REVIEWS. 



CHEMISTRY. 



Practical Agricultural Chemistry. — By S. J. M. Auld, 



D.Sc, F.I.C., and D. R. Edwardes-Ker, B.A., B.Sc. 



243 pages. 32 illustrations. 8-in.X5-in. 



(John Murray. Price 5/- net.) 



The authors of this handbook call attention to the fact that 



students at agricultural colleges frequently finish their course 



without having grasped the essential connection between their 



laboratory work and the chemical changes in Nature which it is 



intended to make clear. For this reason they have dwelt fully 



on the qualitative examination of plant products, which in their 



experience is likely to be of more service to the general student 



than the study of quantitative methods. On this point, however, 



we should be inclined to differ from them, since there can be 



little doubt qualitative chemistry gains much by being taught 



quantitatively. It must not be inferred from this that 



quantitative work is neglected, for full outlines are given of 



methods of analysing plants and their constituents, soils, 



fertilisers, and feeding stuffs, and dairy products, the ground 



covered being that required for the London B.Sc. degree in 



Agricultural Chemistry. In general these methods are 



accurate and up-to-date, although inaccuracies may be noted 



in certain places. For example, in the determination of the 



Iodine value by Hiibl's method insufficient time is allowed 



for the absorption, and the iodine value given for linseed oil 



(172) is far lower than is usual when a longer time is allowed. 



A little more space might have been given with advantage to 



some special subjects, such as, for instance, the analysis of 



water and the difficult problem of interpreting the analytical 



results. „ . ., 



C. A. M. 



A Text-book of Experimental Metallurgy and Assaying. — 



By A. Roland Gower. 163 pages. 50 illustrations. 



7§-in.X5-in. 



(Chapman & Hall. Price 3/6 net.) 



Metallurgical processes are too often learned by rote with- 

 out any thorough understanding of the chemical reactions 

 upon which they are based. Such rule-of-thumb methods 

 may give good results with the more common ores, but leave 

 the metallurgist at a loss when he is called upon to assay 

 minerals of unusual composition. The author of this book, 

 therefore, rightly lays stress upon the necessity for the 

 student to learn the chemistry of metallurgy, though he 

 assumes that some elementary knowledge has already been 

 acquired. The book has been considerably enlarged since 

 its first appearance many years ago, and now covers the 

 ground required for the Lower Examination of the Board of 

 Education in this subject. The exercises are simply described 

 and good diagrams are provided where necessary, so that the 

 book should prove most helpful to beginners. Among the 

 various assays is included a section on the examination of 

 fuels, including the determination of the calorific value. The 

 value of this would have been increased by directions for 

 obtaining an average sample, which is one of the chief 



difficulties in the analysis of coal. „ . ,, 



C. A. M. 



An Introduction to the Chemistry of Plant Products. — 



P. Haas, D.Sc, and T. G. Hill, A.R.C.S., F.L.S. 401 pages. 



9§-in.X6-in. 



(Longmans, Green & Co. Price 7/6 net.) 



The aim of this book is to enable students of botany and 

 vegetable physiology to understand the nature of the chemical 

 changes that take place in plants, and the biological meaning 

 of those changes. The principal groups of chemical con- 

 stituents in plants, such as fats, carbohydrates, pigments, 

 proteins, and enzymes are, therefore, described at some 

 length, their chief qualitative reactions and methods for their 

 estimation being also outlined in each of the sections. As a 

 rule, the analytical methods given are full enough for a 



trained chemist to follow without having recourse to another 

 work, but in some instances either too much or too little 

 detail is given. This is notably the case in the section dealing 

 with the analysis of the fats and oils, where the directions are 

 more than are required for understanding the meaning of an 

 analysis, but are not sufficient to obviate the need of reference 

 to other books. For instance, since the analytical methods 

 are given at length, tables of the values of the principal 

 vegetable oils and fats should have been added as an aid to 

 the interpretation of the results. 



In this connection it may be noted that the insoluble 

 bromide test, devised by Hehner and the present reviewer, is 

 here incorrectly described as the " hexabromide test," whereas 

 the evidence points to the compound being the bromide of a 

 mixed glyceride and certainly not a hexabromide. But these 

 are only minor defects in a most valuable book, which ought 

 to find a place upon the shelves of every agricultural chemist 

 and botanist. It should be added that there is an excellent 

 index, and that full references are given in footnotes to the 

 authorities quoted in the text. 



C. A. M. 



GEOGRAPHY. 



Maps and Survey. — By Arthur R. Hinks. 206 pages. 

 24 illustrations. 8f-in.X 5i-in. 



(The Cambridge University Press. Price 6/- net.) 



Those interested in Geography, and particularly those 

 connected with the teaching of the subject in universities and 

 colleges, have to thank Mr. Hinks for two valuable contributions 

 this year to the available literature on the practical side of 

 the science. Except for official publications of this country 

 and the United States, the systematic works on maps and 

 map-making in English have been special treatises by pure 

 mathematicians, or articles in the encyclopaedias. In " Maps 

 and Survey," as in " Map Projections," the demand on the 

 mathematics of the reader is not large, and the special needs 

 of the geographer have been kept in the forefront. 



The present volume consists of chapters on Maps, Map 

 Analysis, Route Traversing, Simple Land Survey, Compass 

 and Plane Table Sketching, Topographical Survey, Geodetic 

 Survey and Survey Instruments. There are numerous illus- 

 trations, mostly of a high order, and the student who can 

 handle and examine the instruments and engage in simple 

 exercises easily devised will obtain from this cheap and well- 

 written book training of a nature his predecessors found it 

 difficult to acquire. 



No doubt the parts on plane-table and theodolite work will 

 appeal most to this class of reader, and both are interesting 

 and well done. Here, as throughout the book, the author 

 indicates the possibilities and particular applicabilities of each 

 instrument, the errors permissible, and methods of obtaining 

 accuracy. We were struck, for example, by the treatment of 

 resection and the triangle of error in plane-table survey, and 

 the adjustment of rounds of angles taken by the theodolite. 

 Geodesy is a branch of the science of Geography that is not 

 widely studied or appreciated, and the most interesting 

 chapter on Geodetic Survey should do much towards develop- 

 ing a wider and more intelligent knowledge of this fascinating 

 subject. For Geographers and Geologists alike the theory of 

 Isostasy has no little importance and the present volume 

 presents a useful introduction to it. 



We found the first two chapters a little " slow " ; and yet 

 they contain a great deal of useful matter which can be got 

 at by the much slower process of examining maps of many 

 kinds of details. To learn intelligently the maps must be 

 studied, but the book provides valuable fore-knowledge and a 

 guide to the work. It is difficult to see how some dullness 

 could be avoided. 



In Chapter IV., a slight alteration of the text would 

 conduce to readier grasping of the method of simple levelling. 



358 



