244 JOWETT AND MUFF : GLACIATIOX OF BRADFORD, ETC. 
are readily correlated with the evidence of the limits of the drift, 
and a complete series of lakes and overflow channels may be 
traced corresponding to the period of maximum extension of 
tlieice. 
VII . — Conclusions . 
The nature and distribution of the glacial deposits and the 
evidence from striated rock-surfaces indicate a general ice- 
movement in Airedale from N.W. to S.E. The Airedale glacier 
is by no means of local origin, but should rather be regarded as 
a great composite lobe of ice receiving its original supply of ice 
and stones in part from the ice-sheet which invaded Lancashire 
from the north and north-west, but chiefly from the snow-fields 
which had accumulated upon the extensive high plateau of 
North West Yorkshire. 
The Irish Sea ice-sheet pressed in upon the Lancashire plain, 
reached far up the western flanks of the Pennines. and prevented 
any flow of ice from the N.W. Yorkshire uplands down the 
natural slope of the ground towards the Irish Sea. Consequently 
ice accumulated to a great thickness in the basin-like hollow in 
which Skipton, Hellifield, Gisburn, and Barnoldswick are situated. 
Being unable to escape westwards the ice moved across the 
comparatively low and open country in an easterly direction 
towards Skipton. and a portion of it continued in this direction, 
passing through the depression in the hills leading into Wharfe- 
dale. 
The Avide and low-l3ang valley of the Aire with its natural 
slope to the south-east afforded an unobstructed outlet for the 
constantly increasing accumulation of ice. Hence most of the 
ice flowed out in this direction. The widespread distribution 
of the glacial deposits clearly indicates that when the ice-sheet 
was at its greatest extension the moors north and west of Combe 
Hill were completely over-ridden. Stretching away to the 
east, north, and west from Combe Hill was one vast sea of ice. 
from which the highest part of Rumbles Moor stood out as a 
" nunatak.'" Southwards, however, a very different scene 
appeared. Although drift has been traced high up the western 
slopes of the Pennines. there is no evidence to show that any lobe 
of ice has crossed the Pennines between Combe Hill and the 
