Popular Science Monthly/Volume 14/February 1879/Sketch of Elisha Gray
By GEORGE B. PRESCOTT.
ELISHA GRAY, the inventor of the Speaking Telephone, was born at Barnesville, Belmont County, Ohio, August 2, 1835. During his boyhood he was profoundly interested in all the phenomena of nature, and had an intense desire, whenever he saw any manifestation of physical force, to become acquainted with the secret of its operation. Among all the phenomena throughout the domain of physics, nothing took such hold upon his mind as that exhibited in the various effects produced by the action of electricity, and he read whatever he could find relating to this subject with the same eagerness and interest that most boys would read "Robinson Crusoe" or the "Arabian Nights."
While yet a boy he constructed a Morse register, all the parts of which were made of wood, with the exception of the magnet, armature, and embossing point in the end of the lever (which latter he made by filing a nail down to a point). He had the magnet bent into a U-form by a blacksmith, and then wound it with brass bell-wire, which was insulated with strips of cotton cloth wrapped around it by hand. For a battery he made use of a candy-jar, in which he placed coils of sheet copper and zinc, with a solution of blue vitriol. With these materials he succeeded in making a very good electro-magnet, which would tain nearly a pound weight, and which, when mounted as a part of the instrument, performed the work of actuating the armature with perfect success.
At quite an early age he was apprenticed to a blacksmith, and worked with him at that business about one year. He found, however, that this business was too laborious for him, and relinquished it to become an apprentice to a carpenter, joiner, and boat-builder, with whom he served a full apprenticeship, during which time he was employed in almost every department of woodwork. The prime motive which actuated him through all these years that he had worked at the bench was his thirst for knowledge. He felt sure that, with his trade as his capital, he could work his way through a course of study. In pursuance of this idea, after the time had expired for which he had apprenticed himself, he began a regular course of study, and, by working a portion of each day and during vacation at his trade, was enabled to pay his necessary expenses and keep up with his class. Here, as everywhere else, the capacity and ability to master everything relating to physical science was perhaps the most prominent characteristic exhibited during his collegiate course. While studying natural philosophy, it was his custom to make and carry with him into the class such apparatus as could be readily constructed and would serve to illustrate the lesson. His habit of actually constructing everything which he saw or read of, so far as his facilities would allow, was the best possible method of fixing the principles of its operation firmly in his mind.
Mr. Gray's career as a professional electrician and inventor dates from the year 1865. His first patent for electrical or telegraphic apparatus was granted October 1, 1867. Since that time he has made a considerable number of electrical inventions, many of which have been patented. Including cases now pending, the number amounts to about forty in this country and thirty in foreign countries. Thirty of the United States cases and twenty-five of the foreign relate to the telephone.
His attention was first called to the subject of telephonic transmission in the winter of 1867. In the course of his experiments during this winter and spring, he made use of a vibrating electrotome or reed in the primary circuit of an induction coil, and an electro-magnet having a polarized armature, in the secondary circuit. A Morse transmitting key was also inserted in the last-mentioned circuit. When the electrotome was in operation, and the Morse key in the secondary circuit was closed, he noticed a singing sound in the electro-magnet, and, by working the key as if transmitting a Morse message, the signals were audibly produced on the magnet by long and short sounds, representing the dots and dashes of the Morse alphabet. He saw in it a method for transmitting signals for telegraphic purposes, and also about the same time conceived the idea of arranging a key-board, having electrotomes tuned to the different tones in the scale. He did not, however, at this time realize the full value of the invention, as his attention was mainly directed to the capacity of the apparatus for transmitting musical tones through an electric circuit.
