62 PROCEEDINGS OP THE AMERICAN ACADEMY 



the same potential could be found, and by means of a telephone of 

 low resistance the Morse signals sent from Nova Scotia to Florida 

 could be heard in France. With the light of our present knowledge 

 the expenditure of energy on the dynamo-electric engine would seem 

 to be enormous. 



The points made in this paper are as follows : — 



1. Disturbances in telephone circuits usually attributed to effects of 

 induction are, in general, due to contiguous grounds of battery circuits. 

 A return wire is the only way to obviate these disturbances. 



2. The well-defined equipotential surfaces in the neighborhood of 

 battery grounds show the theoretical possibility of telegraphy across 

 bodies of water without the employment of a cable, and leads us to 

 greatly extend the practical limit set by Steinhill. 



3. Earth currents have an intermittent character, with periods of 

 maxima and minima, which may occur several times a minute during 

 the entire day. 



