THE LAKES OF SNOWDONIA AND EASTERN CARNARVONSHIRE. 447 



lake margin. 14 - 5 per cent, of the total superficial area lies between the 160 feet and 

 the 180 feet subaqueous lines, so that in all 24*5 per cent, of the total area is covered by 

 water attaining depths of over 160 feet. The 140 feet and 120 feet contour-lines follow 

 the 160 feet line closely on all sides except to the north, where the interval between them 

 becomes greater. The 100 feet contour-line encloses 52 '8 per cent, of the total area, 

 so that more than half of the lake is over 100 feet deep. The remaining contour-lines 

 follow pretty closely the outline of the lake margin, and lie very near each other on the 

 eastern, northern, and especially the western margins. On the south side there is a 

 somewhat greater interval between them, indicating a slope which is not quite so steep. 

 The 40 feet line encloses in all 82*2 per cent, of the total area, leaving only 17 '8 per 

 cent, for depths under 40 feet. The slope to the lake bottom is steep from all sides, 

 but is especially so from the eastern and western margins opposite the middle of the 

 lake. The slope is remarkable along the face of the great precipice which falls sheer 

 into the water on the western margin. Here a depth of 55 feet was obtained at a 

 distance of only 3 feet from the face of the rock. 



The steepness of the sides and the form of the lake bottom are brought out clearly 

 in the sections which are given (Plate VIII.). The waters of Llyn Dulyn are seen to 

 fill up a deep funnel-shaped basin. 



17. Llyn Eigiau. — This lake is situated about a mile and a half due north of Llyn 

 Cawlyd, in the lower part of Cwm Eigiau. The main axis runs nearly north and south. 

 It is probable that the lake formerly covered a much larger area, for an alluvial flat is 

 found extending far up into Cwm Eigiau, and low marshy ground borders the lake on 

 the east, and extends outwards for a considerable distance from the lake margin. On 

 the left or west side the precipitous rocks of Craig Eigiau rise steeply from the water's 

 edge to a height of nearly 2400 feet. The river Eigiau, coming down the cwm, enters 

 the lake near its head, at the right hand corner, where a small delta has been formed. 

 Just beyond this, to the right is a shallow bay covered with rushes, and from this bay 

 escapes the river Porthlwyd ; it makes its way north-eastwards into the Vale of Conway. 

 A few other small rills enter the lake on the west side, and a tiny streamlet flows out at 

 the foot. The lake is widest in its upper reaches ; at a point a little above the middle it 

 becomes constricted, owing to a promontory jutting out from the west side. To the 

 north of this it broadens out a little again, to become very narrow once more near the 

 foot. 



The height of the surface of the water above sea-level is, according to the Ordnance 

 Survey map (1887), 1219 feet. The total length of the lake is 1690 yards, and it has a 

 maximum width of 520 yards. The main breadth is 255 yards, this being 15 per cent. 

 of the length. Its waters cover an area of about 431,200 square yards. 



The soundings were taken in July 1901 under most favourable conditions. It was 

 sometimes difficult to fix points accurately on the lake margins, owing to the rather 

 imperfect character of the Ordnance Survey map of this region. The total number of 

 soundings taken was 90. The lake was found to be shallow, the greatest depth found 



