Part 10 (1/2)

BABUYAN ISLANDS.

Horsburgh says (volume ii., page 442), coral-reefs line the sh.o.r.es of the harbour in Fuga; and the charts show there are other reefs about these islands. Camiguin has its sh.o.r.e in parts lined by coral-rock (Horsburgh, page 443); about a mile off sh.o.r.e there is between thirty and thirty-five fathoms. The plan of Port San Pio Quinto shows that its sh.o.r.es are fringed with coral; coloured red.--BASHEE Islands: Horsburgh, speaking of the southern part of the group (volume ii., page 445) says the sh.o.r.es of both islands are fortified by a reef, and through some of the gaps in it, the natives can pa.s.s 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 sh.o.r.es, 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 pa.s.sage 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 s.p.a.ce 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 sh.o.r.e of k.u.mI (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 sh.o.r.e, 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 cla.s.sed 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 (lat.i.tude 20 deg 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 s.h.i.+p 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 circ.u.mstance 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 s.p.a.ce, 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 s.p.a.ce 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 atoll 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 pa.s.sed it, any reefs at all.--CEYLON: a s.p.a.ce about eighty miles in length of the south-western and southern sh.o.r.es of these islands has been described by Mr. Twynam (”Naut. Mag.” 1836, pages 365 and 518); parts of this s.p.a.ce appear to be very regularly fringed by coral-reefs, which extend from a quarter to half a mile from the sh.o.r.e. 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 sh.o.r.e: 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 sh.o.r.es, which I have also coloured red.--At Venloos Bay the sh.o.r.e 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 sh.o.r.es, 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, sh.e.l.ls, 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 MALHA bank consists of a series of narrow banks, with from eight to sixteen fathoms on them; they are arranged in a semicircular manner, round a s.p.a.ce 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 cla.s.s;--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 sh.o.r.e. 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 cla.s.s; as seems probable from their great extension, or to the fringing cla.s.s; uncoloured.

--BOURBON. The greater part of the sh.o.r.es 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.

SEYCh.e.l.lES.

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 MAHE 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. sh.o.r.e 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 sh.o.r.e. 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 sh.e.l.ls; are only about twenty feet in height, and are environed by reefs, some attached to the sh.o.r.e, 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 Seych.e.l.les; relying chiefly on Captain F. Moresby and Dr. Allan, it appears that the greater number, namely--PLATTE, ALPHONSE, COETIVI, GALEGA, PROVIDENCE, ST. PIERRE, ASTOVA, a.s.sOMPTION, 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 cla.s.s. 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 circ.u.mference, 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 sh.o.r.e. 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.

COMORO GROUP.

MAYOTTA, according to Horsburgh (volume i., page 216, 4th edition), is completely surrounded by a reef, which runs at the distance of three, four, and in some places even five miles from the land; in an old chart, published by Dalrymple, a depth in many places of thirty-six and thirty-eight fathoms is laid down within the reef. In the same chart, the s.p.a.ce of open water within the reef in some parts is even more than three miles wide: the land is bold and peaked; this island, therefore, is encircled by a well-characterised barrier-reef, and is coloured pale blue.--JOHANNA; Horsburgh says (volume I. page 217) this island from the N.W. to the S.W.

point, is bounded by a reef, at the distance of two miles from the sh.o.r.e; in some parts, however, the reef must be attached, since Lieutenant Boteler (”Narr.” volume i., page 161) describes a pa.s.sage through it, within which there is room only for a few boats. Its height, as I am informed by Dr.

Allan, is about 3,500 feet; it is very precipitous, and is composed of granite, greenstone, and quartz; coloured blue.--MOHILLA; on the S. side of this island there is anchorage, in from thirty to forty-five fathoms, between a reef and the sh.o.r.e (Horsburgh, volume i., page 214); in Captain Owen's chart of Madagascar, this island is represented as encircled; coloured blue.--GREAT COMORO Island is, as I am informed by Dr. Allan, about 8,000 feet high, and apparently volcanic; it is not regularly encircled; but reefs of various shapes and dimensions, jut out from every headland on the W., S., and S.E. coasts, inside of which reefs there are channels, often parallel with the sh.o.r.e, with deep water. On the north-western coasts the reefs appear attached to the sh.o.r.es. The land near the coast is in some places bold, but generally speaking it is flat; Horsburgh says (volume i., page 214) the water is profoundly deep close to the Sh.o.r.e, from which expression I presume some parts are without reefs.

From this description I apprehend the reef belongs to the barrier cla.s.s; but I have not coloured it, as most of the charts which I have seen, represent the reefs round it as very much less extensive than round the other islands in the group.

