LAKE-BASINS OP CUMBERLAND AND WESTMORELAND. 163 



e. Windermere and Coniston. — In the case of these lakes I am 

 inclined to believe, from the evidence brought forward on page 154, 

 that the ice-sheet supplied from the various dales within a circular 

 northern sweep from Wetherlam to Wansfell Pike, and crossing the 

 whole area of ground directly between these heights (fig. 22, 

 PI. VII. D), passed southwards, and, becoming concentrated in the 

 already existing north-and-south valleys, was effective in forming 

 the long slight grooves in which the lakes of Windermere, Esth- 

 waite, and Coniston now lie*. 



Windermere is divided into two basins by Belle Isle and 

 other islands : in the upper reach, the bottom is beneath the sea- 

 level for a distance of 3 miles ; and in the lower the bottom just 

 reaches the sea-levelf . Fig. 25 is a transverse section through 

 the deepest part of Windermere, near Wray Castle ; and fig. 26 is 

 another, crossing some 2| miles above the foot of the lake. The 

 transverse section in fig. 23 crosses about | of a mile north of 

 Belle Isle. 



It is not quite clear why the islands at the centre of Windermere 

 should have been spared by denudation to divide the present lake 

 into two basins, since, so far as I can learn, there is nothing in the 

 superior hardness of the rocks at that spot to explain it. It is the 

 case, however, that just in that neighbourhood the valley widens 

 somewhat ; and thus perhaps the ice was enabled to spread laterally ; 

 while we may reasonably suppose that the islands represent only 

 the degraded stumps of rocky hills which stood well above the valley- 

 bottom in preglacial times. 



IV. Influence op Geological Structure on Lake-origin. 



I do not think any case can be pointed to in which a lake-hollow 

 has been directly formed at a certain spot because of the presence of 

 particular geological features at that spot. As a general rule, the 

 lakes in this district lie with their longer axis in a direction across 

 that of the strike of the strata, and this because the valleys in 

 which they have been formed had that direction previously. That 

 faults pass through some of the lakes is but little to the point, as it 

 was probably the existence of such faults, bringing together beds 

 of different degrees of hardness, that gave the initial directions to 

 some of the valleys. Moreover most of the largest lakes do not 

 apparently lie along lines of fault, and even those with such long 

 straight courses as Windermere and Coniston do not, according to 

 Mr. Aveline, run wholly along any large fault ; for while at the 



* In the figures I have purposely drawn the upper surface of the ice level ; 

 but of course this would not always be so in nature. 



t The soundings used in this section and in that of Coniston were taken 

 many years ago by Mr. P. C. Crosthwaite. The greatest depth of Winder- 

 mere, 234 feet, has been found by Mr. De Ranee just opposite Wray Castle, 

 and the greatest depth of Coniston, 174 feet, by Messrs. Aveline and Camerod, 

 who have taken the depths of this lake throughout. Mr. Cameron has sounded 

 Esthwaite Water and found its deepest part to be only 51 feet. 



Q.J.G.S. No.122. n 



