Vol. 68.] &LACIATION OF THE BLACK COMBE DISTRICT. 447 



district was completely swamped beneath an ice-sheet formed by the 

 confluence of the Lake-District ice-cap and the Irish-Sea ice- sheet. 



(iii) The Lake-District ice invaded the area from three main 

 directions : (a) the Broughton Valley ; (6) the Duddon Valley 

 and high ground on the west ; and (c) Eskdale. 



(iv) The overmastering pressure of the Irish-Sea ice diverted the 

 seaward flow of the Lake-District ice to the south or south-east, 

 and in some cases forced it inland. 



(v) The Lower Boulder Clay of the coastal-plain is the ground- 

 moraine, chiefly of the Irish-Sea ice-sheet. 



(vi) In the Lower Boulder Clay of the westward mountain- 

 slopes there is evidence botli of the interweaving of drifts of distant 

 and strictly local origin, and of a certain amount of movement of 

 ice inland. 



(vii) Stages of withdrawal of the ice from the hills were marked 

 by the occurrence of moraines, moraine-terraces, ti^ails of boulders, 

 and perched blocks. 



(viii) Valleys, which are now for the most part either dry or 

 occupied by insignificant streamlets, and do not accord with the 

 pre-Glacial drainage-system of the district, represent channels 

 subsequently cut by the marginal drainage of the shrinking glaciers 

 or by the overflow waters from ice-dammed lakes. 



(ix) On the granitic and volcanic tracts south of the mouth of 

 Eskdale, the excavation of marginal channels followed upon a slight 

 re-advance of the ice, which overrode gravels previously accumu- 

 lated as a marginal outwash-fan. 



(x) The sand and gravel of the plain was accumulated during 

 the period which followed upon the cutting of the marginal 

 channels upon its eastern border. The material was, in the main, 

 deposited in embayments of the ice-margin, frequently beneath 

 temporary sheets of water, but some parts were entangled with the 

 melting edge of the Irish-Sea ice. 



(xi) Sand and gravel were also accumulated at the extremities of 

 lobes of ice thrust into the mouths of valleys, such as the Whicham 

 Valley and Duddon Estuary. 



(xii) The ice-lobes held up lakes in the lower ends of the valleys. 

 The Whicham- Valley Lake at first drained into the Duddon 

 Estuary by the Gill-Scar overflow, but afterwards through the 

 obstructing barrier. 



(xiii) The Upper Boulder Clay seems to be the result of a 

 restricted re-advance of the Irish-Sea ice, Avhich overrode the sands 

 and gravels of the plain. 



(xiv) The Lake-District ice, after the maximum glaciation, with- 

 drew concurrently with the Irish-Sea ice, and corrie-glaciers lingered 

 in sheltered combes at a late stage. 



(xv) Certain hanging valleys are due to the oversteepening of 

 hill-slopes, or overdeepening of main valleys by glacial action. 



Q. J. G. S. No. 271. 2 k 



