IO4 Inquiry concerning the Nature of Heat, 



tween motion and a state of rest, so there can be no 

 relation between any degree of heat and absolute cold, 

 or a total privation of heat ; hence it is evident that 

 all attempts to determine the place of absolute cold, on 

 the scale of a thermometer, must be nugatory. 



It seems probable that motion is an essential quality 

 of matter, and that rest is nowhere to be found in the 

 universe. 



We well know that all those bodies which fall under 

 the cognizance of our senses are in motion ; and there 

 are many appearances which seem to indicate that the 

 constituent particles of all bodies are also impressed 

 with continual motions among themselves, and that it is 

 these motions (which are capable of augmentation and 

 diminution) that constitute the heat or temperature of 

 sensible bodies. 



The only effects of which we have any idea result- 

 ing from the action of one body on another are a change 

 of velocity or a change of direction, or both. We per- 

 ceive, it is true, that certain bodies have a power of 

 affecting certain other bodies at a distance; but this is 

 no proof that the effects produced are essentially differ- 

 ent from those which result from collision ; for, if an 

 elastic body be interposed between the two bodies, their 

 actions on each other may be communicated through 

 such intermediate elastic body, which, when the action 

 is at an end, and the effects resulting from it on the 

 two bodies have taken place, will be in the same state 

 precisely in which it was before the action began. 



If a bell or any other solid body, perfectly elastic, 

 placed in a perfectly elastic fluid, and surrounded by 

 other perfectly elastic solid bodies, were struck and 

 made to vibrate, its vibrations would by degrees be 



