Heat of Granite and Basalt at High Temperatures. 59 



■one of which was capable of yielding several ratios of trans- 

 formation; and in the majority of cases the two circuits were 

 connected in series, the pressures employed ranging from 

 about 10 to about 40 volts. As before, the actual regulation 

 is effected by means of a choking coil, but is rendered auto- 

 matic by the arrangement shown in fig. 1. 



Fig. 1. 



C 



Jo^|-<=cm 



A is a small metal arm about 1*8 cm. long, rigidly 

 attached to the movable current coil of a wattmeter of the 

 Siemens Dynamometer type, which measures the 



energy 



