"The sea leaves other traces also, besides shells, of its presence in districts that have really been submerged, yet there are no signs whatever to be found of them in all England, except the _post_-glacial raised beaches. Furthermore, in all the area occupied by glacial deposits there are no true sea-beaches, no cliffs nor sea-worn caves, no barnacle-encrusted rocks, nor rocks bored by Pholas or Saxicava. Are we to believe that these never existed; or that, having existed, they have been obliterated by subsequent denudations? To make good the former proposition, it would be necessary as a preliminary to show that the movement of subsidence and re-elevation was so rapid, and the interval between so brief, that no time was allowed for any marine erosion to take place. If this were so, it would be the most stupendous catastrophe of which we have any geological record; but we are not left in doubt regarding the duration of the submerged condition, for the occurrence of forty feet of gravel upon the summits of the hills indicates plainly that, if they were accumulated by the sea, the land must have stood at that level for a very long period, amply sufficient for the formation of a well-marked coast-line. "The alternative proposition, that post-glacial denudation had removed the traces of subsidence, is equally at variance with the evidence. Post-glacial denudation has left kames and drumlins, and all the other forms of glacial deposits, in almost perfect integrity; the small kettle-holes are not yet filled up; and it is therefore quite out of the question that the far more enduring features, such as sea-cliffs, shore platforms, and beaches, should have been destroyed. "The only reasonable conclusion is, that these evidences of marine action never existed, because the land in glacial times was never depressed below its present level. If the level were different at all (as I think may have been the case on the western side of England), it was higher, and not lower. "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.