o24 PROCEEDINGS OF THE AMERICAN ACADEMY. 



speed for synchronism has been attained by watching the spot of light, 

 or by listening to a telephone which is inserted in place of the galva- 

 nometer. "With the latter one hears slow beats as the contact moves over 

 the wave. Opposite are given some examples of the records obtained 

 with the device. 



ROGEKS L.ARORATORY OF PllYSICS, 

 J unt, l'JOU. 



