902 EEPORT— 1888. 



to the denudation of the softer Rhsetic beds and Red Marls, which connected the 

 island with the mainland towards the north-east, while northwards and westwards 

 the river channel has been widened by tidal action. The cliffs south of Barry Island 

 rise to a height of about 50 feet. Whitmore Bay, on the same side, between the 

 two headlands, is a beach of sand and shingle at low tide. North of it a little blown 

 Band occurs on the face of the slopes. 



From Cold Knap, west of Barry Island, where the Carboniferous limestone is 

 exposed, the cliffs are about 50 feet high. Thence to St. Donat's the general 

 direction of the cliffs is east and west ; they are formed of the Lower Lias limestones 

 and shales, but essentially of limestone. The beds have, on the whole, a slight 

 easterly dip ; but this is counteracted by numerous small faults, so that the same 

 beds are presented to our view, undulating here and there, and dipping now and again 

 in other directions. 



East of Porthkerry the cliffs rise to an elevation of nearly 200 feet, and they attain 

 a similar height on the west. Further on, as far as East Aberthaw, the cliffs are 

 under 100 feet, and in some places not more than 50 feet. At high water the sea 

 washes the cliffs along the greater part of this distance, but for a short extent east 

 of Pleasant Harbour, East Aberthaw, there are wooded cliffs some little distance 

 (about 300 yards) from the high-water mark of ordinary tides. The interval is ' 

 occupied by alluvium, covered here and there with patches of shingle ; bej'ond is an 

 expanse of shingle, extending another 300 yards to low- water mark. But the shingle 

 is of no great thickness, and is based on mud and Lias rock. Eastwards the coarse 

 shingle stretches along the base of the cliffs over ledges and platforms of Lias. 



The alluvium before mentioned indicates that the river Ddaw formerly flowed out 

 to sea further eastward than it does now. 



West of the port of Aberthaw there is an expanse of alluvial ground protected 

 by embankments. This is bordered by hillocks of blown sand, and these rise about 

 20 feet above the shingle beach. Ijordering the blown sand there is a ridge of 

 thick shingle, and bej'ond this, between tide-marks, is an expanse of shingle on mud, 

 with sand here and there. 



The shingle consists of rolled pebbles and boulders of blue Lias limestone, and it 

 is these stones which constitute the celebrated Aberthaw lime. All the ' lime' taken 

 away has been shipi^ed in the form of pebbles or boulders, taken preferably between 

 high and low water mark ; for these stones are considered to yield a better lime than 

 those heaped up at a higher level, and which have been exposed to the sun's rays, 

 &c. Stones from this latter position are, however, employed locally in the lime-kilns. 

 I was informed in 1887 that fifty or sixty years ago there used sometimes to be about 

 twenty vessels in the harbour loading with beach pebbles. Since the introduction of 

 railways, limes from other districts, such as Harburj^ Bugby, &c., have to a great 

 extent diminished the trade at Aberthaw. 



The material has travelled from the west, and owing to the encroachments of the 

 sea it has been heaped on to old alluvial ground — portions of the old estuary of the 

 Ddaw. In the blue ,mud that here covers the platforms of Lias, on both sides of 

 the present river, the occurrence of ScroMcularia jjlana was noticed by Mr. H. W. 

 Bristow. He observed that the mud was from 8 to 10 feet thick in places ; and 

 intervening between it and the Lias there is, south-west of Gilston, a bed of white 

 calcareous tufa, with land-shells (Helix) ; a bed which he noticed also at Tresilian, in 

 that case directly under the shingle. 



There are no cliffs for some distance west of Aberthaw, not in fact until we 

 approach Summerhouse Point. Thence to Dunraven the cliffs are formed of the 

 Lower Lias limestones, with subordinate layers of clay and shale. They vary in 

 height, attaining a maximum elevation of 235 feet at Whitmore Stairs, between Nash 

 Point and Dunraven, and overhanging in places west of the Summerhouse, where 

 the dip of the strata is seaward. 



The beach consists of ledges and platforms of Lias rock, from 160 to 200 yards 

 broad or more, covered here and there by coarse boulder-shingle of Lias rock and 

 occasionally by sand. South-west of Llantwit-Major the Lias strata on the foreshore 

 are much jointed, and the sea works off huge masses of rock ; here there is a great 

 bank of boulders. Where the stream from Llantwit flows out to sea a peaty deposit, 

 containing nuts, leaves, and twigs, was noticed by Mr. Bristow. This bed rested on 

 blue clay with ScroUcvlaria, beneath which there was a deposit of tufa. The whole 

 was overlaid by boulders and shingle. Here and there along the coast great falls of 

 'the cliff take place ; at other points, as at Tresilian, there are caverns, which tend to 

 Bhow that in certain places the cliffs have not recently suffered great destruction. 



