OTi THE NATUItE OF HEAt. 



Q59 



tions, which we have supposed to constitute heat; and to 

 show in what respect they differ from other vibrations. 



The important and manifest difference between these ?i- Difference be- 

 brations, of sound, for example, and of heat, is, that in ^j^^^j^^j ^f 

 the former the mass, in the latter, the particles only of that heat and 

 mass, vibrate; and this distinction is sufficient to explain the *°"" 

 necessary and consequent difference in the laws observed by 

 these vibrations. The facility with which ihe mass of any 

 body vibrates will be proportionate to the elasticity of the 

 body; but it is plain, that the vibration of the particles of 

 the fuass will obey laws as different as the vibrations them- 

 selves are different: accordingly, who, after this considera- 

 tion, vvould expect thai the elasticity of any body should 

 regulate the vibration of its particles only? It is argued 

 indeed, that the vibration of the mass of any body must 

 ultimately be referred to tht condition of its particles; this 

 I readily admit: yet it proves nothing; it does not prove 

 that the converse of this is true; namely, that the vibration 

 of the particles must be determined by the condition of the 

 ma'os. 



Perhaps it was the want of considering^ the necessary dif- Other objec* 

 ference between the vibrations of heat and of sound, that ^'°"^* 

 has led to some other objections to this theory. It has been 

 said, that no body could communicate heat to another, (if 

 heat were vibration), unless the second made a sort of con- 

 cord with the first. Another objection is still more futile; 

 the vibrations, if such constituted heat, would, it is said, 

 ** gradually relax and die away," 



Sources of Caloric, 



For the same reason, that this part of the subject wae Sources of 

 tiealed with brevity in the former part of this discussion, 1 ^^^'• 

 niiy be equally concise in this place. The intimate connec- 

 tioi between motion, friction, percussion, &:c. and heat, 

 has lately been so much attended to, and so satisfactorily 

 explained by the theory of vibration, that nothing scarcely 

 rennins to be added on this point. 



Ihe light and heat produced by the transition of the elec- 

 tric fluid from one body to another is extremely" analogous 

 to tie sound produced by the motion of air through tubes. 



S 2 If 



