528 THE POPULAR SCIENCE MONTHLY. 



reproduce electrically an exact copy of the atmospheric vibrations pro- 

 duced 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 lon- 

 gitudinal vibrations of the thread from one membrane to the other 

 confirmed the idea that he had formed a year previous ; and it imme- 

 diately 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 tele- 

 graphically 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 car- 

 ried on by persons at long distances apart, and that he has devised an 

 instrument capable of vibrating responsively to all the tones of the hu- 

 man 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 corre- 

 sponding 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. 



