82 Reviews —Geikie’s Text-Book of Geology. 
quartzite, under one form or another, makes several distinct appear- 
ances; clay-slate and shale are divided from each other by the 
entire group of volcanic rocks; and so on. Surely the old-fashioned 
arrangement of rocks into aqueous, igneous, and metamorphic was 
much more manageable than this; and it is hardly likely that such 
a thorough-going believer in the power of metamorphism as Dr. 
Geikie would have found any insurmountable difficulty in classifying 
the individuals in his major groups according to their degree of 
alteration, and making them teach the special lesson which it is clear 
he desires them to convey. 
The third division (Book III.) of the volume is devoted to an 
account of the agencies at present engaged in geological evolution. 
These agencies are classed as hypogene and epigene, and the subject 
is treated with an exhaustiveness that leaves nothing to be desired. 
Geologists have long been aware of the interest Dr. Geikie has taken 
in this special branch of his science, but we were hardly prepared 
for such a masterly command of the entire subject as he has de- 
veloped in these pages. In selection and arrangement of material, 
in sequence and proportion, this section appears to us to leave every- 
thing hitherto attempted in geological text-books in this special 
department far behind. Every conspicuous fact and conclusion 
having a geological bearing hitherto published has its proper place 
in the compilation. It covers the ground embraced generally within 
the limits of Lyell’s “ Principles,” and bespeaks an enthusiastic 
student of that immortal work. But the student has now become a 
master in his turn and has his own story to tell: and admirably he 
tells it. very word falls with its proper weight and has its due 
effect. 
Having fully discussed the great earth-crust-builders and sculptors, 
Dr. Geikie next takes the reader to the study of the architecture of 
the great building itself, and treats in succession of the phenomena 
of stratification, fracture, protrusion, and metamorphism. As a whole 
this section is most extended and complete; but it is very unequal 
in parts, and when contrasted with the foregoing sections appears to 
us to be most decidedly inferior. For the unavoidable drudgery of 
mapping and sectioning the author appears to have lost much of his 
former zest. Some instructive examples of inversion are inserted 
from Heim’s magnificent memoir, but we trust that in a ‘future 
edition we shall see corresponding examples from British localities. 
They are plentiful enough in some areas in our islands, and display 
almost every phenomenon illustrated by Heim. 
In his description of intrusive and volcanic rocks, however, Dr. 
Geikie is himself again, and both in description and illustration the 
paragraphs are admirable. 
But it is in the sub-section upon metamorphism that the author’s 
interest becomes fully aroused. He very carefully distinguishes 
between local and regional metamorphism, tracing the effects of the 
former, by means of well-authenticated examples stage by stage 
until he demonstrates the possible transformation of ordinary clastic 
into actual crystalline rocks. But where he treats of regional meta- 
