22 
KENDALL : THE CLACIER LAKES OF CLEVELAND. 
over the col at Fen Bogs, and consistent with that is a great 
fan of delta deposits which, shelving out from tlie end of Xewton 
Dale, occupies some square miles in what was then a lake in the 
Vale of Pickering (Fig. 6). This delta of coarse gravel is partly 
covered by the warp beds of the lake, showing that Xewton Dale 
ceased to be an overflow before tlie close of the Glacial Period. 
The sequence of events in Eskdale shows that the ice-sheet 
retreated so as to leave a channel of escape by the mouth of the 
Esk before the lobe of ice was withdrawn from the moraine at 
Lealholm. and this lobe seems to have persisted not only after 
the mouth of the Esk, but practically the whole coast -line of 
Yorkshire down as far as Scarborough, was free of ice. A series 
of channels excavated by lake overflows, some of which are still 
occupied by the River Esk, belong to this period. The highest 
of these channels is Wild Slack (Fig. 7), a small, but definite, 
t • 
o •? 
t"0 — 
Fig- 7. 
SECTION ACROSS CRUNKLEY OILL AND THE LEALHOLM MORAINE. 
overflow, which cuts the southern limb of the Lealliolm moraine 
immediately south of Crunkley Gill. It notches slightly the 
525-foot contour, and dies out about the 500-foot contour. 
A small shrinkage of the ice opened a slight!}^ lower gap in 
the moraine on the site of Crunkley Gill, where a spur of rock 
was covered by about 50 feet of drift. A new notch Avas started 
here, and the level of Lake Eskdale was lowered from about 
500 feet, the original level, down to 450 feet, when the outlet 
began to cut into live rock. By this time it had j^robably passed 
tlie critical level of the moraine, and any further witlidrawal of 
