As in the previous editions of this pioneering work, Professor Shand bases his concept of rock types on the chemistry of silicate systems, and thus continues his fight for the abolishment of the "jungle of rock names" which often cripples the perspective of the student.
The book is written for the advanced worker. Its third edition introduces much new material in nearly every chapter and is conveniently divided into two parts. A rough outline of the contents of the nineteen chapters of Part I would include discussions on the fixed constituents of eruptive rocks, the fugitive constituents, the temperature, pressure, and walls of magma on compatible and incompatible phases and on eruptive rock complexes. The discussion on linkage between eruptive rocks and ore deposits, which has been omitted in the wartime edition, is re-introduced and expanded and now covers Chapters X, XI, and XII of Part I. This part is concluded by a classification of eruptive rocks.
The four chapters of Part II dealing respectively with oversaturated, saturated, undersaturated non-feldspathoidal rocks, express the author's system of cl~ssification.
Numerous references are appended to each chapter. H. N. MICHAEL.