CH. xxxv. HEAT PRODUCED BY FRICTION. 351 



which kept in the most heat. It was in this way, and espe- 

 cially in using steam for warming and cooking, that he first 

 began to study the properties of heat, and he became much 

 interested in the different ways in which it may be produced. 



It happened one day, when he was boring a cannon in 

 one of the military workshops of Munich, that he noticed 

 with surprise the great heat produced by the grinding of the 

 borer against the gun. You can easily make a similar ex- 

 periment by boring a hole quickly with a gimlet in a piece 

 of hard wood, and on withdrawing the gimlet you will find 

 that it is hot enough to burn your hand. Rumford examined 

 carefully the gun and the chips which fell from it, and found 

 that they were both hotter than boiling water. 



This led him to consider how it could possibly happen, 

 if heat were a fluid, that the mere rubbing of two metals to- 

 gether should produce it ; and he tried many experiments to 

 find out whether the gun, the chips, or the borer had lost 

 anything in consequence of having given out heat. But he 

 could not discover that they were changed in any way; and 

 moreover, he found that by going on boring he could make 

 them give out heat as long as he liked, whereas if he had 

 been drawing a fluid out of the metals it seemed to him 

 that it ought to come to an end sooner or later. Then he 

 considered whether the heat could come out of the air, and 

 to avoid this he repeated the experiment under water, but 

 still the metals grew hot, and even made the waterVarm, so 

 it was clear they had not drawn any heat from that fluid. 



He now began to suspect that Bacon and Locke might 

 be right, and that the rubbing together of the two metals 

 might set their particles vibrating in some peculiar way so as 

 to cause what we call heat. If this were so, then by great 

 friction he ought to be able to produce any amount of heat, 

 and to prove this he tried the following experiment 



