Page:A Treatise on Geology, volume 1.djvu/307

 CHAP. VI. the valleys of the Isere and the Durance, to the plains of the Rhone: thus have the rocks wasted from around Mont Blanc, and the Col di Balme been strewn over the valley and along the hilly borders of the Rhone, even to the height of some thousand feet on the Jura; near Soleure, the same range of mountains bears the spoils of the Bernese Oberland, swept down by the valley of the Aar, the Claris boulders have gone to Zurich, and those of the Grisons have descended the valley of the Rhine. But, after thus falling to the great Swiss tertiary basins of Geneva, and the valley of the Aar, the blocks have crossed those hollows, and been driven up the opposite slopes of the Jura to a level 2000 feet higher. De Luc (Mém. de la Soc. d'Hist. Nat. de Génève) notices the origin of other rocks besides the granites dispersed in the basin of Geneva, and they support the same conclusion of the decided influence exercised by the present configuration of the country in modifying the direction of diluvial currents.

This influence is, however, in other cases, less sensible. For example, the zircon sienites, porphyries, and transition limestones of Sweden and Norway, have been transported southwards over the country of Scania and across the Baltic, and scattered over the sandy plains of Westphalia, Hanover, Holstein, Zealand, Mecklenburg, Brandenburg, Pomerania, Prussia, and part of Poland between Warsaw and Grodno. Thus, from the Ems and theWeser to the Niemen and the Dwina (and even to the Neva), the country is covered with ruins of the Scandinavian rocks brought across the sea, and carried toward the Carpathians, and the Bohemian and Westphalian mountains, contrary to the natural currents of drainage. De Luc and Brongniart have given many details concerning these remarkable boulders, which appear not equally spread over the large tracts of country mentioned, but assembled in groups in particular situations. These groups are often elliptical in form; the major axis of the figure pointing north and south, or toward the Baltic Sea, across which they have been transported.