The Wealden formation is more local than any of the deposits we have yet considered. The term has a particular reference to the district features of Kent, Surrey, Sussex, and Hampshire, known as the _Wolds_, from the German _wald_, signifying a wood or forest: and as the geological position of the group is in immediate _superior_ connection with the oolites, and _inferior_ to the chalk, the character and history of the Wealden fall to be given in this place. The Specton clay of Yorkshire, displayed along the cliffs adjoining Filey Bay, is considered to belong to the same series as the _gault_ or blue and gray marls of Cambridge, Kent and Sussex; but it contains some characteristic indications of the Kimmeridge clay, and, therefore, we should expect that, in Yorkshire, these two strata are not separated as in the south of England. I. NATURE AND EXTENT OF THE DEPOSIT. The Wealden is a fresh water or estuary formation, as is clearly established by its fossils as well as by its lithology. The group consists of layers of clay, sand, shale, with subordinate beds of limestone, grit, and friable sandstone. The Hastings sands, Tilgate Forest beds, Tunbridge Wells deposits, and the Ashburn lignite shales and ferruginous sands, are all constituents of the series. The Dover Railway traverses the formation between Red Hill and Ashford: the branch leading to Tunbridge Wells affords excellent sections of the clay and sands. Thus occupying, in an irregular triangular form, the south-east of England, the wealden again emerges in the principality of Hanover, and other places in the north of Germany: continuing in the same course, it is again found on the British shores, occurring at Linksfield, near Elgin. It would not be easy to restore, in imagination, the surrounding aspect of the superficial area now occupied by patches of the wealden formation. Take your station on the Peak of Derby, or Shotover Hill, or the heights of Ivanhoe—not so perilous adventure as that of the heroine of the tale on the battlements of Malvoisin—and you overlook a vast extent of vale and woodland, all then one broad expanse of water. This inland sea filled the whole intermediate district traced above, studded, in all probability, with islands, and fringed with shallows and rich arborescent headlands. Sharks prowled and darted in every direction; pterodactyles may be descried looming along the waste; while in terror or in joy, the plesiosaurus reared aloft his far-stretching neck, and then withdrew into his fenny retreats. The saurians, with their strong muscular jaws, are actively engaged, each according to his kind, by the shores or in the waters; while over the busy scene, the fierce-weltering ichthyosaurus looks in wild amazement, his large eyes leaping in their sockets, and spreading dismay among the tenants of the deep, as even now, when a kite enters a thorny brake, or pursues his stealthy flight over the meadows and green fields of timid nestling bird.