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diff --git a/old/66702-0.txt b/old/66702-0.txt deleted file mode 100644 index 8714a99..0000000 --- a/old/66702-0.txt +++ /dev/null @@ -1,5417 +0,0 @@ -The Project Gutenberg eBook of Wireless Telegraphy and Telephony Simply -Explained, by Alfred Morgan - -This eBook is for the use of anyone anywhere in the United States and -most other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms -of the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you -will have to check the laws of the country where you are located before -using this eBook. - -Title: Wireless Telegraphy and Telephony Simply Explained - A Practical Treatise - -Author: Alfred Morgan - -Illustrator: Alfred Morgan - -Release Date: November 10, 2021 [eBook #66702] - -Language: English - -Character set encoding: UTF-8 - -Produced by: James Simmons - -*** START OF THE PROJECT GUTENBERG EBOOK WIRELESS TELEGRAPHY AND TELEPHONY -SIMPLY EXPLAINED *** -Wireless Telegraphy and Telephony Simply Explained - -Transcriber's Note - -This book was transcribed from scans of the original found at Google -Books. I have not transcribed the original book's index. Variant -spelling are not corrected. Some illustrations are rotated. - -WIRELESS TELEGRAPHY - -AND TELEPHONY - -SIMPLY EXPLAINED, - -A PRACTICAL TREATISE - -Embracing Complete and Detailed Explanations of - -the Theory and Practice of Modern Radio - -Apparatus and its Present Day Applications, - -together with a chapter on the - -Possibilities of its Future Development - -BY ALFRED P. MORGAN - -EDITOR MECHANICAL AND ELECTRICAL DEPARTMENT OF THE "BOY'S MAGAZINE," - -AUTHOR OF - -WIRELESS TELEGRAPH CONSTRUCTION FOR AMATEURS, ETC. - -VERY FULLY ILLUSTRATED - -NEW YORK - -THE NORMAN W. HENLEY PUBLISHING CO. - -132 NASSAU STREET - -1916 - -COPYRIGHT 1915 AND 1912 BY - -THE NORMAN W. HENLEY PUBLISHING COMPANY - -Composition, Electrotyping and Printing - -By J. J. LITTLE & Ives Co., New York - -PREFACE - -Probably no marvel of modern science so grips the imagination as the -mystery of those quivering impulses which go forth invisibly to link a -ship sailing over the seas with the shores of the distant land. - -The author has endeavored to furnish a comprehensive explanation, in -simple language, of the theory and practice of this wonderful art, and -to explain, as far as possible, the importance of the position occupied -by wireless telegraphy to-day and the possibilities of to-morrow. - -The title of this book naturally limits the amount of discussion that -can be undertaken, and so, in the space at command, there has not been -any real attempt made to enter into any engineering or constructive -details further than is necessary to make the text clear. - -Much that might properly be made a part of the preface has been embodied -in the book, in order to avoid repetition, and to also bring certain -matter to the attention of those readers who consider a preface to be -merely an opportunity for the author of a book to express opinions very -often quite foreign to the title, and so unconcernedly skip it with -hardly more than a passing glance. - -The author wishes to extend his sincere thanks to Mr. H. W. Young, -Editor of Popular Electricity; to Mr. John Firth, to Colonel George P. -Scriven, and to the Scientific American, for their kindness in supplying -photographs for some of the illustrations, and to his friend, Mr. -Safford Adams, who has kindly read the proofs and made many valuable -suggestions. - -ALFRED P. MORGAN. May, 1915. - -TO - -NIKOLA TESLA - -WHOSE GENIUS HAS HARNESSED ELECTRICITY TO THE DAILY WORK OF MAN AND -WHOSE INVENTIONS ARE THE BASIS OF ALL MODERN WIRELESS TRANSMISSION, THIS -BOOK IS DEDICATED. - -TABLE OF CONTENTS - - PREFACE - - CHAPTER I. INTRODUCTORY: WIRELESS TRANSMISSION AND RECEPTION. THE - ETHER. ELECTRICAL OSCILLATIONS. ELECTROMAGNETIC WAVES. - - CHAPTER II. THE MEANS FOR RADIATING AND INTERCEPTING ELECTRIC WAVES. - AERIAL SYSTEMS. EARTH CONNECTION. - - CHAPTER III. THE TRANSMITTING APPARATUS. - - CHAPTER IV. THE RECEIVING APPARATUS. - - CHAPTER V. TUNING AND COUPLING, DIRECTIVE WAVE TELEGRAPHY. - - CHAPTER VI. THE DIGNITY OF WIRELESS. ITS APPLICATIONS AND SERVICE. - WIRELESS IN THE ARMY AND NAVY. WIRELESS ON AN AEROPLANE. HOW A - MESSAGE IS SENT AND RECEIVED. - - CHAPTER VII. THE EAR. HOW WE HEAR. SOUND AND SOUND WAVES. THE VOCAL - CHORDS. THE STRUCTURE OF SPEECH. - - CHAPTER VIII. THE TELEPHONE TRANSMITTER AND RECEIVER. THE PHOTO - PHONE. THE THERMOPHONE. THE SELENIUM CELL. THE SPEAKING ARC. - - CHAPTER IX. THE WIRELESS TELEPHONE. - - CHAPTER X. REMARKS. THEORY. ACCOMPLISHMENTS. MAXWELL'S HERTZ'S - DISCOVERY. THE FUTURE. - - CATALOGUE OF GOOD, PRACTICAL BOOKS - -LIST OF ILLUSTRATIONS - -Fig. 1.—Throw a stone into a pool of water and little waves will radiate -from the spot where the stone struck. - -Fig. 2.—A Leyden jar is a glass jar lined inside and outside with -tinfoil for about two-thirds of its height. - -Fig. 3.—A static machine, connected to a Leyden jar. - -Fig. 4.—A Leyden jar discharging through a coil of wire. - -Fig. 5.—Curved line representing an oscillatory discharge of a Leyden -jar. - -Fig. 6.—Navy type of Leyden jars. - -Fig. 7.—The simplest practical transmitter. - -Fig. 8.—A cross-section of the aerial and atmosphere. - -Fig. 9.—Under the same conditions, but viewed from above. - -Fig. 10.—A simple receiving arrangement. - -Fig. 11.—An amateur aerial and station. - -Fig. 12.—The Army wireless station at Fort Gibbons. - -Fig. 13.—Lightning discharge near Montclair, N. J. - -Fig. 14.–Photo of double lightning discharge passing to earth near the -First Orange Mountain, Montclair, N. J. - -Fig. 15.—Vertical aerials of the grid, fan and inverted pyramid types. - -Fig. 16.—A diagram showing pyramid aerial. - -Fig. 17.–A diagram illustrating the directive action of a flat-top -aerial. - -Fig. 18.—Aerials of the "V" and inverted "L" types. - -Fig. 19.—A diagram showing the arrangement of a "T" aerial. - -Fig. 20.—Flat top aerials of the inverted "U" and "T" types. - -Fig. 21.—Umbrella aerial. - -Fig. 22.—An amateur aerial (flat top). - -Fig. 23.—Diagram showing the difference between loop and straightaway -aerials. - -Fig. 24.—Showing how wires are arranged and insulated. - -Fig. 25.—Aerial insulator. - -Fig. 26.—Leading-in insulator. - -Fig. 27.–A side view of the aerial shown in Fig. 22. - -Fig. 28.—Diagram showing how batteries may be arranged. - -Fig. 29.—The power plant of a Marconi transatlantic station. - -Fig. 30.—If a magnet be suddenly plunged into a hollow coil of wire a -momentary current will be induced in the coil. - -Fig. 31.—Magnetic phantom formed by a bar magnet. - -Fig. 32.—Magnetic phantom formed by a wire carrying current. - -Fig. 33.—Magnetic phantom formed by a coil of wire carrying current. - -Fig. 34.—Diagram of induction coil. - -Fig. 35.—Induction coil for wireless telegraph purposes. - -Fig. 36.—Induction coil primary and secondary. - -Fig. 37.—Interrupter for induction coil. - -Fig. 38.—Electrolytic interrupter. - -Fig. 39.—Open and closed core transformers. - -Fig. 40.—Lines representing direct and intermittent direct currents. - -Fig. 41.—Diagram representing alternating current. - -Fig. 42.—High potential humming transformer. - -Fig. 43.—High potential closed core transformer for wireless work. - -Fig. 44.—Leyden jar set for oil immersion. - -Fig. 45.—Oil immersed condenser. - -Fig. 46.—Diagram showing construction of condenser. - -Fig. 47.–Tubular condenser. - -Fig. 48.—Helix. - -Fig. 49.—Close coupled helix. - -Fig. 50.—Spark gap. - -Fig. 51.—Circuit showing tuned transmitting system employing close -coupled helix. - -Fig. 52.—Photo of spark gap. - -Fig. 53.—Quenched spark gap. - -Fig. 54.—Diagram of aerial switch. - -Fig. 55.—Photo of aerial switch. - -Fig. 56.—Anchor gap. - -Fig. 57.–Wireless key. - -Fig. 58.—Photo of wireless key. - -Fig. 59.—Key and aerial switch. - -Fig. 60.—Portable receiving set and case. - -Fig. 61.—Complete receiving outfit. - -Fig. 62.—Portable pack set. - -Fig. 63.—Complete receiving set. - -Fig. 64.—Showing the construction of a watch case telephone receiver. - -Fig. 65.—Pickard adjustable telephone receivers. - -Fig. 66.—Illustrating the valve action of a rectifying detector. - -Fig. 67.—A new type of silicon detector. - -Fig. 68.—Diagram drawing analogy between rectifying action of a detector -and pump. - -Fig. 69.—Pyron detector. - -Fig. 70.—Perikon detector. - -Fig. 71.—Silicon detector. - -Fig. 72.—Electrolytic detector. - -Fig. 73.—Electrolytic detector in circuit. - -Fig. 74.—Potentiometer. - -Fig. 75.—Diagram showing how potentiometer is connected in a circuit. - -Fig. 76.—Analogy between swinging and tuning. - -Fig. 77.—Receiving a message in a Marconi transatlantic station. - -Fig. 78.—Tuning coil of the double slide type. - -Fig. 79.—Diagram showing fixed condenser in circuit. - -Fig. 80.–Fixed condenser. - -Fig. 81.—Rotary variable condenser. - -Fig. 82.—Interior of rotary variable condenser, showing construction. - -Fig. 83.—Dr. Seibt's rotary variable condenser. - -Fig. 84.—Sliding plate variable condenser. - -Fig. 85.—Diagram showing arrangement of rotary variable condenser in -receiving circuit. - -Fig. 86.—Chain and ball arranged to illustrate the effect of tuning. - -Fig. 87.—Loose coupled helix. - -Fig. 88.—Hot-wire ammeter. - -Fig. 89.—The principle of the hot-wire ammeter. - -Fig. 90.—Diagram showing loose coupled helix in circuit. - -Fig. 91.—Loose coupled tuning coil. - -Fig. 92.—Loose coupled tuner. - -Fig. 93.—Diagram showing position of loose coupler in circuit. - -Fig. 94.–Fort Gibbons, Alaska, wireless station. - -Fig. 95.—Transmitting condenser. - -Fig. 96.—Braun's method for directing wireless telegraph signals. - -Fig. 97.—Bellini-Tosi radio-goniometer. - -Fig. 98.—Arrangement of Bellini and Tosi for directive wireless -telegraphy. - -Fig. 99.—Complete receiving and transmitting outfit. - -Fig. 100.—Special lightweight wireless telegraph set for airship -service. - -Fig. 101.—Telefunken wireless cart, showing transmitter. - -Fig. 102.—Telefunken wireless cart for military service. - -Fig. 103.—Telefunken wireless wagon set in operation at Fort Leavenworth. - -Fig. 104.—Wireless room aboard the U. S. transport "Buford". - -Fig. 105. The apparatus set up for operation. - -Fig. 106.—Wireless equipped automobile. - -Fig. 107.—Co. Signal Corps at San Antonio. - -Fig. 108.—U. S. Signal Corps pack set shown open and closed. - -Fig. 109.—The receiving apparatus of the airship "America". - -Fig. 110.—Interior of the N. Y. Herald Press station. - -Fig. 111.—Operating the U. S. Signal Corps airship wireless apparatus. - -Fig. 112.—The N. Y. Herald station, showing aerial. - -Fig. 113.—Operator Jack Irwin overhauling the wireless apparatus for the -dirigible balloon "America". - -Fig. 114.—Morse code. - -Fig. 115.—Continental code. - -Fig. 116.—Transmitting equipment of the high-power station at Nauen. - -Fig. 117.—Duplex receiving apparatus. - -Fig. 118.—Breaking-in system. - -Fig. 119.—The receiving apparatus of the station at Nauen. - -Fig. 120.—Diagram of the ear. - -Fig. 121.—The ossicles. - -Fig. 122.—Bon jour. - -Fig. 123.—Experiment showing sounding bodies are in vibration. - -Fig. 124.—Method of registering vibrations of a tuning fork. - -Fig. 125.—Way line made by a bristle attached to a tuning fork prong in -vibration when passed over smoked glass. - -Fig. 126.—Illustrating the action of air waves. - -Fig. 127.—The vocal chords in position for making a sound. - -Fig. 128.—The vocal chords when relaxed. - -Fig. 129.–Koenig's manometric flame apparatus. - -Fig. 130.—Appearance of manometric flame in revolving mirror. - -Fig. 131.—Diagram of a telephone transmitter. - -Fig. 132.—Diagram showing the principle and construction of the -telephone receiver. - -Fig. 133.—The photophone. - -Fig. 134.—Photophone receiving apparatus. - -Fig. 135.—Photophone transmitting apparatus. - -Fig. 136.—Powerful searchlight arranged to transmit speech over a beam -of light. - -Fig. 137.—The electric arc. - -Fig. 138.—Circuit showing how a singing arc is arranged. - -Fig. 139.—A logical form of wireless telephone which is impractical. - -Fig. 140.—DeForest wireless telephone equipment. - -Fig. 141.—Wireless telephone receiving apparatus (induction method). - -Fig. 142.—Fessenden wireless telephone transmitting phonograph music. - -Fig. 143.—Diagram illustrating why damped oscillations will not carry -the voice. - -Fig. 144.—How the sound waves of the voice are impressed upon undamped -oscillations. - -Fig. 145.—Arrangement of the speaking arc. - -Fig. 146.—Diagram showing how a wireless telephone transmitting system -is arranged. - -Fig. 147.—Poulsen wireless telephone equipment. - -Fig. 148.—The Majorana wireless telephone transmitter. - -Fig. 149.—Showing the brush discharge from a Marconi transatlantic -aerial at night. - -Fig. 150.—An amateur wireless' telegraph station. - -Fig. 151.—The high-power naval wireless telegraph station under -construction at Washington, D. C. - -Fig. 152.—The curved lines represent the radius of the government -high-power wireless stations and show the zones over which direct -communication may be had with ships. - -Fig. 153.—The aerial system of a transatlantic station. - -Fig. 154.—Fong Yee, a Chinese amateur wireless operator. - -Fig. 155.—Tesla world power plant. - -Fig. 156.—Twenty-five-foot sparks from a Tesla transformer. - -CHAPTER I. INTRODUCTORY: WIRELESS TRANSMISSION AND RECEPTION. THE ETHER. -ELECTRICAL OSCILLATIONS. ELECTROMAGNETIC WAVES. - -Wireless telegraphy, that marvelous art which has made possible the -instantaneous transmission of intelligence between widely distant parts -having no apparent physical connection save that of the earth, air, and -water, is one of those wonders of science which appeal to the average -mind as either incomprehensible or only explainable through the use of -highly technical language. Contrary to this general opinion, however, -the whole theory and practice of the wireless transmission of messages -is capable of the simplest explanation. - -[Illustration: FIG. 1.—Throw a stone into a pool of water and little -waves will radiate from the spot where the stone struck.] - -Throw a stone into a pool of water. A disturbance is immediately -created, and little waves will radiate from the spot where the stone -struck the water, gradually spreading out into enlarging circles until -they reach the shores or die away. By throwing several stones in -succession with varying intervals between them it would be possible to -so arrange a set of signals that they would convey a meaning to one who -is initiated, standing on the opposite side of the pool. The little -waves are the vehicle which transmits the intelligence, and the water -the medium in which the waves travel. - -Wireless telegraph instruments are simply a means for creating and -detecting waves in a great pool of ether. - -Scientists suppose that all space and matter is pervaded with a -hypothetical medium of extreme tenuity and elasticity, called -luminiferous ether, or simply ether. - -Although ether is invisible, odorless, and practically weightless, it is -not merely the fantastic creation of speculative philosophers, but is as -essential to our existence as the air we breathe and the food we eat. By -imagining and accepting its reality, it is possible to explain and -understand many scientific puzzles. The universe is a vast pool of -ether. It is all-pervading. There is no void. It is diffused even among -the molecules of which solid bodies are composed. The study of this -substance is, perhaps, one of the most fascinating and important duties -of the physicist. - -Ninety million miles away from our earth is a huge flaming body of -vapors and gases, called the sun. This seething mass of flame and heat -furnishes us more than mere winter and summer and night and day, for we -on this earth are not living on our own resources, and the real work of -the world so necessary for even bare existence is accomplished by the -energy of the sun stored up in coal, in plants and trees and mountain -torrents. - -Light is known to be vibrations of an extremely rapid -period—*electromagnetic waves*, they are called. Heat can be shown to be -of the same nature. Traveling at the rate of over 180,000 miles per -second, these two great gifts of the sun come streaming continually down -to us over the inconceivable distance of almost 100,000,000 miles. Both -require a medium for their propagation. The ether supplies it. It is the -substance with which the universe is filled. Incidentally it is also the -seat of all electrical and magnetic forces. - -[Illustration: FIG. 2.—A Leyden jar is a glass jar lined inside and out -with tinfoil for about two-thirds of its height.] - -In throwing the stone into the pool of water, muscular energy of the arm -is transferred to the stone, and the latter, upon striking the surface -of the pond, imparts a portion of that stored energy to the little waves -which are immediately created in the water. In setting up -electromagnetic waves for wireless communication the energy imparted to -the ether is electrical energy, developed by certain interesting -instruments explained further on. - -Let us consider briefly how the waves are created in a wireless -telegraph station. Almost every one has seen and heard the brilliant -snapping spark produced by the discharge of a Leyden jar. A Leyden jar -in its common form is a glass jar lined inside and out with tinfoil for -about two thirds of its height. A brass rod, terminating in a knob, -connects below with the inner coating, usually by means of a loose -chain. It may be described as a device which is capable of storing -electricity in the form of energy and discharging this energy again in -actual electricity. - -This discharge has been the subject of many interesting investigations -of direct interest. - -[Illustration: FIG. 3.—A static machine connected to a Leyden jar.] - -The inner and outer coatings are connected to the terminals of a static -electric machine (an apparatus for generating electricity), and the -machine set in rotation. After the jar has been charged, the electric -machine is disconnected and one end of a coil of heavy wire connected to -the outside coating, while the other end of the wire is made to approach -the knob connected with the inner coating. Before the end of the wire -reaches the knob a discharge occurs through the coil, producing a noisy -brilliant spark between the wire and the knob. The discharge appears -like a single spark, but in reality it is composed of a great many -following each other in rapid succession. The jar discharges its energy, -first by a tremendous rush of current in one direction, and then another -discharge somewhat smaller than the first in the opposite direction. -There is a series of these discharges in reverse directions, but each -discharge is less and less, until the whole amount of energy is -expended. The complete series of discharges takes place in an almost -immeasurable fraction of time. It is from this phenomenon that the -electrical term "high frequency oscillations," so often heard of in -"wireless" parlance, is derived. - -[Illustration: FIG. 4.—A Leyden jar discharging through a coil of wire -produces a brilliant spark and high frequency oscillations are created.] - -[Illustration: FIG. 5.—Curved line representing an oscillatory discharge -of a Leyden jar.] - -[Illustration: FIG. 6.—Navy type of Leyden jars. Coated with copper -deposited upon the surface of the glass.] - -High frequency oscillations are the "pebbles" which, dropped into the -vast pool of ether, everywhere, set up "ripples" called electromagnetic -waves (identical with the electromagnetic waves of light, but longer and -so beyond the limits of our spectrum and the vision of the eye). The -manner in which this is accomplished may be explained by saying that the -charge creates a state of strain in the surrounding ether, and then -abruptly releases it. Ether possesses a high degree of elasticity, so -that when the state of strain is thus suddenly released, it immediately -returns to its former state. The sudden motion of the ether results in -waves which spread out from their source in enlarging circles. - -Wireless telegraphy, as it is practiced to-day, is based upon the fact -that a system of wires or circuits, through which high frequency -oscillations are surging, becomes a source of electromagnetic waves. -Various methods have been devised for making the system more efficient -and capable of giving better results with a given amount of power. - -[Illustration: FIG. 7.—The simplest practical transmitter that it is -possible to devise for the purpose of sending messages.] - -Fig. 7 is a diagram showing the simplest practical transmitter that it -is possible to devise for the purpose of sending messages a sufficient -distance to be of any value. - -It would be impractical to use a static electric machine for wireless -transmission, and so an induction coil or transformer is employed. These -latter instruments are for the purpose of raising electric currents of a -comparatively low voltage to the high potential, where they have the -power of generating high frequency oscillations. - -In the illustration the current from a battery is led into the primary -of an induction coil. The primary is simply a coil consisting of a few -turns of wire, which induces a high voltage in a second coil consisting -of a larger number of turns, and called the secondary. The terminals of -the secondary are led to a spark gap—an arrangement composed of two -polished brass balls, separated by a small air space. One of the balls, -in turn, is connected to a metal plate buried in the earth, and the -other to a network of wires suspended high in the air and insulated from -all surrounding objects. - -As noted above, a Leyden jar consists of two metallic coatings, -separated by a wall of glass. The purpose of the coatings is to form a -conductor and carry an electric charge. A Leyden jar possesses a -characteristic called, in electricity, capacity. Any two conductors -separated by an insulating medium possess "capacity" and all the -properties of a Leyden jar or condenser. - -The waves generated by a Leyden jar would be somewhat weak and confined -to its own immediate neighborhood, so recourse is had to the aerial and -ground, in order to increase the area over which the oscillations exert -their influence in setting up the electric waves. The aerial system -corresponds to one coating of the Leyden jar, and the ground to the -other. The insulating medium in between, corresponding to the glass, or -dielectric, is the atmosphere. - -When the key connected to the induction coil is pressed, the battery -current flows through the primary and induces a high voltage current in -the secondary, which charges the aerial and ground exactly as the static -machine charges the two coatings of the Leyden jar. A spark then leaps -across the spark gap and the current surges back and forth through the -aerial, generating "high frequency oscillations" which, in turn, set up -a state of strain in the surrounding ether, and cause the waves to -travel out from the system. - -[Illustration: FIG. 8. If a cross section of the aerial and atmosphere -could be made in the same manner that an apple is sliced with a knife -and the waves held stationary, they would appear as above.] - -These waves follow the contour of the earth, and so may cross mountains -and valleys, and travel anywhere. They radiate from the aerial like the -ripples from a pebble in a pool of water, in gradually enlarging -circles. If a cross section of the aerial and atmosphere could be made -in the same manner that an apple can be sliced with a knife, and the -waves held stationary long enough to see them, they would appear as in -Fig. 8. The curved lines represent the lines of strain induced by the -oscillations. Each group of lines represents a wave. It will be noticed -as they radiate farther from the aerial that they become larger and -spread out. - -[Illustration: FIG. 9.—Under the same conditions, but when viewed from -above, the appearance would be that of a series of concentric circles.] - -The electromagnetic waves have the power of exciting oscillations in a -conductor on which they impinge. This is made use of for the purpose of -receiving the messages. When the waves strike the aerial of a distant -station they set up high frequency oscillations, which are usually too -weak to make their presence known except with the aid of a sensitive -device, called a detector. - -[Illustration: FIG. 10.—A simple receiving arrangement. The detector -rectifies the oscillatory currents passing from the aerial to the -ground so that they will flow through the telephone receiver and -register as sound.] - -The most prominent type of detector in use to-day is a crystal of -silicon, iron pyrites, zincite or certain other minerals. The mineral is -placed between two contact points, one or both of which are adjustable -so that the most sensitive portion of the mineral may be selected. A -telephone receiver is connected across the terminals of the detector. -When the electromagnetic waves from the transmitting station strike the -aerial of the receiving station, they set up therein a series of high -frequency oscillations, corresponding to the Morse signals emitted from -the transmitter. The oscillations flow back and forth through the aerial -and ground, striking the mineral detector on their journey. The high -frequency oscillations are alternating currents, because they reverse -their direction many thousand times per second. Such a current will not -pass through the telephone receiver, because the little magnets -contained therein exert a choking action on alternating currents of high -frequency and effectually block their passage. The mineral detector acts -as a valve, allowing the current to pass through in one direction, but -not permitting it to return or go in the opposite direction. The result -is a series of impulses flowing in one direction only, and therefore -called a direct current. Such a current will flow through a telephone -receiver and produce a motion of the diaphragm which imparts its motion -to the surrounding air, the result being sound waves audible to the ear. -By varying the periods during which the key is pressed and the -oscillations are being produced, according to a prearranged code, the -sounds in the receiver may be made to assume an intelligible meaning. - -CHAPTER II. THE MEANS FOR RADIATING AND INTERCEPTING ELECTRIC WAVES. -AERIAL SYSTEMS. EARTH CONNECTION. - -Every radiotelegraphic station may be summed up as comprising these -elements: first of all, certain appliances collectively forming the -transmitter and serving to create the waves; secondly, the receiving -apparatus, whose function is to detect the signals of some far-distant -sending station, and lastly, an external organ called the aerial, or -antenna, consisting of a huge system of wires elevated high in the air -above all surrounding objects, either vertically or sloping, or partly -horizontal and partly vertical, which radiates or intercepts the -electromagnetic waves, accordingly as the station is transmitting or -receiving. - -The antenna is at once both the mouth and the ear of the wireless -station. Its site and arrangement will greatly determine the efficiency -and range of the apparatus. - -The site selected is preferably such that the aerial will not be in the -immediate neighborhood of any tall objects, such as trees, smokestacks, -telephone wires, etc., because such objects not only absorb an -appreciable amount of energy when the station is transmitting messages, -but also noticeably shield the aerial from the effects of incoming -signals and limit its range. - -The nature of the ground over which the waves must travel also enters -into the question, and is always considered in locating a station. In -gliding over the surface of the earth, the waves generate weak currents -in the earth itself. If the ground is very stony or dry, these earth -currents encounter considerable resistance, and the possible distance of -transmission over soil of this sort is very much less than if it were -moist. Moist soil and water offer very little resistance, and the -difference in the results obtainable at the receiving station when the -waves travel over an area of this sort is very marked. - -[Illustration: FIG. 11.—An amateur aerial and station.] - -A station which can only send 100 miles over land can send messages -three or four hundred miles over the ocean. - -Forests exert a very decided effect upon the electric waves. Each -individual tree acts as an antenna, reaching up into the air and -absorbing part of the energy. The difference in the range of a station -during the summer months and that of the same station in winter is -considerable. In summer the trees are full of sap and, being much better -conductors of electricity when in this condition, act in the capacity of -innumerable aerials rising in the air, and able to absorb appreciable -amounts of energy. During these same months the air becomes highly -ionized, in which state the air molecules carry an electric charge, and -are particularly opaque to the waves. This condition also usually exists -in the presence of sunlight, the result being that the most favorable -time for the wireless transmission of messages are the hours around -midnight. - -[Illustration: FIG. 12.—The Army wireless station at Fort Gibbons, -Alaska, showing steel lattice work mast and aerial system.] - -Locality is another factor which usually receives a fair share of -attention in selecting the site. Certain sections of the country, for -seemingly no apparent reason, are very hard to transmit messages, either -to or from. Wireless stations located on the Pacific Coast, for -instance, are more efficient than those situated along the Atlantic -seaboard, while those in the tropical regions are only able to send -short distances in comparison to those farther north or south. Messages -seem to travel better in the direction of the lines of longitude than -along the lines of latitude. - -[Illustration: FIG. 13.