CXXvi PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May I906, 



too large for the valley, and has not had time to adjust itself to the 

 new conditions. 



Now, in order that the waters of a lake may be switched off from 

 one valley to a parallel one, it must rise up a tributary of the former 

 until it reaches a col over which the waters of the lake will find 

 egress. This has occurred at the foot of Windermere, and accordingly 

 the lake has a hook-like end, the bent portion turning westward 

 near Ncwby Bridge ; and similar hooks occur, although not so well 

 defined, at the lower ends of some of the other lakes. 



It would appear, then, that diversion has occurred on a fairly- 

 large scale, as the result of glacial action. Nevertheless, I believe 

 that many of the cases which I have described were produced in 

 pre-Glacial times, especially those in the uplands. 



That many of the U-shaped valleys were to some extent widened 

 by ice may be regarded as certain, and this widening may in some 

 cases have been important. I see no evidence, however, that these 

 valleys have been over-deepened by that agent, in some cases to an 

 extent of over 1000 feet ; and, for reasons given above, I regard this 

 deepening as essentially the act of water working along shatter- 

 belts. 



The changes which have taken place since the Glacial Period do 

 not bear upon my present subject in any high degree. The 

 principal events of that time are recorded by Clifton Ward in the 

 Survey Memoir on ' The Geology of the Northern Part of the English 

 Lake District.' 



VIII. Conclusion. 



I have endeavoured to show that, so far as the present physical 

 features of the English Lake District are concerned, the events 

 which produced them are, in a geological sense, recent, beginning 

 with the great period of continent-formation in Middle Tertiary 

 times, and that most of the changes to which the district owes its 

 surface-forms occurred in Miocene and Pliocene times, although 

 these forms owe much of their characters to the structures which 

 were impressed upon the rocks at a period far more remote. 



I regard the shatter-belts as having played the most important 

 role in causing the modification of the lines of drainage which 

 were originally impressed upon the area when the dome was 

 elevated. To the existence of these shatter-belts I attribute that 

 intricate network of upland and lowland which is so marked a 

 feature, particularly in the central portion of the district. 



