THE LAKES OF SNOWDONIA AND EASTERN CARNARVONSHIRE. 441 



foot. The valley narrows a little towards the outlet of the lower lake, and the stream 

 issuing from it joins the Afon Llugwy just below Capel Curig. 



The hills rise to heights of over 1000 feet on both sides of the valley opposite the 

 lakes, but the slope from the left shore is, for a short distance from the lake, a little less 

 steep than is that from the right shore. The land rises to 700 feet just at the head of 

 the upper lake, and the Gwrhyd river makes its way down by means of a waterfall. 

 The upper lake is the broader, and the lower lake narrows rapidly towards its foot. 



These lakes were sounded in June 1901, and for the work I had the assistance of 

 Mr H. Woods, M.A., St John's College, Cambridge. 



Tfie wpiper lake has a length of 760 yards, and a maximum breadth of 412 yards. 

 The total area covered by its waters is about 221,520 square yards, and the mean breadth 

 291 yards, being 38 per cent, of the length. The elevation of the water above sea-level is 

 588 feet. The total number of soundings taken was 63. The lake is nowhere of any 

 great depth, 29 feet being the deepest sounding obtained. The total volume of water is 

 approximately 22 million cubic feet, and the mean depth comes to 11 feet, being 38 per 

 cent, of the maximum depth. The deepest area lies near the middle of the lake, and is 

 almost as broad as long. It is enclosed within the 20 feet contour-line, and corresponds to 

 15*6 per cent, of the total superficial area of the lake. The 10 feet subaqueous line encloses 

 an area somewhat similar in form, but having an irregular prolongation towards the head 

 of the lake. 45 per cent, of the total area lies within the 10 feet line, leaving 55 per 

 cent, for depths under 10 feet. Three sections are given with the map (Plates VI. and 

 VIII.). They show that the form of the lake bottom is fairly simple, the sides sloping 

 gently from both banks. Huge boulders lie in the water at the foot of the lake, just 

 off the projecting tongue of land. 



Tlie lower lake is longer but narrower than the upper lake. It has a total length of 

 880 yards, and its greatest width is 330 yards. The lake covers an area of approxi- 

 mately 174,000 square yards, and its mean breadth is 198 yards, being 22"5 per cent, of 

 its length. The surface stands at practically the same level as that of the upper lake, 

 the elevation given on the Survey map being 587 '9 feet. In all, 38 soundings were 

 taken. The greatest depth recorded is 29 feet, the same as that obtained in the upper 

 lake. The mean depth is only 9 '7 feet; this is 33 per cent, of the maximum depth. 

 The total bulk of water is estimated to be approximately 15 million cubic feet. The 

 deepest area lies a little lower than the head of the lake, and is enclosed within the 20 

 feet contour-line. It is smaller in extent than the area of similar depth in the upper 

 lake, and corresponds to only 9*8 of the total area. 



The 10 feet contour-line is very irregular, the area lying within it being broadest 

 towards the head, and narrowing into a channel as followed towards the lower end of 

 the lake. As much as 62 per cent, of the total area is covered by water under 10 feet 

 deep. The longitudinal section L-M shows that the hollow is deepest at its upper end, 

 and that it is very shallow near the foot of the lake. The bottom is more irregular, as 

 shown by the cross-section N-O, P-Q, than is that of the upper lake. 



