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Limestone Belts of Westchester County, N. Y. 197 
already been begun, at my suggestion, by the accomplished 
lithologist, Dr. G. W. Hawes. 
A. The Hornblendic.—The common hornblendic rock resem- 
bles syenyte, but contains little orthoclase and much triclinic 
feldspar. e latter is mostly of the species oligoclase, ac- 
cording to an optical measurement on cleavage slices. i 
tion, quartz is rather sparingly present. The rock contains 
more or less black mica and sometimes much of it; and as the 
mica increases at the expense of the hornbleude, the rock 
passes into soda-granite (mentioned beyond). The quartz-dio- 
ryte has the same relation to soda-granite that quartz-syenyte 
has to potash or common granite. Garnetsare rare. The rock 
is often a very coarsely crystallized rock (Aa), having the 
which are partly orthoclase; it looks much like hornblende 
The noryte has commonly a dingy, brownish-red color on a 
surface of fracture owing to the smoky-red color of the feld- 
spar, but varies from this to pale gray on one side and black- 
ish-gray on the other. It occurs along the railroad between 
Peekskill and Montrose station, and over the most of the town 
of Cortland east of this line, and to some extent west. 
