HKB
that a mass of water at freezing point is but slowly transformed into ice. These are the facts. The question is what becomes of the heat while 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 solid crust of the earth, like the water of the ocean, represents in its present form a certain quantity of heat set free which implies the same quantity of mechanical force. By the passing of the vaporous state which was the original form of the earth into the fluid state and later into a condition, for the most part solid, a certain quantity of molecular energy was set free in space, the difficulty of which Herr Duehring whispers does not therefore exist. We are frequently brought to a stop in our cosmic observations by lack of knowledge, but nowhere by insuperable theoretical difficulties. The bridge from statics to dynamics is therefore the push from the outside caused by the cooling or heating occasioned by other bodies which influence certain objects in equipoise. The further we explore Herr Duehring's philosophy, the more impossible appear all his attempts to explain rotation from absence of rotation, or to discover the bridge by which that which is purely static, self-contained, can without disturbance come to be the dynamic, in motion.