Such conditions of climate may account for the recovery of the remains of the reindeer and the hippopotamus in the same drift and cave-deposits of Europe’s glacial period. The woolly mammoth and rhinoceros, the musk-ox, reindeer, and other Arctic fauna, may be presumed to have annually retreated from the summer heats, and given place to those animals, the living representatives of which are now found only in tropical Africa. A period of depression followed, during which, throughout an extensive area, all but the highest levels was submerged beneath an Arctic ocean, and the drift and boulders of the highlands of Norway and Scotland were dispersed by means of icebergs over the low levels of what was then an archipelago, in which only the higher peaks of Britain rose out of the sea. Far to the south of the Thames and the Seine, the drift of this Arctic ocean was then accumulating the evidence which now reveals to us the fauna and the arts of quaternary Europe; just as the overlying boulders of the American drift far south in the Ohio valleys show their derivation from the Laurentian mountains of Canada. With the elevation of the old ocean-bed there appears to have been a renewal of an Arctic temperature indicated by the traces of local glaciers in the mountains of Scotland, Cumberland, and Wales; and so the glacial period drew to a close. A gradual rise of temperature carried the lines of ice and perpetual snow further and further northward, excepting in regions of great elevation, as in the Swiss Alps. This was necessarily accompanied with the melting of the glaciers accumulated in the mountain valleys throughout the protracted period of cold. The broken rocks and soil of the highlands were swept into the valleys by torrents of melted ice and snow; the lower valleys were hollowed out and reformed under this novel agency; and the landscape assumed its latest contour of valley, estuary, and river-beds. This is what the elder geologists, including Dean Buckland, accepted for a time as the evidence of the Mosaic deluge. It is now universally recognised as the product of no sudden cataclysm, but the result of operations carried on continuously throughout periods of vast duration, during which the memorials of animal and vegetable life of the pleiocene and pleistocene epochs were slowly imbedded in the accumulated débris of this diluvian reconstruction. The characteristics of the fossil mammals of the post-glacial period differ in many respects so widely from all that we are accustomed to associate with the presence of man, that they help to suggest even an exaggerated idea of antiquity. Nevertheless, there is no break of continuity. Animals still living have their fossil representatives alongside of the pleiocene mastodon, cave-lion, and bear: if indeed the latter be not itself the _ursus ferox_, or grizzly bear of North America, the claws of which are still worn as the proudest trophy of the Red Indian hunter.