510 n. F. Hall — Glacial Deposits of Llandudno. 



stiff, dark bluish-grey clay, very full of small pebbles, principally 

 of slate, all ice-scratched, with many large blocks of Mountain- 

 limestone, G-reenstone, and Volcanic-grits, three, four, and five feet 

 in diameter, in many cases still showing, though exposed to the 

 action of the present sea, ice grooves and smoothing. The general 

 character of this bed is much the same at the Little Orme, the new 

 features being boulders of Old Eed Sandstone, Schist, and Cambrian 

 conglomerate. On the West side of the Little Orme this bed is dis- 

 tinguished by a large quantity of angular fragments of chert. 



At Gogarth, the clay F, where exposed on the shore, and wetted by 

 the tide, is very stiff, but in the cliff it is very hard and compact, more 

 so than many sandstone rocks. It varies very much in its con- 

 stituents, in some places being dark-brown, in others, grey in colour, 

 but everywhere very gritty and sandy, and full of scratched pebbles, 

 with many fragments of chert. Numerous boulders of greenstone, 

 trap, slate, and Old Eed Sandstone, with angular and subangular 

 masses of Mountain-limestone, are contained in it. Slate pebbles are 

 not common in this bed, as in those at the Little Orme, Khos, and Col- 

 wyn, — angular chert fragments are probably the most characteristic. 

 On the top of this bed at Gogarth lies a seam of great boulders of 

 trap, greenstone, slate and Old Eed Sandstone, with masses of 

 Mountain-limestone, left, in all likelihood, when the denudation of its 

 upper surface had washed away the surrounding clay without having 

 the power to carry off the larger fragments. 



At Dyganwy we find a low cliff, about 20 feet high, of black clay, 

 which is evidently derived from the grinding down of the slate, 

 which crops out in the farm-road of Maesdu. This is decidedly the 

 best place to observe ice-markings, as the shore is covered to far 

 below low-water mark with great masses of greenstone, volcanic- 

 ash, conglomerates, and slate, all deeply striated and finely polished. 

 These masses are in greatest quantity at the west end of the cliff, 

 becoming fewer and smaller to the east end, where the clayey 

 matrix changes from black to a dull brown, the result of a change 

 from the slate to the lighter-coloured ash-beds, of which the hills of 

 Bryngosol and Dyganwy, lying immediately behind, are composed. 

 This Boulder-clay I believe at one time to have filled up all the 

 valleys, and to have covered even the mountain-tops, as I found, at a 

 height of at least 400 feet on the Great Orme, a greenstone boulder, 

 which I believe to have been derived from this bed. 



The clay rises in bosses along the shore, giving clear evidence of 

 denudation, and consequent unconformability to the overlying beds. 

 It is now entirely removed from the mountain- tops, and from many 

 of the valleys, showing that it must have been exposed to a very 

 considerable denudation at what I believe to have been the close of 

 the Glacial period. It must then have been depressed below the 

 sea-level for a considerable depth to have allowed the deposition of a 

 bed (E") of 20 feet stratified grey clay, with ice-scratched pebbles 

 sparsely distributed, which occupies one of the hollows in the 

 denuded surface of the bed F at the Little Orme. This stratified 

 clay is clearly a denudation bed, derived from tlie redistribution of 



