Remarks on the Galvanic Battery. 143 



whole time required to bring it to rest, was three minutes 

 from the time of immersion. During the progress of the 

 experiment the hydrogen was evolved so rapidly from the 

 zinc immersed in the s. c. that the bubbles could be ex- 

 ploded by holding a lighted match near the surface of the 

 liquid. As soon , however, as the galvanometer came to rest 

 the evolution of hydrogen had nearly ceased. On remov- 

 ing 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 5. z. or hydrogen. On wash- 

 ing 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 ele- 

 ments, viz : the specific resistance of the liquid and 

 the resistance of the porous cell. Although recent writers 

 have remarked the variation of resistance due to different 

 kinds of earthen cells, yet we have not learned that any 

 one has determined separately the resistance due to the 

 cell and that due to the liquids. By our method it is 

 necessary to use at least two cells of different size. In 

 these experiments three were employed. 



No. 1, White clay cell 0-81 inches in thickness, 6 inches in diame- 

 ter and 7 inches high. 



No. 2, White clay cell 0-15 inches in thickness, 3 inches in diame- 

 ter and 7 inches high. 

 . No. 3, Split-leather cell 006 inches in thickness, 5 inches in diame- 

 ter and 7 inches high, fitted to a bottom of inch pine. 



