76 



PROF. T. Bl'KENJlY HUGHES OX THE 



old blue-grey clay with, boulders, all from the Welsh rocks to the 

 west. 



In the Vale of Clwyd the denudation which cut down through 

 the soft or easily undermined strata of the St. Asaph (or Northern) 

 Drift seems to have been often arrested when it reached the stiff 

 tough older clay which we have called the Arenig (or Western) 

 Drift. 



At the bottom of the cliff beyond Brynelwy, near St. Asaph, where 

 the river had removed the debris from the landslips, a dark blue 

 clay, with boulders of Welsh rocks only, used sometimes to be 

 exposed ; and below the Mount, nearer St. Asaph, the section by the 

 river often shows a similar dark blue boulder-clay overlain irregu- 

 larly by the Marine Sandy Drift (see Section, fig. 3, p. 81). The 

 top of this blue boulder-clay is remanie, as in the Colwyn Sections, 

 only that in the Elwy the remanie surface of the old drift is a 

 boulder-clay, while at Colwyn, in the section next to be described, it 

 is a sandy clay. 



Along the coast in Colwyn Bay a similar dark blue clay full of 

 scratched stones, all of which are from Welsh rocks, is exposed 

 here and there. For instance, at the base of the cliff about 200 

 yards N.W. of the Bath House at Aberrhyd, where the following 

 section (fig. 2) may be seen : — 



Fig. 2. — Section seen in Sea-cliff, about 200 yards N. W. of Bath 

 House, Aberrhyd, Colwyn Bay. (Scale 80 feet to 1 inch). 



a. Chocolate-red clay, with boulders; some scratches. 



b. Sand. 



c. Yellow laminated sandy clay. 



d. Blue clay, with many scratched stones. 



d represents the older clay left by the ice from the great snowy 

 region to the west, which crept downwards from the central 

 gathering-ground, and probably at one time levelled up much of the 

 low-ridged country on the borders of the mountain land. Tn this 

 no trace of organism has ever been found, except, of course, the 

 fossils in the fragments transported from the older rocks. 



Changing somewhat locally according to the source from which 

 it is derived, it still has much in common wherever it occurs ; but its 

 chief character is this, that in the district under examination it 

 contains only material from Welsh mountains in the west. 



This, then, is the oldest drift I know of in the Vale of Clwyd. 

 Call it for local purposes the Arenig Drift, the Western Drift, the 

 Snowdon Drift, the Great Ice Drift, the Older Drift. 



I deprecate the use of the name "Boulder-clay" as a technical 

 term for any subdivision of the series. As a descriptive term for any 



