movement of elevation must also have affected the
Southern Hemisphere, the evidence being equally plain that at the same
comparatively late date glaciers crushed over Southern Africa and South
America.<27> This is seen to prove too much. Again, how can we explain
the fact that some time during the Glacial Age we had a submergence, the
land standing several hundred feet lower than now, but still remained
covered with ice, and over the submerged part there sailed icebergs and
ice-rafts, freighted with their usual _debris_? That such was the state
of things in Europe we are assured by some very good authorities.<28>

Neither do geographical causes afford an adequate explanation of those
changes of temperature that surely took place during the Glacial Age.
These last considerations show us how difficult it is to believe that
geographical causes could have produced the Glacial Age.

We are assured that all through the geological ages the continents had
been increasing in size and compactness, and that just at the close of
the Tertiary Age they received a considerable addition of land to the
north. The astronomer also informs us that at a comparatively recent
epoch the eccentricity of the earth's orbit became very great. The
conditions being favorable, it is not strange that a Glacial Age
supervened.

We have been to considerable length in thus explaining the position
of the scientific world in regard to the cause of the Glacial Age. Our
reason for so doing is that this age is, we think, so connected with
the Paleolithic Age of man, that it seems advisable to have a clear
understanding in regard to it. What we have to say is neither new nor
original. It is simply an earnest endeavor to represent clearly the
conclusions of some of our best scholars on this subject, and we have
tried to give to each theory its due weight. Our conclusions may be
wrong, but, if so, we have the consolation of erring in very good
company.

We have now gone over the ground and are ready to see what dates can be
given. Though the numbers we use seem to be very large indeed, they
are so only in comparison with our brief span of life. They are
insignificant as compared with the extent of time that has surely rolled
by since life appeared on the globe. Let us, therefore, not be dismayed
at the figures the astronomer sets before us.<29>

About two hundred and fifty thousand years ago the earth's path around
the sun was much the same as that of the