566 MR. P. F. KENDALL ON A SYSTEM OF [ Aug. 1902, 
The striations on the coastal tract may probably be referred to 
this period ; and, as Mr. Stather points out in his description of the 
Sands-End strie, they form a consistent series indicating a prac- 
tically continuous route. The striz at Roker may mark the emer- 
gence of the ice from the sea-bed. 
The recession of the Cheviot ice took place in a very singular 
fashion. It appears to have withdrawn from the coastline in 
regular order from south to north, as the Scandinavian and British 
ice-sheets shrank back towards their sources; and thus one after 
another the British river-mouths were freed from obstruction and — 
resumed their normal drainage. But in this shrinkage one most 
noteworthy irregularity is very clearly indicated. After the 
almost complete disengagement of the ice from the mouth of 
the Esk near Whitby, a great lobe still traversed the northern 
watershed and reached the moraine near Lealholm. It must 
have crossed the hills with a somewhat westerly tendency, in order 
to have reached so far up the Valley of the Esk. To this stage 
we may conceivably refer the abandonment of the Tranmire over- 
flow, the reversal of drainage across the spur at Stanghow, and 
the diversion of Boosbeck through the gorge at Slapewath. This 
last diversion is interesting, as it throws an important light upon 
the condition of the country to the westward. The ice-front must 
have stood across the Boosbeck Valley until the Slapewath gorge 
was lowered below the level of the Drift-barrier across Boosbeck, 
that is to say, below 425 feet O.D. From this clue it is possible to 
define some of the further course of the stream; and consequently 
of the ice-front. 
It will be remembered that the overflow-channel into Eskdale by 
way of Kildale is at an altitude of 580 feet; therefore it is quite 
certain that there must have been a line of drainage open into the 
Vale of York. I infer from this that the Teesdale Glacier had 
already withdrawn behind the Magnesian-Limestone escarpment 
of the Tees Valley. 
The last trace of the Cheviot ice-stream to be found in Yorkshire 
is perhaps the line of the Drift-hills which fringe the southern bank 
of the Tees. I do not press this explanation, as I can still perceive 
difficulties in the way of its acceptance ; at the same time, I can see 
no other way of explaining the presence of this ridge of Drift and 
the behaviour of the little River Wiske, which flows northward from 
the Cleveland escarpment to within 14 miles of the Tees, then turns 
southward and joins the Swale. 
X. Tue Spa-Ovrcet or THE LAxKzs. 
One problem remains to be considered, the question of the route 
by which the waters of Lake Pickering ultimately reached the sea. 
There is twofold proof that, while yet the ice-sheet was standing 
against the coast of Yorkshire as far as Flamborough Head, the outlet 
of Lake Pickering had been cut down to 130 feet O.D. The moraine 
across the seaward end has an altitude at its lowest point of only 
