DEIFT-DEPOSruS OF COL^VTN BAT. 105 



there are also others near the Board Schools on the road to Llan- 

 drillo-yn-rhos. jSTearer Col\vyn-Bay Wesleyan Chapel, on the same 

 road, is a sand-pit. I believe the beds of clay and sand are discon- 

 tinuous, and occupy the surface without any particular order. 



3. Rearranged Gravels. — A good deal of the drift surface, especially 

 about Colwyn-Bay village a ad in the neighbourhood of the several 

 brooks before mentioned, shows evidence of having been subaerially 

 redistributed. It is difficult to draw a fine line between these 

 gravels and those undoubtedly belonging to the drift, especially as 

 the surface-deposits had doubtless been previously rearranged or 

 deposited during the emergence of the land from the great submer- 

 sion. At the new station at Old Colwyn, which was being built 

 during my examinations, the excavations showed a shaly gravel 

 occupying the surface. 



Alluvium. — A deposit of marsh clay is to be seen on either side 

 of the embankment between Ehos and the Little Orme's Head. It 

 is only a few feet thick, and rests upon a few inches of peat, 

 which again rests on the " brown Boulder-clay." The surface of 

 the Low-level Boulder-clay is at its minimum elevation at these 

 points. I was unable to measure the heights of the cliffs, but I 

 should judge that the railway was at an average level of about 40 feet 

 above the shore of Colwyn Bay. Towards E-hos the surface-level of 

 the drift declines to near the shore-level. Beyond the embankment 

 towards the Little Orme's Head it rises again to a considerable 

 height. 



Denudation. — The sea has evidently cut into and washed away a 

 great deal of the drift, hence the formation of the cliffs. The 

 " Dingle " at Co1w}ti Bay, and the valley or gully in which runs 

 the brook from Old Colwyn, are very deep narrow cuts in the drift. 

 I attribute their depth and comparative narrowness to the geolo- 

 gical recency of the denudation of the coast, which has brought the 

 " base level of erosion '" nearer to the hills, and so, by quickening the 

 grade of the streams, has enabled them to do more work vertically 

 than horizontally. 



COXCLTJSION. 



It now remains to consider what light the foregoing facts throw 

 upon the difficult question of Glacial geology. 



In the first place I may observe that in few sections is to be 

 seen so clear a line of demarcation between two beds of drift as 

 exists here between the grey TiU and the brown Boulder-clay. 

 This arises from the fact that the clearly marine " Low-level 

 Boulder-clay," and the typical "Till" are in juxtaposition over a 

 comparatively large area. " Till " is evidently a deposit the 

 materials of which generally have not travelled so far as those of 

 the Low-level Boulder- clay. It is here, as elsewhere, largely, if 

 not altogether, made up from the local rocks, the slates, shales, 

 and limestones, and it is no doubt the great quantity of carbonate 

 of lime in it that makes it set so hard. At Penmaenmawr, to the 

 west of Colwyn Bay, and out of the limestone district, I had an 



