240 OUTLINES OF NATURAL PHILOSOPHY. 



This holds both of solids and of fluids. A nail can 

 be made red hot by hammering, and fire may be 

 produced by the friction of one piece of timber 

 against another. COUNT HUMFOIID made water boil 

 by the boring of a cannon. 



The condensation of air produces heat; tinder may 

 be lighted, and gunpowder set fire to, if air be sud- 

 denly compressed by the stroke of a piston. 



335. The greater part of the preceding facts 

 may be explained on the hypothesis, that heat or 

 caloric is an elastic fluid sui generis, the particles 

 of which repel one another, but are strongly at- 

 tracted, though in different degrees, by the parti- 

 cles of all other bodies. 



1. The introduction of this fluid into bodies, must in- 

 crease their volume, and an equilibrium in the fluid 

 will take place over a certain space, when the attrac- 

 tion of the bodies within that space, for the caloric 

 contained in it, is able to balance the repulsion of the 

 particles of the caloric for one another, and this 

 will happen when the caloric is distributed among 

 the bodies, in proportion to the forces with which 

 they attract it. Hence there may be an equilibrium 

 in the caloric of bodies, or a sameness of tempera^ 

 ture, though the quantities of caloric be very dif- 

 ferent ; and from this proceeds the different capaci- 

 ties of bodies for heat, and the conversion of sensi- 

 ble into latent heat, or the contrary, when those ca- 

 pacities are changed. 



2. Caloric 



