144 SCIENCE PROGRESS 



petrologists ensures for this revised edition a hearty welcome. In the eleven 

 years which have elapsed since the last edition appeared, a considerable 

 volume of work on the petrography of the British Islands has appeared, and 

 most of this is incorporated in the edition under review. The increasing 

 importance which is attached to the alkaline rocks has led the author to 

 allot separate chapters to the nepheline-syenites and the phonolites, which 

 formerly were included with the syenites and trachytes respectively. A 

 minor change which will be received with less favour is the transference of 

 the teschenites from the dolerite chapter to the section on gabbros. 



So many of the rarer rock-types have been found in this country in 

 recent years that few of them are now unrepresented by British rocks ; 

 this has enabled the author to omit many of the descriptions of foreign 

 occurrences, and to replace these by illustrations drawn from local sources. 

 It is a question whether the former has not been carried too far ; for example, 

 in the section on diorites, no mention is made of the Cortlandt rocks, some 

 of which have practically attained specific rank. Those parts of the book 

 which are included under the heading " Leading Types," however, form a 

 very complete and concise account of the petrography of these islands. 



The section dealing with sedimentary rocks has not undergone such 

 alteration, but the chapters on metamorphism have been to a great extent 

 rewritten. The former gives the reader some impression of the lack of petro- 

 graphical knowledge concerning sedimentary rocks, especially with reference 

 to the argillaceous types. In this latter connection, more emphasis might 

 have been laid on the occurrence of kaolinitic minerals in fireclays and similar 

 rocks, for there is abundant chemical and microscopical evidence against 

 the view that Hutchings' results are generally applicable. 



The illustrations of microstructures, which formed such a useful feature 

 in previous editions, are supplemented by many additional drawings. While 

 the book fulfils adequately its function as " a guide to the study of rocks in 

 thin slices," its utility would be greatly increased by the introduction of 

 chemical analyses of the more important types. Petrology, in the modern 

 sense of the word, includes much more than the mere description of rock 

 sections, and a proper understanding of the relations of the various rock 

 species must be based, as much as possible, on quantitative data, both 

 chemical and mineralogical. A future edition might well contain such data, 

 together with an account of the quantitative microscopical methods which 

 are now coming into vogue. A. S. 



A Handbook of Mineralogy, Blowpipe Analysis, and Geometrical Crystallo- 

 graphy. By G. Montague Butler, E.M. [Pp. x + 311, vi -|- 80, 

 viii + 155, with 89 + 107 figures.] (New York : John Wiley & Sons, 

 1918. Price i6s. 6d.) 



Tpis book is a reissue, in one volume, of three previously published books 

 on mineralogy, blowpipe analysis, and crystallography respectively. As the 

 last of these was reviewed in this journal recently (Science Progress, 14, 

 163, 1919) it need not be further considered at present. In the first part, a 

 brief account of the various mineral species is given in a somewhat tabular 

 form, the details being arranged under the usual headings, such as hardness, 

 colour, fracture, crystal form, and so forth. Only such information as is 

 likely to be useful in the field identification of minerals is included, but the 

 photographs of specimens and the drawings of crystals which accompany 

 many of the descriptions are so small and indistinct as to be quite useless. 

 The author's evident attempt to standardise the nomenclature suggests that, 

 for the sake of consistency, " topaz " and " turquoise " should be translated 



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