512 H. F. Sail — Glacial Deposits of Llandudno. 



I wish to call your attention to a few points : 

 1st. That colour is no criterion for deciding as to the Glacial bed 

 F, which at Gogarth is dark -brown and grey ; at Dyganwy, almost 

 black; Little Orme, dark grey; Ehos, 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 Mill- 

 stone grit, which is now entirely denuded from the district; the 

 greenstone, trap, slate, and Old Eed Sandstone Boulders found in it, 

 being all traceable to Anglesey as their source. I may here remark, 

 that this clay, on the opposite shore of Anglesey, shows the same 

 composition as at the Orme, except that it contains numerous schist 

 pebbles, which are wanting at the Orme, being probably ground 

 down before reaching that point. The clay east and west of the 

 ■Little Orme and at Ehos, shows the result of the passage of the ice 

 over the Mountain limestone and Silurian beds, the latter supplying 

 the adhesive material which makes the clay here so much stiffer. 

 At Dyganwy the black clay is from the underlying slates, and the 

 greenstone, slate, and volcanic rock boulders, are easily traceable to 

 the hills between Conway and Bangor, the greater sparseness of the 

 pebbles at the east end of the section being due to the main course 

 of the ice being through the valley nearer the Great Orme, its 

 current being retarded eastwards by the Bryngosol and Dyganwy 

 hills, probably deflecting part of the ice-flow through the valley of 

 the Conway, towards Abergonol and Colwyn. At Llandulas the 

 reddish-brown is due to the wearing of the Old Eed Sandstone, 

 which is still found inland, and many large boulders of which are 

 seen on the shore. 



3rd. I conceive this clay to be the result of the pressure and 

 passage of land-ice, disintegrating the whole surface of the country 

 which it capped, and I would confine the term " Boulder-clay " to 

 this one bed, believing it to be the only true Glacial clay. 



4th. This clay is invariably denuded, rising in bosses all along the 

 shore, and having the superposed beds lying unconformably upon it. 



5th. The red clay (D), which is invariable in colour and consti- 

 tuents, shows, to my mind, an undoubted change of conditions in the 

 land during the period of its deposition, being, as I conceive, 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. I have thus endeavoured to 

 point out, 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. Until we 

 know, for instance, in which of these beds particular rocks in the 

 form of boulders are found, such a discussion as that which followed 

 Mr. Morton's paper is useless, as what is referred to by one man as 



