DRIFT-DEPOSITS OF COLWTN BAY. 107 



the gradual submergence of the land, this material lying in the Vale 

 of Clwyd, reinforced by other material continually being worn off 

 the rocks, and working seawards, has washed round the coast 

 towards the Little Orme's Head, and become mixed with other 

 material washed up from the sea-bed and with argillaceous matter 

 from the underlying Till. I^o'ice-sheet will account for this drift. 

 It is evidently a marine drift. The Eskdale-granite boulders which 

 it contains must have travelled to where they lie by floating ice ; 

 for many of the boulders h .ve come from the north, while the sands 

 have been derived from the east. At all events, if this be not a 

 true explanation, all the complicated machinery of at least two ice- 

 sheets will have to be invoked. This appears to me to be un- 

 necessary, especially as it would not explain the structure of the 

 drift, which bears internal evidence of aqueous deposition. 



Discussioir. 



Mr. W. W. SiiTTH remarked on the interest of this paper, as 

 these beds of Colwyn Bay are evidently connected with the drift- 

 deposits of the Yale of Clwyd, proved to be of great thickness in 

 coal-borings at Rhj'l. On the other hand, the classic deposits of 

 Moel Tryfaen might also be connected with the same deposits. 



Dr. HiNDE pointed out that Till, undistinguishable from that 

 in Wales, covers extensive areas in Ils^orth America, far away from 

 any mountains, and that consequently these are not essential to its 

 formation. 



Mr. Whitakee bore witness to the great care with which 

 Mr. Reade worked out his results bj^ tracing the region from which 

 the different stones came. He himself hardly understood the dif- 

 ference between Till and Boulder-clay. 



Dr. Hicks said that in the Yale of Clwj'd we have three stages : 

 — local deposits of gravel, marine sands, and widespread Boulder- 

 clay. He thought that the Boulder-clay was formed by a mixture 

 of local materials and ice-borne blocks. 



Mr. ToPLEY pointed out that the main interest attaching to the 

 paper arose from the care with which the section had been recorded 

 and the origin of the different materials traced. The succession of 

 beds described was that geo orally to be seen in the N"orth of Eng- 

 land, where the drift-deposits are well developed. In Northumber- 

 land and Durham the middle sands usually occur in greatest force 

 near the old preglacial vallej's. 



Pro£ Jttdd, in the absence of the author, further explained his 

 views as to the distinction, character, and relations of the Till and 

 Boulder-clay of the district. 