—Lightning discharge near Montclair, N. J.] - -"Static," that "bugbear" of the wireless operator, is very much more in -evidence in the eastern parts of the United States and in South America -than it is on the western coast of the country. If any one should ask a -wireless operator what "static" is, he would probably reply, "a -nuisance." In reality, it is caused by atmospheric electricity. When -atmospheric electricity "jumps," it is called "lightning." A lightning -discharge sets up very powerful waves in the ether, which strike the -aerial of the wireless station and produce a peculiar rumbling, -scratching sound in the telephone receivers, and sometimes seriously -interfere with a message. In fact, it is possible for a wireless -operator to predict a thunder shower by many hours from the sounds he is -able to hear in his telephone receivers. - -The cause of lightning is the accumulation of electric charges in the -clouds. The electricity resides on the surface of the particles of water -in the cloud. These charges grow stronger as the particles of water -coalesce to form larger drops, because, as they unite, the surface -increases proportionally less than the volume and, being forced to lodge -on a smaller space, the electricity becomes more "concentrated," so to -speak. For this reason the combined charge on the surface of the larger -drop is more intense than were the charges on the separate particles, -and the "potential" is increased. As the countless multitudes of drops -grow larger and larger, in the process of forming rain, the cloud soon -becomes heavily charged. - -Through the effects of a phenomenon called "induction," a charge of the -opposite kind is produced on a neighboring cloud or some object of the -earth beneath. These charges continually strive to burst across the -intervening air and neutralize each other. As soon as the potential -becomes sufficient to break down this layer of air, a lightning stroke -from one to ten miles long takes place. The heated air in the path of -the lightning expands with great force, but immediately other air rushes -in to fill the partial vacuum, thus producing atmospheric waves, which -impress the ear as the sound called thunder. - -Wireless stations belonging to the United States navy and located on -land are usually housed in a small building in the immediate -neighborhood of the tall wooden mast which supports the aerial. -Commercial stations are usually situated on the top floor of a high -office building, or a hotel, and the aerials supported by a steel -lattice-work tower. Amateurs place a small pole on the roof of the -house, or in a tree, and locate their station in any convenient room -near the top of the house. - -[Illustration: FIG. 14.—Photo of double lightning discharge passing -to earth near the First Orange Mountain, Montclair, N. J.] - -[Illustration: FIG. 15.—Vertical aerials of the "grid," "fan" -and "inverted pyramid" types.] - -Aerials are of numerous classes and forms, but the most prominent types -can be divided into two main groups, called respectively, the "Flat-top" -and "vertical" antenna. - -The vertical aerials are the older form, and are usually employed for -long-distance work or ultra-powerful stations. The aerials intended for -transmission from Europe to America, installed by Marconi, consisted of -huge inverted pyramids, supported by four heavy lattice-work towers, -over 200 feet high. Vertical aerials also sometimes take the form of an -umbrella, or fan, where only one supporting pole is available. Iron pipe -masts may be employed for the purpose, by setting on an insulating base. -The umbrella aerial is used extensively in the army and portable sets. - -The flat-top aerials are gradually coming into very extended use. They -are used to the exclusion of all others on shipboard. They need not be -so high as a vertical type aerial in order to be as efficient. Flat-top -aerials consist of a vertical portion and a nearly horizontal portion. -The horizontal portion is practically useless, as far as its work in -radiating waves is concerned, it being used for the purpose of -increasing the capacity of the aerial. An increase in capacity in an -aerial means that more energy can be stored and radiated. Flat-top -aerials have the objection, however, of possessing a directive action; -that is, they receive, or radiate waves, better in one direction than in -the other. A flat-top aerial always receives or transmits better in the -direction that the ends point than in a direction at right angles to the -wires. - -[Illustration: FIG. 16.—A diagram showing pyramid aerial.] - -The accompanying diagram is an illustration to show the effects of the -directive action of a flat-top aerial. The black lines marked A B, and -appearing very much like a little grating, represent an aerial of the -inverted "L" type, looking down on it from above. B is the free end of -the aerial, and A the closed end, or end to which the wires leading down -to the station are attached. If a snapshot of the lines of strain -produced in the ether as the waves move away from the aerial could be -taken, they would appear like the curved lines in the illustration. It -can be readily seen that those passing outward from the aerial in a -direction opposite to that in which the free end points are the -strongest, and that the radiation in that direction is the best. - -[Illustration: FIG. 17.–A diagram illustrating the directive action -of a flat-top aerial.] - -[Illustration: FIG. 18.—Aerials of the "V" and inverted "L" types.] - -The "V" aerial and also the inverted "L" type both receive waves much -better when they come from a direction opposite to that in which the -free end points. - -[Illustration: FIG. 19.—A diagram showing the arrangement of a "T" -aerial.] - -Probably the most interesting feature of the directive action of aerials -lies in the fact that a land station is able to determine the -approximate bearing of a ship signaling with a horizontal aerial. - -[Illustration: FIG. 20.—Flat top aerials of the inverted "U" and "T" -types.] - -It is beyond the scope of the book to enter into all of the engineering -details pertaining to the installation of a wireless station, but a few -remarks and instructions for the benefit of those who may be interested -in this phase of the subject may be appreciated. - -The flat-top "T" aerial gives the best "all around" results. The -vertical and umbrella forms are close seconds. - -[Illustration: FIG. 21.—Umbrella aerial.] - -For the very best results, the top or horizontal portion of a "T" aerial -should be slightly shorter than the vertical section. - -The umbrella type of antenna is very efficient. Instead of a wooden -mast, an iron pipe terminating above in a system of wires, inclining -downward and serving both as part of the aerial and as guys to support -the pole, is often used. The bottom of the pole is placed on an -insulating base, protected from the rain by a small shelter. The wires -are insulated near the lower ends by strain-insulators. The action of -the wires is to serve as a capacity extension to the aerial. - -[Illustration: FIG. 22.—An amateur aerial (flat-top).] - -Vertical aerials are not as efficient as either of those forms just -mentioned. They require to be 50 per cent. higher than a flat-top -aerial, in order to be of the same value. - -The "L" and "V" types are somewhat directional. They are used where the -highest point must be near the station, with a lower point some distance -away. It is possible to secure excellent results with either type. - -The terms straightaway and loop denote the method of connecting the -aerial wires. In the first form the upper or free ends of the wires -terminate at the insulators. In the loop form they are all connected -together, and divided into two sections, each of which is led separately -into the operating room. - -[Illustration: FIG. 23.—Diagram showing the difference between "loop" and -"straightaway" aerials.] - -The straightaway aerial is the most efficient in most cases, but -wherever great height cannot be obtained, or the aerial is necessarily -short, the loop aerial will give the best results. - -Bare copper wire is the best, and is generally used for aerials. -Wherever the stretch is 100 feet or over, however, so that the wires are -subjected to considerable strain from their own weight, phosphor bronze -is used because of its greater tensile strength. Commercial and navy -stations employ stranded wire. High frequency currents have the peculiar -property of traveling near the surface of wires and conductors. They do -not permeate to the center of the wire, as do normal currents. The -surface of a stranded wire is greater in comparison to its cross-section -than a solid conductor of the same diameter, and therefore is often -employed because it offers less resistance to currents of this sort. - -[Illustration: FIG. 24.—Showing how wires are arranged and insulated.] - -Aluminum wire is very light, and causes very little strain on the pole -or cross-arms. It offers more resistance than copper, but some of the -larger sizes may be used with equally good results. - -Iron wire must never be used, even if galvanized or tinned. It possesses -a certain reactance tending to choke off the high frequency currents. - -[Illustration: FIG. 25.—Aerial insulator.] - -The aerial is always very carefully insulated from its supports and -surrounding objects by special insulators, capable of withstanding -severe strains, made of a moulded material having an iron ring imbedded -in each end. - -[Illustration: FIG. 26.—Leading-in insulator.] - -The wires leading from the aerial to the operating room are called the -"rat-tail," or "lead-in." They must be very carefully insulated by -leading through a bushing placed in the wall or window of the operating -room. - -One of the most important factors in a wireless station is the proper -earthing arrangement. The usual method is to use large copper plates -buried in moist earth, or thrown in the sea. On shipboard it is merely -necessary to connect the earth wire to the metallic plates of which the -hull of the vessel is built. Amateurs employ the water or gas pipes in -the house, the former being preferred. Connections are established by -means of a ground clamp. - -In the country, where water-pipes are not available, the best way is to -bury a sheet of copper three or four feet deep in moist earth. - -A very efficient earth can be formed by spreading a large area of -chicken wire netting over the ground. This method is the best where the -earth is very dry or sandy, and no other way is readily convenient. - -[Illustration: FIG. 27.—A side view of the aerial shown in Fig. 22.] - -CHAPTER III. THE TRANSMITTING APPARATUS. - -The principal instruments composing the apparatus used for sending the -wireless messages comprise an induction coil, or in its place a -transformer, a key, a spark gap, a condenser, and a helix. - -The current supply available will determine the type of the instruments, -and whether an induction coil or a transformer is used. Unless current -mains for light and power are already installed, it must be generated by -an engine and dynamo, or recourse had to batteries. Induction coils may -be operated on either direct or alternating current. Dry cells are most -commonly employed to furnish the current for small induction coils, but -a storage or some form of renewable primary cell, such as the Fuller and -Edison, is necessary if the coil is a large one. When dry cells are -used, they should be connected in series multiple, as shown in the -accompanying diagram. This method of connecting distributes the load, -and considerably lengthens the life of the battery. - -[Illustration: FIG. 28.—Diagram showing how batteries may be arranged -in "series" or "series multiple."] - -[Illustration: FIG. 29.—The power plant of a Marconi transatlantic -station, showing engine and generator.] - -When the source of current supply is alternating, an induction coil may -be operated as a transformer. Both induction coils and transformers are -instruments for raising the voltage of the ordinary available current -from a comparatively low value, 6-220 volts, to a quantity -(15,000–20,000 volts), where it can properly charge the aerial and -create a state of strain, or, as it is called in technical parlance, an -electro-static field. - -[Illustration: FIG. 30.—If a magnet is suddenly plunged into a hollow -coil of wire a momentary electric current will be induced in the coil.] - -Both the induction coil and transformer depend for their operation upon -the principles of magnetic induction. In 1831, Michael Faraday, a famous -English chemist and physicist, discovered that if a magnet be suddenly -plunged into a hollow coil of wire, that a momentary current of -electricity is generated in the coil. As long as the magnet remains -motionless, it induces no current in the coil, but when it is moved back -and forth, it sets up the currents. The source of electrical energy is -the mechanical work done in moving the magnet. The medium which changes -the mechanical energy into electricity is called the magnetic field. The -magnetic field is a peculiar state or condition of the space in the -immediate neighborhood of a magnet. Its real nature is very hard to -explain and not easily understood. Suffice it to say, however, that the -current is induced in the coil of wire only when the magnetic field is -changing, either decreasing or increasing. The change is produced by -moving the magnet because its influence on the coil will be great or -small accordingly as it is near or far. - -[Illustration: FIG. 31.—Magnetic phantom formed by bar magnet.] - -It is possible to show the existence of the magnetic field by placing a -sheet of glass over a bar magnet and then sprinkling iron filings on the -glass. They will settle down in curving lines as in Fig. 31, forming a -magnetic phantom. The curved lines formed by the filings represent the -direction of the lines of force which make up the magnetic field. - -If we should examine the space in the immediate neighborhood of a coil -of wire carrying a current of electricity it would be found that a -similar state of affairs existed there and that the coil also possessed -a magnetic field composed of lines of force flowing around it. - -This is readily shown by punching a small hole in a piece of cardboard -and passing a wire carrying a current of electricity through the hole. -If iron filings are sprinkled on the cardboard, they will arrange -themselves in circles around the wires, forming a magnetic phantom and -showing that a coil of wire carrying a current of electricity generates -a magnetic field in its vicinity. By forming the wire into a coil the -magnetic field generated is much stronger, for the then combined effect -of the wires is secured. - -[Illustration: FIG. 32.—Magnetic phantom formed by wire carrying -current.] - -[Illustration: FIG. 33.—Magnetic phantom formed by coil of wire carrying -current.] - -The induction coil and transformer are simply instruments utilizing the -principle that a coil of wire carrying a current possesses a magnetic -field which will induce a current of electricity in another neighboring -coil. - -[Illustration: FIG. 34.—Diagram of an induction coil.] - -The induction coil consists essentially of a primary winding of heavy -wire wound around a soft iron core and surrounded by a secondary coil -consisting of many thousand turns of fine wire, carefully insulated. The -current from a battery is sent through the primary coil and sets up a -magnetic field. The magnetic field induces a current in the secondary -whose voltage is approximately proportional to the ratio of the turns of -the secondary to the primary. Thus, if the secondary contains one -hundred times as many turns of wire as the primary the induced voltage -will be one hundred times the voltage of the original primary current. -The purpose of the iron core is to concentrate the magnetic field and -make the coil more efficient. Since currents are only induced in the -secondary when the magnetic field is changing, an automatic device -called an interrupter or sometimes a vibrator, is employed to rapidly -turn the current flowing through the primary on and off. The interrupter -consists of a spring carrying a platinum point against which presses a -second piece of platinum on the end of an adjustable thumbscrew. -Platinum is necessary because the current of electricity would quickly -oxidize and burn up any other material. The interrupter spring is placed -near the end of the core so that the magnetism of the latter will draw -it forward away from the thumbscrew and interrupt the current. As soon -as the current ceases to flow the core loses its magnetism and the -spring returns to its former position repeating the cycle very rapidly a -large number of times per second. The interrupter is fitted with a -condenser shunted across its terminals to stop sparking at the platinum -points and also to make the currents in the secondary more intense. - -[Illustration: FIG. 35.—Induction coil for wireless telegraph purposes.] - -[Illustration: FIG. 36.—Induction coil, primary and secondary.] - -The voltage of the currents in the secondary is high enough to leap -across an air gap in a torrent of sparks. The spark of an induction coil -intended for wireless work should be thick and heavy. It should be -sufficiently hot and flaming to ignite a piece of paper. A rapid -vibrator giving a high pitched spark is better than a slow one not only -because it causes a more intense and powerful spark but because the -human ear is the most sensitive to high pitched sounds and such a spark -is more easily read at the receiving station. - -[Illustration: FIG. 37.—Interrupter for induction coil.] - -[Illustration: FIG. 38.—Electrolytic interrupter.] - -When the coil is a very large one and operated on the 110 volt current -an electrolytic interrupter is substituted for the mechanical type. One -pole of the current is connected to a lead plate placed in a jar -containing a mixture of sulphuric acid and water. The other side of the -current is connected to a platinum wire placed in a porcelain tube so -that only a small part of the lower end is in contact with the solution. -When the current passes a bubble forms at the end of the wire shielding -it from the liquid, and thus interrupting the current. The bubble is -almost immediately discharged however and the current allowed to flow an -instant before a new one forms. This operation is repeated continuously -at a frequency sometimes as high as a thousand per second. An -electrolytic interrupter is both an expensive and a troublesome device. -There are other types of interrupters of value in wireless service but -the limitations of space prohibit any account. - -[Illustration: FIG. 39.—Open and closed core transformers.] - -The transformer is acknowledged to be the best practice as a means of -stepping up the voltage of a circuit for wireless telegraph purposes. - -Alternating current is necessary to operate a transformer. There are two -distinct types of transformers known as the "open" and "closed core" -accordingly as the shape of the latter is straight like that of an -induction coil or in the form of a hollow rectangle. The closed core -transformer consists of two coils of insulated wire, forming a primary -and a secondary, wound upon a rectangular core like that shown in Fig. -39B. The core is built up of sheets of iron called laminations, to -reduce the heating and increase the efficiency of the machine. - -[Illustration: FIG. 40.—Lines representing direct and intermittent -direct currents.] - -As noted above currents are only induced in a coil when the magnetic -field is changing. The interrupter is employed to rapidly "make" and -"break" the circuit. Every time that the circuit is made the primary -coil creates a field and every time it is broken it is destroyed. A -direct current is a current which passes in one direction only. It may -be represented by a straight line as A in Fig. 40. Its voltage is -usually very constant and does not vary greatly. In the case of electric -lighting circuits the normal voltage is usually 110. If an interrupter -is included in the circuit the current may be represented by a broken -line, the spaces corresponding to the periods when the current is -"broken" and the lines to the periods it is flowing. The interrupter -creates an intermittent direct current. - -[Illustration: FIG. 41.—Diagram representing alternating current.] - -An alternating current is one which reverses its direction and passes -first one way and then the other. It may be represented by the curved -line shown in Fig. 41. It starts at zero and rises to a maximum, -gradually dying away to zero, then passes in the opposite direction, -rising to a maximum and dying away again. This is repeated a definite -number of times per second; when the current rises from zero, reverses -and returns to zero it is said to have passed through a cycle. From a to -c represents a cycle—from a to b is an alternation. The usual frequency -of commercial alternating currents is 60 cycles or 7200 alternations per -minute. - -[Illustration: FIG. 42.—High potential "Humming" transformer.] - -[Illustration: FIG. 43.—High potential closed core transformer -for wireless work.] - -[Illustration: FIG. 44.—Leyden jar set for oil immersion to prevent -losses from brush discharges.] - -From these facts we may readily see why the troublesome interrupter may -be eliminated when alternating current is used. Every time that the -current rises and falls the magnetic field changes. - -Considerable care must be used in proportioning the windings so that -they possess sufficient reactance. Reactance is the tendency of a coil -to resist the flow of an alternating current. A reactance coil is -sometimes placed in circuit with an open core transformer to prevent the -spark from arcing. Arcing is the tendency of the spark to pass across -the gap without charging the condenser and creating any high frequency -oscillations. - -[Illustration: FIG. 45.—Oil immersed condenser] - -The condenser, it will be remembered is the means of storing up the -energy, which suddenly rushing across the spark gap, produces the -oscillations necessary to generate the electric waves. A battery of -leyden jars may be used as a transmitting condenser in connection with -small induction coils. Their objection in large stations is that they -are very cumbersome and some energy is lost by the brush discharges -around the tops of the jars. The usual form of condenser consists of -alternate sheets of tinfoil and glass plates arranged in a pile. The -alternate sheets of tinfoil are connected together to form the terminals -of the instrument. The condenser is usually encased in a wooden box -poured full of wax or oil to increase the insulation and efficiency. -Condensers are arranged in units so that any desired capacity may be -readily secured by adding the proper number of units. The capacity of a -condenser is its relative ability to receive and retain an electrical -charge. - -[Illustration: FIG. 46.—Diagram showing construction of condenser.] - -The helix is an instrument consisting of copper or brass wire wound -around a frame of hard rubber or seasoned wood. A certain amount of -inductance is necessary in a wireless telegraph circuit in order to -develop high frequency oscillations. Inductance is the property of an -electric circuit by virtue of which lines of force are developed around -it. The helix furnishes the inductance in the circuit or at least the -greater part. Connections are established to the turns of the helix by -means of clips which snap on and off the wires. - -[Illustration: FIG. 47.—Tubular condenser.] - -[Illustration: FIG. 48.—Helix.] - -[Illustration: FIG. 49.—Close coupled helix.] - -[Illustration: FIG. 50.—Spark gap.] - -[Illustration: FIG. 51.—Circuit showing tuned transmitting system -employing close coupled helix.] - -The spark gap is the medium for discharging the aerial and condenser and -setting up the oscillations. It usually consists of a pair of electrodes -supported by suitable standards and so arranged that the distance -between the electrodes can be accurately adjusted. The electrodes -usually take the form of hollow faced cylindrical rods having flanges to -radiate the heat generated and prevent the spark from arcing. Various -metals are used for spark gaps. Silver is probably the best but its -expense is prohibitive. A special hard zinc alloy is most generally -used. - -[Illustration: FIG. 52.—Photo of spark gap.] - -[Illustration: FIG. 53.—Quenched spark gap.] - -[Illustration: FIG. 54.—Diagram of aerial switch.] - -[Illustration: FIG. 55.—Photo of aerial switch.] - -Spark gaps take other forms, two of which are interesting and important -enough to describe here. The first is the rotary gap. - -This consists of a number of small electrodes set around the periphery -of a wheel mounted upon the shaft of an electric motor. Two other -adjustable electrodes are so mounted that the small electrodes on the -revolving member pass between. When the motor is set in operation the -wheel revolves at a high rate of speed interrupting the spark and -causing a peculiar musical pitch to be emitted. A rotary spark gap -almost entirely eliminates the arcing of the spark. - -The quenched gap consists of a number of disks of brass about five -inches in diameter having thin mica washers set between and arranged in -a pile as in the illustration. The quenched gap radiates considerably -more energy than any other form of gap and also has the advantage of -being practically noiseless. The crashing discharge of an ordinary gap -produces a very disagreeable penetrating noise hard to eliminate. In -most commercial stations the spark is muffled to a certain extent by -enclosing it in a cylinder of micanite or some other insulating -substance. - -[Illustration: FIG. 56.—Anchor gap.] - -The aerial switch is necessary for quickly connecting the aerial and -ground to either the transmitting or receiving apparatus. Amateurs very -often employ a small "double pole double throw" switch. The switch used -in commercial stations is built in the manner shown in Fig. 55. - -[Illustration: FIG. 57.—Wireless key.] - -An anchor gap is a simple little device consisting of a hard rubber ring -bearing two or three small electrodes or sparking points. It is a -necessary part of the transmitting apparatus wherever a loop aerial is -used. One electrode is connected to the transmitting apparatus and the -other two to the opposite sides of the aerial so that the currents -divide between the two halves and equalize. - -[Illustration: FIG. 58.—Photo of wireless key.] - -The key is a hand operated switch which controls the electric currents -passing through the transformer or coil shutting them on or off at will -and so controlling the electric oscillations in the antenna to send out -short or long trains of ether waves in accordance with the dot or dash -signals of the Morse alphabet. - -[Illustration: FIG. 59.—Key and aerial switch.] - -The key used in a wireless station is necessarily much larger and -heavier than those employed in ordinary Morse line work, in order to -carry the heavy currents used by the transmitter. In spite of their size -and weight, however, such keys when properly designed may be handled -with perfect ease. - -CHAPTER IV. THE RECEIVING APPARATUS. - -The receiving instruments form the most interesting and ingenious part -of a wireless station. They are the ears of the wireless station. They -are wondrously sensitive but yet simple and incapable of much -complication. The receiving station forms an exact counterpart of the -transmitter, and the train of actions taking place are the reverse of -those of the latter. The purpose of the transmitter is to change -ordinary electric currents into electrical oscillations and thus set up -electric waves, while the receptor converts the waves into oscillations -and thence into currents which are capable of manifesting themselves in -a telephone receiver. The instruments necessary for receiving comprise a - -Detector - -Telephone Receivers - -Fixed Condenser - -Tuning Device - -[Illustration: FIG. 60.—Portable receiving set and case.] - -Other instruments such as a potentiometer, test buzzers, variometers, -variable condensers, etc., complete the outfit and improve its -selectivity and sensitiveness. - -[Illustration: FIG. 61.—Complete receiving outfit.] - -The detector forms the most vital part of the receptor. In explaining -its action it may be well to recall and enlarge upon the description -already set forth on page 11, where it was explained that -electromagnetic or as they are more commonly called when identified with -wireless telegraphy, Hertzian waves have the power of exciting -oscillations in any conductor upon which they impinge. Electrical -oscillations, it will be remembered, are alternating currents of very -high frequency. They are generated in the aerial of the receiving -station by the action of the waves coming from the distant transmitting -station. These currents are exceedingly feeble, too feeble in fact to -operate any form of electrical apparatus except a telephone receiver, -which is one of the most sensitive instruments in existence. - -[Illustration: FIG. 62.—Portable pack set. The receiving outfit is -contained in the left hand case; also the key and interrupter. The -tubular condenser, spark gap, and induction coil may be seen in the -right hand case.] - -[Illustration: FIG. 63.—Complete receiving set, consisting of two -"Perikon" detectors, potentiometer, loose coupler, variable condenser, -etc.] - -There are probably more different forms of detector than any other piece -of radiotelegraph apparatus. Those in most common use to-day are the -mineral detectors. A small crystal of certain minerals, iron pyrites, -silicon, galena, etc., is placed between two contact points which are -adjustable so that the pressure may be regulated and the most sensitive -portion of the mineral selected. A telephone receiver is shunted across -the terminals of the detector. - -[Illustration: FIG. 64.—Showing construction of a "watch case" -telephone receiver.] - -A telephone is shown in diagram in Fig. 64. It consists of a U shaped -permanent magnet of bar steel, so mounted as to exert a polarizing -influence upon a pair of little electromagnets, before the poles of -which an iron diaphragm is mounted. For convenience these elements are -assembled within a small cylindrical casing usually of hard rubber. The -permanent magnet exerts a continual pull upon the diaphragm tending to -distort it, concave inwards. When alternating currents are sent through -the receiver coils, that part of the alternation which is flowing in the -proper direction to form a magnetic field flowing in the same direction -as that of the permanent magnet will strengthen the latter and assist it -in attracting the diaphragm and causing it to further approach the -magnet. That portion of the current flowing in the opposite direction -detracts from the magnetic pull and allows the diaphragm to recede from -the magnet. The diaphragm thus takes up a vibrating motion corresponding -to the electrical waves supplied to the coil and it imparts motion to -the surrounding air, the result being sound. - -[Illustration: FIG. 65.—Pickard adjustable telephone receivers for -wireless purposes.] - -It might reasonably be asked why a telephone receiver could not be -directly connected to the aerial and ground so that it would respond -directly to the high frequency currents generated by the incoming waves -without the medium of a detector. There are two very good reasons why -such a method would not be possible, the first being that the little -magnet coils contained in the telephone receivers exert a choking action -upon alternating currents of high frequency which effectually blocks -their passage. Low frequency alternating currents, intermittent direct -currents and continuous direct currents will readily pass, producing a -sound-each time there is any change in their value. The purpose and -action of most types of detectors is to act as a valve allowing the -current to pass through in one direction but not permitting it to pass -in an opposite one. The high frequency oscillating currents may be -represented by a curved line crossing and recrossing a zero line and -gradually decreasing in amplitude as shown by A in Fig. 66. - -[Illustration: FIG. 66.—Illustrating the valve action of a rectifying -detector.] - -[Illustration: FIG. 67.