CLIMATE AND TIME
[Illustration: FRONTISPIECE
N. WINTER SOLSTICE IN APHELION.
N. WINTER SOLSTICE IN PERIHELION.
W. & A. K. Johnston, Edinb^r. and London.]
CLIMATE AND TIME
_IN THEIR GEOLOGICAL RELATIONS_
A THEORY OF
SECULAR CHANGES OF THE EARTH’S CLIMATE
BY JAMES CROLL
OF H.M. GEOLOGICAL SURVEY OF SCOTLAND
LONDON
DALDY, ISBISTER, & CO.
56, LUDGATE HILL
1875
LONDON:
PRINTED BY VIRTUE AND CO.,
CITY ROAD.
PREFACE.
In the following pages I have endeavoured to give a full and concise
statement of the facts and arguments adduced in support of the theory
of Secular Changes of the Earth’s Climate. Considerable portions of
the volume have already appeared in substance as separate papers in
the Philosophical Magazine and other journals during the past ten or
twelve years. The theory, especially in as far as it relates to the
cause of the glacial epoch, appears to be gradually gaining acceptance
with geologists. This, doubtless, is owing to the greatly increased
and constantly increasing knowledge of the drift-phenomena, which has
induced the almost general conviction that a climate such as that of
the glacial epoch could only have resulted from cosmical causes.
Considerable attention has been devoted to objections, and to the
removal of slight misapprehensions, which have naturally arisen in
regard to a subject comparatively new and, in many respects, complex,
and beset with formidable difficulties.
I have studiously avoided introducing anything of a hypothetical
character. All the conclusions are based either on known facts or
admitted physical principles. In short, the aim of the work, as will be
shown in the introductory chapter, is to prove that secular changes of
climate follow, as a necessary effect, from admitted physical agencies,
and that these changes, in as far as the past climatic condition of
the globe is concerned, fully meet the demand of the geologist.
The volume, though not intended as a popular treatise, will be found,
I trust, to be perfectly plain and intelligible even to readers not
familiar with physical science.
I avail myself of this opportunity of expressing my obligations to my
colleagues, Mr. James Geikie, Mr. Robert L. Jack, Mr. Robert Etheridge,
jun., and also to Mr. James Paton, of the Edinburgh Museum of Science
and Art, for their valuable assistance rendered while these pages were
passing through the press. To the kindness of Mr. James Bennie I am
indebted for the copious index at the end of the volume, as well as
for many of the facts relating to the glacial deposits of the West of
Scotland.
JAMES CROLL.
EDINBURGH, _March, 1875_.
CONTENTS.
CHAPTER I.
INTRODUCTION.
PAGE
The Fundamental Problem of Geology.—Geology a Dynamical
Science.—The Nature of a Geological Principle.—Theories
of Geological Climate.—Geological Climate dependent
on Astronomical Causes.—An Important Consideration
overlooked.—Abstract of the Line of Argument pursued in the
Volume 1