Roughly speaking, indeed, one may say that through the long series of
Primary and Secondary formations hardly a trace can be found of ice or
snow, autumn or winter, leafless boughs or pinched and starved
deciduous vegetation. Everything is powerful, luxuriant, vivid. Life,
as Comus feared, was strangled with its waste fertility. Once, indeed,
in the Permian Age, all over the temperate regions, north and south, we
get passing indications of what seems very like a glacial epoch,
partially comparable to that great glaciation on whose last fringe we
still abide to-day. But the Ice Age of the Permian, if such there were,
passed away entirely, leaving the world once more warm and fruitful up
to the very poles under conditions which we would now describe as
essentially tropical.

It was with the Tertiary period--perhaps, indeed, only with the middle
subdivision of that period--that the gradual cooling of the polar and
intermediate regions began. We know from the deposits of the chalk
epoch in Greenland that late in Secondary times ferns, magnolias,
myrtles, and sago-palms--an Indian or Mexican flora--flourished
exceedingly in what is now the dreariest and most ice-clad region of
the northern hemisphere. Later still, in the Eocene days, though the
plants of Greenland had grown slightly more temperate in type, we still
find among the fossils, not only oaks, planes, vines, and walnuts, but
also wellingtonias like the big trees of California, Spanish chestnuts,
quaint southern salisburias, broad-leaved liquidambars, and American
sassafras. Nay, even in glacier-clad Spitzbergen itself, where the
character of the flora already begins to show signs of incipient
chilling, we nevertheless see among the Eocene types such plants as the
swamp-cyprus of the Carolinas and the wellingtonias of the Far West,
together with a rich forest vegetation of poplars, birches, oaks,
planes, hazels, walnuts, water-lilies, and irises. As a whole, this