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is essentially similar) is of a different type to any yet described,
though related to some of them. The present home of the
tar in this case is in amygdules and lenticular fissure veins in
basalt and basalt agglomerate.

Country Rocks. The rocks in the vicinity of the bituminous
deposits are agglomerates and tuffs—locally termed shale—with
which are interbedded numerous and thick flows of basalt, often
amygdaloidal. Many of the basalt flows are very thick—up to
100 feet—and in many instances they possess well developed
columnar structures, as illustrated in Plate XIIIB, individual
columns being 3 or 4 feet in diameter. These flows are much
more resistant to weathering and erosion than are the pyroclastic
rocks; and they form jutting headlands continued seaward in
dangerous reefs, while the softer fragmental rocks are found in
the coves and bays.

Many of the tuffs are pale bluish, fine-grained, soft, frag-
mental rocks and to these the term shale is applied by the pros-
pectors. Other tuffs are light green, banded, and curiously con-
torted. They are light in weight, rather porous, and break
readily, leaving a rough, harsh surface.

Structure. The general structure in the vicinity of Tian
point is monoclinal. Details of structure were not worked out,
but minor deviations in strike and dip have been observed. The
general strike is north 20 degrees west with moderate south-
westerly dips.

Occurrence. The bitumen at Tian point is found in veins
traversing the basalts and agglomerates, and in amygdulesi n
the basalt. It is also found seeping from cracks in the basalt
which in most cases can be proved to be connected with one or
the other of the above occurrences, and probably are so connected
in all cases.

The amygdaloids of Tian point vary greatly in their habit.
In some the number of filled cavities is large, in others they are
fewer; and the size of the individual amygdules varies greatly.
In one commonly occurring type about 40 per cent of the volume
is made up of evenly distributed amygdules averaging less than
one-fourth inch across, and spherical or regularly almond-shaped.
Another type contains fewer, irregularly spaced cavities of large