W. Keeping — Glacial Geology of Wales. 253 



and sandy clay of pale yellowish colour, with waterworn pebbles 

 and a few striated stones. In places this graduates into the under- 

 lying stony clay. 



The main mass of this Cwm Ceirw drift is in an old hollow, ap- 

 parently an old river bed with steep sides, in the centre of the 

 existing valley, the western hill boundary having been destroyed 

 by the encroachment of the sea since the Glacial period ; for where 

 the streamlet has cut back the Till at the north end, it is seen to 

 abut against a nearly vertical wall of solid rock running in the line 

 of the present valley. 



Some remarkable features have been produced in these cliifs by 

 the action of a number of small periodic streamlets which arise as 

 springs a few feet from the surface. These have cut their way back 

 into the Glacial clay, so as to form deep open gorges, with narrow, 

 slit-like seaward openings, also fantastic ridges and pillars, in 

 several cases leaving actual earth pillars, with capping stones, like 

 the well-known examples in the Tyrol. It is a most extraordinary 

 and striking example of streamlet and pluvial denudation. 



Another excellent section is exposed in the railway cutting between 

 Aberystwyth and Bow Street Stations, where the deposit is of the 

 same general nature but more clayey ; also the cliff sections of stiff 

 stony Till opposite the village of Llanrwsted are deserving of notice. 

 In the interior of the country stony clays, similar to those already 

 described, are of frequent and widespread occurrence in the valleys 

 and along the sides of the hills, and they are particularly developed 

 in the open parts of the valleys, where they form broad and thick 

 sheets. Examples are seen in the valley below Llyn Llygad Eheidol 

 and in the Teifi valley below the Teifi Pools. In the Kheidol valley 

 near Aberystwyth this drift was found to be fifteen feet thick in a 

 recent cutting, and it is probably much thicker in places. 



The influence of projecting rocks and sheltered curves in deter- 

 mining the deposition and greater thickness of the stony clay is 

 marked in many places, as in the railway cutting near Bow Street, and 

 at Pen Craig, north of Llanilar, where a " tail " of glacial stony clay 

 has been laid down on the lee side of the protecting knoll of rock. 



Moraines. — The terminal and lateral moraines of Cardiganshire 

 are not such well-marked and striking objects as many of those in 

 Scotland and Snowdonia. Their structure and composition are also 

 different, and, I should say, less typical ; for the surrounding rocks 

 being of a softer and more agillaceous character, the moraines are 

 also of a clayey nature. They may be described generally as clayey 

 masses, full of comminuted shale fragments and grit, studded more 

 or less abundantly with angular and subangular stones. Long lines 

 of such morainic matter occur along the south sides of Cwm Berwyn 

 and in Cwm Ystwyth. The Cwm Ystwyth moraine is less clayey 

 than usual, consisting of a mass of shale fragments and angular 

 stones, like a rubbish-tip of small material, with numerous blocks 

 of grit and slate of all sizes. The deposit has been deeply scored 

 by a number of small freshets which course down the hill-sides in 

 wet weather. 



