N.P.

Difference between aphelion & perihelion distance 14, 212,700 miles.

N. WINTER SOLSTICE

IN THEIR

GEOLOGICAL RELATIONS:

A THEORY OF

SECULAR CHANGES OF THE EARTH'S CLIMATE.

BY

JAMES CROLL,

OF HER MAJESTY'S GEOLOGICAL SURVEY OF SCOTLAND.

NEW YORK:

D. APPLETON AND COMPANY,

1, 3, AND 5 BOND STREET.

1890.

Geol. QE 698 .092 18000

PREFACE TO THE FIRST EDITION.

In the following pages I have endeavoured to give a full aud
concise statement of the facts and arguments adduced in sup-
port 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 con-
stantly 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

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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 con cerned, 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.

EDINBURGH, March, 1875.