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diff --git a/old/55787-0.txt b/old/55787-0.txt deleted file mode 100644 index baeb70f..0000000 --- a/old/55787-0.txt +++ /dev/null @@ -1,1575 +0,0 @@ -The Project Gutenberg EBook of The Telephone, by Alexander Graham Bell - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms of -the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: The Telephone - A lecture entitled Researches in Electric Telephony - -Author: Alexander Graham Bell - -Editor: Frank Bolton - William Edward Langdon - -Release Date: October 21, 2017 [EBook #55787] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK THE TELEPHONE *** - - - - -Produced by Chris Curnow, Paul Marshall and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - - - - - - -Transcriber's Notes: - - Underscores "_" before and after a word or phrase indicate _italics_ - in the original text. - Equal signs "=" before and after a word or phrase indicate =bold= - in the original text. - Carat symbol "^" designates a superscript. - Underscore "_" is used to designates a subscript. - Small capitals have been converted to SOLID capitals. - Illustrations have been moved so they do not break up paragraphs. - Old or antiquated spellings have been preserved. - Typographical errors have been silently corrected but other variations - in spelling and punctuation remain unaltered. - - - - - THE TELEPHONE. - A LECTURE - - ENTITLED - RESEARCHES IN ELECTRIC TELEPHONY, - - BY PROFESSOR ALEXANDER GRAHAM BELL, - - DELIVERED BEFORE - The Society of Telegraph Engineers, - OCTOBER 31ST, 1877. - - PUBLISHED BY THE SOCIETY, - AND EDITED BY - LIEUT.-COL. FRANK BOLTON, C.E., HON. SECRETARY, - AND - WILLIAM EDWARD LANGDON, ACTING SECRETARY. - - London: - E. AND F. N. SPON, 46, CHARING CROSS. - - New York: - 446, BROOME STREET. - - 1878. - _Price One Shilling and Sixpence._ - The right of translation and reproduction is reserved - - - - -EXTRACTS OF PROCEEDINGS OF THE SOCIETY OF TELEGRAPH ENGINEERS. - - - Special General Meeting, held at 25, Great George Street, - Westminster, on Wednesday, the 31st October, 1877. - PROFESSOR ABEL, C.B., F.R.S., President, in the Chair. - -The PRESIDENT: Gentlemen, the Council of the Society of -Telegraph Engineers felt that they were sure of doing what the members -would consider right in summoning a special meeting for the two-fold -purpose of giving a welcome to Professor Bell to this country and -affording the Members an opportunity of hearing from him an account, -which he has been so good as to promise to give us, of the nature, -history, and development of, what may well be called, one of the most -interesting discoveries of our age. Our time is very precious this -evening. We all desire to hear everything Professor Bell can tell us -on this subject, and many gentlemen will probably desire afterwards to -ask questions or discuss the subject, for I see present a great number -of eminent scientific men. I will not waste another moment, but at once -call upon Professor Bell to commence his discourse on the Electric -Telephone. - - - - -RESEARCHES IN ELECTRIC TELEPHONY. - - -By PROFESSOR ALEXANDER GRAHAM BELL. - -PROFESSOR BELL: Mr. President and Gentlemen of the Society of -Telegraph Engineers. It is to-night my pleasure, as well as duty, to -give you some account of the telephonic researches in which I have been -so long engaged. Many years ago my attention was directed to the -mechanism of speech by my father, Alexander Melville Bell, of -Edinburgh, who has made a life-long study of the subject. Many of -those present may recollect the invention by my father of a means -of representing, in a wonderfully accurate manner, the positions of -the vocal organs in forming sounds. Together we carried on quite a -number of experiments, seeking to discover the correct mechanism of -English and foreign elements of speech, and I remember especially an -investigation in which we were engaged concerning the musical relations -of vowel sounds. When vowel sounds are whispered, each vowel seems -to possess a particular pitch of its own, and by whispering certain -vowels in succession a musical scale can be distinctly perceived. Our -aim was to determine the natural pitch of each vowel; but unexpected -difficulties made their appearance, for many of the vowels seemed to -possess a double pitch—one due, probably, to the resonance of the air -in the mouth, and the other to the resonance of the air contained in -the cavity behind the tongue, comprehending the pharynx and larynx. - -I hit upon an expedient for determining the pitch which at that time -I thought to be original with myself. It consisted in vibrating a -tuning-fork in front of the mouth while the positions of the vocal -organs for the various vowel sounds were silently taken. It was found -that each vowel position caused the reinforcement of some particular -fork or forks. - -I wrote an account of these researches to Mr. Alex. J. Ellis, of -London, whom I have very great pleasure in seeing here to-night. In -reply he informed me that the experiments related had already been -performed by Helmholtz, and in a much more perfect manner than I had -done. Indeed, he said that Helmholtz had not only analysed the vowel -sounds into their constituent musical elements, but had actually -performed the synthesis of them. - -He had succeeded in producing, artificially, certain of the vowel -sounds by causing tuning-forks of different pitch to vibrate -simultaneously by means of an electric current. Mr. Ellis was kind -enough to grant me an interview for the purpose of explaining the -apparatus employed by Helmholtz in producing these extraordinary -effects, and I spent the greater part of a delightful day with him in -investigating the subject. At that time, however, I was too slightly -acquainted with the laws of electricity fully to understand the -explanations given; but the interview had the effect of arousing my -interest in the subjects of sound and electricity, and I did not rest -until I had obtained possession of a copy of Helmholtz’ great work,[1] -and had attempted, in a crude and imperfect manner it is true, to -reproduce his results. While reflecting upon the possibilities of -the production of sound by electrical means, it struck me that the -principle of vibrating a tuning-fork by the intermittent attraction -of an electro-magnet might be applied to the electrical production of -music. - -I imagined to myself a series of tuning-forks of different pitches, -arranged to vibrate automatically in the manner shown by Helmholtz, -each fork interrupting at every vibration a voltaic current; and the -thought occurred, “Why should not the depression of a key like that of -a piano direct the interrupted current from any one of these forks, -through a telegraph wire, to a series of electro-magnets operating the -strings of a piano or other musical instrument, in which