“The details of the submergence hypothesis have, so far as I am aware, never been dealt with by its advocates, otherwise I cannot but think that it would have been abandoned long since. It has been stated in general terms that the subsidence was greatest in the north and diminished to zero in the south, but no attempt was made to trace the evidence of extreme subsidence across country and along the principal hill-ranges—in fact, to see how it varied in every direction.
“If we take a traverse of England, say from Flamborough Head upon the east to Moel Tryfaen on the west, and accept as evidence of submergence any true glacial deposits (except, as in the case of the interior of Wales, the deposits are obviously the effects of purely local glaciers and contain, therefore, no shells), we shall find that the subsidence, if any, must have been not simply differential but sporadic.
Fig. 47.—Section of the cliff on the east side of South Sea Landing, Flamborough Head. Scale, 120 feet to 1 inch; length of section 290 yards; average height, 125 feet. (See above map of moraine between Speeton and Flamborough.)
Explanation.—4. Brownish boulder-clay, a band of pebbles; 4a, in places about seven feet from top. 3. Washed gravel, with thin sand-seams, well-bedded, pebbles chiefly erratics. 2. “Basement” boulder-clay, with many included patches of sand, gravel, and silt; 2a, at B, one of these 2b contain shells. 1b. Sand and silt, overlying and in places interbedded with 1. 1. Rubble of angular and subangular chalk-blocks and gravel, with occasional erratic, passes partly into chalky boulder-clay, 1a. x. White chalk, without flints, surface much shaken.
“At Flamborough Head shelly drift attains an altitude of 400 feet, but half a mile from the coast the country is practically driftless even at lower levels. The Yorkshire Wolds were not submerged. On the western flanks of the wolds drift comes in at about 100 to 150 feet, and persists, probably, under the post-glacial warp, from which it again protrudes on the western side of the valley of the Ouse, and however the drift between there and the Pennine water-shed may be interpreted, it shows not a sign of marine origin; but, even granting that it did, we find that it does not reach within a thousand feet of the water-shed. When the water-shed is crossed, however, abundant glacial deposits are met with which are not to be differentiated from others at slightly lower levels which contain shells.
Fig. 48.—Enlarged section of the shelly sand and surrounding clay at B in preceding figure. Scale, 4 feet to 1 inch.
Explanation.—2. “Basement” boulder-clay. 2a. Pure compact blue and brown clay of aqueous origin, bedding contorted and nearly obliterated, but the mass is cut up by shearing planes. 2b. Irregular seam, and scattered streaks, of greenish-yellow sand with many marine shells. 2c. Patch of pale-yellow sand, different from 2b, without trace of fossils.
“If we suppose that the line of our traverse crosses the Pennine Chain at Heald Moor, we shall find that on the eastern side no traces of drift occur above about 300 feet; while the very summit of the water-shed is occupied by boulder-clay, and thence downward the trace is practically continuous, and at about 1,000 feet and downward the drift contains marine shells. Across the great plain of Lancashire and Cheshire the ‘marine’ drift is fully developed—though it may be remarked in parentheses that it contains a shallow-water fauna, albeit ex hypothesi deposited, in part at least, in a depth of 200 fathoms of water—and to the Welsh border at Frondeg, where it again reaches a water-shed at an altitude of 1,450 feet; but at 100 yards to the westward of the summit all traces of subsidence disappear, and through the centre of Wales no sign is visible; then we emerge on the western slopes at Moel Tryfaen, and they assume their fullest dimensions, though only to finish abruptly on the hill-top, and put in no appearance in the lower grounds which extend from there to the sea.