136 A, EF. Bostwick—The Influence of Light 
wood having two holes two and one-half inches square cut in 
it. Over these holes the plates were laid, the edges resting for 
three-eighths of an inch upon rolls of silver foil, through whie 
the connections were made. ‘Two strips of wood were screwed 
down over the edges of the plates to fasten them, and both 
sides of the slab were then covered with black paper, holes 
some years ago. ‘They were all thin enough to transmit light 
i b 
A 5°5 ohms. Connections ‘087 ohms. 
Ag “ “ 3 “ 
A’ 14°56 “ce “ “O87 “ 
B’ 126:73: + “4 083: - 
C 9°33 “ te 045 “ 
D 6'25 “ee 19 “045 “ 
E 10°27 = «€ * "O45: > 24 
Galvanometer.—A Thomson’s reflecting galvanometer of 7096 
ohms resistance was used. Its two coils were connected in 
multiple arc, making the resistance 1774 ohms. The slit was 
system. . 
Eheostat.—A sliding rheostat was used, having two parallel 
platinum wires which could be connected in series or multip! 
