404 Glaciation of Anglesea. 



narrow valley, in, or alongside of which, the Caernarvon 

 and Bangor road runs for several miles. 



The surface of the ground on both sides of the 

 Straits is to a considerable extent composed of glacial 

 detritus, with erratic boulders large and small ( from the 

 north), gravel, sometimes sand, and clay, from which any 

 number of ice-scratched stones may be gathered from 

 well-exposed sections, as, for example, in the Boulder-clay 

 coast-cliff of the Mount at Beaumaris, or anywhere else 

 in similar cliffs round the shores of Anglesea, or, inland, 

 in occasional pits and fresh cuttings on both sides of the 

 Straits. Through these glacial accumulations the rocks 

 of the country frequently appear, sometimes in barren 

 tracts of considerable extent, sometimes in small isolated 

 bosses of gneiss or grit, often covered with heath or 

 furze, while the more fertile grounds of the whole of 

 Anglesea consist chiefly of glacial detritus, with here 

 and there small alluvial meadows by the sides of the 

 streams. 



When freshly stripped of glacial debris, or even of 

 a mere thin turfy soil, the underlying rocks are often 

 found to be ice-smoothed and marked with glacial striae, 

 running generally from about 30 to 40 west of south. 

 The larger valleys of Malldraeth Marsh and the Menai 

 Straits (with others of minor note) run in hollows in 

 the same general direction. 



I have already shown that in mountain regions 

 where glaciers exist, or have in past times existed, the 

 disturbances of the earth's crust that produced the 

 elevation of the mountains go back to periods long 

 antecedent to the last great Glacial epoch. Thus the 

 first great upheaval of the Alps is of pre-Miocene age, 

 and the last, as far as the Alps is concerned, closed the 

 Miocene epoch, while the mountains of Scotland and 



