It is evident that in this age of forests the German Ocean must have been dry land, and the continent of Europe must have extended beyond the Orkneys and Hebrides, probably to the hundred fathom line. Such movements of elevation and depression, so far as we know anything of them, are extremely slow. There has been no change in the fords of rivers in Britain since Roman times, and the spit connecting St. Michael's Mount with Cornwall was dry at ebb and covered at flood as at the present day, when the British carted their tin across it to trade with the Phoenicians 2500 years ago. Mr. Read goes into elaborate calculations based on the time required for these geological changes, and arrives at the conclusion that they point to a date of not less than 50,000 or 60,000 years ago for the commencement of the post-glacial period. These calculations are disputed, but it seems certain that several multiples of the historical standard of say 10,000 years, must be required to measure the period since the glacial age finally disappeared, and the earth, with its existing fauna, climate, and geographical conditions, came fairly into view. This is confirmed by the great changes which have taken place in the distribution of land and water since the quaternary period. Huxley, in an article on the Aryan question, points out that in recent times four great separate bodies of water--the Black Sea, the Caspian, the Sea of Aral, and Lake Balkash--occupied the southern end of the vast plains which extend from the Arctic Sea to the highlands of the Balkan peninsula, of Asia Minor, of Persia and Afghanistan, and of the high plateaux of Central Asia, as far as the Altai. But he says, "This state of things is comparatively modern. At no very distant period the land of Asia Minor was continuous with that of Europe, across the present site of the Bosphorus, forming a barrier several hundred feet high, which dammed up the waters of the Black Sea. A vast extent of Eastern Europe and of west-central Asia thus became one vast Ponto-Aralian Mediterranean, into which the largest rivers of Europe and Asia, the Danube, Volga, Oxus, and Jaxartes, discharged their waters, and which sent its overflow northwards through the present basin of the Obi." The time necessary for such changes goes far to confirm Mellard Read's estimate for the long duration of the recent or post-glacial period.