and the Mode of its Communication. 105 



communicated, by means of the undulations or pulsa- 

 tions they would occasion in the elastic fluid medium, 

 to the other surrounding solid and elastic bodies. If 

 these surrounding bodies should happen to be already 

 vibrating, and with the same velocity as that with which 

 the bell is made to vibrate by the blow, the undulations 

 in the elastic fluid occasioned by the bell would neither 

 increase nor diminish the velocity or frequency of the 

 vibrations of the surrounding bodies ; neither would 

 the undulations caused by the vibrations of these bodies 

 tend to accelerate or to retard the vibrations of the 

 bell. But if the vibrations of the bell were more fre- 

 quent than those of the surrounding bodies, the undu- 

 lations it would occasion in the elastic fluid would tend 

 to accelerate the vibrations of the surrounding bodies ; 

 on the other hand, the undulations occasioned by the 

 slower vibrations of the surrounding bodies would re- 

 tard the vibrations of the bell, and the bell and the 

 surrounding bodies would continue to affect each other 

 until, by the vibrations of the latter being gradually 

 increased and those of the former diminished, in con- 

 sequence of their actions on each other, they would all 

 be reduced to the same tone. 



Supposing now that heat be nothing more than the 

 motions of the constituent particles of bodies among 

 themselves (an hypothesis of ancient date, and which 

 always appeared to me to be very probable), if for the 

 bell we substitute a hot body, the cooling of it will be 

 attended by a series of actions and reactions exactly 

 similar to those just described. 



The rapid undulations occasioned in the surrounding 

 ethereal fluid, by the swift vibrations of the hot body, 

 will act as calorific rays on the neighbouring colder solid 



