Joule. 333 



the last, the particles have a motion round their own axes 

 with different velocities, the particles of elastic fluids 

 moving with the greatest quickness ; and that in ethereal 

 substances the particles move round their own axes 

 and separate from each other, penetrating in right lines 

 through space. Temperature may be conceived to depend 

 on the velocity of the vibrations, increase of capacity on 

 the motion being performed in greater space, etc.' 



This is evidently the work of Rumford and Bernouilli, 

 with additions after passing later through an original and 

 powerful mind. 



We may take the next step and go to Herapath. 1 At 

 p. 14, vol. i., he says :^- 



' Theory of gases. From these considerations it follows 

 that if a number of small bodies be enclosed in any hollow 

 body, and be continually impinging on one another and 

 on the sides of the inclosing body, and if the motions of 

 the bodies be conserved by an equivalent action in the 

 sides of the containing body, then will these small bodies 

 compose a medium, whose elastic force will be like that of 

 air and other gaseous bodies ; for if the bodies be exceed- 

 ingly small, the medium might, like any aeriform body, be 

 compressed into a very small space ; and yet if it had no 

 other tendency than what would arise from the internal 

 collision of its atoms, it would, if left to itself, extend to 

 the occupation of a space of almost indefinite greatness. 

 And its temperature remaining the same, its elasticity 

 would also be greater when occupying a less, and less 

 when occupying a greater space ; for in a compressed state 

 the number of atoms striking against a given portion of 

 the containing vessel must be augmented, and the space in 



1 Mathematical Physics, &c., by John Herapath, two vols. 8vo. 1847. 



