order to convey
+the disease with certainty. In the second animal, however, only the
+bacilli are introduced, and these develop undisturbed in the blood. For
+the infection of the third animal the smallest quantity of this blood
+which can produce an effect is then sufficient, and after this third
+generation the virulence of the blood remains uniform.
+
+We may also imagine another case in which the increase of the virulence
+may go on through more than two generations without any modification
+resulting from natural selection and transmission from animal to
+animal. This would take place if several species of bacteria capable
+of passing into the blood were introduced into the animal at the first
+injection. Let us suppose, for example, that in the same putrefying
+blood which served for the foregoing experiment, the bacilli of
+anthrax were also present, there would then be contained in the blood
+of the first animal not only the septicæmic bacillus, but also
+bacillus anthracis, and of each only a small number; of the anthrax
+bacilli there would be even fewer than of the other, because in mice
+they are deposited chiefly in the spleen, lungs, etc.; while in the
+blood of the heart they are, even in the most favorable cases, only
+sparsely distributed. On the other hand, the anthrax bacilli have
+this advantage, that, provided they be inoculated in considerable
+numbers, they kill even within twenty hours, while the septicæmic
+bacilli only destroy life after fifty hours. In the blood of the second
+animal, therefore, both species of bacilli would be present in larger
+numbers than in the first, although not yet so numerous as if either
+organism had been inoculated singly. Hence a larger quantity of blood
+is necessary to ensure transmission to a third animal. Perhaps this
+might be the case even in the fourth generation, till finally one or
+other variety of bacillus would alone be present in the blood injected.
+Probably this would be the septicæmic bacillus.
+
+In this way the experiments of Coze, Feltz, and Davaine may admit of
+simple explanation and be brought into harmony with my results.
+
+
+
+FOOTNOTES:
+
+[Footnote 39: From the English translation (1880) of _Untersuchungen
+über die Aetiologie der Wundinfectionskrankheiten_ (1878).]
+
+
+
+
+ =TRANSCRIBER’S NOTES=
+
+Simple typographical errors have been silently corrected; unbalanced
+quotation marks were remedied when the change was obvious, and
+otherwise left unbalanced.
+
+Punctuation, hyphenation, and spelling were made consistent when a
+predominant preference was found in the original book; otherwise they
+were not changed.
+
+
+
+*** END OF THE PROJECT GUTENBERG EBOOK 77076 ***
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+<div style='text-align:center'>*** START OF THE PROJECT GUTENBERG EBOOK 77076 ***</div>
+
+
+<figure class="figcenter width500" id="cover" style="width: 1600px;">
+<img src="images/cover.jpg" width="1600" height="2654" alt="An
+anthology of key scientific writings, from Copernicus to Pasteur,
+tracing major discoveries and ideas that shaped modern science through
+original texts.">
+
+</figure>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+
+<div class="chapter">
+<p class="nindc"><span class="large">CLASSICS OF<br>
+MODERN SCIENCE</span></p>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+
+<div class="chapter">
+<div class="blockquot">
+
+<p>THERE is no grander nor more intellectually elevating spectacle than
+that of the utterances of the fundamental investigators in their
+gigantic power. Possessed as yet of no methods—for these were first
+created by their labors and are only rendered comprehensible to us by
+their performances—they grapple with and subjugate the object of their
+inquiry and imprint upon it the forms of conceptual thought.</p>
+
+<p class="right">
+—<span class="allsmcap">ERNST MACH</span></p>
+</div>
+</div>
+
+<figure class="figcenter width500" id="i_title" style="width: 1974px;">
+<img src="images/i_title.jpg" width="1974" height="3188" alt="Title
+page of the book Classics of Modern Science.">
+
+</figure>
+
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+
+<h1>CLASSICS<br>
+<span class="allsmcap">OF</span><br>
+MODERN SCIENCE</h1>
+
+<p class="nindc space-above2">(COPERNICUS TO PASTEUR)</p>
+
+
+<hr class="r65">
+
+
+<p class="nindc space-above2"><span class="allsmcap">EDITED BY</span></p>
+
+<p class="nindc"><span class="large">WILLIAM S. KNICKERBOCKER</span>, <span class="allsmcap">PH.D.</span></p>
+
+<p class="nindc"><span class="allsmcap">PROFESSOR OF ENGLISH IN THE UNIVERSITY<br>
+OF THE SOUTH · EDITOR, THE<br>
+SEWANEE REVIEW</span></p>
+
+
+<figure class="figcenter width500" id="i_title_logo" style="width: 200px;">
+ <img src="images/i_title_logo.jpg" width="200" height="120" alt="decorative">
+</figure>
+
+
+<p class="nindc space-above2">ALFRED · A · KNOPF · NEW YORK</p>
+
+<p class="nindc space-below2">MCMXXVII</p>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p class="nindc space-below2">
+<span class="allsmcap">COPYRIGHT 1927, BY ALFRED · A · KNOPF, INC.<br>
+<br>
+SET UP, ELECTROTYPED, PRINTED AND BOUND BY<br>
+THE VAIL-BALLOU PRESS, BINGHAMTON, N. Y.<br>
+PAPER FURNISHED BY W. F. ETHERINGTON &amp; CO.,<br>
+NEW YORK</span></p>
+
+<p class="nindc space-above2"><span class="allsmcap">MANUFACTURED<br>
+IN THE UNITED STATES OF AMERICA</span></p>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p class="nindc space-above2 space-below2">
+<span class="allsmcap">TO MY FORMER ASSOCIATES OF THE FACULTY,<br>
+AND THE STUDENTS OF THE NEW YORK<br>
+STATE COLLEGE OF FORESTRY AT SYRACUSE<br>
+UNIVERSITY.</span></p>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_vii">[Pg vii]</span></p>
+
+<h2 class="nobreak" id="PREFACE">PREFACE</h2>
+</div>
+
+
+<p>“The history of science,” wrote Du Bois-Reymond, “is the real history
+of mankind.” Gradually we are coming to realize the significance of
+that statement, and the sooner we realize it on a grand scale the more
+shall we hasten the happiness of man.</p>
+
+<p>Fortunately for education, science no longer has to fight for its
+inclusion among the courses offered for study in colleges and
+universities. As scientific knowledge increases and the technique
+of teaching science improves, the exact knowledge of the few more
+rapidly becomes the accepted knowledge of the many. More than that,
+the scientific attitude of mind produces many of the virtues which in
+old-fashioned courses in ethics were taught as objectively as a problem
+in geometry. Patience, endurance, humility, teachableness, honesty,
+accuracy—without these it is impossible for a scientist properly to
+work. And the history of science is as inspiring in its human values as
+are the legends of the saints. Contemplate the heroism of a Galileo,
+the patience of a Darwin, the humility of a Pasteur; a modern eleventh
+chapter of <i>Hebrews</i> might be written listing the names of all
+those men of faith who by quiet work, unremitting in their zeal, one by
+one discovered facts which have made man’s lot easier and happier in
+what was otherwise to him a hostile and unhappy universe.</p>
+
+<p>Little by little, accretion upon accretion, man’s knowledge of
+the physical forces of his universe has been increased, but his
+progress has often been retarded by those who, with good intentions,
+superstitiously feared the power of the gods who, as in the story of
+Brunhilde, encircled their mysteries with a ring of fire. Periodically
+superstition re-arises, but it does not permanently halt the advance
+deploy of armed skirmishers, however much it may temporarily retard
+the advancement of knowledge. Since the seventeenth century, however,
+so remarkable has been the progress of science, so evident have been
+its beneficent achievements, that regardless of the present assault
+upon one phase of science, western civilization is committed to this
+way of discovery. But it is no easy way! “The rapid increase of
+natural<span class="pagenum" id="Page_viii">[Pg viii]</span> knowledge,” wrote Thomas Henry Huxley, “which is the chief
+characteristic of our age, is affected in various ways. The main army
+of science moves to the conquest of the new worlds slowly and surely,
+nor ever cedes an inch of the territory gained. But the advance is
+covered and facilitated by the ceaseless activity of clouds of light
+troops provided with a weapon—always efficient, if not always an
+arm of precision—the scientific imagination. It is the business of
+these <i>enfants perdus</i> of science to make raids into the realms
+of ignorance wherever they see, or think they see, a chance; and
+cheerfully to accept defeat, or it may be annihilation, as the reward
+of error. Unfortunately the public, which watches the progress of the
+campaign, too often mistakes a dashing incursion ... for a forward
+movement of the main body; fondly imagining that the strategic movement
+to the rear, which occasionally follows, indicates a battle lost by
+science.”</p>
+
+<p>It is regrettable that Huxley was compelled to use the metaphor of
+a battle in describing the general advance of scientific knowledge;
+how much better it would have been if he could have used a scientific
+word like <i>enzyme</i> or <i>catalyst</i> in referring to those
+courageous men of the laboratory and the field who went forth alone
+with instruments to discover things as they really are and changed
+fields of knowledge through their discoveries. But if he had employed
+these scientific terms, no one, apart from the select company of
+scientists themselves who have had to evolve a special language of
+their own to express new matters and new meanings, would understand
+him. People who use strange tongues are always suspect to the populace.
+If science is to be “understanded” by the people, the people’s language
+must be used. Fortunately, for the sake of science, scientists
+themselves are now keenly aware of the necessity of presenting their
+findings in language which may be understood by the ordinary man.
+Huxley himself made the <i>liaison</i> in his age, an age in which
+battles were highly idealised. His grandson, however, speaking to
+our age, rephrases the idea in a mode more acceptable to us: “Each
+science or branch of science seems roughly to go through three main
+phases in its development. There is first a preliminary phase in which
+miscellaneous sporadic knowledge is amassed and is dated; theories
+are pursued, often to be proved valueless. There then comes a classic
+or heroic age, in which a general principle of firmly interrelated
+principles<span class="pagenum" id="Page_ix">[Pg ix]</span> is gradually laid down, upon which in its turn a coherent
+architecture of theory can be built, and finally this passes over into
+a period of maturity, in which the position is consolidated, the scope
+of the principles widened, their bases more finally tested, and their
+consequences worked out in fullest detail. Naturally, each stage lasts
+for a considerable time, and in many cases a science which thought
+itself securely embarked upon the third phase is reminded by some
+fundamental discovery that it is still only in the second.”<a id="FNanchor_1" href="#Footnote_1" class="fnanchor">[1]</a></p>
+
+<p>These movements of science have produced a copious literature which
+has not enjoyed the same attention and reading as imaginative books,
+because, once the ideas are known and incorporated into the existing
+body of scientific knowledge, these scientific writings tend to acquire
+chiefly an historical interest. Yet they are monuments of the advance
+of civilization, and deserve a better fate. Many of them are still
+interesting to read as human documents because they illustrate how
+painfully and slowly man’s exact knowledge of verifiable phenomena has
+been accumulated. No one outside of the small company of highly trained
+scientists can read all of them through, yet most of them have sections
+which are as readable and as exciting as any modern novel. It is the
+purpose of this book to present to the young college student and to the
+general reader some of the more representative of these classics in the
+literature of science, bringing together in this convenient form at
+least some reminders of a vast field of reading where one may browse
+for a lifetime with interest and profit. If it be used in conjunction
+with a history of science it will readily supply a vivid sense of
+the movement of the mind of western civilization, increasing in us a
+respect for the effort of our ancestors, and inspire us to encourage
+and to forward the work of contemporary scientists, and restrain us at
+least from hindering them in their efforts.</p>
+
+<p>Although the selections may be used as a textbook in courses like
+Introduction to Modern Civilization, Philosophy, and The History of
+Science now given in the more progressive colleges and universities,
+it may also profitably be used as a text for freshman or sophomore
+readings in English courses given in colleges predominantly technical
+or scientific, like Engineering, Agricultural, and Forestry Colleges.
+In those English courses where emphasis upon ideas is made to provide
+the inspiration for writing, these selections will be found, as I<span class="pagenum" id="Page_x">[Pg x]</span>
+found them in my own work, to stir up considerable discussion and
+to provide opportunities for reading modern scientific literature.
+Moreover, the literary style of science at its best will be found to be
+excellently illustrated in these straightforward, coherent sentences
+written by some of the world’s clearest thinkers. They illustrate
+concretely what Tyndall remarked in his closing words of the famous
+<i>Belfast Address</i>: “It has been said that science divorces itself
+from literature. The statement, like so many others, arises from
+lack of knowledge. A glance at the less technical writings of its
+leaders—of its Helmholtz, its Huxley, and its Du Bois-Reymond—would
+show what breadth of literary culture they command. Where among
+modern writers can you find their superiors in clearness and vigor
+of literary style? Science desires no isolation, but freely combines
+with every effort toward the bettering of man’s estate. Single-handed
+and supported not with outward sympathy, but by inward force, it has
+built at least one great wing of the many-mansioned home which man in
+his totality demands.... The world embraces not only a Newton, but a
+Shakespeare; not only a Boyle, but a Raphael; not only a Kant, but a
+Beethoven; not only a Darwin, but a Carlyle. Not in each of these, but
+in all, is human nature whole. They are not opposed, but supplementary;
+not mutually exclusive, but reconcilable.”</p>
+
+<p class="right">
+<span class="allsmcap">WILLIAM S. KNICKERBOCKER</span>
+</p>
+
+<p class="nind">
+UNIVERSITY OF THE SOUTH<br>
+SEWANEE, TENN.<br>
+<i>April 5, 1927</i></p>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<h2 class="nobreak" id="FOOTNOTES">FOOTNOTES:</h2>
+</div>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_1" href="#FNanchor_1" class="label">[1]</a>
+Julian Huxley, in <i>Harper’s Magazine</i> for April,
+1926.</p>
+
+</div>
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_xi">[Pg xi]</span></p>
+
+<h2 class="nobreak" id="CONTENTS">CONTENTS</h2>
+</div>
+
+
+<table class="autotable">
+<tbody><tr>
+<td class="tdl_ws1">I</td>
+<td class="tdc">FRANCIS BACON (1561-1626)<br>
+<span class="allsmcap">THE METHOD OF INDUCTIVE SCIENCE</span><br>
+<span class="allsmcap">ON THE INTERPRETATION OF NATURE, OR THE</span><br>
+<span class="allsmcap">REIGN OF MAN</span></td>
+<td class="tdr_ws1"><a href="#Page_1">1</a></td>
+</tr><tr>
+<td class="tdl_ws1">II</td>
+<td class="tdc">NICOLAUS COPERNICUS (1473-1543)<br>
+<span class="allsmcap">THE NEW IDEA OF THE UNIVERSE</span></td>
+<td class="tdr_ws1"><a href="#Page_20">20</a></td>
+</tr><tr>
+<td class="tdl_ws1">III</td>
+<td class="tdc">JOHANN KEPLER (1671-1630)<br>
+<span class="allsmcap">ON THE PRINCIPLES OF ASTRONOMY</span></td>
+<td class="tdr_ws1"><a href="#Page_29">29</a></td>
+</tr><tr>
+<td class="tdl_ws1">IV</td>
+<td class="tdc">GALILEO GALILEI (1564-1642)<br>
+<span class="allsmcap">THE COPERNICAN VERSUS THE PTOLEMAIC ASTRONOMIES</span></td>
+<td class="tdr_ws1"><a href="#Page_36">36</a></td>
+</tr><tr>
+<td class="tdl_ws1">V</td>
+<td class="tdc">WILLIAM HARVEY (1578-1667)<br>
+<span class="allsmcap">THE CIRCULATION OF BLOOD IN ANIMALS</span></td>
+<td class="tdr_ws1"><a href="#Page_46">46</a></td>
+</tr><tr>
+<td class="tdl_ws1">VI</td>
+<td class="tdc">ROBERT BOYLE (1627-1691)<br>
+<span class="allsmcap">THE DISCOVERY OF THE LAW OF THE COMPRESSIBILITY</span><br>
+<span class="allsmcap">OF GASSES</span></td>
+<td class="tdr_ws1"><a href="#Page_49">49</a></td>
+</tr><tr>
+<td class="tdl_ws1">VII</td>
+<td class="tdc">CHRISTIAN HUYGHENS (1629-1695)<br>
+<span class="allsmcap">THE WAVE THEORY OF LIGHT</span></td>
+<td class="tdr_ws1"><a href="#Page_52">52</a></td>
+</tr><tr>
+<td class="tdl_ws1">VIII</td>
+<td class="tdc">ANTHONY VON LEEUWENHOECK (1632-1723)<br>
+<span class="allsmcap">OBSERVATIONS ON ANIMALCULÆ</span></td>
+<td class="tdr_ws1"><a href="#Page_62">62</a></td>
+</tr><tr>
+<td class="tdl_ws1">IX</td>
+<td class="tdc">SIR ISAAC NEWTON (1642-1727)<br>
+<span class="allsmcap">THE THEORY OF GRAVITATION</span></td>
+<td class="tdr_ws1"><a href="#Page_67">67</a></td>
+</tr><tr>
+<td class="tdl_ws1">X</td>
+<td class="tdc">BENJAMIN FRANKLIN (1706-1790)<br>
+<span class="allsmcap">THE IDENTITY OF LIGHTNING AND ELECTRICITY</span></td>
+<td class="tdr_ws1"><a href="#Page_72">72</a></td>
+</tr><tr>
+<td class="tdl_ws1">XI</td>
+<td class="tdc">LINNAEUS (1707-1778)<br>
+<span class="allsmcap">THE SEX OF PLANTS</span></td>
+<td class="tdr_ws1"><a href="#Page_76">76</a></td>
+</tr><tr>
+<td class="tdl_ws1">XII</td>
+<td class="tdc">JOSEPH BLACK (1728-1799)<br>
+<span class="allsmcap">THE DISCOVERY OF CARBONIC ACID GAS</span><span class="pagenum" id="Page_xii">[Pg xii]</span></td>
+<td class="tdr_ws1"><a href="#Page_89">89</a></td>
+</tr><tr>
+<td class="tdl_ws1">XIII</td>
+<td class="tdc">JOSEPH PRIESTLEY (1733-1804)<br>
+<span class="allsmcap">THE DISCOVERY OF OXYGEN</span></td>
+<td class="tdr_ws1"><a href="#Page_96">96</a></td>
+</tr><tr>
+<td class="tdl_ws1">XIV</td>
+<td class="tdc">HENRY CAVENDISH (1731-1810)<br>
+<span class="allsmcap">THE COMBINATION OF HYDROGEN AND OXYGEN</span><br>
+<span class="allsmcap">INTO WATER</span></td>
+<td class="tdr_ws1"><a href="#Page_102">102</a></td>
+</tr><tr>
+<td class="tdl_ws1">XV</td>
+<td class="tdc">SIR WILLIAM HERSCHEL (1738-1822)<br>
+<span class="allsmcap">THE DISCOVERY OF URANUS</span><br>
+<span class="allsmcap">ON THE NAME OF THE NEW PLANET</span><br>
+<span class="allsmcap">ON NEBULOUS STARS</span></td>
+<td class="tdr_ws1"><a href="#Page_109">109</a></td>
+</tr><tr>
+<td class="tdl_ws1">XVI</td>
+<td class="tdc">KARL WILHELM SCHEELE (1742-1786)<br>
+<span class="allsmcap">THE CONSTITUENTS OF AIR</span></td>
+<td class="tdr_ws1"><a href="#Page_122">122</a></td>
+</tr><tr>
+<td class="tdl_ws1">XVII</td>
+<td class="tdc">ANTOINE LAURENT LAVOISIER (1743-1794)<br>
+<span class="allsmcap">THE NATURE OF COMBUSTION</span></td>
+<td class="tdr_ws1"><a href="#Page_129">129</a></td>
+</tr><tr>
+<td class="tdl_ws1">XVIII</td>
+<td class="tdc">ALESSANDRO VOLTA (1745-1827)<br>
+<span class="allsmcap">NEW GALVANIC INSTRUMENT</span></td>
+<td class="tdr_ws1"><a href="#Page_135">135</a></td>
+</tr><tr>
+<td class="tdl_ws1">XIX</td>
+<td class="tdc">PIERRE SIMON LAPLACE (1749-1827)<br>
+<span class="allsmcap">THE NEBULAR HYPOTHESIS</span></td>
+<td class="tdr_ws1"><a href="#Page_138">138</a></td>
+</tr><tr>
+<td class="tdl_ws1">XX</td>
+<td class="tdc">EDWARD JENNER (1749-1823)<br>
+<span class="allsmcap">THE THEORY OF VACCINATION</span></td>
+<td class="tdr_ws1"><a href="#Page_148">148</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXI</td>
+<td class="tdc">COUNT RUMFORD (1753-1814)<br>
+<span class="allsmcap">THE NATURE OF HEAT</span></td>
+<td class="tdr_ws1"><a href="#Page_157">157</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXII</td>
+<td class="tdc">JOHN DALTON (1766-1844)<br>
+<span class="allsmcap">THE ATOMIC THEORY</span></td>
+<td class="tdr_ws1"><a href="#Page_166">166</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXIII</td>
+<td class="tdc">MARIE FRANÇOIS XAVIER BICHAT (1771-1802)<br>
+<span class="allsmcap">THE DOCTRINE OF TISSUES</span></td>
+<td class="tdr_ws1"><a href="#Page_168">168</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXIV</td>
+<td class="tdc">AMADEO AVOGADRO (1776-1856)<br>
+<span class="allsmcap">THE MOLECULES IN GASES PROPORTIONAL TO</span><br>
+<span class="allsmcap">THE VOLUMES</span></td>
+<td class="tdr_ws1"><a href="#Page_177">177</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXV</td>
+<td class="tdc">SIR HUMPHREY DAVY (1778-1829)<br>
+<span class="allsmcap">ON SOME NEW PHENOMENA OF CHEMICAL</span><br>
+<span class="allsmcap">CHANGES PRODUCED BY ELECTRICITY<span class="pagenum" id="Page_xiii">[Pg xiii]</span></span></td>
+<td class="tdr_ws1"><a href="#Page_183">183</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXVI</td>
+<td class="tdc">MICHAEL FARADAY (1791-1867)<br>
+<span class="allsmcap">ON FLUID CHLORINE</span><br>
+<span class="allsmcap">ELECTRICITY FROM MAGNETISM</span></td>
+<td class="tdr_ws1"><a href="#Page_190">190</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXVII</td>
+<td class="tdc">JOSEPH HENRY (1797-1878)<br>
+<span class="allsmcap">ON THE PRODUCTION OF CURRENTS AND SPARKS</span><br>
+<span class="allsmcap">OF ELECTRICITY FROM MAGNETISM</span></td>
+<td class="tdr_ws1"><a href="#Page_198">198</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXVIII</td>
+<td class="tdc">SIR CHARLES LYELL (1797-1875)<br>
+<span class="allsmcap">UNIFORMITY IN THE SERIES OF PAST CHANGES</span><br>
+<span class="allsmcap">IN THE ANIMATE AND INANIMATE WORLD</span></td>
+<td class="tdr_ws1"><a href="#Page_206">206</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXIX</td>
+<td class="tdc">CHARLES DARWIN (1809-1882)<br>
+<span class="allsmcap">NATURAL SELECTION</span></td>
+<td class="tdr_ws1"><a href="#Page_226">226</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXX</td>
+<td class="tdc">THEODOR SCHWANN(1810-1882)<br>
+<span class="allsmcap">CELL THEORY</span></td>
+<td class="tdr_ws1"><a href="#Page_245">245</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXXI</td>
+<td class="tdc">HERMANN VON HELMHOLTZ (1821-1894)<br>
+<span class="allsmcap">THE CONSERVATION OF ENERGY</span></td>
+<td class="tdr_ws1"><a href="#Page_273">273</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXXII</td>
+<td class="tdc">LOUIS PASTEUR (1822-1895)<br>
+<span class="allsmcap">INOCULATION FOR HYDROPHOBIA</span></td>
+<td class="tdr_ws1"><a href="#Page_304">304</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXXIII</td>
+<td class="tdc">JAMES CLERK MAXWELL (1831-1879)<br>
+<span class="allsmcap">THE MAXWELL AND HERZ THEORY OF ELECTRICITY</span><br>
+<span class="allsmcap">AND LIGHT</span></td>
+<td class="tdr_ws1"><a href="#Page_320">320</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXXIV</td>
+<td class="tdc">AUGUST WEISMANN (1834-1914)<br>
+<span class="allsmcap">THE CONTINUITY OF THE GERM-PLASM AS THE</span><br>
+<span class="allsmcap">FOUNDATION OF A THEORY OF HEREDITY</span></td>
+<td class="tdr_ws1"><a href="#Page_334">334</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXXV</td>
+<td class="tdc">SIR NORMAN LOCKYER (1836-1920)<br>
+<span class="allsmcap">THE CHEMISTRY OF THE STARS</span></td>
+<td class="tdr_ws1"><a href="#Page_360">360</a></td>
+</tr><tr>
+<td class="tdl_ws1">XXXVI</td>
+<td class="tdc">ROBERT KOCH (1843-1910)<br>
+<span class="allsmcap">THEORY OF BACTERIA</span></td>
+<td class="tdr_ws1"><a href="#Page_374">374</a></td>
+</tr>
+</tbody>
+</table>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+
+<p class="nindc space-above2"><span class="large">
+CLASSICS OF<br>
+MODERN SCIENCE</span>
+</p>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_1">[Pg 1]</span></p>
+
+<h2 class="nobreak" id="I">I<br>
+FRANCIS BACON<br>
+1561-1626</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Francis Bacon, Lord Verulam, is distinguished in the history of
+science for his criticism of the methods of knowledge of his day.
+In his great writings, “The Advancement of Learning” (1605), “Novum
+Organum” (1620), and “De Augmentis Scientiarum” (1623), he cumulatively
+outlined a new method, named after him, whereby all knowledge was
+referred to experience and corrected by experiment. His inductive
+method was epoch-making in that it established the technique underlying
+all modern science.</i></p>
+
+<p><i>He was born in London, January 22, 1561, the son of Sir Nicholas
+Bacon, Lord Keeper of the Seals. In 1573, at the age of twelve, he
+matriculated in Trinity College, Cambridge. After his father’s death,
+in 1579, he led a precarious life, accumulated many debts, and ended
+by accusing his intimate friend, Lord Essex, of treason. In 1607 King
+James appointed him Solicitor. In 1613 he became Attorney General,
+and in 1618 was made Lord Chancellor and knighted Baron Verulam. The
+following year he was impeached for bribery, and imprisoned four days
+for the offense. Thereafter, until his death on April 9, 1626, he gave
+himself wholly to the development of his new scientific method.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE METHOD OF INDUCTIVE SCIENCE<a id="FNanchor_2" href="#Footnote_2" class="fnanchor">[2]</a></p>
+
+<p>They who have presumed to dogmatize on nature, as on some well
+investigated subject, either from self-conceit or arrogance, and in the
+professorial style, have inflicted the greatest injury on philosophy
+and<span class="pagenum" id="Page_2">[Pg 2]</span> learning. For they have tended to stifle and interrupt inquiry
+exactly in proportion as they have prevailed in bringing others to
+their opinion; and their own activity has not counterbalanced the
+mischief they have occasioned by corrupting and destroying that of
+others. They again who have entered upon a contrary course, and
+asserted that nothing whatever can be known, whether they have fallen
+into this opinion from their hatred of the ancient sophists, or from
+the hesitation of their minds, or from an exuberance of learning, have
+certainly adduced reasons for it which are by no means contemptible.
+They have not, however, derived their opinion from true sources,
+and, hurried on by their zeal and some affectation, have certainly
+exceeded due moderation. But the more ancient Greeks (whose writings
+have perished), held a more prudent mean, between the arrogance of
+dogmatism, and the despair of scepticism; and though too frequently
+intermingling complaints and indignation at the difficulty of inquiry,
+and the obscurity of things, and champing, as it were, the bit, have
+still persisted in pressing their point, and pursuing their intercourse
+with nature; thinking, as it seems, that the better method was not to
+dispute upon the very point of the possibility of anything being known,
+but to put it to the test of experience. Yet they themselves, by only
+employing the power of the understanding, have not adopted a fixed
+rule, but have laid their whole stress upon intense meditation, and a
+continual exercise and perpetual agitation of the mind.</p>
+
+<p>Our method, though difficult in its operation, is easily explained.
+It consists in determining the degrees of certainty, whilst we, as it
+were, restore the senses to their former rank, but generally reject
+that operation of the mind which follows close upon the senses, and
+open and establish a new and certain course for the mind from the first
+actual perceptions of the senses themselves. This, no doubt, was the
+view taken by those who have assigned so much to logic; showing clearly
+thereby that they sought some support for the mind, and suspected its
+natural and spontaneous mode of action. But this is now employed too
+late as a remedy, when all is clearly lost, and after the mind, by
+the daily habit and intercourse of life, has come prepossessed with
+corrupted doctrines, and filled with the vainest idols. The art of
+logic, therefore, being (as we have mentioned) too late a precaution,
+and in no way remedying the matter, has tended more to confirm errors,
+than to disclose truth. Our only remaining hope and<span class="pagenum" id="Page_3">[Pg 3]</span> salvation is to
+begin the whole labor of the mind again; not leaving it to itself,
+but directing it perpetually from the very first, and attaining our
+end as it were by mechanical aid. If men, for instance, had attempted
+mechanical labors with their hands alone, and without the power and aid
+of instruments, as they have not hesitated to carry on the labors of
+their understanding with the unaided efforts of their mind, they would
+have been able to move and overcome but little, though they had exerted
+their utmost and united powers. And just to pause awhile on this
+comparison, and look into it as a mirror; let us ask, if any obelisk of
+a remarkable size were perchance required to be moved, for the purpose
+of gracing a triumph or any similar pageant, and men were to attempt it
+with their bare hands, would not any sober spectator avow it to be an
+act of the greatest madness? And if they should increase the number of
+workmen, and imagine that they could thus succeed, would he not think
+so still more? But if they chose to make a selection, and to remove
+the weak, and only employ the strong and vigorous, thinking by this
+means, at any rate, to achieve their object, would he not say that they
+were more fondly deranged? Nay, if not content with this, they were
+to determine on consulting the athletic art, and were to give orders
+for all to appear with their hands, arms, and muscles regularly oiled
+and prepared, would he not exclaim that they were taking pains to rave
+by method and design? Yet men are hurried on with the same senseless
+energy and useless combination in intellectual matters, as long as
+they expect great results either from the number and agreement, or the
+excellence and acuteness of their wits; or even strengthen their minds
+with logic, which may be considered as an athletic preparation, but yet
+do not desist (if we rightly consider the matter) from applying their
+own understandings merely with all this zeal and effort. Whilst nothing
+is more clear, than that in every great work executed by the hand of
+man without machines or implements, it is impossible for the strength
+of individuals to be increased, or that of the multitude to combine.</p>
+
+<p>Having premised so much, we lay down two points on which we would
+admonish mankind lest they should fail to see or to observe them. The
+first of these is, that it is our good fortune (as we consider it), for
+the sake of extinguishing and removing contradiction and irritation of
+mind, to leave the honor and reverence due to the<span class="pagenum" id="Page_4">[Pg 4]</span> ancients untouched
+and undiminished, so that we can perform our intended work, and yet
+enjoy the benefit of our respectful moderation. For if we profess
+to offer something better than the ancients, and yet should pursue
+the same course as they have done, we could never, by any artifice,
+contrive to avoid the imputation of having engaged in a contest or
+rivalry as to our respective wits, excellencies, or talents; which,
+though neither inadmissible nor new (for why should we not blame and
+point out anything that is imperfectly discovered or laid down by
+them, of our own right, a right common to all), yet however just and
+allowable, would perhaps be scarcely an equal match, on account of
+the disproportion of our strength. But since our present plan leads
+us to open an entirely different course to the understanding, and one
+unattempted and unknown to them, the case is altered. There is an end
+to party zeal, and we only take upon ourselves the character of a
+guide, which requires a moderate share of authority and good fortune,
+rather than talents and excellence. The first admonition relates to
+persons, the next to things.</p>
+
+<p>We make no attempt to disturb the system of philosophy that now
+prevails, or any other which may or will exist, either more correct or
+more complete. For we deny not that the received system of philosophy,
+and others of a similar nature, encourage discussion, embellish
+harangues, are employed, and are of service in the duties of the
+professor, and the affairs of civil life. Nay, we openly express and
+declare that the philosophy we offer will not be very useful in such
+respects. It is not obvious, or to be understood in a cursory view,
+nor does it flatter the mind in its preconceived notions, nor will
+it descend to the level of the generality of mankind unless by its
+advantages and effects.</p>
+
+<p>Let there exist, then (and may it be of advantage to both), two
+sources, and two distributions of learning, and in like manner
+two tribes, and as it were kindred families of contemplators or
+philosophers, without any hostility or alienation between them; but
+rather allied and united by mutual assistance. Let there be, in short,
+one method of cultivating the sciences, and another in discovering
+them. And as for those who prefer and more readily receive the former,
+on account of their haste or from motives arising from their ordinary
+life, or because they are unable from weakness of mind to comprehend
+and embrace the other (which must necessarily be the<span class="pagenum" id="Page_5">[Pg 5]</span> case with by
+far the greater number), let us wish that they may prosper as they
+desire in their undertaking, and attain what they pursue. But if any
+individual desire, and is anxious not merely to adhere to, and make
+use of present discoveries, but to penetrate still further, and not
+to overcome his adversaries in disputes, but nature by labor, not in
+short to give elegant and specious opinions, but to know to a certainty
+and demonstration, let him, as a true son of science (if such be his
+wish), join with us; that when he has left the antechambers of nature
+trodden by the multitude, an entrance may at last be discovered to her
+inner apartments. And in order to be better understood, and to render
+our meaning more familiar by assigning determinate names, we have
+accustomed ourselves to call the one method the anticipation of the
+mind, and the other the interpretation of nature.</p>
+
+<p>We have still one request left. We have at least reflected and taken
+pains, in order to render our propositions not only true, but of easy
+and familiar access to men’s minds, however wonderfully prepossessed
+and limited. Yet it is but just that we should obtain this favor from
+mankind (especially in so great a restoration of learning and the
+sciences), that whosoever may be desirous of forming any determination
+upon an opinion of this our work either from his own perceptions,
+or the crowd of authorities, or the forms of demonstrations, he
+will not expect to be able to do so in a cursory manner, and whilst
+attending to other matters; but in order to have a thorough knowledge
+of the subject, will himself, by degrees, attempt the course which we
+describe and maintain; will be accustomed to the subtlety of things
+which is manifested by experience; and will correct the depraved and
+deeply-rooted habits of his mind by a seasonable, and, as it were, just
+hesitation: and then, finally (if he will), use his judgment when he
+has begun to be master of himself.</p>
+
+
+<p class="nindc space-above2 space-below2">
+ON THE INTERPRETATION OF NATURE, OR THE REIGN OF MAN<a id="FNanchor_3" href="#Footnote_3" class="fnanchor">[3]</a></p>
+
+<p>Man acts, then, upon natural bodies (besides merely bringing them
+together or removing them) by seven principal methods: I. By the
+exclusion of all that impedes and disturbs; II. by compression,
+extension, agitation, and the like; III. by heat and cold; IV. by
+detention<span class="pagenum" id="Page_6">[Pg 6]</span> in a suitable place; V. by checking or directing motion; VI.
+by peculiar harmonies; VII. by a seasonable and proper alternation,
+series, and succession of all these, or, at least, of some of them.</p>
+
+<p>I. With regard to the first—common air, which is always at hand, and
+forces its admission, as also the rays of the heavenly bodies, create
+much disturbance. Whatever, therefore, tends to exclude them may
+well be considered as generally useful. The substance and thickness
+of vessels in which bodies are placed when prepared for operations
+may be referred to this head. So also may the accurate methods of
+closing vessels by consolidation, or the <i>lutum sapientiæ</i> as
+the chemists call it. The exclusion of air by means of liquids at
+the extremity is also very useful, as when they pour oil on wine,
+or the juices of herbs, which by spreading itself upon the top like
+a cover, preserves them uninjured from the air. Powders, also, are
+serviceable, for although they contain air mixed up in them, yet they
+ward off the power of the mass of circumambient air, which is seen in
+the preservation of grapes and other fruits in sand or flour. Wax,
+honey, pitch, and other resinous bodies, are well used in order to
+make the exclusion more perfect, and to remove the air and celestial
+influence. We have sometimes made an experiment by placing a vessel or
+other bodies in quicksilver, the most dense of all substances capable
+of being poured round others. Grottoes and subterraneous caves are of
+great use in keeping off the effects of the sun, and the predatory
+action of air, and in the north of Germany are used for granaries.
+The depositing of bodies at the bottom of water may be also mentioned
+here; and I remember having heard of some bottles of wine being let
+down into a deep well in order to cool them, but left there by chance,
+carelessness, and forgetfulness, for several years, and then taken
+out; by which means the wine not only escaped becoming flat or dead,
+but was much more excellent in flavor, arising (as it appears) from
+a more complete mixture of its parts. But if the case require that
+bodies should be sunk to the bottom of water, as in rivers or the sea,
+and yet should not touch the water, nor be enclosed in sealed vessels,
+but surrounded only by air, it would be right to use that vessel which
+has been sometimes employed under water above ships that have sunk, in
+order to enable the divers to remain below and breathe occasionally
+by turns. It was of the following nature:—A hollow tub of metal was
+formed, and sunk<span class="pagenum" id="Page_7">[Pg 7]</span> so as to have its bottom parallel with the surface of
+the water; it thus carried down with it to the bottom of the sea all
+the air contained in the tub. It stood upon three feet (like a tripod),
+being of rather less height than a man, so that, when the diver was
+in want of breath, he could put his head into the hollow of the tub,
+breathe, and then continue his work. We hear that some sort of boat or
+vessel has now been invented, capable of carrying men some distance
+under water. Any bodies, however, can easily be suspended under some
+such vessel as we have mentioned, which has occasioned our remarks upon
+the experiment.</p>
+
+<p>Another advantage of the careful and hermetical closing of bodies is
+this—not only the admission of external air is prevented (of which we
+have treated), but the spirit of bodies also is prevented from making
+its escape, which is an internal operation. For anyone operating on
+natural bodies must be certain as to their quantity, and that nothing
+has evaporated or escaped, since profound alterations take place in
+bodies, when art prevents the loss or escape of any portion, whilst
+nature prevents their annihilation. With regard to this circumstance,
+a false idea has prevailed (which if true would make us despair of
+preserving quantity without diminution), namely, that the spirit of
+bodies, and air when rarefied by a great degree of heat, cannot be so
+kept in by being enclosed in any vessel as not to escape by the small
+pores. Men are led into this idea by the common experiments of a cup
+inverted over water, with a candle or piece of lighted paper in it,
+by which the water is drawn up, and of those cups which, when heated,
+draw up the flesh. For they think that in each experiment the rarefied
+air escapes, and that its quantity is therefore diminished, by which
+means the water or flesh rises by the motion of connection. This is,
+however, most incorrect. For the air is not diminished in quantity,
+but contracted in dimensions, nor does this motion of the rising of
+the water begin till the flame is extinguished, or the air cooled, so
+that physicians place cold sponges, moistened with water, on the cups,
+in order to increase their attraction. There is, therefore, no reason
+why men should fear much from the ready escape of air: for although it
+be true that the most solid bodies have their pores, yet neither air,
+nor spirit, readily suffers itself to be rarefied to such an extreme
+degree; just as water will not escape by a small chink.</p>
+
+<p><span class="pagenum" id="Page_8">[Pg 8]</span></p>
+
+<p>II. With regard to the second of the seven above-mentioned methods, we
+must especially observe, that compression and similar violence have a
+most powerful effect either in producing locomotion, and other motions
+of the same nature, as may be observed in engines and projectiles, or
+in destroying the organic body, and those qualities, which consist
+entirely in motion (for all life, and every description of flame and
+ignition are destroyed by compression, which also injures and deranges
+every machine); or in destroying those qualities which consist in
+position and a coarse difference of parts, as in colors; for the color
+of a flower when whole, differs from that it presents when bruised, and
+the same may be observed of whole and powdered amber; or in tastes,
+for the taste of a pear before it is ripe, and of the same pear when
+bruised and softened, is different, since it becomes perceptibly
+more sweet. But such violence is of little avail in the more noble
+transformations and changes of homogeneous bodies, for they do not,
+by such means, acquire any constantly and permanently new state, but
+one that is transitory, and always struggling to return to its former
+habit and freedom. It would not, however, be useless to make some more
+diligent experiments with regard to this; whether, for instance, the
+condensation of a perfectly homogeneous body (such as air, water, oil,
+and the like) or their rarefaction, when effected by violence, can
+become permanent, fixed, and, as it were, so changed, as to become
+a nature. This might at first be tried by simple perseverance, and
+then by means of helps and harmonies. It might readily have been
+attempted (if we had but thought of it), when we condensed water (as
+was mentioned above), by hammering and compression, until it burst out.
+For we ought to have left the flattened globe untouched for some days,
+and then to have drawn off the water, in order to try whether it would
+have immediately occupied the same dimensions as it did before the
+condensation. If it had not been done so, either immediately, or soon
+afterwards, the condensation would have appeared to have been rendered
+constant; if not, it would have appeared that a restitution took place,
+and that the condensation had been transitory. Something of the same
+kind might have been tried with the glass eggs; the egg should have
+been sealed up suddenly and firmly, after a complete exhaustion of
+the air, and should have been allowed to remain so for some days, and
+it might then have been tried whether, on opening<span class="pagenum" id="Page_9">[Pg 9]</span> the aperture, the
+air would be drawn in with a hissing noise, or whether as much water
+would be drawn into it when immersed, as would have been drawn into it
+at first, if it had not continued sealed. For it is probable (or, at
+least, worth making the experiment) that this might have happened, or
+might happen, because perseverance has a similar effect upon bodies
+which are a little less homogeneous. A stick bent together for some
+time does not rebound, which is not owing to any loss of quantity in
+the wood during the time, for the same would occur (after a larger
+time) in a plate of steel, which does not evaporate. If the experiment
+of simple perseverance should fail, the matter should not be given up,
+but other means should be employed. For it would be no small advantage,
+if bodies could be endued with fixed and constant natures by violence.
+Air could then be converted into water by condensation, with other
+similar effects; for man is more the master of violent motions than of
+any other means.</p>
+
+<p>III. The third of our seven methods is referred to that great practical
+engine of nature as well as of art, cold and heat. Here, man’s power
+limps, as it were, with one leg. For we possess the heat of fire, which
+is infinitely more powerful and intense than that of the sun (as it
+reaches us), and that of animals. But we want cold, except such as we
+can obtain in winter, in caverns, or by surrounding objects with snow
+and ice, which, perhaps, may be compared in degree with the noontide
+heat of the sun in tropical countries, increased by the reflection of
+mountains and walls. For this degree of heat and cold can be borne
+for a short period only by animals, yet it is nothing compared with
+the heat of a burning furnace, or the corresponding degree of cold.
+Everything with us has a tendency to become rarefied, dry, and wasted,
+and nothing to become condensed or soft, except by mixtures, and,
+as it were, spurious methods. Instances of cold, therefore, should
+be searched for most diligently, such as may be found by exposing
+bodies upon buildings in a hard frost, in subterraneous caverns, by
+surrounding bodies with snow and ice in deep places excavated for
+that purpose, by letting bodies down into wells, by burying bodies in
+quicksilver and metals, by immersing them in streams which petrify
+wood, by burying them in the earth (which the Chinese are reported to
+do with their china, masses of which, made for that purpose, are said<span class="pagenum" id="Page_10">[Pg 10]</span>
+to remain in the ground for forty or fifty years, and to be transmitted
+to their heirs as a sort of artificial mine), and the like. The
+condensations which take place in nature, by means of cold, should also
+be investigated, that by learning their causes, they may be introduced
+into the arts; such as are observed in the exudation of marble and
+stones, in the dew upon the panes of glass in a room towards morning
+after a frosty night, in the formation and the gathering of vapors
+under the earth into water, whence spring fountains, and the like.</p>
+
+<p>Besides the substances which are cold to the touch, there are others
+which have also the effect of cold, and condense; they appear, however,
+to act only upon the bodies of animals, and scarcely any further. Of
+these we have many instances, in medicines and plasters. Some condense
+the flesh and tangible parts, such as astringent and inspissating
+medicines, others the spirits, such as soporifics. There are two modes
+of condensing the spirits, by soporifics or provocatives to sleep;
+the one by calming the motion, the other by expelling the spirit. The
+violet, dried roses, lettuces, and other benign or mild remedies,
+by their friendly and gently cooling vapors, invite the spirits to
+unite, and restrain their violent and perturbed motion. Rosewater, for
+instance, applied to the nostrils in fainting fits, causes the resolved
+and relaxed spirits to recover themselves, and, as it were, cherishes
+them. But opiates, and the like, banish the spirits by their malignant
+and hostile quality. If they be applied, therefore, externally, the
+spirits immediately quit the part and no longer readily flow into it;
+but if they be taken internally, their vapor, mounting to the head,
+expels, in all directions, the spirits contained in the ventricles of
+the brain, and since these spirits retreat, but cannot escape, they
+consequently meet and are condensed, and are sometimes completely
+extinguished and suffocated; although the same opiates, when taken in
+moderation, by a secondary accident (the condensation which succeeds
+their union), strengthen the spirits, render them more robust, and
+check their useless and inflammatory motion, by which means they
+contribute not a little to the cure of diseases, and the prolongation
+of life.</p>
+
+<p>The preparations of bodies, also, for the reception of cold should not
+be omitted, such as that water a little warmed is more easily frozen
+than that which is quite cold, and the like.</p>
+
+<p>Moreover, since nature supplies cold so sparingly, we must act like<span class="pagenum" id="Page_11">[Pg 11]</span>
+the apothecaries, who, when they cannot obtain any simple ingredient,
+take a succedaneum, or quid pro quo, as they term it, such as aloes for
+xylobalsamum, cassia for cinnamon. In the same manner we should look
+diligently about us, to ascertain whether there may be any substitutes
+for cold, that is to say, in what other manner condensation can be
+effected, which is the peculiar operation of cold. Such condensations
+appear hitherto to be of four kinds only. 1. By simple compression,
+which is of little avail towards permanent condensation, on account
+of the elasticity of substances, but may still however be of some
+assistance. 2. By the contraction of the coarser, after the escape
+or departure of the finer parts of a given body; as is exemplified
+in induration by fire, and the repeated heating and extinguishing of
+metals, and the like. 3. By the cohesion of the most solid homogeneous
+parts of a given body, which were previously separated, and mixed with
+others less solid, as in the return of sublimated mercury to its simple
+state, in which it occupies much less space than it did in powder, and
+the same may be observed of the cleansing of all metals from their
+dross. 4. By harmony or the application of substances which condense by
+some latent power. These harmonies are as yet but rarely observed, at
+which we cannot be surprised, since there is little to hope for from
+their investigation, unless the discovery of forms and conformation
+be attained. With regard to animal bodies, it is not to be questioned
+that there are many internal and external medicines which condense
+by harmony, as we have before observed, but this action is rare in
+inanimate bodies. Written accounts, as well as report, have certainly
+spoken of a tree in one of the Tercera or Canary Islands (for I do not
+exactly recollect which) that drips perpetually, so as to supply the
+inhabitants, in some degree, with water; and Paracelsus says that the
+herb called <i>ros solis</i> is filled with dew at noon, whilst the sun
+gives out its greatest heat, and all other herbs around it are dry. We
+treat both these accounts as fables; they would, however, if true, be
+of the most important service, and most worthy of examination. As to
+the honey-dew, resembling manna, which is found in May on the leaves
+of the oak, we are of opinion that it is not condensed by any harmony
+or peculiarity of the oak-leaf, but that whilst it falls equally upon
+other leaves it is retained and continues on those of the oak, because
+their texture is closer, and not so porous as that of most of the other
+leaves.</p>
+
+<p><span class="pagenum" id="Page_12">[Pg 12]</span></p>
+
+<p>With regard to heat, man possesses abundant means and power; but his
+observation and inquiry are defective in some respects, and those of
+the greatest importance, notwithstanding the boasting of quacks. For
+the effects of intense heat are examined and observed, whilst those of
+a more gentle degree of heat, being of the most frequent occurrence
+in the paths of nature, are, on that very account, least known. We
+see, therefore, the furnaces, which are most esteemed, employed in
+increasing the spirits of bodies to a great extent, as in the strong
+acids, and some chemical oils; whilst the tangible parts are hardened,
+and, when the volatile part has escaped, become sometimes fixed; the
+homogeneous parts are separated, and the heterogeneous incorporated and
+agglomerated in a coarse lump; and (what is chiefly worthy of remark)
+the junction of compound bodies, and the more delicate conformations
+are destroyed and confounded. But the operation of a less violent heat
+should be tried and investigated, by which more delicate mixtures, and
+regular conformations may be produced and elicited, according to the
+example of nature, and in imitation of the effect of the sun, which we
+have alluded to in the aphorism on the instances of alliance. For the
+works of nature are carried on in much smaller portions, and in more
+delicate and varied positions than those of fire, as we now employ
+it. But man will then appear to have really augmented his power, when
+the works of nature can be imitated in species, perfected in power,
+and varied in quantity; to which should be added the acceleration in
+point of time. Rust, for instance, is the result of a long process,
+but <i>crocus martis</i> is obtained immediately; and the same may be
+observed of natural verdigris and ceruse. Crystal is formed slowly,
+whilst glass is blown immediately: stones increase slowly, whilst
+bricks are baked immediately, etc. In the mean time (with regard to
+our present subject) every different species of heat should, with its
+peculiar effects, be diligently collected and inquired into; that
+of the heavenly bodies, whether their rays be direct, reflected, or
+refracted, or condensed by a burning-glass; that of lightning, flame,
+and ignited charcoal; that of fire of different materials, either open
+or confined, straitened or overflowing, qualified by the different
+forms of the furnaces, excited by the bellows, or quiescent, removed to
+a greater or less distance, or passing through different media; moist
+heats, such as the <i>balneum Mariæ</i>, and the dunghill; the external
+and internal<span class="pagenum" id="Page_13">[Pg 13]</span> heat of animals; dry heats, such as the heat of ashes,
+lime, warm sand; in short, the nature of every kind of heat, and its
+degrees.</p>
+
+<p>We should, however, particularly attend to the investigation and
+discovery of the effects and operations of heat, when made to approach
+and retire by degrees, regularly, periodically, and by proper intervals
+of space and time. For this systematical inequality is in truth the
+daughter of heaven and mother of generation, nor can any great result
+be expected from a vehement, precipitate, or desultory heat. For this
+is not only most evident in vegetables, but in the wombs of animals
+also there arises a great inequality of heat, from the motion, sleep,
+food, and passions of the female. The same inequality prevails in
+those subterraneous beds where metals and fossils are perpetually
+forming, which renders yet more remarkable the ignorance of some of the
+reformed alchemists, who imagined they could attain their object by the
+equable heat of lamps, or the like, burning uniformly. Let this suffice
+concerning the operation and effects of heat; nor is it time for us
+to investigate them thoroughly before the forms and conformations
+of bodies have been further examined and brought to light. When we
+have determined upon our models, we may seek, apply, and arrange our
+instruments.</p>
+
+<p>IV. The fourth mode of action is by continuance, the very steward and
+almoner, as it were, of nature. We apply the term continuance to the
+abandonment of a body to itself for an observable time, guarded and
+protected in the mean while from all external force. For the internal
+motion then commences to betray and exert itself when the external and
+adventitious is removed. The effects of time, however, are far more
+delicate than those of fire. Wine, for instance, cannot be clarified
+by fire as it is by continuance. Nor are the ashes produced by
+combustion so fine as the particles dissolved or wasted by the lapse
+of ages. The incorporations and mixtures, which are hurried by fire,
+are very inferior to those obtained by continuance; and the various
+conformations assumed by bodies left to themselves, such as mouldiness,
+etc., are put a stop to by fire or a strong heat. It is not, in the
+mean time, unimportant to remark that there is a certain degree of
+violence in the motion of bodies entirely confined; for the confinement
+impedes the proper motion of the body. Continuance in an open vessel,
+therefore, is useful for separations, and in one hermetically sealed
+for mixtures, that in a vessel partly closed, but<span class="pagenum" id="Page_14">[Pg 14]</span> admitting the
+air, for putrefaction. But instances of the operation and effect of
+continuance must be collected diligently from every quarter.</p>
+
+<p>V. The direction of motion (which is the fifth method of action) is
+of no small use. We adopt this term, when speaking of a body which,
+meeting with another, either arrests, repels, allows, or directs
+its original motion. This is the case principally in the figure and
+position of vessels. An upright cone, for instance, promotes the
+condensation of vapor in alembics, but when reversed, as in inverted
+vessels, it assists the refining of sugar. Sometimes a curved form,
+or one alternately contracted and dilated, is required. Strainers may
+be ranged under this head, where the opposed body opens a way for
+one portion of another substance and impedes the rest. Nor is this
+process or any other direction of motion carried on externally only,
+but sometimes by one body within another. Thus, pebbles are thrown
+into water to collect the muddy particles, and syrups are refined by
+the white of an egg, which glues the grosser particles together so as
+to facilitate their removal. Telesius, indeed, rashly and ignorantly
+enough attributes the formation of animals to this cause, by means of
+the channels and folds of the womb. He ought to have observed a similar
+formation of the young in eggs which have no wrinkles or inequalities.
+One may observe a real result of this direction of motion in casting
+and modelling.</p>
+
+<p>VI. The effects produced by harmony and aversion (which is the
+sixth method) are frequently buried in obscurity; for these occult
+and specific properties (as they are termed), the sympathies and
+antipathies, are for the most part but a corruption of philosophy. Nor
+can we form any great expectation of the discovery of the harmony which
+exists between natural objects, before that of their forms and simple
+conformations, for it is nothing more than the symmetry between these
+forms and conformations.</p>
+
+<p>The greater and more universal species of harmony are not, however,
+so wholly obscure, and with them, therefore, we must commence. The
+first and principal distinction between them is this; that some bodies
+differ considerably in the abundance and rarity of their substance, but
+correspond in their conformation; others, on the contrary, correspond
+in the former and differ in the latter. Thus the chemists have well
+observed, that in their trial of first principles sulphur and<span class="pagenum" id="Page_15">[Pg 15]</span> mercury,
+as it were, pervade the universe; their reasoning about salt, however,
+is absurd, and merely introduced to compromise earthy dry fixed bodies.
+In the other two, indeed, one of the most universal species of natural
+harmony manifests itself. Thus there is a correspondence between
+sulphur, oil, greasy exhalations, flame, and, perhaps, the substance of
+the stars. On the other hand, there is a like correspondence between
+mercury, water, aqueous vapor, air, and perhaps pure inter-sidereal
+ether. Yet do these two quarternions, or great natural tribes (each
+within its own limits), differ immensely in quantity and density of
+substance, whilst they generally agree in conformation, as is manifest
+in many instances. On the other hand, the metals agree in such quantity
+and density (especially when compared with vegetables, etc.), but
+differ in many respects in conformation. Animals and vegetables, in
+like manner, vary in their almost infinite modes of conformation, but
+range within very limited degrees of quantity and density of substance.</p>
+
+<p>The next most general correspondence is that between individual bodies
+and those which supply them by way of menstruum or support. Inquiry,
+therefore, must be made as to the climate, soil, and depth at which
+each metal is generated, and the same of gems, whether produced in
+rocks or mines, also as to the soil in which particular trees, shrubs,
+and herbs, mostly grow and, as it were, delight; and as to the best
+species of manure, whether dung, chalk, sea sand, or ashes, etc., and
+their different propriety and advantage according to the variety of
+soils. So also the grafting and setting of trees and plants (as regards
+the readiness of grafting one particular species on another) depends
+very much upon harmony, and it would be amusing to try an experiment
+I have lately heard of, in grafting forest trees (garden trees alone
+having hitherto been adopted), by which means the leaves and fruit
+are enlarged, and the trees produce more shade. The specific food of
+animals again should be observed, as well as that which cannot be used.
+Thus the carnivorous cannot be fed on herbs, for which reason the order
+of <i>feuilletans</i>, the experiment having been made, has nearly
+vanished; human nature being incapable of supporting their regimen,
+although the human will has more power over the bodily frame than
+that of other animals. The different kinds of putrefaction from which
+animals are generated should be noted.</p>
+
+<p>The harmony of principal bodies with those subordinate to them<span class="pagenum" id="Page_16">[Pg 16]</span> (such
+indeed may be deemed those we have alluded to above) are sufficiently
+manifest, to which may be added those that exist between different
+bodies and their objects, and, since these latter are more apparent,
+they may throw great light when well observed and diligently examined
+upon those which are more latent.</p>
+
+<p>The more internal harmony and aversion, or friendship and enmity
+(for superstition and folly have rendered the terms of sympathy and
+antipathy almost disgusting) have been either falsely assigned, or
+mixed with fable, or most rarely discovered from neglect. For if
+one were to allege that there is an enmity between the vine and the
+cabbage, because they will not come up well sown together, there is
+a sufficient reason for it in the succulent and absorbent nature of
+each plant, so that the one defrauds the other. Again, if one were
+to say that there is a harmony and friendship between the corn and
+the corn-flower, or the wild poppy, because the latter seldom grow
+anywhere but in cultivated soils, he ought rather to say, there is an
+enmity between them, for the poppy and the corn-flower are produced and
+created by those juices which the corn has left and rejected, so that
+the sowing of the corn prepares the ground for their production. And
+there are a vast number of similar false assertions. As for fables,
+they must be totally exterminated. There remains, then, but a scanty
+supply of such species of harmony as has borne the test of experiment,
+such as that between the magnet and iron, gold and quicksilver, and
+the like. In chemical experiments on metals, however, there are some
+others worthy of notice, but the greatest abundance (where the whole
+are so few in numbers) is discovered in certain medicines, which,
+from their occult and specific qualities (as they are termed), affect
+particular limbs, humors, diseases, or constitutions. Nor should we
+omit the harmony between the motion and phenomena of the moon, and
+their effects on lower bodies, which may be brought together by an
+accurate and honest selection from the experiments of agriculture,
+navigation, and medicine, or of other sciences. By as much as these
+general instances, however, of more latent harmony, are rare, with
+so much the more diligence are they to be inquired after, through
+tradition, and faithful and honest reports, but without rashness and
+credulity, with an anxious and, as it were, hesitating degree of
+reliance. There remains one species of harmony which, though simple
+in its mode of action, is yet most<span class="pagenum" id="Page_17">[Pg 17]</span> valuable in its use, and must
+by no means be omitted, but rather diligently investigated. It is
+the ready or difficult coition or union of bodies in composition, or
+simple juxtaposition. For some bodies readily and willingly mix, and
+are incorporated, others tardily and perversely; thus powders mix best
+with water, chalk, and ashes with oils, and the like. Nor are these
+instances of readiness and aversion to mixture to be alone collected,
+but others, also, of the collocation, distribution, and digestion of
+the parts when mingled, and the predominance after the mixture is
+complete.</p>
+
+<p>VII. Lastly, there remains the seventh, and last of the seven, modes
+of action; namely that by the alternation and interchange of the
+other six; but of this, it will not be the right time to offer any
+examples, until some deeper investigation shall have taken place of
+each of the others. The series, or chain of this alternation, in its
+mode of application to separate effects, is no less powerful in its
+operation, than difficult to be traced. But men are possessed with the
+most extreme impatience, both of such inquiries, and their practical
+application, although it be the clue of the labyrinth in all greater
+works.</p>
+
+<p class="space-above2">
+But it must be noted, that in this our organ, we treat of logic, and
+not of philosophy. Seeing, however, that our logic instructs and
+informs the understanding, in order that it may not, with the small
+hooks, as it were, of the mind, catch at, and grasp mere abstractions,
+but rather actually penetrate nature, and discover the properties and
+effects of bodies, and the determinate laws of their substance (so that
+this science of ours springs from the nature of things, as well as
+from that of the mind); it is not to be wondered at, if it have been
+continually interspersed and illustrated with natural observations and
+experiments, as instances of our method. The prerogative instances are,
+as appears from what has preceded, twenty-seven in number, and are
+termed: solitary instances, migrating instances, conspicuous instances,
+clandestine instances, constitutive, instances, similar instances,
+singular instances, deviating instances, bordering instances,
+instances of power, accompanying and hostile instances, subjunctive
+instances, instances of alliance, instances of the cross, instances
+of divorce, instances of the gate, citing instances, instances of the
+road, supplementary instances, lancing instances, instances of the
+rod, instances of the course, doses of nature, wrestling<span class="pagenum" id="Page_18">[Pg 18]</span> instances,
+suggesting instances, generally useful instances, and magical
+instances. The advantage, by which these instances excel the more
+ordinary, regards specifically either theory or practice, or both. With
+regard to theory, they assist either the senses or the understanding;
+the senses, as in the five instances of the lamp; the understanding,
+either by expediting the exclusive mode of arriving at the form, as in
+solitary instances, or by confining, and more immediately indicating
+the affirmative, as in the migrating, conspicuous, accompanying, and
+subjunctive instances; or by elevating the understanding, and leading
+it to general and common natures, and that either immediately, as in
+the clandestine and singular instances, and those of alliance; or very
+nearly so, as in the constitutive; or still less so, as in the similar
+instances; or by correcting the understanding of its habits, as in
+the deviating instances; or by leading to the grand form or fabric of
+the universe, as in the bordering instances; or by guarding it from
+false forms and causes, as in those of the cross and of divorce. With
+regard to practice, they either point it out, or measure, or elevate
+it. They point it out, either by showing where we must commence in
+order not to repeat the labors of others, as in the instances of power;
+or by inducing us to aspire to that which may be possible, as in the
+suggesting instances; the four mathematical instances measure it. The
+generally useful and the magical elevate it.</p>
+
+<p>Again, out of these twenty-seven instances, some must be collected
+immediately, without waiting for a particular investigation of
+properties. Such are the similar, singular, deviating, and bordering
+instances, those of power, and of the gate, and suggesting, generally
+useful, and magical instances; for these either assist and cure
+the understanding and senses, or furnish our general practice. The
+remainder are to be collected when we furnish our synoptical tables
+for the work of the interpreter, upon any particular nature; for these
+instances, honored and gifted with such prerogatives, are like the
+soul amid the vulgar crowd of instances, and (as we from the first
+observed) a few of them are worth a multitude of the others. When,
+therefore, we are forming our tables they must be searched out with the
+greatest zeal, and placed in the table. And, since mention must be made
+of them in what follows, a treatise upon their nature has necessarily
+been prefixed. We must next, however, proceed to the supports and
+corrections of induction, and thence to concretes, the<span class="pagenum" id="Page_19">[Pg 19]</span> latent process,
+and latent conformations, and the other matters, which we have
+enumerated in their order in the twenty-first aphorism, in order that,
+like good and faithful guardians, we may yield up their fortune to
+mankind upon the emancipation and majority of their understanding; from
+which must necessarily follow an improvement of their estate, and an
+increase of their power over nature. For man, by the fall, lost at once
+his state of innocence, and his empire over creation, both of which can
+be partially recovered even in this life, the first by religion and
+faith, the second by the arts and sciences. For creation did not become
+entirely and utterly rebellious by the curse, but in consequence of the
+Divine decree, “in the sweat of thy brow shalt thou eat bread,” she
+is compelled by our labors (not assuredly by our disputes or magical
+ceremonies), at length, to afford mankind in some degree his bread,
+that is to say, to supply man’s daily wants.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_2" href="#FNanchor_2" class="label">[2]</a>
+Selection from the Preface to the <i>Novum Organum</i>.</p>
+
+</div>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_3" href="#FNanchor_3" class="label">[3]</a>
+Part II, Conclusion of the <i>Novum Organum</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_20">[Pg 20]</span></p>
+<h2 class="nobreak" id="II">II<br>
+NICOLAUS COPERNICUS<br>
+1473-1543</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>One of the first and most striking contributions to modern science
+was the substitution of the Copernican for the Ptolemaic conception of
+the universe.</i></p>
+
+<p><i>Nicolaus Copernicus was born in the Prussian village of Thorn,
+located on the Vistula River, February 19, 1473. Although destined for
+the Church, he became interested in medicine, which he studied at the
+University of Cracow. Later, he turned to mathematics and continued
+his studies at the Universities of Vienna, Bologna, Padua, Ferrara,
+and Rome. Although he settled down as canon at Frauenberg, Poland, and
+gratuitously practised medicine in conjunction with his ecclesiastical
+duties, he found considerable time for other intellectual pursuits.
+Reading widely in the Greek philosophers, he came across a statement
+that the earth moved in its own orbit. This idea deeply appealed to
+him. “Occasioned by this,” he wrote, “I also began to think of a
+motion of the earth, and although the idea seemed absurd, still, as
+others before me had been permitted to assume certain circles in order
+to explain the motions of the stars, I believed it would be readily
+permitted me to try whether on the assumption of some motion of the
+earth better explanations of the revolutions of the heavenly bodies
+might not be found. And thus I have, assuming the motions which I in
+the following work attribute to the earth, after long and careful
+investigation, finally found that when the motions of the other planets
+are referred to the circulation of the earth and are computed for the
+revolution of each star, not only do the phenomena necessarily follow
+therefrom, but the order and magnitude of the stars and all their orbs
+and the heaven itself are so connected that in no part can anything be
+transposed without confusion to the rest and to the whole universe.”</i></p>
+
+<p><i>In 1530 he issue a “Commentariolus” which outlined his theory,<span class="pagenum" id="Page_21">[Pg 21]</span> but
+his prudence prompted him to withhold the publication of his great
+work, “De Orbium Caelestium Revolutionibus,” until 1543. In May of that
+year the first printed copy was laid on his death-bed.</i></p>
+</div>
+
+<p class="nindc space-above2 space-below2">
+THE NEW IDEA OF THE UNIVERSE<a id="FNanchor_4" href="#Footnote_4" class="fnanchor">[4]</a></p>
+
+<p>I can well believe, most holy father, that certain people, when they
+hear of my attributing motion to the earth in these books of mine, will
+at once declare that such an opinion ought to be rejected. Now, my own
+theories do not please me so much as not to consider what others may
+judge of them. Accordingly, when I began to reflect upon what those
+persons who accept the stability of the earth, as confirmed by the
+opinion of many centuries, would say when I claimed that the earth
+moves, I hesitated for a long time as to whether I should publish that
+which I have written to demonstrate its motion, or whether it would
+not be better to follow the example of the Pythagoreans, who used to
+hand down the secrets of philosophy to their relatives and friends only
+in oral form. As I well considered all this, I was almost impelled to
+put the finished work wholly aside, through the scorn I had reason to
+anticipate on account of the newness and apparent contrariness of my
+theory to reason.</p>
+
+<p>My friends, however, dissuaded me from such a course and admonished
+me that I ought to publish my book, which had lain concealed in my
+possession not only nine years, but already into four times the ninth
+year. Not a few other distinguished and very learned men asked me to do
+the same thing, and told me that I ought not, on account of my anxiety,
+to delay any longer in consecrating my work to the general service of
+mathematicians.</p>
+
+<p>But your holiness will perhaps not so much wonder that I have dared to
+bring the results of my night labors to the light of day, after having
+taken so much care in elaborating them, but is waiting instead to
+hear how it entered my mind to imagine that the earth moved, contrary
+to the accepted opinion of mathematicians—nay, almost contrary to
+ordinary human understanding. Therefore I will not conceal from your
+holiness that what moved me to consider another way of reckoning the
+motions of the heavenly bodies was<span class="pagenum" id="Page_22">[Pg 22]</span> nothing else than the fact that the
+mathematicians do not agree with one another in their investigations.
+In the first place, they are so uncertain about the motions of the sun
+and moon that they cannot find out the length of a full year. In the
+second place, they apply neither the same laws of cause and effect, in
+determining the motions of the sun and moon and of the five planets,
+nor the same proofs. Some employ only concentric circles, others use
+eccentric and epicyclic ones, with which, however, they do not fully
+attain the desired end. They could not even discover nor compute the
+main thing—namely, the form of the universe and the symmetry of its
+parts. It was with them as if some should, from different places, take
+hands, feet, head, and other parts of the body, which, although very
+beautiful, were not drawn in their proper relations, and, without
+making them in any way correspond, should construct a monster instead
+of a human being.</p>
+
+<p>Accordingly, when I had long reflected, on this uncertainty of
+mathematical tradition, I took the trouble to read again the books of
+all the philosophers I could get hold of, to see if some one of them
+had not once believed that there were other motions of the heavenly
+bodies. First I found in Cicero that Niceties had believed in the
+motion of the earth. Afterwards I found in Plutarch, likewise, that
+some others had held the same opinion. This induced me also to begin to
+consider the movability of the earth, and, although the theory appeared
+contrary to reason, I did so because I knew that others before me had
+been allowed to assume rotary movements at will, in order to explain
+the phenomena of these celestial bodies. I was of the opinion that I,
+too, might be permitted to see whether, by presupposing motion in the
+earth, more reliable conclusions than hitherto reached could not be
+discovered for the rotary motions of the spheres. And thus, acting on
+the hypothesis of the motion which, in the following book, I ascribe
+to the earth, and by long and continued observations, I have finally
+discovered that if the motion of the other planets be carried over to
+the relation of the earth and this is made the basis for the rotation
+of every star, not only will the phenomena of the planets be explained
+thereby, but also the laws and the size of the stars; all their spheres
+and the heavens themselves will appear so harmoniously connected that
+nothing could be changed in any part of them without confusion in the
+remaining parts and in the whole universe.</p>
+
+<p><span class="pagenum" id="Page_23">[Pg 23]</span></p>
+
+<p class="nindc space-above2 space-below2">
+THAT THE UNIVERSE IS SPHERICAL</p>
+
+<p>First we must remark that the universe is spherical in form, partly
+because this form being a perfect whole requiring no joints, is the
+most complete of all, partly because it makes the most capacious
+form, which is best suited to contain and preserve everything; or
+again because all the constituent parts of the universe, that is the
+sun, moon, and the planets appear in this form; or because everything
+strives to attain this form, as appears in the case of drops of water
+and other fluid bodies if they attempt to define themselves. So no one
+will doubt that this form belongs to the heavenly bodies.</p>
+
+
+<p class="nindc space-above2 space-below2">
+THAT THE EARTH IS ALSO SPHERICAL</p>
+
+<p>That the earth is also spherical is therefore beyond question, because
+it presses from all sides upon its center. Although by reason of
+the elevations of the mountains and the depressions of the valleys
+a perfect circle cannot be understood, yet this does not affect the
+general spherical nature of the earth. This appears in the following
+manner. To those who journey towards the North the north pole of the
+daily revolution of the heavenly sphere seems gradually to rise, while
+the opposite seems to sink. Most of the stars in the region of the Bear
+seem not to set, while some of the southern stars seem not to rise at
+all. So Italy does not see Canopes which is visible to the Egyptians.
+And Italy sees the outermost star of the Stream, which our region of a
+colder zone does not know. On the other hand to those who go towards
+the South the others seem to rise and those to sink which are high in
+our region. Moreover, the inclination of the Poles to the diameter
+of the earth bears always the same relation, which could happen only
+in the case of a sphere. So it is evident that the earth is included
+between the two poles, and is therefore spherical in form. Let us add
+that the inhabitants of the East do not observe the eclipse of the sun
+or of the moon which occurs in the evening, and the inhabitants of the
+West those which occur in the morning, while those who dwell between
+see those later and these earlier. That the water also has the same
+form can be observed from ships, in that the land which cannot be seen
+from the deck, is visible from the mast-tree. And conversely if a light
+be placed at the mast-head it seems<span class="pagenum" id="Page_24">[Pg 24]</span> to those who remain on the shores
+gradually to sink and at last still sinking to disappear. It is clear
+that the water also according to its nature continually presses like
+the earth downward, and does not rise above its banks higher than its
+convexity permits. So the land extends above the ocean as much as the
+land happens to be higher.</p>
+
+<p class="nindc space-above2 space-below2">
+WHETHER THE EARTH HAS A CIRCULAR MOTION, AND CONCERNING THE LOCATION OF
+THE EARTH</p>
+
+<p>As it has been already shown that the earth has the form of a sphere,
+we must consider whether a movement also coincides with this form, and
+what place the earth holds in the universe. Without this there will be
+no secure results to be obtained in regard to the heavenly phenomena.
+The great majority of authors of course agree that the earth stands
+still in the center of the universe, and consider it inconceivable and
+ridiculous to suppose the opposite. But if the matter is carefully
+weighed it will be seen that the question is not yet settled and
+therefore by no means to be regarded lightly. Every change of place
+which is observed is due, namely, to a movement of the observed object
+or of the observer, or to movements of both, naturally in different
+directions, for if the observed object and the observer move in the
+same manner and in the same direction no movement will be seen. Now it
+is from the earth that the revolution of the heavens is observed and it
+is produced for our eyes. Therefore if the earth undergoes no movement
+this movement must take place in everything outside of the earth, but
+in the opposite direction than if everything on the earth moved, and
+of this kind is the daily revolution. So this appears to affect the
+whole universe, that is, everything outside the earth with the single
+exception of the earth itself. If, however, one should admit that this
+movement was not peculiar to the heavens, but that the earth revolved
+from west to east, and if this was carefully considered in regard to
+the apparent rising and setting of the sun, the moon and the stars,
+it would be discovered that this was the real situation. Since the
+sky, which contains and shelters all things, is the common seat of all
+things, it is not easy to understand why motion should not be ascribed
+rather to the thing contained than to the containing, to the located
+rather than to the location. From this supposition follows another
+question of no less importance, concerning the place of the<span class="pagenum" id="Page_25">[Pg 25]</span> earth,
+although it has been accepted and believed by almost all, that the
+earth occupies the middle of the universe. But if one should suppose
+that the earth is not at the center of the universe, that, however,
+the distance between the two is not great enough to be measured on the
+orbits of the fixed stars, but would be noticeable and perceptible on
+the orbit of the sun or of the planets: and if one was further of the
+opinion that the movements of the planets appeared to be irregular
+as if they were governed by a center other than the earth, then such
+an one could perhaps have given the true reasons for the apparently
+irregular movement. For since the planets appear now nearer and now
+farther from the earth, this shows necessarily that the center of their
+revolutions is not the center of the earth: although it does not settle
+whether the earth increases and decreases the distance from them or
+they their distance from the earth.</p>
+
+
+<p class="nindc space-above2 space-below2">
+REFUTATION OF THE ARGUMENT OF THE ANCIENTS THAT THE EARTH REMAINS STILL
+IN THE MIDDLE OF THE UNIVERSE, AS IF IT WERE ITS CENTER</p>
+
+<p>From this and similar reasons it is supposed that the earth rests at
+the center of the universe and that there is no doubt of the fact.
+But if one believed that the earth revolved, he would certainly be
+of the opinion that this movement was natural and not arbitrary. For
+whatever is in accord with nature produces results which are the
+opposite of those produced by force. Things upon which force or an
+outside power has acted, must be injured and cannot long endure: what
+happens by nature, however, preserves itself well and exists in the
+best condition. So Ptolemy feared without good reason that the earth
+and all earthly objects subject to the revolution would be destroyed
+by the act of nature, since this latter is opposed to artificial acts,
+or to what is produced by the human spirit. But why did not he fear
+the same, and in a much higher degree, of the universe, whose motion
+must be as much more rapid as the heavens are greater than the earth?
+Or has the heaven become so immense because it has been driven outward
+from the center by the inconceivable power of the revolution; while if
+it stood still, on the contrary, it would collapse and fall together?
+But surely if this is the case the extent of the heavens would increase
+infinitely. For the more it is driven higher by the outward force of
+the<span class="pagenum" id="Page_26">[Pg 26]</span> movement, so much the more rapid will the movement become, because
+of the ever increasing circle which must be traversed in 24 hours; and
+conversely if the movement grows the immensity of the heavens grows. So
+the velocity would increase the size and the size would increase the
+velocity unendingly. According to the physical law that the endless
+cannot wear away nor in any way move, the heavens must necessarily
+stand still.</p>
+
+<p>But it is said that beyond the sky no body, no place, no vacant space,
+in fact nothing at all exists; then it is strange that some thing
+should be enclosed by nothing. But if the heaven is endless and is
+bounded only by the inner hollow, perhaps this establishes all the more
+clearly the fact that there is nothing outside the heavens, because
+everything is within it, but the heaven must then remain unmoved.
+The highest proof on which one supports the finite character of the
+universe is its movement. But whether the universe is endless or
+limited we will leave to the physiologues; this remains sure for us
+that the earth enclosed between the poles, is bounded by a spherical
+surface. Why therefore should we not take the position of ascribing
+to a movement conformable to its nature and corresponding to its
+form, rather than suppose that the whole universe whose limits are
+not and cannot be known moves? and why will we not recognize that
+the appearance of a daily revolution belongs to the heavens, but the
+actuality to the earth; and that the relation is similar to that of
+which one says: “We run out of the harbor, the lands and cities retreat
+from us.” Because if a ship sails along quietly, everything outside
+of it appears to those on board as if it moved with the motion of
+the boat, and the boatman thinks that the boat with all on board is
+standing still, this same thing may hold without doubt of the motion
+of the earth, and it may seem as if the whole universe revolved. What
+shall we say, however, of the clouds and other things floating, falling
+or raising in the air—except that not only does the earth move with
+the watery elements belonging with it, but also a large part of the
+atmosphere, and whatever else is in any way connected with the earth;
+whether it is because the air immediately touching the earth has the
+same nature as the earth, or that the motion has become imparted to the
+atmosphere. A like astonishment must be felt if that highest region
+of the air be supposed to follow the heavenly motion, as shown by
+those suddenly appearing stars which the Greeks call comets or bearded
+stars, which<span class="pagenum" id="Page_27">[Pg 27]</span> belong to that region and which rise and set like other
+stars. We may suppose that part of the atmosphere, because of its great
+distance from the earth, has become free from the earthly motion. So
+the atmosphere which lies close to the earth and all things floating in
+it would appear to remain still, unless driven here and there by the
+wind or some other outside force, which chance may bring into play;
+for how is the wind in the air different from the current in the sea?
+We must admit that the motion of things rising and falling in the air
+is in relation to the universe a double one, being always made up of a
+rectilinear and a circular movement. Since that which seeks of its own
+weight to fall is essentially earthy, so there is no doubt that these
+follow the same natural law as their whole; and it results from the
+same principle that those things which pertain to fire are forcibly
+driven on high. Earthly fire is nourished with earthly stuff, and it
+is said that the flame is only burning smoke. But the peculiarity of
+the fire consists in this that it expands whatever it seizes upon,
+and it carries this out so consistently that it can in no way and
+by no machinery be prevented from breaking its bonds and completing
+its work. The expanding motion, however, is directed from the center
+outward; therefore if any earthly material is ignited it moves upward.
+So to each single body belongs a single motion, and this is evinced
+preferably in a circular direction as long as the single body remains
+in its natural place and its entirety. In this position the movement
+is the circular movement which as far as the body itself is concerned
+is as if it did not occur. The rectilinear motion, however, seizes
+upon those bodies which have wandered or have been driven from their
+natural position or have been in any way disturbed. Nothing is so much
+opposed to the order and form of the world as the displacement of one
+of its parts. Rectilinear motion takes place only when objects are
+not properly related, and are not complete according to their nature
+because they have separated from their whole and have lost their unity.
+Moreover, objects which have been driven outward or away, leaving out
+of consideration the circular motion, do not obey a single, simple
+and regular motion, since they cannot be controlled simply by their
+lightness or by the force of their weight, and if in falling they have
+at first a slow movement the rapidity of the motion increases as they
+fall, while in the case of earthly fire which is forced upwards—and
+we have no means of knowing any other kind of fire—we will see that
+its motion<span class="pagenum" id="Page_28">[Pg 28]</span> is slow as if its earthly origin thereby showed itself.
+The circular motion, on the other hand, is always regular, because it
+is not subject to an intermittent cause. Those other objects, however,
+would cease to be either light or heavy in respect to their natural
+movement if they reached their own place, and thus they would fit into
+that movement. Therefore if the circular movement is to be ascribed
+to the universe as a whole and the rectilinear to the parts, we might
+say that the revolution is to the straight line as the natural state
+is to sickness. That Aristotle divided motion into three sorts, that
+from the center out, that inward toward the center, and that around
+about the center, appears to be merely a logical convenience, just
+as we distinguish point, line and surface, although one cannot exist
+without the others, and none of them are found apart from bodies. This
+fact is also to be considered, that the condition of immovability is
+held to be nobler and more divine than that of change and inconstancy,
+which latter therefore should be ascribed rather to the earth than
+to the universe, and I would add also that it seems inconsistent to
+attribute motion to the containing and locating element rather than to
+the contained and located object, which the earth is. Finally since the
+planets plainly are at one time nearer and at another time farther from
+the earth, it would follow, on the theory that the universe revolves,
+that the movement of the one and same body which is known to take place
+about a center, that is the center of the earth, must also be directed
+toward the center from without and from the center outward. The
+movement about the center must therefore be made more general, and it
+suffices if that single movement be about its own center. So it appears
+from all these considerations that the movement of the earth is more
+probable than its fixity, especially in regard to the daily revolution,
+which is most peculiar to the earth.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_4" href="#FNanchor_4" class="label">[4]</a>
+Selections from the Introduction to <i>De Orbium
+Caelestium Revolutionibus</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_29">[Pg 29]</span></p>
+<h2 class="nobreak" id="III">III<br>
+JOHANN KEPLER<br>
+1571-1630</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Tycho Brahe (1546-1601), nobleman of Denmark, studied law at
+the University of Copenhagen and became attracted to astronomical
+studies by the occurrence of a predicted eclipse. Constructing his
+own instruments, he made observations of the stars at Augsburg
+and Wittenberg, and in 1576 established the first observatory at
+Huen, where he continued his work for twenty years. Banished from
+Germany, he was invited by Emperor Rudolph to Prague, where he began
+his compilation of the Rudolphin Tables which listed many of his
+observations on the locations of the planets. Hearing of Kepler’s
+interest in astronomy, he secured the young German’s assistance and
+assigned to him the study of the planet Mars, which study Kepler
+continued after Tycho Brahe’s death in 1601.</i></p>
+
+<p><i>Johann Kepler, the son of an innkeeper, was born December 27, 1571,
+in Württemberg and sent to a local school, from which he was removed
+when he was nine years old because of his father’s impoverishment.
+After three years of work in the tavern, he was sent to a monastic
+school and thence to the University of Tübingen. Although he was very
+frail in physique, he was a good student and attained high scholarly
+standing. Becoming interested in the Copernican theory, in 1599 he was
+invited by Tycho Brahe to become his assistant at Prague.</i></p>
+
+<p><i>Kepler found his master’s tables sufficiently accurate in his
+efforts to discover some recognizable motion of the planet Mars which
+would account for its apparent positions. In the course of this work
+he corrected some of the Ptolemaic ideas which Copernicus had not
+completely abandoned. The latter retained the epicycle motion of the
+planets within their larger revolutions in cycles. In comparing this
+theory with his tables, Kepler found that it would not satisfactorily
+account for the positions of Mars; and he was therefore led to the
+long studies and mathematical computations which finally resulted
+in<span class="pagenum" id="Page_30">[Pg 30]</span> his discovery of the orbit of Mars, and to the establishment of
+the first two of his three famous laws: “1. the planet describes an
+ellipse, the sun being in one focus; 2. the straight line joining the
+planet to the sun sweeps out equal areas in equal intervals of time.”
+(Sedgwick and Tyler, pp. 211-213). He published these laws in 1609 in
+his “Commentaries on the Motions of Mars.”</i></p>
+
+<p><i>In 1611, when his patron, Emperor Rudolph, was compelled to
+abdicate, Kepler was left penniless, but he moved to Linz where he was
+appointed to a professorship. In 1619 he published his “Harmony of
+the World,” which contained his third law: “The squares of the times
+of revolution of any two planets (including the earth) about the sun
+are proportional to the cubes of their mean distances from the sun.”
+(Sedgwick and Tyler, p. 213). This was the triumph about which he wrote
+in the year of its discovery, 1618: “What I prophesied twenty-two years
+ago, as soon as I found the heavenly orbits were of the same number
+as the five (regular) solids, what I fully believed long before I
+had seen Ptolemy’s Harmonies, what I promised my friends in the name
+of this book, which I christened before I was sixteen years old, I
+urged as an end to be sought, that for which I joined Tycho Brahe, for
+which I settled at Prague, for which I have spent most of my life at
+astronomical calculations—at last I have brought to light, and seen to
+be true beyond my fondest hopes. It is not eighteen months since I saw
+the first ray of light, three months since the unclouded sun-glorious
+sight! burst upon me. Let nothing confine me: I will indulge my sacred
+ecstasy. I will triumph over mankind by the honest confession that I
+have stolen the golden vases of the Egyptians to raise a tabernacle for
+my God far away from the lands of Egypt. If you forgive me, I rejoice;
+if you are angry, I cannot help it. The book is written; the die is
+cast. Let it be read now or by posterity, I care not which. It may well
+wait a century for a reader, as God had waited six thousand years for
+an observer.” Kepler died at Ratisbon, November 15, 1630.</i></p>
+</div>
+
+<p class="nindc space-above2 space-below2">
+ON THE PRINCIPLES OF ASTRONOMY<a id="FNanchor_5" href="#Footnote_5" class="fnanchor">[5]</a></p>
+
+<p>What is <i>astronomy</i>? It is the science of treating of the causes
+of those celestial appearances which we who live on the earth observe
+and which mark the changes of times and seasons; by the studying of<span class="pagenum" id="Page_31">[Pg 31]</span>
+which we are able to predict for the future the face of the heavens,
+that is, the stellar phenomena, and to assign fixed dates for those
+which have occurred in the past.</p>
+
+<p><i>Why is it called astronomy?</i> From the law (νουος) or governance
+of the stars (ἀστρα), that is, of the motions in which the stars move,
+just as economy is named from the law of domestic affairs (οἰκονουία)
+and paedonomy (παιδονουία) from the ruling of youths.</p>
+
+<p><i>What is the relation of this science to the other sciences?</i> 1)
+It is a branch of physics because it investigates the causes of natural
+objects and events, and because among its subjects are the motions of
+the heavenly bodies, and because it has the same end as physics, to
+inquire into the conformation of the world and its parts.</p>
+
+<p>2) Astronomy is the soul of geography and hydrography, for the various
+appearances of the sky in various districts and regions of the earth
+and sea are known only by astronomy.</p>
+
+<p>3) Chronology is dependent upon it, because the movements of the
+heavenly bodies prescribe seasons and years and date the histories.</p>
+
+<p>4) Meteorology is also its subordinate, for the stars move and
+influence this sublunary nature and even men themselves.</p>
+
+<p>5) It includes a large part of optics, because it has a subject in
+common with that; that is, the light of the heavenly bodies, and
+because it corrects many errors of sight in regard to the character of
+the earth and its motions.</p>
+
+<p>6) It is, however, subordinate to the general subject of mathematics
+and uses arithmetic and geometry as its two wings, studying the extent
+and form of the bodies and motions of the universe and computing the
+periods, by these means expediting its demonstrations and reducing them
+to use and practical value.</p>
+
+<p><i>How many, then, are the branches of astronomical study?</i> The
+departments of the study of astronomy are five; historical, in the
+matter of observations, optical as to the hypothesis, physical as
+to the causes of the hypotheses, arithmetical as to the tables and
+calculations, mechanical as to its instruments.</p>
+
+<p class="space-above2">
+<i>Since we must begin with appearances, explain how the world seems to
+be made up.</i> The world is commonly thought, accepting the testimony
+of the eyes, to be an immense structure consisting of two parts, the
+earth and the sky.</p>
+
+<p><span class="pagenum" id="Page_32">[Pg 32]</span></p>
+
+<p><i>What do men imagine concerning the figure of the earth?</i> The
+earth seems to be a broad plane extending in a circle in every
+direction around the spectator. And from this appearance of a plane
+bounded by a great circle the appellation, <i>orbis terrarum</i>,
+the circle of the earth, has arisen, and has been taken over by the
+Scripture and among other nations.</p>
+
+<p><i>What do men imagine to be the center of the earth?</i> Each nation,
+unless it has become familiar with the notion of the circle, thinks by
+the instinct of nature and the error of vision that its country is in
+the center or middle of this plane circle. So the common people among
+the Jews believe still that Jerusalem, the earliest home of their race,
+is situated at the center of the world.</p>
+
+<p><i>What do men think about the waters?</i> Since men proceeding as far
+as possible in any direction finally came upon the ocean, some have
+thought that the earth is like a disc swimming in the waters, and that
+the waters are held up by the lower part of the sky, whence poets have
+called the ocean, the father of all things. Others believe that a strip
+of land surrounds the ocean which keeps the water from flowing away,
+and these suppose there is land under the water, saying that the water
+is held up by the earth. Besides these there are still others who,
+since the ocean seems higher than the land if it is looked at from the
+edge of the shore, believe that the earth is, as it were, sunk in the
+waters and supernaturally guarded by the omnipotence of God lest the
+waters rushing in from the deep should overwhelm it.</p>
+
+<p><i>What do men imagine to be under both the land and the waters?</i>
+There has been great discussion among men marveling concerning the
+foundation which could bear up the great mass of the earth so that
+it should remain for so many centuries firm and immovable and should
+not sink; and Heraclitus among the early philosophers, and Lactantius
+among the ecclesiastics said that it reached down to the lowest root of
+things.</p>
+
+<p><i>How about the other part of the world, the sky and its extent?</i>
+Men have thought that the sky was not much larger than the earth, and
+indeed was connected with the earth and the ocean at the circumference
+of the circle, so that it bounded the earth; and that anyone going
+that far, if it could be done, would run up against the sky, blocking
+further progress. With this idea of men the Scriptures also agreed.</p>
+
+<p>So also the poets said that Mt. Atlas, a lofty mountain on the<span class="pagenum" id="Page_33">[Pg 33]</span>
+farthest shore of Africa, bore up the sky on his shoulders, and Homer
+placed the Aethiopeans at the extremities of the rising and setting
+sun, thinking that because of the contiguity of the earth and sky
+there, the sun was so close to them that it burned their skin.</p>
+
+<p><i>What form do they ascribe to the sky?</i> The eyes ascribe to the
+sky the shape of a tent, extending over our heads and beyond the
+sun, moon and stars, or rather the shape of an arch overspanning the
+terrestrial plane, with a long curve, so that the part of the sky just
+over the head of the spectator is much nearer to him than the part that
+touches the mountains.</p>
+
+<p><i>What have men conceived in regard to the motion of the sky?</i>
+Whether the sky moves or stands still is not apparent to the sight
+because the tenuity of its substance escapes the eyes, unless indeed
+those things appear to stand still in which the eye can perceive no
+variation. But the changing positions of the sun, moon and stars in
+relation to the ends of the earth was apparent to the eyes. For the
+sun seems to emerge from an opening between the sky and the immovable
+mountains and ocean, as if coming out of a chamber, and having
+traversed the vault of the sky seems to sink again in the opposite
+region; so also the moon, and the planets, and the whole host of stars
+proceed as if strictly marshalled and drawn up in line, first one and
+then the other marching along, each in his order and place.</p>
+
+<p>And so, since the ocean lies beyond the extreme lands, the mass of men
+have thought that the sun plunges into the ocean and is extinguished,
+and from the opposite region a new sun issues forth daily from the
+ocean. The poets have used this figure in their creations. But,
+indeed, there have been even philosophers who have declared that on
+the farthest shores of Lusitania could be heard the roar of the ocean
+extinguishing the flames of the sun, as Strabo recounts.</p>
+
+<hr class="r65">
+
+<p><i>I understand the forms of the sky and the earth and the atmosphere
+surrounding the earth, also the place of the earth in the universe; now
+I would ask what causes the stars to seem to rise daily from the one
+part of the horizon and to sink in the opposite part; the motion of the
+sky or of the earth?</i> The astronomy of Copernicus shows that our
+sight has led us astray in regard to this motion; for the stars do not
+actually come up from beyond the mountains and climb toward the zenith,
+but rather the mountains which surround us and which are a<span class="pagenum" id="Page_34">[Pg 34]</span> part of the
+surface of the earth are revolved along with the whole globe about its
+axis from west to east and by this revolution the immovable stars of
+the east are disclosed to us one after the other, and those of the west
+are obscured, so the stars are not passing over us, but the vertical
+point is moving through the fixed stars.</p>
+
+<p><i>You say that by this marvelous hypothesis may be explained
+satisfactorily all the phenomena of the first motion and the spherical
+theory.</i> Just so, and that is the scope of this section, to
+demonstrate in fact what has been suggested in words.</p>
+
+<p><i>How do you expect to be able to prove this absurd hypothesis,
+and by what arguments?</i> It is possible to demonstrate that this
+first motion results from the revolution of the earth about its axis,
+while the heavenly bodies are at rest (as far as this first motion is
+concerned), by seven kinds of arguments: 1) from the subject of the
+motion; 2) from the velocity of the motion; 3) from the equableness of
+the motion; 4) from the cause of the motion, or the moving principle;
+5) from the motive instruments, that is, the axis and the poles; 6)
+from the object of the first motion; and 7) from the indications or
+results.</p>
+
+<p><i>Demonstrate it then from the subject of the motion.</i> Nature does
+not seek difficult means when she can use simple ones. Now, by the
+rotation of the earth, a very small body, about its axis, toward the
+east, the same thing is accomplished as by the rotation of the immense
+universe about its axis toward the west. Just as it is more likely that
+a man’s head turns in the auditorium than that the auditorium is turned
+about his head, so it is more credible that the earth is rotating from
+west to east, than that the rest of the machine of the universe is
+revolved from east to west, since in both cases the same thing results.</p>
+
+<p>If the first motion is in the heavenly bodies, then they are subject
+to two motions, one common to the whole universe, the other particular
+to each sphere; but it is much more probable that the two motions
+should be distinct in regard to their subjects, so that the second set
+of motions, which is multifold, should belong to each sphere, and the
+first, which is single, should belong to the single body of the earth,
+and to it alone.</p>
+
+<p><i>Why cannot the whole machinery of the universe be moved?</i> The
+universe is either infinite or finite. Suppose it to be the former,
+according to the opinion of William Gilbert, who thinks that the<span class="pagenum" id="Page_35">[Pg 35]</span>
+omnipotence of God is illustrated in this that the universe extends
+outward infinitely, so that the infinite power of the creator would be
+recognized from the infinite extent of the creation. Although this may
+be refuted by metaphysical arguments, no argument on either side can be
+drawn from astronomy, in which trust is placed rather in the evidence
+of the senses than in abstract reasonings not dependent on observation.
+But supposing this universe to be infinite, Aristotle has shown that
+the whole universe should not be moved about in a revolution since it
+is the whole.</p>
+
+<p>But let the universe be finite; then there is nothing outside the
+universe which would locate the universe but should remain quiet
+itself. Where there is nothing that rests there is no motion. For 1)
+motion is the separation of a movable thing from its place and its
+transfer to another place: 2) the motion of a machine about an axis and
+quiescent poles cannot be grasped by the mind where there is nothing in
+respect to which the poles remain still.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_5" href="#FNanchor_5" class="label">[5]</a>
+From <i>The Epitome of Astronomy</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_36">[Pg 36]</span></p>
+<h2 class="nobreak" id="IV">IV<br>
+GALILEO GALILEI<br>
+1564-1642</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Galileo Galilei, born at Pisa, February 15, 1564, was the son of
+a mathematician who, seeing no future in that profession, had him
+educated for the practice of medicine. But when Galileo was about
+eighteen years of age, while observing a large lamp swinging in
+the Pisa cathedral, he noticed that, regardless of the length of
+the oscillation, the time did not vary. In spite of his father’s
+discouragements, therefore, he became absorbed in mathematics and
+abandoned the study of medicine. Applying himself to the study of
+motion, he performed his famous experiment of letting bodies of
+different weights fall from the leaning tower of Pisa, proving that
+things of unequal weight, if heavier than the resistance of air, fall
+with the same speed. The doctrine of inertia which he deduced from
+this and similar experiments decisively answered the opponents of
+Copernicus; for the principle stated that bodies would continue to
+move in the same direction forever unless their course was disturbed
+or opposed by another force, and that the motion of bodies resulted
+from independent forces operating upon them. His treatise on the center
+of gravity in solids earned him a lectureship at the University of
+Pisa.</i></p>
+
+<p><i>Meeting malignant opposition at Pisa, he secured the chair of
+mathematics at Padua (which he held from 1592 to 1610) and there
+continued his observations and experiments in physics and chemistry.
+He succeeded in making a crude thermometer in 1600. In 1609 he learned
+that Hans Lippershey, an optician of Middleburg, had succeeded in
+making a telescope. He thereupon made one of his own and improved it
+until it had a power of magnifying thirty-two times, enabling him to
+discover the mountainous surface of the moon, the moons of the planet
+Jupiter, the fact that Venus showed different<span class="pagenum" id="Page_37">[Pg 37]</span> sides like the moon, and
+that many small stars made up the Milky Way.</i></p>
+
+<p><i>In 1610 he left Padua for Florence, and by 1613 openly declared
+his acceptance of Copernican ideas. Immediately he was opposed by
+theologians, and after being given an opportunity to renounce his
+adherence to the new system of astronomy, was sentenced in 1616 not to
+hold, teach, or defend it. In 1623, when his friend Maffeo was made
+Pope Urban VIII, he wrote his dialogues on the system of the world. He
+had much difficulty in getting them published and succeeded only when
+he assured the authorities that they were not heretical. It was quite
+evident, however, that the dialogues were slightly concealed arguments
+for the acceptance of the Copernican system and consequently in 1633
+he was summoned before the Inquisition and compelled to renounce his
+heresy. In 1637, a few months after he had discovered the librations
+of the moon, he lost his sight. He died five years later, January 8,
+1642.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE COPERNICAN VERSUS THE PTOLEMAIC ASTRONOMIES<a id="FNanchor_6" href="#Footnote_6" class="fnanchor">[6]</a></p>
+
+<p>Formerly I used frequently to visit the marvelous city of Venice
+and to meet there Signore Giovan Francesco Sagredo, a man of most
+distinguished ancestry and remarkable intelligence. Thither also came
+from Florence, Signore Filippo Salviati, whose least claim to renown
+was his noble blood and great wealth; a noble mind, that held no
+enjoyment of greater price than that of study and thought. With both
+of these men I often discussed these questions, in the presence of
+a Peripatetic philosopher, who apparently valued the acquisition of
+knowledge in no way in so high a degree, as he did the renown which his
+interpretations of Aristotle had gained for him.</p>
+
+<p>Now that cruel death has robbed the cities of Venice and Florence
+of these two enlightened men in the bloom of their years, I have
+endeavored, as far as my weak powers may permit, to perpetuate their
+fame in these pages by making them the speakers in this dialogue.
