26 DR T. J. JEHU ON 



yellowish weathered clay becoming sandy in places. At the two ends of the bay the cliffs 

 are rocky, though sand is seen resting above on the rock surface at some places, while at 

 others the rock is covered by fine rubbly material with yellowish weathered clay above. 



Samples of granites from the Dalbeattie area were picked up on the beach below. 

 These had undoubtedly come from the Drift in the cliff above. 



Amongst the shells included in the Lower Boulder Clay the following were recog- 

 nised : — Purpura lapillus (L.), Astarte sulcata (Da Costa), Astarte (Nicania) compressa 

 (Mort.), Gyprina islandica ? (L.), Corhula gibba (Olivi). 



All along this part of the coast the rock surfaces when visible have a mammillated 

 and smoothed appearance where they pass under the Drift deposits. 



Immediately to the south-west of Porth-ysgadan lies a small bay opening westwards 

 to the sea, which appears to be nameless. The two arms of the bay are rocky, with 

 grassy slopes above. Midway between the arms the Drift comes down to the beach in 

 such a way as to suggest that we have here the buried channel of an old stream, or what 

 was once an inlet of the sea. The cliff of Drift reaches a height of about 50 feet. It seems 

 to consist entirely of the Lower Boulder Clay in which shell-fragments are again common. 

 Towards the surface the clay is weathered and yellowish in colour, but there is no 

 reason for separating this from the Lower Boulder Clay. Where, as in this bay, the Sands 

 and Gravels are wanting, it is sometimes difficult to know whether the yellow clay 

 which usually forms the upper part of the cliff is the weathered portion of the Lower 

 Clay or the representative of the Upper Boulder Clay. Where typically developed, 

 however, the Upper Boulder Clay is less homogeneous, somewhat more sandy, and contains 

 more boulders than the Lower Boulder Clay. 



In this small bay, at the two sides, the Lower Boulder Clay appears to be separated 

 from the bed-rock by a little rock rubble. 



Porth-y-givylan lies half a mile further to the south-west and opens westwards. 



It is separated on the north side from the open sea by a ridge or projection of bare rock 



running more or less parallel with the coast-line. The other or mainland side of the 



bay is also rocky in character. Between these rocky sides a mass of Drift forms the 



entire cliff and rests immediately on the modern beach, and it is out of this material 



that the bay is still being eroded. The Drift consists of tough bluish-grey Boulder Clay 



at the base, with included shell-fragments, followed above by a boulder gravel with a 



somewhat clayey matrix, and this in turn is succeeded by a yellowish clay. So we have 



here : — 



3. Yellowish weathered Upper Boulder Clay. 



2. Boulder Gravel. 



1. Lower Boulder Clay. 



These deposits appear to have filled up what was either the channel of a stream 

 or a narrow inlet of the sea. At the present day a small stream is seen on the 

 north-east side of this Drift-filled depression which is cutting out for itself a new channel 

 in the solid rock and coming clown to the beach in a waterfall to escape to sea by a 



