HISTORY OF COLD AND THE ABSOLUTE ZERO. 213 



in 1S19. Kelyino' on Avhat we know now to have been a faulty 

 hypotlie.si.s, they deduced from ol^servations on th(> hcnitino- of air 

 rushing- into a \aeuuni th(» temperatui'e of niimis iJllT as that of the 

 absohite zero. They further endeavored to show, by extending- to 

 lower temperatures the volume or the pressure coetiicients of gases 

 given by (xay-Lussac, that at the same temi)erature of minus i^67- the 

 gases would contract so as to possess no appreciable volume, or, alter- 

 nati^'ely. if the pressure was under consideration it would become so 

 small as to be nonexistent. Although full reference is given to pre- 

 vious work bearing on the same subject, yet curiously enough no 

 UKMition is made of the name of Amontons. Ltcertaiidy gave remark- 

 able suppoi-t to Amontons's notion of the zero to find that simple 

 gases like hydrogen and compound gases like ammonia, hydrochloric, 

 carbonic, and sulphui'ous acids should all ])oint to substantiallv the 

 same vahu; for this tem))(M'atui'(\ IJut the most curious fact about 

 this research of Clement and Desormes is that (iay-Lussac was a 

 bitter op})onent of the validity of "the inferences they drew either 

 from his work or their own. The mode in which (Iay-Lussac 

 regarded the subject may be succinctly put as follows: A (juick 

 compression of air to on(> rifth volume raises its temperature to 800 , 

 and if this could be made much greater and instantaneous the temper- 

 ature might rise to 1,000 or !i,000 \ Conversely, if air under five 

 atmospheres were suddeidy dilated it would absorb as much heat as it 

 had evolved during compression and its temperature would be low- 

 ered l)y 300 . Therefoi'e if air were taken and compi'essed to 50 

 atmospheres or more, the cold ])roduced by its sudden expansion 

 would have no limit. In ordcn* to meet this positioii Clement and 

 Desormes adopted the following reasoning: They pointed out that it 

 had not been pro^'ed that (xay-Lussac was correct in his hypothesis, 

 but that in any cas'.> it tacitly involves the assumption that a limited 

 quantity of matter possesses an unlimited supply of heat. If this 

 were the case, then heat would be uidike any other measurabh* thing or 

 (juality. It is, therefore, more consistent with the course of nature to 

 suppose that the amoimt of heat in a body is like the quantity of elas- 

 tic riuid tilling a vess(>l, which, while definite in original amount, one 

 may make less and less by getting nearer to a complete exhaustion. 

 Further, to realize the at)solute zero in the on(> case is just as impos- 

 sibl(» as to realize the absolute vacuum in the other; and as we do not 

 doubt a z(M'o of pressure, although it is unattainable, for the same rea- 

 son we ought to accept the reality of the absolute zero. We know 

 now that (Jay-Lussac was wrong in supposing the increment of tem- 

 perature arising from a gi\en gaseous compression would produce a 

 corresponding decrement from an identical expansion. After this 

 time the zero of temperature was generally recognized as a fixed ideal 

 point, but in or^er to show that it was hypothetical, a distinction was 



