In as far, then, as the phenomenon of boulders is exhibited in the low lands of Europe (leaving other countries out of the question), it seems quite in conformity with the operations of causes such as have been here explained. But it may next be asked, How does the ice-transporting theory explain the boulders of the Alps? Had the waters been sufficiently elevated to convey icebergs over the Jura chain, the Scandinavian mountains would have been deeply submerged, and no longer, therefore, a source either of ice or of boulders. This is unquestionably a difficulty, unless it be assumed either that some great change of relative altitude has taken place by the uplifting of the Alps since the deposition of its boulders, or that the Alpine boulders have not been conveyed by marine agencies. Lyell supposed it possible that falling “hill-sides” might have dammed up the rallies of Switzerland, and have formed lakes, on which the icebergs from its uplifted glaciers might have floated across to the Jura, and have been carried down to the low country at the base of the Alps, by the sudden bursting of the barrier, and the flood following it; and Wissmann (who strangely enough ranks Lyell, manifestly his precursor in this idea, amongst the advocates of the theory of torrents) in like manner assumes the existence of a large sea extending over the low portion of Switzerland, the country now bordering on the Lake of Constance, and the greater part of Bavaria, on the waters of which the ice of falling glaciers with its cargo of boulders floated across. This sea was not however, like Lyell’s, the result of a secondary accident, but arose, encircled and walled in by mountains, on the last upheaving of the Alps. Its waters overflowing their boundary at the lowest points, according to Wissmann enlarged the passages of discharge, which giving vent to the waters, gradually lowered and finally emptied the sea, leaving the valley of the Rhone and of the Rhine as a relic. If, however, hypotheses of at least equal probability have been rejected either as depending too much on supposititious data, or as being imperfect explanations of the phenomena, there seems no greater reason for admitting these. Such accidents as those suggested by Mr Lyell have indeed occurred in the Alpine regions; rivers have been dammed up either by falling hill-sides or by falling masses of ice, and on bursting through these obstacles, have poured down in fearful destruction on the plain below. But how diminutive are such catastrophes in comparison to that which must have attended on the dispersion of the Alpine boulders! and although the lake of Wissmann’s hypothesis is sufficiently extensive to transport the boulders through a very wide space, it is insufficient to account for those in Franche-compté; whilst, if we suppose with him that the last elevation of the Alps was prior to the deposition of the Molasse, it seems improbable that all the great openings of discharge,