heavier fragments. In Europe, Asia, and North America, down to the 44th or 42d parallel of latitude, and up to the altitude of 2000 feet, these appearances present themselves, and are inexplicable, unless on the ground of the gradual submergence of the northern hemisphere to that extent, and its subjection to a boreal climate which engendered glaciers on its hills, and drifted, during a brief summer, icebergs laden with rocky debris over its waters. The glaciers smoothing, rounding, and grooving the rocks of the higher grounds-the icebergs grinding their way through firth and strait, dropping their burden of mud, sand, and gravel on the sea-bed, or stranding themselves on its shores -complete the necessary arrangements for the production of the geological phenomena of the period. For ages the pliocene lands must have slowly subsided, each step gradually narrowing the boundaries of vegetable and animal life, and driving the surviving species, under the rigours of a deteriorating climate, to higher and higher regions. Race after race would succumb: first the more limited and local, next the more cosmopolitan, and ultimately few of the old flora or fauna would survive, except the more elastic in constitution, and those that had, step by step, retreated into more southern latitudes. How long these conditions continued we have no means of determining in centuries, but, judging from the amount of denudation, the extent and nature of the heterogeneous. deposits, as well as from the slow rate of elevation and submergence now going on in known regions, vast periods must have elapsed during the manifestation of this glacial epoch. At length the downward tendency of these northern latitudes comes to a close; submergence stops and elevation begins. Slowly, and for long under a rigorous climate, the lands of Europe, Asia, and North America emerge from the waters. Glaciers still envelop the higher elevations; icebergs, summer after summer, drift over the waters; and the sea, attacking the soft emerging shores, reassorts and re-deposits the sands, gravels, and clays of the older glacial epoch. By-and-by the deposits become fossiliferous, showing that the ocean was tenanted by shell-fish, seals, whales, and other creatures, whose habitats are now Skeleton of Seal (Phoca vitulina ?), from the Brick-clay of Stratheden, Fifeshire; the icy regions of the arctic circle. Upward, still upward, the land emerges, evincing in its old water-lines and raised beaches the successive steps of its uprise, till ultimately the continents of the northern hemisphere assume, within appreciable limits of current mutation, the configuration and climatology they now present. As the continents Boreal Shells in the Drift of the Clyde.-SMITH. 1, Astarte borealis; 2, Leda oblonga; 3, Saxicava rugosa; 4, Pecten islandicus; emerge and the land surfaces augment, as new atmospheric and oceanic currents are established, and as the post-ter L tiary epoch advances, the boreal races retreat farther to the north, some of the old pliocene families again return and spread over European latitudes, and other and newer forms, in the course of creation, begin to appear. It is now the current era of geological history, whose vital record is the silts and marls of filled-up lakes, the alluvium of rivers and estuaries, the growth of peat-bogs and morasses, the stalagmite of fissures and caverns, and the tufa and ashes of volcanoes. In these superficial accumulations, which meet us at every turn, and are still in course of formation, every imbedded organism is fresh and familiar. With the exception of a few extinctions, the species yet flourish in the same latitudes, and the lists of the paleontologist become identical with those of the botanist and zoologist. The peat-bogs of Europe are replete with the mosses, grasses, willows, hazels, birches, firs, and oaks that still spread over our swamps, and adorn our forests. The tundras of Siberia, the jungle-soil of India, and the cypress-swamps of America, are in like manner composed of the plants now peculiar to these regions; and though in the course of geological change, local features may have varied, the main aspects of the Current Flora continue, zone for zone, and province for province, with little alteration or disturbance. When we turn to the Fauna, the case is much the same. The most ancient lake-marls of Europe are thronged with lymnea, paludina, cyclas, planorbis, scarcely, if at all, distinguishable from those that now people our fresh-water ponds; and the marine shells of our estuarine silts and raised beaches the mussels, cockles, oysters, periwinkles, whelks, silver-shells, and clams-with a few local variations, are identical with those that inhabit the surrounding seas. When we turn to the terrestrial fauna, the change, chiefly through the instrumentality of men, becomes a little more decided and apparent. The mammoth and mastodon, the Irish deer and urus, the cave-bear and hyæna, that seem to have roamed over Europe during the dawn of the post Megaceros Hibernicus, or Gigantic Irish Deer. tertiary period, become extinct, though their congeners still flourish in Asia and Africa. As we ascend to later deposits, species, or, it may be, merely varieties of horse, ass, ox, deer, goat, sheep, bear, wild boar, wolf, and fox become the more frequent forms; and ultimately, in the more recent accumulations, the bones, whether of mammals, birds, reptiles, or fishes, become indistinguishable, even in variety, from those that are now our associates in the scheme of vitality. And it is just in this palpable approach to existing nature that we begin to detect the earliest traces of the human species. First, and far back among the river-silts and peat-bogs and cave-earths, we discover his rude stone-implements and weapons, his tree-canoes, and the embers of the fires which he alone of all animals can either kindle or sustain. Side by side with these remains, occasionally lie bones of the mammoth, rhinoceros, and Irish deer; but whether these may not have been washed up, drifted, and re-assorted from earlier deposits, is a question not always easily determinable. However the question may be ultimately answered, one thing is certain, that just as the mammoths and mastodons drop away, and the horse, ox, goat, and sheep begin to spread over Europe in increasing numbers, so the traces of primeval man become more frequent and unmistakable. In all likelihood-nay, it is all but certain that over the plains and through the forests of the Old World man hunted the Irish deer and speared the mammoth, just as at a later period, and in the same region, he lassoed the wild horse and impounded the urus and buffalo. With regard to this subject, however—viz., the first appearof man—much unnecessary discussion has taken place, and a great deal of uneasy tenderness been displayed. Like other events in geological history, we have at present no means of assigning to it a definite date in years and centuries. The time is merely relative, and all that science can safely do is to ascribe it to an early, though not to the very earliest, stages of the pleistocene epoch. Whether this was six thousand or sixteen thousand years ago, we cannot by any known data determine, though this much is evident, that the amount of change since effected on the physical and vital world, as well as the course of civilisation itself, would, at the current rate of progress, require for their elimination a much more extended period than is usually allowed. And here it may be remarked, that while in these superficial accumulations we find frequent traces of primeval man-his stone-implements, tree-canoes, &c.—we rarely or ever discover the remains of man himself. a human bone has been detected, even in the valley of the Somme, where the flint-implements lie in thousands Not |