118 Chemical Philosophif, [Chap. II. 



heat seems to have been considered as a pecuhar 

 subtile fluid or element; and this opinion appears 

 to have prevailed until the time of lord Bacon. 

 That philosopher was the first, it is believed, who 

 advanced the hypothesis that heat is a quality of 

 matter, and depends on a peculiar vibration of its 

 particles. This opinion was afterwards adopted by 

 Boyle and Newton, whose authority rendered it 

 considerably popular : the ancient opinion, how- 

 ever, w^as still held by many. Boerhaave, at an 

 early period of the eighteenth century, entered the 

 lists against Newton on this subject, and main- 

 tained, w ith great force of argument, that heat is 

 a distinct substance. From the time of Boerhaave 

 till towards the close of the century ujider review, 

 this doctrine Avas almost universally received. 

 Stahl, Macquer, Black, Priestley, Scheele, Bergman, 

 Lavoisier, Crawford, Irvine, Kirwan, Pictet, de la 

 Place, and most other distinguished chemists, t^iough 

 differing as to som^e details of opinion on this sub- 

 ject, all agree in considering heat as a distinct 

 positive substance. 



But, towards the close of the century, the doc- 

 trine of Bacon was revived by count Rumford and 

 Mr. Davy. These philosophers, observing that 

 caloric continues to be extricated from a body 

 subjected to friction, so long as the friction is kept 

 up, and the t(^xture or form of the body is not de- 

 stroyed; and that this heat-yielding process goes on 

 to an indefiulle extent ; concluded that this plieno- 

 menon is inexpUcable on the supposition of heat 

 being matter; and that those effects which have 

 been referred to tlie operation of a peculiar calorific 

 matter, depend entirely on a i-ibratory motion of the 



