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Show 150 NEWER PLIOCENE PERIOD· (Ch. XI, might produce in this region, if the peaks or 'needles,' as they are called, of Mont Blanc were shaken as rudely as many parts of the Andes have been in our own times. The glaciers Oi Chamouni would immediately be covered under a prodigious load of rocky masses thrown down upon them. Let us, then, imagine one of the deep narrow gorges in the course of the Arve, between Chamouni and Cl use, to be stopped up by the slidinO' down of a hill-side (as the Rossberg fell in 1806 *), and a 0 Iake would fill the valley of Chamouni, and the lower parts of tbe glaciers would all be laid under. w:ter. The streams which flow out of arches, at the termmat10n of each O'}acier prove that at the bottom of those icy masses there are 0v aulted' cavities through which the waters flow. Into these hollows the water of the lake would enter, and might thus float up the ice in detached icebergs, for the glaciers are much fissured, and the rents would be greatly increased during a period of earthquakes. Icebergs thus formed might, we conceive, resemble those seen by Captain Scoresby far from land in the Polar seas, which supported fragments of rock and soil, conjectured to be above fifty thousand tons in weight t. Let a subsequent convulsion, then, break suddenly the barrier of the lake, and the flood would instantly carry down the icebergs, together with their burden, to the low country at the base of the Alps. We have stated in the first volume that blocks conveyed on floating icebergs must be deposited in different parts of the bottom of the ocean, in whatever latitudes those icebergs arc dissolved t. European alluviums in y·reat part tertiary.-If those writers who speak of an 'alluvial epoch' intend merely to say that a great part of the European alluviums are tertiary, we fully coincide in that opinion, for the map of Europe, given in our second volume, will show that almost every part of the existing continent of Europe has emerged from beneath the waters • See above, vol. ii. 1st Eu., p. 229; 2<1 Ed. p. 235. 1' See above, vol. i. p. 299, 1st Ed.; p. 342, 2d Eu. t Vol. i. ibiu. Ch. XI.] LOESS OF THE VALLEY OF TilE RHINE, 151 during some one or other of the tertiary periods; and it is probable, that even those districts which were land before the commencement of the tertiary epoch, may have shared in the subtenanean convulsions by which the levels of adjoining countries have since been altered. During such subterranean movements new alluviums would be formed in great abundance, and those of more ancient date so modified as to retain scarcely any of their original distinguishing characters. LOCALITIES OF NEWER PLIOCENE ALLUVIUMS. Sicily.-Assuming, then, that almost all the European alluviums are tertiary, we have next to inquire which of them belong to the newer Pliocene period. It is clear that when a district, like the Val di Noto, is composed of rocks of this age, all the alluvium upon the surface must necessarily belong either to the newer Pliocene or to the Recent epoch. If, therefore, the elevation of the mountains of the Val di Noto was chiefly accomplished antecedently to the recent epoch, we must at once pronounce alluviums, in the position indicated at a., diagram No. 26 (p. 139), to belong to the newer Pliocene era. I am informed, that gravel so situated occurs at Grammichele in Sicily, containing the bones of the mammoth. Loess of the Valley ofthe Rhine.-'rhere is a remarkable alluvium filled with land-shells of recent species, which overspreads a great part of the valley of the Rhine, between Basle and Cologne, which, as it contains no remains of man or his works, we may refer to the newer Pliocene era. 'rhis deposit is provincially termed' Loess,' or, in Alsace, 'Lehm,' and has been described by many geologists, whose observations we have lately had opportunities of verifying *. According toM. Leonhard the loess consists chiefly of argillaceous matter combined with a sixth part of carbonate of lime and a sixth of quartzose and micaceous sand. It may be described as a pulverulent loam, of a dirty yellowish-grey colour, "' Among these we may mention MM. Leonhard, Bronn, Bouc, Voltz, Stcinin· ger, Mcrio.n, Rozet1 and Hibbert. |