1. _Topography._--The driftless area has long been exposed to the processes of degradation. It has been cut into valleys and ridges by streams, and the ridges have been dissected into hills. The characteristic features of a topography fashioned by running water are such as to mark it clearly from surfaces fashioned by other agencies. Rivers end at the sea (or in lakes). Generally speaking, every point at the bottom of a river valley is higher than any other point in the bottom of the same valley nearer the sea, and lower than any other point correspondingly situated farther from the sea. This follows from the fact that rivers make their own valleys for the most part, and a river's course is necessarily downward. In a region of erosion topography therefore, tributary valleys lead down to their mains, secondary tributaries lead down to the first, and so on; or, to state the same thing in reverse order, in every region where the surface configuration has been determined by rain and river erosion, every gully and every ravine descends to a valley. The smaller valleys descend to larger and lower ones, which in turn lead to those still larger and lower. The lowest valley of a system ends at the sea, so that the valley which joins the sea is the last member of the series of erosion channels of which the ravines and gullies are the first. It will thus be seen that all depressions in the surface, worn by rivers, lead to lower ones. The surface of a region sculptured by rivers is therefore marked by valleys, with intervening ridges and hills, the slopes of which descend to them. All topographic features are here determined by the water courses. [Illustration: Fig. 45.--Drainage in the driftless area. The absence of ponds and marshes is to be noted.] The relief features of the glaciated area, on the other hand, lack the systematic arrangement of those of the unglaciated territory, and stream valleys are not the controlling elements in the topography. 2. _Drainage._--The surface of the driftless area is well drained. Ponds and lakes are essentially absent, except where streams have been obstructed by human agency. The drainage of the drift-covered area, on the other hand, is usually imperfect. Marshes, ponds and lakes are of common occurrence. These types are shown by the accompanying maps, Figs. 45 and 46, the one from the driftless area, the other from the drift-covered. [Illustration: Fig. 46.--Drainage in a glaciated region. Walworth and Waukesha counties, Wisconsin, showing abundance of marshes and lakes.]