392 Further Remarks upon Mr. Herapath's Theory. [Nov. 



of such a point ; and it appears to me, that, by his own theory, 

 it may be proved that no such point can exist ; for when the 

 volume is (J, the gas does not exist. If it then begin to exist, it 

 must begin by the production of a first atom infinitely small ; but 

 this atom must be supposed to have some heat, because the law 

 of temperature is now beginning ; and to constitute heat, accord- 

 ing to Mr. H. there must be an intestine motion ; and if so, this 

 atom must consist of smaller particles, which is contrary to 

 supposition. Thus the existence of such a point is disproved an 

 the assumption of Mr. H.'s theory ; which is, therefore, at 

 variance with itself. 



It may also be shown, in the same way, that by diminution of 

 heat, the volume of the gas can never become 0, or, what is the 

 same thing, can never cease to exist ; for so long as there is any 

 intestine motion left in it, there must be more than one infinitely 

 small particle ; and the total abstraction of all heat, or cessation 

 of all intestine motion, cannot cause the disappearance of these 

 particles. 



These difficulties, however, are not peculiar to Mr. H.'s theory ; 

 precisely the same absurdity results from the common theory of 

 lepulsion. According to this theory, the smallest volume to 

 which we can suppose a body reduced must still have some heat 

 in it to give it a physical existence ; and if we suppose no heat 

 left in a body, there can be no separation of particles ; they must 

 be infinitely condensed, or, in other words, the substance cannot 

 exist. 



The fact appears to me to be, that whenever a real zero is said 

 to exist, it is always on the assumption, avowed or implied, of 

 some hypothesis concerning the nature of heat ; and at the same 

 time I am inclined to think, that on most such hypotheses, the 

 doctrine may be as easily refuted as on this. If in such specu- 

 lations we were to set out by defining the term heat in the only 

 way in which it can be rightly defined, viz. from some of its 

 observed properties or effects, we should soon find them all built 

 without a foundation. 



It would hardly seem necessary to remark, that in the present 

 state of our knowledge the physical cause of heat is absolutely 

 beyond the reach of investigation. If it were not that specula- 

 tions concerning what is termed the point of absolute cold had 

 received the sanction of some of the highest names in the 

 scientific world, I would only require of any philosopher engaged 

 in researches of this kind to define, with rigid precision, the term 

 " real zero," or any equivalent expression which he may use ; 

 and I think it would be evident, that he could not define it with- 

 out a reference to some hypothetical physical principle as the 

 cause of heat. I remember lono- ago when I first studied Dr. 

 Thomson's excellent " System," on coming to the chapter enti- 

 tled, " On the Absolute Quantity of Heat in Bodies," being not 

 a little astonished, at finding an author, in general so remarkable 



