CALORIC. 131 



that of the human body. Chemists have agreed to call the 

 matter of heat caloric, in order to distinguish it from the 

 sensation which this matter produces. Caloric has a ten- 

 dency to diffuse itself equally among all substances that 

 come in contact with it. If the hand be put upon a hot 

 body, part of the caloric leaves the hot body, and enters the 

 hand ; this produces the sensation of heat. On the contra- 

 ry if the hand be put upon a cold body, part of the caloric 

 contained in the hand leaves the hand to unite with the cold 

 body ; this produces the sensation of cold. If you pour 

 warm water into one basin, cold water into a second, and a 

 mixture of hot and cold water into a third ; then put the one 

 hand into the cold water and the other into the warm, for 

 two minutes, and after that put both hands into the luke- 

 warm water, to the one hand it will feel cold and to the other 

 hot. Persons ascending from the burning shores of Vera 

 Cruz, on the road to the mountain land of Mexico, will feel 

 the climate become colder, and will put on their great coats, 

 and yet they will meet people descending complaining of the 

 heat. Cold therefore is nothing but a negative quality, sim- 

 ply implying the absence of the usual quantity of caloric. 



Caloric is uniform in its nature ; but there exist in all 

 bodies two portions, very distinct from each other. The 

 One is called sensible heat, or free caloric ; the other latent 

 heat, or combined caloric. Sensible caloric is the matter 

 of heat disengaged from other bodies, or, if united, not chemi- 

 cally united with them. Latent caloric is that portion of the 

 matter of heat which makes no sensible addition to the tem- 

 perature of the bodies in which it exists. Wrought iron, 

 though quite cold, contains a large portion of latent caloric ; 

 and if it be briskly hammered for some time on an anvil, it 

 will become red hot by the action of this species of caloric, 

 which by the percussion of hammering is now evolved and 

 forced out as sensible heat. 



Caloric pervades all bodies ; and this is not the case with 

 any other substance with which we are acquainted. It com- 

 bines with different substances, however, in very different 

 proportions ; and for this reason, one body is said to have a 

 greater capacity for caloric than another. When gaseous 

 substances become liquid, or liquid substances solid, by this 

 change of state they lose in a great measure their capacity 

 for caloric. During the slaking of quick-lime, the caloric 