+The valiant Peripatetic also shall not fail to appear; because of
+his over-weaning love for the commentary of Simplicius, it seemed
+permissible to omit his own name and let him pass under that of his
+favorite author. May the souls of these two great men accept this<span class="pagenum" id="Page_38">[Pg 38]</span>
+public testimony of my undying love; may the recollection of their
+eloquence aid me in setting down for posterity the spoken discussions.</p>
+
+
+<p class="nindc space-above2 space-below2">
+SECOND DAY</p>
+
+<p><span class="allsmcap">SALVIATI</span>: We departed yesterday so often and so far from the
+direct path of our discussion, that I can scarcely return to the right
+point and proceed without your help.</p>
+
+<p><span class="allsmcap">SAGREDO</span>: I find it quite intelligible that you are somewhat at
+a loss, since you have had your head so full of both the things already
+brought forward and things still to be discussed. I, however, who as
+merely a listener have in mind only the things already discussed, may
+I hope set our investigation straight by a brief summary of what has
+been gone over. So, if my memory fails not, the chief result of our
+yesterday’s conversation was that we tested thoroughly which of the
+two theories was the more probable and better grounded; that according
+to which the substance of the heavenly bodies is unproducible,
+indestructible, unchangeable, intangible, in brief not subject to
+any variation aside from change of location, and so presents a fifth
+element which is entirely distinct from our elementary, producible,
+destructible, changeable bodies; or the other view, according to which
+an incongruity between parts of the universe is rejected, our earth
+rather enjoys the same privileges as the rest of the constituent
+bodies of the universe, in a word, is a freely moving ball just as
+the moon, Jupiter, Venus, or any other planet. Finally we noticed the
+many similarities in particular between the earth and the moon, and of
+course with the moon more than any other planet because of the closer
+and more definite knowledge which we possess of it by reason of its
+less distance. Since we agreed that this second opinion possessed the
+greater probability, the logical consequence, it seems to me, is that
+we should investigate the question whether we should hold the world
+immovable, as has been formerly believed in general, or movable as some
+ancient philosophers believed and as some recent ones suppose: and if
+movable, how its movement could have been produced.</p>
+
+<p><span class="allsmcap">SALV.</span>: Let us begin our discussion with the admission
+that whatever sort of motion may be ascribed the earth, we, as its
+inhabitants<span class="pagenum" id="Page_39">[Pg 39]</span> and therefore partakers in the movement, would be
+unconscious of it, as if it did not occur, since we can only take into
+consideration earthly things. Therefore it is necessary that this
+movement should seem to belong to all the other bodies and visible
+objects in common which, separated from the earth, have no share in its
+movement. The correct method of determining whether movement is to be
+attributed to the earth, and what movement, is that one should inquire
+and observe whether an apparent movement can be ascribed to the bodies
+outside of the earth, which belongs to all of them in the same degree.
+So a movement which, for example, can be supposed of the moon, and not
+of Venus or Jupiter or other stars, cannot be peculiar to the earth.
+Now there is such a general movement governing all other objects,
+namely that which the sun, moon, planets, fixed stars, in a word the
+whole universe with the single exception of the earth, seems to follow
+from east to west within the space of twenty-four hours. This, at least
+at first glance, may be just as well attributed to the earth alone, as
+to the rest of the entire universe except the earth.</p>
+
+<p><span class="allsmcap">SAGR.</span>: I understand clearly that your suggestion is correct.
+An objection, however, forces itself upon me that I cannot solve. That
+is, since Copernicus ascribes to the earth a further movement aside
+from the daily one, according to the above mentioned principle this
+should be apparently un-noticeable on the earth, but should be visible
+in the rest of the universe. I come then to the conclusion that either
+he plainly erred when he ascribed to the earth a movement to which
+no counterpart is apparent in the firmament, or else such a movement
+exists, and then Ptolemaus is guilty of a second error in that he did
+not refute with arguments this movement as well as that daily rotation.</p>
+
+<p><span class="allsmcap">SALV.</span>: Your objection is very just. If we take up this
+other movement, you shall see how much superior in intelligence was
+Copernicus to Ptolemaus, in that he saw what this one did not, namely
+how wonderfully this second motion is reflected in the rest of the
+heavenly bodies. For the present, however, we will leave this aside and
+return to our first consideration. Proceeding from the most general
+suppositions, I will present the arguments which seem to favor the
+motion of the earth, in order then to hear the opposing arguments
+of Signore Simplicio. First, then, when we consider the immense
+circumference of the stellar sphere in comparison with the<span class="pagenum" id="Page_40">[Pg 40]</span> smallness
+of the earth, which is contained in that several million times, and
+therefore regard the velocity of motion which would be necessary for
+an entire revolution in the course of a day and night, I am unable to
+understand how any one could hold it more reasonable and credible that
+it is this whole stellar sphere that moves and that the earth remains
+still.</p>
+
+<p><span class="allsmcap">SAGR.</span>: Even if universal phenomena which depend upon these
+movements could be explained as readily by the one hypothesis as by
+the other, yet by the first general impression I would regard as more
+unreasonable the view that the whole universe moves; just as if any
+one should climb to the top of your dome for the purpose of getting
+a view of the city and its environs and then should demand that the
+whole region be made to move around him to save him the trouble of
+turning his head. In any event, there would have to be great advantages
+connected with this theory, which were lacking in the other, in
+order that such an absurdity should be balanced and outweighed and
+should appear more credible than the opposite opinion. But Aristotle,
+Ptolemaus, and Signore Simplicio must find such advantages in their
+theory, and I should be glad if we might hear these advantages if they
+exist, or if they do not, that some one would explain to me why they do
+not and cannot exist.</p>
+
+<p><span class="allsmcap">SALV.</span>: If, in spite of every sort of investigation, I am
+able to find no such differences, I believe I have thereby discovered
+that such difference does not exist. So in my opinion it is useless
+to pursue this further: rather let us proceed. Motion is only so far
+motion and acts as such, if it stands in relation to things which lack
+motion. In relation to things that are all in the same degree affected
+by it, it is as much without effect as if it did not take place. The
+wares with which a ship is loaded move, when they depart from Venice
+and arrive at Aleppo, passing Korfu, Candia, Cyprus etc; since Venice,
+Korfu and Candia remain fixed and do not move with the ship. But in
+respect to the bales, chests, and other pieces of baggage which are
+on the ship as cargo or ballast, the movement of the ship itself from
+Venice to Syria is as good as non-existent, since their position in
+relation to one another does not change; and this is due to the fact
+that the movement is a common one in which they all take part. If of
+the wares on the ship one bale moves only an inch away from the chest,
+this is for it a<span class="pagenum" id="Page_41">[Pg 41]</span> greater movement in relation to the chest, than the
+whole journey of 2,000 miles which they undergo in common.</p>
+
+<p>Therefore, since plainly the motion which many movable bodies undergo
+in common is without effect and, with regard to their mutual position
+toward one another, it is as if it did not exist, for there is no
+change among them; and since it only affects the relative position
+of such bodies as do not share in the movement, for in this case the
+mutual relation is changed; since we have divided the universe into
+two parts, of which one must be movable and the other immovable; then
+for all purposes this movement will be of the same effect whether it
+is ascribed to the earth alone or to all the rest of the universe. For
+the working of such a motion is on nothing but the relative position in
+which the earth and the heavenly bodies stand to one another, and aside
+from this relative position nothing changes. If now it is indifferent
+for accomplishing this result whether the earth alone moves and the
+whole universe rests, or the earth rests and the whole universe is
+subject to one common movement, who can believe that Nature—who by
+common agreement does not employ great means when she can obtain the
+same result by smaller ones—would have undertaken to set in motion
+an immeasurable number of mighty bodies, and that with incredible
+velocity, to accomplish what could be obtained by the moderate motion
+of one single body around the center?</p>
+
+<p><span class="allsmcap">SIMPL.</span>: I do not agree that that mighty movement would be as
+if it did not happen in regard to the sun, the moon, the innumerable
+host of fixed stars. Do you call it nothing that the sun goes from
+one meridian to another, rises from one horizon, sinks under another,
+brings now day, now night; that the moon goes through similar changes
+and likewise the other planets, as well as the fixed stars?</p>
+
+<p><span class="allsmcap">SALV.</span>: All the changes mentioned by you are such only with
+respect to the earth. To demonstrate this, only imagine yourself away
+from the earth; there is then no rising or setting of the sun, no
+horizons, no meridians, no day, no night; in a word, by the movement
+mentioned no change in the relation of the moon to the sun or to any
+other star is evoked. All these changes have reference to the earth;
+they are supposed only because the sun is first visible in China, then
+Egypt, Greece, France, Spain, America, and so on, and so also for the
+moon and the other heavenly bodies. The same process<span class="pagenum" id="Page_42">[Pg 42]</span> would occur in
+the same way, if, without disturbing so vast a part of the universe,
+the earth alone should be revolved.</p>
+
+<p>The difficulty is however doubled since a second very important one is
+added. That is, if one attributes to the firmament this mighty motion,
+one must regard it as necessarily opposed to the particular movements
+of all the planets, all of which indisputably have their own movements
+from west to east, and in comparison very moderate movements at that.
+One is then forced to the conclusion that they depart from that
+rapid daily motion, namely from east to west, to go in the opposite
+direction. But, if we suppose that the earth moves, the opposition of
+motions disappears and the single movement from west to east fits in
+with all the facts and explains them most satisfactorily.</p>
+
+<p><span class="allsmcap">SIMPL.</span>: As far as this opposition of motions is concerned that
+has little importance, since Aristotle proves that the circular motions
+are not opposed to one another and that the apparent opposition cannot
+actually be called so.</p>
+
+<p><span class="allsmcap">SALV.</span>: Does Aristotle prove that or merely suppose it,
+because it aids him for a certain purpose? If, according to his own
+declaration, those things are opposed which mutually destroy one
+another I do not see how two moving bodies which meet one another in a
+circular motion should do one another less harm than if they meet on a
+straight line.</p>
+
+<p><span class="allsmcap">SAGR.</span>: Wait a moment, I pray. Tell me, Signore Simplicio, if
+two knights run into one another with leveled lances on the open field,
+if two squadrons or two streams on their way to the sea break through
+and unite with one another, would you call such collisions opposed
+movements?</p>
+
+<p><span class="allsmcap">SIMPL.</span>: Of course we would call them opposed.</p>
+
+<p><span class="allsmcap">SAGR.</span>: How then is there no opposition in circular motions?
+For the movements mentioned take place upon the surface of the earth
+or water, both of which are recognized to be circular in form and so
+the motions must be circular. Do you understand, Signore Simplicio,
+what circular motions are not opposed to one another? Two circles which
+touch each other on the outside and of which the revolution of one is
+in a reverse direction from that of the other. If, however, one circle
+is within the other, then motions in different directions must be
+opposed to one another.</p>
+
+<p><span class="allsmcap">SALV.</span>: Whether opposed or not opposed is merely a strife of<span class="pagenum" id="Page_43">[Pg 43]</span>
+words. I know that in fact it is simpler and more natural to accomplish
+everything with one motion than to call in two. If you do not wish to
+call them opposite, then call them reverse. Moreover, I mention this
+introduction of a double movement not as something impossible, and in
+no way propose to deduce from it a strong proof for the motion of the
+earth, but merely a high degree of probability for it.</p>
+
+<p>The improbability of the movement of the universe about the earth is
+tripled, however, by the complete upsetting of that arrangement which
+governs all the heavenly bodies whose circular motion is accepted not
+doubtfully but with full assurance. That is, that in such cases the
+larger the orbit the longer the time required for its completion,
+and the smaller, the shorter. Saturn, whose course surpasses all the
+planets in extent, completes it in thirty years. Jupiter revolves in a
+smaller circle in twelve years. Mars in two, the moon in a month. We
+see clearly in the case of the Medicean stars [the moons of Jupiter]
+that the one nearest Jupiter goes through its orbit in a very short
+time, namely, forty-two hours, the next nearest in three and a half
+days, the third in seven days, and the farthest removed in sixteen
+days. This thoroughly constant rule remains unchanged if we ascribe
+the twenty-four hour movement to the revolution of the earth, but if
+we suppose the earth to remain unmoved, we must proceed from the short
+period of the moon to increasingly greater periods, to the two year
+period of Mars, the twelve year period of Jupiter, the thirty year
+period of Saturn, and then abruptly to a disproportionately larger
+orbit, to which must also be ascribed the revolution in twenty-four
+hours. And these suppositions entail the smallest part of the
+disturbance of the otherwise constant law. For when one passes from
+the orbit of Saturn to those of the fixed stars and attributes to them
+even greater orbits, which correspond to the period of revolution
+of many thousands of years, one must pass from this by a much more
+disproportionate transition to that other movement and ascribe to them
+a period of revolution about the earth of twenty-four hours. But if
+the movement of the earth is supposed, the regularity of the period is
+accounted for in the best possible way; from the slow period of Saturn
+we arrive at the immovable fixed star.</p>
+
+<p>A fourth difficulty also is encountered which must be added if
+we suppose the motion of the smaller sphere. I mean the great
+dissimilarity in movements of these stars, some of which must revolve<span class="pagenum" id="Page_44">[Pg 44]</span>
+at a tremendous rate in immense circles, others slowly in smaller
+circles, according as they are placed at greater or smaller distances
+from the pole. And not only the size of the different circles and so
+the velocity of movement varies greatly in different fixed stars, but
+also the same stars change their courses and their velocity; herein
+is the fifth difficulty. That is, those stars which 2,000 years ago
+stood on the equator of the stellar sphere and thereafter moved in
+the greatest circles, must now, since to-day they have moved several
+degrees from it, move more slowly and in smaller circles. Within a
+conceivable time it will happen that one of those which have been
+continually moving will eventually reach the pole and cease to revolve,
+then later, after a period of rest, begin to move again. The other
+stars, however, which undoubtedly move, all have, as has been said, as
+orbit an immense circle and move in it without change.</p>
+
+<p>The improbability is increased (and this may be called a sixth
+difficulty) for him who investigates basic principles, by the fact that
+one cannot imagine the firmness which that immense sphere must possess,
+in whose depths so many stars are so solidly fixed that in spite of
+such varieties of motions they are held together in the revolution
+without in any way changing their relative positions. But if according
+to the most probable view the heavens are fluid, so that each star may
+describe its own orbit, by what law and according to what principles
+are their orbits governed, so that seen from the earth they appear as
+if held in one sphere? To accomplish this it seems to me it would be
+easier and more convenient to make them stationary instead of movable,
+just as the paving stones in the market place are kept in order more
+easily than the troops of children who race over them.</p>
+
+<p>Finally the seventh objection; if we ascribe the daily revolution to
+the highest heavens we must suppose this to be of such power and force
+that it bears along the innumerable crowd of fixed stars, every one a
+body of immense mass and much larger than the earth, further, all the
+planets, although these by their nature move in an opposite direction.
+Moreover, we must suppose that the element of fire and the greater
+portion of the air is also borne along; therefore, singly and alone the
+little earth ball withstands stubbornly and independently this mighty
+force: a supposition that seems to me to have much against it. I cannot
+explain how the earth, a body freely suspended and balanced<span class="pagenum" id="Page_45">[Pg 45]</span> on its
+axis, inclined by nature as much toward motion as the rest, surrounded
+by a fluid medium, is not seized on by this general revolution. We do
+not encounter this difficulty, however, if we suppose the earth to
+move, a body so small, so inconsiderable in comparison with the whole
+universe that it could have no effect at all upon this.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_6" href="#FNanchor_6" class="label">[6]</a>
+Translated from the <i>Dialogo dei due Massima Systemi del
+Mondo</i> (1632).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_46">[Pg 46]</span></p>
+<h2 class="nobreak" id="V">V<br>
+WILLIAM HARVEY<br>
+1578-1657</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>In 1615 William Harvey stated his theory of the circulation of the
+blood, which he derived from patient observations, in his lectures
+on anatomy. The theory was epoch-making in the history of physiology
+because it initiated the study of the chemical constituency of the
+blood and of its function in nutrition.</i></p>
+
+<p><i>Harvey, born April 1, 1578, in the south of England, attended the
+University of Cambridge, and took his degree in 1597. The following
+four years he studied at Padua under Fabricius. In 1602, when he
+returned to England, he began the practice of medicine, and in 1609
+became connected with St. Bartholomew’s Hospital. He published his
+“Excercitatio” in 1628, served for several years as physician to
+Charles I, and retired in 1646 to private life. He died June 3,
+1657.</i></p>
+
+<p><i>He described the process of his discovery as follows: “I frequently
+and seriously bethought me, and long revolved in my mind, what might be
+the quantity of blood which was transmitted, in how short a time its
+passage might be effected, and the like; and not finding it possible
+that this could be supplied by the juices of the ingested aliment
+without the veins on the one hand being drained, and the arteries on
+the other hand becoming ruptured through the excessive charge of blood,
+unless the blood should somehow find its way from the arteries into
+the veins, and so return to the right side of the heart; I began to
+think whether there might not be a motion, as it were, in a circle. Now
+this I afterwards found to be true; and I finally saw that the blood,
+forced by the action of the left ventricle into the arteries, was
+distributed to the body at large, and its several parts, in the same
+manner as it is sent through the lungs, impelled by the right ventricle
+into the pulmonary artery, and that it then passed through the veins
+and along the vena cava, and so round to the left<span class="pagenum" id="Page_47">[Pg 47]</span> ventricle in the
+manner already indicated,—which motion we may be allowed to call
+circular.</i>”</p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE CIRCULATION OF BLOOD IN ANIMALS<a id="FNanchor_7" href="#Footnote_7" class="fnanchor">[7]</a></p>
+
+<p>Thus far I have spoken of the passages of the blood from the veins
+into the arteries, and of the manner in which it is transmitted and
+distributed by the action of the heart; points to which some, moved
+either by the authority of Galen or Columbus, or the reasonings of
+others, will give in their adhesion. But what remains to be said upon
+the quantity and source of the blood which thus passes, is of so novel
+and unheard-of character, that I not only fear injury to myself from
+the envy of the few, but I tremble lest I have mankind at large for my
+enemies, so much doth wont and custom, that become as another nature,
+and doctrine once sown and that hath struck deep root, and respect
+for antiquity influence all men: Still the die is cast, and my trust
+is in my love of truth, and the candour that inheres in cultivated
+minds. And sooth to say, when I surveyed my mass of evidence, whether
+derived from vivisections, and my various reflections on them, or from
+the ventricles of the heart and the vessels that enter into and issue
+from them, the symmetry and size of these conduits,—for nature doing
+nothing in vain, would never have given them so large a relative size
+without a purpose,—or from the arrangement and intimate structure
+of the valves in particular, and of the other parts of the heart in
+general, with many other things besides, I frequently and seriously
+bethought me, and long revolved in my mind, what might be the quantity
+of blood that was transmitted, in how short a time its passage might
+be effected, and the like; and not finding it possible that this could
+be supplied by the juices of the ingested aliment without the veins on
+the one hand becoming drained, and the arteries on the other getting
+ruptured, through the excessive charge of blood, unless the blood
+should somehow find its way from the arteries into the veins, and so
+return to the right side of the heart; I began to think whether there
+might not be <i>A Motion, As It Were, In A Circle</i>. Now this I
+afterward<span class="pagenum" id="Page_48">[Pg 48]</span> found to be true; and I finally saw that the blood, forced
+by the action of the left ventricle into the arteries, was distributed
+to the body at large, and its several parts, in the same manner as it
+is sent through the lungs, impelled by the right ventricle into the
+pulmonary artery, and that it then passes through the veins and along
+the vena cava, and so round to the left ventricle in the manner already
+indicated. Which motions we may be allowed to call circular, in the
+same way as Aristotle says that the air and rain emulate the circular
+motion of the superior bodies; for the moist earth, warmed by the sun,
+evaporates; the vapours drawn upwards are condensed, and descending
+in the form of rain, moisten the earth again; and by this arrangement
+are generations of living things produced; and in like manner too are
+tempests and meteors engendered by the circular motion, and by the
+approach and recession of the sun.</p>
+
+<p>And so, in all likelihood, does it come to pass in the body, through
+the motion of the blood; the various parts are nourished, cherished,
+quickened by the warmer, more perfect, vaporous, spiritous, and, as
+I may say, alimentive blood; which, on the contrary, in contact with
+these parts becomes cooled, coagulated, and, so to speak, effete;
+whence it returns to its sovereign the heart, as if to its source,
+or to the inmost home of the body, there to recover its state of
+excellence, or perfection.</p>
+
+<p>Here it resumes its due fluidity and receives an infusion of natural
+heat—powerful, fervid, a kind of treasury of life, and is impregnated
+with spirits, and it might be said with balsam; and thence it is again
+dispersed; and all this depends on the motion and action of the heart.</p>
+
+<p>The heart, consequently, is the beginning of life; the sun of the
+microcosm, even as the sun in his turn might well be designated the
+heart of the world; for it is the heart by whose virtue and pulse
+the blood is moved, perfected, made apt to nourish, and is preserved
+from corruption and coagulation; it is the household divinity which,
+discharging its function, nourishes, cherishes, quickens the whole
+body, and is indeed the foundation of life, the source of all action.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_7" href="#FNanchor_7" class="label">[7]</a>
+From <i>An Anatomical Disquisition on the Motion of the
+Heart-Blood in Animals</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_49">[Pg 49]</span></p>
+<h2 class="nobreak" id="VI">VI<br>
+ROBERT BOYLE<br>
+1627-1691</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Robert Boyle, fourteenth child of the Earl of Cork, was born
+January 25, 1627, in Munster, Ireland. He went to Eton, studied under
+the rector of Stalbridge, and later traveled on the Continent under
+private tutors. On the death of his father in 1644, he inherited the
+manor at Stalbridge. At the age of eighteen he became associated with
+the English scientific investigators at Oxford who later founded
+the Royal Society, and engaged actively in physical experiments and
+researches. The greatest of his achievements was his discovery of the
+law of the compressibility of gases. He died December 30, 1691.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE DISCOVERY OF THE LAW OF THE COMPRESSIBILITY OF GASES<a id="FNanchor_8" href="#Footnote_8" class="fnanchor">[8]</a></p>
+
+<p>We took a long glass tube, which, by a dexterous hand and the help of a
+lamp, was in such a manner crooked at the bottom, that the part turned
+up was almost parallel to the rest of the tube, and the orifice of
+this shorter leg of the syphon (if I may so call the whole instrument)
+being hermetically sealed, the length of it was divided into inches
+(each of which was subdivided into eight parts) by a straight list of
+paper, which, containing those divisions, was carefully pasted all
+along it. Then putting in as much quicksilver as served to fill the
+arch or bended part of the syphon, that the mercury standing in a level
+might reach in one leg to the bottom of the divided paper, and just
+to the same height or horizontal line in the other, we took care, by
+frequently inclining the tube, so that the air might freely pass<span class="pagenum" id="Page_50">[Pg 50]</span> from
+one leg into the other by the sides of the mercury (we took, I say,
+care), that the air at last included in the shorter cylinder should be
+the same laxity with the rest of the air about it. This done, we began
+to pour quicksilver into the longer leg of the syphon, which, by its
+weight pressing up that in the shorter leg, did by degrees straighten
+the included air; and continuing this pouring in of quicksilver till
+the air in the shorter leg was by condensation reduced to take up but
+half the space it possessed (I say possessed, not filled) before, we
+cast our eyes upon the longer leg of the glass, upon which we likewise
+pasted a slip of paper carefully divided into inches and parts, and we
+observed, not without delight and satisfaction, that the quicksilver
+in that longer part of the tube was 29 inches higher than the other.
+Now that this observation does both very well agree with and confirm
+our hypothesis, will be easily discerned by him that takes notice what
+we teach: and Monsieur Pascal and our English friend’s [Mr. Townley’s]
+experiments prove, that the greater the weight is that leans upon the
+air, the more forcible is its endeavor of dilation, and consequently
+its power of resistance (as other springs are stronger when bent by
+greater weights). For this being considered, it will appear to agree
+rarely well with the hypothesis, that as according to it the air in
+that degree of density, and correspondent measure of resistance, to
+which the weight of the incumbent atmosphere had brought it, was unable
+to counterbalance and resist the pressure of a mercurial cylinder of
+about 29 inches, as we are taught by the Torricellian experiment; so
+here the same air being brought to a degree of density about twice
+as great as that it had before, obtains a spring twice as strong as
+formerly. As may appear by its being able to sustain or resist a
+cylinder of 29 inches in the longer tube, together with the weight of
+the atmospherical cylinder that leaned upon those 29 inches of mercury;
+and, as we just now inferred from the Torricellian experiment, was
+equivalent to them.</p>
+
+<p>(<i>The tube broke at this point and, unable to proceed after several
+similar efforts, Boyle tried the converse experiment—to determine the
+spring of rarefied air. A tube, about 6 feet in length, and sealed at
+one end, was nearly filled with mercury, and into it was placed</i>)—</p>
+
+<p>A slender glass pipe of about the bigness of a swan’s quill, and open
+at both ends; all along of which was pasted a narrow list of paper,
+divided into inches and half-quarters. This slender pipe being<span class="pagenum" id="Page_51">[Pg 51]</span> thrust
+down into the greater tube almost filled with quicksilver, the glass
+helped to make it swell to the top of the tube; and the quicksilver
+getting in at the lower orifice of the pipe filled it up till the
+mercury included in that was near about a level with the surface of
+the surrounding mercury in the tube. There being, as near as we could
+guess, little more than an inch of the slender pipe left above the
+surface of the restagnant mercury, and consequently unfilled therewith,
+the prominent orifice was carefully closed with sealing-wax melted;
+after which the pipe was let alone for a while that the air, dilated a
+little by the heat of the wax, might, upon refrigeration, be reduced
+to its wonted density. And then we observed, by the help of the
+above-mentioned list of paper, whether we had not included somewhat
+more or somewhat less than an inch of air; and in either case we were
+fain to rectify the error by a small hole made (with a heated pin) in
+the wax, and afterward closed up again. Having thus included a just
+inch of air, we lifted up the slender pipe by degrees, till the air
+was dilated to an inch, an inch and a half, two inches, etc., and
+observed in inches and eighths the length of the mercurial cylinder,
+which, at each degree of the air’s expansion, was impelled above the
+surface of the restagnant mercury in the tube. The observations being
+ended, we presently made the Torricellian experiment with the above
+mentioned great tube of 6 feet long, that we might know the height of
+the mercurial cylinder for that particular day and hour, which height
+we found to be 29-3/4 inches.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_8" href="#FNanchor_8" class="label">[8]</a>
+From Thorpe, <i>Essays on Historical Chemistry</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_52">[Pg 52]</span></p>
+<h2 class="nobreak" id="VII">VII<br>
+CHRISTIAN HUYGHENS<br>
+1629-1695</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Christian Huyghens was born at The Hague, April 14, 1629. He
+studied law in Breda, but becoming attracted to the study of
+mathematics he neglected his legal practice for it. In 1655 he
+improved the method of grinding telescopic lenses, and, assisted
+by his brother, discovered the sixth satellite of Saturn and the
+fact that it was belted with rings. In 1657 he presented to the
+States-General the first pendulum clock. In 1678 he evolved his wave
+theory of light, and published it at Leyden in 1690. He died at The
+Hague, June 8, 1695.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE WAVE THEORY OF LIGHT<a id="FNanchor_9" href="#Footnote_9" class="fnanchor">[9]</a></p>
+
+<p>Proofs in optics, as in every science in which mathematics is applied
+to matter, are founded upon facts from experience—as for example,
+that light moves in straight lines, that the angles of incidence and
+reflection are equal, and that light rays are refracted in accordance
+with the law of sines [i. e., that the ratio between the sines of the
+incident and refracted ray is constant for the same substance.] For
+this last law is now as generally and surely known as either of the
+others.</p>
+
+<p>Most writers in optics have been content to assume these facts, but
+others more curious have attempted to discover the source and reason of
+these phenomena, looking upon them as being in themselves interesting
+data. Yet although they have propounded some ingenious theories,
+intelligent readers still require a fuller explanation before being
+entirely satisfied. Therefore I herein offer some considerations on the
+matter with the hope of making clearer this branch of physics which has
+not improperly gained the reputation of being very obscure.</p>
+
+<p>I feel myself particularly indebted to those that first began to study<span class="pagenum" id="Page_53">[Pg 53]</span>
+these profound subjects, and to lead us to hope them capable of orderly
+explanation. Yet I have been surprised to find these very investigators
+accepting arguments far from clear as if proof conclusive. No one has
+yet offered even a probable explanation of the first two remarkable
+phenomena of light,—why it moves in straight lines, and why rays from
+any and all directions can cross one another without interference.</p>
+
+<p>I shall attempt in this treatise to submit clearer and more probable
+reasons, along the lines of modern philosophy, first for the
+transmission of light, and, second, for its reflection when it meets
+certain bodies.</p>
+
+<p>Further, I shall explain the fact of rays said to undergo refraction in
+passing through various transparent bodies. Here I shall consider also,
+the refractions due to the differing densities of the atmosphere. Later
+I shall investigate the remarkable refraction occurring in Icelandic
+crystals. Finally, I shall study the different shapes necessary in
+transparent and reflecting bodies in order to bring together rays upon
+a single point or to deflect them in different ways. Here we shall see
+how easy it is by our new theory to determine not alone the ellipses,
+hyperbolas, and other curves which M. Descartes has so shrewdly
+constructed for this end, but as well the curve that one surface of a
+lens must have when the other surface is known, as spherical, plane, or
+any other figure.</p>
+
+<p>We cannot but believe that light is the motion of a certain material.
+Thus when we reflect on its production, we discover that here on
+the earth it is usually emitted from fire and flame, and that these
+unquestionably contain bodies in rapid motion, since they can soften
+and melt many other more solid substances. If we note its effects, we
+see that when light is brought to a point, as, for example, by concave
+mirrors, it can cause combustion the same as fire: that is, it can
+force bodies apart, a power that certainly argues motion, at least in
+that true science where one believes all natural phenomena to result
+from mechanical causes. Moreover, in my mind we must either admit this
+or give up all hope of ever understanding anything in natural science.</p>
+
+<p>Since, according to this philosophy, it is believed certain that the
+sensation of sight is produced only by the impulse of some form of
+matter against the nerves at the base of the eye, we have yet another
+reason for believing light to be a motion in the substance lying
+between us and the body producing the light.</p>
+
+<p><span class="pagenum" id="Page_54">[Pg 54]</span></p>
+
+<p>As soon as we consider, moreover, the enormous speed with which light
+travels in every direction, and the fact that when rays come from
+different directions, even from those exactly opposite, they cross
+without interference, it must be plain that we do not see luminous
+objects by means of particles transmitted from the objects to us, as a
+shot or an arrow moves through the air. For surely this would not allow
+for the two qualities of light just mentioned, particularly the latter
+(that of speed). Light, then, is transmitted in some other way, a
+comprehension of which we may get from our knowledge of how sound moves
+through the air.</p>
+
+<p>We know that sound is sent out in all directions through the medium of
+the air, a substance invisible and impalpable, by means of a motion
+that is communicated successively from one part of the air to the next;
+and as this movement has the same speed in all directions, it must form
+spherical surfaces that keep enlarging until at last they strike the
+ear. Now there can be no doubt that light likewise reaches us from a
+luminous substance through some motion caused in the matter lying in
+the intervening space,—for we have seen above that this cannot take
+place through transmission of matter from one place to another.</p>
+
+<p>If, moreover, light requires time for its passage—a matter we shall
+discuss in a moment—it will then follow that this movement is caused
+in the substance gradually, and therefore is transmitted, like sound,
+by surfaces and spherical waves. I call these <i>waves</i> because of
+their likeness to those formed when one throws a pebble into water,
+which are examples of gradual propagation in circles, although from a
+different cause and on a plane surface.</p>
+
+<p>In regard to the question of light requiring time for its transmission,
+let us consider whether there is any experimental evidence against it.</p>
+
+<p>What experiments we can make here on the earth with sources of light
+placed at great distances (although indicating that it does not take a
+sensible time for light to pass over these distances) are subject to
+the objection that these distances are yet too small, and that we can
+only argue that the movement of light is enormously fast. M. Descartes
+thought it to be instantaneous and based his opinion upon much better
+reasons taken from the eclipse of the moon. Yet as I shall make clear,
+even this evidence is not decisive. I shall state the matter<span class="pagenum" id="Page_55">[Pg 55]</span> in a
+somewhat different way from his in order more easily to exhibit all the
+consequences.</p>
+
+<p>Suppose S to be the position of the sun, E A part of the orbit of the
+earth, S E M a straight line intersecting in M, the orbit of the moon,
+represented by the circle A M.</p>
+
+<figure class="figcenter width500" id="p055" style="width: 844px;">
+<img src="images/p055.jpg" width="844" height="300" alt="A geometric
+diagram showing lines, angles, and a circle with points S, E, A, M,
+Y, illustrating an astronomical principle.">
+
+</figure>
+
+<p>Now if light requires time—say an hour—to move the distance between
+the earth and the moon, then [at the time of an eclipse] it follows
+that when the earth has come to E its shadow, or the stoppage of the
+light of the sun, will not yet have reached M [the moon], and will
+not for an hour. Counting from the instant the earth reaches E, it
+will be an hour before it will reach M if it is to be obscured there.
+This eclipse will not be seen from the earth for yet another hour.
+Suppose that during these two hours the earth has moved to X, the moon
+appearing eclipsed at M, the sun still being seen at S. For I assume as
+does Copernicus that the sun is fixed and since light moves in straight
+lines, is always seen in its true position.</p>
+
+<p>But as a matter of fact, we are assured that the eclipsed moon always
+appears directly opposite the sun; while on the above supposition [that
+light takes an hour in passing between the moon and the earth], its
+position ought to be back of the straight line by the angle Y X M, the
+supplement of the angle S X M. But this is not the case, for this angle
+Y X M would be very easily noticed, it being about 33 degrees. For by
+our analysis (found in the essay on the causes of the phenomena of
+Saturn), the distance from the sun to the earth, S E, is about 12,000
+times the diameter of the earth, and hence 400 times the distance of
+the moon, which is 30 diameters.<span class="pagenum" id="Page_56">[Pg 56]</span> The angle X M E then will be nearly
+400 times as great as E S X, which is 5 minutes, i. e., the angular
+distance travelled by the earth in two hours [the earth traversing
+almost a degree in a day]. Thus the angle E M X is almost 33 degrees,
+and likewise the angle M X Y, being 5 minutes greater [than E M X].</p>
+
+<p>Now it must be remembered that in this computation it is assumed that
+the speed of light is such as to consume an hour in passing from here
+to the moon. But if we assume it to take only a minute of time, then
+the angle Y X M would amount to only 33 minutes, and if it only takes
+ten seconds, this angle will be less than six minutes. Now so small
+an angle is not observable in a lunar eclipse and hence it is not
+permissible to argue that light is absolutely instantaneous.</p>
+
+<p>It is rather unusual, we admit, to take for granted a speed 100,000
+times as great as that of sound, which (following my experiments)
+travels about 180 toises [about 1150 feet] in a second, or during a
+pulse-beat. Yet this supposition is not at all impossible, for it is
+not necessary to carry a body at such speed but only for motion to
+traverse successively from one point to another.</p>
+
+<p>Hence I do not hesitate in this matter to assume that the passage
+of light takes time, for on this assumption all phenomena can be
+explained, while on the contrary supposition none of them can be
+explained. In fact, it seems to me and to many others as well, that
+M. Descartes, whose purpose has been to discuss all physical matters
+clearly, and who has certainly succeeded in this better than any one
+before him, has written nothing on light and its qualities that is not
+either hard to understand or even incomprehensible.</p>
+
+<p>Moreover, this idea that I have propounded as an hypothesis has lately
+been made a well nigh established fact by that keen calculation of
+Roemer, whose method I will here take occasion to describe, on the
+expectation that he will himself in the future fully confirm this
+theory.</p>
+
+<p>His method, the same as the one we have just discussed, is
+astronomical. He shows not only that light takes time for its passage,
+but calculates also its speed and that this must be at least six times
+as much as the rate I have just given as an estimate.</p>
+
+<p>In his demonstration he uses the eclipses of the small satellites that
+revolve around Jupiter, and very frequently pass into his shadow.
+Roemer’s reasoning is this:</p>
+
+<p><span class="pagenum" id="Page_57">[Pg 57]</span></p>
+
+<figure class="figcenter width500" id="p057" style="width: 1642px;">
+<img src="images/p057.jpg" width="1642" height="600" alt="A diagram
+showing the Sun, Moon, and Earth aligned, illustrating the geometry of
+a solar eclipse and the formation of the Moon's shadow on Earth.">
+
+</figure>
+
+<p>Let S be the sun, B C D E the yearly orbit of the earth, J Jupiter and
+G H the orbit of his nearest satellite, for this one because of its
+short period is better suited to this investigation than any one of the
+other three. Suppose G to be the point where the satellite enters, and
+H where it leaves, Jupiter’s shadow.</p>
+
+<p>Suppose that when the earth is at B, the satellite is seen to emerge
+[at G], at some time before the last quarter. Were the earth to remain
+stationary there, 42-1/2 hours would elapse before the next emergence
+would take place, for this much time is taken by the satellite in
+making one revolution in its orbit and returning to opposition to the
+sun. For example, if the earth remained at B during 30 revolutions,
+then after 30 times 42-1/2 hours, the satellite would again be seen
+to emerge. If in the meantime the earth has moved to C, farther from
+Jupiter, it is clear that if light requires time for its passage, the
+emergence of the satellite will be seen later when the earth is at C
+than when at B. For we must add to the 30 times 42-1/2 hours, the time
+occupied by light in passing over the difference between the distances
+[of the earth from Jupiter] G B and G C, i. e., M C. So in the other
+quarter, when the earth travels from D to E, approaching Jupiter, the
+eclipses will occur earlier when the earth is at E than when at D.</p>
+
+<p>Now by many observations of these eclipses throughout ten years, it is
+shown that these inequalities are actually of some moment, amounting to
+as much as ten minutes or more: whence it is argued that in traversing
+the whole diameter of the earth’s orbit, K L, double the distance from
+the earth to the sun, light takes about 22 minutes.</p>
+
+<p><span class="pagenum" id="Page_58">[Pg 58]</span></p>
+
+<p>The motion of Jupiter in its orbit while the earth passes from B
+to C or from D to E has been taken into consideration in Roemer’s
+calculation, where it is also proved that these inequalities cannot
+be caused by any irregularity or eccentricity in the movement of the
+satellite.</p>
+
+<p>Now if we consider the enormous size of this diameter K L [the earth’s
+orbit] which I have estimated to be about 24,000 times that of the
+earth, we get some comprehension of the extraordinary speed of light.</p>
+
+<p>Even if K L were only 22,000 diameters of the earth, a speed traversing
+this distance in 22 minutes would be equal to the rate of a thousand
+diameters a minute, i. e., 16 2-3 diameters a second (or a pulse-beat)
+which makes more than 1,100 times 100,000 toises, since one diameter of
+the earth equals 2,865 leagues, of which there are 25 to the degree,
+and since in accordance with the very precise calculation made by M.
+Picard in 1609 under orders from the king, each league contains 2,282
+toises.</p>
+
+<p>As I stated before sound moves only 180 toises per second. Hence
+the speed of light is over 600,000 times as great as that of sound,
+which, however, is very different from being instantaneous,—it is the
+difference between any finite number and infinity. The theory that
+light movements are propagated from point to point in time being thus
+demonstrated, it follows that light moves in spherical waves, as does
+sound.</p>
+
+<p>But if they are alike in this regard, they are unlike in others, as
+in the original cause of the motion that transmits them, the medium
+through which they move, and the manner in which they are transmitted
+in it.</p>
+
+<p>We know that sound is caused by the rapid vibration of some body
+(either as a whole or in part), this vibration setting in motion the
+adjoining air. But light movements must arise at every point of the
+luminous body, otherwise all the various parts of the body would not be
+visible. This fact will be clearer from what follows.</p>
+
+<p>In my judgment, this movement of light-giving bodies cannot be more
+satisfactorily explained than by supposing that those that are fluid,
+e. g., a flame, and probably the sun and stars, consist of particles
+that float about in a much rarer medium, that sets them in violent
+motion, causing them to strike against the still more minute particles<span class="pagenum" id="Page_59">[Pg 59]</span>
+of the surrounding ether. In the case of light-giving solids such as
+red-hot metal or carbon we may suppose this movement to be caused by
+the rapid motions of the metal or wood, the particles on the surface
+exciting the ether. Hence the vibration producing light must be much
+shorter and faster than that causing sound, since we do not find that
+sound disturbances give rise to light any more than the wave of the
+hand through the air causes sound.</p>
+
+<p>The next question is in regard to the nature of the medium through
+which the vibration produced by light-giving bodies moves. I have
+named it <i>ether</i>, but it plainly differs from the medium through
+which sound moves. The latter is simply the air we feel and breathe,
+and when it is removed from any space, the medium which carries light
+still remains. This is shown by surrounding the sounding body in a
+glass vessel, and exhausting the air by means of the air-pump that Mr.
+Boyle has devised, and with which he has performed so many striking
+experiments. In trying this experiment, however, it is best to set the
+sounder on cotton or feathers so that it cannot communicate vibrations
+to the glass receiver or the air-pump, a point hitherto neglected.
+Then, when all the air has been exhausted, one catches no sound from
+the metal when it is struck.</p>
+
+<p>Hence we conclude not only that our atmosphere which cannot penetrate
+glass is the medium through which sound acts, but that the medium
+carrying light-vibrations is something different: for after the vessel
+is exhausted of air, light passes through it as easily as before.</p>
+
+<p>The last point is proven even more conclusively by the famous
+experiment of Torricelli. [Fill a long closed glass tube with mercury,
+then invert it.] The top of the glass tube not filled by the mercury
+contains a high vacuum, but transmits light as well as when filled
+with air. This demonstrates that there is within the tube some form
+of matter different from air, and which penetrates either glass or
+mercury, or both, though both are impenetrable to air. And if a like
+experiment is tried with a little water on top of the mercury, it
+becomes equally clear that the substance in question traverses either
+glass or water or both.</p>
+
+<p>In regard to the different methods of transmission of sound and light,
+in the case of sound it is easy to see what happens when one remembers
+that air can be compressed and reduced to a much smaller volume than
+usual, and that it tends with the same force to expand to<span class="pagenum" id="Page_60">[Pg 60]</span> its original
+volume. This quality, considered along with its penetrability retained
+in spite of such condensation seems to show that it consists of small
+particles that float about in rapid vibration in an ether consisting
+of still more minute particles. Sound, then, is caused by the struggle
+of these particles to escape when at any point in the course of a wave
+they are more crowded together than at some other point.</p>
+
+<p>Now the wonderful speed of light considered with its other qualities,
+does not permit us to believe it to be transmitted in the same manner.
+Therefore I shall try to explain the way in which I think it must
+take place. I must first, however, describe that quality of hard
+substances through which they transmit motion one to another. If one
+take a number of balls of the same size of any hard substance, and
+place them touching one another in one line, he will find that on
+letting a ball of the same size strike against one end of the line,
+the motion is transmitted in an instant to the other end of the line.
+The last ball is driven from the line while the others are apparently
+undisturbed, the ball that struck the line coming to a dead stop.
+This is an illustration of a transmission of motion at great speed,
+varying directly as the hardness of the balls. Yet it is certain that
+this transmission is not instantaneous, but requires time. For if the
+movement, or if you wish, the tendency to move, did not pass from one
+ball to another in succession, they would all be set in motion at the
+same instant and would all move forward at the same time. Now this is
+so far from the case that only the last one leaves the row, and it has
+the speed of the ball that first struck the line.</p>
+
+<p>There are other experiments, also demonstrating that all bodies, even
+those thought hardest, such as steel, glass and agate, are really
+elastic, and bend a little, no matter whether they are in rods, balls,
+or bodies of any other shape,—that is, they give slightly at the
+point where struck, and at once regain their former shape. Thus I have
+discovered that in letting a glass or agate ball strike on a large,
+thick, flat piece of the same substance the surface of which has been
+roughened by the breath, the place where it strikes is shown by a
+circular indentation that varies in size directly as the force of the
+blow. This indicates that the materials give when struck and then fly
+back,—an event that necessarily takes time.</p>
+
+<p>Now to apply such a motion to the explanation of light, there is<span class="pagenum" id="Page_61">[Pg 61]</span>
+nothing in the way of our imagining the particles of ether to have
+an almost complete hardness, and an elasticity as perfect as we need
+wish. We need not here discuss the cause of either this hardness or
+elasticity, as this would lead us too far from the question at issue.
+I will remark, however, by the way, that these particles of ether,
+in spite of their minuteness, are also composed of parts and that
+their elasticity depends on a very rapid motion of a subtle substance
+traversing them in all directions and making them take a structure
+that offers a ready passage to this fluid. This agrees with the idea
+of M. Descartes, except that I would not, like him, give the pores the
+shape of round, hollow canals. This is so far from being at all absurd
+or incomprehensible that it is easily credible that nature uses an
+infinite series of different-sized molecules in order to produce her
+marvelous effects.</p>
+
+<p>Moreover, although we do not know the cause of elasticity, we cannot
+have failed to notice that most bodies possess this characteristic;
+hence it is not unreasonable to suppose that it is a quality of the
+minute, invisible particles of the ether. And it is a fact that if one
+looks for some other method of accounting for the gradual transmission
+of light, he will have a hard time finding any supposition better
+suited than elasticity to explain the fact of uniform speed. This
+[uniform speed] seems to be a necessary assumption, for if the motion
+slowed down when distributed over a great mass of matter at a far
+distance from its source, then this great speed would at last be lost.
+On the other hand, we suppose ether to have the property of elasticity
+so that its particles regain their shape with equal activity whether
+struck a hard or gentle blow. Thus the rate at which light would move
+would remain constant.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_9" href="#FNanchor_9" class="label">[9]</a>
+Translated from <i>Traité de la Lumière</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_62">[Pg 62]</span></p>
+<h2 class="nobreak" id="VIII">VIII<br>
+ANTHONY VAN LEEUWENHOECK<br>
+1632-1723</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Born in Delft, Holland, October 24, 1632, Anthony Van Leeuwenhoeck,
+a lens-maker for microscopes, made several important biological
+discoveries. In 1673 he noticed the red globules in the blood; in
+1675 he discovered animalculæ in water; in 1677 he described the
+spermatozoa; in 1690 he traced the passage of blood from the arteries
+into the veins. Among his other achievements were his investigations
+of the tubules of teeth, the solidity of hair, the structure of the
+epidermis, and his descriptions of insect anatomies. He announced most
+of his findings to the Royal Society of London. Against the generally
+accepted idea of spontaneous generation, he held that all things
+generated their kind. He died at Delft, August 26, 1723.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+OBSERVATIONS ON ANIMALCULÆ<a id="FNanchor_10" href="#Footnote_10" class="fnanchor">[10]</a></p>
+
+<p>In the year 1675, I discovered very small living creatures in rain
+water, which had stood but few days in a new earthen pot glazed blue
+within. This invited me to view this water with great attention,
+especially those little animals appearing to me ten thousand times less
+than those represented by M. Swammerdam, and by him called water-fleas,
+or water-lice, which may be perceived in the water with the naked eye.</p>
+
+<p>The first sort I several times observed to consist of 5, 6, 7, or 8
+clear globules without being able to discern any film that held them
+together, or contained them. When these animalcula or living atoms
+moved, they put forth two little horns, continually moving. The<span class="pagenum" id="Page_63">[Pg 63]</span> space
+between these two horns was flat, though the rest of the body was
+roundish, sharpening a little towards the end, where they had a tail,
+near four times the length of the whole body, of the thickness, by my
+microscope, of a spider’s web; at the end of which appeared a globule
+of the size of one of those which made up the body. These little
+creatures, if they chanced to light on the least filament or string,
+or other particle, were entangled therein, extending their body in a
+long round, and endeavoring to disentangle their tail. Their motion of
+extension and contraction continued a while; and I have seen several
+thousands of these poor little creatures, within the space of a grain
+of gross sand, lie fast clustered together in a few filaments.</p>
+
+<p>I also discovered a second sort, of an oval figure; and I imagined
+their head to stand on a sharp end. These were a little longer than
+the former. The inferior part of their body is flat, furnished with
+several extremely thin feet, which moved very nimbly. The upper part of
+the body was round, and had within 8, 10, or 12 globules, where they
+were very clear. These little animals sometimes changed their figure
+into a perfect round, especially when they came to lie on a dry place.
+Their body was also very flexible; for as soon as they struck against
+the smallest fibre or string, their body was bent in, which bending
+presently jerked out again. When I put any of them on a dry place, I
+observed that, changing themselves into a round, their body was raised
+pyramidal-wise, with an extant point in the middle; and having laid
+thus a little while, with a motion of their feet, they burst asunder,
+and the globules were presently diffused and dissipated, so that I
+could not discern the least thing of any film, in which the globules
+had doubtless been enclosed; and at this time of their bursting
+asunder, I was able to discover more globules than when they were alive.</p>
+
+<p>I observed a third sort of little animals, that were twice as long as
+broad, and to my eye eight times smaller than the first. Yet I thought
+I discerned little feet, whereby they moved very briskly, both in round
+and straight line.</p>
+
+<p>There was a fourth sort, which were so small that I was not able to
+give them any figure at all. These were a thousand times smaller than
+the eye of a large louse. These exceeded all the former in celerity. I
+have often observed them to stand still as it were on a point, and then
+turn themselves about with that swiftness, as we see a<span class="pagenum" id="Page_64">[Pg 64]</span> top turn round,
+the circumference they made being no larger than that of a grain of
+small sand, and then extending themselves straight forward, and by and
+by lying in a bending posture. I discovered also several other sorts
+of animals; these were generally made up of such soft parts, as the
+former, that they burst asunder as soon as they came to want water.</p>
+
+<p>May 26, it rained hard; the rain growing less, I caused some of that
+rain-water running down from the house top, to be gathered in a clean
+glass, after it had been washed two or three times with water. And in
+this I observed some few very small living creatures, and seeing them,
+I thought they might have been produced in the leaded gutters in some
+water that had remained there before.</p>
+
+<p>I perceived in pure water, after some days, more of those animals, as
+also some that were somewhat larger. And I imagine, that many thousands
+of these little creatures do not equal an ordinary grain of sand in
+bulk; and comparing them with a cheese-mite, which may be seen to
+move with the naked eye, I make the proportion of one of these small
+water-creatures to a cheese-mite to be like that of a bee to a horse;
+for, the circumference of one of these little animals in water is not
+so large as the thickness of a hair in a cheese-mite.</p>
+
+<p>In another quantity of rain-water, exposed for some days to the air,
+I observed some thousands of them in a drop of water, which were of
+the smallest sort that I had seen hitherto. And in some time after I
+observed, besides the animals already noted, a sort of creatures that
+were eight times as large, of almost a round figure; and as those very
+small animalcula swam gently among each other, moving as gnats do in
+the air, so did these larger ones move far more swiftly, tumbling round
+as it were, and then making a sudden downfall.</p>
+
+<p>In the waters of the river Maese I saw very small creatures of
+different kinds and colours, and so small, that I could very hardly
+discern their figures; but the number of them was far less than those
+found in rain-water. In the water of a very cold well in the autumn, I
+discovered a very great number of living animals very small, that were
+exceedingly clear, and a little larger than the smallest I ever saw.
+In sea-water I observed at first, a little blackish animal, looking as
+if it had been made up of two globules. This creature had a peculiar
+motion, resembling the skipping of a flea on white paper,<span class="pagenum" id="Page_65">[Pg 65]</span> so that it
+might very well be called a water-flea; but it was far less than the
+eye of that little animal, which Dr. Swammerdam calls the water-flea. I
+also discovered little creatures therein that were clear, of the same
+size with the former animal, but of an oval figure, having a serpentine
+motion. I further noticed a third sort, which were very slow in their
+motion; their body was of a mouse colour, clear toward the oval point;
+and before the head and behind the body there stood out a sharp little
+point angle-wise. This sort was a little larger. But there was yet a
+fourth somewhat longer than oval. Yet of all these sorts there were
+but a few of each. Some days after viewing this water, I saw 100 where
+before I had seen but one; but these were of another figure, and not
+only less, but they were also very clear, and of an oblong oval figure,
+only with this difference, that their heads ended sharper; and although
+they were a thousand times smaller than a small grain of sand, yet when
+they lay out of the water in a dry place, they burst in pieces and
+spread into three or four very little globules, and into some aqueous
+matter, without any other parts appearing in them.</p>
+
+<p>Having put about one-third of an ounce of whole pepper in water, and
+it having lain about three weeks in the water, to which I had twice
+added some snow-water, the other water being in great part exhaled;
+I discerned in it with great surprise an incredible number of little
+animals, of divers kinds, and among the rest, some that were three
+or four times as long as broad; but their whole thickness did not
+much exceed the hair of a louse. They had a very pretty motion, often
+tumbling about and sideways; and when the water was let to run off from
+them, they turned round like a top; at first their body changed into an
+oval, and afterwards, when the circular motion ceased, they returned to
+their former length. The second sort of creatures discovered in this
+water, were of a perfect oval figure, and they had no less pleasing or
+nimble a motion than the former; and these were in far greater numbers.
+There was a third sort, which exceeded the two former in number, and
+these had tails like those I had formerly observed in rain-water.
+The fourth sort, which moved through the three former sorts, were
+incredibly small, so that I judged, that if 100 of them lay one by
+another, they would not equal the length of a grain of coarse sand;
+and according to this estimate,<span class="pagenum" id="Page_66">[Pg 66]</span> 1,000,000 of them could not equal the
+dimensions of a grain of such coarse sand. There was discovered a fifth
+sort, which had near the thickness of the former, but almost twice the
+length.</p>
+
+<p>In snow-water, which had been about three years in a glass bottle
+well stopped, I could discover no living creatures; and having poured
+some of it into a porcelain tea-cup, and put therein half an ounce of
+whole pepper, after some days I observed some animalcula, and those
+exceedingly small ones, whose body seemed to me twice as long as broad,
+but they moved very slowly, and often circularly. I observed also a
+vast multitude of oval-figured animalcula, to the number of 8,000 in a
+single drop.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_10" href="#FNanchor_10" class="label">[10]</a>
+From the <i>Transactions of the Royal Society of
+London</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_67">[Pg 67]</span></p>
+<h2 class="nobreak" id="IX">IX<br>
+SIR ISAAC NEWTON<br>
+1642-1727</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Sir Isaac Newton, whose researches in light, gravitation, and
+mathematics are outstanding in the history of modern science, was born
+in Woolsthorpe, Lincolnshire, December 25, 1642. He was the son of an
+English farmer who died before Newton was born. His early education
+was interrupted by his mother’s poverty, but his ingenuity in making
+mechanical toys soon provided a means whereby he was enabled to return
+to school. He entered Cambridge University in 1661 and took his degree
+in 1665; two years later he was made a fellow of the university, and
+in 1669 became professor of mathematics.</i></p>
+
+<p><i>In 1665 he discovered his method of fluxions, not greatly unlike
+Leibnitz’s Differential Calculus. In 1672 he was elected a fellow of
+the Royal Society and shortly afterwards sent them a paper describing
+how he had broken up light by means of a prism, demonstrating by that
+means the compound nature of the sun’s rays.</i></p>
+
+<p><i>In 1687 elaborated his theory of gravitation in “Philosophiæ
+Naturalis Principia Mathematica.” This was the result of his
+reflections and researches dating from 1666, when he attempted to
+explain the moon’s motion by the hypothesis of the assumed influence
+of gravitation. In the meantime, through the use of telescopic
+instruments, French geographers had tested the spherical shape of the
+earth and had made a new and more accurate triangulation. Using the
+data which they supplied, Newton perceived that these data agreed
+with his theory that the force varied inversely as the square of the
+distance. Overcome with the emotion incident to the solution of a
+great problem, he begged a friend to complete his calculations, with
+the result that the new astronomy begun by Copernicus, and continued
+by Brahe, Kepler, and Galileo, was formulated and mathematically
+interpreted by a single mechanical principle.</i></p>
+
+<p><span class="pagenum" id="Page_68">[Pg 68]</span></p>
+
+<p><i>Although he later made some chemical investigations, his papers
+were accidentally destroyed, and it is said that he never recovered
+from the shock of losing them. In 1695 he was made warden, and in 1699
+promoted to the mastership of the mint, which office he retained at a
+munificent salary until his death on March 20, 1727.</i></p>
+</div>
+
+<p class="nindc space-above2 space-below2">
+THE THEORY OF GRAVITATION<a id="FNanchor_11" href="#Footnote_11" class="fnanchor">[11]</a><br>
+BOOK III. PROPOSITION V. THEOREM V. SCHOLIUM</p>
+
+<p>The force which retains the celestial bodies in their orbits has been
+hitherto called centripetal force; but it being now made plain that it
+can be no other than a gravitating force, we shall hereafter call it
+gravity. For the cause of that centripetal force which retains the moon
+in its orbit will extend itself to all the planets.</p>
+
+
+<p class="nindc space-above2 space-below2">
+BOOK III. PROPOSITION VI. THEOREM VI.</p>
+
+<p><i>That all bodies gravitate towards every planet; and that the weights
+of bodies towards any the same planet, at equal distances from the
+centre of the planet, are proportional to the quantities of matter
+which they severally contain.</i></p>
+
+<p>It has been, now of a long time, observed by others, that all sorts of
+heavy bodies (allowance being made for the inequality of retardation
+which they suffer from a small power of resistance in the air) descend
+to the earth <i>from equal heights</i> in equal times; and that
+equality of times we may distinguish to a great accuracy, by the help
+of pendulums. I tried the things in gold, silver, lead, glass, sand,
+common salt, wood, water, and wheat. I provided two wooden boxes,
+round and equal; I filled the one with wood, and suspended an equal
+weight of gold (as exactly as I could) in the centre of oscillation
+of the other. The boxes hanging by equal threads of 11 feet made a
+couple of pendulums perfectly equal in weight and figure, and equally
+receiving the resistance of the air. And, placing the one by the
+other, I observed them to play together forwards and backwards, for
+a long time, with equal vibrations ... and the like happened in the
+other bodies. By these experiments, in bodies of the same weight, I
+could manifestly have discovered a difference of<span class="pagenum" id="Page_69">[Pg 69]</span> matter less than
+the thousandth part of the whole, had any such been. But, without
+all doubt, the nature of gravity towards the planets is the same
+as towards the earth.... Moreover, since the satellites of Jupiter
+perform their revolutions in times which observe the sesquiplicate
+proportion of their distances from Jupiter’s centre—that is, equal
+at equal distances. And, therefore, these satellites, if supposed
+to fall <i>towards Jupiter</i> from equal heights, would describe
+equal spaces in equal times, in like manner as heavy bodies do on
+our earth.... If, at equal distances from the sun, any satellite, in
+proportion to the quantity of its matter, did gravitate towards the
+sun with a force greater than Jupiter in proportion to his, according
+to any given proportion, suppose of <i>d</i> to <i>e</i>; then the
+distance between the centres of the sun and of the satellite’s orbit
+would be always greater than the distance between the centres of the
+sun and of Jupiter nearly in the sub-duplicate of that proportion; as
+by some computations I have found. And if the satellite did gravitate
+towards the sun with a force, lesser in the proportion of <i>e</i> to
+<i>d</i>, the distance of the centre of the satellite’s orbit from
+the sun would be less than the distance of the centre of Jupiter from
+the sun in the sub-duplicate of the same proportion. Therefore if, at
+equal distances from the sun, the accelerative gravity of any satellite
+towards the sun were greater or less than the accelerative gravity of
+Jupiter towards the sun but one 1-1000 part of the whole gravity, the
+distance of the centre of the satellite’s orbit from the sun would be
+greater or less than the distance of Jupiter from the sun by one 1-2000
+part of the whole distance—that is, by a fifth part of the distance
+of the utmost satellite from the centre of Jupiter; an eccentricity of
+the orbit which would be very sensible. But the orbits of the satellite
+are concentric to Jupiter, and therefore the accelerative gravities of
+Jupiter, and of all its satellites towards the sun, are equal among
+themselves....</p>
+
+<p>But further; the weights of all the parts of every planet towards
+any other planet are one to another as the matter in the several
+parts; for if some parts did gravitate more, others less, than for
+the quantity of their matter, then the whole planet, according to the
+sort of parts with which it most abounds, would gravitate more or less
+than in proportion to the quantity of matter in the whole. Nor is it
+of any moment whether these parts are external or internal; for if,
+for example, we should imagine the terrestrial bodies with us to be<span class="pagenum" id="Page_70">[Pg 70]</span>
+raised up to the orb of the moon, to be there compared with its body;
+if the weights of such bodies were to the weights of the external parts
+of the moon as the quantities of matter in the one and in the other
+respectively; but to the weights of the internal parts in a greater or
+less proportion, then likewise the weights of those bodies would be to
+the weight of the whole moon in a greater or less proportion; against
+what we have showed above.</p>
+
+<p>Cor. 1. Hence the weights of bodies do not depend upon their forms and
+textures; for if the weights could be altered with the forms, they
+would be greater or less, according to the variety of forms in equal
+matter; altogether against experience.</p>
+
+<p>Cor. 2. Universally, all bodies about the earth gravitate towards the
+earth; and the weights of all, at equal distances from the earth’s
+centre, are as the quantities of matter which they severally contain.
+This is the quality of all bodies within the reach of our experiments;
+and therefore (by rule 3) to be affirmed of all bodies whatsoever....</p>
+
+<p>Cor. 5. The power of gravity is of a different nature from the power of
+magnetism; for the magnetic attraction is not as the matter attracted.
+Some bodies are attracted more by the magnet; others less; most bodies
+not at all. The power of magnetism in one and the same body may be
+increased and diminished; and is sometimes far stronger, for the
+quantity of matter, than the power of gravity; and in receding from
+the magnet decreases not in the duplicate but almost in the triplicate
+proportion of the distance, as nearly as I could judge from some rude
+observations.</p>
+
+
+<p class="nindc space-above2 space-below2">
+BOOK III. PROPOSITION VII. THEOREM VII.</p>
+
+<p><i>That there is a power of gravity tending to all bodies, proportional
+to the several quantities of matter which they contain.</i></p>
+
+<p>That all the planets mutually gravitate one towards another, we have
+proved before; as well as that the force of gravity towards every
+one of them, considered apart, is reciprocally as the square of the
+distance of places from the centre of the planet. And thence (by prop.
+69, book I, and its corollaries) it follows, that the gravity tending
+towards all the planets is proportional to the matter which they
+contain.</p>
+
+<p><span class="pagenum" id="Page_71">[Pg 71]</span></p>
+
+<p>Moreover, since all the parts of any planet A gravitate towards any
+other planet B; and the gravity of every part is to the gravity of the
+whole as the matter of the part to the matter of the whole; and (by law
+3) to every action corresponds an equal reaction; therefore the planet
+B will, on the other hand, gravitate towards all the parts of the
+planet A; and its gravity towards any one part will be to the gravity
+towards the whole as the matter of the part to the matter of the whole.
+Q. E. D.</p>
+
+<p>Cor. 1. Therefore the force of gravity towards any whole planet arises
+from, and is compounded of, the forces of gravity towards all its
+parts. Magnetic and electric attractions afford us examples of this;
+for all attraction towards the whole arises from the attractions
+towards the several parts. The thing may be easily understood in
+gravity, if we consider a greater planet as formed of a number of
+lesser planets meeting together in one globe, for <i>hence it would
+appear</i> that the force of the whole must arise from the forces of
+the component parts. If it is objected that, according to this law, all
+bodies with us must mutually gravitate one towards another, I answer,
+that since the gravitation towards these bodies is to the gravitation
+towards the whole earth as these bodies are to the whole earth, the
+gravitation towards them must be far less than to fall under the
+observation of our senses.</p>
+
+<p>Cor. 2. The force of gravity towards the several particles of any body
+is reciprocally as the square of the distance from the particles; as
+appears from cor. 3, prop. 74, book I.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_11" href="#FNanchor_11" class="label">[11]</a>
+Translated from the <i>Philosophiæ Naturalis Principia
+Mathematica</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_72">[Pg 72]</span></p>
+<h2 class="nobreak" id="X">X<br>
+BENJAMIN FRANKLIN<br>
+1706-1790</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Benjamin Franklin, representative of the rationalist tendencies
+of the eighteenth century, was born in Boston, January 17, 1706.
+His early life and political missions are intimately related in his
+“Autobiography,” a classic in American literature. Apart from his
+political services to the cause of American independence, he attained
+distinction in the field of scientific researches and experiments. In
+1746 he began the experiments in electricity which resulted in his
+identification of electricity with lightning. He died in Philadelphia,
+April 17, 1790.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE IDENTITY OF LIGHTNING AND ELECTRICITY<a id="FNanchor_12" href="#Footnote_12" class="fnanchor">[12]</a></p>
+
+<p>But points have a property, by which they draw on as well as throw
+off the electrical fluid, at greater distances than blunt bodies can.
+That is, as the pointed part of an electrified body will discharge the
+atmosphere of that body, or communicate it farthest to another body,
+so the point of an unelectrified body will draw off the electrical
+atmosphere from an electrified body, farther than a blunter part of
+the same unelectrified body will do. Thus, a pin held by the head,
+and the point presented to an electrified body, will draw off its
+atmosphere at a foot distance; where, if the head were presented
+instead of the point, no such effect would follow. To understand
+this, we may consider, that, if a person standing on the floor would
+draw off the electrical atmosphere from an electrified body, an iron
+crow and a blunt knitting-needle, held alternately in his hand, and
+presented for that purpose, do not draw with different forces in
+proportion to their different masses. For the man, and what he holds in
+his hand, be it large or small, are connected with the common mass of
+unelectrified matter; and the force with which he draws<span class="pagenum" id="Page_73">[Pg 73]</span> is the same in
+both cases, it consisting in the different proportion of electricity
+in the electrified body, and that common mass. But the force, with
+which the electrified body retains its atmosphere by attracting it, is
+proportioned to the surface over which the particles are placed; that
+is, four square inches of that surface retain their atmosphere with
+four times the force that one square inch retains its atmosphere. And,
+as in plucking the hairs from the horse’s tail, a degree of strength
+not sufficient to pull away a handful at once, could yet easily strip
+it hair by hair, so a blunt body presented cannot draw off a number of
+particles at once, but a pointed one, with no greater force, takes them
+away easily, particle by particle.</p>
+
+<p>These explanations of the power and operation of points, when they
+first occurred to me, and while they first floated in my mind, appeared
+perfectly satisfactory; but now I have written them, and considered
+them more closely, I must own I have some doubts about them; yet, as I
+have at present nothing better to offer in their stead, I do not cross
+them out; for, even a bad solution read, and its faults discovered, has
+often given rise to a good one, in the mind of an ingenious reader.</p>
+
+<p>Nor is it of much importance to us to know the manner in which nature
+executes her laws; it is enough if we know the laws themselves. It is
+of real use to know that China left in the air unsupported, will fall
+and break; but how it comes to fall, and why it breaks, are matters of
+speculation. It is a pleasure indeed to know them, but we can preserve
+our China without it.</p>
+
+<p>Thus, in the present case, to know this power of points may possibly
+be of some use to mankind, though we should never be able to explain
+it. The following experiments, as well as those in my first paper, show
+this power. I have a large prime conductor, made of several thin sheets
+of clothier’s pasteboard, formed into a tube, near ten feet long and a
+foot diameter. It is covered with Dutch embossed paper, almost totally
+gilt. This large metallic surface supports a much greater electrical
+atmosphere than a rod of iron of fifty times the weight would do. It
+is suspended by silk lines, and when charged will strike, at near two
+inches distance, a pretty hard stroke, so as to make one’s knuckles
+ache. Let a person standing on the floor present the point of a needle,
+at twelve or more inches distance from it, and while the needle is
+so presented, the conductor cannot be charged, the point drawing off
+the fire as fast as it is thrown on by the<span class="pagenum" id="Page_74">[Pg 74]</span> electrical globe. Let it
+be charged, and then present the point at the same distance, and it
+will suddenly be discharged. In the dark you may see the light on the
+point, when the experiment is made. And if the person holding the point
+stands upon wax, he will be electrified by receiving the fire at that
+distance. Attempt to draw off the electricity with a blunt body, as
+a bolt of iron round at the end, and smooth, (a silversmith’s iron
+punch, inch thick, is what I use,) and you must bring it within the
+distance of three inches before you can do it, and then it is done
+with a stroke and crack. As the pasteboard tube hangs loose on silk
+lines, when you approach it with the punch-iron, it likewise will move
+towards the punch, being attracted while it is charged, but if, at the
+same instant, a point be presented as before, it retires again, for the
+point discharges it. Take a pair of large brass scales, of two or more
+feet beam, the cords of the scales being silk. Suspend the beam by a
+pack-thread from the ceiling, so that the bottom of the scales may be
+about a foot from the floor; the scales will move round in a circle
+by the untwisting of the pack-thread. Set the iron punch on the end
+upon the floor, in such a place as that the scales may pass over it
+in making their circle; then electrify one scale by applying the wire
+of a charged phial to it. As they move round, you see that scale draw
+nigher to the floor, and dip more when it comes over the punch; and, if
+that be placed at a proper distance, the scale will snap and discharge
+its fire into it. But, if a needle be stuck on the end of the punch,
+its point upward, the scale, instead of drawing nigh to the punch, and
+snapping, discharges its fire silently through the point, and rises
+higher from the punch. Nay, even if the needle be placed upon the floor
+near the punch, its point upward, the end of the punch, though so much
+higher than the needle, will not attract the scale and receive its
+fire, for the needle will get it and convey it away, before it comes
+nigh enough for the punch to act. And this is constantly observable
+in these experiments, that the greater quantity of electricity on the
+pasteboard tube, the farther it strikes or discharges its fire, and the
+point likewise will draw it off at a still greater distance.</p>
+
+<p>Now if the fire of electricity and that of lightning be the same,
+as I have endeavoured to show at large in a former paper, this
+pasteboard tube and these scales may represent electrified clouds. If
+a tube of only ten feet long will strike and discharge its fire on
+the punch at<span class="pagenum" id="Page_75">[Pg 75]</span> two or three inches distance, an electrified cloud of
+perhaps ten thousand acres may strike and discharge on the earth at a
+proportionately greater distance. The horizontal motion of the scales
+over the floor, may represent the motion of the clouds over the earth;
+and the erect iron punch, a hill or high building; and then we see how
+electrified clouds, passing over hills or high buildings at too great
+a height to strike, may be attracted lower till within their striking
+distance, And, lastly, if a needle fixed on the punch with its point
+upright, or even on the floor below the punch, will draw the fire from
+the scale silently at a much greater than the striking distance, and so
+prevent its descending towards the punch; or if in its course it would
+have come nigh enough to strike, yet being first deprived of its fire
+it cannot, and the punch is thereby secured from the stroke; I say, if
+these things are so, may not the knowledge of this power of points be
+of use to mankind, in preserving houses, churches, ships, &amp;c., from
+the stroke of lightning, by directing us to fix, on the highest parts
+of those edifices, upright rods of iron made sharp as a needle, and
+gilt to prevent rusting, and from the foot of those rods a wire down
+the outside of the building into the ground, or down round one of the
+shrouds of a ship, and down her side till it reaches the water? Would
+not these pointed rods probably draw the electrical fire silently out
+of a cloud before it came nigh enough to strike, and thereby secure us
+from that most sudden and terrible mischief?</p>
+
+<p>To determine the question, whether the clouds that contain lightning
+are electrified or not, I would propose an experiment to be tried where
+it may be done conveniently. On the top of some high tower or steeple,
+place a kind of sentry-box, ... big enough to contain a man and an
+electrical stand. From the middle of the stand let an iron rod rise
+and pass bending out of the door, and then upright twenty or thirty
+feet, pointed very sharp at the end. If the electrical stand be kept
+clean and dry, a man standing on it, when such clouds are passing low,
+might be electrified and afford sparks, the rod drawing fire to him
+from a cloud. If any danger to the man should be apprehended (though I
+think there would be none), let him stand on the floor of his box, and
+now and then bring near to the rod the loop of wire that has one end
+fastened to the leads, he holding it by a wax handle, so the sparks, if
+the rod is electrified, will strike from the rod to the wire, and not
+affect him.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_12" href="#FNanchor_12" class="label">[12]</a>
+From Franklin’s correspondence with Peter Collinson, July
+29, 1750. <i>Works of Benjamin Franklin</i>, Philadelphia, 1809, Vol.
+III, pp. 45-49.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_76">[Pg 76]</span></p>
+<h2 class="nobreak" id="XI">XI<br>
+LINNAEUS<br>
+1707-1778</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Carl von Linné [Linnaeus] was born May 13, 1707, at Rashult in
+Smaland, Sweden. At the age of four he showed a precocious interest
+in plants, an interest which seriously interfered with his studies
+when he went to school. When his father was about to remove him, a
+friend urged that the boy be fitted for the profession of medicine.
+Linnaeus entered the university at Lund in 1727, but in the following
+year transferred to Upsala. In 1732, at the expense of the Academy
+of Sciences, he explored Lapland. Later he made pilgrimages to many
+of the most eminent professors of Europe, returning to Stockholm in
+1738. After his marriage, in 1739, he was appointed professor at
+Upsala, where he continued his work in botany and established it on a
+rational basis. He died January 10, 1778, noted as one of the foremost
+botanists of his time, having discovered sex in plants and given his
+name to a famous botanical system of classification.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE SEX OF PLANTS<a id="FNanchor_13" href="#Footnote_13" class="fnanchor">[13]</a></p>
+
+<p>The organs common in general to all plants are: 1st. The root, with its
+capillary vessels, extracting nourishment from the ground. 2nd. The
+leaves, which may be called the limbs, and which, like the feet and
+wings of animals, are organs of motion; for being themselves shaken by
+the external air, they shake and exercise the plant. 3rd. The trunk,
+containing the medullary substance, which is nourished by the bark, and
+for the most part multiplied into several compound plants. 4th. The
+fructification, which is the true body of the plant, set at liberty by
+a metamorphosis, and consists only of the organs<span class="pagenum" id="Page_77">[Pg 77]</span> of generation; it is
+often defended by a calyx, and furnished with petals, by means of which
+it in a manner flutters in the air.</p>
+
+<p>Many flowers have no calyx, as several of the lily tribe, the
+Hippuris, etc., many want the corolla, as grasses, and the plants
+called apetalous; but there are none more destitute of stamina and
+pistilla, those important organs destined to the formation of fruit.
+We therefore infer from experience that the stamina are the male
+organs of generation, and the pistilla of the female; and as many
+flowers are furnished with both at once, it follows that such flowers
+are hermaphrodites. Nor is this so wonderful, as that there should be
+any plants in which the different sexes are distinct individuals; for
+plants being immovably fixed to one spot, cannot like animals, travel
+in search of a mate. There exists, however, in some plants a real
+difference of sex. From seeds of the same mother, some individuals
+shall be produced, whose flowers exhibit stamina without pistilla, and
+may therefore properly be called male; while the rest being furnished
+with pistilla without stamina are therefore denominated females; and
+so uniformly does this take place, that no vegetable was ever found to
+produce female flowers without flowers furnished with stamina being
+produced, either on the same individual or on another plant of the same
+species, and <i>vice versa</i>.</p>
+
+<p>As all seed vessels are destined to produce seeds, so are the stamina
+to bear the pollen, or fecundating powder. All seeds contain within
+their membranes a certain medullary substance, which swells when dipped
+into warm water. All pollen, likewise, contains in its membrane an
+elastic substance, which, although very subtle, and almost invisible,
+by means of warm water often explodes with great vehemence. While
+plants are in flower, the pollen falls from their antheræ, and is
+dispersed abroad, as seeds are dislodged from their situation when
+the fruit is ripe. At the same time that the pollen is scattered, the
+pistillum presents its stigma, which is then in its highest vigour,
+and, for a portion of the day at least, is moistened with a fine dew.
+The stamina either surround this stigma, or if the flowers are of the
+drooping kind, they are bent towards one side, so that the pollen can
+easily find access to the stigma, where it not only adheres by means of
+the dew of that part, but the moisture occasions its bursting, by which
+means its contents are discharged. That issued from it being mixed with
+the fluid of the stigma, is conveyed to rudiments of<span class="pagenum" id="Page_78">[Pg 78]</span> the seed. Many
+evident instances of this present themselves to our notice; but I have
+nowhere seen it more manifest than in the Jacobean Lily (<i>Amarylis
+formosissima</i>), the pistillum of which, when sufficient heat is
+given the plant to make it flower in perfection, is bent downwards and
+from its stigma issues a drop of limpid fluid, so large that one would
+think it in danger of falling to the ground. It is, however, gradually
+reabsorbed into the style about three or four o’clock and becomes
+invisible until about ten the next morning, when it appears again; by
+noon it attains its largest dimensions; and in the afternoon, by a
+gentle and scarcely perceptible decrease it returns to its source. If
+we shake the antheræ over the stigma, so that the pollen may fall on
+this limpid drop, we see the fluid soon after become turbid and assume
+a yellow color; and we perceive little rivulets, or opaque streaks
+running from the stigma towards the rudiments of the seed. Some time
+afterwards, when the drop has totally disappeared, the pollen may be
+observed adhering to the stigma, but of an irregular figure, having
+lost its original form. No one, therefore, can assent to what Morland
+and others have asserted, that the pollen passes into the stigma,
+pervades the style and enters the tender rudiments of the seed, as
+Leeuwenhoeck supposed his worms to enter the ova. A most evident proof
+of the falsehood of this opinion may be obtained from any species of
+<i>Mirabilis</i> (Marvel of Peru), whose pollen is so very large that
+it almost exceeds the style itself in thickness, and, falling on the
+stigma, adheres firmly to it; that organ sucking and exhausting the
+pollen, as a cuttle fish devours everything that comes within its
+grasp. One evening in the month of August, I removed all the stamina
+from three flowers of the <i>Mirabilis Longiflora</i>, at the same time
+destroying all the rest of the flowers which were expanded; I sprinkled
+these three flowers with the pollen of <i>Mirabilis Jalappa</i>; the
+seed-buds swelled, but did not ripen. Another evening I performed a
+similar experiment, only sprinkling the flowers with the pollen of the
+same species; all these flowers produced ripe seeds.</p>
+
+<p>Some writers have believed that the stamina are parts of the
+fructification, which serve only to discharge an impure or
+excrementitious matter, and by no means formed for so important a work
+as generation. But it is very evident that these authors have not
+sufficiently examined the subject; for, as in many vegetables, some<span class="pagenum" id="Page_79">[Pg 79]</span>
+flowers are furnished with stamina only, and others only with pistilla;
+it is altogether impossible that stamina situated at so very great a
+distance from the fruit, as on a different branch, or perhaps on a
+separate plant, should serve to convey any impurities from the embryo.</p>
+
+<p>No physiologist could demonstrate, <i>a priori</i>, the necessity of
+the masculine fluid to the rendering the eggs of animals prolific, but
+experience has established it beyond a doubt. We therefore judge <i>a
+posteriori</i> principally, of the same effect in plants.</p>
+
+<p>In the month of January, 1760, the <i>Antholyza Cunonia</i> flowered
+in a pot in my parlour, but produced no fruit, the air of the room not
+being sufficiently agitated to waft the pollen to the stigma. One day,
+about noon, feeling the stigma very moist, I plucked off one of the
+antheræ, by means of a fine pair of forceps, and gently rubbed it on
+one part of the expanded stigmata. The spike of flowers remained eight
+or ten days longer; when I observed, in gathering the branch for my
+herbarium, that the fruit of that flower only on which the experiment
+had been made, had swelled to the size of a bean. I then dissected this
+fruit and discovered that one of the three cells contained seeds in
+considerable number, the other two being entirely withered.</p>
+
+<p>In the month of April I sowed the seeds of hemp (<i>Cannabis</i>) in
+two different pots. The young plants came up so plentifully, that each
+pot contained thirty or forty. I placed each by the light of a window,
+but in different and remote apartments. The hemp grew extremely well
+in both pots. In one of them I permitted the male and female plants
+to remain together, to flower and bear fruit, which ripened in July,
+being macerated in water, and committed to the earth, sprung up in
+twelve days. From the other, however, I removed all the male plants,
+as soon as they were old enough for me to distinguish them from the
+females. The remaining females grew very well, and presented their long
+pistilla in great abundance, these flowers continuing a very long time,
+as if in expectation of their mates; while the plants in the other pot
+had already ripened their fruit, their pistilla having, quite in a
+different manner, faded as soon as the males had discharged all their
+pollen. It was truly a beautiful and truly admirable spectacle to see
+the unimpregnated females preserve their pistilla so long green and
+flourishing, not permitting them to begin to fade till they had been
+for a very considerable<span class="pagenum" id="Page_80">[Pg 80]</span> time exposed in vain, to the access of the
+male pollen.</p>
+
+<p>Afterwards, when these virgin plants began to decay through age, I
+examined all their calyces in the presence of several botanists and
+found them large and flourishing, although every one of the seed-buds
+was brown, compressed, membranaceous, and dry, not exhibiting any
+appearance of cotyledons or pulp. Hence I am perfectly convinced that
+the circumstance which authors have recorded, of the female hemp having
+produced seeds, although deprived of the male, could only have happened
+by means of pollen brought by the wind from some distant place. No
+experiment can be more easily performed than the above; none more
+satisfactory in demonstrating the generation of plants.</p>
+
+<p>The <i>Clutia tenella</i> was in like manner kept growing in my window
+during the months of June and July. The male plant was in one pot,
+the female in another. The latter abounded with fruit, not one of its
+flowers proving abortive. I removed the two pots into different windows
+of the same apartment; still all the female flowers continued to become
+fruitful. At length I took away the male entirely, leaving the female
+alone, and cutting off all the flowers which it had already borne.
+Every day new ones appeared from the axila of every leaf; each remained
+eight or ten days, after which their foot stalks turning yellow, they
+fell barren to the ground. A botanical friend, who had amused himself
+with observing this phenomenon with me, persuaded me to bring, from the
+stove in the garden, a single male flower, which he placed over one of
+the female ones, then in perfection, tying a piece of red silk around
+its pistillum. The next day the male flower was taken away, and this
+single seed-bud remained, and bore fruit. Afterwards I took another
+male flower out of the same stove, and with a pair of slender forceps
+pinched off one of its antheræ, which I afterwards gently scratched
+with a feather, so that a very small portion of its pollen was
+discharged upon one of the three stigmata of a female flower, the other
+two stigmata being covered with paper. This fruit likewise attained its
+due size, and on being cut transversely, exhibited one cell filled with
+a large seed, and the other two empty. The rest of the flowers, being
+unimpregnated, faded and fell off. This experiment may be performed
+with as little trouble as the former.</p>
+
+<p>The <i>Datisca cannabina</i> came up in my garden from seed ten years<span class="pagenum" id="Page_81">[Pg 81]</span>
+ago, and has every year been plentifully increased by means of its
+perennial root. Flowers in great number have been produced by it; but,
+being all female, they proved abortive. Being desirous of producing
+male plants, I obtained more seeds from Paris. Some more plants were
+raised; but these likewise to my great mortification, all proved
+females, and bore flowers, but no fruit. In the year 1757 I received
+another parcel of seeds. From these I obtained a few male plants, which
+flowered in 1758. These were planted at a great distance from the
+females; and when their flowers were just ready to emit their pollen,
+holding a paper under them, I gently shook the spike of panicle with
+my finger, till the paper was almost covered with the yellow powder. I
+carried this to the females, which were flowering in another part of
+the garden, and placed it over them. The cold nights of the year in
+which this experiment was made, destroyed these Datiscas, with many
+other plants, much earlier than usual. Nevertheless, when I examined
+the flowers of those plants, which I had sprinkled with the fertilizing
+powder, I found the seeds of their due magnitude; while in the more
+remote Datiscas, which had not been impregnated with pollen, no traces
+of seeds were visible.</p>
+
+<p>Several species of Momordica, cultivated by us, like other Indian
+vegetables, in close stoves, have frequently borne female flowers;
+which, although at first very vigorous, after a short time have
+constantly faded and turned yellow, without perfecting any seed, till
+I instructed the gardener, as soon as he observed a female flower, to
+gather a male one, and place it above the female. By this contrivance
+we are so certain of obtaining fruit that we dare pledge ourselves to
+make any female flowers fertile that shall be fixed on.</p>
+
+<p>The <i>Jatropha urens</i> has flowered every year in my hot-house; but
+the female flowers coming before the males, in a week’s time dropped
+their petals and faded before the latter were opened; from which cause
+no fruit has been produced, but the <i>germina</i> themselves have
+fallen off. We have therefore never had any fruit of the Jatropha till
+the year 1752, when the male flowers were in vigour on a tall tree,
+at the same time that the females began to appear on a small Jatropha
+which was growing in a garden-pot. I placed this pot under the other
+tree, by which means the female flowers bore seeds, which grew on being
+sown. I have frequently amused myself with taking the male flowers from
+one plant, and scattering them over the female<span class="pagenum" id="Page_82">[Pg 82]</span> flowers of another, and
+have always found the seeds of the latter impregnated by it.</p>
+
+<p>Two years ago I placed a piece of paper under some of these male
+flowers and afterwards folded up the pollen which had fallen upon it,
+preserving it so folded up, if I remember right, four or six weeks,
+at the end of which time another branch of the same Jatropha was in
+flower. I then took the pollen, which I had so long preserved in paper,
+and strewed it over three female flowers, the only ones at that time
+expanded. The three females proved fruitful, while all the rest, which
+grew in the same bunch, fell off abortive.</p>
+
+<p>The interior petals of the <i>Ornithogalum</i>, commonly but improperly
+called <i>Canadense</i>, cohere so closely together that they only just
+admit the air to the germen and will scarcely permit the pollen of
+another flower to pass; this plant produced every day new flowers and
+fruit, the fructification never failing in any instance; I therefore,
+with the utmost care, extracted the antheræ from one of the flowers
+with a hooked needle, and as I hoped, this single flower proved barren.
+This experiment was repeated about a week after with the same success.</p>
+
+<p>I removed all of the antheræ out of a flower of <i>Chelidonium
+corniculatum</i> (scarlet-horned poppy), which was growing in a remote
+part of the garden, upon the first opening of its petals, and stripped
+off all the rest of the flowers; another day I treated another flower
+of the same plant in a similar manner, but sprinkled the pistillum of
+this with the pollen borrowed from another plant of the same species;
+the result was, that the first flower produced no fruit, but the second
+afforded very perfect seed. My design in this experiment was to prove
+that the mere removal of the antheræ from a flower is not in itself
+sufficient to render the germen abortive.</p>
+
+<p>Having the <i>Nicotiana fruticosa</i> growing in a garden-pot, and
+producing plenty of flowers and seed, I extracted the antheræ from the
+newly expanded flowers before they had burst, at the same time cutting
+away all the other flowers; this germen produced no fruit, nor did it
+even swell.</p>
+
+<p>I removed an urn, in which the <i>Asphodelus fistulosus</i> was
+growing, to one corner of the garden, and from one of the flowers
+which had lately opened, I extracted its antheræ; this caused the
+impregnation<span class="pagenum" id="Page_83">[Pg 83]</span> to fail. Another day I treated another flower in the same
+manner; but, bringing a flower from a plant in a different part of the
+garden, with which I sprinkled the pistillum of the mutilated one, its
+germen became by that means fruitful.</p>
+
+<p><i>Ixia chinensis</i>, flowering in my stove, the windows of which
+were shut, all its flowers proved abortive. I therefore took one of
+its antheræ in a pair of pincers, and with them sprinkled the stigmata
+of two flowers, and the next day one stigma only of a third flower;
+the seed-buds of these flowers remained, grew to a large size and bore
+seed, the fruit of the third, however, contained ripe seed only in one
+of its cells.</p>
+
+<p>To relate more experiments would only be to fatigue the reader
+unnecessarily. All nature proclaims the truth I have endeavored to
+inculcate, and every flower bears witness to it. Any person may make
+the experiment for himself with any plant he pleases, only taking
+care to place the pot in which it is growing, in the window of a room
+sufficiently out of reach of other flowers; and I will venture to
+promise him that he will obtain no perfect fruit unless pollen has
+access to the pistillum.</p>
+
+<p>Logan’s experiments on the Mays are perfectly satisfactory, and
+manifestly show that the pollen does not enter the style, or arrive
+at the germen, but that it is exhausted by the genital fluid of the
+pistillum. And as in animals no conception can take place, unless the
+genital fluid of the female be discharged at the same moment as the
+impregnating liquor of the male; so in plants, generation fails, unless
+the stigma be moist with prolific dew.</p>
+
+<p>Husbandmen know, by long experience, that if rain falls while rye is
+in flower, by coagulating the pollen of its antheræ, it occasions the
+emptiness of many husks in the ear.</p>
+
+<p>Gardeners remark the same thing every year in fruit trees. Their
+blossoms produce no fruit if they have unfortunately been exposed to
+long-continued rains.</p>
+
+<p>Aquatic plants rise above the water at the time of flowering, and
+afterwards again subside, for no other reason, than that the pollen may
+safely reach the stigma.</p>
+
+<p>The white water-lily (<i>Nymphaea alba</i>) raises itself every morning
+out of the water and opens its flowers, so that by noon at least three
+inches of its flower-stalk may be seen above the surface. In the<span class="pagenum" id="Page_84">[Pg 84]</span>
+evening it is closely shut up, and withdrawn again; for about four
+o’clock in the afternoon the flower closes, and remains all night under
+water; which was observed full two thousand years since, even as long
+ago as the time of Theophrastus, who has described this circumstance
+in the <i>Nymphaea Lotus</i>, a plant so much resembling our white
+water-lily that they are only distinguished from each other by the
+leaves of the Lotus being indented. Theophrastus gives the following
+account of this vegetable, in his <i>History of Plants</i>, book IV.,
+chap. 10: “It is said to withdraw its flowers into the Euphrates,
+which continue to descend till midnight, to so great a depth that at
+daybreak they are out of reach of the hand; after which it rises again,
+and in the course of the morning appears above the water, and expands
+its flowers, rising higher and higher, till it is a considerable
+height above the surface.” The very same thing may be observed in the
+<i>Nymphaea alba</i>.</p>
+
+<p>Many flowers close themselves in the evening and before rain, lest the
+pollen should be coagulated; but after the discharge of the pollen
+they always remain open. Such of them as do not shut up, incline their
+flowers downward in those circumstances, and several flowers, which
+come forth in the moisture of spring, droop perpetually. The manner in
+which the Parnassia and Saxifrage move their antheræ to the stigma is
+well known. The common Rue, a plant everywhere to be met with, moves
+one of its antheræ every day to the stigma, till all of them in their
+turns have deposited their pollen there.</p>
+
+<p>The Neapolitan star flower (<i>Ornithogalum nutans</i>) has six broad
+stamina, which stand close together in the form of a bell, the three
+external ones being but half the length of the others; so that it seems
+impossible for their antheræ ever to convey their pollen to the stigma;
+but nature, by an admirable contrivance, bends the summits of these
+external stamina inwards between the other filaments, so that they are
+enabled to accomplish their purpose.</p>
+
+<p>The Plaintain tree (<i>Musa</i>) bears two kinds of hermaphrodite
+flowers; some have imperfect antheræ, others only the rudiments of
+stigmata; as the last mentioned kind appear after the others, they
+cannot impregnate them, consequently no seeds are produced in our
+gardens, and scarcely ever on the plants cultivated in India. An event
+happened this year, which I have long wished for; two plaintain-trees<span class="pagenum" id="Page_85">[Pg 85]</span>
+flowering with me so fortunately that one of them brought forth its
+first female blossoms at the time that male ones began to appear on the
+other. I eagerly ran to collect antheræ from the first plant, in order
+to scatter them over the newly-expanded females, in hopes of obtaining
+seed from them, which no botanist has yet been able to do. But when I
+came to examine the antheræ I found even the largest of them absolutely
+empty and void of pollen, consequently unfit for impregnating the
+females; the seeds of this plant, therefore, can never be perfected in
+our gardens. I do not doubt, however, that real male plants of this
+species may be found in its native country, bearing flowers without
+fruit, which the gardeners have neglected; while the females in this
+country produce imperfect fruit, without seeds, like the female fig;
+and, like that tree, are increased easily by suckers. The fruit,
+therefore, of the plaintain-tree scarcely attains anything like its due
+size, the larger seed-buds only ripening, without containing anything
+in them.</p>
+
+<p>The day would sooner fail me than examples. A female date-bearing palm
+flowered many years at Berlin, without producing any seeds. But the
+Berlin people taking care to have some of the blossoms of the male
+tree, which was then flowering at Leipsic, sent them by the post, they
+obtained fruit by that means; and some dates, the offspring of this
+impregnation, being planted in my garden, sprung up, and to this day
+continue to grow vigorously. Kœmpfer formerly told us how necessary
+it was found by the oriental people, who live upon the produce of
+palm-trees, and are the true Lotophagi, to plant some male trees among
+the females, if they hoped for any fruit; hence, it is the practice of
+those who make war in that part of the world to cut down all the male
+palms, that a famine may afflict their proprietors; sometimes even
+the inhabitants themselves destroy the male trees, when they dread an
+invasion, that their enemies may find no sustenance in the country.</p>
+
+<p>Leaving these instances, and innumerable others, which are so well
+known to botanists that they would by no means bear the appearance of
+novelty, and can only be doubted by those persons who neither have
+observed nature, nor will they take the trouble to study her, I pass
+to a fresh subject, concerning which much new light is wanted; I mean
+hybrid, or mule vegetables, the existence and origin of which we shall
+now consider.</p>
+
+<p><span class="pagenum" id="Page_86">[Pg 86]</span></p>
+
+<p>I shall enumerate three or four real mule plants, to whose origin I
+have been an eye-witness.</p>
+
+<p>1. <i>Veronica spuria</i>, described in Amœnitates Acad. vol. III. p.
+35, came from the impregnation of <i>Veronic maratima</i> by <i>Verbena
+officinalis</i>; it is easily propagated by cuttings, and agrees
+perfectly with its mother in fructification, and with its father in
+leaves.</p>
+
+<p>2. <i>Delphinium hybridum</i>, sprung up in a part of the garden where
+<i>Delphinium clatum</i> and <i>Aconitum Napellus</i> grew together;
+it resembles its mother as much in its internal parts, that is, in
+fructification as it does its father (the <i>Aconitum</i>) in outward
+structure, or leaves; and, owing its origin to plants so nearly allied
+to each other, it propagates itself by seed; some of which I now send
+with this Dissertation.</p>
+
+<p>3. <i>Hieracium Taraxici</i>, gathered in 1753 upon our mountains by
+Dr. Solander, in its thick, brown, woolly calyx; in its stem being
+hairy towards the top, and in its bracteæ, as well as in every part of
+its fructification, resembles so perfectly its mother, <i>Hieracium
+alpinum</i>, that an inexperienced person might mistake one for the
+other; but in the smoothness of its leaves, in their indentations and
+whole structure, it so manifestly agrees with its father, <i>Leontodon
+Taraxacum</i> (Dandelion), that there can be no doubt of its origin.</p>
+
+<p>4. <i>Tragopogon hybridum</i> attracted my notice the autumn before
+last, in a part of the garden where I had planted <i>Tragopogon
+pratense</i>, and <i>Tragopogon porrifolium</i>; but winter coming on,
+destroyed its seeds. Last year, while the <i>Tragopogon pratense</i>
+was in flower I rubbed off its pollen early in the morning, and
+about eight o’clock sprinkled its stigmata with some pollen of the
+<i>Tragopogon porrifolium</i>, marking the calyces by tying a thread
+round them. I afterwards gathered the seeds when ripe, and sowed them
+that autumn in another place; they grew, and produced this year, 1759,
+purple flowers yellow at the base, seeds of which I now send. I doubt
+whether any experiment demonstrates the generation of plants more
+certainly than this.</p>
+
+<p>There can be no doubt that these are all new species produced by
+hybrid generation. And hence we learn, that a mule offspring is
+the exact image of its mother in its medullary substance, internal
+nature, or fructification, but resembles its father in leaves. This
+is a foundation upon which naturalists may build much. For it seems
+probable<span class="pagenum" id="Page_87">[Pg 87]</span> that many plants, which now appear different species of
+the same <i>genus</i>, may in the beginning have been but one plant,
+having arisen merely from hybrid generation. Many of those Geraniums
+which grow at the Cape of Good Hope, and have never been found wild
+anywhere but in the south parts of Africa, and which, as they are
+distinguished from all other Geraniums by their single-leaved calyx,
+many-flowered foot-stalk, irregular corolla, seven fertile stamina,
+and three mutilated ones, and by their naked seeds furnished with
+downy awns; so they agree together in all these characters, although
+very various in their roots, stems and leaves; these Geraniums, I say,
+would almost induce a botanist to believe that the species of one
+<i>genus</i> in vegetables are only so many different plants as there
+have been different associations with the flowers of one species, and
+consequently a <i>genus</i> is nothing else than a number of plants
+sprung from the same mother by different fathers. But whether all
+these species be the offspring of time; whether, in the beginning
+of all things, the Creator limited the number of future species, I
+dare not presume to determine. I am, however, convinced this mode of
+multiplying plants does not interfere with the system or general scheme
+of nature; as I daily observe that insects, which live upon one species
+of a particular <i>genus</i>, are contented with another of the same
+<i>genus</i>.</p>
+
+<p>A person who has once seen the <i>Achyranthes aspera</i>, and remarked
+its spike, the parts of its flower, its small and peculiarly formed
+nectaria, as well as its calyces bent backwards as the fruit ripens,
+would think it very easy at any time to distinguish these flowers
+from all others in the universe; but when he finds the flowers of
+<i>Achyranthes indica</i> agreeing with them even in their minutest
+parts, and at the same time observes the large, thick, obtuse,
+undulated leaves of the last-mentioned plant, he will think he sees
+<i>Achyranthes aspera</i> masked in the foliage of <i>Xanthium
+strumarium</i>. But I forbear to mention any more instances.</p>
+
+<p>Here is a new employment for botanists, to attempt the production of
+new species of vegetables by scattering the pollen of various plants
+over various widowed females. And if these remarks should meet with
+a favourable reception, I shall be the more induced to dedicate what
+remains of my life to such experiments, which recommend themselves by
+being at the same time agreeable and useful. I am persuaded by many
+considerations that those numerous and most<span class="pagenum" id="Page_88">[Pg 88]</span> valuable varieties of
+plants which are used for culinary purposes, have been produced in
+this manner, as the several kinds of cabbages, lettuces, etc.; and I
+apprehend this is the reason of their not being changed by a difference
+of soil. Hence I cannot give my assent to the opinion of those who
+imagine all varieties to have been occasioned by change of soil; for,
+if this were the case, the plants would return to their original form,
+if removed again to their original situation.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_13" href="#FNanchor_13" class="label">[13]</a>
+From the <i>Publications of the Linnaean Society</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_89">[Pg 89]</span></p>
+<h2 class="nobreak" id="XII">XII<br>
+JOSEPH BLACK<br>
+1728-1799</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Joseph Black, born in 1728 at Bordeaux, France, was educated in
+Belfast and at the University of Glasgow. Before he took his M.D.
