Two Paths to the Telephone

Home , Elisha Gray, History of the telephone

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STRIKING PARALLELS between the telephones envisioned by electrode. In Bell's the variation would depend on the changes in the Elisha Gray and Alexander Graham Bell are evident in their respec area of the wedge-shaped needle tip immersedin the bath. The vary tive sketches of the instruments. Both Gray's transmitter(top) and ing current would then pass through an electromagnet(right) at the Bell's (bottom)depended on varying the resistance to the flow of cur receiving end of the circuit; variations in the magnetic field would rent from a battery. Both variations would be caused by the vertical cause a second diaphragm (in Gray's scheme) or a metal reed (in movement of a needle in a liquid bath; the motion would be due to Bell's) to vibrate, thereby reproducing the sound waves that actu the response of a diaphragm to the sound waves of the human voice. ated the transmitter. Gray made the sketch of his device on February In Gray's transmitter the variation in resistance would depend on 11, 1876, some two months after he conceived the idea. Bell made changes in the distance between the tip of the needle and the bottom his sketch on March 9, 24 days after filing his patent application.

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As Alexander Graham Bell was developing the telephone Elisha Gray was doing the same. Bell got the patent, but the episode is nonetheless an instructive example of simultaneous invention

by David A. Hounshell

n one day in 1876-February 14-the one-third interest in the business, and also connected one lead of the second U.S. Patent Office received two Western Electric eventually became the circuit to the zinc bathtub and was clos I communications describing the sole supplier of telegraphic equipment ing the circuit and "taking shocks" from electrical transmission and reception of to Western Union. the induction coil by rubbing his hand, human speech by means of variations in Telegraphy had grown steadily in the which held the other lead, across the sur the resistance of the transmitter. The U.S. from its introduction in 1844, face of the tub. variable-resistance device was the origi and that growth had accelerated in the The vibrating reed made an audible nal telephone. The firstdescription was Civil War years. By the end of the war hum, and when Gray's nephew rubbed in the form of a patent application by some 50,000 miles of telegraph wire had his hand on the tub, a second hum of the a 29-year-old amateur inventor whose been strung over routes totaling nearly same pitch was heard. Gray's interest name became world-famous: Alexander 30,000 miles, and a decade later the fig was piqued. He changed the frequency Graham Bell. The second description, ures had risen to 250,000 miles of wire of the reed and found that the sound which arrived only hours later, came over routes of more than 100,000 miles. made by the rubbing of his hand on the from a 41-year-old professional inven Until 1872, however, each wire could tub changed to match it. The action of tor who had been granted the first of his transmit only one message in one direc the induction coil was to transform the many electrical patents almost a decade tion at a time. Enlarging the transmis on-off impulses imposed on the circuit earlier: Elisha Gray. sion capacity between any two points by the vibrating reed into a sinusoidal Who was Elisha Gray? Why is Bell could be accomplished only by stringing wave of electric current. widely if not universally known as the new wires. Gray was quick to explore the phe inventor of the telephone and Gray, This one-way-at-a-time bottleneck nomenon of what he named vibratory who envisioned the same device at the was built into the telegraph. system be currents, seeking to find some practical same time, known to few except histori cause the transmitted signal consisted of use for their transmission and reception. ans of technology? To answer the ques intermittent pulses of direct current. In Although he found no immediate appli tion it is helpful to have an understand 1872, however, Western Union adopted cation, he so resolutely believed vibrato ing of not only the technical aspects of a "duplex" system of transmission de ry currents would have a major useful this classic example of simultaneous in veloped by Joseph B. Stearns, a Boston ness that he resigned as the superinten vention but also the social ones. In the electrician. A modification of the Morse dent of Western Electric, determined history of the telephone the differences system, the Stearns system allowed two to pursue the matter on an independent between the world of the professional messages to be transmitted simultane full-time basis. In order to do so he se and the world of the amateur appear at ously, one from each end of the wire. cured the financial backing of Samuel S. almost every turn, as will be made clear The adoption of the duplex system ef White, a wealthy manufacturer of den by a brief exploration of the two worlds, fectively doubled the capacity of the tistry equipment in Philadelphia. first Gray's and then Bell's. Western Union network. Could multi With funds at his disposal Gray soon Elisha Gray, born in Barnesville, plex systems be developed, systems that built four experimental devices: two Ohio, in 1835, attended Obedin College, would increase the capacity many times transmitters of frequencies in the audi but he was not graduated owing to ill further? One thing was certain: the in ble range and two receivers. One of health. His early interest in the electrical ventor of a multiplex system could vir the transmitters he called a single-tone aspects of telegraphy led in 1867 to his tually name his own price. transmitter; it was essentially a refine first patent, for a self-adjusting tele ment of his nephew's bathtub apparatus. graph relay. His device attracted the at ray's close relations with Western The other he called a two-tone trans tention of the principal firm in the field, G Union made him aware of the re mitter; it was capable of simultaneous the Western Union Telegraph Compa wards awaiting the successful inventor, ly generating sinusoidal waves of two ny. It also earned Gray enough mon and early in 1874 he hit on a solution different frequencies. One of the two re ey for him to secure a partnership in a almost by pure accident. One day he ceivers seems quaint in retrospect; the Cleveland firm that manufactured tele found his nephew, whom he allowed to other was quite conventional. graphic instruments. He and his partner, use his electrical apparatus, amusing The first receiver consisted of a violin Enos Barton, transformed the company himself in the bathroom with two bat with its strings removed and a silver into the nation's leading maker of elec tery-powered circuits. In one circuit the plate attached to the soundboard. When trical apparatus, renamed it the Western battery caused a reed "electrotome" one of the leads of the induction-coil Electric Manufacturing Company and to vibrate. The vibrations opened and circuit was connected to the plate and in the early 1870's relocated it in Chica closed the other circuit, which included the hand holding the other lead was go. In 1872 Western Union acquired a an induction coil. Gray's nephew had rubbed across the metal surface, as it

