17& CALORIC. 



ing cases in which heat appeared as the result of mechanical 

 action, such as rubbing, which produced no sensible changes,, 

 were met by metaphysical assumptions which were allowed 

 to pass, and gradually acquired a place in the teaching of the 

 schools as sanctioned by authority. These were accepted,, 

 however, only by those who did not study the phenomena,, 

 which did not then command much attention. That the 

 steady stream of heat which may be poured out of a body 

 continuously by the simple process of rubbing it should be 

 the result of occult changes in the body could be held by no- 

 true philosopher who had the phenomenon brought forcibly 

 before him. Thus Rumford, in 1 79 1 , followed by Davy and 

 Young, revived the dynamical theory, and again showed heat 

 to have a mechanical origin. But although they spoke from 

 the Royal Society and Royal Institution, and although 

 nobody seems to have doubted the truth or force of what 

 they said, they could get no considerable following. 



The definite hypothesis of caloric had been found so 

 fitting, had explained so much, and had been such a great 

 simplification, that it was not lightly to be abandoned for a 

 view, which, so far as it was then carried, promised to throw 

 everything again into chaos. Heat might be mechanical, but 

 it was certain that it was measurable, and, for the most part,, 

 had a permanent existence ; in these respects, and many 

 others, the hypothesis of caloric had been found a safe 

 guide, and such guidance was more important than mere 

 views as to the nature of heat. Such views, however 

 incontestable might be the evidence adduced, must be 

 open to doubt so long as they appeared contrary to what 

 was known to be true. Those who advocated the mechani- 

 cal theory had not shown how, in any definite measure,, 

 mechanical effect could correspond with heat, while experi- 



