28 DR T. J. JEHU ON 



Porth Whiting. — For the greater part of its extent the cliffs are rocky, but about 

 the middle of the bay rock rubble is seen forming the base of the cliff where rock in 

 situ is wanting. Above the rubble is a slope of grass which covers what appears to be 

 a clay weathering yellow. At the south-western horn of this bay ice- scratches with a 

 N.E. to S.W. direction were noted on the rock surface just where it disappears under 

 the Drift. Between Porth Whiting and Porth Ferin some well-glaciated rock surfaces 

 are displayed, the vertical face of the rock being sometimes grooved and polished in a 

 direction parallel to the shore-line. Above the rock, fine yellow sand is at places 

 exposed from under the grassy slope, and this is overlaid by greyish Boulder Clay 

 weathering yellow. Further south this stiff Boulder Clay rests immediately on the rock 

 surface, and is even sometimes overlaid by yellow marine-like sand. So it may repre- 

 sent the Lower Boulder Clay. 



At Porth Ferin an artificial cutting has been made through the rock at the top of the 

 cliff. Stiff dark blue boulder clay, which is apparently the Lower Boulder Clay, is seen 

 overlying the rock. It is comparatively stoneless, though some well-glaciated boulders 

 were found in it. 



No sections of the Drift are again seen until we come to Porth Oer. At the north- 

 east end of this bay is solid rock, and on this, at a height of 15 to 18 feet, are beds of 

 sand and gravel more or less concreted and much resembling raised-beach material. 

 Just south of this a roadway runs down to the beach, and on the southern side of it the 

 rocky side of the bay slopes down to the beach and is followed by rock rubble or 

 " Head " which in turn is seen to pass under typical dark greyish-blue Boulder Clay. 

 This is in all probability the Lower Boulder Clay, and it forms the entire cliff opposite 

 the middle of the bay to a height approaching 100 feet. Included in this clay are 

 irregular masses of marine -like sand and here and there a little gravel. Shell-fragments 

 occur in the Boulder Clay, and the following forms were obtained and identified : — 

 Pectunculus glycimeris (L.), Astarte sulcata (Da Costa), Cyprina islandica (L.), Turri- 

 tella communis (L.). 



At the south-west horn of the bay a bench of rock is again seen 10 to 15 feet above 

 the modern beach. It is much like that seen at Porth Colman, and suggests the possi- 

 bility of the presence of an old shore platform here. Stiff* bluish-grey clay (Lower 

 Boulder Clay) rests on it, but at places the clay is separated from the rock by coarse 

 rubbly material about a foot deep. 



No exposures of Drift deposits are seen from Porth Oer to the end of the promontory 

 of Lleyn. The coast is rock-bound with a steep slope, the greater part of which is 

 grassed over. 



Lying to the south-west of the mainland and at a distance of 2|- miles from it is the 

 Isle of Bardsey. It is composed entirely of metamorphosed rocks, probably of pre- 

 Cambrian age. The island has an extreme length of about 1 f miles, and its greatest 

 breadth is three-quarters of a mile. The highest portion of the isle lies in the north-east, 

 facing the mainland. There, from an elevation of about 500 feet, the land slopes away 



