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heights of one inch and corresponding hollows. The only al-
teration in the shales is a slight softening which may be ascribed
to percolating water. Angular blocks of shale are found in the
lower portion of the flow, and the surface of the shale, where
overflowed by basalt, is as clean as if it had been subjected to
erosive water action.

The lower contact of the formation has not been sufficiently
observed to determine the character of the surface on which the
basalts were extruded.

It can be stated that the Masset formation has been acted
on by deforming forces to a considerable extent, though, as the
work done in the areas underlain by this formation was largely
of a reconnaissance nature, the structure has not been worked
out in detail.

In the Slatechuck range, the formation is about horizontal,
with possibly a low westerly dip. At Lawn hill, the strike of
the flows is east and west, dipping 10 to 15 degrees south. This
east-west trend of the folds is seen in many places, although
much of the formation on the west coast strikes from north
20 degrees west to north 20 degrees east, in low folds. In some
cases local folding has been severe, and is accompanied by minor
faulting, but dips of over 20 degrees are uncommon. The
only fault of any magnitude noted is one crossing Frederick
island in an east-west direction, and bringing the Tertiary
basalt flows, which in the northern part of the island dip 20 to
30 degrees south and southwest, sharply against the lower Juras-
sic Maude argillites, also dipping south, but at higher angles.

Thickness. In the Slatechuck range 1,600 feet of piled up
basalt flows are visible in Slatechuck mountain. On the west
coast upwards of 2,500 feet are to be seen in steep hill-sides and
from the folding observed the formation at present is estim-
ated to be upwards of 5,000 feet thick.

Method of Extrusion. From the description of the rock
types in the formation, it is evident that they were formed
during an extensive period of vulcanism, when great explosive
vents vomited forth masses of so-called ash and fragments of
hot lava to form the tuffs and agglomerates. Concurrently
great flows of basalt were poured out, and the formation was