Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/125

 ments as representing marine cliffs ; but he did not attach sufficient weight to the absence of any material of marine origin at their base ; so that there was no evidence of the presence of the sea within the Wealden area. He differed wholly from the author as to the age of the gravels ; for beneath the gravels were silty beds containing Elephant-remains. These gravels he was inclined to refer to a glacial period, as they contain blocks such as could have been transported only by the agency of ice. The elephants found in the valley of the Wey are of the species (E. primigenius) which also occurs in the Selsey beds; and he believed both to be of glacial age. As to the theory of the denudation of the Weald, he professed himself a convert to the views of Messrs. Foster and Topley, and cited what was now going on around Heligoland in illustration of denudation.

Mr. Whitaker observed that the present absence of gravels along parts of the valley of the Thames affords no proof of their not having formerly existed. He pointed out the soft and friable nature of most of the rocks of the Wealden, which would account for their absence in the gravels. The only really hard rock was the Chert of the Lower Greensand, which was abundant in the gravels of East Kent. Angular flints occurred at the base of the chalk escarpment wherever it had been carried back by denudation. The major valley of the Weald had been spoken of ; but he denied that any such valley existed ; it was merely a series of numerous small valleys. He could not conceive the rivers flowing against the dip of the strata, as supposed by Mr. Wood. He did not agree in the view of the denudation of the Weald being such an enormous affair, but thought that it might be due to comparatively small causes.

The President pointed out that beyond Southend there was a section precisely similar to that of Grays. It was a mistake to suppose that pebbles from the Wealden area did not occur in the Thames gravels. He thought that much of the denudation of the Wealden area might have taken place before the glacial period. The presence of Tertiary pebbles in the Wealden area might readily be accounted for by their presence at the edge of the escarpment.

Mr. Searles V. Wood, Jun., in reply, justified himself for having limited his observations to the northern part of the Weald, as it was there only that it could be brought into juxtaposition with the Glacial beds. He maintained that, under certain circumstances, no beaches or marine beds were formed at the base of sea-cliffs. He pointed out that in Postglacial gravels large blocks of rock were frequently found, and protested against limiting all ice-transport to the glacial period. He could not recognize the Selsey beds, with 150 living species, some of southern character, and none extinct, as glacial. The alleged softness of some of the Wealden rocks, when the great excess both of the Lower-Greensand and Hastings-sand areas over that of the Chalk was considered, did not at all remove the contradiction presented by the enormous preponderance of flint over subcretaceous material in the East-Essex gravel. Like Mr. Austen, he attributed the Wey gravels and the Selsey bed to nearly the same period ; but that was a late postglacial, instead of a glacial one.