—A new type of silicon detector in which a -crystal of arsenic may be brought to bear against the surface of one -of several silicon crystals.] - -The detector, acting as a valve, eliminates one half of the alternating -current so that the result may be represented by B, in reality a -pulsating direct current which rises and falls but is able to flow -through the telephone receiver and produce a motion of the diaphragm -with consequent sound waves audible to the ear. - -[Illustration: FIG. 68.—Diagram drawing analogy between rectifying -action of a detector and a pump.] - -The accompanying sketches and the following analogy drawn between the -electric currents and the flow of a stream of water may serve to render -a better conception of how it is possible for the valve action of a -detector to rectify an alternating flow, continuously reversing its -direction to an intermittent current passing in one direction only. The -illustration shows two pumps A and B. Each pump is immersed in a pool of -water and consists of a cylindrical tube T and T' having a small -opening, O and O', at the lower end to admit the water and a piston, P -and P', operating up and down inside the tube. Every time that the -piston P is raised in the pump A it will draw in water through the small -hole O. As soon as it descends, however, the water will reverse its -direction and pass out. The action of the water represents that of an -alternating current because it passes in first one direction and then in -the other. The pump B is fitted with a valve whose action is to permit -the water to flow in one direction only. The valve is fitted to the -piston P'. It is a little flap which opens a hole in the piston when the -latter is descending and closes when it is rising. Suppose that the -piston is raised. Water will be drawn in through the little hole O'. As -soon as the piston reaches the limit of the stroke it commences to -descend. In falling it exerts a slight pressure on the valve which opens -and allows the water to pass through. The hole in the piston is larger -than the hole in the pump and so there is almost none of the water -forced back into the pool. The next up stroke of the piston draws more -water in, that which is on top flowing out through the overflow. The -nature of the stream passing through the hole O' is intermittent, -passing principally in one direction. It may be likened to the -intermittent direct current produced by the detector. - -[Illustration: FIG. 69.—Pyron detector in which a fine wire is brought -to bear against a crystal of iron pyrites.] - -Some of the many forms of detectors are interesting because of the -ingenious manner in which equivalent results are attained. The -illustration shows a type of detector known as the "Perikon." Two -minerals, zincite (oxide of zinc) and chalcopyrites (copper-iron -sulphide), are mounted in adjustable cups so arranged that the surfaces -of the minerals can be brought into variable contact with one another. - -[Illustration: FIG. 70.—Perikon detector.] - -Another very good rectifying detector is that consisting of a flat -surface of highly polished silicon mounted in a small cup. A flat brass -point mounted on the end of an adjustable thumbscrew is brought to bear -on the silicon. - -[Illustration: FIG. 71.—Silicon detector.] - -Other mineral detectors of value are the Pyron, molybenite and galena. - -[Illustration: FIG. 72.—Electrolytic detector.] - -The carborundum detector is a form of crystal rectifier consisting of a -fragment of carborundum held between two carbon blocks. - -The electrolytic detector consists of a very fine platinum wire -(.001-.0003 of an inch in diameter) dipping into a small cup of dilute -nitric acid. A large platinum electrode is sealed in the bottom of the -cup so as to make an electrical connection with the liquid. This form of -detector is exceedingly sensitive, probably more so than any other. The -electrolytic detector requires a battery. When a slight current passes -through the circuit, very minute bubbles are formed at the wire, -insulating it from the liquid and thus shutting off the battery current -from the telephone receivers. However, upon the arrival of any electric -waves and consequent high frequency oscillations the latter destroy the -bubbles clustering around the little wire and permit the current to -flow. Upon the cessation of the high frequency currents the bubbles -immediately form again, only to become broken down by each train of -oscillations produced in the aerial. The intermittent currents can be -detected by a buzz in the telephone receivers. - -[Illustration: FIG. 73.—Electrolytic detector in circuit.] - -The carborundum detector also requires a battery although its action is -somewhat different from that just described. - -[Illustration: FIG. 74.—Potentiometer.] - -When a battery is used in connection with a detector, an instrument -known as a potentiometer becomes necessary. A potentiometer is simply a -device for accurately adjusting the voltage of a battery to a value -where it will render the detector the most responsive to the incoming -signals. - -[Illustration: FIG. 75.—Diagram showing how potentiometer is connected -in circuit.] - -The Tuning Coil is a device for accurately adjusting the oscillation -circuits to receive the waves. - -Its action may be illustrated to a certain extent by pressing down the -loud pedal of a piano and at the same time whistling a note loudly and -clearly. Listen carefully and some of the wires in the piano will be -heard sounding the note whistled. At each vibration of the note of the -whistle a wave of pressure went forth from the lips and reaching the -wires gave them all a tiny impulse. The impulses followed each other -rapidly at definite intervals giving each of the wires the same push -each time. The wires which are tuned to produce the note on the piano -corresponding to that of the whistle will vibrate energetically enough -to produce a sound themselves. They are the wires to which the impulses -are rightly tuned so that each one adds to the motion it has already -acquired. We all know how a child sitting in a swing may be made to -swing back and forth by giving a succession of little impulses properly -timed. The small pushes are superimposed on one another, the result -being a single large motion. - -[Illustration: FIG. 76.—Analogy between swinging and tuning.] - -The "impulses" generated in the receiving aerial are exceedingly weak -and in order to produce an effect must be timed so as to follow one -another in proper succession. Tuning devices are for this purpose and by -their means the receiving circuits and instruments may be carefully -adjusted to the same wave length or "note" as the transmitter so that -the high frequency currents in the aerial will arrive at the proper time -to oscillate or surge back and forth to produce the maximum results. - -In this way it is possible to convey intelligence over long distances by -the repetition of small impulses without it being necessary to send any -very energetic ones. By arranging the stations so that each one emits -its own definite wave different in period or length from that of the -others it is possible to operate several stations at the same time in -the same neighborhood without interfering with one another. The -apparatus is then said to be selective because the instruments can be -adjusted in a few seconds to receive from any desired station and to -exclude others. - -[Illustration: FIG. 77.—Receiving a message in a Marconi transatlantic -station.] - -The tuning coil consists of a cylinder wound with bare copper wire -spaced so that the turns do not touch one another. Variable contacts -called "sliders" are so arranged that connection can be made almost -instantly to any desirable turn of wire. The tuning coil is connected to -the aerial and receiving apparatus in the manner illustrated in Fig. 79. -By moving the sliders back and forth the wave length of the system may -be added to or detracted from and any desired "tune" quickly reached so -that it is possible to listen to any station desirable and exclude the -others. The cylinder over which the wire is wound usually consists of a -thick cardboard tube treated so as to be moisture proof. Bare wire is -preferable to all forms of insulated wire. The coil is usually three to -four inches in diameter and eight to twelve inches long. - -[Illustration: FIG. 78.—Tuning coil of the double slide type.] - -[Illustration: FIG. 79.—Diagram showing fixed condenser in circuit.] - -Tuning coils are known as "single slide," "double slide" and "three -slide" according to the number of contacts they are fitted with. - -[Illustration: FIG. 80.—Fixed condenser.] - -The loading coil is a supplementary tuning coil used to furnish extra -inductance in case it is desirable to obtain a greater range of -resonance or tuning. - -It is merely a single slide tuning coil connected in series with the -regular tuning device. It is not always a necessity but is often part of -the equipment when it may be necessary to adjust the apparatus to -receive long wave lengths. - -Condensers are devices for collecting and storing electricity. They play -a very important part in both the transmitting and receiving operations. -Condensers and Leyden jars have already been described in connection -with the transmitting apparatus. - -The condensers used in receiving are very much smaller in size and -capacity but are the same in principle. There are two general types of -receiving condensers called "fixed" and "variable" accordingly as the -capacity is alterable or not. - -Fixed condensers consist of a few sheets of tinfoil interposed between -sheets of paraffined paper or in some cases mica. The condenser is -inclosed in a suitable case, usually a hollow molded block of insulating -composition, and is provided with suitable terminals to facilitate -connection. - -[Illustration: FIG. 81.—Rotary variable condenser.] - -When a conductor is charged with electricity it has the power of -exerting an opposite charge in any adjacent conductors. The two halves -of a condenser constitute adjacent conductors, the separating medium in -between being called the dielectric. An alternating current will pass -through a condenser because the charge on the plates keeps changing from -negative to positive and back from positive to negative again. A direct -current will not pass through a condenser. - -These facts are utilized to considerable advantage in the receptor of a -wireless station. As has already been explained, the high frequency -oscillatory currents will not readily pass through the coils of the -telephone receivers, but a path is provided through the condenser. The -detector rectifies the alternating current into a direct current which -the condenser opposes and forces to pass through the telephone receiver -and produce sounds. - -When a battery is used in connection with a detector a condenser is also -necessary to oppose the direct current of the battery and prevent it -from flowing around through the tuning coil instead of through the -detector. The capacity of the condenser may be smaller if the resistance -of the telephone receiver is very great for the reason that as the wire -grows smaller it offers greater impedance to the current. The opposite -also holds true and condensers of large capacity are better fitted for -use with telephone receivers of low resistance. - -[Illustration: FIG. 82.—Interior of rotary variable condenser showing -construction.] - -Variable condensers are divided into two general types, the "rotary" and -the "sliding" plate, accordingly as the plates forming the condenser are -adjusted with a rotary or a sliding motion. The rotary type consists of -a number of movable semi-circular aluminum plates which swing between a -series of fixed semi-circular plates of a slightly larger diameter. The -plates must not touch one another and move back and forth with perfect -freedom. The dielectric is formed by the air spacing between the plates. - -[Illustration: FIG. 83.—Dr. Seibt's rotary variable condenser. The plates -are turned from a solid casting and the separation between is only .01 -inch.] - -The advantage of an air dielectric is that no losses of energy take -place through hysterisis. Hysterisis is the lagging which takes place in -the process of charging and discharging. A thumb knob is fitted to the -movable plates and provided with a pointer moving over a graduated scale -so that the degree of capacity in use is indicated. - -[Illustration: FIG. 84.—Sliding plate variable condenser.] - -In the sliding plate type of variable condenser the plates are either -square or rectangular in shape and move back and forth in grooves cut in -a hardwood frame as shown in the illustration. - -Variable condensers are used for tuning and adjusting the receiving -circuit in the same way that a tuning coil is employed, namely to -increase or decrease the electrical length of the circuit so that it -will respond to different wave lengths. The condensers are capable of -finer adjustment than tuning coils because the change is gradual and -even and is not in jumps from one step to another as from one turn to -the next turn of the coil. If the desired point of resonance should -happen to come between two wires of the coil and not in a position to be -reached by the slider, the variable condenser can be adjusted to reach -the exact degree of resonance and thus bring the circuit into finer -adjustment than would otherwise be possible. The exact way in which this -is accomplished and the effect upon the circuit will be left to the next -chapter. - -[Illustration: FIG. 85.—Diagram showing arrangement of rotary variable -condenser in receiving circuit.] - -CHAPTER V. TUNING AND COUPLING, DIRECTIVE WAVE TELEGRAPHY. - -Tuning has been mentioned in several places but not explained in any -greater measure than was necessary to render a conception which would -enable the reader to follow the text intelligently in order not to -depart from the subjects under discussion there and consequently defeat -the purpose of clearness. - -The great importance and value of properly "tuning" the circuit of -radiotelegraphic apparatus cannot be overestimated and for that reason -the subject can hardly be passed without some further explanation. Its -effects are two-fold. In the first place it is always desirable and -highly important that wireless messages should be, so far as is -possible, selective, inasmuch as there are often several stations in the -same immediate neighborhood operating at the same time. This result is -reached by tuning and it is possible for them all to transmit different -messages at the same time without confusion by the proper arrangement of -the wave length. The second effect is the transmission of messages over -long distances with the comparative consumption of small amount of power -by adjusting the "period" or electrical length of the circuits until the -oscillations "flow in harmony" with each other and resonance is secured. - -Perhaps the only way that these results may be made clearly intelligible -is by resort to a graphical example. Suppose that a very heavy weight -were suspended from a chain as shown in the illustration and that it is -struck at regular intervals, once every second, with a hammer. - -Every time that the hammer strikes the ball it will give it an impulse -and cause it to swing slightly. If the chain is short, the ball will -swing faster, while if it is long it will swing more slowly. We will -suppose that the ball is struck from such a direction that it starts to -swing over toward A. The ball is so heavy and the hammer so light in -comparison however that the ball does not swing very far and soon -commences a return journey. If it should return to the point B just as -the hammer delivers another blow the force of the blow will be expended -in stopping the ball rather than adding to its motion because they are -both traveling in opposite directions. However if the chain is -lengthened so that it has a period of swing lasting one second, the -succeeding blow will strike the ball after it has reached the point C -and is on its return journey, thus imparting fresh energy because both -the ball and hammer come together at the right time when they are both -swinging together. Proper adjustment of the length of the chain will -make it possible for the hammer to always descend at the right moment to -add its energy and motion to that previously given the ball. The result -will be considerable increase in the amplitude of the swing. - -[Illustration: FIG. 86.—Chain and ball arranged to illustrate effect -of tuning.] - -From this we may easily perceive how it is possible by shortening or -lengthening the period of an electrical circuit to so adjust it that -resonance is secured and each succeeding oscillation will take place at -the proper time to assist the previous one, not dying away after one or -two surges and becoming what is known in technical language as rapidly -"damped." - -[Illustration: FIG. 87.—Loose coupled helix.] - -The instruments for accomplishing these things consist as previously -explained, in the case of a transmitter, of the helix and in the -receiving station of various tuning coils and condensers. - -[Illustration: FIG. 88.—Hot-wire ammeter.] - -Helix and tuning coils are divided into the "inductive" or "loose" and -the "direct" or close coupled types. Inductive tuning coils are known as -"loose-couplers" and "receiving transformers." Inductive helixes consist -simply of two helixes, separated from one another as shown in the -accompanying illustration. The upper helix, called the secondary, can be -raised or lowered upon a central support. Varying the distance between -the primary and secondary is varying the "coupling." There are several -advantages derived by using loose coupled sending helixes, the chief of -which lie in the fact that it is possible to radiate larger amounts of -energy and also decrease the "damping." - -[Illustration: FIG. 89.—The principle of the hot-wire ammeter.] - -In order to tune a transmitter, the "hot-wire" ammeter is necessary. -This instrument makes use of the property which electrical conductors -possess to become heated and expand when a current is passed through -them. - -The accompanying diagram serves to illustrate the principle of the -"hot-wire" meter. A piece of platinum wire is stretched tightly between -two rigidly fixed posts. A thread leads from the center of the "hot -wire" to a small spindle around which it passes once or twice. The -spindle is also connected to a spring which exerts a continual tendency -to turn the spindle but is prevented from so doing by the thread -attaching to the hot wire. Any tendency on the part of the string to -slacken a little, however, will immediately permit the spring to turn -the spindle. When a high frequency current is passed through the -platinum wire it becomes heated and expands. The expansion of the wire -allows the thread to slacken slightly with the immediate result that the -spindle turns. The spindle carries a pointer at the upper end which -shows the amount of turning. It is therefore easy to tell the -comparative strength of current flowing accordingly as the deflection is -great or small. - -[Illustration: FIG. 90.—Diagram showing loose coupled helix in circuit.] - -The meter is placed in series with the aerial and when the high -frequency currents pass through it they heat and expand a fine wire, -causing the needle to move over a graduated scale and indicate the -amount of current passing. The apparatus is "tuned" or in resonance when -the length of the spark gap, the condenser and the helix have been so -adjusted that the oscillations flow freely through the system and the -maximum amount of current is indicated by the ammeter. - -[Illustration: FIG. 91.—Loose coupled tuning coil.] - -[Illustration: FIG. 92.—Loose coupled tuner.] - -The loose coupled tuning coil consists of two windings wound over two -concentric cylinders, forming a primary and a secondary. The secondary -is the smaller winding and slides in and out of the primary so that the -"coupling" is variable. The primary is adjustable by means of a slider -and the secondary by means of a multi-pointed switch. The slider is -usually connected to the aerial and one end of the coil to the ground. -The detector, etc., are connected to the terminals of the secondary. -Variable condensers may be added with good results to both the primary -and secondary circuits. - -[Illustration: FIG. 93.—Diagram showing position of loose coupler -in circuit.] - -Loose couplers also take the form of doughnut tuners in which the -secondary revolves instead of slides. The coupling is variable in such -an instrument by simply turning the secondary. - -The wave emitted from a transmitter is in reality made up of two waves -of different lengths. The variation in the lengths of these two waves is -dependable upon a factor known as the coefficient of coupling. It is -almost impossible to clearly explain the phenomenon and in order not to -confuse and complicate by a rather lengthy explanation it may be well to -simply state that its effect is to make selective tuning difficult -unless the coupling of the receiving station can be varied to correspond -with that of the transmitter and ask the reader to take it for granted. -Varying the coupling adjusts the difference in the two wave lengths and -when properly accomplished renders the apparatus highly selective. - -[Illustration: FIG. 94.–Fort Gibbons, Alaska, wireless station.] - -[Illustration: FIG. 95.—Transmitting condenser (molded dielectric).] - -Directive Wireless Telegraphy is an interesting phase of this new art -which is receiving considerable attention in the hands of investigators -and has resulted in the devisement of several successful systems for -confining the propagation of the electric waves to certain directions. - -[Illustration: FIG. 96.—Braun's method for directing wireless telegraph -signals.] - -A general diffusion of waves is often very undesirable for the reasons -that the message may be received by an unfriendly neighbor or enemy and -also because it is wasteful of energy. By so directing the waves that -they may be sent over the earth to any desired point of the compass and -only in that direction, it is possible to communicate without disturbing -another station and also for a vessel at sea to secure its bearings and -position by tuning its apparatus to respond to electric waves from two -different known stations. - -The manner in which the problem has been solved varies considerably -according to the inventor. All are interesting and ingenious. - -It will be remembered that electric waves possess all the -characteristics and properties of light waves, etc., and may be -reflected, refracted and polarized. - -Ferdinand Braun has devised a system consisting of a number of metallic -strips arranged to compose a parabolic surface. Another similar set of -strips below the first set completes the arrangement. The two sets are -connected to the terminals of a spark gap and induction coil. This -apparatus acts as a huge reflector and sends out waves in one direction -only, but however interesting and ingenious it may be is not entirely -practical. - -[Illustration: FIG. 97.—Bellini-Tosi radio-goniometer for directive -wireless telegraphy.] - -Another method devised by Braun employs two or more aerials at certain -distances apart. The alternating currents used to excite the -oscillations differ in phase, i. e. are so arranged that they have -different comparative values at the same moment. It is possible to send -very strong signals in a direction lying in the same plane as the -aerials. By the use of three or more antennae suitably differing in -their phase of excitation and situated at the vertices of a triangle it -is possible to send strong signals in certain directions only. - -[Illustration: FIG. 98.—Arrangement of Bellini and Tosi for directive -wireless telegraphy.] - -Messrs. Bellini and Tosi have devised a very ingenious method of -directively transmitting and receiving electric waves as shown in the -accompanying diagrams. The antenna consists of two closed or nearly -closed circuits of triangular shape arranged in two perpendicular -planes. The two aerials each contain a circular coil of wire -perpendicular to each other with their windings in the planes of the -antenna circuits respectively. A third coil is connected to the -receiving apparatus when the messages are incoming and to the condenser, -spark gap and coil when the signals are to be transmitted. - -Waves coming in from any particular direction produce oscillations in -the two aerial circuits whose intensity varies according to the -direction in which the waves These currents passing through the coils -generate a magnetic field having a direction perpendicular to that from -which the waves come. The strength of the currents in the movable coil -will depend upon its position in the resultant magnetic field and will -be at a maximum when the coil embraces as many as possible of the lines -of magnetic force. - -[Illustration: FIG. 99.—Complete receiving and transmitting outfit.] - -By providing the movable coil with a pointer it is possible to thereby -determine the plane in which the station producing the signals lies. Any -ambiguity regarding the final position of the station, whether it is -located in the same direction indicated by the pointer or in the -opposite one, is only removed by general knowledge of the location of -existing stations. - -The processes involved in sending messages are the reverse of those -entering into the receiving apparatus. The movable coil being connected -with the condenser, gap and transformer or induction coil creates a -magnetic field which induces oscillating currents in the other two coils -and consequent waves in the aerial whose strongest exertions will lie in -a plane determined by the third coil. Changing the position of the -latter will send the messages in any direction desired. - -CHAPTER VI. THE DIGNITY OF WIRELESS. ITS APPLICATIONS AND SERVICE. -WIRELESS IN THE ARMY AND NAVY. WIRELESS ON AN AEROPLANE. HOW A -MESSAGE IS SENT AND RECEIVED. - -Wireless telegraphy and that precocious infant, wireless telephony, have -outlived all the speculative and tentative achievements of their early -days and have established themselves in an important and settled -position among our methods of conveying intelligence. - -The field has been so greatly enlarged in recent years and the apparatus -and methods so improved that the broadest possible view of its future -development and importance is justified. And there must inevitably come -the time when our merchant marine and wireless service will come under -such reasonable regulation that it will be removed from any dependence -upon stock jobbing wireless telegraph and telephone companies. - -[Illustration: FIG. 100.—Special light weight wireless telegraph set -for airship service.] - -Official sources show that the equipping of sea-going vessels with -wireless apparatus is progressing at a rapid rate and it is not -difficult in the face of certain facts to appreciate the enormous volume -of business that sooner or later will be handled by wireless. Three -hundred and sixty-three United States naval vessels and about eight -hundred merchant vessels are equipped at this writing. The large number -of commercial shore stations, army forts and posts, and those used by -corporations, isolated stations, etc., for various private purposes -comprise a list which reaches an enormous total. - -[Illustration: FIG. 101.—Telefunken wireless cart, showing -transmitter.] - -Whatever may have been the status of wireless previous to the Titanic -disaster, it now occupies a position far more important than that taken -merely from any commercial standpoint, for it is no longer merely a -convenience to business or a means of furnishing the latest news for the -entertainment of passengers, but is a life-saving proposition taking its -place with the elaborate and costly systems of railroad signals. - -[Illustration: FIG. 102.—Telefunken wireless cart for military service, -showing receiving apparatus.] - -[Illustration: FIG. 103.—Telefunken wireless wagon set in operation -at Fort Leavenworth, Kansas. The aerial is of the umbrella type -supported by a steel pole resting on a porcelain base.] - -It is a curious fact that many of the most startling and newest -inventions find ready and peculiar application as an aid in modern -warfare. The nerves of every war vessel and fort are the wires of the -telephones, telegraphs, telautographs, dynamos, storage batteries etc., -that transmit orders by speech or in writing, find the range, fire the -guns, explode the mines and seek out the enemy with a powerful -searchlight. - -Every battle-ship, cruiser, etc., of the United States Navy is now -equipped and with the completion of the new ultrapowerful station at -Washington the War Department will be enabled to issue instructions to a -ship no matter where it may be on the ocean or in what harbor it may -lie. - -The government maintains an elaborate equipment at the Brooklyn Navy -Yard where the future wireless operators of the Navy are given a course -extending from seven to ten weeks. The first few days are spent in -mastering the theory. The second week usually commences alternate study -and practice of the Continental Code which lasts throughout the entire -course or until thoroughly mastered. Each week some special branch of -study is given out such as repairing and overhauling certain -instruments. At the end of seven weeks the student can usually send and -receive 15 words a minute. He is then given two weeks to prepare for an -examination which if passed rates him as an electrician, third class, -and qualifies him for active work. - -[Illustration: FIG. 104.—Wireless room aboard the U. S. transport -"Buford." It is certain that wireless telegraphy and telephony will -be important factors in military campaigns of the future. For coast -defense, wireless is as valuable as on the ocean.] - -[Illustration: FIG. 105.—The apparatus set up for operation.] - -This method of transmitting army orders is quite dependable. With the -most recent developments and improvements it is now possible to direct -the movements of a great army and navy simultaneously from a centrally -located point. - -[Illustration: FIG. 106.—Wireless equipped automobile.] - -One of the most interesting and spectacular applications of wireless -telegraphy in military service is the wireless telegraph automobile. - -The automobile is a stock pattern touring car of 30 H. P. provided with -a special body arranged to carry six passengers. The seats are elevated -so as to afford storage space below for the entire wireless equipment -and a truly astonishing amount of miscellaneous supplies. - -[Illustration: FIG. 107.—Company D Signal Corps at San Antonio Texas, -1911, showing pack sets and telescoping pole carried by pack mules.] - -The mast used to elevate the aerial is of light steel construction -divided into eight sections which nest into one another with admirable -economy of space. The socket for the foot of the mast is located in the -center of the tonneau. Only a few minutes are required to raise the mast -and aerial. The same gasoline motor employed to drive the automobile -also drives a small dynamo which supplies the electric current for the -transmitting apparatus. - -Two of these cars have been experimentally operated over a number of the -old battle-fields of the Civil War. - -[Illustration: FIG. 108.