CONTENTS. 
xi 
CHAPTER VIII. 
THE CAUSES OF GLACIAL EPOCHS. 
Various suggested causes — Astronomical causes of changes of Climate — Difference 
of Temperature caused by varying distances of the Sun — Properties of air and 
water, snow and ice, in relation to Climate— Effects of snow on Climate— High 
land and great moisture essential to the initiation of a Glacial Epoch — Per- 
petual snow nowhere exists on lowlands — Conditions determining the presence or 
absence of perpetual Snow— Efficiency of Astronomical causes in producing Glaci- 
ation — Action of meteorological causes in intensifying Glaciation — Summary of 
causes of Glaciation — Effect of clouds and fog in cutting off the Sun’s heat — 
South Temperate America as illustrating the influence of Astronomical causes on 
Climate — Geographical changes how far a cause of Glaciation — Land acting as a 
barrier to ocean-currents — The theory of interglacial periods and their probable 
character— Probable effect of winter in aphelion on the climate of Britain— The 
essential principle of climatal change restated — Probable date of the last Glacial 
Epoch— Changes of the sea-level dependent on Glaciation— The planet Mars as 
bearing on the theory of excentricity as a cause of Glacial Epochs 
Pages 121—162 
CHAPTER IX. 
ANCIENT GLACIAL EPOCHS, AND MILD CLIMATES IN THE ARCTIC EEGIONS. 
Mr. Croll’s views on ancient Glacial Epochs — Effects of Denudation in destroying 
the evidence of remote Glacial Epochs — Rise of sea-level connected with Glacial 
Epochs a cause of further denudation — "VVhat evidence of early Glacial Epochs 
may be expected — Evidences of Ice-action during the Tertiary Period — The 
weight of the negative evidence — Temperate climates in the Arctic Regions — 
The Miocene Arctic flora — Mild Arctic climates of the Cretacious Period— Strati- 
graphical evidence of long-continued mild Arctic conditions — The causes of mild 
Arctic climates— Geographical conditions favouring mild northern climates in Ter- 
tiary times — The Indian Ocean as a source of heat in Tertiary times — Condi- 
tion of North America during the Tertiary Period— Effect of high excentricity on 
warm Polar climates — Evidences as to climate in the Secondary and Palaeozoic 
Epochs — "Warm Arctic climates in early Secondary and Palaeozoic times — Con- 
clusions as to the climates of Secondary and Tertiary Periods — General view of 
Geological Climates as dependent on the physical features of the Earth’s surface 
—Estimate of the comparative effects of geographical and physical causes in 
producing changes of climate Pages 163 — 202 
CHAPTER X. 
THE EARTH’S AGE, AND THE RATE OF DEVELOPMENT OF ANIMALS AND PLANTS. 
Various estimates of Geological Time — Denudation and deposition of Strata as a 
measure of Time— How to estimate the thickness of the Sedimentary Rocks— 
How to estimate the average rate of deposition of the Sedimentary Rocks— The 
rate of Geological change probably greater in very remote times— Value of the 
preceding estimate of Geological Time— Organic modification dependent on 
Change of Conditions— Geographical mutations as a motive power in bringing 
about Organic Changes— Climatal revolutions as an agent in producing Organic 
Changes— Present condition of the Earth one of exceptional stability as regards 
Climate— Date of last Glacial Epoch and its bearing on the Measurement of 
Geological time — Concluding Remarks • o Pages 203 229 
