416 
GRACE : THE GLACIAL GEOLOGY OF FURNESS. 
and below 15 feet of Upper Clay. This seems difficult to explain 
except on the assumption that the peat is an Intra-Glacial deposit. 
The exposures along the west coast of Walney shew an almost 
continuous line of sands and gravels from Biggar Bank to Trough Head, 
where it passes out at the top of the drift. It is of very variable 
thickness, but seldom reaches more than three feet. 
The Upper Boulder Clay is a typical boulder clay, red and compact. 
Good exposures are seen at Ormsgill and at the north end of the west 
coast of Walney. It also appears north of Trough Head and at the 
north end of Westfield Point, and can sometimes be seen at the base of 
the sand dunes at Sandscale. 
The Duddox Lake. 
Towards the end of the valley period the ice in the Duddon Estuary 
appears to have commenced shrinking on its eastern margin. The 
first consequence of this was a marginal channel at about 250 feet, 
which cut a notch between Housethwaite Hill and High Haume 
very similar to those described by Prof. Kendall under the name of 
" Severed Spurs."* This Stage was followed by a gradually widening 
lake, the surface of which at first stood just above 200 feet, but sank 
lower and lower, as openings across Furness became available, until 
the water was not far from the present level. Pauses in this sinking 
took place at 200 feet and 100 feet, and we have collected evidence of 
this in the form of (1) Beaches ; (2) Deltas ; (3) Overflows, at both 
levels. 
{a) The Marginal Channel at 250 feet. 
We have found no traces in the shape of gravels or beaches at 
250 feet. The evidence for a stream of water at this height consists 
of the deeply cut notch mentioned above. This is a V-shaped 
valley cutting across the outcrop of the Coniston Limestone and 
leading from the open hillside on the north to a wide amphitheatre 
with a floor below 175 feet, and in direct communication with the 
Hagg Gill Channel. The further course of this channel (No. 4) belongs 
as much to the 200 feet stage (No. 2) as to the 250 feet, but may be 
conveniently followed here. From Hagg Gill Wood to Dalton is a 
wide, deep valley with steep sides and a floor about 120 feet which has 
* QtuiH. Journ. Geol. Soc, Vol. LVIII. (1902), p. 482. 
