Familiarized to such gigantic operations among his native Alps, M. Agassiz came to the conclusion that not only the bowlder drift of Switzerland, but nearly all the superficial accumulations of northern Europe, were to be ascribed to glacial action. In the straths and glens of Scotland he fancied a moraine in every talus of a mountain, and in every bar of a river. He saw the polishing of glaciers in the pass of Killiecrankie, on the sides of Ben Nevis, and the steep promontories of Morven. The parallel roads of Glenroy originated in the same cause. From the Mediterranean to the Arctic zone a polar climate universally prevailed, and the whole was covered with a mantle of ice; vast fields of ice, too, depending from the mountains penetrated into the adjacent valleys; the plains in succession were invaded, and erratic blocks were scattered in every direction; when at last, upon a change of temperature consequent upon other changes in the planetary relations of the earth, all these erosive influences were for a time increased, and the glacial power attained its maximum. Not only the upper and transverse furrows in the Alps but all the lower and great longitudinal valleys of the Cantons were the seats of glaciers during this period. Along the passes of the Rhine, the Rhone, the Drance, the Doire, the Arve, and the Isêre, the irrepressible tide of ice maintained its course, leaving portions of the drift at different elevations, and dropping bowlders on the intermediate hills and on the more distant and loftier barriers of the Jura. Sir R. Murchison opposes all these speculations of Agassiz and others. The elevation of the alpine chain, of which there is abundant evidence in comparatively recent times, he regards as cotemporaneous with the translation of the bowlder-drift, and considers that during the sub-aqueous condition of northern Europe, the Alps and the Jura were from two to three thousand feet below their present altitude. He finds that the famous blocks of Monthey opposite Bex are composed exclusively of the granite of Mont Blanc—that they have been transported on ice-rafts through the gorge of St. Maurice to their present locality—and reasons with justice that had they formed part of a moraine the debris of all the intervening rocks, along the valley through which the glacier passed, must have been associated with them. None of the glaciers of the Alps, he thinks, could have been of the extent implied in the transport through their agency of the Jura blocks, nor have ever the upper longitudinal and flanking valleys around Mont Blanc been filled with general ice-streams. The materials, likewise, of true glacier moraines he conceives can be readily distinguished, on the one hand, from the more ancient alluvia, and, on the other, from tumultuous accumulations of gravel bowlders and far-transported erratic blocks. And, looking at the various causes which have affected the surface, Sir Roderick concludes, that all the