Voly 58. | GLACIER-LAKES IN THH CLEVELAND HILLS, 53) 
(6) Iburndale. 
This valley is deep and rather narrow, forming a V both in plan 
and section. It opens northward into Eskdale at Sleights, and is 
separated from the Murk-Esk Valley on the west by Sleights Moor, 
a broad tract of Lower Estuarine grit, which forms a steep escarp- 
ment on the west, north, and east. ‘This constitutes a watershed 
nowhere falling below 800 feet. On the east, Iburndale is enclosed 
by the high moorlands (of the same grit) of Ugglebarnby and 
Sneaton, which attain an elevation of 700 feet quite near to 
Eskdale; and this altitude, or a still greater one, is maintained 
nearly to the head of the valley. 
Drift-deposits of great thickness occur in the floor of the valley, 
and te a considerable height up its sides. My observations inclined 
me at one time to the belief that no portion of the valley south of 
New May Beck had been invaded by ice, but that opinion has given 
way before an accumulation of facts, which I think cannot be satis- 
factorily explained without such an extension. 
The position of this valley, opening due northward towards the 
invading ice, was selected by me at the outset of this enquiry for 
the eaperimentum crucis. If the obstruction of an ice-barrier 
produced a Jake at Goathland, then [burndale should similarly show 
signs of a lake and overflow. 
The preliminary examination of contoured maps, which has always 
constituted the first reconnaissance in this survey, proved the presence 
of a very suggestive gap in the eastern wall of the valley near its 
head. ‘The field-observations demonstrated in the clearest manner 
its character as that of a lake-overflow. (See map, Pl. X XVI.) 
The intake is an abrupt notch on the lakeward side. It cuts the 
675-foot contour, but the 625-foot contour is not at all indented, 
and the 650 is but little affected, while a deep, thickly peat-filled 
valley, Biller-Howe Dale, of characteristic section, extends eastward 
into the Jugger-Howe-Beck drainage, which constitutes the true 
source of the River Derwent. Other characteristics of this valley 
will be mentioned later. 
Sneaton Moor is a long, gently curved crescent of high ground 
presenting a concavity to the northward. At the maximum exten- 
sion of the ice, this watershed was completely overriden, and the 
ice extended forward to the Iburndale overflow. In the stage of 
retreat, the watershed was trenched by two well-marked lake-over- 
flows, both now streamless where they cross the watershed, and 
containing a considerable depth of peat. A bench-mark at the 
intake of one, Nigh-Middle Slack, indicates a level of 676-9 feet, 
while the other is considerably above 675 feet, though below 700. 
The watershed here is of exceedingly soft muddy shales of the Lower 
Estuarine Series, with a few scattered Drift-pebbles; and I infer 
that no considerable body of water can have drained across, or the 
channels would have been cut more deeply in such easily-eroded 
materials. 
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