climate, in which even the hardier cereals could not have ripened. How account for a state of things so very unlike the present?

Questions in natural science cannot be resolved with all the certainty of questions in astronomical or mathematical science. Adams and Le Verrier could not only infer from the disturbances of Uranus the existence of a hitherto unknown planet, but even indicate its place in the heavens. But though the varying climatal circumstances of our country, and of northern Europe generally, seem to have depended scarce less surely on the varying physical conditions of another country three thousand miles away, than the irregularities of the planet Uranus did upon the mass and position of the planet Neptune, we question whether any amount of skill, or intimacy of acquaintance with the phenomena, could have led to an a priori anticipation of the fact. We shall afterwards show, however, that the climate of northern Europe is mainly dependent on the conditions of Northern. America; and that one certain change in its condition gave to our country the severe climate which obtained when Natica clausa and Tellina proxima lived in the bay of Rothesay; and that it is a result of another certain change in its condition, that the delicate fuschia now expands its purple bells in Bute on the soil by which great deep-lying accumulations of these subarctic shells are covered.

Let us first remark, that during the period of the boreal shells the land was greatly depressed. The subsequent depression,-that represented in the Rothesay excavation by the upper gravel-bed,—that which succeeded the age of the submerged mosses,--that during which the waves broke against the old coast line,-seems to have been restricted to a descent of some thirty, or at most forty, feet beneath the level which the land at present maintains; whereas the previous depression,-that represented by the bed of arenaceous clay and the boreal shells,—must have been a depres

sion of many hundred feet. No such inference, however, could be based on any of the Bute deposits which we have yet seen; and yet we might safely conclude, even from them, that when these deep-sea shells lived where we now find them, the land must have sat comparatively low in the water. When scalps of Pecten Islandicus throve on the argillaceous bed cut open above tide-mark by the little stream which falls into Balnakaillie Bay, and noble Panopea burrowed in its stiff clay, Bute must have existed, not as one, but as three islands, separated from each other by ocean sounds occupying the three valleys by which it is still traversed from side to side. In the neighbouring mainland many a promontory and peninsula must have also existed as detached islands. The long promontory of Cantyre and Knapdale, traversed by open sounds at Tarbert and Crinan, must have formed two of these; the larger part of the shire of Dumbarton, cut off from the mainland by straits passing inwards through the valleys of the Leven and of Loch Long, must also have borne an insular character; Loch Lomond must have existed, not as a freshwater lake, but as an interior sea; and, in fine, the whole geography of the British islands must have been widely different from what it is now. There are other localities, however, in which, from the elevation of the boreal shellbed over the present sea-level, we are justified in inferring that the depression of the land must have been much greater than that indicated by the beds of Bute. The same bed, and containing the same shells, was laid open in forming the Glasgow and Greenock Railway, a little to the west of Port-Glasgow, at an elevation of about fifty feet over the high-water line. It was detected at Airdrie, about fifteen miles inland, in the first instance, at a height of three hundred and fifty feet over the sea, and subsequently at the still more considerable height of five hundred and twenty-four feet. We ourselves have disinterred the same shells from

where they rested, evidently in situ, in Banffshire,-on the top, in one instance, of a giddy cliff, elevated two hundred and thirty feet over the beach,-in another, lying deep in the side of a valley once a long withdrawing firth, but now fully six miles from the sea, and raised about a hundred and fifty feet above it. In Caithness they have been detected. by Mr. Robert Dick at the greatest heights to which the boulder-clay attains; they occur also at very considerable heights in the boulder-clay of the Isle of Man; and were found by Mr. Trimmer in the drift of Moel Tryfon, in North Wales, at the extraordinary elevation over the sea of fifteen hundred feet. When the boreal shells at Airdrie lived, Scotland must have existed as a wintry archipelago, separated into three groups by the oceanic sounds of the great Caledonian Valley, and of the low flat valley, now traversed by the Union Canal, which extends between the Firths of Forth and Clyde. And when the shells of Moel Tryfon lived, only the higher parts of the Highlands of Scotland, and of the Cheviot and Lammermuir groups, could have had their heads elevated over the wintry ice-laden sea of the Pleistocene agents. There are grounds for holding that the period, though one geologically, was of vast extent, that the degree of submergence was greater at one time and less at another; or, more strictly speaking, that the commencement of the period was one of gradual depression in the British area,—that about its middle term all was submerged, save the hill-tops and higher table-lands,-and that our country then began gradually to rise, until, about the close of the wintry con, its level was mayhap scarce a hundred feet lower than it is at present. But though comparatively greater and less at different times, there seems to have been no time during the period, in which the depression was not absolutely great.

