appearance, from their number and minuteness; are easily
carried down by currents, and therefore not only present far greater
surface of contact with the liquid than larger bubbles would do, but are
retained a much longer time in mixture with it. But the bubbles at the
negative surface, though they constitute twice the volume of the gas at the
positive electrode, are nevertheless very inferior in number. They do not
rise so universally from every part of the surface, but seem to be evolved
at different parts; and though so much larger, they appear to cling to the
metal, separating with difficulty from it, and when separated, instantly
rising to the top of the liquid. If, therefore, oxygen and hydrogen had
equal solubility in, or powers of combining with, water under similar
circumstances, still under the present conditions the oxygen would be far
the most liable to solution; but when to these is added its well-known
power of forming a compound with water, it is no longer surprising that
such a compound should be produced in small quantities at the positive
electrode; and indeed the blenching power which some philosophers have
observed in a solution at this electrode, when chlorine and similar bodies
have been carefully excluded, is probably due to the formation there, in
this manner, of oxywater.

718. That more gas was collected from the wires than from the plates, I
attribute to the circumstance, that as equal quantities were evolved in
equal times, the bubbles at the wires having been more rapidly produced, in
relation to any part of the surface, must have been much larger; have been
therefore in contact with the fluid by a much smaller surface, and for a
much shorter time than those at the plates; hence less solution and a
greater amount collected.

719. There was also another effect produced, especially by the use of large
electrodes, which was both a consequence and a proof of the solution of
part of the gas evolved there. The collected gas, when examined, was found
to contain small portions of nitrogen. This I attribute to the presence of
air dissolved in the acid used for decomposition. It is a well-known fact,
that when bubbles of a gas but slightly soluble in water or solutions pass
through them, the portion of this gas which is dissolved displaces a
portion of that previously in union with the liquid: and so, in the
decompositions under consideration, as the oxygen dissolves, it displaces a
part of the air,