Jriv. 1912. 



KNOWLEDGE. 



263 



reviewer has, on several occasions, i>^commended it as one of 

 the most suitable books as introductory guide to organic 

 chemistry. In many respects the present edition may be 

 regarded as a new book ; for it has been thoroughly revised 

 and brought up to date, so as to include the results of the most 

 recent work in this branch of the science. At the same time 

 the plan and character of the work have been kept, so that 

 while the book will now be more helpful to advanced students 

 and for those studying n;edicine, it still remains an excellent 

 guide for the beginner. 



As in the former editions practical work is given its due 

 position, and numerous experiments are described in illustra- 

 tion of the theoretical matter. Practical applications of 

 chemical reactions arc also described in brief outline, and 

 usually in sufficient detail for the purpose in hand. 



We have noticed very few slips, but are the authors correct 



in stating on page 17.2 that fatty acids containing an odd 



number of carbon atoms do not occur in nature ? Within 



the last few years it is claimed that several such acids ic.f>., 



daturic acid) have been discovered. ,, , ,, 



C. A. M. 



Organic Cliciiiistry.~Hy J. E. CoHi-.N, H.Sc. F.K.S. (The 



People's Booksl. 96 pages. 4 illustrations. 65-in. X4J-in. 



(T. C. & E. C. Jack. Price 6d. net.) 



Professor Cohen has undertaken a most difficult task in 

 attempting to compress into a little book of ninety-six pages the 

 whole subject of organic chemistry in such a way that it may be 

 understood by anyone without special chemical knowledge. 



Although parts of his book will answer to this rec]uirement, 

 we cannot help feeling that in other places he is unnecessarily 

 abstruse, and also goes into too much detail. For instance, on 

 page 21, a table of the physical properties of homologous 

 hydrocarbons is given, whereas it seems to us that the space 

 might have been better utilised (for the end in view) with a 

 fuller explanation in simple language of the meaning of the 

 term homologous. 



Outlines are given of some of the principal industries based 

 on reactions in organic chemistry and, in general, these are 

 clear and accurate. It is a pity, however, that the author has 

 fallen into the usual mistake about vinegar-making, and has 

 described incorrectly an obsolete method. 



Regarded as a summary for the student of chemistry, the 

 book is admirable, and the price at which it is pulilished in 

 an attractive form is a matter for wonder. 



C.A.M. 



GEOLOGY. 



TItc Niitural History of Clay. — By A. B. Searle. Cam- 

 bridge Manuals of Science and Literature. 176 pages. 

 18 illustrations. 6i-in.x5-in. 

 (The Cambridge University Press. Price 1 - net.) 

 The term clay is of popular origin and use, hence its 

 adoption as a scientific term is attended with some little con- 

 fusion, owing to the great number of possible definitions, all 

 of which are to some extent unsatisfactory. While everybody 

 knows what clay is, it seems impossible to frame a satisfactory 

 definition. Even plasticity is not an invariable property of 

 clay, for some kaolins are devoid of this character. The author 

 of this excellent little manual objects to clay being described 

 as a '■ mineral," except in a legal sense ; but there is no doubt 

 that the word " mineral " is the old, popular and scientific term 

 for any inorganic natural substance. We agree, however, with 

 the statement (page 3) " . . . . clay is not a mineral, but a 

 rock," if, for "mineral," " mineral-species" is substituted. 



The book is about ev'enly divided between the technology 

 and the geology of clay. The technology of clay is a complex 

 and difficult subject, but the author shews himself perfectly at 

 home in it. nmch more so than in his geology. A clumsily- 

 worded paragraph on page 52 might lead a reader to suppose 

 that a Carboniferous Limestone clay could be accunuilated by 

 the denudation of Coal Measures. The table of " the chief 

 clay rocks, arranged geologically." at the beginning of the 

 book, does not convey much information and might ad\an- 

 tageously have been extended. 



