on the Subject of Heat. 213 



Since the apparatus affords heat continuously, and 

 always to the same amount, we can melt in this way as 

 much ice as we please. 



But whence comes this heat ? This is the contested 

 point, to determine which was the real aim of the ex- 

 periment. 



It is certain that it comes neither from the decom- 

 position cf the water nor from the decomposition of the 

 air Various experiments on this point, which I have 

 described at length in my memoir in the Philosophical 

 Transactions, are more than sufficient to establish this 

 fact beyond doubt. 



Just as little does it come from a change in the ca- 

 pacity for heat brought about by friction in the metal 

 of which the hemispheres are composed. This is shown, 

 first, by the continuance and uniformity of the pro- 

 duction of the heat ; and, secondly, by an experiment 

 bearing directly on this point, by which I am con- 

 vinced that not the slightest change had taken place in 

 the capacity of the metal for heat. 



Just as little does it come from the rods which 

 are attached to the hemispheres, for these rods were 

 always warm, the hemispheres communicating heat to 

 them. 



Much less could this heat come from the air or the 

 water immediately surrounding the hemispheres, for the 

 apparatus communicated heat to both these fluids with- 

 out cessation. 



Whence, then, came this heat? and what is heat 

 actually? 



I must confess that it has always been impossible for 

 me to explain the results of such experiments except by 

 taking refuge in the very old doctrine which rests on 



