October 25, 1906] 



NA TURE 



^IZ 



OUR BOOK SHELF. 



Ri'-sistaiuf. liuliiitaiuc cl Capacitc. Hy M. J. Rudi:!. 



Pp. X + J57. (Paris: (iauthicr-Villars, 1905.) 

 Tills book In devoted entirely to tlie tliree subjects 

 whicli form llir tillc, and it lias evidently been the 

 aiillior's aim In include cverythinfj witliin the limits 

 mentioned likel\- to be of use to enj^ineers or 

 physicists. 



As a wliiili ihc author has .succeeded, and h;is pro- 

 (Uiced a valualile book (il reference. The subjects are 

 treated in the order mentioned. L'nder the heading 

 of resistance, in addition to the usual constants, in- 

 lormalion is t;ivcn as to the conductivities of insu- 

 lators, solid and liquid, and the insulation due to a 

 film of oil between a rotating shaft and its bearings. 

 An account is given of the various rectifiers, including 

 the Cooper-Hewitt. 



Under the heading of inductance a full .and clear 

 statement is given of the usual phenomena, and the 

 \arious methods of calculating coefficients of self- 

 .iiid mutual inductance are explained, but no mention 

 i-- made of a rectangular coil such a.s is used in 

 certain instruments of the dynamometer style. The 

 inductance of cables is also studied, and a reference 

 is made to the apparent increase of resistance of 

 conductors traversed by alternating currents, but no 

 mention is made of the internal self-induction of an 

 iron rail, which is an important factor in the appli- 

 cation of alternating currents to electric traction. 



The initial portions of that part of the book which 

 is devoted to the study of capacity follow the ordinary 

 methods of exposition. Tables of specific inductive 

 capacity of various substances are given, and inform- 

 .11 ion is presented as to the variation of this property 

 with temperature. Following this, the distribution of 

 the potential in a compound condenser is described, 

 as. for instance, in a condenser in which the dielectric 

 is com|X)sed of two plates of glass .separated bv a 

 layer of air. (This matter is of practical importance 

 in the building of high-voltage machines, as brought 

 out by Messrs. Hobart and Turner in their recent book 

 on insulating materials.) A brief reference is made to 

 the electrodynamic condenser proposed bv Mr. Swin- 

 burne, and a .section is devoted to the studv of 

 capacity effects due to cables and overhead trans- 

 mission lines. 



The book would h.a\'e been more complete if the 

 researches of the late Dr. John Hopkinson had been 

 referred to as to the specific inductive capacity of 

 materials at very low temperature. For practical 

 men, however, this volume contains almost evervthing 

 that they are likely to want, and to them it can be 

 thoroughly recommended. 



Xaliinil Phenomena. .1 CoUeclioii of Dcsiriplive and 

 .Speciilatii'c Essavs on some of the Bv-paflis of 

 Nature. By F. .\. Black. Pp. xiv4-;,66.' (London 

 and Edinburgh : Gall and Inglis, n.d.) 

 In- this book Mr. Black offers some essays which 

 might well be of value to the student of phvsio- 

 graphy. Treatises on this subject are usually 

 crammed very full of facts, and more interest might 

 be awakened and ;i wider horizon opened to the 

 student, if he reads such a work as this in connection 

 with the ordinary text-books. There are ten essays 

 .iltogether; four deal with some points connected 

 with our own atmosphere, and four discuss problems 

 of elementary astronomy, arising mainly from the 

 motion of the earth on its axis. The remaining two 

 treat of the Sargasso Sea and the Zodiacal Light with 

 its allied phenomena. These seem to be highwavs 

 rather than by-paths. 



NO. 1930, VOL. 74] 



It would not be correct to say that Mr. Black is 

 always exact in his descriptions; he is apt to be some- 

 what loose, and his book suggests that he has not 

 consulted the moht recent authorities. But he is 

 never so far wrong as to be misleading. He may 

 puzzle the student by apparent contradictions, due to 

 the introduction or exclusion of circumstances which 

 can exercise an important intluence upon the point 

 under consideration. Particularly would we caution 

 the student to beware of those explanations for which 

 the author himself is responsible, and in which he 

 seeks to remove difficulties that have not yet received 

 a satisfactory solution. An example will be found in 

 the discussion on the semi-diurnal barometric in- 

 equality. The author seems, too, to have lost his way 

 in the chaiHer on weather cycles ; but the book is 

 calculated to arouse interest, to stimulate curiosity, 

 to promote further study, and on these grounds one 

 may welcome its appearance. The illustrations arc 

 geiierallv effective, and a verv good index accompanies 

 the book. 



.1 Text-book of General Zoology. Bv Dr. Henry R. 

 Linville and Dr. Henry .\. Kelly. Pp. \ + ^62\ 

 illustrated. (London and Boston : Ginn and Com- 

 pany, 1906.) Price ys. 6d. 



This addition to the long shelf of text-books of 

 zoology has some fresh features. Practical experi- 

 ence has led the authors to begin with the .Arthropods, 

 work down to the Protozoa, and then ascend the 

 vertebrate series. The study of insects has been found 

 the best introduction to the broad problems of zoologv, 

 and in the earlier chapters a modified inductive 

 method is pursued. About half-way through the 

 book, after the student has become familiar with 

 systems of organs, he is introduced to physiological 

 principles, illustrated with special reference to the 

 earthworm. Throughout the book prominence is 

 given to the study of animal behaviour and the 

 environmental conditions. Thus there is a feeling of 

 fresh air through the chapters. The authors have 

 reacted from the position of identifying zoologv with 

 comparative anatomy, and the introduction to the 

 science which they have presented seems to us, not 

 only interesting, but educationally wholesome. Most 

 of the illustrations are original, and many of them 

 are beautiful. 



Science Readers. Book VII. By Vincent T. Murche. 



Pp. 299. (London : Macmillan and Co., Ltd., 190b.) 



Price IS. qd. 

 Object Lessons in Elementary Scie)ice. Stage VII. 



By Vincent T. -Murche. New and revised "edition. 



Pp. xvi + j22. (London: Macmillan and Co., Ltd., 



1906.) Price 2s. 



These books deal with elementary physics. The first 

 is intended for pupils to read in class, lesson by 

 lesson, after they have attended an explanatory and 

 experimental demonstration from the teacher on the 

 subject in hand. The second book contains notes of 

 lessons designed only for the use of teachers. The 

 notes are accompanied by helpful advice, blackboard 

 sketches, and many other evidences of the wide experi- 

 ence of the author. Both volumes are attractively 

 illustrated and well printed, though it may well be 

 doubted if the bewildering profusion of types in the 

 second book adds to its helpfulness. The author is a 

 master of simplicity of expression, and the inform- 

 ation he supplies is, as a rule, trustworthy. The 

 books descr\e the careful consideration of teachers of 

 veiy elementary classes. 



