December 15, 1921] 



NATURE 



495 



his advice on the examination of thin sections 

 and the description of rocks is excellent. 



We cannot agree with his adoption of the 

 meanings attached by Prof. Shand to the terms 

 "saturated" and "unsaturated" as applied to 

 minerals and rocks, meaning saturated or un- 

 saturated with silica. It is always undesirable, we 

 think, to take a recognised word, especially one 

 with a definite scientific meaning already attached 

 to it, and employ it in a more restricted sense. 

 Perhaps the most valuable chapters in the book 

 are those on the interpretation of analyses and 

 their representation by diagrams. We could have 

 wished, perhaps, that greater space could have 

 been given to the subject of the crystallisation of 

 magmas, but this could have been effected only 

 by an increase in the size and cost of the book. 



It is to be regretted that this work was com- 

 pleted before the issue of the report of the Joint 

 Committee of the Geological and Mineralogical 

 Societies on Petrological Nomenclature, to 

 which Dr. Holmes, who was a member of the 

 committee, gave most valuable assistance. It is 

 very desirable that the use of technical terms in 

 petrology should be standardised, at any rate so 

 far as this country is concerned. 



J. W. Evans. 



Our Bookshelf. 



Insect Pests of Farm, Garden and Orchard. Bv 

 E. Dwight Sanderson. Second Edition, 

 Revised and enlarged. By Prof. L. M. _Peairs. 

 Pp. vi + 707. (New York : John Wiley and 

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

 192 1.) 265. net. 

 The first edition of the author's " Insects 

 Injurious to Staple Crops " was puWished ten 

 years ago. The advances made during the past 

 decade have been such that it was considered 

 necessary to rewrite practically the whole book. 

 In its present form it covers all the more im- 

 portant insects affecting the crops of the farm, 

 garden and orchard, besides including two final 

 chapters on household insects and the pests of 

 domestic animals. The work aims at giving a 

 clear idea of the life-history and habits of ever}- 

 species concerned and the best methods of con- 

 trol. There are also chapters on insecticides and 

 spraying and dusting apparatus. It is profusely 

 illustrated, the text-figures numbering more than 

 600, and with few exceptions thev are of a 

 uniform level of excellence. References in the 

 form of footnotes guide the more inquisitive 

 reader to many of the separate bulletins and 

 articles on individual pests. 



Notwithstanding the number of text-books on 

 economic entomology which have appeared in 

 America, the present work will undoubtedly 

 occupy a high place in their ranks. Its compre- 

 hensiveness is truly remarkable and, in fact, it 

 NO. 2720, VOL. 108] 



is difficult to quote any similar work which com- 

 presses so much well-sifted information, and so 

 many good illustrations, within an equally con- 

 venient compass. Chap. 3, however, which 

 deals with the structure and development of in- 

 sects, is rather inadequate. In the first place it 

 should have preceded chap. 2, which treats 

 of beneficial insects. As it stands, the practical 

 grower will have to read chap. 3 first if he 

 is to understand properly the remarks in the pre- 

 ceding chapter. In the second place, a brief 

 account of the principal orders of insects might 

 have been added with advantage, even if at the 

 expense of an additional page. But these points 

 are comparatively trivial in what can be regarded 

 unhesitatingly as an all-round first-rate practical 

 book on insect pests. A. D. Imms. 



Department of Applied Statistics {Computing 

 Section), University of London, University 

 College : Tracts for Computers. Edited by 

 Karl Pearson. No. 6, Smoothing. By 

 E. C. Rhodes. Pp. 60 + 3 diagrams. (Lon- 

 don : Cambridge University Press, 192 1.) 

 35. gd. net. 

 The methods of graduating or " smoothing " a 

 series of more or less irregular data affected by 

 errors of observation or of sampling have of 

 recent years received a good deal of attention ; the 

 present tract is a ven.- valuable contribution to 

 the subject. New methods are developed, which 

 may be described as combinations of tangential or 

 osculatory interpolation with the least-square 

 method of Dr. Sheppard, and these and older 

 methods are compared, both graphically and by 

 finding the sum of the squares of the departures 

 from the graduated curve. The results of this 

 test are rather surprising. The osculating 

 methods used give distinctly worse results than 

 the other four methods employed. By grouping 

 the obser\'ations it is possible to estimate what 

 order of differences is negligible ; if a higher order 

 of differences is employed, the resultant curve 

 tends to bring out something that is not inherent 

 in the data, with very unsatisfactory consequences 

 to the fit obtained. 



North England: An Economic Geography. By 

 L. R. Jones. Pp. viii + 256. (London: G. Rout- 

 ledge and Sons, Ltd., 192 1.) 65. net. 

 There is a distinct need for sound regional text- 

 books of the more intensive type exemplified by 

 this work. It deals with the coal-fields north of 

 the Trent and the Midland Gate, and discusses the 

 industries which have arisen upon and about them, 

 the communications between them, and their great 

 centres of industry- and trade. The basis of dis- 

 cussion is very largely geological. Here there is 

 room for broadening of both foundation and fabric. 

 The book needs an index, and is disfigured by a 

 number of typographical errors, but it is well illus- 

 trated with maps which, for the most part, are 

 clear and illuminating. It makes a very useful 

 book for secondan,- schools and first-year college 

 courses. 



