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

22 THE ARCTIC HOME IN THE VEDAS. of the Pliocene and the whole of the Pleistocene period was marked by violent changes of climate bringing on what is called the Glacial and Inter-Glacial epochs. But it is now conclusively established that before the advent of this period a luxuriant forest vegetation, which can only grow and exist at present in the tropical or temperate climate, flourished in the high latitude of Spitzbergen, where the sun goes below the horizon from Novem- ber till March, thus showing that a warm climate prevailed in the Arctic regions in those days. It was in the Quaternary or the Pleistocene period that the mild climate of these regions underwent sudden alterations, producing what is called the Glacial period. The limits of this Glacial period may not so exactly coincide with those of the Pleistocene as to enable us to say that they were mathematically co-extensive, but, still, in a rough sense we may take these two periods as coinciding with each other. It is impossible within the limits of a short chapter to give even a summary of the evidence proving the existence of one or more Glacial epochs in the Pleistocene period. We may, however, briefly indicate its nature and see what the geologists and the physicists have to say as regards the causes that brought about such extensive changes of climate in the Quaternary era. The existence of the Glacial period is no longer a matter of doubt, though scientific men are not agreed as to the causes which produced it. Ice-sheets have not totally disappeared from the surface of the earth, and we can still watch the action of ice as glaciers in the valleys of the Alps or in the lands near the Pole, like Greenland which is still covered with a sheet of ice so thick as to make it unfit for the growth of plants or the habitation of animals. Studying the effects of glacial action in these places geologists have discovered abundant traces of similar action of ice in former times over the whole of Northern Europe and America. Rounded and scratched stones, till or boulder-clay, and the