672 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



WWIA 

 R 6 

 Explanation of Figure 1. 



A Shell. 



C Box containing mercury cups a, b, c 

 surrounded by compressed hair. 



D, Dj Calibrating tanks. 



E Block containing terminals of galva- 

 nometer. 



F Ammeter. G, G] Galvanometers. 



II Carhart-Clark cell. 



M Mercury cup containing terminals of 

 standard ohm. 



N 220 volt mains. 



Mj, Mo, M 3 Electric motors. 



R 2 Resistances in series with fall of 



potential across heating coil. 

 Resistance in series with Carhart- 

 Clark cell. 

 0.1 ohm in series with ammeter. 

 Standard ohm. 



R 6 , R 7 Adjustable resistances. 

 Resistance in series with galvanom- 

 eter to counterbalance resistance 

 of nickel leads. 

 S, S x Storage cells. 

 T Nickel-lead junction. 



