We have already alluded to another point of view from which these mechanical effects were considered. The level of the land and sea has unmistakably changed. There are mountain eminences ten or fifteen thousand feet in altitude in the interior of continents over which, or through which shells and other products of the sea are profusely scattered. And though, considering the proverbial immobility of the solid land and the proverbial instability of the water, it might at first be supposed much more likely that the sea had subsided than that the land had risen, a more critical examination soon led to a change of opinion. Before our eyes, in some countries, elevations and depressions are taking place, sometimes in a slow secular manner, as in Norway and Sweden, that peninsula on the north rising, and on the south sinking, at such a rate that, to accomplish the whole seven hundred feet of movement, more than twenty-seven thousand years would be required if it had always been uniform as now. Elsewhere, as on the south-western coast of South America, the movement is paroxysmal, the shore line lifting for hundreds of miles instantaneously, and then pausing for many years. In the Morea also, range after range of old sea cliffs exist, some of them more than a thousand feet high, with terraces at the base of each; but the Morea has been well known for the last twenty-five centuries, and in that time has undergone no material change. Again, in Sicily, similar interior sea-cliffs are seen, the rubbish at their bases containing the bones of the hippopotamus and mammoth, proofs of the great change the climate has undergone since the sea washed those ancient beaches. Italy, pre-eminently the historic country, in which, within the memory of man, no material change of configuration has taken place since the Pleistocene period, very late geologically speaking has experienced elevations of fifteen hundred feet. The seven hills of Rome are of the Pliocene, with fluviatile deposits and recent terrestrial shells two hundred feet above the Tiber. There intervened between the older Pliocene and the newer a period of enormous length, as is demonstrated by the accumulated effects taking place in it, and, indeed, the same may be said of every juxtaposed pair of distinctly marked strata. It demanded an inconceivable time for beds once horizontal at the bottom of the sea to be tilted to great inclinations; it required also the enduring exertion of a prodigious force. Ascent and descent may be detected in strata of every age: movements sometimes paroxysmal, but more often of tranquil and secular kind. The coal-bearing strata, by gradual submergence, attained in South Wales a thickness of 12,000 feet, and in Nova Scotia, a total thickness of 14,570 feet; the uniformity of the process of submergence and its slow steadiness is indicated by the occurrence of erect trees at different levels: seventeen such repetitions may be counted in a thickness of 4515 feet. The age of the