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to the sum of the electromotive forces of the interjected links.
But if many discs of metal are laid upon each other, the electro
motive force of the two terminating plates is as great as if they
were laid directly upon each other.
§ 279. Volta himself proved his theory by the so-called
Voltaic pile, in which a disc of zinc, a disc of copper and a
piece of cloth moistened with acidulated water always in the
same order are laid one upon the other and finally the last disc
of copper is connected with the first disc of zinc by means of
a wire. The electricity furnished by this pile is called Voltaic
electricity. 439. By this voltaic pile really the electromotive
force is increased by means of that moistened piece of cloth,
which removes impeding effects and still keeps up conduction.
Besides, this moistened piece of cloth does not only conduct
electricity, it also produces it, and zinc as well as copper are
negatively electrified. Hence by the contact of the acid with
the zinc the electricity of the pile is strengthened, by that with
the copper (which originally shows positive electricity) it is
weakened. But as the negative electricity produced by the acid
in the zinc is somewhat stronger than the electricity caused in
the copper the effect on the whole will be strengthened.
§ 280. It was finally Dr. La Rive, who showed, that in the
voltaic pile it was not the contact between two metals that pro
duced electricity, but that it was a chemical action by which the
electrical equilibrium was disturbed. Especially chemical actions
between metals and liquids are very productive, the liquid show
ing the positive electrical and the metal the negative electrical
condition. An electrical current is produced by immersing a
plate of zinc and a plate of copper in dilute sulphuric acid (this
is called the simple voltaic element or couple). As long as the
metals are not in contact the couple is opera, when they are con
