Vol. 58.] GLACIER-LAKES IN THE CLEVELAND HILLS. 497 
The characteristic erratics of the western series occur throughout 
the Vale of York, and in particular the Shap Granite is found from 
side to side of the Vale, and even, on the western edge, to within 
2 or 3 miles of the outermost lateral moraine, as at Lindrick Farm 
near Ripon. 
The northern group of erratics was brought by an ice-movement, 
which may for present purposes be regarded as having originated 
in the Tweed Valley. The ice generated in the head of that 
valley appears to have flowed without hindrance as far as the 
neighbourhood of Coldstream, where, at one stage, instead of 
pursuing its direct course down to the sea at Berwick, it turned 
sharply round the projecting end of the Cheviots through an angle 
of about 140°, and took a course almost directly southward,’ 
What the constraining agent was, which bent a great glacier 20 
miles wide through so rapid a turn, 1s not quite so clear as in the 
case of the Teesdale Glacier. When we observe, however, the way in 
which the whole of the Eastern Scottish glaciers suffer deflection, 
either northward or southward, as they approach the coast-line, it 
seems impossible to resist the conclusion pressed upon us with such 
skill and force by the late Dr. Croll and Prof. James Geikie, that it 
was the overmastering influence of a Scandinavian ice-sheet filling 
the North Sea, and bearing down upon the whole coast-line of 
Britain, from Norfolk to Caithness. The Tweeddale ice was un- 
doubtedly driven to the southward over the seaward portion of 
Northumberland, and, to judge by the great profusion of the 
-porphyrites among the Yorkshire erratics, and the large proportion 
which they bear to the other erratics in certain deposits and in 
particular districts, I think it highly probable that the ice which 
swept the belt of porphyrite-lavas fringing the Cheviots, did actually 
invade the Cleveland Hills and much of the coast-line farther 
south. The Cheviot porphyrites form a notable element in the 
Drift as far westward at least as Scarth Nick, near Ingleby 
Arnecliffe, and I am disposed to regard them as the natural 
associates of the fragmentary marine shells, with the distribution 
of which theirs very closely agrees.” 
It appears to me not improbable that the T'weed-Cheviot ice 
passed off the land on to the bed of the North Sea somewhere. 
between the mouth of the Coquet and that of the Tyne, and that 
it re-invaded the land, under pressure from the east, somewhere 
about Roker, or perhaps a little to the northward of that place. 
The striations at Roker clearly indicate a movement in from 
seaward, and at several places on that coast worn flints have been 
found in the Drift.* I have found them abundantly myself at 
West Hartlepool, and I think that they must have come from the 
sea-floor. 
1 P. F. Kendall & H. B. Muff, Geol. Mag. 1901, p. 513. 
* For many important facts regarding the distribution of these rocks, see 
J. W. Stather, Geol. Mag. 190], p. 17. 
3 R. Howse, Trans. N. of Engl. Inst. Min. Eng. vol. xiii (1863-64) p. 178. 
