1 24 Inquiry concerning the Nature of Heat, 



can be of no use in explaining the phenomena in ques- 

 tion. 



The results of the two last mentioned experiments 

 appear to me to be very important ; and I do not see 

 how they can be reconciled with the opinions of modern 

 chemists respecting the nature of heat. 



In order to simplify our speculations on this ab- 

 struse subject, we have hitherto supposed that difference 

 of temperature depends solely on the difference of the 

 times of the vibrations of the component particles of 

 bodies. It is possible, however, and even probable, 

 that it depends principally on the 'velocities of those 

 particles ; for it is easy to perceive that, the more rapid 

 the motions of those particles are, the greater their elon- 

 gations must be in their vibrations, and the more, of 

 course, will the volume of the body they compose be 

 expanded. 



It is well known that the pulsations occasioned in an 

 elastic fluid by the vibrations of an elastic solid body 

 proceed from that body in all directions, and that these 

 pulsations are everywhere (that is to say, at all distances 

 from the body) isochronous with the vibrations of the 

 solid body ; it is known, also, that the mean velocity of 

 any individual particle of the fluid is less in proportion 

 as the distance of the particle is greater from the centre 

 from which these pulsations proceed. 



In the case of the pulsations occasioned in the air by 

 the vibrations of sonorous bodies, those pulsations are 

 everywhere isochronous with the vibrations of the sono- 

 rous body, and the time, or frequency, of these pulsa- 

 tions, determines the note ; but it is the velocity of the 

 particles of the air, or the breadth of the wave, on 

 which the force or strength of the sound depends ; and 



