t
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CHAP. descent, is very steep ; but tliis is greatly altered by eircuinstances, and
Fob.
182C.
■ , the growth or age of the island. Those parts of the strip which are
beyond the reach of the ivaves are no longer inhabited by tlie animals
tliat reared them, but have their cells filled ivith a hard calcareous
substance, and present a brown rugged appearance. Tlie parts which
are still immersed, or are dry at low water only, are intersected by small
channels and are so full of hollows, that the tide as it recedes leaves
small lakes of water npon them. The width of the plain or strip of dead
coral, in the islands which fell under our observation, in no instance exceeded
half a mile from the usual wash of the sea to the edge of the
lagoon, and in general was only about tliree or four liundred yards.
Beyond these limits, on the lagoon side in particular, where the coral was
less mutilated by the waves, there was frequently a ledge, tw-o or three
feet under water at high tide*, thirty to fifty yards in w-idth ; after which
the sides of the island descended rapidly, apparently by a succession of
inclined ledges formed by numerous columns united at their capitals,
with spaces between them in which the sounding-lead descended several
fathoms. This formation, though not clearly established as applying to
all the islands, was so conspicuous in some as to justify the conclusion
with regard to others. At Bow and Matilda Islands, I have been
tolerably minute in my descriptions of them, and it will be unnecessary
here to repeat what has been said there ; but these two, as also Henderson's
Island, afford good examples of what I have been describing.
To enable the reader more readily to comprehend the nature of these
singular formations, I subjoin a sketch and a section of a coral island,
with the slope of the sides of several of them, laid down according to
the soundings and the depths at which attempts w-ere made to reacli
the bottom.
R E FER EN C E S .
Fio. t.
AB Section of one side of the strip of coral inclo.sing the lagoon.
C, C The lagoon, protracted according to the depth found at Gambier Island.
D D Coralline in it.
Z The PaclSc.
i
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r
• At Bow Island, on the sea side, it t
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