38o 



NA TURE 



[August i6, 1906 



are none of us rich enough to care to throw aside a 

 copy of a three-dollar book when four or five pages 

 of it have become too dirty or too tattered to please 

 our fastidiousness. 



We do not know a more excellent book on its 

 subject. P. H. C. 



OUR BOOK SHELF. 



Die neucren Wandlungen der elchtrischcn Tlicorien 



einschiesslich der Elektroiientheorie zwei Vortragc. 



By Dr. Gustave Holzmiiller. Pp. viii+iig. 



(Berlin : Julius Springer, 1906.) 

 In this little book the author publishes some lectures 

 delivered before a society of German engineers. The 

 subjects for discussion do not seem to have been 

 selected on any principle, and are inadequately repre- 

 sented by the title. The first chapter deals with 

 Newtonian potential, the second with logarithmic 

 potential; neither of these topics can be described as 

 " neueren Wandlungen." We then proceed to the 

 theories of electromagnetism based on " action at a 

 distance," and are informed at the conclusion that 

 these developments are also not new, having been 

 superseded by the Faraday-Maxwell theory, to which 

 the next chapter is devoted. The author devotes a 

 considerable amount of space to analogical represent- 

 ations of the electric field, but the electromagnetic 

 theory of light is considered beyond his scope. 



No doubt the author knows best what is likely 

 to interest his hearers ; it is sufficient for our purpose 

 to note that his treatment is undeniably accurate. 

 But it should be pointed out that the information 

 which he assumes that his readers possess is rather 

 heterogeneous. The training of German engineers 

 must be very different from that of their English 

 colleagues if they require a lengthy proof that the 

 conservation of mechanical energy is a consequence 

 of the Newtonian law of attraction, and yet are ready 

 to plunge, on the next page, into a discussion of the 

 dimensions of electrical units. 



The final chapter deals with the theory of electrons ; 

 it is really a description of some of the more important 

 properties of kathode and Becquerel rays. The 

 mathematical aspects are hardly mentioned, so that 

 the term " electromagnetic mass " is used without a 

 word of explanation as to its meaning. It is to be 

 regretted that in this part of his work, where 

 accuracy is especially desirable in the absence of com- 

 plete text-books, there are to be found many state- 

 ments which require considerable revision. In fact, 

 when we find the author stating that the diameter 

 of an electron has been determined by the application 

 of the kinetic theory of gases, and accounting for 

 the ionisation of a gas b)' the adherence of a slow- 

 moving electron to the neutral molecule, we begin 

 to doubt his competency to lecture or write at all on 

 these subjects. N. R. C. 



The Unity of Will. Studies of an Irraiioiialist. By 

 George Ainslie Hight. Pp. xv + 244. (London: 

 Chapman and Hall, Ltd., 1906.) Price los. 6d. 

 net. 

 Even if the thinking of this book were of the best, it 

 would seem a somewhat expensive morsel at half the 

 price ; and its thinking is not of the best. It pro- 

 fesses to be an exposition of the leading doctrine of 

 Schopenhauer, that in self-consciousness the primacy 

 belongs to will. The author is at the same time 

 careful to explain that he is a Vedantist while 

 Schopenhauer is a Buddhist, but we doubt if the 

 ordinary man will appreciate these fine distinctions. 

 NO. 1920, VOL. 74] 



We rather fear that the ordinary man will be repelled 

 by a certain lack of unity, coherence, systematic 

 statement, and logical proof. Thus, for example, we 

 have a chapter full of irrelevancy on " hysteria and 

 sophistry, the deadly evils of civilisation." Thus, 

 too, we have a small appendix on the notion of life, 

 which explains that everything in the world is in a 

 certain sense alive, and seems to regard it as a valid 

 argument that " the language of the skilled artisan 

 is full of anthropomorphic expressions." A five-page 

 statement of first principles at the end has certain 

 of the merits tliat are so conspicuously lacking in the 

 main body of the volume. 



Diet and Dietetics. By A. Gautier. Edited and 

 translated by Dr. A. j. Rice-Oxley. Pp. xii -1-552. 

 (London : A. Constable and Co., Ltd., 1906.) Price 

 18s. net. 

 This is a translation of the second edition of Prof. 

 Gautier's book published in Paris in 1904. It contains 

 a vast mass of useful information, and is a laudable 

 attempt to be an exhaustive treatise on diet. It deals 

 with the individual articles of food, animal, vegetable, 

 and mineral; with the combinations of these that con- 

 stitute dietaries; it contains (inter alia) discussions, 

 lightened by homely phrases and apt illustrations, on 

 the dietaries of different races, on vegetarianism, on 

 the part played by food as a source of heat and 

 energy, on the alcohol question ; and finally treats of 

 the part played by diet in the cure and alleviation of 

 disease. Prof. Gautier's large experience would lead 

 one to anticipate a useful book ; the arrangement of 

 subjects appears, however, to be rather confusing, 

 and the translator, although as a rule he has done 

 his work ably, is not always happy in rendering the 

 original into acceptable English. 



German Grammar for Science Students. By Prof. 

 W. A. Osborne and Ethel E. Osborne. Pp. viii-l- 

 106. (London : Whittaker and Co.) Price 2s. 6d. 

 net. 

 Science students who have not been taught German 

 in schools will find this volume very useful in enabling 

 them to read scientific papers published in that 

 language. The essential parts of German grammar 

 are described in sixteen lessons, and the exercises, 

 instead of being of the " Have-you-seen-the-hat-of- 

 my-uncle?" type, deal with scientific work and 

 phrases — chiefly relating to chemistry — from the be- 

 ginning to the end. Lists of words commonly met 

 with in scientific German, and terms of frequent 

 occurrence in papers on anatomical, botanical, 

 chemical, physical, mathematical, and physiological 

 subjects are given in an appendix. The book should 

 be particularly valuable to private students. 



LETTER TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



Colour Phenomena in "Boletus coerulescens." 



In reply to the query by Edgar Trcvithick respecting 

 the blue coloration in Boletus, I3ourquelot and Bertrand 

 (Bull. Soc. Myc, 1896, p. 18) have recently investigated 

 the subject, and consider the action due to the presence 

 of an oxidising ferment they have named tyrosinase. This 

 ferment acts on certain chromogenous materials present 

 in the fungus when exposed to the air. 



Geo. Massee. 



Royal Botanic Gardens, Kew. 