+degree he showed that alkalies were formed, not by their absorbing
+“phlogiston,” but by their having carbonic acid gas, or “fixed air,”
+as a component. In 1753 he was appointed lecturer on chemistry at
+Glasgow, and in 1776 became professor of chemistry at Edinburgh. In
+1763 he announced his discovery of latent heat, a principle which
+has been of great practical value. He died in Edinburgh, December 6,
+1799.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE DISCOVERY OF CARBONIC ACID GAS<a id="FNanchor_14" href="#Footnote_14" class="fnanchor">[14]</a></p>
+
+<p>Hoffman, in one of his observations, gives the history of a powder
+called <i>Magnesia Alba</i>, which has been long used, and esteemed as
+a mild and tasteless purgative; but the method of preparing it was not
+generally known before he made it public.</p>
+
+<p>It was originally obtained from a liquor called the <i>Mother of
+nitre</i>, which is produced in the following manner:</p>
+
+<p>Salt-petre is separated from the brine which first affords it, or from
+the water with which it is washed out of nitrous earths, by the process
+commonly used in crystallizing salts. In this process, the brine is
+gradually diminished, and at length reduced to a small quantity of
+an unctuous bitter saline liquor, affording no more salt-petre by
+evaporation, but, if urged with a brisk fire, drying up into a confused
+mass, which attracts water strongly, and becomes fluid again when
+exposed to the open air.</p>
+
+<p>To this liquor the workmen have given the name of the <i>Mother of<span class="pagenum" id="Page_90">[Pg 90]</span>
+nitre</i>; and Hoffman, finding it composed of the magnesia united
+to an acid, obtained a separation of these, either by exposing the
+compound to a strong fire, in which the acid was dissipated, and the
+magnesia remained behind, or by the addition of an alkali, which
+attracted the acid to itself: and this last method he recommends as
+the best. He likewise makes an inquiry into the nature and virtues
+of the powder thus prepared; and observes, that it is an absorbent
+earth, which joins readily with all acids, and must necessarily destroy
+any acidity it meets in the stomach; but that its purgative power is
+uncertain, for sometimes it has not the least effect of that kind.
+As it is a mere insipid earth, he rationally concludes it to be a
+purgative only when converted into a sort of neutral salt by an acid
+in the stomach, and that its effect is therefore proportional to the
+quantity of this acid.</p>
+
+<p>Although magnesia appears from this history of it, to be a very
+innocent medicine; yet, having observed that some hypochondriacs,
+who used it frequently, were subject to flatulencies and spasms, he
+seems to have suspected it of some noxious quality. The circumstances,
+however, which gave rise to his suspicion, may very possibly have
+proceeded from the imprudence of his patients; who, trusting too much
+to magnesia (which is properly a palliative in that disease) and
+neglecting the assistance of other remedies, allowed their disorder
+to increase upon them. It may, indeed, be alleged that magnesia, as a
+purgative, is not the most eligible medicine for such constitutions, as
+they agree best with those that strengthen, stimulate, and warm; which
+the saline purges, commonly used, are not observed to do. But there
+seems at last to be no objection to its use, when children are troubled
+with an acid in their stomach: for, gentle purging, in this case, is
+very proper; and it is often more conveniently procured by means of
+magnesia, than of any other medicine, on account of its being entirely
+insipid.</p>
+
+<p>The above-mentioned Author, observing, some time after, that a bitter
+saline liquor, similar to that obtained from the brine of salt-petre,
+was likewise produced by the evaporation of those waters which contain
+common salt, had the curiosity to try if this would also yield a
+magnesia. The experiment succeeded: And he thus found out another
+process for obtaining this powder; and at the same time<span class="pagenum" id="Page_91">[Pg 91]</span> assured
+himself, by experiments, that the product from both was exactly the
+same.</p>
+
+<p>My curiosity led me, some time ago, to inquire more particularly into
+the nature of magnesia, and especially to compare its properties with
+those of the other absorbent earths, of which there plainly appeared to
+me to be very different kinds, although commonly confounded together
+under one name. I was indeed led to this examination of the absorbent
+earths, partly by the hope of discovering a new sort of lime and
+lime-water, which might possibly be a more powerful solvent of the
+stone, than that commonly used; but was disappointed in my expectations.</p>
+
+<p>I have had no opportunity of seeing Hoffman’s first magnesia, or the
+liquor from which it is prepared, and have therefore been obliged to
+make my experiments upon the second.</p>
+
+<p>In order to prepare it, I at first employed the bitter saline liquor
+called <i>bittern</i>, which remains in the pans after the evaporation
+of sea-water. But as that liquor is not always easily procured, I
+afterwards made use of a salt called Epsom salt, which is separated
+from the bittern by crystallization, and is evidently composed of
+magnesia and the vitriolic acid.</p>
+
+<p>There is likewise a spurious kind of Glauber salt, which yields plenty
+of magnesia, and seems to be no other than Epsom salt, of sea-water
+reduced to crystals of a larger size. And common salt also affords
+a small quantity of this powder; because, being separated from the
+bittern by one hasty crystallization only, it necessarily contains a
+portion of that liquor.</p>
+
+<p>Those who would prepare a magnesia from Epsom salt, may use the
+following process:</p>
+
+<p>Dissolve equal quantities of Epsom salt, and of pearl ashes,
+separately, in a sufficient quantity of water; purify each solution
+from its dregs, and mix them accurately together by violent agitation.
+Then make them just to boil over a brisk fire.</p>
+
+<p>Add now to the mixture, three or four times its quantity of hot water;
+after a little agitation, allow the magnesia to settle to the bottom,
+and decant off as much of the water as possible. Pour on the same
+quantity of cold water; and, after settling, decant it off in the
+same manner. Repeat this washing with the cold water ten or twelve<span class="pagenum" id="Page_92">[Pg 92]</span>
+times, or even oftener, if the magnesia be required perfectly pure for
+chemical experiments.</p>
+
+<p>When it is sufficiently washed, the water may be strained and squeezed
+from it in a linen cloth; for very little of the magnesia passes
+through.</p>
+
+<p>The alkali in the mixture, uniting with the acid, separates it from
+the magnesia; which, not being of itself soluble in water, must
+consequently appear immediately under a solid form. But the powder
+which thus appears is not entirely magnesia; part of it is the neutral
+salt formed from the union of the acid and alkali. This neutral salt
+is found, upon examination, to agree in all respects with vitriolated
+tartar, and requires a large quantity of hot water to dissolve it. As
+much of it is therefore dissolved as the water can take up; the rest
+is dispersed through the mixture, in the form of a powder. Hence the
+necessity of washing the magnesia with so much trouble; for the first
+effusion of hot water is intended to dissolve the whole of the salt,
+and the subsequent additions of cold water to wash away this solution.</p>
+
+<p>The caution given, of boiling the mixture, is not unnecessary: if it
+be neglected, the whole of the magnesia is not accurately separated at
+once; and, by allowing it to rest for some time, that powder concretes
+into minute grains, which, when viewed with the microscope, appear to
+be assemblages of needles diverging from a point. This happens more
+especially when the solutions of the Epsom salt, and of the alkali,
+are diluted with too much water before they are mixed together. Thus,
+if a dram of Epsom salt, and of salt of tartar, be dissolved each in
+four ounces of water, and be mixed, and then allowed to rest three or
+four days, the whole of the magnesia will be formed into these grains.
+Or, if we filtrate the mixture soon after it is made, and heat the
+clear liquor which passes through, it will become turbid, and deposit a
+magnesia.</p>
+
+<p class="space-above2">
+An ounce of magnesia was exposed in a crucible, for about an hour, to
+such a heat as is sufficient to melt copper. When taken out, it weighed
+three drams and one scruple, or had lost 7-12 of its former weight.</p>
+
+<p>I repeated, with the magnesia prepared in this manner, most of<span class="pagenum" id="Page_93">[Pg 93]</span> those
+experiments I had already made upon it before calcination, and the
+result was as follows:—</p>
+
+<p>It dissolves in all the acids, and with these composes salts exactly
+similar to those described in the first set of experiments: But, what
+is particularly to be remarked, it is dissolved without any the least
+degree of effervescence.</p>
+
+<p>It slowly precipitates the corrosive sublimate of mercury, in the form
+of a black powder.</p>
+
+<p>It separates the volatile alkali in salt-ammoniac from the acid, when
+it is mixed with a warm solution of that salt. But it does not separate
+an acid from a calcareous earth, nor does it introduce the least change
+upon lime-water.</p>
+
+<p>Lastly, when a dram of it is digested with an ounce of water in a
+bottle for some hours, it does not make any the least change in the
+water. The magnesia, when dried, is found to have gained ten grains;
+but it neither effervesces with acids, nor does it sensibly affect
+lime-water.</p>
+
+<p>Observing magnesia to lose such a remarkable proportion of its weight
+in the fire, my next attempts were directed to the investigation of
+this volatile part; and, among other experiments, the following seemed
+to throw some light upon it:—</p>
+
+<p>Three ounces of magnesia were distilled in a glass retort and receiver,
+the fire being gradually increased until the magnesia was obscurely red
+hot. When all was cool, I found only five drams of a whitish water in
+the receiver, which had a faint smell of the spirit of hartshorn, gave
+a green colour to the juice of violets, and rendered the solutions of
+corrosive sublimate, and of silver, very slightly turbid. But it did
+not sensibly effervesce with acids.</p>
+
+<p>The magnesia, when taken out of the retort, weighed an ounce, three
+drams, and thirty grains, or had lost more than half of its weight. It
+still effervesced pretty briskly with acids, though not so strongly as
+before this operation.</p>
+
+<p>The fire should have been raised here to the degree requisite for
+the perfect calcination of magnesia. But, even from this imperfect
+experiment, it is evident, that, of the volatile parts contained in
+that powder, a small proportion only is water; the rest cannot, it
+seems, be retained in vessels, under a visible form. Chemists have
+often observed in their distillations that part of a body has vanished
+from<span class="pagenum" id="Page_94">[Pg 94]</span> their senses notwithstanding the utmost care to retain it; and
+they have always found, upon further inquiry, that subtle part to be
+air, which having been imprisoned in the body, under a solid form, was
+set free, and rendered fluid and elastic by the fire. We may therefore
+safely conclude, that the volatile matter lost in the calcination of
+magnesia, is mostly air; and hence the calcined magnesia does not emit
+air, or make an effervescence when mixed with acids.</p>
+
+<p>The water, from its properties, seems to contain a small portion of
+volatile alkali, which was probably formed from the earth, air and
+water, from some of these combined together; and perhaps also from a
+small quantity of inflammable matter, which adhered accidently to the
+magnesia. Whenever chemists meet with this salt, they are inclined to
+ascribe its origin to some animal or putrid vegetable substance; and
+this they have always done, when they obtained it from the calcareous
+earths, all of which afford a small quantity of it. There is, however,
+no doubt, that it can sometimes be produced independently of any such
+mixture, since many fresh vegetables, and tartar, afford a considerable
+quantity of it. And how can it, in the present instance, be supposed,
+that any animal or vegetable matter adhered to the magnesia, while it
+was dissolved by an acid, separated from this by an alkali, and washed
+with so much water?</p>
+
+<p>Two drams of magnesia were calcined in a crucible, in the manner
+described above, and thus reduced to two scruples and twelve grains.
+This calcined magnesia was dissolved in a sufficient quantity of spirit
+of vitriol, and then again separated from the acid by the addition of
+an alkali, of which a large quantity is necessary for this purpose. The
+magnesia being very well washed and dried, weighed one dram and fifty
+grains. It effervesced violently, or emitted a large quantity of air,
+when thrown into acids; formed a red powder, when mixed with a solution
+of sublimate; separated the calcareous earths from an acid, and
+sweetened lime-water; and had thus recovered all those properties which
+it had but just now lost by calcination. Nor had it only recovered
+its original properties, but acquired besides an addition of weight,
+nearly equal to what had been lost in the fire; and as it is found to
+effervesce with acids, part of the addition must certainly be air.</p>
+
+<p>This air seems to have been furnished by the alkali, from which it
+was separated by the acid; for Dr. Hales has clearly proved, that<span class="pagenum" id="Page_95">[Pg 95]</span>
+alkaline salts contain a large quantity of fixed air, which they emit
+in great abundance when joined to a pure acid. In the present case, the
+alkali is really joined to an acid, but without any visible emission
+of air; and yet the air is not retained in it; for the neutral salt,
+into which it is converted, is the same in quantity, and in every other
+respect, as if the acid employed had not been previously saturated with
+magnesia, but offered to the alkali in its pure state, and had driven
+the air out of it in their conflict. It seems therefore evident, that
+the air was forced from the alkali by the acid, and lodged itself in
+the magnesia.</p>
+
+<p>These considerations led me to try a few experiments, whereby I might
+know what quantity of air is expelled from an alkali, or from magnesia,
+by acids.</p>
+
+<p>Two drams of a pure fixed alkaline salt, and an ounce of water, were
+put into a Florentine flask, which, together with its contents, weighed
+two ounces and two drams. Some oil of vitriol diluted with water was
+dropped in, until the salt was exactly saturated; which it was found to
+be, when two drams, two scruples and three grains of this acid had been
+added. The phial with its contents now weighed two ounces, four drams
+and fifteen grains. One scruple, therefore, and eight grains, were lost
+during the ebullition; of which a trifling portion may be water, or
+something of the same kind; the rest is air.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_14" href="#FNanchor_14" class="label">[14]</a>
+From <i>Experiments upon Magnesia, Quicklime, and some
+other Alkaline Substances</i> (1775).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_96">[Pg 96]</span></p>
+<h2 class="nobreak" id="XIII">XIII<br>
+JOSEPH PRIESTLEY<br>
+1733-1804</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Joseph Priestley, born in Yorkshire, England, March 13, 1733, was
+a Unitarian minister. In 1774 he discovered oxygen, which he called
+“dephlogisticated air.” Because of his liberal political ideas he was
+persecuted by his countrymen, and in 1794 emigrated to Northumberland,
+Pennsylvania, where he lived until his death, February 6, 1804.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE DISCOVERY OF OXYGEN<a id="FNanchor_15" href="#Footnote_15" class="fnanchor">[15]</a></p>
+
+<p>Presently, after my return from abroad, I went to work upon the
+<i>mercurius calcinatus</i>, which I had procured from Mr. Cadet; and,
+with a very moderate degree of heat, I got from about one-fourth of
+an ounce of it, an ounce-measure of air, which I observed to be not
+readily imbibed, either by the substance itself from which it had
+been expelled (for I suffered them to continue a long time together
+before I transferred the air to any other place) or by water, in which
+I suffered this air to stand a considerable time before I made any
+experiment upon it.</p>
+
+<p>In this air, as I had expected, a candle burned with a vivid flame; but
+what I observed new at this time (November 19), and which surprised me
+no less than the fact I had discovered before, was, that, whereas a
+few moments agitation in water will deprive the modified nitrous air
+of its property of admitting a candle to burn in it; yet, after more
+than ten times as much agitation as would be sufficient to produce this
+alteration in the nitrous air, no sensible change was produced in this.
+A candle still burned in it with a strong flame; and it<span class="pagenum" id="Page_97">[Pg 97]</span> did not, in
+the least, diminish common air, which I have observed that nitrous air,
+in this state, in some measure does.</p>
+
+<p>But I was much more surprised, when, after two days, in which this air
+had continued in contact with water (by which it was diminished about
+one-twentieth of its bulk) I agitated it violently in water about five
+minutes, and found that a candle still burned in it as well as in
+common air. The same degree of agitation would have made phlogisticated
+nitrous air fit for respiration indeed, but it would certainly have
+extinguished a candle.</p>
+
+<p>These facts fully convinced me, that there must be a very material
+difference between the constitution of air from <i>mercurius
+calcinatus</i>, and that of phlogisticated nitrous air, notwithstanding
+their resemblance in some particulars. But though I did not doubt that
+the air from <i>mercurius calcinatus</i> was fit for respiration, after
+being agitated in water, as every kind of air without exception, on
+which I have tried the experiment, had been, I still did not suspect
+that it was respirable in the first instance; so far was I from having
+any idea of this air being, what it really was, much superior, in this
+respect, to the air of the atmosphere.</p>
+
+<p>In this ignorance of the real nature of this kind of air, I continued
+from this time (November) to the 1st of March following; having, in the
+meantime, been intent upon my experiments on the vitriolic acid air
+above recited, and the various modifications of air produced by spirit
+of nitre, an account of which will follow. But in the course of this
+month, I not only ascertained the nature of this kind of air, though
+very gradually, but was led to it by the complete discovery of the
+constitution of the air we breathe.</p>
+
+<p>Till this 1st of March, 1775, I had so little suspicion of the air from
+<i>mercurius calcinatus</i>, &amp;c., being wholesome, that I had not even
+thought of applying it to the test of nitrous air; but thinking (as my
+reader must imagine I frequently must have done) on the candle burning
+in it after long agitation in water, it occurred to me at last to make
+the experiment; and putting one measure of nitrous air to two measures
+of this air, I found, not only that it was diminished, but that it was
+diminished quite as much as common air, and that the redness of the
+mixture was likewise equal to that of a similar mixture of nitrous and
+common air.</p>
+
+<p>After this I had no doubt but that the air from <i>mercurius
+calcinatus</i><span class="pagenum" id="Page_98">[Pg 98]</span> was fit for respiration, and that it had all the other
+properties of genuine common air. But I did not take notice of what I
+might have observed, if I had not been so fully possessed by the notion
+of there being no air better than common air, that the redness was
+really deeper, and the diminution something greater than common air
+would have admitted.</p>
+
+<p>Moreover, this advance in the way of truth, in reality, threw me back
+into error, making me give up the hypothesis I had first formed, viz.
+that the <i>mercurius calcinatus</i> had extracted spirit of nitre
+from the air; for I now concluded, that all the constituent parts of
+the air were equally, and in their proper proportion, imbibed in the
+preparation of this substance, and also in the process of making red
+lead. For at the same time that I made the above mentioned experiment
+on the air from <i>mercurius calcinatus</i>, I likewise observed that
+the air which I had extracted from red lead, after the fixed air was
+washed out of it, was of the same nature, being diminished by nitrous
+air like common air: but, at the same time, I was puzzled to find that
+air from the red precipitate was diminished in the same manner, though
+the process for making this substance is quite different from that of
+making the two others. But to this circumstance I happened not to give
+much attention.</p>
+
+<p>I wish my reader be not quite tired with the frequent repetition of the
+word surprise, and others of similar import; but I must go on in that
+style a little longer. For the next day I was more surprised than ever
+I had been before, with finding that, after the above-mentioned mixture
+of nitrous air and the air from <i>mercurius calcinatus</i>, had stood
+all night, (in which time the whole diminution must have taken place;
+and, consequently, had it been common air, it must have been made
+perfectly noxious, and entirely unfit for respiration or inflammation)
+a candle burned in it, and even better than in common air.</p>
+
+<p>I cannot, at this distance of time, recollect what it was that I had in
+view in making this experiment; but I know I had no expectation of the
+real issue of it. Having acquired a considerable degree of readiness in
+making experiments of this kind, a very slight and evanescent motive
+would be sufficient to induce me to do it. If, however, I had not
+happened, for some other purpose, to have had a lighted candle before
+me I should probably never have made the trial; and the whole<span class="pagenum" id="Page_99">[Pg 99]</span> train
+of my future experiments relating to this kind of air might have been
+prevented.</p>
+
+<p>Still, however, having no conception of the real cause of this
+phenomenon, I considered it as something very extraordinary; but as
+a property that was peculiar to air that was extracted from these
+substances, and adventitious; and I always spoke of the air to my
+acquaintance as being substantially the same thing with common air.</p>
+
+<p>I particularly remember my telling Dr. Price, that I was myself
+perfectly satisfied of its being common air, as it appeared to be so
+by the test of nitrous air; though, for the satisfaction of others, I
+wanted a mouse to make the proof quite complete.</p>
+
+<p>On the 8th of this month I procured a mouse, and put it into a glass
+vessel, containing two ounce-measures of the air from <i>mercuris
+calcinatus</i>. Had it been common air, a full-grown mouse, as this
+was, would have lived in it about a quarter of an hour. In this air,
+however, my mouse lived a full half hour; and though it was taken out
+seemingly dead, it appeared to have been only exceedingly chilled; for,
+upon being held to fire, it presently revived, and appeared not to have
+received any harm from the experiment.</p>
+
+<p>By this I was confirmed in my conclusion, that the air extracted
+from <i>mercurius calcinates</i>, &amp;c., was, at least, as good as
+common air; but I did not certainly conclude that it was any better;
+because, though one mouse would live only a quarter of an hour in a
+given quantity of air, I knew it was not impossible but that another
+mouse might have lived in it half an hour; so little accuracy is
+there in this method of ascertaining the goodness of air; and indeed
+I have never had recourse to it for my own satisfaction, since the
+discovery of that most ready, accurate, and elegant test that nitrous
+air furnishes. But in this case I had a view to publishing the most
+generally satisfactory account of my experiments that the nature of the
+thing would admit of.</p>
+
+<p>This experiment with the mouse, when I had reflected upon it some time,
+gave me so much suspicion that the air into which I had put it was
+better than common air, that I was induced, the day after, to apply
+the test of nitrous air to a small part of that very quantity of air
+which the mouse had breathed so long; so that, had it been common air,
+I was satisfied it must have been very nearly, if not altogether, as<span class="pagenum" id="Page_100">[Pg 100]</span>
+noxious as possible, so as not to be affected by nitrous air; when,
+to my surprise again, I found that though it had been breathed so
+long, it was still better than common air. For after mixing it with
+nitrous air, in the usual proportion of two to one, it was diminished
+in the proportion of four and one-half to three and one-half; that
+is, the nitrous air had made it two-ninths less than before, and this
+in a very short space of time; whereas I had never found that, in the
+longest time, any common air was reduced more than one-fifth of its
+bulk by any proportion of nitrous air, nor more than one-fourth by any
+phlogistic process whatever. Thinking of this extraordinary fact upon
+my pillow, the next morning I put another measure of nitrous air to the
+same mixture, and, to my utter astonishment, found that it was farther
+diminished to almost one-half of its original quantity. I then put a
+third measure to it; but this did not diminish it any farther; but,
+however, left it one measure less than it was even after the mouse had
+been taken out of it.</p>
+
+<p>Being now fully satisfied that this air, even after the mouse had
+breathed it half an hour, was much better than common air; and having
+a quantity of it still left, sufficient for the experiment, viz. an
+ounce-measure and a half, I put the mouse into it; when I observed that
+it seemed to feel no shock upon being put into it, evident signs of
+which would have been visible, if the air had not been very wholesome;
+but that it remained perfectly at its ease another full half hour, when
+I took it out quite lively and vigorous. Measuring the air the next
+day, I found it to be reduced from one and one-half to two-thirds of an
+ounce-measure. And after this, if I remember well (for in my register
+of the day I only find it noted, that it was considerably diminished
+by nitrous air), it was nearly as good as common air. It was evident,
+indeed, from the mouse having been taken out quite vigorous, that the
+air could not have been rendered very noxious.</p>
+
+<p>For my farther satisfaction I procured another mouse, and putting it
+into less than two ounce-measures of air extracted from <i>mercurius
+calcinatus</i> and air from red precipitate (which, having found
+them to be of the same quality, I had mixed together) it lived
+three-quarters of an hour. But not having had the precaution to set the
+vessel in a warm place, I suspect that the mouse died of cold. However,
+as it had lived three times as long as it could probably have lived in
+the same quantity of common air, and I did not expect much accuracy<span class="pagenum" id="Page_101">[Pg 101]</span>
+from this kind of a test, I did not think it necessary to make any more
+experiments with mice.</p>
+
+<p>Being now fully satisfied of the superior goodness of this kind of air,
+I proceeded to measure that degree of purity, with as much accuracy
+as I could, by the test of nitrous air; and I began with putting one
+measure of nitrous air to two measures of this air, as if I had been
+examining common air; and now I observed that the diminution was
+evidently greater than common air would have suffered by the same
+treatment. A second measure of nitrous air reduced it to two-thirds
+of its original quantity, and a third measure to one-half. Suspecting
+that the diminution could not proceed much farther, I then added only
+half a measure of nitrous air, by which it was diminished still more;
+but not much, and another half-measure made it more than half of its
+original quantity; so that, in this case, two measures of this air took
+more than two measures of nitrous air, and yet remained less than half
+of what it was. Five measures brought it pretty exactly to its original
+dimensions.</p>
+
+<p>At the same time, air from the red precipitate was diminished in
+the same proportion as that from <i>mercurius calcinatus</i>, five
+measures of nitrous air being received by two measures of this without
+any increase of dimensions. Now as common air takes about one-half
+of its bulk of nitrous air, before it begins to receive any addition
+to its dimensions from more nitrous air, and this air took more than
+four half-measures before it ceased to be diminished by more nitrous
+air, and even five half-measures made no addition to its original
+dimensions, I conclude that it was between four and five times as good
+as common air. It will be seen that I have since procured air better
+than this, even between five and six times as good as the best common
+air that I have ever met with.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_15" href="#FNanchor_15" class="label">[15]</a>
+From <i>Experiments and Observations on Different Kinds
+of Air</i>, Vol. II, (1775).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_102">[Pg 102]</span></p>
+<h2 class="nobreak" id="XIV">XIV<br>
+HENRY CAVENDISH<br>
+1731-1810</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Henry Cavendish, the discoverer of hydrogen, was born of English
+parents in Nice, October 10, 1731. He studied at Cambridge University,
+England, and in 1760 joined the Royal Society, devoting his great
+fortune to the advancement of science. He discovered hydrogen in 1766,
+and later, using Priestley’s discovery of oxygen, found that the two
+gases combined under certain physical conditions to produce water.
+Besides his studies in chemistry, he made some interesting discoveries
+in physics. In 1783 he proposed the theory that heat was a motion
+rather than a substance; and in 1798 he computed the density of the
+earth to be about five and a half times that of water. He died at
+Clapham, February 24, 1810.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE COMBINATION OF HYDROGEN AND OXYGEN INTO WATER<a id="FNanchor_16" href="#Footnote_16" class="fnanchor">[16]</a></p>
+
+<p>In Dr. Priestley’s last volume of experiments is related an experiment
+of Mr. Warltire’s, in which it is said that, on firing a mixture of
+common and inflammable air by electricity in a close copper vessel
+holding about three pints, a loss of weight was always perceived, on
+an average about two grains, though the vessel was stopped in such a
+manner that no air could escape by the explosion. It is also related,
+that on repeating the experiment in glass vessels, the inside of the
+glass, though clean and dry before, immediately became dewy; which
+confirmed an opinion he had long entertained, that common air deposits
+its moisture by phlogistication. As the latter experiment seemed likely
+to throw great light on the subject I had in view, I thought it well
+worth examining more closely. The first experiment also, if there was
+no mistake in it, would be very extraordinary and<span class="pagenum" id="Page_103">[Pg 103]</span> curious; but it did
+not succeed with me; for though the vessel I used held more than Mr.
+Warltire’s, namely, 24,000 grains of water, and though the experiment
+was repeated several times with different proportions of common and
+inflammable air, I could never perceive a loss of weight of more than
+one-fifth of a grain, and commonly none at all. It must be observed,
+however, that though there were some of the experiments in which it
+seemed to diminish a little in weight, there were none in which it
+increased.</p>
+
+<p class="space-below2">
+In all the experiments, the inside of the glass globe became dewy,
+as observed by Mr. Warltire; but not the least sooty matter could be
+perceived. Care was taken in all of them to find how much the air was
+diminished by the explosion, and to observe its test. The result is as
+follows, the bulk of the inflammable air being expressed in decimals of
+the common air:</p>
+
+<table class="autotable">
+<thead><tr>
+<th class="tdc bb bt br"><br>Common<br>
+Air</th>
+<th class="tdc bb bt br"><br>Inflammable<br>
+Air</th>
+<th class="tdc bb bt br">Diminution</th>
+<th class="tdc bb bt br">Air Remaining<br>
+after the<br>
+Explosion</th>
+<th class="tdc bb bt br">Test of this<br>
+Air in the<br>
+First Method</th>
+<th class="tdc bb bt">Standard</th>
+</tr>
+</thead>
+<tbody><tr>
+<td class="tdc br">1</td>
+<td class="tdc br">1.241</td>
+<td class="tdc br">.686</td>
+<td class="tdc br">1.555</td>
+<td class="tdc br">.055</td>
+<td class="tdc">.0</td>
+</tr><tr>
+<td class="tdc br">&nbsp;</td>
+<td class="tdc br">1.955</td>
+<td class="tdc br">.642</td>
+<td class="tdc br">1.423</td>
+<td class="tdc br">.063</td>
+<td class="tdc">.0</td>
+</tr><tr>
+<td class="tdc br">&nbsp;</td>
+<td class="tdc br">.706</td>
+<td class="tdc br">.647</td>
+<td class="tdc br">1.059</td>
+<td class="tdc br">.066</td>
+<td class="tdc">.0</td>
+</tr><tr>
+<td class="tdc br">&nbsp;</td>
+<td class="tdc br">.423</td>
+<td class="tdc br">.612</td>
+<td class="tdc br">.811</td>
+<td class="tdc br">.097</td>
+<td class="tdc">.03</td>
+</tr><tr>
+<td class="tdc br">&nbsp;</td>
+<td class="tdc br">.331</td>
+<td class="tdc br">.476</td>
+<td class="tdc br">.855</td>
+<td class="tdc br">.339</td>
+<td class="tdc">.27</td>
+</tr><tr>
+<td class="tdc bb br">&nbsp;</td>
+<td class="tdc bb br">.206</td>
+<td class="tdc bb br">.294</td>
+<td class="tdc bb br">.912</td>
+<td class="tdc bb br">.648</td>
+<td class="tdc bb">.58</td>
+</tr>
+</tbody>
+</table>
+
+<p class="space-above2">
+In these experiments the inflammable air was procured from zinc, as it
+was in all my experiments, except where otherwise expressed: but I made
+two more experiments, to try whether there was any difference between
+the air from zinc and that from iron, the quantity of inflammable air
+being the same in both, namely, 0.331 of the common; but I could not
+find any difference to be depended on between the two kinds of air,
+either in the diminution which they suffered by the explosion, or the
+test of the burnt air.</p>
+
+<p>From the fourth experiment it appears, that 423 measures of inflammable
+air are nearly sufficient to phlogisticate completely 1000 of common
+air; and that the bulk of the remaining air after the explosion is then
+very little more than four-fifths of the common air employed; so that
+as common air cannot be reduced to a much less bulk than that by any
+method of phlogistication, we may safely conclude,<span class="pagenum" id="Page_104">[Pg 104]</span> that when they are
+mixed in this proportion, and exploded, almost all the inflammable air,
+and about one-fifth part of the common air, lose their elasticity, and
+are condensed into the dew which lines the glass.</p>
+
+<p>The better to examine the nature of this dew, 500,000 grain measures
+of inflammable air were burnt with about two and one-half times the
+quantity of common air, and the burnt air made to pass through a glass
+cylinder eight feet long and three-quarters of an inch in diameter,
+in order to deposit the dew. The two airs were conveyed slowly into
+this cylinder by separate copper pipes, passing through a brass plate
+which stopped up the end of the cylinder; and as neither inflammable
+nor common air can burn by themselves, there was no danger of the flame
+spreading into the magazines from which they were conveyed. Each of
+these magazines consisted of a large tin vessel, inverted into another
+vessel just big enough to receive it. The inner vessel communicated
+with the copper pipe, and the air was forced out of it by pouring water
+into the outer vessel; and in order that the quantity of common air
+expelled should be two and one-half times that of the inflammable, the
+water was let into the outer vessels by two holes in the bottom of the
+same tin pan, the hole which conveyed the water into that vessel in
+which the common air was confined being two and one-half times as big
+as the other.</p>
+
+<p>In trying the experiment, the magazines being first filled with their
+respective airs, the glass cylinder was taken off, and water let, by
+the two holes, into the outer vessel, till the airs began to issue from
+the ends of the copper pipes; they were then set on fire by a candle,
+and the cylinder put on again in its place. By this means upwards of
+135 grains of water were condensed in the cylinder, which had no taste
+nor smell, and which left no sensible sediment when evaporated to
+dryness; neither did it yield any pungent smell during evaporation; in
+short, it seemed pure water.</p>
+
+<p>In my first experiment, the cylinder near that part where the air
+was fired was a little tinged with sooty matter, but very slightly
+so; and that little seemed to proceed from the putty with which the
+apparatus was luted, and which was heated by the flame; for in another
+experiment, in which it is contrived so that the luting should not be
+much heated, scarce any sooty tinge could be perceived.</p>
+
+<p>By the experiments with the globe it appeared, that when inflammable<span class="pagenum" id="Page_105">[Pg 105]</span>
+and common air are exploded in a proper proportion, almost all the
+inflammable air, and nearly one-fifth of the common air, lose their
+elasticity, and are condensed into dew. And by this experiment it
+appears, that this dew is plain water, and consequently that almost all
+the inflammable air and about one-fifth of the common air, are turned
+into pure water.</p>
+
+<p>In order to examine the nature of the matter condensed on firing a
+mixture of dephlogisticated and inflammable air, I took a glass globe
+holding 8,800 grain measures, furnished with a brass cock and an
+apparatus for firing air by electricity. This globe was well exhausted
+by an air-pump, and then filled with a mixture of inflammable and
+dephlogisticated air, by shutting the cock, fastening a bent glass tube
+to its mouth, and letting up the end of it into a glass jar inverted
+into water, and containing a mixture of 19,500 grain measures of
+dephlogisticated air, and 37,000 of inflammable; so that, upon opening
+the cock, some of this mixed air rushed through the bent tube, and
+filled the globe. The cock was then shut, and the included air fired by
+electricity, by which means almost all of it lost its elasticity. The
+cock was then again opened, so as to let in more of the same air, to
+supply the place of that destroyed by the explosion, which was again
+fired, and the operation continued till almost the whole of the mixture
+was let into the globe and exploded. By this means, though the globe
+held not more than the sixth part of the mixture, almost the whole of
+it was exploded therein, without any fresh exhaustion of the globe.</p>
+
+<p>As I was desirous to try the quantity and test of this burnt air,
+without letting any water into the globe, which would have prevented my
+examining the nature of the condensed matter, I took a larger globe,
+furnished also with a stop cock, exhausted it by an air-pump, and
+screwed it on upon the cock of the former globe; upon which, by opening
+both cocks, the air rushed out of the smaller globe into the larger,
+till it became of equal density in both; then, by shutting the cock of
+the larger globe, unscrewing it again from the former, and opening it
+under water, I was enabled to find the quantity of the burnt air in
+it; and consequently, as the proportion which the contents of the two
+globes bore to each other was known, could tell the quantity of burnt
+air in the small globe before the communication was made between them.
+By this means the whole quantity of the burnt air was found to be 2,950
+grain measures; its standard was 1.85.</p>
+
+<p><span class="pagenum" id="Page_106">[Pg 106]</span></p>
+
+<p>The liquor condensed in the globe, in weight about thirty grains, was
+sensibly acid to the taste, and by saturation with fixed alkali, and
+evaporation, yielded near two grains of nitre; so that it consisted
+of water united to a small quantity of nitrous acid. No sooty matter
+was deposited in the globe. The dephlogisticated air used in this
+experiment was procured from red precipitate, that is, from a solution
+of quicksilver in spirit of nitre distilled till it acquires a red
+colour.</p>
+
+<p>As it was suspected, that the acid contained in the condensed liquor
+was no essential part of the dephlogisticated air, but was owing to
+some acid vapour which came over in making it and had not been absorbed
+by the water, the experiment was repeated in the same manner, with some
+more of the same air, which had been previously washed with water, by
+keeping it a day or two in a bottle with some water, and shaking it
+frequently; whereas that used in the preceding experiment had never
+passed through water, except in preparing it. The condensed liquor was
+still acid.</p>
+
+<p>The experiment was also repeated with dephlogisticated air, procured
+from red lead by means of oil of vitriol; the liquor condensed was
+acid, but by an accident I was prevented from determining the nature of
+the acid.</p>
+
+<p>I also procured some dephlogisticated air from the leaves of plants, in
+the manner of Doctors Ingenhousz and Priestley, and exploded it with
+inflammable air as before; the condensed liquor still continued acid,
+and of the nitrous kind.</p>
+
+<p>In all these experiments the proportion of inflammable air was such,
+that the burnt air was not much phlogisticated; and it was observed,
+that the less phlogisticated it was, the more acid was the condensed
+liquor. I therefore made another experiment, with some more of the
+same air from plants, in which the proportion of inflammable air was
+greater, so that the burnt air was almost completely phlogisticated,
+its standard being 1-10. The condensed liquor was then not at all acid,
+but seemed pure water; so that it appears, that with this kind of
+dephlogisticated air, the condensed liquor is not at all acid, when the
+two airs are mixed in such a proportion that the burnt air is almost
+completely phlogisticated, but is considerably so when it is not much
+phlogisticated.</p>
+
+<p>In order to see whether the same thing would obtain with air procured
+from red precipitate, I made two more experiments with that<span class="pagenum" id="Page_107">[Pg 107]</span> kind
+of air, the air in both being taken from the same bottle, and the
+experiment tried in the same manner, except that the proportions of
+inflammable air were different. In the first, in which the burnt air
+was almost completely phlogisticated, the condensed liquor was not at
+all acid. In the second, in which its standard was 1.86, that is, not
+much phlogisticated, it was considerably acid; so that with this air,
+as well as with that from plants, the condensed liquor contains, or is
+entirely free from, acid, according as the burnt air is less or more
+phlogisticated; and there can be little doubt but that the same rule
+obtains with any other kind of dephlogisticated air.</p>
+
+<p>In order to see whether the acid, formed by the explosion of
+dephlogisticated air obtained by means of the vitriolic acid, would
+also be of the nitrous kind, I procured some air from turbith mineral,
+and exploded it with inflammable air, the proportion being such that
+the burnt air was not much phlogisticated. The condensed liquor
+manifested an acidity, which appeared, by saturation with a solution
+of salt of tartar, to be of the nitrous kind; and it was found, by the
+addition of some <i>terra ponderosa salita</i>, to contain little or no
+vitriolic acid.</p>
+
+<p>When inflammable air was exploded with common air, in such a proportion
+that the standard of the burnt air was about 4-10, the condensed
+liquor was not in the least acid. There is no difference, however, in
+this respect between common air, and dephlogisticated air mixed with
+phlogisticated in such a proportion as to reduce it to the standard of
+common air; for some dephlogisticated air from red precipitate, being
+reduced to this standard by the addition of perfectly phlogisticated
+air, and then exploded with the same proportion of inflammable air as
+the common air was in the foregoing experiment, the condensed liquor
+was not in the least acid.</p>
+
+<p>From the foregoing experiments it appears, that when a mixture of
+inflammable and dephlogisticated air is exploded in such proportion
+that the burnt air is not much phlogisticated, the condensed liquor
+contains a little acid, which is always of the nitrous kind,
+whatever substance the dephlogisticated air is procured from; but
+if the proportion be such that the burnt air is almost entirely
+phlogisticated, the condensed liquor is not at all acid, but seems
+pure water, without any addition whatever; and as, when they are mixed
+in that proportion, very little air remains after the explosion,
+almost the whole being condensed, it follows that almost the whole
+of the inflammable and<span class="pagenum" id="Page_108">[Pg 108]</span> dephlogisticated air is converted into pure
+water. It is not easy, indeed, to determine from these experiments
+what proportion the burnt air, remaining after the explosions, bore to
+the dephlogisticated air employed, as neither the small nor the large
+globe could be perfectly exhausted of air, and there was no saying
+with exactness what quantity was left in them; but in most of them,
+after allowing for this uncertainty, the true quantity of burnt air
+seemed not more than 1-17 of the dephlogisticated air employed, or
+1-50 of the mixture. It seems, however, unnecessary to determine this
+point exactly, as the quantity is so small, that there can be little
+doubt but that it proceeds only from the impurities mixed with the
+dephlogisticated and inflammable air, and consequently that, if those
+airs could be obtained perfectly pure, the whole would be condensed.</p>
+
+<p>With respect to common air, and dephlogisticated air reduced by the
+addition of phlogisticated air to the standard of common air, the
+case is different; as the liquor condensed in exploding them with
+inflammable air, I believe I may say in any proportion, is not at all
+acid; perhaps because if they are mixed in such a proportion as that
+the burnt air is not much phlogisticated, the explosion is too weak,
+and not accompanied with sufficient heat.</p>
+
+<p>All the foregoing experiments, on the explosion of inflammable air
+with common and dephlogisticated airs, except those which relate to
+the cause of the acid found in the water, were made in the summer
+of the year 1781, and were mentioned by me to Dr. Priestley, who
+in consequence of it made some experiments of the same kind, as he
+relates in a paper printed in the preceding volume of the Transactions.
+During the last summer also, a friend of mine gave some account of
+them to M. Lavoisier, as well as of the conclusion drawn from them
+that dephlogisticated air is only water deprived of phlogiston; but
+at that time so far was M. Lavoisier from thinking any such opinion
+warranted, that, till he was prevailed upon to repeat the experiment
+himself, he found some difficulty in believing that nearly the whole
+of the two airs could be converted into water. It is remarkable, that
+neither of these gentlemen found any acid in the water produced by the
+combustion; which might proceed from the latter having burnt two airs
+in a different manner from what I did; and from the former having used
+a different kind of inflammable air, namely, that from charcoal, and
+perhaps having used a greater proportion of it.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_16" href="#FNanchor_16" class="label">[16]</a>
+From <i>Experiments with Airs—Transactions of Royal
+Society of London</i> (1784).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_109">[Pg 109]</span></p>
+<h2 class="nobreak" id="XV">XV<br>
+SIR WILLIAM HERSCHEL<br>
+1738-1822</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Sir William Herschel was born in Hanover, Germany, November 15,
+1738, the son of a bandmaster. At an early age he was compelled to
+earn his own living by playing in the band of the Hanoverian Guards.
+In 1766, after some years of financial straits, he found work as
+an organist at Bath. Studying languages and mathematics without
+assistance from tutors, he became interested in “the music of the
+spheres” which developed into a scientific attitude in astronomy. He
+managed, in spite of his poverty, to construct specula for a telescope
+and in 1781, with one of his own instruments, he discovered the
+planet Uranus, one of the most romantic discoveries in the history of
+science. Among his other discoveries were two of the satellites of
+Uranus, two more of Saturn, and the fact that the moon was without
+atmosphere; he also described many of the binary stars, discovered
+many nebulous stars (which prepared the way for the nebular theory of
+the universe), and made the inference from the movements of the stars
+that the whole solar system was rushing towards the constellation
+of Hercules. After his death, August 25, 1822, his son, Sir John
+Herschel, continued his work in astronomy.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+I<br>
+<br>
+THE DISCOVERY OF URANUS<a id="FNanchor_17" href="#Footnote_17" class="fnanchor">[17]</a><br>
+<br>
+ACCOUNT OF A COMET</p>
+
+<p>On Tuesday, the 13th of March, 1781, between 10 and 11 in the evening,
+while examining the small stars in the neighborhood of H<span class="pagenum" id="Page_110">[Pg 110]</span> Geminorum, I
+perceived one that appeared visibly larger than the rest: being struck
+with its uncommon magnitude, I compared it to H Geminorum and the
+small star in the quartile between Auriga and Gemini, and finding it
+so much larger than either of them, suspected it to be a comet. I was
+then engaged in a series of observations on the parallax of the fixed
+stars, which I hope soon to have the honour of laying before the R.S.,
+and those observations requiring very high powers, I had ready at hand
+several magnifiers of 227, 460, 932, 1536, 2010, &amp;c., all of which I
+have successfully used on that occasion. The power I had on when I
+first saw the comet was 227. From experience I knew that the diameters
+of the fixed stars are not proportionally magnified with higher powers,
+as the planets are; I therefore now put on the powers of 460 and 932,
+and found the diameter of the comet increased in proportion to the
+power, as it ought to be, on the supposition of its not being a fixed
+star, while the diameters of the stars to which I compared it, were not
+increased in the same ratio. Also, that the comet being magnified much
+beyond what its light would admit of, appeared hazy and ill-defined
+with these great powers, while the stars preserved that lustre and
+distinctness which from many thousand observations I knew they would
+retain. The sequel has shown that my surmises were well founded, this
+proving to be the comet we have lately observed.</p>
+
+
+<p class="nindc space-above2 space-below2">
+II<br>
+<br>
+ON THE NAME OF THE NEW PLANET</p>
+
+<p>By the observations of the most eminent astronomers in Europe it
+appears that the new star, which I had the honour of pointing out
+to them in March, 1781, is a primary planet of our solar system. A
+body so nearly related to us by its similar condition and situation,
+in the unbounded expanse of the starry heavens, must often be the
+subject of conversation, not only of astronomers, but of every lover
+of science in general. This consideration, then, makes it necessary
+to give it a name, by which it may be distinguished from the rest of
+the planets and fixed stars. In the fabulous ages of ancient times
+the appellations of Mercury, Venus, Mars, Jupiter, and Saturn, were
+given to the planets, as being the names of their principal heroes
+and<span class="pagenum" id="Page_111">[Pg 111]</span> divinities. In the present more philosophical era, it would
+hardly be allowable to have recourse to the same method, and call
+on Juno, Apollo, Pallas or Minerva, for a name to our new heavenly
+body. The first consideration in any particular event, or remarkable
+incident, seems to be its chronology; if in any future age it should be
+asked, when this last-found planet was discovered it would be a very
+satisfactory answer to say, “In the reign of King George the Third.” As
+a philosopher, then, the name of Georgium Sidus presents itself to me,
+as an appellation which will conveniently convey the information of the
+time and country where and when it was brought to view.</p>
+
+
+<p class="nindc space-above2 space-below2">
+III<br>
+<br>
+ON NEBULOUS STARS, PROPERLY SO CALLED</p>
+
+<p>In one of his late examinations of a space in the heavens, which
+he had not reviewed before, Dr. H. discovered a star of about the
+eighth magnitude, surrounded with a faintly luminous atmosphere, of a
+considerable extent. The phenomenon was so striking that he could not
+help reflecting on the circumstance that attended it, which appeared to
+be of a very instructive nature, and such as might lead to inferences
+which will throw a considerable light on some points relating to the
+construction of the heavens.</p>
+
+<p>Cloudy or nebulous stars have been mentioned by several astronomers;
+but this name ought not to be applied to the objects which they have
+pointed out as such; for, on examination, they proved to be either
+mere clusters of stars, plainly to be distinguished with his large
+instruments, or such nebulous appearances as might be reasonably
+supposed to be occasioned by a multitude of stars at a vast distance.
+The milky way itself consists entirely of stars, and by imperceptible
+degrees he was led on from most evident congeries of stars to other
+groups in which the lucid points were smaller, but still very plainly
+to be seen; and from them to such wherein they could but barely be
+suspected, till he arrived at last to spots in which no trace of a star
+was to be discerned. But then the gradations to these later were by
+such well-connected steps as left no room for doubt but that all these
+phenomena were equally occasioned by stars, variously dispersed in the
+immense expanse of the universe.</p>
+
+<p><span class="pagenum" id="Page_112">[Pg 112]</span></p>
+
+<p>When Dr. H. pursued these researches, he was in the situation of a
+natural philosopher who follows the various species of animals and
+insects from the height of their perfection down to the lowest ebb of
+life; when, arriving at the vegetable kingdom, he can scarcely point
+out to us the precise boundary where the animal ceases and the plant
+begins; and may even go so far as to suspect them not to be essentially
+different. But recollecting himself, he compares, for instance, one
+of the human species to a tree, and all doubt of the subject vanishes
+before him. In the same manner we pass through gentle steps from a
+coarse cluster of stars, such as the Pleiades, the Præserpe, the milky
+way, the cluster in the Crab, the nebula in Hercules, that near the
+preceding hip of Bootis, the 17th, 38th, 41st of the 7th class of his
+catalogues, the 10th, 20th, 35th of the 6th class, the 33d, 48th, 213th
+of the 1st, the 12th, 150th, 756th of the 2d, and the 18th, 140th,
+725th of the 3d, without any hesitation, till we find ourselves brought
+to an object such as the nebula in Orion, where we are still inclined
+to remain in the once adopted idea, of stars exceedingly remote,
+and inconceivably crowded, as being the occasion of that remarkable
+appearance. It seems, therefore, to require a more dissimilar object
+to set us right again. A glance like that of the naturalist, who casts
+his eye from the perfect animal to the perfect vegetable, is wanting to
+remove the veil from the mind of the astronomer. The object mentioned
+above is the phenomenon that was wanting for this purpose. View, for
+instance, the 19th cluster of the 6th class, and afterwards cast your
+eye on this cloudy star, and the result will be no less decisive than
+that of the naturalist alluded to. Our judgment will be, that the
+nebulosity about the star is not of a starry nature.</p>
+
+<p>But that we may not be too precipitate in these new decisions, let us
+enter more at large into the various grounds which induced us formerly
+to surmise, that every visible object, in the extended and distant
+heavens, was of the starry kind, and collate them with those which now
+offer themselves for the contrary opinion. It has been observed, on a
+former occasion, that all the smaller parts of other great systems,
+such as the planets, their rings and satellites, the comets, and such
+other bodies of the like nature as may belong to them, can never be
+perceived by us, on account of the faintness of light reflected from
+small opaque objects: in the present remarks, therefore, all these are
+to be entirely set aside.</p>
+
+<p><span class="pagenum" id="Page_113">[Pg 113]</span></p>
+
+<p>A well connected series of objects, such as mentioned above, has led
+us to infer that all nebulæ consist of stars. This being admitted, we
+were authorized to extend our analogical way of reasoning a little
+further. Many of the nebulæ had no other appearance than that whitish
+cloudiness, on the blue ground on which they seemed to be projected;
+and why the same cause should not be assigned to explain the most
+extensive nebulosities, as well as those that amounted only to a
+few minutes of a degree in size, did not appear. It could not be
+inconsistent to call up a telescopic milky way, at an immense distance,
+to account for such a phenomenon; and if any part of the nebulosity
+seemed detached from the rest, or contained a visible star or two,
+the probability of seeing a few near stars, apparently scattered over
+the far distant regions of myriads of sidereal collections, rendered
+nebulous by their distance, would also clear up these singularities.</p>
+
+<p>In order to be more easily understood in his remarks on the comparative
+disposition of the heavenly bodies, Dr. H. mentions some of the
+particulars which introduced the ideas of connection and disjunction:
+for these, being properly founded on an examination of objects that
+may be reviewed at any time, will be of considerable importance to the
+validity of what we may advance with regard to the lately discovered
+nebulous stars. On June 27, 1786, he saw a beautiful cluster of very
+small stars of various sizes, about 15' in diameter, and very rich
+of stars. On viewing this object, it is impossible to withhold our
+assent to the idea which occurs, that these stars are connected so far
+with one another as to be gathered together, within a certain space,
+of little extent when compared to the vast expanse of the heavens.
+As this phenomenon has been repeatedly seen in a thousand cases, Dr.
+H. thinks he may justly lay great stress on the idea of such stars
+being connected. On September 9, 1779, he discovered a very small star
+near <i>ε</i> Bootis. The question here occurring, whether it had any
+connection with <i>ε</i> or not, was determined in the negative; for,
+considering the number of stars scattered in a variety of places, it is
+very far from being uncommon, that a star at a great distance should
+happen to be nearly in a line drawn from the sun through <i>ε</i>, and
+thus constitute the observed double star. September 7, 1782, when Dr.
+H. first saw the planetary nebula near υ Aquarii, he pronounced it to
+be a system whose parts<span class="pagenum" id="Page_114">[Pg 114]</span> were connected together. Without entering
+into any kind of calculation, it is evident that a certain degree of
+light within a very small space, joined to the particular shape this
+object presents to us, which is nearly round, and even in its deviation
+consistent with regularity, being a little elliptical, ought naturally
+to give us the idea of a conjunction in the things that produce it.
+And a considerable addition to this argument may be derived from a
+repetition of the same phenomenon, in nine or ten more of a similar
+construction.</p>
+
+<p>When Dr. H. examined the cluster of stars, following the head of the
+Great Dog, he found on March 19, 1786, that there was within this
+cluster a round, resolvable nebula, of about 2' in diameter, and nearly
+an equal degree of light throughout. Here, considering that the cluster
+was free from nebulosity in other parts, and that many such clusters,
+as well as such nebulæ, exist in divers parts of the heavens, it seemed
+very probable that the nebula was unconnected with the cluster; and
+that a similar reason would as easily account for this appearance as
+it had resolved the phenomenon of the double star near e Bootis; that
+is, a casual situation of our sun and the two other objects nearly in
+a line. And though it may be rather more remarkable, that this should
+happen with two compound systems, which are not by far so numerous
+as single stars, we have, to make up for this singularity, a much
+larger space in which it may take place, the cluster being of a very
+considerable extent.</p>
+
+<p>On February 15, 1786, Dr. H. discovered that one of his planetary
+nebulæ had a spot in the centre, which was more luminous than the rest,
+and with long attention, a very bright, round, well-defined centre
+became visible. He remained not a single moment in doubt, but that
+the bright centre was connected with the rest of the apparent disc.
+October 6, 1785, he found a very bright, round nebula, of about 1-1/2'
+in diameter. It has a large, bright nucleus in the middle, which is
+undoubtedly connected with the luminous parts about it. And though
+we must confess, that if this phenomenon, and many more of the same
+nature, recorded in the catalogues of nebulæ, consist of clustering
+stars, we find ourselves involved in some difficulty to account for the
+extraordinary condensation of them about the centre; yet the idea of
+a connection between the outward parts and these very condensed ones
+within, is by no means lessened on that account.</p>
+
+<p><span class="pagenum" id="Page_115">[Pg 115]</span></p>
+
+<p>There is a telescopic milky way, which Dr. H. has traced out in the
+heavens in many sweeps made from the year 1783 to 1789. It takes up
+a space of more than 60 square degrees of the heavens, and there are
+thousands of stars scattered over it: among others, four that form a
+trapezium, and are situated in the well known nebula of Orion, which
+is included in the above extent. All these stars, as well as the four
+mentioned, he takes to be entirely unconnected with the nebulosity
+which involves them in appearance. Among them is also <i>δ</i> Orionis,
+a cloudy star, improperly so called by former astronomers; but it does
+not seem to be connected with the milkiness any more than the rest.</p>
+
+<p>Dr. H. now comes to some other phenomena, that, from their singularity,
+merit undoubtedly a very full discussion. Among the reasons which
+induced us to embrace the opinion that all very faint milky nebulosity
+ought to be ascribed to an assemblage of stars is, that we could
+not easily assign any other cause of sufficient importance for such
+luminous appearances, to reach us at the immense distance we must
+suppose ourselves to be from them. But if an argument of considerable
+force should now be brought forward, to show the existence of luminous
+matter, in a state of modification very different from the construction
+of a sun or star, all objections, drawn from our incapacity of
+accounting for new phenomena on old principles, he thinks, will lose
+their validity.</p>
+
+<p>Hitherto Dr. H. has been showing, by various instances in objects whose
+places are given, in what manner we may form ideas of connection, and
+its contrary, by an attentive inspection of them only; he now relates
+a series of observations, with remarks on them as they are delivered,
+from which he afterwards draws a few simple conclusions, that seem to
+be of considerable importance.</p>
+
+<p>October 16, 1784. A star of about the ninth magnitude, surrounded by a
+milky nebulosity, or chevelure, of about 3' in diameter. The nebulosity
+is very faint, and a little extended or elliptical, the extent being
+not far from the meridian, or a little from north preceding to south
+following. The chevelure involves a small star, which is about 1-1/2'
+north of the cloudy star; other stars of equal magnitude are perfectly
+free from this appearance. (R.A. 5h 57m 4s. P.D. 96° 22'). His present
+judgment concerning this remarkable object is, that the nebulosity
+belongs to the star which is situated<span class="pagenum" id="Page_116">[Pg 116]</span> in its centre. The small one, on
+the contrary, which is mentioned as involved, being one of many that
+are profusely scattered over this rich neighbourhood, he supposes to
+be quite unconnected with this phenomenon. A circle of 3' in diameter
+is sufficiently large to admit another small star, without any bias to
+the judgment he formed concerning the one in question. It might appear
+singular, that such an object should not have immediately suggested
+all the remarks contained in this paper; but about things that appear
+new we ought not to form opinions too hastily, and his observations
+on the construction of the heavens were then but entered on. In this
+case, therefore, it was the safest way to lay down a rule not to reason
+on the phenomena that might offer themselves, till he should be in
+possession of a sufficient stock of materials to guide his researches.</p>
+
+<p>October 16, 1784. A small star of about the 11th or 12th magnitude,
+very faintly affected with milky nebulosity; other stars of the same
+magnitude were perfectly free from this appearance. Another observation
+mentions five or six small stars within the space of 3 or 4', all very
+faintly affected in the same manner, and the nebulosity suspected to
+be a little stronger about each star. But a third observation rather
+opposes this increase of the faintly luminous appearance. (R. A. 6h
+Om 33s. P. D. 96° 13'). Here the connection between the stars and the
+nebulosity is not so evident as to amount to conviction; for which
+reason we shall pass on to the next.</p>
+
+<div class="tb">* * * * * </div>
+
+<p>November 25, 1788. A star of about the 9th magnitude, surrounded with
+very faint milky nebulosity; other stars of the same size are perfectly
+free from that appearance. Less than 1' in diameter. The star is either
+not round or double (a).</p>
+
+<p>March 23, 1789. A bright, considerably well-defined nucleus, with a
+very faint, small, round chevelure (b). The connection admits of no
+doubt; but the object is not perhaps of the same nature with those
+called cloudy stars.</p>
+
+<p>April 14, 1789. A considerable, bright, round nebula; having a large
+place in the middle of nearly an equal brightness; but less bright
+towards the margin (c). This seems rather to approach the planetary
+sort.</p>
+
+<p>March 5, 1790. A pretty considerable star of the 9th or 10th<span class="pagenum" id="Page_117">[Pg 117]</span>
+magnitude, visibly affected with a very faint nebulosity of little
+extent, all around. A power of 300 showed the nebulosity of greater
+extent (d). The connection is not to be doubted.</p>
+
+<p>March 19, 1790. A very bright nucleus, with a small, very faint
+chevelure, exactly round. In a low situation, where the chevelure
+could hardly be seen, this object would put on the appearance of an
+ill-defined, planetary nebula, of 6, 8 or 10" diameter (e).</p>
+
+<p>November 13, 1790. A most singular phenomenon! A star of about the 8th
+magnitude, with a faint luminous atmosphere, of a circular form, and
+of about 3' in diameter. The star is perfectly in the centre, and the
+atmosphere is so diluted, faint, and equal throughout, that there can
+be no surmise of its consisting of stars; nor can there be a doubt of
+the evident connection between the atmosphere and the star. Another
+star not much less in brightness, and in the same field with the above,
+was perfectly free from any such appearance. This last object is so
+decisive in every particular, Dr. H. says, that we need not hesitate
+to admit it as a pattern, from which we are authorised to draw the
+following important consequences:</p>
+
+<p>Supposing the connection between the star and its surrounding
+nebulosity to be allowed, we argue, that one of the two following cases
+must necessarily be admitted: In the first place, if the nebulosity
+consist of stars that are very remote, which appear nebulous on account
+of the small angles their mutual distances subtend at the eye, by which
+they will not only, as it were, run into each other, but also appear
+extremely faint and diluted; then, what must be the enormous size of
+the central point, which outshines all the rest in so superlative a
+degree as to admit of no comparison! In the next place, if the star be
+larger than common, how very small and compressed must be those other
+luminous points that are the occasion of the nebulosity which surrounds
+the central one! As, by the former supposition, the luminous central
+point must far exceed the standard of what we call a star, so, in the
+latter, the shining matter about the centre will be much too small to
+come under the same denomination; we therefore either have a central
+body which is not a star, or have a star which is involved in a shining
+fluid, of a nature totally unknown to us. Dr. H. can adopt no other
+sentiment than the latter, since the probability is certainly not for
+the existence of so enormous a body as would<span class="pagenum" id="Page_118">[Pg 118]</span> be required to shine like
+a star of the eighth magnitude, at a distance sufficiently great to
+cause a vast system of stars to put on the appearance of a very diluted
+milky nebulosity.</p>
+
+<p>But what a field of novelty is here opened to our conceptions! A
+shining fluid, of a brightness sufficient to reach us from the remote
+regions of a star of the 8th, 9th, 10th, or 12th magnitude, and of an
+extent so considerable as to take up 3, 4, 5, or 6 minutes in diameter!
+Can we compare it to the coruscation of the electric fluid in the
+aurora borealis? Or to the more magnificent cone of the zodiacal light
+as we see it in the spring or autumn? The latter, notwithstanding Dr.
+H. has observed it to reach at least 90° from the sun, is yet of so
+little extent and brightness, as probably not to be perceived even by
+the inhabitants of Saturn or the Georgian planet, and must be utterly
+invisible at the remoteness of the nearest fixed star.</p>
+
+<p>More extensive views may be derived from this proof of the existence
+of a shining matter. Perhaps it has been too hastily surmised that
+all milky nebulosity, of which there is so much in the heavens, is
+owing to starlight only. These nebulous stars may serve as a clue to
+unravel other mysterious phenomena. If the shining fluid that surrounds
+them is not so essentially connected with these nebulous stars, but
+that it can also exist without them, which seems to be sufficiently
+probable, and will be examined hereafter, we may with great facility
+explain that very extensive, telescopic nebulosity, which, as before
+mentioned, is expanded over more than 60° of the heavens, about the
+constellation of Orion; a luminous matter accounting much better for it
+than clustering stars at a distance. In this case we may also pretty
+nearly guess at its situation, which must commence somewhere about the
+range of the stars of the 7th magnitude, or a little farther from us,
+and extend unequally in some places perhaps to the regions of those
+of the 9th, 10th, 11th, and 12th. The foundation for this surmise is,
+that not unlikely some of the stars that happen to be situated in a
+more condensed part of it, or that perhaps by their own attraction
+draw together some quantity of this fluid greater than what they are
+entitled to by their situation in it, will, of course, assume the
+appearance of cloudy stars; and many of those named are either in this
+stratum of luminous matter, or very near it.</p>
+
+<p>It has been said above, that in nebulous stars the existence of the
+shining fluid does not seem to be so essentially connected with the<span class="pagenum" id="Page_119">[Pg 119]</span>
+central points that it might not also exist without them. For this
+opinion we may assign several reasons. One of them is the greater
+resemblance of the chevelure of these stars and the diffused extensive
+nebulosity mentioned before, which renders it highly probable that
+they are of the same nature. Now, if this be admitted, the separate
+existence of the luminous matter, or its independence of a central
+star, is fully proved. We may also judge, very confidently, that the
+light of this shining fluid is no kind of reflection from the star in
+the centre; for, as we have already observed, reflected light could
+never reach us at the great distance we are from such objects. Besides,
+how impenetrable would be an atmosphere of a sufficient density to
+reflect so great a quantity of light! And yet we observe, that the
+outward parts of the chevelure are nearly as bright as those that are
+close to the star; so that this supposed atmosphere ought to give no
+obstruction to the passage of the central rays. If therefore this
+matter is self-luminous, it seems more fit to produce a star by its
+condensation than to depend on the star for its existence.</p>
+
+<p>Many other diffused nebulosities, besides that about the constellation
+of Orion, have been observed or suspected; but some of them are
+probably very distant, and run far out into space. For instance, about
+5m in time preceding <i>x</i> Cygni, Dr. H. suspects as much of it
+as covers near 4 square degrees; and much about the same quantity
+44m preceding the 125 Tauri. A space of almost 8 square degrees, 6m
+preceding <i>α</i> Trianguli, seems to be tinged with milky nebulosity.
+Three minutes preceding the 46 Eridani, strong, milky nebulosity is
+expanded over more than 2 square degrees. Fifty-four minutes preceding
+the 13th <i>Canum venaticorum</i>, and again 48m preceding the same
+star, the field of view affected with whitish nebulosity throughout
+the whole breadth of the sweep, which was 2° 39'. Four minutes
+following the 57 Cygni a considerable space is filled with faint,
+milky nebulosity, which is pretty bright in some places, and contains
+the 37th nebula of the 5th class, in the brightest part of it. In the
+neighbourhood of the 44th Piscium, very faint nebulosity appears to
+be diffused over more than 9 square degrees of the heavens. Now all
+these phenomena, as we have already seen, will admit of a much easier
+explanation by a luminous fluid than by stars at an immense distance.</p>
+
+<p>The nature of planetary nebulæ, which has hitherto been involved<span class="pagenum" id="Page_120">[Pg 120]</span> in
+much darkness, may now be explained with some degree of satisfaction,
+since the uniform and very considerable brightness of their apparent
+disc accords remarkably well with a much condensed, luminous fluid;
+whereas, to suppose them to consist of clustering stars, will not so
+completely account for the milkiness or soft tint of their light, to
+produce which it would be required that the condensation of the stars
+should be carried to an almost inconceivable degree of accumulation.
+The surmise of the regeneration of stars, by means of planetary nebulæ,
+expressed in a former paper, will become more probable, as all the
+luminous matter contained in one of them, when gathered together into a
+body of the size of a star, would have nearly such a quantity of light
+as we find the planetary nebulæ to give. To prove this experimentally,
+we may view them with a telescope that does not magnify sufficiently
+to show their extent, by which means we shall gather all their light
+together into a point, when they will be found to assume the appearance
+of small stars; that is, of stars at the distance of those which we
+call of the 8th, 9th, or 10th magnitude. Indeed this idea is greatly
+supported by the discovery of a well-defined, lucid point, resembling
+a star, in the centre of one of them; for the argument which has been
+used, in the case of nebulous stars, to show the probability of the
+existence of luminous matter, which rested on the disparity between a
+bright point and its surrounding shining fluid, may here be alleged
+with equal justice. If the point be a generating star, the further
+accumulation of the already much condensed, luminous matter may
+complete it in time.</p>
+
+<p>How far the light that is perpetually emitted from millions of suns may
+be concerned in this shining fluid, it might be presumptuous to attempt
+to determine; but, notwithstanding the inconceivable subtilty of the
+particles of light, when the number of the emitting bodies is almost
+infinitely great, and the time of the continual emission indefinitely
+long, the quantity of emitted particles may well become adequate to the
+constitution of a shining fluid, or luminous matter, provided a cause
+can be found that may retain them from flying off, or reunite them. But
+such a cause cannot be difficult to guess at, when we know that light
+is so easily reflected, refracted, inflected and deflected; and that,
+in the immense range of its course, it must pass through innumerable
+systems, where it cannot but frequently meet with many obstacles to
+its rectilinear progression not to mention<span class="pagenum" id="Page_121">[Pg 121]</span> the great counteraction
+of the united attractive force of whole sidereal systems, which must
+be continually exerting their power on the particles while they are
+endeavouring to fly off. However, we shall lay no stress on a surmise
+of this kind, as the means of verifying it are wanting; nor is it of
+any immediate consequence to us to know the origin of the luminous
+matter. Let it suffice, that its existence is rendered evident, by
+means of nebulous stars.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_17" href="#FNanchor_17" class="label">[17]</a>
+This excerpt and the one following are from the report
+by Herschel in the <i>Transactions of the Royal Society of London</i>;
+the third is an abstract from the same report, the conclusion, however,
+being by Herschel.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_122">[Pg 122]</span></p>
+<h2 class="nobreak" id="XVI">XVI<br>
+KARL WILHELM SCHEELE<br>
+1742-1786</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Karl Wilhelm Scheele, who discovered independently of the English
+chemists the double constitution of air, was born in Stralsund,
+Pomerania, December 19, 1742. At an early age he manifested interest
+in pharmacy, and during his career as an apothecary engaged in various
+experiments in chemistry. He published his “Treatise on Air and Fire”
+in 1777. He died at Köping, May 21, 1786.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE CONSTITUENTS OF AIR<a id="FNanchor_18" href="#Footnote_18" class="fnanchor">[18]</a></p>
+
+<p>1. It is the object and chief business of chemistry to separate
+skilfully substances into their constituents, to discover their
+properties, and to compound them in different ways. How difficult it
+is, however, to carry out such operations with the greatest accuracy,
+can only be unknown to one who either has never undertaken this
+occupation, or at least has not done so with sufficient attention.</p>
+
+<p>2. Hitherto chemical investigators are not agreed as to how many
+elements or fundamental materials compose all substances. In fact this
+is one of the most difficult problems; some indeed hold that there
+remains no further hope of searching out the elements of substances.
+Poor comfort for those who feel their greatest pleasure in the
+investigation of natural things! Far is he mistaken, who endeavours
+to confine chemistry, this noble science, within such narrow bounds!
+Others believe that earth and phlogiston are the things from which all
+material nature has derived its origin. The majority seem completely
+attached to the peripatetic elements.</p>
+
+<p>3. I must admit that I have bestowed no little trouble upon this<span class="pagenum" id="Page_123">[Pg 123]</span>
+matter in order to obtain a clear conception of it. One may reasonably
+be amazed at the ideas and conjectures which authors have recorded
+on the subject, especially when they give a decision respecting the
+phenomenon of fire; and this very matter was of the greatest importance
+to me. I perceived the necessity of a knowledge of fire, because
+without this it is not possible to make any experiment; and without
+fire and heat it is not possible to make use of the action of any
+solvent. I began accordingly to put aside all explanations of fire; I
+undertook a multitude of experiments in order to fathom this beautiful
+phenomenon as fully as possible. I soon found, however, that one could
+not form any true judgment regarding the phenomena which fire presents,
+without a knowledge of the air. I saw, after carrying out a series of
+experiments, that air really enters into the mixture of fire, and with
+it forms a constituent of flame and of sparks. I learned accordingly
+that a treatise like this, on fire, could not be drawn up with proper
+completeness without taking the air also into consideration.</p>
+
+<p>4. Air is that fluid invisible substance which we continually breathe,
+which surrounds the whole surface of the earth, is very elastic, and
+possesses weight. It is always filled with an astonishing quantity
+of all kinds of exhalations, which are so finely subdivided in it
+that they are scarcely visible even in the sun’s rays. Water vapours
+always have the preponderance amongst these foreign particles. The
+air, however, is also mixed with another elastic substance resembling
+air, which differs from it in numerous properties, and is, with good
+reason, called aerial acid by Professor Bergman. It owes its presence
+to organised bodies, destroyed by putrefaction or combustion.</p>
+
+<p>5. Nothing has given philosophers more trouble for some years than just
+this delicate acid or so-called fixed air. Indeed it is not surprising
+that the conclusions which one draws from the properties of this
+elastic acid are not favourable to all who are prejudiced by previously
+conceived opinions. These defenders of the Paracelsian doctrine believe
+that the air is in itself unalterable; and, with Hales, that it really
+unites with substances thereby losing its elasticity; but that it
+regains its original nature as soon as it is driven out of these by
+fire or fermentation. But since they see that the air so produced is
+endowed with properties quite different from common air, they conclude,
+without experimental proofs, that this air has united with<span class="pagenum" id="Page_124">[Pg 124]</span> foreign
+materials, and that it must be purified from these admixed foreign
+particles by agitation and filtration with various liquids. I believe
+that there would be no hesitation in accepting this opinion, if one
+could only demonstrate clearly by experiments that a given quantity
+of air is capable of being completely converted into fixed or other
+kind of air by the admixture of foreign materials; but since this has
+not been done, I hope I do not err if I assume as many kinds of air as
+experiment reveals to me. For when I have collected an elastic fluid,
+and observe concerning it that its expansive power is increased by heat
+and diminished by cold, while it still uniformly retains its elastic
+fluidity, but also discover in it properties and behavior different
+from those of common air, then I consider myself justified in believing
+that this is a peculiar kind of air. I say that air thus collected must
+retain its elasticity even in the greatest cold, because otherwise an
+innumerable multitude of varieties of air would have to be assumed,
+since it is very probable that all substances can be converted by
+excessive heat into a vapour resembling air.</p>
+
+<p>6. Substances which are subjected to putrefaction or to destruction by
+means of fire diminish, and at the same time consume, a part of the
+air; sometimes it happens that they perceptibly increase the bulk of
+the air, and sometimes finally that they neither increase nor diminish
+a given quantity of air—phenomena which are certainly remarkable.
+Conjectures can here determine nothing with certainty, at least they
+can only bring small satisfaction to a chemical philosopher, who must
+have his proofs in his hands. Who does not see the necessity of making
+experiments in this case, in order to obtain light concerning this
+secret of nature?</p>
+
+<p>7. General properties of ordinary air.</p>
+
+<p>(1.) Fire must burn for a certain time in a given quantity of air.
+(2.) If, so far as can be seen, this fire does not produce during
+combustion any fluid resembling air, then, after the fire has gone
+out of itself, the quantity of air must be diminished between a third
+and a fourth part. (3.) It must not unite with common water. (4.) All
+kinds of animals must live for a certain time in a confined quantity of
+air. (5.) Seeds, as for example peas, in a given quantity of similarly
+confined air, must strike roots and attain a certain height with the
+aid of some water and of a moderate heat.</p>
+
+<p>Consequently, when I have a fluid resembling air in its external<span class="pagenum" id="Page_125">[Pg 125]</span>
+appearance, and find that it has not the properties mentioned, even
+when only one of them is wanting, I feel convinced that it is not
+ordinary air.</p>
+
+<p>8. Air must be composed of elastic fluids of two kinds.</p>
+
+<p>First Experiment.—I dissolved one ounce of alkaline liver of sulphur
+in eight ounces of water; I poured four ounces of this solution into an
+empty bottle capable of holding 24 ounces of water, and closed it most
+securely with a cork; I then inverted the bottle and placed the neck
+in a small vessel with water; in this position I allowed it to stand
+for fourteen days. During this time the solution had lost a part of its
+red colour and had also deposited some sulphur: afterwards I took the
+bottle and held it in the same position in a larger vessel with water,
+so that the mouth was under and the bottom above the water-level, and
+withdrew the cork under the water; immediately water rose with violence
+into the bottle. I closed the bottle again, removed it from the water,
+and weighed the fluid which it contained. There were 10 ounces. After
+substracting from this the four ounces of solution of sulphur there
+remain six ounces, consequently it is apparent from this experiment
+that of 20 parts of air six parts have been lost in 14 days.</p>
+
+<p>9. Second Experiment.—(a) I repeated the preceding experiment with the
+same quantity of liver of sulphur, but with this difference that I only
+allowed the bottle to stand a week tightly closed. I then found that of
+20 parts of air only 4 had been lost. (b) On another occasion I allowed
+the very same bottle to stand four months; the solution still possessed
+a somewhat dark yellow colour. But no more air had been lost than in
+the first experiment, that is to say six parts.</p>
+
+<p>10. Third Experiment.—I mixed two ounces of caustic ley, which
+was prepared from alkali of tartar and unslaked lime and did not
+precipitate lime-water, with half an ounce of the preceding solution of
+sulphur, which likewise did not precipitate lime-water. This mixture
+had a yellow colour. I poured it into the same bottle, and after this
+had stood fourteen days, well closed, I found the mixture entirely
+without colour and also without precipitate. I was enabled to conclude
+that the air in this bottle had likewise diminished, from the fact that
+air rushed into the bottle with a hissing sound after I had made a
+small hole in the cork.</p>
+
+<p>11. Fourth Experiment.—(a) I took four ounces of a solution of<span class="pagenum" id="Page_126">[Pg 126]</span>
+sulphur in lime-water; I poured this solution into a bottle and closed
+it tightly. After 14 days the yellow colour had disappeared, and of 20
+parts of air 4 parts had been lost. The solution contained no sulphur,
+but had allowed a precipitate to fall which was chiefly gypsum. (b.)
+Volatile liver of sulphur likewise diminishes the bulk of air. (c.)
+Sulphur, however, and volatile spirit of sulphur, undergo no alteration
+in it.</p>
+
+<p>12. Fifth Experiment.—I hung up over burning sulphur, linen rags which
+were dipped in a solution of alkali of tartar. After the alkali was
+saturated with the volatile acid, I placed the rags in a flask, and
+closed the mouth most carefully with a wet bladder. After three weeks
+had elapsed I found the bladder strongly pressed down; I inverted
+the flask, held its mouth in water and made a hole in the bladder;
+thereupon water rose with violence into the flask and filled the fourth
+part.</p>
+
+<p>13. Sixth Experiment.—I collected in the bladder the nitrous acid
+which arises on the dissolution of the metals in nitrous acid, and
+after I had tied the bladder tightly I laid it in a flask and secured
+the mouth very carefully with a wet bladder. The nitrous air gradually
+lost its elasticity, the bladder collapsed, and became yellow as if
+corroded by <i>aqua fortis</i>. After 14 days I made a hole in the
+bladder tied over the flask, having previously held it, inverted, under
+water; the water rose rapidly into the flask, and it remained only
+two-thirds empty.</p>
+
+<p>14. Seventh Experiment.—(a.) I immersed the mouth of a flask in a
+vessel with oil of turpentine. The oil rose in the flask a few lines
+every day. After the lapse of 14 days the fourth part of the flask
+was filled with it. I allowed it to stand for three weeks longer, but
+the oil did not rise higher. All those oils which dry in the air, and
+become converted into resinous substances, possess this property. Oil
+of turpentine, however, and linseed oil rise up sooner if the flask is
+previously rinsed out with a concentrated sharp ley. (b.) I poured two
+ounces of colourless and transparent animal oil of Dippel into a bottle
+and closed it very tightly; after the expiration of two months the oil
+was thick and black. I then held the bottle, inverted, under water and
+drew out the cork; the bottle immediately became one-fourth filled with
+water.</p>
+
+<p>15. Eighth Experiment.—(a.) I dissolved two ounces of vitriol of iron
+in thirty-two ounces of water, and precipitated this solution with
+a<span class="pagenum" id="Page_127">[Pg 127]</span> caustic ley. After the precipitate had settled, I poured away the
+clear fluid and put the dark green precipitate of iron so obtained,
+together with the remaining water, into the before-mentioned bottle (§
+8), and closed it tightly. After 14 days (during which time I shook the
+bottle frequently) this green calx of iron had acquired the colour of
+crocus of iron, and of 40 parts of air 12 had been lost. (b.) When iron
+filings are moistened with some water and preserved for a few weeks
+in a well closed bottle, a portion of the air is likewise lost. (c.)
+The solution of iron in vinegar has the same effect upon air. In this
+case the vinegar permits the dissolved iron to fall out in the form of
+a yellow crocus, and becomes completely deprived of this metal. (d.)
+The solution of copper prepared in closed vessels with spirit of salt
+likewise diminishes air. In none of the foregoing kinds of air can
+either a candle burn or the smallest spark glow.</p>
+
+<p>16. It is seen from these experiments that phlogiston, the simple
+inflammable principle, is present in each of them. It is known that the
+air strongly attracts to itself the inflammable part of substances and
+deprives them of it: not only this may be seen from the experiments
+cited, but it is at the same time evident that on the transference of
+the inflammable substance to the air a considerable part of the air
+is lost. But that inflammable substance alone is the cause of this
+action, is plain from this, that, according to the tenth paragraph,
+not the least trace of sulphur remains over, since, according to my
+experiments this colourless ley contains only some vitriolated tartar.
+The eleventh paragraph likewise shows this. But since sulphur alone,
+and also the volatile spirit of sulphur, have no effect upon the air (§
+11. c), it is clear that the decomposition of liver of sulphur takes
+place according to the laws of double affinity—that is to say, that
+the alkalies and lime attract the vitriolic acid, and the air attracts
+the phlogiston.</p>
+
+<p>It may also be seen from the above experiments, that a given quantity
+of air can only unite with, and at the same time saturate, a certain
+quantity of the inflammable substance: this is evident from the ninth
+paragraph, letter b. But whether the phlogiston which was lost by the
+substances was still present in the air left behind in the bottle,
+or whether the air which was lost had united and fixed itself with
+the materials such as liver of sulphur, oils, &amp;c., are questions of
+importance.</p>
+
+<p>From the first view, it would necessarily follow that the inflammable<span class="pagenum" id="Page_128">[Pg 128]</span>
+substance possessed the property of depriving the air of part of its
+elasticity, and that in consequence of this it becomes more closely
+compressed by the external air. In order now to help myself out of
+these uncertainties, I formed the opinion that any such air must
+be specifically heavier than ordinary air, both on account of its
+containing phlogiston and also of its greater condensation. But how
+perplexed was I when I saw that a very thin flask which was filled with
+this air, and most accurately weighed, not only did not counterpoise
+an equal quantity of ordinary air, but was even somewhat lighter. I
+then thought that the latter view might be admissible; but in that case
+it would necessarily follow also that the lost air could be separated
+again from the materials employed. None of the experiments cited seemed
+to me capable of showing this more clearly than that according to the
+tenth paragraph, because this residuum, as already mentioned, consists
+of vitriolated tartar and alkali. In order therefore to see whether the
+lost air had been converted into fixed air, I tried whether the latter
+shewed itself when some of the caustic ley was poured into lime-water;
+but in vain—no precipitation took place. Indeed, I tried in several
+ways to obtain the lost air from this alkaline mixture, but as the
+results were similar to the foregoing, in order to avoid prolixity I
+shall not cite these experiments. Thus much I see from the experiments
+mentioned, that the air consists of two fluids, differing from each
+other, the one of which does not manifest in the least the property
+of attracting phlogiston, while the other, which composes between the
+third and the fourth part of the whole mass of the air, is peculiarly
+disposed to such attraction. But where this latter kind of air has gone
+to after it has united with the inflammable substance, is a question
+which must be decided by further experiments, and not by conjectures.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_18" href="#FNanchor_18" class="label">[18]</a>
+Translated from <i>Treatise on Air and Fire</i> (1777).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_129">[Pg 129]</span></p>
+<h2 class="nobreak" id="XVII">XVII<br>
+ANTOINE LAURENT LAVOISIER<br>
+1743-1794</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Antoine Laurent Lavoisier was born in Paris, August 26, 1743.
+After an early life spent in diligent study, in 1766 he was awarded
+a prize for his essay on the best method of lighting Paris. His
+attention having been called to the English experiments on gases
+made by Priestley and Cavendish, he attacked the current phlogiston
+conception of combustion and stated that Priestley’s “dephlogisticated
+air” was the universal acidifying gas, and gave it the name of
+“oxygen.” Systematizing chemistry and renaming the elements and their
+compounds, he came to believe that chemical reactions had the certainty
+of mathematical equations. From this he derived the idea of the
+persistence of matter, regardless of changes, now established as one of
+the basic concepts of modern science. During the French Revolution a
+charge was brought against him and he was sent to the guillotine on May
+8, 1794.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE NATURE OF COMBUSTION<a id="FNanchor_19" href="#Footnote_19" class="fnanchor">[19]</a></p>
+
+<p>I venture to submit to the Academy to-day a new theory of combustion,
+or rather, to speak with that reserve to whose law I submit myself,
+an hypothesis, by the aid of which all the phenomena of combustion,
+calcination, and even to some extent those accompanying the respiration
+of animals are explained in a very satisfactory manner. I had already
+laid the foundations of this hypothesis p. 279-280 of vol. I. of my
+<i>Opuscules physiques et chimiques</i>; but I admit that trusting
+little to my own knowledge, I did not then dare to put forward an
+opinion which might seem singular, and which was directly<span class="pagenum" id="Page_130">[Pg 130]</span> opposed to
+the theory of Stahl and of many celebrated men who have followed him.</p>
+
+<p>Though perhaps some of the reasons which then checked me still remain
+to-day, nevertheless, the facts which have multiplied since that
+time, and which seem to me favorable to my views, have confirmed
+me in my opinion: though not, perhaps, any stronger, I have become
+more confident, and I think I have sufficient proofs, or at least
+probabilities, so that even those who may not be of my opinion cannot
+blame me for having written.</p>
+
+<p>In general in the combustion of bodies four constant phenomena are
+observable, which seem to be laws from which nature never departs.
+Though these phenomena may be found implicitly stated in other memoirs,
+yet I cannot dispense with recalling them here in a few words.</p>
+
+
+<p class="nindc space-above2 space-below2">
+FIRST PHENOMENON</p>
+
+<p>All combustion sets free matter either of fire or light.</p>
+
+
+<p class="nindc space-above2 space-below2">
+SECOND PHENOMENON</p>
+
+<p>Bodies can burn only in a very small number of kinds of gases (airs),
+or rather there can be combustion only in one kind of air, that which
+Mr. Priestley has named dephlogisticated air, and which I should call
+pure air. Not only will the bodies which we call combustibles not burn
+in a vacuum or in any other kind of air, they are, on the contrary,
+extinguished there as promptly as if they had been plunged into water
+or any other liquid.</p>
+
+
+<p class="nindc space-above2 space-below2">
+THIRD PHENOMENON</p>
+
+<p>In all combustion there is destruction or decomposition of the pure
+air in which the combustion takes place, and the body burned increases
+in weight exactly in proportion to the quantity of air destroyed or
+decomposed.</p>
+
+
+<p class="nindc space-above2 space-below2">
+FOURTH PHENOMENON</p>
+
+<p>In all combustion the body burned changes to an acid by the addition
+of the substance which has increased its weight: thus, for example,<span class="pagenum" id="Page_131">[Pg 131]</span>
+if sulphur is burned under a receiver the product of the combustion is
+vitriolic acid; if phosphorus be burned the product is phosphoric acid;
+if a carboniferous substance, the product is fixed air, otherwise known
+as acid of lime (carbonic acid, etc.).</p>
+
+<p>(Note: I would remark in passing that the number of acids is infinitely
+greater than has been supposed.)</p>
+
+<p>The calcination of metals is subject to exactly the same laws, and it
+is with very great reason that Mr. Macquer has treated it as a slow
+combustion; thus, 1°, in all metallic combustion there is a liberating
+of fire matter (<i>matière du feu</i>); 2°, veritable calcination can
+take place only in pure air; 3°, there is a combination of the air with
+the substance calcined, but with this difference, that in place of
+forming an acid with it there results from it a particular combination
+known as metallic calx.</p>
+
+<p>This is not the place to point out the analogy which exists between the
+respiration of animals, combustion and calcination; I shall return to
+that in the sequel to this memoir.</p>
+
+<p>These different phenomena of the calcination of metals and of
+combustion are explained in a very happy manner by Stahl’s hypothesis;
+but it is necessary with him to suppose the existence of fire matter
+(<i>matière du feu</i>) or of fixed phlogiston in the metals, in
+sulphur and in all bodies which he regards as combustibles; yet if the
+partisans of Stahl’s doctrine are asked to prove the existence of fire
+matter in combustible bodies, they fall necessarily into a vicious
+circle and are obliged to reply that combustible bodies contain fire
+matter because they burn, and that they burn because they contain fire
+matter. It is easy to see that in the last analysis this is explaining
+combustion by combustion.</p>
+
+<p>The existence of fire matter, or phlogiston, in metals, in sulphur,
+etc., is then really only an hypothesis, a supposition which, once
+admitted, explains, it is true, some of the phenomena of calcination
+and combustion; but if I show that these very phenomena may be
+explained in quite as natural a way by the opposite hypothesis, that
+is to say, without supposing the existence of either fire matter or
+phlogiston in the substances called combustible, Stahl’s system will be
+shaken to its foundations.</p>
+
+<p>No doubt you will not fail to ask me first what I understand by fire
+matter. I reply with Franklin, Boerhaave and some of the<span class="pagenum" id="Page_132">[Pg 132]</span> philosophers
+of old, that the matter of fire or of light is a very subtle, very
+elastic fluid, which surrounds every part of the planet we live
+on, which penetrates with more or less ease the substances which
+compose that, and which tends, when it is free, to come to a state of
+equilibrium in all.</p>
+
+<p>I will add, borrowing the chemical phraseology, that this fluid is the
+solvent of a large number of substances; that it combines with them
+in the same way that water does with salt, and the acids with metals,
+and that the bodies thus combined and dissolved by the igneous fluid
+lose in part the properties which they had before the combination and
+acquire new ones which bring them nearer (make them more like) the fire
+matter.</p>
+
+<p>It is thus, as I have shown in a memoir deposited with the secretary
+of this Academy, that every aeriform fluid, every kind of air, is a
+resultant of the combination of some substance, solid or fluid, with
+the matter of fire or of light; and it is to this combination that
+aeriform fluids owe their elasticity, their specific volatility, their
+rarity, and all the other properties which ally (<i>rapprochent</i>)
+them to the igneous fluid.</p>
+
+<p>Pure air, according to this, what Mr. Priestley calls dephlogisticated
+air, is an igneous compound into which the matter of fire or of light
+enters as solvent, and into which some other substance enters as a
+base; but if, in any solution whatever, a substance is presented to
+the base with which that has greater affinity, it unites with this
+instantly and the solvent which it leaves is set free.</p>
+
+<p>The same thing happens with the air in combustion; the substance
+which burns steals away the base; then the fire matter which served
+as its solvent becomes free, regains its rights and escapes with the
+characteristics by which we know it; that is to say, with flame, heat
+and light.</p>
+
+<p>To elucidate whatever may seem obscure in this theory let us apply it
+to some examples: when a metal is calcined in pure air, the base of the
+air, which has less affinity for its own solvent than for the metal,
+unites with the latter as it melts and converts it into metallic calx.
+This combination of the base of the air with the metal is proved 1st,
+by the increase in weight which the latter undergoes in calcination;
+2nd, by the almost total using up of the air under the receiving bell.<span class="pagenum" id="Page_133">[Pg 133]</span>
+But, if the base of the air was held in solution by the fire matter,
+in proportion as this base combined with the metal, the fire matter
+should become free and produce, in freeing itself, flame and light. You
+understand that the more speedy the calcination of the metal, that is
+to say, the more fixation of the air takes place in a given time, the
+more fire matter will be liberated, and, consequently, the more marked
+and obvious the combustion will be.</p>
+
+<p class="space-above2">
+I might apply this theory successively to all combustions, but as
+I shall have frequent occasion to return to this subject, I will
+content myself at this time with these general illustrations. So, to
+resume, the air is composed, according to my idea, of fire matter as
+a dissolvent combined with a substance which serves it as a base,
+and which in some way neutralizes it; whenever a substance for which
+it has a greater affinity is brought into contact with this base, it
+leaves its solvent; then the fire-substance regains its rights, its
+properties, and appears to our eyes with heat, flame and light.</p>
+
+<p>Pure air, the dephlogisticated air of Mr. Priestley, is then, according
+to this opinion, the real combustible body, and perhaps the only one of
+that nature, and it is seen that it is no longer necessary, in order
+to explain the phenomena of combustion, to suppose that there exists
+a large quantity of fire fixed in all the substances which we call
+combustible, but that it is very probable, on the contrary, that very
+little of it exists in metals, in sulphur, phosphorus, and in most of
+the very solid, heavy and compact bodies, and, perhaps even that there
+exists in these substances only free fire matter, in virtue of the
+property which this matter has of putting itself in equilibrium with
+all surrounding bodies.</p>
+
+<p>Another striking reflection which comes to the support of the preceding
+ones, is that almost all substances may exist in three different
+states: under a solid form, under a liquid form, that is to say
+melted, or in the state of air or vapor. These three states depend
+solely on the quantity, more or less, of fire matter with which these
+substances are interpenetrated and with which they are combined.
+Fluidity, vaporization, elasticity, are then properties characteristic
+of the presence of fire and of a great abundance of fire; solidity,
+compactness, on the contrary, are evidences of its absence. By so much
+then<span class="pagenum" id="Page_134">[Pg 134]</span> as it is demonstrated that aeriform substances and air itself
+contain a large quantity of fire in combination, by so much it is
+probable that solid bodies contain little of it.</p>
+
+<p>For the rest, I repeat, in attacking here the doctrine of Stahl, it was
+not my purpose to substitute for it a rigorously demonstrated theory,
+but only an hypothesis which seemed to me more probable, more in
+conformity with the laws of nature, and one which appeared to involve
+less forced explanations and fewer contradictions.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_19" href="#FNanchor_19" class="label">[19]</a>
+<i>On Combustion</i>, Vol. II, p. 225.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_135">[Pg 135]</span></p>
+<h2 class="nobreak" id="XVIII">XVIII<br>
+ALESSANDRO VOLTA<br>
+1745-1827</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Alessandro Volta, born at Como, Italy, February 18, 1745, became
+teacher of physics at Como in 1774, and five years later accepted a
+professorship at Pavia. Becoming interested in Galvani’s experiments
+with electricity on the muscles of a frog, he applied them in his
+attempts to confirm his own theory that the frog’s muscles were a
+sensitive electrometer. In doing this he conceived the voltaic pile,
+which produced the first constant electrical current—a discovery which
+had immense effects in later studies in electricity. He died at Como,
+March 5, 1827.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+NEW GALVANIC INSTRUMENT<a id="FNanchor_20" href="#Footnote_20" class="fnanchor">[20]</a><br>
+<br>
+ON THE ELECTRICITY EXCITED BY THE MERE CONTACT OF CONDUCTING SUBSTANCES
+OF DIFFERENT KINDS</p>
+
+<p>The chief of these results, and which comprehends nearly all the
+others, is the construction of an apparatus which resembles in its
+effects, viz. (such as giving shocks to the arms, &amp;c.,) the Leyden
+phial, and still better, electric batteries weakly charged; acting
+continually, or whose charge, after each explosion, recharges itself
+again; which in short becomes perpetual, from one infallible charge,
+from one action or impulse on the electric fluid; but which besides
+differs essentially from the other, by this continual action which
+is proper to it, and because that instead of consisting, like the
+ordinary phials and electric batteries, in one or more isolated plates,
+or thin layers of those bodies deemed the only electrics, and armed
+with conductors or bodies called non-electrics, this new apparatus is
+formed only of a number of these last bodies, chosen even among the
+best conductors, and so the farthest removed, according to the usual
+opinion, from the electric principle. This astonishing apparatus is<span class="pagenum" id="Page_136">[Pg 136]</span>
+nothing but an assemblage of a number of good conductors of a different
+kind, arranged in a certain manner. Thus, 30, 40, 60, or more pieces
+of copper, or better of silver, each applied to a piece of tin or
+still better of zinc, and an equal number of layers of water, or of
+some other liquid which may be a better conductor than simple water,
+as salt water, lye, &amp;c., or of bits of card or leather, &amp;c., soaked
+in such liquids. Of such layers interposed between each couple or
+combination of two different metals, one such alternate series, and
+always in the same order, of these three kinds of conductors, is all
+that constitutes M. Volta’s new instrument; which imitates so well
+the effects of the Leyden phial or electric batteries; not indeed
+with the force and explosions of these, when highly charged; but only
+equalling the effects of a battery charged to a very weak degree, of
+a battery, however, having an immense capacity, but which besides
+infinitely surpasses the virtue and the power of these same batteries;
+as it has no need, like them, of being charged beforehand, by means
+of a foreign electricity; and as it is capable of giving the usual
+commotion as often as ever it is properly touched. This apparatus, as
+it resembles more the natural electric organ of the torpedo, or of the
+electric eel than the Leyden phial and the ordinary electric batteries,
+M. Volta calls the artificial electric organ. For the construction of
+this instrument, M. Volta provides some dozens of small round metal
+plates of copper, or tin, or best of silver, about an inch in diameter,
+like shillings or half-crowns, and an equal number of plates of tin,
+or much better of zinc, of the same shape and size. These pieces he
+places exactly one upon another, forming a column, pillar or pile. He
+provides also as many round pieces of card, or leather, or such like
+spongy matter, capable of imbibing and retaining much of the water, or
+other liquid, when soaked in it. These soaked roullets or circles are
+to be a little less in diameter than the small metal discs or plates,
+that they may not jut out beyond them. All these discs are then placed
+horizontally on a table, one over another continually alternating, in a
+pile as high as will well support itself without tottering and falling
+down: beginning with a plate of either of the metals, as for instance,
+the silver, then upon that one of zinc, over which is to be put the
+soaked card; then other three discs, over these in the same order, viz.
+a silver, next a zinc, and then another moistened card, &amp;c.</p>
+
+<p><span class="pagenum" id="Page_137">[Pg 137]</span></p>
+
+<p>After having raised the pile to about 20 of these stages or triads of
+plates, it will be already capable, not only of affecting Cavallo’s
+electrometer, assisted by the condenser, so as to raise it 10 or 15°,
+charging it by a simple touching, so as to cause it to give a spark,
+&amp;c., as also to strike the fingers with which we touch the top or
+bottom of the column, with several small snaps, the fingers being
+wetted with water. But if to the 20 sets of triplets of the plates be
+added 20 or 30 more, disposed in the same order, the actions of the
+extended pile will be much stronger, and be felt through the arms up to
+the shoulders; and by continuing the touchings, the pains in the hands
+become insupportable.</p>
+
+<p>M. Volta constructs and combines his apparatus in various ways and
+forms, more or less powerful, convenient or amusing. One is as follows
+(Fig. 1, pl. 13,), which he calls a <i>couronne de tasses</i>. He
+disposes in a row a number of cups of wood, or earth, or glass, or
+any thing but metal, half filled with pure water, or salt water or
+lye; these are all made to communicate in a kind of chain, by several
+metallic arcs of which one arm or link, Aa, or only the extremity A,
+immersed in one of the cups, is of copper, or of copper silvered,
+and the other Z, immersed in the following cup, is of tin, or rather
+of zinc, the other two being soldered together near the crown of
+the arch. It is evident that a series of these cups, thus connected
+together, either in a straight or curved line, by the two metals and
+the intermediate liquid, is similar to the pillar or pile before
+described, and consequently will exhibit similar effects. Thus, to
+produce commotion or sensation in the hands and arms, we need only dip
+one hand into one of the cups and the finger of the other hand into
+another cup, sufficiently far from the former; and the action will be
+so much the stronger as the two cups are farther asunder, or have the
+more intermediate cups; and consequently the greatest by touching the
+first and the last in the chain.</p>
+
+<div class="tb">* * * * * </div>
+
+<p>M. Volta concludes with various remarks and cautions in using this
+instrument; showing that it is perpetual in its virtue, renewing its
+charge spontaneously, and serving most of the purposes of the ordinary
+electrical machines, and even affecting and manifesting its power by
+most of the human senses, viz. feeling, tasting, hearing, and seeing.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_20" href="#FNanchor_20" class="label">[20]</a>
+From the <i>Transactions of the Royal Society of
+London</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_138">[Pg 138]</span></p>
+<h2 class="nobreak" id="XIX">XIX<br>
+PIERRE SIMON LAPLACE<br>
+1749-1827</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Pierre Simon Laplace, born at Beaumont-en-Auge, Normandy, March
+28, 1749, became a teacher of mathematics at Beaufort before he was
+eighteen years old. He gained d’Alembert’s attention by a letter
+which he wrote to him on the principles of mathematics. After 1770
+he engaged with Lagrange in determining the permanency of the solar
+system by studying its perturbations and interactions, and finally
+suggested how these changes were periodic. His monumental work, in five
+volumes, “Mechanics of the Heavens” (1799-1825), gave a comprehensive
+description of the movements of the solar system, and his “System of
+the World” proposed the nebular theory of the origin of the universe.