In the winter of 1874 Mr. Gray observed a singular circumstance in connection with the reproduction of electrically transmitted vibrations through the medium of animal tissue. On going into the bath-room he found his nephew playing with a small induction coil—"taking shocks," as he expressed it, for the amusement of the smaller children. He had connected one end of the secondary coil to the zinc lining of the bath-tub, which was dry at that time. Holding the other end of the coil in his left hand he touched the lining of the tub with the right. In making contact, his hand would glide along the side for a short distance. At these times Mr. Gray noticed a sound proceeding from under his hand at the point of contact, which seemed to have the same pitch and quality as that of the vibrating electrotome, which was within hearing. Mr. Gray immediately took the electrode in his own hand, and, repeating the operation, to his astonishment found that, by rubbing hard and rapidly, he could make a much louder sound than the electrotome was making. He then changed the pitch of the vibration, increasing its rapidity, and found that the pitch of the sound under his hand was also changed, it still agreeing with that of the transmitted vibration. He then moistened his hand and continued the rubbing, but no sound was produced so long as his hand remained wet; but, as soon as the parts in contact became dry, the sound reappeared. So striking was the effect that, by hard rubbing with the dry hand, the noise could be distinctly heard throughout the house.
This experiment produced a profound impression upon his mind, and determined him at once to take the matter up in earnest and see what might be in it. He procured a violin, and, taking off the strings, substituted in their place a thin metal plate provided with a wire connection, so that he could attach it to one pole of the induction coil or battery, thus placing it in the same position, with reference to the body, that the bath-tub was in the original experiment. By rubbing the plate in the same manner as before described, the sound of the electrotome was reproduced, accompanied by the peculiar quality or timbre belonging to the violin. He noticed, however, that the characteristics of the initial vibrations were faithfully preserved, and all that was needed was to sift out such foreign vibrations as were excited in the receiver, owing to its peculiar construction; in which case there would remain the exact character of the transmitted vibrations.
In March, 1874, Mr. Gray undertook to secure letters patent for some of his conceptions, and with that purpose in view had models made, illustrating the idea of a series of transmitters, each tuned to a different pitch, showing a method of receiving musical or other sounds telegraphically, through the medium of animal tissue. In June, 1874, he filed another case, substituting for the animal-tissue receiver an electro-magnet combined with a hollow box of tinned iron, having an opening in one side, while the other was held over the poles of the magnet at such a distance from it as would produce the best effect. With this apparatus he noticed that when he depressed two keys on his transmitter, if these were in the proper relation to each other, a composite tone would be received, thus demonstrating the general fact that, with a transmitter and receiver properly constructed and arranged in the circuit, composite tones of varying quality could be telegraphically transmitted and received.
When the fact dawned upon him, and had been confirmed by demonstration, that sounds of a composite character could be transmitted through a telegraphic circuit and reproduced at the receiving end, and the possibilities of the invention and the great results to which it must eventually lead passed through his mind, he at once foresaw so many possible applications of it that it became a serious question which line of investigation to nrst pursue. Among other conceptions of the probabilities of the invention was that, at an early day, not only musical compositions of a complicated character, but even articulate speech, would be transmitted through a single telegraph wire. He could also see that musical tones, differing in pitch, could be simultaneously transmitted through the wire and analyzed at the receiving end, so that a transmitter and a receiver correspondingly tuned would transmit and receive a tone corresponding to their own pitch, rejecting all others; while at the same time a number of other tones differing in pitch might be simultaneously transmitted and received through the same wire. This he successfully accomplished, sending as many as eight messages simultaneously. Another conception which occurred to him at this time was that of applying the invention to a printing telegraph, so that each type would be actuated by a tone of a particular pitch. Being well conversant with the facts, so far as they were then known in the science of electricity and magnetism, he was fully prepared to avail himself of what had already been done in that line. He was not, however, experimentally conversant to the same extent with the facts in the science of acoustics, but theoretically the subject was a familiar one to him. He devoted considerable time to familiarizing himself experimentally with that science, especially that branch which related to the qualities of composite tones; so that he was able to give the composition of the various vowel sounds, and determine in general the relation between the character of a sound as it seemed to the hearer and the physical fact as it existed in the form of motion, either in the air or any medium through which it was propagated.