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© 1980 SCIENTIFIC AMERICAN, INC was in the bathtub experiment, the tones Could not each tone be made to carry Within a few weeks of the bathtub ep generated by either transmitter were re a telegraph signal? The musical tele isode Gray, in a rush of experimental produced with a richer quality. The oth graph could function as a multiplex-sig activity, had discovered and in his mind er receiver consisted of an electromag nal transmitter if a receiver could be de explored the seemingly boundless pos net and a metal diaphragm. When the vised that was able to segregate the indi sibilities of utilizing audible vibratory magnet caused the diaphragm to vibrate vidual tones of the composite current. currents. In May of 1874, confident that' according to the frequencies of the cur For this purpose, Gray realized, neither he had sufficientlyinvestigated the im rent in the induction-coil circuit, the of his receivers would be of any use. plications of these currents, he demon tones of the transmitters were faithful The magnet-and-diaphragm receiver, strated his transmitters and receivers ly reproduced. The results suggested to however, was perfectly suited to the to audiences of telegraphy experts in Gray three possible applications. third application Gray had in mind. If Washington, New York and Boston. Re The most obvious application and many combinations of tones could be ports of the demonstrations allow the probably the easiest to perfect was what carried by wire and the composite signal inference that he mentioned all three today would be called an electric organ; could then be reproduced electrically, potential applications of this work: the Gray thought of it as a "musical tele would it not be possible to transmit the transmission of music, the transmission graph." He would merely have to build sounds of the human voice? Gray may of multiple messages and the transmis a keyboard consisting of switches that have perceived an irony in this applica sion of the human voice. Gray's tour would actuate a series of single-tone tion. Just as the potential multiplex sys gave rise to a flurry of debate. transmitters, each tuned to a different tem of telegraphy was in need of a re The New York Timesreported one musical pitch. It would even be possi ceiver, so the potential composite-cur Western Union official as saying that ble to sound chords by pressing two or rent system of telephony was in need Gray had taken "the first step toward more keys simultaneously. of a transmitter. Gray saw no easy way doing away with manipulating instru to solve the voice-transmitter problem, ments [that is, telegraph keys] altogeth more immediate commercial appli although he immediately envisioned a er." "In time," the official continued, A cation was implicit in the ability of complex synthesizing device consisting "the operators will transmit the sound a telegraph wire to carry a "composite of a number of individual tone transmit of their own voices over the wire, and current," one consisting of two, four or ters, each responding to a different tone talk with one another instead of tele a much larger number of frequencies. of the human voice. graphing." The leading journal of the industry, The Telegrapher, took the opposite tack. Declaring that the transmission of the human voice was nothing new, the jour nal cited an account it had published five years earlier describing the Reis tele phone. Johann Reis, a German school master and experimenter, had in 1861 coined the word "telephone" to describe a laboratory device he had built to re produce music and the voice. The Teleg rapher noted that the Reis telephone had proved to have "no direct practical ap plication" and remained "a mere scien tific ... curiosity." The Telegrapher also mentioned what it said was an old joke in telegraphic circles. Voice communications had once been tried on the telegraph line be tween Philadelphia and New York, the story went, "but had to be given up on account of the Philadelphia opera tor's breath smelling too strongly of bad whiskey." The journal's view of the Reis telephone was echoed by A. L. Hayes, one of Gray's own patent attorneys and himself an expert in electrical technolo gy. Assuring his client of the novelty and importance of the new discoveries, he went on to say the German instrument was "merely a toy" that could be made to work only with careful handling and that amounted to no more than a scien tific oddity. Reis had died that same year, and interest in his "curiosity" had - languished.

