REVIEWS 159 



the various analyses, but emphasis is laid upon their technical application 

 in order that the student may readily understand why certain precautions 

 are essential in some cases and not in others, and the manner in which the 

 processes in question may depend upon the speed or accuracy of the analyses. 

 Subjects dealt with include such matters as coal, water, Chile saltpetre, 

 basic slag, iron and its ores, soap, oleum, and so on. 



It should be of considerable value to those who have to teach analytical 

 methods to technical students. 



F. A. M. 



The Chemistry oJ Colloids, and some Technical Applications. By W. W. 



Taylor, M.A., D.Sc, Lecturer in Chemical Physiology at the Uni- 

 versity of Edinburgh. [Second Edition. Pp. viii + 352.] (London : 

 E. Arnold & Co., 1921. Price los. 6d. net.) 



The first edition of this book was reviewed in this Journal (vol. x, p. 167) in 

 1916, and the present volume does not differ very appreciably from the earlier 

 edition ; though only some extra 24 pages have been added, this does not 

 mean that a good deal of revision has not been undertaken. This has, 

 however, been done only where either the new matter was a more convincing 

 illustration of an already established theory or the new experimental results 

 had led to changes in the previously accepted theory. 



It is questionable whether too much is not attempted in endeavouring to 

 give the more important applications of colloid chemistry in 28 pages, but at 

 all events these will serve as an introduction to more speciahsed treatises. 



In any case, the fact that a second edition is called for indicates that we 

 are already far from the days when a certain Professor of Chemistry used to 

 advise his students, " Don't marry too young and don't work with anything 

 that isn't crystalline ! " 



Dr. Taylor's book in its revised form will no doubt secure many fresh 

 readers, and can be recommended to all seeking an introductory work on 

 colloid chemistry. 



F. A. M. 



GEOLOGY 



Textbook of Geology. By L. V. Pirsson and C. Schuchert. Part I, 

 Physical Geology, by L. V. Pirsson. [Pp. vii + 470, with 2 plates 

 and 417 text figures.] (New York: John Wiley & Sons, 1920. Price 

 17s. 6d. net.) 



The favourable reception which was accorded this work, first issued in 19 15, 

 has resulted in the necessity for the preparation of this second edition. 

 During the five years which had elapsed since its appearance, the book had 

 established itself as one of the most clearly expressed and impartial dis- 

 cussions of the subject, and its value to the general student had been uni- 

 versally recognised. It is, therefore, all the more regrettable that the 

 appearance of the second edition synchronised with the death of the author ; 

 Prof. Pirsson died at the end of 1919, practically his last work being the 

 revision of the text of this treatise. 



On comparing this edition with the previous one, the only apparent 

 difierence is the addition of thirty pages, various portions of the text being 

 amplified by the addition of further explanatory paragraphs. Otherwise 

 the arrangement and subject-matter remain as in the first edition. The 

 lucidity of the descriptions, the excellence of the diagrams, and the fact 

 that the book can be regarded as thoroughly up to date, combine to render 

 the book one which can be recommended not only to students, but also to 

 the general reader interested in geology. 



A. S. 



