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Updated: June 1, 2025
In the former large spaces consist of sand and SOFT CLAY; and Kotzebue speaks of clay having been found within one of the Marshall atolls. No doubt this clay is calcareous mud, similar to that at Keeling Island, and to that at Bermuda already referred to, as undistinguishable from disintegrated chalk, and which Lieutenant Nelson says is called there pipe-clay.
In the ages succeeding the deposition of the red marl Europe seems to have been broken up into an archipelago of coral reefs and atolls; and the islands of this ancient oolitic ocean were tenanted by numbers of tiny ancestral marsupials, some of which approached in appearance the pouched ant-eaters of Western Australia, while others resembled rather the phalangers and wombats, or turned into excellent imitation carnivores, like our modern friend the Tasmanian devil.
Again, on what have the reef-building corals, which cannot live at great depths, based their encircling structures? This is a great apparent difficulty, analogous to that in the case of atolls, which has generally been overlooked.
To escape this latter most improbable admission, which implies the existence of submarine chains of mountains of almost the same height, extending over areas of many thousand square miles, there is but one alternative; namely, the prolonged subsidence of the foundations, on which the atolls were primarily based, together with the upward growth of the reef-constructing corals.
The ring-formed reefs on the sides of this bifurcating channel are elongated, so that the northern and southern portions of Mahlos Mahdoo may claim, as far as their external outline is concerned, to be considered as distinct and perfect atolls.
But, at the same time, the marine shell-fish which are found in the shallow waters of the shores of New Guinea, are quite different from those which are met with upon the coasts of Australia. Now, the eastern end of Torres Straits is full of atolls, which, in fact, form the northern termination of the Great Barrier Reef which skirts the eastern coast of Australia.
As the reef-building corals require food, are preyed upon by other animals, are killed by sediment, cannot adhere to a loose bottom, and may be easily carried down to a depth whence they cannot spring up again, we need feel no surprise at the reefs both of atolls and barriers becoming in parts imperfect.
In a space as large as four continents, the polyps, strengthened by the lukewarm water, are building up thousands of atolls, ring-shaped islands, reefs and submarine pillars that, when united together by the work of a thousand years, are going to create a new land, an exchange continent in case the human species should lose its present base in some cataclysm of Nature.
The minute coral animalculæ have provided by their industrious labour shelter for the largest vessels. On many of the atolls grow cocoa palms, and only then are the ring-shaped islands inhabitable. How curious they look to one approaching on a vessel! Only the crowns of the palms are seen above the horizon; the island, being low, is out of sight.
After having doubled the shoals of La Fortune and Saya de Malha, and passed off the Seychelles, whilst among the atolls to the south of the Maldive Islands, which are level with the surface of the water and covered with bushy trees ending in a cluster of cocoas, they sighted the island of Ceylon and the Coromandel coast, and cast anchor before Pondicherry.
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