§26 On Heat 6 ? Cold produced by Mecbanical.&c.

The experiments and observations hithertorelated go principally to ascertain facts with-out any reference to the theory of them : Thishowever may be given in a few words, and i sthe same that is ascribed to Mr. Lambert byMessrs. Saussure and Pictet and by them adopt-ed. He conceives that a vacuum has its propercapacity for heat, the same as air, or any othersubstance; and that the capacity of a vacuumfor heat is less than that of an equal volumeit >f atmospherical air; also that the denser air is,the less is its capacity for heat : upon theseprinciples the phenomena are easily referableto that class of chemical facts where heat andcold are generated by the mixture of two dif-ferent bodies.—-If this theory be right, and I-think there is little doubt of it, we may hencebe led into a train of experiments, by which theabsolute capacity of a vacuum for heat may bedetermined; and likewise the capacities of thedifferent gases for heat, by a method whollynew:—but this must be left to future inves-tigation.