103 
JCURNAL OF THE 
Below the narrows (between:2 and S.E. in fig. 3) the 
FIG. 
Fic, 3.—Conditions favoring the develop- 
ment of cascades and rapids in river channels 
crossing belts of inclined slates and crystalline 
schists. 
a=—Argillaceous slates dipping northwest, 
with hard2r and more durable layers at inter- 
vals (as at 3). 6=Crystalline schists, mainly 
of volcanic origin, obscurely schistose, more 
massive and obdurate in places, as where the 
shading is heavier. c—Finely laminated and 
uniform argillaceous slate. 
rock is mainly an argillaceous slate of 
fairly uniform character and easily 
eroded by water action; and the ex- 
istence of this softer material beside 
the belt of hard, obdurate rock which 
itself is not uniform, but has harder 
and softer belts, affords just the con- 
ditions favorable for the development 
of rapids and cascades in the stream 
that crosses both belts. As might be 
expected, these harder rocks (6 in fig. 
3) cross the country in a high, irreg- 
ular ridge, while the surface of the 
region to the southeast, occupied by 
the slaty and sandstone rocks, is less 
hilly and less elevated. The Yadkin 
crosses the harder ridge as a rushing torrent in a deep, 
narrow gorge—the ‘‘Narrows’’—but as soon as it reaches 
the softer slaty reck (at 2 in fig. 3) the current slackens, 
the stream widens and flows on for several miles as a 
smooth and relatively sluggish current. 
For several mjles up-stream from the Narrows the 
rocks are mainly clay slates having a southwest-north- 
east course, and dipping steeply toward the northwest ; 
kad 
