ANDAMAN ISLANDS.—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. The northern Natunas and the Anambas Islands are represented in the charts on a large scale, published in the “Atlas of the Voyage of the ‘Favourite’,” as fringed by reefs of coral, with very shoal water within them.—Tumbelan and Bunoa Islands (1° N.) are represented in the English charts as surrounded by a very regular fringe.— St. Barbes (0° 15′ N.) is said by Horsburgh (volume ii., page 279) to be fronted by a reef, over which boats can land only at high water.—The shore of Borneo at Tunjong Apee is also fronted by a reef, extending not far from the land (Horsburgh, volume ii., page 468). These places I have coloured red; although with some hesitation, as the water is shallow. I might perhaps have added Pulo Leat, in Gaspar Strait, Lucepara, and Carimata; but as the sea is confined and shallow, and the reefs not very regular, I have left them uncoloured.
The water shoals gradually towards the whole west coast of Borneo: I cannot make out that it has any reefs of coral. The islands, however, off the northern extremity, and near the S.W. end of Palawan, are fringed by very distant coral-reefs; thus the reefs in the case of Balabac are no less than five miles from the land; but the sea, in the whole of this district, is so shallow, that the reefs might be expected to extend very far from the land. I have not, therefore, thought myself authorised to colour them. The N.E. point of Borneo, where the water is very shoal, is connected with Magindanao by a chain of islands called the Sooloo Archipelago, about which I have been able to obtain very little information; Pangootaran, although ten miles long, entirely consists of a bed of coral-rock (“Notices of E. Indian Arch.” page 58): I believe from Horsburgh that the island is low; not coloured.—Tahow Bank, in some old charts, appears like a submerged atoll; not coloured. Forrest (“Voyage,” page 21) states that one of the islands near Sooloo is surrounded by coral-rocks; but there is no distant reef. Near the S. end of Basselan, some of the islets in the chart accompanying Forrest’s “Voyage,” appear fringed with reefs; hence I have coloured, though unwillingly, parts of the Sooloo group red. The sea between Sooloo and Palawan, near the shoal coast of Borneo, is interspersed with irregular reefs and shoal patches; not coloured: but in the northern part of this sea, there are two low islets, Cagayanes and Cavilli, surrounded by extensive coral-reefs; the breakers round the latter (Horsburgh, volume ii., page 513) extend five or six miles from a sandbank, which forms the only dry part; these breakers are steep to outside; there appears to be an opening through them on one side, with four or five fathoms within: from this description, I strongly suspect that Cavilli ought to be considered an atoll; but, as I have not seen any chart of it, on even a moderately large scale, I have not coloured it. The islets off the northern end of Palawan, are in the same case as those off the southern end, namely they are fringed by reefs, some way distant from the shore, but the water is exceedingly shallow; uncoloured. The western shore of Palawan will be treated of under the head of China Sea.
PHILIPPINE ARCHIPELAGO.—A chart on a large scale of Appoo shoal, which lies near the S.E. coast of Mindoro, has been executed by Captain D. Ross: it appears atoll-formed, but with rather an irregular outline; its diameter is about ten miles; there are two well-defined passages leading into the interior lagoon, which appears open; close outside the reef all round, there is no bottom with seventy fathoms; coloured blue.—Mindoro: the N.W. coast is represented in several charts, as fringed by a reef, and Luban Island is said, by Horsburgh (volume ii., page 436), to be “lined by a reef.”—Luzon: Mr. Cuming, who has lately investigated with so much success the Natural History of the Philippines, informs me, that about three miles of the shore north of Point St. Jago, is fringed by a reef; as are (Horsburgh, volume ii., page 437) the Three Friars off Silanguin Bay. Between Point Capones and Playa Honda, the coast is “lined by a coral-reef, stretching out nearly a mile in some places,” (Horsburgh); and Mr. Cuming visited some fringing- reefs on parts of this coast, namely, near Puebla, Iba, and Mansinglor. In the neighbourhood of Solon-solon Bay, the shore is lined (Horsburgh ii., page 439) by coral-reefs, stretching out a great way: there are also reefs about the islets off Solamague; and as I am informed by Mr. Cuming, near St. Catalina, and a little north of it. The same gentleman informs me there are reefs on the S.E. point of this island in front of Samar, extending from Malalabon to Bulusan. These appear to be the principal fringing-reefs on the coasts of Luzon; and they have all been coloured red. Mr. Cuming informs me that none of them have deep water within; although it appears from Horsburgh that some few extend to a considerable distance from the shore. Within the Philippine Archipelago, the shores of the islands do not appear to be commonly fringed, with the exception of the S. shore of Masbate, and nearly the whole of Bohol; which are both coloured red. On the S. shore of Magindanao, Bunwoot Island is surrounded (according to Forrest, “Voyage,” page 253), by a coral-reef, which in the chart appears one of the fringing class. With respect to the eastern coasts of the whole Archipelago, I have not been able to obtain any account.
