168 



GEOLOGY 



with other corresponding crests it represents the oldest recorded base- 

 level (or peneplain) of the region. The great gap in the mountain 

 is the Delaware Water-Gap. Below the mountain crest there is an- 

 other plain, developed in a subsequent cycle of erosion, while the valley 

 plain in the foreground represents the work of a still later cycle. 



B D 



Bomdarles 

 /[ppalachian Mountain 



Fig. 160. — Showing certain peculiarities of Appalachian drainage. l=the Susque- 

 hanna; 2= the Potomac: 3= the James; 4= the Roanoke; 5= the Coosa; 6= the 

 Tennessee; 7 =the Kanawha; 8 = head of New River; 9 =head of the French Broad. 



The oldest erosion plain of the Appalachian Mountains, the results 

 of which are seen in the even-crested ridges so characteristic of the 

 system, is sometimes called the Kittatinny hase-level.^ It was com- 



^ Willis. Physiography of the United States. The Northern Appalachians. 



