LACS BARRÉS PAR DES MORAINES

ihe latter case this was effected as far as Ihe lower end of Llyn Padam, on either side of wich, and of Llyn Péris, Ihe glacier, having escaped from the narrow Pass, spread itself out over the high grounds by Ihe slate-quarries, and also flowing across Clegyr, as shown by Ihe slriatiotis marked on Ihe map , it left the Drifl untouched towards the Turbary plain thaï lies between Clegyr and Bethesda.

R. 14. Before leaving the subject of the Welsh moraines and Drift, I must again call attention to the fact that many of the lakes are partially dammed up by moraines, and some of them apparently owe their existence to thèse ice-formed mounds in a manner altogelher peculiar.

The mouth of a valley is surrounded by a mound or séries of unîtcd mounds curving outwards, formed ofearth^ angulary subangular^ and sometimes smoothed and scratched stones, so truly moraine-like in their arrangement , that their origin and the places whense they came are unmislakeable. A deep clear lake lies inside, and the drifl of Ihe glacial sea, fuU of boulders , slopes right up to the outside base of the moraine , with a long smooth outline , showing that the glacier descended to the sea level , and pushing for a certain dislance oui to sea, formed a manne terminal moraine, while ordinary drifl détritus, parUy scattered by floating ice, was accumulating beyond. In Ihe meanwhile the space on and beyond the sea level occupied by the glacier was kept clear of débris ; and when the land arose , and the ice disappeai^ed by an amélioration of climate , the hollow within the terminal moraine became replenished with the water drainage of the surrounding hills , just as in earlier limes it was fiUed with ice formed by a drainage of snow.

Such in Caernarvonshire are the lakes of Llyn Dulyn ' and Mellynllyn', about Iwo miles N. E. of Garnedd Llewelyn ; of Fynnon Llugwy , between Garnedd Llewelyn and the road from Llyn Ogwen

* Long since noticed by H. DanvlB.

* D. A. Illustration : Sketch map showing the course ot the «laeieni of fliiowdoii

and its neighbourhood. — Cette carte rend parfaitement compte du terrain erratique et de l'action des anciens glaciers \ une certaine époque, qui n'était pas l'époque de leur l>lus grande extension.

* Dulyn, Black Pool.

* Dig Horse Pool.