Vol. 58. | GLACIER-LAKES IN THE CLEVELAND HILLS, 561 
washed into the space between the margin of the ice-lobe and the 
hills to form a species of deformed delta, just such as I have 
observed beside the Findelen Glacier. The stream on encountering 
the ice would turn away westward towards the only point of escape, 
Lake Pickering. The lake-level was at this early stage probably 
about 200 or 225, or possibly 250, feet above sea-level, and the extra- 
morainic stream would spread its gravels so as to produce a uniform 
gradient from the floor of the rock-gorge down to the level of the 
lake; hence the glacier would be margined by a bench of gravel 
the surface of which fell from east to west. 
Each valley descending the ice-free slopes west of Forge Valley 
would behave in the same way as the main stream, and would, like 
it, turn along the gravel-bench towards the escape into Lake 
Pickering. Flood-action would periodically operate to level-off the 
larger inequalities of surface of the gravel. 
In the recession of the ice-lobe, successive avenues of escape in 
front of the ice would be found by the stream, and thus every step 
of the retreat would leave a segment of the main channel high and 
dry upon the top of the gravel-terrace. Irregularities in the gravel- 
accumulations in time of flood may account for the curious trans- 
verse interruptions in the slope of a channel. The most remarkable 
case of the kind is that of a dry valley extending in a devious course 
from the inner edge of the terrace at Beedale for nearly a mile, 
until at Rushton-Cottage Pasture it forms a very deep groove like a 
railway-cutting, and enters the valley of Sawdon Beck. It is quite 
clear from its position that this channel at one time carried Beedale 
Beck round the end of the moraine; and I suggest that the closed 
hollow in its course, which is surrounded by the 175-feet contour, 
was produced in the subsidence of a flood which preceded or 
accompaiied a retreat of the ice-front, allowing the present outlet 
of Beedale by Dingdale to open out. Jam bound to say, however, 
that a simpler explanation might be found in irregular solution of 
the underlying rock. 
When the ice-lobe retreated entirely to the eastward of Forge 
Valley, the Derwent would debouch directly into Lake Pickering. 
During some part of this retreat, it seems to me certain that a 
lateral dwindling of the ice-lobe would permit the river to flow 
between the elevated terrace of gravel and the ice. The result 
would be some scarping of the gravel-bank, and a partial re- 
distribution of its materials. Mr. Fox-Strangways has remarked 
that besides the main terrace, ‘ there are two minor terraces, not so 
well marked, at about the 100 and 140-foot contours.’?' I have not 
observed these as very definite features, but the explanation which 
I offer would account for them. 
In the recession from Forge Valley, the phenomena of the ice- 
margin would repeat upon a small scale those already described, and 
the Marra-Mat (Waydale) and other valleys would be produced. 
When the edge of the ice had retreated to the spur forming the 
* Valleys of N.I. Yorks’ Trans. Leicest. Lit. & Phil. Soc. ns. vol. iii (1894) 
p: 309. 
