been wrongly attributed to subsequent infiltration.) Has the slow re-
absorption of this gas, it may be asked, given to the lime in the cells of
the lava, that peculiar fibrous structure, like that of an efflorescing
salt? Finally, I may remark on the great contrast in appearance between
this earthy lime, which must have been heated in a free atmosphere of steam
and other gases, while the white, crystalline, calcareous spar, produced by
a single thin sheet of lava (as at Quail Island) rolling over similar
earthy lime and the debris of organic remains, at the bottom of a shallow
sea.

SIGNAL POST HILL.

This hill has already been several times mentioned, especially with
reference to the remarkable manner in which the white calcareous stratum,
in other parts so horizontal (Figure 2), dips under it into the sea. It has
a broad summit, with obscure traces of a crateriform structure, and is
composed of basaltic rocks (Of these, one common variety is remarkable for
being full of small fragments of a dark jasper-red earthy mineral, which,
when examined carefully, shows an indistinct cleavage; the little fragments
are elongated in form, are soft, are magnetic before and after being
heated, and fuse with difficulty into a dull enamel. This mineral is
evidently closely related to the oxides of iron, but I cannot ascertain
what it exactly is. The rock containing this mineral is crenulated with
small angular cavities, which are lined and filled with yellowish crystals
of carbonate of lime.), some compact, others highly cellular with inclined
beds of loose scoriae, of which some are associated with earthy lime. Like
Red Hill, it has been the source of eruptions, subsequently to the
elevation of the surrounding basaltic plain; but unlike that hill, it has
undergone considerable denudation, and has been the seat of volcanic action
at a remote period, when beneath the sea. I judge of this latter