case a person -might play the tuning-fork piano in one place and the music be audible -from the electromagnetic piano in a distant city?” - -The more I reflected upon this arrangement the more feasible did it -seem to me; indeed, I saw no reason why the depression of a number of -keys at the tuning-fork end of the circuit should not be followed by -the audible production of a full chord from the piano in the distant -city, each tuning-fork affecting at the receiving end that string of -the piano with which it was in unison. At this time the interest which -I felt in electricity led me to study the various systems of telegraphy -in use in this country and in America. I was much struck with the -simplicity of the Morse alphabet, and with the fact that it could be -read by sound. Instead of having the dots and dashes recorded upon -paper, the operators were in the habit of observing the duration of the -click of the instruments, and in this way were enabled to distinguish -by ear the various signals. - -It struck me that in a similar manner the duration of a musical note -might be made to represent the dot or dash of the telegraph code, so -that a person might operate one of the keys of the tuning-fork piano -referred to above, and the duration of the sound proceeding from the -corresponding string of the distant piano be observed by an operator -stationed there. It seemed to me that in this way a number of distinct -telegraph messages might be sent simultaneously from the tuning-fork -piano to the other end of the circuit, by operators each manipulating -a different key of the instrument. These messages would be read by -operators stationed at the distant piano, each receiving operator -listening for signals of a certain definite pitch, and ignoring all -others. In this way could be accomplished the simultaneous transmission -of a number of telegraphic messages along a single wire, the number -being limited only by the delicacy of the listener’s ear. The idea of -increasing the carrying power of a telegraph wire in this way took -complete possession of my mind, and it was this practical end that I -had in view when I commenced my researches in Electric Telephony. - -In the progress of science it is universally found that complexity -leads to simplicity, and in narrating the history of scientific -research it is often advisable to begin at the end. - -In glancing back over my own researches I find it necessary to -designate, by distinct names, a variety of electrical currents by means -of which sounds can be produced, and I shall direct your attention to -several distinct species of what may be termed “telephonic” currents of -electricity. In order that the peculiarities of these currents may be -clearly understood, I shall ask Mr. Frost to project upon the screen a -graphical illustration of the different varieties. - -The graphical method of representing electrical currents here shown is -the best means I have been able to devise of studying in an accurate -manner the effects produced by various forms of telephonic apparatus, -and it has led me to the conception of that peculiar species of -telephonic current here designated as _undulatory_, which has rendered -feasible the artificial production of articulate speech by electrical -means. - -[Illustration: Fig. 1.] - -A horizontal line (_g g´_) is taken as the zero of current, and -impulses of positive electricity are represented above the zero line, -and negative impulses below it, or _vice versâ_. - -The vertical thickness of any electrical impulse (_b_ or _d_), measured -from the zero line, indicates the intensity of the electrical current -at the point observed, and the horizontal extension of the electric -line (_b_ or _d_) indicates the duration of the impulse. - -Nine varieties of telephonic currents may be distinguished, but it will -only be necessary to show you six of these. The three primary varieties -designated as “intermittent,” “pulsatory,” and “undulatory,” are -represented in lines 1, 2, and 3. - -Sub-varieties of these can be distinguished as “direct” or “reversed” -currents according as the electrical impulses are all of one kind or -are alternately positive and negative. “Direct” currents may still -further be distinguished as “positive” or “negative,” according as the -impulses are of one kind or of the other. - -An _intermittent current_ is characterised by the alternate presence -and absence of electricity upon the circuit; - -A _pulsatory current_ results from sudden or instantaneous changes in -the intensity of a continuous current; and - -An _undulatory current_ is a current of electricity, the intensity of -which varies in a manner proportional to the velocity of the motion -of a particle of air during the production of a sound: thus the curve -representing graphically the undulatory current for a simple musical -tone is the curve expressive of a simple pendulous vibration—that is, -a sinusoidal curve. - - Telephonic currents of electricity may be: - - {Direct {Positive 1 Positive intermittent current. - Intermittent { {Negative 2 Negative ” ” - { —— Reversed 3 Reversed ” ” - - {Direct {Positive 4 Positive pulsatory current. - Pulsatory { {Negative 5 Negative ” ” - { —— Reversed 6 Reversed ” ” - - {Direct {Positive 7 Positive undulatory current. - Undulatory { {Positive 8 Negative ” ” - { —— Reversed 9 Reversed ” ” - -And here I may remark, that, although the conception of the undulatory -current of electricity is entirely original with myself, methods of -producing sound by means of intermittent and pulsatory currents have -long been known. For instance, it was long since discovered that -an electro-magnet gives forth a decided sound when it is suddenly -magnetized or demagnetized. When the circuit upon which it is placed is -rapidly made and broken, a succession of explosive noises proceeds from -the magnet. These sounds produce upon the ear the effect of a musical -note when the current is interrupted a sufficient number of times -per second. The discovery of “Galvanic Music,” by Page,[2] in 1837, -led inquirers in different parts of the world almost simultaneously -to enter into the field of telephonic research; and the acoustical -effects produced by magnetization were carefully studied by Marrian,[3] -Beatson,[4] Gassiot,[5] De la Rive,[6] Matteucci,[7] Guillemin,[8] -Wertheim,[9] Wartmann,[10] Janniar,[11] Joule,[12] Laborde,[13] -Legat,[14] Reis,[15] Poggendorff,[16] Du Moncel,[17] Delezenne,[18] -and others.