If one convert a pound of ice at freezing point under normal atmospheric pressure into a pound of water of the same temperature by means of heat there vanishes a quantity of heat which could heat the same pound of water from 0 deg. centigrade to 79 deg. centigrade, or seventy-nine pounds of water one degree centigrade. If one heat this pound of water to boiling point, that is, to one hundred degrees centigrade and change it into steam of the heat of one hundred degrees centigrade there vanishes up to the time when the last of the water is changed into steam a seven fold greater quantity of heat, capable of raising the temperature of 537.2 pounds of water one degree. This dissipated heat is called latent. It is transformed, by cooling the steam, into water again, and the water into ice, so the same mass of heat which was formerly latent, is again set free, that is, as heat capable of being felt and measured. This setting free of heat by the condensation of steam and the freezing of water is the reason that steam if it is cooled off at 100 deg. transforms itself little by little into water, and 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.