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various basalts, usually decomposed, make up the bulk of the
rock, with pieces of augite, altered plagioclase, biotite, etc., in a
chloritic matrix of finer detrital volcanic material. These rocks
are plainly the product of rapid weathering and hasty deposition,
and give little evidence of transportation.

Carbonaceous sandstones have been seen—soft black rocks,
containing finely divided carbonaceous sediment.

SKIDEGATE FORMATION.

Sandstone. The only specimen examined microscopically
from the Skidegate formation was one from the basal beds of
dark reddish, grey, uneven-grained sandstones. In thin section,
angular quartz, with some plagioclase and decomposed volcanic
rocks, was seen to be embedded in a granular calcite matrix
and calcite also replaces feldspar in some instances.

The shales found in the formation are fine, dark grey to
black, massive, and banded carbonaceous rocks.

ETHELINE FORMATION.

In composition the Etheline formation, which consists
only of injected rocks, ranges from dacite to augite andesite.!
All the types are represented as dykes, and all but dacite as
sills. Basalt dykes occur on Graham island, but their general
appearance and lack of alteration indicates that they belong to
the later Masset formation which is almost wholly basaltic, so
far as is known.

Dacite. The dacites are dense rocks of light grey colour,
showing green, blue, and more rarely pink tints, and virtually
all characterized by yellowish or brownish weathering. They
are porphyritic in places. Phenocrysts occur in some of the
rocks in small amounts, and are usually chalky white plagio-
clase, under 5mm.; more rarely they are quartz. Small, irregu-

1 The sill and dyke rocks of Graham island were first described petrographically by C. H.
Clapp (Geol. Surv., Can., Sum. Rept., 1912, p. 25). He supposed them to be connected
with the effusive types, so did not use the nomenclature proper to their position as hypabyssal
rocks. It has seemed preferable to retain the original nomenclature, rather than to cause
confusion by introducing such names as “‘granodiorite-porphyrite,”’ ‘‘diorite-porphyrite,”’
etc., for rocks here called “‘dacite’’ and ‘‘andesite’’ respectively.