ecessary, as has been
supposed, that for the chemical decomposition of water, the action of the
two electricities, positive and negative, should be simultaneous."

[A] Annales de Chimie, tom, xxviii. tom. li. p. 73.

492. It is more than probable that many other views of electro-chemical
decomposition may have been published, and perhaps amongst them some which,
differing from those above, might, even in my own opinion, were I
acquainted with them, obviate the necessity for the publication of my
views. If such be the case, I have to regret my ignorance of them, and
apologize to the authors.

* * * * *

493. That electro-chemical decomposition does not depend upon any direct
attraction and repulsion of the poles (meaning thereby the metallic
terminations either of the voltaic battery, or ordinary electrical machine
arrangements (312.),) upon the elements in contact with or near to them,
appeared very evident from the experiments made in air (462, 465, &c.),
when the substances evolved did not collect about any poles, but, in
obedience to the direction of the current, were evolved, and I would say
ejected, at the extremities of the decomposing substance. But
notwithstanding the extreme dissimilarity in the character of air and
metals, and the almost total difference existing between them as to their
mode of conducting electricity, and becoming charged with it, it might
perhaps still be contended, although quite hypothetically, that the
bounding portions of air were now the surfaces or places of attraction, as
the metals had been supposed to be before. In illustration of this and
other points, I endeavoured to devise an arrangement by which I could
decompose a body against a surface of water, as well as against air or
metal, and succeeded in doing so unexceptionably in the following manner.
As the experiment for very natural reasons requires many precautions, to be
successful, and will be referred to hereafter in illustration of the views
I shall venture to give, I must describe it minutely.

494. A glass basin (fig. 52.), four inches in diameter and four inches
deep, had a division of mica _a_, fixed across the upper part so as to
descend one inch and a half below the edge, and be perfectly water-tight at
the sides: a plate of platina _b_, three inches wide, was put into the
basin on one side of the division _a_, and retained there by a glass block
below, so that any gas produced by it