bination and circulation. Hence the continuance of the action there, and
the continuation of the current. It therefore appears quite as essential
that there should be an electrolyte in the circuit, in order that the
action may be transferred forward, in a _certain constant direction,_ as
that there should be an oxidizing or other body capable of acting directly
on the metal; and it also appears to be essential that these two should
merge into one, or that the principle directly active on the metal by
chemical action should be one of the _ions_ of the electrolyte used.
Whether the voltaic arrangement be excited by solution of acids, or
alkalies, or sulphurets, or by fused substances (476.), this principle has
always hitherto, as far as I am aware, been an _anion_ (943.); and I
anticipate, from a consideration of the principles of electric action, that
it must of necessity be one of that class of bodies.

925. If the action of the sulphuric acid used in the voltaic circuit be
considered, it will be found incompetent to produce any sensible portion of
the electricity of the current by its combination with the oxide formed,
for this simple reason, it is deficient in a most essential condition: it
forms no part of an electrolyte, nor is it in relation with any other body
present in the solution which will permit of the mutual transfer of the
particles and the consequent transfer of the electricity. It is true, that
as the plane at which the acid is dissolving the oxide of zinc formed by
the action of the water, is in contact with the metal zinc, there seems no
difficulty in considering how the oxide there could communicate an
electrical state, proportionate to its own chemical action on the acid, to
the metal, which is a conductor without decomposition. But on the side of
the acid there is no substance to complete the circuit: the water, as
water, cannot conduct it, or at least only so small a proportion that it is
merely an incidental and almost inappreciable effect (970.); and it cannot
conduct it as an electrolyte, because an electrolyte conducts in
consequence of the _mutual_ relation and action of its particles; and
neither of the elements of the water, nor even the water itself, as far as
we can perceive, are _ions_ with respect to the sulphuric acid (848.)[A].

[A] It will be seen that I here agree with Sir Humphry Davy, who has
experimentally supported the opinion that acids and alkalies in
combining do not prod