No. 390.] REVIEWS OF RECENT LITERATURE. 553 
The totals include small amounts of MnO, SrO, BaO, and other 
oxides. 
The Rocks of Mount Rainier. — The volcanics of Mount Rainier? 
are basaltic and andesitic lavas and tuffs, passing into one another 
by almost imperceptible gradations. The predominant andesite is 
hypersthenic, but other pyroxenes often occur with the hypersthene 
and sometimes replace it entirely in the rock mass. The platform 
upon which the volcanics were extruded consists of a granite either 
hornblendic or biotitic. 
Luquer’s Minerals in Rock Sections’ is an attempt to furnish to 
students in as few words as possible an account of the practical 
methods of identifying the minerals occurring in rocks by means of 
their optical and other physical properties as they may be observed 
in thin sections under the microscope. 
The general principles of optics are discussed in the first thirty- 
four pages of the book as an introduction to the description of the 
characteristics of the individual minerals. Unfortunately, this dis- 
cussion is so condensed that it can afford no help to the student 
unless it is accompanied by explanatory lectures. As a summary of 
a course of lectures in optics it might possibly be of value. The 
discussion explains nothing; it is merely a dogmatic statement of 
facts, sometimes so bare of explanatory or illustrative phrases as to 
leave only a confused impression in the mind of the reader. This is 
particularly noticeable in the case of the definitions. For instance, 
the first time the term “ extinction angle ” is used, it is described as 
the angle between the axis of elasticity and the crystallographic axis, 
without reference in any way to the fact of extinction. There is much 
loose expression in this part of the book, which, of course, might 
easily be corrected in a new edition. 
The chapter on the microscopic features of the individual minerals 
covers forty-five pages. Here we find a very concise description of 
the principal diagnostic characters of the minerals most frequently 
found in rocks, with brief remarks on their occurrence. 
A noteworthy feature of the volume is the clear manner in which 
directions are given for the manipulation of the apparatus employed 
1 Smith, G. O. Eighteenth Ann. Rep. U. S. Geol. Survey, Pt. ii, p. 416. 
2 Minerals in Rock Sections. The practical methods of identifying minerals in 
rock sections with the microscope. By L. McI. Luquer, C.E., Ph.D. vii + 117 
pp-, 48 figs. Price $1.40. New York, D. Van Nostrand Co., 1898 
