Excitement of Galvanic Electricity. 301 
zine has received, all. the electricity,, which 
their mutual powers require, if any menstruum 
be presented, which is capable of effecting a 
change in the metallic property of the two 
bodies, a change in their electrical states must, 
at the same time, happen. Bat as tlie altera- 
tion of metallic property is only superficial, 
the change of electrical condition will, also, 
be only at the surface; and the interior; part 
of the zine plate, retaining its. property of 
resistance, the electric fluid, evolved at its 
surface, will necessarily be propelled forwards, 
through the menstruum, to the next copper 
plate of the series. This, however, can only 
happen in a progressive manner, because the 
fluid is but an imperfect conductor, a condi- 
tion indispensible to the maintenance of any 
Galvanic intensity. 
* The explanation of Mr. Cuthbertson... is 
unquestionably a valuable supplement to the 
theory of Volta, in-as much as it takes into 
account the efficiency of chemical menstrua. 
These, consistently with his view, will evolve 
electricity the more. freely, in proportion as 
they destroy more rapidly the metallic pro- 
perty of the plates of zinc. The hypothesis, 
however, is defective, because it fails to 
account for some of the phenomena ;—why, 
for example, the action of the menstruum is 
