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