Glaciers, North Wales. 419 



and there many sea-shells are found in these strata, all 

 of existing species, but the general assemblage of forms 

 indicates an arctic climate comparable to that of 

 Greenland of the present day, a circumstance many 

 years ago pointed out by Mr. James Smith of Jordanhill. 

 The evidence all tends to prove that these strata were 

 deposited during a part of the Glacial epoch, probably 

 towards its close (fig. 85, p. 417). 



After what seems to have been a long period of 

 partial submergence the country gradually rose again, 

 and the evidence of this I will prove chiefly from what 

 I know of North Wales. 



I shall take the Pass of Llanberis as an example, 

 for there we have all the ordinary proofs of the valley 

 having been filled with glacier-ice. First, then, during 

 and after the time of the great ice-sheet, the country 

 to a great extent sunk below the water, and drift was 

 deposited, and must more or less have filled many of the 

 deep narrow valleys of Wales, and which still remains in 

 part in some of the broader expanses of the country. 

 When the land was rising again, the glaciers gradually 

 increased in size, although they never reached the 

 immense magnitude which they attained at the earlier 

 portion of the icy epoch. Still they became so large, 

 that such a valley as the Pass of Llanberis was a second 

 time occupied by ice, which, without invading Anglesea, 

 spread itself into the lowlands beyond, and the result 

 was, that the glacier ploughed out the drift and loose 

 rubbish that more or less cumbered the valley. Other 

 cases, such as those of Nant-ffrancon and Aber, could 

 easily be given. By degrees, however, as we approach 

 nearer our own days, the climate slowly ameliorated, 

 and the glaciers began to decline, till, becoming less 

 and less, here and there as they died away, they left 



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