PHYSICAL CONDITIONS— PLEISTOCENE. 359 



along with the general wreckage of the land. Precisely similar 

 facts confront us in North Germany, where underneath the 

 youngest till we encounter in some places clays with sea-shells, 

 and in others beds of sand and clay with land- and freshwater- 

 shells and bones of the Pleistocene mammals. 



When we get beyond the southern limits reached by the 

 upper boulder-clay, we enter a region which was swept by the 

 floods and torrents coming from the mer de glace — the turbulent 

 waters sometimes" keeping to the valleys, at other times, when 

 these were choked with frozen snow, overflowing upon the inter- 

 vening plateaux. In this region, therefore, we often encounter 

 wide-spread sheets of torrential gravels and sand in which may 

 occur bones of the Pleistocene mammals and flint implements 

 of Palaeolithic workmanship— the relics of the last interglacial 

 epoch. Occasionally the whole thickness of the superficial 

 covering in these districts is composed entirely of such deposits, 

 but now and again we find them overlying river accumulations 

 of a more orderly nature, in which both Palaeolithic relics and 

 mammalian remains may occur in abundance. 



In the great river -valleys of Prance the Palaeolithic and 

 ossiferous deposits are covered for the most part with that cloak 

 of flood -loam or loss which marks the limits reached by the 

 desolating inundations of the last glacial epoch. So likewise 

 in the Ehine, the Danube, and other river-valleys of Germany, 

 the ancient ossiferous gravels and lignites are buried under thick 

 accumulations of the same loamy deposit. Entering the alpine 

 lands of Central Europe, we see how the ice of the last glacial 

 epoch has for the most part cleared out all interglacial accumu- 

 lations, only a few inconsiderable portions having been preserved 

 from the ravages of the ice-plough 3 and it is precisely the same 

 in the hills of Central France and the Pyrenees. Even in 

 regions which were neither glaciated nor subjected to fluvio- 

 glacial action the ossiferous and Palaeolithic deposits are yet 

 frequently overlaid with massive accumulations of angular 

 ddbris, which must have been formed under considerably colder 

 conditions of climate than now obtain. 



