POINCARE'S "THERMODYNAMIQUE" 275 



greater number of these occasions ! He makes, however, one very striking historical 

 statement ( 95) : 



"Clausius...lui donna le nom de Principe de Carnot, bien qu'il 1'eut e'noncd sans 

 avoir connaissance des travaux de Sadi Carnot." 



Still, one naturally expects to find, in a Treatise such as this, some little allusion 

 at least to Thermodynamic Motivity ; to its waste, the Dissipation of Energy ; and 

 to the rest of those important early results of Sir W. Thomson, which have had such 

 immense influence on the development of the subject. We look in vain for any 

 mention of Rankine or of his Thermodynamic Function ; though we have enough, 

 and to spare, of it under its later alias of Entropy. The word dissipation does indeed 

 occur, for we are told in the Introduction that the Principe de Carnot is " la dissipation 

 de tentropie',' 



We find Bunsen and Mousson cited, with regard to the effect of pressure upon 

 melting points, almost before a word is said of James Thomson ; and, when that word 

 does come, it wholly fails to exhibit the real nature or value of the great advance he made. 



Andrews again, a propos of the critical point, and his splendid work on the 

 isothermals of carbonic acid, comes in for the barest mention only after a long 

 discussion of those very curves, and of the equations suggested for them by Van der 

 Waals, Clausius, and Sarrau : though his work was the acknowledged origin of their 

 attempts. 



The reason for all this is, as before hinted, that M. Poincar6 has, in this work, 

 chosen to play almost exclusively the part of the pure technical analyst ; instead of 

 that of the profound thinker, though he is perfectly competent to do that also when 

 he pleases. And, in his assumed capacity, he quite naturally looks with indifference, 

 if not with absolute contempt, on the work of the lowly experimenter. Yet, in strange 

 contradiction to this, and still more in contradiction to his ascription of the Conservation 

 of Energy to Mayer, he says of that principle: "personne n'ignore que c'est un fait 

 experimental." 



But the most unsatisfactory part of the whole work is, it seems to us, the entire 

 ignoration of the true (i.e. the statistical) basis of the second Law of Thermodynamics. 

 According to Clerk Maxwell (Nature, XVII, 278) 



"The touch-stone of a treatise on Thermodynamics is what is called the 

 second law." 



We need not quote the very clear statement which follows this, as it is probably 

 accessible to all our readers. It certainly has not much resemblance to what will be 

 found on the point in M. Poincare's work : so little, indeed, that if we were to judge 

 by these two writings alone it would appear that, with the exception of the portion 

 treated in the recent investigations of v. Helmholtz, the science had been retrograding, 

 certainly not advancing, for the last twenty years. 



In his reply {Nature, March 3, 1892), Poincare' practically confined his 

 attention to the discussion of the Thomson Effect, offering fuller explanations 

 of his meaning. This, however, did not touch on Tail's chief objections 

 which were epitomised as follows (March 10, 1892) : 



35 * 



