DESCRIPTION OF PLATE 3. 
Fig. 2. Four-pole ebonite key. 
a. Wooden base. 
b, b, b, b. Ebonite rods with mercury cups in upper ends. 
Fig. 3. Reversing key, &c. 
a. Wooden base. 
b, b, b, b. Ebonite rods and mercury cup in upper ends. 
c, c. Rods of fused quartz mounted in ebonite ends, and with mercury cups. 
f Tin-foil wrapped on ebonite handle. 
d. Discharging point, only used when determining residual charge to 
connect g', g 1 , thus instantaneously discharging condenser. 
For resistance measurements the legs at opposite corners were metalli¬ 
cally connected as usual in a commutator. 
Fig. 4. Micrometer telescope used with new galvanometer. 
a. Object glass. 
b. Graduated micrometer head. 
c. Scale divided on glass, replacing usual comb. 
d. Movable spider line. 
e. Eye-piece. 
f Brass mounting, carries a and e, and is capable of a universal motion 
(not shown). 
B'ig. 5. Gold dish and aluminium plates. 
a. Aluminium handle used to lift Kj when making film. This is removed 
and replaced by electrode m when film is in position. 
K 1} K 2 . Aluminium plates between which the sulphur film is formed. 
1. Outer zinc dish. 
c. Inner gold dish supported by l. 
s. Surplus sulphur. 
r, r. Quartz rods in sulphur. 
Note. —Since the sketch was made, a zinc dish has been fixed to the 
upper aluminium plate K x . It is scraped true on the bottom and 
joint sealed with sulphur. The dish can then be filled with pounded 
ice, when making mixed sulphur films. 
