Joule. 345 



particles of bodies move, from the other we learn the 

 force and relation of their movements in those great phe- 

 nomena, heat, electricity, and mechanical force. 



It is of course impossible to deny great honour to 

 many men who have laboured on heat. We have great 

 admiration for the work of Dulong and Petit, great illus- 

 trators of atomic action. We may delight in the specu- 

 lative ideas of Clausius, Helmholtz, Clerk Maxwell, and Sir 

 William Thomson, but we must remember that these men 

 represent another department of atomic study. 



They take the Daltonian atom as granted. They take 

 it also as Joule, Dalton's pupil, made it a measure of 

 power, and they seek to go farther in studying its physical 

 properties. 1 We have here a follower worthy of the prophet. 

 Dalton's pupil has become the master of many learners. 



1 In speaking of Joule we do not attach weight to the able but merely 

 speculative papers of Meyer. The comparative value of these is fully dis- 

 cussed in the Thermodynamics of P. G. Tait. 



