256 W. Keeping— Glacial Geology of Wales. 



known amongst " pebble " collectors as one of the ricliest places on 

 our coasts for Agates, Jasper, Onyx, and other polisbable stones, 

 •which are largely gathered by the visitors. Chalk flints are also 

 abundant, together with a great variety of Felsites, Porphyrites, 

 Quartz Felsites, Granites, Greenstones, and Metamorphic rocks, also 

 Mountain Limestone pebbles, often containing fossils. Only a very 

 few of these pebbles can have come originally from any part of 

 Wales, and I have only recognized two of the igneous and metamor- 

 phic pebbles as likely to be of Cymric origin, namely a Felsite from 

 Llanbedrog and a serpentinous rock like those of the Lleyn Penin- 

 sula and Anglesea. 



T regard these beach pebbles as being derived from a Marine 

 Boulder-clay now submerged in Cardigan Bay, out of which the 

 pebbles are washed and carried up the shore by marine currents. 

 It is probably just such a deposit as occurs on the south coast of the 

 low ground in Anglesea and the Lleyn Peninsula, where I have found 

 similar foreign pebbles. 



Efikers. — Near Llanrysted Eoad Eailway Station where the Yst- 

 wyth Valley opens out into a broad plain near the sea, a remarkable 

 curved ridge of sands and gravels strikes right across the valley up to 

 the river, which has cut through it on the west side. It is about 120 ft. 

 high, and from the surrounding hills it has the appearance of a great 

 terminal moraine. But its structure is totally different from moraine, 

 consisting as it does of false-bedded coarse gravels, sands, and finely 

 laminated loam and clay. The great majority of the stones are well 

 rounded by attrition, and not a few are well striated by ice. 



The matrix of the pebble-beds is a coarse sand, the particles not 

 rounded, but rather like the fine sand left from lead washings, only 

 finer. Other seams are altogether coarser in grain, and in places there 

 are beds of finely laminated material which also contain a few stones, 

 most of them angular. Altogether this ridge of gravel and sand 

 bears much resemblance to, and seems to be the representative of, 

 the Eskers of Ireland and the Karnes of Scotland. 



Summary. — Eeviewing our results then, we find that in Central 

 Wales there are abundant proofs of a severe glaciation of the 

 country in the Great Ice age. The principal evidences are seen in the 

 general features and contours of the hills and valleys, in finely 

 polished and striated rock surfaces, in the stony clays or tills, the 

 moraines, and erratic blocks. Excepting the extreme north and 

 south, the glaciers were of strictly local origin, each confined to 

 its own valley, there being no evidence of any confluence of the ice 

 into a great mer de glace. 



In the north the glaciers of North Wales overflowed into the Llyf- 

 nant Valley, and in the south the ice from the mountains of Caer- 

 marthenshire rose over the present watershed into the Teifi Valley 

 and on to Cardigan. 



Lakes and lakelets are numerous, and they are all rock basins ; 

 one of them (Llyn Llygad Eheidol) is probably ice-formed, and 

 some others have morainic matter at their base, but the majority are 

 so situated and of such construction that it is impossible to attribute 

 their formation to the action of glacier-ice. 



