TRANSACTIONS OF THE SECTIONS. 78 



evidently derived from the grinding down of the slate. This is the hest section 

 for the observation of ice-markings. In a hollow in this clay at the Orme there 

 is a deposit of 20 feet of stratitied grey clay, evidently a denudation bed from the 

 boulder-clay, showing, where opened by weathering, distinct ripple- and rain-marks. 

 A contemporaneous bed, the evidence of a shore condition during the depression 

 of the boulder-clay, of 20 feet of irregular and false-bedded sands and gravels 

 lies also above the boulder-clay. At the Little Orme this bed is hardened by car- 

 bonate of lime into a conglomerate, to be seen in the cliff and in enormous fallen 

 masses on the shore. 



The subsidence of the land still continuing the shore condition ceases, and a 

 continuous bed, common everywhere, of red clatj, some 20 feet thick, overlies the 

 lower sands and gi-avels. Then an elevation seems to have taken place, and 

 another series of sands and gi-avels, upwards of 50 feet in thickness, shows another 

 shore condition, best seen in the ballast-pit at Colwyn. Lastly, the thin bed of 

 blue-black clay, without pebbles, is exposed in the Dyganwy section, the result of 

 a second denudation of the boulder-clay, after both the sands and gravels and the 

 red clay had been carried away. This being the sequence of the beds, the author 

 called attention to the following points : — 



1st. That colour is no criterion for deciding as to the F glacial bed, which at 

 Gogarth is dark brown and grey ; at Dyganwy, almost black ; Little Oime, dark 

 grey ; Rhos, a lighter grey ; Colwyn shore, blue ; and Llandulas, red-brown : in 

 fact the colour depends upon the materials of which the rocks in the vicinity are 

 composed. 



2nd. That the materials of which this clay is composed are always those found 

 in the immediate neighbourhood, and even the large boulders can generally be 

 traced to no great distance. Thus the Gogarth clay is evidently the result of the 

 grinding down of the mica-schists and limestones of Anglesey, and probably of the 

 millstone-grit, which is now entirely denuded from the district. The claj^ east and 

 west of the Little Orme and at Rhos shows the result of the passage of the ice 

 over the mountain limestone and Silmian beds, the latter supplying the adhesive 

 material which makes this clay so much stiffer. At Dyganwy the black clay is 

 from the underlying slates, and at Llandulas the reddish-brown is due to the 

 wearing of the Old Red Sandstone, which is still found inland, and many boulders 

 of which are seen on the shore. 



3rd. The author conceived this clay to be the result of the pressure and passage 

 of land-ice, disintegi-ating the whole surface of the country which it capped ; and 

 he would confine the term boulder-clay to this one bed, believing it to be the only 

 true glacial clay. 



4th. This bed is invariably denuded, rising in bosses all along the shore, and 

 having the superposed beds lying unconformably upon it. 



6th. The red clay (D), which is invariable in colour and constituents, showed 

 an undoubted change of conditions in the land dm-ing the period of its deposition, 

 being, as he conceived, the result of extensive denudation in more northern regions, 

 spread over the sea-bottom by currents, the scratched pebbles and boulders being due 

 to melting or stranded icebergs. 



The author argued that with such different constituents for these beds it is time 

 to adopt some more definite names than the general one of boulder-clay, which is 

 commonly applied to the series. He referred to the sections on the eastern coast 

 as confirmatory of his views, as illustrated by his personal observations in Holder- 

 ness, where as clearly distinct a series of beds occurs. 



General Secticm of Drift in the Neighlourhood of Llandudno. 



A. Sand dunes. 



B. Blue-black clay, without pebbles 1 ft. 



C. Sands and gravels, about 50 ft. 



D. Red clay, greatest development 20 ft. 



E. Sands and gravels, greatest development. . 20 ft. 

 E^. Stratified grey clay 20 ft, 



F. Boulder-clay, greatest development 150cd 



G. Mountain-limestone rubble 6 ft. 



H. Bedded mountain limestone. 



