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Wales And Siluria were covered with ice and snow much as Greenland is at 

 the present time, so that during the close of the preglacial continental period 

 the land was almost entirely enveloped in an ice shroud. Large glaciers filled 

 the vales of the higher mountains, ploughed out the glens, and wore down the 

 surfaces, and the land which once sustained the great animals of the Preglacial 

 forest period passed into a phase sterile as that of Greenland. The denudation 

 by land ice and other agencies must have been very great, and probably it went 

 on for age after age until the submergence of the whole of Wales, to an extent 

 of not less than 2,000 feet placed the whole country, with the exception of 

 some of the highest hiUs, beneath the waters of the glacial sea. During this 

 depression of Wales, denudation must also have gone on, for the erosion 

 efifected by ice grinding along the bed of the sea must have been considerable. 

 Boulders carried by icebergs drifted southwards, and when the old ice covered 

 land of the Preglacial period was submerged the boulders were dropped upon 

 surfaces which are now elevated into high Silurian table lands. And with 

 respect to the valleys and river systems I have every reason to believe that 

 their principal features were marked out in Preglacial times, and before the 

 great submergence took place, and Wales had settled below the Glacial ocean. 



I believe that the deposit we term " Till" or Boulder clay was forming and 

 collecting before the old continent was submerged, and that the boulder clay 

 accumulated for ages both during and after the glacial submergence. There is 

 good evidence that the great vale of Usk was filled with boulder clay to the 

 depth of several hundred feet, and that this was eroded by post glacial Usk. 

 I may say the same with the vale of Towy and the valleys of the Wye. The 

 boulder clay probably accumulated both before and during the submergence of 

 the land, and the greater part has been swept out since by the action of post- 

 glacial ice, melting snows, streams, and rivers. Nor is it to be supposed that 

 during what geologists term the Post-glacial period the climate was not very 

 severe. When the land was elevated, after the great submergence, there is good 

 proof that the iron grasp of ice lasted among its hill tops for ages. The ice 

 after the submergence was probably not so extensive as it was during the latter 

 part of the continental ice period when every vale was filled with ice, but there 

 are traces left of glacial action in Wales since the present configuration of the 

 British isles, that we must refer to Post-glacial times. 



Those who travel through Wales as I have done, and endeavour to trace 

 out the last geological changes, will be struck with the masses of rock that 

 have been transported from the position the parent rock occupies in situ, and lie 

 now stranded upon rocks with which they have no connexion. Much of the 

 debris we see scattered about the hills is due to the action of rain and frosts 

 npon the weathered rock surfaces ; but much is not so, for we occasionally find 

 masses of Millstone Grit resting on Old Red Sandstone, and the only way in 

 which we can account for their transport b that they were moved by the aid of 

 melting snows and ice. The remains of an ancient glacier may be traced among 



