Vol. 58.] GLACIER-LAKES IN THE CLEVELAND HILLS. 493 
on High Moor near Peak at 850 feet, and I have found in the 
same district a thin deposit of gravel at Green Dike at 825 feet, 
which yielded pebbles of granite, quartz-porphyry, porphyrite, and 
flint. I do not think that in all cases these scattered pebbles can 
be accepted as evidence of a wider extension of actual Drift-deposits. 
Still less do I consider that it would be safe to infer that they 
necessarily imply the invasion of the area by ice to so great an 
altitude. 
Along the strip of country from Robin Hood’s Bay to Seamer, the 
maximum altitude reached by the Drift falls from about 700 feet at 
Gate Hills, and 825 near Pye Rigg, to 600 feet on Scarborough 
Racecourse ; but the general level between the two points declines 
fairly steadily from 700 down to about 400 feet. Some authors 
have experienced a difficulty in understanding how deposits laid 
down along the edge of a sheet of land-ice should show such varia- 
tions as these, but it should be observed that higher grounds upon 
which such deposits could be laid do not exist continuously along a 
line connecting the two extreme points. At the southern end, it is 
noticeable that the Drift simply touches the front of the moor, and 
does not extend down its gentle westerly slope. Along this strip of 
seaboard, the Dritt, except for a small patch in the bottom of the 
valley near Hackness, nowhere extends more than 4 miles from 
the coast, and the hill-country within is quite destitute of Drift. 
Drift-deposits in the Vale of Pickering do not attain a greater 
altitude than about 350 feet. The patches of gravel and of Boulder- 
Clay at the western end of the Vale are worthy of a more extended 
study than I could devote to them; but Mr. Fox-Strangways records 
that the patch of Boulder-Clay near Thornton Dale contains local 
rocks exclusively, and I have recently examined two areas mapped 
as Boulder-Clay near Helmsley, at the Acres and at Sprotten 
respectively, and such scanty traces as I could find yielded local 
rocks solely. 
The Drift-deposits along the escarpments overlooking the Vale of 
York, though outside the area dealt with in this communication, 
may nevertheless be mentioned, as they have an important bearing 
upon the mode of origin of the Glacial deposits and features herein 
to be described. 
Mr. Fox-Strangways says,} 
‘Taken as a whole, the Glacial deposits never rise much above the 600-foot 
contour-line, and only attain this elevation along the northern escarpment of 
the Oolites; in the south they are not usually more than 400 feet above sea- 
level, except at Oulston, where the gravels rise to nearly the 500-foot contour. 
The Drift extends for a long distance to the southward, and, 
excluding some small patches marked as Boulder-Clay and gravel 
along the edge of the hills, it may be said to terminate in the two 
splendid moraines at York and Escrick respectively.2, The summit- 
1 Mem. Geol. Sury. ‘ Northallerton & Thirsk’ 1886, p. 53. 
* Carvill Lewis, Rep. Brit. Assoc. 1887 (Manchester) p. 692, & ‘ Glac. Geol. of 
Gt. Britain & Ireland’ 1894, p. 188; P. F. Kendall, Proc. Yorks. Geol. & 
Polyt. Soc. n. s. vol. xii (1893) p. 306. 