+His researches were important in the development of modern astronomy
+because he substituted a dynamic for the descriptive point of view. He
+died at Arcueil, March 5, 1827.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE NEBULAR HYPOTHESIS<a id="FNanchor_21" href="#Footnote_21" class="fnanchor">[21]</a></p>
+
+<p>Buffon is the only individual that I know of, who, since the discovery
+of the true system of the world, endeavoured to investigate the origin
+of the planets and satellites. He supposed that a comet, by impinging
+on the Sun, carried away a torrent of matter, which was reunited far
+off, into globes of different magnitudes and at different distances
+from this star. These globes, when they cool and become hardened,
+are the planets and their satellites. This hypothesis satisfies<span class="pagenum" id="Page_139">[Pg 139]</span> the
+first of the five preceding phenomena<a id="FNanchor_22" href="#Footnote_22" class="fnanchor">[22]</a>; for it is evident that all
+bodies thus formed should move very nearly in the plane which passes
+through the centre of the Sun, and through the direction of the torrent
+of matter which has produced them: but the four remaining phenomena
+appear to me inexplicable on this supposition. Indeed, the absolute
+motion of the molecules of a planet ought to be in the same direction
+as the motion of the centre of gravity; but it by no means follows
+from this, that the motion of rotation of a planet should be also in
+the same direction. Thus the Earth may revolve from east to west, and
+yet the absolute motion of each of its molecules may be directed from
+west to east. This observation applies also to the revolution of the
+satellites, of which the direction in the same hypothesis, is not
+necessarily the same as that of the motion of projection of the planets.</p>
+
+<p>The small eccentricity of the planetary orbits is a phenomenon,
+not only difficult to explain on this hypothesis, but altogether
+inconsistent with it. We know from the theory of central forces, that
+if a body which moves in a re-entrant orbit about the Sun, passes
+very near the body of the Sun, it will return constantly to it, at
+the end of each revolution. Hence it follows that if the planets were
+originally detached from the Sun, they would touch it, at each return
+to this star; and their orbits, instead of being nearly circular,
+would be very eccentric. Indeed it must be admitted that a torrent
+of matter detached from the Sun, cannot be compared to a globe which
+just skims by its surface; from the impulsions which the parts of this
+torrent receive from each other, combined with their mutual attraction,
+they may, by changing the direction of their motions, increase the
+distances of their perihelions from the Sun. But their orbits should
+be extremely eccentric, or at least all the orbits would not be q. p.
+circular, except by the most extraordinary chance. Finally, no reason
+can be assigned on the hypothesis of Buffon, why the orbits of more
+than one hundred comets, which have been already<span class="pagenum" id="Page_140">[Pg 140]</span> observed, should be
+all very eccentric. The hypothesis, therefore, is far from satisfying
+the preceding phenomena. Let us consider whether we can assign the true
+cause.</p>
+
+<p>Whatever may be its nature, since it has produced or influenced the
+direction of the planetary motions, it must have embraced them all
+within the sphere of its action; and considering the immense distance
+which intervenes between them, nothing could have effected this but
+a fluid of almost indefinite extent. In order to have impressed on
+them all a motion q. p. circular and in the same direction about the
+Sun, this fluid must environ this star, like an atmosphere. From a
+consideration of the planetary motions, we are therefore brought to
+the conclusion, that in consequence of an excessive heat, the solar
+atmosphere originally extended beyond the orbits of all the planets,
+and that it has successively contracted itself within its present
+limits.</p>
+
+<p>In the primitive state in which we have supposed the Sun to be, it
+resembles those substances which are termed nebulæ, which, when seen
+through telescopes, appear to be composed of a nucleus, more or less
+brilliant, surrounded by a nebulosity, which, by condensing on its
+surface, transforms it into a star. If all the stars are conceived to
+be similarly formed, we can suppose their anterior state of nebulosity
+to be preceded by other states, in which the nebulous matter was more
+or less diffuse, the nucleus being at the same time more or less
+brilliant. By going back in this manner, we shall arrive at a state
+of nebulosity so diffuse, that its existence can with difficulty be
+conceived.</p>
+
+<p>For a considerable time back, the particular arrangement of some stars
+visible to the naked eye, has engaged the attention of philosophers.
+Mitchel remarked long since how extremely improbable it was that the
+stars composing the constellation called the Pleiades, for example,
+should be confined within the narrow space which contains them, by the
+sole chance of hazard; from which he inferred that this group of stars,
+and the similar groups which the heavens present to us, are the effects
+of a primitive law of nature. These groups are a general result of the
+condensation of nebulæ of several nuclei; for it is evident that the
+nebulous matter being perpetually attracted by these different nuclei,
+ought at length to form a group of stars, like to that of the Pleiades.
+The condensation of nebulæ consisting of<span class="pagenum" id="Page_141">[Pg 141]</span> two nuclei, will in like
+manner form stars very near to each other, revolving the one about the
+other like to the double stars, whose respective motions have been
+already recognized.</p>
+
+<p>But in what manner has the solar atmosphere determined the motions of
+rotation and revolution of the planets and satellites? If these bodies
+had penetrated deeply into this atmosphere, its resistance would cause
+them to fall on the Sun. We may therefore suppose that the planets
+were formed at its successive limits, by the condensation of zones of
+vapours, which it must, while it was cooling, have abandoned in the
+plane of its equator.</p>
+
+<p>Let us resume the results which we have given in the tenth chapter of
+the preceding book. The Sun’s atmosphere cannot extend indefinitely;
+its limit is the point where the centrifugal force arising from the
+motion of rotation balances the gravity; but according as the cooling
+contracts the atmosphere, and condenses the molecules which are near
+to it, on the surface of the star, the motion of rotation increases;
+for, in virtue of the principle of areas, the sum of the areas
+described by the <i>radius vector</i> of each particle of the Sun and
+its atmosphere, and projected on the plane of its equator, is always
+the same. Consequently the rotation ought to be quicker, when these
+particles approach to the centre of the Sun. The centrifugal force
+arising from this motion becoming thus greater; the point where the
+gravity is equal to it, is nearer to the centre of the Sun. Supposing,
+therefore, what is natural to admit, that the atmosphere extended at
+any epoch as far as this limit, it ought, according as it cooled,
+to abandon the molecules, which are situated at this limit, and at
+the successive limits produced by the increased rotation of the Sun.
+These particles, after being abandoned, have continued to circulate
+about this star, because their centrifugal force was balanced by their
+gravity. But as this equality does not obtain for these molecules
+of the atmosphere which are situated on the parallels to the Sun’s
+equator, these have come nearer by their gravity to the atmosphere
+according as it condensed, and they have not ceased to belong to it
+inasmuch as by their motion, they have approached to the plane of this
+equator.</p>
+
+<p>Let us now consider the zones of vapours, which have been successively
+abandoned. These zones ought, according to all probability, to form by
+their condensation, and by the mutual attraction of their<span class="pagenum" id="Page_142">[Pg 142]</span> particles,
+several concentrical rings of vapours circulating about the Sun. But
+mutual friction of the molecules of each ring ought to accelerate
+some and retard others, until they all had acquired the same angular
+motion. Consequently the real velocities of the molecules which are
+farther from the Sun, ought to be greatest. The following cause ought
+likewise to contribute to this difference of velocities: The most
+distant particles of the Sun, and which, by the effects of cooling
+and condensation, have collected so as to constitute the superior
+part of the ring, have always described areas proportional to the
+times, because the central force by which they are actuated has been
+constantly directed to this star; but this constancy of areas requires
+an increase of velocity, according as they approach more to each other.
+It appears that the same cause ought to diminish the velocity of the
+particles, which, situated near the ring, constitute its inferior part.</p>
+
+<p>If all the particles of a ring of vapours continued to condense without
+separating, they would at length constitute a solid or a liquid ring.
+But the regularity which this formation requires in all the parts of
+the ring, and in their cooling, ought to make this phenomenon very
+rare. Thus the solar system presents but one example of it; that of the
+rings of Saturn. Almost always each ring of vapours ought to be divided
+into several masses, which, being moved with velocities which differ
+little from each other, should continue to revolve at the same distance
+about the Sun. These masses should assume a spheroidical form, with a
+rotatory motion in the direction of that of their revolution, because
+their inferior particles have a less real velocity than the superior;
+they have therefore constituted so many planets in a state of vapour.
+But if one of them was sufficiently powerful, to unite successively by
+its attraction, all the others about its centre, the ring of vapours
+would be changed into one sole spheroidical mass, circulating about
+the Sun, with a motion of rotation in the same direction with that
+of revolution. This last case has been the most common; however, the
+solar system presents to us the first case, in the four small planets
+which revolve between Mars and Jupiter, at least unless we suppose
+with Olbers, that they originally formed one planet only, which was
+divided by an explosion into several parts, and actuated by different
+velocities. Now if we trace the changes which a further cooling ought
+to produce in the planets<span class="pagenum" id="Page_143">[Pg 143]</span> formed of vapours, and of which we have
+suggested the formation, we shall see to arise in the centre of each
+of them, a nucleus increasing continually, by the condensation of the
+atmosphere which environs it. In this state, the planet resembles the
+Sun in the nebulous state, in which we have first supposed it to be;
+the cooling should therefore produce at the different limits of its
+atmosphere, phenomena similar to those which have been described,
+namely, rings and satellites circulating about its centre in the
+direction of its motion of rotation, and revolving in the same
+direction on their axes. The regular distribution of the mass of rings
+of Saturn about its centre and in the plane of its equator, results
+naturally from this hypothesis, and, without it, is inexplicable. Those
+rings appear to me to be existing proofs of the primitive extension of
+the atmosphere of Saturn, and of its successive condensations. Thus,
+the singular phenomena of the small eccentricities of the orbits of the
+planets and satellites, of the small inclination of these orbits to the
+solar equator, and of the identity in the direction of the motions of
+rotation and revolution of all those bodies with that of the rotation
+of the Sun, follow the hypothesis which has been suggested, and render
+it extremely probable. If the solar system was formed with perfect
+regularity, the orbits of the bodies which compose it would be circles,
+of which the planes, as well as those of the various equators and
+rings, would coincide with the plane of the solar equator. But we may
+suppose that the innumerable varieties which must necessarily exist in
+the temperature and density of different parts of these great masses,
+ought to produce the eccentricities of their orbits, and the deviations
+of their motions, from the plane of this equator.</p>
+
+<p>In the preceding hypothesis, the comets do not belong to the solar
+system. If they be considered, as we have done, as small nebulæ,
+wandering from one solar system to another, and formed by the
+condensation of the nebulous matter, which is diffused so profusely
+throughout the universe, we may conceive that when they arrive in
+that part of space where the attraction of the Sun predominates, it
+should force them to describe elliptic or hyperbolic orbits. But
+as their velocities are equally possible in every direction, they
+must move indifferently in all directions, and at every possible
+inclination to the elliptic; which is conformable to observation. Thus
+the condensation of the nebulous matter, which explains the motions<span class="pagenum" id="Page_144">[Pg 144]</span>
+of rotation and revolution of the planets and satellites in the same
+direction, and in orbits very little inclined to each other, likewise
+explains why the motions of the comets deviate from this general law.</p>
+
+<p>The great eccentricity of the orbits of the comets, is also a result of
+our hypothesis. If those orbits are elliptic, they are very elongated,
+since their greater axes are at least equal to the radius of the sphere
+of activity of the Sun. But these orbits may be hyperbolic; and if the
+axes of these hyperbolæ are not very great with respect to the mean
+distance of the Sun from the Earth, the motion of the comets which
+describe them will appear to be sensibly hyperbolic. However, with
+respect to the hundred comets, of which the elements are known, not
+one appears to move in a hyperbola; hence the chances which assign
+a sensible hyperbola are extremely rare relatively to the contrary
+chances. The comets are so small, that they only become sensible when
+their perihelion distance is inconsiderable. Hitherto this distance
+has not surpassed twice the diameter of the Earth’s orbit, and most
+frequently, it has been less than the radius of this orbit. We may
+conceive, that in order to approach so near to the Sun, their velocity
+at the moment of their ingress within its sphere of activity, must have
+an intensity and direction confined within very narrow limits. If we
+determine by the analysis of probabilities, the ratio of the chances
+which in these limits, assign a sensible hyperbola to the chances which
+assign an orbit, which may without sensible error be confounded with a
+parabola, it will be found that there is at least six thousand to unity
+that a nebula which penetrates within the sphere of the Sun’s activity
+so as to be observed, will either describe a very elongated ellipse,
+or an hyperbola, which, in consequence of the magnitude of its axis
+will be as to sense confounded with a parabola in the part of its orbit
+which is observed. It is not therefore surprising that hitherto no
+hyperbolic motions have been recognized.</p>
+
+<p>The attraction of the planets, and perhaps also the resistance of the
+ethereal media, ought to change several cometary orbits into ellipses,
+of which the greater axes are much less than the radius of the sphere
+of the solar activity. It is probable that such a change was produced
+in the orbit of the comet of 1759, the greater axis of which was not
+more than thirty-five times the distance of the Sun from the Earth. A
+still greater change was produced in the orbits of the comets of 1770
+and of 1805.</p>
+
+<p><span class="pagenum" id="Page_145">[Pg 145]</span></p>
+
+<p>If in the zones abandoned by the atmosphere of the Sun, there are any
+molecules too volatile to be united to each other, or to the planets,
+they ought in their circulation about this star to exhibit all the
+appearances of the zodiacal light, without opposing any sensible
+resistance to the different bodies of the planetary system, both on
+account of their great rarity and also because their motion is very
+nearly the same as that of the planets which they meet.</p>
+
+<p>An attentive examination of all the circumstances of this system
+renders our hypothesis still more probable. The primitive fluidity of
+the planets is clearly indicated by the compression of their figure,
+conformably to the laws of the mutual attraction of their molecules; it
+is moreover demonstrated by the regular diminution of gravity, as we
+proceed from the equator to the poles. This state of primitive fluidity
+to which we are conducted by astronomical phenomena, is also apparent
+from those which natural history points out. But in order fully to
+estimate them, we should take into account the immense variety of
+combinations formed by all the terrestial substances which were mixed
+together in a state of vapour, when the depression of their temperature
+enabled their elements to unite; it is necessary likewise to consider
+the wonderful changes which this depression ought to cause in the
+interior and at the surface of the earth, in all its productions, in
+the constitution and pressure of the atmosphere, in the ocean, and in
+all substances which it held in a state of solution. Finally, we should
+take into account the sudden changes, such as great volcanic eruptions,
+which must at different epochs have deranged the regularity of these
+changes. Geology, thus studied under the point of view which connects
+it with astronomy, may, with respect to several objects, acquire both
+precision and certainty.</p>
+
+<p>One of the most remarkable phenomena of the solar system is the
+rigorous equality which is observed to subsist between the angular
+motions of rotation and revolution of each satellite. It is infinity to
+unity that this is not the effect of hazard. The theory of universal
+gravitation makes infinity to disappear from this improbability, by
+shewing that it is sufficient for the existence of this phenomenon,
+that at the commencement these motions did not differ much. Then,
+the attraction of the planet would establish between them a perfect
+equality; but at the same time it has given rise to a periodic
+oscillation in the axis of the satellite directed to the planet, of
+which oscillation<span class="pagenum" id="Page_146">[Pg 146]</span> the extent depends on the primitive difference
+between these motions. As the observations of Mayer on the libration
+of the Moon, and those which Bouvard and Nicollet made for the
+same purpose, at my request, did not enable us to recognize this
+oscillation; the difference on which it depends must be extremely
+small, which indicates with every appearance of probability the
+existence of a particular cause, which has confined this difference
+within very narrow limits, in which the attraction of the planet might
+establish between the mean motions of rotation and revolution a rigid
+equality, which at length terminated by annihilating the oscillation
+which arose from this equality. Both these effects result from our
+hypothesis; for we may conceive that the Moon, in a state of vapour,
+assumed in consequence of the powerful attraction of the earth the
+form of an elongated spheroid, of which the greater axis would be
+constantly directed towards this planet, from the facility with which
+the vapours yield to the slightest force impressed upon them. The
+terrestrial attraction continuing to act in the same manner, while
+the Moon is in a state of fluidity, ought at length, by making the
+two motions of this satellite to approach each other, to cause their
+difference to fall within the limits, at which their rigorous equality
+commences to establish itself. Then this attraction should annihilate,
+by little and little, the oscillation which this equality produced on
+the greater axis of the spheroid directed towards the earth. It is in
+this manner that the fluids which cover this planet, have destroyed by
+their friction and resistance the primitive oscillations of its axis
+of rotation, which is only now subject to the nutation resulting from
+the actions of the Sun and Moon. It is easy to be assured that the
+equality of the motions of rotation and revolution of the satellites
+ought to oppose the formation of rings and secondary satellites, by the
+atmospheres of these bodies. Consequently observation has not hitherto
+indicated the existence of any such. The motions of the three first
+satellites of Jupiter present a phenomenon still more extraordinary
+than the preceding; which consists in this, that the mean longitude of
+the first, minus three times that of the second, plus twice that of
+the third, is constantly equal to two right angles. There is the ratio
+of infinity to one, that this equality is not the effect of chance.
+But we have seen, that in order to produce it, it is sufficient if at
+the commencement, the mean motions of these three bodies approached<span class="pagenum" id="Page_147">[Pg 147]</span>
+very near to the relation which renders the mean motion of the first,
+minus three times that of the second, plus twice that of the third,
+equal to nothing. Then their mutual attraction rendered this ratio
+rigorously exact, and it has moreover made the mean longitude of the
+first minus three times that of the second, plus twice that of the
+third, equal to a semicircumference. At the same time, it gave rise to
+a periodic inequality, which depends on the small quantity, by which
+the mean motions originally deviated from the relation which we have
+just announced. Notwithstanding all the care Delambre took in his
+observations, he could not recognize this inequality, which, while it
+evinces its extreme smallness, also indicates, with a high degree of
+probability, the existence of a cause which makes it to disappear. In
+our hypothesis, the satellites of Jupiter, immediately after their
+formation, did not move in a perfect vacuo; the less condensable
+molecules of the primitive atmospheres of the Sun and planet would
+then constitute a rare medium, the resistance of which being different
+for each of the stars, might make the mean motions to approach by
+degrees to the ratio in question; and when these movements had thus
+attained the conditions requisite, in order that the mutual attraction
+of the three satellites might render this relation accurately true, it
+perpetually diminished the inequality which this relation originated,
+and eventually rendered it insensible. We cannot better illustrate
+these effects than by comparing them to the motion of a pendulum,
+which, actuated by a great velocity, moves in a medium, the resistance
+of which is inconsiderable. It will first describe a great number of
+circumstances; but at length its motion of circulation perpetually
+decreasing, it will be converted into an oscillatory motion, which
+itself diminishing more and more, by the resistance of the medium, will
+eventually be totally destroyed, and then the pendulum, having attained
+a state of repose, will remain at rest for ever.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_21" href="#FNanchor_21" class="label">[21]</a>
+Translated from <i>Exposition du Système du Monde</i>,
+(Paris, 1796).</p>
+
+</div>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_22" href="#FNanchor_22" class="label">[22]</a>
+viz: “The motions of the planets in the same direction,
+and very nearly in the same plane; the motions of the satellites
+in the same direction as those of the planets; the motions of the
+rotation of these different bodies and also of the sun, in the same
+direction as their motions of projection, and in planes very little
+inclined to each other; the small eccentricity of the orbits of the
+comets and satellites; finally, the great eccentricity of the orbits
+of the comets, their inclinations being at the same time entirely
+indeterminate.”</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_148">[Pg 148]</span></p>
+<h2 class="nobreak" id="XX">XX<br>
+EDWARD JENNER<br>
+1749-1823</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Edward Jenner, born May 17, 1749, at Berkeley, Gloucestershire,
+England, studied surgery under John Hunter at London, and returned
+to his native town to practise. Having learned, about 1796, that
+milk-maids who had caught the cow-pox were immune from small-pox, he
+began at once to make investigations and to conduct experiments. This
+led to his “Inquiry,” published in 1798, in which he made public his
+theory of vaccination. His discovery created widespread interest, but
+although the theory at once met with the most virulent criticism,
+vaccination was soon widely accepted. By 1801, ten thousand persons
+were vaccinated in England, and the beneficent results justified its
+wide adoption. He died of apoplexy, January 26, 1823.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE THEORY OF VACCINATION<a id="FNanchor_23" href="#Footnote_23" class="fnanchor">[23]</a></p>
+
+<p>The deviation of Man from the state in which he was originally placed
+by Nature seems to have proved to him a prolific source of Diseases.
+From the love of splendour, from the indulgences of luxury, and from
+his fondness for amusement, he has familiarised himself with a great
+number of animals, which may not originally have been intended for his
+associates.</p>
+
+<p>The Wolf, disarmed of ferocity, is now pillowed in the lady’s lap. The
+Cat, the little Tyger of our island, whose natural home is the forest,
+is equally domesticated and caressed. The Cow, the Hog, the Sheep, and
+the Horse, are all, for a variety of purposes, brought under his care
+and dominion.</p>
+
+<p>There is a disease to which the Horse, from his state of
+domestication,<span class="pagenum" id="Page_149">[Pg 149]</span> is frequently subject. The Farriers have termed it the
+Grease. It is an inflammation and swelling in the heel, from which
+issues matter possessing properties of a very peculiar kind, which
+seems capable of generating a disease in the Human Body (after it has
+undergone the modification which I shall presently speak of), which
+bears so strong a resemblance to the Small-pox that I think it highly
+probable it may be the source of that disease.</p>
+
+<p>In this Dairy Country a great number of Cows are kept, and the office
+of milking is performed indiscriminately by Men and Maid Servants. One
+of the former having been appointed to apply dressings to the heels
+of a Horse affected with the Grease, and not paying due attention to
+cleanliness, incautiously bears his part in milking the Cows, with some
+particles of the infectious matter adhering to his fingers. When this
+is the case, it commonly happens that a disease is communicated to
+the Cows, and from the Cows to the Dairy-maids, which spreads through
+the farm until most of the cattle and domestics feel its unpleasant
+consequences. This disease has obtained the name of the Cow-pox. It
+appears on the nipples of the Cows in the form of irregular pustules.
+At their first appearance they are commonly of a palish blue, or
+rather of a colour somewhat approaching to livid, and are surrounded
+by an erysipelatous inflammation. These pustules, unless a timely
+remedy be applied, frequently degenerate into phagedenic ulcers, which
+prove extremely troublesome. The animals become indisposed, and the
+secretion of milk is much lessened. Inflamed spots now begin to appear
+on different parts of the hands of the domestics employed in milking,
+and sometimes on the wrists, which quickly run on to suppuration, first
+assuming the appearance of the small vesications produced by a burn.
+Most commonly they appear about the joints of the fingers, and at their
+extremities; but whatever parts are affected, if the situation will
+admit, these superficial suppurations put on a circular form, with
+their edges more elevated than their centre, and of a colour distantly
+approaching to blue. Absorption takes place, and tumours appear in
+each axilla. The system becomes affected—the pulse is quickened; and
+shiverings, with general lassitude and pains about the loins and limbs,
+with vomiting, come on. The head is painful, and the patient is now
+and then even affected with delirium. These symptoms, varying in their
+degrees of violence, generally continue from one day to three or four,<span class="pagenum" id="Page_150">[Pg 150]</span>
+leaving ulcerated sores about the hands, which, from the sensibility of
+the parts, are very troublesome, and commonly heal slowly, frequently
+becoming phagedenic, like those from whence they sprung. The lips,
+nostrils, eyelids, and other parts of the body, are sometimes affected
+with sores; but these evidently arise from their being needlessly
+rubbed or scratched with the patient’s infected fingers. No eruptions
+on the skin have followed the decline of the feverish symptoms in any
+instance that has come under my inspection, one only excepted, and in
+this case a very few appeared on the arms: they were very minute, of a
+vivid red colour, and soon died away without advancing to maturation;
+so that I cannot determine whether they had any connection with the
+preceding symptoms.</p>
+
+<p>Thus the disease makes its progress from the Horse to the nipple of the
+Cow, and from the Cow to the Human Subject.</p>
+
+<p>Morbid matter of various kinds, when absorbed into the system, may
+produce effects in some degree similar; but what renders the Cow-pox
+virus so extremely singular is, that the person who has been thus
+affected is forever after secure from the infection of the Small-pox;
+neither exposure to the <i>variolous effluvia</i>, nor the insertion of
+the matter into the skin producing this distemper.</p>
+
+<div class="blockquot">
+
+<p>[I shall now conclude this Inquiry with some general observations on
+the subject, and on some others which are interwoven with it.]</p>
+</div>
+
+<p>Although I presume it may be unnecessary to produce further testimony
+in support of my assertion “that Cow-pox protects the human
+constitution from the infection of the Small-pox,” yet it affords me
+considerable satisfaction to say that Lord Somerville, the president of
+the Board of Agriculture, to whom this paper was shown by Sir Joseph
+Banks, has found upon inquiry that the statements were confirmed by
+the concurring testimony of Mr. Dolland, a surgeon, who resides in a
+dairy country remote from this, in which these observations were made.
+With respect to the opinion adduced “that the source of the infection
+is a peculiar morbid matter arising in the horse,” although I have not
+been able to prove it from actual experiments conducted immediately
+under my own eye, yet the evidence I have adduced appears sufficient to
+establish it.</p>
+
+<p><span class="pagenum" id="Page_151">[Pg 151]</span></p>
+
+<p>They who are not in the habit of conducting experiments may not be
+aware of the coincidence of circumstances necessary for their being
+managed so as to prove perfectly decisive; nor how often men engaged in
+professional pursuits are liable to interruptions which disappoint them
+almost at the instant of their being accomplished.</p>
+
+<div class="blockquot">
+
+<p>[However, I feel no room for hesitation respecting the common origin
+of the disease, being well convinced that it never appears among the
+cows (except it can be traced to a cow introduced among the general
+herd which has been previously infected, or to an infected servant),
+unless they have been milked by someone who, at the same time, has the
+care of a horse affected with diseased heels.</p>
+
+<p>The spring of 1797, which I intended particularly to have devoted
+to the completion of this investigation, proved, from its dryness,
+remarkably adverse to my wishes; for it frequently happens, while
+the farmers’ horses are exposed to the cold rains which fall at that
+season that their heels become diseased, and no Cow-pox then appeared
+in the neighbourhood.]</p>
+</div>
+
+<p>The active quality of the virus from the horses’ heels is greatly
+increased after it has acted on the nipples of the cow, as it rarely
+happens that the horse affects his dresser with sores, and as rarely
+that a milk-maid escapes the infection when she milks infected cows.
+It is most active at the commencement of the disease, even before it
+has acquired a pus-like appearance; indeed I am not confident whether
+this property in the matter does not entirely cease as soon as it is
+secreted in the form of pus. I am induced to think it does cease,
+and that it is the thin darkish-looking fluid only, oozing from the
+newly-formed cracks in the heels, similar to what sometimes appears
+from erysipelatous blisters, which gives the disease. Nor am I certain
+that the nipples of the cows are at all times in a state to receive
+the infection. The appearance of the disease in the spring and the
+early part of the summer, when they are disposed to be affected with
+spontaneous eruptions so much more frequently than at other seasons,
+induces me to think that the virus from the horse must be received
+upon them when they are in this state, in order to produce effects;
+experiments, however, must determine these points. But it is clear that
+when the Cow-pox virus is once generated, that the cows cannot<span class="pagenum" id="Page_152">[Pg 152]</span> resist
+the contagion, in whatever state their nipples may chance to be, if
+they are milked with an infected hand.</p>
+
+<p>Whether the matter, either from the cow or the horse, will affect the
+sound skin of the human body, I cannot positively determine; probably
+it will not, unless on those parts where the cuticle is extremely thin,
+as on the lips for example. I have known an instance of a poor girl
+who produced an ulceration on her lip by frequently holding her finger
+to her mouth to cool the raging of a Cow-pox sore by blowing upon it.
+The hands of the farmers’ servants here, from the nature of their
+employments, are constantly exposed to those injuries which occasion
+abrasions of the cuticle, to punctures from thorns and such like
+accidents; so that they are always in a state to feel the consequences
+of exposure to infectious matter.</p>
+
+<div class="blockquot">
+
+<p>[It is singular to observe that the Cow-pox virus, although it renders
+the constitution unsusceptible of the variolous, should, nevertheless,
+leave it unchanged with respect to its own action. I have already
+produced an instance to point out this, and shall now corroborate it
+with another.</p>
+
+<p>Elizabeth Wynne, who had the Cow-pox in the year 1759, was inoculated
+with variolous matter, without effect, in the year 1797, and again
+caught the Cow-pox in the year 1798. When I saw her, which was on the
+8th day after she received the infection, I found her infected with
+general lassitude, shiverings, alternating with heat, coldness of the
+extremities, and a quick and irregular pulse. These symptoms were
+preceded by a pain in the axilla.]</p>
+</div>
+
+<p>It is curious also to observe that the virus, which with respect to
+its effects is undetermined and uncertain previously to its passing
+from the horse through the medium of the cow, should then not only
+become more active, but should invariably and completely possess those
+specific properties which induce in the human constitution symptoms
+similar to those of the variolous fever, and effect in it that peculiar
+change which forever renders it unsusceptible of the variolous
+contagion.</p>
+
+<p>May it not then be reasonably conjectured that the source of the
+Small-pox is morbid matter of a peculiar kind, generated by a disease
+in the horse, and that accidental circumstances may have again and
+again arisen, still working new changes upon it, until it has acquired
+the contagious and malignant form under which we now commonly see it
+making its devastations amongst us? And, from a<span class="pagenum" id="Page_153">[Pg 153]</span> consideration of the
+change which the infectious matter undergoes from producing a disease
+on the cow, may we not conceive that many contagious diseases, now
+prevalent among us, may owe their present appearance not to a simple,
+but to a compound origin? For example, is it difficult to imagine that
+the measles, scarlet fever, and the ulcerous sore throat with a spotted
+skin, have all sprung from the same source, assuming some variety in
+their forms according to the nature of their new combinations? The same
+question will apply respecting the origin of many other contagious
+diseases, which bear a strong analogy to each other.</p>
+
+<p>There are certainly more forms than one, without considering the common
+variation between the confluent and distinct, in which the Small-pox
+appears in what is called the natural way. About seven years ago a
+species of Small-pox spread through many of the towns and villages of
+this part of Gloucestershire: it was of so mild a nature that a fatal
+instance was scarcely ever heard of, and consequently so little dreaded
+by the lower orders of the community that they scrupled not to hold the
+same intercourse with each other as if no infectious disease had been
+present among them. I never saw nor heard of an instance of its being
+confluent. The most accurate manner, perhaps, in which I can convey
+an idea of it, is, by saying that had fifty individuals been taken
+promiscuously and infected by exposure to this contagion, they would
+have had as mild and light a disease as if they had been inoculated
+with variolous matter in the usual way. The harmless manner in which it
+showed itself could not arise from any peculiarity either in the season
+or the weather, for I watched its progress upwards of a year without
+perceiving any variation in its general appearance. I consider it then
+as a variety of the Small-pox.</p>
+
+<div class="blockquot">
+
+<p>[In some of the preceding cases I have noticed the attention that was
+paid to the state of the variolous matter previous to the experiment
+of inserting it into the arms of those who had gone through the
+Cow-pox. This I conceived to be of great importance in conducting
+these experiments, and were it always properly attended to by those
+who inoculate for the Small-pox, it might prevent much subsequent
+mischief and confusion. With the view of enforcing so necessary a
+precaution, I shall take the liberty of digressing so far as to
+point out some unpleasant facts relative to mismanagement in this
+particular, which have fallen under my own observation.]</p>
+</div>
+
+<p><span class="pagenum" id="Page_154">[Pg 154]</span></p>
+
+<p>A medical gentleman (now no more), who for many years inoculated
+in this neighbourhood, frequently preserved the variolous matter
+intended for his use, on a piece of lint or cotton, which, in its
+fluid state, was put into a vial, corked, and conveyed into a warm
+pocket; a situation certainly favourable for speedily producing
+putrefaction in it. In this state (not infrequently after it had been
+taken several days from the pustules) it was inserted into the arms
+of his patients, and brought on inflammation of the incised parts,
+swellings of the axillary glands, fever, and sometimes eruptions. But
+what was this disease? Certainly not the Small-pox; for the matter
+having from putrefaction lost, or suffered a derangement in its
+specific properties, was no longer capable of producing that malady,
+those who had been inoculated in this manner being as much subject
+to the contagion of the Small-pox, as if they had never been under
+the influence of this artificial disease; and many, unfortunately,
+fell victims to it, who thought themselves in perfect security. The
+same unfortunate circumstance of giving a disease, supposed to be the
+Small-pox, with inefficacious variolous matter, having occurred under
+the direction of some other practitioners within my knowledge, and
+probably from the same incautious method of securing the variolous
+matter, I avail myself of this opportunity of mentioning what I
+conceive to be of great importance; and, as a further cautionary hint,
+I shall again digress so far as to add another observation on the
+subject of Inoculation.</p>
+
+<p>Whether it be yet ascertained by experiment, that the quantity of
+variolous matter inserted into the skin makes any difference with
+respect to the subsequent mildness or violence of the disease, I know
+not; but I have the strongest reason for supposing that if either the
+punctures or incisions be made so deep as to go through it, and wound
+the adipose membrane, that the risk of bringing on a violent disease is
+greatly increased. I have known an inoculator, whose practice was “to
+cut deep enough (to use his own expression) to see a bit of fat,” and
+there to lodge the matter. The great number of bad cases, independent
+of inflammations and abscesses on the arms, and the fatality which
+attended this practice was almost inconceivable; and I cannot account
+for it on any other principle than that of the matter being placed in
+this situation instead of the skin.</p>
+
+<p>At what period the Cow-pox was first noticed here is not upon<span class="pagenum" id="Page_155">[Pg 155]</span> record.
+Our oldest farmers were not unacquainted with it in their earliest
+days, when it appeared among their farms without any deviation from
+the phenomena which it now exhibits. Its connection with the Small-pox
+seems to have been unknown to them. Probably the general introduction
+of inoculation first occasioned the discovery.</p>
+
+<p>Its rise in this country may not have been of very remote date, as the
+practice of milking cows might formerly have been in the hands of women
+only; which I believe is the case now in some other dairy countries,
+and consequently that the cows might not in former times have been
+exposed to the contagious matter brought by the men servants from the
+heels of horses. Indeed a knowledge of the source of the infection is
+new in the minds of most of the farmers in this neighbourhood, but it
+has at length produced good consequences; and it seems probable from
+the precautions they are now disposed to adopt, that the appearance
+of the Cow-pox here may either be entirely extinguished or become
+extremely rare.</p>
+
+<p>Should it be asked whether this investigation is a matter of mere
+curiosity, or whether it tends to any beneficial purpose, I should
+answer that, notwithstanding the happy effects of inoculation, with
+all the improvements which the practice has received since its first
+introduction into this country, it not very infrequently produces
+deformity of the skin, and sometimes, under the best management, proves
+fatal.</p>
+
+<p>These circumstances must naturally create in every instance some degree
+of painful solicitude for its consequences. But as I have never known
+fatal effects arise from the Cow-pox, even when impressed in the most
+unfavourable manner, producing extensive inflammations and suppurations
+on the hands; and as it clearly appears that this disease leaves the
+constitution in a state of perfect security from the infection of
+the Small-pox, may we not infer that a mode of inoculation may be
+introduced preferable to that at present adopted, especially among
+those families which, from previous circumstances, we may judge to be
+predisposed to have the disease unfavourably? It is an excess in the
+number of pustules which we chiefly dread in the Small-pox; but, in
+the Cow-pox, no pustules appear, nor does it seem possible for the
+contagious matter to produce the disease from effluvia, or by any other
+means than contact, and that probably not simply between the virus and
+the cuticle; so that a single individual in a family might at any<span class="pagenum" id="Page_156">[Pg 156]</span> time
+receive it without the risk of infecting the rest, or of spreading a
+distemper that fills a country with terror.</p>
+
+<div class="blockquot">
+
+<p>[Several instances have come under my observation which justify the
+assertion that the disease cannot be propagated by effluvia. The first
+boy whom I inoculated with the matter of Cow-pox slept in a bed while
+the experiment was going forward, with two children who had never gone
+through either that disease or the Small-pox, without infecting either
+of them.</p>
+
+<p>A young woman who had the Cow-pox to a great extent, several sores
+which maturated having appeared on the hands and wrists, slept in the
+same bed with a fellow-dairymaid, who never had been infected with
+either the Cow-pox or the Small-pox, but no indisposition followed.</p>
+
+<p>Another instance has occurred of a young woman on whose hands were
+several large suppurations from the Cow-pox, who was at the same time
+a daily nurse to an infant, but the complaint was not communicated to
+the child.]</p>
+</div>
+
+<p>In some other points of view the inoculation of this disease appears
+preferable to the variolous inoculation.</p>
+
+<p>In constitutions predisposed to scrofula, how frequently we see the
+inoculated Small-pox rouse into activity that distressful malady.
+This circumstance does not seem to depend on the manner in which the
+distemper has shown itself, for it has as frequently happened among
+those who have had it mildly, as when it has appeared in the contrary
+way. There are many, who from some peculiarity in the habit resist the
+common effects of variolous matter inserted into the skin, and who
+are in consequence haunted through life with the distressing idea of
+being insecure from subsequent infection. A ready mode of dissipating
+anxiety originating from such a cause must now appear obvious. And, as
+we have seen that the constitution may at any time be made to feel the
+fertile attack of Cow-pox, might it not, in many chronic diseases, be
+introduced into the system, with the probability of affording relief,
+upon well-known physiological principles?</p>
+
+<p>Although I say the system may at any time be made to feel the febrile
+attack of Cow-pox, yet I have a single instance before me where the
+virus acted locally only, but it is not in the least probable that
+the same person would resist the action both of Cow-pox virus and the
+variolous.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_23" href="#FNanchor_23" class="label">[23]</a>
+From <i>An Inquiry into the Cause and Effects of the
+Variolae Vaccinae</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_157">[Pg 157]</span></p>
+<h2 class="nobreak" id="XXI">XXI<br>
+COUNT RUMFORD<br>
+1753-1814</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Sir Benjamin Thompson, Count Rumford, was born in Woburn,
+Massachusetts, March 26, 1753, a member of an old New England family.
+After a very romantic youth and early manhood in which he underwent
+many exciting adventures as a British loyalist at the time of the
+American Revolution, he was sent to England with despatches by the
+British expeditionary authorities and there found employment in the
+office of the Secretary of State. After the close of the Revolution
+he went to Bavaria, where he became Minister of War and Grand
+Chamberlain. In 1791 he was made a count of the Holy Roman Empire. In
+1796 President Adams invited him to return to America to become an
+inspector of artillery, but he declined; and at about the same time he
+became interested in problems of heat, light, and fuel. His suggestions
+ultimately became the basis for the doctrine of the conservation of
+energy. He died at Auteuil, August 25, 1814.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE NATURE OF HEAT<a id="FNanchor_24" href="#Footnote_24" class="fnanchor">[24]</a></p>
+
+<p>After I had long meditated upon a way of putting this interesting
+problem entirely out of doubt by a perfectly conclusive experiment, I
+thought finally that I had discovered it, and I think so still.</p>
+
+<p>I argued that if the existence of caloric was a fact, it must be
+absolutely impossible for a body or for several individual bodies,
+which together made one whole, to communicate this substance
+continuously to various other bodies by which they were surrounded,
+without this substance gradually being entirely exhausted.</p>
+
+<p><span class="pagenum" id="Page_158">[Pg 158]</span></p>
+
+<p>A sponge filled with water, and hung by a thread in the middle of a
+room filled with dry air, communicates its moisture to the air, it is
+true, but soon the water evaporates and the sponge can no longer give
+out moisture. On the contrary, a bell sounds without interruption when
+it is struck, and gives out its sound as often as we please without the
+slightest perceptible loss. Moisture is a substance; sound is not.</p>
+
+<p>It is well known that two hard bodies, if rubbed together, produce
+much heat. Can they continue to produce it without finally becoming
+exhausted? Let the result of experiment decide this question.</p>
+
+<p>It would be too tedious to describe here in detail all the experiments
+which I undertook with a view of answering in a decisive manner this
+important and disputed question. They may be found in my memoir, “On
+the Source of Heat excited by Friction.” I have had it printed in
+the <i>Philosophical Transactions</i> for the year 1798; still these
+experiments bear too close a relation to my later researches on heat
+for me to omit attempting at least to give the reader a clear idea of
+the experiments and of their results.</p>
+
+<p>The apparatus which I used in these investigations is too complicated
+to be represented in this place; still it will not be difficult for
+the reader to form a conception of the principal experiments and their
+results.</p>
+
+<p>Let A be the vertical section of a brass rod which is an inch in
+diameter and is fastened in an upright position on a stout block,
+B; it is provided at its upper end with a massive hemisphere of the
+same metal, three and a half inches in diameter. C is a similar rod,
+likewise vertical, to the lower end of which is fastened a similar
+hemisphere. Both hemispheres must fit each other in such a way that
+both the rods stand in a perfectly straight vertical line.</p>
+
+<p>D is the vertical section of a globular metallic vessel twelve inches
+in diameter, which is provided with a cylindrical neck three inches
+long and three and three-quarter inches in diameter. The rod A goes
+through a hole in the bottom of the vessel, is soldered into the
+vessel, and serves as a support to keep it in its proper position.</p>
+
+<p>The centre of the ball, made up of the two hemispheres which lie the
+one upon the other, is in the centre of the globular vessel, so that,
+if the vessel is filled with water, the water covers the ball as well
+as a part of each of the brass rods.</p>
+
+<p><span class="pagenum" id="Page_159">[Pg 159]</span></p>
+
+<p>If now the hemispheres be pressed strongly together, and at the same
+time the rod C be turned, by some means or other, about its axis,
+a very considerable quantity of heat is generated by means of the
+friction which takes place between the flat surfaces of the two
+hemispheres.</p>
+
+<p>The quantity of the heat excited in this manner is exactly proportional
+to the force with which the two surfaces are pressed together, and to
+the rapidity of the friction. When this force was equal to the pressure
+of ten thousand pounds, and when the rod was turned with such rapidity
+about its axis that it revolved thirty-two times a minute, the quantity
+of heat generated by the continual rubbing of the two surfaces together
+was extraordinarily great. It was equal to the quantity given off by
+the flame of nine wax-candles of moderate size all burning together.</p>
+
+<p>The quantity of heat generated in this manner during a given time is
+manifestly the same, whether the globular vessel D is filled with
+water, and the surfaces of the two hemispheres rub on each other in
+this liquid, or whether there is no water in the vessel, and the
+apparatus by which the friction is produced is simply surrounded by air.</p>
+
+<p>The source of the heat which is generated by this apparatus is
+inexhaustible. As long as the rod C is turned about its axis, so long
+will heat be produced by the apparatus, and always to the same amount.</p>
+
+<p>If the globe-shaped vessel D is filled with water, this water becomes
+hotter and hotter, and finally begins to boil. I have myself in this
+way boiled a considerable quantity of water.</p>
+
+<p>If this experiment is performed in winter when the temperature of the
+air is but little above the freezing-point, and if the vessel D is
+filled with a mixture of water and pounded ice, the quantity of heat
+caused in a given time by the rubbing together of the two surfaces can
+be expressed very exactly by the amount of ice melted by this heat.</p>
+
+<p>Since the apparatus affords heat continuously, and always to the same
+amount, we can melt in this way as much ice as we please.</p>
+
+<p>But whence comes this heat? This is the contested point, to determine
+which was the real aim of the experiment.</p>
+
+<p>It is certain that it comes neither from the decomposition of the
+water nor from the decomposition of the air. Various experiments
+on<span class="pagenum" id="Page_160">[Pg 160]</span> this point, which I have described at length in my memoir in
+the <i>Philosophical Transactions</i>, are more than sufficient to
+establish this fact beyond doubt.</p>
+
+<p>Just as little does it come from a change in the capacity for heat
+brought about by friction in the metal of which the hemispheres are
+composed. This is shown, first, by the continuance and uniformity of
+the production of the heat; and, secondly, by an experiment bearing
+directly on this point, by which I am convinced that not the slightest
+change had taken place in the capacity of the metal for heat.</p>
+
+<p>Just as little does it come from the rods which are attached to
+the hemispheres, for these rods were always warm, the hemispheres
+communicating heat to them.</p>
+
+<p>Much less could this heat come from the air of the water immediately
+surrounding the hemispheres, for the apparatus communicated heat to
+both these fluids without cessation.</p>
+
+<p>Whence, then, came this heat? and what is heat actually?</p>
+
+<p>I must confess that it has always been impossible for me to explain
+the results of such experiments except by taking refuge in the very
+old doctrine which rests on the supposition that heat is nothing but a
+vibratory motion taking place among the particles of bodies.</p>
+
+<p>A bell, on being struck, immediately gives forth a sound, and the
+oscillations of the air produced by these vibrations forthwith cause a
+quivering motion in those bodies with which they come in contact. On
+the other hand, a sponge filled with water cannot give off its moisture
+to the bodies in its vicinity for any length of time without itself
+losing moisture.</p>
+
+<p>A very illustrious philosopher, for whom I have always entertained the
+greatest respect, and whom, moreover, I have the good fortune to count
+among my most intimate friends, M. Bertholet, has, in his admirable
+<i>Essai de Statique Chimique</i>, attempted to explain the results
+of this investigation, and to reconcile them with that theory of heat
+which is founded upon the hypothesis of caloric.</p>
+
+<p>If a man as learned, as honest, as worthy, and as renowned as is
+M. Bertholet spares no pains in opposing the errors of a natural
+philosopher or chemist, one cannot and dare not keep silence unless he
+wishes to acknowledge himself vanquished. If, however, one can produce
+proofs—a fortunate thing for all those who find themselves driven to
+similar self-vindication—that the objections of M. Bertholet<span class="pagenum" id="Page_161">[Pg 161]</span> have no
+foundation, he has done very much towards establishing beyond doubt the
+opinions and facts in question.</p>
+
+<p>I will now endeavor to answer the objections which M. Bertholet has
+offered to my explanation of the above-mentioned experiments; and, that
+the reader may be in a position to give to these objections their just
+value, I will insert them here in the writer’s own words.</p>
+
+<div class="blockquot">
+
+<p>“Count Rumford has made a curious experiment with regard to the heat
+which may be excited by friction. He causes a blunt borer to revolve
+very rapidly (this borer revolved about its axis only thirty-two times
+a minute) in a brass cylinder weighing thirteen pounds, English weight
+(the cylinder weighed one hundred and thirteen pounds and somewhat
+more), and says that he observed that this borer in the course of
+two (one and a half) hours, and under a pressure equal to 100 cwt.,
+reduced to powder 4145 grains (8-1/2 ounces Troy) of brass, and that
+an amount of heat was generated during this operation sufficient
+to bring to boil 26.38 pounds of water, previously cooled to the
+freezing-point. He asserts that he did not discover the slightest
+difference between the specific heat of the metallic dust and that of
+the brass which had not experienced the friction. Hence he supposes
+that the heat was excited by the pressure alone, and was not at all
+due to caloric, as is the opinion of most chemists.</p>
+
+<p>“I will for the present satisfy myself with simply inquiring whether
+it necessarily follows from this experiment that we must renounce
+entirely the received theory of caloric, according to which it is
+regarded as a substance which enters into combination with bodies, or
+whether this result cannot be explained in a satisfactory manner by
+applying to the case in question those laws of nature in accordance
+with which the operations of heat are manifested under other
+conditions.</p>
+
+<p>“If the evolution of heat be regarded as a consequence of the decrease
+of volume caused by the pressure, then not only the metallic powder,
+but also all the rest of the brass cylinder must have contributed,
+though not in an equal manner, to this evolution, by the powerful
+expansive effort of that portion which experienced the greatest
+pressure, and consequently acquired the greatest temperature, without
+being able to assume the dimensions proper to this same temperature on
+account of the less heated and less expanded parts; consequently there
+must have arisen, necessarily, a certain condensation of the metal
+in respect of its natural dimensions, which condensation gradually
+decreased from the point where the pressure was greatest to the
+surface. We may suppose<span class="pagenum" id="Page_162">[Pg 162]</span> that this operation took place in a similar
+manner in all parts of the cylinder.</p>
+
+<p>“As a consequence of this decrease of volume, an amount of caloric was
+given out equal to that which would have caused a similar increase
+of volume, on the supposition, that is, that the specific heat of
+the metal does not change through this range of the scale of the
+thermometer, and that the expansions are equal; and this, considering
+the range of temperatures and the consequent expansions, is probably
+not far from the truth. The entire amount of heat disengaged would
+have raised the cylinder to about 180° of Reaumur’s scale; and if
+the expansion of brass by heat is equal to that of iron, which has
+been found to be 1-75000 for each degree of the thermometer, the 180
+degrees would have caused an expansion of 18-75000 in each direction,
+and the decrease of volume must have brought about the same degree of
+heat if we suppose that the pressure stood in equal relation to this
+expansion.</p>
+
+<p>“Now there is a change, and sometimes a very considerable one, wrought
+in the specific gravity of a metal, by percussion, by the action of
+a fly-wheel, or by the compression of a wire-drawing machine. It
+appears, for example, that the specific gravity of platina and of
+iron, on being forged, is thus increased by a twentieth part.</p>
+
+<p>“Hence it appears that the experiment of Count Rumford is far from
+explaining satisfactorily a property which is well known, and called
+in question by no one.</p>
+
+<p>“It is easy, it is true, to arrange side by side in an imposing manner
+the phenomena of heat; if, however, you were to say to one who has
+little or no knowledge of chemical speculations, ‘Count Rumford’s
+cylinder has, in the course of two hours, by means of a violent
+friction, afforded all the heat required to dissolve in water, without
+changing its temperature, 15 kilogrammes of ice, or as much as 2
+hectogrammes (6-1/2 ounces) of oxygen would require [<i>sic</i>] in
+its combination with phosphorus,’ I do not know at which of these
+phenomena he would be most astonished.</p>
+
+<p>“The slight changes which can take place in the amount of combined
+caloric have so inconsiderable an influence on the capacity for work
+of the caloric within the narrow limits of the thermometric scale,
+that it cannot be computed. Moreover, we have not, as yet, adequate
+data for determining the nature of the changes in this respect which
+take place in a solid body in consequence of the particular condition
+of condensation into which it has been brought by means of certain
+mechanical force, and by degrees of heat differing greatly from each
+other.</p>
+
+<p>“Besides, Rumford, in the experiment to determine the specific heat
+of the filings of bell-metal thus obtained, heated them to the
+temperature<span class="pagenum" id="Page_163">[Pg 163]</span> of boiling water. But this extremely elastic heat would
+very naturally as soon as left to itself, and especially during the
+operation just mentioned, resume that state of expansion and that
+capacity for heat which is proper to it at a given temperature, so
+that the effect of the pressure to which it has been subjected partly
+disappears again, just as a piece of metal which has been hammered
+resumes its natural properties on being annealed.”</p>
+</div>
+
+<p>In reply to these remarks, I will call to mind what follows.</p>
+
+<p>1st. The discovery which I made, that no considerable change had
+taken place in the specific heat of the metallic dust produced by the
+friction, led me in no way to the supposition that the heat excited
+in the experiment could not come from the caloric set free. I only
+found that the source of this heat was inexhaustible. To explain this
+phenomenon, which has never yet been explained, is the point now in
+question, and I do not see how it can be explained except by giving up
+altogether the hypothesis adopted in regard to caloric.</p>
+
+<p>2d. If we actually suppose (and it is far from having been proved)
+that the simple pressing together of a metal is sufficient to expel
+the caloric contained in it; still the explanation of such a natural
+phenomenon would be advanced little or none; for since the action of
+the force which causes the pressure is continuous, the condensation
+of the metal brought about by this force would in a short time reach
+its maximum; and if really in this operation ever so much caloric had
+been disengaged from the metal, still it would very soon disperse. The
+rubbing surfaces, on the contrary, continue to give forth heat, and
+that always to the same amount.</p>
+
+<p>3d. In regard to the objection made to the experiment which was
+undertaken with a view of determining whether a change had taken place
+in the capacity of the metallic dust for heat, this can very readily be
+answered, and in such a way that nothing, it seems to me, can be said
+against it. If the temperature of boiling water were really sufficient
+to give to these small, forcibly condensed particles of metal the
+quantity of heat necessary to bring them back to their original
+condition as far as their capacity for heat is concerned, then, as the
+water by which the apparatus was surrounded finally began to boil,
+they must, without doubt, have taken the necessary amount of heat from
+this water. If, now, these particles of metal received finally from
+the water the caloric which in the beginning they imparted to it,
+the question<span class="pagenum" id="Page_164">[Pg 164]</span> arises, whence came the caloric which served to heat,
+not only the water, but also the metal and the objects immediately
+surrounding it?</p>
+
+<p>I am far from desiring to deceive anyone by an imposing arrangement
+of facts; but the facts in my experiments were so very striking that
+it was altogether impossible for me to help instituting comparisons
+and making calculations with regard to them which would make them
+clear, especially to those not yet sufficiently acquainted with such
+investigations.</p>
+
+<p>I will now close my remarks with an entirely new computation. I will
+show whether it is probable that the metal could supply all the heat
+which was produced by friction in the experiment in question. If we are
+to make this supposition, we must, in the first place, allow that all
+the heat came directly from the particles of metal which were separated
+from the solid mass of metal by the friction; for, since the mass
+remained in the same condition throughout the entire experiment, it is
+evident that it could contribute in no measure to the effect produced.</p>
+
+<p>We will now inquire how much heat would have been developed if the
+experiment had been carried on without cessation, until the whole mass
+of metal had been reduced to powder by the friction.</p>
+
+<p>After the experiment had lasted an hour and a half, there were 4145
+grains (Troy) of the metallic dust, and during that time an amount of
+heat was produced by the friction sufficient to raise 26.58 pounds of
+ice-cold water to the boiling point.</p>
+
+<p>Since the mass of metal weighed 113.13 pounds, or 791,190 grains, all
+this metal would have been reduced to powder if the experiment had
+lasted uninterruptedly, day and night, for 477-1/2 hours, or for 19
+days 21-1/2 hours, and during this time an amount of heat would have
+been produced sufficient to have raised 5078 pounds of water to the
+boiling-point.</p>
+
+<p>Since the metal used in this experiment showed a capacity for heat
+which was to that of water as 0.11 to 1, it is evident that this amount
+of heat would have been sufficient to raise a mass of the same metal
+46,165 pounds in weight through 180 degrees of Fahrenheit’s scale, or
+from the temperature of melting ice to that of boiling water.</p>
+
+<p>This amount of heat would be sufficient to melt a mass of metal sixteen
+times heavier than that which I used in the experiment.</p>
+
+<p>Is it at all conceivable that such an enormous quantity of caloric<span class="pagenum" id="Page_165">[Pg 165]</span>
+could really be present in this body? But even this supposition would
+be by no means sufficient for the explanation of the fact in question,
+as I have shown by a decisive experiment that the capacity of the metal
+for heat has not sensibly altered.</p>
+
+<p>Whence, then, came the caloric which the apparatus furnished in such
+abundance?</p>
+
+<p>I leave this question to be answered by those persons who believe in
+the actual existence of caloric.</p>
+
+<p>In my opinion, I have made it sufficiently evident that it was
+impossible for it to come from the metallic bodies which were rubbed
+together, and I am absolutely unable to imagine how it can have come
+from any other object in the neighborhood of the apparatus, for all
+these objects received their heat constantly from the apparatus itself.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_24" href="#FNanchor_24" class="label">[24]</a>
+From <i>An Enquiry Concerning the Source of Heat Excited
+by Friction</i> (1798)—<i>Transactions of the Royal Society of
+London</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_166">[Pg 166]</span></p>
+<h2 class="nobreak" id="XXII">XXII<br>
+JOHN DALTON<br>
+1766-1844</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>John Dalton, son of a weaver, was born in Cumberland,
+England, September 5, 1766. After an early life spent in teaching in
+elementary schools, in 1793 he became a teacher of mathematics and
+philosophy at New College, Manchester. He began his researches into the
+combination of gases in 1800 and discovered that gases expanded equally
+with the same pressure and heat. He announced his discovery in a paper
+read before the Manchester Society in 1801. From further experiments
+he derived his theory that gases combined with one another in definite
+proportions, and evolved his atomic theory to explain the results.
+Awarded the King’s medal in 1822, he was further honored by a pension
+granted in 1833. He died May 27, 1844.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE ATOMIC THEORY<a id="FNanchor_25" href="#Footnote_25" class="fnanchor">[25]</a></p>
+
+<p>There are three distinctions in the kinds of bodies, or three states,
+which have more especially claimed the attention of philosophical
+chemists; namely, those which are marked by the terms elastic fluids,
+liquids, and solids. A very familiar instance is exhibited to us
+in water, of a body which, in certain circumstances, is capable of
+assuming all the three states. In steam we recognize a perfectly
+elastic fluid, in water a perfect liquid, and in ice a complete solid.
+These observations have tacitly led to the conclusion which seems
+universally adopted, that all bodies of sensible magnitude, whether
+liquid or solid, are constituted of a vast number of extremely small
+particles, or atoms<span class="pagenum" id="Page_167">[Pg 167]</span> of matter bound together by a force of attraction,
+which is more or less powerful according to circumstances, and which
+as it endeavours to prevent their separation, is very properly called
+in that view, attraction of cohesion; but as it collects them from a
+dispersed state (as from steam into water) it is called attraction of
+aggregation, or more simply, affinity. Whatever names it may go by,
+they will signify one and the same power. It is not my design to call
+in question this conclusion, which appears completely satisfactory;
+but to show that we have hitherto made no use of it, and that the
+consequence of the neglect has been a very obscure view of chemical
+agency, which is daily growing more so in proportion to the new lights
+attempted to be thrown upon it.</p>
+
+<p>The opinions I more particularly allude to, are those of Bertholet
+on the Laws of chemical affinity; such as that chemical agency is
+proportional to the mass, and that in all chemical unions there exist
+insensible gradations in the proportions of the constituent principles.
+The inconsistence of these opinions, both with reason and observation,
+cannot, I think, fail to strike every one who takes a proper view of
+the phenomena.</p>
+
+<p>Whether the ultimate particles of a body, such as water, are all
+alike, that is, of the same figure, weight, etc., is a question of
+some importance. From what is known, we have no reason to apprehend
+a diversity in these particulars: if it does exist in water, it must
+equally exist in the elements constituting water, namely, hydrogen and
+oxygen. Now it is scarcely possible to conceive how the aggregates
+of dissimilar particles should be so uniformly the same. If some of
+the particles of water were heavier than others, if a parcel of the
+liquid on any occasion were constituted principally of these heavier
+particles, it must be supposed to affect the specific gravity of the
+mass, a circumstance not known. Similar observations may be made on
+other substances. Therefore we may conclude that the ultimate particles
+of all homogeneous bodies are perfectly alike in weight, figure, etc.
+In other words, every particle of water is like every other particle
+of water; every particle of hydrogen is like every other particle of
+hydrogen, etc.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_25" href="#FNanchor_25" class="label">[25]</a>
+From a note entitled <i>On the Constitution of Bodies</i>
+which Dalton wrote and had incorporated in Thomas Thompson’s <i>System
+of Chemistry</i> (3d edition, 1807).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_168">[Pg 168]</span></p>
+<h2 class="nobreak" id="XXIII">XXIII<br>
+MARIE FRANÇOIS XAVIER BICHAT<br>
+1771-1802</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Bichat was born in the French town of Thoirette (Department of
+Ain), November 14, 1771. At the University of Lyons he was especially
+interested in anatomy, surgery, and natural history. In 1793, because
+of the Revolution, he fled to Paris, where he studied under the eminent
+surgeon Desault. In 1800 he distinguished between animal and organic
+functions and after many dissections he developed, in 1801, his famous
+doctrine of tissues. He died July 22, 1802, from injuries received in a
+fall.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE DOCTRINE OF TISSUES<a id="FNanchor_26" href="#Footnote_26" class="fnanchor">[26]</a><br>
+<br>
+OBJECT OF THE WORK</p>
+
+<p>The general doctrine of this work has not precisely the character of
+any of those which have prevailed in medicine. Opposed to that of
+Boerhaave, it differs from that of Stahl and those authors who, like
+him, refer everything in the living economy to a single principle,
+purely speculative, ideal, and imaginary, whether designated by the
+name of soul, vital principle, or archeus. The general doctrine of this
+work consists in analyzing with precision the properties of living
+bodies, in showing that every physiological phenomenon is ultimately
+referable to these properties considered in their natural state;
+that every pathological phenomenon derives from their augmentation,
+diminution, or alteration; that every therapeutic phenomenon has for
+its principle the restoration of that part of the natural type, from
+which it has been changed; in determining with precision the cases
+in which each property is brought into action; in distinguishing
+accurately in physiology<span class="pagenum" id="Page_169">[Pg 169]</span> as well as in medicine, that which is
+derived from one, and that which flows from others; in ascertaining by
+rigorous induction the natural and morbific phenomena which the animal
+properties produce, and those which are derived from the organic;
+and in pointing out when the animal sensibility and contractility
+are brought into action, and when the organic sensibility and the
+sensible or insensible contractility. We shall be easily convinced upon
+reflection, that we cannot precisely estimate the immense influence
+of the vital properties in the physiological sciences, before we have
+considered these properties in the point of view in which I have
+presented them. It will be said, perhaps, that this manner of viewing
+them is still a theory; I will answer that it is a theory like that
+which shows in the physical sciences, gravity, elasticity, affinity,
+etc., as the primitive principles of the facts observed in these
+sciences. The relation of these properties as causes to the phenomena
+as effects, is an axiom so well known in physics, chemistry, astronomy,
+etc., at the present day, that it is unnecessary to repeat it. If this
+work establishes an analogous axiom in the physiological sciences, its
+object will be attained.</p>
+
+
+<p class="nindc space-above2 space-below2">
+OBSERVATIONS UPON THE ORGANIZATION OF ANIMALS</p>
+
+<p>The properties, whose influence we have just analyzed, are not
+absolutely inherent in the particles of matter that are the seat of
+them. They disappear when these scattered particles have lost their
+organic arrangement. It is to this arrangement that they exclusively
+belong; let us treat of it here in a general way.</p>
+
+<p>All animals are an assemblage of different organs, which, executing
+each a function, concur in their own manner, to the preservation of
+the whole. It is several separate machines in a general one, that
+constitutes the individual. Now these separate machines are themselves
+formed by many textures of a very different nature, and which really
+compose the elements of these organs. Chemistry has its simple bodies,
+which form, by the combination of which they are susceptible, the
+compound bodies; such are caloric, light, hydrogen, oxygen, carbon
+azote, phosphorus, etc. In the same way anatomy has its simple
+textures, which, by their combinations four with four, six with six,
+eight with eight, etc., make the organs. These textures, are, 1st,
+the cellular; 2d, the nervous of animal life; 3d, the nervous of
+organic<span class="pagenum" id="Page_170">[Pg 170]</span> life; 4th, the arterial; 5th, the venous; 6th, the texture
+of the exhalants; 7th, that of the absorbents and their glands; 8th,
+the osseous; 9th, the medullary; 10th, the cartilaginous; 11th, the
+fibrous; 12th, the fibro-cartilaginous; 13th, the muscular of animal
+life; 14th, the muscular of organic life; 15th, the mucous; 16th, the
+serous; 17th, the synovial; 18th, the glandular; 19th, the dermoid;
+20th, the epidermoid; 21st, the pilous.</p>
+
+<p>These are the true organized elements of our bodies. Their nature is
+constantly the same, wherever they are met with. As in chemistry, the
+simple bodies do not alter, notwithstanding the different compound ones
+they form. The organized elements of man form the particular object of
+this work.</p>
+
+<p>The idea of thus considering abstractly the different simple textures
+of our bodies, is not the work of the imagination; it rests upon the
+most substantial foundation, and I think it will have a powerful
+influence upon physiology as well as practical medicine. Under whatever
+point of view we examine them, it will be found that they do not
+resemble each other; it is nature and not science that has drawn the
+line of distinction between them.</p>
+
+<p>1st. Their forms are everywhere different; here they are flat, there
+round. We see the simple textures arranged as membranes, canals,
+fibrous fasciæs, etc. No one has the same external character with
+another, considered as to their attributes of thickness or size.
+These differences of form, however, can only be accidental, and the
+same texture is sometimes seen under many different appearances; for
+example, the nervous appears as a membrane in the retina, and as cords
+in the nerves. This has nothing to do with their nature; it is then
+from the organization of the properties that the principal differences
+should be drawn.</p>
+
+<p>2dly. There is no analogy in the organization of the simple textures.
+We shall see that this organization results from parts that are common
+to all, and from those that are peculiar to each; but the common parts
+are all differently arranged in each texture. Some unite in abundance
+the cellular texture, the blood vessels and the nerves; in others, one
+or two of these three common parts are scarcely evident or entirely
+wanting. Here there are only the exhalants and absorbents of nutrition;
+there the vessels are more numerous for other purposes. The capillary
+network, wonderfully multiplied, exists in certain textures;<span class="pagenum" id="Page_171">[Pg 171]</span> in
+others this network can hardly be demonstrated. As to the peculiar
+part, which essentially distinguishes the texture, the differences
+are striking. Color, thickness, hardness, density, resistance, etc.,
+nothing is similar. More inspection is sufficient to show a number of
+characteristic attributes of each clearly different from the others.
+Here is a fibrous arrangement, there a granulated one; here it is
+lamellated, there circular. Notwithstanding these differences, authors
+are not agreed as to the limits of the different textures. I have had
+recourse, in order to leave no doubt upon this point, to the action
+of different re-agents. I have examined every texture, submitted them
+to the action of caloric, air, water, the acids, the alkalies, the
+neutral salts, etc., drying, putrefaction, maceration, boiling, etc.;
+the products of many of these actions have altered in a different
+manner each kind of texture. Now it will be seen that the results have
+almost all been different, that in these various changes each acts in
+a particular way, each gives results of its own, no one resembling
+another.</p>
+
+<p>There has been considerable inquiry to ascertain whether the arterial
+coats are fleshy, whether the veins are of an analogous nature, etc. By
+comparing the results of my experiments upon the different textures,
+the question is easily resolved. It would seem at first view that all
+these experiments upon the intimate texture of systems answer but
+little purpose; I think, however, that they have effected a useful
+object, in fixing with precision the limits of each organized texture;
+for the nature of these textures being unknown, their differences can
+be ascertained only by the different results they furnish.</p>
+
+<p>3rdly. In giving to each system a different organic arrangement,
+nature has also endowed them with different properties. You will
+see in the subsequent part of this work, that what we call texture
+presents degrees indefinitely varying, from the muscles, the skin,
+the cellular membrane, etc., which enjoy it in the highest degree,
+to the cartilages, the tendons, the bones, etc., which are almost
+destitute of it. Shall I speak of the vital properties? See the
+animal sensibly predominant in the nerves, contractility of the same
+kind particularly marked in the voluntary muscles, sensible organic
+contractility, forming the peculiar property of the involuntary,
+insensible contractility and sensibility of the same nature, which is
+not separated from it more than from the preceding, characterizing
+especially the glands, the skin, the serous<span class="pagenum" id="Page_172">[Pg 172]</span> surfaces, etc., etc. See
+each of these simple textures combining, in different degrees, more or
+less of these properties, and consequently living with more or less
+energy.</p>
+
+<p>There is but little difference arising from the number of vital
+properties they have in common; when these properties exist in many,
+they take in each a distinctive and peculiar character. This character
+is chronic, if I may so express myself, in the bones, the cartilages,
+the tendons, etc.; it is acute in the muscles, the skin, the glands,
+etc.</p>
+
+<p>Independently of this general difference, each texture has a particular
+kind of force, of sensibility, etc. Upon this principle rests the whole
+theory of secretion, of exhalation, of absorption, and of nutrition.
+The blood is a common reservoir, from which each texture chooses that
+which is adapted to its sensibility, to appropriate and keep it, and
+afterwards reject it.</p>
+
+<p>Much has been said since the time of Bordeu, of the peculiar life of
+each organ, which is nothing else than that particular character which
+distinguishes the combination of the vital properties of one organ
+from those of another. Before these properties had been analyzed with
+exactness and precision, it was clearly impossible to form a correct
+idea of this peculiar life. From the recount I have just given of it,
+it is evident that the greatest part of the organs being composed of
+very different simple textures, the idea of a peculiar life can only
+apply to these simple textures, and not to the organs themselves.</p>
+
+<p>Some examples will render the point of doctrine which is important,
+more evident. The stomach is composed of the serous, organic muscular,
+mucous, and of almost all the common textures, as the arterial, the
+venous, etc., which we can consider separately. Now if you should
+attempt to describe in a general manner, the peculiar life of the
+stomach, it is evidently impossible that you could give a very precise
+and exact idea of it. In fact the mucous surface is so different
+from the serous, and both so different from the muscular, that by
+associating them together, the whole would be confused. The same is
+true of the intestines, the bladder, the womb, etc.; if you do not
+distinguish what belongs to each of the textures that form the compound
+organs, the term peculiar life will offer nothing but vagueness and
+uncertainty. This is so true, that oftentimes the same textures
+alternately belong or are foreign to their organs. The same portion of<span class="pagenum" id="Page_173">[Pg 173]</span>
+the peritoneum, for example, enters or does not enter, into the gastric
+viscera, according to their fulness or vacuity.</p>
+
+<p>Shall I speak of the pectoral organs? What has the life of the
+fleshy texture of the heart in common with that of the membrane that
+surrounds it? Is not the pleura independent of the pulmonary texture?
+Has this texture nothing in common with the membrane that surrounds
+the bronchia? Is it not the same with the brain with relation to its
+membranes, of the different parts of the eye, the ear, etc.?</p>
+
+<p>When we study a function it is necessary carefully to consider in a
+general manner, the compound organ that performs it; but when you
+wish to know the properties and life of this organ, it is absolutely
+necessary to decompose it. In the same way, if you seek only general
+notions of anatomy, you can study each organ as a whole; but it is
+essential to separate the textures, if you have a desire to analyze
+with accuracy its intimate structure.</p>
+
+
+<p class="nindc space-above2 space-below2">
+CONSEQUENCES OF THE PRECEDING PRINCIPLES RELATIVE TO DISEASE</p>
+
+<p>What I have been saying leads to important consequences, as it respects
+those acute or chronic diseases that are local; for those which, like
+most fevers, affect almost simultaneously every part, cannot be much
+elucidated by the anatomy of systems. The first then will engage our
+attention.</p>
+
+<p>Since diseases are only alterations of the vital properties, and each
+texture differs from the others in its properties, it is evident that
+there must be a difference also in the diseases. In every organ, then,
+composed of different textures, one may be diseased, while the others
+remain sound; now this happens in a great many cases; let us take the
+principal organs, for example.</p>
+
+<p>1st. Nothing is more rare than affections of the mass of the
+brain; nothing is more common than inflammation of the <i>tunica
+arachnoides</i> that covers it. 2d. Oftentimes one membrane of the
+eye only is affected, the others preserving their ordinary degree of
+vitality. 3d. In convulsions or paralysis of the muscles of the larynx,
+the mucous surface is unaffected; and on the other hand, the muscles
+perform their functions as usual in catarrhs of this surface. Both
+these affections<span class="pagenum" id="Page_174">[Pg 174]</span> are foreign to the cartilages, and <i>vice versa</i>.
+4th. We observe a variety of different alterations in the texture
+of the pericardium, but hardly ever in that of the heart itself; it
+remains sound while the other is inflamed. The ossification of the
+common membrane of the red blood does not extend to the neighboring
+textures. 5th. When the membrane of the bronchia is the seat of
+catarrh, the pleura is hardly affected at all, and reciprocally in
+pleurisy the first is scarcely ever altered. In peripneumonia, when an
+enormous infiltration in the dead body shows the excessive inflammation
+that has existed during life in the pulmonary texture, the serous and
+mucous surfaces often appear not to have been affected. Those who open
+dead know that they are frequently healthy in incipient phthisis.
+6th. We speak of a bad stomach, a weak stomach; this most commonly
+should be understood as applying to the mucous surface only. Whilst
+this secretes with difficulty the nutritive juices, without which
+digestion is impaired, the serous surface exhales as usual its fluid,
+the muscular coat continues to contract, etc. In ascites, in which
+the serous surface exhales more lymph than in a natural state, the
+mucous oftentimes performs its functions perfectly well, etc. 7th.
+All authors have said much of the inflammation of the stomach, the
+intestines, the bladder, etc. For myself, I believe that this disease
+rarely ever affects at first the whole of any of these organs, except
+in the case where poison or some other deleterious substance acts upon
+them. There are for the mucous surface of the stomach and intestines,
+acute and chronic catarrhs; for the peritoneum serous inflammations;
+perhaps even for the layer of organic muscles that separates the two
+membranes, there is a particular kind of inflammation, though we have
+as yet hardly anything certain upon this point; but the stomach, the
+intestines, and the bladder are not suddenly affected with these
+three diseases. A diseased texture can affect those near it, but the
+primitive affection seizes only upon one. I have examined a great
+number of bodies in which the peritoneum was inflamed either upon the
+intestines, the stomach, the pelvis, or universally; now very often
+when this affection is chronic, and almost always when it is acute,
+the subjacent organs remain sound. I have never seen this membrane
+exclusively diseased upon one organ, while that of neighboring ones
+remain untouched; its affection is propagated more or less remotely.
+I know not why authors have hardly ever spoken of its inflammation,<span class="pagenum" id="Page_175">[Pg 175]</span>
+and have placed to the account of the subjacent viscera that which
+most often belongs only to this. There are almost as many cases
+of peritonitis as of pleurisy, and yet while these last have been
+particularly noticed the others are almost entirely overlooked.
+Oftentimes that part of the peritoneum corresponding to an organ,
+is much inflamed; we see it in the case of the stomach; we observe
+especially after the suppression of the lochia or the menses, that it
+is the portion that lines the pelvis that is first affected. But soon
+the affection becomes more or less general; at least examinations after
+death prove it satisfactorily. 8th. Certainly the acute or chronic
+catarrh of the bladder, or womb even, has nothing in common with the
+inflammation of that portion of the peritoneum corresponding with
+these organs. 9th. Every one knows that diseases of the periosteum
+have oftentimes no connection with the bone, and <i>vice versa</i>,
+that frequently the marrow is for a long time affected, while both the
+others remain sound. There is no doubt that the osseous, medullary
+and fibrous textures have their peculiar affections which we shall
+not confound with the idea we may form of the diseases of the bones.
+The same can be said of the intestines, of the stomach, etc., in
+relation to their mucous, serous, muscular textures, etc. 10th. Though
+the muscular and tendinous textures are combined in a muscle, their
+diseases are very different. 11th. You must not think that the synovial
+is subject to the same diseases as the ligaments that surround it, etc.</p>
+
+<p>I think the more we observe diseases, and the more we examine bodies,
+the more we shall be convinced of the necessity of considering local
+diseases, not under the relations of the compound organs, which are
+rarely ever affected as a whole, but under that of their different
+textures, which are almost always attacked separately.</p>
+
+<p>When the phenomena of disease are sympathetic, they follow the same
+laws as when they arise from a direct affection. Much has been said
+of the sympathies of the stomach, the intestines, the bladder, the
+lungs, etc. But it is impossible to form an idea of them, if they
+are referred to the organ as a whole, separate from the different
+textures. 1st. When in the stomach, the fleshy fibres contract by the
+influence of another organ and produce vomiting, they alone receive
+the influence, which is not extended either to the serous or mucous
+surfaces; if it were, they would be the seat, the one of exhalation,
+the other of sympathetic exhalation and secretion. 2d. It<span class="pagenum" id="Page_176">[Pg 176]</span> is certain
+that when the action of the liver is sympathetically increased, so
+that it pours out more bile, the portion of peritoneum that covers it
+does not throw out more serum, because it is not affected by it. It
+is the same of the kidney, the pancreas, etc. 3d. For the same reason
+the gastric organs upon which the peritoneum is spread do not partake
+of the sympathetic influences that it experiences. I shall say as much
+of the lungs in relation to the pleura, the brain in relation to the
+<i>tunica arachnoides</i>, the heart to the pericardium, etc. 4th. It
+is undeniable that in all sympathetic convulsions, the fleshy texture
+alone is affected, and that the tendinous is not so at all. 5th. What
+has the fibrous membrane of the testicles in common with the sympathies
+of its peculiar texture? 6th. No doubt a number of sympathetic pains
+that we refer to the bones, are seated exclusively in the marrow.</p>
+
+<p>I could cite many other examples to prove, that it is not this or that
+organ that sympathizes as a whole, but only this or that texture in
+the organs; besides, this an immediate consequence of the nature of
+sympathies. In fact the sympathies are but aberrations of the vital
+properties; now these properties vary according to each texture; the
+sympathies of these textures then would do the same.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_26" href="#FNanchor_26" class="label">[26]</a>
+Translated from <i>Traité sur les Membranes</i> (1800).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_177">[Pg 177]</span></p>
+<h2 class="nobreak" id="XXIV">XXIV<br>
+AMADEO AVOGADRO<br>
+1776-1856</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Avogadro, who continued the researches of Dalton and Gay-Lussac,
+was born in Turin, Italy, June 9, 1776. In 1796, after receiving the
+doctor’s degree in law from the University of Turin, he was employed
+by the government for the following ten years. He began his work in
+science in 1806 and three years later was made professor of physics at
+Vercelli. In 1811 he announced his famous law. According to Merz, since
+the time of Boyle “it had been known that equal volumes of different
+gases under equal pressure change their volumes equally if the
+pressure is varied equally, and it was also known that equal volumes
+of different gases under equal pressure change their volumes equally
+with equal rise of temperature. These facts suggested to Avogadro, and
+almost simultaneously to Ampère, the very simple assumption that this
+is owing to the fact that equal volumes of different gases contain an
+equal number of the smallest independent particles of matter. This is
+Avogadro’s celebrated hypothesis. It was the first step in the direct
+physical verification of the atomic view of matter.”</i></p>
+
+<p><i>In 1820 Avogadro became professor of physics at Turin University,
+where he remained for many years. He died July 9, 1856.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE MOLECULES IN GASES PROPORTIONAL TO THE VOLUMES<a id="FNanchor_27" href="#Footnote_27" class="fnanchor">[27]</a><br>
+<br>
+I.</p>
+
+<p>M. Gay-Lussac has shown in an interesting Memoir (<i>Mémoires de la
+Société d’Arcueil</i>, Tome II.) that gases always unite in a very<span class="pagenum" id="Page_178">[Pg 178]</span>
+simple proportion by volume, and that when the result of the union is a
+gas, its volume also is very simply related to those of its components.
+But the quantitative proportions of substances in compounds seem only
+to depend on the relative number of molecules which combine, and on the
+number of composite molecules which result. It must then be admitted
+that very simple relations also exist between the volumes of gaseous
+substances and the numbers of simple or compound molecules which form
+them. The first hypothesis to present itself in this connection, and
+apparently even the only admissible one, is the supposition that the
+number of integral molecules in any gases is always the same for equal
+volumes, or always proportional to the volumes. Indeed, if we were
+to suppose that the number of molecules contained in a given volume
+were different for different gases, it would scarcely be possible
+to conceive that the law regulating the distance of molecules could
+give in all cases relations so simple as those which the facts just
+detailed compel us to acknowledge between the volume and the number
+of molecules. On the other hand, it is very well conceivable that
+the molecules of gases being at such a distance that their mutual
+attraction cannot be exercised, their varying attraction for caloric
+may be limited to condensing a greater or smaller quantity around
+them, without the atmosphere formed by this fluid having any greater
+extent in the one case than in the other, and, consequently, without
+the distance between the molecules varying; or, in other words, without
+the number of molecules contained in a given volume being different.
+Dalton, it is true, has proposed a hypothesis directly opposed to
+this, namely, that the quantity of caloric is always the same for the
+molecules of all bodies whatsoever in the gaseous state, and that the
+greater or less attraction for caloric only results in producing a
+greater or less condensation of this quantity around the molecules,
+and thus varying the distance between the molecules themselves. But
+in our present ignorance of the manner in which this attraction of
+the molecules for caloric is exerted, there is nothing to decide
+us <i>a priori</i> in favour of the one of these hypotheses rather
+than the other; and we should rather be inclined to adopt a neutral
+hypothesis, which would make the distance between the molecules and
+the quantities of caloric vary according to unknown laws, were it not
+that the hypothesis we have just proposed is based on that simplicity
+of relation between the volumes of gases<span class="pagenum" id="Page_179">[Pg 179]</span> on combination, which would
+appear to be otherwise inexplicable.</p>
+
+<p>Setting out from this hypothesis, it is apparent that we have the means
+of determining very easily the relative masses of the molecules of
+substances obtainable in the gaseous state, and the relative number
+of these molecules in compounds; for the ratios of the masses of the
+molecules are then the same as those of the densities of the different
+gases at equal temperature and pressure, and the relative number of
+molecules in a compound is given at once by the ratio of the volumes
+of the gases that form it. For example, since the numbers 1.10359 and
+0.07321 express the densities of the two gases oxygen and hydrogen
+compared to that of atmospheric air as unity, and the ratio of the two
+numbers consequently represents the ratio between the masses of equal
+volumes of these two gases, it will also represent on our hypothesis
+the ratio of the masses of their molecules. Thus the mass of the
+molecule of oxygen will be about 15 times that of the molecule of
+hydrogen, or, more exactly, as 15.074 to 1. In the same way the mass
+of the molecule of nitrogen will be to that of hydrogen as 0.96913 to
+0.07321, that is, as 13, or more exactly 13.238, to 1. On the other
+hand, since we know that the ratio of the volumes of hydrogen and
+oxygen in the formation of water is 2 to 1, it follows that water
+results from the union of each molecule of oxygen with two molecules of
+hydrogen. Similarly, according to the proportions by volume established
+by M. Gay-Lussac for the elements of ammonia, nitrous oxide, nitrous
+gas, and nitric acid, ammonia will result from the union of one
+molecule of nitrogen with three of hydrogen, nitrous oxide from one
+molecule of oxygen with two of nitrogen, nitrous gas from one molecule
+of nitrogen with one of oxygen, and nitric acid from one of nitrogen
+with two of oxygen.</p>
+
+
+<p class="nindc space-above2 space-below2">
+II.</p>
+
+<p>There is a consideration which appears at first sight to be opposed to
+the admission of our hypothesis with respect to compound substances.
+It seems that a molecule composed of two or more elementary molecules
+should have its mass equal to the sum of the masses of these molecules;
+and that in particular, if in a compound one molecule of one substance
+unites with two or more molecules of another substance, the number
+of compound molecules should remain the same<span class="pagenum" id="Page_180">[Pg 180]</span> as the number of
+molecules of the first substance. Accordingly, on our hypothesis when
+a gas combines with two or more times its volume of another gas, the
+resulting compound, if gaseous, must have a volume equal to that of
+the first of these gases. Now, in general, this is not actually the
+case. For instance, the volume of water in the gaseous state is, as
+M. Gay-Lussac has shown, twice as great as the volume of oxygen which
+enters into it, or, what comes to the same thing, equal to that of the
+hydrogen instead of being equal to that of the oxygen. But a means
+of explaining facts of this type in conformity with our hypothesis
+presents itself naturally enough: we suppose, namely, that the
+constituent molecules of any simple gas whatever (i. e., the molecules
+which are at such a distance from each other that they cannot exercise
+their mutual action) are not formed of a solitary elementary molecule,
+but are made up of a certain number of these molecules united by
+attraction to form a single one; and further, that when molecules of
+another substance unite with the former to form a compound molecule,
+the integral molecule which should result splits up into two or more
+parts (or integral molecules) composed of half, quarter, &amp;c., the
+number of elementary molecules going to form the constituent molecule
+of the first substance, combined with half, quarter, &amp;c., the number of
+constituent molecules of the second substance that ought to enter into
+combination with one constituent molecule of the first substance (or,
+what comes to the same thing, combined with a number equal to this last
+of half-molecules, quarter-molecules, &amp;c., of the second substance);
+so that the number of integral molecules of the compound becomes
+double, quadruple, &amp;c., what it would have been if there had been no
+splitting-up, and exactly what is necessary to satisfy the volume of
+the resulting gas.</p>
+
+<p>On reviewing the various compound gases most generally known, I only
+find examples of duplication of the volume relatively to the volume of
+that one of the constituents which combines with one or more volumes
+of the other. We have already seen this for water. In the same way,
+we know that the volume of ammonia gas is twice that of the nitrogen
+which enters into it. M. Gay-Lussac has also shown that the volume of
+nitrous oxide is equal to that of the nitrogen which forms part of
+it, and consequently is twice that of the oxygen. Finally, nitrous
+gas, which contains equal volumes of nitrogen and<span class="pagenum" id="Page_181">[Pg 181]</span> oxygen, has a
+volume equal to the sum of the two constituent gases, that is to say,
+double that of each of them. Thus in all these cases there must be a
+division of the molecule into two; but it is possible that in other
+cases the division might be into four, eight, &amp;c. The possibility of
+this division of compound molecules might have been conjectured <i>a
+priori</i>; for otherwise the integral molecules of bodies composed
+of several substances with a relatively large number of molecules,
+would come to have a mass excessive in comparison with the molecules
+of simple substances. We might therefore imagine that nature had some
+means of bringing them back to the order of the latter, and the facts
+have pointed out to us the existence of such means. Besides, there
+is another consideration which would seem to make us admit in some
+cases the division in question; for how could one otherwise conceive
+a real combination between two gaseous substances uniting in equal
+volumes without condensation, such as takes place in the formation of
+nitrous gas? Supposing the molecules to remain at such a distance that
+the mutual attraction of those of each gas could not be exercised,
+we cannot imagine that a new attraction could take place between the
+molecules of one gas and those of the other. But on the hypothesis
+of division of the molecule, it is easy to see that the combination
+really reduces two different molecules to one, and that there would be
+contraction by the whole volume of one of the gases if each compound
+molecule did not split up into two molecules of the same nature. M.
+Gay-Lussac clearly saw that, according to the facts, the diminution of
+volume on the combination of gases cannot represent the approximation
+of their elementary molecules. The division of molecules on combination
+explains to us how these two things may be made independent of each
+other.</p>
+
+
+<p class="nindc space-above2 space-below2">
+III.</p>
+
+<p>Dalton, on arbitrary suppositions as to the most likely relative number
+of molecules in compounds, has endeavoured to fix ratios between the
+masses of the molecules of simple substances. Our hypothesis, supposing
+it well founded, puts us in a position to confirm or rectify his
+results from precise data, and, above all, to assign the magnitude of
+compound molecules according to the volumes of the gaseous compounds,
+which depend partly on the division of molecules entirely unsuspected
+by this physicist.</p>
+
+<p><span class="pagenum" id="Page_182">[Pg 182]</span></p>
+
+<p>Thus Dalton supposes that water is formed by the union of hydrogen and
+oxygen, molecule to molecule. From this, and from the ratio by weight
+of the two components, it would follow that the mass of the molecule of
+oxygen would be to that of hydrogen as 7-1/2 to 1 nearly, or, according
+to Dalton’s evaluation, as 6 to 1. This ratio on our hypothesis is,
+as we saw, twice as great, namely, as 15 to 1. As for the molecule of
+water, its mass ought to be roughly expressed by 15 + 2 = 17 (taking
+for unity that of hydrogen), if there were no division of the molecule
+into two; but on account of this division it is reduced to half, 8-1/2,
+or more exactly 8.537, as may also be found directly by dividing the
+density of aqueous vapour 0.625 (Gay-Lussac) by the density of hydrogen
+0.0732. This mass only differs from 7, that assigned to it by Dalton,
+by the difference in the values for the composition of water; so that
+in this respect Dalton’s result is approximately correct from the
+combination of two compensating errors,—the error in the mass of the
+molecule of oxygen, and his neglect of the division of the molecule.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_27" href="#FNanchor_27" class="label">[27]</a>
+Translated from <i>Essai d’une manière de déterminer
+les masses relatives des molécules élémentaires des corps,
+et les proportions selon lesquelles elles entrent dans les
+combinaisons</i>—<i>Journal de Physique</i>, (1811).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_183">[Pg 183]</span></p>
+<h2 class="nobreak" id="XXV">XXV<br>
+SIR HUMPHREY DAVY<br>
+1778-1829</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Born December 17, 1778, in Cornwall, Sir Humphrey Davy was
+apprenticed in 1794 to a surgeon-apothecary at Penzance in whose
+service he became interested in chemistry. Made superintendent of a
+hospital in 1798, he had opportunities for gaining acquaintance with
+influential men who in turn recommended him to Count Rumford. Through
+the latter’s assistance he was appointed lecturer on chemistry at the
+newly-founded Royal Institution where, in spite of his unattractive
+appearance, he gained considerable reputation. In 1807 he advanced a
+theory which partly explained electrolysis; in the following year he
+discovered strontium and magnesium; and in 1809, chlorine. In 1812 he
+was knighted; and shortly after his marriage, in the same year, he
+injured an eye while experimenting and was compelled to interrupt his
+work for a short time. In 1815 he invented the safety-lamp used by
+miners. In 1818 he was created a baronet, and was elected President
+of the Royal Society in 1820. He died May 29, 1829, at Geneva,
+Switzerland, at the age of fifty-one.</i></p>
+</div>
+
+
+<p class="nindc space-above2">
+ON SOME NEW PHENOMENA OF CHEMICAL CHANGES PRODUCED BY ELECTRICITY<a id="FNanchor_28" href="#Footnote_28" class="fnanchor">[28]</a></p>
+
+<p class="right">
+<i>Read November 19, 1807.</i>
+</p>
+
+<p class="nindc space-below2">
+INTRODUCTION.</p>
+
+<p>In the Bakerian Lecture which I had the honour of presenting to the
+Royal Society last year, I described a number of decompositions<span class="pagenum" id="Page_184">[Pg 184]</span>
+and chemical changes produced in substances of known composition by
+electricity, and I ventured to conclude from the general principles
+on which the phenomena were capable of being explained, that the new
+methods of investigation promised to lead to a more intimate knowledge
+than had hitherto been obtained, concerning the true elements of bodies.</p>
+
+<p>This conjecture, then sanctioned only by strong analogies, I am now
+happy to be able to support by some conclusive facts. In the course of
+a laborious experimental application of the powers of electro-chemical
+analysis, to bodies which have appeared simple when examined by common
+chemical agents, or which at least have never been decomposed, it has
+been my good fortune to obtain new and singular results.</p>
+
+<p>Such of the series of experiments as are in a tolerably mature state,
+and capable of being arranged in a connected order, I shall detail
+in the following sections, particularly those which demonstrate the
+decomposition and composition of the fixed alkalies, and the production
+of the new and extraordinary bodies which constitute their bases.</p>
+
+<p>In speaking of novel methods of investigation, I shall not fear to be
+minute. When the common means of chemical research have been employed,
+I shall mention only results. A historical detail of the progress
+of the investigation, of all the difficulties that occurred, and of
+the manner in which they were overcome, and of all the manipulations
+employed, would far exceed the limits assigned to this Lecture. It is
+proper to state, however, that when general facts are mentioned, they
+are such only as have been deduced from processes carefully performed
+and often repeated.</p>
+
+
+<p class="nindc space-above2 space-below2">
+ON THE METHODS USED FOR THE DECOMPOSITION OF THE FIXED ALKALIES</p>
+
+<p>The researches I had made on the decomposition of acids, and of
+alkaline and earthy neutral compounds, proved that the powers of
+electrical decomposition were proportional to the strength of the
+opposite electricities in the circuit, and to the conducting power and
+degree of concentration of the materials employed.</p>
+
+<p>In the first attempts, that I made on the decomposition of the fixed
+alkalies, I acted upon aqueous solutions of potash and soda, saturated<span class="pagenum" id="Page_185">[Pg 185]</span>
+at common temperatures, by the highest electrical power I could
+command, and which was produced by a combination of Voltaic batteries
+belonging to the Royal Institution, containing 24 plates of copper and
+zinc of 12 inches square, 100 plates of 6 inches, and 150 of 4 inches
+square, charged with solutions of alum and nitrous acid; but in these
+cases, though there was a high intensity of action, the water of the
+solutions alone was affected, and hydrogen and oxygen disengaged with
+the production of much heat and violent effervescence.</p>
+
+<p>The presence of water appearing thus to prevent any decomposition, I
+used potash in igneous fusion. By means of a stream of oxygen gas from
+a gasometer applied to the flame of a spirit lamp, which was thrown
+on a platina spoon containing potash, this alkali was kept for some
+minutes in a strong red heat, and in a state of perfect fluidity.
+The spoon was preserved in communication with the positive side of
+the battery of the power of 100 of 6 inches, highly charged; and the
+connection from the negative side was made by a platina wire.</p>
+
+<p>By this arrangement some brilliant phenomena were produced. The potash
+appeared a conductor in a high degree, and as long as the communication
+was preserved, a most intense light was exhibited at the negative wire,
+and a column of flame, which seemed to be owing to the development of
+combustible matter, arose from the point of contact.</p>
+
+<p>When the order was changed, so that the platina spoon was made
+negative, a vivid and constant light appeared at the opposite point:
+there was no effect of inflammation round it; but aeriform globules,
+which inflamed in the atmosphere, rose through the potash.</p>
+
+<p>The platina, as might have been expected, was considerably acted upon;
+and in the cases when it had been negative, in the highest degree.</p>
+
+<p>The alkali was apparently dry in this experiment; and it seemed
+probable that the inflammable matter arose from its decomposition.
+The residual potash was unaltered; it contained indeed a number of
+dark grey metallic particles, but these proved to be derived from the
+platina.</p>
+
+<p>I tried several experiments on the electrization of potash rendered
+fluid by heat, with the hopes of being able to collect the combustible<span class="pagenum" id="Page_186">[Pg 186]</span>
+matter, but without success; and I only attained my object by employing
+electricity as the common agent for fusion and decomposition.</p>
+
+<p>Though potash, perfectly dried by ignition, is a non-conductor, yet it
+is rendered a conductor by a very slight addition of moisture, which
+does not perceptibly destroy its aggregation; and in this state it
+readily fuses and decomposes by strong electrical powers.</p>
+
+<p>A small piece of pure potash, which had been exposed for a few seconds
+to the atmosphere, so as to give conducting power to the surface, was
+placed upon an insulated disc of platina, connected with the negative
+side of the battery of the power of 250 of 6 and 4, in a state of
+intense activity; and a platina wire, communicating with the positive
+side, was brought in contact with the upper surface of the alkali. The
+whole apparatus was in the open atmosphere.</p>
+
+<p>Under these circumstances a vivid action was soon observed to take
+place. The potash began to fuse at both its points of electrization.
