CYCLES OF EROSION IN PENNSYLVANIA 553 
surfaces on the Ordovician (Martinsburg) shale which reach 600 
feet, and to corresponding altitudes on Delaware and Potomac 
rivers (see Figs. 13 and 14). At this altitude it is widespread in 
® « 
Fic. 15.—Honeybrook and Harrisburg peneplains in the Boyertown quadrangle. 
The Honeybrook peneplain corresponds with the surface of the upland on the left at 
an altitude of 800 feet and the Harrisburg with the upland in the distance on the right 
at an altitude of 600 feet, as seen from the northeast end of Long Hill, looking north 
55 east. 
Fic. 16.—Remnants of Early Brandywine and Harrisburg peneplains in the 
Harrisburg quadrangles. The surface of the upland represents the Early Brandy- 
wine peneplain upon which the hills, rising to an altitude of 740 feet and perhaps to 
the level of the Harrisburg peneplain, stand as monadnocks. The view is from a 
point on the Sunderland level one-half mile northwest of Maiden Creek, looking 
southwest. 
the central Piedmont province and descends on the border of the 
upland to 500 feet (North and South Chester Valley Hills in the 
Schuylkill Valley). The Harrisburg does not appear in the “fall- 
line” zone, but probably descends below sea-level beneath the 
