Phrsical Geography of the Quaternary or Epoch.—The remains of human art attributed to the Miocene and Pliocene of the Tertiary are too few, and their actual age is too uncertain, for us to accept the presence of our species on the earth at that time as demonstrated. On the contrary, it is highly unlikely that a creature so finely organized as man could have survived for so long a period as that hypothesis involves. We may there fore consider the era of his advent to have been some time in what De Mortillet calls "Quaternary time," and the geologic conditions which then prevailed may profitably occupy our attention.
At its commencement there was much more water, and correspondingly less land, near the northern pole of the earth than at present. The vast tundras of Siberia and the plains of Northern Europe quite down to the latitude of Poland were covered with an open sea. The Black Sea, the Caspian, the Persian Gulf, and the Indian Ocean were united by a broad and not deep water-way, through which the currents of the tepid tropical sea flowed toward the pole. On the other hand, the now-dissevered land areas of the Northern Atlantic were connected into one continent. No separation existed between Northern Africa and the Iberian Peninsula. Italy, Sardinia, Sicily, and Malta are but the fragments of one original continuous territory which extended southward to Tunis and Tripoli. Most of Northern England and Scotland was under water, but the valley of the Thames was above the ocean, and the south coast of England, extending much farther into the sea than at present, was united to Wales, to Ireland, and to a long coast-line which, trending north-westward, embraced Iceland, and the southern point of Greenland, and continued unbroken to include Labrador, Newfoundland, and other parts of the continent of America in high northern latitudes. The existence of this land-bridge between the Old and New Worlds in the early Quaternary (Pleistocene) Epoch is attested by the close similarity of the fauna and flora of the two continents in high latitudes, by the presence in both of the same species of living land-shells, by the uniformity of glacial action in both areas, and finally by the demonstrable presence of early man on each side of the bridge.
The Glacial or Ice brought about the violent catastrophe which resulted in the dissevering of the two hemispheres by a broad and cold ocean? The reply is, that the same mighty glaciers which levelled the prairies of the West, which scooped out the basins of the Great Lakes between Canada and the United States, which tore into shreds the coasts of Maine, of Scotland, and of Norway, leaving them seamed with deep fjords and scarred peninsulas,—this same irresistible force descended on the rather narrow strip of land which at the close of the Tertiary united Europe and America, and tore it into fragments, of which but a few, as Iceland, the Faroe Islands, and Newfoundland, survive above the engulf ing waves. Man, ignorant, defenceless, and feeble, could oppose to this
overwhelming catastrophe only the marvellous tenacity of life with which lie is endowed (see Vol. I. p. 32) and the resources suggested by his intelligence wherewith to combat the changes which took place in his environment. These were different in the two continents, and led him, as before observed, into divergent paths of development. We shall follow his career first in the one hemisphere and then in the other, begin ning with that in which there is reason to believe lie commenced his existence as man.
Relations of Glacial Phenomena to will be seen from the above that the Glacial Age of the geologist is the most important landmark in the early history of the human species. The archreolo gist who would explore the remotest tracts of his science must acquaint himself with the localities occupied by the great glaciers, the phenomena which remain to attest their advance and retrogression, and the periods of time during which they continued in different areas. The investigations of numerous observers have already thrown much light on these ques tions. For instance, we have learned that the glacial area is invariably defined by the presence of striae or scratches upon the surface of rocks, by beds of so-called "till," a mixture of clay, coarse sand, and angular stones, and by the large heaps of broken rocks and boulders, known as "terminal moraines," which mark the limits of the ice-sheet.
the study of these phenomena it has been ascertained that the great glacier in the Northern Hemisphere did not extend equally in all directions from the pole. On the contrary, not more than one half of the surface at the latitude of Go° N. was covered by it. It began at the longitude of Tcheskaia Bay in Northern Russia, and extended westward to the Mackenzie River in British America. Stretching southward from a line connecting these two points, the ice-sheet deposited its terminal moraines in the suburbs of London in Europe, and in the State of Kentucky in the United States. On the other hand, Siberia and Alaska have revealed no glacial signs which can be attributed to this great geologic event. Their moraines are assignable to local glaciers only. It will readily be seen what a controlling influence this geographical distribution of the ice-sheet must have exerted on the migrations of primitive man.