—U. S. Signal Corps pack sets shown open and -closed. Receiving apparatus on the left.] - -The tests were made under all sorts of road and weather conditions but -no great difficulty was experienced in establishing communication over -distances varying from 35 to 50 miles. - -There is probably no application of wireless telegraphy, however, quite -as picturesque as the combination of wireless and an aeroplane and the -idea of a double seated aeroplane carrying an aviator and a wireless -operator hovering over a hostile country to keep the commanding officer -informed of all conditions and movements of the enemy. - -[Illustration: FIG. 109.—The receiving apparatus of the airship -"America" (Wellman expedition).] - -The huge dirigible balloon Akron in which Melville Vanniman proposed to -cross the Atlantic Ocean was fitted with wireless equipment in order to -transmit news of the expedition en route to various of the daily -newspapers of New York and London and also in case of an accident or -emergency to summon aid. - -[Illustration: FIG. 110.—Interior of the N. Y. "Herald" (O. H. X.) -press station.] - -The equipment is interesting because of the peculiar conditions imposed -upon instruments to be used under such circumstances. A three kilowatt -transformer, the latest type of musical rotary gap and a valve detector -were included in the outfit. It was proposed to obtain the necessary -ground connection by trailing a 1200 foot phosphor bronze ground lead in -the ocean. The frame of the balloon was to be used as the aerial. Should -it have become necessary to take the lifeboat which the balloon carried, -a kite would have been raised and by substituting a copper wire in lieu -of a string an aerial provided, and once more a CQ D and its appeal for -aid would have gone vibrating forth through the ether. - -[Illustration: FIG. 111.—Operating the U. S. Signal Corps airship -wireless apparatus.] - -Several enterprising newspapers have recognized the value of wireless -telegraphy in collecting shipping news and have installed outfits for -the assistance of their reporting bureau. This innovation in modern -journalism has quickly developed into a useful feature of those -publications which have seen fit to adopt it. When the baseball season -is under way every steamship within calling distance wants the latest -baseball scores or sporting results. - -[Illustration: FIG. 112.—The N. Y. "Herald" station, showing aerial.] - -[Illustration: FIG. 113.—Operator Jack Irwin overhauling the wireless -apparatus for the dirigible balloon "America."] - -Railroads have found an auxiliary wireless service to be of the utmost -value in relieving the heavily loaded wire lines between important -centers. During some of the winter storms and blizzards, when miles of -wires were down in all directions, wireless has been the sole means of -communication in certain instances. - -The process of sending a wireless message is very simple. The aerial -switch is usually kept in such a position that the receiving instruments -are connected to the ground and aerial so that the operator is always -able to hear any one calling him. We will suppose for illustration that -the land station at 42 Broadway, New York City, wishes to transmit a -message to the steamer "Horatio Hall." - -[Illustration: FIG. 114.—Morse code.] - -Every wireless station on land or sea has assigned to it two or more -"call letters," which distinguish it from all other stations, and serve -as the key to messages intended for it to receive and when signed to a -message as an indication of its origin. The "call" of the land station -in this case is N. Y., and that of the steamer, J. H. - -[Illustration: FIG. 115.—Continental code.] - -In order to send the message to the ship, N. Y. throws the aerial into -position for sending. This act also starts the motor generator set -supplying current to the transformer. Pressing the key, the operator -then signals in the telegraph code J. H., J. H., J. H.—M. S. G.–N. -Y.—and gives the "finish" signal. M. S. G. is the abbreviation for -message. The N. Y. operator then throws his switch back into the -receiving position and waits for a reply. If one is not forthcoming -shortly the calling process is repeated. - -[Illustration: FIG. 116.—Transmitting equipment of the high power -station at Nauen, twenty-five miles northwest of Berlin, Germany, -showing six induction coils (in the foreground) arranged to charge -the Leyden jars (composed of 360 units).] - -[Illustration: FIG. 117.—Duplex receiving apparatus. The set to -the left may be adjusted to receive short wave lengths and that to -the right to receive long waves. When the handle of the "listening" -key, shown in the center of the illustration, is in the center, -the left hand phone of the head set is connected to the instruments -on the left and the right hand phone to those on the right, so -that the operator is always ready to receive either short or long -waves if received. Swinging the key connects both phones to -either set at will.] - -As soon as the operator on board the steamer hears the call, he waits -until the finish signal is received, and then responds in the following -manner: N. Y., N. Y., N. Y.—J. H.—O. K., O. K.—G. A.—G. A.—N. Y., J. -H.—and gives the "finish signal." O. K. is the abbreviation for "all -right," and G. A. means "go ahead." Upon receipt of this, the land -station transmits the body of the message, and signs its call and finish -signal. If the steamer understands the message, she replies "O. K.," and -signs. - -[Illustration: FIG. 118.—Breaking-in system.] - -There are two Codes in general use for wireless telegraph purposes, the -Morse and Continental. It takes about five per cent. longer space of -time to send a message in Continental than it does in Morse, but the -former has the advantage of not containing any letters requiring proper -spacing in order to be recognizable. American coastwise steamers use the -Morse code; transatlantic ships use the Continental code. - -One of the greatest disadvantages of most systems of wireless telegraphy -lies in the fact that no arrangement is provided for simultaneously -transmitting and receiving wireless signals. It is usually necessary for -one operator listening to another to have to wait until the finish -signal is given before he can reply or interrupt in case he cannot -understand part of the message, because the receiving apparatus of the -transmitting station is necessarily disconnected from the aerial and the -ground during the period a message is being sent. If it were to be -connected at this time the powerful currents of the transmitter would -rush through the receiving apparatus into the ground without setting up -any very powerful waves in the aerial and seriously injure the delicate -receiving instruments. - -The Breaking-in-System is a method of simultaneously transmitting and -receiving wireless signals. This is accomplished by providing the -transmitting key with a second set of contacts, so arranged that when -the key is released between the dots and dashes of the code the aerial -and ground are automatically connected to the receiving apparatus. When -the key is pressed the receptor is automatically cut off. The advantages -of such a system are more or less obvious. When interference or a -misunderstanding occurs the fact can be immediately signaled to the -sending operator, and the message commenced over again. - -[Illustration: FIG. 119.—The receiving apparatus of the station at Nauen. -The message is being printed on tape by a recording device.] - -CHAPTER VII. THE EAR. HOW WE HEAR. SOUND AND SOUND WAVES. THE VOCAL -CHORDS. THE STRUCTURE OF SPEECH. - -On either side of the head, lodged in a cavity which they do not -completely fill, and situated in the midst of a dense and solid mass of -bone, entering into the base of the skull and forming the temporal bone, -are two membraneous bags called the membraneous labyrinth and the scala -media of the cochlea. Each bag is filled with a liquid, and is also -surrounded and supported by a fluid which fills the cavity in which they -are lodged. Certain small, hard bodies, free to move around, lie in the -fluid of the bag. The ends of the auditory nerve of hearing are -distributed around the wall of the sac, so that they are subjected to -the blows of the little particles of calcareous sand, or otoconia, as -they are called, whenever the fluid in the bags is disturbed. - -[Illustration: FIG. 120.—Diagram of the ear.] - -The membraneous lining on which the ultimate ends of the nerves are -spread is virtually a sensitive beach, and the little otoconia, showers -of pebbles and sand, which are raised and let fall by each succeeding -wavelet of sound. This wonderful mechanism constitutes the inner ear. - -The ear, as a whole, consists of three parts: the outer ear, which is a -trumpet-shaped passageway called the pinna serving to collect the sound -waves and pass them on through the auditory canal to a small membrane -called the eardrum; the ossicles, a series of three little bones, the -hammer, the anvil, and the stirrup, they are called; and the inner ear -just described. - -[Illustration: FIG. 121.—The ossicles.] - -The foot of the stirrup is connected with an oval membrane, which closes -a hole in the inner ear. - -Sounds passing through the auditory canal cause the drum to vibrate and -send tremors through the bones to the liquid in the little sacs. The -tumbling of the "pebbles" against the filaments of the auditory nerve -sends the intelligence to the brain. - -The impression which the mind receives through the organ of hearing is -called sound. - -All bodies which produce sounds are in a state of vibration, and they -communicate their vibrations to the surrounding air and thus set it into -waves, just as a stick waved back and forth in a pool of water creates -ripples. - -Sound implies vibration, and whenever a sound is heard some substance, a -solid, a liquid, or a gas is in vibration and the surrounding air is in -unison with it. - -[Illustration: FIG. 122.—Bon jour ("good day" in French) as represented -by a wave picture. The picture was made by a mirror arranged to move -under the influence of the voice and to cast a beam of light upon a -strip of sensitized paper.] - -Sound has been likened to a picture painted not in the space and color -of substance but in time and motion. What really passes out from the -source is merely a rhythmical motion of the air particles, manifesting -themselves as changes in pressure, spreading out in ever-widening -spheres through the atmosphere. The order of these compressions is -different for every sound. The musical sounds of an orchestra embody a -different set of vibrations for each note of each particular instrument. -If the fluctuations in pressure of a sound wave are irregular and -non-periodic, the sound is called a noise; if they are cyclic, and -follow a regular and sufficiently rapid periodic lag, the sound is -musical. - -We may easily satisfy ourselves that in every instance in which the -sensation of sound is produced the body from whence the sound comes must -have been thrown into a state of rapid tremor, implying the existence of -a motion to and fro of the particles of which it consists. - -[Illustration: FIG. 123.—Experiment showing sounding bodies are in -vibration.] - -If the face of a tuning fork prong be touched with a small ball of cork -suspended from a fine silk fiber, after the fork has been struck and -caused to emit its note, the cork will be violently repelled from the -latter. Why? Because the prong of the fork is in vibration. - -If a small wire or bristle is fastened to the prong of the fork and a -piece of smoked glass drawn across it while the fork is giving forth a -sound, the trace of the point will appear as a wavy line, showing that -while the glass was drawn along the prong went to and fro many times. - -The vibrations or disturbances set up in the air by a sound emitting -body are known as sound waves. These waves consist of a series of -condensations and rarefactions succeeding each other at regular -intervals, each air particle swinging to and fro in a very short path. - -[Illustration: FIG. 124.—Method of registering vibrations of a -tuning fork.] - -Air waves cannot be seen by the naked eye, but their nature may be -easily represented or illustrated. Fig. 126 gives a pictorial -representation of the crowding together of the air particles during the -passage of a wave. The loudness of the sound depends upon the amount and -suddenness of the change in pressure, and the note or pitch on the -number of complete to and fro motions of the particles per second. - -[Illustration: FIG. 125.—Wavy line made by a bristle attached to a -tuning fork prong in vibration when passed over smoked glass.] - -The timbre of a sound or the quality that distinguishes the note of a -violin from that of a piano depends upon the smoothness or abruptness of -the changes in pressure. Therein lies the difficulty of the production -of sound by means of a phonograph or telephone, for the sound waves must -resemble each other in every detail in order that the result may be like -the original. - -[Illustration: FIG. 126.—Illustrating the action of air waves.] - -The mechanism with which we speak or sing is composed of two flexible -membranes, stretched side by side across a small cylindrical box located -at the top of the windpipe. The membranes are called the vocal chords, -and the box the larynx. The chords are so arranged and controlled by -muscles that their tension may be changed at will. In breathing, the air -to and from the lungs passes freely between the chords. When the -controlling muscles are tightened, so as to stretch the chords, the -edges are also brought parallel and quite close to each other. If the -breath from the lungs is then forced through the narrow slit between -them, they vibrate like the reed of a musical instrument, and produce -the sounds of the voice. The multitude of sounds which it is possible -for a human being to produce are the result of various degrees of -stretching of the vocal chords, together with the movements of the -mouth, lips and tongue. - -[Illustration: FIG. 127.—The vocal cords in position for making a -sound.] - -[Illustration: FIG. 128.—The vocal when relaxed.] - -Speech is the sound produced by the vocal chords of a human being, -modified by the movements of the lips, tongue, and cavity of the mouth. -The consonants are made by movements of the tongue and lips obstructing -the sounds at their beginning or end, while the vowels are formed by a -steady voice modified by the resonance of the different shapes or sizes -given the parts of the mouth. The waves produced in this manner are -transmitted to the ear, and the sensation of sound is caused by the -impact of the otoconia against the auditory nerve, giving a series of -impressions, musical or unmusical, pleasing or displeasing, as the case -may be. Many interesting experiments showing the nature of the sounds of -the human voice may be performed by means of a simple apparatus invented -by Koenig of Paris. A box is separated into two compartments by a rubber -membrane. Gas is led into one of these compartments by a rubber tube, -and then allowed to issue to a burner. The other compartment is -connected to a megaphone. - -[Illustration: FIG. 129.—Koenig's manometric flame apparatus.] - -[Illustration: FIG. 130.—Appearance of manometric flames in a revolving -mirror.] - -Two pieces of mirror are arranged so as to revolve in front of the -lighted jet or burner. When the human voice is produced in front of the -megaphone, the air waves strike the membrane and cause changes of -pressure in the gas. The height of the flames varies with each change in -the pressure, and when viewed in the mirror resemble a band of light -having an edge like a saw. The teeth are faithful representations of the -changes in the voice, and immediately take on a new appearance when a -new sound is emitted. The shape of the teeth changes with the tone, and -the number of teeth with the pitch. Fig. 130 shows the flames produced -by singing the sound oo, as in tool. The same sound an octave lower in -pitch will show as in B, where there are just one-half as many teeth or -vibrations. The sound of oo is a simple sound. If o on the note is sung -into the megaphone, the image in the mirror will appear like that shown -by C, being made up of alternating large and small teeth, the former -corresponding to every alternate vibration of the octave of the higher -sound coinciding with a vibration of the octave below. - -[Illustration: FIG. 130 a.] - -The sound causing the flame to appear, as in D, is made up of two simple -vibrations combined. - -CHAPTER VIII. THE TELEPHONE TRANSMITTER AND RECEIVER. THE PHOTO PHONE. -THE THERMOPHONE. THE SELENIUM CELL. THE SPEAKING ARC. - -The telephone is an instrument for the transmission of sounds to a -distance by the agency of electricity, wherein the speaker talks to an -elastic plate of thin sheet-iron, which vibrates and transmits its every -movement, electrically, causing it to vibrate in an identical manner and -emit the same sounds. - -The transmission of the vibrations depends upon well known principles of -electricity, and consists, not of an actual transmission of the sounds, -but the passage of electric waves, or impulses, which keep perfect -accord and agree in phase and period with the atmospheric waves produced -by the voice. These in turn, through the medium of an electromagnet, -cause vibrations of a plate or membrane, which agitates the air in a -manner similar to the original disturbance, and thus emits sounds. - -The parts of the apparatus which take up the sound waves and change them -into electric currents compose the transmitter. In the form of -transmitter most commonly used, the motions of the diaphragm cause -variations in the strength of a current flowing from a battery by -varying the resistance in the path of the electric current. - -The sounds are directed to the mouthpiece, which causes the vibrations -of the air to strike the diaphragm, on the back and center of which is -fastened a small cup shaped piece of carbon. A second cup is mounted in -a rigid position directly in back of the first. The space between is -filled with small polished granules of carbon. - -[Illustration: FIG. 131.—Diagram of a telephone transmitter.] - -When these are in a perfectly free and loose state their resistance to -an electric current is very great, and they allow almost none to flow. - -When slightly compressed their resistance is greatly lowered, and they -permit the current to pass. The vibrations of the diaphragm exert a -varying pressure upon the granules, with a corresponding variation in -their resistance and the amount of current flowing. - -[Illustration: FIG. 132.—Diagram showing the principle and -construction of the telephone receiver.] - -The receiver, as has already been explained, consists of a thin iron -disk, placed very near but not quite touching the end of a small bar of -steel, permanently magnetized, about which is wound a coil of fine -insulated wire. The ends of this coil are connected to the wires leading -from the transmitter and battery. The varying currents of electricity, -produced by the transmitter, generate corresponding changes in the -magnetism of the receiving instrument, and thus, by alternately -attracting and repelling the diaphragm, cause it to vibrate and emit -sounds. - -[Illustration: FIG. 133.—The photophone.] - -Alexander Graham Bell, the ingenious inventor of the telephone, with the -aid of Sumner Tainter was the first who achieved success in the attempts -to transmit speech without the aid of connecting wires between the -source of intelligence and the receptor. - -In 1873 Willoughby Smith announced that the element selenium possesses -the abnormal property of changing its electrical resistance under the -influence of light. Bell and Tainter took advantage of this discovery, -and devised selenium cells, in which selenium is formed into narrow -strips between the edges of broad conducting plates of brass. The -resistance of the cell in the darkness is approximately twice the -resistance when illuminated. - -[Illustration: FIG. 134.—Photophone receiving apparatus.] - -[Illustration: FIG. 135.—Photophone transmitting apparatus, using -acetylene flame to furnish light.] - -This property of the cell was immediately applied to the construction of -the photophone, an instrument which transmits sounds to a distance by -means of a beam of light reflected to a distant spot from a thin mirror -thrown into vibration by the voice. Over fifty different forms were -devised but the most successful consisted of a transmitter composed of a -glass disk, silvered to reflect a pencil of light focused from the sun, -or an arc lamp. This glass disk was used as a diaphragm similar to that -of an ordinary telephone transmitter, except that the rear side of it -was made free to reflect the beam of light. Bell used for this purpose -disks about two inches in diameter and the thickness of ordinary paper. -The receiver consisted of a parabolic reflector, with a selenium cell -placed at its focus. In series with the cell was placed a battery and -telephone receiver. - -When the membrane was set into vibration by the sound waves, it became -alternately concave and convex, the normally parallel rays of light -correspondingly converging and diverging. The receiving station was thus -under the influence of light rays of rapidly varying intensity in -perfect phase with the vibrations of the voice. The reflector -concentrated the rays on the selenium cell, and their varying strength -changed its resistance and caused a pulsating current to flow through -the receiver and reproduce the speech produced at the transmitter. - -In another arrangement employed by Bell and Tainter, they used the rays -of a powerful electric arc lamp, and by varying the electric current -supplying the arc caused the light to fluctuate and produce the same -results at the receiver. - -These ingenious inventors also devised a method of transmitting speech -called the thermophone. The transmitter remained the same as in the -photophone–a thin silvered membrane, or glass diaphragm, stretched -across the back of a mouthpiece, and arranged to reflect the rays of the -sun, or the light of an arc lamp. - -The receiver was a small glass bulb containing a plate of mica covered -with lampblack, or little charred pieces of cork. The glass bulb was -placed in the focus of a reflector, which collected the rays and -concentrated them. The variations in the intensity of the heat -radiations caused the air in the bulb to expand or contract with each -vibration. Rubber tubes extended from the bulb to the ears of the -observer, and the pulsations of air, traveling through the tube as sound -waves, would strike the ear-drum and reproduce the speech. - -[Illustration: FIG. 136.—Powerful searchlight arranged to transmit -speech over a beam of light.] - -Both of these methods were later very much improved by the employment of -Koenig's manometric flame in place of the silvered mirror as a -transmitter. As explained in the last chapter, speech delivered into the -mouthpiece causes the gas to become compressed or rarefied in direct -accordance with the sound waves, and the flame rises and falls with a -rapidity too great to be detected by the naked eye. These rapid -alterations in the intensity of the illumination of the flame act on the -selenium cell, and reproduce the original voice perfectly in the -telephone receiver. - -[Illustration: FIG. 137.—The Electric arc.] - -It is obvious, however, that such methods as these are only capable of -transmitting speech over very limited distances, and if greater ranges -are to be traversed much more powerful transmitters must be employed for -the purpose. - -Ernest Ruhmer, after long and laborious researches, finally succeeded in -transmitting speech many miles by taking advantage of the speaking arc, -discovered by Simon, who observed that an arc lamp gave out a loud -rattling noise if its current supply was interfered with. An electric -arc consists of two carbon rods, connected to a generator. When the -carbons are brought into contact for a moment and then drawn apart to a -short distance, a kind of electric flame or arc is produced between the -points of carbon, and a brilliant white light is emitted by the white -hot points of the carbon electrodes. - -Ruhmer immediately made the arc serve as a telephone receiver and speak -by utilizing the pulsating current of a telephone transmitter to vary -the current supplying the arc. - -[Illustration: FIG. 138.—Circuit showing how a singing arc is arranged.] - -The arc could thus be made to sing, whistle or reproduce music and the -human voice perfectly, if the sounds were clearly conveyed into the -transmitter. Further investigations showed that every alteration of -current caused by the action of the transmitter also caused an -alteration in the intensity of the light and radiation of the lamp. The -speaking arc could therefore be used as a perfect photophone transmitter -by directing the rays toward the receiving station with the aid of a -parabolic reflector. - -In 1902 Ruhmer performed a series of experiments in Germany on the -Wannsee, near Berlin. A large motorboat, the Germania, was fitted with -an electric searchlight connected with a microphone, so as to form a -speaking arc. The receiving station was located on the shore, so that -the distance between the stations could be easily enlarged by moving the -boat. - -The receptor was an ordinary selenium cell, placed at the focus of a -large reflector and connected with a telephone receiver and battery. No -difficulty was encountered in reproducing the speech over varying -distances up to about three miles. - -CHAPTER IX. THE WIRELESS TELEPHONE. - -The applications of any of the wireless telephone systems thus far -described are very limited, for at the best they only operate under the -most favorable conditions, and then over rather limited distances. In -the case of any system whereby the speech must be transmitted over a -beam of light, the great resulting limitations are that the transmission -can only take place in a straight line over water or clear country, and -that stormy weather or a fog will interrupt communication. - -None of these objections are present, however, when recourse is had to -Hertzian, or electromagnetic waves. Wireless transmission of speech has -therefore followed in the wake of wireless telegraphy, and the methods -and apparatus employed are very similar. - -Some who have followed the text closely might reasonably ask why it -would not be possible to establish wireless telephony by simply -connecting a telephone transmitter in some manner to an ordinary -wireless telegraph, and by directing speech into the latter, vary the -strength of the oscillations emitted. - -Such a system, at first thought, seems very plausible, and many -experimenters have devised countless methods trying to attain this -result, only to meet with ultimate failure. The reason is very simple. - -Suppose that an induction coil, having a high-speed interruptor, and -therefore able to produce a very rapid stream of sparks at the gap, is -connected to the aerial and ground in the usual manner and a telephone -transmitter placed in series with the ground wire. When the coil is set -in operation the sparks jump across the gap, each spark setting up a -train of oscillations. If speech is conveyed into the transmitter, the -resistance in the path of the oscillations will be varied and -correspondingly also the strength of the waves emitted. The sounds will -be reproduced to a certain extent by the receptor. Whistling, certain -musical tones, and words containing many vowels are sometimes heard in -the receptor, with sufficient distinctness to be recognizable. The voice -cannot, however, be heard at all times, and the system is of no real -value other than an interesting experiment. - -[Illustration: FIG. 139.—A "logical" form of wireless telephone which -is impracticable.] - -[Illustration: FIG. 140.—De Forest wireless telephone equipment.] - -The reason is very simple and readily explained. For the sake of -clearness we will suppose that the speed of the interruptor attached to -the coil is 100 per second. It will therefore produce 100 sparks per -second at the spark gap if the electrodes are close together. The -passage of the sparks is not continuous, each one only occupying a very -small space of time. The pause between each is very distinct, although -it could not be detected with the naked eye. The ten straight lines in -Fig. 141 represent ten sparks which cover a period of one-tenth of a -second, since they pass at the rate of 100 per second. Each spark -produces a train of oscillations, which surge back and forth in the -aerial, rapidly dying out, however, or becoming damped in the manner -already explained. - -[Illustration: FIG. 141.–Wireless telephone receiving apparatus -(induction method).] - -[Illustration: FIG. 142.—Fessenden wireless telephone transmitting -phonograph music.] - -It may now readily be realized that there are long pauses between the -sparks when there are no oscillations in the aerial, and, consequently, -no electromagnetic waves passing between the transmitter and receptor -during those periods. - -The wavy line, C, represents the vibrations of the human voice when -producing speech. Part of it has been represented by a continuous line, -and part by a dotted line. The portions represented by the dotted line -occur when there are no oscillations in the aerial, and consequently -these portions are not transmitted. The continuous portions are the only -ones reaching the receptor. Literally, there are "holes in the voice," -and the result is a jumble of sounds, sometimes bearing a resemblance to -speech, but usually untranslatable. - -[Illustration: FIG. 143.—Diagram illustrating the reason why damped -oscillations will not carry the voice.] - -The fault lies in the method of producing the oscillations which are -damped and therefore do not exist continuously. If they could be made to -keep on swinging and at a sufficiently high speed so that their tone -would be inaudible and not confuse the speech, the problem would be -solved. In other words, three things are necessary for the successful -operation of a wireless telephone. - -1. A means of producing and radiating a stream of undampened electrical - waves sufficiently continuous to transmit the upper harmonics of the - voice, on which the quality and recognition of the speech depends. -2. Means for varying or modulating the stream of electrical waves in - accordance with the sound waves. -3. A receiver, continuously responsive and capable of corresponding - with sufficient rapidity to the speech harmonics. - -In order to obtain the desired result, recourse is had to an arc lamp as -a generator of undamped high frequency oscillations. - -When an arc is properly connected with a condenser and an impedance coil -it will emit a musical note. The note is due to rapid changes in the -arc, a very important factor which led to its recognition as a a value -in wireless telephony. - -[Illustration: FIG. 144.