There is a valuable concluding chapter on the nature of the 



ultimate clay-material. As the author shows, no finality is yet 

 reached in this ilifficuit problem. There is an irritating 

 multiplicity of uses of the term " clay " in this chapter. 

 Sometimes it means a geological unit, sometimes " true clay " 

 or the mysterious clay-substance, " clayite," or " pelinite." A 

 characteristic example of this confusion occurs on page 139. 

 Many of the terms, however, are concisely defined later on 

 (page 149). 



A short bibliography of the more important works on clay, 

 and an adc<iuate index, are provided. This little book may be 

 reconnnended to all interested in the technological or geological 

 aspects of clay as a concise and well written introduction to 

 the subject. ^ ,,, ..- 



Stanford's Geological Map of Central linropc. 

 16Mn.X10.5-in. Scale, 1 : 6,336,000. 

 (E. Stanford. Price 5/-.) 

 This is a geological map of a part of Europe, reduced from 

 the Carte Geologique Internationale de 1' Europe on a scale of 

 one hundred miles to an inch. It includes the region between 

 North Germany and Sardinia, and between Ireland and 

 Hungary. In the colouring all the igneous rocks, of whatever 

 age, are lumped together ; as are also the metamorphic. 

 Cambrian and Ordovician, Upper Silurian and Devonian, 

 Carboniferous and Permian, respectively make groups to which 

 one colour is assigned. The terms Ordovician and Upper 

 Silurian are, or should be. nuitually exclusive. One should 

 have either Ordovician and Silurian, or Lower and Upper 

 Silurian. Objection might also be taken to the term Broverian 

 as of too local significance to be used to designate the sedi- 

 mentary series below the Cambrian. The map will be useful 

 for purposes of broad stratigraphical comparison. 



G. W. T. 



Mineralogy. — I'ourth edition. By F. H. HaicU. Ph.D., 



F.G.S. 253 pages. 124 illustrations. 7i-in.X 5-in. 



(Whittaker & Co. Price 4/- net.) 



This fourth edition of a popular text-book has been entirely 

 re-written and much enlarged, and is, to all intents and 

 purposes, a new book. A text-book of mineralogy falls 

 naturally into two parts ; one dealing with the properties of 

 minerals in general, the other descriptive. Dividing his book 

 in this way. Dr. Hatch deals with the morphological, physical, 

 and chemical characters of minerals in an admirably lucid 

 way considering the complexity and difficulty of presentation 

 of the subject in a small compass. The crystallographical 

 chapter is exceedingly compact and understandable. The 

 trigonal sub-system, however, might have been mentioned 

 when dealing with the hexagonal. Moreover, its most 

 important form, the rhombohedron, is only mentioned in 

 connection with the obsolete conception of hemihedrism, 

 which is retained in the book. 



In the descriptive part the minerals are arranged under the 

 he.ads of rock-formers, ores, salts, and gems. This classifi- 

 cation, as the author admits, is not free from inconsistencies, 

 but nevertheless seems to have a practical value and con- 

 venience in teaching. A good index makes it easy for the 

 student to look up any particular mineral, notwithstanding its 

 possibly anomalous place in the classification. ,^ ,,, ^ 



The Mineral Kingdom. — By Dr. Reinhard Brauns, trans- 

 lated, with additions, by L. J. Spexcer, M.A., F.G.S. Parts 

 17-20. 56 pages. 39 illustrations. 12-in.X8Ji-in. 

 (WiUiams lS: Norgate. Price 2/- net per part.) 



These four recently published parts of this fine work 

 maintain the standard set up by the earlier parts. They are 

 mainly concerned with the rock-forming minerals, the felspars, 

 felspathoids, zeolites, pyroxenes, ainphiboles. and micas. 

 Some mention might have been made of the now well- 

 ascertained occurrence of primary analcite in igneous rocks, 

 with the consequent recognition of a series of analcite-rocks 

 analogous to those characterised by leucite and nepheline 

 respectively. 



Numerous beautiful plates, some in colour, are issued with 



