CKS.

In crossing the Atlantic we hove-to, during the morning of February
16th, 1832, close to the island of St. Paul's. This cluster of
rocks is situated in 0 degrees 58' north latitude, and 29 degrees
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 feldspathic 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.

(PLATE 4. INCRUSTATION OF SHELLY SAND.)

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 sa