Page 224 - Lokmanya Tilak Samagra (khand 2)

PREHISTORIC TIMES 11
views entertained by geologists on the subject. European geologists
think that as the beginning of the post-Glacial period was marked
with great movements of elevation and depression of land and
as these movements take place very slowly, the commencement
of the post-Glacial period cannot be placed later than 50 or 60
thousand years ago. Many American geologists, on the other
hand, are of opinion that the close of the last Glacial period must
have taken place at a much more recent date. They draw this
inference from the various estimates of time required for the
erosion of valleys and accumulation of alluvial deposits since the
last Glacial period. Thus according to Gilbert, the post-Glacial
gore of Niagara at the present rate of erosion must have been ex~
cavated within 7000 years.* Other American geologists from
similar observations at various other places have arrived at the
conclusion that not more than about 8000 years have elapsed since
the close of the last Glacial period. This estimate agrees very well
with the approximate date of the Neolithic period ascertained
from the amount of silt in some of the lakes in Switzerland. But
it differs materially from the estimate of the European geologists.
It is difficult to decide, in the present state of our knowledge, which
of these estimates is correct. Probably the Glacial and the
post-Glacial period may not, owing to local causes have commenced
or ended at one and the same time in different places, just as the
ages of Stone and Bronze were not synchronous in different
countries. Prof. Geikie does not accept the American estimate
on the ground that it is inconsistent wirh the high antiquity of the
Egyptian civilisation, as ascertained by recent researches. But
if no traces of glaciation are yet found in Africa this objection
loses its force, while the arguments by which the American view is
supported remain uncontradicted.
There are other reasons which go to support the same view.
All the evidence regarding the existence of the Glacial period comes
Jrom the North of Europe and America; but no traces of glacia-
tion have been yet discovered in the Northern Asia or North
Alaska. It is not to be supposed, however, that the northern part
of Asia did not enjoy a genial climate in early times. As observed
by Prof. Geikie, " everywhere throughout this vast region alluvial

• See Geikie's Fragments of Earth Lore, p. 286; also Dr. Bonney's
Story of our Planet, p. 560.