December 29, 1898] 



NATURE 



199 



comes infinitesimal as « increases indefinitely ; and it 

 should have been stated explicitly that / is a definite 

 symbol obeying the law /- = - i, together with the usual 

 laws of operation, and that if (I is positive v' - '^ 's under- 

 stood to mean ^ja Qi. If these last precautions are not 

 taken, it cannot be proved, for instance, that ^/ - a 

 X ^f - /> = - tjab, and, jn fact, the authors' treatment 

 of this identity is defective. Then such problems as 

 " factor a ■'r b" are perfectly unmeaning, especially after 

 chapters on surds and complex numbers ; probably the 

 answer intended is { ^fa + i y/i) [Ja-i^b), but any 

 number of others might be constructed, for instance 

 { 'J'' + yji + V4<"5') ( V" + \'b - i/4abX and so on. It 

 ought to be unnecessary to say that all questions on 

 factors should be put in a perfectly definite way. 



It is a pity that the elementary theory of graphs has 

 not been included ; every teacher who has tried the ex- 

 periment must have realised the value of plotting off the 

 graphs of even the simplest functions such as x, x-, 

 xl(i - x), and so on. Another remarkable fact is that not 

 a single word is said about partial fractions : this is a 

 serious omission, and, in fact, a whole chapter on rational 

 functions might be added with advantage. 



This volume ends with a chapter on the binomial 

 theorem for a positive integral exponent. The examples 

 are very numerous, and appear to be well graded : they 

 are intended to provide teachers with alternative sets for 

 difierent years. The student should on no account try to 

 work them out seriatim. G. B. M. 



Distribution dc Fenergie par coiirants polypluises. By J. 



Rodet. Pp. 338. (Paris : Gauthier-Vlllars, 1898.) 

 The present work is perhaps, in point of thoroughness of 

 treatment, the best on this subject we have yet seen. It 

 is written, not as an introduction to a hitherto unknown 

 subject, but as an account of a well-established branch of 

 engineering. 



In this country, the comparative absence of water- 

 power near our industrial centres, and the resulting small 

 •demand for long-distance power-transmission, has led to 

 -a relative indifference to this important subject. What 

 limited field for such transmissions does exist, seems at 

 present to arise rather from the vastness of our towns, 

 than from the existence of available water-power. 



The economy in electrical transmissions of energy, 

 which accompanies the employment of high-pressure 

 •currents, has led to the use of the readily-transformed 

 alternating current. And while, as M. Rodet remarks, 

 electric lighting can be carried out equally well with 

 ■single-phase currents as with polyphase, yet, for purposes 

 •of motive power, the absence of a good motor to run 

 on single-phase circuits, and the excellence of the 

 rotary field motor, necessitates the use of polyphase 

 •currents by which alone the rotary magnetic field can 

 be produced. 



.Starting with an historical summary, M. Rodet deals 

 successively with generator, line, and motor. While keep- 

 ing the essentially practical aspect of his subject in view, 

 •and citing from time to time, by way of illustration, the 

 •conditions of actual installations, the author, nevertheless, 

 does not hesitate to launch into ample theoretical investi- 

 gations where he deems these called for. At the conclusion 

 •of the main part, a short but interesting chapter on meters 

 for polyphase currents is given. 



Of more general interest, however, are the descriptions 

 of installations. These form a most interesting conclusion 

 to the work. We observe that just one quarter of the 

 ■examples selected by the author as types for description 

 are two-phase transmissions ; the rest are three-phase 

 •installations, and these include several of importance in 

 south-west France. 



The illustrations are for the most part simple and 

 NO. 1522, VOL. 59] 



clear. English readers will feel the lack of an alpha- 

 betical index, and would prefer to have titles to the 

 illustrations. The work should, however, prove of great 

 value to engineers who wish to make a special study of 

 polyphase current machinery. D. K. M. 



My Horse ; My Love. By Sarah Buckman-Linard. Pp. 

 xii -I- 227. (London : T. Fisher Unwin, 1898.) 



It is a little difficult to classify Mrs. Bucknian-Linard's 

 book. It is not a treatise, nor a text-book, nor a story. 

 It is written in a conversational style not always easily 

 followed. Here is a sentence which demands exceptional 

 powers of perception : — " In some the odour is perceptible 

 to themselves only, while in others it is such a powerful 

 means of defence as to make the pursuing victim wish he 

 had never been born, which floods cannot drown nor fires 

 quench, if any part escape, and only six feet of earth 

 can extinguish " (p. 22). The book is divided into 

 chapters, but the title of the chapter is little indication of 

 its contents ; e.g. Chapter ii. is headed " Facilities for 

 Breeding in America," and after a few generalisations on 

 the subject mentioned in the title the following questions 

 are dealt with : — Is it possible that human beings have the 

 same diseases as horses .'' Are the symptons easily 

 recognised (reference is made to the symptons of 

 glanders)? Is it possible to mend a broken leg? 

 Chapters are also included on jockeys, the Derby day, and 

 training. At the same time there is a quantity of inform- 

 ation about the horse, scattered here and there in the 

 volume ; and if it had been systematically arranged in half 

 the compass, it might have proved useful. 



Matter., Energy, Force and Work. By Silas W. Holman. 

 Pp. xiv -I- 257. (New York : The Macmillan Company, 

 1898.) 



Prof. Holman here addresses students and teachers 

 of physics and chemistry on the concepts and definitions 

 of physical science. Some knowledge of the experimental 

 side of the subject and its phenomena and laws is 

 assumed, and the logical expression and sequence of the 

 ideas put forward should prove of great value to 

 engineers, and others who have to apply physical and 

 chemical knowledge, in enabling them to think clearly 

 when dealing with the fundamental ideas on which all 

 successful practice must be based. The book is divided 

 into two parts : the first is concerned with a consideration 

 of matter, motion, energy, force and work; the second 

 with the kinetic theory of gases, Le Sage's theory of 

 gravitation, the vortex-atom theory, and the nature of 

 energy and matter. Prof. Holman describes the first 

 part as " a sporadic attempt at clear, consecutive setting 

 forth of individual thought," the second as intended " to 

 give more concreteness to the concepts than could 

 properly be introduced into the first part." The volume 

 deserves to be widely read. 



The Way the World Went Then. By Isabella Barclay 

 Pp. xiv -I- 153. (London : Edward Stanford, 1898.) 



The author of this volume did not live to see it through 

 the press, and the MS. has been edited by two lady 

 friends, who contribute the preface and a summary of 

 three pages, in which they state what they think the 

 author would have included in the second part of her 

 work had she lived. It would be unkind to subject a 

 \olume produced under these conditions to severe 

 criticism, and we will merely say that, although the 

 book affords evidence of a fervent desire to present the 

 earth's history in a simple and interesting manner, it is 

 seriously misleading in many matters of fact, and un- 

 equal in treatment. The volume is daintily bound, and 

 has some attractive illustrations. 



