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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.


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