June. 1915. 



KNOWLEDGE. 



Table 33. Long-period Variable Stars. 



191 



Night Minima of Algol 3'' 2''-3m, 5'' ll^-lc, S" S''-Qc,23'' 4" -0 m, 26"' 0"-8 m, 28'' Q^-e c, 31" b" ■ 5 e. 



Period a-" 20" 48'" -9. 

 Principal Minima of li Lyrae July 8* ll^-Sc, 21'' Q^-ec. Period 12" 21" 47'°-5. 



Variable Stars.— Stars reaching their maxima in or near Double Stars and Clusters.— The tables of these, 



July, 1915, are included. The lists in recent months may given three years ago, are again available, and readers are 

 also be consulted (see Table 33). referred to the corresponding month of three years ago. 



REVIEWS. 



BIOLOGY. 



Insects and Man. — By C. A. Ealand. 343 pages, 16 plates. 

 100 figures. 9-in. x 5 J-in. 



(Grant Richards. Price 12/- net.) 



Mr. C. A. Ealand has worthily performed a valuable task, 

 and it is to be hoped that his book will be widely read. 

 Within the last five.and-twenty years, it is true that the 

 public mind has been gradually awakening to the immense 

 role played by insects, not only in the economy of nature, 

 but in direct relation to the Ufe, happiness, and wealth of 

 mankind. Written in a popular manner, this work will 

 help to impress us, not only with what has been done, 

 but with what there still remaiias to do. The importance 

 of trained scientific research is clearly insisted upon ; 

 but one might wish that the author had been even more 

 emphatic. To take but one instance. Those who listened 

 at a recent meeting of the Zoological Society to Professor 

 Maxwell Lefroy's paper on the Housefly and its means of 

 extermination were painfully reminded of the gaps in our 

 knowledge of the habits of one of the commonest of insects 

 that pave thp way to its destruction. Though the housefly 

 has long been known as a carrier of disease and death, 

 especially among infants, yet the number of experts in 

 this country who are studying the problem might be 

 counted almost on the fingers of one hand. No public money 

 is being spent to further the research, and the work is going 

 but slowly forward. True it is still, as it was in the days of 

 Hosea, " My people are destroyed for lack of knowledge." 



After an introduction in which a general survey is taken 

 of the structure and life-history of insects, the first chapter 

 deals with the relations of insects to plant Ufe, special 

 notice being taken of those injurious to crops and vines, 

 e.g., the Hessian fly, locust, and phylloxera, in wliich not 

 only the intelligent public, but the general zoologist will 

 find much that is novel and interesting. Next come the 

 blood-sucking insects — flies, lice, and ticks — which may be 

 carriers of disease to man, and they occupy some seventy 

 pages. The etiology of malaria, yellow fever, bubonic 

 plague, and relapsing fever is fully described, and the 

 author does justice to the splendid work of the Americans 

 in the Isthmus of Panama. Finally, the enemies of live- 

 stock and human parasites are described, and the book ends 

 with an account of what is being done in the way of insect 

 control. There is an extensive bibliography of the sources 

 of information conveyed m the book, which must not be 



looked on as a work of reference, but as a stimulating 

 general surxey of one of the most important branches of 

 biological science (.see Figures 170-173). 



^ M. D. H. 



BOTANY. 



Trees and Shrubs Hardy in the British Isles.— By W. J. 

 Bean. 2 volumes. 688 and 735 pages, gj-in. x6i-m. 

 (John Murray. Price 42/- net.) 

 Loudon's great work on trees and shrubs grown in Britain 

 has never yet been superseded, but Mr. Bean's book is the 

 most complete treatise of the kind that has appeared since 

 Loudon's, and it naturally includes a considerable number 

 of trees and shrubs that have been introduced into this 

 country during the intervening seventy years. The work 

 is planned on a generous scale. For instance, the first 

 volume contains what might weU have been pubhshed as 

 an independent book deahng with the general characters of 

 trees and shrubs, methods of planting, and so on, though 

 only occupying one-sixth of tliis volume. The remainder of 

 the' work deals in a detailed manner with an astonishingly 

 large number of species, the genera being taken in alpha- 

 betical order — certainlv the best arrangement for a work of 

 reference. This encyclopaedic work, lavishly illustrated by 

 clear line drawings, as well as by excellent photographic 

 plates, and showing throughout the sure signs of careful and 

 thorough first-hand experience, is absolutely indispensable 

 to all who are interested, whether for pleasure or profit, 

 in trees and shrubs which grow outdoors in this country. 

 The very magnitude of the work almost forbids criticism, 

 but one could wish that all the larger genera represented had 

 been provided with keys to enable rapid identification of 

 the species ; such keys are given in a few cases, however, 

 and, in any case, this is a small point. We have nothing 

 but praise for this magnificent treatise, by far the most 

 complete that has yet appeared on the subject. The pnce 

 is extremely moderate, considering the size and amount of 

 illustrations. 



CRYSTALLOGKA PHY. 

 X Rays and Crystal Slriicttire.—'By W. H. Bragg and W. L. 

 Bragg. 228 pages. 75 figures. 4 plates. 8i-in- xSJ-in. 

 (G. Bell & Sons. Price 7/6 net.) 

 Until a short time ago the atomic theorj- proposed by 

 Dalton had remained of the nature of an hypothesis, and it 

 is only in the last decade that this conception of matter has 