—How the sound waves of the voice are impressed -upon undamped oscillations.] - -When the condenser and inductance are shunted across an arc supplied -with direct current, the condenser immediately becomes charged, and the -current through the arc is diminished. The potential difference across -the latter is therefore instantly increased, tending to further charge -the condenser. This increase of charge reacts on the arc, increasing its -current. The condenser discharges, through the inductance coil, and -becomes charged in the opposite direction, just like a spring, which -released, goes beyond its normal position and then returns. - -The operation is repeated many times per second (usually over -1,000,000), setting up persistent undamped oscillations. - -[Illustration: FIG. 145.—Arrangement of the speaking arc.] - -Perhaps a better conception of how it is possible for a continuous -current, such as that which supplies the arc, to change into alternating -current, vibrating backward and forward, may be gained by comparison -with the steady forward motion of a violin bow, which produces a to and -fro motion of the strings. - -[Illustration: FIG. 146.—Diagram showing how a wireless telephone -transmitting system is arranged.] - -It was later discovered by Poulsen that if one of the arc electrodes was -kept cool by making it of copper and passing water through it that the -efficiency was greatly increased. A further improvement was obtained by -burning the arc in an atmosphere of coal gas or hydrogen. By surrounding -the arc with a powerful magnetic field, its resistance is greatly -increased and the voltage raised. - -[Illustration: FIG. 147.—Poulsen wireless telephone equipment. The -condenser shunted around the are usually consists of a number of metal -plates, placed above one another in a tank of insulating oil. The -inductance is simply a single helix or bare wire.] - -By connecting a telephone transmitter to the arc in the same manner that -it is connected to the speaking arc, the oscillations can be varied in -accordance with the vibrations of the voice. The apparatus is connected -to the aerial and the earth through the medium of a loose-coupled helix, -formed by providing the helix in series with the arc and condenser, with -a secondary winding. - -[Illustration: FIG. 148.—The Majorana wireless telephone transmitter.] - -The ordinary carbon transmitter, in its common form, is unsuited for -wireless telephonic work, on account of its inability to handle large -amounts of power. Many modifications have been designed, the usual -procedure being to make it on a larger scale. - -One of the most interesting forms, and also probably the best, is that -devised by an Italian inventor, Majorana. - -Its action will be clear from the illustration. T is a tube in which -water or some other liquid is allowed to flow in the direction of the -arrow. The bottom of the tube is contracted so that the stream will -issue in a fine jet. The tube is made of strong, rigid material, except -at one point, D, where an opening is covered with a thin elastic -diaphragm. This diaphragm is connected by means of a short rod to a -second diaphragm, which is provided with a mouthpiece. The water -normally flows out of the jet in a smooth, unbroken column, breaking -into drops at about the point A. As soon as it is disturbed in any way, -however, the distance from the outlet of the tube and the point where -the drops commence becomes shortened. The vibrations of the voice, -thrown into the mouthpiece and striking the diaphragm, are transmitted -to the membrane through the medium of the little rod, and so cause -corresponding changes in the pressure of the fluid in the tube. Each -variation or disturbance in the pressure increases or decreases the -length of the stream before it breaks into drops. - -A pair of fine wires are inserted in the stream where the contractions -are the strongest. - -Connection is established between the wires by the liquid. If the stream -is narrow its resistance will be greater than if it were expanded at -that point. The contracted portion of the liquid will jump up and down -with the vibrations of the voice, and thus alter the amount of current -flowing. - -The receiving apparatus consists of some form of detector and a -telephone receiver and battery. The usual form of detector employed is -the electrolytic. The currents generated in the receiving aerial by the -incoming waves vary in amplitude with those of the transmitting aerial, -and, being in perfect accordance with the vibrations conveyed into the -transmitter, cause the detector and telephone transmitter to reproduce -the speech perfectly. - -Experiments in wireless telephony have developed an interesting type of -detector, known as the "Audion." This consists of a six-volt, -low-candlepower, incandescent lamp, having a small, nickel plate -fastened a short distance from the filament, and a "grid" bent from wire -placed midway between the two. When the filament is lighted from a -battery, it throws off a stream of extremely small particles charged -with electricity and called "ions." - -These ions pass through the grid and discharge against the plate. When -the aerial is connected to the "grid," and the plate to the ground, the -stream of ions carries that part of the alternating current in the -aerial which flows in the same direction, across, but does not allow the -current tending to pass in the opposite direction. In reality it is a -valve, or "rectifier," opening one way and closing the other; thus -changing the current into an intermittent, direct current, capable of -manifesting itself in a telephone receiver. - -[Illustration: FIG. 149.—Showing the brush discharge from a Marconi -transatlantic aerial at night.] - -The Audion is a very sensitive device, and is much employed for wireless -telephone purposes. - -With such a system it has been found possible to transmit speech and -music to a distance of two hundred miles. In fact, even greater -distances have been covered, and there does not seem to be any good -reason why it is limited to any range. - -Transmission by wireless telephone is considerably more distinct than by -wire line, and the fine inflections of the voice are brought out much -better. - -Unlike the ordinary line telephone, no rumbling or roaring noises are -heard which confuse the speech, and there is absolute silence in the -wireless telephone receiver, except when talking is going on. Any noises -or sounds produced in the transmitting station, such as walking about -the room, or the breathing of the person speaking into the transmitter, -are reproduced faithfully at the receiving station many miles away. - -CHAPTER X. REMARKS. THEORY. ACCOMPLISHMENTS. MAXWELL'S HERTZ'S DISCOVERY. -THE FUTURE. - -The history of wireless telegraphy and telephony is a striking example -of how it is possible for scientists laboring in the field of pure -research and stimulated by accumulated knowledge and imagination to -arrive at discoveries of the most vital importance. Heinrich Hertz and -Clerk Maxwell in experimental effort to attain other results unwittingly -laid the foundation of this art. - -In 1867 Maxwell proposed the theory that light is not mere mechanical -motion of the ether, but consists of electrical undulations. These -undulations are partly magnetic and partly electrical. Moreover, -according to the theory, the phenomena of electromagnetism and also that -of light are due to certain modes of motion in the ether, electric -currents, and magnetism, being due to whirls, or body displacements in -the substance of the ether, while light is due to vibrations to and fro. - -Twenty years later Hertz discovered the most convincing experimental -proofs of Maxwell's wonderful theory, and succeeded in producing -electromagnetic waves in such a manner that their propagation through -space could be examined, and it readily showed that while they were much -longer than the ordinary waves of light, they possessed the same -properties, were capable of being reflected, polarized, refracted, etc., -and traveled at the same speed. - -The waves that Hertz produced are the electromagnetic or Hertzian waves -of radiotelegraphy. - -Many thousand commercial wireless stations dot the face of the earth. -Daily time signals, weather reports and storm warnings flash to ships -far out in the ocean from government observatories. Late at night, in -the midnight hours, when the world is asleep, powerful land stations -commence to whisper press dispatches, and the next morning the ocean -daily, containing the same news as our morning paper, is laid on the -breakfast table of the ocean greyhound. A distress signal sends revenue -cutters scurrying along the coast, and brings rescue to hundreds of -imperiled lives. The Navy Department issues an order, and a few minutes -later it is in the hands of the commanding officer of a fleet, a -thousand miles away. Wireless links two continents across a table, and -yet this wonderful apparatus is so simple that a sixteen-year-old boy -can build instruments with a little guidance and listen to a far-distant -station, 1,500 miles away, spell out its news. - -[Illustration: FIG. 150.—An amateur wireless telegraph station.] - -[Illustration: FIG. 151.—The high-power Naval wireless telegraph -station under construction at Washington, D. C.] - -Wireless telegraphy is part of the established order of things. The -wireless telephone is practical for limited distance, but is not a -commercial rival of the telegraph. Great distances are claimed, but they -are matters for proof and speculation. - -There is no immediate possibility that wireless telephony will take the -place of local exchanges. If the time ever does come that it in any way -tends to supplant the line telephone for some uses, it is more than -probable that each subscriber must have his own generating station and -call up direct. - -There is a very decided field of opportunity for wireless telephony for -long-distance work. The present systems of long-distance wires are very -expensive to construct and maintain, and are subject to the whims of -storms and the elements. - -Wireless telephones will not only transmit the speech more clearly and -distinctly, but have the further advantages that the initial cost is -very much lower than that of wire lines, the maintenance is almost nil -in comparison, the depreciation is smaller, the number of employees -required is less, and a break-down is limited to the inside of the -station, where it could be quickly remedied by the substitution of a -duplicate spare piece of apparatus. - -Furthermore, no franchises or rights of way would need to be purchased. -No serious difficulty would be encountered because of interference. - -Wireless telephony, like wireless telegraphy, but to an even greater -extent, is peculiarly suited for the conveyance of marine intelligence. -Wireless telephony occupies a unique position in this regard-no operator -is required. The additional expense of an operator is an objection to -the wireless telegraph in many cases, and forbids its installation. -Anybody can operate the wireless telephone. It is also much -quicker-words can be spoken more rapidly than they can be put into Morse -signals and translated. - -[Illustration: FIG. 152.—--The curved lines represent the radius of -the government high power wireless stations and show the zones over -which direct communication may be had with ships.] - -[Illustration: FIG. 153.—The aerial system of a transatlantic station.] - -The wireless telephone enables a passenger on board ship to communicate -direct with his home by relaying the message over the line wires. By the -same means the captain of a ship can call his home office and -communicate with the owner of the vessel. - -Telegraphs and telephones are the nerves of the world, carrying swift -messages from its brain centers to its hands, annihilating distance in -thought. All differences between men as individuals and people as -nations can be traced to the lack of close contact. Reduce or annihilate -all distance in thought and action, and mankind would possess unbounded -opportunities for peaceful economic and healthful development. No force -more vital than the possibilities of wireless has ever presented itself -or could be demanded to attain such an end. Such a statement, in the -light of actual developments, might even be considered conservative, and -is neither absurd nor the dream of a vivid imagination. The greatest -obstacle to all efforts in radically new directions is the resistance of -the human race. The antagonism of prejudice and skepticism can only -disappear when the world as a whole grasps a new proof and learns to -appreciate it. Inertia must be overcome, and the great masses set to -thinking and striving toward an end before the aweing genie finally -bursts forth and amazes the Aladdins of science. - -Within the memory of older men and women are primers of science, which -speculate about the developments of electrical force, and guardedly -discuss its possibilities. - -And now, electricity—this mysterious agent-has multiplied the muscular -strength of man a billion times. The tasks of Hercules are now but -chores to be accomplished by the closing of a switch. Mighty rivers roar -through intake and turbine to drive the wheels of industry in a distant -city and turn the night into day. Any attempt to chronicle all the -applications of this wondrous power would be absurd. Such is electricity -to-day. - -Only a few years ago Langley launched his famous aerodrome over the -waters of the Potomac, while the world stood by and sneered, ridiculed a -man whose work is now one of the classics of aeronautical literature, -and scoffed at a machine whose principles embodied the conclusions of -years of careful thought and scientific effort. - -A decade later and aeroplanes have become a living reality. A man and a -little frame of sticks and canvas can throw off the fetters of gravity -and go soaring dizzily two miles up into the blue sky, and daring more, -come skimming and diving back to earth with motor dead. Such wonders -only came to pass, however, when numbers of men accepted the problem as -one to be solved by trying, and bent their energies toward its solution. -Science has not reached the limits of its resources. It never will. The -art of wireless may always be embarrassed by novelty in many directions. - -[Illustration: FIG. 154.–Fong Yee, a Chinese amateur wireless operator -at Oakland, Cal., who is also an aviator and has been summoned home by -the republican Chinese government to demonstrate apparatus of his own -invention to the Chinese army.] - -One of the greatest steps forward toward the day when methods and -appliances regarded as permanent as the mountains will pass and be -considered only as the curious remnants of a cruder age is the interest -of 200,000 wireless amateurs in the United States. Some of these will -develop into men who will bring some of the wonders of the future to -their full fruition. - -[Illustration: FIG. 155.—Tesla world power plant (experimental -station).] - -What is this great change that can be coolly and precisely forecast? -Along what lines will these wonderful developments come? The answer is -"wireless"-not the wireless of a Marconi or a De Forest, but the -wireless of a Tesla--of "high potential magnifying transmitters"-of -"nodes" and "loops"--of oscillatory currents that leave their conductors -behind-the "wireless" of the day when a system is introduced enabling -any person to reach any other on the globe, not simply through a spoken -word or thought conveyed, but visually a perfect transmission of images -which will enable one person to see another, as though that other were -by his side-"wireless" of a time when the great operations of commerce -and industry will be vitalized by huge wireless power stations, turning -the machinery of factories, lighting cities, or sending swift aeroplanes -and ships darting to the farthest points of the earth. - -Of course, there may be something of the dramatic in such assertions, -but they are founded upon scientific facts, and, if imaginary, are -scientifically imaginary. The wonderful mysteries of oscillatory -currents, whose natural medium is the ether, currents which object to -being confined to wires and cables, and defy all ordinary laws; currents -that will melt masses of metal with the violence of an explosion, but -yet pass through the human body without producing any sensation; -currents that will instantly manifest themselves 2,000 miles away from -their source, with no visible means of propagation, are the open sesame -to the treasures of a wonderful future. - -There are many places in the world where water power is available -capable of generating almost unlimited electrical energy. The present -difficulty lying in the way of its utilization is the limitation of -electrical transmission by wire, for not only is the cost of long lines -of copper tremendous, but power can only be carried in this manner for -limited distances. Central distributing wireless power stations could -send the power of Niagara, which alone might be made to supply a fifth -of all the power in the United States, and the energy of Victoria to the -ends of the earth with little loss. The Great Falls of Zambesi, in the -heart of Africa, could be made to run the subway trains, the factories, -lights, railroads, ferries, trucks, heaters, etc., in that vast, most -complex, most bewildering and inspiring city of the Western World, the -City of New York. Ocean vessels would no longer carry thousands of tons -of coal, locomotives would not wheeze and cough a trail of soot and -smoke through the country, chimneys would cease to belch, and aeroplanes -would travel silently and swiftly overhead. - -[Illustration: FIG. 156.—Twenty-five foot sparks from a Tesla -transformer.] - -It is easy, in the face of certain facts, to conjure up situations which -would be pleasant and make for the betterment of the world. Any one -whose imagination is vivid enough can make a prediction, but when the -great truth is accidentally revealed, or experimentally confirmed, as -the case may be, and rendered absolutely sure of accomplishment, will -its incalculable consequences continue to baffle the imagination and -carry us further into the land of wonderment? Only the future knows. - -THE END. - - - -BOOKS FOR HOME STUDY - -OPPORTUNITY - -PRACTICAL SCIENTIFIC - -TECHNICAL - -EACH BOOK IN THIS CATALOGUE IS WRITTEN BY - -AN EXPERT AND IS WRITTEN SO YOU - -CAN UNDERSTAND IT - -THE NORMAN W. HENLEY PUBLISHING COMPANY - -Publishers of Scientific and Practical Books 132 Nassau Street - -New York, U. S. A. - -Any book in this Catalogue sent prepaid on receipt of price. - - -CATALOGUE OF GOOD, PRACTICAL BOOKS - -AUTOMOBILE - -THE MODERN GASOLINE AUTOMOBILE-ITS DESIGN, CONSTRUCTION, MAINTENANCE AND -REPAIR. By VICTOR W. PAGE, M. E. The latest and most complete treatise -on the Gasoline Automobile ever issued. Written in simple language by a -recognized authority, familiar with every branch of the automobile -industry. Free from technical terms. Everything is explained so simply -that anyone of average intelligence may gain a comprehensive knowledge -of the gasoline automobile, The information is up-to-date and includes, -in addition to an exposition of principles o construction and -description of all types of automobiles and their components, valuable -money-saving hints on the care and operation of motor cars propelled by -internal combustion engines. 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Every part of -the automobile, its equipment, accessories, tools, supplies, spare parts -necessary, etc., have been discussed comprehensively. If you are or -intend to become a motorist, or are in any way interested in the modern -Gasoline Automobile, this is a book you cannot afford to be without -Nearly 600 6 x 9 pages—and more than 500 new and specially made detail -illustrations as well as many full page and double page plates, showing -all parts of the automobile. Including nine large folding plates. Price -$2.50 - -BALLOONS AND FLYING MACHINES - -MODEL BALLOONS AND FLYING MACHINES. WITH A SHORT ACCOUNT OF THE PROGRESS -OF AVIATION. By J. H. ALEXANDER. This book has been written with a view -to assist those who desire to construct a model airship or flying -machine. It contains five folding plates of working drawings, each sheet -containing a different sized machine. Much instruction and amusement can -be obtained from the making and flying of these models. 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This chart is really a dictionary of the boiler -room--the names of more than 200 parts being given. It is -educational-worth many times its cost. 25 cents. - -CIVIL ENGINEERING - -HENLEY'S ENCYCLOPEDIA OF PRACTICAL ENGINEERING AND ALLIED TRADES. Edited -by JOSEPH G. HORNER, A. M. I. E. M. This set of five volumes contains -about 2,500 pages with thousands of illustrations, including -diagrammatic and sectional drawings with full explanatory details.. This -work covers the entire practice of Civil and Mechanical Engineering. The -best known experts in all branches of engineering have contributed to -these volumes. The Cyclopedia is admirably well adapted to the needs of -the beginner and the self-taught practical man, as well as the -mechanical engineer, designer, draftsman, shop superintendent, foreman, -and machinist. The work will be found a means of advancement to any -progressive man. 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Fully -illustrated with folding plates, It has been the aim of the authors, in -preparing this book, to produce ore which shall be of use and benefit to -those who are associated with, or interested in, the modern developments -of the industry. Contents: I. Introductory. II. General Classification -of Fuels. III. Coal Washing. IV. The Sampling and Valuation of Coal, -Coke, etc. V. The Calorific Power of Coal and Coke. VI. Coke Ovens. VII: -Coke Ovens, continued. VIII. Coke Ovens, continued. IX. Charging and -Discharging of Coke Ovens, X. Cooling and Condensing Plant. XI. Gas -Exhausters. XII. Composition and Analysis of Ammoniacal Liquor. XIII. -Working-up of Ammoniacal Liquor. XIV. Treatment of Waste Gases from -Sulphate Plants. XV. Valuation of Ammonium Sulphate. XVI. Direct -Recovery of Ammonia from Coke Oven Gases. XVII. Surplus Gas from Coke -Oven. Useful Tables. Very fully illustrated. Price $3.50 net. - -COMPRESSED AIR - -COMPRESSED AIR IN ALL ITS APPLICATIONS. By GARDNER D. 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This work is fully illustrated, with detailed engravings. -Price $2.00 - -CONCRETE FROM SAND MOLDS. By A. A. HOUGHTON. A Practical Work treating -on a process which has heretofore been held as a trade-secret by the few -who possessed it, and which will successfully mold every and any class -of ornamental concrete work. The process of molding concrete with sand -molds is of the utmost practical value, possessing the manifold -advantages of a low cost of molds, the ease and rapidity of operation, -perfect details to all ornamental designs, density, and increased -strength of the concrete, perfect curing of the work without attention -and the easy removal of the molds regardless of any undercutting the -design may have. 192 pages. Fully illustrated. Price $2.00 - -CONCRETE WALL FORMS. By A. A. HOUGHTON. A new automatic wall clamp is -illustrated with working drawings. 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The author -has brought together in this work all the salient matter of interest to -the user of concrete and its many diversified products. The matter is -presented in logical and systematic order, clearly written, fully -illustrated and free from involved mathematics. Everything of value to -the concrete user is given including kinds of cement employed in -construction, concrete architecture, inspection and testing, -waterproofing, coloring and painting, rules, tables, working, and cost -data. The book comprises thirty-three chapters, as follows: -Introductory. Kinds of Cements and How They are Made. Properties, -Testing and Requirements of Hydraulic Cement. Concrete and its -Properties. Sand, Broken Stone and Gravel for Concrete. How to -Proportion the Materials. How to Mix and Place Concrete. Forms for -Concrete Construction. The Architectural and Artistic Possibilities of -Concrete. Concrete Residences. Mortars, Plasters and Stucco and How to -Use Them. The Artistic Treatment of Concrete Surfaces. Concrete Building -Blocks. The Making of Ornamental Concrete. Concrete Pipes, Fences, -Posts, Etc. Essential Features and Advantages of Reenforced Concrete. -How to Design Reenforced Concrete Beams, Slabs and Columns. Explanations -of the Methods and Principles in Designing Reenforced Concrete Beams and -Slabs. Systems of Reenforcement Employed. Reenforced Concrete in Factory -and General Building Construction. Concrete in Foundation Work. Concrete -Retaining Walls, Abutments, and Bulkheads. Concrete Arches and Arch -Bridges. Concrete Beam and Girder Bridges. Concrete in Sewerage and -Drainage Works. Concrete Tanks, Dams and Reservoirs. Concrete Sidewalks, -Curbs and Pavements. Concrete in Railroad Constructions. The Utility of -Concrete on the Farm. The Waterproofing of Concrete Structure. Grout or -Liquid Concrete and Its Use. Inspection of Concrete Work. Cost of -Concrete Work. Some of the special features of the book are: 1. The -Attention Paid to the Artistic and Architectural Side of Concrete Work. -2. The Authoritative Treatment of the Problem of Waterproofing Concrete. -3. An Excellent Summary of the Rules to be Followed in Concrete -Construction. 4. The Valuable Cost Data and Useful Tables given. A -valuable Addition to the Library of Every Cement and Concrete User. -Price $2.50 - -WATERPROOFING CONCRETE. By MYRON H. LEWIS. Modern Methods of -Waterproofing Concrete and Other Structures. A condensed statement of -the Principles, Rules, and Precautions to be Observed in Waterproofing -and Damp-proofing Structures and Structural Materials. Paper binding. -Illustrated. Price 50 cents. - -DICTIONARIES - -STANDARD ELECTRICAL DICTIONARY. By T. O'CONOR SLOANE. An indispensable -work to all interested in electrical science. Suitable alike for the -student and professional. A practical hand-book of reference containing -definitions of about 5,000 distinct words, terms and phrases. The -definitions are terse and concise and include every term used in -electrical science. Recently issued. An entirely new edition. Should be -in the possession of all who desire to keep abreast with the progress of -this branch of science. Complete, concise and convenient. 682 pages. 393 -illustrations. Price $3.00 - -DIES-METAL WORK - -DIES: THEIR CONSTRUCTION AND USE FOR THE MODERN WORKING OF SHEET METALS. -By J. V. WOODWORTH. A most useful book, and one which should be in the -hands of all engaged in the press working of metals; treating on the -Designing, Constructing, and Use of Tools, Fixtures and Devices, -together with the manner in which they should be used in the Power -Press, for the cheap and rapid production of the great variety sheet -metal articles now in use. It is designed as a guide to the production -of sheet metal parts at the minimum of cost with the maximum of output. -The hardening and tempering of Press tools and the classes of work which -may be produced to the best advantage by the use of dies in the power -press are fully treated. Its 505 illustrations show dies, press fixtures -and sheet metal working devices, the descriptions of which are so clear -and practical that all metal-working mechanics will be able to -understand how to design, construct and use them. Many of the dies and -press fixtures treated were either constructed by the author or under -his supervision. Others were built by skilful mechanics and are in use -in large sheet metal establishments and machine shops. Price $3.00 - -PUNCHES, DIES AND TOOLS FOR MANUFACTURING IN PRESSES. By J. V. -WOODWORTH. This work is a companion volume to the author's elementary -work entitled "Dies, Their Construction and Use." It does not go into -the details of die making to the extent of the author's previous book, -but gives a comprehensive review of the field of operations carried on -by presses. A large part of the information given has been drawn from -the author's personal experience. It might well be termed an -Encyclopedia of Die Making. Punch Making, Die Sinking, Sheet Metal -Working, and Making of Special Tools, Sub-presses, Devices and -Mechanical Combinations for Punching, Cutting, Bending, Forming, -Piercing, Drawing, Compressing and Assembling Sheet Metal Parts, and -also Articles of other Materials in Machine Tools. 2nd Edition. Price. -$4.00 - -DROP FORGING, DIE SINKING AND MACHINE FORMING OF STEEL. By J. V. -WOODWORTH. - -This is a practical treatise on Modern Shop Practice, Processes, -Methods, Machines, Tools, and Details, treating on the Hot and Cold -Machine-Forming of Steel and Iron into Finished shapes; Together with -Tools, Dies, and Machinery involved in the manufacture of Duplicate -Forgings and Interchangeable Hot and Cold Pressed Parts from Bar and -Sheet Metal. This book fills a demand of long standing for information -regarding drop forging, die-sinking and machine forming of steel and the -shop practice involved, as it actually exists in the modern drop forging -shop. The processes of die-sinking and force-making, which are -thoroughly described and illustrated in this admirable work, are rarely -to be found explained in such a clear and concise manner as is here set -forth. The process of die-sinking relates to the engraving or sinking of -the female or lower dies, such as are used for drop forgings, hot and -cold machine forging, swedging and the press working of metals. The -process of force-making relates to the engraving or raising of the male -or upper dies used in producing the lower dies for the press-forming and -machine-forging of duplicate parts of metal. - -In addition to the arts above mentioned the book contains explicit -information regarding the drop forging and hardening plants, designs, -conditions, equipment, drop hammers, forging machines, etc., machine -forging, hydraulic forging, autogenous welding and shop practice. The -book contains eleven chapters, and the information contained in these -chapters is just what will prove most valuable to the forged metal -worker. All operations described in the work are thoroughly illustrated -by means of perspective half-tones and outline sketches of the machinery -employed. 300 detailed illustrations. Price $2.50 - -DRAWING-SKETCHING PAPER - -LINEAR PERSPECTIVE SELF-TAUGHT. By HERMAN T. C. KRAUS. This work gives -the theory and practice of linear perspective, as used in architectural, -engineering, and mechanical drawings. Persons taking up the study of the -subject by themselves will be able by the use of the instruction given -to readily grasp the subject, and by reasonable practice become good -perspective draftsmen. The arrangement of the book is good; the plate is -on the left-hand, while the descriptive text follows on the opposite -page, so as to be readily referred to. The drawings are on sufficiently -large scale to show the work clearly and are plainly figured. The whole -work makes a very complete course on perspective drawing, and will be -found of great value to architects, civil and mechanical engineers, -patent attorneys, art designers, engravers, and draftsmen. $2.50 - -PRACTICAL PERSPECTIVE. By RICHARDS and COLVIN. Shows just how to make -all kinds of mechanical drawings in the only practical perspective -isometric. Makes everything plain so that any mechanic can understand a -sketch or drawing in this way. Saves time in the drawing room, and -mistakes in the shops. Contains practical examples of various classes of -work. 3rd Edition. 