Atmological Theories.—Hypotheses of the relations of heat and air almost necessarily involve a reference to the forces by which the composition of bodies is produced, and thus cannot properly be treated of, till we have surveyed the condition of chemical knowledge. But we may say a few words on one such hypothesis; I mean the hypothesis on the subject of the atmological laws of heat, proposed by Laplace, in the twelfth Book of the Mécanique Céléste, and published in 1823. [185] It will be recollected that the main laws of phenomena for which we have to account, by means of such an hypothesis, are the following:—
(1.) The law of Boyle and Mariotte, that the elasticity of an air varies as its density. See Chap. iii., [Sect. 1] of this Book.
(2.) The Law of Gay-Lussac and Dalton, that all airs expand equally by heat. See Chap. ii. [Sect. 1].
(3.) The production of heat by sudden compression. See Chap. ii. [Sect. 2].
(4.) Dalton’s principle of the mechanical mixture of airs. See Chap. iii. [Sect. 3].
(5.) The Law of expansion of solids and fluids by heat. See Chap. ii. [Sect. 1].
(6.) Changes of consistence by heat, and the doctrine of latent heat. See Chap. ii. [Sect. 3].
(7.) The Law of the expansive force of steam. See Chap. iii. [Sect. 4].
Besides these, there are laws of which it is doubtful whether they are or are not included in the preceding, as the low temperature of the air in the higher parts of the atmosphere. (See Chap. iii. [Sect. 5].)
Laplace’s hypothesis[71] is this:—that bodies consist of particles, each of which gathers round it, by its attraction, a quantity of caloric: that the particles of the bodies attract each other, besides attracting the caloric, and that the particles of the caloric repel each other.