448 MR T. J. JEHU ON 



being only 32 feet. The mean depth is only 9*2 feet, and this is 29 per cent, of the 

 maximum depth. The total bulk of water contained in the lake is estimated to be 

 about 36 million cubic feet. 



Llyn Eigiau is deepest about a quarter of a mile from the upper end. The area 

 enclosed within the 30 feet line is exceedingly small, amounting to only '3 per cent, of 

 the total superficial area. The 20 feet contour-line gives but a small oval-shaped area, 

 which encloses only 27 per cent, of the total area. An isolated sounding of 22 feet was 

 obtained also near the western margin, at a distance of less than a quarter of a mile from 

 the foot of the lake. As much as 60*8 per cent, of the total area corresponds to depths 

 under 10 feet. The 10 feet subaqueous line encloses an area which is smaller at the 

 head, becomes constricted at the neck, and passes as a somewhat narrow channel to end 

 at a distance of about 330 yards from the foot of the lake. 



The bottom was found to be largely covered with boulders and stones, and at places 



rushes encroach well into the lake from the margins. Eigiau is evidently becoming 



gradually silted up, and shows a stage in the process somewhat less advanced than that 



, seen in the case of Llyn Ogwen. Sections are given with the map (Plates Yll. and 



VIII.), which help to make clear the configuration of the lake bottom. 



VI. General Summary of the Characters op the Lakes. 



For convenience of reference and comparison, the more important details concerning 

 the different lakes are gathered together into three Tables. In Table I. are arranged 

 the statistics for each of the sixteen lakes with regard to the number of soundings, 

 length, maximum and mean breadth, ratio of average breadth to length, elevation of the 

 surface of the water above sea-level, the maximum and mean depth, the ratio of mean to 

 maximum depth, the superficial area of the surface, and the estimated volume of water 

 contained in each lake. In Table II. all the measurements are given again in metric 

 units, but the ratios are not repeated. Table III. shows the percentage of superficial 

 area corresponding to different depths of water in the case of each lake. The arrange- 

 ment of depths in the different lakes is shown at a glance, and an indication given of 

 the form of the depressions in which the lakes lie. 



It will be noticed that five of the lakes, namely, Dinas, Gwynant, Cwellyn, Padarn, 

 . and Peris, lie at comparatively low levels, having the surface of their waters at eleva- 

 tions of less than 500 feet above sea-level. All these lie in the valleys which imme- 

 diately encircle the base of Snovvdon. Their positions relative to the valleys in which 

 they lie differ considerably, Padarn and Peris occurring at the foot of a valley just 

 before it opens out on to the low grounds ; Cwellyn lying high up its valley, at no great 

 distance from the head; and Gwynant and Dinas being situated along the course of 

 another valley, the former at a considerable distance below the head, and the latter still 

 farther down. 





