THE LAKES OF SNOWDONIA AND EASTERN CARNARVONSHIRE. 430 



deeper part of the lake are clue either to small rocky knobs projecting upwards from 

 the lake bottom, or to the irregular distribution of boulders, possibly to both. 



11. Llyn Ogwen. — This lake is situated at the head of the Pass of Nant Francon, 

 and lies at an altitude of nearly 1000 feet above sea-level. It is a fine sheet of water, 

 nearly a mile in length, and much celebrated for its trout. The main axis of the lake 

 runs due east and west. It is bounded on both sides by lofty mountains. On the 

 northern side Y Braich Ddu, a shoulder of Carnedd Dafydd, slopes down from a height 

 of over 3000 feet to the water's edge ; at the south, the rugged mass of Y Tryfan lifts 

 its peaked crown to a height almost as great, and beyond lie the Glyders. The lake 

 is broadest at the eastern end, and narrows towards the west, where the hills press in 

 from both sides to form a gorge. Looking along the lake from the eastern end, one 

 would think that it was shut in to the west by lofty hills, which appear to stretch right 

 across the valley. But at the foot of the lake the gorge becomes still narrower, and 

 then terminates abruptly, the outflowing river plunging over rock down the Falls of 

 Ogwen into the deep and flat valley of Nant Francon, which lies below. Nant Francon 

 signifies "the Glen of the Beavers": these animals formerly existed in Wales, and their 

 skin was in much demand in the tenth century, as shown by the laws of the king, 

 Howell Dda. From the upper end of the lake an alluvial tract stretches eastwards 

 for about half a mile, and a few hundred yards further lies the watershed, which only 

 rises to an elevation of 1050 feet. So the lake was originally considerably larger, and 

 it is quite possible that formerly it drained, eastwards towards Capel Curig, as has been 

 suggested by Brend.* The present watershed is marked by a mound of drift. But 

 at the head of the alluvial tract, bare rock is seen stretching most of the way across 

 the valley as a low ridge. 



The surface of the lake, according to the Ordnance Survey map, stands at an 

 altitude of 984'4 feet above sea-level. The exact length of the lake is 1700 yards, 

 and its maximum breadth 415 yards. The total area covered by its waters is approxi- 

 mately 456,400 square yards, and the mean breadth 268 yards, being 16 per cent, of 

 the length. The Afon Dena enters the lake at its head near the left margin. 

 Another streamlet, coming down from Ffynnon Lloer, a small mountain tarn lying well 

 up on the Carnedd Dafydd, flows into the head of the lake at the opposite corner. 

 The only other stream worth noting is one coming down from Cwm Bochlwyd on the 

 left, and running into Llyn Ogwen near its lower end, its point of entrance being 

 marked by a delta. The Holyhead road runs along the left margin ; and the cliffs 

 above the road are beautifully glaciated, and on them are stranded a number of 

 erratics. 



A well-marked promontory, made up chiefly of huge blocks and boulders which 

 have rolled down from the slopes above, projects into the water from the southern side 

 opposite the middle of the lake. The northern shore-line is more regular, and the 

 hill-sides rise steeply from the lake-margin. 



* Geol. Mag. 1897, p. 404. 



