NORTH-WEST OF ENGLAND AND NORTH WALES. 113 



glaciated. It is a curious fact that so few stones are glaciated in 

 these upper valleys, and so many in the lowlands. The slaty rock 

 of the hills on either side protrudes in great splinters and pinnacles, 

 showing that if it ever had been smoothed down by ice, great denuda- 

 has since taken place. The Drift in the gorge consists of clay and 

 stones. It is evident that a tremendous amount of Drift has been 

 removed by denudation. 



At Bangor, west of the station, the railway-cutting shows lamin- 

 ated current-bedded and contorted gravels and sand lying upon the 

 upturned edges of the Silurian rocks ; in places at the base is packed 

 angular debris, and there are some beds of laminated clayey loam in 

 the gravel. These laminated clays are also to be seen in the ballast- 

 pit below the station. 



At Ogwen Bank in the bed of the Ogwen are magnificent glaciated 

 corrugations in the direction of the stream ; but the} r are disconnected, 

 as if the stream had roughly quarried out some of the rock between. 

 Further up the stream is an inclined flank of slate rock splendidly 

 polished, with perfectly straight and parallel striations running 

 across it diagonally ; and lying against this rock is a laminated con- 

 torted gravel-drift containing large blocks at the base. On the 

 opposite side of the stream this gravel-drift is overlain by a grey 

 Drift containing angular pieces of slate and also rounded boulders, 

 and over all is a cover of alluvium. 



East of Beaumaris, near the Menai Straits, is a cliff of Boulder-clay, 

 of a brownish grey colour generally, containing large boulders, and 

 capped with a reddish clay with pebbles from a great variety of 

 rocks. The Boulder-clay contains a great many large Mountain- 

 limestone blocks, some being smoothed and glaciated. Shell-frag- 

 ments are also to be found, but sparsely. Beyond this section, 

 towards Puffin Island, are several lower cliffs of Boulder-clay. 



On the railway by Menai Bridge station, in a cutting for a siding, 

 in 1872, lying upon a shaly rock of the Carboniferous series was 

 a black laminated band, then a yellow one, and over this a 

 grey-coloured laminated band, all composed of fine scales of shale 

 beautifully arranged in laminae. Capping it all was a Boulder- clay, 

 varying in colour from brown to yellowish white and blue, evidently 

 from the Carboniferous shales and clays. Near Menai Bridge, and 

 on the level of the last section, was a brown clay containing large 

 angular blocks of a coarse gritty sandstone (Carboniferous). 



The railway from Caernarvon to Pen-y-Croes, soon after leaving 

 Caernarvon, is cut through a boulder-drift entirely composed of stones. 

 At Dinas there is a cutting, about 21 feet deep, through Boulder-clay 

 very full of stones ; and from this place to Pen-y-Croes are frequent 

 cuttings in Drift composed wholly of boulders and gravel. Ah Pen-y- 

 Croes are mounds of fine sandy gravel ; and a further inspection shows 

 that there is a broad expanse of gravel cut up by streams into undu- 

 lating outlines and mounds, filling up and spreading round the valley- 

 mouth. This gravel continues across Caernarvonshire to Afon Wen. 

 There must have been a vast denudation to supply all this material 

 together with that which has been washed away. 