iscouraged by the negative opinions RECEIVING APPARATUS, a stringless violin witb a silver plate covering tbe soundboard, D on voice communication, Gray was devised by Gray in 1874 to draw attention to tbe "vibratory curreuts" first made audible by tbe batbtnb experiment (see top illustration on opposite poge). Here one lead from tbe in turned in the summer of 1874 to the duction coil connects to tbe silver plate. Tbe demonstrator (Gray in tbis instance) bolds tbe development of the remaining applica otber lead in bis band and rubs bis fingers along tbe metal surface. Tbe musical tone tbus gener tions: the musical telegraph and multi ated duplicated tbe tone of bis transmitter, a metal reed tbat vibrated at audio frequencies. plexing. For the transmission of music

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BATTERY FOR -'- INDUCTION-COIL CIRCUIT T I I� __ ___ ------?» LEA D TO BATHTUB INDUCTION COIL

BATHTUB EXPERIMENT, based on a chance discovery by Gray's contacts, one of them fixed to the reed, simultaneously closed and nephew in 1874, involved the circuits illustrated here. The first cir opened a second circuit (color). An induction coil in this circuit con cuit, at the left, was closed and opened by the back-and-forth mo verted the interrupted current into a continuous sinusoidal current of tion of a spring-loaded metal reed that vibrated at a fixed frequency. the same frequency as the tone of the reed. When one of the leads When the circuit was closed, it energized an electromagnet. The re from the induction coil (right) was attached to a zinc tub, and the ex sponse of the reed to the attraction of the magnet reopened the circuit perimenter, holding the other lead, rubbed his hand across the tub's and the action of the spring promptly reclosed it. A second pair of surface, a sound was heard identical in pitch with the tone of the reed.

he built an organlike apparatus with an Royal Institution, and J. Latimer Clark, more about audio-frequency currents, array of single-tone transmitters cover then perhaps the most eminent figure in as they would be called today, he built ing a range of one octave; later it was British telegraphy. Gray also took ad what he called a "mechanical" transmit enlarged to a two-octave apparatus. To vantage of the visit to test how well his ter. The vibrating reed was replaced by improve the tone quality of the receiver vibratory currents performed when they two cams, mounted on a shaft rotated at Gray made the diaphragm larger by re were conducted by submarine cables. speeds equal to audio frequencies, that placing the flat metal plate with a wash He concluded that there were no techni opened and closed two sets of contact basin; thereafter the device was known cal obstacles in the way of transform points. Adjustable "elastic springs" were as the washbasin receiver. ing musical telegraphy into a multiplex included for regulating the pressure be In August and September of 1874 message system, where both he and his tween the points. Gray toured England with these devices backer White knew the greatest financial The first time Gray tested his mechan and others. Among those for whom he rewards would lie. ical transmitter, on January I, 1875, he demonstrated them was John Tyndall, For the rest of 1874 Gray concentrat observed something completely unex who succeeded Michael Faraday at the ed on multiplexing. In an effort to learn pected. With only one set of contact

ADVANCED TRANSMITTER AND RECEIVER were two of ered a range of one octaH. The up ended washbasin at the right the devices Gray took to England in 1874. The keyboard device at formed the diaphragm of a receiving apparatus. Paired electromag the left incorporated an array of single-tone transmitters that cov- nets translated "vibratory currents" into vibrations of the diaphragm.

