266 
THEORY OF GALVANISM. 
Comparison 
of this with 
Cuthhertson’s 
theory. 
Objections, 
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 electricity 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 
plat's. Here, being, in some degree, accumulated, it is extri- 
cated in larger quantity, 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 zinc end of the pile in any assignable de- 
gree of force. 
The hypothesis of Dr. Bostock agrees, then, with that ad- 
vanced by Mr. Cuthbertscn, 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 term- 
ing, in general language, “ a loss of metallic property,” to be 
the process of oxidation ; and it adds, also, the important and 
necessary explanation cf the transmission of hydrogen across 
the fluid of the cells, and the appearance of hydrogen gas at 
the surface of the copper plates. In these respects, it is cer- 
tainly more adequate to account for the phenomena. It is 
chiefly objectionable, inasmuch as the data on which it is 
founded are altogether gratuitous. For what other evidence 
have we, than those very phenomena of the pile, which the 
theory is brought to explain, that electricity is evolved by the 
oxidation of me,tals, or that hydrogen is capable of forming, 
with the electric fluid, a combination so little energetic as to 
be destroyed by the mere approach of a conducting body ? The 
, theory is imperfect, also, in taking no account of that change 
in the relative quantity of electricity in two metallic plates, 
which, according to the. observations of Bennett and Volta, 
must necessarily happen when their surfaces are put in apposi- 
tion - *. 
* Berzelius seems to have proved, by a most acute and ingenious 
experiment, in his “ Electro- chemical Principles,” published in our 
The 
