| OCR Text |
Show 316 [Ch. XXII. extremity of the Isle of Wight, part of the fresh-water series is vertical, like the marine. Hence it is now as~ertained that as the chalk is horizontal at the southern extremity of the Isle of Wight, while it is vertical in. the centre of that isl~nd, so the Eocene strata are horizontal m the north of the 1sland, and vertical in the centre. We have only to imagine that the great flexure of the secondary and tertiary beds, so ingeniously su crcrested by Mr. Webster in his theoretical section *, extended bb to the fresh-water formations, in order to comprehend how a very simple series of movements may have brought the whole of the Isle of Wight groups into their present position. we are unable to assign a precise date to the convulsions which produced this great curve in the stratified rocks of the Isle of Wight; but we may observe that, although subsequent to the deposition of the fresh-water beds, it does not follow that it was not produced in the Eocene period. It may have been contemporaneous with those movements which raised the central parts of the London and Hampshire basins, which, as we before explained, were subsequent to the principal elevation and denudation of the central axis of theW eald. Land has certainly been elevated on our eastern coast since the commencement of the older Pliocene period, as is attested by the moderate height attained by :he crag ~trata t. But these chano·es of level may have been partial, and If the crag does not exte;d farther over the Eocene formations, and into the Weald y alley, it is probably because those regions were dry land when the strata of crag were forming in the sea. The first land that rose in the south-eastern extremity of England may have been placed, as we before hinted, where we now find the central axis of elevation in the Weald. Perhaps the chalk islands there formed may have supported that tropical vegetation whereof we find memorials in the fossil * Englefield's Isle of Wight, plate XLVII. fig. 1. . t We alluded, at p. 182, to the supposeu discovery of recent marme shells at the height of 140 feet above the sea. in Sheppey; but we have since .learnt f~om Professor Sedgwick, that the information communicated to the Geolog1cal Society on this subject was erroneous. Ch. XXII.] EOCENE ALLUVIUMS. 317 plants of Shcppey; and the shores of those islands may have been frequented, during the ovipositing season, by the turtles and crocodiles, of which the teeth and skeletons are imbedded in the London clay*. Eocene alluviums.-The river which produced that body of water in which the fresh-water strata of Hampshire originated, must have drained some contiguous lands which may have emerged during the Eocene period. On these lands we may suppose the Paleothere, Anoplothere, and Moschus of Binstead to have lived. The discovery of the two former genera, associated as they are with weU-known Eocene species of testacea, is most interesting. It shows that in England, or rather on the space now occupied by part of our island, as well as in the Paris basin, Auvergne, Cantal, and Velay, there were mammalia of a peculiar type during the Eocene period. Yet we have never found a single fragment of the bones of any of these quadrupeds in our alluviums or cave breccias. In these formations we find the bones of the mastodon and mammoth, of the rhinoceros, hippopotamus, lion, hyrena, bear, and other quadrupeds, all of extinct species. They are accompanied by recent fresh-water shells, or by the marine fossils of the crag, and evidently belong to an epoch posterior to the Eocene. Where, then, are the terrestrial alluviums of that surface which was inhabited by the Paleothere and its congeners? Have the remains which were buried at so remote a period decomposed, so that they no longer afford any zoological characters which might enable us to distinguish the Eocene from more modem alluviums? It seems clear that a peculiar and rare combination of favourable circumstances is required to preserve mammiferous or other remains in terrestrial alluviums in sufficient quantity to afford the geologist the means of assigning the date of such deposits. For this reason we are scarcely able, at present, to form any conjecture as to the relative ages of the numerous • We ha~e introduceu thestl islands into the map of Europe, in the :lnu volume, which may be suppusctl to rdattl to the commencement of lhe Eocene period. |
