312 DISCOURSE ON THE STUDY 



(346.) The nature of heat has hitherto been 

 chiefly studied under the general heads of 

 1st, Its sources, or the phenomena which it usually 



accompanies. 



2d, Its communication from its sources to sub- 

 stances capable of receiving it, and from these 

 to others, with a view to discover the laws 

 which regulate its distribution through space 

 or through the bodies which occupy it. 

 3d, Its effects, on our senses, and on the bodies to 

 which it is communicated in its various de- 

 grees of intensity, by which, means are afforded 

 us of measuring these degrees. 

 4th, Its intimate relations to the atoms of matter, 

 as exhibited in its capability of acquiring a 

 latent state under certain circumstances, and 

 of entering into something like chemical com- 

 binations. 



(347.) The most obvious sources of heat are, the 

 sun, fire, animal life, fermentations, violent chemical 

 actions of all kinds, friction, percussion, lightning., 

 or the electric discharge, in whatever manner pro- 

 duced, the sudden condensation of air, and others, 

 so numerous, and so varied, as to show the ex- 

 tensive and important part it has to perform in the 

 economy of nature. The discoveries of chemists, 

 however, have referred most of these to the general 

 head of chemical combination. Thus, fire, or the 

 combustion of inflammable bodies, is nothing more 

 than a violent chemical action attending the com- 

 bination of their ingredients with the oxygen of the 

 air. Animal heat is, in like manner, referable to a 

 process bearing no remote analogy to a slow com- 