50 cents. - -SELF-TAUGHT MECHANICAL DRAWING AND ELEMENTARY MACHINE DESIGN. By F. L. -SYLVESTER, M.E., Draftsman, with additions by ERIK OBERG, associate -editor of "Machinery." This is a practical treatise on Mechanical -Drawing and Machine Design, comprising the first principles of geometric -and mechanical drawing, workshop mathematics, mechanics, strength of -materials and the calculations and design of machine details. The -author's aim has been to adapt this treatise to the requirements of the -practical mechanic and young draftsman and to present the matter in as -clear and concise a manner as possible. To meet the demands of this -class of students, practically all the important elements of machine -design have been dealt with, and in addition algebraic formulas have -been explained, and the elements of trigonometry treated in the manner -best suited to the needs of the practical man. The book is divided into -20 chapters, and in arranging the material, mechanical drawing, pure and -simple, has been taken up first, as a thorough understanding of the -principles of representing objects facilitates the further study of -mechanical subjects. This is followed by the mathematics necessary for -the solution of the problems in machine design which are presented -later, and a practical introduction to theoretical mechanics and the -strength of materials. The various elements entering into machine -design, such as cams, gears, sprocket wheels, cone pulleys, bolts, -screws, couplings, clutches, shafting and flywheels have been treated in -such a way as to make possible the use of the work as a textbook for a -continuous course of study. It is easily comprehended and assimilated -even by students of limited previous training. 330 pages, 215 -engravings. Price. $2.00 - -A NEW SKETCHING PAPER. A new specially ruled paper to enable you to make -sketches or drawings in isometric perspective without any figuring or -fussing. It is being used for shop details as well as for assembly -drawings, as it makes one sketch do the work of three, and no workman -can help seeing just what is wanted. Pads of 40 sheets, 6 x 9 inches, 25 -cents. Pads of 40 sheets, 9 x 12 inches. 50 cents; 40 sheets, 12 x 18, -Price $1.00. - -ELECTRICITY - -ARITHMETIC OF ELECTRICITY. By Prof. T. O'CONOR SLOANE. A practical -treatise on electrical calculations of all kinds reduced to a series of -rules, all of the simplest forms, and involving only ordinary -arithmetic; each rule illustrated by one or more practical problems, -with detailed solution of each one. This book is classed among the most -useful works published on the science of electricity covering as it does -the mathematics of electricity in a manner that will attract the -attention of those who are not familiar with algebraical formulas. 20th -Edition. 160 pages. Price $1.00 - -COMMUTATOR CONSTRUCTION. By WM. BAXTER, JR. The business end of any -dynamo or motor of the direct current type is the commutator. This book -goes into the designing, building, and maintenance of commutators, shows -how to locate troubles and how to remedy them; everyone who fusses with -dynamos needs this. 25 cents. - -DYNAMO BUILDING FOR AMATEURS, OR HOW TO CONSTRUCT A FIFTY-WATT DYNAMO. -By ARTHUR J. WEED, Member of N. Y. Electrical Society. A practical -treatise showing in detail the construction of a small dynamo or motor, -the entire machine work of which can be done on a small foot lathe. -Dimensioned working drawings are given for each piece of machine work -and each operation is clearly described. This machine, when used as a -dynamo, has an output of fifty watts; when used as a motor it will drive -a small drill press or lathe. It can be used to drive a sewing machine -on any and all ordinary work. The book is illustrated with more than -sixty original engravings showing the actual construction of the -different parts. Among the contents are chapters on 1. Fifty Watt -Dynamo. 2. Side Bearing Rods. 3. Field Punchings. 4. Bearings. 5. -Commutator. 6. Pulley. 7. Brush Holders. 8. Connection Board. 9. -Armature Shaft. 10. Armature. 11. Armature Winding. 12. Field Winding. -13. Connecting and Starting. Price, paper, 50 cents. Cloth. $1.00. - -ELECTRIC FURNACES AND THEIR INDUSTRIAL APPLICATIONS. By J. WRIGHT This -is a book which will prove of interest to many classes of people; the -manufacturer who desires to know what product can be manufactured -successfully in the electric furnace, the chemist who wishes to post -himself on the electro-chemistry, and the student of science who merely -looks into the subject from curiosity. The book is not so scientific as -to be of use only to the technologist, nor so unscientific as to suit -only the tyro in electro-chemistry; it is a practical treatise of what -has been done, and of what is being done, both experimentally and -commercially with the electric furnace. In important processes not only -are the chemical equations given, but complete thermal data are set -forth and both the efficiency of the furnace and the cost of the product -are worked out, thus giving the work a solid commercial value aside from -its efficacy as a work of reference. The practical features of furnace -building are given the space that the subject deserves. The forms and -refractory materials used in the linings, the arrangement of the -connections to the electrodes, and other important details are -explained. 288 pages. New Revised Edition. Fully illustrated. Price -$3.00 - -ELECTRIC LIGHTING AND HEATING POCKET BOOK. By SYDNEY F. WALKER. This -book puts in convenient form useful information regarding the apparatus -which is likely to be attached to the mains of an electrical company. -Tables of units and equivalents are included and useful electrical laws -and formulas are stated. One section is devoted to dynamos, motors, -transformers and accessory apparatus; another to accumulators, another -to switchboards and related equipment, a fourth to a description of -various systems of distribution, a fifth section to a discussion of -instruments, both for portable use and switchboards; another section -deals with electric lamps of various types and accessory appliances, and -the concluding section is given up to electric heating apparatus. In -each section a large number of commercial types are described, frequent -tables of dimensions being included. A great deal of detail information -of each' line of apparatus is given and the illustrations shown give a -good idea of the general appearance of the apparatus under discussion. -The book also contains much valuable information for the central station -engineer. 438 pages. 300 engravings. Bound in leather pocket book form. -Price $3.00 - -ELECTRIC WIRING, DIAGRAMS AND SWITCHBOARDS. By NEWTON HARRISON. A -thoroughly practical treatise covering the subject of Electric Wiring in -all its branches, including explanations and diagrams which are -thoroughly explicit and greatly simplify the subject. Practical -every-day problems in wiring are presented and the method of obtaining -intelligent results clearly shown. Only arithmetic is used. Ohm's law is -given a simple explanation with reference to wiring for direct and -alternating currents. The fundamental principle of drop of potential in -circuits is shown with its various applications. The simple circuit is -developed with the position of mains, feeders and branches; their -treatment as a part of a wiring plan and their employment in -house-wiring clearly illustrated. Some simple facts about testing are -included in connection with the wiring. Molding and conduit work are -given careful consideration; and switchboards are systematically -treated, built up and illustrated, showing the purpose they serve, for -connection with the circuits, and to shunt and compound wound machines. -The simple principles of switchboard construction, the development of -the switchboard, the connections of the various instruments including -the lightning arrester, are also plainly set forth. Alternating current -wiring is treated, with explanations of the power factor, conditions -calling for various sizes of wire and a simple way of obtaining the -sizes for single-phase, two-phase and three-phase circuits. This is the -only complete work issued showing and telling you what you should know -about direct and alternating current wiring. It is a ready reference. -The work is free from advanced technicalities and mathematics, -arithmetic being used throughout. It is in every respect a handy, -well-written, instructive, comprehensive volume on wiring for the -wireman, foreman, contractor, or electrician. 272 pages; 105 -illustrations. Price $1.50 - -ELECTRIC TOY MAKING, DYNAMO BUILDING, AND ELECTRIC MOTOR CONSTRUCTION. -By PROF. T. O'CONOR SLOANE. This work treats of the making at home of -electrical toys, electrical apparatus, motors, dynamos and instruments -in general, and is designed to bring within the reach of young and old -the manufacture of genuine and useful electrical appliances. The work is -especially designed for amateurs and young folks. Thousands of our young -people are daily experimenting, and busily engaged in making electrical -toys and apparatus of various kinds. The present work is just what is -wanted to give the much needed information in a plain, practical manner, -with illustrations to make easy the carrying out of the work. 19th -Edition. Price $1.00 - -ELECTRICIAN'S HANDY BOOK. By PROF. T. O’CONOR SLOANE. This work of 768 -pages is intended for the practical electrician who has to make things -go. The entire field of electricity is covered within its pages. Among -some of the subjects treated are: The Theory of the Electric Current and -Circuit, Electro-Chemistry, Primary Batteries, Storage Batteries, -Generation and Utilization of Electric Powers, Alternating Current, -Armature Winding, Dynamos and Motors, Motor Generators, Operation of the -Central Station Switchboards, Safety Appliances, Distribution of -Electric Light and Power, Street Mains, Transformers, Arc and -Incandescent Lighting, Electric Measurements, Photometry, Electric -Railways, Telephony, Bell-Wiring, Electro-Plating, Electric Heating, -Wireless Telegraphy, etc. It contains no useless theory; everything is -to the point. It teaches you just what you want to know about -electricity. It is the standard work published on the subject. Forty-one -chapters, 610 engravings, handsomely bound in red leather with title and -edges in gold. Price: $3.50 - -ELECTRICITY IN FACTORIES AND WORKSHOPS, ITS COST AND CONVENIENCE. - -By ARTHUR P. HASLAM. - -A practical book for power producers and power users showing what a -convenience the electric motor, in its various forms, has become to the -modern manufacturer. It also deals with the conditions which determine -the cost of electric driving, and compares this with other methods of -producing and utilizing power. - -Among the chapters contained in the book are: The Direct Current Motor; -The Alternating Current Motor; The Starting and Speed Regulation of -Electric Motors; The Rating and Efficiency of Electric Motors; The Cost -of Energy as Affected by Conditions of Working, The Question for the -Small Power User; Independent Generating Plants; Oil and Gas Engine -Plants; Steam Plants; Power Station Tariffs; The Use of Electric Power -in Textile Factories; Electric Power in Printing Works; The Use of -Electric Power in Engineering Workshops Miscellaneous Application of -Electric Power; The Installation of Electric Motors; The Lighting of -Industrial Establishments 312 pages. Very fully illustrated. Price $2.50 - -ELECTRICITY SIMPLIFIED. By PROF. T. O'CONOR SLOANE. The object of -"Electricity Simplified" is to make the subject as plain as possible and -to show what the modern conception of electricity is; to show how two -plates of different metals immersed in acid can send a message around -the globe; to explain how a bundle of copper wire rotated by a steam -engine can be the agent in lighting our streets, to tell what the volt, -ohm and ampere are, and what high and low tension mean; and to answer -the questions that perpetually arise in the mind in this age of -electricity. 172 pages. Illustrated. Price $1.00 - -HOUSE WIRING. By THOMAS W. POPPE. This work describes and illustrates -the actual installation of Electric Light Wiring, the manner in which -the work should be done, and the method of doing it. The book can be -conveniently carried in the pocket. It is intended for the Electrician, -Helper and Apprentice. It solves all Wiring Problems, and contains -nothing that conflicts with the rulings of the National Board of Fire -Underwriters. It gives just the information essential to the Successful -Wiring of a Building. Among the subjects treated are: Locating the -Meter. Panel Boards. Switches. Plug Receptacles. Brackets. Ceiling -Fixtures. The Meter Connections. The Feed Wires. The Steel Armored Cable -System. The Flexible Steel Conduit System. The Ridig Conduit System. A -digest of the National Board of Fire Underwriters' rules relating to -metallic wiring systems. Various switching arrangements explained and -diagrammed. The easiest method of testing the Three and Four-way -circuits explained. The grounding of all metallic wiring systems and the -reason for doing so shown and explained. The insulation of the metal -parts of lamp fixtures and the reason for the same described and -illustrated. 125 pages. Fully illustrated. Flexible cloth. Price 50 -cents. - -HOW TO BECOME A SUCCESSFUL ELECTRICIAN. By PROF. T. O'CONOR SLOANE. -Every young man who wishes to become a successful electrician should -read this book. It tells in simple language the surest and easiest way -to become a successful electrician. The studies to be followed, methods -of work, field of operation and the requirements of the successful -electrician are pointed out and fully explained. Every young engineer -will find this an excellent stepping-stone to more advanced works on -electricity which he must master before success can be attained. Many -young men become discouraged at the very out-start by attempting to read -and study books that are far beyond their comprehension. This book -serves as the connecting link between the rudiments taught in the public -schools and the real study of electricity. It is interesting from cover -to cover. Fifteenth edition. 202 pages. Illustrated. Price $1.00 - -MANAGEMENT OF DYNAMOS. By LUMMIS-PATERSON. A handbook of theory and -practice. This work is arranged in three parts. The first part covers -the elementary theory of the dynamo. The second part, the construction -and action of the different classes of dynamos in common use are -described; while the third part relates to such matters as affect the -practical management and working of dynamos and motors. The following -chapters are contained in the book: Electrical Units; Magnetic -Principles; Theory of the Dynamo; Armature; Armature in Practice; Field -Magnets; Field Magnets in Practice; Regulating Dynamos; Coupling -Dynamos; Installation, Running, and Maintenance of Dynamos; Faults in -Dynamos; Faults in Armatures; Motors. 292 pages. 117 illustrations. -Price $1.50 - -STANDARD ELECTRICAL DICTIONARY. By T. O'CONOR SLOANE. An indispensable -work to all interested in electrical science. Suitable alike for the -student and professional. A practical hand-book of reference containing -definitions of about 5,000 distinct words, terms and phrases. The -definitions are terse and concise and include every term used in -electrical science. Recently issued. An entirely new edition. Should be -in the possession of all who desire to keep abreast with the progress of -this branch of science. In its arrangement and typography the book is -very convenient. The word or term defined is printed in black-faced type -which readily catches the eye, while the body of the page is in smaller -but distinct type. The definitions are well worded, and so as to be -understood by the non-technical reader. The general plan seems to be to -give an exact, concise definition, and then amplify and explain in a -more popular way. Synonyms are also given, and references to other words -and phrases are made. A very complete and accurate index of fifty pages -is at the end of the volume; and as this index contains all synonyms, -and as all phrases are indexed in every reasonable combination of words, -reference to the proper place in the body of the book is readily made. -It is difficult to decide how far a book of this character is to keep -the dictionary form, and to what extent it may assume the encyclopedia -form. For some purposes, concise, exactly worded definitions are needed; -for other purposes, more extended descriptions are required. This book -seeks to satisfy both demands, and does it with considerable success. -Complete, concise, and convenient. 682 pages. 393 illustrations. Twelfth -edition. Price $3.00 - -SWITCHBOARDS. By WILLIAM BAXTER, JR. This book appeals to every engineer -and electrician who wants to know the practical side of things. It takes -up all sorts and conditions of dynamos, connections and circuits and -shows by diagram and illustration just how the switchboard should be -connected. Includes direct and alternating current boards, also those -for arc lighting, incandescent, and power circuits. Special treatment on -high voltage boards for power transmission. 2nd Edition. 190 pages. -Illustrated. Price $1.60 - -TELEPHONE CONSTRUCTION, INSTALLATION, WIRING, OPERATION AND MAINTENANCE. -By W. H. RADCLIFFE and H. C. Cushing. This book gives the principles of -construction and operation of both the Bell and Independent instruments; -approved methods of installing and wiring them; the means of protecting -them from lightning and abnormal currents; their connection together for -operation as series or bridging stations; and rules for their inspection -and maintenance. Line wiring and the wiring and operation of special -telephone systems are also treated. Intricate mathematics are avoided, -and all apparatus, circuits and systems are thoroughly described. The -appendix contains definitions of units and terms used in the text. -Selected wiring tables, which are very helpful, are also included. Among -the subjects treated are Construction, Operation, and installation of -Telephone Instruments, Inspection and Maintenance of Telephone -Instruments; Telephone Line Wiring; Testing Telephone Line Wires and -Cables; Wiring and Operation of Special Telephone Systems; etc. 100 -pages, 125 illustrations. $1.00 - -WIRELESS TELEGRAPHY AND TELEPHONY SIMPLY EXPLAINED. By ALFRED P. MORGAN. - -This is undoubtedly one of the most complete and comprehensible -treatises on the subject ever published, and a close study of its pages -will enable one to master all the details of the wireless transmission -of messages. The author has filled a long felt want and has succeeded in -furnishing, a lucid, comprehensible explanation in simple language of -the theory and practice of wireless telegraphy and telephony. Among the -contents are: Introductory; Wireless Transmission and Reception—The -Aerial System, Earth Connections—The Transmitting Apparatus, Spark Coils -and Transformers, Condensers, Helixes, Spark Gaps, Anchor Gaps, Aerial -Switches—The Receiving Apparatus, Detectors, etc.—Tuning and Coupling, -Tuning Coils, Loose Couplers, Variable Condensers, Directive Wave -Systems-Miscellaneous Apparatus: Telephone Receivers, Range of Stations, -Static, Interference Wireless Telephones, Sound and Sound Waves, The -Vocal Cords and Ear—Wireless Telephones, How Sounds are changed into -Electric Waves Wireless Telephones, The Apparatus-Summary. 200 pages. -150 engravings. Price $1.00 - -WIRELESS TELEPHONES AND HOW THEY WORK. By JAMES ERSKINE-MURRAY. - -This work is free from elaborate details and aims at giving a clear -survey of the way in which Wireless Telephones work. It is intended for -amateur workers and for those whose knowledge of electricity is slight. -Chapters contained: How We Hear; Historical; The Conversion of Sound -into Electric Waves; Wireless Transmission; The Production of -Alternating Currents of High Frequency; How the Electric Waves are -Radiated and Received; The Receiving Instruments; Detectors; -Achievements and Expectations; Glossary of Technical Words, Cloth. Price -$1.00 - -WIRING A HOUSE. By HERBERT PRATT. - -Shows a house already built; tells just how to start about wiring it; -where to begin; what wire to use; how to run it according to Insurance -Rules; in fact just the information you need. Directions apply equally -to a shop. Fourth edition. 25 cents. - -FACTORY MANAGEMENT, ETC. - -MODERN MACHINE SHOP CONSTRUCTION, EQUIPMENT AND MANAGEMENT. - -By O. E. PERRIGO, M.E. - -The only work published that describes the modern machine shop or -manufacturing plant from the time the grass is growing on the site -intended for it until the finished product is shipped. By a careful -study of its thirty-two chapters the practical man may economically -build, efficiently equip, and successfully manage the modern machine -shop or manufacturing establishment. Just the book needed by those -contemplating the erection of modern shop buildings, the re-building and -re-organization of old ones, or the introduction of modern shop methods, -time and cost system. It is a book written and illustrated by a -practical shop man for practical shop men who are too busy to read -theories and want facts. It is the most complete all around book of its -kind ever published. It is a practical book for practical men, from the -apprentice in the shop to the president in the office. It minutely -describes and illustrates the most simple and yet the most efficient -time and cost system yet devised. Price $6.00 - -FUEL - -COMBUSTION OF COAL AND THE PREVENTION OF SMOKE. By WM. M. BARR. This -book has been prepared with special reference to the generation of heat -by the combustion of the common fuels found in the United States, and -deals particularly with the conditions necessary to the economic and -smokeless combustion of bituminous coals in Stationary and Locomotive -Steam Boilers. The presentation of this important subject is systematic -and progressive. The arrangement of the book is in a series of practical -questions to which are appended accurate answers, which describe in -language, free from technicalities, the several processes involved in -the furnace combustion of American fuels; it clearly states the -essential requisites for perfect combustion, and points out the best -methods for furnace construction for obtaining the greatest quantity of -heat from any given quality of coal. Nearly 350 pages, fully -illustrated. Price $1.00 - -SMOKE PREVENTION AND FUEL ECONOMY. By BOOTH and KERSHAW. A complete -treatise for all interested in smoke prevention and combustion, being -based on the German work of Ernst Schmatolla, but it is more than a mere -translation of the German treatise, much being added. The authors show -as briefly as possible the principles of fuel combustion, the methods -which have been and are at present in use, as well as the proper -scientific methods for obtaining all the energy in the coal and burning -it without smoke. Considerable space is also given to the examination of -the waste gases, and several of the representative English and American -mechanical stoker and similar appliances are described. The losses -carried away in the waste gases are thoroughly analyzed and discussed in -the Appendix, and abstracts are also here given of various patents on -combustion apparatus. The book is complete and contains much of value to -all who have charge of large plants. 194 pages. Illustrated. Price $2.80 - -GAS ENGINES AND GAS - -GASOLINE ENGINES: THEIR OPERATION, USE AND CARE. By A. HYATT VERRILL. -The Simplest, Latest and Most Comprehensive popular work published on -Gasoline Engines describing what the Gasoline engine is; its -construction and operation; how to install it; how to select it; how to -use it and how to remedy troubles encountered. Intended for owners, -Operators and Users of Gasoline Motors of all kinds. This work fully -describes and illustrates the various types of Gasoline engines used in -Motor Boats, Motor Vehicles and Stationary Work. The parts, accessories -and Appliances are described, with chapters on ignition, fuel, -lubrication, operation and engine troubles. Special attention is given -to the care, operation and repair of motors with useful hints and -suggestions on emergency repairs and make-shifts. A complete glossary of -technical terms and an alphabetically arranged table of troubles and -their symptoms form most valuable and unique features of this manual. -Nearly every illustration in the book is original, having been made by -the author. Every page is full of interest and value. A book which you -cannot afford to be without. 320 pages. Nearly 150 specially made -engravings. Price $1.50 - -GAS, GASOLINE, AND OIL ENGINES. By GARDNER D. HISCOX. Just issued, 20th -revised and enlarged edition. Every user of a gas engine needs this -book. Simple, instructive, and right up-to-date. The only complete work -on the subject. Tells all about the running and management of gas, -gasoline and oil engines, as designed and manufactured in the United -States. Explosive motors for stationary, marine and vehicle power are -fully treated, together with illustrations of their parts and tabulated -sizes, also their care and running are included. Electric ignition by -induction coil and jump spark' are fully explained and illustrated, -including valuable information on the testing for economy and power and -the erection of power plants. The rules and regulations of the Board of -Fire Underwriters in regard to the installation and management of -gasoline motors is given in full, suggesting the safe installation of -explosive motor power. A list of United States Patents issued on gas, -gasoline, and oil engines and their adjuncts from 1875 to date is -included. 484 pages. 410 engravings Price $2.50 - -MODERN GAS ENGINES AND PRODUCER GAS PLANTS. By R. E. MATHOR, M.E. A -guide for the gas engine designer, user, and engineer in the -construction, selection, purchase installation, operation, and -maintenance of gas engines. More than one book on gas engines has been -written, but not one has thus far even encroached on the field covered -by this book. Above all Mr. Mathor's work is a practical guide. -Recognizing the need of a volume that would assist the gas engine user -in understanding thoroughly the motor upon which he depends for power, -the author has discussed his subject without the help of any mathematics -and without elaborate theoretical explanations. Every part of the gas -engine is described in detail, tersely, clearly, with a thorough -understanding of the requirements of the mechanic. Helpful suggestions -as to the purchase of an engine, its installation, care, and operation -form a most valuable feature of the work. 320 pages. 175 detailed -illustrations. Price $2.50 - -GAS ENGINE CONSTRUCTION, OR HOW TO BUILD A HALF-HORSE-POWER GAS ENGINE. -By PARSELL and WEED. A practical treatise of 300 pages describing the -theory and principles of the action of Gas Engines of various types and -the design and construction of a half-horse power Gas Engine, with -illustrations of the work in actual progress, together with the -dimensioned working drawings giving clearly the sizes of the various -details; for the student, the scientific investigator and the amateur -mechanic. This book treats of the subject more from the standpoint of -practice than that of theory. The principles of operation of Gas Engines -are clearly and simply described and then the actual construction of a -half-horse power engine is taken up, step by step, showing in detail the -making of the Gas Engine. 3d Edition. 300 pages. Price $2.50 - -THE GASOLINE ENGINE ON THE FARM: ITS OPERATION, REPAIR AND USES. By XENO -W. PUTNAM. This is a practical treatise on the Gasoline and Kerosene -engine intended for the man who wants to know just how to manage his -engine and how to apply it to all kinds of farm work to the best -advantage. The book includes selecting the most suitable engine for farm -work, its most convenient and efficient installation, with chapters on -troubles, their remedies and how to avoid them. The care and management -of the farm tractor in plowing, harrowing, harvesting and road grading -are fully covered; also plain directions are given for handling the -tractor on the road. Special attention is given to relieving farm life -of its drudgery by applying power to the disagreeable small tasks which -must otherwise be done by hand. Many homemade contrivances for cutting -wood, supplying kitchen, garden and barn with water, loading, hauling -and unloading hay, delivering grain to the bins or the feed trough are -included; also full directions for making the engine milk the cows, -churn, wash, sweep the house and clean the windows, etc. Very fully -illustrated with drawings of working parts and cuts showing Stationary, -Portable and Tractor Engines doing all kinds of farm work. 300 pages. -Nearly 150 engravings. 12mo. Price $1.50 - -CHEMISTRY OF GAS MANUFACTURE. By H. M. ROYLES. This book covers points -likely to arise in the ordinary course of the duties of the engineer or -manager of a gas works not large enough to necessitate the employment of -a separate chemical staff. It treats of the testing of the raw materials -employed in the manufacture of illuminating coal gas, and of the gas -produced. The preparation of standard solutions is given as well as the -chemical and physical examination of gas coal including among its -contents-Preparations of Standard Solutions, Coal, Furnaces, Testing and -Regulation. Products of Carbonization. Analysis of Crude Coal Gas. -Analysis of Lime. Ammonia. Analysis of Oxide of Iron. Naphthalene. -Analysis of Fire-Bricks and Fire-Clay. Weldom and Spent Oxide. -Photometry and Gas Testing. Carburetted Water Gas. Metropolis Gas. -Miscellaneous Extracts. Useful Tables. $4.50 - -GEARING AND CAMS - -BEVEL GEAR TABLES. By D. AG. ENGSTROM. A book that will at once commend -itself to mechanics and draftsmen. Does a way with all the trigonometry -and fancy figuring on bevel gears and makes it easy for anyone to lay -them out or make them just right. There are 36 full-page tables that -show every necessary dimension for all sizes or combinations you're apt -to need. No puzzling figuring or guessing. Gives placing distance, all -the angles (including cutting angles), and the correct cutter to use. A -copy of this prepares you for anything in the bevel gear line. $1.00 - -CHANGE GEAR DEVICES. By OSCAR E. PERRIGO. A practical book for every -designer, draftsman, and mechanic interested in the invention and -development of the devices for feed changes on the different machines -requiring such mechanism. All the necessary information on this subject -is taken up, analyzed, classified, sifted, and concentrated for the use -of busy men who have not the time to go through the masses of irrelevant -matter with which such a subject is usually encumbered and select such -information as will be useful to them. It shows just what has been done, -how it has been done, when it was done, and who did it. It saves time in -hunting up patent records and re-inventing old ideas. 