The instant this takes
place, a perfect atoll is formed: I have said, remove the high land
from within an encircling barrier-reef, and an atoll is left, and
the land has been removed. We can now perceive how it comes that
atolls, having sprung from encircling barrier-reefs, resemble them
in general size, form, in the manner in which they are grouped
together, and in their arrangement in single or double lines; for
they may be called rude outline charts of the sunken islands over
which they stand. We can further see how it arises that the atolls
in the Pacific and Indian Oceans extend in lines parallel to the
generally prevailing strike of the high islands and great
coast-lines of those oceans. I venture, therefore, to affirm that
on the theory of the upward growth of the corals during the sinking
of the land, all the leading features in those wonderful
structures, the lagoon-islands or atolls, which have so long
excited the attention of voyagers, as well as in the no less
wonderful barrier-reefs, whether encircling small islands or
stretching for hundreds of miles along the shores of a continent,
are simply explained. (20/13. It has been highly satisfactory to me
to find the following passage in a pamphlet by Mr.
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