560 MR. P. F. KENDALL ON A SYSTEM OF [ Aug. 19025 
objections, still remaining. I ought, however, to remark that there 
are several facts which might be interpreted as evidence of an uplift 
of the Yorkshire coast since Glacial times, and one which might be 
regarded as evidence of a differential movement. Dr. W. Y. Veitch’ 
has described a raised beach at Cat Nab, near Saltburn, and his obser- _ 
vations are confirmed by Mr. Barrow.” The beach is clearly post- 
Glacial, and is about 30 feet above sea-level. Mr. Lamplugh has 
‘described a band of shell-silt in the Speeton cliffs containing 
estuarine molluscs, as, for example, Cardiwm edule and Scrobicularia 
ptperata, with the paired valves in apposition and the siphonal ends 
upward. They occur at an altitude of about 80 feet above sea-level. 
Lastly, I may mention that, whereas at Barnby Dun borings 
indicate the rock-floor to be at least 170 feet below Ordnance- 
datum, yet none of the borings made in the bed of the Humber or 
in Holderness struck a hollow of sufficient depth to afford an outlet 
to such a valley. A boring on Reeds Island made by Mr. Villiers 
(of Beverley) in 1888, found rock at a depth of 95 feet from the 
surface, or about 85 feet below Ordnance-datum. If the evidence 
regarding the Humber were complete enough to justify the 
assertion that no such hollow or channel existed, then it might 
be allowable, or even necessary, to attribute the discrepancy 
between the levels of the Barnby-Dun Valley and its seaward outlet 
to a differential movement and uplift along the coastline. 
I mention these facts so as to assure critics of my views that 
the alternatives have been considered. 
The persistent westerly ‘aberration’ of the debouchure of the 
valleys points to the operation of some constraining agent which is 
no longer present ; and when the deserted high-level channels which 
linked these valleys together are reviewed, and found to indicate a 
similar persistent tendency, the constraining agent seems to be 
clearly indicated—ice in the form of a glacier-lobe would produce 
this effect. Upon this hypothesis, the edge of the great ice-sheet 
(which I have traced by its morainic deposits on Seamer Moor) 
passed farther inland, where it encountered the feeble opposition of 
the range of heights to the south of Scarborough, and so was enabled 
to thrust its way up the Vale of Pickering to, and a little beyond, 
Wykeham. The phase of maximum extension is, on this view, 
indicated approximately by the gravel-patch on Gallows Hill. 
After a very brief sojourn at this extreme extension, a protracted 
halt took place about Wykeham, and I regard the great gravel-mass 
there as the terminal moraine of this ice-lobe. Under the con- 
ditions now set up, we may suppose the Forge-Valley overflow to 
have come into operation, and a vast quantity of water from the 
extensive area of land and ice to have come down the incipient 
valley. 
This stream would bring over a few erratics, along with immense 
quantities of gravel and stones obtained from the denudation of the 
gorge ; and these materials, mingled with lateral moraine, would be 
1 Proc. Yorks. Geol. & Polyt. Soc. n. 8. vol. viii (1883) ». 221. 
* Mem. Geol. Surv. ‘ North Cleveland ’ 1888, p. 71. 
