Here are all things once more assembled, and as the tree of knowledge no longer bars from the tree of life, we can innocently search into all the mysteries, and see all the qualities and shapes, of every earthly object. Nor is London less privileged and distinguished by its geological treasures and multifarious condition of things beneath. The capital stands on the tertiary _Eocene_ strata, or last of the rocky series of the island. The pre-Adamic arrangements all here cease, the boundaries betwixt the old and the new world are here drawn. The age of HUMANITY dawns. And, interred in the deposits immediately below, lie the last of a series of monsters which preceded man’s introduction upon the stage, and between whom and all his race an unequal war of merciless extermination must have prevailed. The reasoning animal, indeed, at once the most helpless and most potent of nature’s offspring, could but ill have existed under a constitution of the elements which fostered the Palæotheriums and Chæropotami of the tertiary age. Neither the romance of geology nor the era of prodigies, therefore, are yet over. The curtain once more requires to be lifted from the dark regions of the past, ere we approach the arrangements, forms, and distribution of animal and vegetable life, of the epoch in which our own lot has been cast. I. THE TERTIARY GROUP consists of a series of well-marked and closely connected beds of clays, sands, gravel, brecciated conglomerate, marls, and limestones; some of which are of marine, and some of fresh water origin—points only to be determined by their respective fossil remains. Some lithological distinctions may also be established; the marine deposits are less minutely laminated than those of the fresh water; and also, in general, the beds are thicker, and their sediments more confused in their arrangement. “Limestones, and fine light-colored clays,” says Mr. Phillips, “constitute the principal mass of the fresh water sediments; while sands, and blue and variously-colored clays, more particularly mark the marine depositions. The latter appear like the products of littoral agitation, as if the wearing of cliffs of older strata had furnished the materials of these newer rocks; while the former resemble the accumulations from the wasting surface of chalky and argillaceous countries.”