REVIEWS 159 



A Text-book o£ Geology. By Philip Lake, M.A., F.G.S., and R. H. Rastall, 

 M.A., F.G.S. [Pp. xiv + 508, with 33 plates and 134 text-figures.] 

 Third Edition. (London : Edward Arnold, 1920. Price 21s. net.) 



In the ten years which have elapsed since the appearance of the first edition, 

 this book has proved its value to geological students. The publication of the 

 third edition, therefore, is very welcome, especially as this is no mere reprint 

 of the previous ones, but rather an enlarged and thoroughly up-to-date treatise 

 on the subject. While the arrangement of the earlier editions has been 

 retained, the various sections have undergone considerable revision, much 

 recent work having been incorporated and several new sections added. 

 Amongst the former may be noted the chapter on ore-deposits, which has 

 been entirely rewritten, and which, though necessarily brief, gives an ex- 

 cellent summary of the subject. In the section on coral reefs an account 

 is given of the recent American work, which has gone far to substantiate 

 Darwin's theory of their formation. 



The chapter on the sedimentary rocks contains a new section on " petro- 

 leum " and another on " concretions," in which, however, Liesegang's hypo- 

 thesis might have been extended to these structures in sediments as well as in 

 igneous rocks. At the end of the book a useful chapter on the history of 

 igneous activity in the British Isles is appended. The occurrences of igneous 

 rock are classified into five groups — Pre-Cambrian, Ordovician, Caledonian, 

 Armorican, and Tertiary — and the relationship of each to the earth movements 

 of the period indicated. While the Carboniferous volcanic and intrusive 

 masses are described with the Caledonian group, no mention is made of the 

 interesting Permo-Carboniferous masses of Ayrshire. 



The book is excellently printed and has numerous well-chosen and well- 

 reproduced illustrations ; a full index is also provided. 



A. S. 



Mineralogy : An introduction to the Study of Minerals and Crystals. By 



E. H. Kraus, Ph.D., Sc.D., and W. F. Hunt, Ph.D. [Pp. xiv + 561, 

 with 696 text-figures.] (New York : McGraw-Hill Book Co., 1920. 

 Price 27s.) 



This book provides, for the elementary student, a useful survey of the whole 

 field of mineralogy, and, as the information is given in a clear and attractive 

 manner, it should have a wide circle of readers. The first thirteen chapters 

 are concerned with the general aspect of the subject, and include an elementary 

 account of crystallography, a section on the polarising microscope, and dis- 

 cussions of the physical and chemical properties of minerals, concluding with 

 a description of the methods used in qualitative blowpipe analyses. The 

 trigonal system is included in the hexagonal, and no mention is made of the 

 reference of crystals in the former to three axes instead of four. The substi- 

 tution of the phrase " crystal-elements " by " elements of crystaUisation " 

 is unnecessary, and does not make for greater clearness. In the section on 

 hardness, only Moh's scale is described, the more exact methods of determina- 

 tion being ignored. 



In the descriptive part about one hundred and fifty minerals are treated, 

 the properties, mode of origin, and localities being given for each. Notes on 

 the uses to which each mineral is put are included, a feature which greatly 

 improves the interest and utility of the book. The tendency to regard minerals 

 as purely museum specimens is unfortunate, and it is to be hoped that, in the 

 future, greater attention will be paid to the economic values of these substances. 

 The last part of the volume is taken up with tables for the determination of 

 the minerals described. While the illustrations, which include portraits of a 

 number of distinguished mineralogists, are, on the whole, well reproduced, the 

 photographic reproductions of crystal models and mineral specimens are not 



