COUNT RUM FORD i6i 



have no foundation, he has done very much towards estabhshing be- 

 yond doubt the opinions and facts in question. 



I will now endeavor to answer the objections which M. Berthoiet 

 has offered to my explanation of the above-mentioned experiments ; 

 and, that the reader may be in a position to give to these objec- 

 tions their just value, I will insert them here in the writer's own 

 words. 



"Count Rumford has made a curious experiment with regard to the 

 heat which may be excited by friction. 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 and a half) hours, and under a pressure equal to lOO cwt., 

 reduced to powder 4145 grains (85^ 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 slightest di.fference 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 experiment that we must renounce en- 

 tirely 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 satisfactory manner by applying to 

 the case in question those laws of nature in accordance with which the 

 operations of heat are manifested under other conditions. 



"If the evolution of heat be regarded as a consequence of the de- 

 crease of volume caused by the pressure, then not only the metallic pow- 

 der, but also all the rest of the brass cylinder must have contributed, 

 though not in an equal manner, to this evolution, by the powerful ex- 

 pansive effort of that portion which experienced the greatest pressure, 

 and consequently acquired the greatest temperature, without being able 

 to assume the dimensions proper to this same temperature on account 

 of the less heated and less expanded parts ; consequently there must have 

 arisen, necessarily, a certain condensation of the metal in respect of its 

 natural dimensions, which condensation gradually decreased from the 

 point where the pressure was greatest to the surface. We may suppose 



