THE ELECTRO-MOTOGRAPH. 263 



release from friction by a change in electric condition in the first instrument 

 failed simply from ignorance of some slight matters of detail, that in the 

 electro-motograph are corrected and made practical. In the musical 

 telephone the releasing of the frictional resistance by electric action caused 

 the sounding-board of a guitar to vibrate, and thus set up sonorous vibra- 

 tions. In the electro-motograph the mica disc takes the place of the guitar, 

 and, by the improved construction of the apparatus, intricate and complex 

 vibrations, such as are produced in speaking, are reproduced in their 

 original or even in greater volume. When the apparatus is at rest the 

 diaphragm is motionless, and electric currents shot through the apparatus 

 produce no effect. In the same manner the mere turning of the cylinder 

 without electric action produces no effect, except to pull the diaphragm 

 slightly out of shape. If while the cylinder is being turned an electric 

 impulse arrives, the pull on the diaphragm, caused by the friction of the 

 strip on the cylinder, is more or less released, and the diaphragm is free to 

 vibrate or spring back into its original condition. If now, the electric 

 impulses follow one another in regular order in correspondence with the 

 sonorous vibrations imparted to the transmitting telephone, the alternate 

 slipping and catching of the metal strip on the cylinder will follow in the 

 same order, and thus the diaphragm will be made to vibrate in unison with 

 the original vibrations, and thus reproduce the original words. As the 

 mica disc is much larger than the disc of the transmitting instrument, the 

 amplitude of its swing may be much greater, and consequently it will repeat 

 the words with greater power. The electro-motograph is practically an 

 apparatus for transforming electric action received from a distance into 

 mechanical work. The amount of electric action has nothing to do with 

 the amount of the mechanical work performed, because the movement of 

 the cylinder is controlled by power independently of the electric action, the 

 electricity merely releasing this power by destroying the friction in greater 

 or less degree. The electric action set up by the sonorous vibrations at the 

 transmitting end of the line may be very slight, while the mechanical action 

 at the distant end may be powerful, and in this manner the amplitude of 

 the vibrations may be increased to an indefinite extent, and a whisper may 

 reappear as a loud shout. 



" The electro-motograph is not only a solution of the telephone, making 

 it capable of sounds of every quality and pitch and in greatly increased 

 volume, but by this conversion of electrical action into mechanical work 

 at a distance makes it possible to unite the telephone and phonograph. 

 Telephonic messages by the electro-motograph may be impressed upon a 

 self-acting (clock-work) phonograph, the same current starting and stopping 

 the phonograph after the manner of the stock-reporting machines, and 

 afterward the phonograph may be made to repeat the message impressed 

 upon it." 



[The above extract, which explains the principle fully, has been taken from 

 a long article on the subject which formerly appeared in Scribners Magazine"^ 



