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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