340 



NATURE 



[November ii, 1920 



The Elements of Electro-Technics. By A. P. 

 Young'. Pp. viii + 348. (London : Sir Isaac 

 Pitman and Sons, Ltd., 1920.) Price ys. 6d. 

 net. 



This work is addressed as much to those con- 

 nected with the electrical industry who are not 

 directly associated with the technical side as to 

 students about to embark upon an electrical career. 

 The subject is looked at from the practical engin- 

 eering point of view, but shows some departure 

 from conventional lines. The elementary prin- 

 ciples of currents and their effects are well set out, 

 and of the later chapters those on the magnetisa- 

 tion of iron, measuring instruments, and insulating 

 materials may be picked out as the best examples 

 of well-selected information arranged with origin- 

 ality. In the last mentioned there is a cood deal 

 not found in the ordinary text-book, including a 

 most useful summary of the composition, prepara- 

 tion, and properties of a number of insulating 

 materials in common use. Another subject not 

 always treated satisfactorily in elementary books is 

 that of the magneto for ignition purposes, of which 

 there is a brief but clear sketch. 



The field covered is larger than would appear 

 at first sight, and ranges over such • diverse 

 branches of electrical applications as Rontgen rays 

 and electric furnaces. The continuous-current 

 dynamo and motor are dealt with comparatively 

 briefly, but alternating currents and their applica- 

 tions do not form part of the scheme. The student 

 would be well advised to turn to Mr. Young for 

 his introduction to the subject of measuring instru- 

 ments. 



Modern Explosives. By S. I. Levy. (I'ltman's 

 Common Commodities and Industries.) 

 Pp. ix-t-109. (London: Sir Isaac Pitman and 

 Sons, Ltd., n.d.) Price 3s. net. 



This book gives a popular and interesting account 

 of the manufacture of explosives, with special 

 reference to the work carried out during the Great 

 War in the national factories in this country. 

 Although avoiding technical details, the author 

 has given a reasonable and well-balanced treat- 

 ment of his subject in the space at his disposal. 

 One or two slips may be noted. The oxidation 

 of ammonia was not " discovered by the German 

 chemist Ostwald " (p. 28), but by the English 

 clergyman the Rev. A. Milner, although it is 

 usually attributed to the French chemist Kuhl- 

 mann. The phrase " Haber-Ostwald process," 

 mistakenly adopted by the Department of Ex- 

 plosives Supply during the war, has doubtless led 

 the author astray. The statement that " the con- 

 tact process . . . was not successful when first 

 attempted in this country, and was first applied 

 in Germany . . . by . . . Dr. Knecht [sic] " (p. 35), 

 is inaccurate in view of Messel's work. The final 

 chapter, on "Chemistry and National Welfare," 

 although not directly connected with the subject, 

 is very apposite at the present time, when many 

 of the lessons taught by the war seem to be 

 receding into obscurity. 



NO. 2663, VOL,. 106] 



An Introduction to Entomology. By Prof. J. H. 

 Comstock. Part i. Second edition, entirely re- 

 written. Pp. xviii-f220. (Ithaca, N.Y. : The 

 Comstock Publishing Co., 1920.) Price 2.50 

 dollars net. 



We have no hesitation in commending this book 

 as a clear and thoroughly up-to-date elementary 

 account of the general structure and metamor- 

 phosis of insects. It constitutes the first part of a 

 treatise on entomology that tfie author has in 

 preparation. The section devoted to the external 

 anatomy of insects is particularly valuable. 



The detailed studies of recent morphologists 

 have left the terminology applicable to the various 

 sclerites and regions in a very confused state ; the 

 nomenclature adopted in this book is well chosen, 

 and should contribute towards establishing sta- 

 bility. W^ith regard to the internal anatomy we 

 are of opinion that the author should deal with 

 the muscular system more fully in the final work. 

 Rather more detailed reference to the adipose 

 tissue and a mention at least of the corpora allata 

 are also called for. These points are raised in 

 a friendly spirit, and in response to Prof. Com- 

 stock's invitation for suggestions of any desfrable 

 changes to be made before the present part is 

 incorporated in the complete work. 



Throughout the book the author exhibits clear 

 insight in the selection of the essentials of his 

 subject, and the printing and illustrations are par- 

 ticularly good ; there is also a useful and not too 

 lengthy bibliography. A. D. Imms. 



Physiography. By Prof. Rollin D. Salisbury. 

 Third edition, revised. (.'\merican Science 

 Series, .Advanced Course.) Pp. xv -f 676 -t- xxvi 

 plates. (New York : Henry Holt and Co., 1919.) 



Prof. Salisbury contrives to maintain the some- 

 what colourless subject of modern physiography 

 as a study for the class-room by representing it 

 as a description of the shaping of the present 

 surface of the earth, and of the relations of air 

 and water to the land. Questions of earth-history 

 are left to geology, and of life on the globe to 

 geography. His book might serve as an intro- 

 duction to either of these sciences. Huxley's 

 " Physiography " made a far wider appeal, and 

 Prof. Salisbury has recently stated his own appre- 

 ciation of geography as encouraging personal 

 observation and verification. 



We cannot help feeling that in the present work, 

 the success of which is shown by its third edition, 

 the author has been hampered by educational 

 custom rather than by choice of subject. The small 

 size of many of the illustrations of broad natural 

 features is in keeping with the crispness of de- 

 scription. The use of parts of the maps of the 

 U.S. Geological Survey as full-page plates is an 

 admirable feature. The work has been brought 

 up to date, with cautious references to the "upper 

 air," and a description of the activity of Lassen 

 Peak from 19 14 onwards. May we suggest that 

 the crystals shown on p. 71 should not be described 

 as snowflakes? G. A. J. C. 