[19] It should also be mentioned that Gore[20] obtained -loud musical notes from mercury, accompanied by singularly beautiful -crispations of the surface during the course of experiments in -electrolysis; Page[21] produced musical tones from Trevelyan’s bars -by the action of the galvanic current; and further it was discovered -by Sullivan[22] that a current of electricity is generated by the -vibration of a wire composed partly of one metal and partly of another. -The current was produced so long as the wire emitted a musical note, -but stopped immediately upon the cessation of the sound. - -For several years my attention was almost exclusively directed to -the production of an instrument for making and breaking a voltaic -circuit with extreme rapidity, to take the place of the transmitting -tuning-fork used in Helmholtz’ researches. I will not trouble you -with the description of all the various forms of apparatus that were -devised, but will merely direct your attention to one of the best of -them, shown in fig. 2. In the transmitting instrument T, a steel reed -_a_ is employed, which is kept in continuous vibration by the action of -an electro-magnet _e_ and local battery. In the course of its vibration -the reed strikes alternately against two fixed points _m_, _l_, and -thus completes alternately a local and a main circuit. When the key -K is depressed an intermittent current from the main battery B is -directed to the line-wire W, and passes through the electro-magnet E of -a receiving instrument R at the distant end of the circuit, and thence -to the ground G. The steel reed A is placed in front of the receiving -magnet, and when its normal rate of vibration is the same as the reed -of the transmitting instrument it is thrown into powerful vibration, -emitting a musical tone of a similar pitch to that produced by the reed -of the transmitting instrument, but if it is normally of a different -pitch it remains silent. - -[Illustration: Fig. 2.] - -[Illustration: Fig. 3. Fig. 4. Fig. 5.] - -A glance at figs. 3, 4, and 5 will show the arrangement of such -instruments upon a telegraphic circuit, designed to enable a number -of telegraphic despatches to be transmitted simultaneously along the -same wire. The transmitters and receivers that are numbered alike have -the same pitch or rate of vibration. Thus the reed of T´ is in unison -with the reeds T´ and R´ at all the stations upon the circuit, so that -a telegraphic despatch sent by the manipulation of the key K´ at the -station shown in fig. 3 will be received upon the receiving instruments -K´ at all the other stations upon the circuit. Without going into -details, I shall merely say that the great defects of this plan of -multiple telegraphy were found to consist, firstly, in the fact that -the receiving operators were required to possess a good musical ear in -order to discriminate the signals; and secondly, that the signals could -only pass in one direction along the line (so that two wires would be -necessary in order to complete communication in both directions). The -first objection was got over by employing the device which I term a -“vibratory circuit-breaker,” shown in the next diagram, whereby musical -signals can be automatically recorded. - -[Illustration: Fig. 6.] - -Fig. 6 shows a receiving instrument R, with a vibratory circuit-breaker -_v_ attached. The light spring-lever _v_ overlaps the free end of the -steel reed A, and normally closes a local circuit, in which may be -placed a Morse-sounder or other telegraphic apparatus. When the reed -A is thrown into vibration by the passage of a musical signal, the -spring arm _v_ is thrown upwards, opening the local circuit at the -point 5. When the spring-arm _v_ is so arranged as to have normally a -much slower rate of vibration than the reed A_{1}, the local circuit -is found to remain permanently open during the vibration of A, the -spring-arm _v_ coming into contact with the point 5 only upon the -cessation of the receiver’s vibration. Thus the signals produced by the -vibration of the reed A are reproduced upon an ordinary telegraphic -instrument in the local circuit. - -Fig. 7 shows the application of electric telephony to autographic -telegraphy. - -[Illustration: Fig. 7.] - -T, T´, &c., represent the reeds of transmitting instruments of -different pitch, R, R´, &c., the receivers at the distant station -of corresponding pitch, and, _r_, _r´_, &c., the vibratory -circuit-breakers attached to the receiving instruments, and connected -with metallic bristles, 21, resting upon chemically prepared paper -P. The message, or picture, to be copied, is written upon a metallic -surface, F__0_, with non-metallic ink, and placed upon a metallic -cylinder 7, connected with the main battery B; and the chemically -prepared paper P, upon which the message is to be received, is placed -upon a metallic cylinder connected with the local battery B´ at the -receiving station. When the cylinders at either end of the circuit are -rotated in the direction of the arrows—but not necessarily at the same -rate of speed—a _fac simile_ of whatever is written or drawn upon the -metallic surface F__0_ appears upon the chemically prepared paper P. - -The method by means of which the musical signals may be sent -simultaneously in both directions along the same circuit is shown in -our next illustration, figures 8, 9, and 10. The arrangement is similar -to that shown in figures 3, 4, and 5, excepting that the intermittent -current from the transmitting instruments is passed through the -primary wires of an induction coil, and the receiving instruments are -placed in circuit with the secondary wire. In this way free earth -communication is secured at either end of the circuit, and the musical -signals produced by the manipulation of any key are received at all the -stations upon the line. The great objection to this plan is the extreme -complication of the parts and the necessity of employing local and main -batteries at every station. It was also found by practical experiment -that it was difficult, if not impossible, upon either of the plans -here shown, to transmit simultaneously the number of musical tones -that theory showed to be feasible. Mature consideration revealed the -fact that this difficulty lay in the nature of the electrical current -employed, and was finally obviated by the invention of the _undulatory_ -current. - -It is a strange fact that important inventions are often made almost -simultaneously by different persons in different parts of the world, -and the idea of multiple telegraphy as developed in the preceding -diagrams seems to have occurred independently to no less than four -other inventors in America and Europe. Even the details of the -arrangements upon circuit—shown in figures 3, 4, 5, and 8, 9, 10—are -extremely similar in the plans proposed by Mr. Cromwell Varley of -London, Mr. Elisha Gray of Chicago, Mr. Paul La Cour of Copenhagen, and -Mr. Thomas Edison of Newark, New Jersey. Into the question of priority -of invention, of course, it is not my intention to go to-night. - -[Illustration: Fig. 8. Fig. 9. Fig. 10.] - -That the difficulty in the use of an intermittent current may be more -clearly understood, I shall ask you to accompany me in my explanation -of the effect produced when two musical signals