Initially, both Bell and Elisha Gray focused on harmonic telegraphy: the idea of using multiple tones, singly or in combination, to send multiple messages down the same wire. For Bell, this goal emerged from one of his themes. Bell's family was very involved with teaching the deaf. His father, Alexander Melville, developed a special 'visual speech' alphabet which deaf people could use to read how to make specific sounds. As a boy, Bell would participate in demonstrations in which he was placed out of earshot; his father would ask a member of the audience to make a sound, then he would write it in visible speech; Bell would enter, read what his father had written, and make the sound. So Bell inherited a family theme, or mission, having to do with teaching the deaf and making speech visible to the deaf.
Gray's themes are harder to reconstruct than Bell's, because Gray left less in the way of written records and the only biography, by Lloyd Taylor, is an unpublished work of uneven quality (Taylor, Unpublished Manuscript). Elisha Gray was born in Barnesville, Ohio in 1835. He magnaged to build a working model of Morse's telegraph before he was ten, but the death of his father and his mother's precarious health made Elisha the primary breadwinner in the family at the age of 12. He took up carpentry until he could enroll as a student at Oberlin College, where he encountered a mentor in the form of his science teacher, Charles Churchill, who inspred Gray's continued interest in electronics and telegraph , (Hounshell, 1975). Here the themes of hard work and telegraph invention seem to join, though we know very little about this period in Gray's life.
Like Bell, Gray often overworked to the point of illness--he managed to put himself through five years of Oberlin but paid with five years of convalescence (Hounshell, 1975). He gained much of his knowledge through his hands: "While studying natural philosophy, it was my custom to make and carry with me into the class such apparatus as could be readily constructed and would serve to illustrate the lesson. My habit of actually constructing everything which I saw or read of so far as my facilities would allow, was the best possible method of fixing the principles of its operation firmly in my mind" (Gray, 1977, p. 6).
His electrical researches paid off in 1867, when he developed a new form of telegraph relay. He formed a partnership with Enos Barton in 1869; they founded the Western Electric Company, which became. the major manufacturer of telegraph equipment for Western Union. Bell's father introduced Alec to the scientific community; Gray's hard struggle for survival inclined him more to the world of business.
Each inventor suspected the other of stealing his ideas at various points. Gray submitted a patent application for a multiple harmonic telegraph on February 23, 1875; two days later Bell submitted one for his. These closely timed submissions foreshadow the competition over the telephone, in which Gray filed a caveat on the same day Bell filed a patent. (A caveat was a document that could be filed with the patent office to signal an inventor's intention to submit a patent at a future date, when her invention was closer to realization).
So the famous controversy between Bell and Gray over the speaking telegraph, or what we now call the telephone , was really one episode in a continuing controversy over multiple telegraphy. In the telegraphy controversy, we will focus on the way in which Gray and Bell evolved similar mechanical representations for receivers; in the telephone, we will show how they evolved similar transmitters. In both cases, however, there were important differences in how each inventor viewed the function of devices that appear similar on the benchtop. An invention that looks the same in hindsight was not always viewed as the same by the inventors at the time.
Gray later claimed he got the first idea for using musical tones to send telegraph messages in 1867, when he was using a vibrating metal reed, or rheotome, in a circuit with an electromagnet and a telegraph key. When he closed the key, he "noticed a singing sound in the electro-magnet, and by working the [telegraph] 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" (Gray, 1977). Gray makes this sound like an entirely serendipitous experimental result, but by this time, he probably had heard of--and even seen demonstrated--the first telephone, constructed by Philip Reis in Germany in 1854. This device was designed to transmit musical tones. The transmitter consisted of a lever with a point, which rested on a membrane; when one sung a note, the membrane would cause the lever bounce, alternately making and breaking contact with a piece of platinum in the middle of the membrane. This intermittent, on-off current would alternately magnetize and de-magnetize a receiving electromagnet, which would reproduce whatever tone had been sung into the membrane. The Reis apparatus was widely known at the time (1880). Gray later referred to his musical telegraph devices as telephones. Unlike Bell, Gray did not document his sources; therefore, it is hard to be sure where his background knowledge came from.
Gray's next mental model for a harmonic telegraph came from observing his nephew touching a zinc-lined bathtub with one hand while in the other he held a coil connected to a vibrating rheotome, an electromagnetic device which produced a tone. When his nephew's hand glided along the zinc, Gray heard the bathtub emit the same tone as the rheotome. When Gray put himself in his nephew's position, he found he could alther the pitch and volume by changing the speed and pressure with which he rubbed the zinc.
It was Pasteur who said that chance favors the prepared mind. In this case, a child's game provided Gray with a mental model for a musical telegraph. A single telegraph receiver could potentially reproduce multiple tones. He was so excited by the potential of this discovery that he resigned as superintendent of Western Electric to pursue his inventions full time.