88 pages. $1.00 - -DRAFTING OF CAMS. By Louis ROUILLION. - -The laying out of cams is a serious problem unless you know how to go at -it right. This puts you on the right road for practically any kind of -cam you are likely to run up against. 25 cents. - -HYDRAULICS - -HYDRAULIC ENGINEERING. By GARDNER D. HISCOX. A treatise on the -properties, power, and resources of water for all purposes. Including -the measurement of streams, the flow of water in pipes or conduits; the -horse-power of falling water; turbine and impact water-wheels, wave -motors, centrifugal, reciprocating, and airlist pumps. - -With 300 figures and diagrams and 36 practical tables. All who are -interested in water-works development will find this book a useful one, -because it is an entirely practical treatise upon a subject of present -importance, and cannot fail in having a far-reaching influence, and for -this reason should have a place in the working library of every -engineer. Among the subjects treated are: Historical-Hydraulics, -Properties of Water; Measurement of the flow of Streams; Flow from -Subsurface orifices and nozzles; Flow of water in Pipes; Siphons of -various kinds; Dams and Great Storage Reservoirs; City and Town Water -Supply; Wells and their reenforcement; Air lift methods of raising -water; artesian wells; Irrigation of Arid districts; Water Power, Water -Wheels; Pumps and Pumping Machinery; Reciprocating Pumps; Hydraulic -Power Transmission; Hydraulic Mining; Canals; Ditches; Conduits and Pipe -Lines; Marine Hydraulics; Tidal and Sea Wave power, etc. 320 pages. -Price $4.00 - -ICE AND REFRIGERATION - -POCKET BOOK OF REFRIGERATION AND ICE MAKING. By A. J. WALLIS-TAYLOR This -is one of the latest and most comprehensive reference books published on -the subject of refrigeration and cold storage. It explains the -properties and refrigerating effect of the different fluids in use, the -management of refrigerating machinery and the construction and -insulation of cold rooms with their required pipe surface for different -degrees of cold; freezing mixtures and non-freezing brines, temperatures -of cold rooms for all kinds of provisions, cold storage charges for all -classes of goods, ice making and storage of ice, data and memoranda for -constant reference by refrigerating engineers, with nearly one hundred -tables containing valuable references to every fact and condition -required in the installment and operation of a refrigerating plant. -Illustrated. (5th Edition, revised.) Price $1.50 - -INVENTIONS PATENTS - -INVENTOR'S MANUAL, HOW TO MAKE A PATENT PAY. - -This is a book designed as a guide to inventors in perfecting their -inventions, taking out their patents and disposing of them. It is not in -any sense a Patent Solicitor's Circular, nor a Patent Broker's -Advertisement. No advertisements of any description appear in the work. -It is a book containing a quarter of a century's experience of a -successful inventor, together with notes based upon the experience of -many other inventors. Among the subjects treated in this work are: How -to Invent. How to Secure a Good Patent. Value of Good Invention. How to -exhibit an Invention. How to Interest Capital. How to Estimate the value -of a Patent. Value of Design Patents. Value of Foreign Patents. Value of -Small Inventions. Advice on Selling Patents. Advice on the formation of -Stock Companies. Advice on the Formation of Limited Liability Companies. -Advice on Disposing of Old Patents. Advice as to Patent Attorneys. -Advice as to Selling Agents. Forms of Assignments. License and -Contracts. State Laws Concerning Patent Rights. 1900 Census of the -United States by counties of over 10,000 population. Revised edition. -120 pages. Price $1.00 - -KNOTS - -KNOTS, SPLICES AND ROPE WORK. By A. HYATT VERRILL. This is a practical -book giving complete and simple directions for making all the most -useful and ornamental knots in common use, with chapters on Splicing, -Pointing, Seizing, Serving, etc. This book is fully illustrated with one -hundred and fifty original engravings which show how each knot, tie or -splice is formed and its appearance when finished. The book will be -found of the greatest value to Campers, Yachtsmen, Travelers, Boy Scouts -in fact to anyone having occasion to use or handle rope or knots for any -purpose. The book is thoroughly reliable and practical and is not only a -guide but a teacher. It is the standard work on the subject. Among the -contents are: 1. Cordage, Kinds of Rope, Construction of Rope, Parts of -Rope Cable and Bolt Rope, Strength of Rope, Weight of Rope. 2. Simple -knots and Bends. Terms used in Handling Rope. Seizing Rope. 3. Ties and -Hitches. 4. Noose, Loops and Mooring Knots. 5. Shortenings, Grommets and -Selvages. 6. Lashings. Seizings and Splices. 7. Fancy Knots and Rope -Work. 128 pages. 150 original engravings. Price 60 cents. - -LATHE WORK - -MODERN AMERICAN LATHE PRACTICE. By OSCAR E. PERRIGO. This is a new book -from cover to cover, and the only complete American work on the subject -written by a man who knows not only how work ought to be done, but who -also knows how to do it, and how to convey this knowledge to others. It -is strictly up-to-date in its descriptions and illustrations, which -represent the very latest practice in lathe and boring mill operations -as well as the construction of and latest developments in the -manufacture of these important classes of machine tools. Lathe history -and the relations of the Lathe to manufacturing are given; also a -description of the various devices for Feeds and Thread Cutting -mechanisms from early efforts in this direction to the present time. -Lathe design is thoroughly discussed, including Back Gearing, Driving -Cones, Thread Cutting Gears, and all the essential elements of the -modern Lathe. The classification of Lathes is taken up, giving the -essential differences of the several types of Lathes, including, as is -usually understood, Engine Lathes, Bench Lathes, Speed Lathes, Forge -Lathes, Gap Lathes, Pulley Lathes, Forming Lathes, Multiple Spindle -Lathes, Rapid Reduction Lathes, Precision Lathes, Turret Lathes, Special -Lathes, Electrically Driven Lathes, etc. 424 pages. 314 illustrations. -Price $2.50 - -PRACTICAL METAL TURNING. By JOSEPH G. HORNER. This important and -practical subject is treated in a full and exhaustive manner and nothing -of importance is omitted. The principles and practice and all the -different branches of Turning are considered and well illustrated. All -the different kinds of Chucks of usual forms, as well as some unusual -kinds, are shown. A feature of the book is the important section devoted -to modern Turret practice; Boring is another subject which is treated -fully; and the chapter on Tool Holders illustrates a large number of -representative types. Thread Cutting is treated at reasonable length; -and the last chapter contains a good deal of information relating to the -High-Speed Steels and their work. The numerous tools used by machinists -are illustrated, and also the adjuncts of the lathe. In fact, the entire -subject is treated in such a thorough manner as to make this book the -standard one on the subject. It is indispensable to the manager, -engineer, and machinist as well as to the student, amateur, and -experimental, man who desires to keep up-to-date. 400 pages, fully -illustrated. Price $3.50 - -TURNING AND BORING TAPERS. By FRED H. COLVIN. There are two ways to turn -tapers; the right way and one other. This treatise has to do with the -right way; it tells you how to start the work properly, how to set the -lathe, what tools to use and how to use them, and forty and one other -little things that you should know. Fourth edition. 25 cents. - -LIQUID AIR - -LIQUID AIR AND THE LIQUEFACTION OF GASES. By T. O'CONOR SLOANE. This -book gives the history of the theory, discovery, and manufacture of -Liquid Air, and contains an illustrated description of all the -experiments that have excited the wonder of audiences all over the -country. It shows how liquid air, like water, is carried hundreds of -miles and is handled in open buckets. It tells what may be expected from -it in the near future. A book that renders simple one of the most -perplexing chemical problems of the century. Startling developments -illustrated by actual experiments. It is not only a work of scientific -interest and authority, but is intended for the general reader, being -written in a popular style-easily understood by every one. Second -edition. 365 pages. Price $2.00 - -LOCOMOTIVE ENGINEERING - -AIR-BRAKE CATECHISM. By ROBERT H. BLACKALL. This book is a standard text -book. It covers the Westinghouse Air-Brake Equipment, including the No. -5 and the No. 6 E. T Locomotive Brake Equipment; the K (Quick-Service) -Triple Valve for Freight Service; and the Cross-Compound Pump. The -operation of all parts of the apparatus is explained in detail, and a -practical way of finding their peculiarities and defects, with a proper -remedy, is given. It contains 2,000 questions with their answers, which -will enable any railroad man to pass any examination on the subject of -Air Brakes. Endorsed and used by air-brake instructors and examiners on -nearly every railroad in the United States. 25th Edition. 350 pages, -fully illustrated with folding plates and diagrams. $2.00 - -AMERICAN COMPOUND LOCOMOTIVES. By FRED. H. COLVIN. - -The only book on compounds for the engineman or shopman that shows in a -plain, practical way the various features of compound locomotives in -use. Shows how they are made, what to do when they break down or balk. -Contains sections as follows:-A Bit of History. Theory of Compounding -Steam Cylinders. Baldwin Two-Cylinder Compound. Pittsburg Two-Cylinder -Compound. Rhode Island Compound. Richmond Compound. Rogers Compound. -Schenectady Two-Cylinder Compound. Vauclain Compound. Tandem Compounds. -Baldwin Tandem. The Colvin-Wightman Tandem. Schenectady Tandem. Balanced -Locomotives. Baldwin Balanced Compound. Plans for Balancing. Locating -Blows. Breakdowns. Reducing Valves. Drifting. Valve Motion. -Disconnecting. Power of Compound Locomotives. Practical Notes. Fully -illustrated and containing ten special "Duotone" inserts on heavy Plate -Paper, showing different types of Compounds. 142 pages. Price $1.00 - -APPLICATION OF HIGHLY SUPERHEATED STEAM TO LOCOMOTIVES. By ROBERT GARBE. - -A practical book. Contains special chapters on Generation of Highly -Superheated Steam; Superheated Steam and the Two-Cylinder Simple Engine; -Compounding and Superheating; Designs of Locomotive Superheaters; -Constructive Details of Locomotives using Highly Superheated Steam; -Experimental and Working Results. Illustrated with folding places and -tables. Price $2.50 - -COMBUSTION OF COAL AND THE PREVENTION OF SMOKE. By WM. M. BARR. This -book has been prepared with special reference to the generation of heat -by the combustion of the common fuels found in the United States, and -deals particularly with the conditions necessary to the economic and -smokeless combustion of bituminous coal in Stationary and Locomotive -Steam Boilers. The presentation of this important subject is systematic -and progressive. The arrangement of the book is in a series of practical -questions to which are appended accurate answers, which describe in -language, free from technicalities, the several processes involved in -the furnace combustion of American fuels; it clearly states the -essential requisites for perfect combustion, and points out the best -methods of furnace construction for obtaining the greatest quantity of -heat from any given quality of coal. Nearly 350 pages, fully -illustrated. Price $1.00 - -DIARY OF A ROUND HOUSE FOREMAN. By T. S. REILLY. This is the greatest -book of railroad experiences ever published. Containing a fund of -information and suggestions along the line of handling men, organizing, -etc., that one cannot afford to miss. 176 pages. Price $1.00 - -LINK MOTIONS, VALVES AND VALVE SETTING. By FRED H. COLVIN, Associate -Editor of "American Machinist." - -A handy book for the engineer or machinist that clears up the mysteries -of valve setting. Shows the different valve gears in use, how they work, -and why. Piston and slide valves of different types are illustrated and -explained. A book that every railroad man in the motive power department -ought to have. Contains chapters on Locomotive Link Motion, Valve -Movements, Setting Slide Valves, Analysis by Diagrams, Modern Practice, -Slip of Block, Slide Valves, Piston Valves, Setting Piston Valves, -Joy-Allen Valve Gear, Walschaert Valve Gear, Gooch Valve Gear, -Alfree-Hubbell Valve Gear, etc., etc. Fully illustrated. Price 50 cents. - -LOCOMOTIVE BOILER CONSTRUCTION. By FRANK A. KLEINHANS. The construction -of boilers in general is treated, and following this, the locomotive -boiler is taken up in the order in which its various parts go through -the shop. Shows all types of boilers used; gives details of -construction; practical facts, such as life of riveting, punches and -dies; work done per day, allowance for bending and flanging sheets, and -other data. Locomotive boilers present more difficulty in laying out and -building than any other type, and for this reason the author uses them -as examples. Anyone who can handle them can tackle anything. Contains -chapters on Laying Out Work; Flanging and Forging; Punching; Shearing: -Plate Planing; General Tables; Finishing Parts; Bending; Machinery -Parts; Riveting; Boiler Details; Smoke Box Details; Assembling and -Caulking; Boiler Shop Machinery, etc., etc. There isn't a man who has -anything to do with boiler work, either new or repair work, who doesn't -need this book. The manufacturer, superintendent, foreman, and boiler -worker all need it. No matter what the type of boiler, you'll find a -mint of information that you wouldn't be without. Over 400 pages, five -large folding plates. Price: $3.00 - -LOCOMOTIVE BREAKDOWNS AND THEIR REMEDIES. By GEO. L. FOWLER. Revised by -WM. W. Wood, Air-Brake Instructor. Just issued. Revised pocket edition. -It is out of the question to try and tell you about every subject that -is covered in this pocket edition of Locomotive Breakdowns. Just imagine -all the common troubles that an engineer may expect to happen some time, -and then add all of the unexpected ones, troubles that could occur, but -that you had never thought about, and you will find that they are all -treated with the very best methods of repair. Walschaert Locomotive -Valve Gear Troubles, Electric Headlight Troubles, as well as Questions -and Answers on the Air Brake are all included. 294 pages. 7th Revised -Edition. Fully illustrated. $1.00 - -LOCOMOTIVE CATECHISM. By ROBERT GRIMSHAW. The revised edition of -"Locomotive Catechism," by Robert Grimshaw, is a New Book from Cover to -Cover. It contains twice as many pages and double the number of -illustrations of previous editions. Includes the greatest amount of -practical information ever published on the construction and management -of modern locomotives. Specially Prepared Chapters on the Walschaert -Locomotive Valve Gear, the Air Brake Equipment and the Electric Head -Light are given. It commends itself at once to every Engineer and -Fireman, and to all who are going in tor examination or promotion. In -plain language, with full complete answers, not only all the questions -asked by the examining engineer are given, but those which the young and -less experienced would ask the veteran, and which old hands ask as -"stickers." It is a veritable Encyclopedia of the Locomotive, is -entirely free from mathematics, easily, understood and thoroughly -up-to-date. Contains over 4,000 Examination Questions with their -Answers. 825 pages, 437 illustrations and three folding plates. 28th -Revised Edition. $2.50 - -PRACTICAL INSTRUCTOR AND REFERENCE BOOK FOR LOCOMOTIVE FIREMEN AND -ENGINEERS. By CHAS. F. LOCKHART. An entirely new book on the Locomotive. -It appeals to every railroad man, as it tells him how things are done -and the right way to do them. Written by a man who has had years of -practical experience in locomotive shops and on the road firing and -running. The information given in this book cannot be found in any other -similar treatise. Eight hundred and fifty-one questions with their -answers are included, which will prove specially helpful to those -preparing for examination. Practical information on: The Construction -and Operation of Locomotives. Breakdowns and their Remedies; Air. Brakes -and Valve Gears. Rules and Signals are handled in a thorough manner. As -a book of reference it cannot be excelled. The book is divided into six -parts, as follows: 1. The Fireman's Duties. 2. General description of -the Locomotive. 3. Breakdowns and their Remedies. 4. Air Brakes. 5. -Extracts from Standard Rules. 6. Questions for examination. The 851 -questions have been carefully selected and arranged. These cover the -examinations required by the different railroads. 368 pages. 88 -illustrations. Price $1.50 - -PREVENTION OF RAILROAD ACCIDENTS, OR SAFETY IN RAILROADING. By GEORGE -BRADSHAW. This book is a heart-to-heart talk with Railroad Employees, -dealing with facts, not theories, and showing the men in the ranks, from -every-day experience, how accidents occur and how they may be avoided. -The book is illustrated with seventy original photographs and drawings -showing the safe and unsafe methods of work. No visionary schemes, no -ideal pictures. Just plain facts and Practical Suggestions are given. -Every railroad employee who reads the book is a better and safer man to -have in railroad service. It gives just the information which will be -the means of preventing many injuries and deaths. All railroad employees -should procure a copy, read it, and do your part in preventing -accidents. 169 pages. Pocket Size. Fully illustrated. Price 50 cents. - -TRAIN RULE EXAMINATIONS MADE EASY. By G. E. COLLINGWOOD. This is the -only practical work on train-rules in print. Every detail is covered, -and puzzling points are explained in simple, comprehensive language, -making it a practical treatise for the Train Dispatcher, Engineman, -Trainman, and all others who have to do with the movements of trains. -Contains complete and reliable information of the Standard Code of -Train. Rules for single track. Shows Signals in Colors, as used on the -different roads. Explains fully the practical application of train -orders, giving a clear and definite understanding of all orders which -may be used. The meaning and necessity for certain rules are explained -in such a manner that the student may know beyond a doubt the rights -conferred under any orders he may receive or the action required by -certain rules. As nearly all roads require trainmen to pass regular -examinations, a complete set of examination questions, with their -answers, are included. These will enable the student to pass the -required examinations with credit to himself and the road for which he -works. - -256 pages. Fully illustrated with Train Signals in colors. Price $1.26 - -TRAIN RULES AND DESPATCHING. By H. A. DALBY. Every railroad man, no -matter what department he's in, needs a copy of this book. It gives the -standard rules for both single and double track, shows all the signals, -with colors wherever necessary, and has a list of towns where time -changes, with a map showing the whole country. The rules are explained -wherever there is any doubt about their meaning or where they are -modified by different railroads. It's the only practical book on train -rules in print. Over 220 pages. Leather cover. Price $1.50 - -THE WALSCHAERT AND OTHER MODERN RADIAL VALVE GEARS FOR LOCOMOTIVES. By -WM. W. Wood. If you would thoroughly understand the Walschaert Valve -Gear you should possess a copy of this book, as the author takes the -plainest form of a steam engine-a stationary engine in the rough, that -will only turn its crank in one direction and from it builds up—with the -reader's help—a modern locomotive equipped with the Walschaert Valve -Gear, complete. The points discussed are clearly illustrated; two large -folding plates that show the positions of the valves of both inside or -outside admission type, as well as the links and other parts of the gear -when the crank is at nine different points in its revolution, are -especially valuable in making the movement clear. These employ sliding -cardboard models which are contained in a pocket in the cover. The book -is divided into five general divisions, as follows: I. Analysis of the -gear. II. Designing and erecting the gear. III. Advantages of the gear. -IV. Questions and answers relating to the Walschaert Valve Gear. V. -Setting valves with the Walschaert Valve Gear; the three primary types -of locomotive valve motion; modern radial valve gears other than the -Walschaert; the Hobart All-free valve and valve gear, with questions and -answers on breakdowns; the Baker-Pilliod valve gear; the Improved -Baker-Pilliod Valve Gear, with questions and answers on breakdowns. The -questions with full answers given will be especially valuable to firemen -and engineers in preparing for an examination for promotion. 245 pages. -Third Revised Edition. Price $1.50 - -WESTINGHOUSE E-T AIR-BRAKE INSTRUCTION POCKET BOOK. By WM. W. Wood, -Air-Brake Instructor. Here is a book for the railroad man, and the man -who aims to be one. It is without doubt the only complete work published -on the Westinghouse E-T Locomotive Brake Equipment. Written by an Air -Brake Instructor who knows just what is needed. It covers the subject -thoroughly. Everything about the New Westinghouse Engine and Tender -Brake Equipment, including the Standard No. 5 and the Perfected No. 6 -Style of brake, is treated in detail. Written in plain English and -profusely illustrated with Colored Plates, which enable one to trace the -flow of pressures throughout the entire equipment. The best book ever -published on the Air Brake. Equally good for the beginner and the -advanced engineer. Will pass any one through any examination. It informs -and enlightens you on every point. Indispensable to every engineman and -trainman. Contains examination questions and answers on the E-T -equipment. Covering what the E-T Brake is. How it should be operated. -What to do when defective. Not a question can be asked of the engineman -up for promotion on either the No. 5 or the No. 6 E-T equipment that is -not asked and answered in the book. If you want to thoroughly understand -the E-T equipment get a copy of this book. It covers every detail. Makes -Air Brake troubles and examinations easy. Price $1.50 - -MACHINE SHOP PRACTICE - -AMERICAN TOOL MAKING AND INTERCHANGEABLE MANUFACTURING. By J. V. -WOODWORTH. - -A "shoppy" book, containing no theorizing, no problematical or -experimental devices, there are no badly proportioned and impossible -diagrams, no catalogue cuts, but a valuable collection of drawings and -descriptions of devices, the rich fruits of the author's own experience. -In its 500-odd pages the one subject only, Tool Making, and whatever -relates thereto, is dealt with. The work stands without a rival. It is a -complete practical treatise on the art of American Tool Making and -system of interchangeable manufacturing as carried on to-day in the -United States. In it are described and illustrated all of the different -types and classes of small tools, fixtures, devices, and special -appliances which are in general use in all machine manufacturing and -metal working establishments where economy, capacity, and -interchangeability in the production of machined metal parts are -imperative. The science of jig making is exhaustively discussed, and -particular attention is paid to drill jigs, boring, profiling and -milling fixtures and other devices in which the parts to be machined are -located and fastened within the contrivances. All of the tools, -fixtures, and devices illustrated and described have been or are used -for the actual production of work, such as parts of drill presses, -lathes, patented machinery, typewriters, electrical apparatus, -mechanical appliances, brass goods, composition parts, mould products, -sheet metal articles, drop forgings, jewelry, watches, medals, coins, -etc. 531 pages. Price $4.00 - -HENLEY'S ENCYCLOPEDIA OF PRACTICAL ENGINEERING AND ALLIED TRADES. Edited -by JOSEPH G. HORNER, A.M.I., M.E. This set of five volumes contains -about 2,500 pages with thousands of illustrations, including -diagrammatic and sectional drawings with full explanatory details. This -work covers the entire practice of Civil and Mechanical Engineering. The -best known expert in all branches of engineering have contributed to -these volumes. The Cyclopedia is admirably well adapted to the needs of -the beginner and the self-taught practical man, as well as the -mechanical engineer, designer, draftsman, shop superintendent, foreman, -and machinist. The work will be found a means of advancement to any -progressive man. It is encyclopedic in scope, thorough and practical in -its treatment of technical subjects, simple and clear in its descriptive -matter, and without unnecessary technicalities or formulae. The articles -are as brief as may be and yet give a reasonably clear and explicit -statement of the subject, and are written by men who have had ample -practical experience in the matters of which they write. It tells you -all you want to know about engineering and tells it so simply, so -clearly, so concisely, that one cannot help but understand. As a work of -reference it is without a peer. $6.00 per volume. For complete set of -five volumes, price $25.00 - -MACHINE SHOP ARITHMETIC. By COLVIN-CHENEY. This is an arithmetic of the -things you have to do with daily. It tells you plainly about: how to -find areas of figures; how to find surface or volume of balls or -spheres; handy ways for calculating; about compound gearing; cutting -screw threads on any lathe; drilling for taps; speeds of drills, taps, -emery wheels, grindstones, milling cutters, etc.; all about the Metric -system with conversion tables; properties of metals; strength of bolts -and nuts; decimal equivalent of an inch. All sorts of machine shop -figuring and 1,001 other things, any one of which ought to be worth more -than the price of this book to you, and it saves you the trouble of -bothering the boss. 6th Edition. 131 pages. Price 50 cents. - -MODERN MACHINE SHOP CONSTRUCTION, EQUIPMENT AND MANAGEMENT. By OSCAR E. -PERRIGO. The only work published that describes the Modern Machine Shop -or Manufacturing Plant from the time the grass is growing on the site -intended for it until the finished product is shipped. Just the book -needed by those contemplating the erection of modern shop buildings, the -rebuilding and reorganization of old ones, or the introduction of Modern -Shop Methods, time and cost systems. It is a book written and -illustrated by a practical shop man for practical shop men who are too -busy to read theories and want facts. It is the most complete all-around -book of its kind ever published. 400 large quarto pages. 225 original -and specially-made illustrations. Price $5.00 - -MECHANICAL APPLIANCES, MECHANICAL MOVEMENTS AND NOVELTIES OF -CONSTRUCTION. By GARDNER D. HISCOX. This is a supplementary volume to -the one upon mechanical movements. Unlike the first volume, which is -more elementary in character, this volume contains illustrations and -descriptions of many combinations of motions and of mechanical devices -and appliances found in different lines of machinery. Each device being -shown by a line drawing with a description showing its working parts and -the method of operation. From the multitude of devices described, and -illustrated, might be mentioned, in passing, such items as conveyors and -elevators, Prony brakes, thermometers, various types of boilers, solar -engines, oil-fuel burners, condensers, evaporators, Corliss and other -valve gears, governors, gas engines, water motors of various -descriptions, air ships, motors and dynamos, automobile and motor -bicycles, railway block signals, car couplers, link and gear motions, -ball bearings, breech block mechanism for heavy guns, and a large -accumulation of others of equal importance. 1,000 specially made -engravings. 396 octavo pages. Price $2.50 - -MECHANICAL MOVEMENTS, POWERS, AND DEVICES. By GARDNER D. HISCOX. This is -a collection of 1,890 engravings of different mechanical motions and -appliances, accompanied by appropriate text, making it a book of great -value to the inventor, the draftsman, and to all readers with mechanical -tastes. The book is divided into eighteen sections or chapters in which -the subject matter is classified under the following heads: Mechanical -Powers; Transmission of Power; Measurement of Power, Steam Power; Air -Power Appliances; Electric Power and Construction, Navigation and Roads; -Gearing; Motion and Devices; Controlling Motion; Horological; Mining; -Mill and Factory Appliances; Construction and Devices; Drafting Devices: -Miscellaneous Devices, etc. 12th edition. 400 octavo pages. Price $2.50 - -MACHINE SHOP TOOLS AND SHOP PRACTICE. By W. H. VANDERVOORT. A work of -555 pages and 673 illustrations, describing in every detail the -construction, operation, and manipulation of both hand and machine -tools. Includes chapters on filing, fitting, and scraping surfaces; on -drills, reamers, taps, and dies; the lathe and its tools; planers, -shapers, and their tools; milling machines and cutters; gear cutters and -gear cutting; drilling machines and drill work; grinding machines and -their work; hardening and tempering; gearing, belting and transmission -machinery: useful data and tables. 6th edition, Price $3.00 - -THE MODERN MACHINIST. By JOHN T. USHER. This is a book showing, by plain -description and by profuse engravings, made expressly for the work, all -that is best, most advanced, and of the highest efficiency in modern -machine shop practice, tools, and implements, showing the way by which -and through which, as Mr. Maxim says, "American machinists have become -and are the finest mechanics in the world." Indicating as it does, in -every line, the familiarity of the author with every detail of daily -experience in the shop, it cannot fail to be of service to any man -practically connected with the shaping or finishing of metals. There is -nothing experimental or visionary about the book, all devices being in -actual use and giving good results. It might be called a compendium of -shop methods, showing a variety of special tools and appliances which -will give new ideas to many mechanics, from the superintendent down to -the man at the bench. It will be found a valuable addition to any -machinist's library, and should be consulted whenever a new or difficult -job is to be done, whether it is boring, milling, turning, or planing, -as they are all treated in a practical manner. Fifth Edition. 