The Natural History of Igneous Rocks

406 Pages·2011·30.71 MB·English

by  Alfred Harker

CAMBRIDGE LIBRARY COLLECTION
Books of enduring scholarly value
Earth Sciences
In the nineteenth century, geology emerged as a distinct academic
discipline. It pointed the way towards the theory of evolution, as scientists
including Gideon Mantell, Adam Sedgwick, Charles Lyell and Roderick
Murchison began to use the evidence of minerals, rock formations and
fossils to demonstrate that the earth was older by millions of years than the
conventional, Bible-based wisdom had supposed. They argued convincingly
that the climate, flora and fauna of the distant past could be deduced from
geological evidence. Volcanic activity, the formation of mountains, and the
action of glaciers and rivers, tides and ocean currents also became better
understood. This series includes landmark publications by pioneers of the
modern earth sciences, who advanced the scientific understanding of our
planet and the processes by which it is constantly re-shaped.
The Natural History of Igneous Rocks
Alfred Harker (1859-1939) was a prominent petrologist who spent his
career at St John's College, Cambridge, lecturing on and researching rock
formations and related geological activity. He was elected a fellow of the
Royal Society in 1902, and was president of the Geological Society from 1916
to 1918. He used his Cambridge lectures as the foundation for this book (first
published in 1909), offering an introduction to the development of rocks and
related volcanic activity. With more than one hundred diagrams of various
aspects of geological formations, this work also provides a visual guide to
the location and formation of igneous rocks. Over the course of the work, he
covers the themes of vulcanicity, rock structure, crystallization, the role of
magma and the principles of rock classification, giving a broad picture of the
field of petrology around the beginning of the twentieth century.
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The Natural History
of Igneous Rocks
ALFRED HARKER
CAMBRIDGE
UNIVERSITY PRESS
CAMBRIDGE UNIVERSITY PRESS
Cambridge, New York, Melbourne, Madrid, Cape Town,
Singapore, Sao Paolo, Delhi, Tokyo, Mexico City
Published in the United States of America by Cambridge University Press, New York
www.cambridge.org
Information on this title: www.cambridge.org/9781108028134
© in this compilation Cambridge University Press 2011
This edition first published
This digitally printed version 2011
ISBN 978-1-108-02813-4 Paperback
This book reproduces the text of the original edition. The content and language reflect
the beliefs, practices and terminology of their time, and have not been updated.
Cambridge University Press wishes to make clear that the book, unless originally published
by Cambridge, is not being republished by, in association or collaboration with, or
with the endorsement or approval of, the original publisher or its successors in title.
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THE NATURAL HISTORY
OF IGNEOUS ROCKS
BY
ALFRED HARKER
M.A., F.R.S.
FELLOW OF ST. JOHN'S COLLEGE
LECTURER IN PETROLOGY IN THE UNIVERSITY OF CAMBRIDGE
WITH 112 DIAGRAMS AND 2 PLATES
METHUEN & CO.
36 ESSEX STREET W.C.
LONDON
First Published in igog
PREFACE
T
HE following pages are, in substance, a course of
lectures delivered at Cambridge; and, in offering
them to a larger audience, the general plan of treat-
ment has been retained.
Igneous action and igneous rocks are first considered from
a purely geological standpoint. In emphasizing this aspect,
I have been influenced by a conviction that the subject has
not yet been accorded its due place as an integral part of
historical geology.
The middle portion of the book deals with the crystalliza-
tion of igneous rock-magmas, regarded as complex solutions.
Although the subject is one which might be more skilfully
handled by a professed chemist, a presentation of it as it
appears to a petrologist may be not less useful to the
student. I have in the main followed Professor Vogt, whose
writings in the last few years have thrown so much light
upon the matter.
Some of the questions briefly and tentatively touched in
the concluding chapters are of a more speculative character,
but so fundamental in their scope that they could not be
passed over in silence.