THE BEAVER BAY GROUP. 311 
shows a rock composed chiefly of clouded orthoclase and oligoclase, and 
large quartz areas. A few clusters of rounded particles of augite are seen. 
The augite is older than the feldspars and the feldspars older than the 
quartz. The latter ingredient does not saturate the feldspars after the 
usual manner of secondary quartz, but molds itself around them or invades 
them in large areas, or even includes broken pieces of feldspars. 
At B, of Fig. 20, the rock is a fine-grained, brownish-black, conchoid- 
ally fracturing diabase of the ordinary type, with chlorite and quartz pseud- 
amygdules, rising in a low ledge above the shingle of the beach. Expos- 
ures CC, also low, are of the same kind of rock, mingled with which are 
seams and patches of brick-red felsite, the black and red presenting the 
appearance of having been in a semi-fused condition together. The red 
felsite in the thin section shows a red matrix, saturated with exceedingly 
thin fibers of secondary quartz arranged in sheaf-like bundles. Quite large 
quartz areas are also contained, which are not single individuals as in the 
quartzes of a quartz-porphyry. It is possibly only a phase of the pink rock 
of the south wall of the bay. 
Beyond the point C there are 80 paces of a beach without ledge, be- 
yond which again rises the north wall of the bay, DE. This wall is composed 
as indicated in the following figure. The west part of the wall is made up 
A ] ( 
~EN [fj hed as bebS ite ee 
[ oa ed LF = is / be ‘ & 4 ; 
= (Bs ey SSS ead hee Ne | ‘cart 
j Ca pS SSS S — 
y We wi fa Pe are a | 
eas > lf ji / al [ | 
Fic. 21.—Section of wall DE of Fig. 20. 
of plainly bedded fine-grained diabase, laumontitic amygdaloid, and luster- 
mottled melaphyr. These are terminated by a narrow ravine 15 feet wide 
and 100 feet deep, the east face of which is made up of the pink felsite 
which forms the rest of the point. This face is beautifully slicken-sided, 
being polished in some places to a glassy surface, and marked from top to 
