304 On. the Theories of the. 
the union of the evolved electricity. with 
nascent hydrogen, and by the attraction of 
the next copper plate for electricity, At the 
surface of this plate, the hydrogen and elec- 
tricity are supposed to separate ; the hydrogen 
to be disengaged in the state of gas, and the 
electricity to be conveyed onwards to the next 
zinc plate. Here, being in some degree 
accumulated, it is extricated in larger quan- 
tity, and in a more concentrated form, than 
before. By a repetition of the same train of 
operations, the electric fluid continues to 
accumulate in each successive pair; until, by 
a sufficient extension of the arrangement, it 
may be made to exist at the zine end of the 
pile in any assignable degree of force. 
.. The hypothesis of Dr. Bostock agrees, then, 
with that advanced by Mr. Cuthbertson, in 
pointing out the more oxidable metal as the 
source of the electricity, which is put in action 
by Galvanic arrangements. It goes farther, 
however, and defines that change, which Mr. 
Cuthbertson was satisfied with terming, in 
general language, “ a loss of metallic pro- 
perty,” to be the process of oxidation ; and it 
adds also the important and necessary expla- 
nation of the transmission of hydrogen across 
the fluid of the cells, and the appearance of 
hydrogen gas at pe surface of the copper 
