OF NATURAL PHILOSOPHY. 311 



the other phenomena which arise on the application 

 of fire, or of any other heating cause. We should 

 be greatly deceived if we referred only to sensation 

 as an indication of the presence of this cause. 

 Many of those things which excite in our organs, 

 and especially of those of taste, a sensation of heat, 

 owe this property to chemical stimulants, and not 

 at all to their being actually hot. This error of 

 judgment has produced a corresponding confusion 

 of language, and hence had actually at one period * 

 crept into physical philosophy a great many illogical 

 and absurd conclusions. Again, there are a number 

 of chemical agents, which, from their corroding, 

 blackening, and dissolving, or drying up the parts 

 of some descriptions of bodies, and producing on 

 them effects not generally unlike (though intrin- 

 sically very different from) those produced by heat, 

 are said, in loose and vulgar language, to burn 

 them ; and this error has even become rooted into 

 a prejudice, by the fact that some of these agents 

 are capable of becoming actually and truly hot 

 during their action on moist substances, by reason 

 of their combination with the water the latter con- 

 tain. Thus, quicklime and oil of vitriol both ex- 

 ercise a powerful corrosive action on animal and 

 vegetable substances, and both become violently 

 hot by their combination with water. They are^ 

 therefore, set down in vulgar parlance as substances 

 of a hot nature ; whereas, in their relations to the 

 physical cause of heat, they agree with the gene- 

 rality of bodies similarly constituted. 



* Novum Organum, part ii. table 2. (24), (30), &c. on ths 

 form or nature of heat. 



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