40 NEW YORK STATE MUSEUM 
of Berkey and to that of the geologists who have worked in the 
contiguous portion of New Jersey. 
Thus, the hornblendic gneiss generally associated with the ores in 
the mines of Orange county is essentially the equivalent of the 
Pochuck gneiss of the New Jersey geologists and the Peekskull 
diorite gneiss of the West Point quadrangle (but see part 3, 
p, 48-54) ; and a granite in the vicinity of the O'Neill and Forshee 
mines, with its associated syntectic not far away, may be correlated 
with the Canada Hill granite of the West Point area without raising 
any serious question of accuracy as to the correlation, and the 
pegmatites are similar in character and relations to those described 
in the various New Jersey reports (see, however, part 3). The 
exception is an extremely coarse, highly quartzose, more or less 
feldspathic, and at times almost pegmatitic, white or light-colored 
granite grading in places to brownish and pinkish, intimately asso- 
ciated with the ore, occurring almost invariably next to or in the 
immediate vicinity of the ore bodies, almost always forming parts of 
the walls, and so involved with the ore and the pegmatites that the 
writer believes it to be genetically related to them, and has thus 
described this rock in part 3, and has called it the “ Pochuck 
granite.” In other places this same granite is heavily involved with 
the ‘“ Pochuck-Grenville”’ (see part 3, p. 48-54), and it may have a 
wider distribution than at first sight would appear. 
The writer believes that the igneous rocks of the Highlands, not 
including the Cortlandt series of basic eruptives or the late Pre- 
cambrian basic dikes, have been derived from one magma; they are 
related to one another in such a way as to indicate that the intrusion 
of these igneous bodies into the ancient Grenville series was a con- 
tinuous process involving the consecutive invasions of magmatic 
masses of varying compositions due to the gradual differentiation of 
a single primary magma. 
