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