212 HISTORY OF COLD AND THE ABSOLUTE ZERO. 



may be, but they have not proved satisfactory. Our knowledge of 

 the degrees of heat may be compared to what we shoidd huxe of a 

 chain, the two ends of which were hidden from us and tlie middle only 

 exposed to our view. We might put distinct marks on some of the 

 links, and nmnber the rest according as they are nearest to or further 

 removed from the principal links; but not knowing the distance of 

 any links from the end of the chain we could not compare them 

 together with respect to their distance, or say that one link was twice 

 as far from the end of the chain as another." 



It is interesting to observe, however, that Black was evidently well 

 acquainted with the work of Amontons and stronglj' supports his 

 inference as to the nature of air. Thus, in discussing the general 

 cause of vaporization, Black says that some philosophers have adopted 

 the view "that every palpable elastic tliiid in nature is produced and 

 preserved in this form by the action of heat. Mr. Amontons, an 

 ingenious member of the late Royal Academy of Sciences, at Paris, 

 was the first who proposed this idea with respect to the atmosphere. 

 He supposed that it might be deprived of the whole of its elasticity 

 and condensed and even frozen into a solid matter were it in our 

 power to apply to it a sufficient cold; that it is a substance that dijSers 

 from others by being incomparably more volatile, and which is there- 

 fore converted into vapor and preserved in that form by a weaker 

 heat than any that ever happened or can obtain in this globe, and 

 which therefore can not appear under any other form than the one it 

 now wears so long as the constitution of the woi'ld remains the same 

 as at present." The views that Black attributes to Amontons have 

 been generally associated with the name of Lavoisier, who practically 

 admitted similar possi))ilities as to the nature of air; but it is not 

 likeh^ that in such matters Black would counuit any mistake as to the 

 real author of a particular idea, especially in his own department of 

 knowledge. Black's own special contribution to low-temperature 

 studies was his explanation of the interaction of mixtures of ice 

 with salts and acids by applying the doctrine of the latent heat of 

 fluidity of ice to account for the frigoritic effect. In a similar way 

 Black explained the origin of the cold produced in (/ullen's remarka- 

 ble experiment of the evaporation of ether under the receiver of an 

 air pump by pointing out that the latent heat of vaporization in this 

 case necessitated such a result. Thus, l)y applying his own discov- 

 eries to latent heat, Black gave an intelligent explanation of the cause 

 of all the low-temperature phenomena known in his day. 



After the gaseous laws had been delinitely fornudatod bv Ciay- 

 Lussac and Dalton, the ([uestion of the absolute zero of temperature, 

 as deduced from the ]iroperties of gas(\s, was revived by (^lenient and 

 Desormes. These distinguished investigators presented a paper on 

 the subject to the French Academy in isi^}, which, it appears, was 

 rejected by that body. The authors sul)se([ueiitly elected to publish it 



