HEAT. 67 



ing the phenomena, and requires the assumption, that the 

 particles of a gas exercise an attraction for each other as do 

 the particles of a solid, though different in degree, perhaps in 

 kind. Whether this be so or not, there can be no doubt that 

 both gases and solids expand or contract according to the in- 

 verse contraction or expansion of other neighbouring bodies, 

 and so far resemble each other in their relations to heat and 

 cold. The extent to which such expansion or contraction 

 can be carried, seems to be limited only by the correlative 

 state of other bodies ; these again, by others, and so on, as 

 far as we may judge, throughout the universe. 



Adopting the explanation above given of the decomposi- 

 tion of water by heat, heat would have the same relation to 

 chemical affinity as it has to physical attraction ; its imme- 

 diate tendency is antagonistic to both, and it is only by a sec- 

 ondary action that chemical affinity is apparently promoted 

 by heat. This view would explain how heat may promote 

 changes of the equilibrium of chemical affinity among mixed 

 compound substances, by decomposing certain compounds and 

 separating elementary constituents whose affinity is greater, 

 when they are brought within the sphere of attraction for the 

 substance with which they are mixed, than for those with 

 which they were originally chemically united : thus an intense 

 heat being applied to a mixture of chlorine and the vapour 

 of water, occasions the production of muriatic acid, libera- 

 ting oxygen. 



Carrying out this view, it would appear that a sufficient 

 intensity of heat might yield indefinite powers of decomposi- 

 tion ; and there seems some probability of bodies now sup- 

 posed to be elementary, being decomposed or resolved into 

 further elements by the application of heat of sufficient inten- 

 sity ; or, reasoning conversely, it may fairly be anticipated 

 that bodies, which will not enter into combination at a certain 

 temperature, will enter into combination if their temperature 

 be lowered, and that thus new compounds may be formed by 