+There was a violent effervescence at the upper surface; at the lower,
+or negative surface, there was no liberation of elastic fluid; but
+small globules having a high metallic lustre, and being precisely
+similar in visible characters to quicksilver, appeared, some of which
+burnt with explosion and bright flame, as soon as they were formed, and
+others remained, and were merely tarnished, and finally covered by a
+white film which formed on their surfaces.</p>
+
+<p>These globules, numerous experiments soon showed to be the substance
+I was in search of, and a peculiar inflammable principle the basis
+of potash. I found that the platina was in no way connected with the
+result, except as the medium for exhibiting the electrical powers of
+decomposition; and a substance of the same kind was produced when
+pieces of copper, silver, gold, plumbago, or even charcoal were
+employed for completing the circuit.</p>
+
+<p>The phenomenon was independent of the presence of air; I found that it
+took place when the alkali was in the vacuum of an exhausted receiver.</p>
+
+<p>The substance was likewise produced from potash fused by means of
+a lamp, in glass tubes confined by mercury, and furnished with
+hermetically inserted platina wires by which the electrical action
+was transmitted. But this operation could not be carried on for any
+considerable time; the glass was rapidly dissolved by the action of<span class="pagenum" id="Page_187">[Pg 187]</span>
+the alkali, and this substance soon penetrated through the body of the
+tube.</p>
+
+<p>Soda, when acted upon in the same manner as potash, exhibited an
+analogous result; but the decomposition demanded greater intensity
+of action in the batteries, or the alkali was required to be in much
+thinner and smaller pieces. With the battery of 100 of 6 inches in full
+activity I obtained good results from pieces of potash weighing from
+40 to 70 grains, and of a thickness which made the distance of the
+electrified metallic surfaces nearly a quarter of an inch; but with a
+similar power it was impossible to produce the effects of decomposition
+on pieces of soda of more than 15 or 20 grains in weight, and that only
+when the distance between the wires was about 1/8 or 1/10 of an inch.</p>
+
+<p>The substance produced from potash remained fluid at the temperature of
+the atmosphere at the time of its production; that from soda, which was
+fluid in the degree of heat of the alkali during its formation, became
+solid on cooling, and appeared having the lustre of silver.</p>
+
+<p>When the power of 250 was used, with a very high charge for the
+decomposition of soda, the globules often burnt at the moment of their
+formation, and sometimes violently exploded and separated into smaller
+globules, which flew with great velocity through the air in a state of
+vivid combustion, producing a beautiful effect of continued jets of
+fire.</p>
+
+
+<p class="nindc space-above2 space-below2">
+THEORY OF THE DECOMPOSITION OF THE FIXED ALKALIES; THEIR COMPOSITION
+AND PRODUCTION</p>
+
+<p>As in all decompositions of compound substances which I had previously
+examined, at the same time that combustible bases were developed at
+the negative surface in the electrical circuit, oxygen was produced,
+and evolved or carried into combination at the positive surface, it
+was reasonable to conclude that this substance was generated in a
+similar manner by the electrical action upon the alkalies; and a number
+of experiments made above mercury, with the apparatus for excluding
+external air, proved that this was the case.</p>
+
+<p>When solid potash, or soda in its conducting state, was included<span class="pagenum" id="Page_188">[Pg 188]</span>
+in glass tubes furnished with electrified platina wires, the new
+substances were generated at the negative surfaces; the gas given out
+at the other surface proved by the most delicate examination to be pure
+oxygen; and unless an excess of water was present, no gas was evolved
+from the negative surface.</p>
+
+<p>In the synthetical experiments, a perfect coincidence likewise will be
+found.</p>
+
+<p>I mentioned that the metallic lustre of the substance from potash
+immediately became destroyed in the atmosphere, and that a white crust
+formed upon it. This crust I soon found to be pure potash, which
+immediately deliquesced, and new quantities were formed, which in their
+turn attracted moisture from the atmosphere till the whole globule
+disappeared, and assumed the form of a saturated solution of potash.</p>
+
+<p>When globules were placed in appropriate tubes containing common air
+or oxygen gas confined by mercury, an absorption of oxygen took place;
+a crust of alkali instantly formed upon the globule; but from the want
+of moisture for its solution, the process stopped, the interior being
+defended from the action of the gas.</p>
+
+<p>With the substance from soda, the appearances and effects were
+analogous.</p>
+
+<p>When the substances were strongly heated, confined in given proportions
+of oxygen, a rapid combustion with a brilliant white flame was
+produced, and the metallic globules were found converted into a white
+and solid mass, which in the case of the substance from potash was
+found to be potash, and in the case of that from soda, soda.</p>
+
+<p>Oxygen gas was absorbed in this operation, and nothing emitted which
+affected the purity of the residual air.</p>
+
+<p>The alkalies produced were apparently dry, or at least contained no
+more moisture than might well be conceived to exist in the oxygen
+gas absorbed; and their weights considerably exceeded those of the
+combustible matters consumed.</p>
+
+<p>The processes on which these conclusions are founded will be fully
+described hereafter, when the minute details which are necessary will
+be explained, and the proportions of oxygen, and of the respective
+inflammable substances which enter into union to form the fixed
+alkalies, will be given.</p>
+
+<p>It appears, then, that in these facts there is the same evidence
+for<span class="pagenum" id="Page_189">[Pg 189]</span> the decomposition of potash and soda into oxygen and two
+peculiar substances, as there is for the decomposition of sulphuric
+and phosphoric acids and the metallic oxides into oxygen and their
+respective combustible bases.</p>
+
+<p>In the analytical experiments, no substances capable of decomposition
+are present but the alkalies and a minute portion of moisture; which
+seems in no other way essential to the result, than in rendering them
+conductors at the surface: for the new substances are not generated
+till the interior, which is dry, begins to be fused; they explode when
+in rising through the fused alkali they come in contact with the heated
+moistened surface; they cannot be produced from crystallised alkalies,
+which contain much water; and the effect produced by the electrization
+of ignited potash, which contains no sensible quantity of water,
+confirms the opinion of their formation independently of the presence
+of this substance.</p>
+
+<p>The combustible bases of the fixed alkalies seem to be repelled as
+other combustible substances, by positively electrified surfaces, and
+attracted by negatively electrified surfaces, and the oxygen follows
+the contrary order; or the oxygen being naturally possessed of the
+negative energy, and the bases of the positive, do not remain in
+combination when either of them is brought into an electrical state
+opposite to its natural one. In the synthesis, on the contrary, the
+natural energies or attractions come in equilibrium with each other;
+and when these are in a low state at common temperatures, a slow
+combination is effected; but when they are exalted by heat, a rapid
+motion is the result; and as in other like cases with the production of
+fire.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_28" href="#FNanchor_28" class="label">[28]</a>
+From the <i>Transactions of the Royal Society of
+London</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_190">[Pg 190]</span></p>
+<h2 class="nobreak" id="XXVI">XXVI<br>
+MICHAEL FARADAY<br>
+1791-1867</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Born on September 22, 1791, at Newington, Surrey, England,
+Michael Faraday was the son of a blacksmith. After an early and very
+elementary education, he was apprenticed in 1805 to a book-binder in
+whose service he read widely and thus educated himself. Developing an
+interest in physics, he attended the evening lectures of Sir Humphrey
+Davy who, in 1813, engaged him as an assistant. Seven years later he
+wrote a history of electro-magnetism and succeeded, in the same year,
+in getting a needle to rotate fully around a live wire. In 1823 he
+liquefied chlorine, an experiment which destroyed the old notion of the
+permanent distinction between gases and liquids. In 1831 he discovered
+magneto-electric induction and advanced the conception of “lines of
+magnetic force.” In 1845, in trying to send polarized rays of light
+through heavy magnetized glass, he found that the magnet’s action
+interrupted the passage of the light and that magnetization caused the
+plane of polarization to rotate. He died August 25, 1867.</i></p>
+</div>
+
+
+<p class="nindc space-above2">
+ON FLUID CHLORINE<a id="FNanchor_29" href="#Footnote_29" class="fnanchor">[29]</a></p>
+
+<p class="right">
+<i>Read March 13, 1823.</i>
+</p>
+
+<p>It is well known that before the year 1810, the solid substance
+obtained by exposing chlorine, as usually procured, to a low
+temperature, was considered as the gas itself reduced into that form;
+and that Sir Humphrey Davy first showed it to be a hydrate, the pure
+dry gas not being considerable even at a temperature of 40° F.</p>
+
+<p>I took advantage of the late cold weather to procure crystals of this<span class="pagenum" id="Page_191">[Pg 191]</span>
+substance for the purpose of analysis. The results are contained
+in a short paper in the Quarterly Journal of Science, Vol. XV. Its
+composition is very nearly 27.7 chlorine, 72.3 water, or 1 proportional
+of chlorine, and 10 of water.</p>
+
+<p>The President of the Royal Society having honoured me by looking at
+these conclusions, suggested, that an exposure of the substance to
+heat under pressure, would probably lead to interesting results; the
+following experiments were commenced at his request. Some hydrate
+of chlorine was prepared, and being dried as well as could be by
+pressure in bibulous paper, was introduced into a sealed glass tube,
+the upper end of which was then hermetically closed. Being placed
+in water at 60°, it underwent no change; but when put into water
+at 100°, the substance fused, the tube became filled with a bright
+yellow atmosphere, and, on examination, was found to contain two
+fluid substances: the one, about three-fourths of the whole, was of
+a faint yellow colour, having very much the appearance of water; the
+remaining fourth was a heavy bright yellow fluid, lying at the bottom
+of the former, without any apparent tendency to mix with it. As the
+tube cooled, the yellow atmosphere condensed into more of the yellow
+fluid, which floated in a film on the pale fluid, looking very like
+chloride of nitrogen; and at 70° the pale portion congealed, although
+even at 32° the yellow portion did not solidify. Heated up to 100° the
+yellow fluid appeared to boil, and again produced the bright coloured
+atmosphere.</p>
+
+<p>By putting the hydrate into a bent tube, afterwards hermetically
+sealed, I found it easy, after decomposing it by a heat of 100°, to
+distil the yellow fluid to one end of the tube, and so separate it from
+the remaining portion. In this way a more complete decomposition of the
+hydrate was effected, and, when the whole was allowed to cool, neither
+of the fluids solidified at temperatures above 34°, and the yellow
+portion not even at 0°. When the two were mixed together they gradually
+combined at temperatures below 60°, and formed the same solid substance
+as that first introduced. If, when the fluids were separated, the tube
+was cut in the middle, the parts flew asunder as if with an explosion,
+the whole of the yellow portion disappeared, and there was a powerful
+atmosphere of chlorine produced; the pale portion on the contrary
+remained, and when examined, proved to be a weak solution of chlorine
+in water, with a little muriatic acid, probably from the<span class="pagenum" id="Page_192">[Pg 192]</span> impurity of
+the hydrate used. When that end of the tube in which the yellow fluid
+lay was broken under a jar of water, there was an immediate production
+of chlorine gas.</p>
+
+<p>I at first thought that muriatic acid and euchlorine had been formed;
+then, that two new hydrates of chlorine had been produced; but at
+last I suspected that the chlorine had been entirely separated from
+the water by the heat and condensed into a dry fluid by the mere
+pressure of its own abundant vapour. If that were true, it followed,
+that chlorine gas, when compressed, should be condensed into the
+same fluid, and, as the atmosphere in the tube in which the fluid
+lay was not very yellow at 50° or 60°, it seemed probable that the
+pressure required was not beyond what could readily be obtained by a
+condensing syringe. A long tube was therefore furnished with a cap and
+stop-cock, then exhausted of air and filled with chlorine, and being
+held vertically with the syringe upwards, air was forced in, which
+thrust the chlorine to the bottom of the tube, and gave a pressure of
+about 4 atmospheres. Being now cooled, there was an immediate deposit
+in films, which appeared to be hydrate, formed by water contained in
+the gas and vessels, but some of the yellow fluid was also produced.
+As this however might also contain a portion of the water present,
+a perfectly dry tub and apparatus were taken, and the chlorine left
+for some time over a bath of sulphuric acid before it was introduced.
+Upon throwing in air and giving pressure, there was now no solid film
+formed, but the clear yellow fluid was deposited, and more abundantly
+still upon cooling. After remaining some time it disappeared, having
+gradually mixed with the atmosphere above it, but every repetition of
+the experiment produced the same results.</p>
+
+<p>Presuming that I had now a right to consider the yellow fluid as pure
+chlorine in the liquid state, I proceeded to examine its properties,
+as well as I could when obtained by heat from the hydrate. However
+obtained, it always appears very limpid and fluid, and excessively
+volatile at common pressure. A portion was cooled in its tube to 0°;
+it remained fluid. The tube was then opened, when a part immediately
+flew off, leaving the rest so cooled by the evaporation as to remain a
+fluid under the atmospheric pressure. The temperature could not have
+been higher than 40° in this case; as Sir Humphrey Davy has shown
+that dry chlorine does not condense at that temperature under common
+pressure. Another tube was opened at a temperature<span class="pagenum" id="Page_193">[Pg 193]</span> of 50°; a part of
+the chlorine volatilised, and cooled the tube so much as to condense
+the atmospheric vapour on it as ice.</p>
+
+<p>A tube having the water at one end and the chlorine at the other was
+weighed, and then cut in two; the chlorine immediately flew off, and
+the loss being ascertained was found to be 1.6 grains: the water
+left was examined and found to contain some chlorine: its weight was
+ascertained to be 5.4 grains. These proportions, however, must not
+be considered as indicative of the true composition of hydrate of
+chlorine; for, from the mildness of the weather during the time when
+these experiments were made, it was impossible to collect the crystals
+of hydrate, press, and transfer them, without losing much chlorine; and
+it is also impossible to separate the chlorine and water in the tube
+perfectly, or keep them separate, as the atmosphere within will combine
+with the water, and gradually reform the hydrate.</p>
+
+<p>Before cutting the tube, another tube had been prepared exactly like it
+in form and size, and a portion of water introduced into it, as near as
+the eye could judge, of the same bulk as the fluid chlorine: this water
+was found to weigh 1.2 grains; a result, which, if it may be trusted,
+would give the specific gravity of fluid chlorine as 1.33; and from its
+appearance in, and on water, this cannot be far wrong.</p>
+
+
+<p class="nindc space-above2">ELECTRICITY FROM MAGNETISM</p>
+
+<p class="right">
+<i>Read November 24, 1831.</i>
+</p>
+
+<p>1. The power which electricity of tension possesses of causing an
+opposite electrical state in its vicinity has been expressed by the
+general term Induction; which, as it has been received into scientific
+language, may also, with propriety, be used in the same general sense
+to express the power which electrical currents may possess of inducing
+any particular state upon matter in their immediate neighborhood,
+otherwise indifferent. It is with this meaning that I purpose using it
+in the present paper.</p>
+
+<p>2. Certain effects of the induction of electrical currents have already
+been recognized and described: as those of magnetization; Ampère’s
+experiments of bringing a copper disc near to a flat spiral; his
+repetition with electro-magnets of Arago’s extraordinary experiments,
+and perhaps a few others. Still it appeared unlikely that these<span class="pagenum" id="Page_194">[Pg 194]</span>
+could be all the effects which induction by currents could produce;
+especially as, upon dispensing with iron, almost the whole of them
+disappear, whilst yet an infinity of bodies, exhibiting definite
+phenomena of induction with electricity of tension still remain to be
+acted upon by the induction of electricity in motion.</p>
+
+<p>3. Further: whether Ampère’s beautiful theory were adopted, or any
+other, or whatever reservation were mentally made, still it appeared
+very extraordinary, that, as every electric current was accompanied by
+a corresponding intensity of magnetic action at right angles to the
+current, good conductors of electricity, when placed within the sphere
+of this action, should not have any current induced through them, or
+some sensible effect produced equivalent in force to such a current.</p>
+
+<p>4. These considerations, with their consequence, the hope of obtaining
+electricity from ordinary magnetism, have stimulated me at various
+times to investigate experimentally the inductive effect of electric
+currents. I lately arrived at positive results; and not only had my
+hopes fulfilled, but obtained a key which appeared to me to open out a
+full explanation of Arago’s magnetic phenomena, and also to discover a
+new state, which may probably have great influence in some of the most
+important effects of electric currents.</p>
+
+<p>5. These results I purpose describing, not as they were obtained, but
+in such a manner as to give the most concise view of the whole.</p>
+
+
+<p class="nindc space-above2 space-below2">
+EVOLUTION OF ELECTRICITY FROM MAGNETISM</p>
+
+<p>27. A welded ring was made of soft round bar-iron, the metal being
+seven-eighths of an inch in thickness, and the ring six inches in
+external diameter. Three helices were put round one part of this ring,
+each containing about twenty-four feet of copper wire one-twentieth
+of an inch thick; they were insulated from the iron and each other,
+and superposed in the manner before described (6), occupying about
+nine inches in length upon the ring. They could be used separately or
+conjointly; the group may be distinguished by the letter A. On the
+other part of the ring about sixty feet of similar copper wire in two
+pieces were applied in the same manner, forming a helix B, which had
+the same common direction with the helices of A, but being separated
+from it at each extremity by about half an inch of the uncovered iron.</p>
+
+<p><span class="pagenum" id="Page_195">[Pg 195]</span></p>
+
+<p>28. The helix B, was connected by copper wires with a galvanometer
+three feet from the ring. The helices of A were connected end to
+end so as to form one common helix, the extremities of which were
+connected with a battery of ten pairs of plates four inches square. The
+galvanometer was immediately affected, and to a degree far beyond what
+has been described when with a battery of tenfold power helices without
+iron were used (10); but though the contact was continued, the effect
+was not permanent, for the needle soon came to rest in its natural
+position, as if quite indifferent to the attached electro-magnetic
+arrangement. Upon breaking the contact with the battery, the needle
+was again powerfully deflected, but in the contrary direction to that
+induced in the first instance.</p>
+
+<p>29. Upon arranging the apparatus so that B should be out of use, the
+galvanometer be connected with one of the three wires of A (27), and
+the other two made into a helix through which the current from the
+trough (28) was passed, similar but rather more powerful effects were
+produced.</p>
+
+<p>30. When the battery contact was made in one direction, the
+galvanometer-needle was deflected on the one side; if made in the other
+direction, the deflection was on the other side. The deflection on
+breaking the battery contact was always the reverse of that produced
+by completing it. The deflection on making a battery contact always
+indicated an induced current in the opposite direction to that from
+the battery; but on breaking the contact the deflection indicated
+an induced current in the same direction as that of the battery.
+No making or breaking of the contact at B side, or in any part of
+the galvanometer circuit, produced any effect at the galvanometer.
+No continuance of the battery current caused any deflection of the
+galvanometer-needle. As the above results are common to all these
+experiments, and to similar ones with ordinary magnets to be hereafter
+detailed, they need not be again particularly described.</p>
+
+<p>31. Upon using the power of 100 pairs of plates (10) with this ring,
+the impulse at the galvanometer, when contact was completed or broken,
+was so great as to make the needle spin round rapidly four or five
+times, before the air and terrestrial magnetism could reduce its motion
+to mere oscillation.</p>
+
+<p>39. But as might be supposed that in all the preceding experiments of
+this section, it was by some peculiar effect taking place during the<span class="pagenum" id="Page_196">[Pg 196]</span>
+formation of the magnet, and not by its mere virtual approximation,
+that the momentary induced current was excited, the following
+experiment was made. All the similar ends of the compound hollow
+helix (34) were bound together by copper wire, forming two general
+terminations, and these were connected with the galvanometer. The soft
+iron cylinder (34) was removed, and a cylindrical magnet three-quarters
+of an inch in diameter and eight inches and a half in length, used
+instead. One end of this magnet was introduced into the axis of the
+helix and then, the galvanometer-needle being stationary, the magnet
+was suddenly thrust in; immediately the needle was deflected in the
+same direction as if the magnet had been formed by either of the two
+preceding processes (34, 36). Being left in, the needle resumed its
+first position, and then the magnet being withdrawn the needle was
+deflected in the opposite direction. These effects were not great; but
+by introducing and withdrawing the magnet, so that the impulse each
+time should be added to those previously communicated to the needle,
+the latter could be made to vibrate through an arc of 180° or more.</p>
+
+<p>40. In this experiment the magnet must not be passed entirely through
+the helix, for then a second action occurs. When the magnet is
+introduced the needle at the galvanometer is deflected in a certain
+direction; but being in, whether it be pushed quite through or
+withdrawn, the needle is deflected in a direction the reverse of that
+previously produced. When the magnet is passed in and through at one
+continuous motion, the needle moves one way, is then suddenly stopped,
+and finally moves the other way.</p>
+
+<p>41. If such a hollow helix as that described (34) be laid east and west
+(or in any other constant position), and a magnet be retained east and
+west, its marked pole always being one way; then whichever end of the
+helix the magnet goes in at, and consequently whichever pole of the
+magnet enters first, still the needle is deflected the same way: on the
+other hand, whichever direction is followed in withdrawing the magnet,
+the deflection is constant, but contrary to that due to its entrance.</p>
+
+<p>57. The various experiments of this section prove, I think, most
+completely the production of electricity from ordinary magnetism.
+That its intensity should be very feeble and quantity small,
+cannot be considered wonderful, when it is remembered that like
+thermo-electricity<span class="pagenum" id="Page_197">[Pg 197]</span> it is evolved entirely within the substance of
+metals retaining all their conducting power. But an agent which is
+conducted along the metallic wires in the manner described; which,
+whilst so passing possesses the peculiar magnetic actions and force
+of a current of electricity; which can agitate and convulse the limbs
+of a frog; and which, finally, can produce a spark by its discharge
+through charcoal (32), can only be electricity. As all the effects can
+be produced by ferruginous electro-magnets (34), there is no doubt that
+arrangements like the magnets of Professors Moll, Henry, Ten Eyke, and
+others, in which as many as two thousand pounds have been lifted, may
+be used for these experiments; in which case not only a brighter spark
+may be obtained, but wires also ignited, and, as the current can pass
+liquids (23), chemical action be produced. These effects are still
+more likely to be obtained when the magneto-electric arrangements to
+be explained in the fourth section are excited by the powers of such
+apparatus.</p>
+
+<p>58. The similarity of action, almost amounting to identity, between
+common magnets and either electro-magnets or volta-electric currents,
+is strikingly in accordance with and confirmatory of M. Ampère’s
+theory, and furnishes powerful reasons for believing that the action
+is the same in both cases; but, as a distinction in language is still
+necessary, I propose to call the agency thus exerted by ordinary
+magnets, magneto-electric or magnelectric induction (26).</p>
+
+<p>59. The only difference which powerfully strikes the attention as
+existing between volta-electric and magneto-electric induction, is the
+suddenness of the former, and the sensible time required by the latter:
+but even in this early state of investigation there are circumstances
+which seem to indicate, that upon further inquiry this difference will,
+as a philosophical distinction, disappear (68).</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_29" href="#FNanchor_29" class="label">[29]</a>
+This excerpt and the one following are from the
+<i>Transactions of the Royal Society of London</i>.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_198">[Pg 198]</span></p>
+<h2 class="nobreak" id="XXVII">XXVII<br>
+JOSEPH HENRY<br>
+1797-1878</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Born at Albany, New York, December 17, 1797, Joseph Henry prepared
+for the profession of medicine, but an appointment as an assistant
+engineer on the state road diverted his interests toward mechanics.
+In 1826 he was appointed instructor of physics at Albany Institute,
+now the Albany Boys Academy, where he conducted his first experiments
+in electricity. In 1828 he first produced a strong electro-magnet by
+winding fine insulated wire around a piece of soft iron, and soon
+succeeded in exciting his electro-magnet at a distance by the use of
+high intensity batteries made up of many cells. Demonstrating that
+the number of coils of fine wire about a magnet had as much influence
+as the intensity of the current and that after winding many coils
+around the soft iron magnet it could still be made magnetic, he
+suggested the principle which Morse later used in the telegraph. In
+1832 he discovered that in a long conductor the primary current, by an
+induction upon itself, produced a number of secondary currents that
+greatly increased the intensity of the discharge.</i></p>
+
+<p><i>He was appointed professor of natural philosophy at Princeton
+University in 1832 and became secretary of the Smithsonian Institution
+in 1846. He died in Washington, May 13, 1878.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+ON THE PRODUCTION OF CURRENTS AND SPARKS OF ELECTRICITY FROM
+MAGNETISM<a id="FNanchor_30" href="#Footnote_30" class="fnanchor">[30]</a></p>
+
+<p>Although the discoveries of Oersted, Arago, Faraday, and others, have
+placed the intimate connection of electricity and magnetism in a most
+striking point of view, and although the theory of Ampère has referred
+all the phenomena of both these departments of science to the<span class="pagenum" id="Page_199">[Pg 199]</span> same
+general laws, yet until lately one thing remained to be proved by
+experiment, in order more fully to establish their identity; namely,
+the possibility of producing electrical effects from magnetism.
+It is well known that surprising magnetic results can readily be
+obtained from electricity, and at first sight it might be supposed
+that electrical effects could with equal facility be produced from
+magnetism; but such has not been found to be the case, for although the
+experiment has often been attempted, it has nearly as often failed.</p>
+
+<p>It early occurred to me that if galvanic magnets on my plan were
+substituted for ordinary magnets, in researches of this kind, more
+success might be expected. Besides their great powers these magnets
+possess other properties, which render them important instruments in
+the hands of the experimenter; their polarity can be instantaneously
+reversed, and their magnetism suddenly destroyed or called into full
+action, according as the occasion may require. With this view, I
+commenced, last August, the construction of a much larger galvanic
+magnet than, to my knowledge, had before been attempted, and also made
+preparations for a series of experiments with it on a large scale,
+in reference to the production of electricity from magnetism. I was,
+however, at that time accidentally interrupted in the prosecution of
+these experiments, and have not been able since to resume them until
+within the last few weeks, and then on a much smaller scale than was
+at first intended. In the meantime, it has been announced in the 117th
+number of the <i>Library of Useful Knowledge</i>, that the result
+so much sought after has at length been found by Mr. Faraday of the
+Royal Institution. It states that he has established the general fact,
+that when a piece of metal is moved in any direction, in front of a
+magnetic pole, electrical currents are developed in the metal, which
+pass in a direction at right angles to its own motion, and also that
+the application of this principle affords a complete and satisfactory
+explanation of the phenomena of magnetic rotation. No detail is given
+of the experiments, and it is somewhat surprising that results so
+interesting, and which certainly form a new era in the history of
+electricity and magnetism, should not have been more fully described
+before this time in some of the English publications; the only mention
+I have found of them is the following short account from the <i>Annals
+of Philosophy</i> for April, under the head of Proceedings of the Royal
+Institution:</p>
+
+<p><span class="pagenum" id="Page_200">[Pg 200]</span></p>
+
+<div class="blockquot">
+
+<p>“Feb. 17.—Mr. Faraday gave an account of the first two parts of
+his researches in electricity; namely, Volta-electric induction and
+magneto-electric induction. If two wires, A and B, be placed side by
+side, but not in contact, and a Voltaic current be passed through
+A, there is instantly a current produced by induction in B, in the
+opposite direction. Although the principal current in A be continued,
+still the secondary current in B is not found to accompany it, for
+it ceases after the first moment, but when the principal current is
+stopped, then there is a second current produced in B, in the opposite
+direction to that of the first produced by the inductive action, or in
+the same direction as that of the principal current.</p>
+
+<p>“If a wire, connected at both extremities with a galvanometer,
+be coiled in the form of a helix around a magnet, no current of
+electricity takes place in it. This is an experiment which has been
+made by various persons hundreds of times, in the hope of evolving
+electricity from magnetism, and in other cases in which the wishes of
+the experimenter and the facts are opposed to each other, has given
+rise to very conflicting conclusions. But if the magnet be withdrawn
+from or introduced into such a helix, a current of electricity is
+produced whilst the magnet is in motion, and is rendered evident by
+the deflection of the galvanometer. If a single wire be passed by a
+magnetic pole, a current of electricity is induced through it which
+can be rendered sensible.”</p>
+</div>
+
+<p>Before having any knowledge of the method given in the above account, I
+had succeeded in producing electrical effects in the following manner,
+which differs from that employed by Mr. Faraday, and which appears to
+me to develop some new and interesting facts. A piece of copper wire,
+about thirty feet long and covered with elastic varnish, was closely
+coiled around the middle of the soft iron armature of the galvanic
+magnet described in Vol. XIX of the <i>American Journal of Science</i>,
+and which, when excited, will readily sustain between six hundred and
+seven hundred pounds. The wire was wound upon itself so as to occupy
+only about one inch of the length of the armature which is seven inches
+in all. The armature, thus furnished with the wire, was placed in its
+proper position across the ends of the galvanic magnet, and there
+fastened so that no motion could take place. The two protecting ends
+of the helix were dipped into two cups of mercury, and there connected
+with a distant galvanometer by means of two copper wires, each about
+forty feet long. This arrangement<span class="pagenum" id="Page_201">[Pg 201]</span> being completed, I stationed myself
+near the galvanometer and directed an assistant at a given word to
+immerse suddenly, in a vessel of dilute acid, the galvanic battery
+attached to the magnet. At the instant of immersion, the north end
+of the needle was deflected 30° to the west, indicating a current
+of electricity from the helix surrounding the armature. The effect,
+however, appeared only as a single impulse, for the needle, after a few
+oscillations, resumed its former undisturbed position in the magnetic
+meridian, although the galvanic action of the battery, and consequently
+the magnetic power, was still continued. I was, however, much surprised
+to see the needle suddenly deflected from a state of rest to about 20°
+to the east, or in a contrary direction when the battery was withdrawn
+from the acid, and again deflected to the west when it was re-immersed.
+This operation was repeated many times in succession, and uniformly
+with the same result, the armature the whole time remaining immovably
+attached to the poles of the magnet, no motion being required to
+produce the effect, as it appeared to take place only in consequence of
+the instantaneous development of the magnetic action in one, and the
+sudden cessation of it in the other.</p>
+
+<p>This experiment illustrates most strikingly the reciprocal action of
+the two principles of electricity and magnetism, if indeed it does not
+establish their absolute identity. In the first place, magnetism is
+developed in the soft iron of the galvanic magnet by the action of the
+currents of electricity from the battery, and secondly, the armature,
+rendered magnetic by contact with the poles of the magnet, induces in
+its turn currents of electricity in the helix which surrounds it; we
+have thus, as it were, electricity converted into magnetism and this
+magnetism again into electricity.</p>
+
+<p>Another fact was observed which is somewhat interesting, inasmuch as it
+serves in some respects to generalize the phenomena. After the battery
+had been withdrawn from the acid, and the needle of the galvanometer
+suffered to come to a state of rest after the resulting deflection, it
+was again deflected in the same direction by partially detaching the
+armature from the poles of the magnet to which it continued to adhere
+from the action of the residual magnetism, and in this way, a series of
+deflections, all in the same direction, was produced by merely slipping
+off the armature by degrees until the contact<span class="pagenum" id="Page_202">[Pg 202]</span> was entirely broken. The
+following extract from the register of the experiments exhibits the
+relative deflections observed in one experiment of this kind.</p>
+
+<p>At the instant of immersion of the battery, deflection 40° west.</p>
+
+<p>At the instant of emersion of the battery, deflection 18° east.</p>
+
+<p>Armature partially detached, deflection 7° east.</p>
+
+<p>Armature entirely detached, deflection 12° west.</p>
+
+<p>The effect was reversed in another experiment, in which the needle was
+turned to the west in a series of deflections by dipping the battery
+but a small distance into the acid at first and afterwards immersing it
+by degrees.</p>
+
+<p>From the foregoing facts it appears that a current of electricity is
+produced, for an instant, in a helix of copper wire surrounding a piece
+of soft iron whenever magnetism is induced in the iron; and a current
+in an opposite direction when the magnetic action ceases; also that an
+instantaneous current in one or the other direction accompanies every
+change in the magnetic intensity of the iron.</p>
+
+<p>Since reading the account before given of Mr. Faraday’s method of
+producing electrical currents I have attempted to combine the effects
+of motion and induction; for this purpose a rod of soft iron ten inches
+long and one inch and a quarter in diameter, was attached to a common
+turning lathe, and surrounded with four helices of copper wire in such
+a manner that it could be suddenly and powerfully magnetized, while
+in rapid motion, by transmitting galvanic currents through three of
+the helices; the fourth being connected with the distant galvanometer
+was intended to transmit the current of induced electricity; all the
+helices were stationary while the iron rod revolved on its axis within
+them. From a number of trials in succession, first with the rod in one
+direction, then in the opposite, and next in a state of rest, it was
+concluded that no perceptible effect was produced on the intensity of
+the magneto-electric current by a rotary motion of the iron combined
+with its sudden magnetization.</p>
+
+<p>The same apparatus, however, furnished the means of measuring
+separately the relative power of motion and induction in producing
+electrical currents. The iron rod was first magnetized by currents
+through the helices attached to the battery and while in this state
+one of its ends was quickly introduced into the helix connected with
+the galvanometer; the deflection of the needle in this case was
+seven degrees.<span class="pagenum" id="Page_203">[Pg 203]</span> The end of the rod was next introduced into the same
+helix while in its natural state and then suddenly magnetized; the
+deflection in this instance amounted to thirty degrees, showing a great
+superiority in the method of induction.</p>
+
+<p>The next attempt was to increase the magneto-electric effect while the
+magnetic power remained the same, and in this I was more successful.
+Two iron rods six inches long and one inch in diameter were each
+surrounded by two helices and then placed perpendicularly on the
+face of the armature, and between it and the poles of the magnet,
+so that each rod formed, as it were, a prolongation of the poles,
+and to these the armature adhered when the magnet was excited. With
+this arrangement, a current from one helix produced a deflection of
+thirty-seven degrees; from two helices both on the same rod, fifty-two
+degrees, and from three fifty-nine degrees; but when four helices
+were used, the deflection was only fifty-five degrees, and when to
+these were added the helix of smaller wire around the armature, the
+deflection was no more than thirty degrees. This result may perhaps
+have been somewhat affected by the want of proper insulation in the
+several spires of the helices; it, however, establishes the fact that
+an increase in the electric current is produced by using at least
+two or three helices instead of one. The same principle was applied
+to another arrangement which seems to afford the maximum of electric
+development from a given magnetic power; in place of the two pieces of
+iron and the armature used in the last experiments, the poles of the
+magnet were connected by a single rod of iron, bent into the form of a
+horse-shoe, and its extremities filed perfectly flat so as to come in
+perfect contact with the faces of the poles; around the middle of the
+arch of this horse-shoe, two strands of copper wire were tightly coiled
+one over the other. A current from one of these helices deflected the
+needle one hundred degrees, and when both were used the needle was
+deflected with such force as to make a complete circuit. But the most
+surprising effect was produced when, instead of passing the current
+through the long wires to the galvanometer, the opposite ends of the
+helices were held nearly in contact with each other, and the magnet
+suddenly excited; in this case a small but vivid spark was seen to pass
+between the ends of the wires, and this effect was repeated as often as
+the state of intensity of the magnet was changed.</p>
+
+<p>In these experiments the connection of the battery with the wires<span class="pagenum" id="Page_204">[Pg 204]</span> from
+the magnet was not formed by soldering, but by two cups of mercury,
+which permitted the galvanic action on the magnet to be instantaneously
+suspended and the polarity to be changed and rechanged without removing
+the battery from the acid; a succession of vivid sparks was obtained
+by rapidly interrupting and forming the communication by means of one
+of these cups; but the greatest effect was produced when the magnetism
+was entirely destroyed and instantaneously reproduced by a change of
+polarity.</p>
+
+<p>It appears from the May number of the <i>Annals of Philosophy</i> that
+I have been anticipated in this experiment of drawing sparks from the
+magnet by Mr. James D. Forbes of Edinburgh, who obtained a spark on the
+30th of March; my experiment being made during the last two weeks of
+June. A simple notification of his result is given, without any account
+of the experiment, which is reserved for a communication to the Royal
+Society of Edinburgh; my result is therefore entirely independent of
+his and was undoubtedly obtained by a different process.</p>
+
+
+<p class="nindc space-above2 space-below2">
+ELECTRICAL SELF-INDUCTION IN A LONG HELICAL WIRE</p>
+
+<p>I have made several other experiments in relation to the same subject,
+but which more important duties will not permit me to verify in time
+for this paper. I may, however, mention one fact which I have not seen
+noticed in any work, and which appears to me to belong to the same
+class of phenomena as those before described; it is this: when a small
+battery is moderately excited by diluted acid, and its poles, which
+should be terminated by cups of mercury, are connected by a copper
+wire not more than a foot in length, no spark is perceived when the
+connection is either formed or broken; but if a wire thirty or forty
+feet long be used instead of the short wire, though no spark will be
+perceptible when the connection is made, yet when it is broken by
+drawing one end of the wire from its cup of mercury, a vivid spark
+is produced. If the action of the battery be very intense, a spark
+will be given by the short wire; in this case it is only necessary to
+wait a few minutes until the action partially subsides, and until no
+more sparks are given from the short wire; if the long wire be now
+substituted a spark will again be obtained. The effect appears somewhat
+increased by coiling the wire into a helix; it seems also to depend in<span class="pagenum" id="Page_205">[Pg 205]</span>
+some measure on the length and thickness of the wire. I can account for
+these phenomena only by supposing the long wire to become charged with
+electricity, which by its reaction on itself projects a spark when the
+connection is broken.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_30" href="#FNanchor_30" class="label">[30]</a>
+Silliman’s <i>American Journal of Science</i>, July,
+1832, Vol. XXII, pp. 403-408; <i>Scientific Writings</i>, Vol. I., p.
+73.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_206">[Pg 206]</span></p>
+<h2 class="nobreak" id="XXVIII">XXVIII<br>
+SIR CHARLES LYELL<br>
+1797-1875</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Sir Charles Lyell, the son of a Scottish botanist of literary
+tastes, was born at Kinnordy, Scotland, November 14, 1797. He went to
+Oxford University, from which he graduated in 1819. He was admitted to
+the bar in 1825. In 1827 he abandoned law for geology, and published
+his “Principles of Geology” in 1830-1833. Lyell’s thesis was that
+all the past changes of the earth were explainable by forces now
+operative—an idea which underlies modern geology. He published his
+“Antiquity of Man” in 1863, providing proofs of man’s long existence
+on earth and thus contributing to the establishment of the Darwinian
+theory. He died February 22, 1875.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+UNIFORMITY IN THE SERIES OF PAST CHANGES IN THE ANIMATE AND INANIMATE
+WORLD<a id="FNanchor_31" href="#Footnote_31" class="fnanchor">[31]</a></p>
+
+
+<p><i>Origin of the doctrine of alternate periods of repose and
+disorder.</i>—It has been truly observed that when we arrange the
+fossiliferous formations in chronological order, they constitute
+a broken and defective series of monuments; we pass without any
+intermediate gradations from systems of strata which are horizontal, to
+other systems which are highly inclined—from rocks of peculiar mineral
+composition to others which have a character wholly distinct—from one
+assemblage of organic remains to another, in which frequently nearly
+all the species, and a large part of the genera, are different. These
+violations of continuity are so common as to constitute in most regions
+the rule rather than the exception, and they have been considered by
+many geologists as conclusive in favour of sudden revolutions in the
+inanimate and animate world. We have already seen that according to<span class="pagenum" id="Page_207">[Pg 207]</span>
+the speculations of some writers, there have been in the past history
+of the planet alternate periods of tranquility and convulsion, the
+former enduring for ages, and resembling the state of things now
+experienced by man; the other brief, transient, and paroxysmal, giving
+rise to new mountains, seas, and valleys, annihilating one set of
+organic beings and ushering in the creation of another.</p>
+
+<p>It will be the object of the present chapter to demonstrate that
+these theoretical views are not borne out by a fair interpretation of
+geological monuments. It is true that in the solid framework of the
+globe we have a chronological chain of natural records, many links of
+which are wanting: but a careful consideration of all the phenomena
+leads to the opinion that the series was originally defective—that
+it has been rendered still more so by time—that a great part of what
+remains is inaccessible to man, and even of that fraction which is
+accessible nine-tenths or more are to this day unexplored.</p>
+
+<p>The readiest way, perhaps, of persuading the reader that we may
+dispense with great and sudden revolutions in the geological order
+of events is by showing him how a regular and uninterrupted series
+of changes in the animate and inanimate world must give rise to such
+breaks in the sequence, and such unconformability of stratified rocks,
+as are usually thought to imply convulsions and catastrophes. It is
+scarcely necessary to state that the order of events thus assumed to
+occur, for the sake of illustration, should be in harmony with all
+the conclusions legitimately drawn by geologists from the structure
+of the earth, and must be equally in accordance with the changes
+observed by man to be now going on in the living as well as in the
+inorganic creation. It may be necessary in the present state of science
+to supply some part of the assumed course of nature hypothetically;
+but if so, this must be done without any violation of probability,
+and always consistently with the analogy of what is known both of the
+past and present economy of our system. Although the discussion of so
+comprehensive a subject must carry the beginner far beyond his depth,
+it will also, it is hoped, stimulate his curiosity, and prepare him to
+read some elementary treatises on geology with advantage, and teach
+him the bearing on that science of the changes now in progress on the
+earth. At the same time it may enable him the better to understand the
+intimate connection between the Second and Third Books of this work,
+one of which is occupied with the changes<span class="pagenum" id="Page_208">[Pg 208]</span> of the inorganic, the latter
+with those of the organic creation.</p>
+
+<p>In pursuance, then, of the plan above proposed, I will consider
+in this chapter, first, the laws which regulate the denudation of
+strata and the deposition of sediment; secondly, those which govern
+the fluctuation in the animate world; and thirdly, the mode in which
+subterranean movements affect the earth’s crust.</p>
+
+
+<p class="space-above2">
+<i>Uniformity of change considered, first, in reference to denudation
+and sedimentary deposition.</i>—First, in regard to the laws governing
+the deposition of new strata. If we survey the surface of the globe,
+we immediately perceive that it is divisible into areas of deposition
+and non-deposition; or, in other words, at any given time there are
+spaces which are the recipients, others which are not the recipients,
+of sedimentary matter. No new strata, for example, are thrown down on
+dry land, which remains the same from year to year; whereas, in many
+parts of the bottom of seas and lakes, mud, sand, and pebbles are
+annually spread out by rivers and currents. There are also great masses
+of limestone growing in some seas, chiefly composed of corals and
+shells, or, as in the depths of the Atlantic, of chalky mud made up of
+foraminifera and diatomaceæ.</p>
+
+<p>As to the dry land, so far from being the receptacle of fresh
+accessions of matter, it is exposed almost everywhere to waste away.
+Forests may be as dense and lofty as those of Brazil, and may swarm
+with quadrupeds, birds, and insects, yet at the end of thousands of
+years one layer of black mould a few inches thick may be the sole
+representative of those myriads of trees, leaves, flowers, and fruits,
+those innumerable bones and skeletons of birds, quadrupeds, and
+reptiles, which tenanted the fertile region. Should this land be at
+length submerged, the waves of the sea may wash away in a few hours
+the scanty covering of mould, and it may merely import a darker shade
+of colour to the next stratum of marl, sand, or other matter newly
+thrown down. So also at the bottom of the ocean where no sediment is
+accumulating, seaweed, zoophytes, fish, and even shells, may multiply
+for ages and decompose, leaving no vestige of their form or substance
+behind. Their decay, in water, although more slow, is as certain and
+eventually as complete as in the open air. Nor can they be perpetuated
+for indefinite periods in a fossil state, unless imbedded in some
+matrix which is impervious to water, or which at least does not allow
+a free percolation of that fluid, impregnated as it usually is, with
+a<span class="pagenum" id="Page_209">[Pg 209]</span> slight quantity of carbonic or other acid. Such a free percolation
+may be prevented either by the mineral nature of the matrix itself,
+or by the superposition of an impermeable stratum; but if unimpeded,
+the fossil shell or bone will be dissolved and removed, particle after
+particle, and thus entirely effaced, unless petrification or the
+substitution of some mineral for the organic matter happen to take
+place.</p>
+
+<p>That there has been land as well as sea at all former geological
+periods, we know from the fact that fossil trees and terrestrial plants
+are imbedded in rocks of every age, except those which are so ancient
+as to be very imperfectly known to us. Occasionally lacrustine and
+fluviatile shells, or the bones of amphibious or land reptiles, point
+to the same conclusion. The existence of dry land at all periods of the
+past implies, as before mentioned, the partial deposition of sediment,
+or its limitation to certain areas; and the next point to which I shall
+call the reader’s attention is the shifting of these areas from one
+region to another.</p>
+
+<p>First, then, variations in the site of sedimentary deposition are
+brought about independently of subterranean movements. There is always
+a slight change from year to year, or from century to century. The
+sediment of the Rhone, for example, thrown in the Lake of Geneva, is
+now conveyed to a spot a mile and a half distant from that where it
+accumulated in the tenth century, and six miles from the point where
+the delta began originally to form. We may look forward to the period
+when this lake will be filled up, and then the distribution of the
+transported matter will be suddenly altered, for the mud and sand
+brought down from the Alps will thenceforth, instead of being deposited
+near Geneva, be carried nearly 200 miles southwards, where the Rhone
+enters the Mediterranean.</p>
+
+<p>In the deltas of large rivers, such as those of the Ganges and Indus,
+the mud is first carried down for many centuries through one arm,
+and on this being stopped up it is discharged by another, and may
+then enter the sea at a point 50 or 100 miles distant from its first
+receptacle. The direction of marine currents is also liable to be
+changed by various accidents, as by the heaping up of new sandbanks, or
+the wearing away of cliffs and promontories.</p>
+
+<p>But, secondly, all these causes of fluctuation in the sedimentary areas
+are entirely subordinate to those great upward or downward<span class="pagenum" id="Page_210">[Pg 210]</span> movements
+of lands, which will be presently spoken of, as prevailing over large
+tracts of the globe. By such elevation or subsidence certain spaces
+are gradually submerged, or made gradually to emerge: in the one case
+sedimentary deposition may be suddenly renewed after having been
+suspended for one or more geological periods, in the other as suddenly
+made to cease after having continued for ages.</p>
+
+<p>If deposition be renewed after a long interval, the new strata will
+usually differ greatly from the sedimentary rocks previously formed
+in the same place, and especially if the older rocks have suffered
+derangement, which implies a change in the physical geography of the
+district since the previous conveyance of sediment to the same spot. It
+may happen, however, that, even where the two groups, the superior and
+the inferior, are horizontal and conformable to each other, they may
+still differ entirely in mineral character, because, since the origin
+of the older formation, the geography of some distant country has
+been altered. In that country rocks before concealed may have become
+exposed by denudation; volcanoes may have burst out and covered the
+surface with scoriæ and lava; or new lakes, intercepting the sediment
+previously conveyed from the upper country, may have been formed by
+subsidence; and other fluctuations may have occurred, by which the
+materials brought down from thence by rivers to the sea have acquired a
+distinct mineral character.</p>
+
+<p>It is well known that the stream of the Mississippi is charged with
+sediment of a different colour from that of the Arkansas and Red
+Rivers, which are tinged with red mud, derived from rocks of porphyry
+and red gypseous clays in “the far west.” The waters of the Uruguay,
+says Darwin, draining a granitic country, are clear and black, those
+of the Parana, red. The mud with which the Indus is loaded, says
+Burnes, is of a clayey hue, that of the Chenab, on the other hand, is
+reddish, that of the Sutlej is more pale. The same causes which make
+these several rivers, sometimes situated at no great distance the one
+from the other, to differ greatly in the character of their sediment,
+will make the waters draining the same country at different epochs,
+especially before and after great revolutions in physical geography,
+to be entirely dissimilar. It is scarcely necessary to add that marine
+currents will be affected in an analogous manner in consequence of the
+formation of new shoals, the emergence of new islands, the subsidence
+of others, the gradual waste of neighbouring<span class="pagenum" id="Page_211">[Pg 211]</span> coasts, the growth of
+new deltas, the increase of coral reefs, volcanic eruptions, and other
+changes.</p>
+
+
+<p class="space-above2">
+<i>Uniformity of change considered, secondly, in reference to the
+living creation.</i>—Secondly, in regard to the vicissitudes of
+the living creation, all are agreed that the successive groups of
+sedimentary strata found in the earth’s new crust are not only
+dissimilar in mineral composition for reasons above alluded to, but are
+likewise distinguishable from each other by their organic remains. The
+general inference drawn from the study and comparison of the various
+groups, arranged in chronological order, is this: that at successive
+periods distinct tribes of animals and plants have inhabited the land
+and waters, and that the organic types of the newer formations are more
+analogous to species now existing than those of more ancient rocks. If
+we then turn to the present state of the animate creation, and inquire
+whether it has now become fixed and stationary, we discover that, on
+the contrary, it is in a state of continual flux—that there are many
+causes in action which tend to the extinction of species, and which are
+conclusive against the doctrine of their unlimited durability.</p>
+
+<p>There are also causes which give rise to new varieties and races in
+plants and animals, and new forms are continually supplanting others
+which had endured for ages. But natural history has been successfully
+cultivated for so short a period, that a few examples only of local,
+and perhaps but one or two of absolute, extirpation of species can as
+yet be proved, and these only where the interference of man has been
+conspicuous. It will nevertheless appear evident, from the facts and
+arguments detailed in the chapters which treat of the geographical
+distribution of species in the next volume, that man is not the only
+exterminating agent; and that, independently of his intervention, the
+annihilation of species is promoted by the multiplication and gradual
+diffusion of every animal or plant. It will also appear that every
+alteration in the physical geography and climate of the globe cannot
+fail to have the same tendency. If we proceed still farther, and
+inquire whether new species are substituted from time to time for those
+which die out, we find that the successive introduction of new forms
+appears to have been a constant part of the economy of the terrestrial
+system, and if we have no direct proof of the fact it is because the
+changes take place so slowly as not to come within the period of exact
+scientific observation. To enable the reader to appreciate<span class="pagenum" id="Page_212">[Pg 212]</span> the gradual
+manner in which a passage may have taken place from an extinct fauna to
+that now living, I shall say a few words on the fossils of successive
+Tertiary periods. When we trace the series of formations from the more
+ancient to the more modern, it is in these Tertiary deposits that we
+first meet with assemblages of organic remains having a near analogy to
+the fauna of certain parts of the globe in our own time. In the Eocene,
+or oldest subdivisions, some few of the testacea belong to existing
+species, although almost all of them, and apparently all the associated
+vertebrata, are now extinct. These Eocene strata are succeeded by a
+great number of more modern deposits, which depart gradually in the
+character of their fossils from the Eocene type, and approach more and
+more to that of the living creation. In the present state of science,
+it is chiefly by the aid of shells, that we are enabled to arrive at
+these results, for of all classes the testacea are the most generally
+diffused in a fossil state, and may be called the medals principally
+employed by nature in recording the chronology of past events. In the
+Upper Miocene rocks (No. 5 of the table, p. 135) we begin to find a
+considerable number, although still a minority, of recent species,
+intermixed with some fossils common to the preceding, or Eocene,
+epoch. We then arrive at the Pliocene strata, in which species now
+contemporary with man begin to preponderate, and in the newest of
+which nine-tenths of the fossils agree with species still inhabiting
+the neighbouring sea. It is in the Post-Tertiary strata, where all
+the shells agree with species now living, that we have discovered the
+first or earliest known remains of man associated with the bones of
+quadrupeds, some of which are of extinct species.</p>
+
+<p>In thus passing from the older to the newer members of the Tertiary
+system, we meet with many chasms, but none which separate entirely,
+by a broad line of demarcation, one state of the organic world from
+another. There are no signs of an abrupt termination of one fauna and
+flora, and the starting into life of new and wholly distinct forms.
+Although we are far from being able to demonstrate geologically an
+insensible transition from the Eocene to the Miocene, or even from the
+latter to the recent fauna, yet the more we enlarge and perfect our
+general survey, the more nearly do we approximate to such a continuous
+series, and the more gradually are we conducted from times when many of
+the genera and nearly all the species were extinct,<span class="pagenum" id="Page_213">[Pg 213]</span> to those in which
+scarcely a single species flourished, which we do not know to exist
+at present. Dr. A. Philippi, indeed, after an elaborate comparison
+of the fossil tertiary shells of Sicily with those now living in the
+Mediterranean, announced, as the result of his examination, that there
+are strata in that island which attest a very gradual passage from a
+period when only thirteen in a hundred of the shells were like the
+species now living in the sea, to an era when the recent species had
+attained a proportion of ninety-five in a hundred. There is, therefore,
+evidence, he says, in Sicily of this revolution in the animate world
+having been effected “without the intervention of any convulsion
+or abrupt changes, certain species having from time died out, and
+others having been introduced, until at length the existing fauna was
+elaborated.”</p>
+
+<p>In no part of Europe is the absence of all signs of man or his works,
+in strata of comparatively modern date, more striking than in Sicily.
+In the central parts of that island we observe a lofty table-land and
+hills, sometimes rising to the height of 3,000 feet, capped with a
+limestone, in which from 70 to 85 per cent of the fossil testacea are
+specifically identical with those now inhabiting the Mediterranean.
+These calcareous and other argillaceous strata of the same age are
+intersected by deep valleys which appear to have been gradually formed
+by denudation, but have not varied materially in width or depth since
+Sicily was first colonized by the Greeks. The limestone, moreover,
+which is of so late a date in geological chronology, was quarried for
+building those ancient temples of Girgenti and Syracuse, of which the
+ruins carry us back to a remote era in human history. If we are lost
+in conjectures when speculating on the ages required to lift up these
+formations to the height of several thousand feet above the sea, and
+to excavate the valleys, how much more remote must be the era when the
+same rocks were gradually formed beneath the waters!</p>
+
+<p>The intense cold of the Glacial period was spoken of in the tenth
+chapter. Although we have not yet succeeded in detecting proofs of the
+origin of man antecedently to that epoch, we have yet found evidence
+that most of the testacea, and not a few of the quadrupeds, which
+preceded, were of the same species as those which followed the extreme
+cold. To whatever local disturbances this cold may have given rise in
+the distribution of species, it seems to have done little in effecting
+their annihilation. We may conclude, therefore, from a<span class="pagenum" id="Page_214">[Pg 214]</span> survey of
+the tertiary and modern strata, which constitute a more complete and
+unbroken series than rocks of older date, that the extinction and
+creation of species have been, and are, the result of a slow and
+gradual change in the organic world.</p>
+
+
+<p class="space-above2">
+<i>Uniformity of change considered, thirdly, in reference to
+subterranean movements.</i>—Thirdly, to pass on to the last of the
+three topics before proposed for discussion, the reader will find, in
+the account given in the Second Book, Vol. II., of the earthquakes
+recorded in history, that certain countries have, from time immemorial,
+been rudely shaken again and again; while others, comprising by
+far the largest part of the globe, have remained to all appearance
+motionless. In the regions of convulsion rocks have been rent asunder,
+the surface has been forced up into ridges, chasms have opened, or the
+ground throughout large spaces has been permanently lifted up above
+or let down below its former level. In the regions of tranquillity
+some areas have remained at rest, but others have been ascertained,
+by a comparison of measurements made at different periods, to have
+arisen by an insensible motion, as in Sweden, or to have subsided very
+slowly, as in Greenland. That these same movements, whether ascending
+or descending, have continued for ages in the same direction has been
+established by historical or geological evidence. Thus we find on the
+opposite coasts of Sweden that brackish water deposits, like those
+now forming in the Baltic, occur on the eastern side, and upraised
+strata filled with purely marine shells, now proper to the ocean, on
+the western coast. Both of these have been lifted up to an elevation
+of several hundred feet above high-water mark. The rise within the
+historical period has not amounted to many yards, but the greater
+extent of antecedent upheaval is proved by the occurrence in inland
+spots, several hundred feet high, of deposits filled with fossil shells
+of species now living either in the ocean or the Baltic.</p>
+
+<p>It must in general be more difficult to detect proofs of slow and
+gradual subsidence than of elevation, but the theory which accounts for
+the form of circular coral reefs and lagoon islands, and which will
+be explained in the concluding chapter of this work, will satisfy the
+reader that there are spaces on the globe, several thousand miles in
+circumference, throughout which the downward movement has predominated
+for ages, and yet the land has never, in a single instance, gone down
+suddenly for several hundred feet at once. Yet geology<span class="pagenum" id="Page_215">[Pg 215]</span> demonstrates
+that the persistency of subterranean movements in one direction has
+not been perpetual throughout all past time. There have been great
+oscillations of level, by which a surface of dry land has been
+submerged to a depth of several thousand feet, and then at a period
+long subsequent raised again and made to emerge. Nor have the regions
+now motionless been always at rest; and some of those which are at
+present the theatres of reiterated earthquakes have formerly enjoyed
+a long continuance of tranquillity. But, although disturbances have
+ceased after having long prevailed, or have recommenced after a
+suspension of ages, there has been no universal disruption of the
+earth’s crust or desolation of the surface since times the most
+remote. The non-occurrence of such a general convulsion is proved by
+the perfect horizontality now retained by some of the most ancient
+fossiliferous strata throughout wide areas.</p>
+
+<p>That the subterranean forces have visited different parts of the globe
+at successive periods is inferred chiefly from the unconformability of
+strata belonging to groups of different ages. Thus, for example, on the
+borders of Wales and Shropshire, we find the slaty beds of the ancient
+Silurian system inclined and vertical, while the beds of the overlying
+carboniferous shale and sandstone are horizontal. All are agreed that
+in such a case the older set of strata had suffered great disturbance
+before the deposition of the newer or carboniferous beds, and that
+these last have never since been violently fractured, nor have ever
+been bent into folds, whether by sudden or continuous lateral pressure.
+On the other hand, the more ancient or Silurian group suffered only a
+local derangement, and neither in Wales nor elsewhere are all the rocks
+of that age found to be curved or vertical.</p>
+
+<p>In various parts of Europe, for example, and particularly near Lake
+Wener in the south of Sweden, and in many parts of Russia, the
+Silurian strata maintain the most perfect horizontality; and a similar
+observation may be made respecting limestones and shales of like
+antiquity in the great lake district of Canada and the United States.
+These older rocks are still as flat and horizontal as when first
+formed; yet, since their origin, not only have most of the actual
+mountain-chains been uplifted, but some of the very rocks of which
+those mountains are composed have been formed, some of them by igneous
+and others by aqueous action.</p>
+
+<p>It would be easy to multiply instances of similar unconformability<span class="pagenum" id="Page_216">[Pg 216]</span>
+in formations of other ages; but a few more will suffice. The
+carboniferous rocks before alluded to as horizontal on the borders
+of Wales are vertical in the Mendip hills in Somersetshire, where
+the overlying beds of the New Red Sandstone are horizontal. Again,
+in the Wolds of Yorkshire the last-mentioned sandstone supports on
+its curved and inclined beds the horizontal Chalk. The Chalk again is
+vertical on the flanks of the Pyrenees, and the tertiary strata repose
+unconformably upon it.</p>
+
+<p>As almost every country supplies illustrations of the same phenomena,
+they who advocate the doctrine of alternate periods of disorder and
+repose may appeal to the facts above described, as proving that every
+district has been by turns convulsed by earthquakes and then respited
+for ages from convulsions. But so it might with equal truth be affirmed
+that every part of Europe has been visited alternately by winter and
+summer, although it has always been winter and always summer in some
+part of the planet, and neither of these seasons has ever reigned
+simultaneously over the entire globe. They have been always shifting
+from place to place; but the vicissitudes which recur thus annually
+in a single spot are never allowed to interfere with the invariable
+uniformity of seasons throughout the whole planet.</p>
+
+<p>So, in regard to subterranean movements, the theory of the perpetual
+uniformity of the force which they exert on the earth’s crust is quite
+consistent with the admission of their alternate development and
+suspension for long and indefinite periods within limited geographical
+areas.</p>
+
+<p>If, for reasons before stated, we assume a continual extinction of
+species and appearance of others on the globe, it will then follow
+that the fossils of strata formed at two distant periods on the same
+spot will differ even more certainly than the mineral composition of
+those strata. For rocks of the same kind have sometimes been reproduced
+in the same district after a long interval of time; whereas all the
+evidence derived from fossil remains is in favour of the opinion that
+species which have once died out have never been reproduced. The
+submergence, then, of land must be often attended by the commencement
+of a new class of sedimentary deposits, characterized by a new set of
+fossil animals and plants, while the reconversion of the bed of the sea
+into land may arrest at once and for an indefinite time the formation
+of geological monuments. Should the land again sink,<span class="pagenum" id="Page_217">[Pg 217]</span> strata will again
+be formed; but one or many entire revolutions in animal or vegetable
+life may have been completed in the interval.</p>
+
+<p>As to the want of completeness in the fossiliferous series, which
+may be said to be almost universal, we have only to reflect on what
+has been already said of the laws governing sedimentary deposition,
+and those which give rise to fluctuations in the animate world, to
+be convinced that a very rare combination of circumstances can alone
+give rise to such a superposition and preservation of strata as will
+bear testimony to the gradual passage from one state of organic life
+to another. To produce such strata nothing less will be requisite
+than the fortunate coincidence of the following conditions: first, a
+never-failing supply of sediment in the same region throughout a period
+of vast duration; secondly, the fitness of the deposit in every part
+for the permanent preservation of imbedded fossils; and, thirdly, a
+gradual subsidence to prevent the sea or lake from being filled up and
+converted into land.</p>
+
+<p>It will appear in the chapter on coral reefs, that, in certain parts
+of the Pacific and Indian Oceans, most of these conditions, if not
+all, are complied with, and the constant growth of coral, keeping
+pace with the sinking of the bottom of the sea, seems to have gone on
+so slowly, for such indefinite periods, that the signs of a gradual
+change in organic life might probably be detected in that quarter of
+the globe if we could explore its submarine geology. Instead of the
+growth of coralline limestone, let us suppose, in some other place,
+the continuous deposition of fluviatile mud and sand, such as the
+Ganges and Brahmapootra have poured for thousands of years into the
+Bay of Bengal. Part of this bay, although of considerable depth,
+might at length be filled up before an appreciable amount of change
+was effected in the fish, mollusca, and other inhabitants of the sea
+and neighbouring land. But if the bottom be lowered by sinking at
+the same rate that it is raised by fluviatile mud, the bay can never
+be turned into dry land. In that case one new layer of matter may be
+superimposed upon another for a thickness of many thousand feet, and
+the fossils of the inferior beds may differ greatly from those entombed
+in the uppermost, yet every intermediate gradation may be indicated in
+the passage from an older to a newer assemblage of species. Granting,
+however, that such an unbroken sequence of monuments may thus be
+elaborated in certain parts of the sea, and<span class="pagenum" id="Page_218">[Pg 218]</span> that the strata happen
+to be all of them well adapted to preserve the included fossils from
+decomposition, how many accidents must still concur before these
+submarine formations will be laid open to our investigation! The whole
+deposit must first be raised several thousand feet, in order to bring
+into view the very foundation; and during the process of exposure the
+superior beds must not be entirely swept away by denudation.</p>
+
+<p>In the first place, the chances are nearly as three to one against
+the mere emergence of the mass above the waters, because nearly
+three-fourths of the globe are covered by the ocean. But if it be
+upheaved and made to constitute part of the dry land, it must also,
+before it can be available for our instruction, become part of that
+area already surveyed by geologists. In this small fraction of land
+already explored, and still very imperfectly known, we are required to
+find a set of strata deposited under peculiar conditions, and which,
+having been originally of limited extent, would have been probably much
+lessened by subsequent denudation.</p>
+
+<p>Yet it is precisely because we do not encounter at every step the
+evidence of such gradations from one state of the organic world to
+another, that so many geologists have embraced the doctrine of great
+and sudden revolutions in the history of the animate world. Not content
+with simply availing themselves, for the convenience of classification,
+of those gaps and chasms which here and there interrupt the continuity
+of the chronological series, as at present known, they deduce, from the
+frequency of these breaks in the chain of records, an irregular mode of
+succession in the events themselves, both in the organic and inorganic
+world. But, besides that some links of the chain which once existed are
+now entirely lost and others concealed from view, we have good reason
+to suspect that it was never complete originally. It may undoubtedly be
+said that strata have been always forming somewhere, and therefore at
+every moment of past time Nature has added a page to her archives; but,
+in reference to this subject, it should be remembered that we can never
+hope to compile a consecutive history by gathering together monuments
+which were originally detached and scattered over the globe. For, as
+the species of organic beings contemporaneously inhabiting remote
+regions are distinct, the fossils of the first of several periods which
+may be preserved in any one country, as in America for example, will
+have no<span class="pagenum" id="Page_219">[Pg 219]</span> connection with those of a second period found in India, and
+will therefore no more enable us to trace the signs of a gradual change
+in the living creation, than a fragment of Chinese history will fill up
+a blank in the political annals of Europe.</p>
+
+<p>The absence of any deposits of importance containing recent shells in
+Chili, or anywhere on the western shore of South America, naturally led
+Mr. Darwin to the conclusion that “where the bed of the sea is either
+stationary or rising, circumstances are far less favourable than where
+the level is sinking to the accumulation of conchiferous strata of
+sufficient thickness and extension to resist the average vast amount
+of denudation.” In like manner the beds of superficial sand, clay, and
+gravel, with recent shells, on the coasts of Norway and Sweden, where
+the land has risen in Post-tertiary times, are so thin and scanty as to
+incline us to admit a similar proposition. We may in fact assume that
+in all cases where the bottom of the sea has been undergoing continuous
+elevation, the total thickness of sedimentary matter accumulating
+at depths suited to the habitation of most of the species of shells
+can never be great, nor can the deposits be thickly covered with
+superincumbent matter, so as to be consolidated by pressure. When they
+are upheaved, therefore, the waves on the beach will bear down and
+disperse the loose materials; whereas, if the bed of the sea subsides
+slowly, a mass of strata containing abundance of such species as live
+at moderate depths, may be formed and may increase in thickness to any
+amount. It may also extend horizontally over a broad area, as the water
+gradually encroaches on the subsiding land.</p>
+
+<p>Hence it will follow that great violations of continuity in the
+chronological series of fossiliferous rocks will always exist, and the
+imperfection of the record, though lessened, will never be removed by
+future discoveries. For not only will no deposits originate on the
+dry land, but those formed in the sea near land, which is undergoing
+constant upheaval, will usually be too slight in thickness to endure
+for ages.</p>
+
+<p>In proportion as we become acquainted with larger geographical
+areas, many of the gaps, by which a chronological table is rendered
+defective, will be removed. We were enabled by aid of the labours of
+Prof. Sedgwick and Sir Roderick Murchison, to intercalate, in 1838,
+the marine strata of the Devonian period, with their fossil<span class="pagenum" id="Page_220">[Pg 220]</span> shells,
+corals, and fish, between the Silurian and Carboniferous rocks.
+Previously the marine fauna of these last-mentioned formations wanted
+the connecting links which now render the passage from the one to
+the other much less abrupt. In like manner the Upper Miocene has no
+representative in England, but in France, Germany, and Switzerland it
+constitutes a most instructive link between the living creation and the
+middle of the great Tertiary period. Still we must expect, for reasons
+before stated, that chasms will forever continue to occur, in some
+parts of our sedimentary series.</p>
+
+
+<p class="space-above2">
+<i>Concluding remarks on the consistency of the theory of gradual
+change with the existence of great breaks in the series.</i>—To
+return to the general argument pursued in this chapter, it is assumed,
+for reasons above explained, that a slow change of species is in
+simultaneous operation everywhere throughout the habitable surface
+of sea and land; whereas the fossilization of plants and animals is
+confined to those areas where new strata are produced. These areas,
+as we have seen, are always shifting their position, so that the
+fossilizing process, by means of which the commemoration of the
+particular state of the organic world, at any given time, is effected,
+may be said to move about, visiting and revisiting different tracts in
+succession.</p>
+
+<p>To make still more clear the supposed working of this machinery, I
+shall compare it to a somewhat analogous case that might be imagined
+to occur in the history of human affairs. Let the mortality of the
+population of a large country represent the successive extinction
+of species, and the births of new individuals the introduction of
+new species. While these fluctuations are gradually taking place
+everywhere, suppose commissioners to be appointed to visit each
+province of the country in succession, taking an exact account of the
+number, names and individual peculiarities of all the inhabitants,
+and leaving in each district a register containing a record of this
+information. If, after the completion of one census, another is
+immediately made on the same plan, and then another, there will at
+last be a series of statistical documents in each province. When
+those belonging to any one province are arranged in chronological
+order, the contents of such as stand next to each other will differ
+according to the length of the intervals of time between the taking of
+each census. If, for example, there are sixty provinces, and all the
+registers are made in a single year and renewed annually, the number
+of births and deaths<span class="pagenum" id="Page_221">[Pg 221]</span> will be so small, in proportion to the whole
+of the inhabitants, during the interval between the compiling of two
+consecutive documents, that the individuals described in such documents
+will be nearly identical; whereas, if the survey of each of the sixty
+provinces occupies all the commissioners for a whole year, so that they
+are unable to revisit the same place until the expiration of sixty
+years, there will then be an almost entire discordance between the
+persons enumerated in two consecutive registers in the same province.
+There are, undoubtedly, other causes, besides the mere quantity of
+time, which may augment or diminish the amount of discrepancy. Thus,
+at some periods, a pestilential disease may have lessened the average
+duration of human life; or a variety of circumstances may have caused
+the births to be unusually numerous, and the population to multiply;
+or a province may be suddenly colonized by persons migrating from
+surrounding districts.</p>
+
+<p>These exceptions may be compared to the accelerated rate of
+fluctuations in the fauna and flora of a particular region, in which
+the climate and physical geography may be undergoing an extraordinary
+degree of alteration.</p>
+
+<p>But I must remind the reader that the case above proposed has no
+pretensions to be regarded as an exact parallel to the geological
+phenomena which I desire to illustrate; for the commissioners are
+supposed to visit the different provinces in rotation; whereas the
+commemorating processes by which organic remains become fossilized,
+although they are always shifting from one area to the other, are yet
+very irregular in their movements. They may abandon and revisit many
+spaces again and again, before they once approach another district;
+and, besides this source of irregularity, it may often happen that,
+while the depositing process is suspended, denudation may take place,
+which may be compared to the occasional destruction by fire or other
+causes of some of the statistical documents before mentioned. It is
+evident that where such accidents occur the want of continuity in the
+series may become indefinitely great, and that the monuments which
+follow next in succession will by no means be equidistant from each
+other in point of time.</p>
+
+<p>If this train of reasoning be admitted, the occasional distinctness of
+the fossil remains, in formations immediately in contact, would be a
+necessary consequence of the existing laws of sedimentary deposition<span class="pagenum" id="Page_222">[Pg 222]</span>
+and subterranean movement, accompanied by a constant dying-out and
+renovation of species.</p>
+
+<p>As all the conclusions above insisted on are directly opposed to
+opinions still popular, I shall add another comparison, in the hope of
+preventing any possible misapprehension of the argument. Suppose we
+had discovered two buried cities at the foot of Vesuvius, immediately
+superimposed upon each other, with a great mass of tuff and lava
+intervening, just as Portici and Resina, if now covered with ashes,
+would overlie Herculaneum. An antiquary might possibly be entitled to
+infer, from the inscriptions on public edifices, that the inhabitants
+of the inferior and older city were Greeks, and those of the modern
+town Italians. But he would reason very hastily if he also concluded
+from these data, that there had been a sudden change from the Greek
+to the Italian language in Campania. But if he afterwards found three
+buried cities, one above the other, the intermediate one being Roman,
+while, as in the former example, the lowest was Greek and the uppermost
+Italian, he would then perceive the fallacy of his former opinion and
+would begin to suspect that the catastrophes, by which the cities
+were inhumed, might have no relation whatever to the fluctuations in
+the language of the inhabitants; and that, as the Roman tongue had
+evidently intervened between the Greek and Italian, so many other
+dialects may have been spoken in succession, and the passage from the
+Greek to the Italian may have been very gradual, some terms growing
+obsolete, while others were introduced from time to time.</p>
+
+<p>If this antiquary could have shown that the volcanic paroxysms of
+Vesuvius were so governed as that cities should be buried one above the
+other, just as often as any variation occurred in the language of the
+inhabitants, then, indeed, the abrupt passage from a Greek to a Roman,
+and from a Roman to an Italian city, would afford proof of fluctuations
+no less sudden in the language of the people.</p>
+
+<p>So, in Geology, if we could assume that it is part of the plan of
+Nature to preserve, in every region of the globe, an unbroken series
+of monuments to commemorate the vicissitudes of the organic creation,
+we might infer the sudden extirpation of species, and the simultaneous
+introduction of others, as often as two formations in contact are found
+to include dissimilar organic fossils. But we must shut our eyes to the
+whole economy of the existing causes, aqueous, igneous, and<span class="pagenum" id="Page_223">[Pg 223]</span> organic,
+if we fail to perceive that such is not the plan of Nature.</p>
+
+<p>I shall now conclude the discussion of a question with which we have
+been occupied since the beginning of the fifth chapter—namely, whether
+there has been any interruption, from the remotest periods, of one
+uniform and continuous system of change in the animate and inanimate
+world. We were induced to enter into that inquiry by reflecting how
+much the progress of opinion in Geology had been influenced by the
+assumption that the analogy was slight in kind, and still more slight
+in degree, between the causes which produced the former revolutions
+of the globe, and those now in every-day operation. It appeared clear
+that the earlier geologists had not only a scanty acquaintance with
+existing changes, but were singularly unconscious of the amount of
+their ignorance. With the presumption naturally inspired by this
+unconsciousness, they had no hesitation in deciding at once that time
+could never enable the existing powers of nature to work out changes
+of great magnitude, still less such important revolutions as those
+which are brought to light by Geology. They therefore felt themselves
+at liberty to indulge their imaginations in guessing at what might be,
+rather than inquiring what is; in other words, they employed themselves
+in conjecturing what might have been the course of Nature at a remote
+period, rather than in the investigation of what was the course of
+Nature in their own times.</p>
+
+<p>It appeared to them far more philosophical to speculate on the
+possibilities of the past, than patiently to explore the realities of
+the present; and having invented theories under the influences of such
+maxims, they were consistently unwilling to test their validity by the
+criterion of their accordance with the ordinary operations of Nature.
+On the contrary, the claims of each new hypothesis to credibility
+appeared enhanced by the great contrast, in kind or intensity, of the
+causes referred to and those now in operation.</p>
+
+<p>Never was there a dogma more calculated to foster indolence, and
+to blunt the keen edge of curiosity, than this assumption of the
+discordance between the ancient and existing causes of change. It
+produced a state of mind unfavourable in the highest degree to the
+candid reception of the evidence of those minute but incessant
+alterations which every part of the earth’s surface is undergoing,
+and by which the condition of its living inhabitants is continually
+made to vary. The student, instead of being encouraged with the
+hope of interpreting<span class="pagenum" id="Page_224">[Pg 224]</span> the enigmas presented to him in the earth’s
+structure—instead of being prompted to undertake laborious inquiries
+into the natural history of the organic world, and the complicated
+effects of the igneous and aqueous causes now in operation—was taught
+to despond from the first. Geology, it was affirmed, could never rise
+to the rank of an exact science; the greater number of phenomena
+must forever remain inexplicable, or only be partially elucidated by
+ingenious conjectures. Even the mystery which invested the subject was
+said to constitute one of its principal charms, affording, as it did,
+full scope to the fancy to indulge in a boundless field of speculation.</p>
+
+<p>The course directly opposed to this method of philosophizing consists
+in an earnest and patient inquiry, how far geological appearances are
+reconcilable with the effect of changes now in progress, or which
+may be in progress in regions inaccessible to us, but of which the
+reality is attested by volcanoes and subterranean movements. It also
+endeavours to estimate the aggregate result of ordinary operations
+multiplied by time, and cherishes a sanguine hope that the resources
+to be derived from observation and experiment, or from the study of
+Nature such as she now is, are very far from being exhausted. For this
+reason all theories are rejected which involve the assumption of sudden
+and violent catastrophes and revolutions of the whole earth, and its
+inhabitants—theories which are restrained by no reference to existing
+analogies, and in which a desire is manifested to cut, rather than
+patiently to untie, the Gordian knot.</p>
+
+<p>We have now, at least, the advantage of knowing, from experience, that
+an opposite method has always put geologists on the road that leads
+to truth—suggesting views which, although imperfect at first, have
+been found capable of improvement, until at last adopted by universal
+consent; while the method of speculating on a former distinct state of
+things and causes has led invariably to a multitude of contradictory
+systems, which have been overthrown one after the other—have been
+found incapable of modification—and which have often required to be
+precisely reversed.</p>
+
+<p>The remainder of this work will be devoted to an investigation of the
+changes now going on in the crust of the earth and its inhabitants.
+The importance which the student will attach to such researches will
+mainly depend on the degree of confidence which he feels in the
+principles above expounded. If he firmly believes in the resemblance
+or<span class="pagenum" id="Page_225">[Pg 225]</span> identity of the ancient and present system of terrestrial changes,
+he will regard every fact collected respecting the causes in diurnal
+action as affording him a key to the interpretation of some mystery in
+the past. Events which have occurred at the most distant periods in
+the animate and inanimate world will be acknowledged to throw light
+on each other, and the deficiency of our information respecting some
+of the most obscure parts of the present creation will be removed.
+For as, by studying the external configuration of the existing land
+and its inhabitants, we may restore in imagination the appearance of
+the ancient continents which have passed away, so may we obtain from
+the deposits of ancient seas and lakes an insight into the nature
+of the subaqueous processes now in operation, and of many forms of
+organic life which, though now existing, are veiled from sight. Rocks,
+also, produced by subterranean fire in former ages, at great depths
+in the bowels of the earth, present us, when upraised by gradual
+movements, and exposed to the light of heaven, with an image of those
+changes which the deep-seated volcano may now occasion in the nether
+regions. Thus, although we are mere sojourners on the surface of the
+planet, chained to a mere point in space, enduring but for a moment of
+time, the human mind is not only enabled to number worlds beyond the
+unassisted ken of mortal eye, but to trace the events of indefinite
+ages before the creation of our race, and is not even withheld from
+penetrating into the dark secrets of the ocean, or the interior of
+the solid globe; free, like the spirit which the poet described as
+animating the universe,</p>
+
+<div class="poetry-container">
+<div class="poetry">
+ <div class="stanza">
+ <div class="verse indent17">—<i>ire per omnes</i></div>
+ <div class="verse indent0"><i>Terrasque, tractusque maris, coelumque profundum</i>.</div>
+ </div>
+</div>
+</div>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_31" href="#FNanchor_31" class="label">[31]</a>
+From the <i>Principles of Geology</i>, Bk. I, Ch. XIII.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_226">[Pg 226]</span></p>
+<h2 class="nobreak" id="XXIX">XXIX<br>
+CHARLES DARWIN<br>
+1809-1882</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Charles Robert Darwin, the grandson of Erasmus Darwin, was born at
+Shrewsbury, England, February 12, 1809. He studied at both Edinburgh
+and Cambridge, and graduated from the latter in 1831. From 1831 to 1836
+he served as a naturalist on the “Beagle,” which made a trip around the
+world in the interests of science. The voyage served as a post-graduate
+course for Darwin, who then first adopted his evolutionary ideas and
+developed as an original investigator. Reading Malthus, in 1838, on
+the problem of population and the food supply, he integrated Malthus’
+ideas into his own views of biology. In 1844 be began his “Origin of
+Species,” which he completed in 1859. In 1858 he received a paper
+from Alfred Russell Wallace, then in the Malay Archipelago, which
+proposed the same theory of natural selection. Darwin believed that
+when organisms increased much faster than the means of subsistence,
+the ratios varied, and in the conditions produced by these natural
+causes only those organisms survived which were best fitted to their
+environment. He applied his concept to human evolution in his “Descent
+of Man,” published in 1871. He died April 19, 1882, and was buried in
+Westminster Abbey.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+NATURAL SELECTION<a id="FNanchor_32" href="#Footnote_32" class="fnanchor">[32]</a></p>
+
+<p>How will the struggle for existence, briefly discussed in the last
+chapter, act in regard to variation? Can the principle of selection,
+which we have seen is so potent in the hands of man, apply under
+nature? I think we shall see that it can act most efficiently. Let
+the endless number of slight variations and individual differences
+occurring in our domestic productions, and, in a lesser degree, in
+those<span class="pagenum" id="Page_227">[Pg 227]</span> under nature, be borne in mind; as well as the strength of the
+hereditary tendency. Under domestication, it may be truly said that the
+whole organization becomes in some degree plastic. But the variability,
+which we almost universally meet with in our domestic production, is
+not directly produced, as Hooker and Asa Gray have well remarked, by
+man; he can neither originate varieties, nor prevent their occurrence;
+he can only preserve and accumulate such as do occur. Unintentionally
+he exposes organic beings to new and changing conditions of life, and
+variability ensues; but similar changes of conditions might and do
+occur under nature. Let it also be borne in mind how infinitely complex
+and close-fitting are the mutual relations of all organic beings to
+each other and to their physical conditions of life; and consequently
+what infinitely varied diversities of structure might be of use to
+each being under changing conditions of life. Can it then be thought
+improbable, seeing that variations useful to man have undoubtedly
+occurred, that other variations useful in some way to each being in the
+great and complex battle of life, should occur in the course of many
+successive generations? If such do occur, can we doubt (remembering
+that many more individuals are born than can possibly survive) that
+individuals having any advantage, however slight, over others, would
+have the best chance of surviving and of procreating their kind? On the
+other hand, we may feel sure that any variation in the least degree
+injurious would be rigidly destroyed. This preservation of favourable
+individual differences and variations, and the destruction of those
+which are injurious, I have called Natural Selection, or the Survival
+of the Fittest. Variations neither useful nor injurious would not be
+affected by natural selection, and would be left either a fluctuating
+element, as perhaps we see in certain polymorphic species, or would
+ultimately become fixed, owing to the nature of the organism and the
+nature of the conditions.</p>
+
+<p>Several writers have misapprehended or objected to the term Natural
+Selection. Some have even imagined that natural selection induces
+variability, whereas it implies only the preservation of such
+variations as arise and are beneficial to the being under its
+conditions of life. No one objects to agriculturists speaking of the
+potent effects of man’s selection; and in this case the individual
+differences given by nature, which man for some object selects, must of
+necessity first<span class="pagenum" id="Page_228">[Pg 228]</span> occur. Others have objected that the term selection
+implies conscious choice in the animals which become modified; and it
+has even been urged that, as plants have no volition, natural selection
+is not applicable to them! In the literal sense of the word, no doubt,
+natural selection is a false term; but who ever objected to chemists
+speaking of the elective affinities of the various elements?—and yet
+an acid cannot strictly be said to elect the base with which it in
+preference combines. It has been said that I speak of natural selection
+as an active power or Deity; but who objects to an author speaking
+of the attraction of gravity as ruling the movements of the planets?
+Everyone knows what is meant and is implied by such metaphorical
+expressions; and they are almost necessary for brevity. So again it is
+difficult to avoid personifying the word Nature; but I mean by Nature,
+only the aggregate action and product of many natural laws, and by laws
+the sequence of events as ascertained by us. With a little familiarity
+such superficial objections will be forgotten.</p>
+
+<p>We shall best understand the probable course of natural selection by
+taking the case of a country undergoing some slight physical change,
+for instance, of climate. The proportional numbers of its inhabitants
+will almost immediately undergo a change, and some species will
+probably become extinct. We may conclude, from what we have seen of the
+intimate and complex manner in which the inhabitants of each country
+are bound together, that any change in the numerical proportions of
+the inhabitants, independently of the change of climate itself, would
+seriously affect the others. If the country were open on its borders,
+new forms would certainly immigrate, and this would likewise seriously
+disturb the relations of some of the former inhabitants. Let it be
+remembered how powerful the influence of a single introduced tree
+or mammal has been shown to be. But in the case of an island, or of
+a country partly surrounded by barriers, into which new and better
+adapted forms could not freely enter, we should then have places in the
+economy of nature which would assuredly be better filled up, if some
+of the original inhabitants were in some manner modified; for, had the
+area been open to immigration, these same places would have been seized
+on by intruders. In such cases, slight modifications, which in any
+way favoured the individuals of any species, by better adapting them
+to their altered<span class="pagenum" id="Page_229">[Pg 229]</span> conditions, would tend to be preserved; and natural
+selection would have free scope for the work of improvement.</p>
+
+<p>We have good reason to believe, as shown in the first chapter, that
+changes in the conditions of life give a tendency to increased
+variability; and in the foregoing cases the conditions have changed,
+and this would manifestly be favourable to natural selection, by
+affording a better chance of the occurrence of profitable variations.
+Unless such occur, natural selection can do nothing. Under the term
+of “variations,” it must never be forgotten that mere individual
+differences are included. As man can produce a great result with
+his domestic animals and plants by adding up in any given direction
+individual differences, so could natural selection, but far more easily
+from having incomparably longer time for action. Nor do I believe
+that any great physical change, as of climate, or any unusual degree
+of isolation to check immigration, is necessary in order that new and
+unoccupied places should be left for natural selection to fill up by
+improving some of the varying inhabitants. For as all the inhabitants
+of each country are struggling together with nicely balanced forces,
+extremely slight modifications in the structure or habits of one
+species would often give it an advantage over others; and still further
+modifications of the same kind would often still further increase the
+advantage, as long as the species continued under the same conditions
+of life and profited by similar means of subsistence and defense. No
+country can be named in which all the native inhabitants are now so
+perfectly adapted to each other and to the physical conditions under
+which they live, that none of them could be still better adapted or
+improved; for in all countries, the natives have been so far conquered
+by naturalized productions, that they have allowed some foreigners to
+take firm possession of the land. And as foreigners have thus in every
+country beaten some of the natives, we may safely conclude that the
+natives might have been modified with advantage, so as to have better
+resisted the intruders.</p>
+
+<p>As man can produce, and certainly has produced, a great result by his
+methodical and unconscious means of selection, what may not natural
+selection effect? Man can act only on external and visible characters:
+Nature, if I may be allowed to personify the natural preservation or
+survival of the fittest, cares nothing for appearances, except in so
+far as they are useful to any being. She can act on<span class="pagenum" id="Page_230">[Pg 230]</span> every internal
+organ, on every shade of constitutional difference, on the whole
+machinery of life. Man selects only for his own good: Nature only for
+that of the being which she tends. Every selected character is fully
+exercised by her, as is implied by the fact of their selection. Man
+keeps the natives of many climates in the same country; he seldom
+exercises each selected character in some peculiar and fitting manner;
+he feeds a long and a short-beaked pigeon on the same food; he does
+not exercise a long-backed or long-legged quadruped in any peculiar
+manner; he exposes sheep with long and short wool to the same climate.
+He does not allow the most vigorous males to struggle for the females.
+He does not rigidly destroy all inferior animals, but protects during
+each varying season, as far as lies in his power, all his productions.
+He often begins his selection by some half-monstrous form; or at
+least by some modification prominent enough to catch the eye or to
+be plainly useful to him. Under nature, the slightest differences of
+structure or constitution may well turn the nicely-balanced scale in
+the struggle for life, and so be preserved. How fleeting are the wishes
+and efforts of man! how short his time! and consequently how poor will
+be his results, compared with those accumulated by Nature during whole
+geological periods! Can we wonder, then, that Nature’s productions
+should be far “truer” in character than man’s productions; that they
+should be infinitely better adapted to the most complex conditions of
+life, and should plainly bear the stamp of far higher workmanship?</p>
+
+<p>It may metaphorically be said that natural selection is daily and
+hourly scrutinizing, throughout the world, the slightest variations;
+rejecting those that are bad, preserving and adding up all that are
+good; silently and sensibly working, whenever and wherever opportunity
+offers, at the improvement of each organic being in relation to its
+organic and inorganic conditions of life. We see nothing of these slow
+changes in progress, until the hand of time has marked the lapse of
+ages, and then so imperfect is our view into long-past geological ages,
+that we see only that the forms of life are now different from what
+they formerly were.</p>
+
+<p>In order that any great amount of modification should be effected in
+a species, a variety when once formed must again, perhaps after a
+long interval of time, vary or present individual differences of the
+same favourable nature as before; and these must be again preserved,<span class="pagenum" id="Page_231">[Pg 231]</span>
+and so onwards step by step. Seeing that individual differences of
+the same kind perpetually recur, this can hardly be considered as an
+unwarrantable assumption. But whether it is true, we can judge only by
+seeing how far the hypothesis accords with and explains the general
+phenomena of nature. On the other hand, the ordinary belief that the
+amount of possible variation is a strictly limited quantity is likewise
+a simple assumption.</p>
+
+<p>Although natural selection can act only through and for the good of
+each being, yet characters and structures, which we are apt to consider
+as of very trifling importance, may thus be acted on. When we see
+leaf-eating insects green, and bark-feeders mottled gray; the Alpine
+ptarmigan white in winter, the red-grouse the colour of heather,
+we must believe that these tints are of service to these birds and
+insects in preserving them from danger. Grouse, if not destroyed at
+some period of their lives, would increase in countless numbers;
+they are known to suffer largely from birds of prey; and hawks are
+guided by eyesight to their prey—so much so, that on parts of the
+Continent persons are warned not to keep white pigeons, as being the
+most liable to destruction. Hence natural selection might be effective
+in giving the proper colour to each kind of grouse, and in keeping
+that colour, when once acquired, true and constant. Nor ought we to
+think that the occasional destruction of an animal of any particular
+colour would produce little effect: we should remember how essential
+it is in a flock of white sheep to destroy a lamb with the faintest
+trace of black. We have seen how the colour of the hogs, which feed on
+the “paint-root” in Virginia, determines whether they shall live or
+die. In plants, the down on the fruit and the colour of the flesh are
+considered by botanists as characters of the most trifling importance:
+yet we hear from an excellent horticulturist, Downing, that in the
+United States smooth-skinned fruits suffer far more from a beetle, a
+Curculio, than those with down; that purple plums suffer far more from
+a certain disease than yellow plums; whereas another disease attacks
+yellow-fleshed peaches far more than those with other coloured flesh.
+If, with all the aids of arts, these slight differences make a great
+difference in cultivating the several varieties, assuredly, in a state
+of nature, where the trees would have to struggle with other trees and
+with a host of enemies, such differences would effectually settle which
+variety, whether a smooth<span class="pagenum" id="Page_232">[Pg 232]</span> or downy, a yellow or purple-fleshed fruit,
+should succeed.</p>
+
+<p>In looking at many small points of difference between species, which,
+as far as our ignorance permits us to judge, seem quite unimportant,
+we must not forget that climate, food, etc., have no doubt produced
+some direct effect. It is also necessary to bear in mind that, owing to
+the law of correlation, when one part varies, and the variations are
+accumulated through natural selection, other modifications, often of
+the most unexpected nature, will ensue.</p>
+
+<p>As we see that those variations which, under domestication, appear at
+any particular period of life, tend to reappear in the offspring at the
+same period; for instance, in the shape, size, and flavour of the seeds
+of the many varieties of our culinary and agricultural plants; in the
+caterpillar and cocoon stages of the varieties of the silkworm; in the
+eggs of poultry, and in the colour of the down of their chickens; in
+the horns of our sheep and cattle when nearly adult; so in a state of
+nature natural selection will be enabled to act on and modify organic
+beings at any age, by the accumulation of variations profitable at that
+age, and by their inheritance at a corresponding age. If it profit
+a plant to have its seeds more and more widely disseminated by the
+wind, I can see no greater difficulty in this being effected through
+natural selection, than in the cotton planter increasing and improving
+by selection the down in the pods on his cotton trees. Natural
+selection may modify and adapt the larva of an insect to a score of
+contingencies, wholly different from those which concern the mature
+insect; and these modifications may effect, through correlation, the
+structure of the adult. So, conversely, modifications in the adult may
+affect the structure of the larva; but in all cases natural selection
+will insure that they shall not be injurious: for if they were so, the
+species would become extinct.</p>
+
+<p>Natural selection will modify the structure of the young in relation
+to the parent, and of the parent in relation to the young. In social
+animals it will adapt the structure of each individual for the benefit
+of the whole community; if the community profits by the selected
+change. What natural selection cannot do, is to modify the structure
+of one species; without giving it any advantage, for the good of
+another species; and though statements to this effect may be found
+in works of natural history, I cannot find one case which will bear
+investigation. A structure used only once in an animal’s<span class="pagenum" id="Page_233">[Pg 233]</span> life, if
+of high importance to it, might be modified to any extent by natural
+selection; for instance, the great jaws possessed by certain insects,
+used exclusively for opening the cocoon—or the hard tip of the beak of
+unhatched birds, used for breaking the egg. It has been asserted, that
+of the best short-beaked tumbler-pigeons a greater number perish in the
+egg than are able to get out of it; so that fanciers assist in the act
+of hatching. Now if nature had to make the beak of a full-grown pigeon
+very short for the bird’s own advantage, the process of modification
+would be very slow, and there would be simultaneously the most rigorous
+selection of all the young birds within the egg, which had the most
+powerful and hardest beaks, for all with weak beaks would inevitably
+perish; or, more delicate and more easily broken shells might be
+selected, the thickness of the shell being known to vary like every
+other structure.</p>
+
+<p>It may be well here to remark that with all beings there must be much
+fortuitous destruction, which can have little or no influence on
+the course of natural selection. For instance a vast number of eggs
+or seeds are annually devoured, and these could be modified through
+natural selection only if they varied in some manner which protected
+them from their enemies. Yet many of these eggs or seeds would perhaps,
+if not destroyed, have yielded individuals better adapted to their
+conditions of life than any of those which happened to survive. So
+again a vast number of mature animals and plants, whether or not they
+be the best adapted to their conditions, must be annually destroyed by
+accidental causes, which would not be in the least degree mitigated
+by certain changes of structure or constitution which would in other
+ways be beneficial to the species. But let the destruction of the
+adults be ever so heavy, if the number which can exist in any district
+be not wholly kept down by such causes,—or again let the destruction
+of eggs or seeds be so great that only a hundredth or a thousandth
+part are developed,—yet of those which do survive, the best adapted
+individuals, supposing that there is any variability in a favourable
+direction, will tend to propagate their kind in larger numbers than the
+less well adapted. If the numbers be wholly kept down by the causes
+just indicated, as will often have been the case, natural selection
+will be powerless in certain beneficial directions; but this is no
+valid objection to its efficiency at other times and in other ways; for
+we are far from having any reason to suppose that many species<span class="pagenum" id="Page_234">[Pg 234]</span> ever
+undergo modification and improvement at the same time in the same area.</p>
+
+
+<p class="nindc space-above2 space-below2">
+SEXUAL SELECTION</p>
+
+<p>Inasmuch as peculiarities often appear under domestication in one sex
+and become hereditarily attached to that sex, so no doubt it will be
+under nature. Thus it is rendered possible for the two sexes to be
+modified through natural selection in relation to different habits
+of life, as is sometimes the case; or for one sex to be modified in
+relation to the other sex, as commonly occurs. This leads me to say
+a few words on what I have called Sexual Selection. This form of
+selection depends, not on a struggle for existence in relation to other
+organic beings or to external conditions, but on a struggle between the
+individuals of one sex, generally the males, for the possession of the
+other sex. The result is not death to the unsuccessful competitor, but
+few or no offspring. Sexual selection is, therefore, less rigorous than
+natural selection. Generally, the most vigorous males, those which are
+best fitted for their places in nature, will leave most progeny. But in
+many cases, victory depends not so much on general vigour, as on having
+special weapons, confined to the male sex. A hornless stag or spurless
+cock would have a poor chance of leaving numerous offspring. Sexual
+selection, by always allowing the victor to breed, might surely give
+indomitable courage, length to the spur, and strength to the wing to
+strike in the spurred leg, in nearly the same manner as does the brutal
+cockfighter by the careful selection of his best cocks. How low in the
+scale of nature the law of battle descends, I know not; male alligators
+have been described as fighting, bellowing, and whirling round, like
+Indians in a war-dance, for the possession of the females; male
+salmons have been observed fighting all day long; male stag-beetles
+sometimes bear wounds from the huge mandibles of other males; the
+males of certain hymenopterous insects have been frequently seen by
+that inimitable observer, M. Fabre, fighting for a particular female
+who sits by, an apparently unconcerned beholder of the struggle, and
+then retires with the conquerer. The war is, perhaps, severest between
+the males of polygamous animals, and these seem oftenest provided with
+special weapons. The males of carnivorous animals are already well
+armed; though to them and to others, special means of defence may be
+given through means of<span class="pagenum" id="Page_235">[Pg 235]</span> sexual selection, as the mane of the lion, and
+the hooked jaw to the male salmon; for the shield may be as important
+for victory as the sword or spear.</p>
+
+<p>Amongst birds, the contest is often of a more peaceful character.
+All those who have attended to the subject believe that there is the
+severest rivalry between the males of many species to attract, by
+singing, the females. The rock-thrush of Guiana, birds of paradise,
+and some others, congregate; and successive males display with the
+most elaborate care, and show off in the best manner, their gorgeous
+plumage; they likewise perform strange antics before the females,
+which, standing by as spectators, at last choose the most attractive
+partner. Those who have closely attended to birds in confinement well
+know that they often take individual preferences and dislikes: thus
+Sir R. Heron has described how a pied peacock was eminently attractive
+to all his hen birds. I cannot here enter on the necessary details;
+but if man can in a short time give beauty and an elegant carriage to
+his bantams, according to his standard of beauty, I can see no good
+reason to doubt that female birds, by selecting, during thousands
+of generations, the most melodious or beautiful males, according
+to their standard of beauty, might produce a marked effect. Some
+well-known laws, with respect to the plumage of male and female birds,
+in comparison with the plumage of the young, can partly be explained
+through the action of sexual selection on variations occuring at
+different ages, and transmitted to the males alone or to both sexes at
+corresponding ages; but I have not space here to enter on this subject.</p>
+
+<p>Thus it is, as I believe, that when the males and females of any
+animal have the same general habits of life, but differ in structure,
+colour, or ornament, such differences have been mainly caused by sexual
+selection: that is, by individual males having had, in successive
+generations, some slight advantage over other males, in their weapons,
+means of defence, or charms, which they have transmitted to their
+male offspring alone. Yet, I would not wish to attribute all sexual
+differences to this agency: for we see in our domestic animals
+peculiarities arising and becoming attached to the male sex, which
+apparently have not been augmented through selection by man. The tuft
+of hair on the breast of the wild turkey-cock cannot be of any use, and
+it is doubtful whether it can be ornamental in the eyes of the female<span class="pagenum" id="Page_236">[Pg 236]</span>
+bird;—indeed, had the tuft appeared under domestication, it would have
+been called a monstrosity.</p>
+
+
+<p class="nindc space-above2 space-below2">
+ON THE DEGREE TO WHICH ORGANISATION TENDS TO ADVANCE</p>
+
+<p>Natural Selection acts exclusively by the preservation and accumulation
+of variations, which are beneficial under the organic and inorganic
+conditions to which each nature is exposed at all periods of life. The
+ultimate result is that each creature tends to become more and more
+improved in relation to its conditions. This improvement inevitably
+leads to the gradual advancement of the organisation of the greater
+number of living beings throughout the world. But here we enter on
+a very intricate subject, for naturalists have not defined to each
+other’s satisfaction what is meant by an advance in organisation.
+Amongst the vertebrata the degree of intellect and an approach in
+structure to man clearly come into play. It might be thought that
+the amount of change which the various parts and organs pass through
+in their development from the embryo to maturity would suffice as a
+standard of comparison; but there are cases, as with certain parasitic
+crustaceans, in which several parts of the structure become less
+perfect, so that the mature animal cannot be called higher than its
+larva. Von Bar’s standard seems the most widely applicable and the
+best, namely, the amount of differentiation of the parts of the same
+organic being, in the adult state as I should be inclined to add, and
+their specialisation for different functions; or, as Milne Edwards
+would express it, the completeness of the division of physiological
+labour. But we shall see how obscure this subject is if we look,
+for instance, to fishes, amongst which some naturalists rank those
+as highest which, like the sharks, approach nearest to amphibians;
+whilst other naturalists rank the common bony or teleostean fishes as
+the highest, inasmuch as they are most strictly fishlike, and differ
+most from the other vertebrate classes. We see still more plainly
+the obscurity of the subject by turning to plants, amongst which the
+standard of intellect is of course quite excluded; and here some
+botanists rank those plants as highest which have every organ, as
+sepals, petals, stamens, and pistils, fully developed in each flower;
+whereas other botanists, probably with more truth, look at the plants
+which have their several organs much modified and reduced in number as
+the highest.</p>
+
+<p><span class="pagenum" id="Page_237">[Pg 237]</span></p>
+
+<p>If we take as the standard of high organisation, the amount of
+differentiation and specialisation of the several organs in each
+being when adult (and this will include the advancement of the brain
+for intellectual purposes), natural selection clearly leads towards
+this standard; for all physiologists admit that the specialisation
+of organs, inasmuch as in this state they perform their functions
+better, is an advantage to each being; and hence the accumulation
+of variations tending towards specialisation is within the scope of
+natural selection. On the other hand, we can see, bearing in mind that
+all organic beings are striving to increase at a high ratio and to
+seize on every unoccupied or less well occupied place in the economy of
+nature, that it is quite possible for natural selection gradually to
+fit a being to a situation in which several organs would be superfluous
+or useless: in such cases there would be retrogression in the scale of
+organisation. Whether organisation on the whole has actually advanced
+from the remotest geological periods to the present day will be more
+conveniently discussed in our chapter on Geological Succession.</p>
+
+<p>But it may be objected that if all organic beings thus tend to rise
+in the scale, how is it that throughout the world a multitude of the
+lowest forms still exist; and how is it that in each great class some
+forms are far more highly developed than others? Why have not the
+more highly developed forms everywhere supplanted and exterminated
+the lower? Lamarck, who believed in an innate and inevitable tendency
+towards perfection in all organic beings, seems to have felt this
+difficulty so strongly, that he was led to suppose that new and simple
+forms are continually being produced by spontaneous generation. Science
+has not as yet proved the truth of this belief, whatever the future
+may reveal. On our theory the continued existence of lowly organisms
+offers no difficulty; for natural selection, or the survival of the
+fittest, does not necessarily include progressive development—it only
+takes advantage of such variations as arise and are beneficial to each
+creature under its complex relations of life. And it may be asked
+what advantage, as far as we can see, would it be to an infusorian
+animalcule—to an intestinal worm—or even to an earth-worm, to be
+highly organised. If it were no advantage, these forms would be left,
+by natural selection, unimproved or but little improved, and might
+remain for indefinite ages in their present lowly condition. And
+geology tells us that some of the lowest forms, as the infusoria<span class="pagenum" id="Page_238">[Pg 238]</span> and
+rhizopods, have remained for an enormous period in nearly their present
+state. But to suppose that most of the many now existing low forms
+have not in the least advanced since the first dawn of life would be
+extremely rash; for every naturalist who has dissected some of the
+beings now ranked as very low in the scale, must have been struck with
+their really wondrous and beautiful organisation.</p>
+
+<p>Nearly the same remarks are applicable if we look to the different
+grades of organisation within the same great group; for instance,
+in the vertebrata, to the co-existence of mammals and fish—amongst
+mammalia, to the co-existence of man and the ornithorhynchus—amongst
+fishes, to the co-existence of the shark and the lancelet
+(<i>Amphioxus</i>), which latter fish in the extreme simplicity of
+its structure approaches the invertebrate classes. But mammals and
+fish hardly come into competition with each other; the advancement
+of the whole class of mammals, or of certain members in this class,
+to the highest grade would not lead to their taking the place of
+fishes. Physiologists believe that the brain must be bathed by warm
+blood to be highly active, and this requires aërial respiration;
+so that warm-blooded mammals when inhabiting the water lie under a
+disadvantage in having to come continually to the surface to breathe.