MADAGASCAR.

My information is chiefly derived from the published charts by Captain Owen, and the accounts given by him and by Lieutenant Boteler. Commencing at the S.W. extremity of the island; towards the northern part of the STAR BANK (in lat.i.tude 25 deg S.) the coast for ten miles is fringed by a reef; coloured red. The sh.o.r.e immediately S. of ST. AUGUSTINE'S BAY appears fringed; but TULLEAR Harbour, directly N. of it, is formed by a narrow reef ten miles long, extending parallel to the sh.o.r.e, with from four to ten fathoms within it. If this reef had been more extensive, it must have been cla.s.sed as a barrier-reef; but as the line of coast falls inwards here, a submarine bank perhaps extends parallel to the sh.o.r.e, which has offered a foundation for the growth of the coral; I have left this part uncoloured.

From lat.i.tude 22 deg 16' to 21 deg 37', the sh.o.r.e is fringed by coral-reefs (see Lieutenant Boteler's ”Narrative,” volume ii., page 106), less than a mile in width, and with shallow water within. There are outlying coral-shoals in several parts of the offing, with about ten fathoms between them and the sh.o.r.e, and the depth of the sea one mile and a half seaward, is about thirty fathoms. The part above specified is engraved on a large scale; and as in the charts on rather a smaller scale the same fringe of reef extends as far as lat.i.tude 33 deg 15'; I have coloured the whole of this part of the coast red. The islands of JUAN DE NOVA (in lat.i.tude 17 deg S.) appear in the charts on a large scale to be fringed, but I have not been able to ascertain whether the reefs are of coral; uncoloured. The main part of the west coast appears to be low, with outlying sandbanks, which, Lieutenant Boteler (volume ii., page 106) says, ”are faced on the edge of deep water by a line of sharp-pointed coral-rocks.” Nevertheless I have not coloured this part, as I cannot make out by the charts that the coast itself is fringed. The headlands of NARRENDA and Pa.s.sANDAVA Bays (14 deg 40') and the islands in front of RADAMA HARBOUR are represented in the plans as regularly fringed, and have accordingly been coloured red. With respect to the EAST COAST OF MADAGASCAR, Dr. Allan informs me in a letter, that the whole line of coast, from TAMATAVE, in 18 deg 12', to C. AMBER, at the extreme northern point of the island, is bordered by coral-reefs. The land is low, uneven, and gradually rising from the coast. From Captain Owen's charts, also, the existence of these reefs, which evidently belong to the fringing cla.s.s, on some parts, namely N. of BRITISH SOUND, and near NGONCY, of the above line of coast might have been inferred. Lieutenant Boteler (volume i., page 155) speaks of ”the reef surrounding the island of ST. MARY'S at a small distance from the sh.o.r.e.” In a previous chapter I have described, from the information of Dr. Allan, the manner in which the reefs extend in N.E. lines from the headlands on this coast, thus sometimes forming rather deep channels within them, this seems caused by the action of the currents, and the reefs spring up from the submarine prolongations of the sandy headlands. The above specified portion of the coast is coloured red. The remaining S.E. portions do not appear in any published chart to possess reefs of any kind; and the Rev. W. Ellis, whose means of information regarding this side of Madagascar have been extensive, informs me he believes there are none.

EAST COAST OF AFRICA.

Proceeding from the northern part, the coast appears, for a considerable s.p.a.ce, without reefs. My information, I may here observe, is derived from the survey by Captain Owen, together with his narrative; and that by Lieutenant Boteler. At MUKDEESHA (10 deg 1' N.) there is a coral-reef extending four or five miles along the sh.o.r.e (Owen's ”Narr.” volume i, page 357) which in the chart lies at the distance of a quarter of a mile from the sh.o.r.e, and has within it from six to ten feet water: this then is a fringing-reef, and is coloured red. From JUBA, a little S. of the equator, to LAMOO (in 2 deg 20' S.) ”the coast and islands are formed of madrepore”

(Owen's ”Narrative,” volume i., page 363). The chart of this part (ent.i.tled DUNDAS Islands), presents an extraordinary appearance; the coast of the mainland is quite straight and it is fronted at the average distance of two miles, by exceedingly narrow, straight islets, fringed with reefs.

Within the chain of islets, there are extensive tidal flats and muddy bays, into which many rivers enter; the depths of these s.p.a.ces varies from one to four fathoms--the latter depth not being common, and about twelve feet the average. Outside the chain of islets, the sea, at the distance of a mile, varies in depth from eight to fifteen fathoms. Lieutenant Boteler (”Narr.”