oo^ NKW VdUK srATK Ml SKIM 



face si ra mill and ilic woakiioss of (he ihkIciIn iii^- beds. Between 

 tlic iiiTace of ilie riiesia and (he old land lies the stripped belt, or 

 " iuiiei- lowland" wliicli lias been opened up bv the subsequent 

 streams. Tin diamains | fiii". 2(11)] show the biginuinji" of the drain- 

 ap' system on a coastal jdain and [tig. iMd] the eompleted slm]ile 

 euesta. Tt will be perceived that the inner lowland is wi«lened 

 by the gradual seaward retreat of the in face of the euesta. By 

 this process the altitude above sea level, of the upper edge of the 



Fig-. 209 Diagram of simple coastal plain after elevation, showing- simple consequent 



drainage 



Fig. 210 Coastal plain after erosion and formation of euesta topog:rapliy 



euesta, gradually diminishes owing to the gentle seaward dip of 

 the strata. At the same time the hight of the inface of the euesta 

 may increase, for by its seaward retreat lower and lower strata are 

 uncovered, the edges of which become incorporated in the basal 

 portion of the inface of the euesta. As before stated, if the ui)per 

 layer is very resistant, while the basal strata are easily eroded, 

 the inface of the euesta Avill be steep and rugged. This is essen- 

 tially the case with the front of the Helderberg escarpment at the 

 Indian T.ad<lei'. which for purposes of illustration may be com- 

 I'arcil with a normal euesta front or inface, while the Hudson 

 valley between it and the old land of the Taconic region repre- 



