Vol. 54.] MAEH^E DRIFT AT COLWYN BAY. 583 



DlSCTJSSION. 



Dr. Hicks thought it important that the mound of high-level 

 drift in Colwyn Ea)^ should he recorded, as hitherto it does not 

 appear to have been descrihed. East and M^est of Colwyn Bay, 

 along the coast of jS'orth Wales, numerous sections of drift at 

 the same and higher elevatiors have been described by various 

 writers, as have also the low-level drifts in Colwyn I3ay. 



Mr, GooDCHiLD remarked that the Author had referred to the 

 deposits as marine, without giving any reason in support of the 

 view that they were really of that nature. He referred to several 

 possible explanations of the occurrence of sands and gravels in such 

 positions. He thought that they were englacial, and furnished no 

 proof of an}" submergence. 



Prof. Hull concurred with the Author that the beds of gravel which 

 he described w^erc of marine origin, and that (as a previous speaker 

 had stated) they belong to the series of stratified deposits at various 

 points and levels all along the flanks of the North Welsh hills. The 

 Author had not indicated the presence of sea-shells ; but that was no 

 objection to the view of the marine origin of the beds. All beds of 

 gravel on our shores do not necessarily contain shells ; and if shells 

 had originally existed they may have been dissolved away by the 

 percolation of acidulated rain-water during a period of thousands of 

 years. As regards the view that the shell-bearing gravels of North 

 Wales had been pushed up into their places by an ice-sheet from 

 the Irish Sea, he wished to remind geologists that Sir Andrew 

 Ramsay had shown that, while the northern ice-sheet had crossed 

 tho comparatively low ground of Anglesey (in a south-westerly 

 direction, as indicated by the striae on the rocks), it had never invaded 

 the Caernarvonshire mountains; while, on the other hand, he had 

 recognized the shelly gravels as evidence of submergence to the 

 extent of 1200 and 1500 feet as compared with the presenc sea-level. 

 No authority was more competent to determine these physical 

 questions as regards North Wales ; and in the speaker's opinion 

 these views, and no others, could adequately explain the presence 

 of stratified gravels on the flanks of the Welsh moun'^ains. 



Mr. A, E. Saltee would like to hear from the Author what 

 definite evidence there was in favour of a marine origin of this 

 deposit. In the Thames Basin, drifts containing a series of erratics 

 similar to those exhibited could be traced in a north-westerly direction 

 as far as the gap in the Oolitic strata at Moreton-in-the-Marsh, at 

 heights up to 300 or 400 feet above CD. Like many drift-deposits 

 farther south, this one was on a watershed and may have had an 

 origin similar to theirs : that is. the drift-gravels had protected the 

 soft underlying strata, while softer rocks around had been denuded 

 away. 



The Rev. J. F. Blake also spoke. 



The Atjthok said that, although he had not found marine shells 

 in the drift of the mound, its structure and composition satisfled 

 him that it is an outlier of the marine drift found at lower levels 

 Q. J. G. S. No. 215. 2 s 



