468 



NATURE 



[February 9, 191 1 



known relating to his subject. The glossary of tech- 

 nical terms which follows the preface will be useful, 

 and there is also a comprehensive introduction of 

 upwards of thirty pages in which the structure is 

 fully described, and clearly illustrated by diagrams. 

 These are points which are frequently too much 

 neglected by entomological authors, but which are of 

 real practical importance. Besides general remarks 

 and a section on structure, the introduction deals with 

 larvae, vocal organs, sexual dimorphism, food and 

 habits, and classification. The Lamellicornia beetles 

 are mostly vegetable feeders, or dung or carrion 

 beetles, and some of them, like our own cock- 

 chafers, are very destructive to grass in the larval 

 stage, and to leaves of trees when mature. Some, 

 chiefly belonging to the groups described in the present 

 volume, inhabit the nests of ants and termites in the 

 larval stage, and are tended by these insects for the 

 sake of their secretions, while the dung and carrion 

 beetles are general scavengers. 



The Lamellicornia, as their name implies, are dis- 

 tinguished by their short lamellated antennae, which 

 may be observed in a well-developed and character- 

 istic form in our common cockchafers. Mr. Arrow 

 recognises three main families, the Scarabaeidae, 

 Passalidae, and Lucanidae. The Passalidae are not 

 European ; the Lucanidae are the stag-beetles. The 

 Scarabeeidae are divided into two smaller divisions, 

 the Pleurosticti, with four subfamilies represented in 

 the Indian fauna, and the Laparosticti, with eight. 



The general arrangement of the volume is similar 

 to that adopted in previous volumes of the " Fauna of 

 India," and need not be further commented on here. 

 Eight species are represented on each of the coloured 

 plates. 



We congratulate Mr. Arrow on the completion of 

 an excellent piece of work, and hope that entomolo- 

 gists , may have reason to be grateful to him for a 

 long series of equally excellent volumes. 



W. F. K. 



ELECTRIC MOTORS. 

 Electric Motors. Continuous, Polyphase, and Single- 

 phase Motors : Their Theory and Construction. By 

 Henry M. Hobart. Second edition, entirely re- 

 written, revised, and enlarged. Pp. xxiv + 748. 

 (London : Whittaker and Co., 19 10.) Price 185. 

 net, 



THE first edition of this work appeared in 1904. 

 Since then remarkable advances have been made 

 in electrical engineering. A foremost place in this 

 progress must be given to electric motors, and more 

 especially to that class employing commutators, in con- 

 nection with both single- and poly-phase alternating 

 currents. Indeed, the electrification of railwaj's has 

 made the variable-speed single-phase motor with a 

 good starting torque indispensable, for at present the 

 single-phase system alone seems to fulfil the require- 

 ments of main line electric traction. Also the poly- 

 phase induction motor is no longer to retain the great 

 disadvantage in the matter of speed regulation, which 

 makes it inferior to the continuous-current shunt 

 motor, for successful means are now known whereby 

 NO. 2154, VOL. 85] 



the speed may be varied economically over a wide 

 range. 



Both these problems are discussed in the present 

 edition, and form part of the new material contained 

 therein, but we find the treatment is mainly descrif)- 

 tive and too general to be of much use to anyoiv 

 seriously engaged in the design or manufacture of 

 these machines. Admittedly the subject is a difficult 

 one, at any rate, more difficult than the design of 

 ordinary continuous-current and induction motors. 

 Nevertheless, in a book on the theory and construc- 

 tion of electric motors room ought to be made for a 

 proper scientific study of these recent developments. 



Coming to the other and major part of the boolc 

 dealing with more or less standard motors, we do not 

 find much improvement on the first edition. To a 

 scientific engineer the author's style is too round- 

 about, illogical, and non-mathematical. A German 

 engineer would probably call it " unpedagogisch." For 

 instance, the author treats the principles of desij^n 

 by means of examples. Surely the classical way of 

 developing formulae from the theory, followed by prac- 

 tical details, and illustrated by examples, is far better. 

 Nor — to judge from his examples — does the author 

 appear to have kept pace with the times. We can 

 onlv think that many of the designs, both of continu- 

 ous- and alternating-current motors, have long since 

 been repudiated by their respective firms. 



The methods of calculation advocated by the author 

 are often open to objection, but to cite instances would 

 take us too far, as the list before us is really too long 

 to choose from. We think enough has been said, 

 however, to show that, while appreciating the im- 

 mense amount of information the writer has collected, 

 we cannot agree he has produced a book which can be 

 regarded as a standard treatise on the theory and 

 construction of electric motors for the use of students 

 or scientifically-trained engineers. 



Stanley P. Smith. '* 



1 



THE GEOLOGY OF GERMANY. 

 (i) Lehrhuch der Geologic von Deutschland. Eine 

 Einfiihrung in die erklarende Landschaftskunde fiir 

 Lehrende und Lernende. By Prof. J. Walther. Pp. 

 xv-t-358. (Leipzig: Quelle and Meyer, 1910.) 

 Price 7.60 marks. 



(2) Geologic von Deutschland und den angrenzenden 

 Gebieten. By Prof. R. Lepsius. Zweiter Teil, 

 Lief, ii., Das nordliche und" ostliche Deutschland. 

 Pp. vi -I- 247-548. (Leipzig: W. Engelmann, 1910.) 

 Price 10 marks. 



(3) Geologic von Ostpreussen. By Prof. A. Torn- 

 quist. Pp. vii-l-231. (Berlin: Gebruder Born- 

 traeger, 1910.) Price 10 marks. 



(i) T)ROF. WALTHER has been fortunately com- 

 -L pelled to write an account of the geology of 

 Germany, in furtherance of the scheme to which he 

 stands committed. He is one of those educational 

 leaders who believe that knowledge of literature and 

 of cosmopolitan science is insufficient for the citizen. 

 The Fatherland itself, solum patriae, must be under- 

 stood in order to be loved. We rhust not begin and 

 end with arranging minerals in cabinets and pointing 