of different pitch -are simultaneously directed along the same circuit. Fig. 11 shows an -arrangement whereby the reeds _a a´_ of two transmitting instruments -are caused to interrupt the current from the same battery, B. We shall -suppose the musical interval between the two reeds to be a major third, -in which case their vibrations are in the ratio of 4 to 5, _i.e._, -4 vibrations of _a_ are made in the same time as 5 vibrations of -_a^1_. A^2 and B^2 represent the intermittent currents produced, -4 impulses of B^2 being made in the same time as 5 impulses of A^2. -The line A^2 + B^2 represents the resultant effect upon the main line -when the reeds _a_ and _a^1_ are simultaneously caused to make and -break the same circuit, and from the illustration you will perceive -that the resultant current, whilst retaining a uniform intensity, -is less interrupted when both reeds are in operation than when one -alone is employed. By carrying your thoughts still further you will -understand that when a large number of reeds of different pitch or of -different rates of vibration are simultaneously making and breaking the -same circuit the resultant effect upon the main line is practically -equivalent to one continuous current. - -[Illustration: Fig. 11.] - -It will also be understood that the maximum number of musical -signals that can be simultaneously directed along a single wire -without conflict depends very much upon the ratio which the -“make” bears to the “break;” the shorter the contact made, and -the longer the break, the greater the number of signals that can -be transmitted without confusion, and _vice versâ_. The apparatus -by means of which this theoretical conclusion has been verified is -here to-night, and consists of an ordinary parlour harmonium, the -reeds of which are operated by wind in the usual manner. In front of -each reed is arranged a metal screw, against which the reed strikes -in the course of its vibration. By adjusting the screw the duration -of the contact can be made long or short. The reeds are connected -with one pole of a battery, and the screws against which they strike -communicate with the line-wire, so that intermittent impulses from the -battery are transmitted along the line-wire during the vibration of the -reeds. - -[Illustration: Fig. 12.] - -[Illustration: Fig. 13.] - -[Illustration: Fig. 14.] - -We now proceed to the next illustration. Without entering into the -details of the calculation you will see that with a pulsatory current -the effect of transmitting musical signals simultaneously is nearly -equivalent to a continuous current of minimum intensity—see A^2 + B^2, -fig. 12; but when undulatory currents are employed the effect is -different—see fig. 13. The current from the battery B is thrown into -waves by the inductive action of iron or steel reeds M M´, vibrated in -front of electro-magnets _e e´_, placed in circuit with the battery; -A^2 and B^2 represent the undulations caused in the current by the -vibration of the magnetised bodies, and it will be seen that there are -four undulations of B^2 in the same time as five undulations of A^2. -The resultant effect upon the main line is expressed by the curve A^2 -+ B^2, which is the algebraical sum of the sinusoidal curves A^2 and -B^2. A similar effect is produced when reversed undulatory currents -are employed as shown in fig. 14, where the current is produced by -the vibration of permanent magnets M M´ in front of electro-magnets -(_e e´_), united upon a circuit without a voltaic battery. It will be -understood from figs. 13 and 14 that the effect of transmitting musical -signals of different pitches simultaneously along a single wire is -not to obliterate the vibratory character of the current as in the -case of intermittent and pulsatory currents, but to change the shapes -of the electrical undulations. In fact, the effect produced upon the -current is precisely analogous to the effect produced in the air by the -vibration of the inducing bodies M M´. Hence it should be possible to -transmit as many musical tones simultaneously through a telegraph wire -as through the air. The possibility of using undulatory currents for -the purposes of multiple telegraphy enabled me to dispense entirely -with the complicated arrangements of the circuit shown in figs. 3, -4, 5, and 8, 9, 10, and to employ a single battery for the whole -circuit, retaining only the receiving instruments formerly shown. This -arrangement is represented in figs. 15, 16, and 17. Upon vibrating the -steel reed of a receiver R, R´, at any station by any mechanical means, -the corresponding reeds at all the other stations are thrown into -vibration, reproducing the signal. By attaching the steel reeds to the -poles of a powerful permanent magnet, as shown in fig. 19, the signals -can be produced without the aid of a battery. - -[Illustration: Fig. 15. Fig. 16. Fig. 17.] - -[Illustration: Fig. 18.[23]] - -I have formerly stated that Helmholtz was enabled to produce vowel -sounds artificially by combining musical tones of different pitches -and intensities. His apparatus is shown in fig. 18. Tuning-forks of -different pitch are placed between the poles of electro-magnets (_a^1_, -_a^2_, &c.), and are kept in continuous vibration by the action of an -intermittent current from the fork _b_. Resonators 1, 2, 3, &c. are -arranged so as to reinforce the sounds, in a greater or less degree, -according as the exterior orifices are enlarged or contracted. - -Thus it will be seen that upon Helmholtz’s plan the tuning-forks -themselves produce tones of uniform intensity, the loudness being -varied by an external reinforcement; but it struck me that the same -results would be obtained, and in a much more perfect manner, by -causing the tuning-forks themselves to vibrate with different degrees -of amplitude. I therefore devised the apparatus shown in fig. 19, which -was my first form of articulating telephone. In this figure a harp of -steel rods is employed attached to the poles of a permanent magnet -N.S. When any one of the rods is thrown into vibration an undulatory -current is produced in the coils of the electro-magnet E, and the -electro-magnet E´ attracts the rods of the harp H´ with a varying -force, throwing into vibration that rod which is in unison with -that vibrated at the other end of the circuit. Not only so, but the -amplitude of vibration in the one will determine the amplitude of -vibration in the other, for the intensity of the induced current -is determined by the amplitude of the inducing vibration, and the -amplitude of the vibration at the receiving end depends upon the -intensity of the attractive impulses. When we sing into a piano, -certain of the strings of the instrument are set in vibration -sympathetically by the action of the voice with different degrees of -amplitude, and a sound, which is an approximation to the vowel uttered, -is