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39 
near the level of existing rivers; but there are caves containing 
relics uf human inhabitants, which have been left high up in the 
limestone cliffs, whilst the rivers have worn away the gorge below toa 
great depth. This is shown by the presence of certain pebbles in the 
deposits within the cave, which must have rolled across the interval, 
from the other side of the valley, whilst a floor existed at the level of 
the cave. If this excavation be due to the violent rush of the 
torrent from the increased slope of its channel, caused by the rising 
of the land, what was the rate of elevation? Further, some few of 
the caves contain stone implements of ruder make than those left 
in others ; and the valley gravels left behind as terraces and isolated 
patches by the rivers, which have deepened and narrowed thin 
channeis, also contain such rude and even ruder implements, care- 
‘ fully, but roughly chipped, and doubtless serving very well 
the purpose to which these early people applied them. These 
gravels contain remains of the Arctic animals. Their age is to be 
reckoned by the time required for their formation and their distri- 
bution. The subsequent excavation of lower valleys, and the other 
stages of time already indicated, necessarily lengthen their 
chronology. Their existence is owing to the early formation of 
gravel plats and plains of loam out of the débris of the land, when 
it was far above its present height ; and when Western Europe had 
been raised so high out of water as to comprise the British Islands 
as far as the well-known ‘‘hundred-fathom-line,’’ which when 
raised to the water level would of course add at least 600-ft. to the 
height of the land’s surface. The Alps were much higher than 
now ;‘and probably Snowdon stood at least 2,000-ft. higher than at 
present. ‘This elevation originated in the great alteration of the 
earth’s crust in this portion of the globe, by contraction of its axis, 
immediately after the long ‘Tertiary Period” of geologists, 
bringing in the new conditions of geography, hydrography, and 
distribution of life in what is known as the ‘ Pleistocene Period.”’ 
The great uprise of land was probably then; it introduced enormous 
glaciers, grooving out the great gorges, which, after vast and con- 
tinuous changes, the greatest rivers have scarcely yet filled up with 
their plain-making detritus. Whether men existed or not in this 
earliest part of the Pleistocene period is as yet unproved. A great 
reaction took place, and a great and gradual subsidence lowered 
plain and mountain, until Snowdon sank to be an island not more 
than 1,000-ft. at most in height, and the shoulders of the mountain 
were below the great Northern Sea; for when it rose again, Moel 
Tryfaen (now 1,300-ft. above the sea) bore up the well-known 
sands and shingle with marine shells, in witness of the change. 
Man had set foot in this region by that time, for when the giaciers, 
during some of their oscillations, occupied the great vaies of 
Western Yorkshire, one of them left some of the characteristic 
