hile it is latent?

The mechanical theory of heat according to which the heat of a body at
a certain temperature is dependent upon the greater or less vibration
of the smallest physical parts (molecules) a vibration which can,
under certain conditions, be transformed into some other form of
motion, shows the whole thing completely, that the latent heat has
performed work, has been expended in work. By the melting of the ice
the close connection of the separate particles is broken asunder and
changed into a loose relationship; by the conversion of water into
steam at boiling point a condition is entered where the separate
molecules exercise no noticeable influence upon each other, and under
the influence of heat fly from one another in all directions. It is
now evident that the separate molecules of a body in the gaseous state
are endowed with much greater energy than in the fluid state, and in
the fluid state than in the solid. Latent heat is therefore not
dissipated, it is merely transformed and has taken on the form of
molecular elasticity.

As soon as conditions are at an end under which the molecules can
exercise this relative freedom with regard to each other as soon
namely as the temperature falls below one hundred degrees to zero,
this elasticity becomes released and the molecules come together with
the same force with which they formerly flew apart, but only to
appear again as heat, as exactly the same quantity of heat as was
latent before. This explanation is of course a hypothesis, as is the
whole mechanical theory of heat, in so far as no one has yet seen a
molecule, much less a molecule in motion. Like all recent theories,
this hypothesis is full of flaws but it can at least offer an
explanation which does not conflict with the uncreatability and
indestructibility of motion and it is able to give an account of the
whereabouts of the heat in the transformation. Latent heat is
therefore by no means an obstacle in the way of the mechanical theory
of heat. On the contrary this theory for the first time provides a
rational explanation of the subject and an obstacle arises from the
fact in particular that the physicists make use of the old and
ineffective expression "latent heat" to signify the heat transformed
into some other shape by molecular energy.

The static conditions of the solid, liquid and gaseous states
therefore represent mechanical work in so far as mechanical work is a
measure of heat. Thus the