Strange as it may appear, the records of geology assure us that such changes in the climate of Northwestern Europe have actually happened within a comparatively recent period—certainly within the human epoch. Thus it has been well ascertained that at a time when rude tribes of men, unacquainted with the use of metals, were hunting reindeer in Southern France, a vast area in Northern Europe was buried under a great sheet of ice—a veritable mer de glace—like those ice-sheets which cover up such extensive areas in the Arctic and Antarctic regions. Had any one at that time approached the shores of Northwestern Europe, he would have encountered, some fifty miles outside of the present western shores of Ireland and the Hebrides, a vast vertical wall of ice, like that which confronted Sir J. Clark Ross, Commodore Wilkes, and the Challenger expedition, and barred all approach to the Antarctic pole. Could our voyager have surmounted the Scoto-Hibernian ice-wall, he would have discovered that he stood on the verge of an interminable plain of snow and ice, extending eastward as far as the eye could reach. Here and there upon the far horizon he would have observed a few inconsiderable rocky hills, representing the upper portions of our highest mountains—for the ice which then buried our low grounds was not less than three thousand feet thick. Had he advanced inland until he reached those rocky heights he would have found the icy plain sweeping away in all directions, and bounded only by the horizon; and had he continued his journey toward the east, across what is now the German Ocean, he would have encountered nothing to break the monotonous level until he approached a low line of snow covered hills and mounds, marking the site of the ice-drowned Scandinavian Peninsula. After attaining these hills, had our imaginary wanderer now shaped his course toward the south, he must next have traversed a distance of more than five hundred miles before he reached the termination of the ice-sheet in Saxony. During this extraordinary condition of things the Arctic-Alpine plants and animals (which are now characteristic of lofty elevations in Central and Northwestern Europe, and of the low grounds of the higher latitudes) occupied the low-lying plains and valleys of middle Europe, a flora like that of Lapland growing in South Germany, Switzerland, etc., and pines and spruce-firs flourishing in Northeastern France, while reindeer, glutton, Arctic fox, lemming, marmot, and others were the prevailing animals of those regions. When we think of the conditions which now obtain in Europe, can we conceive of any stronger contrast than that which is suggested by the few facts which are here summarized? Instead of the splendid navies of war-ships, ocean-liners, and other craft which now crowd its waters, the English Channel had formerly its fleets of ice-floes, and the walrus haunted the coasts of Northern France. When such extreme conditions obtained, it can hardly be doubted that the Gulf Stream, as we know it now, had no existence in the North Atlantic.
