TRANSACTIONS OF WAGNER 

 34 



THE LIFE FEATURES OF THE COASTAL PLAIN AND THE PIEDMONT 



These estuaries are the upper portions of "drowned" valleys which have been 

 invaded by the sea in a general sinking movement of the Coastal Plain over 

 wide areas. The beginning of this subsidence is a geologically recent event, 

 though a broad belt of coastal plain has already disappeared beneath the 

 bordering sea. Along its western edge the Coastal Plain lies against the old 

 crystalline rock of Appalachia. The first settlers along the lower Delaware 

 noted the contrast between the two regions. They marked the Piedmont as a 

 low rise of land to the north and west — the beginning of a rolling "upland" 

 country. To the tidal mouths of the streams that flowed down from this up- 

 land the early settlers gave the name of "creeks," a term proper enough for a 

 tidal inlet, though it has been curiously extended to the upper courses of these 

 streams, that in a rightful sense are not creeks at all, but "brooks." The 

 Piedmont is a plateau of moderate elevation, varying from two hundred to six 

 hundred feet above sea-level, and extending westward to the Blue Ridge. It 

 is traversed in its Middle Atlantic portion by several considerable streams, as 

 the Delaware, Schuylkill, and Susquehanna, which head beyond its western 

 limits and flow through comparatively wide valleys, while the numerous smaller 

 tributaries of these rivers have dissected the plateau into a rolling upland of 

 hill and dale. The line of demarcation between this upland Piedmont coun- 

 try and the Coastal Plain lowland may be traced for a long distance as a more 

 or less conspicuous elevation from the western side of the lower Hudson to 

 Alabama. It is the easternmost Hmit of the archean gniess and schists of the 

 old Appalachian land, and as such it marks a "fall-Hne" of rivers from their 

 Piedmont courses on to the Coastal Plain. Above this "fall-line" the streams 

 pursue a more or less rough-and-tumble course, much beset with "rifts" of 

 eroded rock and loose shingle, in marked contrast to their deeper, smooth- 

 flowing reaches on the Coastal Plain alluvium. This geologic feature exerted 

 an interesting influence in the history of settlement, as it marked the upper 

 limit of tide-water navigation in conjunction with water-power facilities from 

 rapids and falls, and it thus became the site of towns, some of which grew into 

 large cities. Trenton, Philadelphia, Baltimore, Washington, Richmond, Peters- 

 burg, Raleigh, Augusta, and Macon are located on the "fall-line." In the 

 Philadelphia district this boundary between Coastal Plain and Piedmont is 

 marked by the 200-foot contour (U. S. Topographical Survey Maps). It pre- 

 sents a well-defined rise of land — the "upland terrace," trending along the west- 

 ern edge of the flat lowland expanse of Coastal Plain . From various points it 