produced from the piano. Theory shows, that, had the piano a very -much larger number of strings to the octave, the vowel sounds would be -perfectly reproduced. My idea of the action of the apparatus, shown in -fig. 19, was this: Utter a sound in the neighbourhood of the harp H, -and certain of the rods would be thrown into vibration with different -amplitudes. At the other end of the circuit the corresponding rods of -the harp H´ would vibrate with their proper relations of force, and the -_timbre_ of the sound would be reproduced. The expense of constructing -such an apparatus as that shown in fig. 19 deterred me from making the -attempt, and I sought to simplify the apparatus before venturing to -have it made. - -[Illustration: Fig. 19.] - -[Illustration: Fig. 20.] - -I have before alluded to the invention by my father of a system of -physiological symbols for representing the action of the vocal organs, -and I had been invited by the Boston Board of Education to conduct a -series of experiments with the system in the Boston school for the deaf -and dumb. It is well known that deaf mutes are dumb merely because -they are deaf, and that there is no defect in their vocal organs to -incapacitate them from utterance. Hence it was thought that my father’s -system of pictorial symbols, popularly known as visible speech, might -prove a means whereby we could teach the deaf and dumb to use their -vocal organs and to speak. The great success of these experiments -urged upon me the advisability of devising methods of exhibiting the -vibrations of sound optically, for use in teaching the deaf and dumb. -For some time I carried on experiments with the manometric capsule -of Koenig, and with the phonautograph of Léon Scott. The scientific -apparatus in the Institute of Technology in Boston was freely placed at -my disposal for these experiments, and it happened that at that time -a student of the Institute of Technology, Mr. Maurey, had invented an -improvement upon the phonautograph. He had succeeded in vibrating by -the voice a stylus of wood about a foot in length which was attached to -the membrane of the phonautograph, and in this way he had been enabled -to obtain enlarged tracings upon a plane surface of smoked glass. With -this apparatus I succeeded in producing very beautiful tracings of the -vibrations of the air for vowel sounds. Some of these tracings are -shown in fig. 20. I was much struck with this improved form of -apparatus, and it occurred to me that there was a remarkable likeness -between the manner in which this piece of wood was vibrated by the -membrane of the phonautograph and the manner in which the _ossiculæ_ -of the human ear were moved by the tympanic membrane. I determined -therefore to construct a phonautograph modelled still more closely -upon the mechanism of the human ear, and for this purpose I sought -the assistance of a distinguished aurist in Boston, Dr. Clarence J. -Blake. He suggested the use of the human ear itself as a phonautograph, -instead of making an artificial imitation of it. The idea was novel and -struck me accordingly, and I requested my friend to prepare a specimen -for me, which he did. The apparatus, as finally constructed, is shown -in fig. 21. The _stapes_ was removed and a stylus of hay about an -inch in length was attached to the end of the incus. Upon moistening -the membrana-tympani and the ossiculæ with a mixture of glycerine and -water, the necessary mobility of the parts was obtained; and upon -singing into the external artificial ear the stylus of hay was thrown -into vibration, and tracings were obtained upon a plane surface -of smoked glass passed rapidly underneath. While engaged in these -experiments I was struck with the remarkable disproportion in weight -between the membrane and the bones that were vibrated by it. It -occurred to me that if a membrane as thin as tissue paper could control -the vibration of bones that were, compared to it, of immense size and -weight, why should not a larger and thicker membrane be able to vibrate -a piece of iron in front of an electro-magnet, in which case the -complication of steel rods shown in my first form of telephone, fig. -19, could be done away with, and a simple piece of iron attached to a -membrane be placed at either end of the telegraphic circuit. - -[Illustration: Fig. 21.] - -[Illustration: Fig. 22.] - -[Illustration: Fig. 23.] - -Fig. 22 shows the form of apparatus that I was then employing for -producing undulatory currents of electricity for the purposes of -multiple telegraphy. A steel reed A was clamped firmly by one extremity -to the uncovered leg _h_ of an electro-magnet E, and the free end of -the reed projected above the covered leg. When the reed A was vibrated -in any mechanical way, the battery current was thrown into waves, and -electrical undulations traversed the circuit B E W E´, throwing into -vibration the corresponding reed A´ at the other end of the circuit. -I immediately proceeded to put my new idea to the test of practical -experiment, and for this purpose I attached the reed A (fig. 23) -loosely by one extremity to the uncovered pole _h_ of the magnet, and -fastened the other extremity to the centre of a stretched membrane -of goldbeaters’ skin _n_. I presumed that upon speaking in the -neighbourhood of the membrane _n_ it would be thrown into vibration -and cause the steel reed A to move in a similar manner, occasioning -undulations in the electrical current that would correspond to the -changes in the density of the air during the production of the sound; -and I further thought that the change of the intensity of the current -at the receiving end would cause the magnet there to attract the reed -A´ in such a manner that it should copy the motion of the reed A, in -which case its movements would occasion a sound from the membrane _n´_ -similar in _timbre_ to that which had occasioned the original vibration. - -[Illustration: Fig. 24.] - -The results, however, were unsatisfactory and discouraging. My friend -Mr. Thomas A. Watson, who assisted me in this first experiment, -declared that he heard a faint sound proceed from the telephone at -his end of the circuit, but I was unable to verify his assertion. -After many experiments attended by the same only partially-successful -results, I determined to reduce the size and weight of the spring as -much as possible. For this purpose I glued a piece of clock spring, -about the size and shape of my thumbnail, firmly to the centre of the -diaphragm, and had a similar instrument at the other end (fig. 24); -we were then enabled to obtain distinctly audible effects. I remember -an experiment made with this telephone, which at the time gave me -great satisfaction and delight. One of the telephones was placed in my -lecture-room in the Boston University, and the other in the basement -of the adjoining building. One of my students repaired to