g8 WORK OF RUNNING WATER 



Adjustment has been carried to a high degree of perfection in 

 many parts of the Appalachian system. Here, as in all other 

 mountains of similar structure, strata of unequal hardness were 

 folded into ridges. The folds were then truncated by erosion, 



Figs. 88-90. Figs. 91-93. 



Figs. 88-90. Diagrams illustrating piracy, where the stream which does not 

 flow over rock of superior hardness captures those which do. Fig. 89 represents a 

 further development of the drainage shown in Fig. 88, and Fig. 90 represents a still 

 later stage. 



Figs. 91-93. Diagrams to illustrate piracy where the competing streams all 

 cross a hard layer. The diagrams represent successive stages of development. 



exposing the more and the less resistant beds (H and S, Fig. 86, 

 respectively) in alternate belts along the flanks of the truncated 

 folds (truncated at ab and cd). The streams, especially the lesser 

 ones, now flow along the strike of the weaker beds much more 



