30 



NATURE 



[May io, 1900 



motions, with suitable illustrations, are fully explained. 

 On "beating-up," the author has some instructive in- 

 formation respecting the movement of the crank for 

 carrying the batten or going part against the fell of the 

 fabric. He supplies a table showing the motion of the 

 crank, and treats of the length of the crank-arm and the 

 eccentricity of movement. The concluding portions of 

 the book are devoted to weft-stop motions, mechanism 

 for governing the warp and taking-up of the fabric, the 

 construction of temples and selvage motions. There is 

 also a chapter on the arrangement of weaving -rooms or 

 sheds, with a plate illustrative of the positions of the 

 looms and other machinery. The book should be in 

 the possession of all those interested in the construction 

 of power looms. 



OUR BOOK SHELF. 



Legons cf Opftque geoni^friqtte ci I' Usage des iillves de 

 Mathhnatiques spdciales. Par E. Wallon, Professeur 

 au Lycee Janson-de-Sailly. Pp.343. (Paris : Gauthier- 

 Villars, 1900.) 

 This book has been v ritten at the desire of Prof. 

 Wallon's students, to whom a graceful tribute is paid, 

 in the preface, for the assistance which their questions, 

 doubts and objections have rendered in developing the 

 author's methods of teaching. To look on one's students 

 as collaborators, that is certainly the secret of suQcessful 

 teaching ; and, as here presented. Prof. Wallon's lectures 

 are certainly successful in giving a systematic and clearly 

 defined outline to the science of geometrical optics. The 

 diagrams are well drawn and numerous, and the mathe- 

 matical proofs are simple and yet sufficient. There is, 

 however, little that is novel to be found in the course of 

 these lectures ; indeed, in a few cases it might be 

 objected that there was a tendency to lag behind 

 the times. Thus, in discussing refraction equivalents. 



Newton's law, that — 



2 _ 



and Dale's law, that 



d 



n - I 

 d 



constant, and Gladstone 



constant, are alone men- 



tioned {n being the refractive index, and d the density 



of the substance). Lorenz's law, that -^-^^ — = con- 



{n^ + 2)d 

 stant, is now most generally accepted. For gases, in 

 which n is nearly equal to unity, all three laws hold 

 with about equal accuracy. But Lorenz's law appears 

 to hold in passing from .the gaseous to the liquid state, 

 and must therefore be accepted as the most general. 



An interesting chapter is devoted to the subject of the 

 human eye, in which the most well known optical proper- 

 ties of that organ are discussed. In the ensuing chapter, 

 on optical instruments, a particularly good account is 

 given of the optical systems comprised in telescopes and 

 microscopes of various patterns. It is surprising, how- 

 ever, that the ophthalmoscope and ophthalmometer are 

 not mentioned, and are in fact so seldom found described 

 m works on geometrical optics. Both instruments involve 

 interesting optical arrangements, and their practical 

 usefulness would render a description of their details 

 still more interesting. E. E. 



Therapeutic Electricity and Practical Muscle Testing. By 



W. S. Hedley, M.D., M.R.C.S. England. Pp. ix -f 278 ; 



3 plates ; 99 illustrations. (Lo.idon : T. and A. 



Churchill, 1899.) 

 The increased use of electro-therapeutic methods renders 

 the appearance of Dr. Hedley's book welcome. The 

 profession have for some time looked somewhat askance 

 at this departure in therapeutics, and are, in many branches 

 of this practice, rather inclined to regard the good effect 



NO- 1593. VOL, 62] 



of the treatment as moral and not actual. The work 

 before us considers the whole subject from a scientific 

 standpoint, and any one interested in it will gain con- 

 siderable profit from its perusal. 



The reader must be warned at once that the book con- 

 tains no mention of radiography or the application of the 

 Rontgen rays to the healing art, either from a diagnostic or 

 therapeutic standpoint The author, in his preface, admits- 

 that the work is a therapeutical one, and to some extent 

 apologises for the description of such instruments as the 

 cyscoscope, &c. No doubt he thinks the profession is 

 in possession of sufficient literature upon the subject of 

 radiography,, which may or may not be true ; the sphere 

 of usefulness of the book would, however, certainly have 

 been increased by the inclusion of this subject. 



The work is divided into three parts. The reason for 

 this classification is not quite evident ; a part as a classi- 

 fication unit seems, in the author's hands, to differ to no 

 material extent from a chapter. Further, each part is 

 chaptered separately, which, without some very special 

 object is to be gained, is a bad plan ; from this it follows 

 that the book contains three Chapters i., &c. 



The first part is mostly concerned with those general 

 physical considerations which have a special bearing 

 upon what the author in the first chapter of Part ii. calls 

 the electro-therapeutic outfit. A good account is given 

 in Chapter vii. (p. 65) of currents of great frequency 

 and high potential, which, as has been frequently shown, 

 are of great therapeutic value. Much technical detail is 

 given, both of a purely electrical and electro-physiological 

 character. 



One of the most useful chapters from the standpoint of 

 the general physician is Chapter v. Part ii., upon the 

 action of muscles and the consequences of their paralysis. 

 In Chapter x. Part iii., an interesting account of cala- 

 phoresis is . given. Very frequent mention is made of 

 authors' names and no reference added, nor is there an 

 index of authors at the end, or anything in the shape of 

 a bibliography. Mere chance or whim has apparently 

 guided the author in giving or omitting the full reference 

 of a work cited ; in some cases the full reference of 

 important monographs is withheld, in others that of 

 trivial ones given. This method cannot be too severely 

 deprecated. 



To sum up our remarks, it is with the manner and not 

 the matter of the book we find fault. It is full of usetul 

 and, indeed, essential information to those working in 

 this field ; the author has spared no pains to collect fact 

 bearing upon and elucidating his subject. 



Lessons in Botany. By Prof George F. Atkinson, Ph. B. 

 Pp. XV -1-365. (New York : Henry Holt and Co., 1900.) 

 Thk present volume is, in a sense, an abridged edition 

 of an excellent text-book by the same author, which 

 appeared a year or two ago. The subject-matter is care- 

 fully arranged to suit the convenience of teacher land 

 pupil, and altogether the book is one which should prove 

 useful in this country as well as in America. Naturally, 

 from the British point of view, the difficulty of obtaining 

 the needful specimens occasionally may turn up, though 

 this would not recur very often. We can confidently 

 recommend Prof Atkinson's book to the notice of 

 teachers. 



Outlines of Plant Life., with special reference to Form 

 and Function. By Prof. Charles Reid Barnes. Pp. 

 vi -1-308. (New York : Henry Holt and Co., 1900.) 

 This is a work intended for school use. It has some 

 points of merit, especially the special part on ecology, in 

 which the examples are well chosen and fully illustrated. 

 The illustrations, though almost all are (with due acknow- 

 ledgment) borrowed from other works, are distinctly 

 good. We think the book a useful one, and the exercises 

 which are interspersed through the volume add to its 

 value. 



