93 
feldspars are crowded with minute inclusions of opaque 
rods. Ilmenite, with leucoxene borders, apatite, and zir- 
con are accessory constituents. 
Gabbro. A specimen of gabbro from the south side of 
Murray’s pit contains a considerable quantity of green 
hornblende, and of colourless augite surrounded by 
primary reaction rims of hornblende. There is also 
a small amount of strongly pleochroic hypersthene. The 
subordinate remaining portion consists of plagioclase 
which alters both to scapolite and to paragonite. The 
rock is a hornblende-hypersthene-gabbro. Osann has 
described a rock from the same place which carried en- 
statite instead of hypersthene [2]. 
Exposures of gabbro at the northern edge of the hill 
differ from this in that they hold reddish-brown biotite 
and a monoclinic pyroxene having the pleochroism of 
_hypersthene. Some sections of the pyroxene extinguish 
obliquely at angles like those of augite, while others 
have straight extinction, and in some sections the former 
have a slight greenish colour which serves to distinguish 
them from the latter. It seems likely, therefore, that a 
part of the pyroxene is hypersthene. 
Other exposures near the margins of the hill, more 
especially on the south and west sides, are intermediate 
between the gabbro of the centre of the hill and the diorites 
at the extreme borders. They show the same derivation 
of hornblende from augite and in some cases a notable 
amount of primary epidote. Hypersthene is absent, 
however. Scapolite is a common mineral in these rocks, 
and in the peripheral diorites. 
= ANNOTATED GUIDE—(Continued). 
iles and 
Kilometres. 
79:1m. Papineauville—Alt. 149 ft. (45-4 _m.). North 
126-8 km.of the track at Papineauville railway station is 
a section showing the relation of the Grenville 
limestone to other members of the Pre-Cambrian. 
The limestone which is banded, dips east 65° and 
strikes N. 42° E. magnetic. Intercalated with 
it, as illustrated in the accompanying section, 
is a dioritic gneiss, in part altered to a mica- 
schist, and also, a more distinctly intrusive 
binary granite. 
