404 
GRACE : THE GLACIAL GEOLOGY OF FURNESS. 
rock erosion during Glacial times must have been as much as 350 to 
450 feet. 
Originally the Ash Gill Beck and the Torver Beck passed through 
separate gaps near Torver Park, but they must have united somewhere 
near Torver, as there is only one gap leading into the lake. Now, the 
Torver Beck has captured the lesser stream on the moor, and left its 
lower course as a dry gap. The bed of the combined streams as it 
comes down into the present Torver valley is a succession of cascades. 
Its course across the valley bottom is not in line with its previous 
course, and suggests that it is making for the gap once used by the 
Ash Gill Beck. Through this it cascades again into the lake, confirming 
the suggestion that the valley at Torver originated during Glacial 
times, and that the present level of the lake is much lower than the 
pre-Glacial level of the stream into which the Beck ran. 
The conclusion we draw from these facts, and the details of the 
Yewdale valley — which have been previously described by Prof. Marr, 
and are, therefore, omitted here — is that the present Coniston Basin 
can be regarded as almost entirely the product of glacial erosion, and 
that, in pre-Glacial times, the slopes from the mountains on the west 
flowed in smooth curves, considerably higher than the present surface, 
down to a shallow valley above the site of the present lake. 
The Sub-Glacial Surface. 
If all Glacial and Post-Glacial deposits were removed from Furness 
a surprisingly large portion of the Sub-Glacial surface would be below 
present sea level. Large areas in the Lickle Valley and Steers Pool 
Valley on the w^est, and in the Rusland and Windermere Valleys on the 
east, have been eroded below O.D., and, in the centre, Coniston "Water 
goes 42 feet below O.D., and, if lake deposits were removed, would 
probably be deeper. Much of the Crake Valley, too, and a large area 
around Ulverston, and another area east of Barrow, shew no sign of 
solid rock above sea level. Very little information can be obtained 
regarding the Sub-Glacial surface beneath these deposits. In the 
Duddon Estuary, the thickest Drift of which we have obtained records 
reaches to 150 feet below sea level. A boring in the valley south of 
Furness Abbey is recorded as passing through Drift to a depth of 
about 400 feet below O.D.* The rest of the borings in the same 
* Memoirs of Geol. Survey : Geol. of Furness, 91 N.W. 
