Page 241 - Lokmanya Tilak Samagra (khand 2)

28 SAMAGRA TILAK - 2 • THE ARCTIC HOME
would take place. " I cannot say ", he observes," " when the last
( Glacial epoch ) took place, nor when the next may be expected.
No one who is competent to deal with mathematical formulffi
would venture on such predictions in the present state of our
knowledge."* Prof. Newcomb of New York, another astro-
nomer of repute, in his review of Dr. Croll' Climate and Time
has also pointed out how in the present state of astronomical
knowledge it is impossible to place any reliance on the values of
eccentricity computed for epoches, distant by millions of years,
as the value of this eccentricity depends upon elements, many of
which are uncertain, and this is especially the case when one has
to deal with long geological eras. The only reply made by Dr.
Croll to this criticism is that his figures were correctly worked up
from the value of the eccentricity according to the latest correc-
tion of Mr. Stockwell.t This, however, is hardly a satisfactory
reply, inasmuch as Prof. Newcomb's objection refers not w the
correctness of the mathematical work, but to the impossibility of
correctly ascertaining the very data from which the value of the
eccentricity were obtained.
It was once supposed that the duration of each of Dr. Croll's
different periods admirably fitted in with the geological evidence,
and fully corroborated the estimates of time supposed to be
required for the extensive geographical changes which accompanied
the Glacial and Inter-Glacial periods. But geologists have now
begun to take a more sober view of this extravagant figures and
calculations. According to Croll's calculation there were three
periods of maximum eccentricity during the last three million
years, and there should, therefore, be three periods of glaciation
corresponding to these, each including several Glacial and Inter-
Glacial epochs. But there is no geological evidence of the existence
of such Glacial epochs in early geological eras, except, perhaps,
ir the Permian and Carboniferous periods of the Palffioloic or
the Primary age. An attempt is made to meet this objection by
replying that though the eccentricity was greatest at one period in
the early geological eras, yet, as the geographical distribution of
land and water was then essentially different from what it was in
the Quaternary era the high value of the eccentricity did not

" On the Cause of an Ice Age, p. r 32 .
t Climate and Cosmology, p. 39.