160 J. C. WARD ON THE GLACIAL ORIGIN OF THE 



water in this case with those of Buttermere and Derwentwater given 

 in the former paper, we find as follows* : — 



Lake. Ice. 



Wastwater 250 1300 



Buttermere 90 850 



Derwentwater 73 900 



that is to say, while the depth of Wastwater is about three times 

 as great as that of Buttermere and Derwentwater, the thickness of 

 ice which may have moved over these spots before the lake-basins 

 were made is considerably more than one third greater in the first 

 case than in the other two. Another point to be considered is the 

 fact that the deepest part of the lake occurs just beyond the spot 

 where a great accession of ice must have joined the main glacier 

 from down the wide double valley in which Over Beck and Nether 

 Beck run, and the line of greatest depth immediately swerves 

 over to the opposite shore, beneath the steep Screes, where the 

 greatest pressure would be exercised (PI. VII. A, figs. 6 & 7). These 

 facts tend strongly to support the theory of glacial erosion. 



If I am right in the supposition that a line of granite extends up 

 the valley beneath the lake, it is possible that the nature of the rock 

 may have facilitated the erosion. 



b. Grasmere and Easdale. — In PI. VII. B, fig. 12 is a longitudinal 

 section through Codale and Easdale Tarns, and Grasmere ; and the 

 mountains shown in outline are those lying to the north. I think 

 I may safely say I have rather under- than overrated the thickness 

 of the ice which passed over these tarns and lakes; and it will 

 be seen at once how insignificant are the hollows in which these lie, 

 as compared with this thickness. Figs. 13 and 14 are transverse 

 sections along the lines drawn on the map, PI. VII. C. Prof. Hull 

 considered f Easdale Tarn, together with Stickle and Blea Tarns, 

 to be moraine-dammed. Doubtless he was unaware of the depth of 

 Easdale (71 feet), a depth very considerable for so small an upland 

 lake. There are, indeed, moraines about the foot of the tarn, though 

 the high bank just on the north side of the stream is a great ice- 

 worn mass of rock covered with a coating of moraine-drift upon 

 its western flank. The stream also shows rock in its bed directly 

 after leaving the lake and only some few feet below its level ; and 

 I think this tarn is, when the depth is considered, almost as 

 good an example of a rock-basin as possible. 



Codale Tarn, more than 600 feet above Easdale, is another good 

 case of such a basin ; and ice-scratches may be seen upon its eastern 

 shore, pointing as if certainly made by ice coming straight up out 

 of the rocky hollow. I was unable to ascertain its depth, though it 

 would seem to be but shallow, very likely less than half that of 



* It should be borne in mind that in all the drawings giving the thickness of 

 the ice and the depth of the water on a true scale, a low estimate of the former 

 has always been taken, 



t " On the Vestiges of Extinct Glaciers in the Lake-districts of Cumberland 

 and Westmoreland," Edin. New Phil. Journ. ser. 2, vol. xi. p. 31. 



