b, b
lions.
PA C IF IC AND BE ERING’S STRAIT.
Break of the sea, outside which the descent is very steep.
Descent of the sides of several islands.
ditto ditto off the points which are shallower.
Soundings npon coral.
No bottom at these depths.
F ig . 3 .
Habitable part of the island.
Greatest depth at which it is supposed the coral animals can commence their opera-
1 8 9
All these islands are situated within the trade-wind, with the exception
ofOeno, which is only on the verge ofit, and follow one general
rule in having their windward side higher and more perfect than the
other, and not unfrequently well wooded, while the other is only a
half-drowned reef, or wholly under water. At Gambier and Matilda
Islands this inequality was very conspicuous, the weather side of both
being wooded, and of the former, inhabited, while the other sides were
from twenty to thirty feet under water, where they might be perceived
equally narrow, and well defined. It is on the leeward side also that
the entrances into the lagoons generally occur, though they are sometimes
situated in a side that runs in the direction of the wind, as at Bow
Island ; but I do not know of any one being to windward. The fact,
if it be found to be general with regard to other coral islands, is curious,
and is not fully accounted for by the continued operation of the trade-
wind upon its side, as the coincidence would suggest. After the reef
has arrived at the surface of the sea, it is easy to conceive what would
be the effect of the trade-wind ; but it does not seem possible that its
influence could he felt so fiir under water as some of the reefs are
situated.
All the points or angles ofthese islands descend into the sea with
less abruptness than the sides, and, I think, with more regularity. The
wedge-shaped space that the meeting of the two sides would form in
the lagoon is filled up by the ledges there being broader ; in such
places, as well as iu the narrow parts of the lake, the coralline are in
greater numbers, though, generally speaking, all the lagoons are more
or less incumbered with them. They appear to rise to the surface in
Î
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h e .