CALORIC A SELF ACTIVE PRINCIPLE. 109 



Why then does caloric repel its own particles, 

 and attract those of ponderable matter, with forces 

 that vary inversely as the squares of the distance ? 

 To this primary and leading question I answer, 

 that caloric repels its own particles because they 

 are of the same nature, and attracts those of pon- 

 derable matter because they are of a totally 

 different nature ; that in every variety of state 

 caloric is an essentially active principle, and 

 incomparably more refined than any description 

 of ponderable matter, even when expanded into 

 the subtile form of light ; for it permeates the 

 most dense and opaque bodies, which are wholly 

 impervious to light. And that the forces of 

 caloric diminish in proportion as the squares of 

 the distance augment, is obvious from the fact, 

 that all aethereal emanations are necessarily dif- 

 fused in the same ratio, on radiating from any 

 given centre.* 



That caloric is a self-active principle has been 

 already shewn by its power of moving itself, and 

 of giving motion to other bodies, the activity of 

 which is augmented by every addition, and dimi- 

 nished by every abstraction of heat; proving, 



* It would therefore seem to follow, that there must be a limit 

 to the diffusion of caloric; that it is not infinitely subtile and 

 divisible ; but that there must be a definite number 6f particles in 

 any given quantity of it. It is only by its extension throughout 

 illimitable space that it can be regarded as infinite ; for we shall 

 find that, while it governs all the operations of the material 

 universe, it is itself governed by invariable and necessarily fixed 

 laws. Yet there is reason to believe that its great activity depends 

 on its extreme subtilty and refinement. 