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SUBSTITUTE FOR REEDS, devised by Gray late in 1874, was a quency range on January 1, 1875, Gray found that changing the pres belt-driven camsbaft. Two cams opened and closed sets of contact sure between points altered the output of interrupted current in such points, and springs allowed for adjustment of the pressure between a way that his washbasin receiver emitted various voicelike sounds. the points. Testing his "mechanical transmitter" in the audio-fre- He concluded that a simple device could transmit the human voice.

GRAY'S TELEPHONE, in the form presented in his Patent Office left resulted in electromagnet-powered vibrations of the receiver dia caveat application of February 14, 1876, differed little from the ap phragm at the right. Although Gray might have contested BeD's pat paratus he had sketched three days earlier. The slight changes in cur ent application, filed earlier the same day, he accepted the advice of rent produced by the movement of the transmitter diaphragm at the his patent attorney and his financial backer and dropped the matter.

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© 1980 SCIENTIFIC AMERICAN, INC points in operation he found, not unex perimental apparatus of the Helmholtz scarlet fever. Hubbard viewed Western pectedly, that the washbasin receiver type was available at M.I.T. and sug Union as an enemy of progress in teleg produced tones that varied in frequency gested that he and Bell repeat the experi raphy, believing the monopoly was sti according to the speed of the camshaft. ments someday. He also lent Bell a copy fling innovation. The two men naturally When he then adjusted the tension of the of a recent book on acoustics by Tyn talked about telegraphy, and in October spring, however, thereby either lessen dall. Bell was soon in contact with oth of 1874 Bell disclosed that he was work ing or increasing the pressure between ers who were interested in investigating ing on a multiplex scheme. Hubbard the points, he found he "was able to imi sound, among them Charles R. Cross, had predicted even before he knew Bell tate many different [voice] sounds." He assistant to the physicist Edward C. that "one wire [might eventually] be at once concluded that the complex syn Pickering at M.I.T., and the Boston used for four or possibly eight mes thesizing voice transmitter he had con physician Clarence J. Blake, lecturer on sages. " He now provided Bell with ceived of earlier was unnecessary. Some otology at the Harvard Medical School. enough money to hire an expert in the much simpler device could be made to The background of Bell's work on the field of electrical studies and pay for the transmit the human voice. telephone was therefore acoustical. The services of the expert's instrument mak Even with the prospect of voice com immediate path to that work, however, er. The quality of Bell's apparatus soon munication so much improved, how was like Gray's the multiplex telegraph. improved. Perhaps Hubbard's most im ever, Gray did not pursue it. Instead he Bell began to pursue such an invention portant contribution to the partnership chose to continue the development of late in 1872, when he read an account in was his insistence that Bell keep his a multiplex telegraph as a potentially a Boston newspaper of Western Union's mind on the main goal: multiplex te far more profitable venture. His strides adoption of the Stearns duplex system. legraphy. toward this goal are evident in the num If Stearns had become rich by devising By_ the summer of 1875 Bell's work ber of patent applications he filedearly a system that could transmit only two had convinced him it was possible to in 1875. He was soon to learn that his messages at a time, and those in oppo transmit speech, the same conclusion work was coming "into interference," as site directions, what wealth awaited the that had been reached earlier that year it is said in patent law, with the applica man who invented a system that could by Gray. Although Gray had set the no tions of another inventor. That inventor do more? tion aside in favor of further work on was Alexander Graham Bell. The Helmholtz apparatus gave Bell a multiplex telegraphy, Bell's keen inter starting point. Helmholtz had devised a est in the voice made him feel that such y coincidence Bell was also in hot way of generating an intermittent cur an achievement would be of the first im B pursuit of a multiplex-telegraph rent at audio frequencies by using the portance. Like Gray, Bell had initially system working within the audio-fre vibrating end of one tine of a tuning fork conceived of a complex voice transmit quency spectrum. (What Gray called vi as an interrupter. He then employed the ter, but experiments with tuned steel bratory currents Bell called undulatory intermittent current to drive other tun reeds in transmitters and receivers led currents.) The youthful Bell was an am ing forks. The method suggested to Bell him to devise an instrument for both ateur, but he knew that a pot of gold a way of