CALORIC. The name given in chymistry to that agent which produces the phenomena of heat and combustion. It is hypothetically regarded as a subtile fluid, the particles of which repel one another, and are attracted by all other substances. It is ponderable, and, by its distribution in various proportions, among the particles of matter, gives use to three gene ral forms of gas, liquids, and solids. The par ticles of water, by losing caloric, have their co hesion so much increu..efl, that they assume the solid form of ice ; by adding caloric they again become fluid; and by a still further ad dition, they are converted into vapour. Calo ric exists in different states—free or uncom bined, and in a state of combination. In the former condition, it creates the sensation of heat, and produces expansion in other bodies. The power which it has of exciting the sensa tion of heat, and occasioning expansion, is un derstood by the expression of its temperature. This is supposed to vary with the given quan tity of free caloric in a given quantity of mat ter ; a high temperature being ascribed to the presence of a large quantity of freecaloric, and a low temperature to that of a small quantity.
We are ignorant, however, of the extremities of temperature, and may compare it to a chain, of which a few of the middle links only are exposed to our observation, while its extremi ties are concealed from our view. With re gard to combined caloric, it has been shown, that solids, during liquefaction, imbibe a quan tity of caloric, which ceases to be obvious both to our senses and the thermometer. The same is also true of solids and liquids in their conversion into vapours and gases ; a portion of caloric, which is essential to the elasticity of the product, ceases to become apparent When ever this effect takes place, cold is said to be produced; by which we are only to under stand the passage of caloric from a free to a latent form. The sources of caloric are six, viz the sun's rays, combustion, percussion, friction, the mixture of different substances, and electricity.