xi.] PERIODS OF UPHEAVAL. 281 



the Severn, the rhinoceros ranged over the south- 

 western counties ; enormous elk and oxen, of species 

 now extinct, inhabited the vast fir and larch forests 

 which stretched from Norfolk to the farthest part of 

 Wales ; hyenas and bears double the size of our 

 modern ones, and here and there the sabre-toothed 

 tiger, now extinct, prowled out of the caverns in the 

 limestone hills, to seek their bulky prey. 



We see, too, a period whether the same as this, or 

 after it, I know not yet in which the mountains of 

 Wales and Cumberland rose to the limits of eternal 

 frost, and Snowdon was indeed Snowdon, an alp down 

 whose valleys vast glaciers spread far and wide ; while 

 the reindeer of Lapland, the marmot of the Alps, and 

 the musk ox of Hudson's Bay, fed upon alpine plants, 

 a few of whose descendants still survive, as tokens of 

 the long past age of ice. And at every successive up- 

 heaval of the western mountains the displaced waters 

 of the ocean swept over the lower lands, filling the 

 valley of the Thames and of the Wey with vast beds 

 of drift gravel, containing among its chalk flints, 

 fragments of stone from every rock between here 

 and Wales, teeth of elephants, skulls of ox and musk 

 ox ; while icebergs, breaking away from the glaciers 

 of the Welsh Alps, sailed down over the spot where 

 we now are, dropping their imbedded stones and silt, 

 to confuse more utterly than before the records of a 

 world rocking and throbbing above the shocks of the 

 nether fire. 



At last the convulsions get weak. The German 

 Ocean becomes sea once more; the north-western Alps 

 sink again to a level far lower even than their present 

 one; only to rise again, but not so high as .before; 



