LAND WATERS STREAMS 169 



the water-courses, and later the valley plains, come to be located 

 on the outcrops of the less resistant layers, while the outcrops of 

 the stronger beds become ridges. 



If the axis of an eroded anticline were horizontal, a given hard 

 layer, the arch of which has been cut off, would, after erosion, out- 

 crop on both sides of the axis. When the topography had become 

 mature, these outcrops would constitute parallel ridges, or parallel 

 lines of hills; when the region had been base-leveled, the outcrops 

 would be in parallel belts, though no longer ridges or hills. The 



Fig. 137. A canoe-shaped valley bordered by a ridge formed by the out- 

 crop of a hard layer in a plunging syncline. The ridge bounding the 

 canoe- valley is separated from an outer ridge by a curved valley, under- 

 lain by relatively weak rock. (Willis.) 



lower the plane of truncation, the farther apart the outcrops would 

 be in the anticline, and the nearer together in the syncline (compare 

 outcrop of H, along ab and cd, Fig. 128). 



If, on the other hand, the axis of the anticline or syncline is not 

 horizontal, that is, if it plunges (dips), the topographic result will 

 be different. In this case the outcrops of a given layer on opposite 

 sides of an anticline would converge in the direction of plunge, and 

 come together at the end. At a stage of erosion antedating plana- 

 tion (say late maturity) there would be a ridge or a succession of 

 hills, in the position corresponding to the outcrop of a hard layer, 