Let us next remark, as very important to our argument, that not only was the period one of depression in the British

area, but also very extensively in the northern hemisphere generally. The shell-beds of Uddevalla,-identical in the character and species of their organisms with those of the Clyde, are elevated two hundred feet above the neighbouring Cattegat; and in Russia Sir Roderick Murchison detected similar beds in the valley of the Dwina, lying nearly two hundred miles south-east of Archangel, and at least a hundred and fifty feet over the level of the White Sea. It is not uninteresting to mark, in the list of shells given by Sir Roderick in his great work on Russia, and which were the product, he states, of not more than two hours' exploration among these far inland beds, exactly the names of the same species that occurred in the Rothesay excavation, or may be found in the Pleistocene deposits of the Kyles. We recognise as the prevailing forms, Natica clausa, Pecten Islandicus, Astarte elliptica, Astarte compressa, Mya truncata in both its boreal and more ordinary varieties, and Tellina proxima, with many others. The inscriptions borne by the Pleistocene of both Sweden and Russia are formed of the same character as those exhibited by the Pleistocene of our own country, and tell exactly the same story. But it is of still more importance to our argument, that the Pleistocene of America is also inscribed with similar characters, and is coupled with similar evidence. Shell-beds identical in their contents with those of the Clyde, Uddevalla, and the valley of the Dwina, have been detected in the neighbourhood of Quebec, at the height of two hundred feet over the Atlantic, and traced onwards by Mr. Logan, the accomplished State-geologist for the Canadas, to the height of four hundred and sixty feet. And in these American beds, separated from those of the Dwina by a hundred and twenty degrees of longitude, Pecten Islandicus, Natica clausa, Mya truncata, Saxicava rugosa, and Tellina proxima, are the prevailing forms. How very wide the geographic area which these shells must have possessed of old! A de

pression of the North American Continent to the amount of but four hundred and sixty feet would greatly affect its contour. It would cut it off from Southern America-the highest point over which the Panama Railway passed was but two hundred and fifty feet over the level of the seaand unite the Atlantic and Pacific Oceans by a broad channel, more than thirty fathoms in depth. But from various other appearances the American geologists claim for their country a much greater depression than even that of Moel Tryfon in Wales. It must have been depressed at least two thousand feet, and a wide sea must have passed through the valley of the Mississippi into what is now the Lake district, and from thence into Hudson's Bay and the Arctic Seas. And now, let the reader mark the probable effects on the climate of Northern Europe generally, and on that of Britain in particular, of so extensive a submergence of the American Continent.

No other countries in the world situated under the same lines of latitude enjoy so genial a climate as that enjoyed by the British islands in the present day. The bleak coasts of Labrador lie in the same parallels as those of Britain and Ireland; St. John's, in Newfoundland, is situated considerably to the south of Torquay in Devon; and Cape Farewell, in Greenland, to the south of Lerwick, the capital of the Shetland Islands. But how very different the climate of these bleak occidental lands, from that which renders Great Britain one of the first of agricultural countries! At Nain, in Labrador, situated in the same latitude as Edinburgh, the ground-frost at the depth of a few feet from the surface never thaws, but forms an ungenial rock-like subsoil, against which the labourer breaks his tool, and over which the cereals fail to ripen. From the northern coasts of Newfoundland, though lying under the same latitudinal lines as the extreme south of England, there forms in winter a thick cake of ice, which, binding up the stormy