"The second case is more striking. The announcement was made that shells had been found on a hill called Gloppa near Oswestry, in Shropshire, and, as it lay about five miles to the westward of Mackintosh's boundary of the Irish Sea Glacier, and therefore well within the area of exclusively Welsh boulders, it furnished an excellent opportunity of putting the theory to the test. An examination of the boulders associated with the shells showed that the whole suite of Galloway and Cumbrian erratics such as belong to the Irish Sea Glacier were present in great abundance. Not only this, but in the midst of the series of shell-bearing gravels I observed a thin lenticular bed of greenish clay, which upon examination was found to be crowded with well-scratched specimens of Welsh rocks; but neither a morsel of shell nor a single pebble of a foreign rock could be found, either by a careful examination in the field or by washing the clay at home, and examining with a lens the sand and stones separated out. "The fact that predictions such as these have been verified affords a very striking corroboration of the theory put forward; and, though shells cannot be found in every deposit in which they might, _ex hypothesi_, be found, yet the strict limitation of them to situations which conform to those assigned upon theoretical grounds cannot be ascribed to mere coincidence. If the land had ever been submerged during any part of the Glacial epoch to a depth of 1,400 feet, it is inconceivable that clear and indisputable evidence should not be found in abundance in the sheltered valleys of the Lake District and Wales, which would have been deep, quiet fiords, in which vast colonies of marine creatures would have found harbour, as they do in the deep lochs of Scotland to-day. "It has been urged, in explanation of this absence of marine remains in the great hill-centres, that the 'second glaciation' might have destroyed them; but to do this would require that the ice should make a clean and complete sweep of all the loose deposits both in the hollows of the valleys and on the hill-sides, and further that it should destroy all the shells and all the foreign stones which floated in during the submergence. At the same time we should have to suppose that the drift which lay in the paths of the great glaciers was not subjected to any interference whatever. But, assuming that these difficulties were explained, there would still remain the fact that the valleys which have never been glaciated--as, for example, those of Derbyshire--show no signs whatever of any marine deposits, nor of marine action in any form whatever.