526 THE POPULAR SCIENCE MONTHLY. 



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 telegraphi- 

 cally transmitted and received. 



When the fact dawned upon him, and had been confirmed by dem- 

 onstration, 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 iirst 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 trans- 

 mitted 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 simul- 

 taneously. 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 electri- 

 city 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 sci- 

 ence, 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 dia- 

 phragm made of a thin sheet of tinned iron. It will be observed that 

 this instrument embraces all the substantial features in the mechanical 



