supervention of an arctic climate. So long as the glaciers and the mer de glace were on the increase, any remains of man or his works left within areas subsequently covered by the ice-sheet would be buried in the moraine profonde, with little chance of being recovered, so that evidence of his existence prior to the maximum period of glaciation can only be looked for in non-glaciated districts. But as the ice began to wane and was gradually passing away, the river-drift deposits and terminal moraines would remain scattered over the land, subject only to disturbance by the ordinary agencies of denudation. In the circumstances, any worked objects, such as stone implements, dropped into these sedimentary deposits, or washed down by rivulets, might remain as part of their contents to the present day.
Stone Implements.
Flint implements of a peculiar type, now admittedly the work of human hands, together with remains of extinct mammalia, have been found among the stranded gravels and brick-earth deposits of these ancient rivers in many localities throughout Europe. In non-glaciated districts it is often difficult to say whether such relics are pre- or post-glacial, as the date of their deposition might be at any time during the Glacial Epoch.
The final excavation and clearing out of the present valleys and waterways of Europe was principally due to the erosive effect of these torrential rivers, laden, as they must have been, with glacial detritus. The disintegrated materials swept down by them—gravel, sand, loam, or brick-earth—were deposited here and there along their banks, and what remains of them may now be found in patches at various elevations, sometimes as high as 100 feet or more, above their present beds. Such deposits are occasionally observed on isolated prominences, as on the cliffs above Southampton Water, and those of Reculver in the lower Thames; and hence it may be difficult to trace the course of the original rivers which transported them. But this merely indicates the enormous length of time that has elapsed since the earlier gravels were deposited—a time sufficient to allow of the very trend of some of the cross streams
