The nearest approach to a base-leveled region within the area here under consideration is in the vicinity of Camp Douglas and Necedah (see Plate I). This is indeed one of the best examples of a base-leveled plain known. Here the broad plain, extending in some directions as far as the eye can reach, is as low as it could be reduced by the streams which developed it. The erosion cycle which produced the plain was, however, not completed, for above the plain rise a few conspicuous hills (Plates XVII and XVIII, and Fig. 17), and to the west of it lie the highlands marking the level from which the low plain was reduced. Where a region has been clearly base-leveled, isolated masses or ridges of resistant rock may still stand out conspicuously above it. The quartzite hill at Necedah is an example. Such hills are known as _monadnocks_. This name was taken from Mount Monadnock which owes its origin to the removal of the surrounding less resistant beds. The name has now become generic. Many of the isolated hills on the peneplain east of Camp Douglas are perhaps due to superior resistance, though the rock of which they are composed belongs to the same formation as that which has been removed. [Illustration: Fig. 17.--Sketch, looking northwest from Camp Douglas.] CHARACTERISTICS OF VALLEYS AT VARIOUS STAGES OF DEVELOPMENT. In the early stages of its development a depression made by erosion has steep lateral slopes, the exact character of which is determined by many considerations. Its normal cross-section is usually described as V-shaped (Fig. 18). In the early stages of its development, especially if in unconsolidated material, the slopes are normally convex inward. If cut in solid rock, the cross section may be the same, though many variations are likely to appear, due especially to the structure of the rock and to inequalities of hardness. If a stream be swift enough to carry off not only all the detritus descending from its slopes, but to abrade its bed effectively besides, a steep-sided gorge develops. If it becomes deep, it is a canyon. For the development of a canyon, the material of the walls must be such as is capable of standing at a high angle. A canyon always indicates that the down-cutting of a stream keeps well ahead of the widening. [Illustration: Fig. 18.--Diagrammatic cross-section of a young valley.] Of young valleys in loose material (drift) there are many examples in the eastern portion of the area here described. Shallow canyons or gorges in rock are also found. The gorge of Skillett creek at and above the Pewit's nest about three miles southwest from Baraboo, the gorge of Dell creek two miles south of Kilbourn City, and the Dalles of the Wisconsin at Kilbourn City may serve as illustrations of this type of valley. [Illustration: Fig. 19.--Diagrammatic profile of a young valley.]