260 
THEORY OF GALVANISM. 
sition of different kinds of metals. The best way of exhibiting 
this fact is to take two discs or plates, the one of copper, the 
other of zinc 5 to apply them to each other, for an instant, by 
their flat faces, and afterwards, separating them dexterously, to 
bring them into contact with the electrometer. The instru- 
ment indicates, by (he divergence of its gold leaves, what kind 
of electricity each of the plates has acquired j which proves to 
be positive in the zinc plate, and negative in the copper one. 
Voltasupposed To explain the phenomena, in the experiment which has 
to^ie set in been just described, it has been supposed by Volta, that, during 
motion by the ^e contact of the plates, a movement of the electric fluid takes 
place from one plate to the other and that the zinc acquires 
just as much as the copper has lost. The metals, therefore, he 
denominates motors of electricity, and the process itself electro- 
motion, the latter of which terms has been adopted by Mr. 
Davy. From subsequent experiments, Volta ascertained that 
the metals stand to each other, in this respect, in the following 
order ; it being understood that the first gives up electricity to 
the second j the second to the third 5 the third to the fourth 5 
and so on : 
Silver, 
Copper, 
Iron, 
Tin, 
Lead, 
Zinc. 
His theory It is to this transference of electricity, that Volta ascribes the 
of^thepde^re w ^°^ e °f the phenomena, exhibited by Galvanic combinations, 
electrometers, According to his view, the interposed fluids act entirely by their 
mere^on- UldS P ower of conducting electricity, and not at all by any chemical 
doctors. property. The effect of a series of Galvanic plates, or of a 
Galvanic pile, he believes to be nothing more than the sum 
total of the effects of several similar couples or pairs. Why the 
evolved electricity is determined to one end of the series, and 
exists there in its greatest force, I shall attempt to explain by 
the following illustrations. 
Illustration. if a plate of zinc be brought into contact, on both sides, with 
a plate 
