वेदों की प्राचीनता एवं काल-निर्णय / ओरायन (लोकमान्य बाल गंगाधर तिलक - खगोलीय वैदिक शोध)

xii CONTENTS.
PAGE
CHAPTER II.
THE GLACIAL PERIOD.
Geological climate—Uniform and gentle in early ages—Due to dif-
ferent distribution of land and water—Climatic changes in the
Quarternary era—The Glacial epoch— Its existence undoubtedly
proved—Extent of glaciation—At least two Glacial periods —
Accompanied by elevation and depression of land — Mild and
genial inter-glacial climate even in the Arctic regions—Various
theories regarding the cause of the Ice Age stated—Lyell's theory
of geographical changes —Showing long duration of the Glacial
period—Croll's theory—Effect of the precession of the equinoxes
on the duration and intensity of seasons —The cycle of 21,000
years—The effect enhanced by the eccentricity of the earth's orbit
—Maximum difference of 33 days between the duration of sum-
mer and winter—Sir Robert Ball's calculations regarding the
average heat received by each hemisphere in summer and winter
—Short and warm summers and long and cold winters, giving
rise to a Glacial epoch—Dr. Croll's extraordinary estimate re-
garding the duration of the glacial epoch—Based on the maxi-
mum value of the eccentricity of the earth's orbit—Questioned by
astronomers and geologists —Sir Robert Ball's and Newcomb's
view —Croll's estimates inconsistent with geological evidence—
Opinions of Prof. Geikie and Mr. Hudleston—Long duration of the
Glacial period—Summary of results. . . . . 20
CHAPTER III.
THE ARCTIC REGIONS.
Existence of a Circum-polar continent in early times—Probable also
in the Inter-glacial period—Milder climate at the time—Neces-
sity of examining Vedic Myths—Difference between Polar and
circumpolar characteristics—The precession of the equinoxes used
as chronometer in Vedic chronology—Characteristics of the North
Pole—The horizontal motion of the celestial hemisphere—Spin-
ning round of the stars without rising or setting—The Sun rising
in the South—A day and a night of six months each—Aurora
Borealis —Continuous fortnightly moonlight, and long morning