omposition of
the same quantity of water there, and the oxidation of the same quantity of
zinc by it (924. 949.). The same result recurs in every other cell; the
electro-chemical equivalent of water must be decomposed in each, before the
current can pass through it; for the quantity of electricity passed and the
quantity of electrolyte decomposed, _must_ be the equivalents of each
other. The action in each cell, therefore, is not to increase the quantity
set in motion in any one cell, but to aid in urging forward that quantity,
the passing of which is consistent with the oxidation of its own zinc; and
in this way it exalts that peculiar property of the current which we
endeavour to express by the term _intensity_, without increasing the
_quantity_ beyond that which is proportionate to the quantity of zinc
oxidized in any single cell of the series.

991. To prove this, I arranged ten pairs of amalgamated zinc and platina
plates with dilute sulphuric acid in the form of a battery. On completing
the circuit, all the pairs acted and evolved gas at the surfaces of the
platina. This was collected and found to be alike in quantity for each
plate; and the quantity of hydrogen evolved at any one platina plate was in
the same proportion to the quantity of metal dissolved from any one zinc
plate, as was given in the experiment with a single pair (864. &c.). It was
therefore certain, that, just as much electricity and no more had passed
through the series of ten pair of plates as had passed through, or would
have been put into motion by, any single pair, notwithstanding that ten
times the quantity of zinc had been consumed.

992. This truth has been proved also long ago in another way, by the action
of the evolved current on a magnetic needle; the deflecting power of one
pair of plates in a battery being equal to the deflecting power of the
whole, provided the wires used be sufficiently large to carry the current
of the single pair freely; but the _cause_ of this equality of action could
not be understood whilst the definite action and evolution of electricity
(783. 869.) remained unknown.

993. The superior decomposing power of a battery over a single pair of
plates is rendered evident in two ways. Electrolytes held together by an
affinity so strong as to resist the action of the current from a single
pair, yield up their elements to the current excited by many pairs; and
that body which is decomposed by the action of one or of f