It is 540
miles distant from the coast of America, and 350 from the island
of Fernando Noronha. The highest point is only fifty feet above
the level of the sea, and the entire circumference is under
three-quarters of a mile. This small point rises abruptly out
of the depths of the ocean. Its mineralogical constitution
is not simple; in some parts the rock is of a cherty, in others
of a felspathic nature, including thin veins of serpentine. It
is a remarkable fact, that all the many small islands, lying
far from any continent, in the Pacific, Indian, and Atlantic
Oceans, with the exception of the Seychelles and this little
point of rock, are, I believe, composed either of coral or of
erupted matter. The volcanic nature of these oceanic islands
is evidently an extension of that law, and the effect of those
same causes, whether chemical or mechanical, from which it
results that a vast majority of the volcanoes now in action
stand either near sea-coasts or as islands in the midst of the
sea.
The rocks of St. Paul appear from a distance of a brilliantly
white colour. This is partly owing to the dung of a
vast multitude of seafowl, and partly to a coating of a hard
glossy substance with a pearly lustre, which is intimately
united to the surface of the rocks. This, when examined
with a lens, is found to consist of numerous exceedingly
thin layers, its total thickness being about the tenth of an
inch.
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