transmitting multiple mes purposes that consisted of a reed at awaited the inventor of a practical mul sages. If several Helmholtz tuning-fork tached to the center of a diaphragm. tiplex telegraph. Furthermore, although interrupters were tuned to different fre Both the transmitter and the receiver Bell was an amateur inventor, he was a quencies, each interrupter could trans were placed near one of the poles of an thoroughgoing professional in his own mit a separate message. This scheme left electromagnet with a slightly but per field: elocution and speech therapy. His Bell facing the same problem Gray had manently magnetized core. father, Alexander M. Bell, professor faced: devising a receiver that could sort With this pair of instruments Bell and of elocution at the University of Edin out the combined messages. Bell, how his assistant were able, on July I, 1875, burgh, had won international recogni ever, was proceeding more on blind to transmit and receive what Bell de tion for his system of teaching the deaf faith than Gray. He had yet to learn scribed as "vocal sounds. " These sounds to speak, and his son had an intimate whether it was even possible to transmit were not, however, speech. The system knowledge of the physiology of human composite tones by wire. required that Bell or his assistant shout speech. Indeed, he had already put for From late in 1872 through most of into the diaphragm of the transmitting ward a theory of vowel tones. 1873 Bell worked off and on at his mul instrument. The diaphragm was agitat One consequence of this work was tiplex-telegraph scheme. Unlike Gray, ed by the sound waves, which caused the profound. Alexander J. Ellis, a prom who employed a professional instru reed to vibrate. The motion generated a inent British phonetician who had ment maker, Bell built his own appa weak "undulatory current" in the trans learned of Bell's theory, pointed out to ratus. Because he had almost no me mitting electromagnet, which actuat him that the same theory had been ad chanical skill the apparatus was crude. ed the receiving electromagnet, causing vanced in a classic work, "On the Sensa For example, at first he could not rig a the receiving diaphragm to reproduce tion of Tone as a Physiological Basis for Helmholtz interrupter that would work the movements of the transmitting dia the Theory of Music, " by the German for more than a few seconds. His being phragm. polymath Hermann von Helmholtz. an amateur at invention was no mere Bell was captivated by the potential of Ellis also called Bell's attention to the artificial distinction. these instruments. (It is worth noting electrically driven tuning fork used by that the first commercial telephones, Helmholtz in many of his experiments. Tate in the spring of 1874 Bell learned which appeared in 1877, were not Bell acquired a French edition of Helm L about Gray's work with vibratory much more than improved versions of holtz' book and read it during his pas currents. He at once accelerated the the 1875 magnet-and-diaphragm instru sage from England to America in 1870. pace of his own work. Up to then Bell's ments.) Hubbard, however, was less When Bell settled in Boston in 187 1 to efforts had been almost without success, than interested; like Gray and Gray's teach at the School for Deaf Mutes, he but his faith in his multiplex scheme re backer he kept his sights on the develop found others who were closely acquaint mained strong. That faith might well ment of the multiplex telegraph. ed with Helmholtz' acoustical work, have faltered, however, if he had not By this time Gray and Bell were play among them Lewis Monroe, a friend of found himself in partnership with Gar ing cat and mouse with each other. the Bell family's and professor of elocu diner G. Hubbard, a telegraphy enthusi Each suspected that the other was spy tion at the Massachusetts Institute of ast. Hubbard had hired Bell to tutor his ing on him; each believed his own work Technology. Monroe told Bell that ex- daughter, who had been made deaf by was the more advanced, but each wor-

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BELL'S EXPERIMENTS, urgently pursued after he had filedhis magnet at the left caused its magnetic field to fluctuate. The fluctua patent application, included some, such as the one illustrated here, tions produced corresponding fluctuations in the current and hence that used electromagnets in both the transmitter and the receiver. in the field of the electromagnet at the right, making the steel reed Bell had tried a similar approach in 1875 but without success. He did above it vibrate with the same frequency as that of the tuning fork. A not return to the magnetoelectric transmitter-receiver system until more advanced state of such a transmitter-receiver was the system after he had successfully transmitted speech with a variable-resis Bell exhibited at the Centennial Exhibition in Philadelphia in June, tance instrument. Here the vibration of a tuning fork near the electro- 1876. It was the one used for the first commercial telephone in 1877.

