324 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. 



Rogers Laboratory of Physics, 

 June, 1900. 



