474 



NA TURE 



[October 7, 19: 



opportunity for a young student to produce a work of 

 absolutely first-class value. It is to be hoped that 

 Dr. Malinowski will be able to publish in full the 

 remainder of his material, which, judging from this 

 sample, will mark a distinct progress in ethnographical 

 research and interpretation. A. C. Haddon. 



Pure and Applied Electricity. 



(1) Einjuhrung in die Theorie der Elektrizitat und des 

 Magnetismus. Zum Gebraucli bei Vortragen, sowie 

 zum Selbstunterricht. Von Prof. Dr. Max Planck. 

 Pp. v + 208. (Leipzig: S. Hirzel, 1922.) 42 marks. 



(2) Elettrotecnica elementare con numerosi problem! . 

 By A. Occhialini. Vol. 1 : Magnetismo — Elettro- 

 statica — Elettrochimica — Elettrodinamica — Eleltro- 

 magnetismo — Induzione elettromagnetica. Pp. v + 

 344. (Firenze : Felice Le Monnier, n.d.) n.p. 



(3) Installations ilectriques industrielles : choix du 

 matiriel. Par R. Cabaud. Pp. 316. (Paris : J.-B. 

 Bailliere et Fils, 1922.) 10 francs. 



THE first of these three books discusses the ground- 

 work of the theory of electricity, the next dis- 

 cusses the experimental laws and their laboratory 

 applications, and the third is a severely practical work 

 for the commerical electrician. They are all intro- 

 ductions to the subject, but they are intended for very 

 different classes of readers. 



(1) Dr. Max Planck's work is philosophical, and pre- 

 supposes a knowledge of mathematics and of the 

 mathematical theory of electricity which is possessed 

 by few . The foundations on which the ordinary 

 mathematical equations rest are examined, and par- 

 ticular stress is laid on the units in which they are 

 measured. The Gaussian, the electrostatic, and the 

 electromagnetic systems of units are considered. The 

 work will be very welcome to the pure theorist and will 

 increase his confidence in the soundness of the physical 

 basis of the mathematical theory. The clear dis- 

 tinction made between magnetic force and magnetic 

 induction is very convincing. The experimenter will 

 find little that is directly helpful to him in this book, 

 but he will appreciate, however, the author's method 

 of getting the capacity of an ellipsoid and the deductions 

 that can be made from it. 



(2) The second work under notice is very similar to 

 the standard English books on experimental electricity 

 and magnetism. The author's descriptions of the 

 main phenomena are very clear, and the numerous 

 examples given are instructive. A very full discussion 

 is given of the problem of a number of batteries of 

 different electromotive forces and resistances in parallel 

 with one another. A thorough knowledge of this 



NO. 2762, VOL. I 10] 



problem is a great help to students when they come to 

 the corresponding problems of dynamos or alternators 

 running in parallel with one another. The definition 

 given of the temperature coefficient of metals, however, 

 is not sufficiently accurate for modern requirements. 

 The rating of a dynamo depends on its temperature 

 after a run at full load, and the temperature of the coils 

 is computed from their measured resistance and a 

 knowledge of the temperature coefficient of copper. 

 As the problem is one of great commercial importance 

 it is necessary to distinguish between the temperature 

 coefficeint of the volume resistivity, the mass resistivity, 

 and the constant mass resistance. These are all 

 different and vary with the lower of the two tempera- 

 tures considered. The approximate formula? for the 

 self-induction of a coil are given, but we think that 

 their limitations should have been stated. 



(3) M. Cabaud's book is very general and can be 

 appreciated only by a technical expert. It presupposes 

 a thorough knowledge of practical electrical engineering. 

 In the first section of the book a general discussion is 

 given of the kind of electric machine required to do 

 special work ; for example, whether a direct-current 

 or an alternating-current machine will be the more 

 useful. In the latter case also the question of whether 

 it is to be single phase or polyphase is considered. The 

 efficiency of the machine, its heating under load, the 

 elect ric strength of the insulating wrappings, etc., have 

 all to be considered. In the second section the char- 

 acteristics of the machines, whether rotating or station- 

 ary, are described. In the last section the usefulness 

 of the various characteristics are discussed, and the 

 important question of the best guarantees that should 

 be demanded from the manufacturers is considered. 



The Petroleum Industry. 



(1) Encyclopedic Scientifique : Bibliotheque de geologic 

 et de mineralogie appliquees : Les Gisements de 

 pel/ole. Par Jean Chautard. Pp. viii + viii + 330. 

 (Paris : Gaston Doin, 1922.) 14 fr. 



(2) The Oil Encyclopedia. By Marcel Mitzakis. Pp. 

 xvi + 551. (London: Chapman and Hall, Ltd., 

 1922.) 21s. net. 



(3) The Economics of Petroleum. By Joseph E. 

 Pogue. Pp. ix + 375. (New York: J. Wiley and 

 Sons, Inc. ; London : Chapman and Hall, Ltd., 

 i9 21 -) 3P- net. 



THE " Encyclopedie Scientifique " constitutes a 

 comparativelynewdeparture in French technical 

 literature, and lias for its scope the ultimate publication 

 of some thousand volumes dealing with the various 

 phases of pure and applied science. M. Jean Chautard's 



