Page 234 - Lokmanya Tilak Samagra (khand 2)

THE GLACIAL PERIOD 21

in North-Western Europe, by two alternations of genial and
rainy-cold climate before the present climatic conditions be-
came established.+
But though the fact of the Ice Age and the existence of a
milder climate within the Arctic regions in the Inter-Glacial
time is indubitably proved yet scientific men have not been as
yet able to trace satisfactorily the causes of this great catastrophe.
Such immense mass of ice as covered the whole of Northern
Europe and America during this period could not, like anything
else, come out of nothing. There must be heat enough in
certain parts of the globe to create by evaporation sufficient
vapour and aerial currents are required to transfer it to the colder
regions of the globe, there to be precipitated in the form of ice.
Any theory regarding the cause of the Ice Age which fails to
take this fact into account is not only inadequate but worthless.
A succession of Glacial periods, or at any rate, the occurrence
of two Glacial periods, must again be accounted for by the
theory that may be proposed to explain these changes; and if we
test the different theories advanced in this way, many of them
will be at once found to be untenable. It was, for instance, once
urged that the Gulf Stream, which at present, imparts warmth
to the countries in the North-West of Europe, might have been
turned away from its course in the Pleistocene period by the
submergence of the Isthmus of Panama, thus converting the
countries on the North-Western coast of Europe into lands
covered by ice. There is, however, no geological evidence to
show that the Isthmus of Panama was submerged in the Pleisto-
cene period and we must, therefore, give up this hypothesis.
Another theory started to account for the catastrophe was that
the earth must have passed through cold and hot regions of space,
thus giving rise w Glacial and Inter-Glacial periods respectively.
But this too is unsupported by any evidence. A third sugges-
tion advanced was that the supply of solar heat on earth must
have varied in such a way as to give rise to warm and cold clima:.
tes but this was shown to be a mere conjecture. A change in
the position of the earth's axis might indeed cause such sudden
changes in the climate; but a change in the axis means a change
in the equator and as the earth owing to its diurnal rotation

t Prehistoric Europe, p. 530.