Vol. 68.] GLACIATION OY THE BLACK COMBE DISTEICT. 411 



south-east side of a southv/ard-entering tributary has been polished 

 by ice moving in a south-easterly direction. A similar example 

 occurs about 400 yards from the head of Whicham Beck. 



During the maximum glaciation the ice apparently filled White- 

 combe and its tributary, Blackcombe Valley. The watershed at 

 Whitecombe Head (1429 feet) is covered with peat, but the 

 passage of ice over it is revealed by the presence of a few small 

 boulders of quartz-porphyry and volcanic rocks in slaty rubble 

 beneath the peat, ^ear the head of the combe the ice appears 

 to have overridden a mass of weathered and unstriated slate, 

 in which the stream has now cut a gorge. Farther down, a 

 true slaty boulder-clay with striated stones sets in, and in the 

 lower parts of the valley becomes almost' continuous with that 

 spread over the floor of Blackcombe.^ A few yards below Whicham 

 Mill Pord the slate is turned over to the south by the downstream 

 ice-movement. 



North of Black Combe a few boulders of Eskdale Granite lie 

 upon the drift-covered slopes south of the Fell road from Bootle to 

 Broughton, and about 550 yards south-east of the eastern boundary 

 of the granite. Stoneside Hill and the ground more than half a mile 

 to the west of it, south of the granite outcrop, are free from drift, 

 the only erratics noted being volcanics. Moutonne surfaces on 

 Stoneside Hill point to an ice-movement slightly east of south; 

 but the chief streams of boulders from the granite passed to the 

 north-west of the hill in the direction of Bootle Fell, where they 

 occur in considerable numbers. 



On the gentle slope north of Black-Combe summit there are a 

 few scattered boulders of coarse ash, and of pale quartz-porphyry 

 with white mica, like that of the dykes exposed in Grain sgill Beck 

 (between the 1000-foot and 1250-foot levels) about a mile to the 

 north. Their occurrence seems to prove that the mountain-top 

 was buried beneath ice laden with very little debris. 



(iii) Eskdale. — It is important to decide how much of the ice 

 moving along the coast should be considered as Irish-Sea ice, and 

 how much as of local origin. When a tributary glacier has added 

 its quota to the edge of a main glacier, it may for a time retain its 

 individuality as a distinct stream, yet it eventually becomes 

 incorporated in the main stream and takes its name. So, in this 

 case, ice-streams descending from Eskdale, and the valleys of the 

 Mite, Bleng, Trt, Esk, and Ehen, farther north, added their share 

 to the fringe of the Irish-Sea ice-sheet and travelled down the 

 coast alongside it and one another, each for some time preserving 

 its identity. After travelling a few miles, however, these streams, 

 and the different types of drift carried along by them, to a great 

 extent intermingled. The edge of the ice was also crowded inland, 

 and so the drift from one formation was moved inland across other 

 formations to the east. It seems well, therefore, to regard the local 

 additions to the Irish-Sea ice as part of that body. 



^ This was possibly the result of later cirque-glaciation. 



