BEACH AND BOULDERS NEAR. BRAtTNTON AND CROYDE. 663 



be sufficient to justify our dismissing several of the hypotheses 

 suggested. 



They are not flints of the kind used by primaeval man for the 

 manufacture of implements. 



Their numbers, wide distribution, and constant association with 

 ancient deposits at very various levels make the hypothesis that 

 they were accidentally introduced quite untenable. They go back to 

 times far earlier than any ships that carried ballast. 



They are irregularly iron-stained, subangular gravel- stones, not 

 flints derived directly from the chalk. 



They are of the same kind as those common in the high-level marine 

 deposits of Wales * and the north of England, and occur all round our 

 western coasts. 



They are found on the St.-David's plateau. They have been 

 brought to me by Mr. P. J. H. Jenkinson from the gravels that 

 occur here and there all over the Scilly Isles. They are handed on 

 to lower levels by every later denudation, and are generally to be 

 picked up in every modern shingle. They form part of the great 

 gravel banks of unknown age that lie off our south-west coast. 



They do not appear in the older boulder-clays of Wales, but came 

 in with the shore-drifting that mixed up the debris of the northern 

 ice-sheets with that from the Cambrian mountains, and dates from 

 the Moel-Tryfan and St.-Asaph stage of the Pleistocene. 



It is perfectly clear that the upper part of this cliff below the 

 talus consists of nothing but blown sand. We have only to walk 

 south as far as Braunton Burrows to see a similar deposit now in 

 process of formation. The sand is blown up against preexisting 

 dunes, so as to show in section steeply inclined beds, just as it does 

 where blown against the hill-sides of Saunton Down or Middle 

 Borough. A few stones are carried here and there far up the sand- 

 slope and in between the dunes. Shells are transported some dis- 

 tance up by the waves, and still further by the wind. Certain 

 species are carried in by gulls and crows. I saw here among the 

 sand-dunes the shells of Patella vidgata, Pecten varius, Mytilus 

 edulis, Mactra shdtorum, Scrobiculana piperata. On the coast of 

 Pembrokeshire I have seen the shell of Nassa reticulata rolling up 

 a steep sand-dune in a gale of wind. The shells of land-mollusca, 

 such as Helix virgata, II. aspera, H. nemoralis, JBidimus acutus, &c, 

 are also blown about and rest in any sheltered hollow, or even in a 

 footprint ; but they do not occur indiscriminately throughout the 

 mass, so that it often happens that over large tracts not a single 

 specimen can be seen. 



At the north end of the dunes the sand creeps up the hillside, 

 extending in irregular hummocks as far at any rate as Saunton 

 Court. If any change of current were to destroy the great barrier 

 of blown sand, so that the sea rolled in below Saunton Court, and 

 the sand next the hill were hardened a little by percolating water, 

 we should have cliffs precisely similar to those now seen along the 

 south side of Saunton Down and round by Middle Borough almost 

 * Quart. Journ. Geol. Soc. vol. xliii. 1887, p. 83. 



