NA TURE 



[August 12, 1922 



Our Bookshelf. 



Columns : A Treatise on the Strength and Design of 

 Compression Members. By Dr. E. H. Salmon. 

 (Oxford Technical Publications.) Pp. xvi + 279. 

 (London : Henry Frowde and Hodderand Stoughton, 

 1921.) 315. 6d. net. 



The question of the strength of columns is one of con- 

 siderable difficulty, on both the theoretical and the 

 experimental side, and the author is to be congratu- 

 lated on the value of his contribution to this subject. 



Dr. Salmon's book consists of three parts : Part 1 

 is a bibliography arranged chronologically and gives 

 the author's name and the title of the work. Part 2 

 is an analytical discussion covering various methods 

 of fixing the ends ; in each case ideal conditions are 

 first assumed, and then departures from these con- 

 ditions are considered until the ordinary column is 

 reached. Part 3, synthetical, contains accounts of 

 various formulae used in practice and the experimental 

 evidence on which they are based. The last two parts 

 are taken substantially from a thesis submitted for the 

 D.Sc. (Engineering) degree of the University of London. 

 Part 1 in the thesis was historical, consisting of short 

 summaries of each important memoir, including experi- 

 mental work ; it is unfortunate that, owing to the 

 present impossibility of publishing the complete work, 

 this section has been compressed into a bibliography 

 of sixteen pages. The treatment in Part 2 is mathe- 

 matical without unnecessary refinements. 



Apart from the advantage of the presentation in one 

 volume of much valuable work, hitherto scattered in 

 many books and journals, the author's systematic 

 treatment has led him to elucidate various new points, 

 and will undoubtedly stimulate the reader in the same 

 direction. For the same reason the suggestions given 



for future research must carry weight. Dr. Sab 1 



considers that the most pressing point for future 

 research on columns is the question of the degree of 

 imperfection common in practical direction-fixed ends. 

 This matter is of great importance in other structural 

 members as well as in culumns, e.g. arch ribs and 

 encastre beams. We can thoroughly recommend the 

 volume to all who are interested in the subject of the 

 strength of materials. 



A Text-Book of Mineralogy : With an extended Treatise 

 on Crystallography and Physical Mineralogy. By 

 Prof. Edward S. Dana. Third edition, revised and 

 enlarged by Prof. William E. Ford. Pp. ix + 720. 

 (New York : J. Wiley and Sons, Inc. ; London : 

 Chapman and Hall, Ltd., 1922.) 25s. net. 

 Tins well-known book was first published in the year 

 1877, and a second edition appeared in 1898. The 

 present third edition leaves the form essentially un- 

 changed, the close relation between the author's 

 " System of Mineralogy " and this book having rendered 

 it inadvisable to revise the chemical classification of the 

 minerals until a new edition of that larger work can be 

 undertaken. The distinguished author is now professoi 

 emeritus at Yale ; he still retains the post of curator 

 of Mineralogy, however, but being well advanced in 

 years the revision of the lunik has been undertaken by 

 Prof. Ford. 



NO. 2754, VOL. I 10] 



The principal changes appear to be the introduction 

 of a section on stereographic and gnomonic projections, 

 and improvements in the description and explanation 

 of the optical properties of crystals. The reference 

 to the very important recent work on the elucidation 

 of crystal structure by means of X-rays, however, 

 occupies only slightly more than one page, without 

 a single illustration. On the other hand, however, 

 there is a much longer and really valuable section on 

 the determination of the refractive indices of micro- 

 scopic crystals by the more recent improved microscopic 

 methods of F. Becke and F. E. Wright. 



We are glad to see that the references to classes of 

 lower than full systematic symmetry as " hemihedral " 

 and " tetartohedral " (possessing a half or a quarter 

 of the full number of faces) is now only a passing one, 

 as to an antiquated, misconceived, more or less dis- 

 carded and inadequate method of description. The 

 crystal classes are now referred to as possessing eai 1 1 

 their own definite elements of symmetry, the only 

 trulv scientific method of distinguishing them. 



A. E. H.T. 



General Economic Geology : A Text-hook. By Prof. W. 



Harvey Emmons. Pp. xiii + 516. (New York and 



London : McGraw-Hill Book Co., Inc., 1922.) 20s. 

 Students and others interested in economic geology 

 will appreciate Prof. Emmons's volume. The scope of 

 the work is extremely wide and all of the following are 

 dealt with : coal, petroleum, natural gas, metalliferous 

 and non-metalliferous minerals of economic importance, 

 and building stones. 



The text as a whole shows a great resemblance 

 to that of two of the author's previous works, e.g. 

 " Geology of Petroleum " and " Principles of Economic 

 Geology," but the section on coal is entirelv new. 

 The chapter on oil appears to be a precis from the 

 former of the two books mentioned, and some parts 

 dealing with mineral deposits have largely the same 

 text and diagrams of the corresponding earlier work. 

 The chapters on the non-metallic minerals, however, 

 have been greatly enlarged, and contain much additional 

 information. 



It is evident that the author has written his " General 

 Economic Geology " primarily for an American public, 

 since all his examples, where possible, are from American 

 localities, with little or no mention of occurrences of 

 equal or greater importance in other parts of the world. 

 An outstanding example of this is the 70 pages which 

 he devotes to the coalfields of North America to the 

 exclusion of fields elsewhere. 



The value of the book is greatly enhanced by the 

 addition of an excellent bibliography, which will allow 

 of a more specialised study of particular areas when 

 required. Moreover, the text throughout is plentifully 

 supplemented with maps, diagrams, and half-tone 

 blocks. 



Imperial Institute Handbooks. The Agricultural and 

 Forest Products of British West Africa. By Gerald 

 ('. Dudgeon. Second edition. Pp. xii -t- 176 + 

 plates. (London : J. Murray, 1922.) 7.J. 6d. net. 

 Since the first edition of this handbook appeared in 

 191 r many changes have taken place. The develop- 

 ment of British West Africa has experienced a serious 



