G. W. Hough on the Galvanic Battery. 187 
the resistance is again increased by polarization. The conduct- 
ing power of s,z. was found to be essentially the same between 
30 : 
° B. and saturation, At 1° B. it was one fourth, at 7° one 
half, and at 14° three fourths as great as for a saturated solu- 
tion 
On the use of the negative metal in Daniell’s Battery.—The 
negative metal in Daniell’s battery is only useful as a conduc- 
tor of the current. 
For the purpose of testing the correctness of this conclusion, 
experiments were made with the following metals as the nega- 
tive plate: 1, Copper; 2, sheet lead ; 3, sheet iron; 4, sheet 
iron tinned (the ordinary sheet tin); 5, sheet zinc; 6, cast zinc. 
€ s.c. was a saturated solution, and the s.z. had a specitic 
gravity of 25° B. The quantity of electricity and the electro- 
motive force was found to be the same for copper, lead, iron 
and tin. When zine was used for both the positive and nega- 
tive metal, the action was somewhat different, For two or 
three seconds after immersion in the s. ¢. there was a small neg- 
ative current, after which the galvanometer needle was gradu- 
ally deflected until it indicated a quantity of electricity nearly 
equal to the normal condition of the element. then re- 
mained at rest. for a few seconds after which it receded and 
stood at a degree indicating about one half the quantity. The 
whole time required to bring it to rest, was three minutes from 
the time of immersion. During the progress of the experi- 
ment the hydrogen was evolved so rapidly from the zine im- 
mersed in the s.c, that the bubbles could be exploded by hold- 
ing a lighted match near the surface of the liquid. As soon, 
however, as the galvanometer came to rest, the evolution of hy- 
drogen had nearly ceased. On removing the zinc it was found 
covered with a loose copper powder, not reguline metal but 
such as is deposited when a large battery is employed to act on 
a small surface. This powder did not adhere closely to the 
zinc, but was separated by a thin layer of s.2 or hydrogen. 
On washing the zinc and repeating the experiment, precisely 
similar results were obtained. Although the zinc was capable 
of conducting the maximum quantity of electricity, yet the 
electro-motive force was considerably less than for the other 
metals. A careful examination of these experiments, leads us 
to the conclusion that the negative metal in Daniell’s battery, 
only acts as a conductor of the electricity. ‘ 
On the internal resistance of the battery.—In a battery with 
two liquids the internal resistance is made up of two elements, 
