82 
DYNAMICAL GEOLOGY 
they often merit. This neglect is not so much simple oversight, 
as it is apparent hopelessness of possible analysis due partly, 
perhaps, to the fact that so many of the factors involved are 
naturally expected to find little direct expression either geologi¬ 
cally or geographically. Then, too, the evaluation of such changes 
are doubtless so relatively inconsequental and uncertain as to be 
lost among those of more striking local features. Visible physiog¬ 
nomy of sphericity changes would be anticipated as about the 
very last thing to be geologically recorded. Small wonder then 
that they are so little liable to demand serious consideration. 
Yet, we seemingly recently attain something even on this score. 
In a purely theoretically way the keen Newton early attacked 
the sphericity problem. Between the date, about 1680, when he 
demonstrated mathematically that our rotating globe was appreci¬ 
ably oblate in form and that the length of its axis was twenty- 
one miles less than the equatorial diameter, and the time when 
actual measurements were made by geodesists proving the con¬ 
ception, a century and a half elapsed, so slow was the clue taken 
up. So amazingly accurate were the British philosopher’s calcu¬ 
lations that modern results make only small rectification neces¬ 
sary. 
In past geological ages the earth’s oblateness was not always 
the same as it is today. Fifty-seven millions of years back, or 
about at the close of the Paleozoic time perhaps, when the sidereal 
day was only about one-fourth as long as at present, or of six 
and three-fourths hours duration, the difference between the axial 
and equitorial diameter must have been very much greater than 
now. The direct deformal effect of a diminishing rate of rota¬ 
tion would be a rising of the polar regions and a. sinking of 
equator belt. Such polar expansion would ordinarily probably 
leave little or no geological impress because of the slowness with 
which the change took place and its masking by more conspicuous 
epicene operations. 
Bulging of the polar tracts would have another obscure effect 
of large dimensions. There would be a tendency for the crust 
to stretch from time to time. Such secular stretching would 
necessarily be so gradual and so likely to be overshadowed by 
other crustal movements that it could hardly be expected to be 
