126 Transactions of the Academy of Science of St. Louis 
on Jonca Creek may be part of the same mass. The irregularity 
of the southeastern boundary of the mass is due to the fact that 
some of the granite along the boundary belongs to an intrusion 
earlier than the stock. 
Haworth maps several hills in the granite area as being 
capped by rhyolite and the granite-rhyolite contact would repre- 
sent the roof of the stock. According to Tarr (43), one hill 
mapped as porphyry is granite and another is granite porphyry 
and it is possible that the rock of most of these hills represents 
intrusions into the granite and the hills owe their relief to the 
superior resistance to erosion of this rock. The felsite on Knob- 
lick Mountain and to the south and east may be a roof pendant. 
The Graniteville granite mass is apparently a small boss 
elongated north and south. The granite south of Graniteville, 
on the Black River Road, is part of the same mass but is sep- 
arated from it by a valley filled with sedimentary rocks. Sup- 
port of the idea that the granite has the same width throughout 
its length that it has at the ends, is obtained from the fact 
that a drill-hole in the valley cuts felsite just outside of the line 
connecting the west boundaries of the two outcrops (53). The 
contact between granite and felsite on the hill east of Granite- 
ville is vertical as is shown by the fact that it may be traced in 
an almost straight line from top to bottom of the hill in’ a south- 
erly direction. Tarr (43) reported a sharp vertical contact at 
the southern granite exposure. 
The two small intrusions of granite east of Ironton are 
probably connected, in which case the mass is more elongated 
than that of Graniteville and might be called a dike rather than 
a boss. With the granite is a dike or sill of felsite to be des- 
cribed later. 
The granite porhyry in the Edgehill quadrangle(11) is ap- 
parently an intrusion into the felsite. It occurs in three sepa- 
rate outcrops, but these are separated by a valley filled with 
sedimentary rocks so that probably all three areas represent 
the same mass. The granite porphyry is quite irregular in out- 