+With fishes, members of the shark family would not tend to supplant the
+lancelet; for the lancelet, as I hear from Fritz Müller, has as sole
+companion and competitor on the barren, sandy shore of South Brazil,
+an anomalous annelid. The three lowest orders of mammals, namely,
+marsupials, edentata, and rodents, co-exist in South America in the
+same region with numerous monkeys, and probably interfere little with
+each other. Although organisation, on the whole, may have advanced and
+be still advancing throughout the world, yet the scale will always
+present many degrees of perfection; for the high advancement of certain
+whole classes, or of certain members of each class, does not at all
+necessarily lead to the extinction of those groups with which they do
+not enter into close competition. In some cases, as we shall hereafter
+see, lowly organised forms appear to have been preserved to the present
+day, from inhabiting confined or peculiar stations, where they have
+been subjected to less severe competition, and where their scanty
+numbers have retarded the chance of favourable variations arising.</p>
+
+<p>Finally, I believe that many lowly organised forms now exist<span class="pagenum" id="Page_239">[Pg 239]</span>
+throughout the world, from various causes. In some cases variations or
+individual differences of a favourable nature may never have arisen
+for natural selection to act on and accumulate. In no case, probably,
+has time sufficed for the utmost possible amount of development.
+In some few cases there has been what we must call retrogression
+of organisation. But the main cause lies in the fact that under
+very simple conditions of life a high organisation would be of no
+service,—possibly would be of actual disservice, as being of a more
+delicate nature, and more liable to be put out of order and injured.</p>
+
+<p>Looking to the first dawn of life, when all organic beings, as we may
+believe, presented the simplest structure, how, it has been asked,
+could the first steps in the advancement of differentiation of parts
+have arisen? Mr. Herbert Spencer would probably answer that, as soon as
+simple unicellular organism came by growth or division to be compounded
+of several cells, or became attached to any supporting surface, his law
+“that homologous units of any order become differentiated in proportion
+as their relations to incident forces become different” would come into
+action. But as we have no facts to guide us, speculation on the subject
+is almost useless. It is, however, an error to suppose that there would
+be no struggle for existence, and, consequently, no natural selection,
+until many forms had been produced; variations in a single species
+inhabiting an isolated station might be beneficial, and thus the whole
+mass of individuals might be modified, or two distinct forms might
+arise. But, as I remarked towards the close of the Introduction, no
+one ought to feel surprise at much remaining as yet unexplained on the
+origin of species, if we make due allowance for our profound ignorance
+on the mutual relations of the inhabitants of the world at the present
+time, and still more so during past ages.</p>
+
+
+<p class="nindc space-above2 space-below2">
+CONVERGENCE OF CHARACTER</p>
+
+<p>Mr. H. C. Watson thinks that I have overrated the importance of
+divergence of character (in which, however, he apparently believes),
+and that convergence, as it may be called, has likewise played a
+part. If two species, belonging to two distinct though allied genera,
+had both produced a large number of new and divergent forms, it is
+conceivable that these might approach each other so closely that they
+would have all to be classed under the same genus; and thus the<span class="pagenum" id="Page_240">[Pg 240]</span>
+descendants of two distinct genera would converge into one. But it
+would in most cases be extremely rash to attribute to convergence a
+close and general similarity of structure in the modified descendants
+of widely distinct forms. The shape of a crystal is determined solely
+by the molecular forces, and it is not surprising that dissimilar
+substances should sometimes assume the same form; but with organic
+beings we should bear in mind that the form of each depends on an
+infinitude of complex relations, namely, on the variations which have
+arisen, those being due to causes far too intricate to be followed
+out,—on the nature of the variations which have been preserved or
+selected, and this depends on the surrounding physical conditions, and
+in a still higher degree on the surrounding organisms with which each
+being has come into competition,—and lastly, on inheritance (in itself
+a fluctuating element) from innumerable progenitors, all of which have
+had their forms determined through equally complex relations. It is
+incredible that the descendants of two organisms, which had originally
+differed in a marked manner, should ever afterwards converge so closely
+as to lead to a near approach to identity throughout their whole
+organisation. If this had occurred, we should meet with the same form,
+independently of genetic connection, recurring in widely separated
+geological formations; and the balance of evidence is opposed to any
+such an admission.</p>
+
+<p>Mr. Watson has also objected that the continued action of natural
+selection, together with divergence of character, would tend to make
+an indefinite number of specific forms. As far as mere inorganic
+conditions are concerned, it seems probable that a sufficient number
+of species would soon become adapted to all considerable diversities
+of heat, moisture, &amp;c.; but I fully admit that the mutual relations
+of organic beings are more important; and as the number of species in
+any country goes on increasing, the organic conditions of life must
+become more and more complex. Consequently there seems at first sight
+no limit to the amount of profitable diversification of structure, and
+therefore no limit to the number of species which might be produced.
+We do not know that even the most prolific area is fully stocked with
+specific forms: at the Cape of Good Hope and in Australia, which
+support such an astonishing number of species, many European plants
+have become naturalised. But geology shows<span class="pagenum" id="Page_241">[Pg 241]</span> us, that from an early part
+of the tertiary period the number of species of shells, and that from
+the middle part of this same period the number of mammals, has not
+greatly or at all increased. What then checks an indefinite increase
+in the number of species? The amount of life (I do not mean the number
+of specific forms) supported on an area must have a limit, depending
+so largely as it does on physical conditions; therefore, if an area
+be inhabited by very many species, each or nearly each species will
+be represented by few individuals; and such species will be liable to
+exterminate from accidental fluctuations in the nature of the seasons
+or in the number of their enemies. The process of extermination in
+such cases would be rapid, whereas the production of new species
+must always be slow. Imagine the extreme case of as many species as
+individuals in England, and the first severe winter or very dry summer
+would exterminate thousands on thousands of species. Rare species, and
+each species will become rare if the number of species in any country
+becomes indefinitely increased, will, on the principle often explained,
+present within a given period few favourable variations; consequently,
+the process of giving birth to new specific forms would thus be
+retarded. When any species becomes very rare, close interbreeding will
+help to exterminate it; authors have thought that this comes into play
+in accounting for the deterioration of the Aurochs in Lithuania, of Red
+Deer in Scotland, and of Bears in Norway, &amp;c. Lastly, and this I am
+inclined to think is the most important element, a dominant species,
+which has already beaten many competitors in its own home, will tend to
+spread and supplant many others. Alph. de Candolle has shown that those
+species which spread widely, tend generally to spread very widely;
+consequently, they will tend to supplant and exterminate several
+species in several areas, and thus check the inordinate increase of
+specific forms throughout the world. Dr. Hooker has recently shown that
+in the S. E. corner of Australia, where, apparently, there are many
+invaders from different quarters of the globe, the endemic Australian
+species have been greatly reduced in number. How much weight to
+attribute to these several considerations I will not pretend to say;
+but conjointly they must limit in each country the tendency to an
+indefinite augmentation of specific forms.</p>
+
+<p><span class="pagenum" id="Page_242">[Pg 242]</span></p>
+
+
+<p class="nindc space-above2 space-below2">
+SUMMARY OF CHAPTER</p>
+
+<p>If under changing conditions of life organic beings present individual
+differences in almost every part of their structure, and this cannot
+be disputed; if there be, owing to their geometrical rate of increase,
+a severe struggle for life at some age, season, or year, and this
+certainly cannot be disputed; then, considering the infinite complexity
+of the relations of all organic beings to each other and to their
+conditions of life, causing an infinite diversity in structure,
+constitution, and habits, to be advantageous to them, it would be a
+most extraordinary fact if no variations had ever occurred useful to
+each being’s own welfare, in the same manner as so many variations
+have occurred useful to man. But if variations useful to any organic
+being ever do occur, assuredly individuals thus characterised will
+have the best chance of being preserved in the struggle for life; and
+from the strong principle of inheritance, these will tend to produce
+offspring similarly characterised. This principle of preservation,
+or the survival of the fittest, I have called Natural Selection. It
+leads to the improvement of each creature in relation to its organic
+and inorganic conditions of life; and consequently, in most cases, to
+what must be regarded as an advance in organisation. Nevertheless,
+low and simple forms will long endure if well fitted for their simple
+conditions of life.</p>
+
+<p>Natural selection, on the principle of qualities being inherited at
+corresponding ages, can modify the egg, seed, or young, as easily as
+the adult. Amongst many animals, sexual selection will have given its
+aid to ordinary selection, by assuring to the most vigorous and best
+adapted males the greatest number of offspring. Sexual selection will
+also give characters useful to the males alone, in their struggles or
+rivalry with other males; and these characters will be transmitted to
+one sex or to both sexes, according to the form of inheritance which
+prevails.</p>
+
+<p>Whether natural selection has really thus acted in adapting the
+various forms of life to their several conditions and stations, must
+be judged by the general tenor and balance of evidence given in the
+following chapters. But we have already seen how it entails extinction;
+and how largely extinction has acted in the world’s history, geology
+plainly declares. Natural selection, also, leads to divergence of
+character;<span class="pagenum" id="Page_243">[Pg 243]</span> for the more organic beings diverge in structure, habits,
+and constitution, by so much the more can a large number be supported
+on the area,—of which we see proof by looking to the inhabitants of
+any small spot, and to the productions naturalised in foreign lands.
+Therefore, during the modification of the descendants of any one
+species, and during the incessant struggle of all species to increase
+in numbers, the more diversified the descendants become, the better
+will be their chance of success in the battle for life. Thus the small
+differences distinguishing varieties of the same species, steadily tend
+to increase, till they equal the greater differences between species of
+the same genus, or even of distinct genera.</p>
+
+<p>We have seen that it is the common, the widely diffused and widely
+ranging species, belonging to the larger genera within each class,
+which vary most; and these tend to transmit to their modified offspring
+that superiority which now makes them dominant in their own countries.
+Natural selection, as has just been remarked, leads to divergence of
+character and to much extinction of the less improved and intermediate
+forms of life. On these principles, the nature of the affinities, and
+the generally well-defined distinctions between the innumerable organic
+beings in each class throughout the world, may be explained. It is
+a truly wonderful fact—the wonder of which we are apt to overlook
+from familiarity—that all animals and all plants throughout all time
+and space should be related to each other in groups, subordinate to
+groups, in the manner which we everywhere behold—namely, varieties of
+the same species most closely related, species of the same genus less
+closely and unequally related, forming sections and sub-genera, species
+of distinct genera much less closely related, and genera related in
+different degrees, forming sub-families, families, orders, sub-classes
+and classes. The several subordinate groups in any class cannot be
+ranked in a single file, but seem clustered round points, and these
+round other points, and so on in almost endless cycles. If species had
+been independently created, no explanation would have been possible of
+this kind of classification; but it is explained through inheritance
+and the complex action of natural selection, entailing extinction and
+divergence of character....</p>
+
+<p>The affinities of all the beings of the same class have sometimes been
+represented by a great tree. I believe this simile largely speaks<span class="pagenum" id="Page_244">[Pg 244]</span> the
+truth. The green and budding twigs may represent existing species; and
+those produced during former years may represent the long succession
+of extinct species. At each period of growth all the growing twigs
+have tried to branch out on all sides, and to overtop and kill the
+surrounding twigs and branches, in the same manner as species and
+groups of species have at all times overmastered other species in the
+great battle for life. The limbs divided into great branches, and these
+into lesser and lesser branches, were themselves once, when the tree
+was young, budding twigs; and this connection of the former and present
+buds by ramifying branches may well represent the classification of
+all extinct and living species in groups subordinate to groups. Of the
+many twigs which flourished when the tree was a mere bush, only two or
+three, now grown into great branches, yet survive and bear the other
+branches; so with the species which lived during long-past geological
+periods, very few have left living and modified descendants. From
+the first growth of the tree, many a limb and branch has decayed and
+dropped off; and these fallen branches of various sizes may represent
+those whole orders, families, and genera which have now no living
+representatives, and which are known to us only in a fossil state. As
+we here and there see a thin straggling branch springing from a fork
+low down in a tree, and which by some chance has been favoured and is
+still alive on its summit, so we occasionally see an animal like the
+Ornithorhynchus or Lepidosiren, which in some small degree connects by
+its affinities two large branches of life, and which has apparently
+been saved from fatal competition by having inhabited a protected
+station. As buds give rise by growth to fresh buds, and these, if
+vigorous, branch out and overtop on all sides many a feebler branch, so
+by generation I believe it has been with the great Tree of Life, which
+fills with its dead and broken branches the crust of the earth, and
+covers the surface with its ever-branching and beautiful ramifications.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_32" href="#FNanchor_32" class="label">[32]</a>
+From the <i>Origin of Species</i>. Ch. IV.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_245">[Pg 245]</span></p>
+<h2 class="nobreak" id="XXX">XXX<br>
+THEODOR SCHWANN<br>
+1810-1882</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Theodor Schwann, the son of a Prussian printer, was born at Neuss,
+Prussia, December 7, 1810. He first studied medicine, but was persuaded
+to devote himself to science by Johannes Mueller, who appointed him
+assistant in the anatomical museum. In 1838 he was called to the
+Catholic University of Louvain, and later removed to Liège. One of
+the first to suggest the chemical explanation of life, he discovered
+the presence and function of pepsin as a ferment in digestion. In
+1839 he established his great theory that all life is composed of
+inter-connected cellular units—a conception which revolutionized
+biology. He died at Liège on January 11, 1882.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+CELL THEORY<a id="FNanchor_33" href="#Footnote_33" class="fnanchor">[33]</a></p>
+
+<p>The various opinions entertained with respect to the fundamental powers
+of an organized body may be reduced to two, which are essentially
+different from one another. The first is, that every organism
+originates with an inherent power, which models it into conformity
+with a predominant idea, arranging the molecules in the relation
+necessary for accomplishing certain purposes held forth by this idea.
+Here, therefore, that which arranges and combines the molecules is a
+power acting with a definite purpose. A power of this kind would be
+essentially different from all the powers of inorganic nature, because
+action goes on in the latter quite blindly. A certain impression is
+followed of necessity by a certain change of quality and quantity,<span class="pagenum" id="Page_246">[Pg 246]</span>
+without regard to any purpose. In this view, however, the fundamental
+power of the organism (or the soul, in the sense employed by Stahl)
+would, inasmuch as it works with a definite individual purpose, be
+much more nearly allied to the immaterial principle, endued with
+consciousness which we must admit operates in man.</p>
+
+<p>The other view is, that the fundamental powers of organized bodies
+agree essentially with those of inorganic nature, that they work
+altogether blindly according to laws of necessity and irrespective
+of any purpose, that they are powers which are as much established
+with the existence of matter as the physical powers are. It might be
+assumed that the powers which form organized bodies do not appear at
+all in inorganic nature, because this or that particular combination
+of molecules, by which the powers are elicited, does not occur in
+inorganic nature, and yet they might not be essentially distinct
+from physical and chemical powers. It cannot, indeed, be denied that
+adaptation to a particular purpose, in some individuals even in a
+high degree, is characteristic of every organism; but, according to
+this view, the source of this adaptation does not depend upon each
+organism being developed by the operation of its own power in obedience
+to that purpose, but it originates as in inorganic nature, in the
+creation of the matter with its blind powers by a rational Being. We
+know, for instance, the powers which operate in our planetary system.
+They operate, like all physical powers, in accordance with blind laws
+of necessity, and yet is the planetary system remarkable for its
+adaptation to a purpose. The ground of this adaptation does not lie in
+the powers, but in Him, who has so constituted matter with its powers,
+that in blindly obeying its laws it produces a whole suited to fulfil
+an intended purpose. We may even assume that the planetary system
+has an individual adaptation to a purpose. Some external influence,
+such as a comet, may occasion disturbances of motion, without thereby
+bringing the whole into collision; derangements may occur on single
+planets, such as a high tide, &amp;c., which are yet balanced entirely by
+physical laws. As respects their adaptation to a purpose, organized
+bodies differ from these in degree only; and by this second view we are
+just as little compelled to conclude that the fundamental powers of
+organization operate according to laws of adaptation to a purpose, as
+we are in inorganic nature.</p>
+
+<p>The first view of the fundamental powers of organized bodies may<span class="pagenum" id="Page_247">[Pg 247]</span> be
+called the teleological, the second the physical view. An example will
+show at once, how important for physiology is the solution of the
+question as to which is to be followed. If, for instance, we define
+inflammation and suppuration to be the effort of the organism to remove
+a foreign body that has been introduced into it; or fever to be the
+effort of the organism to eliminate diseased matter, and both as the
+result of the “autocracy of the organism,” then these explanations
+accord with the teleological view. For, since by these processes the
+obnoxious matter is actually removed, the process which effects them
+is one adapted to an end; and as the fundamental power of the organism
+operates in accordance with definite purposes, it may either set these
+processes in action primarily, or may also summon further powers of
+matter to its aid, always, however, remaining itself the “primum
+movens.” On the other hand, according to the physical view, this is
+just as little an explanation as it would be to say, that the motion of
+the earth around the sun is an effort of the fundamental power of the
+planetary system to produce a change of seasons on the planets, or to
+say, that ebb and flood are the reaction of the organism of the earth
+upon the moon.</p>
+
+<p>In physics, all those explanations which were suggested by a
+teleological view of nature, as “horror vacui,” and the like, have
+long been discarded. But in animated nature, adaptation—individual
+adaptation—to a purpose is so prominently marked, that it is
+difficult to reject all teleological explanations. Meanwhile it must
+be remembered that those explanations, which explain at once all
+and nothing, can be but the last resources, when no other view can
+possibly be adopted; and there is no such necessity for admitting the
+teleological view in the case of organized bodies. The adaptation of
+a purpose which is characteristic of organized bodies differs only in
+degree from what is apparent also in the inorganic part of nature;
+and the explanation that organized bodies are developed, like all the
+phenomena of inorganic nature, by the operation of blind laws framed
+with the matter, cannot be rejected as impossible. Reason certainly
+requires some ground for such adaptation, but for her it is sufficient
+to assume that matter with the powers inherent in it owes its existence
+to a rational Being. Once established and preserved in their integrity,
+these powers may, in accordance with their immutable laws of blind
+necessity, very well produce combinations, which manifest, even in
+a high<span class="pagenum" id="Page_248">[Pg 248]</span> degree, individual adaptation to a purpose. If, however,
+rational power interpose after creation merely to sustain, and not
+as an immediately active agent, it may, so far as natural science is
+concerned, be entirely excluded from the consideration of the creation.</p>
+
+<p>But the teleological view leads to further difficulties in the
+explanation, and especially with respect to generation. If we assume
+each organism to be formed by a power which acts according to a certain
+predominant idea, a portion of this power may certainly reside in the
+ovum during generation; but then we must ascribe to this subdivision
+of the original power, at the separation of the ovum from the body of
+the mother, the capability of producing an organism similar to that
+which the power, of which it is but a portion, produced: that is, we
+must assume that this power is infinitely divisible, and yet that each
+part may perform the same actions as the whole power. If, on the other
+hand, the power of organized bodies reside, like the physical powers,
+in matter as such, and be set free only by a certain combination of the
+molecules, as, for instance, electricity is set free by the combination
+of a zinc and copper plate, then also by the conjunction of molecules
+to form an ovum the power may be set free, by which the ovum is capable
+of appropriating to itself fresh molecules, and these newly-conjoined
+molecules again by this very mode of combination acquire the same
+power to assimilate fresh molecules. The first development of the
+many forms of organized bodies—the progressive formation of organic
+nature indicated by geology—is also much more difficult to understand
+according to the teleological than the physical view.</p>
+
+<p>Another objection to the teleological view may be drawn from the
+foregoing investigation. The molecules, as we have seen, are not
+immediately combined in various ways, as the purpose of the organism
+requires, but the formation of the elementary parts of organic
+bodies is regulated by laws which are essentially the same for all
+elementary parts. One can see no reason why this should be the case,
+if each organism be endued with a special power to frame the parts
+according to the purpose which they have to fulfil: it might much
+rather be expected that the formative principle, although identical
+for organs physiologically the same, would yet in different tissues
+be correspondingly varied. This resemblance of the elementary parts
+has, in the<span class="pagenum" id="Page_249">[Pg 249]</span> instance of plants, already led to the conjecture that
+the cells are really the organisms, and that the whole plant is an
+aggregrate of these organisms arranged according to certain laws.
+But since the elementary parts of animals bear exactly similar
+relations, the individuality of an entire animal would thus be lost;
+and yet precisely upon the individuality of the whole animal does the
+assumption rest, that it possesses a single fundamental power operating
+in accordance with a definite idea.</p>
+
+<p>Meanwhile, we cannot altogether lay aside teleological views if all
+phenomena are not clearly explicable by the physical view. It is,
+however, unnecessary to do so, because an explanation, according to
+the teleological view, is only admissible when the physical can be
+shown to be impossible. In any case it conduces much more to the object
+of science to strive, at least, to adopt the physical explanation.
+And I would repeat that, when speaking of a physical explanation of
+organic phenomena, it is not necessary to understand an explanation by
+known physical powers, such, for instance, as that universal refuge
+electricity, and the like; but an explanation by means of powers which
+operate like the physical powers, in accordance with strict laws of
+blind necessity, whether they be also to be found in inorganic nature
+or not.</p>
+
+<p>We set out, therefore, with the supposition that an organized body
+is not produced by a fundamental power which is guided in its
+operation by a definite idea, but is developed, according to blind
+laws of necessity, by powers which, like those of inorganic nature,
+are established by the very existence of matter. As the elementary
+materials of organic nature are not different from those of the
+inorganic kingdom, the source of the organic phenomena can only
+reside in another combination of these materials, whether it be in a
+peculiar mode of union of the elementary atoms to form atoms of the
+second order, or in the arrangement of these conglomerate molecules
+when forming either the separate morphological elementary parts of
+organisms, or an entire organism. We have here to do with the latter
+question solely, whether the cause of organic phenomena lies in the
+whole organism, or in its separate elementary parts. If this question
+can be answered, a further inquiry still remains as to whether the
+organism or its elementary parts possess this power through the<span class="pagenum" id="Page_250">[Pg 250]</span>
+peculiar mode of combination of the conglomerate molecules, or through
+the mode in which the elementary atoms are united into conglomerate
+molecules.</p>
+
+<p>We may, then, form the two following ideas of the cause of organic
+phenomena, such as growth, &amp;c. First, that the cause resides in the
+totality of the organism. By the combination of the molecules into
+a systematic whole, such as the organism is in every stage of its
+development, a power is engendered, which enables such an organism to
+take up fresh material from without, and appropriate it either to the
+formation of new elementary parts, or to the growth of those already
+present. Here, therefore, the cause of the growth of the elementary
+parts resides in the totality of the organism. The other mode of
+explanation is, that growth does not ensue from a power resident in the
+entire organism, but that each separate elementary part is possessed of
+an independent power, an independent life, so to speak; in other words,
+the molecules in each separate elementary part are so combined as to
+set free a power by which it is capable of attracting new molecules,
+and so increasing, and the whole organism subsists only by means of
+the reciprocal action of the single elementary parts. So that here the
+single elementary parts only exert an active influence on nutrition,
+and totality of the organism may indeed be a condition, but is not in
+this view a cause.</p>
+
+<p>In order to determine which of these two views is the correct one,
+we must summon to our aid the results of the previous investigation.
+We have seen that all organized bodies are composed of essentially
+similar parts, namely, of cells; that these cells are formed and grow
+in accordance with essentially similar laws; and, therefore, that these
+processes must, in every instance, be produced by the same powers. Now,
+if we find that some of these elementary parts, not differing from the
+others, are capable of separating themselves from the organism, and
+pursuing an independent growth, we may thence conclude that each of
+the other elementary parts, each cell, is already possessed of power
+to take up fresh molecules and growth; and that, therefore, every
+elementary part possesses a power of its own, an independent life, by
+means of which it would be enabled to develop itself independently,
+if the relations which it bore to external parts were but similar to
+those in which it stands in the organism. The ova of animals afford us
+example of such independent cells, growing apart from the<span class="pagenum" id="Page_251">[Pg 251]</span> organism.
+It may, indeed, be said of the ova of higher animals, that after
+impregnation the ovum is essentially different from the other cells of
+the organism; that by impregnation there is a something conveyed to the
+ovum, which is more to it than an external condition for vitality, more
+than nutrient matter; and that it might thereby have first received
+its peculiar vitality, and therefore that nothing can be inferred from
+it with respect to the other cells. But this fails in application to
+those classes which consist only of female individuals, as well as
+with the spores of the lower plants; and, besides, in the inferior
+plants any given cell may be separated from the plant, and then grow
+alone. So that here are whole plants consisting of cells, which can
+be positively proved to have independent vitality. Now, as all cells
+grow according to the same laws, and consequently the cause of growth
+cannot in one case lie in the cell, and in another in the whole
+organism; and since it may be further proved that some cells, which
+do not differ from the rest in their mode of growth, are developed
+independently, we must ascribe to all cells an independent vitality,
+that is, such combinations of molecules as occur in any single cell,
+are capable of setting free the power by which it is enabled to take
+up fresh molecules. The cause of nutrition and growth resides not in
+the organism as a whole, but in the separate elementary parts—the
+cells. The failure of growth in the case of any particular cell, when
+separated from an organized body, is as slight an objection to this
+theory as it is an objection against the independent vitality of a bee,
+that it cannot continue long in existence after being separated from
+its swarm. The manifestation of the power which resides in the cell
+depends upon conditions to which it is subject only when in connexion
+with the whole (organism).</p>
+
+<p>The question, then, as to the fundamental power of organized bodies
+resolves itself into that of the fundamental powers of the individual
+cells. We must now consider the general phenomena attending the
+formation of cells, in order to discover what powers may be presumed
+to exist in the cells to explain them. These phenomena may be arranged
+in two natural groups: first, those which relate to the combination of
+the molecules to form a cell, and which may be denominated the plastic
+phenomena of the cells; secondly, those which result from chemical
+changes either in the component particles of the cell itself, or in the
+surrounding cytoblastema, and which may be called metabolic<span class="pagenum" id="Page_252">[Pg 252]</span> phenomena
+(<i>to metabolikon</i>, implying that which is liable to occasion or to
+suffer change).</p>
+
+<p>The general plastic appearances in the cells are, as we have seen,
+the following: at first a minute corpuscle is formed (the nucleolus);
+a layer of substance (the nucleus) is then precipitated around it,
+which becomes more thickened and expanded by the continual deposition
+of fresh molecules between those already present. Deposition goes on
+more vigorously at the outer part of this layer than at the inner.
+Frequently the entire layer, or in other instances the outer part of
+it only, becomes condensed to a membrane, which may continue to take
+up new molecules in such a manner that it increases more rapidly in
+superficial extent than in thickness, and thus an intervening cavity is
+necessarily formed between it and the nucleolus. A second layer (cell)
+is next precipitated around this first, in which precisely the same
+phenomena are repeated, with merely the difference that in this case
+the processes, especially the growth of the layer and the formation of
+the space intervening between it and the first layer (the cell-cavity),
+go on more rapidly and more completely. Such were the phenomena in
+the formation of most cells; in some, however, there appeared to be
+only a single layer formed, while in others (those especially in which
+the nucleolus was hollow) there were three. The other varieties in
+the development of the elementary parts were (as we saw) reduced to
+these—that if two neighbouring cells commence their formation so near
+to one another that the boundaries of the layers forming around each
+of them meet at any spot, a common layer may be formed enclosing the
+two incipient cells. So at least the origin of nuclei, with two or
+more nucleoli, seemed explicable, by a coalescence of the first layers
+(corresponding to the nucleus), and the union of many primary cells
+into one secondary cell by a similar coalescence of the second layers
+(which correspond to the cell). But the further development of these
+common layers proceeds as though they were only an ordinary single
+layer. Lastly, there were some varieties in the progressive development
+of the cells, which were referable to an unequal deposition of the new
+molecules between those already present in the separate layers. In this
+way modifications of form and division of the cells were explained.
+And among the number of the plastic phenomena in the cells we may
+mention, lastly, the formation of secondary deposits; for instances
+occur in which one or<span class="pagenum" id="Page_253">[Pg 253]</span> more new layers, each on the inner surface of
+the previous one, are deposited on the inner surface of a simple or of
+a secondary cell.</p>
+
+<p>These are the most important phenomena observed in the formation and
+development of cells. The unknown cause, presumed to be capable of
+explaining these processes in the cells, may be called the plastic
+power of the cells. We will, in the next place, proceed to determine
+how far a more accurate definition of this power may be deduced from
+these phenomena.</p>
+
+<p>In the first place, there is a power of attraction exerted in the
+very commencement of the cell, in the nucleolus, which occasions the
+addition of new molecules to those already present. We may imagine
+the nucleolus itself to be first formed by a sort of crystallization
+from out of a concentrated fluid. For if a fluid be so concentrated
+that the molecules of the substance in solution exert a more powerful
+mutual attraction than is exerted between them and the molecules of
+the fluid in which they are dissolved, a part of the solid substance
+must be precipitated. One can readily understand that the fluid must be
+more concentrated when new cells are being formed in it than when those
+already present have merely to grow. For if the cell is already partly
+formed, it exerts an attractive force upon the substance still in
+solution. There is then a cause for the deposition of this substance,
+which does not co-operate when no part of the cell is yet formed.
+Therefore, the greater the attractive force of the cell is, the less
+concentration of the fluid is required; while, at the commencement of
+the formation of a cell, the fluid must be more than concentrated. But
+the conclusion which may be thus directly drawn, as to the attractive
+power of the cell, may also be verified by observation. Wherever the
+nutrient fluid is not equally distributed in a tissue, the new cells
+are formed in that part into which the fluid penetrates first, and
+where, consequently, it is most concentrated. Upon this fact, as we
+have seen, depended the difference between the growth of organized and
+unorganized tissues. And this confirmation of the foregoing conclusion
+by experience speaks also for the correctness of the reasoning itself.</p>
+
+<p>The attractive power of the cells operates so as to effect the addition
+of new molecules in two ways,—first, in layers, and secondly, in such
+a manner in each layer that the new molecules are deposited between
+those already present. This is only an expression of the fact; the<span class="pagenum" id="Page_254">[Pg 254]</span>
+more simple law, by which several layers are formed and the molecules
+are not all deposited between those already present, cannot yet be
+explained. The formation of layers may be repeated once, twice, or
+thrice. The growth of the separate layers is regulated by a law,
+that the deposition of new molecules should be greatest at the part
+where the nutrient fluid is most concentrated. Hence the outer part
+particularly becomes condensed into a membrance both in the layer
+corresponding to the nucleus and in that answering to the cell, because
+the nutrient fluid penetrates from without, and consequently is more
+concentrated at the outer than at the inner part of each layer. For
+the same reason the nucleus grows rapidly, so long as the layer of the
+cell is not formed around it, but it either stops growing altogether,
+or at least grows much more slowly as soon as the cell-layer has
+surrounded it; because then the latter receives the nutrient matter
+first, and, therefore, in a more concentrated form. And hence the cell
+becomes, in a general sense, much more completely developed, while
+the nucleus-layer usually remains at a stage of development, in which
+the cell-layer had been in its earlier period. The addition of new
+molecules is so arranged that the layers increase more considerably in
+superficial extent than in thickness; and thus an intervening space
+is formed between each layer and the one preceding it, by which cells
+and nuclei are formed into actual hollow vesicles. From this it may be
+inferred that the deposition of new molecules is more active between
+those which lie side by side along the surface of the membrane, than
+between those which lie one upon the other in its thickness. Were it
+otherwise, each layer would increase in thickness, but there would be
+no intervening cavity between it and the previous one, there would be
+no vesicles, but a solid body composed of layers.</p>
+
+<p>Attractive power is exerted in all the solid parts of the cell. This
+follows, not only from the fact that new molecules may be deposited
+everywhere between those already present, but also from the formation
+of secondary deposits. When the cavity of a cell is once formed,
+material may be also attracted from its contents and deposited in
+layers; and as this deposition takes place upon the inner surface
+of the membrane of the cell, it is probably that which exerts the
+attractive influence. This formation of layers on the inner surface of
+the cell-membrane is, perhaps, merely a repetition of the same process
+by<span class="pagenum" id="Page_255">[Pg 255]</span> which, at an earlier period, nucleus and cell were precipitated as
+layers around the nucleolus. It must, however, be remarked that the
+identity of these two processes cannot be so clearly proved as that of
+the processes by which nucleus and cell are formed; more especially
+as there is a variety in the phenomena, for the secondary deposits in
+plants occur in spiral forms, while this has at least not yet been
+demonstrated in the formation of the cell-membrane and the nucleus,
+although by some botanical writers the cell-membrane itself is supposed
+to consist of spirals.</p>
+
+<p>The power of attraction may be uniform throughout the whole cell,
+but it may also be confined to single spots; the deposition of new
+molecules is then more vigorous at these spots, and the consequence of
+this uneven growth of the cell-membrane is a change in the form of the
+cell.</p>
+
+<p>The attractive power of the cells manifest a certain form of election
+in its operation. It does not take up all the substances contained in
+the surrounding cytoblastema, but only particular ones, either those
+which are analogous with the substance already present in the cell
+(assimilation), or such as differ from it in chemical properties. The
+several layers grow by assimilation, but when a new layer is being
+formed, different material from that of the previously-formed layer
+is attracted: for the nucleolus, the nucleus and cell-membrane are
+composed of materials which differ in their chemical properties.</p>
+
+<p>Such are the peculiarities of the plastic power of the cells, so far as
+they can as yet be drawn from observation. But the manifestations of
+this power presuppose another faculty of the cells. The cytoblastema,
+in which the cells are formed, contains the elements of the materials
+of which the cell is composed, but in other combinations; it is
+not a mere solution of cell-material, but it contains only certain
+organic substances in solution. The cells, therefore, not only attract
+materials from out of the cytoblastema, but they must have the faculty
+of producing chemical changes in its constituent particles. Besides
+which, all the parts of the cell itself may be chemically altered
+during the process of its vegetation. The unknown cause of all these
+phenomena, which we comprise under the term metabolic phenomena of the
+cells, we will denominate the metabolic power.</p>
+
+<p>The next point which can be proved is, that this power is an attribute
+of the cells themselves, and that the cytoblastema is passive under<span class="pagenum" id="Page_256">[Pg 256]</span>
+it. We may mention vinous fermentation as an instance of this. A
+decoction of malt will remain for a long time unchanged; but as soon as
+some yeast is added to it, which consists partly of entire fungi and
+partly of a number of single cells, the chemical change immediately
+ensues. Here the decoction of malt is the cytoblastema; the cells
+clearly exhibit activity, the cytoblastema, in this instance even a
+boiled fluid, being quite passive during the change. The same occurs
+when any simple cells, as the spores of the lower plants, are sown in
+boiled substances.</p>
+
+<p>In the cells themselves again, it appears to be the solid parts, the
+cell-membrane and the nucleus, which produce the change. The contents
+of the cell undergo similar and even more various changes than the
+external the cytoblastema, and it is at least probable that these
+changes originate with the solid parts composing the cells, especially
+the cell-membrane, because the secondary deposits are formed on
+the inner surface of the cell-membrane, and other precipitates are
+generally formed in the first instance around the nucleus. It may
+therefore, on the whole, be said that the solid component particles of
+the cells possess the power of chemically altering the substances in
+contact with them.</p>
+
+<p>The substances which result from the transformation of the contents
+of the cell are different from those which are produced by change
+in the external cytoblastema. What is the cause of this difference,
+if the metamorphosing power of the cell-membrane be limited to its
+immediate neighbourhood merely? Might we not much rather expect that
+converted substance would be found without distinction on the inner
+as on the outer surface of the cell-membrane? It might be said that
+the cell-membrane converts the substance in contact with it without
+distinction, and that the variety in the products of this conversion
+depends only upon a difference between the convertible substance
+contained in the cell and the external cytoblastema. But the question
+then arises, as to how it happens that the contents of the cell differ
+from the external cytoblastema. If it be true that the cell-membrane,
+which at first closely surrounds the nucleus, expands in the course of
+its growth, so as to leave an interspace between it and the cell, and
+that the contents of the cell consist of fluid which has entered this
+space merely by imbibition, they cannot differ essentially from the
+external cytoblastema. I think therefore that, in order to explain the<span class="pagenum" id="Page_257">[Pg 257]</span>
+distinction between the cell-contents and the external cytoblastema,
+we must ascribe to the cell-membrane not only the power in general of
+chemically altering the substances which it is either in contact with,
+or has imbibed, but also of so separating them that certain substances
+appear on its inner, and others on its outer surface. The secretion of
+substances already present in the blood, as, for instance, of urea, by
+the cells with which the urinary tubes are lined, cannot be explained
+without such a faculty of the cells. There is, however, nothing so
+very hazardous in it, since it is a fact that different substances are
+separated in the decompositions produced by the galvanic pile. It might
+perhaps be conjectured from this peculiarity of the metabolic phenomena
+in the cells, that a particular position of the axes of the atoms
+composing the cell-membrane is essential for the production of these
+appearances.</p>
+
+<p>Chemical changes occur, however, not only in the cytoblastema and the
+cell-contents, but also in the solid parts of which the cells are
+composed, particularly the cell-membrane. Without wishing to assert
+that there is any intimate connexion between the metabolic power
+of the cells and galvanism, I may yet, for the sake of making the
+representation of the process more clear, remark that the chemical
+changes produced by a galvanic pile are accompanied by corresponding
+changes in the pile itself.</p>
+
+<p>The more obscure the cause of the metabolic phenomena in the cells
+is, the more accurately we must mark the circumstances and phenomena
+under which they occur. One condition to them is a certain temperature,
+which has a maximum and a minimum. The phenomena are not produced in
+a temperature below 0° or above 80° R.; boiling heat destroys this
+faculty of the cells permanently; but the most favorable temperature is
+one between 10° and 32° R. Heat is evolved by the process itself.</p>
+
+<p>Oxygen, or carbonic acid, in a gaseous form or lightly confined, is
+essentially necessary to the metabolic phenomena of the cells. The
+oxygen disappears and carbonic acid is formed, or <i>vice versa</i>,
+carbonic acid disappears, and oxygen is formed. The universality of
+respiration is based entirely upon this fundamental condition to the
+metabolic phenomena of the cells. It is so important that, as we shall
+see further on, even the principal varieties of form in organized
+bodies are occasioned by this peculiarity of the metabolic process in
+the cells.</p>
+
+<p><span class="pagenum" id="Page_258">[Pg 258]</span></p>
+
+<p>Each cell is not capable of producing chemical changes in every organic
+substance contained in solution, but only in particular ones. The fungi
+of fermentation, for instance, effect no changes in any other solutions
+than sugar; and the spores of certain plants do not become developed in
+all substances. In the same manner it is probable that each cell in the
+animal body converts only particular constituents of the blood.</p>
+
+<p>The metabolic power of the cells is arrested not only by powerful
+chemical actions, such as destroy organic substances in general, but
+also by matters which chemically are less uncongenial; for instance,
+concentrated solutions of neutral salts. Other substances, as arsenic,
+do so in less quantity. The metabolic phenomena may be altered in
+quality by other substances, both organic and inorganic, and a change
+of this kind may result even from mechanical impressions on the cells.</p>
+
+<p>Such are the most essential characteristics of the fundamental powers
+of the cell, so far as they can as yet be deduced from the phenomena.
+And now, in order to comprehend distinctly in what the peculiarity of
+the formative process of a cell, and therefore in what the peculiarity
+of the essential phenomenon in the formation of organized bodies
+consist, we will compare this process with a phenomenon of inorganic
+nature as nearly as possible similar to it. Disregarding all that
+is specially peculiar to the formation of cells, in order to find a
+more general definition in which it may be included with a process
+occurring in inorganic nature, we may view it as a process in which a
+solid body of definite and regular shape is formed in a fluid at the
+expense of a substance held in solution by that fluid. The process of
+crystallization in inorganic nature comes also within this definition,
+and is, therefore, the nearest analogue to the formation of cells.</p>
+
+<p>Let us now compare the two processes, that the difference of the
+organic process may be clearly manifest. First, with reference to the
+plastic phenomena, the forms of cells and crystals are very different.
+The primary forms of crystals are simple, always angular, and bounded
+by plane surfaces; they are regular, or at least symmetrical, and
+even the very varied secondary forms of crystals are almost, without
+exception, bounded by plane surfaces. But manifold as is the form of
+cells, they have very little resemblance to crystals; round surfaces
+predominate, and where angles occur, they are never quite sharp, and
+the polyhedral crystal-like form of many cells results only from<span class="pagenum" id="Page_259">[Pg 259]</span>
+mechanical causes. The structure too of cells and of crystals is
+different. Crystals are solid bodies, composed merely of layers placed
+one upon another; cells are hollow vesicles, either single, or several
+inclosed one within another. And if we regard the membranes of these
+vesicles as layers, there will still remain marks of difference between
+them and crystals; these layers are not in contact, but contain fluid
+between them, which is not the case with crystals; the layers in the
+cells are few, from one to three only; and they differ from each
+other in chemical properties, while those of crystals consist of the
+same chemical substance. Lastly, there is also a great difference
+between crystals and cells in their mode of growth. Crystals grow by
+apposition, the new molecules are set only upon the surface of those
+already deposited, but cells increase also by intussusception, that
+is to say, the new molecules are deposited also between those already
+present.</p>
+
+<p>But greatly as these plastic phenomena differ in cells and in crystals,
+the metabolic are yet more different, or rather they are quite peculiar
+to cells. For a crystal to grow, it must be already present as such in
+the solution, and some extraneous cause must interpose to diminish its
+solubility. Cells, on the contrary, are capable of producing a chemical
+change in the surrounding fluid, of generating matters which had not
+previously existed in it as such, but of which only the elements were
+present in another combination. They therefore require no extraneous
+influence to effect a change of solubility; for if they can produce
+chemical changes in the surrounding fluid, they may also produce
+such substances as could not be held in solution under the existing
+circumstances, and therefore need no external cause of growth. If a
+crystal be laid in a pretty strong solution, of a substance similar
+even to itself, nothing ensues without our interference, or the crystal
+dissolves completely: the fluid must be evaporated for the crystal
+to increase. If a cell be laid in a solution of a substance, even
+different from itself, it grows and converts this substance without
+our aid. And this it is from which the process going on in the cells
+(so long as we do not separate it into its several acts) obtains that
+magical character, to which attaches the idea of Life.</p>
+
+<p>From this we perceive how very different are the phenomena in the
+formation of cells and of crystals. Meanwhile, however, the points
+of resemblance between them should not be overlooked. They agree in<span class="pagenum" id="Page_260">[Pg 260]</span>
+this important point, that solid bodies of a certain regular shape are
+formed in obedience to definite laws at the expense of a substance
+contained in solution in a fluid; and the crystal, like the cell, is
+so far an active and positive agent as to cause the substances which
+are precipitated to be deposited on itself, and nowhere else. We
+must, therefore, attribute to it as well as to the cell a power to
+attract the substance held in solution in the surrounding fluid. It
+does not indeed follow that these two attractive powers, the power of
+crystallization—to give it a brief title—and the plastic power of the
+cells, are essentially the same. This could only be admitted, if it
+were proved that both powers acted according to the same laws. But this
+is seen at the first glance to be by no means the case: the phenomena
+in the formation of cells and crystals, are, as we have observed, very
+different, even if we regard merely the plastic phenomena of the cells,
+and leave their metabolic power (which may possibly arise from some
+other peculiarity of organic substance) for a time entirely out of the
+question.</p>
+
+<p>Is it, however, possible that these distinctions are only secondary,
+that the power of crystallization and the plastic power of the cells
+are identical, and that an original difference can be demonstrated
+between the substance of cells and that of crystals, by which we
+may perceive that the substance of cells must crystallize as cells
+according to the laws by which crystals are formed, rather than in the
+shape of the ordinary crystals? It may be worth while to institute such
+an inquiry.</p>
+
+<p>In seeking such a distinction between the substance of cells and that
+of crystals, we may say at once that it cannot consist in anything
+which the substance of cells has in common with those organic
+substances which crystallize in the ordinary form. Accordingly, the
+more complicated arrangement of the atoms of the second order in
+organic bodies cannot give rise to this difference; for we see in
+sugar, for instance, that the mode of crystallization is not altered by
+this chemical composition.</p>
+
+<p>Another point of difference by which inorganic bodies are distinguished
+from at least some of the organic bodies, is the faculty of imbibition.
+Most organic bodies are capable of being infiltrated by water, and
+in such a manner that it penetrates not so much into the interspaces
+between the elementary tissues of the body, as into the simple
+structureless tissues, such as areolar tissue, &amp;c.; so that they form
+an homogeneous mixture, and we can neither distinguish particles<span class="pagenum" id="Page_261">[Pg 261]</span>
+of organic matter, nor interspaces filled with water. The water
+occupies the infiltrated organic substances, just as it is present in
+a solution, and there is as much difference between the capacity for
+imbibition and capillary permeation, as there is between a solution and
+the phenomena of capillary permeation. When water soaks through a layer
+of glue, we do not imagine it to pass through pores, in the common
+sense of the term; and this is just the condition of all substances
+capable of imbibition. They possess, therefore, a double nature,
+they have a definite form like solid bodies; but like fluids, on the
+other hand, they are also permeable by anything held in solution. As
+a specifically lighter fluid poured on one specifically heavier so
+carefully as not to mix with it, yet gradually penetrates it, so also,
+every solution, when brought into contact with a membrane already
+infiltrated with water, bears the same relations to the membrane, as
+though it were a solution. And crystallization being the transition
+from the fluid to the solid state, we may conceive it possible, or
+even probable, that if bodies, capable of existing in an intermediate
+state between solid and fluid could be made to crystallize, a
+considerable difference would be exhibited from the ordinary mode of
+crystallization. In fact, there is nothing, which we call a crystal,
+composed of substance capable of imbibition; and even among organized
+substances, crystallization takes place only in those which are capable
+of imbibition, as fat, sugar, tartaric acid, &amp;c. The bodies capable of
+imbibition, therefore, either do not crystallize at all, or they do so
+under a form so different from the crystal that they are not recognized
+as such.</p>
+
+<p>Let us inquire what would most probably ensue if material capable of
+imbibition crystallized according to the ordinary laws, what varieties
+from the common crystals would be most likely to show themselves,
+assuming only that the solution has permeated through the parts of
+the crystal already formed, and that new molecules can therefore
+be deposited between them. The ordinary crystals increase only by
+apposition; but there may be an important difference in the mode of
+this apposition. If the molecules were all deposited symmetrically
+one upon another, we might indeed have a body of a certain external
+form like a crystal; but it would not have the structure of one,
+it would not consist of layers. The existence of this laminated
+structure in crystals presupposes a double kind of apposition of their
+molecules; for in each layer the newly-deposited molecules coalesce,
+and become<span class="pagenum" id="Page_262">[Pg 262]</span> continuous with those of the same layer already present;
+but those molecules which form the adjacent surfaces of two layers
+do not coalesce. This is a remarkable peculiarity in the formation
+of crystals, and we are quite ignorant of its cause. We cannot yet
+perceive why the new molecules, which are being deposited on the
+surface of a crystal (already formed up to a certain point), do not
+coalesce and become continuous with those already deposited, like the
+molecules in each separate layer, instead of forming, as they do, a
+new layer; and why this new layer does not constantly increase in
+thickness, instead of producing a second layer around the crystal, and
+so on. In the meantime we can do no more than express the fact in the
+form of a law, that the coalescing molecules are deposited rather along
+the surface beside each other, than in the thickness upon one another,
+and thus, as the breadth of the layer depends upon the size of the
+crystal, so also the layer can attain only a certain thickness, and
+beyond this, the molecules which are being deposited cannot coalesce
+with it, but must form a new layer.</p>
+
+<p>If we now assume that bodies capable of imbibition could also
+crystallize, the two modes of junction of the molecules should be
+shown also by them. Their structure should also be laminated, at least
+there is no perceptible reason for a difference in this particular,
+as the very fact of layers being formed in common crystals shows that
+the molecules need not be all joined together in the most exact manner
+possible. The closest possible conjunction of the molecules takes place
+only in the separate layers. In the common crystals this occurs by
+apposition of the new molecules on the surface of those present and
+coalescence with them. In bodies capable of imbibition, a much closer
+union is possible, because in them the new molecules may be deposited
+by intussusception between those already present. It is scarcely,
+therefore, too bold an hypothesis to assume, that when bodies capable
+of imbibition crystallize, their separate layers would increase by
+intussusception; and that this does not happen in ordinary crystals,
+simply because it is impossible.</p>
+
+<p>Let us then imagine a portion of the crystal to be formed: new
+molecules continue to be deposited, but do not coalesce with the
+portion of the crystal already formed; they unite with one another
+only, and form a new layer, which, according to analogy with the common
+crystals, may invest either the whole or a part of the crystal. We
+will<span class="pagenum" id="Page_263">[Pg 263]</span> assume that it invests the entire crystal. Now, although this
+layer be formed by the deposition of new molecules between those
+already present instead of by apposition, yet this does not involve
+any change in the law, in obedience to which the deposition of the
+coalescing molecules goes on more vigorously in two directions,
+that is, along the surface, than it does in the third direction
+corresponding to the thickness of the layer; that is to say, the
+molecules which are deposited by intussusception between those already
+present, must be deposited much more vigorously between those lying
+together along the surface of the layer than between those which lie
+over one another in its thickness. This deposition of molecules side
+by side is limited in common crystals by the size of the crystal, or
+by that of the surface on which the layer is formed; the coalescence
+of molecules therefore ceases as regards that layer, and a new one
+begins. But if the layers grow by intussusception in crystals capable
+of imbibition, there is nothing to prevent the deposition of more
+molecules between those which lie side by side upon the surface, even
+after the lamina has invested the whole crystal; it may continue to
+grow without the law by which the new molecules coalesce requiring to
+be altered. But the consequence is, that the layer becomes, in the
+first instance more condensed, that is, more solid substance is taken
+into the same space; and afterwards it will expand and separate from
+the completed part of the crystal so as to leave a hollow space between
+itself and the crystal; this space fills with fluid by imbibition,
+and the first-formed portion of the crystal adheres to a spot on its
+inner surface. Thus, in bodies capable of imbibition, instead of a new
+layer attached to the part of the crystal already formed, we obtain a
+hollow vesicle. At first this must have the shape of the body of the
+crystal around which it is formed, and must, therefore, be angular,
+if the crystal is angular. If, however, we imagine this layer to be
+composed of soft substance capable of imbibition, we may readily
+comprehend how such a vesicle must very soon become round or oval. But
+the first-formed part of the crystal also consists of substance capable
+of imbibition, so that it is very doubtful whether it must have an
+angular form at all. In common crystals atoms of some one particular
+substance are deposited together, and we can understand how a certain
+angular form of the crystal may result if these atoms have a certain
+form, or if in certain axes they attract each other differently. But in
+bodies capable of imbibition, an atom of one substance<span class="pagenum" id="Page_264">[Pg 264]</span> is not set upon
+another atom of the same substance, but atoms of water come between;
+atoms of water, which are not united with an atom of solid substance,
+so as to form a compound atom, as in the water of crystallization, but
+which exist in some other unknown manner between the atoms of solid
+substance. It is not possible, therefore, to determine whether that
+part of the crystal which is first formed must have an angular figure
+or not.</p>
+
+<p>An ordinary crystal consists of a number of laminæ; when so small as
+to be but just discernible, it has the form which the whole crystal
+afterwards exhibits, at least as far as regards the angles; we must
+therefore suppose that the first layer is formed around a very small
+corpuscle, which is of the same shape as the subsequent crystal. We
+will call this the primitive corpuscle. It is doubtful what may be
+the shape of this corpuscle in the crystals which are capable of
+imbibition. The first layer, then, is formed around the corpuscle
+in the way mentioned; it grows by intussusception, and thus forms
+a hollow, round or oval vesicle, to the inner surface of which the
+primitive corpuscle adheres. As all the new molecules that are being
+deposited may be placed in this layer without any alteration being
+required in the law which regulates the coalescence of the molecules
+during crystallization, we must conclude that it remains the only
+layer, and becomes greatly expanded, so as to represent all the
+layers of an ordinary crystal. It is, however, a question whether
+there may not exist some reasons why several layers can be formed.
+We can certainly conceive such to be the case. The quantity of the
+solid substance that must crystallize in a given time, depends upon
+the concentration of the fluid; the number of molecules that may,
+in accordance with the law already mentioned, be deposited in the
+layer in a given time depends upon the quantity of the solution
+which can penetrate the membrane by imbibition during that time. If
+in consequence of the concentration of the fluid there must be more
+precipitated in the time than can penetrate the membrane, it can only
+be deposited as a new layer on the outer surface of the vesicle. When
+this second layer is formed, the new molecules are deposited in it, and
+it rapidly becomes expanded into a vesicle, on the inner surface of
+which the first vesicle lies with its primitive corpuscle. The first
+vesicle now either does not grow at all, or at any rate much more
+slowly, and then only when the endosmosis into the cavity of the second
+vesicle proceeds so rapidly that all<span class="pagenum" id="Page_265">[Pg 265]</span> that might be precipitated while
+passing through it, is not deposited. The second vesicle, when it is
+developed at all, must needs be developed relatively with more rapidity
+than the first; for as the solution is in the most concentrated state
+at the beginning, the necessity for the formation of a second layer
+then occurs sooner; but when it is formed, the concentration of the
+fluid is diminished, and this necessity occurs either later or not at
+all. It is possible, however, that even a third, or fourth, and more,
+may be formed; but the outermost layer must always be relatively the
+most vigorously developed; for when the concentration of the solution
+is only so strong, that all that must be deposited in a certain time,
+can be deposited in the outermost layer, it is all applied to the
+increase of this layer.</p>
+
+<p>Such, then, would be the phenomena under which substances capable of
+imbibition would probably crystallize, if they did so at all. I say
+probably, for our incomplete knowledge of crystallization and the
+faculty of imbibition, does not as yet admit of our saying anything
+positively <i>a priori</i>. It is, however, obvious that these are the
+principal phenomena attending the formation of cells. They consist
+always of substance capable of imbibition; the first part formed is
+a small corpuscle, not angular (nucleolus), around this a lamina is
+deposited (nucleus), which advances rapidly in its growth, until a
+second lamina (cell) is formed around it. This second now grows more
+quickly and expands into a vesicle, as indeed often happens with
+the first layer. In some rarer instances only one layer is formed;
+in others, again, there are three. The only other difference in the
+formation of cells is, that the separate layers do not consist of the
+same chemical substance, while a common crystal is always composed
+of one material. In instituting a comparison, therefore, between the
+formation of cells and crystallization, the above-mentioned differences
+in form, structure, and mode of growth fall altogether to the ground.
+If crystals were formed from the same substance as cells, they would
+probably, in these respects, be subject to the same conditions as the
+cells. Meanwhile the metabolic phenomena, which are entirely absent in
+crystals, still indicate essential distinctions.</p>
+
+<p>Should this important difference between the mode of formation of
+cells and crystals lead us to deny all intimate connexion of the two
+processes, the comparison of the two may serve at least to give a clear
+representation of the cell-life. The following may be conceived to be<span class="pagenum" id="Page_266">[Pg 266]</span>
+the state of the matter: the material of which the cells are composed
+is capable of producing chemical changes in the substance with which it
+is in contact, just as the well-known preparation of platinum converts
+alcohol into acetic acid. This power is possessed by every part of the
+cell. Now, if the cytoblastema be so changed by a cell already formed,
+that a substance is produced which cannot become attached to that cell,
+it immediately crystallizes as the central nucleolus of a new cell. And
+then this converts the cytoblastema in the same manner. A portion of
+that which is converted may remain in the cytoblastema in solution,
+or may crystallize as the commencement of new cells; another portion,
+the cell-substance, crystallizes around the central corpuscle. The
+cell-substance is either soluble in the cytoblastema, and crystallizes
+from it, so soon as the latter becomes saturated with it; or else it is
+insoluble, and crystallizes at the time of its formation, according to
+the laws of crystallization of bodies capable of imbibition mentioned
+above, forming in this manner one or more layers around the central
+corpuscle, and so on. If we conceive the above to represent the mode
+of formation of cells, we regard the plastic power of the cells as
+identical with the power by which crystals grow. According to the
+foregoing description of the crystallization of bodies capable of
+imbibition, the most important plastic phenomena of the cells are
+certainly satisfactorily explained. But let us see if this comparison
+agrees with all the characteristics of the plastic power of the cells.</p>
+
+<p>The attractive power of the cells does not always operate
+symmetrically; the deposition of new molecules may be more vigorous in
+particular spots, and thus produce a change in the form of the cell.
+This is quite analogous to what happens in crystals; for although
+in them an angle is never altered, there may be much more material
+deposited on some surfaces than on others; and thus, for instance,
+a quadrilateral prism may be formed out of a cube. In this case new
+layers are deposited on one, or on two opposite sides of a cube. Now,
+if one layer in cells represent a number of layers in a common crystal,
+it may be easily perceived that instead of several new layers being
+formed on two opposite surfaces of a cell, the one layer would grow
+more at those spots, and thus a round cell would be elongated into a
+fibre; and so with the other changes of form. Division of the cells
+can have no analogue in common crystals, because that which is once
+deposited is incapable of any further change. But this phenomenon
+may be<span class="pagenum" id="Page_267">[Pg 267]</span> made to accord with the representation of crystals capable
+of imbibition.... And if we ascribe to a layer of a crystal capable
+of imbibition the power of producing chemical changes in organic
+substances, we can very well understand also the origin of secondary
+deposits on its inner surface as they occur in cells. For if, in
+accordance with the laws of crystallization, the lamina has become
+expanded into a vesicle, and its cavity has become filled by imbibition
+with a solution of organic substance, there may be materials formed
+by means of the converting influence of the lamina, which cannot any
+longer be held in solution. These may, then, either crystallize within
+the vesicle, as new crystals capable of imbibition under the form of
+cells; or if they are allied to the substance of the vesicle, they may
+so crystallize as to form part of the system of the vesicle itself:
+the latter may occur in two ways, the new matters may be applied to
+the increase of the vesicle, or they may form new layers on its inner
+surface from the same cause which led to the first formation of the
+vesicle itself as a layer. In the cells of plants these secondary
+deposits have a spiral arrangement. This is a very important fact,
+though the laws of crystallization do not seem to account for the
+absolute necessity of it. If, however, it could be mathematically
+proved from the laws of the crystallization of inorganic bodies, that
+under the altered circumstances in which bodies capable of imbibition
+are placed, these deposits must be arranged in spiral forms, it might
+be asserted without hesitation that the plastic power of cells and the
+fundamental powers of crystals are identical.</p>
+
+<p>We come now, however, to some peculiarities in the plastic power of
+cells, to which we might, at first sight, scarcely expect to find
+anything analogous in crystals. The attractive power of the cells
+manifests a certain degree of election in its operation; it does
+not attract every substance present in the cytoblastema, but only
+particular ones; and here a muscle-cell, there a fat-cell, is generated
+from the same fluid, the blood. Yet crystals afford us an example
+of a precisely similar phenomenon, and one which has already been
+frequently adduced as analogous to assimilation. If a crystal of nitre
+be placed in a solution of nitre and sulphate of soda, only the nitre
+crystallizes; when a crystal of sulphate of soda is put in, only the
+sulphate of soda crystallizes. Here, therefore, there occurs just the
+same selection of the substance to be attracted.</p>
+
+<p><span class="pagenum" id="Page_268">[Pg 268]</span></p>
+
+<p>We observed another law attending the development of the plastic
+phenomena in the cells, viz. that a more concentrated solution is
+requisite for the first formation of a cell than for its growth when
+already formed, a law upon which the difference between organized and
+unorganized tissues is based. In ordinary crystallization the solution
+must be more than saturated for the process to begin. But when it is
+over, there remains a mother lye, according to Thénard, which is no
+longer saturated at the same temperature. This phenomenon accords
+precisely with the cells; it shows that a more concentrated solution is
+requisite for the commencement of crystallization than for the increase
+of a crystal already formed. The fact has indeed been disputed by
+Thomson; but if, in the undisputed experiment quoted above, the crystal
+of sulphate of soda attracts the dissolved sulphate of soda rather
+than the dissolved nitre, and <i>vice versa</i>, the crystal of nitre
+attracts the dissolved nitre more than the dissolved sulphate of soda,
+it follows that a crystal does attract a salt held in solution, because
+the experiment proves that there are degrees of this attraction. But if
+there be such an attraction exerted by a crystal, then the introduction
+of a crystal into a solution of a salt, affords an efficient cause for
+the deposition of this salt, which does not exist when no crystal is
+introduced. The solution must therefore be more concentrated in the
+latter case than in the former, though the difference be so slight
+as not to be demonstrable by experiment. It would not, however, be
+superfluous to repeat the experiments. In the instance of crystals
+capable of imbibition, this difference may be considerably augmented,
+since the attraction of molecules may increase perhaps considerably by
+the penetrating of the solution between those already deposited.</p>
+
+<p>We see then how all the plastic phenomena in the cells may be compared
+with phenomena which, in accordance with the ordinary laws of
+crystallization, would probably appear if bodies capable of imbibition
+could be brought to crystallize. So long as the object of such a
+comparison were merely to render the representation of the process
+by which cells are formed more clear, there could not be much urged
+against it; it involves nothing hypothetical, since it contains no
+explanation; no assertion is made that the fundamental power of the
+cells really has something in common with the power by which crystals
+are formed. We have, indeed, compared the growth of organisms with
+crystallization, in so far as in both cases solid substances are
+deposited<span class="pagenum" id="Page_269">[Pg 269]</span> from a fluid, but we have not therefore asserted the
+identity of the fundamental powers. So far we have not advanced beyond
+the data, beyond a certain simple mode of representing the facts.</p>
+
+<p>The question is, however, whether the exact accordance of the phenomena
+would not authorize us to go further. If the formation and growth of
+the elementary particles of organisms have nothing more in common with
+crystallization than merely the deposition of solid substances from out
+of a fluid, there is certainly no reason for assuming any more intimate
+connexion of the two processes. But we have seen, first, that the laws
+which regulate the deposition of the molecules forming the elementary
+particles of organisms are the same for all elementary parts; that
+there is a common principle in the development of all elementary parts,
+namely, that of the formation of cells; it was then shown that the
+power which induced the attachment of the new molecules did not reside
+in the entire organism, but in the separated elementary particles (this
+we called the plastic power of the cells); lastly, it was shown that
+the laws, according to which the new molecules combine to form cells,
+are (so far as our incomplete knowledge of the laws of crystallization
+admits of our anticipating their probability) the same as those by
+which substances capable of imbibition would crystallize. Now the
+cells do, in fact, consist only of material capable of imbibition;
+should we not then be justified in putting forth the proposition, that
+the formation of the elementary parts of organisms is nothing but a
+crystallization of substance, capable of imbibition, and the organism
+nothing but an aggregate of such crystals capable of imbibition?</p>
+
+<p>To advance so important a point as absolutely true, would certainly
+need the clearest proof; but it cannot be said that even the premises
+which have been set forth have in all points the requisite force. For
+too little is still known of the cause of crystallization to predict
+with safety (as was attempted above) what would follow if a substance
+capable of imbibition were to crystallize. And if these premises were
+allowed, there are two other points which must be proved in order to
+establish the proposition in question: 1. That the metabolic phenomena
+of the cells, which have not been referred to in the foregoing
+argument, are as much the necessary consequence of the faculty of
+imbibition, or of some other peculiarity of the substance of cells, as
+the plastic phenomena are. 2. That if a number of crystals capable of
+imbibition<span class="pagenum" id="Page_270">[Pg 270]</span> are formed, they must combine according to certain laws
+so as to form a systematic whole, similar to an organism. Both these
+points must be clearly proved, in order to establish the truth of the
+foregoing view. But it is otherwise if this view be adduced merely as
+an hypothesis, which may serve as a guide for new investigations. In
+such case the inferences are sufficiently probable to justify such
+an hypothesis, if only the two points just mentioned can be shown to
+accord with it.</p>
+
+<p>With reference to the first of these points, it would certainly be
+impossible, in our ignorance as to the cause of chemical phenomena in
+general, to prove that a crystal capable of imbibition must produce
+chemical changes in substances surrounding it; but then we could not
+infer, from the manner in which spongy platinum is formed, that it
+would act so peculiarly upon oxygen and hydrogen. But in order to
+render this view tenable as a possible hypothesis, it is only necessary
+to see that it may be a consequence. It cannot be denied that it may:
+there are several reasons for it, though they certainly are but weak.
+For instance, since all cells possess this metabolic power, it is more
+likely to depend on a certain position of the molecules, which in all
+probability is essentially the same in all cells, than on the chemical
+combination of the molecules, which is very different in different
+cells. The presence, too, of different substances on the inner and
+outer surface of the cell-membrane in some measure implies that a
+certain direction of the axes of the atoms may be essential to the
+metabolic phenomena of the cells. I think, therefore, that the cause of
+the metabolic phenomena resides in that definite mode of arrangement
+of the molecules which occurs in crystals, combined with the capacity
+which the solution has to penetrate between these regularly deposited
+molecules (by means of which, presuming the molecules to possess
+polarity, a sort of galvanic pile will be formed), and that the same
+phenomena would be observed in an ordinary crystal, if it could be
+rendered capable of imbibition. And then perhaps the differences
+of quality in the metabolic phenomena depend upon their chemical
+composition.</p>
+
+<p>In order to render tenable the hypothesis contained in the second
+point, it is merely necessary to show that crystals capable of
+imbibition can unite with one another according to certain laws. If
+at their first formation all crystals were isolated, if they held
+no relation whatever<span class="pagenum" id="Page_271">[Pg 271]</span> to each other, the view would leave entirely
+unexplained how the elementary parts of organisms, that is, the
+crystals in question, become united to form a whole. It is therefore
+necessary to show that crystals do unite with each other according
+to certain laws, in order to perceive, at least, the possibility
+of their uniting also to form an organism, without the need of any
+further combining power. But there are many crystals in which a union
+of this kind, according to certain laws, is indisputable; indeed they
+often form a whole, so like an organism in its entire form, that
+groups of crystals are known in common life by the names of flowers,
+trees, etc. I need only refer to the ice-flowers on the windows, or
+to the lead-tree, etc. In such instances a number of crystals arrange
+themselves in groups around others, which form an axis. If we consider
+the contact of each crystal with the surrounding fluid to be an
+indispensable condition to the growth of crystals which are not capable
+of imbibition, but that those which are capable of imbibition, in which
+the solution can penetrate whole layers of crystals, do not require
+this condition, we perceive that the similarity between organisms and
+these aggregations of crystals is as great as could be expected with
+such difference of substance. As most cells require for the production
+of their metabolic phenomena, not only their peculiar nutrient fluid,
+but also the access of oxygen and the power of exhaling carbonic acid,
+or <i>vice versa</i>; so, on the other hand, organisms in which there
+is no circulation of respiratory fluid, or in which at least it is not
+sufficient, must be developed in such a way as to present as extensive
+a surface as possible to the atmospheric air. This is the condition of
+plants, which require for their growth that the individual cells should
+come into contact with the surrounding medium in a similar manner,
+if not in the same degree as occurs in a crystal tree, and in them
+indeed the cells unite into a whole organism in a form much resembling
+a crystal tree. But in animals the circulation renders the contact of
+the individual cells with the surrounding medium superfluous, and they
+may have more compact forms, even though the laws by which the cells
+arrange themselves are essentially the same.</p>
+
+<p>The view then that organisms are nothing but the form under which
+substances capable of imbibition crystallize, appears to be compatible
+with the most important phenomena of organic life, and may be so
+far admitted, that it is a possible hypothesis; or attempt towards
+an explanation<span class="pagenum" id="Page_272">[Pg 272]</span> of these phenomena. It involves very much that is
+uncertain and paradoxical, but I have developed it in detail, because
+it may serve as a guide for new investigations. For even if no relation
+between crystallization and the growth of organisms be admitted
+in principle, this view has the advantage of affording a distinct
+representation of the organic processes; an indispensable requisite for
+the institution of new inquiries in a systematic manner, or for testing
+by the discovery of new facts a mode of explanation which harmonizes
+with phenomena already known.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_33" href="#FNanchor_33" class="label">[33]</a>
+Translated from <i>Mikroskopische Untersuchungen über die
+Wachstum der Tiere und der Pflanzen</i> (Berlin, 1839) by Henry Smith
+in the <i>Publications of the Sydenham Society</i> (1847).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_273">[Pg 273]</span></p>
+<h2 class="nobreak" id="XXXI">XXXI<br>
+HERMANN VON HELMHOLTZ<br>
+1821-1894</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Hermann von Helmholtz, born at Potsdam, Prussia, August 31, 1821,
+studied medicine at the University of Berlin, from which he received
+his degree in 1842. He then entered the German Army as surgeon and
+in 1847 published his paper on “The Conservation of Energy,” which
+summarized historically the development of the idea. In 1849 he was
+appointed professor of physiology and general pathology at Königsberg.
+In 1855 he was called to Bonn, and in 1858 was elected to the chair of
+physiology at Heidelberg.</i></p>
+
+<p><i>In 1851 he invented the ophthalmoscope and later at Heidelberg he
+continued his researches in the subject of sight, and also cleared up
+the problem of the mechanical causes of sound. In 1871 he was appointed
+professor of physics at the University of Berlin, where he remained
+until his death, September 8, 1894.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE CONSERVATION OF ENERGY<a id="FNanchor_34" href="#Footnote_34" class="fnanchor">[34]</a></p>
+
+<p>A new conquest of very general interest has been recently made by
+natural philosophy. In the following pages I will endeavour to give a
+notion of the nature of this conquest. It has reference to a new and
+universal natural law, which rules the action of natural forces in
+their mutual relations towards each other, and is as influential on
+our theoretic views of natural processes as it is important in their
+technical applications.</p>
+
+<p>Among the practical arts which owe their progress to the development of
+the natural sciences, from the conclusion of the middle ages downwards,
+practical mechanics, aided by the mathematical science which bears the
+same name, was one of the most prominent. The<span class="pagenum" id="Page_274">[Pg 274]</span> character of the art
+was, at the time referred to, naturally very different from its present
+one. Surprised and stimulated by its own success, it thought no problem
+beyond its power, and immediately attacked some of the most difficult
+and complicated. Thus it was attempted to build automaton figures which
+should perform the functions of men and animals. The wonder of the last
+century was Vaucanson’s duck, which fed and digested its food; the
+flute player of the same artist, which moved all its fingers correctly;
+the writing boy of the older, and the pianoforte player of the younger
+Droz: which latter, when performing, followed its hands with its eyes,
+and at the conclusion of the piece bowed courteously to the audience.
+That men like those mentioned, whose talent might bear comparison with
+the most inventive heads of the present age, should spend so much
+time in the construction of these figures, which we at present regard
+as the merest trifles, would be incomprehensible, if they had not
+hoped in solemn earnest to solve a great problem. The writing boy of
+the elder Droz was publicly exhibited in Germany some years ago. Its
+wheel-work is so complicated, that no ordinary head would be sufficient
+to decipher its manner of action. When, however, we are informed that
+this boy and its constructor, being suspected of the black art, lay
+for a time in the Spanish Inquisition, and with difficulty obtained
+their freedom, we may infer that in those days even such a toy appeared
+great enough to excite doubts as to its natural origin. And though
+these artists may not have hoped to breathe into the creature of
+their ingenuity a soul gifted with moral completeness, still there
+were many who would be willing to dispense with the moral qualities
+of their servants if, at the same time, their immoral qualities could
+also be got rid of; and accept, instead of the mutability of flesh
+and bones, services which should combine the regularity of a machine
+with the durability of brass and steel. The object, therefore, which
+the inventive genius of the past century placed before it with the
+fullest earnestness, and not as a piece of amusement merely, was boldly
+chosen, and was followed up with an expenditure of sagacity which has
+contributed not a little to enrich the mechanical experience which a
+later time knew how to take advantage of. We no longer seek to build
+machines which shall fulfil the thousand services required of one man,
+but desire, on the contrary, that a machine shall perform one service,
+but shall occupy in doing it the place of a thousand men.</p>
+
+<p><span class="pagenum" id="Page_275">[Pg 275]</span></p>
+
+<p>From these efforts to imitate living creatures, another idea, also by
+a misunderstanding, seems to have developed itself, which, as it were,
+formed the new philosopher’s stone of the seventeenth and eighteenth
+centuries. It was now the endeavour to construct a perpetual motion
+machine. Under this term was understood a machine which, without being
+wound up, without consuming in the working of it, falling water, wind
+or any other natural force, should still continue in motion, the motive
+power being perpetually supplied by the machine itself. Beasts and
+human beings seemed to correspond to the idea of such an apparatus, for
+they moved themselves energetically and incessantly as long as they
+lived, were never wound up, and nobody set them in motion. A connection
+between the taking in of nourishment and the development of force did
+not make itself apparent. The nourishment seemed only necessary to
+grease, as it were, the wheel-work of the animal machine, to replace
+what was used up, and to renew the old. The development of force out of
+itself seemed to be the essential peculiarity, the real quintessence of
+organic life. If, therefore, men were to be constructed, a perpetual
+motion must first be found.</p>
+
+<p>Another hope also seemed to take up incidentally the second place,
+which, in our wiser age, would certainly have claimed the first rank
+in the thoughts of men. The perpetual motion was to produce work
+inexhaustibly without corresponding consumption, that is to say, out
+of nothing. Work, however, is money. Here, therefore, the practical
+problem which the cunning heads of all centuries have followed in the
+most diverse ways, namely, to fabricate money out of nothing, invited
+solution. The similarity with the philosopher’s stone sought by the
+ancient chemists was complete. That also was thought to contain the
+quintessence of organic life, and to be capable of producing gold.</p>
+
+<p>The spur which drove men to inquiry was sharp, and the talent of some
+of the seekers must not be estimated as small. The nature of the
+problem was quite calculated to entice poring brains, to lead them
+round a circle for years, deceiving ever with new expectations, which
+vanished upon nearer approach, and finally reducing these dupes of
+hope to open insanity. The phantom could not be grasped. It would be
+impossible to give a history of these efforts, as the clearer heads,
+among whom the elder Droz must be ranked, convinced themselves of the
+futility of their experiments, and were naturally not inclined to
+speak much about them. Bewildered intellects, however, proclaimed<span class="pagenum" id="Page_276">[Pg 276]</span>
+often enough that they had discovered the grand secret; and as the
+incorrectness of their proceedings was always speedily manifest, the
+matter fell into bad repute, and the opinion strengthened itself more
+and more that the problem was not capable of solution; one difficulty
+after another was brought under the dominion of mathematical mechanics,
+and finally a point was reached where it could be proved that, at least
+by the use of pure mechanical forces, no perpetual motion could be
+generated.</p>
+
+<p>We have here arrived at the idea of the driving force or power of
+a machine, and shall have much to do with it in future. I must,
+therefore, give an explanation of it. The idea of work is evidently
+transferred to machines by comparing their arrangements with those of
+men and animals to replace which they were applied. We still reckon
+the work of steam engines according to horse-power. The value of
+manual labor is determined partly by the force which is expended in
+it (a strong laborer is valued more highly than a weak one), partly,
+however, by the skill which is brought into action. A machine, on the
+contrary, which executes work skilfully, can always be multiplied to
+any extent; hence its skill has not the high value of human skill in
+domains where the latter cannot be supplied by machines. Thus the idea
+of the quantity of work in the case of machines has been limited to the
+consideration of the expenditure of force; this was the more important,
+as indeed most machines are constructed for the express purpose of
+exceeding, by the magnitude of their effects, the powers of men and
+animals. Hence, in a mechanical sense, the idea of work is become
+identical with that of the expenditure of force, and in this way I will
+apply it.</p>
+
+<p>How, then, can we measure this expenditure, and compare it in the case
+of different machines?</p>
+
+<p>I must here conduct you a portion of the way—as short a portion
+as possible—over the uninviting field of mathematico-mechanical
+ideas, in order to bring you to a point of view from which a more
+rewarding prospect will open. And though the example which I shall
+here choose, namely, that of a water-mill with iron hammer, appears
+to be tolerably romantic, still, alas, I must leave the dark forest
+valley, the spark-emitting anvil, and the black Cyclops wholly out of
+sight, and beg a moment’s attention to the less poetic side of the
+question, namely, the machinery. This is driven by a water-wheel, which
+in its turn is<span class="pagenum" id="Page_277">[Pg 277]</span> set in motion by the falling water. The axle of the
+water-wheel has at certain places small projections, thumbs, which,
+during the rotation, lift the heavy hammer and permit it to fall again.
+The falling hammer belabors the mass of metal, which is introduced
+beneath it. The work therefore done by the machine consists, in this
+case, in the lifting of the hammer, to do which the gravity of the
+latter must be overcome. The expenditure of force will, in the first
+place, other circumstances being equal, be proportioned to the weight
+of the hammer; it will, for example, be double when the weight of the
+hammer is doubled. But the action of the hammer depends not upon its
+weight alone, but also upon the height from which it falls. If it falls
+through two feet, it will produce a greater effect than if it falls
+through only one foot. It is, however, clear that if the machine, with
+a certain expenditure of force, lifts the hammer a foot in height, the
+same amount of force must be expended to raise it a second foot in
+height. The work is therefore not only doubled when the weight of the
+hammer is increased twofold, but also when the space through which it
+falls is doubled. From this it is easy to see that the work must be
+measured by the product of the weight into the space through which it
+ascends. And in this way, indeed, do we measure in mechanics.</p>
+
+<p>The unit of work is a foot-pound, that is, a pound weight, raised to
+the height of one foot.</p>
+
+<p>While the work in this case consists in the raising of the heavy
+hammer-head, the driving force which sets the latter in motion is
+generated by falling water. It is not necessary that the water should
+fall vertically, it can also flow in a moderately inclined bed; but
+it must always, where it has water-mills to set in motion, move from
+a higher to a lower position. Experiment and theory coincided in
+teaching, that when a hammer of a hundred weight is to be raised one
+foot, to accomplish this at least a hundred weight of water must fall
+through the space of one foot; or what is equivalent to this, two
+hundred weight must fall full half a foot, or four hundred weight a
+quarter of a foot, etc. In short, if we multiply the weight of the
+falling water by the height through which it falls, and regard, as
+before, the product as the measure of the work, then the work performed
+by the machine in raising the hammer can, in the most favourable case,
+be only equal to the number of foot-pounds of water which have fallen
+in the same<span class="pagenum" id="Page_278">[Pg 278]</span> time. In practice, indeed, this ratio is by no means
+attained; a great portion of the work of the falling water escapes
+unused, inasmuch as part of the force is unwillingly sacrificed for the
+sake of obtaining greater speed.</p>
+
+<p>I will further remark, that this relation remains unchanged whether
+the hammer is driven immediately by the axle of the wheel, or
+whether—by the intervention of wheel-work, endless screws, pulleys,
+ropes—the motion is transferred to the hammer. We may, indeed, by
+such arrangements, succeed in raising a hammer of ten hundred weight,
+when by the first simple arrangement, the elevation of a hammer of one
+hundred weight might alone be possible; but either this heavier hammer
+is raised to only one-tenth of the height, or tenfold the time is
+required to raise it to the same height; so that, however we may alter,
+by the interposition of machinery, the intensity of the acting force,
+still in a certain time, during which the mill-stream furnishes us with
+a definite quantity of water, a certain definite quantity of work, and
+no more, can be performed.</p>
+
+<p>Our machinery, therefore, has, in the first place, done nothing more
+than make use of the gravity of the falling water in order to overpower
+the gravity of the hammer, and to raise the latter. When it has lifted
+the hammer to the necessary height, it again liberates it, and the
+hammer falls upon the metal mass which is pushed beneath it. But why
+does the falling hammer here exercise a greater force than when it is
+permitted simply to press with its own weight on the mass of metal? Why
+is its power greater as the height from which it falls is increased?
+We find, in fact, that the work performed by the hammer is determined
+by its velocity. In other cases, also, the velocity of moving masses
+is a means of producing great effects. I only remind you of the
+destructive effects of musket-bullets, which, in a state of rest, are
+the most harmless things in the world. I remind you of the windmill,
+which derives its force from the moving air. It may appear surprising
+that motion, which we are accustomed to regard as a non-essential and
+transitory endowment of bodies, can produce such great effects. But
+the fact is, that motion appears to us, under ordinary circumstances,
+transitory, because the movement of all terrestrial bodies is resisted
+perpetually by other forces, friction, resistance of the air, etc.,
+so that motion is incessantly weakened and finally neutralized. A
+body, however, which is opposed by no resisting force,<span class="pagenum" id="Page_279">[Pg 279]</span> when once set
+in motion, moves onward eternally with undiminished velocity. Thus
+we know that the planetary bodies have moved without change, through
+space, for thousands of years. Only by resisting forces can motion
+be diminished or destroyed. A moving body, such as the hammer or the
+musket-ball, when it strikes against another, presses the latter
+together, or penetrates it, until the sum of the resisting forces which
+the body struck presents to its pressure, or to the separation of its
+particles, is sufficiently great to destroy the motion of the hammer
+or of the bullet. The motion of a mass regarded as taking the place of
+working force is called the living force (<i>vis viva</i>) of the mass.
+The word “living” has of course here no reference whatever to living
+beings, but is intended to represent solely the force of the motion as
+distinguished from the state of unchanged rest—from the gravity of
+a motionless body, for example, which produces an incessant pressure
+against the surface which supports it, but does not produce any motion.</p>
+
+<p>In the case before us, therefore, we had first power in the form of
+a falling mass of water, then in the form of a lifted hammer, and,
+thirdly, in the form of the living force of the fallen hammer. We
+should transform the third form into the second, if we, for example,
+permitted the hammer to fall upon a highly elastic steel beam strong
+enough to resist the shock. The hammer would rebound, and in the most
+favourable case would reach a height equal to that from which it
+fell, but would never rise higher. In this way its mass would ascend:
+and at the moment when its highest point has been attained, it would
+represent the same number of raised foot-pounds as before it fell,
+never a greater number; that is to say, living force can generate the
+same amount of work as that expended in its production. It is therefore
+equivalent to this quantity of work.</p>
+
+<p>Our clocks are driven by means of sinking weights, and our watches by
+means of the tension of springs. A weight which lies on the ground, an
+elastic spring which is without tension, can produce no effects; to
+obtain such we must first raise the weight or impart tension to the
+spring, which is accomplished when we wind up our clocks and watches.
+The man who winds the clock or watch communicates to the weight or
+to the spring a certain amount of power, and exactly so much as is
+thus communicated is gradually given out again during the following
+twenty-four hours, the original force being thus slowly<span class="pagenum" id="Page_280">[Pg 280]</span> consumed
+to overcome the friction of the wheels and the resistance which the
+pendulum encounters from the air. The wheel-work of the clock therefore
+exhibits no working force which was not previously communicated to it,
+but simply distributes the force given to it uniformly over a longer
+time.</p>
+
+<p>Into the chamber of an air-gun we squeeze, by means of a condensing
+air-pump, a great quantity of air. When we afterwards open the cock of
+a gun and admit the compressed air into the barrel, the ball is driven
+out of the latter with a force similar to that exerted by ignited
+powder. Now we may determine the work consumed in the pumping-in of the
+air, and the living force which, upon firing, is communicated to the
+ball, but we shall never find the latter greater than the former. The
+compressed air has generated no working force, but simply gives to the
+bullet that which has been previously communicated to it. And while we
+have pumped for perhaps a quarter of an hour to charge the gun, the
+force is expended in a few seconds when the bullet is discharged; but
+because the action is compressed into so short a time, a much greater
+velocity is imparted to the ball than would be possible to communicate
+to it by the unaided effort of the arm in throwing it.</p>
+
+<p>From these examples you observe, and the mathematical theory has
+corroborated this for all purely mechanical, that is to say, for
+moving forces, that all our machinery and apparatus generate no
+force, but simply yield up the power communicated to them by
+natural forces—falling water, moving wind, or by the muscles of
+men and animals. After this law had been established by the great
+mathematicians of the last century, a perpetual motion, which should
+make only use of pure mechanical forces, such as gravity, elasticity,
+pressure of liquids and gases, could only be sought after by bewildered
+and ill-instructed people. But there are still other natural forces
+which are not reckoned among the purely moving forces—heat,
+electricity, magnetism, light, chemical forces, all of which
+nevertheless stand in manifold relation to mechanical processes. There
+is hardly a natural process to be found which is not accompanied by
+mechanical actions, or from which mechanical work may not be derived.
+Here the question of a perpetual motion remained open; the decision of
+this question marks the progress of modern physics.</p>
+
+<p>In the case of the air-gun, the work to be accomplished in the
+propulsion<span class="pagenum" id="Page_281">[Pg 281]</span> of the ball was given by the arm of the man who pumped in
+the air. In ordinary firearms, the condensed mass of air which propels
+the bullet is obtained in a totally different manner, namely, by the
+combustion of the powder. Gunpowder is transformed by combustion for
+the most part into gaseous products, which endeavor to occupy a much
+larger space than that previously taken by the volume of the powder.
+Thus, you see, that, by the use of gunpowder, the work which the human
+arm must accomplish in the case of the air-gun is spared.</p>
+
+<p>In the mightiest of our machines, the steam engine, it is a strongly
+compressed aeriform body, water, vapour, which, by its effort to
+expand, sets the machine in motion. Here, also, we do not condense the
+steam by means of an external mechanical force, but by communicating
+heat to a mass of water in a closed boiler, we change this water
+into steam, which, in consequence of the limits of the space, is
+developed under strong pressure. In this case, therefore, it is the
+heat communicated which generates the mechanical force. The heat thus
+necessary for the machine we might obtain in many ways; the ordinary
+method is to procure it from the combustion of coal.</p>
+
+<p>Combustion is a chemical process. A particular constituent of our
+atmosphere, oxygen, possesses a strong force of attraction, or, as
+it is named in chemistry, a strong affinity for the constituents of
+the combustible body, which affinity, however, in most cases, can
+only exert itself at high temperatures. As soon as a portion of the
+combustible body, for example, the coal, is sufficiently heated,
+the carbon unites itself with great violence to the oxygen of the
+atmosphere and forms a peculiar gas, carbonic acid, the same which we
+see foaming from beer and champagne. By this combination, light and
+heat are generated; heat is generally developed by any combination
+of two bodies of strong affinity for each other; and when the heat
+is intense enough, light appears. Hence, in the steam engine, it is
+chemical processes and chemical forces which produce the astonishing
+work of these machines. In like manner the combustion of gunpowder is a
+chemical process which, in the barrel of the gun, communicates living
+force to the bullet.</p>
+
+<p>While now the steam engine develops for us mechanical work out of
+heat, we can conversely generate heat by mechanical forces. A skilful
+blacksmith can render an iron wedge red hot by hammering.<span class="pagenum" id="Page_282">[Pg 282]</span> The axes of
+our carriages must be protected, by careful greasing, from ignition
+through friction. Even lately this property has been applied on a large
+scale. In some factories, where a surplus of water power is at hand,
+this surplus is applied to cause a strong iron plate to rotate swiftly
+upon another, so that they become strongly heated by friction. The heat
+so obtained warms the room, and thus a stove without fuel is provided.
+Now, could not the heat generated by the plates be applied to a small
+steam engine, which in its turn should be able to keep the rubbing
+plates in motion? The perpetual motion would thus be at length found.
+This question might be asked, and could not be decided by the older
+mathematico-mechanical investigations. I will remark, beforehand, that
+the general law which I will lay before you answers the question in the
+negative.</p>
+
+<p>By a similar plan, however, a speculative American set some time ago
+the industrial world of Europe in excitement. The magneto-electric
+machines often made use of in the case of rheumatic disorders are well
+known to the public. By imparting a swift rotation to the magnet of
+such a machine, we obtain powerful currents of electricity. If those
+be conducted through water, the latter will be reduced into its two
+components, oxygen and hydrogen. By the combustion of hydrogen, water
+is again generated. If this combustion takes place, not in atmospheric
+air, of which oxygen only constitutes a fifth part, but in pure oxygen,
+and if a bit of chalk be placed in the flame, the chalk will be raised
+to a white heat, and give us the sun-like Drummond’s light. At the same
+time, the flame develops a considerable quantity of heat. Our American
+proposed to utilize in this way the gases obtained from electrolytic
+decomposition, and asserted that by the combustion a sufficient amount
+of heat was generated to keep a small steam engine in action, which
+again drove his magneto-electric machine, decomposed the water, and
+thus continually prepared its own fuel. This would certainly have been
+the most splendid of all discoveries; a perpetual motion which, besides
+the force which kept it going, generated light like the sun, and
+warmed all around it. The matter was by no means badly cogitated. Each
+practical step in the affair was known to be possible; but those who at
+that time were acquainted with the physical investigations which bear
+upon this subject could have affirmed, on first hearing the report,
+that the matter was to be numbered among<span class="pagenum" id="Page_283">[Pg 283]</span> the numerous stories of the
+fable-rich America; and indeed a fable it remained.</p>
+
+<p>It is not necessary to multiply examples further. You will infer from
+those given, in what immediate connection heat, electricity, magnetism,
+light, and chemical affinity, stand with mechanical forces.</p>
+
+<p>Starting from each of these different manifestations of natural forces
+we can set every other in motion, for the most part not in one way
+merely, but in many ways. It is here as with the weaver’s web—</p>
+
+<div class="poetry-container">
+<div class="poetry">
+ <div class="stanza">
+ <div class="verse indent0">Where a step stirs a thousand threads</div>
+ <div class="verse indent0">The shuttles shoot from side to side,</div>
+ <div class="verse indent0">The fibres flow unseen,</div>
+ <div class="verse indent0">And one shock strikes a thousand combinations.</div>
+ </div>
+</div>
+</div>
+
+<p>Now it is clear that if by any means we could succeed, as the above
+American professed to have done, by mechanical forces, to excite
+chemical, electrical, or other natural processes, which, by any circuit
+whatever, and without altering permanently the active masses in the
+machine, could produce mechanical force in greater quantity than that
+at first applied, a portion of the work thus gained might be made use
+of to keep the machine in motion, while the rest of the work might be
+applied to any other purpose whatever. The problem was, to find in
+the complicated net of reciprocal actions, a track through chemical,
+electrical, magnetical, and thermic processes, back to mechanical
+actions, which might be followed with a final gain of mechanical work;
+thus would the perpetual motion be found.</p>
+
+<p>But, warned by the futility of former experiments, the public had
+become wiser. On the whole, people did not seek much after combinations
+which promised to furnish a perpetual motion, but the question was
+inverted. It was no more asked, how can I make use of the known and
+unknown relations of natural forces so as to construct a perpetual
+motion? but it was asked, if a perpetual motion be impossible, what are
+the relations which must subsist between natural forces? Everything
+was gained by this inversion of the question. The relations of natural
+forces rendered necessary by the above assumption, might be easily
+and completely stated. It was found that all known relations of force
+harmonize with the consequences of that assumption, and a series of
+unknown relations were discovered at<span class="pagenum" id="Page_284">[Pg 284]</span> the same time, the correctness of
+which remained to be proved. If a single one of them could be proved
+false, then a perpetual motion would be possible.</p>
+
+<p>The first who endeavoured to travel this way was a Frenchman, named
+Carnot, in the year 1824. In spite of a too limited conception of
+his subject, and an incorrect view as to the nature of heat, which
+led him to some erroneous conclusions, his experiment was not quite
+unsuccessful. He discovered a law which now bears his name, and to
+which I will return further on.</p>
+
+<p>His labors remained for a long time without notice, and it was not
+till eighteen years afterwards, that is, in 1842, that different
+investigators in different countries, and independent of Carnot, laid
+hold of the same thought.</p>
+
+<p>The first who saw truly the general law here referred to, and expressed
+it correctly, was a German physician, J. R. Mayer, of Heilbronn,
+in the year 1842. A little later, in 1843, a Dane, named Colding,
+presented a memoir to the Academy of Copenhagen, in which the same law
+found utterance, and some experiments were described for its further
+corroboration. In England, Joule began about the same time to make
+experiments having reference to the same subject. We often find, in the
+case of questions to the solution of which the development of science
+points, that several heads, quite independent of each other, generate
+exactly the same series of reflections.</p>
+
+<p>I myself, without being acquainted with either Mayer or Colding, and
+having first made the acquaintance of Joule’s experiments at the end of
+my investigation, followed the same path. I endeavoured to ascertain
+all the relations between the different natural processes, which
+followed from our regarding them from the above point of view. My
+inquiry was made public in 1847, in a small pamphlet bearing the title,
+“On the Conservation of Force.”</p>
+
+<p>Since that time the interest of the scientific public for this subject
+has gradually augmented. A great number of the essential consequences
+of the above manner of viewing the subject, the proof of which was
+wanting when the first theoretic notions were published, have since
+been confirmed by experiment, particularly by those of Joule; and
+during the last year the most eminent physicist of France, Regnault,
+has adopted the new mode regarding the question, and by fresh
+investigations on the specific heat of gases has contributed<span class="pagenum" id="Page_285">[Pg 285]</span> much to
+its support. For some important consequences the experimental proof
+is still wanting, but the number of confirmations is so predominant,
+that I have not deemed it too early to bring the subject before even a
+non-scientific audience.</p>
+
+<p>How the question has been decided you may already infer from what has
+been stated. In the series of natural processes there is no circuit
+to be found, by which mechanical force can be gained without a
+corresponding consumption. The perpetual motion remains impossible. Our
+reflections, however, gain thereby a higher interest.</p>
+
+<p>We have thus far regarded the development of force by natural
+processes, only in its relation to its usefulness to man, as mechanical
+force. You now see that we have arrived at a general law, which holds
+good wholly independent of the application which man makes of natural
+forces; we must therefore make the expression of our new law correspond
+to this more general significance. It is in the first place clear, that
+the work which, by any natural process whatever, is performed under
+favourable conditions by a machine, and which may be measured in the
+way already indicated, may be used as a measure of force common to
+all. Further, the important question arises, “If the quantity of force
+cannot be augmented except by corresponding consumption, can it be
+diminished or lost?” For the purpose of our machines it certainly can,
+if we neglect the opportunity to convert natural processes to use, but
+as investigation has proved, not for a nature as a whole.</p>
+
+<p>In the collision and friction of bodies against each other, the
+mechanics of former years assumed simply that living force was lost.
+But I have already stated that each collision and each act of friction
+generates heat; and, moreover, Joule has established by experiment
+the important law that for every foot-pound of force which is lost a
+definite quantity of heat is always generated, and that when work is
+performed by the consumption of heat, for each foot-pound thus gained
+a definite quantity of heat disappears. The quantity of heat necessary
+to raise the temperature of a pound of water a degree of the centigrade
+thermometer, corresponds to a mechanical force by which a pound weight
+would be raised to the height of 1350 feet; we name this quantity the
+mechanical equivalent of heat. I may mention here that these facts
+conduct of necessity to the conclusion, that the heat is not, as was
+formerly imagined, a fine imponderable substance,<span class="pagenum" id="Page_286">[Pg 286]</span> but that, like
+light, it is a peculiar shivering motion of the ultimate particles of
+bodies. In collision and friction, according to this manner of viewing
+the subject, the motion of the mass of a body which is apparently lost
+is converted into a motion of the ultimate particles of the body; and
+conversely, when mechanical force is generated by heat, the motion of
+the ultimate particles is converted into a motion of the mass.</p>
+
+<p>Chemical combinations generate heat, and the quantity of this heat is
+totally independent of the time and steps through which the combination
+has been effected, provided that other actions are not at the same
+time brought into play. If, however, mechanical work is at the same
+time accomplished, as in the case of the steam engine, we obtain as
+much less heat as is equivalent to this work. The quantity of work
+produced by chemical force is in general very great. A pound of the
+purest coal gives when burnt, sufficient heat to raise the temperature
+of 8086 pounds of water one degree of the centigrade thermometer; from
+this we can calculate that the magnitude of the chemical force of
+attraction between the particles of a pound of coal and the quantity
+of oxygen that corresponds to it is capable of lifting a weight of one
+hundred pounds to a height of twenty miles. Unfortunately, in our steam
+engines, we have hitherto been able to gain only the smallest portion
+of this work; the greater part is lost in the shape of heat. The best
+expansive engines give back as mechanical work only eighteen per cent.
