492 



PROCEEDINGS OP THE AMERICAN ACADEMY 



The arrangement of the apparatus was as follows: — 



R. The steel strip enclosed in a glass tube to protect it from drauglits 

 of air. 



W. "NVheatstone's bridge. 



Gy . Tlionipsou astatic galvanometer. 



aSj . Shunt for the same. 



G^. Ballistic galvanometer. 



/Sj. Shunt for the same. 



E. Quadrant electrometer. 



B^ . Battery of twelve Bunsen cells. 



B^ . Battery of two Leclanche cells. 



7?.; . Do. do. do. 



Kj^ . Key for battery B.^ and galvanometer G^ . 



Ko . Key for passing current from B^ through strip. 



Ag. Key in auxiliary circuit with commutator C, and a second coil of 

 galvanometer G^ , for bringing the needle quickly to rest with- 

 out heating strip R. 



The two galvanometers were arranged to throw their spots of light 

 on the same scale. The key K^ was first depressed, R being then in 

 the bridge circuit, and the spot of G^ was brought to zero by adjusting 

 the resistance c. a was always 1,000 ohms, and h one ohm. On A'j 



