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