the distant -telephone to observe the effects of articulate speech, while I uttered -the sentence, “Do you understand what I say?” into the telephone placed -in the lecture-hall. To my delight an answer was returned through -the instrument itself, articulate sounds proceeded from the steel -spring attached to the membrane, and I heard the sentence, “Yes, -I understand you perfectly.” It is a mistake, however, to suppose -that the articulation was by any means perfect, and expectancy no -doubt had a great deal to do with my recognition of the sentence; -still, the articulation was there, and I recognised the fact that the -indistinctness was entirely due to the imperfection of the instrument. -I will not trouble you by detailing the various stages through which -the apparatus passed, but shall merely say that after a time I produced -the form of instrument shown in fig. 25, which served very well as -a receiving telephone. In this condition my invention was exhibited -at the Centennial Exhibition in Philadelphia. The telephone shown in -fig. 24 was used as a transmitting instrument, and that in fig. 25 as -a receiver, so that vocal communication was only established in one -direction. - -[Illustration: Fig. 25.] - -Another form of transmitting telephone exhibited in Philadelphia -intended for use with the receiving telephone (fig. 25) is represented -by fig. 26. - -A platinum wire attached to a stretched membrane completed a voltaic -circuit by dipping into water. Upon speaking to the membrane, -articulate sounds proceeded from the telephone in the distant room. The -sounds produced by the telephone became louder when dilute sulphuric -acid, or a saturated solution of salt, was substituted for the water. -Audible effects were also produced by the vibration of plumbago in -mercury, in a solution of bichromate of potash, in salt and water, in -dilute sulphuric acid, and in pure water. - -The articulation produced from the instrument shown in fig. 25 was -remarkably distinct, but its great defect consisted in the fact that it -could not be used as a transmitting instrument, and thus two telephones -were required at each station, one for transmitting and one for -receiving spoken messages. - -[Illustration: Fig. 26.] - -It was determined to vary the construction of the telephone -shown in fig. 24, and I sought by changing the size and tension -of the membrane, the diameter and thickness of the steel spring, -the size and power of the magnet, and the coils of insulated wire -around their poles, to discover empirically the exact effect of each -element of the combination, and thus to deduce a more perfect -form of apparatus. It was found that a marked increase in the -loudness of the sounds resulted from shortening the length of the -coils of wire, and by enlarging the iron diaphragm which was -glued to the membrane. In the latter case, also, the distinctness -of the articulation was improved. Finally, the membrane of goldbeaters’ -skin was discarded entirely, and a simple iron plate was -used instead, and at once intelligible articulation was obtained. -The new form of instrument is that shown in fig. 27, and, as had -been long anticipated, it was proved that the only use of the -battery was to magnetize the iron core of the magnet, for the -effects were equally audible when the battery was omitted and a -rod of magnetized steel substituted for the iron core of the magnet. - -It was my original intention, as shown in fig. 19, and it was always -claimed by me, that the final form of telephone would be operated by -permanent magnets in place of batteries, and numerous experiments had -been carried on by Mr. Watson and myself privately for the purpose of -producing this effect. - -[Illustration: Fig. 27.] - -At the time the instruments were first exhibited in public the results -obtained with permanent magnets were not nearly so striking as when a -voltaic battery was employed, wherefore we thought it best to exhibit -only the latter form of instrument. - -The interest excited by the first published accounts of the operation -of the telephone led many persons to investigate the subject, and I -doubt not that numbers of experimenters have independently discovered -that permanent magnets might be employed instead of voltaic batteries. -Indeed one gentleman, Professor Dolbear, of Tufts College, not only -claims to have discovered the magneto-electric telephone, but I -understand charges me with having obtained the idea from him through -the medium of a mutual friend. - -[Illustration: Fig. 28.] - -A still more powerful form of apparatus was constructed by using a -powerful compound horse-shoe magnet in place of the straight rod which -had been previously used (see fig. 28). Indeed the sounds produced by -means of this instrument were of sufficient loudness to be faintly -audible to a large audience, and in this condition the instrument was -exhibited in the Essex Institute, in Salem, Massachusetts, on the 12th -Feb. 1877, on which occasion a short speech shouted into a similar -telephone in Boston, sixteen miles away, was heard by the audience in -Salem. The tones of the speaker’s voice were distinctly audible to an -audience of 600 people, but the articulation was only distinct at a -distance of about 6 feet. On the same occasion, also, a report of the -lecture was transmitted by word of mouth from Salem to Boston, and -published in the papers the next morning. - -[Illustration: Fig. 29.] - -From the form of telephone shown in fig. 27 to the present form of -the instrument (fig. 29) is but a step. It is in fact the arrangement -of fig. 27 in a portable form, the magnet F H being placed inside -the handle and a more convenient form of mouthpiece provided. The -arrangement of these instruments upon a telegraphic circuit is shown in -fig. 30. - -[Illustration: Fig. 30.] - -And here I wish to express my indebtedness to several scientific -friends in America for their co-operation and assistance. I would -specially mention Professor Peirce and Professor Blake, of Brown -University, Dr. Channing, Mr. Clarke, and Mr. Jones. In Providence, -Rhode Island, these gentlemen have been carrying on together -experiments seeking to perfect the form of apparatus required, and -I am happy to record the fact that they communicated to me each new -discovery as it was made, and every new step in their investigations. -It was, of course, almost inevitable that these gentlemen should -retrace much of the ground that had been gone over by me, and so it -has happened that many of their discoveries had been anticipated by -my own researches; still, the very honourable way in which they from -time to time placed before me the results of their discoveries entitles -them to my warmest thanks and to my highest esteem. It was always my -belief that a certain ratio would be found between the several parts of -a telephone, and that the size of the