BABUYAN ISLANDS.—Horsburgh says (volume ii., page 442), coral-reefs line the shores of the harbour in Fuga; and the charts show there are other reefs about these islands. Camiguin has its shore in parts lined by coral-rock (Horsburgh, page 443); about a mile off shore there is between thirty and thirty-five fathoms. The plan of Port San Pio Quinto shows that its shores are fringed with coral; coloured red.—BABUYAN ISLANDS: Horsburgh, speaking of the southern part of the group (volume ii., page 445) says the shores of both islands are fortified by a reef, and through some of the gaps in it, the natives can pass in their boats in fine weather; the bottom near the land is coral-rock. From the published charts, it is evident that several of these islands are most regularly fringed; coloured red. The northern islands are left uncoloured, as I have been unable to find any account of them.—FORMOSA. The shores, especially the western one, seem chiefly composed of mud and sand, and I cannot make out that they are anywhere lined by reefs; except in a harbour (Horsburgh, volume ii., page 449) at the extreme northern point: hence, of course, the whole of this island is left uncoloured. The small adjoining islands are in the same case.— PATCHOW, or MADJIKO-SIMA GROUPS. Patchuson has been described by Captain Broughton (“Voy. to the N. Pacific,” page 191); he says, the boats, with some difficulty, found a passage through the coral-reefs, which extend along the coast, nearly half a mile off it. The boats were well sheltered within the reef; but it does not appear that the water is deep there. Outside the reef the depth is very irregular, varying from five to fifty fathoms; the form of the land is not very abrupt; coloured red.—Taypin-san; from the description given (page 195) by the same author, it appears that a very irregular reef extends, to the distance of several miles, from the southern island; but whether it encircles a space of deep water is not evident; nor, indeed, whether these outlying reefs are connected with those more immediately adjoining the land; left uncoloured. I may here just add that the shore of Kumi (lying west of Patchow), has a narrow reef attached to it in the plan of it, in La Peyrouse’s “Atlas;” but it does not appear in the account of the voyage that it is of coral; uncoloured.—LOO CHOO. The greater part of the coast of this moderately hilly island, is skirted by reefs, which do not extend far from the shore, and which do not leave a channel of deep water within them, as may be seen in the charts accompanying Captain B. Hall’s voyage to Loo Choo (see also remarks in Appendix, pages xxi. and xxv.). There are, however, some ports with deep water, formed by reefs in front of valleys, in the same manner as happens at Mauritius. Captain Beechey, in a letter to me, compares these reefs with those encircling the Society Islands; but there appears to me a marked difference between them, in the less distance at which the Loo Choo reefs lie from the land with relation to the probable submarine inclination, and in the absence of an interior deep water-moat or channel, parallel to the land. Hence, I have classed these reefs with fringing-reefs, and coloured them red.—PESCADORES (west of Formosa). Dampier (volume i., page 416), has compared the appearance of the land to the southern parts of England. The islands are interlaced with coral-reefs; but as the water is very shoal, and as spits of sand and gravel (Horsburgh, volume ii., page 450) extend far out from them, it is impossible to draw any inferences regarding the nature of the reefs.
CHINA SEA.—Proceeding from north to south, we first meet the Pratas Shoal (latitude 20° N.) which, according to Horsburgh (volume ii., page 335), is composed of coral, is of a circular form, and has a low islet on it. The reef is on a level with the water’s edge, and when the sea runs high, there are breakers mostly all round, “but the water within seems pretty deep in some places; although steep-to in most parts outside, there appear to be several parts where a ship might find anchorage outside the breakers;” coloured blue.—The Paracells have been accurately surveyed by Captain D. Ross, and charts on a large scale published: but few low islets have been formed on these shoals, and this seems to be a general circumstance in the China Sea; the sea close outside the reefs is very deep; several of them have a lagoon-like structure; or separate islets (Prattle, Robert, Drummond, etc.) are so arranged round a moderately shallow space, as to appear as if they had once formed one large atoll.— Bombay Shoal (one of the Paracells) has the form of an annular reef, and is “apparently deep within;” it seems to have an entrance (Horsburgh, volume ii., page 332) on its west side; it is very steep outside.—Discovery Shoal, also is of an oval form, with a lagoon-like space within, and three openings leading into it, in which there is a depth from two to twenty fathoms. Outside, at the distance (Horsburgh, volume ii., page 333) of only twenty yards from the reef, soundings could not be obtained. The Paracells are coloured blue.