In April of 1874 Gray attempted to patent a musical telegraph, which consisted of a two-tone transmitter, consisting of two single-pole electromagnets, each with a vibrating armature. Each armature made and broke contact with a platinum point which switched the current on and off to the coil. Because each electromagnet had a different electrical resistance, each electromagnet exerted a different magnetic pull on its armature and thus caused each armature to vibrate at a different frequency. Each coil and armature combination was controlled by its own telegraph key, so that each frequency could be sent separately or simultaneously. These electromagnets were connected to an induction coil which functioned like a modern transformer and stepped up the current before it was sent out onto the telegraph line. For the zinc bathtub, Gray substituted a grounded piece of galvanized tin. The patent drawing shows a man--presumably Gray himself--holding the wire from the coil in one hand and touching the tin with the other (see Figure 9 from Gray's patent 166,096). The transmitter sent two different, audible tones which were reproduced on the tin plate receiver as the man rubbed it.
Figure 9: Drawing of Elisha Gray in a circuit from his Animal Tissue Patent 166,096. In this case, Gray himself was the animal tissue. In later patents, he substituted other materials.
The patent office initially rejected this application, on the grounds that one could not patent a circuit which included a person. So Gray converted the person into a slot into which he could substitute a variety of animal tissues, ranging from oyster shell to leather. He was eventually granted a patent in February of 1876.
By then, Gray had moved on. He expanded his two-tone transmitter to a two-octave device that could send twenty-four different pitches (two octaves) over one telegraphic circuit. Each tone was generated by a single tone transmitter tuned to a different pitch. Gray often used several single tone transmitters inside more complex devices capable of sending multiple tones, such as his two octave transmitter and printing telegraph. Because he used the single tone transmitter by inserting it into slots in different inventions, it became one of Gray's mechanical representations.
Gray also developed several receivers to take the place of the awkward animal tissue combination. His mental model was the telephone receiver developed by Philip Reis. According to Gray, the principle of the Reis receiver was that 'when a coil of wire surrounding a bar of iron or the core of an electromagnet is traversed by an electric current, the said bar will be slightly elongated, and if these currents succeed each other with sufficient rapidity, a vibratory motion will be given to said bar, and it will give forth a musical tone.'
All of Gray's receivers embodied this principle and hence were capable of reproducing several tones simultaneously, but they employed different mechanical representations in the amplification of the vibrating core of the electromagnets. So while the Reis receiver functioned as Gray's receiver mental model, these mechanical representations came from several other sources. For example, he used a variety of resonant cavities to amplify the sound. He got the idea of using a tin drum from a combination of the tin he used in his animal tissue patents and experiments with a violin with a metal plate on the back. His previous experience with using a bathtub as a receiver led him to substitute a wash basin.
He systematically tested every type of receiver with his two-octave transmitter With these instruments Gray gave several impressive demonstrations in New York and Washington in May and June, 1874, after which he returned home to Chicago.
Gray claimed that, upon returning to Chicago, he worked on the problem of creating a reliable harmonic telegraph transmitter. His two-octave transmitter could theoretically have been used for such a purpose, but Gray apparently thought it more suited to sending composite tones than isolated individual messages. His solution to the transmitter problem was to use "an ordinary electro-magnet and a reed made of a piece of watch-spring, one end of which is fixed to one pole of the magnet while the other free end projects over the other pole, a short distance from it, so as to form an armature" (Gray, 1977, pp. 21-2). Each of these springs could be tuned to a particular frequency. These springs produced an excellent tone for a short time, "but the slightest change in the adjustment, even a jar of the table, causes it to break into nodes, and give a note a chord or an octave away from its fundamental" (Gray, 1977, p. 23). At this point, I want to turn back to Bell, who evolved a device that looked very similar to Gray's reed transmitter, foreshadowing the later conflict between the inventors over the telephone.
When Elisha Gray began his multiple telegraph work, he was already an accomplished electrical inventor. Bell's area of expertise, by contrast, was speech and audition. In 1863, his father, Alexander Melville, had challenged Alec and his older brother Melly to manufacture an artificial mouth and nasal passage, complete with vocal chords. The inspiration was Wheatstone's version of an 18th century device for imitating the human voice. The boys eventually succeeded in making the device say "mama" so realistically that a tenant came down to see what was the matter with the baby (Bruce, 1973, p. 37). Bell learned a great deal about how consonants and vowels are formed from this exercise, and it also taught him the value of using a heuristic he would later call 'follow the analogy of nature'.
Like Elisha Gray, much of Bell's knowledge came through building and tinkering, but Bell was gaining expertise in speech, rather than electricity. In another set of experiments, he discovered that he could hold a vibrating tuning fork in front of his mouth and while moving his tongue through the positions of the vowels, one of the vowel positions would cause the fork to resonate. He experimented with combinations of tuning forks and vowels, making what he thought were important discoveries. But when he sent a letter to Alexander Ellis, the great phonetician, he learned that he had been replicating experiments conducted by Hermann von Helmholtz. He derived some comfort from the fact that he had followed in the footsteps of one of the world's greatest scientists.