instrument was immaterial; but -Professor Peirce was the first to demonstrate the extreme smallness -of the magnets which might be employed. And here, in order to show -the parallel lines in which we were working, I may mention the fact -that two or three days after I had constructed a telephone of the -portable form (fig. 29), containing the magnet inside the handle, Dr. -Channing was kind enough to send me a pair of telephones of a similar -pattern, which had been invented by the Providence experimenters. The -convenient form of mouthpiece shown in fig. 29, now adopted by me, was -invented solely by my friend Professor Peirce. I must also express -my obligations to my friend and associate, Mr. Thomas A. Watson, of -Salem, Massachusetts, who has for two years past given me his personal -assistance in carrying on my researches. - -In pursuing my investigations I have ever had one end in view, the -practical improvement of electric telegraphy; but I have come across -many facts which, while having no direct bearing upon the subject of -telegraphy, may yet possess an interest for you.[24] - -For instance, I have found that a musical tone proceeds from a piece of -plumbago or retort-carbon when an intermittent current of electricity is -passed through it, and I have observed the most curious audible effects -produced by the passage of reversed intermittent currents through the -human body. A rheotome was placed in circuit with the primary wires of -an induction coil, and the fine wires were connected with two strips -of brass. One of these strips was held closely against the ear, and a -loud sound proceeded from it whenever the other slip was touched with -the other hand. The strips of brass were next held one in each hand. -The induced currents occasioned a muscular tremor in the fingers. Upon -placing my forefinger to my ear a loud crackling noise was audible, -seemingly proceeding from the finger itself. A friend who was present -placed my finger to his ear, but heard nothing. I requested him to hold -the strips himself. He was then distinctly conscious of a noise (which -I was unable to perceive) proceeding from his finger. In this case a -portion of the induced currents passed through the head of the observer -when he placed his ear against his own finger: and it is possible that -the sound was occasioned by a vibration of the surfaces of the ear and -finger in contact. - -When two persons receive a shock from a Ruhmkorff’s coil by clasping -hands, each taking hold of one wire of the coil with the free hand, a -sound proceeds from the clasped hands. The effect is not produced when -the hands are moist. When either of the two touches the body of the -other a loud sound comes from the parts in contact. When the arm of -one is placed against the arm of the other, the noise produced can be -heard at a distance of several feet. In all these cases a slight shock -is experienced so long as the contact is preserved. The introduction -of a piece of paper between the parts in contact does not materially -interfere with the production of the sounds, but the unpleasant effects -of the shock are avoided. - -When an intermittent current from a Ruhmkorff’s coil is passed through -the arms a musical note can be perceived when the ear is closely -applied to the arm of the person experimented upon. The sound seems to -proceed from the muscles of the fore-arm and from the biceps muscle. -Mr. Elisha Gray[25] has also produced audible effects by the passage of -electricity through the human body. - -An extremely loud musical note is occasioned by the spark of a -Ruhmkorff’s coil when the primary circuit is made and broken with -sufficient rapidity; when two rheotomes of different pitch are caused -simultaneously to open and close the primary circuit a double tone -proceeds from the spark. - -A curious discovery, which may be of interest to you, has been made -by Professor Blake. He constructed a telephone in which a rod of -soft iron, about six feet in length, was used instead of a permanent -magnet. A friend sang a continuous musical tone into the mouthpiece of -a telephone, like that shown in fig. 29, which was connected with the -soft iron instrument alluded to above. It was found that the loudness -of the sound produced in this telephone varied with the direction in -which the iron rod was held, and that the maximum effect was produced -when the rod was in the position of the dipping-needle. This curious -discovery of Professor Blake has been verified by myself. - -When a telephone is placed in circuit with a telegraph line, the -telephone is found seemingly to emit sounds on its own account. The -most extraordinary noises are often produced, the causes of which -are at present very obscure. One class of sounds is produced by the -inductive influence of neighbouring wires and by leakage from them, the -signals of the Morse alphabet passing over neighbouring wires being -audible in the telephone, and another class can be traced to earth -currents upon the wire, a curious modification of this sound revealing -the presence of defective joints in the wire. - -Professor Blake informs me that he has been able to use the railroad -track for conversational purposes in place of a telegraph wire, and -he further states that when only one telephone was connected with the -track the sounds of Morse operating were distinctly audible in the -telephone, although the nearest telegraph-wires were at least forty -feet distant. - -Professor Peirce has observed the most curious sounds produced from -a telephone in connection with a telegraph wire during the aurora -borealis; and I have just heard of a curious phenomenon lately observed -by Dr. Channing. In the city of Providence, Rhode Island, there is an -overhouse wire about one mile in extent with a telephone at either end. -On one occasion the sound of music and singing was faintly audible -in one of the telephones. It seemed as if some one were practising -vocal music with a pianoforte accompaniment. The natural supposition -was that experiments were being made with the telephone at the other -end of the circuit, but upon inquiry this proved not to have been the -case. Attention having thus been directed to the phenomenon, a watch -was kept upon the instruments, and upon a subsequent occasion the same -fact was observed at both ends of the line by Dr. Channing and his -friends. It was proved that the sounds continued for about two hours, -and usually commenced about the same time. A searching examination of -the line disclosed nothing abnormal in its condition, and I am unable -to give you any explanation of this curious phenomenon. Dr. Channing -has, however, addressed a letter upon the subject to the editor of -one of the Providence papers, giving the names of such songs as were -recognised, with full details of the observations, in the hope that -publicity may lead to the discovery of the