poles, or
rather points, have no mutual decomposing dependence, may be shown by
substituting a wire, or the finger, for one of them, a change which does
not at all interfere with the other, though it stops all action at the
changed pole. This fact may be observed by turning the machine for some
time; for though bubbles will rise from the point left unaltered, in
quantity sufficient to cover entirely the wire used for the other
communication, if they could be applied to it, yet not a single bubble will
appear on that wire.

[A] Nicholson's Journal, 4to. vol. I. pp. 311, 299. 349.

329. When electro-chemical decomposition takes place, there is great reason
to believe that the _quantity_ of matter decomposed is not proportionate to
the intensity, but to the quantity of electricity passed (320.). Of this I
shall be able to offer some proofs in a future part of this paper (375.
377.). But in the experiment under consideration, this is not the case. If,
with a constant pair of points, the electricity be passed from the machine
in sparks, a certain proportion of gas is evolved; but if the sparks be
rendered shorter, less gas is evolved; and if no sparks be passed, there is
scarcely a sensible portion of gases set free. On substituting solution of
sulphate of soda for water, scarcely a sensible quantity of gas could be
procured even with powerful sparks, and nearly none with the mere current;
yet the quantity of electricity in a given time was the same in all these
cases.

330. I do not intend to deny that with such an apparatus common electricity
can decompose water in a manner analogous to that of the voltaic pile; I
believe at present that it can. But when what I consider the true effect
only was obtained, the quantity of gas given off was so small that I could
not ascertain whether it was, as it ought to be, oxygen at one wire and
hydrogen at the other. Of the two streams one seemed more copious than the
other, and on turning the apparatus round, still the same side in relation
to the machine; gave the largest stream. On substituting solution of
sulphate of soda for pure water (329.), these minute streams were still
observed. But the quantities were so small, that on working the machine for
half an hour I could not obtain at either pole a bubble of gas larger than
a small grain of sand. If the conclusion which I have drawn (377.) relating
to the amount of chemical action be correct, this ought to be the case.

331. I h