which power, whatever be its cause, or manner of operation, we
name Attraction.

Thus the particles of all bodies may be considered as subjected to the
action of two opposite powers, the one repulsive, the other attractive,
between which they remain in equilibrio. So long as the attractive force
remains stronger, the body must continue in a state of solidity; but if,
on the contrary, heat has so far removed these particles from each
other, as to place them beyond the sphere of attraction, they lose the
adhesion they before had with each other, and the body ceases to be
solid.

Water gives us a regular and constant example of these facts; whilst
below Zero[2] of the French thermometer, or 32 deg. of Fahrenheit, it
remains solid, and is called ice. Above that degree of temperature, its
particles being no longer held together by reciprocal attraction, it
becomes liquid; and, when we raise its temperature above 80 deg., (212
deg.) its particles, giving way to the repulsion caused by the heat,
assume the state of vapour or gas, and the water is changed into an
aeriform fluid.

The same may be affirmed of all bodies in nature: They are either solid
or liquid, or in the state of elastic aeriform vapour, according to the
proportion which takes place between the attractive force inherent in
their particles, and the repulsive power of the heat acting upon these;
or, what amounts to the same thing, in proportion to the degree of heat
to which they are exposed.

It is difficult to comprehend these phenomena, without admitting them as
the effects of a real and material substance, or very subtile fluid,
which, insinuating itself between the particles of bodies, separates
them from each other; and, even allowing the existence of this fluid to
be hypothetical, we shall see in the sequel, that it explains the
phenomena of nature in a very satisfactory manner.

This substance, whatever it is, being the cause of heat, or, in other
words, the sensation which we call _warmth_ being caused by the
accumulation of this substance, we cannot, in strict language,
distinguish it by the term _heat_; because the same name would then very
improperly express both cause and effect. For this reason, in the memoir
which I published in 1777[3], I gave it the names of _igneous fluid_ and
_matter of heat_. And, since that time, in the work[4] published by Mr
de Morveau, Mr Berthollet, Mr de Fourcroy, and myself, upon the
reformation of chemical nomen