hi Fluids. 375 



When, to the established laws which have been discov- 

 ered in the operations of nature in the change of form 

 in substances that appear to us to ht simple, we add those 

 which have been found to obtain in the changes of form 

 of bodies that are known to be compounded, we shall per- 

 haps be able to conceive some more distinct ideas with 

 regard to the nature of those mechanical operations 

 which take place in chemical processes. I call them tne- 

 chanical, — for mechanical they must of necessity be, ac- 

 cording to the most rigid interpretation of that expres- 

 sion. 



But the hypothesis of the existence of intense Heat in 

 the midst of cold liquids is so new, and seems to be so 

 contrary to the result of all our experience and observa- 

 tion, that I feel it to be necessary to take some pains to 

 illustrate the matter. 



And first, we must not expect always to find traces re- 

 maining of the existence of intense Heat, even where 

 there are the strongest reasons to think it has actually 

 existed ; for as often as Heat is dispersed or carried off, 

 before it has had time to produce any changes of form, 

 or chemical changes or combinations in the bodies to 

 which it is communicated, it leaves no marks behind it. 



Fire-arms are often found to miss fire, even when many 

 live sparks from the flint and steel actually fall into the 

 pan among the priming; but nobody, surely, will pre- 

 tend that the small particles of red-hot iron which fall 

 among the grains of the gunpowder, and cool in contact 

 with them, are not intensely hot, — incomparably more 

 so than would be necessary to inflame the powder were 

 their Heat of sufficient duration to produce that effect. 

 Had these small sparks been invisible, it is highly prob- 

 able that their existence would never have been suspected. 



