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
amusing to watch how quickly a large and active crab
(Graspus), which inhabits the crevices of the rock, stole the
fish from the side of the nest, as soon as we had disturbed
the parent birds. Sir W. Symonds, one of the few persons
who have landed here, informs me that he saw the crabs
dragging even the young birds out of their nests, and devouring
them. Not a single plant, not even a lichen, grows
on this islet; yet it is inhabited by several insects and
spiders. The following list completes, I believe, the
terrestrial fauna: a fly (Olfersia) living on the booby, and
a tick which must have come here as a parasite on the birds;
a small brown moth, belonging to a genus that feeds on feathers;
a beetle (Quedius) and a woodlouse from beneath the dung; and
lastly, numerous spiders, which I suppose prey on these small
attendants and scavengers of the water-fowl. The often repeated
description of the stately palm and other noble tropical
plants, then birds, and lastly man, taking possession of
the coral islets as soon as formed, in the Pacific, is probably
not correct; I fear it destroys the poetry of this story, that
feather and dirt-feeding and parasitic insects and spiders
should be the first inhabitants of newly formed oceanic
land.
The smallest rock in the tropical seas, by giving a foundation
for the growth of innumerable kinds of sea-weed and
compound animals, supports likewise a large number of fish.
The sharks and the seamen in the boats maintained a constant
struggle which should secure the greater share of the
prey caught by the fishing-lines. I have heard that a rock
near the Bermudas, lying many miles out at sea, and at a
considerable depth, was first discovered by the circumstance
of fish having been observed in the neighbourhood.
FERNANDO NORONHA, Feb. 20th. - As far as I was enabled
to observe, during the few hours we stayed at this place, the
constitution of the island is volcanic, but probably not of a
recent date. The most remarkable feature is a conical hill,
about one thousand feet high, the upper part of which is
exceedingly steep, and on one side overhangs its base. The
rock is phonolite, and is divided into irregular columns. On
viewing one of these isolated masses, at first one is inclined
to believe that it has been suddenly pushed up in a semi-fluid
state. At St. Helena, however, I ascertained that some
pinnacles, of a nearly similar figure and constitution, had
been formed by the injection of melted rock into yielding
strata, which thus had formed the moulds for these gigantic
obelisks. The whole island is covered with wood; but from
the dryness of the climate there is no appearance of luxuriance.
Half-way up the mountain, some great masses of the
columnar rock, shaded by laurel-like trees, and ornamented
by others covered with fine pink flowers but without a single
leaf, gave a pleasing effect to the nearer parts of the scenery.
BAHIA, OR SAN SALVADOR. BRAZIL, Feb. 29th. - The day
has passed delightfully. Delight itself, however, is a weak
term to express the feelings of a naturalist who, for the first
time, has wandered by himself in a Brazilian forest. The
elegance of the grasses, the novelty of the parasitical plants,
the beauty of the flowers, the glossy green of the foliage,
but above all the general luxuriance of the vegetation, filled
me with admiration. A most paradoxical mixture of sound
and silence pervades the shady parts of the wood. The noise
from the insects is so loud, that it may be heard even in a
vessel anchored several hundred yards from the shore; yet
within the recesses of the forest a universal silence appears
to reign. To a person fond of natural history, such a day
as this brings with it a deeper pleasure than he can ever hope
to experience again. After wandering about for some hours,
I returned to the landing-place; but, before reaching it, I
was overtaken by a tropical storm. I tried to find shelter
under a tree, which was so thick that it would never have
been penetrated by common English rain; but here, in a
couple of minutes, a little torrent flowed down the trunk.
It is to this violence of the rain that we must attribute the
verdure at the bottom of the thickest woods: if the showers
were like those of a colder climate, the greater part would
be absorbed or evaporated before it reached the ground. I
will not at present attempt to describe the gaudy scenery
of this noble bay, because, in our homeward voyage, we
called here a second time, and I shall then have occasion to
remark on it.
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