in the cabin was slightly phosphorescent in the dark.
ST. PAUL'S ROCKS.--In crossing the Atlantic we hove-to during the
morning of February 16th, close to the island of St. Paul's. This
cluster of rocks is situated in 0 degs. 58' north latitude, and 29
degs. 15' west longitude. 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. It contains much animal matter, and its origin, no doubt, is
due to the action of the rain or spray on the birds' dung. Below some
small masses of guano at Ascension, and on the Abrolhos Islets, I found
certain stalactitic branching bodies, formed apparently in the same
manner as the thin white coating on these rocks. The branching bodies
so closely resembled in general appearance certain nulliporae (a family
of hard calcareous sea-plants), that in lately looking hastily over my
collection I did not perceive the difference. The globular extremities
of the branches are of a pearly texture, like the enamel of teeth, but
so hard as just to scratch plate-glass. I may here mention, that on a
part of the coast of Ascension, where there is a vast accumulation of
shelly sand, an incrustation is deposited on the tidal rocks by the
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