Charles C. Darwin

Darwin, C. R. 1842. The structure and distribution of coral reefs.
Being the first part of the geology of the voyage of the Beagle, under
the command of Capt. Fitzroy, R.N. during the years 1832 to 1836.
London: Smith Elder and Co.

Persian Gulf is reference in pages 122, 137, and 191.

Originally at: http://darwin-online.org.uk/content/frameset?itemID=F271&viewtype=text&pageseq=209&keywords=gulf%20persian

Page 122:

reefs, but where the sea is very shallow, for in this case the reefs generally lie far from the land, and become very irregular, they have been coloured. Thirdly, if I had the means of ascertaining the fact, I should not colour a reef merely coating the edges of a submarine crater, or of a level submerged bank; for such superficial formations differ essentially, even when not in external appearance, from reefs whose foundations as well as superficies have been wholly formed by the growth of coral. Fourthly, in the Red Sea, and within some parts of the East Indian Archipelago, (if the imperfect charts of the latter can be trusted,) there are many scattered reefs, of small size, represented in the chart by mere dots, which rise out of deep water: these cannot be arranged under either of the three classes: in the Red Sea, however, some of these little reefs, from their position, seem once to have formed parts of a continuous barrier. There exist, also, scattered in the open ocean, some linear and irregularly-formed strips of coral-reef, which, as shown in the last chapter, are probably allied in their origin to atolls; but as they do not belong to that class, they have not been coloured; they are very few in number, and of insignificant dimensions. Lastly,

Voyage, p. 41). Mr. M'Clelland (Report of Committee for investigating Coal in India, p. 39) has shown that the volcanic band passing through Barren Island must be extended northwards. It appears by an old chart, that Cheduba was once an active volcano; (See also Silliman's North American Journal, vol. xxxviii. p. 385.) In Berghaus' Phys. Atlas, 1840, No. 7 of Geological Part, a volcano on the coast of Pondicherry is said to have burst forth in 1757. Ordinaire (Hist. Nat. des Volcans, p. 218) says that there is one at the month of the Persian Gulf, but I have not coloured it, as he gives no particulars. A volcano in Amsterdam, or St. Paul's, in the southern part of the Indian Ocean, has been seen (Naut. Mag. 1838, p. 842) in action. Dr. J. Allan, of Forres, informs me in a letter, that when he was at Joanna, he saw at night flames, apparently volcanic, issuing from the chief Comoro Island, and that the Arabs assured him that they were volcanic, adding that the volcano burned more during the wet season. I have marked this as a volcano, though with some hesitation, on account of the possibility of the flame arising from gaseous sources.

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height between 30 and 40 feet; and Mr. Salt (Travels in Abyssinia) describes a similar formation a little southward on the opposite shore at Amphila. Moreover, near the mouth of the Gulf of Suez, although on the coast opposite to that on which Dr. Rüppell says that the modern beds attain a height of only 30 to 40 feet, Mr. Burton* found a deposit replete with existing species of shells, at the height of 200 feet. In an admirable series of drawings by Capt. Moresby, I could see how continuously the cliff-bounded low plains of this formation extended with a nearly equable height, both on the eastern and western shores. The southern coast of Arabia seem to have been subjected to the same elevatory movement, Dr. Malcolmson found at Sahar low cliffs containing shells and corals, apparently of recent species. The Persian Gulf abounds with coral reefs; but as it is difficult to distinguish them from sand-banks in this shallow sea, I have coloured only some near the mouth; towards the head of the gulf Mr. Ainsworth† says that the land is worn into terraces, and that the beds contain organic remains of existing forms. The West Indian Archipelago of "fringed" islands, alone remains to be mentioned: evidence of an elevation within a late tertiary epoch of nearly the whole of this great area, may be found in the works of almost all the naturalists who have visited it. I will give some of the principal references in a note.‡

It is very remarkable, on reviewing these details to observe in how many instances fringing-reefs round the shores, have coincided with the existence on the land of upraised organic

* Lyell's Principles of Geology, 5th edition, vol. iv. p. 25.

† Ainsworth's Assyria and Babylon, p. 217.

‡ On Florida and the north shores of the Gulf of Mexico, Rogers' Report to Brit. Assoc. vol. iii. p. 14.—On the shores of Mexico, Humboldt, Polit. Essay on New Spain, vol. I. p. 62. (I have also some corroborative facts with respect to the shores of Mexico.)—Honduras and the Antilles, Lyell's Principles, 5th ed. vol. iv. p. 22.—Santa Cruz and Barbadoes, Prof. Hovey, Silliman's Journ vol. xxv. p. 74.—St. Domingo, Courrojolles, Jour. de Phys. tom. liv. p. 106.—Bahamas, United Service Journ. No. lxxi. pp. 218 and 224.—Jamaica, De la Beche Geol. Man. p. 142. —Cuba, Taylor in Lond. and Edin. Phil. Mag. vol. xi. p. 17. Dr. Daubeny also at a meeting of the Geolog. Soc. orally described some very modern beds lying on the N.W. parts of Cuba. I might have added many other less important references.

Page 191:

From the description given in Owen's Nar. (vol. i. p. 162) the shore from Mozambique to Delaga Bay appear to be low and sandy: many of the shoals and islets off this line of coast are of coral formation; but from their small size and lowness, it is not possible, from the charts, to know whether they are truly fringed. Hence this portion of coast is left uncoloured, as are likewise those parts more northward, of which no mention has been made in the foregoing pages, from the want of information.

PERSIAN GULF.—From the charts lately published on a large scale by the East Indian Company, it appears that several parts, especially the southern shores of this gulf, are fringed by coral-reefs; but as the water is very shallow, and as there are numerous sand-banks, which are difficult to distinguish on the chart from reefs, I have not coloured the upper part red. Towards the mouth, however, where the water is rather deeper, the Islands of Ormuz and Larrack, appear so regularly fringed, that I have coloured them red. There are certainly no atolls in the Persian Gulf. The shores of Immaum, and of the promontory forming the southern headland of the Persian Gulf, seem to be without reefs. The whole S. W. part (except one or two small patches) of Arabia Felix, and the shores of Socotra appear from the charts and memoir of Capt. Haines (Geograph. Journ., 1839, p. 125,) to be without any reefs. I believe there are no extensive coral-reefs on any part of the coasts of India, except on the low promontory of Madura (as already mentioned) in front of Ceylon.

RED SEA.—My information is chiefly derived from the admirable charts published by the East Indian Company in 1836, from personal communication with Capt. Moresby, one of the surveyors, and from the excellent memoir, "über die Natur der Corallen-Bänken des Rothen Meeres," by Ehrenberg. The plains immediately bordering the Red Sea seem chiefly to consist of a sedimentary formation of the newer tertiary period. The shore is, with the exception of a few parts, fringed by coral-reefs. The water is generally profoundly deep close to the shore; but this fact, which has attracted the attention of most voyagers, seem to have no necessary connection with the presence of reefs; for Capt. Moresby, particularly observed to me, that, in lat. 24° 10 ' on the eastern side, there is a piece of coast, with very deep water close to it, without any reefs, but not differing in other respects from the usual nature of the coast-line. The most remarkable feature in the Red Sea is the chain of submerged banks, reefs, and islands, lying some way from the shore,