CALORIC. 177 



ence had established as an axiom, that perpetual motion 

 was impossible, and that mechanical effect was destructible, 

 how then could heat, which was measurable and continued 

 to exist, be mechanical force ? This question had to be 

 answered before the caloric hypothesis could be abandoned, 

 if, indeed, it can be said to have been abandoned, because 

 the name, and certain assumptions tacked on are dropped, 

 while all that was clearly defined in the hypothesis, 

 having been found true and in accordance with the 

 mechanical theory, is retained. That "caloric" was not 

 intended to convey an idea of the materiality of heat is 

 clearly shown in the extract (which follows those from 

 Hooke) from the "Traite Elementaire de Chimie," by Lavoi- 

 sier, who invented the name, and that it did not necessarily 

 convey this idea is shown by the number of philosophers, 

 who, though for long unconvinced of the conclusions drawn 

 from the mechanical theory, still disclaimed any belief as to 

 the materiality of heat. 



Extract from " Micrographia" by Robert Hooke^p. 12: — 



"First what is the cause of fluidness? And this I conceive 

 to be nothing else but a certain pulse or shake of heat ; for 

 heat being nothing else but a very brisk and vehement 

 agitation of the parts of a body (as I have elsewhere made 

 probable) the parts of a body are thereby made to loose 

 from one another that they easily move any way and become 

 fluid. That I may explain this by a gross Similitude. Let 

 us suppose a dish of sand set upon some body that is very 

 much agitated and shaken by some quick and strong 

 vibrating motion, as on a milstone turned round upon the 

 understone, very violently, whilst it is empty, or on a very 

 stiff drum-head which is vehemently or nimbly beaten with 

 N 



