o strong a chemical attraction between oxygen and
metals, I suppose they are naturally in different states of electricity?

MRS. B.

Yes; it appears that all metals are united with the positive, and that
oxygen is the grand source of the negative electricity.

CAROLINE.

Does not then the acid act on the plates of copper, as well as on those
of zinc?

MRS. B.

No; for though copper has an affinity for oxygen, it is less strong than
that of zinc; and therefore the energy of the acid is only exerted upon
the zinc.

It will be best, I believe, in order to render the action of the Voltaic
battery more intelligible, to confine our attention at first to the
effect produced on two plates only. (PLATE VI. fig. 2.)

If a plate of zinc be placed opposite to one of copper, or any other
metal less attractive of oxygen, and the space between them (suppose of
half an inch in thickness), be filled with an acid or any fluid capable
of oxydating the zinc, the oxydated surface will have its capacity for
electricity diminished, so that a quantity of electricity will be
evolved from that surface. This electricity will be received by the
contiguous fluid, by which it will be transmitted to the opposite
metallic surface, the copper, which is not oxydated, and is therefore
disposed to receive it; so that the copper plate will thus become
positive, whilst the zinc plate will be in the negative state.

This evolution of electrical fluid however will be very limited; for as
these two plates admit of but very little accumulation of electricity,
and are supposed to have no communication with other bodies, the action
of the acid, and further developement of electricity, will be
immediately stopped.

EMILY.

This action, I suppose, can no more continue to go on, than that of a
common electrical machine, which is not allowed to communicate with
other bodies?

MRS. B.

Precisely; the common electrical machine, when excited by the friction
of the rubber, gives out both the positive and negative electricities.--
(PLATE VI. Fig. 3.) The positive, by the rotation of the glass cylinder,
is conveyed into the conductor, whilst the negative goes into the
rubber. But unless there is a communication made between the rubber and
the ground, but a very inconsiderable quantity of electricity can be
excited; for the rubber, like the plates of the battery, has too small a
capacity to admit of an accumulation of electricity. Unless therefore
the ele