Those grey bosses of rock that rise out of Loch Maree and form the base and outworks of Slioch are portions of the very oldest known land-surface of Europe, as incalculably more ancient than the rest of the Highlands, as the Highlands in turn are more ancient than the Alps or the Apennines. Their heights and hollows existed before the red sandstones were laid down. To this day, you can walk along the shore-line of the vanished lake or sea in which these sandstones accumulated, and can mark how hill after hill, and valley after valley, sank under its waters, and were buried beneath its quietly gathering sand and shingle. That primeval land-surface, slowly settling down, came at last to lie under several thousand feet of such sediment. Long subsequently, after the sand, hardened into sandstone and the gravel, consolidated into conglomerate, had been partially raised out of water, came the time when the white rock of Ben Eay and Craig Roy gathered as fine white sand on the sea-bottom. Some beds of this compacted sand are filled with millions of the burrows of sea-worms that lived in it, and higher up come bands of shale and limestone containing here and there trilobites, shells, corals, sponges and other organisms belonging to an age anterior to that of even the very oldest fossiliferous rocks of most of the rest of Britain. These sheets of marine sediment point to a period when there were no hills in north-west Scotland, for the primeval heights still lay deeply buried, and a shoreless sea spread far and wide over the region. At length after a vast interval of time came an epoch of gigantic terrestial disturbance, when north-western Europe, from the North Cape to the south of Ireland, was convulsed; when the solid crust of the earth was folded, crumpled, and fractured, until its shattered rocks, crushed and kneaded together, acquired the crystalline characters which they now display. In the course of these tremendous displacements (to which there is no parallel in the later geological history of this country) huge slices of the earth's crust, many hundreds of feet thick and many miles long, were wrenched asunder and pushed bodily westwards, sometimes for a distance of ten miles. By this means portions of the oldest rocks of the region were torn off and planted on the top of the youngest. The whole country, thus broken up, underwent many subsequent mutations, and was finally left to be gradually worn down by the various agents that have carved the surface of the land into its present shape.