Pee alt 
Sane aN 
RFS a . 
GEOGNOSY OF THE APPALACHIANS. 457 
schists of the White Mountain series, and are sometimes accom- 
panied by pyroxene, garnet, idocrase, sphene and graphite, as in 
the corresponding rocks of the Laurentian, which this series, in its 
more gneissic portions, closely resembles, though apparently dis- 
tinct geognostically. The limestones are intimately associated 
with the highly micaceous schists containing staurolite, andalusite, 
eyanite and garnet. These schists are sometimes highly plumbag- 
inous, as seen in the graphitic mica-schist holding garnets in 
Nelson, New Hampshire, and that associated with cyanite in Corn- 
wall, Conn. To this third series of crystalline schists belong the 
concretionary granitic veins abounding in beryl, tourmaline and 
lepidolite, and occasionally containing tinstone and columbite. 
Granitic veins in the Laurentian gneisses frequently contain tour- 
maline, but have not, so far as yet known, yielded the other min- 
eral species just mentioned. * 
Keeping in mind the characteristics of these “ihe series, it will 
be easy to trace them southward cal the aid of the concise and ac- 
curate descriptions which Prof. H. D. Rogers has given us of the 
rocks of Pennsylvania. In his iojuit on the geology of this state 
he has distinguished three districts of various crystalline schists, 
which are by him included together under the name of gneissic - 
or hypozoic rocks. Of these districts the most northern, or the 
South Mountain belt, to the northwest of the Mesozoic basin, is 
said to be the continuation of the Highlands of New York and New 
Jersey, which, crossing the Delaware near Easton, is continued 
southward through Pennsylvania and. Maryland into Virginia, 
where it appears in the Blue Ridge. The gneiss of this district 
in Pennsylvania is described as differing considerably from that of 
the southernmost district, being massive and granitoid, often horn- 
blendic, with much magnetic iron, but destitute of any consider- 
able beds of micaceous, talcose or chloritic slate, which mark the 
rocks of the southern district. These characters are sufficient to 
line rocks. The gneiss of the middle district of Pennsylvania, to 
the south of the Mesozoic, but north of the Chester valley, is de- 
scribed by Rogers as resembling that of the South Mountain or 
* Hunt, Notes on Granitic Rocks; Amer. Jour. Sci., III, i, 182. 
