106 TRANSACTIONS OF THE [Frp. 23 
are not as conspicuous as would be the case in a non-crystalline 
limestone, Still, there is a whitening of the limestone and an 
increase in the amount of silicates, while the graphite scales 
become much larger than usual, 
In the river gorge at Hailesboro the granite is very micaceous 
and dark colored, and at the lower end of the gorge becomes 
decidedly gneissoid. The same transitions into granulite and 
non-micaceous varieties are also shown. 
West of Hailesboro there is a break in the granite ridge 
where Matoon Creek flows, and beyond this, about two miles 
from the village, the rock shows a gradual transition into a very 
dark variety which has the mineralogical composition of a 
diorite though perfectly continuous with the main body of 
granite. Several alternations between the ordinary granite and 
the more basic phase, are seen in this vicinity. There are also 
many dikes of pegmatite, which may be regarded as the com- 
plement of the basic masses, the two together illustrating well 
the tendency towards differentiation of rock magmas, which is 
such a potent factor in the development of igneous rocks. 
The small bodies of granite which are scattered over the 
region sometimes resemble closely the granite of the main 
ridge, but oftener are coarse aggregates of quartz and feldspar. 
Sometimes the grain becomes finer, and they assume the char- 
acter of graphic granite. The ordinary granitite always occurs 
in the form of irregular bosses, but the pegmatite, both as 
bosses and as sharply defined dikes, cutting either gneiss, 
limestone, or granite. The pegmatite masses are usually of 
limited extent, but at B4 there is an outcrop covering several 
acres. The rock here shows, what is not uncommon elsewhere, 
considerable tourmaline very irregularly distributed, and 
occasionally some mica. This outcrop exhibits a perfect irrup- 
tive contact with the lmestone, like that of the main body of 
granite described above. 
The pegmatites often show traces of metamorphism in the 
production of incipient foliation, and the shattering of small 
rock masses. 
Mechanical Effects of Metamorphism.—Attention has already 
been given to certain mechanical effects of metamorphism, in 
speaking of gneissoid structure and the brecciated sandstone, 
But some other instances seem of sufficient interest to merit 
description. 
At the eorner of Clinton and Barney streets, in Gouverneur, 
is an outcrop of limestone containing abundant fragments of a 
nearly black schist. These fragments constitute, perhaps, one- 
