_Topographic forms resulting from stream deposition._--The topographic forms resulting from stream deposition are various. At the bottoms of steep slopes, temporary streams build _alluvial cones_ or _fans_. Along its flood-plain portion, a stream deposits more or less sediment on its flats. The part played by deposition in building a river flat has already been alluded to. A depositing stream often wanders about in an apparently aimless way across its flood plain. At the bends in its course, cutting is often taking place on the outside of a curve while deposition is going on in the inside. The valley of the Baraboo illustrates this process of cutting and building. Fig. 2, Plate XX, is based upon the features of the valley within the city of Baraboo. Besides depositing on its flood-plain, a stream often deposits in its channel. Any obstruction of a channel which checks the current of a loaded stream occasions deposition. In this way "bars" are formed. Once started, the bar increases in size, for it becomes an obstacle to flow, and so the cause of its own growth. It may be built up nearly to the surface of the stream, and in low water, it may become an island by the depression of the surface water. In some parts of its course, as about Merrimac, the Wisconsin river is marked by such islands at low water, and by a much larger number of bars. At their debouchures, streams give up their loads of sediment. Under favorable conditions deltas are built, but delta-building has not entered into the physical history of this region to any notable extent. _Rejuvenation of Streams._