walls. The surface of the fronds is beautifully glossy; and
those parts formed where fully exposed to the light are of a
jet black colour, but those shaded under ledges are only grey.
I have shown specimens of this incrustation to several
geologists, and they all thought that they were of volcanic
or igneous origin! In its hardness and translucency -- in
its polish, equal to that of the finest oliva-shell -- in the
bad smell given out, and loss of colour under the blowpipe -- it
shows a close similarity with living sea-shells. Moreover, in
sea-shells, it is known that the parts habitually covered and
shaded by the mantle of the animal, are of a paler colour
than those fully exposed to the light, just as is the case with
this incrustation. When we remember that lime, either as a
phosphate or carbonate, enters into the composition of the
hard parts, such as bones and shells, of all living animals, it
is an interesting physiological fact [6] to find substances
harder than the enamel of teeth, and coloured surfaces as well
polished as those of a fresh shell, reformed through inorganic
means from dead organic matter -- mocking, also, in
shape, some of the lower vegetable productions.

We found on St. Paul's only two kinds of birds -- the
booby and the noddy. The former is a species of gannet,
and the latter a tern. Both are of a tame and stupid
disposition, and are so unaccustomed to visitors, that I could
have killed any number of them with my geological hammer.
The booby lays her eggs on the bare rock; but the tern makes
a very simple nest with sea-weed. By the side of many of
these nests a small flying-fish was placed; which I suppose,
had been brought by the male bird for its partner. It was