ed at various
intervals in the world's past history, they must depend upon some
frequently recurring cause. Such a cause, therefore, Dr. Croll began
ingeniously to hunt about for.

He found it at last in the eccentricity of the earth's orbit. This world
of ours, though usually steady enough in its movements, is at times
decidedly eccentric. Not that I mean to impute to our old and
exceedingly respectable planet any occasional aberrations of intellect,
or still less of morals (such as might be expected from Mars and Venus);
the word is here to be accepted strictly in its scientific or
Pickwickian sense as implying merely an irregularity of movement, a
slight wobbling out of the established path, a deviation from exact
circularity. Owing to a combination of astronomical revolutions, the
precession of the equinoxes and the motion of the aphelion (I am not
going to explain them here; the names alone will be quite sufficient for
most people; they will take the rest on trust)--owing to the
combination of these profoundly interesting causes, I say, there occur
certain periods in the world's life when for a very long time together
(10,500 years, to be quite precise) the northern hemisphere is warmer
than the southern, or _vice versa_. Now, Dr. Croll has calculated that
about 250,000 years ago this eccentricity of the earth's orbit was at
its highest, so that a cycle of recurring cold and warm epochs in either
hemisphere alternately then set in; and such cold spells it was that
produced the Great Ice Age in Northern Europe. They went on till about
80,000 years ago, when they stopped short for the present, leaving the
climate of Britain and the neighbouring continent with its existing
inconvenient Laodicean temperature. And, as there are good reasons for
believing that my old master and his contemporaries lived just before
the greatest cold of the Glacial Epoch, and that his immediate
descendants, with the animals on which they feasted, were driven out of
Europe, or out of existence, by the slow approach of the enormous ice
sheet, we may, I think, fairly conclude that his date was somewhere
about B.C. 248,000. In any case we must at least admit, with Mr. Andrew
Lang, the laureate of the twenty-five thousandth century, that

He lived in the long long agoes;
'Twas the manner of primitive man.

The old master, then, carved his bas-relief in pre-Glacial Europe, just
at the moment before the temporary extinction of his race