ELECTRIC DISCHARGE WITH THE CHLORIDE OF SILVER BATTERY. 209 
to the positive, spreads backwards until, with a current of 0 '01 57 5 W, it 
covers the whole terminal. The following are the observations of the lengths 
of wire illuminated which correspond to the various strengths of currents 
with 1200 cells : — 
Currents. 0-00238 0-00263 0-00277 0 00347 0 00555 0 01023 0-01158 0-01575 Weber. 
Lengths. 2 2-5 4-5 7 9 13-5 ' 15*75 19 Inches. 
Tube 161, Hydrogen. 
202. — The difference of the strata in tubes of different diameter'" at the same 
pressure and with the same current is very clearly brought out in tube 161, 
composed of two portions, one being 18 inches long and 1 *65 inch internal 
diameter, the other 17 '5 inches long and 0 1 975 inch diameter, the ratio of the 
sectional areas being 2 '8 6 4 to 1. The terminal in the small tube is a point; 
in the large one a ring. With 4800 cells, the point (small tube) positive 
C. 0 ’02825 W, there were produced in the small tube 62 disc-shaped strata, 
and in the large tube twelve saucer-shaped strata occupying half of the length 
of the large tube ; beyond these the discharge was dark. With the point 
negative, C. 0 ’02 451, there were produced in the small tube 54 discs, and in the 
large tube thirteen saucer-shaped, completely filling it. The number of strata 
does not therefore appear to be in the inverse ratio of the areas. The strata 
in the small tube were blue, but at times, with a large current, carmine, as in 
the capillary part of a spectrum-analysis tube, the strata in the large tube 
being much fainter and pink. The appearance when the point was positive 
Fig. 62. 
62 a. 
? N 
TUBE 161 p 
7 — ^ ■ S 2 a " 
a P 

N 
- - .... — ! — & ■ ' 9 ■. 
* Spottiswoode (Proc. Roy. Soc., xxv., 1876-77, p. 79) describes an experiment “on a hydrogen 
tube of conical form the diameter of which varied from capillary size to \ inch, the capillary end being at 
the bottom, the positive terminal at the top. The principal interest of this tube consists in showing the 
influence of diameter upon the velocity of proper motion. The wider the tube the freer, it seems, the 
striae are to move.’’ 
2 E 
MDCCCLXXVIII, 
