Sketch of a valley at the stage of development corresponding to the cross section shown in Fig. 18. Illustration: FIG. 2. Sketch of a valley at the stage of development corresponding to the cross section shown in Fig. 20.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XX. FIG. 1. Sketch of a part of a valley at the stage of development corresponding to the cross section shown in Fig 21. Illustration: FIG. 2. Sketch of a section of the Baraboo valley.] _Transportation and Deposition._ Sediment is carried by streams in two ways: (1) by being rolled along the bottom, and (2) by being held in suspension. Dissolved mineral matter (which is not sediment) is also carried in the water. By means of that rolled along the bottom and carried in suspension, especially the former, the stream as already stated abrades its bed. The transporting power of a stream of given size varies with its velocity. Increase in the declivity or the volume of a stream increases its velocity and therefore its transportive power. The transportation effected by a stream is influenced (1) by its transporting power, and (2) by the size and amount of material available for carriage. Fine material is carried with a less expenditure of energy than an equal amount of coarse. With the same expenditure of energy therefore a stream can carry a greater amount of the former than of the latter. Since the transportation effected by a stream is dependent on its gradient, its size, and the size and amount of material available, it follows that when these conditions change so as to decrease the carrying power of the river, deposition will follow, if the stream was previously fully loaded. In other words, a stream will deposit when it becomes overloaded. Overloading may come about in the following ways: (1) By decrease in gradient, checking velocity and therefore carrying power; (2) by decrease in amount of water, which may result from evaporation, absorption, etc.; (3) by change in the shape of the channel, so that the friction of flow is increased, and therefore the force available for transportation lessened; (4) by lateral drainage bringing in more sediment than the main stream can carry; (5) by change in the character of the material to which the stream has access; for if it becomes finer, the coarse material previously carried will be dropped, and the fine taken; and (6) by the checking of velocity when a stream flows into a body of standing water.