COUNT RUMFORD 163 



of boiling water. But this extremely elastic heat would very naturally 

 as soon as left to itself, and especially during the operation just men- 

 tioned, resume that state of expansion and that capacity for heat which 

 is proper to it at a given temperature, so that the effect of the pressure 

 to which it has been subjected partly disappears again, just as a piece 

 of metal which has been hammered resumes its natural properties on 

 being annealed." 



In reply to these remarks, I will call to mind what follows. 



1st. The discovery which I made, that no considerable change had 

 taken place in the specific heat of the metallic dust produced by the 

 friction, led me in no way to the supposition that the heat excited in 

 the experiment could not come from the caloric set free. I only 

 found that the source of this heat was inexhaustible. To explain this 

 phenomenon, which has never yet been explained, is the point now in 

 question, and I do not see how it can be explained except by giving 

 up altogether the hypothesis adopted in regard to caloric. 



2d. If we actually suppose (and it is far from having been proved) 

 that the simple pressing together of a metal is sufficient to expel 

 the caloric contained in it ; still the explanation of such a natural phe- 

 nomenon would be advanced little or none ; for since the action of the 

 force which causes the pressure is continuous, the condensation of the 

 metal brought about by this force would in a short time reach its maxi- 

 mum ; and if really in this operation ever so much caloric had been 

 disengaged from the metal, still it would very soon disperse. The 

 rubbing surfaces, on the contrary, continue to give forth heat, and 

 that always to the same amount. 



3d. In regard to the objection made to the experiment which was 

 undertaken with a view of determining whether a change had taken 

 place in the capacity of the metallic dust for heat, this can very readily 

 be answered, and in such a way that nothing, it seems to me, can be 

 said against it. If the temperature of boiling water were really suffi- 

 cient to give to these small, forcibly condensed particles of metal the 

 quantity of heat necessary to bring them back to their original condi- 

 tion as far as their capacity for heat is concerned, then, as the water 

 by which the apparatus was surrounded finally began to boil, they 

 must, without doubt, have taken the necessary amount of heat from 

 this water. If, now, these particles of metal received finally from the 

 water the caloric which in the beginning they imparted to it, the ques- 



