May 27, 1909] 



NA TURE 



;65 



The book is wonderfully free from misprints, at 

 lea<it of a serious character, and on the whole the 

 book is one which can be highly recommended to all 

 students who wish to obtain a first acquaintance with 

 the subject of physical chemistry. In language it is 

 clear and well-expressed, and the practical illustrations 

 which are appended to most of the chapters will be 

 foimd very useful for laboratory work. The cost 

 of the book, also, is extraordinarily low. A grave 

 omission on the part of the publishers is the date of 

 publication on the title-page. .A. F. 



ELECTRICAL E.XGI^EERIXG. 

 (i) Transformers, for Single and Multiphase Currents. 

 A Treatise on their Theory, Construction, and Use. 

 By Prof. Gisbert Kapp. Second, revised and en- 

 larged edition. Pp. ix+363.- (London : Whittaker 

 and Co., 1908.) Price 105. 6d. net. 

 (2) Electrical Engineer's Pocket Book. A Hand- 

 book of Useful Data for Electricians and Electrical 

 Engineers. By Horatio A. Foster, with the Colla- 

 boration of Eminent Specialists. Fifth edition, 

 completely revised and enlarged. Pp. xxxvi+1599. 

 (London : A. Constable and Co., Ltd., 1908.) Price 

 2is. net. 

 (i) A NEW edition of Prof. Kapp's well-known 

 •i»- book on transformers is bound to be in- 

 teresting to all electrical engineers. Moreover, when 

 the new edition is so much enlarged as to become 

 practically a new book, the publication is of still 

 greater importance. 



The first two chapters are introductory in char- 

 acter, and deal respectively with general principles 

 and with the losses in transformers. We cannot 

 but feel some regret that the constants for hysteresis 

 loss are not given in the form KxB'"'. This form 

 gives practically the same result as the B''* formula 

 if a suitable value of K is chosen (as Prof. Kapp 

 states on p. 17), and the calculation of the loss if 

 the index is 1:, can be much more readily made. 

 The second chapter includes some valuable results 

 of tests on the newer alloyed irons. 



One of the best of the new chapters is chapter iii., 

 where the subject of heating of transformers is dealt 

 with very completely. The method of estimating 

 temperature rise graphically for intermittent loads by 

 combining the heating and cooling curves is very 

 clearly given. Chapter v. is a very interesting one, 

 dealing with the much neglected subject of the design 

 of choking coils; the method of determining the neces- 

 sary volume of the air-gap to give a certain amount 

 of wattless current is both novel and useful. 



In chapter vi. the design of the core of a traps- 

 former is considered, and a good deal of space is 

 devoted to the discussion of the distribution of losses 

 in a transformer. Some exception must be taken to 

 the statement on p. 123 : — 



" The law of equal losses gives the maximum 

 .efficiency of a transformer which is the right size 

 for the load. .Arnold's law ^ gives it for a trans- 

 former which is slightly too large for the load." 



1 Copper loss =o*8 hysteresis loss +eddy current loss. 

 NO. 2065, VOL. 80] 



Arnold's law and the law of equal loss are ob- 

 tained on totally different premises, and both laws 

 are correct for the given premises. It is true also 

 that for a transformer designed on Arnold's law a 

 higher efficiency can be obtained by increasing the 

 load until the copper loss is equal to the iron loss, 

 but this load may be more than the transformer can 

 stand, and it is no more accurate to say that Arnold's 

 law gives maximum efficiency for a transformer that 

 is slightly too large for its load than it would be to 

 say that the law of equal losses gives the maximum 

 efficiency for a transformer that is slightly too small 

 for its load. 



In chapter vii. the design of a shell transformer is 

 worked out in detail. One must enter a protest 

 against the introduction of " Fill Factor." This is 

 a literal translation of the German " Fiillfaktor," but 

 the English "Space Factor," introduced by Thomp- 

 son, is now so well recognised that it seems a pity 

 to use another term. 



In chapter viii. the transformer theory is worked 

 out in the same clear way as is. done in the earlier 

 edition. Prof. Kapp's well-known diagrams are de- 

 scribed in detail, as well as the simplified drop diagram 

 now so largely used. In the next chapter the calcu- 

 lation of magnetic leakage is considered, and some 

 useful formulae ar-e given for calculating it in specific 

 cases. 



Chapter x. deals with the measurement of power; 

 the usual methods of measuring power are described, 

 including the three amperemeter and three voltmeter 

 methods. Students might perhaps have been warned 

 of the' great accuracy of measurement in voltage and 

 current which is necessary to obtain good results with 

 these two methods. Chapter xi. deals with the test- 

 ing of transformers, and includes also a description 

 of most of the modern iron-testers, including the 

 Epstein tester for total loss, the Grassot fiuxometer, 

 and Prof. Kapp's device for measuring magnetic 

 quality. 



The next chapter deals with a number of subjects, 

 including safety appliances for transformers, three- 

 wire transformers, auto-transformers, series working, 

 and Scott's system of transformation from two-phase 

 to three-phase working. It is similar to the corre- 

 sponding one in the earlier edition, though the matter 

 is greatly increased and brought up to date. 



The last chapter gives some examples of modern 

 single-phase and three-phase transformers, and is 

 one of the most valuable in the book, both for the 

 student and the designer. Not only are many plates 

 and drawings included, but the details of the designs 

 are worked out in many cases. 



This book is likely to remain a standard treatise on 

 the subject in English for some time. 



(2) The " Electrical Engineer's Pocket Book " is 

 similar to many other pocket books of the same class 

 already on the market. It aims, howi?ver, at giving 

 more complete and comprehensive information than 

 most of these compilations, and deals with such sub- 

 jects as electrochemistry, illuminating engineering, 

 electrolytic action, firing mechanism for guns, electro- 

 metallurgy and X-rays, while more than 250 pages 



