EROSIONAL HISTORY OF DRIFTLESS AREA 17 



Fig. 4. A series of plats of stream courses of different histories. 



AA is a part of the course of Maple river taken from the Casselton, No. Dak. topo- 

 graphic sheet. It has a consequent course in youth of its first cycle. Curves devel- 

 oped on low. flat land. 



BB Rock river. Waterloo, Wis. sheet. A consequent stream on the surface of 

 glacial drift. 



CC Deerfield river, Wilmington, Vt. sheet. A stream in harmony with rock hardness 

 and topography. 



DD Platte river, Leavenworth, Kas. sheet. Meanders developed in old age. 

 EE Big Sioux river, Elkpoint, So. Dak. sheet. Meanders developed in old age. 



