- 488 Inquiry concerning the Soiirce of 



produced by giving the water free access to these surfaces, 

 I now made the 



Experiment No. 4. 



The piston which closed the end of the bore of the 

 cylinder being removed, the blunt borer and the cylinder 

 were once more put together ; and the box being fixed 

 in its place, and filled with water, the machinery was 

 again put in motion. 



There was nothing in the result of this experiment 

 that renders it necessary for me to be very particular in 

 my account of it. Heat was generated as in the former 

 experiments, and, to all appearance, quite as rapidly ; 

 and I have no doubt but the water in the box would have 

 been brought to boil, had the experiment been continued 

 as long as the last. The only circumstance that sur- 

 prised me was, to find how little difference was occasioned 

 in the noise made by the borer in rubbing against the 

 bottom of the bore of the cylinder, by filling the bore 

 with water. This noise, which was very grating to the 

 ear, and sometimes almost insupportable, was, as nearly 

 as I could judge of it, quite as loud and as disagreeable 

 when the surfaces rubbed together were wet with water 

 as when they were in contact with air. 



By meditating on the results of all these experiments, 

 we are naturally brought to that great question which has 

 so often been the subject of speculation among philoso- 

 phers ; namely, 



What is Heat ? Is there any such thing as an igneous 

 fluid? Is there anything that can with propriety be 

 called caloric? 



We have seen that a very considerable quantity of 

 Heat may be excited in the friction of two metallic sur- 



