506 MR. P. F. KENDALL ON A SYSTEM OF [Aug. Igo2, 
Murk Esk and Eller Beck. ‘These channels all indicated a flow 
towards Fen Bogs. Details, with the field-observations, will be given 
later. The distribution of the Drift furnished equally clear evidence 
of the ice-invasion which would produce such a series of barriers. 
Boulder-Clay and other Glacial accumulations extend completely 
across the Northern Cleveland watershed from Whitby westward to. 
Stonegate; and they not only extend far up the Valley of the Esk 
itself to Lealholm, but also follow closely the boundary that might 
be assigned, solely on the evidence of the overflow-channels, to the 
ice in the valley of the Murk Esk. Indeed the precision with which, 
upon this evidence alone, I have been able to delimit the ice-margin 
convinces me that, in lake-overflows, we have a means of defining 
Glacial boundaries of the greatest value. 
At the maximum extension of the ice, the Northern Cleveland 
watershed, as I have stated, was completely overridden as far west as 
the Stonegate Valley; but the lobate ice-margin appears never to have 
crossed Lealholm Rigg, or at least to have left no clear trace either 
as overflow, moraine, or any very definite Drift-deposit, though, in 
the village of Lealholm at 625 feet, clay with foreign stones is 
exposed, and scattered pebbles occur above the 700-foot contour. 
An ice-lobe must have ascended Eskdale for a mile above the 
village of Lealholm, and laid down a moraine extending quite across 
the valley, obliterating the old course of the Esk. 
This moraine has been cut through by the railway at its lowest 
point, and consists apparently of stony Boulder-Clay with fragmentary 
shells, but without admixture of sand or gravel. On the southern 
side of Eskdale, much Drift is observable up to altitudes of about 
700 feet ; but no recognizable moraine which could be referred to 
this stage is to be seen until Glaisdale is reached, where a great 
ridge of Drift extends across the valley with a minimum altitude 
of 450 feet, and a height above the valley which it obstructs of 
over 100 feet. In similar relation to the main valley is another 
morainic barrier across the Butler-Beck (Egton-Grange) valley. 
The continuation of the line of maximum extension is much 
more definitely indicated from this moraine (which may not 
represent the extreme limit of the ice, and on the other hand 
may represent a later phase when the ice-front extended in a more 
westerly direction though not at so great an altitude) onward by a 
splendid series of overflow-channels. The first of these is a great 
trench deepening and falling towards the south, which cuts across 
the edge of Murk-Mire Moor. The sill of the intake is at an 
altitude of 714 or 715 feet (Ordnance Survey B.M.), and it extends 
for a distance of 14 miles as a deep groove of characteristic section, 
filled with moss and swamp so as to be impassable in the winter, 
when alone I have seen it. 
After this stretch of complete trough, the channel is continued for 
another mile to Hazel Head by a marginal channel, which for the 
greater part of the distance is a mere shelf lacking an iceward 
retaining-wall, but in some parts that function is performed by some 
gravel-mounds. This shelf runs out, and disappears near the 