—Macclesfield Bank: this is a coral-bank of great size, lying east of the Paracells; some parts of the bank are level, with a sandy bottom, but, generally, the depth is very irregular. It is intersected by deep cuts or channels. I am not able to perceive in the published charts (its limits, however, are not very accurately known) whether the central part is deeper, which I suspect is the case, as in the Great Chagos Bank, in the Indian Ocean; not coloured.—Scarborough Shoal: this coral-shoal is engraved with a double row of crosses, forming a circle, as if there was deep water within the reef: close outside there was no bottom, with a hundred fathoms; coloured blue.—The sea off the west coast of Palawan and the northern part of Borneo is strewed with shoals: Swallow Shoal, according to Horsburgh (volume ii., page 431) “is formed, like most of the shoals hereabouts, of a belt of coral-rocks, “with a basin of deep water within.”—Half-Moon Shoal has a similar structure; Captain D. Ross describes it, as a narrow belt of coral-rock, “with a basin of deep water in the centre,” and deep sea close outside.—Bombay Shoal appears (Horsburgh, volume ii., page 432) “to be a basin of smooth water surrounded by breakers.” These three shoals I have coloured blue.—The Paraquas Shoals are of a circular form, with deep gaps running through them; not coloured.—A bank gradually shoaling to the depth of thirty fathoms, extends to a distance of about twenty miles from the northern part of Borneo, and to thirty miles from the northern part of Palawan. Near the land this bank appears tolerably free from danger, but a little further out it is thickly studded with coral-shoals, which do not generally rise quite to the surface; some of them are very steep-to, and others have a fringe of shoal-water round them. I should have thought that these shoals had level surfaces, had it not been for the statement made by Horsburgh “that most of the shoals hereabouts are formed of a belt of coral.” But, perhaps that expression was more particularly applied to the shoals further in the offing. If these reefs of coral have a lagoon-like structure, they should have been coloured blue, and they would have formed an imperfect barrier in front of Palawan and the northern part of Borneo. But, as the water is not very deep, these reefs may have grown up from inequalities on the bank: I have not coloured them.—The coast of China, Tonquin, and Cochin-China, forming the western boundary of the China Sea, appear to be without reefs: with regard to the two last-mentioned coasts, I speak after examining the charts on a large scale in the “Atlas of the Voyage of the ‘Favourite’.”
INDIAN OCEAN.—South Keeling has been specially described: nine miles north of it lies North Keeling, a very small atoll, surveyed by the “Beagle,” the lagoon of which is dry at low water.—Christmas Island, lying to the east, is a high island, without, as I have been informed by a person who passed it, any reefs at all.—CEYLON: a space about eighty miles in length of the south-western and southern shores of these islands has been described by Mr. Twynam (“Naut. Mag.” 1836, pages 365 and 518); parts of this space appear to be very regularly fringed by coral-reefs, which extend from a quarter to half a mile from the shore. These reefs are in places breached, and afford safe anchorage for the small trading craft. Outside, the sea gradually deepens; there is forty fathoms about six miles off shore: this part I have coloured red. In the published charts of Ceylon there appear to be fringing-reefs in several parts of the south-eastern shores, which I have also coloured red.—At Venloos Bay the shore is likewise fringed. North of Trincomalee there are also reefs of the same kind. The sea off the northern part of Ceylon is exceedingly shallow; and therefore I have not coloured the reefs which fringe portions of its shores, and the adjoining islets, as well as the Indian promontory of Madura.
CHAGOS, MALDIVA, and LACCADIVE ARCHIPELAGOES.—These three great groups which have already been often noticed, are now well-known from the admirable surveys of Captain Moresby and Lieutenant Powell. The published charts, which are worthy of the most attentive examination, at once show that the Chagos and Maldiva groups are entirely formed of great atolls, or lagoon-formed reefs, surmounted by islets. In the Laccadive group, this structure is less evident; the islets are low, not exceeding the usual height of coral-formations (see Lieutenant Wood’s account, “Geographical Journal”, volume vi., page 29), and most of the reefs are circular, as may be seen in the published charts; and within several of them, as I am informed by Captain Moresby, there is deepish water; these, therefore, have been coloured blue. Directly north, and almost forming part of this group, there is a long, narrow, slightly curved bank, rising out of the depths of the ocean, composed of sand, shells, and decayed coral, with from twenty-three to thirty fathoms on it. I have no doubt that it has had the same origin with the other Laccadive banks; but as it does not deepen towards the centre I have not coloured it. I might have referred to other authorities regarding these three archipelagoes; but after the publication of the charts by Captain Moresby, to whose personal kindness in giving me much information I am exceedingly indebted, it would have been superfluous.
