The principal part of this paper was devoted to a description of alluvial terraces, as seen along the banks of the Rhine at Bonn, Mainz, and Basle, and in the valley of the Arve, the well-known tributary of the Rhone. These terraces, which rise high above the reach of the present river, yet slope in the same direction. The intermediate hollow or trough in which the river runs, has evidently been cut out of what was at first an entire sloping sheet of detrital matter, filling the valley from side to side up to a certain height. At the lower part of the Arve valley, the detrital matter has been discharged across the valley of the Rhone, so as to form a barrier for the Lake of Geneva.