1% Examination of the received Do&rines 



(A) Heat is diffufed through all the bodies in nature} 

 whether folids, liquids, or aeriform fluids. 



(B) Heat tends to an equilibrium ; fo that, when by any 

 means it is accumulated in particular fubftances, a portion is 

 quickly given off to the furrounding bodies to bring the whole 

 to one common temperature. On the other hand, where 

 bodies have been deprived of a portion of it, heat is given off 

 to them by, or heat panes to them from, the furrounding 

 bodies, to reftore the equilibrium. 



(C) Solids, by the addition of heat, affume the form of 

 liquids, and liquids the aeriform ftate. On the other hand, 

 gafes, by an abftra&ion of heat, become liquids; and liquids. 

 folids. 



(D) The dimenfions of bodies are enlarged when heat is 

 poured into them, and vice verfa. 



The laws we have enumerated are general, and the objec- 

 tions that may be ftated again ft the truth of any of them fo 

 few, and fo eafily obviated, that they cannot affec~f. any in- 

 ference drawn from them. The apparent exceptions relate 

 chiefly to the change of volume in fome particular fubftances 

 when paffing from the liquid to the folid form, or the con- 

 trary. Water, for inftance, in paffing into the ftate of ice, 

 aflumes a larger volume, though heat is then paffing out of 

 it. The fubftance, however, is only apparently enlarged. 

 In freezing, the water afTumes a cryftalline form ; the crys- 

 tals, (hooting in every direction, crowd againft, and, as it 

 were, joftle each other, caufing vacuities, which conftitute 

 no real part of the matter. We may compare this pheno- 

 menon to what takes place in a bundle of chips of wood, 

 which will always, however clofely packed, occupy an ap- 

 parently larger fpace than the fame weight of ligneous matter 

 as arranged by nature in the tree. Another apparent excep- 

 tion may be noticed in clay, which diminiflies the more in 

 bulk the greater the quantity of heat poured into it : but here 

 there is a milnomer — it is not clay, but a mixture of clay and 

 water that is diminifhed in bulk. The water is driven off; 

 and, where there is a diminution of matter, a reduction of 

 volume rouft follow. Clay is therefore not au exception to 



the 



