130 Reviews — Professor Grenville Cole's Mineralogy. 



thick, the chief metallic mineral being native gold. Gold-silver 

 quartz veins are the most widely distributed, and they occur in the 

 Mi. Stevens Group and in the volcanic and intrusive rocks. 



Some formations other than those mentioned occur over limited 

 areas on the eastern side of Taku Arm, and all are described. The 

 origin of the ore deposits is also discussed. There are views of mines 

 and mine-works, and a small colour-printed geological map. 



IV. — Outlines of MiifERALOGr for Geological Students. By 

 Gkenville a. J. Cole. 8vo ; pp. 339 + '^ii; with 124 figures 

 in the text. London: Longmans, Green & Co., 1913. Price. 

 5s. net. 



THE need of a good elementary textbook of mineralogy, which 

 meets the requirements of geological students, must be felt by 

 many. Professor Cole has set himself to supply this need and has 

 successfully accomplished a difficult task. His large experience in 

 the training of geologists has enabled him to anticipate their difficulties 

 and to present theories and facts in a most lucid way, omitting nothing 

 that is essential to a clear presentation of the subject. 



The treatment of the physical and chemical properties of minerals 

 is clear and calls for little comment. The descriptions of the use of 

 Walker's Balance and of Sollas's Diffusion Column for the determina- 

 tion of specific gravity will both be found useful for practical work. 



The chapters on crystallography are necessarily brief, but are well 

 written. The seven crystallographic systems are taken in order of 

 increasing symmetry, with the hexagonal and trigonal systems last. 

 Exception may be taken to the use of the Bravais-Miller indices for 

 the trigonal system, as this presents serious disadvantages. The 

 advantages of using Millerian indices for this system are many, as 

 pointed out recently by Dr. Tutton, but Professor Cole urges that 

 " it presents a difficulty in the abolition of the vertical crystallographic 

 axis ; moreover, the notation of the individual crystal-faces . . . gives 

 symbols absolutely different from those of all the other systems ". 

 Surely this is not the case. The projection of a trigonal crystal on 

 Miller's axes gives indices for all the faces which ai'e exactly similar 

 to those for the corresponding faces of a cubic crystal, projected with 

 one triad axis in the vertical position. 



In the description of optical characters, due emphasis is laid on the 

 use of convergent light in the determination of minerals. A useful 

 innovation is the reproduction of Siethoff's diagram for the repre- 

 sentation of the isogyres of a biaxial crystal. 



The chemical methods most useful in mineral determinations are 

 described, and the special tests for individual minerals are given in 

 the descriptive part of the book. 



The chapters dealing with descriptive mineralogy are preceded by 

 an interesting discussion on classification and nomenclature. The 

 classification has been chosen to meet the demands of students of 

 chemistry, mining, and geology, and is one which the author has 

 found to work admirably in practice. It is based on Mendeleeff's 

 periodic classification of elements. Compounds are grouped together 



