Suppose the bed of the Firth of Forth were raised above the level of the sea and covered over with verdure, and that, in ignorance of the previous topography of the locality, a mason were to excavate on the lately-born land the foundation for a dwelling-house. Immediately below the grass he would com? upon layers of hardened mud containing oyster-beds, with detached valves of cockles, mussels, fish-bones, and perhaps the tooth of an anchor or the timber of some old herring-boat. Now, if he were gifted with but ordinary intelligence, what would he at once conclude from these remains? Plainly, that the spot on which he stood had once been the bed of the sea. And if in place of appearing as dry mud and sand these deposits had got hardened into shale and sandstone, and the shells, too, had become hard and stony, this would not alter his convictions. He would still assert positively that he stood upon an old sea-bottom. And suppose further, that all this were far away from any sea, still such a circumstance could make no change in his opinion; he would rightly assert that the place of sea and land might vary, and that the ocean's being now many miles distant could be no argument against the waves having once rolled over the site of the intended dwelling-house. Let us further imagine that he continues his trench, and in sinking deeper comes to a bed of dark peat with snail-shells and bones of sheep, deer, and oxen. What will he infer from these? Clearly that they represent an old land-surface, once covered with vegetation and browsed over by ruminant animals, and that this old land-surface has at some distant period been submerged beneath the sea. Suppose, moreover, that below the peat there were a thin bed of reeds and rushes intermingled with the mouldering remains of fresh-water shells. He would in that case infer that before the formation of the peat the locality was occupied by a lake. Putting now all these deductions together, our mason would have evolved a very interesting history. He would have ascertained that in a bygone age the spot on which he stood was the site of a lake, tenanted by delicate shells and fringed with reeds and rushes, where the coot and the mallard may have reared their young; that in process of time the vegetation gained upon the water, choking up the lake, so as gradually to form a soil firm enough to support sheep, deer, and oxen, and yielding shady coverts whither the antlered stag could retire and lay him down to die; that in after years the sea had encroached upon the peat-moss, and oyster-beds begun to form where cattle had been wont to browse; that again the ocean receded, and the land emerged to assume new verdure and receive new inhabitants.