2io THE POPULAR SCIENCE MONTHLY. 



tion, the additional phenomena of latent or specific heats were not at 

 all irreconcilable or difficult of explanation. 



Thus Lavoisier and Laplace, in their famous "Memoire sur la Cha- 

 leur " of 1780, though still retaining and defending the ideas of caloric, 

 admitted the frictional excitation of heat to be "favorable" to the 

 dynamical hypothesis. But it is, on the other hand, to be remem- 

 bered that the earlier experiments devoted to the study of this point 

 had been by no means unmistakable in their indications, directed as 

 they had been rather to the detection of some suspected influence of 

 the rubbing surfaces than to the investigation of any possible relation 

 between the heat produced and the energy expended in producing it. 



The material hypothesis was, therefore, the prevailing one, when 

 about the year 1797 Count Rumford, 1 while engaged in superintend- 

 ing the construction of cannon at the military arsenal at Munich, be- 

 came impressed by the considerable generation of heat accompanying 

 their boring. And as he thought upon the explanation of the phe- 

 nomenon consistent with the then prevailing ideas as to the intimate 

 nature of heat, it seemed to him impossible that an apparently un- 

 limited supply of any substance could be separated from so inconsid- 

 erable a quantity of borings. The doubt increased when, upon mak- 

 ing the determination, he found the specific heat of this debris to be 

 the same, apparently, as that of the mass of metal from which it had 

 been separated: for in some obscure manner the " capacity" for heat 

 of any body, or the total quantity of it which it might hold in any 

 particular state, was considered to be intimately connected with, if 

 not entirely defined by, its specific heat. 



But, though he quoted this experiment as sufficiently conclusive 

 that the heat set free by friction could not have been produced at the 

 expense of any caloric latent in the metal, he undertook the following 

 more elaborate investigation to determine all the circumstances which 

 might possibly exert an influence on its production: and it appears, 

 both from his method of procedure and the arguments with which he 

 supplemented his results, that he had fully comprehended the philo- 

 sophical consequences of each rival theory. 



In view of the preeminent importance of these first conclusive and 

 well-understood experiments, both with respect to the establishment 

 of the dynamic theory upon an experimental basis, and the undoubted 

 claim of their author to be considered as its founder, we here give as 

 detailed an account of his investigations as may be thought admissible 

 in a work intended merely for didactic purposes ; and we conceive a 

 fidl statement upon this most important point to be the more de- 

 sirable, from the fact that the completeness with which he then 

 demolished the material hypothesis, and the maturity of his views 

 respecting the dynamical nature of heat, do not of late seem to 



1 " Inquiry concerning the Source of the Heat which is excited by Friction," " Phil- 

 osophical Transactions," 1798, p. 80. "Complete Works," Am. Ac. ed., p. 400. 



