"I may now follow its boundaries on the Welsh coast, and pursue the line to the final melting-place of the glacier. From the Little Orme's Head the line of confluence with the native ice is pretty clearly defined. It runs in, perhaps, half a mile from the shore, until the broad low tract of the Vale of Clwyd is reached. Here the northern ice obtained a more complete mastery, and pushed in even as far as Denbigh. This extreme limit was probably attained as a mere temporary episode. Horizontal striæ on a vertical face of limestone on the crags dominating the mouth of the vale on the eastern side attest beyond dispute the action of a mass of land-ice moving in from the north. "I may here remark, that in this district the deposits furnish a very complete record of the events of the Glacial period. In the cliffs on the eastern side of the Little Orme's Head, and at several other points along the coast towards the east, a sequence may be observed as follows: "4. Boulder-clay with northern erratics and shells. "3. Sands and gravels with northern erratics and shells. "2. Boulder-clay with northern erratics and shells. "1. Boulder-clay with Welsh erratics and no shells. "A similar succession is to be seen in the Vale of Clwyd. The interpretation is clear: In the early stages of glaciation the Welsh ice spread without hindrance to, and laid down, bed No. 1; then the northern ice came down, bringing its typical erratics and the scourings of the sea-bottom, and laid down the variable series of clays, sands, and gravels which constitute Nos. 2, 3, and 4 of the section. [Illustration: Fig. 42.--The Cefn Cave, in Vale of Clwyd. (Trimmer.) _a_, Entrance; _b_, mud with pebbles and wood covered with stalagmite; _c_, mud, bones, and angular fragments of limestone; _d_, sand and silt, with fragments of marine shells; _e_, fissure; _f_, northern drift; _g_, cave cleared of mud; _h_, river Elwy, 100 feet below; _i_, limestone rock.] "In the Vale of Clwyd an additional interest is imparted to the study of the drift from the circumstance that the remains of man have been found in deposits in caves sealed with drift-beds. The best example is the Cae Gwyn caves, in which flint implements and the bones and teeth of various extinct animals were found embedded in 'cave-earth' which was overlaid by bedded deposits of shell-bearing drift, with erratics of the northern type. "It has been supposed that the drift-deposits were marine accumulations; but it is inconceivable that the cave could ever have been subjected to wave-action without the complete scouring out of its contents.