It is evident, on our theory, that coasts merely fringed by reefs
cannot have subsided to any perceptible amount; and therefore they
must, since the growth of their corals, either have remained
stationary or have been upheaved. Now it is remarkable how
generally it can be shown, by the presence of upraised organic
remains, that the fringed islands have been elevated: and so far,
this is indirect evidence in favour of our theory. I was
particularly struck with this fact, when I found, to my surprise,
that the descriptions given by MM. Quoy and Gaimard were
applicable, not to reefs in general as implied by them, but only to
those of the fringing class; my surprise, however, ceased when I
afterwards found that, by a strange chance, all the several islands
visited by these eminent naturalists could be shown by their own
statements to have been elevated within a recent geological era.
Not only the grand features in the structure of barrier-reefs and
of atolls, and of their likeness to each other in form, size, and
other characters, are explained on the theory of subsidence--which
theory we are independently forced to admit in the very areas in
question, from the necessity of finding bases for the corals within
the requisite depth--but many details in structure and exceptional
cases can thus also be simply explained.
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