Pro/. W. Keeping — Geology of Aberystwyth. 541 



rock -surfaces are seen as well marked as in an Alpine valley where 

 the glacier has but lately retired. These are the tool-markings of 

 our ancient glaciers and they are marvellously well preserved. 



But these Welsh glaciers were not confined within the limits of 

 the present valleys ; they often overspread such boundaries to open 

 out upon the lower hills, and, it may have been, there to form a con- 

 tinuous sheet many miles in breadth. The hills around Aberystwyth 

 are from about 300 to 700 feet high, and over all these the glacial 

 deposits of stony clay, etc., may be seen with all their usual charac- 

 ters, and with numerous large transported blocks left there as the 

 glacier retired. On the higher ground to the east of Llanfihangel 

 crowds of these blocks cover the ground, and above Cwm Symlog 

 large masses are seen stranded at above 1000 feet.' These blocks 

 too are often strewn over the sides of valleys, where they were left 

 at the edges of the glaciers as they dwindled away. 



It is remarkable that those puzzling mounds of false-bedded 

 sand and gravel, known as Osar in Scandinavia, were distinguished 

 by the ancient Celtic peoples both of Scotland and Ireland. By 

 the former they were called Karnes ; by the latter Eskers. 



Nor were the people of that other great branch of the Celtic 

 race, the Cymri, wanting in the same extraordinary discrimination 

 in detecting these ridges ; for here in Wales the name Esgair or 

 Escair is by no means uncommon, — evidently the same word as 

 the Irish Esker. Eor example, we may point out the name " Esgair 

 Annos," which designates a characteristic Esker east of Ehyader.- 



Near Llanrwsted Road, Aberystwyth, an enormous Esker is seen 

 stretching its broad back more than 100 feet high across the 

 valley of the Ystwith, like a terminal moraine. Through it the 

 river has cut its present channel down to and into the solid 

 Cambrian rock. 



Two railway cuttings afford us excellent views of the structure of 

 this Esker. At once we are struck with the great irregularity and 

 steep false-bedding of the deposits, i.e. the layers of material were 

 not thrown down horizontally ; and, looking closer at the anatomy 

 of the section, we find combined evidences of both water and ice- 

 action. There is the stratification of water ; the false-bedding of 

 rapid currents and eddies; and there are the subangular and well- 

 scratched stones, telling us of the work of ice. Many of the pebbles 

 are of the ice-formed types, but some are perfectlj'' rounded. 



We have no evidence of any modern encroachment of the sea 

 up to where this giant Esker lies. I look to the combined actions 

 of ice and water, and perhaps snow, to explain its formation. It 

 is contrary to experience that the sea should pile up a huge bank 

 of materials so little water-worn, with so many of the stones still 



1 All these blocks are from the local grit and hard shale-beds, or more rarely a 

 conglomerate from Plynlimmon. In the Tstwyth Valley, and towards Machynlleth, 

 a pale-coloured hard granular and felsitic-looking rock occurs, whose origin is not 

 yet known to me. 



2:It seems probable, from subsequent observations, that this local name Esc/air, 

 may sometimes have been applied to mounds of a diiferent origin and structui-e fnom 

 that of Eskers properly so called. 



