258 
The third specimen is a dark gray, very fine-grained rock 
in which the microscope reveals the presence of granules of a 
green spinel, scales of biotite and muscovite, and quite small 
syenite-like grains, lying evenly distributed over a fine-grained 
aggregate of felspar, probably orthoclase. 
A more divergent type is represented by a number of very 
heavy specimens of black hornfels. Felspar is usually absent 
here, and its component elements are small rounded grains of 
a colourless or greenish augite and of black iron ore, amalgam- 
ated with very small scales of brown biotite. Brown garnet and 
titanite often occur too, and sometimes the augite is replaced 
by a greenish-brown hornblende. 
An andalusite hornfels has been found represented among 
a series of specimens collected by Dr. Sreensrrur in 1888 on 
the Iganek. This rock is distinctly stratified of a rather dark 
reddish-gray colour, and speckled with scales of biotite about 
one millimeter in size. Under the microscope the biotite is seen 
to be of a light brown colour, its quantity being rather incon- 
siderable, as the rock is essentially made up of andalusite, 
quartz, felspar, muscovite, and small specks of iron ore. The 
andalusite is colourless; it occurs in anhedra several millimeters 
in extent entirely filled by granules of the other minerals. This 
rock has, no doubt, originated in an argillaceous bed, and the 
same is probably the case with a hornfels rich in biotite col- 
lected near the top of the mountain, and in which the col- 
ourless minerals are quite filled by very fine sillimanite-like 
needles. 
BASEMENT GRANITE AND SANDSTONE AREAS. 
As will be seen from the geological map (Pl. IV) the 
country west and south of the Igaliko batholite is made up of 
basement rock, mainly granite and sandstone. The sandstone 
