488 MR. P, F, KENDALL ON A SYSTEM OF [Aug. 1902, © 
thickens again to the southward with a falling surface, it is clear 
that an old watershed extends across the valley. 
In the neighbourhood of York, the Drift has in many places been 
proved to rest upon a rock-floor about 50 feet below sea-level : 
southward it descends lower still, namely, to 74 feet at Cawood, 
and in a boring at Barnby Dun, near Doncaster, I saw Drift-clay 
being brought up from a depth of about 170 feet below Ordnance- 
datum.’ 
In the Vale of Pickering, according to Mr. Fox-Strangways,” the 
superficial deposits reach a thickness of 107 feet, and 
‘if the superficial deposits were removed, the sea would again enter this. 
valley to beyond Malton.’ (Loc. cit. footnote.) 
The foregoing facts, especially those regarding the country about 
York and the Vale of Pickering, show that in pre-Glacial times the 
land must have stood very much above its present level, the 
Barnby-Dun boring indicating a minimum of probably 170 feet ; 
but there is a most perplexing complication introduced by the 
evidence obtainable in Holderness, to which I purpose reverting 
on some future occasion. 
The researches of Mr. Lamplugh have shown that the ancient 
coastline south of Flamborough Head swept in behind (that is, west 
and south-west of) Bridlington, and he has admirably described the 
contents of an old sea-beach, clearly of pre-Glacial age, as it is. 
covered by the oldest Glacial deposits of the district, which lies at the. 
foot of a buried seaworn cliff at Sewerby. This cliff can be traced 
by borings and other excavations round to the Humber at Hessle ; 
and the whole district of Holderness consists of Glacial deposits. 
resting upon an old plain of marine denudation extending out from 
the foot of the cliff. The beach is practically at the level of the 
existing beach.® What relation in time this level of the land 
bore to the period of elevation, when the deep valleys were excavated, 
it is not easy to ascertain: but the Sewerby-beach stage seems to 
have been a long one, judging by the magnitude of the denuded 
floor under Holderness. The excavation of the broad Vale of 
York must also have been a very slow operation. 
No marine or estuarine fossils have been discovered in the super- 
ficial deposits of eitherthe Vale of York or that of Pickering, but 
near Speeton an estuarine deposit of pre-Glacial or early Glacial age 
occurs at an altitude of 90 feet above sea-level.* This, however, is 
outside the Vale of Pickering, or at least on the seaward face of the 
Chalk-escarpment which swings round out of the Vale. Moreover, 
if its present position is due to any general earth-movement, and 
1 I have prepared a map showing the depth of the rock-floor from Seaton 
Carew to Barnby Dun, which will be published in the Proceedings of the Yorks. 
Geological & Polytechnic Society. 
2 Mem. Geol Surv. ‘ Jurassic Rocks of Britain ’ vol. i (1892) p. 432. 
3 The maximum difference of level does not exceed 5 feet. See G. W. 
Lamplugh, etc.‘ Report on an Ancient Sea-beach’ Rep. Brit. Assoc. 1888 (Bath) 
. 336. 
PS See G. W. Lamplugh, ‘ Drifts of Flamborough Head’ Quart. Journ. Geol. 
Soe. vol. xlvii (1891) p. 384, 
“a 
