A Strati graphical Study 
129 
to review briefly what appears to have been the drainage history 
of the area. One of these cliff's is just north of Mary Ann Furnace, 
the other is on the western border of the township where Lost Run 
enters it. In several other places we find exposed ledges, espe- 
cially on the slopes capped by the Pottsville formation. These 
two cliff's, it is supposed, mark critical points in the stream con- 
test of the region. 
a. An inspection of the topographic sheet (fig. i ) suggests that 
the oldest drainage line had a general southwest course through 
the area; this stream had its sources somewhere north or northeast 
of Mary Ann township. The villages of Hickman and Wilkins’ 
Corners are situated in this valley, which was tributary to the 
‘'Newark river,” a stream belonging to the reconstructed, south- 
west flowing drainage investigated by Tight. ^ The cross-section of 
this valley, for a distance reaching from a point a mile and a half 
east of Wilkins’ Corners to the extreme southwest corner of the 
township, is a flat mature arc, as revealed by the rock contours. 
The present direction of stream flow shows that the drainage in 
this wide part of the valley has been directly reversed. The streams 
of the western half of the township now unite near Wilkins’ Cor- 
ners; this stream, Wilkins’ Run, after flowing eastward for about 
one and one-half miles through the old, wide valley, follows a 
narrow rock-walled valley for about three-fourths of a mile, then 
joins the Rocky Fork. A short distance east of this place of junc- 
tion we find the narrowest point in the valley of the Rocky Fork; 
from this point the valley flares both up and down stream; the up- 
stream portion of the present Rocky Fork valley belonged to the 
“Newark river” system, and was captured by south-flowing drain- 
age. 
The ledges of rock along Lost Run also mark a divide which 
has been cut down by diversion, thus extending the drainage basin 
of another south-flowing stream. 
b. When these drainage changes occurred, and the agent or 
processes involved, are directly important in the physiography of 
the area, and indirectly associated with its stratigraphy. Three 
time-definitions may be considered : (i) incidental to, or subsequent 
to, Wisconsin glaciation; (2) incidental to Illinoian glaciation, or 
at sometime during the Illinoian-Wisconsin interval; (3) antedat- 
ing the Illinoian epoch. 
^ Professional Paper, No. JJ, U. S. Geol. Surv., p, l8, 1903. 
