EXPERIMENT STATION BULLETINS. 



673 



Fig. 7. 



Complete Setup. 



1. Batli. 2. (Jalvanonictcr. ,3 aijd 4. Curtis Coils, ."i. Docailc Ri'sislaut'e iu bridge 

 circuit. G. Switch controlling bridge and galvanometer circuit. 7. Bridge. 8. Condenser. 



SOURCE OF CURRENT. 



The source of current is a 60 cycle rotary converter. The first con- 

 verter used was a large stationary type run on a constant potential of 

 110 volts from an Edison storage battery. The first studies were made in 

 the electrical power laboratory of the physics department. Later work 

 was done in the botanical laboratory and the current derived from a small 

 portable 1/10 hor.se power, 60 cycle, rotary converter. (Fig. 8). This 

 was obtained from the Holtzer Cabot Electric Company of Boston. It 

 proved very satisfactor3^ A variable transformer was used in connection 

 with this converter to cut the current down to 6 volts. This was then 

 connected with the bridge circuit and the stationary coils of the gal- 



