We can easily picture to ourselves the appearance which the British Islands would thus at different periods present. At one time, nearly the whole of England would be under water, with, however, a few islands representing the higher peaks of Cornwall; others scattered over the site of the West Riding of Yorkshire; and a hilly tract of land over what is now Wales. Scotland must have existed in a sorely mutilated state. A thick-set archipelago would represent the Cheviot Hills, and the country south of the Forth and the Clyde; north of which there would intervene a broad strait, with a comparatively large area of undulating land beyond, stretching across what is now the area of the Grampian Hills. A narrow fiord would run along the site of the Caledonian Canal, cutting the country into two parts, and running far into it on either side as deep lochs and bays. I have had such a condition of things vividly recalled when on the summit of a lofty hill in early morning, while the mists were still floating over the lower grounds, and only the higher hill-tops, like so many islands, rose above the sea of cloud. It was not a little interesting to cast the eye athwart this changing scene, and mark how each well-known peak and eminence looked when deprived of its broad sweep of base. What before had always seemed an abrupt precipitous summit, now took the form of a lonely rock or deep-sea stack, that might have served as a haunt for the gull and the gannet. The long swelling hill rose above the mist as a low undulating island, treeless and barren. It was easy to think of that wide expanse of mist as the veritable domain of ocean, to picture the time when these were veritable islands lashed by the surge, and to conjure up visions of ice-floes drifting through the narrows, or stranding on the rocks, amid a scene of wide-spread nakedness and desolation. CHAPTER IV. Interior of the boulder Wide intervals of Geology--Illustration--Long interval between the formation of the boulder as part of a sand-bed, and its striation by glacial action--Sketch of the intervening ages--The boulder a Lower Carboniferous rock--Cycles of the astronomer and the geologist contrasted--Illustration--Plants shown by the boulder once grew green on land--Traces of that ancient land--Its seas, shores, forests, and lakes, all productive of material aids to our comfort and power--Plants of the Carboniferous era--Ferns--Tree-ferns--Calamites--Asterophyllites-- Lepidodendron--Lepidostrobus--Stigmaria--Scene in a ruined palace--Sigillaria--Coniferæ, Cycadeæ--Antholites, the oldest known flower--Grade of the Carboniferous flora--Its resemblance to that of New Zealand.