performer, and thus afford a -solution of the mystery. - -My friend Mr. Frederick A. Gower communicated to me a curious -observation made by him regarding the slight earth connection required -to establish a circuit for the telephone, and together we carried on a -series of experiments with rather startling results. We took a couple -of telephones and an insulated wire about 100 yards in length into a -garden, and were enabled to carry on conversation with the greatest -ease when we held in our hands what should have been the earth wire, so -that the connection with the ground was formed at either end through -our bodies, our feet being clothed with cotton socks and leather boots. -The day was fine, and the grass upon which we stood was seemingly -perfectly dry. Upon standing upon a gravel walk the vocal sounds, -though much diminished, were still perfectly intelligible, and the same -result occurred when standing upon a brick wall one foot in height, but -no sound was audible when one of us stood upon a block of freestone. - -One experiment which we made is so very interesting that I must speak -of it in detail. Mr. Gower made earth connection at his end of the line -by standing upon a grass plot, whilst at the other end of the line I -stood upon a wooden board. I requested Mr. Gower to sing a continuous -musical note, and to my surprise the sound was very distinctly audible -from the telephone in my hand. Upon examining my feet I discovered that -a single blade of grass was bent over the edge of the board, and that -my foot touched it. The removal of this blade of grass was followed by -the cessation of the sound from the telephone, and I found that the -moment I touched with the toe of my boot a blade of grass or the petal -of a daisy the sound was again audible. - -The question will naturally arise, Through what length of wire can the -telephone be used? In reply to this I may say that the maximum amount -of resistance through which the undulatory current will pass, and yet -retain sufficient force to produce an audible sound at the distant end, -has yet to be determined; no difficulty has, however, been experienced -in laboratory experiments in conversing through a resistance of 60,000 -ohms, which has been the maximum at my disposal. On one occasion, not -having a rheostat at hand, I may mention having passed the current -through the bodies of sixteen persons, who stood hand in hand. The -longest length of real telegraph line through which I have attempted -to converse has been about 250 miles. On this occasion no difficulty -was experienced so long as parallel lines were not in operation. Sunday -was chosen as the day on which it was probable other circuits would -be at rest. Conversation was carried on between myself, in New York, -and Mr. Thomas A. Watson, in Boston, until the opening of business -upon the other wires. When this happened the vocal sounds were very -much diminished, but still audible. It seemed, indeed, like talking -through a storm. Conversation though possible could be carried on with -difficulty, owing to the distracting nature of the interfering currents. - -I am informed by my friend Mr. Preece that conversation has been -successfully carried on through a submarine cable, sixty miles in -length, extending from Dartmouth to the Island of Guernsey, by means of -hand telephones similar to that shown in fig. 30. - -Footnotes: - -[1] Helmholtz. _Die Lehre von dem Tonempfindungen._ (English -Translation by Alexander J. Ellis, _Theory of Tone_.) - -[2] _C. G. Page._ “The Production of Galvanic Music.” Silliman’s Journ. -1837, xxxii. p. 396; Silliman’s Journ. July, 1837, p. 354; Silliman’s -Journ. 1838, xxxiii. p. 118; Bibl. Univ. (new series), 1839, ii. p. 398. - -[3] _J. P. Marrian._ Phil. Mag. xxv. p. 382; Inst. 1845, p. 20; Arch. -de l’Électr. v. p. 195. - -[4] _W. Beatson._ Arch. de l’Électr. v. p. 197; Arch. de Sc. Phys. et -Nat. (2d series), ii. p. 113. - -[5] _Gassiot._ See “Treatise on Electricity,” by De la Rive, i. p. 300. - -[6] _De la Rive._ Treatise on Electricity, i. p. 300; Phil. Mag. xxxv. -p. 422; Arch. de l’Électr. v. p. 200; Inst. 1846, p. 83; Comptes -Rendus, xx. p. 1287; Comp. Rend. xxii. p. 432; Pogg. Ann. lxxvi. p. -637; Ann. de Chim. et de Phys. xxvi. p. 158. - -[7] _Matteucci._ Inst. 1845, p. 315; Arch, de l’Électr. v. 389. - -[8] _Guillemin._ Comp. Rend. xxii. p. 264; Inst. 1846, p. 30; Arch. d. -Sc. Phys. (2d series), i. p. 191. - -[9] _G. Wertheim._ Comp. Rend. xxii. pp. 336, 544; Inst. 1846, pp. 65, -100; Pogg. Ann. lxviii. p. 140; Comp. Rend. xxvi. p. 505; Inst. 1848, -p. 142; Ann. de Chim. et de Phys., xxiii. p. 302; Arch. d. Sc. Phys. et -Nat. viii. p. 206; Pogg. Ann. lxxvii. p. 43; Berl. Ber. iv. p. 121. - -[10] _Elie Wartmann._ Comp. Rend. xxii. p. 544; Phil. Mag. (3d series), -xxviii. p. 544; Arch. d. Sc. Phys. et Nat. (2d series), i. p. 419; -Inst. 1846, p. 290; Monatscher. d. Berl. Akad. 1846, p. 111. - -[11] _Janniar._ Comp. Rend, xxiii. p. 319; Inst. 1846, p. 269; Arch. d. -Sc. Phys. et Nat. (2d. series), ii. p. 394. - -[12] _J. P. Joule._ Phil. Mag. xxv. pp. 76, 225; Berl. Ber. iii. p. 489. - -[13] _Laborde._ Comp. Rend. l. p. 692; Cosmos, xvii. p. 514. - -[14] _Legat._ Brix. Z. S. ix. p. 125. - -[15] _Reis._ “Téléphonie.” Polytechnic Journ. clxviii. p. 185; -Böttger’s Notizbl. 1863, No. 6. - -[16] _J. C. Poggendorff._ Pogg. Ann. xcviii. p. 192; Berliner -Monatsber. 1856, p. 133; Cosmos, ix. p. 49; Berl. Ber. xii. p. 241; -Pogg. Ann. lxxxvii. p. 139. - -[17] _Du Moncel._ Exposé, ii. p. 125; also, iii. p. 83. - -[18] _Delezenne._ “Sound produced by Magnetization,” Bibl. Univ. (new -series), 1841, xvi. p. 406. - -[19] See London Journ. xxxii. p. 402; Polytechnic Journ. ex. p. 16; -Cosmos, iv. p. 43; Glösener—Traité général, &c. p. 350; Dove.-Repert. -vi. p. 58; Pogg. Ann. xliii. p. 411; Berl. Ber. i. p. 144; Arch. d. -Sc. Phys. et Nat. xvi. p. 406; Kuhn’s Encyclopædia der Physik, pp. -1014-1021. - -[20] _Gore._ Proceedings of Royal Society, xii. p. 217. - -[21] _C. G. Page._ “Vibration of Trevelyan’s bars by the galvanic -current.” Silliman’s Journal, 1850, ix. pp. 105-108. - -[22] _Sullivan._ “Currents of Electricity produced by the vibration of -Metals,” Phil. Mag. 1845, p. 261; Arch. de l’Électr. x. p. 480. - -[23] The full description of this figure will be found in Mr. Alexander -J. Ellis’s translation of Helmholtz’s work, “Theory of Tone.” - -[24] See _Researches in Telephony_.—Trans. of American Acad. of Arts -and Sciences, vol. xii. p. 1. - -[25] _Elisha Gray._ Eng. Pat. Spec. No. 2646, Aug. 1874. - - - - - USEFUL BOOKS ON TELEGRAPHY, &c. - - - _Just published, Parts XIII. and XIV., in one vol._ - _demy 8vo, sewed, 5s._ - - =Journal of the Society of Telegraph Engineers=, - - INCLUDING ORIGINAL COMMUNICATIONS ON TELEGRAPH AND - ELECTRICAL SCIENCE. - - Edited by Major FRANK BOLTON and J. 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