+of the heat generated by the fuel.</p>
+
+<p>From a similar investigation of all the other known physical and
+chemical processes, we arrive at the conclusion that Nature as a whole
+possesses a store of force which cannot in any way be either increased
+or diminished. And that, therefore, the quantity of force in Nature is
+just as eternal and unalterable as the quantity of matter. Expressed
+in this form, I have named the general law “The Principle of the
+Conservation of Force.”</p>
+
+<p>We cannot create mechanical force, but we may help ourselves from the
+general store-house of Nature. The brook and the wind, which drive our
+mills, the forest and the coal-bed, which supply our steam engines and
+warm our rooms, are to us the bearers of a small portion of the great
+natural supply which we draw upon for our purposes, and the actions of
+which we can apply as we think fit. The possessor of a mill claims the
+gravity of the descending rivulet, or<span class="pagenum" id="Page_287">[Pg 287]</span> the living force of the moving
+wind, as his possession. These portions of the store of Nature are what
+give his property its chief value.</p>
+
+<p>Further, from the fact that no portion of force can be absolutely lost,
+it does not follow that a portion may not be inapplicable to human
+purposes. In this respect the inferences drawn by William Thomson from
+the law of Carnot are of importance. This law, which was discovered
+by Carnot during his endeavours to ascertain the relations between
+heat and mechanical force, which, however, by no means belongs to the
+necessary consequences of the conservation of force, and which Clausius
+was the first to modify in such a manner that it no longer contradicted
+the above general law, expresses a certain relation between the
+compressibility, the capacity for heat, and the expansion by heat of
+all bodies. It is not yet considered as actually proved, but some
+remarkable deductions having been drawn from it, and afterwards proved
+to be facts by experiment, it has attained thereby a great degree
+of probability. Besides the mathematical form in which the law was
+first expressed by Carnot, we can give it the following more general
+expression:—“Only, when heat passes from a warmer to a colder body,
+and even then only partially, can it be converted into mechanical work.”</p>
+
+<p>The heat of a body which we cannot cool further, cannot be changed
+into another form of force; into the electric or chemical force, for
+example. Thus, in our steam engines, we convert a portion of the heat
+of the glowing coal into work, by permitting it to pass to the less
+warm water of the boiler. If, however, all the bodies in nature had
+the same temperature, it would be impossible to convert any portion of
+their heat into mechanical work. According to this, we can divide the
+total force store of the universe into two parts, one of which is heat,
+and must continue to be such; the other, to which a portion of the heat
+of the warmer bodies, and the total supply of chemical, mechanical,
+electrical, and magnetical forces belong, is capable of the most varied
+changes of form, and constitutes the whole wealth of change which takes
+place in nature.</p>
+
+<p>But the heat of the warmer bodies strives perpetually to pass to
+bodies less warm by radiation and conduction, and thus to establish
+an equilibrium of temperature. At each motion of a terrestrial body,
+a portion of mechanical force passes by friction or collision into
+heat, of which only a part can be converted back again into mechanical<span class="pagenum" id="Page_288">[Pg 288]</span>
+force. This is also generally the case in every electrical and chemical
+process. From this, it follows that the first portion of the store of
+force, the unchangeable heat, is augmented by every natural process,
+while the second portion, mechanical, electrical, and chemical force,
+must be diminished; so that if the universe be delivered over to
+the undisturbed action of its physical processes, all force will
+finally pass into the form of heat, and all heat come into a state of
+equilibrium. Then all possibility of a further change would be at an
+end, and the complete cessation of all natural processes must set in.
+The life of men, animals, and plants, could not of course continue if
+the sun had lost its high temperature, and with it his light,—if all
+the components of the earth’s surface had closed those combinations
+which their affinities demand. In short, the universe from that time
+forward would be condemned to a state of eternal rest.</p>
+
+<p>These consequences of the law of Carnot are, of course, only valid,
+provided that the law, when sufficiently tested, proves to be
+universally correct. In the mean time there is little prospect of the
+law being proved incorrect. At all events we must admire the sagacity
+of Thomson, who, in the letters of a long known little mathematical
+formula, which only speaks of the heat, volume, and pressure of bodies,
+was able to discern consequences which threatened the universe, though
+certainly after an infinite period of time, with eternal death.</p>
+
+<p>I have already given you notice that our path lay through a thorny and
+unrefreshing field of mathematico-mechanical developments. We have
+now left this portion of our road behind us. The general principle
+which I have sought to lay before you has conducted us to a point from
+which our view is a wide one, and aided by this principle, we can now
+at pleasure regard this or the other side of the surrounding world,
+according as our interest in the matter leads us. A glance into the
+narrow laboratory of the physicist, with its small appliances and
+complicated abstractions, will not be so attractive as a glance at the
+wide heaven above us, the clouds, the rivers, the woods, and the living
+beings around us. While regarding the laws which have been deduced
+from the physical processes of terrestrial bodies, as applicable also
+to the heavenly bodies, let me remind you that the same force which,
+acting at the earth’s surface, we call gravity (<i>Schwere</i>), acts
+as gravitation in the celestial spaces, and also manifests its power in
+the motion of the immeasurably distant double<span class="pagenum" id="Page_289">[Pg 289]</span> stars which are governed
+by exactly the same laws as those subsisting between the earth and
+moon; that, therefore, the light and heat of terrestrial bodies do not
+in any way differ essentially from those of the sun, or of the most
+distant fixed star; that the meteoric stones which sometimes fall from
+external space upon the earth are composed of exactly the same simple
+chemical substances as those with which we are acquainted. We need,
+therefore, feel no scruple in granting that general laws to which all
+terrestrial natural processes are subject, are also valid for other
+bodies than the earth. We will, therefore, make use of our law to
+glance over the household of the universe with respect to the store of
+force, capable of action, which it possesses.</p>
+
+<p>A number of singular peculiarities in the structure of our planetary
+system indicate that it was once a connected mass with a uniform
+motion of rotation. Without such an assumption, it is impossible to
+explain why all the planets move in the same direction round the sun,
+why they all rotate in the same direction round their axes, why the
+planes of their orbits, and those of their satellites and rings all
+nearly coincide, why all their orbits differ but little from circles;
+and much besides. From these remaining indications of a former state,
+astronomers have shaped an hypothesis regarding the formation of our
+planetary system, which, although from the nature of the case it must
+ever remain an hypothesis, still in its special traits is so well
+supported by analogy, that it certainly deserves our attention. It
+was Kant who, feeling great interest in the physical description of
+the earth and the planetary system, undertook the labour of studying
+the works of Newton, and as an evidence of the depth to which he had
+penetrated into the fundamental ideas of Newton, seized the notion
+that the same attractive force of all ponderable matter which now
+supports the motion of the planets, must also aforetime have been able
+to form from matter loosely scattered in space the planetary system.
+Afterwards, and independent of Kant, Laplace, the great author of the
+<i>Mecanique Celeste</i>, laid hold of the same thought, and introduced
+it among astronomers.</p>
+
+<p>The commencement of our planetary system, including the sun, must,
+according to this, be regarded as an immense nebulous mass which filled
+the portion of space which is now occupied by our system, far beyond
+the limits of Neptune, our most distant planet. Even<span class="pagenum" id="Page_290">[Pg 290]</span> now we perhaps
+see similar masses in the distant regions of the firmament, as patches
+of nebulæ, and nebulous stars; within our system also, comets, the
+zodiacal light, the corona of the sun during a total eclipse, exhibit
+remnants of a nebulous substance, which is so thin that the light
+of the stars passes through it unenfeebled and unrefracted. If we
+calculate the density of the mass of our planetary system, according to
+the above assumption, for the time when it was a nebulous sphere, which
+reached to the path of the outmost planet, we should find that it would
+require several cubic miles of such matter to weigh a single grain.</p>
+
+<p>The general attractive force of all matter must, however, impel these
+masses to each other, and to condense, so that the nebulous sphere
+became incessantly smaller, by which, according to mechanical laws, a
+motion of rotation originally slow, and the existence of which must be
+assumed, would gradually become quicker and quicker. By the centrifugal
+force which must act most energetically in the neighbourhood of the
+equator of the nebulous sphere, masses could from time to time be torn
+away, which afterwards would continue their courses separate from the
+main mass, forming themselves into single planets, or, similar to the
+great original sphere, into planets with satellites and rings, until
+finally the principal mass condensed itself into the sun. With regard
+to the origin of heat and light, this view gives us no information.</p>
+
+<p>When the nebulous chaos first separated itself from other fixed star
+masses, it must not only have contained all kinds of matter which was
+to constitute the future planetary system, but also, in accordance
+with our new law, the whole store of force which at one time must
+unfold therein its wealth of actions. Indeed in this respect an immense
+dower was bestowed in the shape of the general attraction of all the
+particles for each other. This force, which on the earth exerts itself
+as gravity, acts in the heavenly spaces as gravitation. As terrestrial
+gravity when it draws a weight downwards performs work and generates
+<i>vis viva</i>, so also the heavenly bodies do the same when they draw
+two portions of matter from distant regions of space towards each other.</p>
+
+<p>The chemical forces must have been also present, ready to act; but as
+these forces can only come into operation by the most intimate<span class="pagenum" id="Page_291">[Pg 291]</span> contact
+of the different masses, condensation must have taken place before the
+play of chemical forces began.</p>
+
+<p>Whether a still further supply of force in the shape of heat was
+present at the commencement we do not know. At all events, by aid of
+the law of the equivalence of heat and work, we find in the mechanical
+forces, existing at the time to which we refer, such a rich source of
+heat and light, that there is no necessity whatever to take refuge in
+the idea of a store of these forces originally existing. When through
+condensation of the masses their particles came into collision,
+and clung to each other, the <i>vis viva</i> of their motion would
+be thereby annihilated, and must reappear as heat. Already in old
+theories, it has been calculated that cosmical masses must generate
+heat by their collision, but it was far from anybody’s thought to make
+even a guess at the amount of heat to be generated in this way. At
+present we can give definite numerical values with certainty.</p>
+
+<p>Let us make this addition to our assumption; that, at the commencement,
+the density of the nebulous matter was a vanishing quantity, as
+compared with the present density of the sun and planets; we can then
+calculate how much work has been performed by the condensation; we can
+further calculate how much of this work still exists in the form of
+mechanical force, as attraction of the planets towards the sun, and as
+<i>vis viva</i> of their motion, and find by this how much of the force
+has been converted into heat.</p>
+
+<p>The result of this calculation is, that only about the 454th part
+of the original mechanical force remains as such, and that the
+remainder, converted into heat, would be sufficient to raise a mass
+of water equal to the sun and planets taken together, not less than
+twenty-eight millions of degrees of the centigrade scale. For the
+sake of comparison, I will mention that the highest temperature which
+we can produce by the oxyhydrogen blowpipe, which is sufficient to
+fuse and vaporize even platina, and which but few bodies can endure,
+is estimated at about two thousand centigrade degrees. Of the action
+of a temperature of twenty-eight millions of such degrees we can
+form no notion. If the mass of our entire system were pure coal,
+by the combustion of the whole of it only the 3500th part of the
+above quantity would be generated. This is also clear, that such a
+development of heat must have presented the greatest obstacle to the<span class="pagenum" id="Page_292">[Pg 292]</span>
+speedy union of the masses, that the larger part of the heat must have
+been diffused by radiation into space, before the masses could form
+bodies possessing the present density of the sun and planets, and that
+these bodies must once have been in a state of fiery fluidity. This
+notion is corroborated by the geological phenomena of our planet; and
+with regard to the other planetary bodies, the flattened form of the
+sphere, which is the form of equilibrium of a fluid mass, is indicative
+of a former state of fluidity. If I thus permit an immense quantity of
+heat to disappear without compensation from our system, the principle
+of the conservation of force is not thereby invaded. Certainly for our
+planet it is lost, but not for the universe. It has proceeded outwards,
+and daily proceeds outwards into infinite space; and we know not
+whether the medium which transmits the undulations of light and heat
+possesses an end where the rays must return, or whether they eternally
+pursue their way through infinitude.</p>
+
+<p>The store of force at present possessed by our system, is also
+equivalent to immense quantities of heat. If our earth were by a sudden
+shock brought to rest on her orbit—which is not to be feared in the
+existing arrangements of our system—by such a shock a quantity of heat
+would be generated equal to that produced by the combustion of fourteen
+such earths of solid coal. Making the most unfavourable assumption as
+to its capacity for heat, that is, placing it equal to that of water,
+the mass of the earth would thereby be heated 11,200 degrees; it would
+therefore be quite fused and for the most part reduced to vapour. If,
+then, the earth, after having been thus brought to rest, should fall
+into the sun, which of course would be the case, the quantity of heat
+developed by the shock would be four hundred times greater.</p>
+
+<p>Even now, from time to time, such a process is repeated on a small
+scale. There can hardly be a doubt that meteors, fire-balls, and
+meteoric stones are masses which belong to the universe, and before
+coming into the domain of our earth, moved like the planets round the
+sun. Only when they enter our atmosphere do they become visible and
+fall sometimes to the earth. In order to explain the emission of light
+by these bodies, and the fact that for some time after their descent
+they are very hot, the friction was long ago thought of which they
+experience in passing through the air. We can now calculate that a
+velocity of 3,000 feet a second, supposing the whole of the friction<span class="pagenum" id="Page_293">[Pg 293]</span>
+to be expended in heating the solid mass, would raise a piece of
+meteoric iron 1,000° C. in temperature, or, in other words, to a vivid
+red heat. Now the average velocity of the meteors seems to be thirty or
+forty times the above amount. To compensate this, however, the greater
+portion of the heat is, doubtless, carried away by the condensed mass
+of air which the meteor drives before it. It is known that bright
+meteors generally leave a luminous trail behind them, which probably
+consists of several portions of the red-hot surfaces. Meteoric masses
+which fall to the earth often burst with a violent explosion, which
+may be regarded as a result of the quick heating. The newly-fallen
+pieces have been for the most part found hot, but not red-hot, which
+is easily explainable by the circumstances, that during the short time
+occupied by the meteor in passing through the atmosphere, only a thin,
+superficial layer is heated to redness, while but a small quantity of
+heat has been able to penetrate to the interior of the mass. For this
+reason the red heat can speedily disappear.</p>
+
+<p>Thus has the falling of the meteoric stone, the minute remnant of
+processes which seems to have played an important part in the formation
+of the heavenly bodies, conducted us to the present time, where we
+pass from the darkness of hypothetical views to the brightness of
+knowledge. In what we have said, however, all that is hypothetical is
+the assumption of Kant and Laplace, that the masses of our system were
+once distributed as nebulæ in space.</p>
+
+<p>On account of the rarity of the case, we will still further remark,
+in what close coincidence the results of science here stand with the
+earlier legends of the human family, and the forebodings of poetic
+fancy. The cosmogony of ancient nations generally commences with chaos
+and darkness.</p>
+
+<p>Neither is the Mosaic tradition very divergent, particularly when we
+remember that that which Moses names heaven is different from the blue
+dome above us, and is synonymous with space, and that the unformed
+earth, and the waters of the great deep, which were afterwards divided
+into waters above the firmament, and waters below the firmament,
+resembled the chaotic components of the world.</p>
+
+<p>Our earth bears still the unmistakable traces of its old fiery fluid
+condition. The granite formations of her mountains exhibit a structure,
+which can only be produced by the crystallization of fused masses.
+Investigation still shows that the temperature in mines, and borings,<span class="pagenum" id="Page_294">[Pg 294]</span>
+increases as we descend; and if this increase is uniform, at the depth
+of fifty miles, a heat exists sufficient to fuse all our minerals. Even
+now our volcanoes project, from time to time, mighty masses of fused
+rocks from their interior, as a testimony of the heat which exists
+there. But the cooled crust of the earth has already become so thick,
+that, as may be shown by calculations of its conductive power, the heat
+coming to the surface from within, in comparison with that reaching the
+earth from the sun, is exceedingly small, and increases the temperature
+of the surface only about one-thirtieth of a degree centigrade; so that
+the remnant of the old store of force which is enclosed as heat within
+the bowels of the earth, has a sensible influence upon the processes
+at the earth’s surface, only through the instrumentality of volcanic
+phenomena. These processes owe their power almost wholly to the action
+of other heavenly bodies, particularly to the light and heat of the
+sun, and partly also, in the case of the tides, to the attraction of
+the sun and moon.</p>
+
+<p>Most varied and numerous are the changes which we owe to the light
+and heat of the sun. The sun heats our atmosphere irregularly, the
+warm rarefied air ascends, while fresh cool air flows from the sides
+to supply its place: in this way winds are generated. This action is
+most powerful at the equator, the warm air of which incessantly flows
+in the upper regions of the atmosphere towards the poles: while just
+as persistently, at the earth’s surface, the trade wind carries new
+and cool air to the equator. Without the heat of the sun all winds
+must, of necessity, cease. Similar currents are produced by the same
+cause in the waters of the sea. Their power may be inferred from the
+influence which in some cases they exert upon climate. By them the warm
+water of the Antilles is carried to the British Isles, and confers upon
+them a mild, uniform warmth and rich moisture; while, through similar
+causes, the floating ice of the North Pole is carried to the coast
+of Newfoundland, and produces cold. Further, by the heat of the sun,
+a portion of the water is converted into vapour which rises in the
+atmosphere, is condensed to clouds, or falls in rain and snow upon the
+earth, collects in the form of springs, brooks, and rivers, and finally
+reaches the sea again, after having gnawed the rocks, carried away the
+light earth, and thus performed its part in the geologic changes of the
+earth; perhaps, besides all this it has driven our water-mill upon its
+way. If the heat of the sun were withdrawn,<span class="pagenum" id="Page_295">[Pg 295]</span> there would remain only a
+single motion of water, namely, the tides, which are produced by the
+attraction of the sun and moon.</p>
+
+<p>How is it now, with the motions and the work of organic beings? To
+the builders of the automata of the last century, men and animals
+appeared as clockwork which was never wound up, and created the force
+which they exerted out of nothing. They did not know how to establish
+a connection between the nutriment consumed and the work generated.
+Since, however, we have learned to discern in the steam-engine this
+origin of mechanical force, we must inquire whether something similar
+does not hold good with regard to men. Indeed, the continuation of
+life is dependent on the consumption of nutritive materials: these
+are combustible substances, which, after digestion and being passed
+into the blood, actually undergo a slow combustion, and finally enter
+into almost the same combinations with the oxygen of the atmosphere
+that are produced in an open fire. As the quantity of heat generated
+by combustion is independent of the duration of the combustion and
+the steps in which it occurs, we can calculate from the mass of the
+consumed material how much heat, or its equivalent work is thereby
+generated in an animal body. Unfortunately, the difficulty of the
+experiments is still very great; but within those limits of accuracy
+which have been as yet attainable, the experiments show that the heat
+generated in the animal body corresponds to the amount which would be
+generated by the chemical processes. The animal body therefore does not
+differ from the steam-engine, as regards the manner in which it obtains
+heat and force, but does differ from it in the manner in which the
+force gained is to be made use of. The body is, besides, more limited
+than the machine in the choice of its fuel; the latter could be heated
+with sugar, with starch-flour, and butter, just as well as with coal
+or wood; the animal body must dissolve its materials artificially, and
+distribute them through its system; it must, further, perpetually renew
+the used-up materials of its organs, and as it cannot itself create
+the matter necessary for this, the matter must come from without.
+Liebig was the first to point out these various uses of the consumed
+nutriment. As material for the perpetual renewal of the body, it seems
+that certain definite albuminous substances which appear in plants, and
+form the chief mass of the animal body, can alone be used. They form
+only a portion of the mass of nutriment taken daily; the remainder,
+sugar, starch,<span class="pagenum" id="Page_296">[Pg 296]</span> fat, are really only materials for warming, and are
+perhaps not to be superseded by coal, simply because the latter does
+not permit itself to be dissolved.</p>
+
+<p>If, then, the processes in the animal body are not in this respect to
+be distinguished from inorganic processes, the question arises, whence
+comes the nutriment which constitutes the source of the body’s force?
+The answer is, from the vegetable kingdom; for only the material of
+plants, or the flesh of plant-eating animals, can be made use of for
+food. The animals which live on plants occupy a mean position between
+carnivorous animals, in which we reckon man, and vegetables, which
+the former could not make use of immediately as nutriment. In hay and
+grass the same nutritive substances are present as in meal and flour,
+but in less quantity. As, however, the digestive organs of man are not
+in a condition to extract the small quantity of the useful from the
+great excess of the insoluble, we submit, in the first place, these
+substances to the powerful digestion of the ox, permit the nourishment
+to store itself in the animal’s body, in order in the end to gain it
+for ourselves in a more agreeable and useful form. In answer to our
+question, therefore, we are referred to the vegetable world. Now when
+what plants take in and what they give out are made the subjects of
+investigation, we find that the principal part of the former consists
+in the products of combustion which are generated by the animal.
+They take the consumed carbon given off in respiration, as carbonic
+acid, from the air, the consumed hydrogen as water, the nitrogen in
+its simplest and closest combinations as ammonia; and from these
+materials, with the assistance of small ingredients which they take
+from the soil, they generate anew the compound combustible substances,
+albumen, sugar, oil, on which the animal subsists. Here, therefore,
+is a circuit which appears to be a perpetual store of force. Plants
+prepare fuel and nutriment, animals consume these, burn them slowly
+in their lungs, and from the products of combustion the plants again
+derive their nutriment. The latter is an eternal source of chemical,
+the former of mechanical forces. Would not the combination of both
+organic kingdoms produce the perpetual motion? We must not conclude
+hastily: further inquiry shows, that plants are capable of producing
+combustible substances only when they are under the influence of the
+sun. A portion of the sun’s rays exhibits a remarkable relation to
+chemical forces,—it<span class="pagenum" id="Page_297">[Pg 297]</span> can produce and destroy chemical combinations;
+and these rays, which for the most part are blue or violet, are called
+therefore chemical rays. We make use of their action in the production
+of photographs. Here compounds of silver are decomposed at the place
+where the sun’s rays strike them. The same rays overpower in the green
+leaves of plants the strong chemical affinity of the carbon of the
+carbonic acid for oxygen, give back the latter free to the atmosphere,
+and accumulate the other, in combination with other bodies, as woody
+fibre, starch, oil, or resin. These chemically active rays of the sun
+disappear completely as soon as they encounter the green portions of
+the plants, and hence it is that in daguerreotype images the green
+leaves of plants appear uniformly black. Inasmuch as the light coming
+from them does not contain the chemical rays, it is unable to act upon
+the silver compounds.</p>
+
+<p>Hence a certain portion of force disappears from the sunlight, while
+combustible substances are generated and accumulated in plants; and
+we can assume it as very probable, that the former is the cause of
+the latter. I must indeed remark, that we are in possession of no
+experiments from which we might determine whether the vis viva of the
+sun’s rays which have disappeared, corresponds to the chemical forces
+accumulated during the same time; and as long as these experiments are
+wanting, we cannot regard the stated relation as a certainty. If this
+view should prove correct, we derive from it the flattering result,
+that all force, by means of which our bodies live and move, finds
+its source in the purest sunlight; and hence we are all, in point
+of nobility, not behind the race of the great monarch of China, who
+heretofore alone called himself Son of the Sun. But it must also be
+conceded that our lower fellow-beings, the frog and leech, share the
+same ethereal origin, as also the whole vegetable world, and even the
+fuel which comes to us from the ages past, as well as the youngest
+offspring of the forest with which we heat our stoves and set our
+machines in motion.</p>
+
+<p>You see, then, that the immense wealth of ever-changing meteorological,
+climatic, geological, and organic processes of our earth are almost
+wholly preserved in action by the light and heat-giving rays of the
+sun; and you see in this a remarkable example, how Proteus-like the
+effects of a single cause, under altered external conditions, may
+exhibit itself in nature. Besides these, the earth experiences an
+action<span class="pagenum" id="Page_298">[Pg 298]</span> of another kind from its central luminary, as well as from its
+satellite the moon, which exhibits itself in the remarkable phenomenon
+of the ebb and flow of the tide.</p>
+
+<p>Each of these bodies excites, by its attraction upon the waters of the
+sea, two gigantic waves, which flow in the same direction round the
+world, as the attracting bodies themselves apparently do. The two waves
+of the moon, on account of her greater nearness, are about three and a
+half times as large as those excited by the sun. One of these waves has
+its crest on the quarter of the earth’s surface which is turned towards
+the moon, the other is at the opposite side. Both these quarters
+possess the flow of the tide, while the regions which lie between have
+the ebb. Although in the open sea the height of the tide amounts to
+only about three feet, and only in certain narrow channels, where the
+moving water is squeezed together, rises to thirty feet, the might of
+the phenomena is nevertheless manifest from the calculation of Bessel,
+according to which a quarter of the earth covered by the sea possesses,
+during the flow of the tide, about 25,000 cubic miles of water more
+than during the ebb, and that therefore such a mass of water must, in
+six and a quarter hours, flow from one quarter of the earth to the
+other.</p>
+
+<p>The phenomena of the ebb and flow, as already recognized by Mayer,
+combined with the law of the conservation of force, stand in remarkable
+connection with the question of the stability of our planetary system.
+The mechanical theory of the planetary motions discovered by Newton
+teaches, that if a solid body in absolute vacuo, attracted by the sun,
+move around him in the same manner as the planets, this motion will
+endure unchanged through all eternity.</p>
+
+<p>Now we have actually not only one, but several such planets, which
+move around the sun, and by their mutual attraction create little
+changes and disturbances in each other’s paths. Nevertheless Laplace,
+in his great work, the <i>Mecanique Celeste</i>, has proved that in
+our planetary system all these disturbances increase and diminish
+periodically, and can never exceed certain limits, so that by this
+cause the external existence of the planetary system is unendangered.</p>
+
+<p>But I have already named two assumptions which must be made: first,
+that the celestial spaces must be absolutely empty; and secondly, that
+the sun and planets must be solid bodies. The first is at least the<span class="pagenum" id="Page_299">[Pg 299]</span>
+case as far as astronomical observations reach, for they have never
+been able to detect any retardation of the planets, such as would
+occur if they moved in a resisting medium. But on a body of less mass,
+the comet of Encke, changes are observed of such a nature: this comet
+describes ellipses round the sun which are becoming gradually smaller.
+If this kind of motion, which certainly corresponds to that through a
+resisting medium, be actually due to the existence of such a medium,
+a time will come when the comet will strike the sun; and a similar
+end threatens all the planets, although after a time, the length of
+which baffles our imagination to conceive of it. But even should the
+existence of a resisting medium appear doubtful to us, there is no
+doubt that the planets are not wholly composed of solid materials which
+are inseparably bound together. Signs of the existence of an atmosphere
+are observed on the Sun, on Venus, Mars, Jupiter, and Saturn. Signs
+of water and ice upon Mars; and our earth has undoubtedly a fluid
+portion on its surface, and perhaps a still greater portion of fluid
+within it. The motions of the tides, however, produce friction, all
+friction destroys <i>vis viva</i>, and the loss in this case can only
+affect the <i>vis viva</i> of the planetary system. We come thereby to
+the unavoidable conclusion, that every tide, although with infinite
+slowness, still with certainty, diminishes the store of mechanical
+force of the system; and as a consequence of this, the rotation of
+the planets in question round their axes must become more slow; they
+must therefore approach the sun, or their satellites must approach
+them. What length of time must pass before the length of our day is
+diminished one second by the action of the tide cannot be calculated,
+until the height and time of the tide in all portions of the ocean are
+known. This alteration, however, takes place with extreme slowness,
+as is known by the consequences which Laplace has deduced from the
+observations of Hipparchus, according to which, during a period of
+2000 years, the duration of the day has not been shortened by the
+one-three-hundredth part of a second. The final consequence would be,
+but after millions of years, if in the mean time the ocean did not
+become frozen, that one side of the earth would be constantly turned
+towards the sun, and enjoy a perpetual day, whereas the opposite side
+would be involved in eternal night. Such a position we observe in our
+moon with regard to the earth, and also in the case of the satellites<span class="pagenum" id="Page_300">[Pg 300]</span>
+as regards their planets; it is, perhaps, due to the action of the
+mighty ebb and flow to which these bodies, in the time of their fiery
+fluid condition, were subjected.</p>
+
+<p>I would not have brought forward these conclusions, which again
+plunge us in the most distant future, if they were not unavoidable.
+Physico-mechanical laws are, as it were, the telescopes of our
+spiritual eye, which can penetrate into the deepest night of time, past
+and to come.</p>
+
+<p>Another essential question as regards the future of our planetary
+system has reference to its future temperature and illumination.
+As the internal heat of the earth has but little influence on the
+temperature of the surface, the heat of the sun is the only thing which
+essentially affects the question. The quantity of heat falling from the
+sun during a given time upon a given portion of the earth’s surface
+may be measured, and from this it can be calculated how much heat in a
+given time is sent out from the entire sun. Such measurements have been
+made by the French physicist Pouillet, and it has been found that the
+sun gives out a quantity of heat per hour equal to that which a layer
+of the densest coal ten feet thick would give out by its combustion;
+and hence in a year a quantity equal to the combustion of a layer of
+seventeen miles. If this heat were drawn uniformly from the entire mass
+of the sun, its temperature would only be diminished thereby one and
+one-third of a degree centigrade per year, assuming its capacity for
+heat to be equal to that of water. These results can give us an idea of
+the magnitude of the emission, in relation to the surface and mass of
+the sun; but they cannot inform us whether the sun radiates heat as a
+glowing body, which since its formation has its heat accumulated within
+it, or whether a new generation of heat by chemical processes takes
+place at the sun’s surface. At all events the law of the conservation
+of force teaches us that no process analogous to those known at the
+surface of the earth, can supply for eternity an inexhaustible amount
+of light and heat to the sun. But the same law also teaches that the
+store of force at present existing, as heat, or as what may become
+heat, is sufficient for an immeasurable time. With regard to the store
+of chemical force in the sun, we can form no conjecture, and the
+store of heat there existing can only be determined by very uncertain
+estimations. If, however, we adopt the very probable view, that the<span class="pagenum" id="Page_301">[Pg 301]</span>
+remarkably small density of so large a body is caused by its high
+temperature, and may become greater in time, it may be calculated that
+if the diameter of the sun were diminished only the ten-thousandth
+part of its present length, by this act a sufficient quantity of heat
+would be generated to cover the total emission for 2100 years. Such a
+small change besides it would be difficult to detect even by the finest
+astronomical observations.</p>
+
+<p>Indeed, from the commencement of the period during which we possess
+historic accounts, that is, for a period of about 4000 years, the
+temperature of the earth has not sensibly diminished. From these old
+ages we have certainly no thermometric observations, but we have
+information regarding the distribution of certain cultivated plants,
+the vine, the olive tree, which are very sensitive to changes of the
+mean annual temperature, and we find that these plants at the present
+moment have the same limits of distribution that they had in the times
+of Abraham and Homer; from which we may infer backwards the constancy
+of the climate.</p>
+
+<p>In opposition to this it has been urged, that here in Prussia the
+German knights in former times cultivated the vine, cellared their
+own wine and drank it, which is no longer possible. From this the
+conclusion has been drawn, that the heat of our climate has diminished
+since the time referred to. Against this, however, Dove has cited the
+reports of ancient chroniclers, according to which, in some peculiarly
+hot years, the Prussian grape possessed somewhat less than its usual
+quantity of acid. The fact also speaks not so much for the climate of
+the country as for the throats of the German drinkers.</p>
+
+<p>But even though the force store of our planetary system is so immensely
+great, that by the incessant emission which has occurred during the
+period of human history it has not been sensibly diminished, even
+though the length of the time which must flow by, before a sensible
+change in the state of our planetary system occurs, is totally
+incapable of measurement, still the inexorable laws of mechanics
+indicate that this store of force, which can only suffer loss and not
+gain, must be finally exhausted. Shall we terrify ourselves by this
+thought? Men are in the habit of measuring the greatness and the wisdom
+of the universe by the duration and the profit which it promises to
+their own race; but the past history of the earth already shows what
+an insignificant moment the duration of the existence of our race
+upon<span class="pagenum" id="Page_302">[Pg 302]</span> it constitutes. A Nineveh vessel, a Roman sword awakes in us the
+conception of grey antiquity. What the museums of Europe show us of the
+remains of Egypt and Assyria we gaze upon with silent astonishment, and
+despair of being able to carry our thoughts back to a period so remote.
+Still must the human race have existed for ages, and multiplied itself
+before the pyramids of Nineveh could have been erected. We estimate the
+duration of human history at 6000 years; but immeasurable as this time
+may appear to us, what is it in comparison with the time during which
+the earth carried successive series of rank plants and mighty animals,
+and no men; during which in our neighbourhood the amber-tree bloomed,
+and dropped its costly gum on the earth and in the sea; when in
+Siberia, Europe and North America groves of tropical palms flourished;
+where gigantic lizards, and after them elephants, whose mighty remains
+we still find buried in the earth, found a home? Different geologists,
+proceeding from different premises, have sought to estimate the
+duration of the above creative period, and vary from a million to nine
+million years. And the time during which the earth generated organic
+beings is again small when we compare it with the ages during which the
+world was a ball of fused rocks. For the duration of its cooling from
+2000° to 200° centigrade, the experiments of Bishop upon basalt show
+that about 350 millions of years would be necessary. And with regard
+to the time during which the first nebulous mass condensed into our
+planetary system, our most daring conjectures must cease. The history
+of man, therefore, is but a short ripple in the ocean of time. For a
+much longer series of years than that during which man has already
+occupied this world, the existence of the present state of inorganic
+nature favourable to the duration of man seems to be secured, so that
+for ourselves and for long generations after us, we have nothing
+to fear. But the same forces of air and water, and of the volcanic
+interior, which produced former geological revolutions, and buried one
+series of living forms after another, act still upon the earth’s crust.
+They more probably will bring about the last day of the human race than
+those distant cosmical alterations of which we have spoken, and perhaps
+force us to make way for new and more complete living forms, as the
+lizards and the mammoth have given place to us and our fellow-creatures
+which now exist.</p>
+
+<p>Thus the thread which was spun in darkness by those who sought a<span class="pagenum" id="Page_303">[Pg 303]</span>
+perpetual motion has conducted us to a universal law of nature, which
+radiates light into the distant nights of the beginning and of the
+end of the history of the universe. To our own race it permits a long
+but not an endless existence; it threatens it with a day of judgment,
+the dawn of which is still happily obscured. As each of us singly
+must endure the thought of his death, the race must endure the same.
+But above the forms of life gone by, the human race has higher moral
+problems before it, the bearer of which it is, and in the completion of
+which it fulfils its destiny.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_34" href="#FNanchor_34" class="label">[34]</a>
+Translated from <i>Über die Erhaltung der Kraft</i>
+(Berlin, 1847).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_304">[Pg 304]</span></p>
+<h2 class="nobreak" id="XXXII">XXXII<br>
+LOUIS PASTEUR<br>
+1822-1895</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Louis Pasteur was born at Dôle, France, December 27, 1822, the son
+of a tanner. Educated at Arbois, Besançon, and the École Normale,
+he was appointed assistant professor of chemistry at the last-named
+institution. His first important work was in demonstrating the
+asymmetry of molecules. In 1863 he investigated fermentation and showed
+that it was caused by the growth of bacteria and later proved that it
+was also the cause of putrefaction, a suggestion which Lister employed
+in developing antiseptic surgery. In 1865 Pasteur discovered the
+bacillus which caused the silkworm disease. Taking up the principle of
+inoculation he applied it to small-pox and later extended it to other
+infectious diseases. He died September 28, 1895.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+INOCULATION FOR HYDROPHOBIA<a id="FNanchor_35" href="#Footnote_35" class="fnanchor">[35]</a></p>
+
+<p>Gentlemen:—Your Congress meetings are the place for the discussion
+of the gravest problems of medicine; they serve also to point out the
+great landmarks of the future. Three years ago, on the eve of the
+London Congress, the doctrine of micro-organisms, the ætiological cause
+of transmissible maladies, was still the subject of sharp criticisms.
+Certain refractory minds continued to uphold the idea that “disease is
+in us, from us, by us.”</p>
+
+<p>It was expected that the decided supporters of the theory of the
+spontaneity of diseases would make a bold stand in London; but no
+opposition was made to the doctrine of “exteriority,” or external
+causes, the first cause of contagious diseases, and those questions
+were not discussed at all.</p>
+
+<p><span class="pagenum" id="Page_305">[Pg 305]</span></p>
+
+<p>It was there seen, once again, that when all is ready for the final
+triumph of truth, the united conscience of a great assembly feels it
+instinctively and recognises it.</p>
+
+<p>All clear-sighted minds had already foreseen that the theory of the
+spontaneity of diseases received its death-blow on the day when it
+became possible reasonably to consider the spontaneous generation of
+microscopic organisms as a myth, and when, on the other hand, the
+life-activity of those same beings was shown to be the main cause of
+organic decomposition and of all fermentation.</p>
+
+<p>From the London Congress, also, dates the recognition of another very
+hopeful progress; we refer to the attenuation of different viruses,
+to the production of varying degrees of virulence for each virus, and
+their preservation by suitable methods of cultivation; to the practical
+application, finally, of those new facts in animal medicine.</p>
+
+<p>New microbic prophylactic viruses have been added to those of
+fowl-cholera and of splenic fever. The animals saved from death by
+contagious diseases are now counted by hundreds of thousands, and the
+sharp opposition which those scientific novelties met with at the
+beginning was soon swept away by the rapidity of their onward progress.</p>
+
+<p>Will the circle of practical applications of those new notions be
+limited in future to the prophylaxis of animal distempers? We must
+never think little of a new discovery, nor despair of its fecundity;
+but more than that, in the present instance, it may be asserted that
+the question is already solved in principle. Thus, splenic fever is
+common to animals and man, and we make bold to declare that, were it
+necessary to do so, nothing could be easier than to render man also
+proof against that affection. The process which is employed for animals
+might, almost without a change, be applied to him also. It would simply
+become advisable to act with an amount of prudence which the value of
+the life of an ox or a sheep does not call for. Thus, we should use
+three or four vaccine-viruses instead of two, of progressive intensity
+of virulence, and choose the first ones so weak that the patient
+should never be exposed to the slightest morbid complication, however
+susceptible to the disease he might be by his constitution.</p>
+
+<p>The difficulty, then, in the case of human diseases, does not lie in
+the application of the new method of prophylaxis, but rather in the<span class="pagenum" id="Page_306">[Pg 306]</span>
+knowledge of the physiological properties of their viruses. All our
+experiments must tend to discover the proper degree of attenuation
+for each virus. But experimentation, if allowable on animals, is
+criminal on man. Such is the principal cause of the complication of
+researches bearing on diseases exclusively human. Let us keep in mind,
+nevertheless, that the studies of which we are speaking were born
+yesterday only, that they have already yielded valuable results, and
+that new ones may be fairly expected when we shall have gone deeper
+into the knowledge of animal maladies, and of those in particular which
+affect animals in common with man.</p>
+
+<p>The desire to penetrate farther forward in that double study led me to
+choose rabies as the subject of my researches, in spite of the darkness
+in which it was veiled.</p>
+
+<p>The study of rabies was begun in my laboratory four years ago, and
+pursued since then without other interruption than what was inherent
+to the nature of the researches themselves, which present certain
+unfavourable conditions. The incubation of the disease is always
+protracted, the space disposed of is never sufficient, and it thus
+becomes impossible at a given moment to multiply the experiments as
+one would like. Notwithstanding those material obstacles, lessened by
+the interest taken by the French Government in all questions of great
+scientific interest, we now no longer count the experiments which we
+have made, my fellow workers and myself. I shall limit myself to-day to
+an exposition of our latest acquisitions.</p>
+
+<p>The name alone of a disease, and of rabies above all others, at once
+suggests to the mind the notion of a remedy.</p>
+
+<p>But it will, in the majority of cases, be labour lost to aim in the
+first instance at discovering a mode of cure. It is, in a manner,
+leaving all progress to chance. Far better to endeavour to acquaint
+oneself, first of all, with the nature, the cause, and the evolution of
+the disease, with a glimmering hope, perhaps, of finally arriving at
+its prophylaxis.</p>
+
+<p>To this last method we are indebted for the result that rabies is no
+longer to-day to be considered as an insoluble riddle.</p>
+
+<p>We have found that the virus of rabies develops itself invariably in
+the nervous system, brain, and spinal cord, in the nerves, and in the
+salivary glands; but it is not present at the same moment in every
+one of those parts. It may, for example, develop itself at the lower
+extremity<span class="pagenum" id="Page_307">[Pg 307]</span> of the spinal cord, and only after a time reach the brain.
+It may be met with at one or at several points of the encephalon whilst
+being absent at certain other points of the same region.</p>
+
+<p>If an animal is killed whilst in the power of rabies, it may require
+a pretty long search to discover the presence here or there in the
+nervous system, or in the glands, of the virus of rabies. We have been
+fortunate enough to ascertain that in all cases, when death has been
+allowed to supervene naturally, the swelled-out portion, or bulb, of
+the medulla oblongata nearest to the brain, and uniting the spinal
+cord with it, is always rabid. When an animal has died of rabies (and
+the disease always ends in death), rabid matter can with certainty be
+obtained from its bulb, capable of reproducing the disease in other
+animals when inoculated into them, after trephining, in the arachnoid
+space of the cerebral meninges.</p>
+
+<p>Any street dog whatsoever, inoculated in the manner described with
+portions of the bulb of an animal which has died of rabies, will
+certainly develop the same disease. We have thus inoculated several
+hundreds of dogs brought without any choice from the pound. Never once
+was the inoculation a failure. Similarly also, with uniform success,
+several hundred guinea-pigs, and rabbits more numerous still.</p>
+
+<p>Those two great results, the constant presence of the virus in the
+bulb at the time of death, and the certainty of the reproduction
+of the disease by inoculation into the arachnoid space, stand out
+like experimental axioms, and their importance is paramount. Thanks
+to the precision of their application, and to the well-known daily
+repetition of those two criteria of our experiments, we have been
+able to move forward steadily and surely in that arduous study. But,
+however solid those experimental bases, they were, nevertheless,
+incapable in themselves of giving us the faintest notion as to some
+method of vaccination against rabies. In the present state of science
+the discovery of a method of vaccination against some virulent malady
+presupposes:</p>
+
+<p>1. That we have to deal with a virus capable of assuming diverse
+intensities, of which the weaker ones can be put to vaccinal or
+protective uses.</p>
+
+<p>2. That we are in possession of a method enabling us to reproduce those
+diverse degrees of virulence at will.</p>
+
+<p>At the present time, however, science is acquainted with one sort of
+rabies only—viz., dog rabies.</p>
+
+<p><span class="pagenum" id="Page_308">[Pg 308]</span></p>
+
+<p>Rabies, whether in dog, man, horse, ox, wolf, fox, etc., comes
+originally from the bite of a mad dog. It is never spontaneous,
+neither in the dog nor in any other animal. There are none seriously
+authenticated among the alleged cases of so-called spontaneous rabies,
+and I add that it is idle to argue that the first case of rabies of
+all must have been spontaneous. Such an argument does not solve the
+difficulty, and wantonly calls into question the as yet inscrutable
+problem of the origin of life. It would be quite as well, against the
+assertion that an oak tree always proceeded from another oak tree, to
+argue that the first of all oak trees that ever grew must have been
+produced spontaneously. Science, which knows itself, is well aware that
+it would be useless for her to discuss about the origin of things;
+she is aware that, for the present at any rate, that origin is placed
+beyond the ken of her investigations.</p>
+
+<p>In fine, then, the first question to be solved on our way towards the
+prophylaxis of rabies is that of knowing whether the virus of that
+malady is susceptible of taking on varying intensities, after the
+manner of the virus of fowl-cholera or of splenic fever.</p>
+
+<p>But in what way shall we ascertain the possible existence of varying
+intensities in the virus of rabies? By what standard shall we measure
+the strength of a virus which either fails completely or kills? Shall
+we have recourse to the visible symptoms of rabies? But those symptoms
+are extremely variable, and depend essentially on the particular point
+of the encephalon or of the spinal cord where the virus has in the
+first instance fixed and developed itself. The most caressing rabies,
+for such do exist, when inoculated into another animal of the same
+species, give rise to furious rabies of the intensest type.</p>
+
+<p>Might we then perhaps make use of the duration of incubation as a
+means of estimating the intensity of our virus? But what can be more
+changeful than the incubative period? Suppose a mad dog were to bite
+several sound dogs: one of them will take rabies in one month or six
+weeks, another after two or three months or more. Nothing, too, is more
+changeful than the length of incubation according to the different
+modes of inoculation. Thus, other circumstances the same, after bites
+or hypodermic inoculation rabies occasionally develops itself, and at
+other times aborts completely; but inoculations on the brain are never
+sterile, and give the disease after a relatively short incubation.</p>
+
+<p><span class="pagenum" id="Page_309">[Pg 309]</span></p>
+
+<p>It is possible, nevertheless, to gauge with sufficient accuracy the
+degree of intensity of our virus by means of the time of incubation,
+on condition that we make use exclusively of the intra-cranial mode
+of inoculation; and secondly, that we do away with one of the great
+disturbing influences inherent to the results of inoculation made
+by bites, under the skin or in the veins, by injecting the right
+proportion of material.</p>
+
+<p>The duration of incubation, as a matter of fact, may depend largely
+on the quantity of efficient virus—that is to say, on the quantity
+of virus which reaches the nervous system without diminution or
+modification. Although the quantity of virus capable of giving rabies
+may be, so to speak, infinitely small, as seen in the common fact of
+the disease developing itself after rabid bites which, as a rule,
+introduce into the system a barely appreciable weight of virus, it
+is easy to double the length of incubation by simply changing the
+proportion of those very small quantities of inoculated matter. I may
+quote the following examples:—</p>
+
+<p>On May 10, 1882, we injected into the popliteal vein of a dog ten drops
+of a liquid prepared by crushing a portion of the bulb of a dog, which
+had died of ordinary canine madness, in three or four times its volume
+of sterilised broth.</p>
+
+<p>Into a second dog we injected 1/100th of that quantity, into a third
+1/200th. Rabies showed itself in the first dog on the eighteenth day
+after the injection, on the thirty-fifth day in the second dog, whilst
+the third one did not take the disease at all, which means that, for
+the last animal, with the particular mode of inoculation employed, the
+quantity of virus injected was not sufficient to give rabies. And yet
+that dog, like all dogs, was susceptible of taking the disease, for it
+actually took it twenty-two days after a second inoculation, performed
+on September 3, 1882.</p>
+
+<p>I now take another example bearing on rabbits, and by a different mode
+of inoculation. This time, after trephining, the bulb of a rabbit
+which had died of rabies after inoculation of an extremely powerful
+virus is triturated and mixed with two or three times its volume of
+sterilised broth. The mixture is allowed to stand a little, and then
+two drops of the supernatant liquid are injected after trephining into
+a first rabbit, into a second rabbit one-fourth of that quantity, and
+in succession into other rabbits, 1/16th, 1/64th, 1/128th, and 1/152nd<span class="pagenum" id="Page_310">[Pg 310]</span>
+of that same quantity. All those rabbits died of rabies, the incubation
+having been eight days, nine and ten days for the third and fourth,
+twelve and sixteen days for the last ones.</p>
+
+<p>Those variations in the length of incubation were not the result of
+any weakening or diminution of the intrinsic virulence of the virus
+brought on possibly by its dilution, for the incubation of eight days
+was at once recovered when the nervous matter of all those rabbits was
+inoculated into new animals.</p>
+
+<p>Those examples show that, whenever rabies follows upon bites or
+hypodermic inoculations, the differences in respect of length of
+incubation must be chiefly ascribed to the variations, at times within
+considerable limits, of the ever-undeterminate proportions of the
+inoculated viruses which reach the central nervous system.</p>
+
+<p>If, therefore, we desire to make use of the length of incubation as a
+measure of the intensity of the virulence, it will be indispensable
+to have recourse to inoculation on the surface of the brain, after
+trephining, a process the action of which is absolutely certain,
+coupled with the use of a larger quantity of virus than what is
+strictly sufficient to give rise to rabies. By those means the
+irregularities in the length of incubation for the same virus tend to
+disappear completely, because we always have the maximum effect which
+that virus can produce; that maximum coincides with a minimum length of
+incubation.</p>
+
+<p>We have thus, finally, become possessed of a method enabling us to
+investigate the possible existence of different degrees of virulence,
+and to compare them with one another. The whole secret of the method,
+I repeat, consists in inoculating on the brain, after trephining, a
+quantity of virus which, although small in itself, is still greater
+than what is simply necessary to reproduce rabies. We thus disengage
+the incubation from all disturbing influences and render its duration
+dependent exclusively on the activity of the particular virus used,
+that activity being in each case estimated by the minimum incubation
+determined by it.</p>
+
+<p>This method was applied in the first instance to the study of canine
+madness, and in particular to the question of knowing whether
+dog-madness was always one and the same, with perhaps the slight
+variations which might be due to the differences of race in diverse
+dogs.</p>
+
+<p>We accordingly got hold of a number of dogs affected with ordinary
+street rabies, at all times of the year, at all seasons of the same<span class="pagenum" id="Page_311">[Pg 311]</span>
+year or of different years, and belonging to the most dissimilar canine
+races. In each case the bulbar portion of the medulla oblongata was
+taken out from the recently dead animal, triturated and suspended in
+two or three times its volume of sterilised liquid, making use all
+along of every precaution to keep our materials pure, and two drops
+of this liquid injected after trephining into one or two rabbits.
+The inoculation is made with a Pravaz syringe, the needle of which,
+slightly curved at its extremity, is inserted through the dura-mater
+into the arachnoid space. The results were as follows: all the rabbits,
+from whatever sort of dog inoculated, showed a period of incubation
+which ranged between twelve and fifteen days, without almost a single
+exception. Never did they show an incubation of eleven, ten, nine, or
+eight days, never an incubation of several weeks or of several months.</p>
+
+<p>Dog-rabies, the ordinary rabies, the only known rabies, is thus
+sensibly one in its virulence, and its modifications, which are very
+limited, appear to depend solely on the varying aptitude for rabies
+of the different known races. But we are going now to witness a deep
+change in the virulence of dog-rabies.</p>
+
+<p>Let us take one, any one, of our numerous rabbits, inoculated with the
+virus of an ordinary mad dog, and, after it has died, extract its bulb,
+prepare it just as described, and inject two drops of the bulb-emulsion
+into the arachnoid space of a second rabbit, whose bulb will in turn
+and in time be injected into a third rabbit, the bulb of which again
+will serve for a fourth rabbit, and so on.</p>
+
+<p>There will be evidence, even from the first few passages, of a marked
+tendency towards a lessening of the period of incubation in the
+succeeding rabbits. Just one example:</p>
+
+<p>Towards the end of the year 1882 fifteen cows and one bull died of
+rabies on a farm situated in the neighbourhood of the town of Melun.
+They had been bitten on October 2 by the farm dog, which had become
+mad. The head of one of the cows, which had died on November 15, was
+sent to my laboratory by M. Rossignol, a veterinary surgeon in Melun.
+A number of experiments were made on dogs and rabbits, and showed that
+the following parts, the only encephalic (or those pertaining to the
+brain) ones tested, were rabid: the bulb, the cerebellum, the frontal
+lobe, the sphenoidal lobe. The rabbits trephined and inoculated with
+those different parts showed the first symptoms of rabies on the
+seventeenth and eighteenth days after<span class="pagenum" id="Page_312">[Pg 312]</span> inoculation. With the bulb of
+one of those rabbits two more were inoculated, of which one took rabies
+on the fifteenth day, the other on the twenty-third day.</p>
+
+<p>We may notice, once for all, that when rabies is transferred from one
+animal to another of a different species, the period of incubation is
+always very irregular at first in the individuals of the second species
+if the virus had not yet become fixed in its maximum virulence for the
+first species. We have just seen an example of that phenomenon, since
+one of the rabbits had an incubation of fifteen days, the other of
+twenty-three days, both having received the same virus and all other
+circumstances remaining apparently the same for them.</p>
+
+<p>The bulb of the first one of those last rabbits which died was
+injected into two more rabbits, still after trephining. One of them
+took rabies on the tenth day, the other on the fourteenth day. The
+bulb of the first one that died was again injected into a couple of
+new rabbits, which developed the disease in ten days and twelve days
+respectively. A fifth time two new animals were inoculated from the
+first one that died, and they both took the disease on the eleventh day
+after inoculation: similarly, a sixth passage was made, and gave an
+incubation of eleven days, twelve days for the seventh passage, ten and
+eleven for the eighth, ten days for the ninth and tenth passages, nine
+days for the eleventh, eight and nine days for the twelfth, and so on,
+with differences of twenty-four hours at the most, until we got to the
+twenty-first passage, when rabies declared itself in eight days, and
+subsequently to that always in eight days up to the fiftieth passage,
+which was only effected a few days ago. That long experimental series
+which is still going on was begun on November 15, 1882, and will be
+kept up for the purpose of preserving in our rabies virus that maximum
+virulence which it has come to now for some considerable time, as it is
+easy to calculate.</p>
+
+<p>Allow me to call your attention to the ease and safety of the
+operations for trephining and then inoculating the virus. Throughout
+the last twenty months we have been able without a single interruption
+in the course of the series to carry the one initial virus through a
+succession of rabbits which were all trephined and inoculated every
+twelfth day or so.</p>
+
+<p>Guinea-pigs reach more rapidly the maximum virulence of which they are
+susceptible. The period of incubation is in them also variable<span class="pagenum" id="Page_313">[Pg 313]</span> and
+irregular at the beginning of the series of successive passages, but
+it soon enough fixes itself at a minimum of five days. The maximum
+virulence in guinea-pigs is reached after seven or eight passages only.
+It is worth noting that the number of passages required before reaching
+the maximum virulence, both in guinea-pigs and in rabbits, varies with
+the origin of the first virus with which the series is begun.</p>
+
+<p>If now this rabies with maximum virulence be transferred again into the
+dog from guinea-pig or rabbit, there is produced a dog-virus which in
+point of virulence goes far beyond that of ordinary canine madness.</p>
+
+<p>But, a natural query—of what use can be that discovery as to the
+existence and artificial production of diverse varieties of rabies,
+every one of them more violent and more rapidly fatal than the habitual
+madness of the dog? The man of science is thankful for the smallest
+find he can make in the field of pure science, but the many, terrified
+at the very name of hydrophobia, claim something more than mere
+scientific curiosities. How much more interesting it would be to become
+acquainted with a set of rabies viruses which should, on the contrary,
+be possessed of attenuated degrees of virulence! Then, indeed, might
+there be some hope of creating a number of vaccinal rabies viruses
+such as we have done for the virus of fowl-cholera, of the microbe of
+saliva, of the red evil of swine (swine-plague), and even of acute
+septicæmia. Unfortunately, however, the methods which had served for
+those different viruses showed themselves to be either inapplicable
+or inefficient in the case of rabies. It therefore became necessary
+to find out new and independent methods, such, for example, as the
+cultivation <i>in vitro</i> of the mortal rabies virus.</p>
+
+<p>Jenner was the first to introduce into current science the opinion that
+the virus which he called the grease of the horse, and which we call
+now more exactly horse-pox, probably softened its virulence, so to
+speak, in passing through the cow and before it could be transferred
+to man without danger. It was therefore natural to think of a possible
+diminution of the virulence of rabies by a number of passages through
+the organisms of some animal or other, and the experiment was worth
+trying. A large number of attempts were made, but the majority of the
+animal species experimented on exalted the virulence after the manner
+of rabbits and guinea-pigs; fortunately, however, it was not so with
+monkey.</p>
+
+<p><span class="pagenum" id="Page_314">[Pg 314]</span></p>
+
+<p>On December 6, 1883, a monkey was trephined and inoculated with the
+bulb of a dog, which had itself been similarly inoculated from a child
+who had died of rabies. The monkey took rabies eleven days later, and
+when dead served for inoculation into a second monkey, which also took
+the disease on the eleventh day. A third monkey, similarly inoculated
+from the second one, showed the first symptoms on the twenty-third
+day, etc. The bulb of each one of the monkeys was inoculated, after
+trephining, into two rabbits each time. The rabbits inoculated from the
+first monkey developed rabies between thirteen and sixteen days, those
+from the second monkey between fourteen and twenty days, those from
+the third monkey between twenty-six and thirty days, those from the
+fourth monkey both of them after the twenty-eighth day, those from the
+fifth monkey after twenty-seven days, those from the sixth monkey after
+thirty days.</p>
+
+<p>It cannot be doubted after that, that successive passages through
+monkeys, and from the several monkeys to rabbits, do diminish the
+virulence of the virus for the latter animals; they diminish it for
+dogs also. The dog inoculated with the bulb of the fifth monkey gave
+an incubation of no less than fifty-eight days, although it had been
+inoculated in the arachnoid space.</p>
+
+<p>The experiments were renewed with fresh sets of monkeys and led
+to similar results. We were therefore actually in possession of a
+method by means of which we could attenuate the virulence of rabies.
+Successive inoculations from monkey to monkey elaborate viruses which,
+when transferred to rabbits, reproduce rabies in them, but with a
+progressively lengthening period of incubation. Nevertheless, if one of
+those rabbits be taken as the first for inoculations through a series
+of rabbits, the rabies thus cultivated obeys the law which we have seen
+before, and has its virulence increased at each passage.</p>
+
+<p>The practical application of those facts gives us a method for the
+vaccination of dogs against rabies. As a starting point, make use of
+one of the rabbits inoculated from a monkey sufficiently removed from
+the first animal of the monkey series for the inoculation—hypodermic
+or intra-venous—of that rabbit’s bulb not to be mortal for a new
+rabbit. The next vaccinal inoculations are made with the bulbs of
+rabbits derived by successive passages from that first rabbit.</p>
+
+<p>In the course of our experiments we made use, as a rule, for
+inoculation, of the virus of rabbits which had died after an incubation
+of<span class="pagenum" id="Page_315">[Pg 315]</span> four weeks, repeating three or four times each the vaccinal
+inoculations made with the bulbs of rabbits derived in succession
+from one another and from the first one of the series, itself coming
+directly from the monkey. I abstain from giving more details, because
+certain experiments which are actually going on allow me to expect that
+the process will be greatly simplified.</p>
+
+<p>You must be feeling, gentlemen, that there is a great blank in my
+communication; I do not speak of the micro-organism of rabies. We have
+not got it. The process for isolating it is still imperfect, and the
+difficulties of its cultivation outside the bodies of animals have not
+yet been got rid of, even by the use, as pabulum, of fresh nervous
+matter. The methods which we employed in our study of rabies ought all
+the more perhaps, on that account, to fix attention. Long still will
+the art of preventing diseases have to grapple with virulent maladies
+the micro-organic germs of which will escape our investigations. It is,
+therefore, a capital scientific fact that we should be able, after all,
+to discover the vaccination process for a virulent disease without yet
+having at our disposal its special virus and whilst yet ignorant of how
+to isolate or to cultivate its microbe.</p>
+
+<p>As soon as the method for the vaccination of dogs was firmly
+established, and we had in our possession a large number of dogs which
+had been rendered refractory to rabies, I had the idea of submitting
+to a competent committee those of the facts which appeared destined in
+future to serve as a basis for the vaccination of dogs against rabies.
+That course was suggested to me in prevision of the later practical
+application of the method, by the recollection of the opposition with
+which Jenner’s discovery met at its beginning.</p>
+
+<p>I spoke of my project to M. Fallières, the Minister of Public
+Instruction, who was pleased to approve of it and gave commission to
+the following gentlemen to control the facts which I had summarily
+communicated to the Academy of Sciences in its sitting of May 19 last:
+Messrs. Béclard, Paul Bert, Bouley, Aimeraud, Villemin, Vulpian. M.
+Bouley was appointed president, Dr. Villemin, secretary, and the
+commission at once set to work. I have the pleasure of informing
+you that it has just sent in a first report to the Minister. I was
+acquainted with it here, and the following are in a few words, the
+facts related in that first report on rabies. I had given to the
+commission nineteen vaccinated dogs in succession—that is to say,<span class="pagenum" id="Page_316">[Pg 316]</span>
+dogs which had been rendered refractory by preventive inoculations.
+Thirteen only of them had after their vaccination been already
+submitted to the test-inoculation on the brain.</p>
+
+<p>The nineteen dogs were, for the sake of comparison, divided into
+sets along with nineteen more control dogs brought from the pound
+without any sort of selection. To begin with, two refractory dogs
+and two control dogs were on June 1 trephined and inoculated under
+the dura-mater, on the surface of the brain, with the bulb of a dog
+affected with ordinary street rabies.</p>
+
+<p>On June 3 another refractory dog and another control dog were bitten by
+a furious street mad dog.</p>
+
+<p>The same furious mad dog was on June 4 made to bite still another
+refractory and another control dog. On June 6 the furious dog which
+had been utilised on June 3 and 4 died. The bulb was taken out and
+inoculated, after trephining, into three refractory dogs and three
+control dogs. On June 10 another street mad dog, having been secured,
+was, by the commission, made to bite one refractory and one control
+dog. On June 16 the commission had two new dogs, a refractory one and
+a control one, bitten by one of the control dogs of June 1, which had
+been seized with rabies on June 14 in consequence of the inoculation
+after trephining which it had received on June 1.</p>
+
+<p>On June 19 the commission got three refractory and three control dogs
+inoculated before their own eyes in the popliteal vein with the bulb
+of an ordinary street mad dog. On June 20 they had inoculated in
+their presence, and still in a vein, ten dogs altogether, six of them
+refractory and four just brought from the pound.</p>
+
+<p>On June 28, the Commission hearing that M. Paul Simon, a veterinary
+surgeon, had a furious biting mad dog, had four of their dogs, two
+refractory and two control dogs, taken to his place and bitten by the
+mad dog.</p>
+
+<p>The Rabies Commission have, therefore, experimented on thirty-eight
+dogs altogether—namely, nineteen refractory dogs and nineteen control
+dogs susceptible of taking the disease. Those of the dogs which have
+not died in consequence of the operations themselves are still under
+observation, and will long continue to be. The commission, reporting
+up to the present moment on their observations as to the state of the
+animals tried and tested by them, find that out of the nineteen control
+dogs six were bitten, of which six three have taken<span class="pagenum" id="Page_317">[Pg 317]</span> rabies. Seven
+received intra-venous inoculations, of which five have died of rabies.
+Five were trephined and inoculated on the brain; the five have died of
+rabies.</p>
+
+<p>On the other hand, not one of the nineteen vaccinated dogs has taken
+rabies.</p>
+
+<p>In the course of the experiments, on July 13, one of the refractory
+dogs died in consequence of a black diarrhœa which had begun in the
+first days of July. In order to ascertain whether rabies had anything
+to do with it as the cause of death, its bulb was at once inoculated,
+after trephining, into three rabbits and one guinea-pig. All four
+animals are still to-day in perfect health, a certain proof that the
+dog died of some common malady, and not of rabies.</p>
+
+<p>The second report of the Commission will be concerned with the
+experiments made as to the refractoriness to rabies of twenty dogs to
+be vaccinated by the Commission themselves.</p>
+
+<p>(<i>M. Pasteur then announced that he had just received that same
+morning the first report addressed to M. Fallières by the Official
+Commission on Rabies. It states that twenty-three refractory dogs were
+bitten by ordinary mad dogs, and that not one of them had taken rabies.
+On the other hand, within two months after the bites, 66 per cent. of
+the normal dogs similarly bitten had already taken the disease.</i>)</p>
+
+
+<p class="space-above2 space-below2">
+<i>November 1, 1886.—New Communication on Rabies.</i>—On October 26,
+1885, I acquainted the Academy with a method of prophylaxis of rabies
+after bites. Numerous applications on dogs had justified me in trying
+it on man. As early as March 1, 350 persons bitten by dogs undoubtedly
+mad, and several more by dogs simply suspected of rabies, had already
+been treated at my laboratory by Dr. Grancher. And in consideration
+of the happy results obtained it appeared to me that it had become
+necessary to found an establishment for anti-rabic vaccinations.</p>
+
+<p>To-day, October 31, 1886, 2,490 persons have received the preventive
+inoculations in Paris alone. The treatment was in the first instance
+uniform for the great majority of the patients, notwithstanding the
+different conditions presented by them as to age, sex, the number of
+bites received, their seat, their depth, and the time which had elapsed
+since the occurrence of the accident. It lasted ten days,<span class="pagenum" id="Page_318">[Pg 318]</span> the patient
+receiving every day an injection prepared from the spinal marrow of a
+rabbit, beginning with that of fourteen days’ and ending with that of
+five days’ desiccation.</p>
+
+<p class="space-below2">
+Those 2,490 cases are subdivided according to nationality in the
+following manner:</p>
+
+
+<table class="autotable">
+<tbody><tr>
+<td class="tdl">Russia</td>
+<td class="tdr">191</td>
+</tr><tr>
+<td class="tdl">Italy</td>
+<td class="tdr">165</td>
+</tr><tr>
+<td class="tdl">Spain</td>
+<td class="tdr">107</td>
+</tr><tr>
+<td class="tdl">England</td>
+<td class="tdr">80</td>
+</tr><tr>
+<td class="tdl">Belgium</td>
+<td class="tdr">57</td>
+</tr><tr>
+<td class="tdl">Austria</td>
+<td class="tdr">52</td>
+</tr><tr>
+<td class="tdl">Portugal</td>
+<td class="tdr">25</td>
+</tr><tr>
+<td class="tdl">Roumania</td>
+<td class="tdr">22</td>
+</tr><tr>
+<td class="tdl">United States</td>
+<td class="tdr">18</td>
+</tr><tr>
+<td class="tdl">Holland</td>
+<td class="tdr">14</td>
+</tr><tr>
+<td class="tdl">Greece</td>
+<td class="tdr">10</td>
+</tr><tr>
+<td class="tdl">Germany</td>
+<td class="tdr">9</td>
+</tr><tr>
+<td class="tdl">Turkey</td>
+<td class="tdr">7</td>
+</tr><tr>
+<td class="tdl">Brazil</td>
+<td class="tdr">3</td>
+</tr><tr>
+<td class="tdl">India</td>
+<td class="tdr">2</td>
+</tr><tr>
+<td class="tdl">Switzerland</td>
+<td class="tdr">2</td>
+</tr><tr>
+<td class="tdl">France and Algeria</td>
+<td class="tdr">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1,726</td>
+</tr>
+</tbody>
+</table>
+
+<p class="space-above2">
+The number of French persons has been considerable, amounting to 1,726,
+and it will be enough to confine ourselves to the category formed by
+them as a basis for discussing the degree of efficacy of the method.</p>
+
+<p>Out of the total 1,726 cases treated, the treatment has failed ten
+times—namely, in the following cases:</p>
+
+<p>The children: Lagut, Peytel, Clédière, Moulis, Astier, Videau.</p>
+
+<p>The woman: Leduc, seventy years old.</p>
+
+<p>The men: Marius Bouvier (thirty years), Clergot (thirty), and Norbert
+Magnevon (eighteen).</p>
+
+<p>I leave out of count two other persons, Louise Pelletier and Moermann,
+whose deaths must be attributed to their tardy arrival at the
+laboratory, Louise Pelletier thirty-six days, and Moermann forty-three
+days after they had been bitten.</p>
+
+<p>We have therefore ten deaths for 1,726 cases, or 1 in 170; such<span class="pagenum" id="Page_319">[Pg 319]</span> are,
+for France and Algeria, the results of the first year’s application of
+the method.</p>
+
+<p>Those statistics, taken as a whole, demonstrate the efficacy of the
+treatment, as proved further by the relatively large number of deaths
+which occurred amongst bitten persons who had not been vaccinated.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_35" href="#FNanchor_35" class="label">[35]</a>
+From Address delivered August 10, 1884 at the Copenhagen
+meeting of the International Medical Congress.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_320">[Pg 320]</span></p>
+<h2 class="nobreak" id="XXXIII">XXXIII<br>
+JAMES CLERK MAXWELL<br>
+1831-1879</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>James Clerk Maxwell, born November 13, 1831, attended Edinburgh
+University 1847-1850. Entering Cambridge, he graduated second wrangler
+in 1854. He then taught for four years in Marischal College, Aberdeen,
+and in 1860 was called to King’s College, London, where he remained for
+the following eight years. He early revealed his mathematical genius
+and before he was nineteen had the honor of reading several pages
+before the Royal Society of Edinburgh. He developed by mathematics the
+theory that electricity was a condition of stress or strain in the
+ether, a wave moving in the same medium as light and traveling at the
+same rate of speed. The theory was substantiated by the experiments of
+Hertz, a pupil of Helmholtz, who in 1887 proved the existence of the
+waves which now bear his name. Maxwell died at Cambridge, November 5,
+1879.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE MAXWELL AND HERTZ THEORY OF ELECTRICITY AND LIGHT<a id="FNanchor_36" href="#Footnote_36" class="fnanchor">[36]</a></p>
+
+<p>It was at the moment when the experiments of Fresnel were forcing
+the scientific world to admit that light consists of the vibrations
+of a highly attenuated fluid filling interplanetary spaces that the
+researches of Ampère were making known the laws of the mutual action
+of currents and were so enunciating the fundamental principles of
+electro-dynamics.</p>
+
+<p>It needed but one step to the supposition that that same fluid, the
+ether, which is the medium of luminous phenomena, is at the same<span class="pagenum" id="Page_321">[Pg 321]</span>
+time the vehicle of electrical action. In imagination Ampère made
+this stride; but the illustrious physicist could not foresee that the
+seducing hypothesis with which he was toying, a mere dream for him, was
+ere long to take a precise form and become one of the vital concerns of
+exact science.</p>
+
+<p>A dream it remained for many years, till one day, after electrical
+measurements had become extremely exact, some physicist, turning over
+the numerical data, much as a resting pedestrian might idly turn over
+a stone, brought to light an odd coincidence. It was that the factor
+of transformation between the system of electro-statical units and the
+system of electro-dynamical units was equal to the velocity of light.
+Soon the observations directed to this strange coincidence became so
+exact that no sane head could longer hold it a mere coincidence. No
+longer could it be doubted that some occult affinity existed between
+optical and electrical phenomena. Perhaps, however, we might be
+wondering to this day what this affinity could be were it not for the
+genius of Clerk Maxwell.</p>
+
+
+<p class="nindc space-above2 space-below2">
+DISPLACEMENT CURRENTS</p>
+
+<p>The reader is aware that solid bodies are divided into two classes,
+conductors through which electricity can move in the form of a galvanic
+current, and nonconductors, or dielectrics. The electricians of former
+days regarded dielectrics as quite inert, having no part to play but
+that of obstinately refusing passage to electricity. Had that been so,
+any one non-conductor might be replaced by any other without making
+any difference in the phenomena; but Faraday found that that was not
+the case. Two condensers of the same form and dimensions put into
+connection with the same source of electricity do not take the same
+charge, though the thickness of the isolating plate be the same, unless
+the matter of that plate be chemically the same. Now Clerk Maxwell had
+too deeply studied the researches of Faraday not to comprehend the
+importance of dielectrics and the imperative obligation to recognize
+their active part.</p>
+
+<p>Besides, if light is but an electric phenomenon, when it traverses a
+thickness of glass electrical events must take place in that glass. And
+what can be the nature of those events? Maxwell boldly answers, they
+are, and must be, currents.</p>
+
+<p>All the experience of his day seemed to contradict this. Never had<span class="pagenum" id="Page_322">[Pg 322]</span>
+currents been observed except in conductors. How was Maxwell to
+reconcile his audacious hypothesis with a fact so well established
+as that? Why is it that under certain circumstances those supposed
+currents produce manifest effects, while under ordinary conditions they
+can not be observed at all?</p>
+
+<p>The answer was that dielectrics resist the passage of electricity not
+so much more than conductors do, but in a different manner. Maxwell’s
+idea will best be understood by a comparison.</p>
+
+<p>If we bend a spring, we meet a resistance which increases the more
+the spring is bended. So, if we can only dispose of a finite force, a
+moment will come when the motion will cease, equilibrium being reached.
+Finally, when the force ceases the spring will in flying back restore
+the whole of the energy which has been expended in bending it.</p>
+
+<p>Suppose, on the other hand, that we wish to displace a body plunged
+into water. Here again a resistance will be experienced, but it will
+not go on increasing in proportion as the body advances, supposing it
+to be maintained at a constant velocity. So long as the motive force
+acts, equilibrium will never, then, be attained; nor when the force
+is removed will the body in the least tend to return, nor can any
+portion of the energy expended be restored. It will, in fact, have been
+converted into heat by the viscosity of the water.</p>
+
+<p>The contrast is plain; and we ought to distinguish elastic resistance
+from viscous resistance. Using these terms, we may express Maxwell’s
+idea by saying that dielectrics offer an elastic resistance, conductors
+a viscous resistance, to the movements of electricity. Hence, there
+are two kinds of currents; currents of displacement which traverse
+dielectrics and ordinary currents of conduction which circulate in
+conductors.</p>
+
+<p>Currents of the first kind, having to overcome an elastic resistance
+which continually increases, naturally can last but a very short time,
+since a state of equilibrium will quickly be reached.</p>
+
+<p>Currents of conduction, on the other hand, having only a viscous
+resistance to overcome, must continue so long as there is any
+electromotive force.</p>
+
+<p>Let us return to the simile used by M. Cornu in his notice in the
+Annuaire du Bureau des Longitudes for 1893. Suppose we have in a
+reservoir water under pressure. Lead a tube plumb downward into<span class="pagenum" id="Page_323">[Pg 323]</span> the
+reservoir. The water will rise in the tube, but the rise will stop
+when hydrostatic equilibrium is attained—that is, when the downward
+pressure of the water in the tube above the point of application of the
+first pressure on the reservoir, and due to the weight of the water,
+balances that first pressure. If the pipe is large, there will be no
+friction or loss of head, and the water so raised can be used to do
+work. That represents a current of displacement.</p>
+
+<p>If, on the other hand, the water flows out of the reservoir by a
+horizontal pipe, the motion will go on till the reservoir is emptied;
+but if the tube is small and long there will be a great loss of energy
+and considerable production of heat by friction. That represents a
+current of conduction.</p>
+
+<p>Though it would be vain, not to say idle, to attempt to represent all
+details, it may be said that everything happens just as if the currents
+of displacement were acting to bend a multitude of little springs.
+When the currents cease, electrostatic equilibrium is established,
+and the springs are bent the more, the more intense is the electric
+field. The accumulated work of the springs—that is, the electrostatic
+energy—can be entirely restored as soon as they can unbend, and so it
+is that we obtain mechanical work when we leave the conductors to obey
+the electrostatic attractions. Those attractions must be due to the
+pressure exercised on the conductors by the bent springs. Finally, to
+pursue the image to the death, the disruptive discharge may be compared
+to the breaking of the springs when they are bent too much.</p>
+
+<p>On the other hand, the energy employed to produce conduction currents
+is lost, being wholly converted into heat, like that spent in
+overcoming the viscosity of fluids. Hence it is that the conducting
+wires become heated.</p>
+
+<p>From Maxwell’s point of view it seems that all currents are in closed
+circuits. The older electricians did not so opine. They regarded the
+current circulating in a wire joining the two poles of a pile as
+closed; but if in place of directly uniting the two poles we place them
+in communication with the two armatures of a condenser, the momentary
+current which lasts while the condenser is getting charged was not
+considered as a current round a closed circuit. It went, they thought,
+from one armature through the wire, the battery, the other wire, to
+the other armature, and there it stopped. Maxwell, on the contrary,
+supposed that in the form of a current of displacement it passes
+through<span class="pagenum" id="Page_324">[Pg 324]</span> the nonconducting plate of the condenser, and that precisely
+what brings it to cessation is the opposite electromotive force set up
+by the displacement of electricity in this dielectric.</p>
+
+<p>Currents become sensible in three ways—by their heating effects, by
+their actions on other currents and on magnets, and by the induced
+currents to which they give rise. We have seen why currents of
+conduction develop heat and why currents of displacement do not.
+But Maxwell’s hypothetical currents ought at any rate to produce
+electro-magnetic and inductive effects. Why do these effects not
+appear? The answer is, that it is because a current of displacement
+can not last long enough. That is to say, they can not last long in
+one direction. Consequently in a dielectric no current can long exist
+without alteration. But the effects ought to and will become observable
+if the current is continually reversed at sufficiently short intervals.</p>
+
+
+<p class="nindc space-above2 space-below2">
+THE NATURE OF LIGHT</p>
+
+<p>Such, according to Maxwell, is the origin of light. A luminiferous wave
+is a series of alternating currents produced in dielectrics, in air, or
+even in the interplanetary void, and reversed in direction a million
+of million of times per second. The enormous induction due to these
+frequent alternations sets up other currents in the neighboring parts
+of the dielectric, and so the waves are propagated.</p>
+
+<p>Calculation shows that the velocity of propagation would be equal to
+the ratio of the units, which we know is the velocity of light.</p>
+
+<p>Those alternative currents are a sort of electrical oscillation. Are
+they longitudinal, like those of sound, or are they transversal, like
+those of Fresnal’s ether? In the case of sound the air undergoes
+alternative condensations and rarefactions. The ether of Fresnal, on
+the other hand, behaves as if it were composed of incompressible layers
+capable only of slipping over one another. Were these currents in open
+paths, the electricity carried from one end to the other would become
+accumulated at one extremity. It would thus be condensed and rarefied
+like air, and its vibrations would be longitudinal. But Maxwell only
+admits currents in closed circuits; accumulation is impossible, and
+electricity behaves like<span class="pagenum" id="Page_325">[Pg 325]</span> the incomprehensible ether of Fresnel, with
+its transversal vibrations.</p>
+
+
+<p class="nindc space-above2 space-below2">
+EXPERIMENTAL VERIFICATION</p>
+
+<p>We thus obtain all the results of the theory of waves. Yet this was not
+enough to decide the physicists to adopt the ideas of Maxwell. It was a
+seductive hypothesis; but physicists consider hypotheses which lead to
+no distinct observational consequences as beyond the borders of their
+province. That province, so defined, no experimental confirmation of
+Maxwell’s theory invaded for twenty-five years.</p>
+
+<p>What was wanted was some issue between the two theories not too
+delicate for our coarse methods of observation to decide. There was but
+one line of research along which any <i>experimentum crucis</i> was to
+be met with.</p>
+
+<p>The old electro-dynamics makes electro-magnetic induction take place
+instantaneously; but according to Maxwell’s doctrine it propagates
+itself with the velocity of light.</p>
+
+<p>The point was then to measure, or at least to make certain, a velocity
+of propagation of inductive effects. This is what the illustrious
+German physicist Hertz has done by the method of interferences.</p>
+
+<p>The method is well known in its application to optical phenomena. Two
+luminous rays from one identical center interfere when they reach the
+same point after pursuing paths of different lengths. If the difference
+is one, two, or any whole number of wave lengths, the two lights
+re-enforce one another so that if their intensities are equal, that of
+their combination is four times as great. But if the difference is an
+odd number of half wave lengths, the two lights extinguish one another.</p>
+
+<p>Luminiferous waves are not peculiar in showing this phenomenon;
+it belongs to every periodic change which is propagated with
+definite velocity. Sound interferes just as light does, and so must
+electro-dynamic induction if it is strictly periodic and has a definite
+velocity of propagation. But if the propagation is instantaneous there
+can be no interference, since in that case there is no finite wave
+length.</p>
+
+<p>The phenomenon, however, could not be observed were the wave length
+greater than the distance within which induction is sensible.<span class="pagenum" id="Page_326">[Pg 326]</span> It is
+therefore requisite to make the period of alternation as short as
+possible.</p>
+
+
+<p class="nindc space-above2 space-below2">
+ELECTRICAL EXCITERS</p>
+
+<p>We can obtain such currents by means of an apparatus which constitutes
+a veritable electrical pendulum. Let two conductors be united by a
+wire. If they have not the same electric potential the electrical
+equilibrium is disturbed and tends to restore itself, just as the molar
+equilibrium is disturbed when a pendulum is carried away from the
+position of repose.</p>
+
+<p>A current is set up in the wire, tending to equalize the potential,
+just as the pendulum begins to move so as to be carried back to the
+position of repose. But the pendulum does not stop when it reaches that
+position. Its inertia carries it farther. Nor, when the two electrical
+conductors reach the same potential, does the current in the wire
+cease. The equilibrium instantaneously existing is at once destroyed by
+a cause analogous to inertia, namely self-induction. We know that when
+a current is interrupted it gives rise in parallel wires to an induced
+current in the same direction. The same effect is produced in the
+circuit itself, if that is not broken. In other words, a current will
+persist after the cessation of its causes, just as a moving body does
+not stop the instant it is no longer driven forward.</p>
+
+<p>When, then, the two potentials become equal, the current will go on and
+give the two conductors relative charges opposite to those they had
+at first. In this case, as in that of the pendulum, the position of
+equilibrium is passed, and a return motion is inevitable. Equilibrium,
+again instantaneously attained, is at once again broken for the same
+reason; and so the oscillations pursue one another unceasingly.</p>
+
+<p>Calculation shows that the period depends on the capacity of the
+conductors in such a way that it is only necessary to diminish that
+capacity sufficiently (which is easily done) to have an electric
+pendulum capable of producing an alternating current of extremely short
+period.</p>
+
+<p>All that was well enough known by the theoretical researches of Lord
+Kelvin and by the experimentation of Federson on the oscillatory
+discharge of the Leyden jar. It was not that which constituted the
+originality of Hertz.</p>
+
+<p><span class="pagenum" id="Page_327">[Pg 327]</span></p>
+
+<p>But it is not enough to construct a pendulum; it is further requisite
+to set it into oscillation. For that, it is necessary to carry it off
+from equilibrium and to let it go suddenly, that is to say, to release
+it in a time short as compared to the period of its oscillation.</p>
+
+<p>For if, having pulled a pendulum to one side by a string, we were to
+let go of the string more slowly than the pendulum would have descended
+of itself, it would reach the vertical without momentum, and no
+oscillation would be set up.</p>
+
+<p>In like manner, with an electric pendulum whose natural period is, say,
+a hundred-millionth of a second, no mechanical mode of release would
+answer the purpose at all, sudden as it might seem to us with our more
+than sluggish conceptions of promptitude. How, then, did Hertz solve
+the problem?</p>
+
+<figure class="figcenter width500" id="p327" style="width: 974px;">
+<img src="images/p327.jpg" width="974" height="600" alt="A diagram of
+an early electric coil or solenoid setup, showing a wire coil connected
+to terminals, illustrating electromagnetic induction or a basic
+electromagnet.">
+
+</figure>
+
+<p>To return to our electric pendulum, a gap of a few millimeters is
+made in the wire which joins the two conductors. This gap divides our
+apparatus into two symmetrical parts, which are connected to the two
+poles of a Ruhmkorff coil. The induced current begins to charge the
+two conductors, and the difference of their potential increases with
+relative slowness.</p>
+
+<p>At first the gap prevents a discharge from the conductors; the air in
+it plays the rôle of insulator and maintains our pendulum in a position
+diverted from that of equilibrium.</p>
+
+<p>But when the difference of potential becomes great enough, a spark will
+jump across. If the self-induction is great enough and the capacity
+and resistance small enough, there will be an oscillatory discharge
+whose period can be brought down to a hundred-millionth of a second.<span class="pagenum" id="Page_328">[Pg 328]</span>
+The oscillatory discharge would not, it is true, last long by itself;
+but it is kept up by the Ruhmkorff coil, whose current is itself
+oscillatory with a period of about a hundred-thousandth of a second,
+and thus the pendulum gets a new impulse as often as that.</p>
+
+<p>The instrument just described is called a resonance exciter. It
+produces oscillations which are reversed from a hundred million to a
+thousand million times per second. Thanks to this extreme frequency,
+they can produce inductive effects at great distances. To make these
+effects sensible another electric pendulum is used, called a resonator.
+In this the coil is suppressed. It consists simply of two little
+metallic spheres very near to one another, with a long wire connecting
+them in a roundabout way.</p>
+
+<p>The induction due to the exciter will set the resonator in vibration
+the more intensely the more nearly the natural periods of vibration
+are the same. At certain phases of the vibration the difference of
+potential of the two spheres will be just great enough to cause the
+sparks to leap across.</p>
+
+
+<p class="nindc space-above2 space-below2">
+PRODUCTION OF THE INTERFERENCES</p>
+
+<p>Thus we have an instrument which reveals the inductive waves which
+radiate from the exciter. We can study them in two ways. We may either
+expose the resonator to the direct induction of the exciter at a great
+distance, or else make this induction act at a small distance on a long
+conducting wire which the electric wave will follow and which in its
+turn will act at a small distance on the resonator.</p>
+
+<p>Whether the wave is propagated along a wire or across the air,
+interferences can be produced by reflection. In the first case it
+will be reflected at the extremity of the wire, which it will again
+pass through in the opposite direction. In the second case it can be
+reflected on a metallic leaf which will act as a mirror. In either case
+the reflected ray will interfere with the direct ray, and positions
+will be found in which the spark of the resonator will be extinguished.</p>
+
+<p>Experiments with a long wire are the easier and furnish much valuable
+information, but they cannot furnish an <i>experimentum crucis</i>,
+since in the old theory, as in the new, the velocity of the electric
+wave in a wire should be equal to that of light. But experiments on
+direct induction at great distances are decisive. They not only show
+that<span class="pagenum" id="Page_329">[Pg 329]</span> the velocity of propagation of induction across air is finite,
+but also that it is equal to the velocity of the wave propagated along
+a wire, conformably to the ideas of Maxwell.</p>
+
+
+<p class="nindc space-above2 space-below2">
+SYNTHESIS OF LIGHT</p>
+
+<p>I shall insist less on other experiments of Hertz, more brilliant
+but less instructive. Concentrating with a parabolic mirror the wave
+of induction that emanates from the exciter, the German physicist
+obtained a true pencil of rays of electric force, susceptible of
+regular reflection and refraction. These rays, were the period but
+one-millionth of what it is, would not differ from rays of light.
+We know that the sun sends us several varieties of radiations, some
+luminiferous, since they act on the retina, others dark, infra-red, or
+ultraviolet, which reveal themselves in chemical and calorific effects.
+The first owe the qualities which render them sensible to us to a
+physiological chance. For the physicist, the infra-red differs from red
+only as red differs from green; it simply has a greater wave length.
+That of the Hertzian radiations is far greater still, but they are mere
+differences of degree, and if the ideas of Clerk Maxwell are true, the
+illustrious professor of Bonn has effected a genuine synthesis of light.</p>
+
+
+<p class="nindc space-above2 space-below2">
+CONCLUSION</p>
+
+<p>Nevertheless, our admiration for such unhoped-for successes must not
+let us forget what remains to be accomplished. Let us endeavor to take
+exact account of the results definitely acquired.</p>
+
+<p>In the first place, the velocity of direct induction through air is
+finite; for otherwise interferences could not exist. Thus the old
+electro-dynamics is condemned. But what is to be set up in its place?
+Is it to be the doctrine of Maxwell, or rather some approximation to
+that, for it would be too much to suppose that he had foreseen the
+truth in all its details? Though the probabilities are accumulating, no
+complete demonstration of that doctrine has ever attained.</p>
+
+<p>We can measure the wave length of the Hertzian oscillations. That
+length is the product of the period into the velocity of propagation.
+We should know the velocity if we knew the period; but this last is
+so minute that we cannot measure it; we can only calculate it by a<span class="pagenum" id="Page_330">[Pg 330]</span>
+formula due to Lord Kelvin. That calculation leads to figures agreeable
+to the theory of Maxwell; but the last doubts will only be dissipated
+when the velocity of propagation has been directly measured. (See Note
+I.)</p>
+
+<p>But this is not all. Matters are far from being as simple as this
+brief account of the matter would lead one to think. There are various
+complications.</p>
+
+<p>In the first place, there is around the exciter a true radiation of
+induction. The energy of the apparatus radiates abroad, and if no
+source feeds it, it quickly dissipates itself and the oscillations
+are rapidly extinguished. Hence arises the phenomenon of multiple
+resonance, discovered by Messrs. Sarasin and De la Rive, which at first
+seemed irreconcilable with the theory.</p>
+
+<p>On the other hand, we know that light does not exactly follow the
+laws of geometrical optics, and the discrepancy, due to diffraction,
+increases proportionately to the wave length. With the great waves
+of the Hertzian undulations these phenomena must assume enormous
+importance and derange everything. It is doubtless fortunate, for the
+moment at least, that our means of observation are as coarse as they
+are, for otherwise the simplicity which struck us would give place to
+a dedalian complexity in which we should lose our way. No doubt a good
+many perplexing anomalies have been due to this. For the same reason
+the experiments to prove a refraction of the electrical waves can
+hardly be considered as demonstrative.</p>
+
+<p>It remains to speak of a difficulty still more grave, though doubtless
+not insurmountable. According to Maxwell, the coefficient of
+electrostatic induction of a transparent body ought to be equal to the
+square of its index of refraction. Now this is not so. The few bodies
+which follow Maxwell’s law are exceptions. The phenomena are plainly
+far more complex than was at first thought. But we have not yet been
+able to make out how matters stand, and the experiments conflict with
+one another.</p>
+
+<p>Much, then, remains to be done. The identity of light with a vibratory
+motion in electricity is henceforth something more than a seductive
+hypothesis; it is a probable truth. But it is not yet quite proved.</p>
+
+<p><span class="allsmcap">NOTE I.</span>—Since the above was written another great step
+has been taken. M. Blondlot has virtually succeeded, by ingenious
+experimental contrivances, in directly measuring the velocity of a
+disturbance<span class="pagenum" id="Page_331">[Pg 331]</span> along a wire. The number found differs little from the
+ratio of the units; that is, from the velocity of light, which is
+300,000 kilometers per second. Since the interference experiments made
+at Geneva by Messrs. Sarasin and De la Rive have shown, as I said
+above, that induction is propagated in air with the same velocity as an
+electric disturbance which follows a conducting wire, we must conclude
+that the velocity of the induction is the same as that of light, which
+is a confirmation of the ideas of Maxwell.</p>
+
+<p>M. Fizeau had formerly found for the velocity of electricity a number
+far smaller, about 180,000 kilometers. But there is no contradiction.
+The currents used by M. Fizeau, though intermittent, were of small
+frequency and penetrated to the axis of the wire, while the currents of
+M. Blondlot, oscillatory and of very short period, remained superficial
+and were confined to a layer of less than a hundredth of a millimeter
+in thickness. One may readily suppose the laws of propagation are not
+the same in the two cases.</p>
+
+<p><span class="allsmcap">NOTE II.</span>—I have endeavored above to render the explanation
+of the electrostatic attractions and of the phenomena of induction
+comprehensible by means of a simile. Now let us see what Maxwell’s idea
+is of the cause which produces the mutual attractions of currents.</p>
+
+<p>While the electrostatic attractions are taken to be due to a multitude
+of little springs—that is to say, to the elasticity of the ether—it
+is supposed to be the living force and inertia of the same fluid which
+produce the phenomena of induction and electro-dynamical effects.</p>
+
+<p>The complete calculation is far too extended for these pages, and I
+shall again content myself with a simile. I shall borrow it from a well
+known instrument—the centrifugal governor.</p>
+
+<p>The living force of this apparatus is proportional to the square of the
+angular velocity and to the square of the distance of the balls.</p>
+
+<p>According to the hypothesis of Maxwell, the ether is in motion in
+galvanic currents, and its living force is proportional to the square
+of the intensity of the current, which thus correspond, in the parallel
+I am endeavoring to establish, to the angular velocity of rotation.</p>
+
+<p>If we consider two currents in the same direction, the living force,
+with equal intensity, will be greater the nearer the currents are to
+one another. If the currents have opposite directions, the living force
+will be greater the farther they are apart.</p>
+
+<p>In order to increase the angular velocity of the regulator and
+consequently<span class="pagenum" id="Page_332">[Pg 332]</span> its living force, it is necessary to supply it with
+energy and consequently to overcome a resistance which we call its
+inertia.</p>
+
+<p>In the same way, in order to increase the intensity of a current, we
+must augment the living force of the ether, and it will be necessary to
+supply it with energy and to overcome a resistance which is nothing but
+the inertia of the ether and which we call the induction.</p>
+
+<p>The living force will be greater if the currents are in the same
+direction and near together. The energy to be furnished the counter
+electromotive force of induction will be greater. This is what we
+express when we say that the mutual action of two currents is to be
+added to their self-induction. The contrary is the case when their
+directions are opposite.</p>
+
+<p>If we separate the balls of the regulator, it will be necessary, in
+order to maintain the angular velocity, to furnish energy, because with
+equal angular velocity the living force is greater the more the balls
+are separated.</p>
+
+<p>In the same way, if two currents have the same direction and are
+brought toward one another, it will be necessary, in order to maintain
+the intensity to supply energy, because the living force will be
+augmented. We shall, therefore, have to overcome an electromotive
+force of induction which will tend to diminish the intensity of the
+currents. It would tend on the contrary to augment it, if the currents
+had the same direction and were carried apart, or if they had opposite
+directions and were brought together.</p>
+
+<p>Finally, the centrifugal force tends to increase the distance between
+the balls, which would augment the living force were the angular
+velocity to be maintained.</p>
+
+<p>In like manner, when the currents have the same direction, they attract
+each other—that is to say, they tend to approach each other, which
+would increase the living force if the intensity were maintained.
+If their directions are opposed they repel one another and tend to
+separate, which would again tend to increase the living force were the
+intensity kept constant.</p>
+
+<p>Thus the electrostatic effects would be due to the elasticity of the
+ether and the electro-dynamical phenomena to the living force. Now,
+ought this elasticity itself to be explained, as Lord Kelvin thinks, by
+rotations of small parts of the fluid? Different reasons may render<span class="pagenum" id="Page_333">[Pg 333]</span>
+this hypothesis attractive; but it plays no essential part in the
+theory of Maxwell, which is quite independent of it.</p>
+
+<p>In the same way, I have made comparisons with divers mechanisms. But
+they are only similes, and pretty rough ones. A complete mechanical
+explanation of electrical phenomena is not to be sought in the volumes
+of Maxwell, but only a statement of the conditions which any such
+explanation has to satisfy. Precisely what will confer long life on the
+work of Maxwell is its being unentangled with any special mechanical
+hypothesis.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_36" href="#FNanchor_36" class="label">[36]</a>
+Translated from a paper by M. Henri Poincaré.</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_334">[Pg 334]</span></p>
+<h2 class="nobreak" id="XXXIV">XXXIV<br>
+AUGUST WEISMANN<br>
+1834-1914</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>August Weismann was born at Frankfort-on-Main, January 17, 1834,
+and studied medicine at Göttingen, 1852-1856. He was physician to the
+Austrian Archduke for two years (1860-62), but was compelled to retire
+because of his poor eyesight. He was called to the chair of zoology
+at Freiburg University. After a close study of Darwin’s theory, he
+published in 1876 his “Studies in the Theories of Descent,” a book
+which at once attracted much attention among scientists, for it
+proposed the theory of the germ-plasm as the basis of heredity, and
+denied the theory of the transmissibility of acquired characteristics.
+He died at Freiburg-in-Baden, November 6, 1914.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE CONTINUITY OF THE GERM-PLASM AS THE FOUNDATION OF A THEORY OF
+HEREDITY<a id="FNanchor_37" href="#Footnote_37" class="fnanchor">[37]</a><br>
+<br>
+INTRODUCTION</p>
+
+<p>When we see that, in the higher organisms, the smallest structural
+details, and the most minute peculiarities of bodily and mental
+disposition, are transmitted from one generation to another; when we
+find in all species of plants and animals a thousand characteristic
+peculiarities of structure continued unchanged through long series of
+generations; when we even see them in many cases unchanged throughout
+whole geological periods; we very naturally ask for the causes of
+such a striking phenomenon: and inquire how it is that such facts
+become possible, how it is that the individual is able to transmit its
+structural features<span class="pagenum" id="Page_335">[Pg 335]</span> to its offspring with such precision. And the
+immediate answer to such a question must be given in the following
+terms:—“A single cell out of the millions of diversely differentiated
+cells which compose the body, becomes specialized as a sexual cell; it
+is thrown off from the organism and is capable of reproducing all the
+peculiarities of the parent body, in the new individual which springs
+from it by cell-division and the complex process of differentiation.”
