350 Miss Eyton — Drift-heds of Llandrillo Bay, 



here so well defined witliin a short space, and it is the more desirable 

 to do so, because the encroachments of the sea are annually pro- 

 ducing great changes in this district. 



1. The Boulder -clay. — This deposit attains its greatest thickness 

 on the east of Penmaen Khos, in the little vale of Llandulas, where 

 its height cannot be much less in some places than 200 feet above 

 the sea level. It forms a fine cliff, where it reposes against the 

 mountain, rising sheer up from the beach nearly to the limestone 

 summit. From thence it slopes gradually downwards to the centre 

 of the valley, forming a terrace of from twenty to fifty feet above 

 the beach. Very curious are the figures into which the recent wave- 

 action has moulded the plastic cla}^ along this terrace. Turrets, 

 caves, and buttresses rise in miniature imitation of the bolder 

 scenery of a more rocky sea-board. 



The littoral zone is strewn with huge boulders and sub-angular 

 fragments, which have been left by tlie denuding acticm of the waves, 

 the clay and lighter material being borne away, while the heavier 

 portions remained in, or near their original site. -Many of these are 

 derived from the subjacent Carboniferous Limestone, others from 

 the dark grey Cambrian rocks of the Snowdon district. I have found 

 among them beautiful specimens of corals, smooth and polished, as 

 though fresh from the hand of the lapidary, while the scratches and 

 strias on the blocks in this gigantic stoneyard might have been left 

 but yesterday by the workman's chisel. 



Crossing the littoral zone, we find the Boulder-clay again re- 

 appearing just above low-water-mark. It is, indeed, merely con- 

 cealed by the sand and shingle of the beach, showing that a con- 

 tinuous slope once extended into what is now the bed of the sea. 

 The whole belt of Carboniferous Limestone, underlying the clay, is 

 rent by huge fissures, commencing near the summits of the hills, 

 and increasing in width and length as they proceed downwards. 

 They are frequently exposed in the course of the quarrying opera- 

 tions, which are extensively carried on in this locality, and are 

 generally found to be filled with Boulder-claj^ and its included 

 debris, the sides being coated with stalagmitic concretions of a 

 dark red colour, derived from the oxide of iron,^ contained in the 

 clay. From this and from a similar tint imparted to the limestone, 

 where the clay has rested against it, the name Penmaen Ehos (red- 

 head-land) is derived. The quarrymen informed us that they some- 

 times found deer's horns in these fissures, but we were unable to 

 procure any. The rents appear to have been formed by frosts ; a 

 little water being lodged in a crevice in the rock froze, thus en- 

 larging the crack ; next winter the process was repeated on a larger 

 scale, and so on, until the mild Pliocene climate had changed into 

 the cold of the Glacial epoch, and the great rivers of ice came crash- 

 ing and grinding over the land, involving all in one common ruin, 

 — ruin from which, however, phoenix-like, new life was to arise. 



It will be seen from the foregoing observations that the Boulder- 

 clay in this locality once occupied a veiy much larger space than at 

 ^ Anhydi-atcd peroxide according to Mr. George Maw. 



