NATURE 



65 



THURSDAY, JULY 21, 1910. 



.4 STANDARD TREATISE ON PHYSICS. 

 Traitt' de Physique. By O. D. Chwolson. Trans- 

 lated from the Russian and German editions by E. 

 Davaux. Second volume, fourth fascicule. Pp. 

 641-1188. Third volume, first fascicule. Pp. vii + 

 408. Fourth volume, first fascicule. Pp. vii + 430. 

 Figures in text. (Paris : Hermann et Fils, igog.) 

 Price 17, 13 and 12 francs respectively. 



SINCE this is a French translation of a work 

 which has already been reviewed in part 

 as a German translation (from the Russian), we will 

 not do more than examine those parts in which it 

 differs from its previous forms or which have not 

 previously been reviewed here. It is by no means a 

 mere translation. Extensive additions have been 

 made under Prof. Chwolson 's supervision with the 

 object of maintaining the book level with the rapid 

 advances in physics that have taken place. These 

 have been made with the author's usual discriminative 

 ability. If there is one quali'ty more than another 

 which strikes us about this te.Kt-book it is the rare 

 combination of knowledge and good judgment 

 which everywhere characterises it. Other volumes 

 which we know may be more encyclopaedic. If our 

 object is to find out all that has been done on any 

 special subject we may be disappointed if we turn up 

 the subject here. But if our object is to find a judi- 

 cious selection of the best that has been thought and 

 written on physical questions, then we know of no 

 better source from which our object can be attained. 

 In other words, this is a text-book of a preeminent 

 order, written by one who has a unique command 

 over all branches of physical science, and who is as 

 alive to the most recent developments as to those 

 portions which have now become classical. 



Of the additions to the fourth fascicule, which deal> 

 with diffraction, double refraction, and polarisation of 

 light, we may point out the account of recent work 

 by Dufet on the remarkable anomalous dispersion of 

 the optic axes in the case of the sulphates of neo- 

 dymium and praseodymium which is exhibited in the 

 region of optical absorption. Several additional pages 

 are devoted to an account of the optical properties of 

 liquid crystals as studied by Lehmann and others. 

 Two lengthy paragraphs are added by the translator 

 dealing with the reflection and refraction of polarised 

 light according to Green, and with the gyrostatic 

 theory of light. These paragraphs certainly supple- 

 ment the rest of the chapter into which they are 

 inserted, and, as many readers will be glad to have 

 them, no exception can be taken in regard to their 

 insertion. But it may be intimated that they are 

 considerably more mathematical than the greater part 

 of the book, and they therefore do not harmonise verv 

 well with the rest. 



We are certainly surprised to find that wh.ni is 

 essentially a distinct treatise is bound up with this 

 fascicule, and constitutes the end of the second 

 volume. This consists of a note on the theorv of 

 deforniable bodies, by MM. E. and F. Cosserat. This 

 XO. 2125, VOL. 84] 



note is 220 pages long, and it does not in any sense 

 harmonise with the work with which it is incorpor- 

 ated. Prof. Chwolson 's work is emphatically experi- 

 mental in character; the note is as strikingly mathe- 

 matical. We do not wish in the slightest degree to 

 discredit either the matter or the manner of the note 

 taken by itself. But there does not seem to be any 

 justification for loading a text-book which is neces- 

 sarily very bulky by matter which will probably never 

 be consulted at the same time as the body of the book 

 itself. The MM. Cosserat's note is a distinct and 

 useful treatise, and should be quite able to stand on 

 its own feet. 



The changes in the first fascicule of the third 

 volume are not so considerable. This part deals with 

 thermometry, specific heats, thermochemistry, and 

 thermal conductivity. So far as we can find, there 

 is only one additional section, which treats in a 

 general way of the problem of Fourier, and gives a 

 short account of the allied researches of M. Poincare. 

 This is a verv useful addition. 



The first part of the fourth volume has not yet 

 been reviewed in these columns, and it deserves a 

 more extended notice. Its subject-matter is the 

 stationary electric field. The introduction to this part 

 is specially noteworthy. It has seemed to Prof. 

 Chwolson necessary to commence by giving a sum- 

 mary of the singular and exceptional situation in 

 which the science of electrical and magnetic pheno- 

 mena now is. At the present time one may distin- 

 guish no fewer than three various points of view from 

 which these subjects are regarded. We have, in the 

 first place, to deal with the external structure of a 

 very great number of different phenomena which, per- 

 ceived by our senses, awaken in us a representation 

 more or less definite of what is proceeding, or, more 

 exactly, of what seems to us to proceed in a given 

 direction and under given conditions. Thence arises 

 a description of phenomena and of the laws and rules 

 by which those phenomena are regulated. Secondly, 

 we may place ourselves at another point of 

 view, and consider the practical applications ; or, 

 thirdly, we may endeavour to explain these phenomena 

 by showing that they are the necessary consequence 

 of the existence of a certain substratum to which the 

 laws of mechanics and thermodynamics are applicable. 

 In regard to this third point of view. Prof. Chwolson 

 declares that — 



" Without wishing to exaggerate, we may say, after 

 having glanced rapidly over the facts, that there does 

 not exist at this moment in the part of this science 

 which has for its object the explanation of phenomena, 

 any theory which is firmly established upon which we 

 may rely in a manner free from all possible doubt to 

 give an account of all phenomena." 



He recognises, however, three fundamental concep- 

 tions which excite three distinct images or pictures 

 which give a more or less exact representation of the 

 intimate cause of phenomena. These he designates 

 by the letters A, B, and C. The image A, adopted 

 in a general manner up to the year 1870, was con- 

 structed on the notion of two electricities, enjoying 

 the propertv of acting instantaneously at a distance. 



D 



