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PREFACE. 

THE method of treatment adopted in this Text-Book is one which, 
while conducting the class of Geology in the University of Hdin- 
burgh, I have found to afford the student a good grasp of the general 
principles of the science, and at the same time a familiarity with and 
interest in details of which he is enabled to see the bearing in the 
general system of knowledge. A portion of the volume appeared in 
the autumn of 1879 as the article “Geology ” in the Encyclopedia 
Britannica. My leisure since that date has been chiefly devoted to 
expanding those sections of the treatise which could not be adequately 
developed in the pages of a general work of reference. 
While the book will not, I hope, repel the general reader who cares 
to know somewhat in detail the facts and principles of one of the 
most fascinating branches of natural history, it is intended primarily 
for students, and is therefore adapted specially for their use. The 
digest given of each subject will be found to be accompanied by 
references to memoirs where a fuller statement may be sought. It 
has long been a charge against the geologists of Great Britain that, 
like their countrymen in general, they are apt to be somewhat 
insular in their conceptions, even in regard to their own branch of 
science.’ Of course, specialists who have devoted themselves to the 
investigation of certain geological formations or of a certain group 
of fossil animals, have made themselves familiar with what has been 
written upon their subject in other countries. But I am afraid 
there is still not a little truth in the charge, that the general body 
of geologists here is but vaguely acquainted with geological types 
and illustrations other than such as have been drawn from the area 
of the British Isles. More particularly is the accusation true in 
regard to American geology. Comparatively few of us have any 
adequate conception of the simplicity and grandeur of the examples 
_ by which the principles of the science have been enforced on the 
other side of the Atlantic. 
Fully sensible of this natural tendency, I have tried to keep it in 
constant view as a danger to be avoided as far as the conditions of 
my task would allow. In a text-book designed for use in Britain 
the illustrations must obviously be in the first place British. A 
truth can be enforced much more vividly by an example culled from 
familiar ground than by one taken from a distance. But I have striven 
to widen the vision of the student by indicating to him that while the 
1 See, for instance, K. C. von Leonhard, who, in his Basalt-Gebilde (1832), says :— 
“Hin Tadel, welcher viele geognostische Schriftsteller Englands nicht ungerecht trifit, 
ist ihre Unbekanntschaft mit der Litteratur des Auslandes; sie eignen sich das Gute 
fremder Nationen zu wenig an. Auch kommt ihnen unnéthige Umstandlichkeit und 
_ ermidende Weitschweifigkeit und eine Art gewissenhafter Peinlichkeit nicht selten zu 
Schulden, so dass manche ihrer Biicher sehr lesenswiirdig, aber nicht besonders lesbar 
sind.”—Vol. i. p. 40. 
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