64 



NA TURE 



[November 19, 1908 



ELECTRICAL TESTING. 

 Laboratory and Factory Tests in Electrical Engineer- 

 ing. By George F. Sever and Fitzhugh Townsend. 

 Second edition, revised and enlarged. Pp. xii + 269. 

 (London : A. Constable and Co., Ltd. ; N'ew York : 

 D. van Nostrand Co., 1908.) Price los. 6d. net. 



IT is almost unavoidable that a book on laboratory 

 practice, written by men whose duty it is to plan 

 and superintend the work done by students, must 

 savour somewhat of the instruction sheets which at 

 universities are supplied to the laboratory classes. It 

 is equally unavoidable that such instruction cannot 

 be given in perfectly general terms, but must be 

 adapted more or less to the syllabus in use at each 

 particular university, and to the plant provided for 

 the laboratory. Thus a work on laboratory tests 

 may be exceedinglv useful to students working at 

 the particular laboratorv to which it refers, but 

 whether students at other institutions will be able to 

 derive much benefit from it is doubtful. The ad- 

 vanced student and the scientific engineer, who is 

 already in practice, will probably also be able to 

 derive some advantage from the book under review, 

 but he would reap the same advantage with less 

 mental labour from any elementary text-book on elec- 

 trical engineering. The words " factory tests " in the 

 title must be taken to mean that the tests used in a 

 particular laboratory may more or less also be used 

 in a factory. This is, of course, true of all work 

 carried out in a modern well-equipped laboratory, and, 

 therefore, not a distinctive feature of the methods 

 described in the present work. 



It is certainly difficult to compress into 260 pages 

 the whole subject of electrical testing, and want of 

 space may be the reason why the authors have treated 

 certain subjects in a very brief — one is almost 

 tempted to say sketchy — manner, but I think they 

 have not been judicious in the matter of curtailment, 

 inasmuch as they have shortened or omitted alto- 

 gether the exposition of general principles. On the 

 other hand, they have unduly expanded the mere 

 routine of testing. As an example of sketchy treat- 

 ment of fundamental matters, take the Heyland 

 diagram on p. 172 of the induction motor, which 

 is given on the assumption that the motor has 

 neither ohmic nor iron losses, and the various vectors 

 are indiscriminately referred to as representing mag- 

 netomotive forces, currents, flux, or electromotive 

 forces, without a word of explanation. That such 

 treatment of a difficult subject must have seemed to 

 the authors themselves somewhat unsatisfactory may 

 be gathered from the following sentence, which occurs 

 on p. 173 :— 



" This diagram has been so fully discussed 

 in the literature of the induction motor that 

 it is not thought necessary to reproduce the proof of 

 it here." 



Just so. The authors assume that the funda- 

 mental principles are known, and content them- 

 selves with giving mere rules for testing. 



The book is divided into three parts. The first 

 deals with preliminary measurements and with tests 

 of continuous-current machines. In the second part 

 NO. 203S, VOL. 79] 



we come to alternating-current machines and trans- 

 formers, and then follows the third part, which bears 

 the title "Electrical Measurements." This title is 

 rather misleading, for here we find such subjects as 

 the determination of the leakage coefficient of a 

 dynamo, the Hopkinson method of testing for per- 

 meability, Ewing's hysteresis tester, Ewing's mag- 

 netic bridge, the plotting of the hysteretic loop— all 

 subjects which one would rather call magnetic, not 

 electrical, tests. However, a title which only fits 

 part of the contents is not a serious matter, but 

 that some electrical tests are treated in a very super- 

 ficial manner is a decided drawback. Thus the Wheat- 

 stone bridge, which logically ought to have found 

 a place in the first part, is dismissed in two pages 

 of letterpress and a very imperfect diagram, whilst 

 no mention is made of Varley's bridge or Thomson's 

 double bridge. The potentiometer fares even worse. 

 The diagram on p. 250 is crude and incomplete, and 

 it is no help to the reader to be told on p. 251 that 

 " for commercial use the potentiometer is usually ar- 

 ranged in some compact and convenient form." It 

 is precisely the instrument as practically used with 

 all its refinements that the reader expects to find 

 in a book on laboratory and factory testing. 



The third part also deals with tests on batteries 

 and photometric work. Since both these subjects to- 

 gether occupy barely nine pages, it is clear that the 

 treatment can only be very superficial. One feature 

 of the book which strikes the reader as peculiar is 

 that the authors omit in most cases to mention the 

 origin of the methods they describe. Thus, Scott's 

 name is not mentioned in connection with the change 

 from three- to two-[)hase circuits, nor is Heyland's 

 name mentioned when describing his diagram. Quite 

 apart from the consideration that it is only fair to 

 give credit where it is due, the suppression of such 

 references is inconvenient to the reader. Certain dis- 

 coveries, inventions, methods, or tests are known 

 under the names of the men who first published them, 

 and are usually identified in this manner. By omit- 

 ting such means of identification, the young student 

 loses touch with the subject he is supposed to acquire. 



GiSBERT KaPP. 



SCHOOL .ALGEBR.iS. 

 (i) Elementary .Algebra— A School Course. By W. D. 

 Eggar. Pp. viii + 324-1-28. (London : E. .\inold, 

 n.d.) Price 3X. 6d. 



(2) ,4 A'ra' .Algebra. By S. Barnard .-md J. M. Child. 

 Vol. i., containing Parts i., ii-, and iii., with 

 Answers. Pp. x+371. (London : Macmillan and 

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(3) Algebra for Secondary Schools. By Dr. Charles 

 Davison. Pp. viii-t-623. (Cambridge : University 

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(4) The Eton Algebra. Part i. By P. Scoones and 

 L. Todd. Pp. xxv-l-184. (London: Macmillan and 

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(i) T^HIS book covers most of the ground required 

 1 for boys who are not specialising in mathe- 

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