on the Subject of Heat. 2 1 5 



"Count Rumford has made a curious experiment 

 with regard to the heat which may be excited by fric- 

 tion. He causes a blunt borer to revolve very rapidly 

 (this borer revolved about its axis only thirty-two times a 

 minute} in a brass cylinder weighing thirteen pounds, 

 English weight (the cylinder weighed one hundred and 

 thirteen pounds and somewhat more\ and says that he 

 observed that this borer in the course of two (one ana 

 a half) hours, and under a pressure equal to 100 

 cwt., reduced to powder 4145 grains (8J ounces Troy) 

 of brass, and that an amount of heat was generated 

 during this operation sufficient to bring to boil 26.38 

 pounds of water, previously cooled to the freezing- 

 point. He asserts that he did not discover the slight- 

 est difference between the specific heat of the metallic 

 dust and that of the brass which had not experienced 

 the friction. Hence he supposes that the heat was 

 excited by the pressure alone, and was not at all due to 

 caloric, as is the opinion of most chemists. 



" I will for the present satisfy myself with simply 

 inquiring whether it necessarily follows from this ex- 

 periment that we must renounce entirely the received 

 theory of caloric, according to which it is regarded as 

 a substance which enters into combination with bodies, 

 or whether this result cannot be explained in a satis- 

 factory manner by applying to the case in question 

 those laws of nature in accordance with which the opera- 

 tions of heat are manifested under other conditions. 



"If the evolution of heat be regarded as a conse- 

 quence of the decrease of volume caused by the pressure, 

 then not only the metallic powder but also all the rest 

 of the brass cylinder must have contributed, though not 

 in an equal manner, to this evolution, by the powerful 



