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. This theory, moreover, is totally
inapplicable to the northern Maldiva atolls in the Indian Ocean
(one of which is 88 miles in length, and between 10 and 20 in
breadth), for they are not bounded like ordinary atolls by narrow
reefs, but by a vast number of separate little atolls; other little
atolls rising out of the great central lagoon-like spaces. A third
and better theory was advanced by Chamisso, who thought that from
the corals growing more vigorously where exposed to the open sea,
as undoubtedly is the case, the outer edges would grow up from the
general foundation before any other part, and that this would
account for the ring or cup-shaped structure.
Pages:
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902