3H 



NA TURE 



[August 4, 1898 



some general idea of the scope and purpose of the work. 

 After a general treatment of alternating currents, chiefly 

 following the law of sines, the practical measurement of 

 power in alternating circuits, the effects of phase dis- 

 placement, effects of capacity, displacement currents, are 

 all dealt with. Then the transformer is introduced by 

 (i) a chapter on mutual inductance, in which the theory of 

 some important cases of mutually influencing currents is 

 explained, and the rationale of the growth of the current 

 in the outer layers of a conductor and its penetration in- 

 wards are touched upon, and (2) a chapter in which the 

 very important case of two mutually influencing circuits, 

 containing simple harmonic electromotive forces, is very 

 well explained by means of vector diagrams. 



Here we may incidentally remark that we very much 

 prefer on the whole the analytical treatment of this kind 

 of problem, supplemented by a full graphical exhibition 

 of the results, to an attempt to give a graphical treat- 

 ment purely of the subject. The analysis is easy enough, 

 if only people will concentrate their attention on the 

 thing to be understood, and generally be at a little real 

 trouble. The purely graphical process is somewhat 

 fatiguing after all, and, while the student may under- 

 stand a discussion of such a problem as this, he is not 

 likely, unless he obtains some skill in analysis, to be 

 very self-dependent in new questions which may arise. 

 A great deal of the girding at mathematicians and ex- 

 alting of so-called common-sense and practical methods 

 of treatment (often only illustrations of results otherwise 

 to be demonstrated) is the veriest clap-trap. 



However, of anything of this kind there is not a trace 

 in Mr. Hay's book ; on the contrary, no difficulty is 

 shirked, and he takes a course which, whether we think 

 it the best or not in all cases, has been suggested to him 

 by experience gained in the efficient school of electrical 

 engineering of which he is in charge at Liverpool. 



The running of alternators is next entered on, and 

 synchronous motors, and single phase and polyphase 

 currents, and induction motors generally, with the 

 measurement of power in polyphase circuits, conclude 

 the book. 



Want of space prevents our giving a fuller appreciation 

 of this unpretending but very scientific and accurate 

 little book. It is in all respects a piece of good work, 

 and has already proved, we doubt not, thoroughly 

 acceptable to students. 



Mr. Russell Robb's treatise on electric wiring gives a 

 useful account of systems of distribution, methods of 

 wiring, and the code of rules for electric wiring now 

 accepted by underwriters throughout the country. The 

 first two chapters on the electrical units. Ohm's law, and 

 such subjects, seem to us for the most part unnecessary. 

 The explanations and analogies are very briefly and 

 somewhat vaguely stated, and an elementary knowledge 

 of 'these subjects on the part of the reader had better 

 have been taken for granted. Certainly it is not here 

 given, and the only effect the generalities stated can 

 have will be to lead the ordinary business man, e.g. the 

 town councillor interested in an electric lighting scheme, 

 to delude himself into fancying he knows what current, 

 electromotive force, and resistance really signify. How- 

 ever, Mr. Robb has done a very useful thing in printing 

 the other parts of his book. The style and get-up of the 

 NO. 1 501, VOL. 58] 



book are very good, though the size of page, paper, &c., 

 do not strike us as very well chosen. A smaller page, 

 thinner paper, and flexible covers, with excision of the 

 introductory matter referred to above, would have given 

 a much lighter and more convenient book to carry about 

 for reference when wanted. A. GRAY. 



THE ANGORA GOAT. 

 The Angora Goat j and a Paper on the Ostrich. By 

 S. C. Cronwright Schreiner. 8vo. Pp. xv -f- 296 ; 

 illustrated. (London : Longmans, Green, and Co., 

 1898.) 



NO one taking up this little volume and looking 

 merely at the cover would have the slightest 

 intimation that it included a chapter on ostriches, and 

 since some of the notes contained therein are of con- 

 siderable interest, it is well that its existence should be 

 noted. Another surprise is the absence of either preface 

 or introduction, although, perhaps, the book is none the 

 worse for the omission. 



When a work commences with references to popular 

 natural histories as the sources of the scientific inform- 

 ation, it may be taken as a general rule that the author 

 is insufficiently acquainted with his subject, and is a 

 stranger to the methods of zoological research. Athough 

 thus handicapping himself at the start, Mr. Schreiner 

 very soon shows that he has a complete grasp of all the 

 essential facts connected with the Angora goat and its 

 relations to other wild and domesticated breeds, both 

 from the point of view of the naturalist and from that of 

 the agriculturist and the manufacturer. And he has 

 succeeded in producing a work which cannot fail to be 

 of considerable interest to all those intereste d in the 

 origin of our domestic animals. 



Since Darwin's time, it must be confessed that the 

 attention devoted by naturalists to domesticated animals 

 has been of the very slightest ; and this is distinctly to 

 be regretted, since there seems little doubt that much 

 is to be learned from them concerning the capacity for 

 variability in species. And here it may be mentioned 

 that a gallery exhibiting the different breeds of domest- 

 icated animals is a desideratum in this country. If it 

 cannot be attempted in the British Museum, it might be 

 commended to the attention of the Royal Agricultural 

 Society. 



To return to our subject, the author is quite orthodox 

 in accepting the descent of the domestic breeds from the 

 Persian wild goat {Capra hircus (sgagrus, as it may well 

 be called), and rejecting the markhor heresy. He next 

 proceeds to show that there is no decisive evidence as 

 to when or where the wild goat was first domesticated, 

 but that there is great probability the Angora breed is 

 one of considerable antiquity. 



" It seems quite clear," he writes, " that from remote 

 times the mohair goat developed in the region of Central 

 Asia Minor, and gradually became localised there, the 

 territory which it occupied eventually being restricted to 

 that portion which pre-eminently suited it, the region 

 round Angora, until at last the pure-bred animal was 

 found only there. A continuous course of in-breeding, 

 through a long period of time, fixed it true to type, and 

 made it eventually a thoroughbred ; but this also made 

 it small and delicate." 



