W. M. Fontaine—Geology of the Blue Ridge. 99 
The Catoctin Mountains, as cut by the extension of this line, 
do not form a continuous range. In its stead, we have isolated 
elevations, composed of ribs of quartzite standing nearly verti- 
ca e west of Liberty, for four or five miles, we have 
mica schists and hornblende schists, much decayed and eroded. 
Succeeding these come hornblende schists, presenting the same 
character, and all with moderate southeast dip. On reaching 
“Big Otter Creek,” about two and a half miles from the Blue 
idge, we see a ledge of protogine, showing a width of 600 
cally to the southeast. This rock, which from its position is 
the equivalent of the pinite porphyry, is composed of quartz, 
dull white feldspar, and talc, arranged with granitoid texture. 
eta or hornblende rock. The exposures here are bad, and 
the passage from one rock to another cannot be traced, for the 
surface of all these rocks is much decayed and conceale 
clay. Dip of both southeast. This syenite is composed of 
apparent protrusion. The latter contains white orthoclase, much 
homblende and a little quartz. This extensive belt reaches 
to within half a mile of the main mountain. It is here suc- 
seeded by a very coarse syenite, which exactly resembles that 
described at Balcony Falls, in the preceding section, with the 
oreced 
om the valley is composed of the same coarse syenite, showing, 
wWever a considerable proportion of white triclinic feldspar. 
featan Pr oet@phy of the locality presents some noteworthy 
es, 
