106 T. MELLAED KEADE ON THE 



opportunity of examining in the foundations of the British Schools, 

 of which I happened to be the architect, the Till lying on the hill- 

 side. Here and all about Penmaenmawr, after getting below the 

 surface-affected portion, it was a hard grey Till full of large 

 boulders and stones which were generally more or less rounded and 

 waterworn. I noticed one slightly striated. These stones were so 

 large and iirmly imbedded that they were used in some cases for 

 the foundations, being built into the walls without removal. The 

 Till at Colwyn Bay is bluer, more clayey, and of a finer texture, 

 and contains not nearly so many large boulders, though the total 

 bulk of the stones in it may not be very dissimilar. According to 

 my experience, true Till is rarely, if ever, found except in the 

 neighbourhood of mountains or quickly sloping ground. In the 

 present instance, I am inclined to believe that it has been formed 

 by ice and snow descending from the mountains and accumulating 

 the disintegrated matter at the foot. It does not appear to be the 

 ground-moraine of a hill-and-valley-ignoring ice-sheet, as the con- 

 tained stones lack the definiteness of direction one would expect to 

 result from such an agency. It is better to admit that we are 

 largely ignorant of the various modes in which land-ice acts — its 

 effects, with our limited knowledge, belonging more to speculation 

 and theory than to fact. 



Be this as it may, when we come to the overlying deposit of 

 brown Boulder-clay, no such difficulties occur. It is undoubtedly 

 an aqueous-marine deposit, and part of the extensive sheet of Low- 

 level Boulder-clay and sands which occupies aU the plains of the 

 North of England, from the margin of the mountains to the coasts 

 of the Irish Sea, and, skirting the coast of Wales, here and there 

 intrudes upon the lower valleys. With the exception of the portion 

 of this deposit which approaches the limestone headlands, where it 

 is mixed with the detritus therefrom, the extensive sheet of drift, 

 which I have described as lying in Colwyn Bay, is composed to a 

 large extent of travelled materials. The sands and clays of which 

 it is composed are not what the immediate coast or mountains could 

 yield. It is, in fact, a deposit almost identical with the sandier of 

 the Boulder-clays near Liverpool, which are composed principally of 

 Triassic debris, mixed with travelled and striated rocks. I have pre- 

 viously stated " The sands and clays of Colwyn are evidently derived 

 from the Triassic rocks of the Vale of Clwyd " *. This further and 

 more careful examination over a large area has confirmed me in this 

 opinion. Pour and a half miles east of Old Colwyn, the Triassic 

 sandstones set in and extend eastwards a distance of nine miles 

 across the mouth of the Yale of Clwyd. Most probably these 

 rocks also extend seawards. The materials of which the bulk of 

 the Colwyn drift is composed, has in the first place probably been 

 worn off the Triassic sandstone by subaerial agencies, including 

 under that head ice and frost, and has worked gradually down the 

 valley, it may be, to the plains now occupied by the Irish Sea. On 



* Quart. Journ. Geol. Soc. vol. xxxix. p. 118. 



