October 3, 1902.] 



SCIENCE. 



549 



in former experiments having been due to 

 the great contraction of the mercury in the 

 thermometer in passing into the solid state. 

 From this it followed that the enormous 

 natural and artificial colds which had gen- 

 erally been believed in had no proved ex- 

 istence. Still the possible existence of a 

 zero of temperature very different from 

 that deduced from gas thermometry had 

 the support of such distinguished names 

 as those of Laplace and Lavoisier. In 

 their great memoir on ' Heat, ' after making 

 what they consider reasonable hypotheses 

 as to the relation between specific heat and 

 total heat, they calculate values for the 

 zero which range from 1,500° to 3,000° 

 below melting ice. On the whole, they 

 regard the absolute zero as being in any 

 ease 600° below the freezing-point. Lavoi- 

 sier, in his 'Elements of Chemistry' pub- 

 lished in 1792, goes further in the direction 

 of indefinitely lowering the zero of tem- 

 perature when he says, 'We are still very 

 far from being able to produce the degree 

 of absolute cold, or total deprivation of 

 heat, being unacquainted with any degree 

 of coldness which we cannot suppose cap- 

 able of still further augmentation; hence 

 it follows we are incapable of causing the 

 ultimate particles of bodies to approach 

 each other as near as possible, and thus 

 these particles do not touch each other in 

 any state hitherto known.' Even as late 

 as the beginning of the nineteenth century 

 we find Dalton, in his new system of ' Chem- 

 ical Philosophy,' giving ten calculations of 

 this value, and adopting finally as the nat- 

 ural zero of temperature minus 3,000° C. 

 In Black's lectures we find that he takes 

 a very cautious view with regard to the 

 zero of temperature, but as usual is admir- 

 ably clear with regard to its exposition. 

 Thus he says, "We are ignorant of the 

 lowest possible degree or beginning of heat. 

 Some ingenious attempts have been made 

 to estimate what it may be, but they have 



not proved satisfactory. Our knowledge 

 of the degrees of heat may be compared to 

 what we should have of a chain, the two 

 ends of which were hidden from us and the 

 middle only exposed to our view. We 

 might put distinct marks on some of the 

 links, and number 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 to- 

 gther with respect to their distance or say 

 that one link was twice as far from the 

 end of the chain as another. " It is inter- 

 esting to observe, however, that Black was 

 evidently well acquainted with the work of 

 Amontons and strongly supports his in- 

 ference as to the nature of air. Thus, in 

 discussing the general cause of vaporiza- 

 tion. Black says that some philosophers have 

 adopted the view "that every palpable 

 elastic fluid in nature is produced and pre- 

 served 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 differs from others by being 

 incomparably more volatile, and which is 

 therefore converted into vapor and pre- 

 served in that form by a weaker heat than 

 any that ever happened or can obtain 

 in this globe, and which, therefore, cannot 

 appear under any other form than the one 

 it now wears, so long as the constitution of 

 the world remains the same as at present. ' ' 

 The views that Black attributes to Amon- 

 tons have been generally associated with 

 the name of Lavoisier, who practically ad- 

 mitted similar possibilities as to the nature 

 of air ; but it is not likely that in such mat- 

 ters Black would commit any mistake as 



