VI PREFACE. 



the flowing of waters, the transformations of 

 chemistry, the operations of vitality, and the 

 revolutions of the heavenly bodies. 



But as the ancients never explained the 

 laws by which elementary caloric operates in 

 the generation of force and motion, nor the 

 manner in which it is related to electricity and 

 light; their speculations have exerted little 

 influence on the physical theories of modern 

 philosophers, who have, strangely enough, 

 disregarded nearly all that was most valuable 

 in the science of antiquity. At the present 

 time, it remains undecided, whether caloric is 

 an exceedingly subtile and active essence, as 

 maintained by the early Hindoos, Egyptians, 

 Phoenicians, Chaldeans, Persians, and Arabi- 

 ans, as well as the more enlightened Greeks 

 and Romans ; or whether it consists in mere 

 motion and vibration among the particles of 

 ponderable matter, as supposed by Bacon, 

 Boyle, Hooke, Rumford, Davy, Young, and 

 others. 



One of the most important modern discove- 

 ries was that of latent or combined heat, by 

 Dr. Black. When he proved by accurate ex- 

 periments, that definite measures of caloric are 

 required to convert solids into liquids, and that 



