674 SCIENCE PROGRESS 



usually very scattered ; an attempt to collect the available information into 

 one volume calls, therefore, for sympathetic treatment. In Chemical Disin- 

 fection and Sterilisation the authors have rendered great service to those inter- 

 ested in this question both from its bacteriological and chemical aspect. The 

 book is divided essentially into two parts, the first dealing more particularly 

 with the practical side, such as the disinfection of air, sterilisation and preser- 

 vation of food, sterihsation of water, wood preservation, etc., and the second 

 with the chemical substances used in disinfection. A chapter is added on 

 bacteriological methods of standardising disinfectents, and the value of the 

 book is increased by a bibliography at the end of each chapter. 



Valuable though the book may be as a work of reference, it unfortunately 

 shows many signs of haste in composition, more particularly in the earlier chap- 

 ters. The authors make a habit of splitting the infinitive, and careless wording 

 is far from rare. Such expressions as " the expense is four or five times less " ; 

 " if tinned fruits show a strongly marked crystalline appearance on the interior 

 surface, they are unsafe to be eaten " ; " mercuric chloride has even been pro- 

 posed to be introduced "; " preservation in sxiitable {of&cially improved) cold 

 storage rooms " may raise a passing smile, but others are incomprehensible, as, 

 for example: " It has been stated that one part of bleaching powder with two 

 parts of sulphuric acid of specific gravity 1-53 and enough water to cover the 

 powder, evolved three times as much chlorine as when hydrochloric is used. 

 This may be due to the heat generated by the sulphuric acid, as the amounts 

 yielded are theoretically the same. ... If the insoluble, and therefore solid, 

 sulphate of lime keeps back less chlorine than does the deliquescent calcium 

 chloride, the difierence in the yield might be explained." 



It is to be regretted that a book, so excellent in other respects, is marred in 

 this way, and it is to be hoped that when the necessity for a new edition arises 

 a careful revision will be made. O. L. B. 



Petrographic Methods and Calculations. By A. Holmes, D.Sc, A.R.C.Sc, 

 F.G.S. (Pp. XX -f 516, with 4 plates and 83 text figures). (London: 

 Thomas Murby & Co., 1921. Price 315. 6d. net.) 

 Much of the petrographic work which has been published in the past few 

 years tends to show that the subject is undergoing a transition, so far as its 

 methods are concerned, from the qualitative to the quantitative stage, and 

 this book is no less indicative of the change. While most previous treatises 

 on the subject have been mainly devoted to a description of the optical 

 methods used for the determination of minerals, in the present instance, only 

 two chapters are occupied with this branch, most of the remainder being 

 concerned with more quantitative aspects of the science. The scope of the 

 book may be seen from the chapter headings, which are as follows : Petrology, 

 its Scope, Aims and Applications ; Specific Gravity of Minerals and Rocks ; 

 Separation of Minerals ; Optical Examination of Minerals ; Examination of 

 Detrital Sediments ; Preparation of Thin Sections ; Microchemical and 

 Staining Methods ; Examination of Thin Sections ; Textures and Structures 

 of Rocks ; Chemical Analyses and their Interpretation ; Graphical Repre- 

 sentation of Chemical Analyses. While, in the chapter on Specific Gravity, 

 the treatment of the subject is very full, and even includes a detailed descrip- 

 tion of Day and Sosman's apparatus for high temperature work, the omission 

 of any reference to recent work in the thermal expansion of rocks is noticeable. 

 In the section on the optical examination of minerals a brief account of the 

 petrological microscope ought to have been included, in order to render the 

 book more or less self-contained. The description of the methods of examina- 

 tion of detrital sediments is largely based on Boswell's well-known works on 

 Sands, and must be regarded as giving a good account of a subject which, 

 until recently, was somewhat neglected. The discussion of mechanical 

 analyses, however, is rather inadequate, one notable omission being any 



