THE INVENTORS OF THE TELEGRAPH AND TELEPHONE. 657 



the resistance of the selenium will be affected by vibration of the mirror. 

 If, then, the mirror be used as a transmitting diaphragm, like that of 

 a telephone transmitter, words spoken to the mirror will be repeated 

 by a telephone in the circuit of which the selenium, is placed and 

 through which aii electric current is kept flowing. 



In this address an attempt has been made to sketch very briefly the 

 development of the application of electricity to the transmission of 

 intelligence. Many important applications (as, for example, fire-alarms 

 and railway vSigual systems, etc) have not been referred to, and a host 

 of important contributors have, as a matter of necessity, been entirely 

 iguored. To go into detail and do justice to everyone who has con- 

 tributed to the present state of the electric telegraph was an imj)ossi- 

 bility and has not been attem])ted. 

 H. Mis. Ill 12 



