DRIFTS OF THE VALE OP CLWYD. 



113 



in sharp relief and showing a chemically fretted surface, not such 

 as is seen on stones rolled in a current, though common on those 

 found travelling in rainwash. This proof of the action of aci- 

 dulated water makes it probable that, had there been shells in 

 that drift, they would have perished altogether, leaving no trace. 



The surface of the solid rock over and round the mouth of the 

 cave was similarly weathered, and the deep undercut ledges are such 

 as are commonly found along all cliffs of the Mountain Limestone 

 when exposed to chemical and ordinary subaerial weathering, and not 

 rounded off by breakers or by ice-action. There was no trace of 

 smoothing by ice. 



The scratched stones from the west prove nothing. There can 

 have been no man or hyaena there when the ice-sheet from Snowdon 

 and Arenig carried morainic matter across the Yale of Clwyd. 



There are no scratched stones among the rocks peculiar to the 

 drift of the submergence. All the glaciated stones in that are 

 derivative; they are washed from old Arenig and Snowdonian 

 drift into the St. Asaph Drift and into the rainwash, and are 

 being handed on still. On the coast at the present time they are 

 seen, still retaining their striations, some distance from the drift 

 from which they have been derived. 



"We must remember, too, that the drift blocked only one end 

 of the caves of Plas Heaton and Cae Gwyn, so that there is no 

 difficulty about the manner of occurrence of any of the objects 

 except those in and under the drift at the upper entrance in each 

 case. 



Past VII. 

 Conclusion. 



To sum up, I offer the following tentative classification of the 

 principal drifts of the Vale of Clwyd. I place the Talargoch gravels 

 above the St. Asaph clay and sands. The surface of the ground 

 at Talargoch is at a considerably higher level than St. Asaph, and 

 mining-operations have proved the gravels to extend to a much 

 greater depth than the level of the river below St. Asaph ; but the 

 central parts of a submerged valley would not receive such rapid 

 additions from the denudation of the surrounding area as would 

 gather along the shore. If we ever recognize the equivalents of 

 the Talargoch gravel near St. Asaph it will probably be, as sug- 

 gested above, in the upper gravel and sand of the section south of 

 Brynelwy. 



Q.J.G.S. No. 169. 



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