CH. xxxiv. COUNT RUMFORD. 331 



Accordingly he studied how fire-places could best be built 

 to prevent coal being wasted, and invented a lamp which 

 gave a brilliant light, without burning so much oil as other 

 lamps did. He even went so far as to make a complete 

 set of experiments on different clothing materials, in order 

 to see which kept in the most heat. It was in this way, 

 and especially 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 



