In
Turning Down The Edges, It Actually Punched Many Small
Holes Quite Through The Tin!
I was a good deal surprised by finding two species of
coral of the genus Millepora (M. complanata and alcicornis),
possessed of the power of stinging.
The stony branches or
plates, when taken fresh from the water, have a harsh feel
and are not slimy, although possessing a strong and disagreeable
smell. The stinging property seems to vary in
different specimens: when a piece was pressed or rubbed on
the tender skin of the face or arm, a pricking sensation was
usually caused, which came on after the interval of a second,
and lasted only for a few minutes. One day, however, by
merely touching my face with one of the branches, pain was
instantaneously caused; it increased as usual after a few
seconds, and remaining sharp for some minutes, was perceptible
for half an hour afterwards. The sensation was as
bad as that from a nettle, but more like that caused by the
Physalia or Portuguese man-of-war. Little red spots were
produced on the tender skin of the arm, which appeared as if
they would have formed watery pustules, but did not. M.
Quoy mentions this case of the Millepora; and I have heard
of stinging corals in the West Indies. Many marine animals
seem to have this power of stinging: besides the Portuguese
man-of-war, many jelly-fish, and the Aplysia or sea-slug
of the Cape de Verd Islands, it is stated in the voyage
of the Astrolabe, that an Actinia or sea-anemone, as well as
a flexible coralline allied to Sertularia, both possess this
means of offence or defence. In the East Indian sea, a
stinging sea-weed is said to be found.
Two species of fish, of the genus Scarus, which are common
here, exclusively feed on coral: both are coloured of a
splendid bluish-green, one living invariably in the lagoon,
and the other amongst the outer breakers. Mr. Liesk assured
us, that he had repeatedly seen whole shoals grazing with
their strong bony jaws on the tops of the coral branches: I
opened the intestines of several, and found them distended
with yellowish calcareous sandy mud. The slimy disgusting
Holuthuriae (allied to our star-fish), which the Chinese
gourmands are so fond of, also feed largely, as I am informed by
Dr. Allan, on corals; and the bony apparatus within their
bodies seems well adapted for this end. These Holuthuriae,
the fish, the numerous burrowing shells, and nereidous
worms, which perforate every block of dead coral, must be
very efficient agents in producing the fine white mud which
lies at the bottom and on the shores of the lagoon. A portion,
however, of this mud, which when wet resembled
pounded chalk, was found by Professor Ehrenberg to be
partly composed of siliceous-shielded infusoria.
April 12th. - In the morning we stood out of the lagoon
on our passage to the Isle of France. I am glad we have
visited these islands: such formations surely rank high
amongst the wonderful objects of this world. Captain Fitz
Roy found no bottom with a line 7200 feet in length, at the
distance of only 2200 yards from the shore; hence this island
forms a lofty submarine mountain, with sides steeper even
than those of the most abrupt volcanic cone. The saucer-shaped
summit is nearly ten miles across; and every single
atom, [10] from the least particle to the largest fragment of
rock, in this great pile, which however is small compared
with very many other lagoon-islands, bears the stamp of
having been subjected to organic arrangement. We feel surprise
when travellers tell us of the vast dimensions of the
Pyramids and other great ruins, but how utterly insignificant
are the greatest of these, when compared to these mountains
of stone accumulated by the agency of various minute
and tender animals! This is a wonder which does not at
first strike the eye of the body, but, after reflection,
the eye of reason.
I will now give a very brief account of the three great
classes of coral-reefs; namely, Atolls, Barrier, and Fringing-
reefs, and will explain my views [11] on their formation. Almost
every voyager who has crossed the Pacific has expressed
his unbounded astonishment at the lagoon-islands, or
as I shall for the future call them by their Indian name of
atolls, and has attempted some explanation. Even as long
ago as the year 1605, Pyrard de Laval well exclaimed, "C'est
[picture]
une merveille de voir chacun de ces atollons, environne d'un
grand banc de pierre tout autour, n'y ayant point d'artifice
humain." The accompanying sketch of Whitsunday Island
in the Pacific, copied from, Capt. Beechey's admirable Voyage,
gives but a faint idea of the singular aspect of an atoll:
it is one of the smallest size, and has its narrow islets united
together in a ring. The immensity of the ocean, the fury of
the breakers, contrasted with the lowness of the land and the
smoothness of the bright green water within the lagoon, can
hardly be imagined without having been seen.
The earlier voyagers fancied that the coral-building animals
instinctively built up their great circles to afford themselves
protection in the inner parts; but so far is this from
the truth, that those massive kinds, to whose growth on the
exposed outer shores the very existence of the reef depends,
cannot live within the lagoon, where other delicately-branching
kinds flourish. Moreover, on this view, many species
of distinct genera and families are supposed to combine for
one end; and of such a combination, not a single instance
can be found in the whole of nature. The theory that has
been most generally received is, that atolls are based on
submarine craters; but when we consider the form and size of
some, the number, proximity, and relative positions of others,
this idea loses its plausible character: thus Suadiva atoll is
44 geographical miles in diameter in one line, by 34 miles in
another line; Rimsky is 54 by 20 miles across, and it has a
strangely sinuous margin; Bow atoll is 30 miles long, and on
an average only 6 in width; Menchicoff atoll consists of three
atolls united or tied together.
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