"For the remainder of the southern area the evidence is plain that there has been no considerable subsidence during glacial times. The presence over large areas of chalk country of the 'clay with flints'--a deposit produced by the gradual solution of the chalk and the accumulation in situ of its insoluble residue--is absolute demonstration that for immense periods of time the country has been exempt from any considerable aqueous action. The enormous accumulations of china clay upon the granite bosses of Cornwall and Devon tell the same tale. A few erratics have been found at low levels at various points on the southern coasts, usually not above the reach of the waves. These consist of rocks which may have been floated by shore-ice from the Channel Islands or the French coast. "This imperfect survey of the evidence against the supposed submergence has been rendered the more difficult by the fact that it is not considered necessary to produce the evidence of marine shells in all cases. Indeed, it has been argued that post-Tertiary beds covering thousands of square miles might be absolutely destitute of shells without prejudice to the theory of their formation in the sea. "But such a suggestion, one would think, could hardly come from anyone familiar with marine Tertiary deposits, or even with the appearance of modern sea-beaches. Admitting, however, for the purposes of argument, that the beaches along a great extent of coast might be devoid of shells, it cannot be argued that the deep waters were destitute of life; and hence the boulder-clays, if of marine origin, should contain a great abundance of shells and other remains, and, once entombed, it is beyond belief that they could all be removed from such a deposit in the short lapse of post-glacial time. "Now, some of the boulder-clays--as, for example, those of Lancashire and Cheshire--are held to be of marine origin, and this is indeed a vital necessity to the submergence theory; for, if these are not marine deposits, neither are the other shelly deposits; but these boulder-clays are absolutely indistinguishable from those lying within the hill-centres, and, as it passes belief that such deposits could be of diverse origin and yet possess an identical structure and arrangement, then we should have a right to demand that these clays should have enclosed shells and should still contain them, but they do not.