Sahia de Malhabank consists of a series of narrow banks, with from eight to sixteen fathoms on them; they are arranged in a semicircular manner, round a space about forty fathoms deep, which slopes on the S.E. quarter to unfathomable depths; they are steep-to on both sides, but more especially on the ocean-side. Hence this bank closely resembles in structure, and I may add from Captain Moresby’s information in composition, the Pitt’s Bank in the Chagos group; and the Pitt’s Bank, must, after what has been shown of the Great Chagos Bank, be considered as a sunken, half-destroyed atoll; hence coloured blue.—Cargados Carajos Bank. Its southern portion consists of a large, curved, coral-shoal, with some low islets on its eastern edge, and likewise some on the western side, between which there is a depth of about twelve fathoms. Northward, a great bank extends. I cannot (probably owing to the want of perfect charts) refer this reef and bank to any class;—therefore not coloured.—Ile de Sable is a little island, lying west of C. Carajos, only some toises in height (“Voyage of the ‘Favourite’,” volume i., page 130); it is surrounded by reefs; but its structure is unintelligible to me. There are some small banks north of it, of which I can find no clear account.—Mauritius. The reefs round this island have been described in the chapter on fringing-reefs; coloured red. —Rodriguez. The coral-reefs here are exceedingly extensive; in one part they project even five miles from the shore. As far as I can make out, there is no deep-water moat within them; and the sea outside does not deepen very suddenly. The outline, however, of the land appears to be (“Life of Sir J. Makintosh,” volume ii., page 165) hilly and rugged. I am unable to decide whether these reefs belong to the barrier class; as seems probable from their great extension, or to the fringing class; uncoloured. —Bourbon. The greater part of the shores of this island are without reefs; but Captain Carmichael (Hooker’s “Bot. Misc.”) states that a portion, fifteen miles in length, on the S.E. side, is imperfectly fringed with coral reefs: I have not thought this sufficient to colour the island.
SEYCHELLES.—The rocky islands of primary formation, composing this group, rise from a very extensive and tolerably level bank, having a depth between twenty and forty fathoms. In Captain Owen’s chart, and in that in the “Atlas of the Voyage of the ‘Favourite’,” it appears that the east side of Mahé and the adjoining islands of St. Anne and Cerf, are regularly fringed by coral-reefs. A portion of the S.E. part of Curieuse Island, the N., and part of the S.W. shore of Praslin Island, and the whole west side of Digue Island, appear fringed. From a MS. account of these islands by Captain F. Moresby, in the Admiralty, it appears that Silhouette is also fringed; he states that all these islands are formed of granite and quartz, that they rise abruptly from the sea, and that “coral-reefs have grown round them, and project for some distance.” Dr. Allan, of Forres, who visited these islands, informs me that there is no deep water between the reefs and the shore. The above specified points have been coloured red. Amirantes Islands: The small islands of this neighbouring group, according to the MS. account of them by Captain F. Moresby, are situated on an extensive bank; they consist of the debris of corals and shells; are only about twenty feet in height, and are environed by reefs, some attached to the shore, and some rather distant from it.—I have taken great pains to procure plans and information regarding the several islands lying between S.E. and S.W. of the Amirantes, and the Seychelles; relying chiefly on Captain F. Moresby and Dr. Allan, it appears that the greater number, namely—Platte, Alphonse, Coetivi, Galega, Providence, St. Pierre, Astova, Assomption, and Glorioso, are low, formed of sand or coral-rock, and irregularly shaped; they are situated on very extensive banks, and are connected with great coral-reefs. Galega is said by Dr. Allan, to be rather higher than the other islands; and St. Pierre is described by Captain F. Moresby, as being cavernous throughout, and as not consisting of either limestone or granite. These islands, as well as the Amirantes, certainly are not atoll-formed, and they differ as a group from every other group with which I am acquainted; I have not coloured them; but probably the reefs belong to the fringing class. Their formation is attributed, both by Dr. Allan and Captain F. Moresby, to the action of the currents, here exceedingly violent, on banks, which no doubt have had an independent geological origin. They resemble in many respects some islands and banks in the West Indies, which owe their origin to a similar agency, in conjunction with an elevation of the entire area. In close vicinity to the several islands, there are three others of an apparently different nature: first, Juan de Nova, which appears from some plans and accounts to be an atoll; but from others does not appear to be so; not coloured. Secondly Cosmoledo; “this group consists of a ring of coral, ten leagues in circumference, and a quarter of a mile broad in some places, enclosing a magnificent lagoon, into which there did not appear a single opening” (Horsburgh, volume i., page 151); coloured blue. Thirdly, Aldabra; it consists of three islets, about twenty-five feet in height, with red cliffs (Horsburgh, volume i., page 176) surrounding a very shallow basin or lagoon. The sea is profoundly deep close to the shore. Viewing this island in a chart, it would be thought an atoll; but the foregoing description shows that there is something different in its nature; Dr. Allan also states that it is cavernous, and that the coral-rock has a vitrified appearance. Is it an upheaved atoll, or the crater of a volcano?—uncoloured.