I have taken the series of drift deposits seen in Britain and in Canada as typical, and the previous discussion has had reference to them. But it would be unfair not to inform the reader that this succession of deposits after all belongs to the margins of our continents rather then to their great central areas. This is the case at least in North America, where in the region of the great lakes the oldest glaciated surfaces are overlaid by thick beds of stratified clay, without marine fossils, and often without either stones or boulders, though these sometimes occur, especially toward the north. The clay, however, contains drifted fragments of coniferous trees. Above this clay are sand and gravel, and the principal deposit of travelled stones and boulders rests on these. I cannot affirm that a similar succession occurs on the great inland plains of Europe and Asia: but I think it probable that to some extent it does. The explanation of this inland drift by the advocates of a great continental glacier is as follows: (1) In the Pliocene period the continents were higher then at present, and many deep valleys, since filled up, were cut in them. (2) In the Post-pliocene these elevated continents became covered with ice, by the movement of which the valleys were deepened and the surfaces striated. (3) This ice-period was followed by a depression and submergence, in which the clays were deposited, filling up old channels, and much changing the levels of the land. Lastly, as the land rose again from this submergence, sand and gravel were deposited, and boulders scattered over the surface by floating ice. The advocates of floating ice as distinguished from a continental glacier, merely dispense with the latter, and affirm that the striation under the clay, as well as that connected with the later boulders, is the effect of floating bergs. The occurrence of so much drift wood in the clay favours their view, as it is more likely that there would be islands clothed with trees in the sea, then that these should exist immediately after the country had been mantled in ice. The want of marine shells is a difficulty in either view, but may be accounted for by the rapid deposition of the clay and the slow spreading of marine animals over a submerged continent under unfavourable conditions of climate. In any case the reader will please observe that theorists must account for both the interior and marginal forms of these deposits. Let us tabulate the facts and the modes of accounting for them.