320 pages. -250 illustrations. Price $2.50 - -MODERN MILLING MACHINES: THEIR DESIGN, CONSTRUCTION AND OPERATION. By -JOSEPH G. HORNER. This book describes and illustrates the Milling -Machine and its work in such a plain, clear, and forceful manner, and -illustrates the subject so clearly and completely, that the up-to-date -machinist, student, or mechanical engineer cannot afford to do without -the valuable information which it contains. It describes not only the -early machines of this class, but notes their gradual development into -the splendid machines of the present day, giving the design and -construction of the various types, forms, and special features produced -by prominent manufacturers, American and foreign. Milling cutters in all -their development and modernized forms are illustrated and described, -and the operations they are capable of producing upon different classes -of work are carefully described in detail, and the speeds and feeds -necessary are discussed, and valuable and useful data given for -determining these usually perplexing problems. The book is the most -comprehensive work published on the subject. 304 pages. 300 -illustrations. Price $4.00 - -"SHOP KINKS." By ROBERT GRIMSHAW. A book of 400 pages and 222 -illustrations, being entirely different from any other book on machine -shop practice. Departing from conventional style, the author avoids -universal or common shop usage and limits his work to showing special -ways of doing things better, more cheaply and more rapidly than usual. -As a result the advanced methods of representative establishments of the -world are placed at the disposal of the reader. This book shows the -proprietor where large savings are possible, and how products may be -improved. To the employee it holds out suggestions that, properly -applied, will hasten his advancement. No shop can afford to be without -it. It bristles with valuable wrinkles and helpful suggestions, It will -benefit all, from apprentice to proprietor. Every machinist, at any age, -should study its pages. Fifth Edition. Price $2.50 - -THREADS AND THREAD CUTTING. By COLVIN and STABEL. This clears up many of -the mysteries of thread-cutting, such as double and triple threads, -internal threads, catching threads, use of hobs, etc. Contains a lot of -useful hints and several tables. 3rd Edition. Price 25 cents. - -TOOLS FOR MACHINISTS AND WOOD WORKERS, INCLUDING INSTRUMENTS OF -MEASUREMENT. By JOSEPH G. HORNER. The principles upon which cutting -tools for wood, metal, and other substances are made are identical, -whether used by the machinist, the carpenter, or by any other skilled -mechanic in their daily work, and the object of this book is to give a -correct and practical description of these tools as they are commonly -designed, constructed, and used. 340 pages, fully illustrated. Price -$3.50 - -MANUAL TRAINING - -ECONOMICS OF MANUAL TRAINING. By LOUIS ROUILLION. The only book -published that gives just the information needed by all interested in -Manual Training, regarding Buildings, Equipment, and Supplies. Shows -exactly what is needed for all grades of the work from the Kindergarten -to the High and Normal School. Gives itemized lists of everything used -in Manual Training Work and tells just what it ought to cost. Also shows -where to buy supplies, etc. Contains 174 pages, and is fully -illustrated. 2nd Edition. Price $1.50 - -MARINE ENGINEERING - -MARINE ENGINES AND BOILERS, THEIR DESIGN AND CONSTRUCTION. By Dr. G. -BAUER, LESLIE S. ROBERTSON, and S. BRYAN DONKIN. in the words of. Dr. -Bauer, the present work owes its origin to an oft felt want of a -Condensed Treatise, embodying the Theoretical and Practical Rules used -in Designing Marine Engines and Boilers. The need for such a work has -been felt by most engineers engaged in the construction and working of -Marine Engines, not only by the younger men, but also by those of -greater experience. The fact that the original German work was written -by the chief engineer of the famous Vulcan Works, Stettin, is in itself -a guarantee that this book is in all respects thoroughly up-to-date, and -that it embodies all the information which is necessary for the design -and construction of the highest types of marine engines and boilers. It -may be said that the motive power which Dr. Bauer has placed in the -fast German liners that have been turned out of late years from the -Stettin Works, represent the very best practice in marine engineering of -the present day. This work is clearly written, thoroughly systematic, -theoretically sound; while the character of its plans, drawings, tables, -and statistics is without reproach. The illustrations are careful -reproductions from actual working drawings, with some well-executed -photographic views of completed engines and boilers. - -550 illustrations and numerous tables. $9.00 net - -MODERN SUBMARINE CHART. A cross-section view, showing clearly and -distinctly all the interior of a Submarine of the latest type. You get -more information from this chart, about the construction and operation -of a Submarine, than in any other way. No Details omitted-everything is -accurate and to scale. It is absolutely correct in every detail, having -been approved by Naval Engineers. All the machinery and devices fitted -in a modern Submarine Boat are shown and to make the engraving more -readily understood all the features are shown in operative form with -Officers and Men in the act of performing the duties assigned to them in -service conditions. This CHART IS REALLY AN ENCYCLOPEDIA OF A SUBMARINE. -It is educational and worth many times its cost. Mailed in a Tube for 25 -cents. 744 pages. - -MINING - -ORE DEPOSITS, WITH A CHAPTER ON HINTS TO PROSPECTORS. By J. P. JOHNSON -This book gives a condensed account of the ore-deposits at present known -in South Africa. It is also intended as a guide to the prospector. Only -an elementary knowledge of geology and some mining experience are -necessary in order to understand this work. With these qualifications, -it will materially assist one in his search for metalliferous mineral -occurrences and, so far as simple ores are concerned, should enable one -to form some idea of the possibilities of any he may find. Among the -chapters given are: Titaniferous and Chromiferous Iron -Oxides–Nickel–Copper–Cobalt–Tin–Molybdenum–Tungsten–Lead–Mercury -–Antimony–Iron-Hints to Prospectors. $2.00 - -PHYSICS AND CHEMISTRY OF MINING. By T. H. BYROM. A practical work for -the use of all preparing for examinations in mining or qualifying for -colliery managers' certificates. The aim of the author in this excellent -book is to place clearly before the reader useful and authoritative data -which will render him valuable assistance in his studies. The only work -of its kind published. The information incorporated in it will prove of -the greatest practical utility to students, mining engineers, colliery, -managers, and all others who are specially interested in the present-day -treatment of mining problems. Among its contents are chapters on: The -Atmosphere; Laws Relating to the Behavior of Gases; The Diffusion of -Gases; Composition of the Atmosphere: Sundry Constituents of the -Atmosphere; Water; Carbon; Fire-Damp; Combustion; Coal Dust and Its -Action; Explosives; Composition of Various Coals and Fuels; Methods of -Analysis of Coal; Strata Adjoining the Coal Measures; Magnetism and -Electricity; Appendix; Useful Tables, etc.; Miscellaneous Questions. 160 -pages. Illustrated. $2.00 - -PRACTICAL COAL MINING. By T. H. COCKIN. An important work, containing -428 pages and 213 illustrations, complete with practical details, which -will intuitively impart to the reader, not only a general knowledge of -the principles of coal mining, but also considerable insight into allied -subjects. This treatise is positively up to date in every instance, and -should be in the hands of every colliery engineer, geologist, mine -operator, superintendent, foreman, and all others who are interested in -or connected with the industry. 2nd Edition. $2.50 - -PATTERN MAKING - -PRACTICAL PATTERN MAKING. By F. W. BARROWS. This is a very complete and -entirely practical treatise on the subject of pattern making, -illustrating pattern work in wood and metal. From its pages you are -taught just what you should know about pattern making. It contains a -detailed description of the materials used by pattern makers, also the -tools, both those for hand use, and the more interesting machine tools; -having complete chapters on the band saw, The Buzz Saw, and the Lathe. -Individual patterns of many different kinds are fully illustrated and -described, and the mounting of metal patterns on plates for molding -machines is included. Rules, Formulas and Tables are included, -containing simple and original methods for finding the weight of -castings, both from the pattern itself and from the drawings. This -section contains some new and practical formulas, which will be found -very useful in estimating weights, with the accuracy required for -quotations to prospective customers. Ali of these rules are simple, and -can be put to practical use by the ordinary, every-day man, and they -have been proved by years of actual use. Plain rules for keeping down -the cost of patterns, with a complete system for checking the cost of -and marking the patterns, and a card record showing what the pattern is, -material used, where located in safe, with its cost and date of -production, is included. The book closes with an original and practical -method for the inventory and valuation of patterns. Containing 326 pages -and 150 detailed illustrations. Price $2.00 - -PERFUMERY - -HENLEY'S TWENTIETH CENTURY BOOK OF RECEIPTS, FORMULAS AND PROCESSES. -Edited by G. D. HISCOX. The most valuable Techno-chemical Receipt Book -published. Contains over 10,000 practical receipts, many of which will -prove of special value to the perfumer, a mine of information, -up-to-date in every respect. Price, Cloth, $3.00; half morocco $4.00 - -PERFUMES AND THEIR PREPARATION. By G. W. ASKINSON, Perfumer. A -comprehensive treatise, in which there has been nothing omitted that -could be of value to the Perfumer. Complete directions for making -handkerchief perfumes, smelling-salts, sachets, fumigating pastilles: -preparations for the care of the skin, the mouth, the hair, cosmetics, -hair dyes and other toilet articles are given, also a detailed -description of aromatic substances: their nature, tests of purity, and -wholesale manufacture. A book of general, as well as professional -interest, meeting the wants not only of the druggist and perfume -manufacturer, but also of the general public. Third edition. 312 pages. -Illustrated. $3.00 - -PLUMBING - -MECHANICAL DRAWING FOR PLUMBERS. By R. M. STARBUCK. A concise, -comprehensive and practical treatise on the subject of mechanical -drawing in its various modern applications to the work of all who are in -any way connected with the plumbing trade. Nothing will so help the -plumber in estimating and in explaining work to customers and workmen as -a knowledge of drawing, and to the workman it is of inestimable value if -he is to rise above his position to positions of greater responsibility, -Among the chapters contained are: 1. Value to plumber of knowledge of -drawing; tools required and their use; common views needed in mechanical -drawing. 2. Perspective versus mechanical drawing in showing plumbing -construction. 3. Correct and incorrect methods in plumbing drawing; plan -and elevation explained. 3. Floor and cellar plans and elevation; scale -drawings; use of triangles. 5. Use of triangles; drawing of fittings, -traps, etc. 6. Drawing plumbing elevations and fittings. 7. Instructions -in drawing plumbing elevations. 8. The drawing of plumbing fixtures; -scale drawings. 9. Drawing of fixtures and fittings. 10. Inking of -drawings. 11. Shading of drawings. 12. Shading of drawings. 13. -Sectional drawings; drawing of threads. 14. Plumbing elevations from -architect's plan. 15. Elevations of separate parts of the plumbing -system. 16. Elevations from architect's plans. 17. Drawing of detail -plumbing connections. 18. Architect's plans and plumbing elevations of -residence. 19. Plumbing elevations of residence (continued); plumbing -plans for cottage. 20. Plumbing elevations; roof connections. 21. Plans -and plumbing elevations for six-flat building. 22. Drawing of various -parts of the plumbing system; use of scales. 23. Use of architect's -scales. 24. Special features in the illustrations of country plumbing. -25. Drawing of wrought iron piping, valves, radiators, coils, etc. 26. -Drawing of piping to illustrate heating systems. 150 illustrations. -Price $1.50 - -MODERN PLUMBING ILLUSTRATED. By R. M. STARBUCK. This book represents the -highest standard of plumbing work. It has been adopted and used as a -reference book by the United States Government, in its sanitary work in -Cuba, Porto Rico, and the Philippines, and by the principal Boards of -Health of the United States and Canada. It gives connections, sizes and -working data for all fixtures and groups of fixtures. It is helpful to -the master plumber in demonstrating to his customers and in figuring -work. It gives the mechanic and student quick and easy access to the -best modern plumbing practice. Suggestions for estimating plumbing -construction are contained in its pages. This book represents, in a -word, the latest and best up-to-date practice, and should be in the -hands of every architect, sanitary engineer and plumber who wishes to -keep himself up to the minute on this important feature of construction. -Contains following chapters, each illustrated with a full-page plate: -Kitchen sink, laundry tubs, vegetable wash sink; lavatories, pantry -sinks, contents of marble slabs; bath tub, foot and sitz bath, shower -bath; water closets, venting of water closets; low-down water closets, -water closets operated by flush valves, water closet range; slop sink, -urinals, the bidet: hotel and restaurant sink, grease trap; -refrigerators, safe wastes, laundry waste; lines of refrigerators, bar -sinks, soda fountain sinks; horse stall, frost-proof water closets; -connections for S traps, venting; connections for drum traps; soil pipe -connections; supporting of soil pipe; main trap and fresh air inlet; -floor drains and cellar drains, subsoil drainage; water closets and -floor connections; local venting; connections for bath rooms; -connections for bath rooms, continued; connections for bath rooms, -continued; connections for bath rooms, continued; examples of poor -practice; roughing-work ready for test; testing of plumbing system; -method of continuous venting; continuous venting for two-floor work; -continuous venting for two lines of fixtures on three or more floors; -continuous venting of water closets; plumbing for cottage house; -construction for cellar piping; plumbing for residence, use of special -fittings; plumbing for two-flat house; plumbing for apartment building; -plumbing for double apartment building; plumbing for office building; -plumbing for public toilet rooms; plumbing for public toilet rooms, -continued; plumbing for bath establishment; plumbing for engine house, -factory plumbing; automatic flushing for schools, factories, etc.; use -of flushing valves; urinals for public toilet rooms; the Durham system, -the destruction of pipes by electrolysis; construction of work without -use of lead; Automatic sewage lift, automatic sump tank; country -plumbing; construction of cesspools; septic tank and automatic sewage -siphon; country plumbing; water supply for country house; thawing of -water mains and service by electricity; double boilers; hot water supply -of large buildings; automatic control of hot water tank; suggestions for -estimating plumbing construction. 400 octavo pages, fully illustrated by -55 full-page engravings. Price $4.00 - -STANDARD PRACTICAL PLUMBING. By R. M. STARBUCK. A complete practical -treatise of 450 pages covering the subject of Modern Plumbing in all its -branches, a large amount of space being devoted to a very complete and -practical treatment of the subject of Hot Water Supply and Circulation -and Range Boiler Work. Its thirty chapters include about every phase of -the subject one can think of, making it an indispensable work to the -master plumber, the journeyman plumber, and the apprentice plumber, -containing chapters on: the plumber's tools; wiping solder, composition -and use; joint wiping; lead work; traps; siphonage of traps; venting; -continuous venting; house sewer and sewer connections; house drain; soil -piping, roughing; main trap and fresh air inlet;' floor, yard, cellar -drains, rain leaders, etc.; fixture wastes: water closets; ventilation; -improved plumbing connections; residence plumbing; plumbing for hotels, -schools, factories, stables, etc.; modern country plumbing; filtration -of sewage and water supply; hot and cold supply; range boilers; -circulation; circulating, pipes; range boiler problems; hot water for -large buildings; water lift and its use; multiple connections for hot -water boilers; heating of radiation by supply system; theory for the -plumber; drawing for the plumber. Fully illustrated by 347 engravings. -Price $3.00 - -RECEIPT BOOK - -HENLEY'S TWENTIETH CENTURY BOOK OF RECEIPTS, FORMULAS AND PROCESSES. -Edited by GARDNER D. HISCOX. The most valuable Techno-chemical Receipt -Book published, including over 10,000 selected scientific, chemical, -technological, and practical receipts and processes. This is the most -complete Book of Receipts ever published, giving thousands of receipts -for the manufacturer of valuable articles for everyday use. Hints, -Helps, Practical Ideas, and Secret Processes are revealed within its -pages. It covers every branch of the useful arts and tells thousands of -ways of making money an just the book everyone should have at his -command. Modern in its treatment of every subject that properly falls -within its scope, the book may truthfully be said to present the very -latest formulas to be found in the arts and industries and to retain -those processes which long experience has proven worthy of a permanent -record. To present here even a limited number of the subjects which find -a place in this valuable work would be difficult. Suffice to say that in -its pages will be found matter of intense interest and immeasurable -practical value to the scientific amateur and to him who wishes to -obtain a knowledge of the many processes used in the arts, trades and -manufactures, a knowledge which will render his pursuits more -instructive and remunerative. Serving as a reference book to the small -and large manufacturer and supplying intelligent seekers with the -information necessary to conduct a process, the work will be found of -inestimable worth to the Metallurgist, the Photographer, the Perfumer, -the Painter, the Manufacturer of Glues, Pastes, Cements, and Mucilages, -the Compounder of Alloys, the Cook, the Physician, the Druggist, the -Electrician, the Brewer, the Engineer, the Foundryman, the Machinist, -the Potter, the Tanner, the Confectioner, the Chiropodist, the Manicure, -the Manufacturer of Chemical Novelties and Toilet Preparations, the -Dyer, the Electroplater, the Enameler, the Engraver, the Provisioner, -the Glass Worker, the Goldbeater, the Watchmaker, the Jeweler, the Hat -Maker, the Ink Manufacturer, the Optician, the Farmer, the Dairyman, the -Paper Maker, the Wood and Metal Worker, the Chandler and Soap Maker, the -Veterinary Surgeon, and the Technologist in general. A mine of -information, and up-to-date in every respect. A book which will prove of -value to EVERYONE, as it covers every branch of the Useful Arts. 800 -pages. Price $3.00 - -WHAT IS SAID OF THIS BOOK: - -"Your Twentieth Century Book of Receipts, Formulas and Processes duly -received. I am glad to have a copy of it, and if I could not replace it -money couldn't buy it. It is the best thing of the sort I ever saw." -(Signed) M. E. TRUX, Sparta, Wis. "There are few persons who would not -be able to find in the book some single formula that would repay several -times the cost of the book." Merchant's Record and Show Window. - -RUBBER - -RUBBER HAND STAMPS AND THE MANIPULATION OF INDIA RUBBER. - -By T. O'CONOR SLOANE. This book gives full details on all points, -treating in a concise and simple manner the elements of nearly -everything it is necessary to understand for a commencement in any -branch of the India Rubber Manufacture. The making of all kinds of -Rubber Hand Stamps, Small Articles of India Rubber, U. S. Government -Composition, Dating Hand Stamps, the Manipulation of Sheet Rubber, Toy -Balloons, India Rubber Solutions, Cements, Blackings, Renovating -Varnish, and Treatment for India Rubber Shoes, etc.; the Hektograph -Stamp Inks, and Miscellaneous Notes, with a Short Account of the -Discovery, Collection, and Manufacture of India Rubber are set forth in -a manner designed to be readily understood, the explanations being plain -and simple. Including a chapter on Rubber Tire Making and Vulcanizing; -also a chapter on the uses of rubber in Surgery and Dentistry. Third -revised and enlarged edition 175 pages. Illustrated. $1.00 - -SAWS - -SAW FILINGS AND MANAGEMENT OF SAWS. By ROBERT GRIMSHAW. A practical hand -book on filing, gumming, swaging, hammering, and the brazing of band -saws, the speed, work, and power to run circular saws, etc. A handy book -for those who have charge of saws, or for those mechanics who do their -own filing, as it deals with the proper shape and pitches of saw teeth -of all kinds and gives many useful hints and rules for gumming, setting, -and tiling, and is a practical aid to those who use saws for any -purpose. New edition, revised and enlarged. Illustrated. Price $1.00 - -STEAM ENGINEERING - -AMERICAN STATIONARY ENGINEERING. By W. E. CRANE. This book begins at the -boiler room and takes in the whole power plant. A plain talk on -every-day work about engines, boilers, and their accessories. It is not -intended to be scientific or mathematical. All formulas are in simple -form so that any one understanding plain arithmetic can readily -understand any of them. The author has made this the most practical book -in print; has given the results of his years of experience, and has -included about all that has to do with an engine room or a power plant. -You are not left to guess at a single point. You are shown clearly what -to expect under the various conditions; how to secure the best results; -ways of preventing "shut downs" and repairs; in short, all that goes to -make up the requirements of a good engineer, capable of taking charge of -a plant. It's plain enough for practical men and yet of value to those -high in the profession. A partial list of contents is: The boiler room, -cleaning boilers, firing, feeding; pumps; inspection and repair; -chimneys, sizes and cost; piping; mason work; foundations; testing -cement; pile driving; engines, slow and high speed; valves; valve -setting; Corliss engines, setting valves, single and double eccentric; -air pumps and condensers; different types of condensers; water needed; -lining up; pounds; pins not square in crosshead or crank; engineers' -tools; pistons and piston rings; bearing metal; hardened copper; drip -pipes from cylinder jackets; belts, how made, care of; oils; greases; -testing lubricants; rules and tables, including steam tables; areas of -segments; squares and square root; cubes and cube root; areas and -circumferences of circles. Notes on: Brick work; explosions; pumps; pump -valves; heaters, economizers; safety valves; lap, lead, and clearance. -Has a complete examination for a license, etc., etc. Second edition. 285 -pages. Illustrated. Price $2.00 - -EMINENT ENGINEERS. By DWIGHT GODDARD. Everyone who appreciates the -effect of such great inventions as the Steam Engine, Steamboat, -Locomotive, Sewing Machine, Steel Working, and other fundamental -discoveries, is interested in knowing a little about the men who made -them and their achievements. Mr. Goddard has selected thirty-two of the -world's engineers who have contributed most largely to the advancement -of our civilization by mechanical means, giving only such facts as are -of general interest and in a way which appeals to all, whether mechanics -or not. 280 pages. 35 illustrations. Price $1.50 - -ENGINE RUNNER'S CATECHISM. By ROBERT GRIMSHAW. A practical treatise for -the stationary engineer, telling how to erect, adjust and run the -principal stearn engines in use in the United States. Describing the -principal features of various special and well-known makes of engines: -Temper Cut-off, Shipping and Receiving Foundations, Erecting and -Starting, Valve Setting, Care and Use, Emergencies, Erecting and -Adjusting Special Engines. The questions asked throughout the catechism -are plain and to the point, and the answers are given in such simple -language as to be readily understood by anyone. All the instructions -given are complete ad up-to-date; and they are written in a popular -style, without any technicalities or mathematical formulae. The work is -of a handy size for the pocket, clearly and well printed, nicely bound, -and profusely illustrated. To young engineers this catechism will be of -great value, especially to those who may be preparing to go forward to -be examined for certificates of competency; and to engineers generally -it will be of no little service, as they will find in this volume more -really practical and useful information than is to be found anywhere -else within a like compass. 387 pages. Seventh edition. Price $2.00 - -ENGINE TESTS AND BOILER EFFICIENCIES. By J. BUCHETTI. This work fully -describes and illustrates the method of testing the power of steam -engines, turbines and explosive motors. The properties of steam and the -evaporative power of fuels. Combustion of fuel and chimney draft; with -formulas explained or practically computed 255 pages, 179 illustrations. -$3.00 - -HORSEPOWER CHART. Shows the horsepower of any stationary engine without -calculation. No matter what the cylinder diameter of stroke; the steam -pressure or cut off; the revolutions, or whether condensing or -non-condensing, it's all there. Easy to use, accurate, and saves time -and calculations. Especially useful to engineers and designers. 50 -cents. - -MODERN STEAM ENGINEERING IN THEORY AND PRACTICE. By GARDNER D. HISCOX. -This is a complete and practical work issued for Stationary Engineers -and firemen dealing with the care and management of boilers, engines, -pumps, superheated steam, refrigerating machinery, dynamos, motors, -elevators, air compressors, and all other branches with which the modern -engineer must be familiar. Nearly 200 questions with their answers on -steam and electrical engineering, likely to be asked by the Examining -Board, are included. Among the chapters are: Historical; steam and its -properties; appliances for the generation of steam; types of boilers; -chimney and its work; heat economy of the feed water; steam pumps and -their work; incrustation and its work; steam above atmospheric pressure; -flow of steam from nozzles; superheated steam and its work; adiabatic -expansion of steam; indicator and its work; steam engine proportions; -slide valve engines and valve motion; Corliss engine and its valve gear; -compound engine and its theory; triple and multiple expansion engine. -steam turbine; refrigeration; elevators and their management; cost of -power; steam engine troubles; electric power and electric plants. 487 -pages. 405 engravings. Price $3.00 - -STEAM ENGINE CATECHISM. By ROBERT GRIMSHAW. This unique volume of 413 -pages is not only a catechism on the question and answer principle; but -it contains formulas and worked-out answers for all the Steam problems -that appertain to the operation and management of the Steam Engine. -Illustrations of various valves and valve gear with their principles of -operation are given. Thirty-four Tables that are indispensable to every -engineer and fireman that wishes to be progressive and is ambitious to -become master of his calling are within its pages. It is a most valuable -instructor in the service of Steam Engineering. Leading engineers have -recommended it as a valuable educator for the beginner as well as a -reference book for the engineer. It is thoroughly indexed for every -detail. Every essential question on the Steam Engine with its answer is -contained in this valuable work. Sixteenth edition. Price $2.00 - -STEAM ENGINEER’S ARITHMETIC. By COLVIN-CHENEY. A practical pocket book -for the steam engineer. Shows how to work the problems of the engine -room and shows "why." Tells how to figure horse-power of engines and -boilers; area of boilers; has tables of areas and circumferences; steam -tables; has a dictionary of engineering terms. Puts you on to all all of -the little kinks in figuring whatever there is to figure around a power -plant. Tells you about the heat unit; absolute zero; adiabatic -expansion; duty of engines; factor of safety; and 1,001 other things; -and everything is plain and simple--not the hardest way to figure, but -the easiest. 2nd Edition. 50 cents. - -STEAM HEATING AND VENTILATION - -PRACTICAL STEAM, HOT-WATER HEATING AND VENTILATION. By A. G. KING. - -This book is the standard and latest work published on the subject and -has been prepared for the use of all engaged in the business of steam, -hot water heating, and ventilation. It is an original and exhaustive -work. Tells how to get heating contracts, how to install heating and -ventilating apparatus, the best business methods to be used, with -"Tricks of the Trade" for shop use. Rules and data for estimating -radiation and cost and such tables and information as make it an -indispensable work for everyone interested in steam, hot water heating, -and ventilation. It describes all the principal systems of steam, hot -water, vacuum, vapor, and vacuum-vapor heating, together with the new -accelerated systems of hot water circulation, including chapters on -up-to-date methods of ventilation and the fan or blower system of -heating and ventilation. Containing chapters on: I. Introduction. II. -Heat. III. Evolution of artificial heating apparatus. IV. Boiler surface -and settings. V. The chimney flue. VI. Pipe and fittings. VII. Valves, -various kinds. VIII. Forms of radiating surfaces. IX. Locating of -radiating surfaces. X. Estimating radiation. XI. Steam-heating -apparatus. XII. Exhaust-steam heating. XIII. Hot-water heating. XIV. -Pressure systems of hot-water work. XV. Hot-water appliances. XVI. -Greenhouse heating. XVII. Vacuum vapor and vacuum exhaust heating. -XVIII. Miscellaneous heating. XIX. Radiator and pipe connections. XX. -Ventilation. XXI. Mechanical ventilation and hot-blast heating. XXII. -Steam appliances. XXIII. District heating. XXIV. Pipe and boiler -covering. XXV. Temperature regulation and heat, control. XXVI. Business -methods. XXVII. Miscellaneous. XXVII. Rules, tables and useful -information. 367 pages. 300 detailed engravings. Price $3.00 - -STEAM PIPES - -STEAM PIPES: THEIR DESIGN AND CONSTRUCTION. By WM. H. BOOTH. The work is -well illustrated in regard to pipe joints, expansion offsets, flexible -joints, and self-contained sliding joints for taking up the expansion of -long pipes. In fact, the chapters on the flow of steam and expansion of -pipes are most valuable to all steam fitters and users. 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