Bell's first idea for a multiple telegraph came from a conversation with Ellis about Helmholtz's apparatus for artificially producing vowel tones, by means of combinations of tuning forks and resonant chambers. Ellis had to do some translating from the German for Bell, and as a result, Bell got the false impression that the device transmitted vowel sounds, when in fact it created them. If vowels could be transmitted, why not consonants and, eventually, speech?
Here we begin to see one of the distinctions between discoverer and inventor. Helmholtz invented apparatus in order to develop and test hypotheses; he was not concerned about commercial applications. Bell, on the other hand, was looking for a way to achieve financial independence, and transformed Helmholtz's apparatus into a mental model of how speech and tones might be transmitted over a wire.
Bell's initial focus was not on speech but on the reverse salient. Why not take two forks that produced exactly the same tone and turn one into a telegraph transmitter and the other into a receiver? If one could do this with one pair of forks, why not do it with four, eight or even sixteen distinct tones, all carrying information down the same wire?
Like Edison, Bell read everything he could get his hands on that was related to his invention ideas. From J. Baille's The Wonders of Electricity Bell got the idea of substituting a steel plate for a tuning fork. Books like Baille's served almost as catalogues of possible electro-mechanical variations for inventors; like Gray, Bell found he had to transform existing components into mechanical representations he could work with. Figure 10 shows several of the stages in the evolution of Bell's steel reed transceiver. The result was a steel reed device whose pitch could be precisely tuned simply by adjusting the length of it that was allowed to hang over the electromagnet. I call Bell's device a 'transceiver' because Bell intended to use the same as both transmitter and receiver.
Figure 10: Three stages in the evolution of Bell's reed mechanical representation, starting with tuning forks at the top, then switching to a steel reed in a sounding, and finally an adjustable reed over the poles of an electromagnet. He also employed a design in which the reed vibrated over the single pole of an electromagnet . His work in this area was influenced by sources like Baille's Wonders of Electricity ((Baille, 1872).
Bell had great difficulty putting these reed relays into an effective multiple telegraph circuit, which led him to develop a new theme, or role, for himself in November of 1873, when he wrote, "It became evident to me, that with my own crude workmanship, and with the limited time and means at my disposal, I could not hope to construct any better models. I therefore from this time devoted less time to practical experiment than to the theoretical development of the details of the invention" *(Bell, 1876, p. 8).
Gray, in contrast, was a master at constructing complex circuits. But in this account, we will focus on how he developed a mechanical representation that bears a resemblance to Bell's. Figure 11 shows the evolution of Gray's reed mechanical representation. In order to make his reed assemblage better able to transmit single tones, Gray made the spring into a heavier metal reed, filed the end of the reed to tune it, and added a small spring to dampen its vibrations. For a single-tone or analyzing receiver, he first tried a tuning fork attached to one pole of an electromagnet. Then he substituted a spring or lever for the fork. Next, he tried a steel ribbon clamped on both ends: "The length and size of the ribbon depend upon the note we wish to receive upon it. If it is a high note, we make it thinner and shorter; if it is a low note, we make it thicker and longer. If this ribbon is tuned to that it will give a certain note when made to vibrate mechanically, and the note which corresponds to its fundamental is then transmitted through its magnet, it will respond and vibrate in unison with its transmitted note; but if another note be sent which varies at all from its fundamental, it will not respond. If a composite tone is sent, the ribbon will respond when its own note is being sent as part of the composite tone, but as soon as its own tone is left out it will immediately stop. This I am able to select out and indicate when any note is being sent, in fact, to analyze the tones which are passing over the line" (Ashley, October 21, 1876).
Figure 11: The evolution of Gray's reed mechanical representations. Note the way in which Gray appears to operate in separate transmitter and receiver slots, ending up with different mechanical representations for each.
Unlike Bell, Gray was not working to get a single preferred mechanical representation. He had specific ways of configuring his reed when it was to serve as a transmitter and as a receiver. This difference in function between Bell's and Gray's apparently similar devices illustrates why I use the term mechanical representation. Bell and Gray saw different possibilities in their reed devices.
Gray wanted to patent a variety of transmitters and receivers that could be used in combination. Therefore, Figure 11* is somewhat misleading--it shows that Gray could work incrementally to improve his transmitters and receivers, but does not show all the other variations he was generating at a similar time. Gray's cognitive style could be best described by a matrix: he developed a set of alternate mechanical representations for transmitters and receivers, and tested and patented many of the possible combinations. In Gray's case, substitution of mechanical representations in different slots did not lead to radical changes in his overall mental model of how a multiple harmonic telegraph might work; instead, it gave him more variations to experiment with as he tried to reduce his ideas to practice.
This page was last edited: Wednesday, July 14, 1999