Reviews—Greikie’s Text-Book of Geology. 81 
in the forefront of the book. It appeals to the intellect and imagi- 
nation of the educated reader, and that upon his most vulnerable 
side, and compels his keen interest in the subject at the very com- 
mencement. 
In the second division of the volume (Book II.) the author treats 
of the fully developed earth of the present; here, as everywhere 
throughout the work, following invariably the same order in his 
descriptions ;—proceeding from the general to the special, from 
without, inwards. In the first section of this Buok, he carries the 
reader in imagination through the outer coverings of air, water, and 
visible earth-crust, until he stands with him once more peering 
curiously into the mists of recent speculation respecting the actual 
state of the earth’s interior. Nearly one-half of this sub-section is 
devoted to the discussion of the various theories hitherto advanced 
as to subterranean heat and pressure, and the probable extent of 
geological time. The diverse results of Hopkins, Delaunay, 
Thomson, Mallet, Darwin, and Fisher, are all passed in review. 
One can hardly avoid the inference that the author has a leaning 
towards the views of the Scottish authorities, and one would per- 
sonally have preferred a much fuller treatment of the views of 
Fisher and Le Conte ; but upon the whole this sub-section is the best 
summary of opinion we actually possess. 
The second section of the Book (Book II. Part 2) is devoted to a 
description of the minerals and rocks which constitute the accessible 
earth-crust. From beginning to end of this part we feel that we are 
in the presence of a master of his subject, one who is familiar with 
every stage, and knows how to smooth over every difficulty. After 
a brief glance at the main chemical rock-forming elements, the 
author passes on rapidly to the chief rock-forming minerals, giving 
just such descriptions as are generally capable of verification by 
hand-specimens, and carefully avoiding all mineralogical terms but 
such as are actually necessary. While we heartily sympathize with 
him in his avoidance of long definitions of crystalline forms, we can 
hardly help regretting that at least a short sketch of the chief 
crystalline types and their major derivatives had been inserted for 
the benefit of those private students of the science who have no 
leisure to follow out a complete mineralogical course, and to whom, 
as a consequence, many of the definitions on pages 63 to 85 will be 
partly incomprehensible. 
_ To the sub-section which follows (Sect. IV.) treating chiefly of the 
microscopic characters of rocks, and which is essentially a new feature 
in geological text-books, no exception can be taken; it is excellent 
throughout. 
But in the next section (Section V.), which is devoted to lithology, 
it does not appear to us that the Author is quite so successful. He 
classifies rocks under the two main heads—crystalline and clastic, 
dividing the former into stratified, foliated, and massive; and the 
latter into sands, clays, tuffs, and fragmental organic rocks. As a 
consequence of this arrangement, compact limestone finds a place at 
one end of the entire rock-series, and chalk almost at the other; 
DECADE II.—VoL. X.—NO. Il. 6 
