246 



NATURE 



[January 14, 1892 



■equation, with the result of wholly falsifying all that 

 follows. On the other hand, we must fully recognize that, 

 when more formidable analysis is really required (as, for 

 instance, in the treatment of v. Helmholtz's monocyclic 

 and polycyclic systems), M. Poincare seems to feel so 

 thoroughly at home as to criticize with freedom. 



One test of the soundness of an author, writing on 

 Thermodynamics, is his treatment of temperature, and 

 his introduction of absolute temperature. M. Poincare 

 gets over this part of his work very expeditiously. In 

 §§ 15-17 temperature, /, is conventionally defined as in 

 the Centigrade thermometer by means of the volume of 

 a given quantity of mercury ; or by any continuous 

 function of that volume which increases along with it. 

 Next (§ 22) absolute temperature, T, is defined, provision- 

 ally and with a caution, as 273 +/ ; from the (so-called) 

 laws of Mariotte and Gay-Lussac. Then, fiinally (§ 118), 

 absolute temperature is virtually defined afresh as the 

 reciprocal of Carnot's function. [We say virtually, as 

 we use the term in the sense defined by Thomson. M. 

 Poincard's Fonciion de Carnot is a different thing.] But 

 there seems to be no hint given as to the results of 

 experiments made expressly to compare these two defini- 

 tions. Nothing, for instance, in this connection at all 

 events, is said about the long-continued early experi- 

 mental work of Joule and Thomson, which justified them 

 in basing the measurement of absolute temperature on 

 Carnot's function. 



In saying this, however, we must most expUcitly dis- 

 claim any intention of charging M. Poincare with even 

 a trace of that sometimes merely invidious, sometimes 

 purely Chauvinistic, spirit which has done so much to 

 embitter discussions of the history of the subject. On 

 the contrary, we consider that he gives far too little pro- 

 minence to the really extraordinary merits of his own 

 countryman Sadi Carnot. He writes not as a partisan 

 but rather as one to whom the history of the subject is a 

 matter of all but complete indifference. So far, in fact, 

 •does he carry this that the name of Mayer, which fre- 

 quently occurs, seems to be spelled incorrectly on by 

 far the 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 I'eut enonce 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 I'^ntropy. The word dissipation does 

 indeed occur, for we are told in the Introduction that the 

 Principe de Carnot is " la dissipation de Pentropie.'' 



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 

 NO. I 159, VOL. 45] 



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. 

 Poincare has, in this work, chosen to play almost exclu- 

 sively the part of the pure technical analyst ; instead of 

 that of the profound thinker, though he is perfectly com- 

 petent to do that also when he pleases. And, in his as- 

 sumed 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 Con- 

 servation of Energy to Mayer, he says of that principle : — 

 " personne n'ignore que c'est un fait experrtnental." 



Even the elaborate thermo-electric experiments of Sir W. 

 Thomson, Magnus, &c., are altogether ignored. What 

 else can we gather from passages like the following.? 



( § 287) " Sir W. Thomson admet qu'il existe une 

 " force electromotrice au contact de deux portions d'un 

 " meme conducteur a des temperatures diffcrentes ; il 

 " assimile done ces deux portions a deux conducteurs 

 " de nature differente, assimilation qui parait tr^s vrai- 

 " semblable." 



(§ 291) "... si I'effet Thomson a pu etre mis en 

 " evidence par I'experience, on n'a pu jusqu'ici constater 

 " I'existence des forces electromotrices qui lui donnent 

 " naissance." 



Everyone who comes to this work of M. Poincare fresh 

 from the study of Clerk-Maxwell's litile treatise (or of the 

 early papers of Thomson, to which it owed much) will 

 feel as if ti-ansferred to a totally new world. Let him 

 look, for instance, at Maxwell's treatment of the Thermo- 

 dynamic Relations, Intrinsic and Available Energy, &c., 

 and then turn to pp. 148-150 of M. Poincare's work. 

 There he will find at least a large portion of these most 

 important matters embodied in what it seems we are now 

 to call the lumctions caract^ristiijucs de M. Massieu ! 



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. Helm- 

 holtz, the science had been retrograding, certainly not 

 advancing, for the last twenty years. P. G. T. 



INSECT PESTS. 

 Hand-book of the Destructive Insects of Victoria. By 

 C. French, F.L.S., Government Entomologist. Part I. 

 Prepared by Order of the Victorian Department of 

 Agriculture. (Melbourne, 1891.) 



THE appearance of this volume affords another proof, 

 if any were required, of the wholesome activity, 

 now noticeable in all progressive countries, directed 