ried that the other might achieve the logue of the toy. The electric transmitter three months before he took any patent decisive breakthrough. Gray, however, would consist of a voice chamber (the action. In February of 1876 he finally gradually came to the conclusion that can) and a diaphragm (the bottom of the put his ideas on paper. Instead of apply Bell's effort had been derailed. In Octo can). If one end of a wire was attached to ing for a patent, however, Gray filed ber of 1875 Gray wrote his patent attor the diaphragm and the other end was what was known at the time as a caveat, ney: "Bell seems to be spending all his immersed in a liquid with a high electri or warning. energies in [the] talking telegraph. While cal resistance, the movement of the wire A caveat was supposed to give the this is very interesting scientificallyit in response to the vibrations of the di Patent Office formal notice of an inven has no commercial value at present, for aphragm could be transformed into a tor's basic concept. The idea was that [the telegraph industry] can do more vibratory current that faithfully repro after filing a caveat the inventor would business over a line by methods already duced the various frequencies of speech. develop the concept into a workable de in use than by that system. I don't want Gray already knew that his electromag vice and then apply for a patent. The at present to spend my time and money net-and-diaphragm receiver could turn procedure was intended to give a certain for that which will bring no reward. " the vibratory current back into sound amount of protection to inventors' con All the same, when later that month waves. cepts. On this occasion Gray's patent at Gray happened to see two boys playing torney wrote to White, Gray's backer, with a homemade toy known as a "lov Although the device seemed to Gray that the inventor's "talking telegraph ca ers' telegraph," he immediately realized .fl. to lack commercial application, he veat" potentially interfered with a pat how an electric telephone should be believed it would work and intended ent application from Bell. "As Gray's constructed. A lovers' telegraph is what to patent it. He already knew that the caveat was filed on the same day as would be known today as a tin-can tele movement of a wire in a liquid could Bell's application, but later in the day," phone. Two cans with the top removed produce vibrations in an electric cur the attorney reported, "the Commis are connected by a string knotted inside rent. While he was still a proprietor sioner holds that he is not entitled to an a hole punched in the bottom of each of Western Electric the company had interference and Bell's application has can. When the string is stretched tight, made and sold liquid rheostats: devices been ordered to issue .... We could still sounds uttered into one of the cans make that changed the resistance of a circuit have an interference by Gray's coming its bottom vibrate. The vibrations are by varying the depth to which a metal tomorrow and promptly filing an ap carried by the taut string to the bottom rod was submerged in a liquid with a plication for a patent. If you want this of the other can, where the sounds are high electrical resistance. Because of done, telegraph me in the morning, on coarsely reproduced. his pressing work on the multiplex tele receipt of this,and I will have the papers Gray recognized the electrical ana- graph, however, he waited more than ready in time to stop the issue of Bell's

174,5:37 Table, ironing, J. V. Six ...... •.....•...... 174,3�5 AN Tailor's drafting apparatus, P. Rondel...... 174,443 174,.t90 .. W Po 174,4il Tank-tHler. automatic, A. Haerle ...... 17.1,420 StatioDnry about as g 174,5C2 Teapot handle, J. A. Graff ...... 174,5�0 174,4U Telegraphy, A. G. Bell ...... 174,465 174,586 Tether, S. L. Boyles ...... 174.407 NDEX 174,559 Thill coupling, 'V. H. Cornell ...... 174,413 I CHINI Thrashing machines, spike for. C. Wilde ...... 174,453 number 01 174,582 o tl � lu:,, 'o 1 �

PATENT NO. 174,465 was one of 270-odd granted by the U.S. Pat Bell had filedhis telephone patent application• .This "officialnotice" ent Office during the week ending March 7, 1876, three weeks after was published in the April 8, 1876, issue of SCIENTIFIC AMERICAN.

