THE COPLEY MEDALIST OF 1871 461 



dowment, comes out in an instructive manner. With- 

 drawn from mechanical appliances, Mayer fell back upon 

 reflection, selecting with marvellous sagacity, from exist- 

 ing physical data, the single result on which could be 

 founded a calculation of the mechanical equivalent of 

 heat. In the midst of mechanical appliances, Joule re- 

 sorted to experiment, and laid the broad and firm founda- 

 tion which has secured for the mechanical theory the ac- 

 ceptance it now enjoys. A great portion of Joule's time 

 was occupied in actual manipulation; freed from this, 

 Mayer had time to follow the theory into its most ab- 

 struse and impressive applications. With their places re- 

 versed, however, Joule might have become Mayer, and 

 Mayer might have become Joule. 



It does not lie within the scope of these brief articles 

 to enter upon the developments of the Dynamical Theory 

 accomplished since Joule and Mayer executed their mem- 

 orable labors. 



