556 



NA rURE 



[April 17, 1902 



theory and thus do not serve to establish it. (The 

 simplicity and directness of Pellat's theoretical investiga- 

 tion seem noteworthy when compared with the discus- 

 sions of Gouy and of Larmor ; ' in each of the latter some 

 of the apparent forces have to be explained away, and 

 they appear to contradict each other. It may be that in 

 such discussions too much importance is at present 

 assigned to Maxwell's stress-system in the absence of 

 more definite knowledge concerning the transmission of 

 force between itther and matter, if the use of such a 

 phrase is permissible.) 



Prof. Duhem points out that Maxwell, in obtaining his 

 first estimate of the velocity with which electromagnetic 

 waves are; propagated,- confounds Lame's coefficient of 

 rigidity with one of his own, which is really double the 

 former, and that on correcting this mistake a velocity is 

 obtained which exceeds that of light in the ratio of V2 

 to I. This work of Maxwell's is, however, generally 

 regarded as containing only the germ of a tTieory of 

 light and as indicating that the two velocities concerned 

 are of the same order of magnitude. 



The author concludes by lauding the electrodynamic 

 theory of Helmholtz, which he regards as satisfactorily 

 reconciling the electromagnetic theory of light with the 

 ancient theories of electricity and magnetism. 



it is surprising to find no reference whatever to Larmor 

 or to H. A. Lorentz in the historical sketch of this branch 

 of the subject. 



Although some of the mistakes pointed out by Prof. 

 Duhem are real and important, the view taken through- 

 out, as will be gathered from the above, appears a very 

 narrow one. W. McF. Orr. 



OUR BOOK SHELF. 



Clinical Pathology and Practical Morbid Histology. By 



J. Strangeways Pigg, M..-\. Second edition. Pp.107; 



5 plates and 6 figures. (London : Strangeways and 



Sons, 1901.) Price ^s. 

 This is a small interleaved handbook for use in the 

 laboratory, dealing with the different methods employed 

 in examining blood and other normal and pathological 

 fluids and morbid tissues. 



The descriptions of the various methods referred to 

 are brief and concise, and the steps of each operation are 

 tabulated in exact sequence, with perhaps the exception 

 of 24, D, where steps 6 and 5 should obviously be trans- 

 posed. Objection may be raised to such an arrangement 

 as being too dogmatic and allowing no scope for in- 

 dividual ingenuity, but, on the other hand, those who 

 have to deal with large classes of students, to whom the 

 book is chiefly directed, will agree that some such method 

 is absolutely necessary if one would instil the principles 

 underlying good technique. 



The general "get-up" of the book is good ; there are 

 very few printers' errors save an occasional missing letter 

 at the end of a line, or the interpolation of a letter from 

 another fount of type. " The illustrations," we are told, 

 "are diagrams only," a description obviously applying to 

 those of apparatus and urinary sediments — which latter, 

 by the way, would have been more useful had they been 

 bound up in somewhat closer proximity to the letter- 

 press relating to them — but hardly fair to the two coloured 

 plates of blood-cells. These are, in spite of their accuracy, 

 beautiful and artistic, and reflect nothing but credit on 

 artist and lithographer. 



1 Fhil. Trans. 1897, A. p. 248. 



- '* Scientific Papers," vol. i, p. 500. 



NO. 1694, VOL. 65] 



The methods set out in the text are, for the most part, 

 well chosen and well described ; those dealmg with 

 morbid histology are, however, by far the most successful. 

 In blood work, we notice, the author recommends 

 Cabol's "two-cover-slip' method of spreading films — a 

 method which in the hands of experts yields, perhaps, lo 

 per cent, of stainable specimens^and quite ignores the 

 simpler method introduced by Manson, in which gutta- 

 percha tissue or a piece of cigarette paper is employed. 



We notice, too, in the preparation of cover-glass films 

 from pus or sputum, that extremely dirty and slovenly 

 method of pressing out a small portion of the material 

 between two cover-glasses and then sliding them apart, 

 is given as the usual method. We hope that this is not 

 the universal practice in Cambridge laboratories. 



The sections dealing with bacteriological methods and 

 urinalysis are certainly disappointing — in the latter the 

 methods are few in number and, in our opinion, not 

 always happily chosen, whilst fuller indications of the 

 fallacies which attend some of the tests would have 

 enhanced their value. In that portion dealing with 

 bacteriological investigations, many of the methods might 

 find favour in the clinical laboratory, but would certainly 

 be taboo in the well-regulated bacteriological laboratory. 

 We notice, too, that the author invariably uses Carbol- 

 gentian-violet in staining by the method he terms Gram's ; 

 it is true the actual stain is easier to prepare, but its 

 results are decidedly inferior to those yielded by the 

 Anilin-gentian-violet originally described by (iram. 



As we have before mentioned, the book is intended 

 for the medical student, and as such is of distinct value, 

 a fact sufficiently evidenced by the success with which the 

 first edition has met 



The Balancing of Engines. By W. E. Dalby, M.A., 



B Sc. Pp. xi -H 283. (London : Edward Arnold, 



1902.) Price lay. i>d. net. 

 This work is of a character which can be studied with 

 interest. It deals with a subject of great importance to 

 mechanical engineers, and one which is coming more 

 and more to the front in the design of high-speed 

 engines and machinery. 



Prof. Dalby is the author or several papers dealing 

 with this important subject, read before the Institutions 

 of Naval .-Vrchitects and Mechanical Engineers ; these 

 papers are largely drawn upon in the present volume. 



"The main object of the book is to develop a semi- 

 graphical method which may be consistently used to 

 attack problems connected with the balancing of the 

 inertia forces arising from the relative motion of the 

 parts of an engine or machine." This we learn from 

 the preface, and, what is more, it requires nothing but 

 the knowledge of the four rules of arithmetic and good 

 draughtsmanship to apply satisfactorily the methods so 

 well described. 



The balancing of the working part of locomotives has 

 always been treated from different points of view, and 

 the practice of a particular drawing office largely governed 

 the result ; in fact, not many years ago an eminent loco- 

 motive engineer looked upon the balancing of his 

 locomotives as an unnecessary addition to their weight. 



Chapter iv. deals with this very important subject in 

 a clear, concise and practical manner, and even only 

 for this one chapter all interested in locomotive design 

 should possess this volume. The author advises that 

 those interested in locomotive work should begin 

 chapter iv., after working the e.xamples of arts. 4S and 

 49, progress being tested by working the exercises at the 

 end of the book. 



The treatment is simple, several types of Lancashire 

 and Yorkshire Railway Company's locomotives being 

 taken as examples, and little thought will be necessary 

 to carefully follow the threads of the argument. The 

 experimental apparatus described to illustrate the 



