i8

Faraday's Researches

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.

66. 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 (65), 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 (113) relating to the amount of chemical action be
correct, this ought to be the case.

67. I have been the more anxious to assign the true value of
this experiment as a test of electro-chemical action, because I
shall have occasion to refer to it in cases of supposed chemical
action by magneto-electric and other electric currents (72, 82)
and elsewhere. But, independent of it, there cannot be now
a doubt that Dr. Wollaston was right in his general conclusion;
and that voltaic and common electricity have powers of chemical
decomposition, alike in their nature, and governed by the same
law of arrangement.

68. iv. Physiological effects.—The power of the common
electric current to shock and convulse the animal system, and
when weak to affect the tongue and the eyes, maybe considered
as the same with the similar power of voltaic electricity, account
being taken of the intensity of the one electricity and duration
qf the other. When a wet thread was interposed in the course
of the current of common electricity from the battery (27)
charged by eight or ten x revolutions of the machine in good

1 Or even from thirty to forty.s Journal, 4to, vol. i. pp. 241, 299, 349.