Coral Reefs

Page 101

I have, therefore, not coloured any of the islands in this part of the sea; I think it, however, exceedingly probable that some of them ought to be blue. I may add that there is a harbour on the S.E. coast of BOUTON which, according to an old chart, is formed by a reef, parallel to the shore, with deep water within; and in the "Voyage of the 'Coquille'," some neighbouring islands are represented with reefs a good way distant, but I do not know whether with deep water within. I have not thought the evidence sufficient to permit me to colour them.


Commencing with the west coast and outlying islands, ENGANO Island is represented in the published chart as surrounded by a narrow reef, and Napier, in his "Sailing Directions," speaks of the reef being of coral (also Horsburgh, volume ii., page 115); coloured red.--RAT Island (3 deg 51' S.) is surrounded by reefs of coral, partly dry at low water, (Horsburgh, volume ii., page 96).--TRIESTE Island (4 deg 2' S.). The shore is represented in a chart which I saw at the India House, as fringed in such a manner, that I feel sure the fringe consists of coral; but as the island is so low, that the sea sometimes flows quite over it (Dampier, "Voyage," volume i., page 474), I have not coloured it.--PULO DOOA (latitude 3 deg). In an old chart it is said there are chasms in the reefs round the island, admitting boats to the watering-place, and that the southern islet consists of a mass of sand and coral.--PULO PISANG; Horsburgh (volume ii., page 86) says that the rocky coral-bank, which stretches about forty yards from the shore, is steep to all round: in a chart, also, which I have seen, the island is represented as regularly fringed.--PULO MINTAO is lined with reefs on its west side (Horsburgh, volume ii., page 107).--PULO BANIAK; the same authority (volume ii., page 105), speaking of a part, says it is faced with coral-rocks.--MINGUIN (3 deg 36' N.). A coral-reef fronts this place, and projects into the sea nearly a quarter of a mile ("Notices of the Indian Arch." published at Singapore, page 105).--PULO BRASSA (5 deg 46' N.). A reef surrounds it at a cable's length (Horsburgh, volume ii., page 60). I have coloured all the above-specified points red. I may here add, that both Horsburgh and Mr. Moor (in the "Notices" just alluded to) frequently speak of the numerous reefs and banks of coral on the west coast of Sumatra; but these nowhere have the structure of a barrier-reef, and Marsden ("History of Sumatra") states, that where the coast is flat, the fringing-reefs extend furthest from it. The northern and southern points, and the greater part of the east coast, are low, and faced with mud banks, and therefore without coral.


The chart represents the islands of this group as fringed by reefs. With regard to GREAT NICOBAR, Captain Moresby informs me, that it is fringed by reefs of coral, extending between two and three hundred yards from the shore. The NORTHERN NICOBARS appear so regularly fringed in the published charts, that I have no doubt the reefs are of coral. This group, therefore, is coloured red.


From an examination of the MS. chart, on a large scale, of this island, by Captain Arch. Blair, in the Admiralty, several portions of the coast appear fringed; and as Horsburgh speaks of coral-reefs being numerous in the vicinity of these islands, I should have coloured them red, had not some expressions in a paper in the "Asiatic Researches" (volume iv., page 402) led me to doubt the existence of reefs; uncoloured.

The coast of MALACCA, TENASSERIM and the coasts northward, appear in the greater part to be low and muddy: where reefs occur, as in parts of MALACCA STRAITS, and near SINGAPORE, they are of the fringing kind; but the water is so shoal, that I have not coloured them. In the sea, however, between Malacca and the west coast of Borneo, where there is a greater depth from forty to fifty fathoms, I have coloured red some of the groups, which are regularly fringed.

Charles Darwin

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