Reflections on Heat. 167 



made him superior to all animals, and master of land 

 and sea. 



It is not at all surprising that an agent at once so 

 powerful and so manageable, so beneficent and so ter- 

 rible, should have become an object of admiration and 

 even of adoration among the nations of the earth ; but 

 it is more than surprising that a subject, the investiga- 

 tion of which is of such interest, should have been for 

 so long a time neglected. 



This indifference to an object at once so curious and 

 so interesting can only be attributed to that lack of at- 

 tention with which men always regard those things that 

 they are accustomed to have before them at all times. 



A proof that our knowledge on the subject of heat is 

 still extremely limited and imperfect lies in the differ- 

 ence of opinion which exists among fhe learned on the 

 nature of heat and its mode of action. Some regard it 

 as a substance^ others as a vibratory motion of the particles 

 of matter of which a body is composed. 



Those who have adopted the hypothesis of a peculiar 

 calorific substance which they call caloric suppose that 

 the heating of a body is always the result of an accumu- 

 lation of this substance in the body; on the other hand, 

 those who regard heat as a vibratory motion which is 

 conceived to exist always with greater or less rapidity 

 among the particles of all bodies, consider heat as an 

 acceleration of this motion. 



On the hypothesis of vibratory motion, a body which 

 has become cold is thought to have lost nothing except 

 motion ; on the other hypothesis it is supposed to have 

 lost some material substance, that is, caloric. 



The eminent French philosophers, who proposed, 

 twenty-five years ago, the modern hypothesis of caloric, 



