Looking across the Minch we see Skye and the mountains of the north-west Highlands, and those regions, as we know, have also been subjected to extreme glaciation. From the appearances presented by the mountains of Ross-shire we are compelled to believe that all that region was buried in ice up to a height of not less than 3000 feet--the ice-sheet was probably even as much as 3500 feet in thickness. The evidence shows that the under portion of this vast ice-sheet flowed slowly off the country into the Minch by way of the great sea-lochs. Thus we know that an enormous mass crept down Loch Carron and united with another great stream stealing out from the mountains of Skye, to flow north through the hollows of Raasay Sound and the Inner Sound into the Minch. So deep was the ice that it completely smothered the island of Raasay (1272 feet high) and overflowed all the lofty trappean table-lands of Skye. From the Coolins, as a centre-point, another movement of the ice-sheet was towards the south-west, against the islands of Rum, Cannay, and Eigg. Further north similar vast masses of ice streamed out into the Minch, from Loch Torridon, Gairloch, Loch Ewe, and Loch Broom. The direction of the glaciation in the north of Skye, which is towards north-west, shows that the glacier-mass which overflowed that area must eventually have reached the shores of the Long Island. In short, there cannot be a reasonable doubt that the immense sheet of ice that streamed off the north-west Highlands must have filled up entirely the basin of the Minch, and thereafter streamed across the Outer Hebrides. But it may be objected that if the Outer Hebrides were overflowed by ice that streamed from the mainland across the north end of Skye, we ought to get many fragments of Skye rocks and Ross-shire rocks too in the sub-glacial débris or till of Lewis and Harris, and the north end of North Uist. But all such fragments are apparently wanting. True, there are bits of stone like the igneous rocks of Skye often met with in the Hebridean till, but as veins or dykes of precisely the same kind of rock occur in the Long Island itself, we cannot say that the stones referred to are other than native. A little reflection will show us, however, that it is extremely improbable indeed that stones derived from Skye and the mainland should ever have been dragged on under the ice, and deposited amongst the till of the Long Island. There is only one part of the whole Outer Hebrides where we might have anticipated that fragments from the mainland should occur; and there, sure enough, they put in an appearance.