Vol. 58. | GLACIER-LAKES IN THE CLEVELAND HILLS. 523 
moraine above Lealholm Bridge, but it also extended across the 
valley and up beyond Goathland. Round the margin of this in- 
vading sheet, a deep overflow-channel was soon initiated, running 
down the Stonegate Valley. This channel, upon the retreat of the 
ice from the Moorsholm watershed, took the whole drainage 
from the Lockwood Hills, and probably the Boosbeck Valley, east- 
ward. 
The Drift-maps of the Geological Survey show an extension of 
the gravels on Black-Dyke Moor, for which there is no corresponding 
overflow. This was laid down at the maximum extension of the 
ice, and no definite channel would be produced, as Lake Eskdale 
would be at its highest level (725 feet). The gravel is mapped at 
an altitude exceeding 725 feet, but below 750. 
The first clear indication of a channel to carry drainage from the 
westward is Hardale Slack, an immense trench cut in the plateau 
of Roxby Old Moor and running quite through it. This is a 
typical example of a severed spur. Its upper end cuts through the 
700-foot contour, and there is a long stretch of peat-swamp which 
conceals a deeper channel. (See map, Pl. XXIV.) 
A beautiful example of a deserted oxbow is found on the south 
side of the channel, immediately west of Black-Dyke Slack. It 
isolates a small conical hill, and was no doubt produced by a 
temporary forward movement of the ice-front, which compelled 
the water flowing past it to cut a small marginal ‘in-and-out’ 
channel round its edge. 
A second, and much greater intake, Tranmire Slack, comes 
directly through the plateau from the north-west; and a third, 
Moses Slack, of lesser size. from the north. ‘These two latter 
originated as mere gutters to carry water flowing directly off the 
ice itself. Their arrangement and disposition is what I have 
generally found in cases where the ice came quite on to, or over- 
rode, the watershed. 
We may now consider the series of channels carrying the water 
through to Tranmire Slack, first describing those of the Moorsholm 
area. Hardale Slack seems to have been a channel formed during 
or near the maximum extension of the ice, for the marginal 
drainage of the country from Danby Peat-Holes eastward. There 
is a fine gravelly moraine, which extends from Great Dinnond 
through Little Dinnond, Middle Rigg, and Good-Goose Thorn. 
Flow seems to have taken place Alone ite outside of this moraine, 
and there is a more or less defined channel all through. It is best 
seen at Good-Goose Thorn, where its position is marked upon the 
6-inch maps by two ponds. At the upper end it lies between 725 
and 750 feet, but to the eastward the 725-foot contour is cut com- 
pletely through. 
A slight retreat of the ice-front opened another series of channels 
in this region. Three small marginal channels cut across a spur 
of the hill marked ‘ Water Dittins (B.8.)’, above the 700-foot 
contour, and open into a valley of the same name. ‘The line of flow 
