208 TRANSACTIONS OF THE [Apr. 24 
deformation in the bending and breaking of twinning lamelle 
and very marked undulatory extinction. 
The pyroxene is colorless or pale green, with extinction angle 
of about 45°. There is a certain amount of alteration to 
chlorite, but the most noticeable change is the passage into dark 
green uralite. The uralite, as a rule, makes up only a small 
part of the individual, but in a few cases has replaced most of 
the pyroxene. Besides the uralite there is present a small 
amount of hornblende, which seems to be original. 
Biotite is present in large quantities, partly in large plates, 
and partly in small scales of secondary origin. 
The relation of the dark band to the surrounding rock is 
such that it must be regarded as belonging to the gneiss just as 
much as the other dark bands; and yet from its mineralogical 
composition there can be little doubt that it is intrusive. The 
same explanation must apply to many of the dark bands, though 
it is not often so clearly indicated. 
GRANITE, 
There is evidence of a long time break between the gneiss 
and the granite, with corresponding structural differences ; but 
in mineralogical composition there is considerable similarity 
between the two rocks, the most marked difference being the 
greater amount of plagioclase in the gneiss. 
The granite is usually of a light gray color, and of rather 
coarse grain, but there are many wide variations from this 
general type. Similar variations occur in its mineralogical 
composition ; the rock being, as a rule, a biotite granite, or 
granitite, but showing many local transitions into pegmatite, 
tourmaline granite, hornblende granite, diorite, etc. 
The quartz of the granite is either clear white and colorless, 
or milky, the latter appearance being due to the presence of 
abundant fluid inclusions. The microscope shows, in many 
instances, besides these fluid inclusions, slender, black, hair-like 
bodies usually regarded as rutile. These vary considerably in 
number, size and arrangement. In some sections they are scat- 
tered quite irregularly through the quartz, while in others they 
show a tendency towards parallelism. In a single case the hairs 
form two distinct groups. The first consists of quite short bodies 
scattered very irregularly through the quartz. The second 
group consists of unusually long hairs, so arranged as to form 
a network with square meshes, The hairs of the net are more 
abundant in one direction than the other, the most numerous 
