46 B GEOLOGICAL SURVEY OF CANADA

In these rocks, which come across from Moresby island, traces of coppet
were observed at several points. The mineral wealth of the series, however,
appears to be small, and nothing of importance was seen in any part of
the island. These rocks occupy the southern portion of the western half
of the island to the vicinity of Hippa island, when the country becomes

gradually lower and the rocks of the second series appear in increasing
volume. |

The second group of igneous rocks is for the most part of the age of the
later Tertiary. They not only cut the Cretaceous shale and sandstone
but in places rest upon the Tertiary sedimentary shales, as at Tow hill
and several other points. They are generally basic, often basaltic, dark
green somewhat rough trap rocks, in places showing an apparent bedded
structure but roughly divided into four square blocks. In places, as at
Tow hill, the lower portion of the mass, which has a height of 275 feet,
is bedded in sheets or layers of one foot to eighteen inches thick, while

the upper part is of the columnar variety to the top of the exposure.

The columnar form is well seen at a number of places along the
northern half of the west coast, and at some points on the southern sea-
board, as along the western entrance of Skidegate channel. In the islands
of Masset inlet, volcanic conglomerates are met with, frequently interbed-
ded with columnar trap flows, and at one island near the lower end of the
inlet expansion the rocks contain masses of obsidian. The northern por-
tion of this inlet expansion, from the entrance past the Big island to the
head beyond the Ain river, shows frequent exposures of the later diabase,
which cuts across the Pre-Cretaceuos igneous rocks and forms large mass-
es. In places these bedded newer volcanics strongly resemble at a dis-
tance roughly bedded sandstones, but their crystalline character is easily
recognized on closer inspection. No minerals of economic importance were
Seen in the rocks of this newer series.

On the west shore of the island between Frederick island and Tian
point, a distance of about ten miles along the coast, these rocks are well
exposed and form a very large portion of the shore. An interesting oe-
currence in this locality is the presence of thickened petroleum, now in the
form of a viscous tar which fills cavities in the blackish diabase and
which, when the rock is broken, can be drawn out into strings. There
are no indications of sedimentary rocks anywhere in the area. About
ten miles in length of this part of the coast was taken up as a mining
district during the past summer (1905), the object being a search for pe-
troleum. The preliminary investigations were not attended with any
great measure of success.