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The Cambridge Manuals of Science
and Literature
ROCKS AND THEIR ORIGINS
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CAMBRIDGE UNIVERSITY PRESS
London: FETTER LANE, E.C.
C. F. CLAY, Manager
London: WILLIAM WESLEY & SON, 28, ESSEX STREET, STRAND
Berlin: A. ASHER AND CO.
Leipzig: F. A. BROCKHAUS
New York: G. P. PUTNAM'S SONS
Bombay and Calcutta: MACMILLAN AND CO., Ltd.
All rights reserved
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ROCKS AND THEIR
ORIGINS
BY
GRENVILLE A. J. COLE
Professor of Geology in the Royal
College of Science for Ireland
Cambridge:
at the University Press
1912
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PRINTED BY JOHN CLAY, M.A.
AT THE UNIVERSITY PRESS
With the exception of the coat of arms at
the foot, the design on the title page is a
reproduction of one used by the earliest known
Cambridge printer, John Siberch, 1521
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PREFACE
This little book is intended for those who are notspecialists in geology, and it may perhaps beaccepted as a contribution for the general reader.To all who are interested in the earth, the study ofrocks is an important branch of natural history. Ifdetailed works on petrology are to be consultedlater, F. W. Clarke's Data of Geochemistry (Bulletin,U.S. Geological Survey, ed. 2, 1911) must on no accountbe overlooked. Its numerous references to publishedpapers, and the attention given to rock-origins, makeit a worthy companion to C. Doelter's Petrogenesis.Many things have perforce been omitted from thepresent essay. It seemed unnecessary to review theCarbonaceous rocks, since the most important of thesehave been admirably dealt with in E. A. N. Arber'sNatural History of Coal, published as a volumein this series. I should like to have describedoccurrences of rock-salt, of massive gypsum, andother products of arid lands, where "black alkali"poisons the surface, and the casual pools are- vi -fringed with white and crumbling crusts. Rock-taluses,and all the varied alluvium carried seawardas the outwash of continental land, well deserve achapter to themselves. But there is really no endto the subject, which embraces all the