of
sand, varying in depth, and mixed in different scanty proportions with
vegetable soil, scarcely hides from view the base, which is of granite.
In several places vast blocks of this stone lie scattered about, as free
from vegetation and the injuries of weather as if they had fallen but
yesterday: and, what is remarkable, most of them, probably all, are
evidently detached from the stone upon which they rest, so entirely that
they might be dragged from the places where they lie, if it were thought
worth while to apply a power sufficient to produce so useless an effect.
It should seem then that these loose blocks have fallen from some place
higher than that upon which they were found; but that is impossible, for
they are higher than any other part of the island. And the supposition
that the injuries of the air and the rain caused the removal of that part
of the granite which might originally have been of a corresponding height
with these remaining blocks, seems hardly admissible in the present
instance. Perhaps subterraneous or volcanic fire may have caused this
curious appearance.

The great bulk of these blocks renders them so conspicuous, that the
attention is first struck with them upon approaching the island. But,
besides granite, there is on the north side, where the island is
particularly low and narrow, a slip of calcareous earth, of a few hundred
yards in length, which discovers itself near the broken surface of the
water. It is not for the most part pure, for broken pieces of the granite
are mixed with it in various proportions. Some parts are a mere mass of
these broken pieces cemented together by the calcareous matter; whilst
others are an almost perfect chalk, and are capable of being burnt into
excellent lime. Broken sea shells and other exuviae of marine animals are
apparent throughout the whole mass.

Upon the beach at the foot of this chalky rock, was found a very
considerable quantity of the black metallic particles which appear
in the granite as black shining specks, and are in all probability
grains of tin.

To find this small bed of the remains of shell animals, of which chalk is
formed wherever found, in such an unexpected situation, excited some
surprise; and Mr. Bass endeavoured to investigate the cause of this
deposit, by examining the form of the neighbouring parts of the island.

The result of his inquiries and conjectures amounted to this: that as
traces of the sea, and of the effects of r