50 



SCIENCE. 



[N. S. Vol. XVI. No. 405. 



to the real author of a particular idea, es- 

 pecially in his own department of knowl- 

 edge. Black's own special contribution to 

 low- temperature studies was his explana- 

 tion of the interaction of mixtures of ice 

 with salts and acids by applying the doc- 

 trine of the latent heat of fluidity of ice 

 to account for the frigorific effect. In a 

 similar way Black explained the origin of 

 the cold produced in CuUen's remarkable 

 experiment of the evaporation of ether 

 under the receiver of an air-pump by point- 

 ing out that the latent heat of vaporization 

 in this case necessitated such a result. 

 Thus, by applying his own discoveries of 

 latent heat. Black gave an intelligent ex- 

 planation of the cause of all the low-tem- 

 perature phenomena known in his day. 



After the gaseous laws had been def- 

 initely formulated by Gay-Lussac and 

 Dalton, the question of the absolute zero 

 of temperature, as deduced from the prop- 

 erties of gages, was revived by Clement and 

 Desormes. These distinguished investi- 

 gators presented a paper on the subject to 

 the French Academy in 1812, which, it ap- 

 pears, was rejected by that body. The 

 authors subsequently elected to publish it 

 in 1819. Relying on what we know now to 

 have been a faulty hypothesis, they deduced 

 from observations on the heating of air 

 rushing into a vacuum the temperature of 

 minus 267 degrees as that of the absolute 

 zero. They further endeavored to show, 

 by extending to lower temperatures the 

 volume or the pressure coefficients of gases 

 given by Gay-Lussac, that at the same 

 temperature of minus 267 degrees the gases 

 would contract so as to possess nO' appre- 

 ciable volume, or, alternatively, if the pres- 

 sure was under consideration, it would be- 

 come so small as to be non-existent. Al- 

 though full reference is given to previous 

 work bearing on the same subject, yet, 

 ciiriously enough, no mention is made of 

 the name of Amontons. It certainly gave 



remarkable support to Amontons' notion 

 of the zero to find that simple gases like 

 hydrogen and compound gases like am- 

 monia, hydrochloric, carbonic and sul- 

 phurous acids should all point to substan- 

 tially the same value for this temperature. 

 But the most curious fact about this re- 

 search of Clement and Desormes is that 

 Gay-Lussac was a bitter opponent of the 

 validity of the inferences they drew either 

 from his work or their own. The mode in 

 which Gay-Lussac regarded the subject 

 may be succinctly put as follows: A quick 

 compression of air to one fifth volume 

 raises its temperature to 300 degrees, and 

 if this could be made much greater and in- 

 stantaneous the temperature might rise to 

 1,000 or 2,000 degrees. Conversely, if air 

 under five atmospheres were suddenly di- 

 lated, it would absorb as much heat as it 

 had evolved during compression, and its 

 temperature would be lowered by 300 de- 

 grees. Therefore, if air were taken and 

 compressed to fifty atmospheres or more, 

 the cold produced by its sudden expansion 

 would have no limit. In order to meet 

 this position Clement and Desormes 

 adopted the following reasoning: They 

 pointed out that it had not been proved 

 that Gay-Lussac was correct in his hypoth- 

 esis, but that in any ease 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 unlike any other measurable thing 

 or quality. It is, therefore, more con- 

 sistent with the course of nature to suppose 

 that the amount of heat in a body is like 

 the quantity of elastic fluid filling a ves- 

 sel, which, while definite in original 

 amount, one may make less and less by 

 getting nearer to a complete exhaustion. 

 Further, to realize the absolute zero in the 

 one case is just as impossible as to realize 

 the absolute vacuum in the other; and as 

 we do not doubt a zero of pressure, 