The early part of 1874 he devoted principally to the construction of various devices for telegraphically transmitting musical tones. Among the receivers which he used was an electro-magnet with a circular diaphragm made of a thin sheet of tinned iron. It will be observed that this instrument embraces all the substantial features in the mechanical construction of the speaking telephone of to-day. When used in connection with his articulating transmitter, which was developed at a later date, articulate words have been received upon it; and when a duplicate of the instrument is inserted in a closed circuit, which includes a galvanic battery, it becomes a speaking telephone capable of acting both as a transmitter and as a receiver. Mr. Gray did not know at that time, however, that he could use it as a transmitter, although he had fully demonstrated its ability to receive sounds of varying quality. At that date his conception of a transmitter for the transmission of articulate words was a mechanism which would employ such tones as were needed, and would enable one to manipulate them in whatever manner was requisite to produce the desired effect. In other words, he supposed it would be necessary to construct a mechanism similar to the vocal organs of the throat, which would mold electrical waves into the same form that the air is molded when a spoken word is uttered. This seemed too complicated a machine to be easily constructed; hence he determined to experiment particularly in the direction of the more perfect transmission of composite tones, so that each individual tone would have its individuality and place properly preserved in the clang of which it was a part; and to the analysis of the same at the receiving end, so that any particular tone would respond upon one instrument, and one only. This general result once attained, it was his purpose to make an application of it to multiple, printing, and autographic telegraphy. While engaged in these experiments he was continually on the alert for developments that might assist him to solve the interesting problem already before his mind, that of transmitting spoken words. Shortly after he constructed a transmitter, consisting of a revolving shaft, upon which were mounted two eccentric cams, having one or more projections. These actuated two small levers, causing them to vibrate upon their respective break-points, through which points a battery current passed. He employed, in connection with this transmitter, a receiver which was adapted to the reception of all varieties of sounds.
When this apparatus was put in operation a sound of peculiar quality, not unlike that of the human voice when in great distress, proceeded from the receiver. By altering the tension of the spring in various ways he was able to imitate many different sounds involving the vowels only, and succeeded, among other things, in producing a groan with all its inflections in the greatest perfection. Up to the time of making this experiment Mr. Gray had associated in his mind, in connection with transmission of spoken words, a complicated mechanism. This experiment produced an entire change in his views, and he came to the conclusion that in solving the problem of transmitting spoken words it was not necessary to consider the mechanism of the vocal organs at all, but simply the physical results produced in the atmosphere by them, and all that was necessary, therefore, was to devise a transmitter that would reproduce electrically an exact copy of the atmospheric vibrations produced by any sound whatever.
During a visit in Milwaukee at this time, Mr, Gray saw for the first time a toy called the lovers' telegraph, consisting of a membrane stretched over the end of a tube, and having a thread attached to the center, the other end of which was attached to a similar membrane. The fact that spoken words were distinctly transmitted by the longitudinal vibrations of the thread from one membrane to the other confirmed the idea that he had formed a year previous; and it immediately solved in his mind the problem of making a transmitter that would copy electrically the physical vibrations of the air produced by articulate sounds. He determined to put this into practical shape, and file it in the records of the Patent-Office. He accordingly put his speaking telephone into the form of drawings and specifications, and filed them in the United States Patent-Office, February 14, 1876. In his specification he states that he has invented a new art of telegraphically transmitting vocal sounds whereby the tones of the human voice can be transmitted through a telegraphic circuit, and reproduced at the receiving end of the line, so that actual conversations can be carried on by persons at long distances apart, and that he has devised an instrument capable of vibrating responsively to all the tones of the human voice, and by which they are rendered audible.
His method of providing an apparatus capable of responding to the various tones of the human voice was a diaphragm stretched across one end of a chamber, carrying an apparatus for producing fluctuations in the potential of the electric current, and consequently varying in its power. The vibrations thus imparted were to be transmitted through an electric circuit to the receiving station, in which circuit was included an electro-magnet of ordinary construction, acting upon a diaphragm to which was attached a piece of soft iron, and which diaphragm was stretched across a receiving vocalizing chamber, similar to the corresponding vocalizing chamber at the transmitting end.
This is the first description on record of an articulating telephone which transmits and reproduces the spoken words of the human voice at a distance by means of electricity, and instruments constructed in exact accordance with Mr. Gray's drawings and specifications, filed at the time above stated, are good articulating telephones. Moreover, Mr. Gray's method of producing articulate speech by varying the resistance of a battery current is much more effective than that of Professor Bell subsequently invented, which depends upon magneto-induction currents generated by the action of the voice, as is fully proved by the great superiority of Edison's carbon telephone, which is based upon this principle.