1896.] Recent Literature. 929 
in a few discriminating sentences, analyses of many varieties are given 
and the structures and textures of all are well described. One of the 
most commendable features of the volume is the use of only the more 
important rock-names in the body of the text—the less important ones 
being relegated to a very comprehensive glossary which forms a con- 
venient appendix to the book. In this respect, as in some others, the 
volume under review is very much more satisfactory to the untechnical 
reader than the other volumes of similar character that have recently 
come under our notice. 
The work opens with a description of the rock-forming minerals and 
_a discussion of the principles of rock classification. Following this 
are the descriptions of the rocks. These are divided into Igneous, 
Aqueous (including Eolian) and Metamorphic rocks. Each class is 
divided into groups according to chemical composition, and each group 
is further subdivided according to texture. The classification is an 
eminently practical one, and at the same time it can give no offense to 
the micoscopical lithologist. 
In the discussion of the rock-types each chapter begins with a list of 
analyses; this is followed by comments upon them. Then comes a 
description of varieties, a statement of relationships, a paragraph on 
geological occurrence, one on alterations and one on distribution. In 
that portion of the book that deals with the igneous rocks the glasses 
are first taken up, then the porphyritic varieties and, finally, the 
granitic ones. The aqueous rocks are grouped as mechanical sedi- 
ments, limestones, organic remains and precipitates from solution. Of 
the metamorphic rocks two great classes are recognized, viz., those pro- 
duced by contact action and those produced by regional metamor- 
phism. 
The above outline of the contents of the volume is very brief, but it 
is sufficiently full to indicate that the author has covered well the field 
that such a treatise as this one should cover. This book should find a 
wide sale among engineers as well as among all teachers who introduce 
into their courses on geology a description of rocks. _ It isa far more 
valuable synopsis of the characteristics of rock types to place in the 
hands of geological students than the synopses contained in the large 
text books on geology.—W. S. B. 