+Then the more precise question follows: “How is it that such a single
+cell can reproduce the <i>tout ensemble</i> of the parent with all the
+faithfulness of a portrait?”</p>
+
+<p>The answer is extremely difficult; and no one of the many attempts
+to solve the problem can be looked upon as satisfactory; no one of
+them can be regarded as even the beginning of a solution or as a
+secure foundation from which a complete solution may be expected in
+the future. Neither Häeckel’s “Perigenesis of the Plastidule,” nor
+Darwin’s “Pangenesis,” can be regarded as such a beginning. The former
+hypothesis does not really treat of that part of the problem which
+is here placed in the foreground, viz., the explanation of the fact
+that the tendencies of heredity are present in single cells, but it
+is rather concerned with the question as to the manner in which it
+is possible to conceive the transmission of a certain tendency of
+development into the sexual cell, and ultimately into the organism
+arising from it. The same may be said of the hypothesis of His, who,
+like Häeckel regards heredity as the transmission of certain kinds of
+motion. On the other hand, it must be conceded that Darwin’s hypothesis
+goes to the very root of the question, but he is content to give, as
+it were, a provisional or purely formal solution, which, as he himself
+says, does not claim to afford insight into the real phenomena, but
+only to give us the opportunity of looking at all the facts of heredity
+from a common standpoint. It has achieved this end, and I believe it
+has unconsciously done more, in that the thoroughly logical application
+of its principles has shown that the real causes of heredity cannot
+lie in the formation of gemmules or in any allied phenomena. The
+improbabilities to which any such theory would lead are so great that
+we can affirm with certainty that its details cannot accord with
+existing facts. Furthermore, Brooks’ well-considered and brilliant
+attempt to modify the theory of Pangenesis cannot escape the reproach
+that it is based upon possibilities, which one might certainly describe
+as improbabilities.<span class="pagenum" id="Page_336">[Pg 336]</span> But although I am of the opinion that the whole
+foundation of the theory of Pangenesis, however it may be modified,
+must be abandoned, I think, nevertheless, its author deserves great
+credit, and that its production has been one of those indirect roads
+along which science has been compelled to travel in order to arrive
+at the truth. Pangenesis is a modern revival of the oldest theory of
+heredity, that of Democritus, according to which the sperm is secreted
+from all parts of the body of both sexes during copulation, and is
+animated by a bodily force; according to this theory also, the sperm
+from each part of the body reproduces the same part.</p>
+
+<p>If, according to the received physiological and morphological ideas
+of the day, it is impossible to imagine that gemmules produced by
+each cell of the organism are at all times to be found in all parts
+of the body, and furthermore that these gemmules are collected in the
+sexual cells, which are then able to reproduce again in a certain
+order each separate cell of the organism, so that each sexual cell is
+capable of developing into the likeness of the parent body; if all
+this is inconceivable, we must inquire for some other way in which we
+can arrive at a foundation for the true understanding of heredity. My
+present task is not to deal with the whole question of heredity, but
+only with the single although fundamental question—“How is it that a
+single cell of the body can contain within itself all the hereditary
+tendencies of the whole organism?” I am here leaving out of account
+the further question as to the forces and the mechanism by which these
+tendencies are developed in the building-up of the organism. On this
+account I abstain from considering at present the views of Nägeli, for
+as will be shown later on, they only slightly touch this fundamental
+question, although they may certainly claim to be of the highest
+importance with respect to the further question alluded to above.</p>
+
+<p>Now if it is impossible for the germ-cell to be, as it were, an extract
+of the whole body, and for all the cells of the organism to dispatch
+small particles to the germ-cells, from which the latter derive their
+power of heredity; then there remain, as it seems to me, only two other
+possible, physiologically conceivable, theories as to the origin of
+germ-cells, manifesting such powers as we know they possess. Either
+the substance of the parent germ-cell is capable of undergoing a
+series of changes which, after the building-up of a new individual
+leads back again to identical germ-cells; or the germ-cells are not
+derived at all,<span class="pagenum" id="Page_337">[Pg 337]</span> as far as their essential and characteristic substance
+is concerned, from the body of the individual, but they are derived
+directly from the parent germ-cell.</p>
+
+<p>I believe that the latter view is the true one: I have expounded it
+for a number of years, and have attempted to defend it, and to work
+out its further details in various publications. I propose to call it
+the theory of “The Continuity of the Germ-plasm,” for it is founded
+upon the idea that heredity is brought about by the transference from
+one generation to another of a substance with a definite chemical,
+and above all, molecular constitution. I have called this substance
+“germ-plasm,” and have assumed that it possesses a highly complex
+structure, conferring upon it the power of developing into a complex
+organism. I have attempted to explain heredity by supposing that in
+each ontogeny a part of the specific germ-plasm contained in the
+parent egg-cell is not used up in the construction of the body of
+the offspring, but is reserved unchanged for the formation of the
+germ-cells of the following generation.</p>
+
+<p>It is clear that this view of the origin of germ-cells explains the
+phenomena of heredity very simply, inasmuch as heredity becomes thus
+a question of growth and of assimilation,—the most fundamental of
+all vital phenomena. If the germ-cells of successive generations are
+directly continuous, and thus only form, as it were, different parts
+of the same substance, it follows that these cells must, or at any
+rate may, possess the same molecular constitution, and that they
+would therefore pass through exactly the same stages under certain
+conditions of development, and would form the same final product. The
+hypothesis of the continuity of the germ-plasm gives an identical
+starting point to each successive generation, and thus explains how it
+is that an identical product arises from all of them. In other words,
+the hypothesis explains heredity as part of the underlying problems
+of assimilation and of the causes which act directly during ontogeny;
+it therefore builds a foundation from which the explanation of these
+phenomena can be attempted.</p>
+
+<p>It is true that this theory also meets with difficulties, for it seems
+to be unable to do justice to a certain class of phenomena, viz.,
+the transmission of so-called acquired characters. I therefore gave
+immediate and special attention to this point in my first publication
+on heredity, and I believe that I have shown that the hypothesis of
+the transmission<span class="pagenum" id="Page_338">[Pg 338]</span> of acquired characters—up to that time generally
+accepted—is, to say the least, very far from being proved, and
+that entire classes of facts which have been interpreted under this
+hypothesis may be quite as well interpreted otherwise, while in many
+cases they must be explained differently. I have shown that there is
+no ascertained fact which, at least up to the present time, remains
+in irrevocable conflict with the hypothesis of the continuity of
+the germ-plasm; and I do not know any reason why I should modify
+this opinion to-day, for I have not heard of any objection which
+appears to be feasible. E. Roth has objected that in pathology we
+everywhere meet with the fact that acquired local disease may be
+transmitted to the offspring as a predisposition; but all such cases
+are exposed to the serious criticism that the very point that first
+needs to be placed on a secure footing is incapable of proof, viz.,
+the hypothesis that the causes which in each particular case led to
+the predisposition were really acquired. It is not my intention, on
+the present occasion, to enter fully into the question of acquired
+characters; I hope to be able to consider the subject in greater detail
+at a future date. But in the meantime I should wish to point out that
+we ought, above all, to be clear as to what we really mean by the
+expression “acquired character.” An organism cannot acquire anything
+unless it already possesses the predisposition to acquire it: acquired
+characters are therefore no more than local or sometimes general
+variations which arise under the stimulus provided by certain external
+influences. If by the long-continued handling of a rifle, the so-called
+“<i>Exercierknochen</i>” (a bony growth caused by the pressure of
+the weapon in drilling) is developed, such a result depends upon
+the fact that the bone in question, like every other bone, contains
+within itself a predisposition to react upon certain mechanical
+stimuli, by growth in a certain direction and to a certain extent. The
+predisposition towards an “<i>Exercierknochen</i>” is therefore already
+present, or else the growth could not be formed; and the same reasoning
+applies to all other “acquired characters.”</p>
+
+<p>Nothing can arise in an organism unless the predisposition to it is
+pre-existent, for every acquired character is simply the reaction
+of the organism upon a certain stimulus. Hence I should never have
+thought of asserting that predispositions cannot be transmitted, as
+E. Roth appears to believe. For instance, I freely admit that the
+predisposition to an “<i>Exercierknochen</i>” varies, and that a
+strongly marked<span class="pagenum" id="Page_339">[Pg 339]</span> predisposition may be transmitted from father to son,
+in the form of bony tissue with a more susceptible constitution. But
+I should deny that the son could develop an “<i>Exercierknochen</i>”
+without having drilled, or that, after having drilled, he could
+develop it more easily than his father, on account of the drilling
+through which the latter first acquired it. I believe that this is as
+impossible as that the leaf of an oak should produce a gall without
+having been pierced by a gall-producing insect, as a result of the
+thousands of antecedent generations of oaks which have been pierced by
+such insects, and have thus “acquired” the power of producing galls. I
+am also far from asserting that the germ-plasm—which, as I hold, is
+transmitted as the basis of heredity from one generation to another—is
+absolutely unchangeable or totally uninfluenced by forces residing in
+the organism within which it is transformed into germ-cells. I am also
+compelled to admit that it is conceivable that organisms may exert a
+modifying influence upon their germ-cells, and even that such a process
+is to a certain extent inevitable. The nutrition and growth of the
+individual must exercise some influence upon its germ-cells; but in the
+first place this influence must be extremely slight, and in the second
+place it cannot act in the manner in which it is usually assumed that
+it takes place. A change of growth at the periphery of an organism,
+as in the case of an “<i>Exercierknochen</i>,” can never cause such a
+change in the molecular structure of the germ-plasm as would augment
+the predisposition to an “<i>Exercierknochen</i>,” so that the son
+would inherit an increased susceptibility of the bony tissue or even of
+the particular bone in question. But any change produced will result
+from the reaction of the germ-cell upon changes of nutrition caused by
+alteration in growth at the periphery, leading to some change in the
+size, number, or arrangement of its molecular units. In the present
+state of our knowledge there is reason for doubting whether such
+reaction can occur at all; but, if it can take place, at all events
+the quality of the change in the germ-plasm can have nothing to do
+with the quality of the acquired character, but only with the way in
+which the general nutrition is influenced by the latter. In the case of
+the “<i>Exercierknochen</i>” there would be practically no change in
+the general nutrition, but if such a bony growth could reach the size
+of a carcinoma, it is conceivable that a disturbance of the general
+nutrition of the body might ensue. Certain experiments on plants—on
+which Nägeli showed that they can be<span class="pagenum" id="Page_340">[Pg 340]</span> submitted to strongly varied
+conditions of nutrition for several generations, without the production
+of any visible hereditary change—show that the influence of nutrition
+upon the germ-cells must be very slight, and that it may possibly leave
+the molecular structure of the germ-plasm altogether untouched. This
+conclusion is also supported by comparing the uncertainty of these
+results with the remarkable precision with which heredity acts in the
+case of those characters which are known to be transmitted. In fact,
+up to the present time, it has never been proved that any changes in
+general nutrition can modify the molecular structure of the germ-plasm,
+and far less has it been rendered by any means probable that the
+germ-cells can be affected by acquired changes which have no influence
+on general nutrition. If we consider that each so-called predisposition
+(that is, a power of reacting upon a certain stimulus in a certain way,
+possessed by any organism or by one of its parts) must be innate, and
+further that each acquired character is only the predisposed reaction
+of some part of an organism upon some external influence; then we must
+admit that only one of the causes which produce any acquired character
+can be transmitted, the one which was present before the character
+itself appeared, viz., the predisposition; and we must further
+admit that the latter arises from the germ, and that it is quite
+immaterial to the following generation whether such predisposition
+comes into operation or not. The continuity of the germ-plasm is amply
+sufficient to account for such a phenomenon, and I do not believe that
+any objection to my hypothesis, founded upon the actually observed
+phenomena of heredity, will be found to hold. If it be accepted, many
+facts will appear in a light different from that which has been cast
+upon them by the hypothesis which has been hitherto received,—a
+hypothesis which assumes that the organism produces germ-cells afresh,
+again and again, and that it produces them entirely from its own
+substance. Under the former theory the germ-cells are no longer looked
+upon as the product of the parent’s body, at least as far as their
+essential part—the specific germ-plasm—is concerned: they are rather
+considered as something which is to be placed in contrast with the
+<i>tout ensemble</i> of the cells which make up the parent’s body, and
+the germ-cells of succeeding generations stand in a similar relation
+to one another as a series of generations of unicellular organisms,
+arising by a continued process of cell-division. It is true that in
+most cases the generations of germ-cells<span class="pagenum" id="Page_341">[Pg 341]</span> do not arise immediately
+from one another as complete cells, but only as minute particles of
+germ-plasm. This latter substance, however forms the foundation of the
+germ-cells of the next generation, and stamps them with their specific
+character. Previous to the publication of my theory, C. Jäger, and
+later M. Nussbaum, have expressed ideas upon heredity which come very
+near to my own. Both of these writers started with the hypothesis that
+there must be a direct connection between the germ-cells of succeeding
+generations, and they tried to establish such a continuity by supposing
+that the germ-cells of the offspring are separated from the parent
+germ-cell before the beginning of embryonic development, or at least
+before any histological differentiation has taken place. In this form
+their suggestion cannot be maintained, for it is in conflict with
+numerous facts. A continuity of the germ-cells does not now take place,
+except in very rare instances; but this fact does not prevent us from
+adopting a theory of the continuity of the germ-plasm, in favour of
+which much weighty evidence can be brought forward. In the following
+pages I shall attempt to develop further the theory of which I have
+just given a short account, to defend it against any objections which
+have been brought forward, and to draw from it new conclusions which
+may perhaps enable us more thoroughly to appreciate facts which are
+known, but imperfectly understood. It seems to me that this theory of
+continuity of the germ-plasm deserves at least to be examined in all
+its details, for it is the simplest theory upon the subject, and the
+one which is most obviously suggested by the facts of the case, and we
+shall not be justified in forsaking it for a more complex theory until
+proof that it can be no longer maintained is forthcoming. It does not
+presuppose anything except facts which can be observed at any moment,
+although they may not be understood,—such as assimilation, or the
+development of like organisms from like germs; while every other theory
+of heredity is founded on hypotheses which cannot be proved. It is
+nevertheless possible that continuity of the germ-plasm does not exist
+in the manner in which I imagine that it takes place, for no one can at
+present decide whether all the ascertained facts agree with and can be
+explained by it. Moreover, the ceaseless activity of research brings to
+light new facts every day, and I am far from maintaining that my theory
+may not be disproved by some of these. But even if it should have to
+be abandoned at a later period, it seems to<span class="pagenum" id="Page_342">[Pg 342]</span> me that, at the present
+time, it is a necessary stage in the advancement of our knowledge, and
+one which must be brought forward and passed through, whether it prove
+right or wrong, in the future. In this spirit I offer the following
+considerations, and it is in this spirit that I should wish them to be
+received.</p>
+
+
+<p class="nindc space-above2 space-below2">
+THE GERM-PLASM</p>
+
+<p>I entirely agree with Strasburger when he says, “The specific qualities
+of organisms are based upon nuclei”; and I further agree with him in
+many of his ideas as to the relation between the nucleus and cell-body:
+“Molecular stimuli proceed from the nucleus into the surrounding
+cytoplasm; stimuli which, on the one hand, control the phenomena of
+assimilation in the cell, and, on the other hand, give to the growth
+of the cytoplasm, which depends upon nutrition, a certain character
+peculiar to the species.” “The nutritive cytoplasm assimilates, while
+the nucleus controls the assimilation, and hence the substances
+assimilated possess a certain constitution and nourish in a certain
+manner the cyto-idioplasm and the nuclear idioplasm. In this way the
+cytoplasm takes part in the phenomena of construction, upon which the
+specific form of the organism depends. This constructive activity
+of the cyto-idioplasm depends upon the regulative influence of the
+nuclei.” The nuclei therefore “determine the specific direction in
+which an organism develops.”</p>
+
+<p>The opinion—derived from the recent study of the phenomena of
+fertilization—that the nucleus impresses its specific character
+upon the cell, has received conclusive and important confirmation
+in the experiments upon the regeneration of Infusoria, conducted
+simultaneously by M. Nussbaum at Bonn, and by A. Gruber at Freiburg.
+Nussbaum’s statement that an artificially separated portion of a
+<i>Paramaecium</i>, which does not contain any nuclear substance,
+immediately dies, must not be accepted as of general application, for
+Gruber has kept similar fragments of other Infusoria alive for several
+days. Moreover, Gruber had previously shown that individual Protozoa
+occur, which live in a normal manner, and are yet without a nucleus,
+although this structure is present in other individuals of the same
+species. But the meaning of the nucleus is made clear by the fact,
+published by Gruber, that such artificially separated fragments of<span class="pagenum" id="Page_343">[Pg 343]</span>
+Infusoria are incapable of regeneration, while on the other hand those
+fragments which contain nuclei always regenerate. It is therefore only
+under the influence of the nucleus that the cell substance re-develops
+into the full type of the species. In adopting the view that the
+nucleus is the factor which determines the specific nature of the cell,
+we stand on a firm foundation upon which we can build with security.</p>
+
+<p>If therefore the first segmentation nucleus contains, in its molecular
+structure, the whole of the inherited tendencies of development, it
+must follow that during segmentation and subsequent cell-division, the
+nucleoplasm will enter upon definite and varied changes which must
+cause the differences appearing in the cells which are produced; for
+identical cell-bodies depend, <i>ceteris paribus</i>, upon identical
+nucleoplasm, and conversely different cells depend upon differences
+in the nucleoplasm. The fact that the embryo grows more strongly in
+one direction than in another, that its cell-layers are of different
+nature and are ultimately differentiated into various organs and
+tissues,—forces us to accept the conclusion that the nuclear substance
+has also been changed in nature, and that such changes take place
+during ontogenetic development in a regular and definite manner.
+This view is also held by Strasburger, and it must be the opinion of
+all who seek to derive the development of inherited tendencies from
+the molecular structure of the germ-plasm, instead of from preformed
+gemmules.</p>
+
+<p>We are thus led to the important question as to the forces by which the
+determining substance or nucleoplasm is changed, and as to the manner
+in which it changes during the course of ontogeny, and on the answer
+to this question our further conclusions must depend. The simplest
+hypothesis would be to suppose that, at each division of the nucleus,
+its specific substance divides into two halves of unequal quality, so
+that the cell-bodies would also be transformed; for we have seen that
+the character of a cell is determined by that of its nucleus. Thus in
+any Metazoon the first two segmentation spheres would be transformed in
+such a manner that one only contained the hereditary tendencies of the
+endoderm and the other those of the ectoderm, and therefore, at a later
+stage, the cells of the endoderm would arise from the one and those of
+the ectoderm from the other; and this is actually known to occur. In
+the course of further division the nucleoplasm of the first ectoderm
+cell would again divide unequally, <i>e. g.</i>, into the<span class="pagenum" id="Page_344">[Pg 344]</span> nucleoplasm
+containing the hereditary tendencies of the nervous system, and into
+that containing the tendencies of the external skin. But even then,
+the end of the unequal division of nuclei would not have been nearly
+reached; for, in the formation of the nervous system, the nuclear
+substance which contains the hereditary tendencies of the sense-organs
+would, in the course of further cell-division, be separated from that
+which contains the tendencies of the central organs, and the same
+process would continue in the formation of all single organs, and in
+the final development of the most minute histological elements. This
+process would take place in a definitely ordered course, exactly as
+it has taken place throughout a very long series of ancestors; and
+the determining and directing factor is simply and solely the nuclear
+substance, the nucleoplasm, which possesses such a molecular structure
+in the germ-cell that all such succeeding stages of its molecular
+structure in future nuclei must necessarily arise from it, as soon as
+the requisite external conditions are present. This is almost the same
+conception of ontogenetic development as that which has been held by
+embryologists who have not accepted the doctrine of evolution: for we
+have only to transfer the primary cause of development, from an unknown
+source within the organism, into the nuclear substance, in order to
+make the views identical.</p>
+
+<p class="space-above2">
+I believe I have shown that theoretically hardly any objection can be
+raised against the view that the nuclear substance of somatic cells
+may contain unchanged germ-plasm, or that this germ-plasm may be
+transmitted along certain lines. It is true that we might imagine <i>a
+priori</i> that all somatic nuclei contain a small amount of unchanged
+germ-plasm. In Hydroids such an assumption cannot be made, because only
+certain cells in a certain succession possess the power of developing
+into germ-cells; but it might well be imagined that in some organisms
+it would be a great advantage if every part possessed the power of
+growing up into the whole organism and of producing sexual cells under
+appropriate circumstances. Such cases might exist if it were possible
+for all somatic nuclei to contain a minute fraction of unchanged
+germ-plasm. For this reason, Strasburger’s other objection against my
+theory also fails to hold; viz., that certain plants can be propagated
+by pieces of rhizomes, roots, or even by means of leaves, and that
+plants produced in this manner may finally give rise<span class="pagenum" id="Page_345">[Pg 345]</span> to flowers, fruit
+and seeds, from which new plants arise. “It is easy to grow new plants
+from the leaves of begonia which have been cut off and merely laid upon
+moist sand, and yet in the normal course of ontogeny the molecules of
+germ-plasm would not have been compelled to pass through the leaf; and
+they ought therefore to be absent from its tissue. Since it is possible
+to raise from the leaf a plant which produces flower and fruit, it is
+perfectly certain that special cells containing the germ-substance
+cannot exist in the plant.” But I think that this fact only proves
+that in begonia and similar plants all the cells of the leaves or
+perhaps only certain cells contain a small amount of germ-plasm, and
+that consequently these plants are specially adapted for propagation
+by leaves. How is it then that all plants cannot be reproduced in this
+way? No one has ever grown a tree from the leaf of the lime or oak,
+or a flowering plant from the leaf of the tulip or convolvulus. It
+is insufficient to reply that in the last mentioned cases the leaves
+are more strongly specialized, and have thus become unable to produce
+germ-substance; for the leaf-cells in these different plants have
+hardly undergone histological differentiation in different degrees.
+If, notwithstanding, the one can produce a flowering plant, while the
+others have not this power, it is of course clear that reasons other
+than the degree of histological differentiation must exist; and,
+according to my opinion, such a reason is to be found in the admixture
+of a minute quantity of unchanged germ-plasm with some of their nuclei.</p>
+
+<p>In Sach’s excellent lectures on the physiology of plants, we read on
+page 723—“In the true mosses almost any cell of the roots, leaves and
+shoot-axes, and even of the immature sporogonium, may grow out under
+favourable conditions, become rooted, form new shoots, and give rise to
+an independent living plant.” Since such plants produce germ-cells at
+a later period, we have here a case which requires the assumption that
+all or nearly all cells must contain germ-plasm.</p>
+
+<p>The theory of the continuity of the germ-plasm seems to me to be
+still less disproved or even rendered improbable by the facts of the
+alternation of generations. If the germ-plasm may pass on from the egg
+into certain somatic cells of an individual, and if it can be further
+transmitted along certain lines, there is no difficulty in supposing
+that it may be transmitted through a second, third, or through any
+number of individuals produced from the former by budding. In fact, in<span class="pagenum" id="Page_346">[Pg 346]</span>
+the Hydroids, on which my theory of the continuity of the germ-plasm
+has been chiefly based, alternation of generations is the most
+important means of propagation.</p>
+
+
+<p class="nindc space-above2 space-below2">
+THE SIGNIFICANCE OF THE POLAR BODIES</p>
+
+<p>We have already seen that the specific nature of a cell depends upon
+the molecular structure of its nucleus; and it follows from this
+conclusion that my theory is further, and as I believe strongly,
+supported, by the phenomenon of the expulsion of polar bodies, which
+has remained inexplicable for so long a time.</p>
+
+<p>For if the specific molecular structure of a cell-body is caused
+and determined by the structure of the nucleoplasm, every kind of
+cell which is histologically differentiated must have a specific
+nucleoplasm. But the egg-cell of most animals, at any rate during
+the period of growth, is by no means an indifferent cell of the most
+primitive type. At such a period its cell-body has to perform quite
+peculiar and specific functions; it has to secrete nutritive substances
+of a certain chemical nature and physical constitution, and to store
+up this food material in such a manner that it may be at the disposal
+of the embryo during its development. In most cases the egg-cell
+also forms membranes which are often characteristic of particular
+species of animals. The growing egg-cell is therefore histologically
+differentiated: and in this respect resembles a somatic cell. It
+may perhaps be compared to a gland-cell, which does not expel its
+secretion, but deposits it within its own substance. To perform such
+specific functions it requires a specific cell-body, and the latter
+depends upon a specific nucleus. It therefore follows that the growing
+egg-cell must possess nucleoplasm of specific molecular structure,
+which directs the above mentioned secretory functions of the cell.
+The nucleoplasm of histologically differentiated cells may be called
+histogenetic nucleoplasm, and the growing egg-cell must contain such
+a substance, and even a certain specific modification of it. This
+nucleoplasm cannot possibly be the same as that which, at a later
+period, causes embryonic development. Such development can only be
+produced by the true germ-plasm of immensely complex constitution, such
+as I have previously attempted to describe. It therefore follows that
+the nucleus of the egg-cell contains two kinds of nucleoplasm:—germ
+and a peculiar modification<span class="pagenum" id="Page_347">[Pg 347]</span> of histogenetic nucleoplasm, which
+may be called ovogenetic nucleoplasm. This substance must greatly
+preponderate in the young egg-cell, for, as we have already seen, it
+controls the growth of the latter. The germ-plasm, on the other hand,
+can only be present in minute quantity at first, but it must undergo
+considerable increase during the growth of the cell. But in order
+that the germ-plasm may control the cell-body, or, in other words, in
+order that embryonic development may begin, the still preponderating
+ovogenetic nucleoplasm must be removed from the cell. This removal
+takes place in the same manner as that in which differing nuclear
+substances are separated during the ontogeny of the embryo: viz., by
+nuclear division, leading to cell-division. The expulsion of the polar
+bodies is nothing more than the removal of ovogenetic nucleoplasm from
+the egg-cell. That the ovogenetic nucleoplasm continues greatly to
+preponderate in the nucleus up to the very last, may be concluded from
+the fact that two successive divisions of the latter and the expulsion
+of two polar bodies appear to be the rule. If in this way a small part
+of the cell-body is expelled from the egg, the extrusion must in all
+probability be considered as an inevitable loss, without which the
+removal of the ovogenetic nucleoplasm cannot be effected.</p>
+
+
+<p class="nindc space-above2 space-below2">
+ON THE NATURE OF PARTHENOGENESIS</p>
+
+<p>It is well known that the formation of polar bodies has been repeatedly
+connected with the sexuality of germ-cells, and that it has been
+employed to explain the phenomena of parthenogenesis. I may now perhaps
+be allowed to develop the views as to the nature of parthenogenesis at
+which I have arrived under the influence of my explanation of polar
+bodies.</p>
+
+<p>The theory of parthenogenesis adopted by Minot and Balfour is
+distinguished by its simplicity and clearness, among all other
+interpretations which had been hitherto offered. Indeed, their
+explanation follows naturally and almost as a matter of course, if the
+assumption made by these observers be correct, that the polar body is
+the male part of the hermaphrodite egg-cell. An egg which has lost its
+male part cannot develop into an embryo until it has received a new
+male part in fertilization. On the other hand, an egg which does not
+expel its male part may develop without fertilization, and thus we are
+led<span class="pagenum" id="Page_348">[Pg 348]</span> to the obvious conclusion that parthenogenesis is based upon the
+non-expulsion of polar bodies. Balfour distinctly states “that the
+function of forming polar cells has been acquired by the ovum for the
+express purpose of preventing parthenogenesis.”</p>
+
+<p>It is obvious that I cannot share this opinion, for I regard the
+expulsion of polar bodies as merely the removal of the ovogenetic
+nucleoplasm, on which depended the development of the specific
+histological structure of the egg-cell. I must assume that the
+phenomena of maturation in the parthenogenetic egg and in the sexual
+egg are precisely identical, and that in both, the ovogenetic
+nucleoplasm must in some way be removed before embryonic development
+can begin.</p>
+
+<p>Unfortunately the actual proof of this assumption is not so complete
+as might be desired. In the first place, we are as yet uncertain
+whether polar bodies are or are not expelled by parthenogenetic eggs;
+for in no single instance has such expulsion been established beyond
+doubt. It is true that this deficiency does not afford any support
+to the explanation of Minot and Balfour, for in all cases in which
+polar bodies have not been found in parthenogenetic eggs, these
+structures are also absent from the eggs which require fertilization
+in the same species. But although the expulsion of polar bodies in
+parthenogenesis has not yet been proved to occur, we must assume it to
+be nearly certain that the phenomena of maturation, whether connected
+or unconnected with the expulsion of polar bodies, are the same in the
+eggs which develop parthenogenetically and in those which are capable
+of fertilization, in one and the same species. This conclusion depends,
+above all, upon the phenomena of reproduction in bees, in which,
+as a matter of fact, the same egg may be fertilized or may develop
+parthenogenetically, as I shall have occasion to describe in greater
+detail at a later period.</p>
+
+<p>Hence when we see that the eggs of many animals are capable of
+developing without fertilization, while in other animals such
+development is impossible, the difference between the two kinds of eggs
+must rest upon something more than the mode of transformation of the
+nucleus of the germ-cell into the first segmentation nucleus. There
+are, indeed, facts which distinctly point to the conclusion that the
+difference is based upon quantitative and not qualitative relations.
+A large number of insects are exceptionally reproduced by the
+parthenogenetic method, <i>e. g.</i>, in Lepidoptera. Such development
+does<span class="pagenum" id="Page_349">[Pg 349]</span> not take place in all the eggs laid by an unfertilized female,
+but only in part, and generally a small fraction of the whole, while
+the rest die. But among the latter there are some which enter upon
+embryonic development without being able to complete it, and the
+stage at which development may cease also varies. It is also known
+that the eggs of higher animals may pass through the first stages of
+segmentation without having been fertilized. This was shown to be
+the case in the egg of the frog by Leuckart, in that of the fowl by
+Oellacher, and even in the egg of mammals by Hensen.</p>
+
+<p>Hence in such cases it is not the impulse to development, but the power
+to complete it, which is absent. We know that force is always bound up
+with matter, and it seems to me that such instances are best explained
+by the supposition that too small an amount of that form of matter
+is present, which, by its controlling agency, effects the building
+up of the embryo by the transformation of mere nutritive material.
+This substance is the germ-plasm of the segmentation nucleus, and I
+have assumed above that it is altered in the course of ontogeny by
+changes which arise from within, so that when sufficient nourishment
+is afforded by the cell-body, each succeeding stage necessarily
+results from the preceding one. I believe that changes arise in the
+constitution of the nucleoplasm at each cell-division which takes place
+during the building up of the embryo, changes which either correspond
+or differ in the two halves of each nucleus. If, for the present, we
+neglect the minute amount of unchanged germ-plasm which is reserved
+for the formation of the germ-cells, it is clear that a great many
+different stages in the development of somatic nucleoplasm are thus
+formed, which may be denominated as stages 1, 2, 3, 4, etc., up to
+<i>n</i>. In each of these stages the cells differ more as development
+proceeds, and as the number by which the stage is denominated becomes
+higher. Thus, for instance, the two first segmentation spheres would
+represent the first stage of somatic nucleoplasm, a stage which may
+be considered as but slightly different in its molecular structure
+from the nucleoplasm of the segmentation nucleus; the first four
+segmentation spheres would represent the second stage; the succeeding
+eight spheres the third, and so on. It is clear that at each successive
+stage the molecular structure of the nucleoplasm must be further
+removed from that of the germ-plasm, and that, at the same time, the
+cells of each successive stage must also diverge more widely<span class="pagenum" id="Page_350">[Pg 350]</span> among
+themselves in the molecular structure of their nucleoplasm. Early in
+development each cell must possess its own peculiar nucleoplasm, for
+the further course of development is peculiar to each cell. It is
+only in the later stages that equivalent or nearly equivalent cells
+are formed in large numbers, cells in which we must also suppose the
+existence of equivalent nucleoplasm.</p>
+
+<p>If we may assume that a certain amount of germ-plasm must be contained
+in the segmentation nucleus in order to complete the whole process of
+the ontogenetic differentiation of this substance; if we may further
+assume that the quantity of germ-plasm in the segmentation nucleus
+varies in different cases; then we should be able to understand why
+one egg can only develop after fertilization, while another can
+begin its development without fertilization, but cannot finish it,
+and why a third is even able to complete its development. We should
+also understand why one egg only passes through the first stages of
+segmentation and is then arrested, while another reaches a few more
+stages in advance, and a third develops so far that the embryo is
+nearly completely formed. These differences would depend upon the
+extent to which the germ-plasm, originally present in the egg, was
+sufficient for the development of the latter; development will be
+arrested as soon as the nucleoplasm is no longer capable of producing
+the succeeding stage, and is thus unable to enter upon the following
+nuclear division.</p>
+
+<p>From a general point of view such a theory would explain many
+difficulties, and it would render possible an explanation of the
+phyletic origin of parthenogenesis, and an adequate understanding
+of the strange and often apparently abrupt and arbitrary manner
+of its occurrence. In my works on Daphnidae I have already laid
+especial stress upon the proposition that parthenogenesis in insects
+and Crustacea certainly cannot be an ancestral condition which has
+been transmitted by heredity, but that it has been derived from a
+sexual condition. In what other way can we explain the fact that
+parthenogenesis is present in certain species or genera, but absent
+in others closely allied to them; or the fact that males are entirely
+wanting in species of which the females possess a complete apparatus
+for fertilization? I will not repeat all the arguments with which I
+attempted to support this conclusion. Such a conclusion may be almost
+certainly accepted for the Daphnidae, because parthenogenesis does not
+occur<span class="pagenum" id="Page_351">[Pg 351]</span> in their still living ancestors, the Phyllopods, and especially
+the Estheridae. In Daphnidae the cause and object of the phyletic
+development of parthenogenesis may be traced more clearly than in any
+other group of animals. In Daphnidae we can accept the conclusion with
+greater certainty than in all other groups, except perhaps the Aphidae,
+that parthenogenesis is extremely advantageous to species in certain
+conditions of life; and that it has only been adopted when, and as far
+as, it has been beneficial; and further, that at least in this group
+parthenogenesis became possible and was adopted in each species as soon
+as it became useful. Such a result can be easily understood if it is
+only the presence of more or less germ-plasm which decides whether an
+egg is or is not capable of development without fertilization.</p>
+
+<p>If we now examine the foundations of this hypothesis we shall find that
+we may at once accept one of its assumptions, viz., that fluctuations
+occur in the quantity of germ-plasm in the segmentation nucleus; for
+there can never be absolute equality in any single part of different
+individuals. As soon therefore as these fluctuations become so great
+that parthenogenesis is produced, it may become, by the operation of
+natural selection, the chief mode of reproduction of the species or
+of certain generations of the species. In order to place this theory
+upon a firm basis, we have simply to decide whether the quantity of
+germ-plasm contained in the segmentation nucleus is the factor which
+determines development; although for the present it will be sufficient
+if we can render this view to some extent probable, and show that it is
+not a contradiction of established facts.</p>
+
+<p>At first sight this hypothesis seems to encounter serious difficulties.
+It will be objected that neither the beginning nor the end of embryonic
+development can possibly depend upon the quantity of nucleoplasm in the
+segmentation nucleus, since the amount may be continually increased
+by growth; for it is well known that during embryonic development
+the nuclear substance increases with astonishing rapidity. By an
+approximate calculation I found that in the egg of a Cynips the
+quantity of nuclear substance present at the time when the blastoderm
+was about to be formed, and when there were twenty-six nuclei, was even
+then seven times as great as the quantity which had been contained
+in the segmentation nucleus. How then can we imagine that embryonic
+development would ever be arrested from want of nuclear<span class="pagenum" id="Page_352">[Pg 352]</span> substance, and
+if such deficiency really acted as an arresting force, how then could
+development begin at all? We might suppose that when germ-plasm is
+present in sufficient quantity to start segmentation, it must also be
+sufficient to complete the development; for it grows continuously, and
+must presumably always possess a power equal to that which it possessed
+at the beginning, and which was just sufficient to start the process of
+segmentation. If at each ontogenetic stage the quantity of nucleoplasm
+is just sufficient to produce the following stage, we might well
+imagine that the whole ontogeny would necessarily be completed.</p>
+
+<p>The flaw in this argument lies in the erroneous assumption that the
+growth of nuclear substance is, when the quality of the nucleus and
+the conditions of nutrition are equal, unlimited and uncontrolled. The
+intensity of growth must depend upon the quantity of nuclear substance
+with which growth and the phenomena of segmentation commenced. There
+must be an optimum quantity of nucleoplasm with which the growth of
+the nucleus proceeds most favourably and rapidly, and this optimum
+will be represented in the normal size of the segmentation nucleus.
+Such a size is just sufficient to produce, in a certain time and
+under certain external conditions, the nuclear substance necessary
+for the construction of the embryo, and to start the long series
+of cell-divisions. When the segmentation nucleus is smaller, but
+large enough to enter upon segmentation, the nuclei of the two first
+embryonic cells will fall rather more below the normal size, because
+the growth of the segmentation nucleus, during and after division will
+be less rapid on account of its unusually small size. The succeeding
+generations of nuclei will depart more and more from the normal size in
+each respective stage, because they do not pass into a resting stage
+during embryonic development, but divide again immediately after their
+formation. Hence nuclear growth would become less vigorous as the
+nuclei fell more and more below the optimum size, and at last a moment
+would arrive when they would be unable to divide, or would be at least
+unable to control the cell-body in such a manner as to lead to its
+division.</p>
+
+<p>The first event of importance for embryonic development is the
+maturation of the egg, <i>i. e.</i>, the transformation of the
+nucleus of the germ-cell into a nuclear spindle and the removal of
+the ovogenetic nucleoplasm by the separation of polar bodies, or by
+some analogous<span class="pagenum" id="Page_353">[Pg 353]</span> process. There must be some cause for this separation,
+and I have already tried to show that it may lie in the quantitative
+relations which obtain between the two kinds of nucleoplasm contained
+in the nucleus of the egg. I have suggested that the germ-plasm, at
+first small in quantity, undergoes a gradual increase, so that it
+can finally oppose the ovogenetic nucleoplasm. I will not further
+elaborate this suggestion, for the ascertained facts are insufficient
+for the purpose. But the appearances witnessed in nuclear division
+indicate that there are opposing forces, and that such a contest is
+the motive cause of division; and Roux may be right in referring the
+opposition to electrical forces. However this may be, it is perfectly
+certain that the development of this opposition is based upon internal
+conditions arising during growth in the nucleus itself. The quantity
+of nuclear thread cannot by itself determine whether the nucleus can
+or cannot enter upon division; if so, it would be impossible for two
+divisions to follow each other in rapid succession, as is actually
+the case in the separation of the two polar bodies, and also in their
+subsequent division. In addition to the effects of quantity, the
+internal conditions of the nucleus must also play an important part in
+these phenomena. Quantity alone does not necessarily produce nuclear
+division, or the nucleus of the egg would divide long before maturation
+is complete, for it contains much more nucleoplasm than the female
+pronucleus, which remains in the egg after the expulsion of the polar
+bodies, and which is in most cases capable of further division. But
+the fact that segmentation begins immediately after the conjugation of
+male and female pronuclei, also shows that quantity is an essential
+requisite. The effect of fertilization has been represented as
+analogous to that of the spark which kindles the gunpowder. In the
+latter case an explosion ensues, in the former segmentation begins.
+Even now many authorities are inclined to refer the polar repulsion
+manifested in the nuclear division which immediately follows
+fertilization, to the antagonism between male and female elements. But,
+according to the important discoveries of Flemming and van Beneden, the
+polar repulsion in each nuclear division is not based on the antagonism
+between male and female loops, but depends upon the antagonism and
+mutual repulsion between the two halves of the same loop. The loops of
+the father and those of the mother remain together and divide together
+throughout the whole ontogeny.</p>
+
+<p><span class="pagenum" id="Page_354">[Pg 354]</span></p>
+
+<p>What can be the explanation of the fact that nuclear division follows
+immediately after fertilization, but that without fertilization it
+does not occur in most cases? There is only one possible explanation,
+viz., the fact that the quantity of the nucleus has been suddenly
+doubled, as the result of conjugation. The difference between the male
+and female pronuclei cannot serve as an explanation, even though the
+nature of this difference is entirely unknown, because polar repulsion
+is not developed between the male and female halves of the nucleus, but
+within each male and each female half. We are thus forced to conclude
+that increase in the quantity of the nucleus affords an impulse for
+division, the disposition towards it being already present. It seems
+to me that this view does not encounter any theoretical difficulties,
+and that it is an entirely feasible hypothesis to suppose that, besides
+the internal conditions of the nucleus, its quantitative relation to
+the cell-body must be taken into especial account. It is imaginable, or
+perhaps even probable, that the nucleus enters upon division as soon
+as its idioplasm has attained a certain strength, quite apart from the
+supposition that certain internal conditions are necessary for this
+end. As above stated, such conditions may be present, but division may
+not occur because the right quantitative relation between nucleus and
+cell-body, or between the different kinds of nuclear idioplasm has not
+been established. I imagine that such a quantitative deficiency exists
+in an egg which, after the expulsion of the ovogenetic nucleoplasm
+in the polar bodies, requires fertilization in order to begin
+segmentation. The fact that the polar bodies were expelled proves that
+the quantity of the nucleus was sufficient to cause division, while
+afterwards it was no longer sufficient to produce such a result.</p>
+
+<p>This suggestion will be made still clearer by an example. In <i>Ascaris
+megalocephala</i> the nuclear substance of the female pronucleus
+forms two loops, and the male pronucleus does the same; hence the
+segmentation nucleus contains four loops, and this is also the case
+with the first segmentation spheres. If we suppose that in embryonic
+development the first nuclear division requires such an amount of
+nuclear substance as is necessary for the formation of four loops,—it
+follows that an egg, which can only form two or three loops from its
+nuclear reticulum, would not be able to develop parthenogenetically,
+and that not even the first division would take place. If we further<span class="pagenum" id="Page_355">[Pg 355]</span>
+suppose that, while four loops are sufficient to start nuclear
+division, these loops must be of a certain size and quantity in order
+to complete the whole ontogeny (in a certain species), it follows
+that eggs possessing a reticulum which contains barely enough nuclear
+substance to divide into four segments, would be able to produce
+the first division and perhaps also the second and third, or some
+later division, but that at a certain point during ontogeny, the
+nuclear substance would become insufficient, and development would be
+arrested. This will occur in eggs which enter upon development without
+fertilization, but are arrested before its completion. One might
+compare this retardation leading to the final arrest of development,
+to a railway train which is intended to meet a number of other trains
+at various junctions, and which can only travel slowly because of some
+defect in the engine. It will be a little behind time at the first
+junction, but it may just catch the train, and it may also catch the
+second or even the third; but it will be later at each successive
+junction, and will finally arrive too late for a certain train; and
+after that it will miss all the trains at the remaining junctions. The
+nuclear substance grows continuously during development, but the rate
+at which it increases depends upon the nutritive conditions together
+with its initial quantity. The nutritive changes during the development
+of an egg depend upon the quantity of the cell-body which was present
+at the outset, and which cannot be increased. If the quantity of
+the nuclear substance is rather too small at the beginning, it will
+become more and more insufficient in succeeding stages, as its growth
+becomes less vigorous, and differs more from the standard it would
+have reached if the original quantity had been normal. Consequently it
+will gradually fall more and more short of the normal quantity, like
+the train which arrives later and later at each successive junction,
+because its engine, although with the full pressure of steam, is unable
+to attain the normal speed.</p>
+
+<p>It will be objected that four loops cannot be necessary for nuclear
+division in <i>Ascaris</i>, since such division takes place in the
+formation of the polar bodies, resulting in the appearance of the
+female pronucleus with only two loops. But this fact only shows that
+the quantity of nuclear substance necessary for the formation of four
+loops is not necessary for all nuclear divisions; it does not disprove
+the assumption that such a quantity is required for the division of
+the<span class="pagenum" id="Page_356">[Pg 356]</span> segmentation nucleus. In addition to these considerations we must
+not leave the substance of the cell-body altogether out of account,
+for, although it is not the bearer of the tendencies of heredity, it
+must be necessary for every change undergone by the nucleus, and it
+surely also possesses the power of influencing changes to a large
+extent. There must be some reason for the fact that in all animal eggs
+with which we are acquainted, the nucleus moves to the surface of the
+egg at the time of maturation, and there passes through its well known
+transformation. It is obvious that it is there subjected to different
+influences from those which would have acted upon it in the center of
+the cell-body, and it is clear that such an unequal cell-division as
+takes place in the separation of the polar bodies could not occur if
+the nucleus remained in the center of the egg.</p>
+
+<p>This explanation of the necessity for fertilization does not exclude
+the possibility that, under certain circumstances, the substance of the
+egg-nucleus may be larger, so that it is capable of forming four loops.
+Eggs which thus possess sufficient nucleoplasm, viz., germ-plasm, for
+the formation of the requisite four loops of normal size (namely, of
+the size which would have been produced by fertilization), can and must
+develop by the parthenogenetic method.</p>
+
+<p>Of course the assumption that four loops must be formed has only
+been made for the sake of illustration. We do not yet know whether
+there are always exactly four loops in the segmentation nucleus. I
+may add that, although the details by which these considerations are
+illustrated are based on arbitrary assumptions, the fundamental view
+that the development of the egg depends, <i>ceteris paribus</i>, upon
+the quantity of nuclear substance, is certainly right, and follows as
+a necessary conclusion from the ascertained facts. It is not unlikely
+that such a view may receive direct proof in the results of future
+investigations. Such proof might, for instance, be forthcoming if we
+were to ascertain, in the same species, the number of loops present
+in the segmentation nucleus of fertilization, as compared with those
+present in the segmentation nucleus of parthenogenesis.</p>
+
+<p>The reproductive process in bees will perhaps be used as an argument
+against my theory. In these insects the same egg will develop into a
+female or male individual, according as fertilization has or has not
+taken place, respectively. Hence one and the same egg is capable<span class="pagenum" id="Page_357">[Pg 357]</span> of
+fertilization, and also of parthenogenetic development, if it does
+not receive a spermatozoon. It is in the power of the queen-bee to
+produce male or female individuals: by an act of will she decides
+whether the egg she is laying is to be fertilized or unfertilized.
+She “knows beforehand” whether an egg will develop into a male or a
+female animal, and deposits the latter kind in the cells of queens and
+workers, the former in the cells of drones. It has been shown by the
+discoveries of Leuckart and von Siebold that all the eggs are capable
+of developing into male individuals, and that they are only transformed
+into “female eggs” by fertilization. This fact seems to be incompatible
+with my theory as to the cause of parthenogenesis, for if the same
+egg, possessing exactly the same contents, and above all the same
+segmentation nucleus, may develop sexually or parthenogenetically, it
+appears that the power of parthenogenetic development must depend on
+some factor other than the quantity of germ-plasm.</p>
+
+<p>Although this appears to be the case, I believe that my theory
+encounters no real difficulty. I have no doubt whatever that the same
+egg may develop with or without fertilization. From a careful study of
+the numerous excellent investigations upon this point which have been
+conducted in a particularly striking manner by Bessels (in addition
+to the observers quoted above), I have come to the conclusion that
+the fact is absolutely certain. It must be candidly admitted that
+the same egg will develop into a drone when not fertilized, or into
+a worker or queen when fertilized. One of Bessels’ experiments is
+sufficient to prove this assertion. He cut off the wings of a young
+queen and thus rendered her incapable of taking “the nuptial flight.”
+He then observed that all the eggs which she laid developed into
+male individuals. This experiment was made in order to prove that
+drones are produced by unfertilized eggs; but it also proves that the
+assertion mentioned above is correct, for the eggs which ripen first
+and are therefore first laid, would have been fertilized had the queen
+been impregnated. The supposition that, at certain times, the queen
+produces eggs requiring fertilization, while at other times her eggs
+develop parthenogenetically, is quite excluded by this experiment; for
+it follows from it that the eggs must all be of precisely the same
+kind, and that there is no difference between the eggs which require
+fertilization and those which do not.</p>
+
+<p><span class="pagenum" id="Page_358">[Pg 358]</span></p>
+
+<p>But does it therefore follow that the quantity of germ-plasm in
+the segmentation nucleus is not the factor which determines the
+beginning of embryonic development? I believe not. It can be very
+well imagined that the nucleus of the egg, having expelled the
+ovogenetic nucleoplasm, may be increased to the size requisite for the
+segmentation nucleus in one of two ways: either by conjugation with
+a sperm-nucleus, or by simply growing to double its size. There is
+nothing improbable in this latter assumption, and one is even inclined
+to inquire why such growth does not take place in all unfertilized
+eggs. The true answer to this question must be that nature pursues
+the sexual method of reproduction, and that the only way in which the
+general occurrence of parthenogenesis could be prevented was by the
+production of eggs which remained sterile unless they were fertilized.
+This was effected by a loss of the capability of growth on the part of
+the egg-nucleus after it had expelled the ovogenetic nucleoplasm.</p>
+
+<p>The case of the bee proves in a very striking manner that the
+difference between eggs which require fertilization, and those which
+do not, is not produced until after the maturation of the egg and the
+removal of the ovogenetic nucleoplasm. The increase in the quantity of
+the germ-plasm cannot have taken place at any earlier period, or else
+the nucleus of the egg would always start embryonic development by
+itself, and the egg would probably be incapable of fertilization. For
+the relation between egg-nucleus and sperm-nucleus is obviously based
+upon the fact that each of them is insufficient by itself, and requires
+completion. If such completion had taken place at an early stage the
+egg-nucleus would either cease to exercise any attractive force upon
+the sperm-nucleus, or else conjugation would be effected, as in Fol’s
+interesting experiments upon fertilization by many spermatozoa; and,
+as in these experiments, malformation of the embryo would result. In
+Daphnidae I believe I have shown that the summer eggs are not only
+developed parthenogenetically, but also that they are never fertilized;
+and the explanation of this incapacity for fertilization may perhaps be
+found in the fact that their segmentation nucleus is already formed.</p>
+
+<p>We may therefore conclude that, in bees, the nucleus of the egg, formed
+during maturation, may either conjugate with the sperm-nucleus, or
+else if no spermatozoon reaches it the egg may, under the<span class="pagenum" id="Page_359">[Pg 359]</span> stimulus of
+internal causes, grow to double its size, thus attaining the dimensions
+of the segmentation nucleus. For our present purpose we may leave
+out of consideration the fact that in the latter case the individual
+produced is a male, and in the former case a female.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_37" href="#FNanchor_37" class="label">[37]</a>
+From <i>Essays upon Heredity and Kindred Biological
+Problems</i>, Vol. I (1889).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_360">[Pg 360]</span></p>
+<h2 class="nobreak" id="XXXV">XXXV<br>
+SIR NORMAN LOCKYER<br>
+1836-1920</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Sir Joseph Norman Lockyer, born at Rugby, England, May 17, 1836,
+entered the War Office in 1857. Through his own exertions he educated
+himself in science and was one of the first to suggest the hypothesis
+that the earth and other spheres were the result of the aggregation
+of meteorites. He was also the first to apply the spectroscope to
+the corona of the sun, revealing the chemical composition of solar
+prominences as chiefly hydrogen, calcium, and helium. He died at
+Sidmouth, Devonshire, August 16, 1920.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THE CHEMISTRY OF THE STARS<a id="FNanchor_38" href="#Footnote_38" class="fnanchor">[38]</a></p>
+
+<p>The importance of practical work, the educational value of the seeking
+after truth by experiment and observation on the part of even young
+students, are now generally recognized. That battle has been fought
+and won. But there is a tendency in the official direction of seats of
+learning to consider what is known to be useful, because it is used,
+in the first place. The fact that the unknown, that is, the unstudied,
+is the mine from which all scientific knowledge with its million
+applications has been won is too often forgotten.</p>
+
+<p>Bacon, who was the first to point out the importance of experiment in
+the physical sciences, and who predicted the applications to which I
+have referred, warns us that “<i>lucifera experimenta non fructifera
+quaerenda</i>”; and surely we should highly prize those results which
+enlarge the domain of human thought and help us to understand the
+mechanism of the wonderful universe in which our lot is cast, as well
+as those which add to the comfort and the convenience of our lives.</p>
+
+<p>It would be also easy to show by many instances how researches,<span class="pagenum" id="Page_361">[Pg 361]</span>
+considered ideally useless at the time they were made, have been the
+origin of the most tremendous applications. One instance suffices.
+Faraday’s trifling with wires and magnets has already landed us in one
+of the greatest revolutions which civilization has witnessed; and where
+the triumphs of electrical science will stop no man can say.</p>
+
+<p>This is a case in which the useless has been rapidly sublimed into
+utility so far as our material wants are concerned.</p>
+
+<p>I propose to bring to your notice another “useless” observation
+suggesting a line of inquiry which I believe sooner or later is
+destined profoundly to influence human thought along many lines.</p>
+
+<p>Fraunhofer at the beginning of this century examined sunlight and
+starlight through a prism. He found that the light received from the
+sun differed from that of the stars. So useless did his work appear
+that we had to wait for half a century till any considerable advance
+was made. It was found at last that the strange “lines” seen and named
+by Fraunhofer were precious indications of the chemical substances
+present in worlds immeasurably remote. We had, after half a century’s
+neglect, the foundation of solar and stellar chemistry, an advance in
+knowledge equaling any other in its importance.</p>
+
+<p>In dealing with my subject I shall first refer to the work which
+has been done in more recent years with regard to this chemical
+conditioning of the atmospheres of stars, and afterwards very briefly
+show how this work carries us into still other new and wider fields of
+thought.</p>
+
+<p>The first important matter which lies on the surface of such a general
+inquiry as this is that if we deal with the chemical elements as judged
+by the lines in their spectra we know for certain of the existence of
+oxygen, of nitrogen, of argon, representing one class of gases, in no
+celestial body whatever; whereas, representing other gases, we have a
+tremendous demonstration of the existence of all the known lines of
+hydrogen and helium.</p>
+
+<p>We see, then, that the celestial sorting out of gases is quite
+different from the terrestrial one.</p>
+
+<p>Taking the substances classed by the chemist as non-metals, we find
+carbon and silicium—I prefer, on account of its stellar behavior, to
+call it silicium, though it is old fashioned—present in celestial
+phenomena. We have evidence of this in the fact that we have a
+considerable development of carbon in some stars and an indication
+of silicium in others. But these are the only non-metals observed.<span class="pagenum" id="Page_362">[Pg 362]</span>
+Now, with regard to the metallic substances which we find, we deal
+chiefly with calcium, strontium, iron, and magnesium. Others are not
+absolutely absent, but their percentage quantity is so small that they
+are negligible in a general statement.</p>
+
+<p>Now do these chemical elements exist indiscriminately in all the
+celestial bodies, so that practically, from a chemical point of view,
+the bodies appear to us of similar chemical constitution? No; it is not
+so.</p>
+
+<p>From the spectra of those stars which resemble the sun, in that they
+consist of an interior nucleus surrounded by an atmosphere which
+absorbs the light of the nucleus, and which, therefore, we study by
+means of this absorption, it is to be gathered that the atmospheres
+of some stars are chiefly gaseous—i. e., consisting of elements we
+recognize as gases here—of others chiefly metallic, of others again
+mainly composed of carbon or compounds of carbon.</p>
+
+<p>Here, then, we have spectroscopically revealed the fact that there is
+considerable variation in the chemical constituents which build up the
+stellar atmospheres.</p>
+
+<p>This, though a general, is still an isolated statement. Can we connect
+it with another? One of the laws formulated by Kirchhoff in the infancy
+of spectroscopic inquiry has to do with the kind of radiation given
+out by bodies at different temperatures. A poker placed in a fire
+first becomes red, and, as it gets hotter, white hot. Examined in a
+spectroscope, we find that the red condition comes from the absence of
+blue light; that the white condition comes from the gradual addition of
+blue as the temperature increases.</p>
+
+<p>The law affirms that the hotter a mass of matter is the farther its
+spectrum extends into the ultraviolet.</p>
+
+<p>Hence the hotter a star is the farther does its complete or continuous
+spectrum lengthen out toward the ultraviolet and the less it is
+absorbed by cooler vapors in its atmosphere.</p>
+
+<p class="space-below2">
+Now, to deal with three of the main groups of stars, we find the
+following very general result:</p>
+
+<table class="autotable">
+<tbody><tr>
+<td class="tdl">Gaseous stars</td>
+<td class="tdr">Longest spectrum.</td>
+</tr><tr>
+<td class="tdl">Metallic stars</td>
+<td class="tdr">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Medium spectrum.</td>
+</tr><tr>
+<td class="tdl">Carbon stars</td>
+<td class="tdr">Shortest spectrum.</td>
+</tr>
+</tbody>
+</table>
+
+<p class="space-above2">
+We have now associated two different series of phenomena, and we are
+enabled to make the following statement:</p>
+
+<p><span class="pagenum" id="Page_363">[Pg 363]</span></p>
+
+<table class="autotable">
+<tbody><tr>
+<td class="tdl">Gaseous stars</td>
+<td class="tdr">Highest temperature.</td>
+</tr><tr>
+<td class="tdl">Metallic stars</td>
+<td class="tdr">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Medium temperature.</td>
+</tr><tr>
+<td class="tdl">Carbon stars</td>
+<td class="tdr">Lowest temperature.</td>
+</tr>
+</tbody>
+</table>
+
+<p class="space-above2">
+Hence the differences in apparent chemical constitutions are associated
+with differences of temperature.</p>
+
+<p>Can we associate with the two to which I have already called attention
+still a third class of facts? Laboratory work enables us to do this.
+When I began my inquiries the idea was, one gas or vapor, one spectrum.
+We now know that this is not true; the systems of bright lines given
+out by radiating substances change with the temperature.</p>
+
+<p>We can get the spectrum of a well known compound substance—say
+carbonic oxide; it is one special to the compound; we increase the
+temperature so as to break up the compound, and we then get the spectra
+of its constituents, carbon and oxygen.</p>
+
+<p>But the important thing in the present connection is that the spectra
+of the chemical elements behave exactly in the same way as the spectra
+of known compounds do when we employ temperatures far higher than those
+which break up the compounds; and indeed in some cases the changes
+are more marked. For brevity I will take for purposes of illustration
+three substances, and deal with one increase of temperature only, a
+considerable one and obtainable by rendering a substance incandescent,
+first by a direct current of electricity, as happens in the so-called
+“arc lamps” employed in electric lighting, and next by the employment
+of a powerful induction coil and battery of Leyden jars. In laboratory
+parlance we pass thus from the arc to the jar-spark. In the case of
+magnesium, iron, and calcium, the changes observed on passing from
+the temperature of the arc to that of the spark have been minutely
+observed. In each, new lines are added or old ones are intensified at
+the higher temperature. Such lines have been termed “enhanced lines.”</p>
+
+<p>These enhanced lines are not seen alone; outside the region of high
+temperature in which they are produced, the cooling vapors give us the
+cool lines. Still we can conceive the enhanced lines to be seen alone
+at the highest temperature in a space sufficiently shielded from the
+action of all lower temperatures, but such a shielding is beyond our
+laboratory expedients.</p>
+
+<p><span class="pagenum" id="Page_364">[Pg 364]</span></p>
+
+<p class="space-below2">
+In watching the appearance of these special enhanced lines in stellar
+spectra we have a third series of phenomena available, and we find that
+the results are absolutely in harmony with what has gone before. Thus:</p>
+
+<table class="autotable">
+<tbody><tr>
+<td class="tdl">Gaseous stars</td>
+<td class="tdc">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Highest temperature&nbsp;&nbsp;</td>
+<td class="tdl">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Strong helium and faint enhanced lines.</td>
+</tr><tr>
+<td class="tdl">Metallic stars</td>
+<td class="tdc">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Medium temperature</td>
+<td class="tdl">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Feeble helium and strong enhanced lines.</td>
+</tr><tr>
+<td class="tdl">Carbon stars</td>
+<td class="tdc">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>
+<td class="tdl">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;No helium and strong arc lines.</td>
+</tr><tr>
+<td class="tdl"></td>
+<td class="tdc">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Lowest temperature</td>
+<td class="tdl">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Faint arc lines.</td>
+</tr>
+</tbody>
+</table>
+
+<p class="space-above2">
+It is clear now, not only that the spectral changes in stars are
+associated with, or produced by, changes of temperature, but that
+the study of the enhanced spark and the arc lines lands us in the
+possibility of a rigorous stellar thermometry, such lines being more
+easy to observe than the relative lengths of spectrum.</p>
+
+<p>Accepting this, we can take a long stride forward and, by carefully
+studying the chemical revelations of the spectrum, classify the stars
+along a line of temperature. But which line? Were all the stars in
+popular phraseology created hot? If so, we should simply deal with
+the running down of temperature, and because all the hottest stars
+are chemically alike, all cooler stars would be alike. But there are
+two very distinct groups of coolest stars; and since there are two
+different kinds of coolest stars, and only one kind of hottest stars,
+it cannot be merely a question either of a running up or a running down
+of temperature.</p>
+
+<p>Many years of very detailed inquiry have convinced me that all stars
+save the hottest must be sorted out into two series—those getting
+hotter and those, like our sun, getting cooler, and that the hottest
+stage in the history of a star is reached near the middle of its life.</p>
+
+<p>The method of inquiry adopted has been to compare large-scale
+photographs of the spectra of the different stars taken by my
+assistants at South Kensington; the complete harmony of the results
+obtained along various lines of other work carries conviction with it.</p>
+
+<p>We find ourselves here in the presence of minute details exhibiting the
+workings of a chemical law, associated distinctly with temperature;
+and more than this, we are also in the presence of high temperature
+furnaces, entirely shielded by their vastness from the presence of
+those distracting phenomena which we are never free<span class="pagenum" id="Page_365">[Pg 365]</span> from in the most
+perfect conditions of experiment we can get here.</p>
+
+<p>What, then, is the chemical law? It is this: In the very hottest
+stars we deal with the gases hydrogen, helium, and doubtless others
+still unknown, almost exclusively. At the next lowest temperatures we
+find these gases being replaced by metals in the state in which they
+are observed in our laboratories when the most powerful jar-spark is
+employed. At a lower temperature still the gases almost disappear
+entirely, and the metals exist in the state produced by the electric
+arc. Certain typical stars showing these chemical changes may be
+arranged as follows:</p>
+
+<figure class="figcenter width500" id="p365" style="width: 2245px;">
+<img src="images/p365.jpg" width="2245" height="605" alt="A diagram
+showing the temperature evolution of stars, from stars getting hotter,
+to the hottest stars, then to stars cooling, listing specific stars
+along this progression.">
+
+</figure>
+
+<p>This, then, is the result of our first inquiry into the existence of
+the various chemical elements in the atmospheres of stars generally.
+We get a great diversity, and we know that this diversity accompanies
+changes of temperature. We have also found that the sun, which we
+independently know to be a cooling star, and Arcturus are identical
+chemically.</p>
+
+<p>We have now dealt with the presence of the various chemical elements
+generally in the atmospheres of stars. The next point we have to
+consider is, whether the absorption which the spectrum indicates for
+us takes place from top to bottom of the atmosphere or only in certain
+levels.</p>
+
+<p>In many of these stars the atmosphere may be millions of miles high. In
+each the chemical substances in the hottest and coldest portions may be
+vastly different. The region, therefore, in which this absorption takes
+place, which spectroscopically enables us to discriminate star from
+star, must be accurately known before we can obtain the greatest amount
+of information from our inquiries.</p>
+
+<p>Our next duty then, clearly, is to study the sun—a star so near us
+that we can examine the different parts of its atmosphere, which we
+cannot do in the case of the more distant stars. By doing this we
+may secure facts which will enable us to ascertain in what parts of<span class="pagenum" id="Page_366">[Pg 366]</span>
+the atmosphere the absorption takes place which produces the various
+phenomena on which the chemical classification has been based.</p>
+
+<p>It is obvious that the general spectrum of the sun, like that of stars
+generally, is built up of all the absorptions which can make themselves
+felt in every layer of its atmosphere from bottom to top; that is, from
+the photosphere to the outermost part of the corona. Let me remind you
+that this spectrum is changeless from year to year.</p>
+
+<p>Now, sun-spots are disturbances produced in the photosphere; and the
+chromosphere, with its disturbances, called prominences, lies directly
+above it. Here, then, we are dealing with the lowest part of the sun’s
+atmosphere. We find first of all that, in opposition to the changeless
+general spectrum, great changes occur with the sun-spot period, both in
+the spots and chromosphere.</p>
+
+<p>The spot spectrum is indicated, as was found in 1866, by the widening
+of certain lines; the chromospheric spectrum, as was found in 1868, by
+the appearance at the sun’s limb of certain bright lines. In both cases
+the lines affected, seen at any one time, are relatively few in number.</p>
+
+<p>In the spot spectrum, at a sun-spot minimum, we find iron lines chiefly
+affected; at a maximum they are chiefly of unknown or unfamiliar
+origin. At the present moment the affected lines are those recorded
+in the spectra of vanadium and scandium, with others never seen in
+a laboratory. That we are here far away from terrestrial chemical
+conditions is evidenced by the fact that there is not a gram of
+scandium available for laboratory use in the world at the present time.</p>
+
+<p>Then we have the spectrum of the prominences and the chromosphere. That
+spectrum we are enabled to observe every day when the sun shines, as
+conveniently as we can observe that of sun spots. The chromosphere is
+full of marvels. At first, when our knowledge of spectra was very much
+more restricted than now, almost all the lines observed were unknown.
+In 1868 I saw a line in the yellow, which I found behaved very much
+like hydrogen, though I could prove that it was not due to hydrogen;
+for laboratory use the substance which gave rise to it I called helium.
+Next year I saw a line in the green at 1474 of Kirchhoff’s scale. That
+was an unknown line, but in some subsequent researches I traced it to
+iron. From that day to this we have observed a large number of lines.
+They have<span class="pagenum" id="Page_367">[Pg 367]</span> gradually been dragged out from the region of the unknown,
+and many are now recognized as enhanced lines, to which I have already
+called attention as appearing in the spectra of metals at a very high
+temperature.</p>
+
+<p>But useful as the method of observing the chromosphere without an
+eclipse, which enables us</p>
+
+<div class="poetry-container">
+<div class="poetry">
+ <div class="stanza">
+ <div class="verse indent0">“... to feel from world to world,”</div>
+ </div>
+</div>
+</div>
+
+<p class="nind">
+as Tennyson has put it, has proved, we want an eclipse to see it face
+to face.</p>
+
+<p>A tremendous flood of light has been thrown upon it by the use of large
+instruments constructed on a plan devised by Respighi and myself in
+1871. These give us an image of the chromosphere painted in each one
+of its radiations, so that the exact locus of each chemical layer is
+revealed. One of the instruments employed during the Indian eclipse of
+this year is that used in photographing the spectra of stars, so that
+it is now easy to place photographs of the spectra of the chromosphere
+obtained during a total eclipse and of the various stars side by side.</p>
+
+<p>I have already pointed out that the chemical classification indicated
+that the stars next above the sun in temperature are represented by γ
+Cygni and Procyon, one on the ascending, the other on the descending
+branch of the temperature curve.</p>
+
+<p>Studying the spectra photographed during the eclipse of this year we
+see that practically the lower part of the sun’s atmosphere, if present
+by itself, would give us the lines which specialize the spectra of γ
+Cygni or Procyon.</p>
+
+<p>I recognize in this result a veritable Rosetta stone, which will enable
+us to read the celestial hieroglyphics presented to us in stellar
+spectra, and help us to study the spectra and to get at results much
+more distinctly and certainly than ever before.</p>
+
+<p>One of the most important conclusions we draw from the Indian eclipse
+is that, for some reason or other, the lowest, hottest part of the
+sun’s atmosphere does not write its record among the lines which build
+up the general spectrum so effectively as does a higher one.</p>
+
+<p>There was another point especially important on which we hoped for
+information, and that was this: Up to the employment of the prismatic
+camera insufficient attention had been directed to the fact<span class="pagenum" id="Page_368">[Pg 368]</span> that in
+observations made by an ordinary spectroscope no true measure of the
+height to which the vapors or gases extended above the sun could be
+obtained; early observations, in fact, showed the existence of glare
+between the observer and the dark moon; hence it must exist between us
+and the sun’s surroundings.</p>
+
+<p>The prismatic camera gets rid of the effects of this glare, and its
+results indicate that the effective absorbing layer—that, namely,
+which gives rise to the Fraunhofer lines—is much more restricted in
+thickness than was to be gathered from the early observations.</p>
+
+<p>We are justified in extending these general conclusions to all the
+stars that shine in the heavens.</p>
+
+<p>So much, then, in brief, for solar teachings in relation to the record
+of the absorption of the lower parts of stellar atmospheres.</p>
+
+<p>Let us next turn to the higher portions of the solar surroundings, to
+see if we can get any effective help from them.</p>
+
+<p>In this matter we are dependent absolutely upon eclipses, and I shall
+fulfill my task very badly if I do not show you that the phenomena
+then observable when the so-called corona is visible, full of awe and
+grandeur to all, are also full of precious teaching to the student
+of science. This also varies like the spots and prominences with the
+sun-spot period.</p>
+
+<p>It happened that I was the only person that saw both the eclipse of
+1871 at the maximum of the sun-spot period and that of 1878 at minimum;
+the corona of 1871 was as distinct from the corona of 1878 as anything
+could be. In 1871 we got nothing but bright lines, indicating the
+presence of gases; namely, hydrogen and another, since provisionally
+called coronium. In 1878 we got no bright lines at all, so I stated
+that probably the changes in the chemistry and appearance of the corona
+would be found to be dependent upon the sun-spot period, and recent
+work has borne out that suggestion.</p>
+
+<p>I have now specially to refer to the corona as observed and
+photographed this year in India by means of the prismatic camera,
+remarking that an important point in the use of the prismatic camera is
+that it enables us to separate the spectrum of the corona from that of
+the prominences.</p>
+
+<p>One of the chief results obtained is the determination of the position
+of several lines of probably more than one new gas, which, so far, have
+not been recognized as existing on the earth.</p>
+
+<p><span class="pagenum" id="Page_369">[Pg 369]</span></p>
+
+<p>Like the lowest hottest layer, for some reason or other, this upper
+layer does not write its record among the lines which build up the
+general spectrum.</p>
+
+
+<p class="nindc space-above2 space-below2">
+GENERAL RESULTS REGARDING THE LOCUS OF ABSORPTION IN STELLAR ATMOSPHERES</p>
+
+<p>We learn from the sun, then, that the absorption which defines the
+spectrum of a star is the absorption of a middle region, one shielded
+both from the highest temperature of the lowest reaches of the
+atmosphere, where most tremendous changes are continually going on and
+the external region where the temperature must be low, and where the
+metallic vapors must condense.</p>
+
+<p>If this is true for the sun it must be equally true for Arcturus,
+which exactly resembles it. I go further than this, and say that in
+the presence of such definite results as those I have brought before
+you it is not philosophical to assume that the absorption may take
+place at the bottom of the atmosphere of one star or at the top of the
+atmosphere of another. The <i>onus probandi</i> rests upon those who
+hold such views.</p>
+
+<p>So far I have only dealt in detail with the hotter stars, but I have
+pointed out that we have two distinct kinds of coolest ones, the
+evidence of their much lower temperature being the shortness of their
+spectra. In one of these groups we deal with absorption alone, as in
+those already considered; we find an important break in the phenomena
+observed; helium, hydrogen, and metals have practically disappeared,
+and we deal with carbon absorption alone.</p>
+
+<p>But the other group of coolest stars presents us with quite new
+phenomena. We no longer deal with absorption alone, but accompanying
+it we have radiation, so that the spectra contain both dark lines and
+bright ones. Now, since such spectra are visible in the case of new
+stars, the ephemera of the skies, which may be said to exist only for
+an instant relatively, and when the disturbance which gives rise to
+their sudden appearance has ceased, we find their places occupied by
+nebulæ, we cannot be dealing here with stars like the sun, which has
+already taken some millions of years to slowly cool, and requires more
+millions to complete the process into invisibility.</p>
+
+<p>The bright lines seen in the large number of permanent stars which<span class="pagenum" id="Page_370">[Pg 370]</span>
+resemble these fleeting ones—new stars, as they are called—are those
+discerned in the once mysterious nebulæ which, so far from being stars,
+were supposed not many years ago to represent a special order of
+created things.</p>
+
+<p>Now the nebulæ differ from stars generally in the fact that in their
+spectra we have practically to deal with radiation alone; we study them
+by their bright lines; the conditions which produce the absorption by
+which we study the chemistry of the hottest stars are absent.</p>
+
+
+<p class="nindc space-above2 space-below2">
+A NEW VIEW OF STARS</p>
+
+<p>Here, then, we are driven to the perfectly new idea that some of the
+cooler bodies in the heavens, the temperature of which is increasing
+and which appear to us as stars, are really disturbed nebulæ.</p>
+
+<p>What, then, is the chemistry of the nebulæ? It is mainly gaseous;
+the lines of helium and hydrogen and the flutings of carbon, already
+studied by their absorption in the groups of stars to which I have
+already referred, are present as bright ones.</p>
+
+<p>The presence of the lines of the metals iron, calcium, and probably
+magnesium, shows us that we are not dealing with gases merely.</p>
+
+<p>Of the enhanced metallic lines there are none; only the low temperature
+lines are present, so far as we yet know. The temperature, then, is
+low, and lowest of all in those nebulæ where carbon flutings are seen
+almost alone.</p>
+
+
+<p class="nindc space-above2 space-below2">
+A NEW VIEW OF NEBULÆ</p>
+
+<p>Passing over the old views, among them one that the nebulæ were holes
+in something dark which enabled us to see something bright beyond, and
+another that they were composed of a fiery fluid, I may say that not
+long ago, they were supposed to be masses of gases only, existing at a
+very high temperature.</p>
+
+<p>Now, since gases may glow at a low temperature as well as at a high
+one, the temperature evidence must depend upon the presence of cool
+metallic lines and the absence of the enhanced ones.</p>
+
+<p>The nebulæ, then, are relatively cool collections of some of the
+permanent gases and of some cool metallic vapors, and both gases and
+metals are precisely those I have referred to as writing their records
+most visibly in stellar atmosphere.</p>
+
+<p><span class="pagenum" id="Page_371">[Pg 371]</span></p>
+
+<p>Now, can we get more information concerning this association of certain
+gases and metals? In laboratory work it is abundantly recognized that
+all meteorites (and many minerals) when slightly heated give out
+permanent gases, and under certain conditions the spectrum of the
+nebulæ may in this way be closely approximated to. I have not time to
+labor this point, but I may say that a discussion of all the available
+observations to my mind demonstrates the truth of the suggestion, made
+many years ago by Professor Tait before any spectroscopic facts were
+available, that the nebulæ are masses of meteorites rendered hot by
+collisions.</p>
+
+<p>Surely human knowledge is all the richer for this indication of the
+connection between the nebulæ, hitherto the most mysterious bodies in
+the skies, and the “stones that fall from heaven.”</p>
+
+
+<p class="nindc space-above2 space-below2">
+CELESTIAL EVOLUTION</p>
+
+<p>But this is, after all, only a stepping stone, important though it be.
+It leads us to a vast generalization. If the nebulæ are thus composed,
+they are bound to condense to centers, however vast their initial
+proportions, however irregular the first distribution of the cosmic
+clouds which compose them. Each pair of meteorites in collision puts us
+in mental possession of what the final stage must be. We begin with a
+feeble absorption of metallic vapors round each meteorite in collision;
+the space between the meteorites is filled with the permanent gases
+driven out farther afield and having no power to condense. Hence
+dark metallic and bright gas lines. As time goes on the former must
+predominate, for the whole swarm of meteorites will then form a gaseous
+sphere with a strongly heated center, the light of which will be
+absorbed by the exterior vapor.</p>
+
+<p>The temperature order of the group of stars with bright lines as well
+as dark ones in their spectra has been traced, and typical stars
+indicating the chemical changes have been as carefully studied as those
+in which absorption phenomena are visible alone, so that now there are
+no breaks in the line connecting the nebulæ with the stars on the verge
+of extinction.</p>
+
+<p>Here we are brought to another tremendous outcome—that of the
+evolution of all cosmical bodies from meteorites, the various stages
+recorded by the spectra being brought about by the various conditions
+which follow from the conditions.</p>
+
+<p><span class="pagenum" id="Page_372">[Pg 372]</span></p>
+
+<p>These are, shortly, that at first collisions produce luminosity among
+the colliding particles of the swarm, and the permanent gases are given
+off and fill the interspaces. As condensation goes on, the temperature
+at the center of condensation always increasing, all the meteorites
+in time are driven into a state of gas. The meteoritic bombardment
+practically now ceases for lack of material, and the future history
+of the mass of gas is that of a cooling body, the violent motions in
+the atmosphere while condensation was going on now being replaced by a
+relative calm.</p>
+
+<p>The absorption phenomena in stellar spectra are not identical at
+the same mean temperature on the ascending and descending sides of
+the curve, on account of the tremendous difference in the physical
+conditions.</p>
+
+<p>In a condensing swarm, the center of which is undergoing meteoritic
+bombardment from all sides, there cannot be the equivalent of the
+solar chromosphere; the whole mass is made up of heterogeneous vapor
+at different temperatures and moving with different velocities in
+different regions.</p>
+
+<p>In a condensed swarm, of which we can take the sun as a type, all
+action produced from without has practically ceased; we get relatively
+a quiet atmosphere and an orderly assortment of the vapors from top to
+bottom, disturbed only by the fall of condensed metallic vapors. But
+still, on the view that the differences in the spectra of the heavenly
+bodies chiefly represent differences in degree of condensation and
+temperature, there can be <i>au fond</i>, no great chemical difference
+between bodies of increasing and bodies of decreasing temperature.
+Hence we find at equal mean temperatures on opposite sides of the
+temperature curve this chemical similarity of the absorbing vapors
+proved by many points of resemblance in the spectra, especially the
+identical behavior of the enhanced metallic and cleveite lines.</p>
+
+
+<p class="nindc space-above2 space-below2">
+CELESTIAL DISSOCIATION</p>
+
+<p>The time you were good enough to put at my disposal is now exhausted,
+but I cannot conclude without stating that I have not yet exhausted
+all the conceptions of a high order to which Fraunhofer’s apparently
+useless observation has led us.</p>
+
+<p>The work which to my mind has demonstrated the evolution of the<span class="pagenum" id="Page_373">[Pg 373]</span> cosmos
+as we know it from swarms of meteorites, has also suggested a chemical
+evolution equally majestic in its simplicity.</p>
+
+<p>A quarter of a century ago I pointed out that all the facts then
+available suggested the hypothesis that in the atmospheres of the sun
+and stars various degrees of “celestial dissociation” were at work,
+a “dissociation” which prevented the coming together of the finest
+particles of matter which at the temperature of the earth and at all
+artificial temperature yet attained here compose the metals, the
+metalloids and compounds.</p>
+
+<p>On this hypothesis the so-called atoms of the chemist represent not the
+origins of things, but only early stages of the evolutionary process.</p>
+
+<p>At the present time we have tens of thousands of facts which were not
+available twenty-five years ago. All these go to the support of the
+hypothesis, and among them I must indicate the results obtained at the
+last eclipse, dealing with the atmosphere of the sun in relation to
+that of the various stars of higher temperature to which I called your
+attention. In this way we can easily explain the enhanced lines of iron
+existing practically alone in Alpha Cygni. I have yet to learn any
+other explanation.</p>
+
+<p>I have nothing to take back, either from what I then said or what I
+have said since on this subject, and although the view is not yet
+accepted, I am glad to know that many other lines of work which are now
+being prosecuted tend to favor it.</p>
+
+<p>I have no hesitation in expressing my conviction that in a not distant
+future the inorganic evolution to which we have been finally led by
+following up Fraunhofer’s useless experiment will take its natural
+place side by side with that organic evolution, the demonstration of
+which has been one of the glories of the nineteenth century.</p>
+
+<p>And finally now comes the moral of my address. If I have helped to show
+that observations having no immediate practical bearing may yet help
+on the thought of mankind, and that this is a thing worth the doing,
+let me express a hope that such work shall find no small place in the
+future University of Birmingham.</p>
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_38" href="#FNanchor_38" class="label">[38]</a>
+From an address delivered at the University of Birmingham
+(1900).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<p><span class="pagenum" id="Page_374">[Pg 374]</span></p>
+<h2 class="nobreak" id="XXXVI">XXXVI<br>
+ROBERT KOCH<br>
+1843-1910</h2>
+</div>
+
+
+<div class="blockquot">
+
+<p><i>Robert Koch, born at Klausthal, Hanover, Germany, December 11,
+1843, graduated from Göttingen in 1866. After a short period as
+assistant surgeon in the General Hospital in Hamburg, he practised
+medicine at Langenhagen, Kackwitz, and Wollstein from 1872 to 1880,
+during which time he began his researches in bacteriology. By 1878 he
+had placed bacteriology on a scientific basis. In 1880 he was called
+to Berlin as chief of the Sanitary Institute, where he continued his
+studies of tuberculosis and cholera. After inventing new microscopical
+appliances and a new technique, in 1882 he stated his discovery of
+the tubercle bacillus. In 1883, after publishing a method for the
+prevention of anthrax by inoculation, he was sent by his government
+to Egypt and India to investigate cholera. During that work he
+discovered the cholera bacillus. In 1884 he returned to Germany and
+in the following year went to France as cholera commissioner. In 1888
+he published a paper on the prophylaxis of infectious diseases in the
+army. In later years he investigated the bubonic plague, malaria, and
+sleeping-sickness. He died at Baden-Baden, May 28, 1910.</i></p>
+</div>
+
+
+<p class="nindc space-above2 space-below2">
+THEORY OF BACTERIA<a id="FNanchor_39" href="#Footnote_39" class="fnanchor">[39]</a></p>
+
+<p>I am well aware that the investigations above described are very
+imperfect. It was necessary, in order to have time for those parts
+of the investigation which seemed the most important and essential,
+to omit the examination of many organs, such as the brain, heart,
+retina, etc., which ought not to pass unnoticed in researches on
+infective diseases. For the same reason no record was kept of the
+temperature,<span class="pagenum" id="Page_375">[Pg 375]</span> although this would undoubtedly have yielded most
+interesting results. I have intentionally refrained from entering into
+details of morbid anatomy, as only the etiology interested me, and as
+I did not feel qualified to undertake a study of the morbid anatomy of
+traumatic infective diseases. I must therefore leave this part of the
+investigation to those who are better able to undertake it.</p>
+
+<p>Nevertheless I consider that the results of my researches are
+sufficiently definite to enable me to deduce from them some well
+founded conclusions.</p>
+
+<p>In this summary I shall, however, confine myself to the most obvious
+conclusions. It has indeed of late become too common to draw the most
+sweeping conclusions as to infective diseases in general from the
+most unimportant observations on bacteria. I shall not follow this
+custom, although the material at my command would furnish rich food
+for meditation. For the longer I study infective diseases the more am
+I convinced that generalisations of new facts are here a mistake, and
+that every individual infective disease or group of closely allied
+diseases must be investigated for itself.</p>
+
+<p>As regards the artificial traumatic infective diseases observed by me,
+the conditions which must be established before their parasitic nature
+can be proved, we completely fulfilled in the case of the first five,
+but only partially in that of the sixth. For the infection was produced
+by such small quantities of fluid (blood, serum, pus, etc.) that the
+result cannot be attributed to a merely chemical poison.</p>
+
+<p>In the materials used for inoculation bacteria were without exception
+present, and in each disease a different and well marked form of
+organism could be demonstrated.</p>
+
+<p>At the same time, the bodies of those animals which died of the
+artificial traumatic infective diseases contained bacteria in
+such numbers that the symptoms and the death of the animals were
+sufficiently explained. Further, the bacteria found were identical
+with those which were present in the fluid used for inoculation, and a
+definite form of organisms corresponded in every instance to a distinct
+disease.</p>
+
+<p>These artificial traumatic infective diseases bear the greatest
+resemblance to human traumatic infective diseases, both as regards
+their origin from putrid substances, their course, and the result of
+post-mortem examination. Further, in the first case, just as in the
+last,<span class="pagenum" id="Page_376">[Pg 376]</span> the parasitic organisms could be only imperfectly demonstrated
+by the earlier methods of investigation; not till an improved method of
+procedure was introduced was it possible to obtain complete proof that
+they were parasitic diseases. We are therefore justified in assuming
+that human traumatic infective diseases will in all probability be
+proved to be parasitic when investigated by these improved methods.</p>
+
+<p>On the other hand, it follows from the fact that a definite pathogenic
+bacterium, e. g., the septicæmic bacillus, cannot be inoculated on
+every variety of animal (a similar fact is also true with regard to the
+bacillus anthracis); that the septicæmia of mice, rabbits, and man are
+not under all circumstances produced by the same bacterial form. It is
+of course possible that one or other of the bacteric forms found in
+animals also play a part in such diseases in the human subject. That,
+however, must be especially demonstrated for each case; <i>a priori</i>
+one need only expect that bacteria are present; as regards form, size
+and conditions of growth, they may be similar, but not always the same,
+even in what appear to be similar diseases in different animals.</p>
+
+<p>Besides the pathogenic bacteria already found in animals there are no
+doubt many others. My experiments refer only to those diseases which
+ended fatally. Even these are in all probability not exhausted in the
+six forms mentioned. Further experiments on many different species
+of animals, with the most putrid substances and with every possible
+modification in the method of application, will doubtless bring to
+light a number of other infective diseases, which will lead to further
+conclusions regarding infective diseases and pathogenic bacteria.</p>
+
+<p>But even in the small series of experiments which I was able to carry
+out, one fact was so prominent that I must regard it as constant,
+and, as it helps to remove most of the obstacles to the admission of
+the existence of a centagium vivum for traumatic infective diseases,
+I look on it as the most important result of my work. I refer to
+the differences which exist between pathogenic bacteria and to the
+constancy of their characters. A distinct bacteric form corresponds, as
+we have seen, to each disease, and this form always remains the same,
+however often the disease is transmitted from one animal to another.
+Further, when we succeed in reproducing the same disease <i>de novo</i>
+by the injection of putrid substances, only the same bacteric form
+occurs which was before found to be specific for that disease.</p>
+
+<p>Further, the differences between these bacteria are as great as could<span class="pagenum" id="Page_377">[Pg 377]</span>
+be expected between particles which border on the invisible. With
+regard to these differences, I refer not only to the size and form
+of the bacteria, but also to the conditions of their growth, which
+can be best recognized by observing their situation and grouping. I
+therefore study not only the individual alone, but the whole group of
+bacteria, and would, for example, consider a micrococcus which in one
+species of animal occurred only in masses (i. e., in a zooglæa form),
+as different from another which in the same variety of animal, under
+the same conditions of life, was only met with as isolated individuals.
+Attention must also be paid to the physiological effect, of which I
+scarcely know a more striking example than the case of the bacillus
+and the chain-like micrococcus growing together in the cellular tissue
+of the ear; the one passing into the blood and penetrating into the
+white blood corpuscles, the other spreading out slowly into the tissues
+in its vicinity and destroying everything around about; or again, the
+case of the septicæmic and pyæmic micrococci of the rabbit in their
+different relations to the blood; or lastly, the bacilli only extending
+over the surface of the aural cartilage in the erysipetalous disease,
+as contrasted with the bacillus anthracis, likewise inoculated on the
+rabbit’s ear, but quickly passing into the blood.</p>
+
+<p>As, however, there corresponds to each of the diseases investigated a
+form of bacterium distinctly characterized by its physiological action,
+by its conditions of growth, size, and form, which, however often the
+disease be transmitted from one animal to another, always remains the
+same and never passes over into another form, e. g., from the spherical
+to the rod shaped, we must in the meantime regard these different forms
+of pathogenic bacteria as distinct and constant species.</p>
+
+<p>This is, however, an assertion that will be much disputed by botanists,
+to whose special province this subject really belongs.</p>
+
+<p>Amongst those botanists who have written against the subdivision of
+bacteria into species, is Nägeli, who says, “I have for ten years
+examined thousands of different forms of bacteria, and I have not yet
+seen any absolute necessity for dividing them even into two distinct
+species.”</p>
+
+<p>Brefeld also states that he can only admit the existence of specific
+forms justifying the formation of distinct species when the whole
+history of development has been traced by cultivation from spore to
+spore in the most nutritive fluids.</p>
+
+<p><span class="pagenum" id="Page_378">[Pg 378]</span></p>
+
+<p>Although Brefeld’s demand is undoubtedly theoretically correct it
+cannot be made a <i>sine qua non</i> in every investigation on
+pathogenic bacteria. We should otherwise be compelled to cease our
+investigations into the etiology of infective diseases till botanists
+have succeeded in finding out the different species of bacteria by
+cultivation and development from spore to spore. It might then very
+easily happen that the endless trouble of pure cultivation would be
+expended on some form of bacterium which would finally turn out to be
+scarcely worthy of attention. In practice only the opposite method can
+work. In the first place certain peculiarities of a particular form of
+bacterium different from those of other forms, and in the second place
+its constancy, compel us to separate it from other less known and less
+interesting, and provisionally to regard it as a species. And now, to
+verify this provisional supposition, the cultivation from spore to
+spore may be undertaken. If this succeeds under conditions which cut
+out all sources of fallacy, and if it furnishes a result corresponding
+to that obtained by the previous observations, then the conclusions
+which were drawn from these observations and which led to its being
+ranked as a distinct species must be regarded as valid.</p>
+
+<p>On this, which as it seems to me is the only correct practical method,
+I take my stand, and, till the cultivation of bacteria from spore to
+spore shows that I am wrong, I shall look on pathogenic bacteria as
+consisting of different species.</p>
+
+<p>In order, however, to show that I do not stand alone in this view, I
+shall here mention the opinion of some botanists who have already come
+to a similar conclusion.</p>
+
+<p>Cohn states that, in spite of the fact that many dispute the necessity
+of separating bacteria into genera or species, he must nevertheless
+adhere to the method as yet followed by him, and separate bacteria
+of a different form and fermenting power from each other, so long as
+complete proof of their identity is not given.</p>
+
+<p>From his investigations on the effects of different temperatures and
+of desiccation on the development of bacterium termo, Eidam came to
+the conclusion that different forms of bacteria require different
+conditions of nutriment, and that they behave differently towards
+physical and chemical influences. He regards these facts as a further
+proof of the necessity of dividing organisms into distinct species.</p>
+
+<p>I shall bring forward another reason to show the necessity of looking<span class="pagenum" id="Page_379">[Pg 379]</span>
+on the pathogenic bacteria which I have described as distinct species.
+The greatest stress, in investigations on bacteria, is justly laid on
+the so-called pure cultivations, in which only one definite form of
+bacterium is present. This evidently arises from the view that if, in a
+series of cultivations, the same form of bacterium is always obtained,
+a special significance must attach to this form: it must indeed be
+accepted as a constant form, or in a word as a species. Can, then,
+a series of pure cultivations be carried out without admixture of
+other bacteria? It can in truth be done, but only under very limited
+conditions. Only such bacteria can be cultivated pure, with the aids
+at present at command, which can always be known to be pure, either by
+their size and easily recognizable form, as the bacillus anthracis, or
+by the production of a characteristic coloring matter as the pigment
+bacteria. When, during a series of cultivations, a strange species of
+bacteria has by chance got in, as may occasionally happen under any
+circumstances, it will in these cases be at once observed, and the
+unsuccessful experiment will be thrown out of the series without the
+progress of investigation being thereby necessarily interfered with.</p>
+
+<p>But the case is quite different when attempts are made to carry
+out cultivations of very small bacteria, which, perhaps, cannot be
+distinguished at all without staining; how are we then to discover the
+occurrence of contamination? It is impossible to do so, and therefore
+all attempts at pure cultivation in apparatus, however skilfully
+planned and executed, must, as soon as small bacteria with but little
+characteristic appearances are dealt with, be considered as subject to
+unavoidable sources of fallacy, and in themselves inconclusive.</p>
+
+<p>But nevertheless a pure cultivation is possible, even in the case
+of the bacteria which are smallest and most difficult to recognise.
+This, however, is not conducted in cultivation apparatus, but in
+the animal body. My experiments demonstrate this. In all the cases
+of a distinct disease, e. g., of septicæmia of mice, only the small
+bacilli were present, and no other form of bacterium was ever found
+with it, unless in the case where that causing the tissue gangrene was
+intentionally inoculated at the same time. In fact, there exists no
+better cultivation apparatus for pathogenic bacteria than the animal
+body itself. Only a very limited number of bacteria can grow in the
+body, and the penetration of organisms into it is so difficult that
+the uninjured living body may be regarded as completely isolated
+with respect to other forms of<span class="pagenum" id="Page_380">[Pg 380]</span> bacteria than those intentionally
+introduced. It is quite evident, from a careful consideration of
+the two diseases produced in mice—septicæmia and gangrene of the
+tissue—that I have succeeded in my experiments in obtaining a pure
+cultivation. In the putrefying blood, which was the cause of these two
+diseases, the most different forms of bacteria were present, and yet
+only two of these found in the living mouse the conditions necessary
+for their existence. All the others died, and these two alone, a small
+bacillus and a chain-like micrococcus, remained and grew. These could
+be transferred from one animal to another as often as was desired,
+without suffering any alteration in their characteristic form, in
+their specific physiological action and without any other variety of
+bacteria at any time appearing. And further, as I have demonstrated, it
+is quite in the power of the experimenter to separate these two forms
+of bacteria from each other. When the blood in which only the bacilli
+are present is used, these alone are transmitted, and thenceforth are
+obtained quite pure; while on the other hand, when a field mouse is
+inoculated with both forms of bacteria, the bacilli disappear, and
+the micrococcus can be then cultivated pure. Doubtless an attempt to
+unite these two forms again in the same animal by inoculation would
+have been successful. In short, one has it completely in one’s power
+to cultivate several varieties of bacteria together, to separate them
+from each other, and eventually to combine them again. Greater demands
+can hardly be made on a pure cultivation, and I must therefore regard
+the successive transmission of artificial infective diseases as the
+best and surest method of pure cultivation. And it can further claim
+the same power of demonstrating the existence of specific forms of
+bacteria, as must be conceded to any faultless cultivation experiments.</p>
+
+<p>From the fact that the animal body is such an excellent apparatus for
+pure cultivation, and that, as we have seen, when the experiments are
+properly arranged and sufficient optical aids used, only one specific
+form of bacterium can be found in each distinct case of artificial
+traumatic infective disease, we may now further conclude that when, in
+examining a traumatic infective disease, several different varieties
+of bacteria are found, as e. g., chains of small granules, rods, and
+long, oscillating threads—such as were seen together by Coze and Feltz
+in the artificial septicæmia of rabbits—we have to do either with a
+combined infective disease,—that is, not a pure one,—or, what in the
+case<span class="pagenum" id="Page_381">[Pg 381]</span> cited is more probable, an inexact and inaccurate observation.
+When, therefore, several species of bacteria occur together in any
+morbid process, before definite conclusions are drawn as to the
+relations of the disease in question to the organisms, either proof
+must be furnished that they are all concerned in the morbid process,
+or an attempt must be made to isolate them and to obtain a true
+pure cultivation. Otherwise we cannot avoid the objection that the
+cultivation was not pure, and therefore not conclusive. I shall only
+briefly refer to a further necessary consequence of the admission of
+the existence of different species of pathogenic bacteria. The number
+of the species of these bacteria is limited; for, of the numerous
+diverse forms present in putrid fluids, one or but few can in the most
+favorable cases develop in the animal body. Those which disappear
+are, for that species of animal at least, not pathogenic bacteria.
+If, however, as follows from the foregoing, there exist hurtful and
+harmless bacteria, experiments performed on animals with the latter,
+e. g., with bacterium termo, prove absolutely nothing for or against
+the behavior of the former—the pathogenic—forms. But almost all the
+experiments of this nature have been carried out with the first mixture
+of different species of bacteria which came to hand without there being
+any certainty that pathogenic bacteria were in reality present in the
+mixture. It is therefore evident that none of these experiments can
+be regarded as furnishing evidence of any value for or against the
+parasitic nature of infective diseases.</p>
+
+<p>In all my experiments, not only have the form and size of the bacteria
+been constant, but the greatest uniformity in their actions on the
+animal organisms has been observed, though no increase of virulence, as
+described by Coze and Feltz, Davaine, and others. This leads me to make
+some remarks on the supposed law of the increasing virulence of blood
+when transmitted through successive animals, discovered or confirmed by
+the investigators just named.</p>
+
+<p>The discovery of this law has, as is well known, been received with
+great enthusiasm, and it has excited no little interest owing to its
+intimate bearing on the doctrine of natural selection (Anpassung and
+Vererbung). Some investigators, who are in other things very exact,
+have allowed themselves to be blinded by the seductive theory that
+the insignificant action of a single putrefactive bacterium may, by
+continued natural selection in passing from animal to animal, be
+increased<span class="pagenum" id="Page_382">[Pg 382]</span> in virulence till it becomes deadly though a drop of the
+infective liquid be diluted in a quadrillion times. They have founded
+thereon the most beautiful practical applications, not suspecting that
+the bacteria in question have never been certainly demonstrated.</p>
+
+<p>The original works of Coze and Feltz, as also that of Davaine, are
+not at my disposal for reference; and I cannot therefore enter into
+a complete criticism of them. So far, however, as I can gather from
+the references accessible to me, especially from the detailed notices
+in Virchow and Hirch’s “Jahnesbericht,” no complete proof that the
+virulence of septicæmic blood increases from generation to generation
+seems to have been furnished. Apparently blood more and more diluted
+was injected, and astonishment was felt when this always acted, the
+effect being then ascribed to its increasing virulence. But controlling
+experiments to ascertain whether the septicæmic blood were not already
+as virulent in the second and third generations as in the twenty-fifth,
+do not seem to have been made. My experiments so far support and are in
+accordance with those of Coze, Feltz, and Davaine in that for the first
+infection of an animal relatively large quantities of putrid fluid are
+necessary; but in the second generation, or at the latest in the third,
+the full virulence was attained, and afterwards remained constant.</p>
+
+<p>Of my artificial infective diseases the septicæmia of the mouse has
+the greatest correspondence with the artificial septicæmia described
+by Davaine. If we were to experiment with this disease in the same
+manner as Davaine experimented, we would, if no controlling experiments
+were employed, find the same increase in virulence of the disease. It
+would only be necessary to use blood in slowly decreasing quantities in
+order to obtain in this way any progressive increase of the virulence
+that might be desired. I, however, took from the second or third
+animal the smallest possible quantity of material for inoculation, and
+thus arrived more quickly at the greatest degree of virulence. Till,
+therefore, I am assured that, in the septicæmia observed by Davaine,
+such controlling experiments were made, I can only look on an increase
+in virulence as holding good for the earlier generations. In order
+to explain this we do not, however, require to have recourse to the
+magical wand of natural selection; a feasible explanation can be very
+naturally furnished. Let us take again the septicæmia of mice, as being
+the most suitable example.</p>
+
+<p><span class="pagenum" id="Page_383">[Pg 383]</span></p>
+
+<p>If two drops of putrefying blood be injected into such an animal
+there is introduced not only a number of totally distinct species
+of bacteria, but also a certain amount of dissolved putrid poison
+(sepsin), not sufficient to produce a fatal effect, but yet certainly
+not without influence on the health of the animal. Different factors
+must therefore be considered as affecting the health of the animal. On
+the one hand there is the dissolved poison, on the other the different
+species of bacteria, of which, however, perhaps only two, as in the
+example before us, can multiply in the body of the mouse and there
+exert a continuous noxious influence. Only one of these two species can
+penetrate into the blood, and if the blood alone be used for further
+inoculations, only this one variety will come victorious out of the
+battle for existence. The further development of the experiment depends
+entirely on the quantity of the putrid poison, and on the relation
+of the two forms of bacteria to each other in point of numbers. If
+one injects a large amount of septic poison and a large number of
+that variety of bacteria which increase locally (in this case the
+chain-like micrococci causing the gangrene of the tissue), but only a
+very small number of the bacteria which pass into the blood (here the
+bacilli), the first animal experimented on will die, as a result of the
+preponderation influence of the first two factors before many bacilli
+can have got into the blood and multiplied there. Of the blood of this
+first animal, containing, as it does, proportionately very few bacilli,
+one-fifth to one-tenth of a drop must be inoculated in order to convey
+the disease with certainty. In the second animal, however, only the
+bacilli are introduced, and these develop undisturbed in the blood. For
+the infection of the third animal the smallest quantity of this blood
+which can produce an effect is then sufficient, and after this third
+generation the virulence of the blood remains uniform.</p>
+
+<p>We may also imagine another case in which the increase of the virulence
+may go on through more than two generations without any modification
+resulting from natural selection and transmission from animal to
+animal. This would take place if several species of bacteria capable
+of passing into the blood were introduced into the animal at the first
+injection. Let us suppose, for example, that in the same putrefying
+blood which served for the foregoing experiment, the bacilli of
+anthrax were also present, there would then be contained in the blood
+of the first animal not only the septicæmic bacillus, but also<span class="pagenum" id="Page_384">[Pg 384]</span>
+bacillus anthracis, and of each only a small number; of the anthrax
+bacilli there would be even fewer than of the other, because in mice
+they are deposited chiefly in the spleen, lungs, etc.; while in the
+blood of the heart they are, even in the most favorable cases, only
+sparsely distributed. On the other hand, the anthrax bacilli have
+this advantage, that, provided they be inoculated in considerable
+numbers, they kill even within twenty hours, while the septicæmic
+bacilli only destroy life after fifty hours. In the blood of the second
+animal, therefore, both species of bacilli would be present in larger
+numbers than in the first, although not yet so numerous as if either
+organism had been inoculated singly. Hence a larger quantity of blood
+is necessary to ensure transmission to a third animal. Perhaps this
+might be the case even in the fourth generation, till finally one or
+other variety of bacillus would alone be present in the blood injected.
+Probably this would be the septicæmic bacillus.</p>
+
+<p>In this way the experiments of Coze, Feltz, and Davaine may admit of
+simple explanation and be brought into harmony with my results.</p>
+
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote">
+
+<p class="nind"><a id="Footnote_39" href="#FNanchor_39" class="label">[39]</a>
+From the English translation (1880) of <i>Untersuchungen
+über die Aetiologie der Wundinfectionskrankheiten</i> (1878).</p>
+
+</div>
+</div>
+
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<div class="transnote spa1">
+<p class="nindc"><b>TRANSCRIBER’S NOTES</b></p>
+
+<p>Simple typographical errors have been silently corrected; unbalanced
+quotation marks were remedied when the change was obvious, and
+otherwise left unbalanced.</p>
+
+<p>Punctuation, hyphenation, and spelling were made consistent when a
+predominant preference was found in the original book; otherwise they
+were not changed.
+</p>
+</div></div>
+<div style='text-align:center'>*** END OF THE PROJECT GUTENBERG EBOOK 77076 ***</div>
+</body>
+</html>
+
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