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

THE GLACIAL PERIOD. 21
that in the distant geological ages the climate of our planet
must have been characterised by similar rotations of hot and
cold seasons. But such a supposition is directly contradicted by
geological evidence. The inclination of the earth's axis to the
plane of the ecliptic, or what is technically called the obliquity of
the ecliptic, is not the sole cause of climatic variations on the
surface of the globe. High altitude and the existence of oceanic
and aerial currents, carrying and diffusing the heat of the equatorial
region to the other parts of the globe, have been found to produce
different climates in countries having the same latitude. The
Gulf Stream is a notable instance of such oceanic currents, and
had it not been for this stream the climate in the North-West of
Europe would have been quite different from what it is at present.
Again, if the masses of land and water be differently distributed
from what they are at present, there is every reason to suppose
that different climatic conditions will prevail on the surface of the
globe from those which we now experience, as such a distribution
would materially alter the course of oceanic and aerial currents
going from the equator to the Poles. Therefore, in the early
geological ages, when the Alps were low and the Himalayas not
yet upheaved, and when Asia and Africa were represented only
by a group of islands, we need not be surprised if, from geological
evidence of fossil fauna and flora, we find that an equable and
uniform climate prevailed over the whole surface of the globe as
the result of these geographical conditions. In Mesozoic and
Cainozoic times this state of things appears to have gradually
changed. But though the climate in the Secondary and the
Tertiary era was not probably as remarkably uniform as in the
Primary, yet there is clear geological evidence to show
that until the close of the Pliocene period in the Tertiary
era the climate was not yet differentiated into zones and there
were then no hot and cold extremes as at present. The close