Cleanness the Essential Condition       97
of exceedingly attenuated but solid strata, is considered as
proved by facts, some of which are quoted in the Giornale di
Fisica for 1824;^1 and though the theory requires that they
should assume this state at high temperatures, and though the
similar films of aqueous and other matter are dissipated by the
action of heat, still the facts are considered as justifying the
conclusion against all opposition of reasoning.
 350.	The power or force which makes combustible gas or
vapour abandon its elastic state in contact with a solid, that it
may cover the latter with a thin stratum of its own proper sub-
stance, is considered as being neither attraction nor affinity.
It is able also to extend liquids and solids in concrete laminae
over the surface of the acting solid body, and consists in a
repulsion, which is developed from the parts of the solid body
by the simple fact of attenuation, and is highest when the
attenuation is most complete.   The force has a progressive
development, and acts most powerfully, or at first, in the direc-
tion in which the dimensions of the attenuated mass decrease,
and then in the direction of the angles or corners which from
any cause may exist on the surface.   This force not only causes
spontaneous diffusion of gases and other substances over the
surface, but is considered as very elementary in its nature, and
competent to account for all the phenomena of capillarity,
chemical affinity, attraction of aggregation, rarefaction, ebulli-
tion, volatilisation, explosion, and other thermometric effects,
as well as inflammation, detonation, etc., etc.   It is considered
as a form of heat to which the term native caloric is given, and is
still further viewed as the principle of the two electricities and
the two magnetisms.
 351.	I have been the more anxious to give a correct abstract
of Dr. Fusinieri's view, both because I cannot form a distinct
idea of the power to which he refers the phenomena, and because
of my imperfect knowledge of the language in which the memoir
is written.   I would therefore beg to refer those who pursue the
subject to the memoir itself.
 352.	Not feeling, however, that the problem has yet been
solved, I venture to give the view which seems to me sufficient,
upon known principles, to account for the effect.
 353.	It may be observed of this action, that, with regard to
platina, it cannot be due to any peculiar, temporary condition,
either of an electric or of any other nature: the activity of plates
rendered either positive or negative by the pole, or cleaned with
^1 pp. 138, 371.
G