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© 1980 SCIENTIFIC AMERICAN, INC patent, but my judgment is against it." When the letter reached White, the inventor happened to be visiting him. White firmlyimpressed on Gray that he should concentrate on multiplex teleg raphy. Since the attorney too had ad vised against proceeding further, Gray dropped the matter. The telephone was left to Alexander Graham Bell.

he experts in telegraphy, including TGray, had concluded that the tele phone was not worth serious attention. Bell had remained steadfast in his belief that a successful telephone would be an invention of the first importance. Most of his draft patent application dealt with the devices tested in July of 1875 (which came to be known as the "magneto electric telephone "). As an afterthought, however, he inserted a description of a different kind of transmitter. "Electrical undulations," he wrote, "may also be caused by alternately in creasing and diminishing the resistance of the circuit .... For instance, let mercu ry or some other liquid form part of a voltaic circuit. Then the more deeply the conducting wire is immersed in the liq uid, the less resistance does the liquid offer to the passage of the current. Hence the vibration of the conducting wire in a liquid included in the circuit occasions undulations in the current." Bell had clearly misjudged the electri cal properties of mercury; it is a low resistance liquid, not a high-resistance �.------� one. Why he did so is something of a puzzle, because he had been familiar ! Sneak5P.anis h with the electrical properties of mercury i � since he had first read about them in Helmholtz. It is also not entirely clear just how Bell conceived of a variable-re = like a ruplomat! = sistance transmitter, that is, what prece What sort of people need to learn a The FSl's ProgrammatiC Spanish I dents he relied on. There is even some I foreign language as quickly and effec· Course comes in two volumes. You I • tively as possible? Foreign Service per· may order one or both courses: question as to how and when the de sonnel, that's who. Members of 0 Volum e I, Basic. • scriptive paragraph found its way into • America's diplomatic corps are assign· ( 11 cassettes, 16 hours), instructor's I his final patent specification. Finally, l ed to U.S. embassies abroad, where manua l and 464-page text, $115 • pne may wonder why he filedan appli they must be able to converse fluently 0 in every situation. Volume II, Advanced. cation rather than a caveat. His concepts • Now you can learn to speak Spanish (8 cassettes, 11'/2 hours), instruc · I had not been, in terms of patent law, just as these diplomatic personnel do. tor's manual and 614 page text, $98 I ( ew York residents add sales tax.) I "reduced to practice," a fact the Patent • with the Foreign Service Insti· N Office either overlooked or ignored. tute's Programmatic Spanish Course. Your cassettes are shipped to you in I • The U.S. Departmen t of Sta handsome library binders. These questions have been sources of te has I • spent tens of thousands of dollars de · TO OR DER, JUST CLIP THIS A D and speculation for more than a century veloping this course. It's by far the mail with your name and address, and aI and need not detain us here. • most effective way to learn Spanish at check or money order. Or, charge to • In June of 1876 Gray saw Bell demon your own convenience and at your own your credit card (American Express, I pace. VISA, Master Charge, Diners Club) I by strate his telephone at the Centennial • The ProgrammatiC Spanish Course encloSing card number, expiration • Exhibition in Philadelphia. He latertold consists of a series of tape cassettes date, and your signature. an associate: "As to Bell's talking tele and an accompanying textbook. You The F oreign Service Institute's I simply follow the spoken and written Sp anish course is unconditionally I graph, it only creates interest in scientif • I instructions, listening and repeating. guaranteed. Try it for three weeks. If ic circles. [Its] commercial value will be • By the end of the course,. you'll find you're not convinced it's the fastest, • limited." So did the professional Gray • yoursel� learning and speaking entirely easiest, most painless way to learn continue to misjudge tile importance of In Spanish! Spanish, return it and we'll refundI the telephone even after its successful This course turns your cassette every penny you paid! Order today! • I player �nto a "teaching machine." Many other FSI language realization. In contrast, the amateur Bell • With . courses ItS unique "programma tic" learning also available. Write US' • wrote his father two weeks after filing • method, you set your own pace-. ".,,'''' • his patent application (and nearly two Audlo·Forum testing yourself, correcting errors,pt.A-Q rein.1 weeks before he was first to hear human • forcing accurate responses. De • speech through his instrument): "The E • . ��k�9��y 0017 -...,.... whole thing is mine-and I am sure of IiII�UDlft.�ftftl .. r ....., 1m ' �!�(212)753.1783 �\ , blJ_ fame, fortune and success." �.------.�,

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