In the southern part of the Low Archipelago, Elizabeth Island is described by Captain Beechey (Beechey's "Voyage in the Pacific," page 46, 4to edition.), as being quite flat, and about eighty feet in height; it is entirely composed of dead corals, forming a honeycombed, but compact rock. In cases like this, of an island having exactly the appearance, which the elevation of any one of the smaller surrounding atolls with a shallow lagoon would present, one is led to conclude (with little better reason, however, than the improbability of such small and low fabrics lasting, for an immense period, exposed to the many destroying agents of nature), that the elevation has taken place at an epoch not geologically remote. When merely the surface of an island of ordinary formation is strewed with marine bodies, and that continuously, or nearly so, from the beach to a certain height, and not above that height, it is exceedingly improbable that such organic remains, although they may not have been specially examined, should belong to any ancient period. It is necessary to bear these remarks in mind, in considering the evidence of the elevatory movements in the Pacific and Indian Oceans, as it does not often rest on specific determinations, and therefore should be received with caution. Six of the COOK AND AUSTRAL Islands (S.W. of the Society group), are fringed; of these, five were described to me by the Rev. J. Williams, as formed of coral-rock, associated with some basalt in Mangaia), and the sixth as lofty and basaltic. Mangaia is nearly three hundred feet high, with a level summit; and according to Mr. S. Wilson (Couthouy's "Remarks," page 34.) it is an upraised reef; "and there are in the central hollow, formerly the bed of the lagoon, many scattered patches of coral-rock, some of them raised to a height of forty feet." These knolls of coral-rock were evidently once separate reefs in the lagoon of an atoll. Mr. Martens, at Sydney, informed me that this island is surrounded by a terrace-like plain at about the height of a hundred feet, which probably marks a pause in its elevation. From these facts we may infer, perhaps, that the Cook and Austral Islands have been upheaved at a period probably not very remote.
SAVAGE Island (S.E. of the Friendly group), is about forty feet in height. Forster ("Observations made during Voyage round the World," page 147.) describes the plants as already growing out of the dead, but still upright and spreading trees of coral; and the younger Forster ("Voyage," volume ii., page 163.) believes that an ancient lagoon is now represented by a central plain; here we cannot doubt that the elevatory forces have recently acted. The same conclusion may be extended, though with somewhat less certainty, to the islands of the FRIENDLY GROUP, which have been well described in the second and third voyages of Cook. The surface of Tongatabou is low and level, but with some parts a hundred feet high; the whole consists of coral-rock, "which yet shows the cavities and irregularities worn into it by the action of the tides." (Cook's "Third Voyage" (4to edition), volume i., page 314.) On Eoua the same appearances were noticed at an elevation of between two hundred and three hundred feet. Vavao, also, at the opposite or northern end of the group, consists, according to the Rev. J. Williams, of coral-rock. Tongatabou, with its northern extensive reefs, resembles either an upraised atoll with one half originally imperfect, or one unequally elevated; and Anamouka, an atoll equally elevated. This latter island contains (Ibid., volume i., page 235.) in its centre a salt-water lake, about a mile-and-a-half in diameter, without any communication with the sea, and around it the land rises gradually like a bank; the highest part is only between twenty and thirty feet; but on this part, as well as on the rest of the land (which, as Cook observes, rises above the height of true lagoon-islands), coral-rock, like that on the beach, was found. In the NAVIGATOR ARCHIPELAGO, Mr. Couthouy ("Remarks on Coral-Formations," page 50.) found on Manua many and very large fragments of coral at the height of eighty feet, "on a steep hill-side, rising half a mile inland from a low sandy plain abounding in marine remains." The fragments were embedded in a mixture of decomposed lava and sand. It is not stated whether they were accompanied by shells, or whether the corals resembled recent species; as these remains were embedded they possibly may belong to a remote epoch; but I presume this was not the opinion of Mr. Couthouy. Earthquakes are very frequent in this archipelago.
Still proceeding westward we come to the NEW HEBRIDES; on these islands, Mr. G. Bennett (author of "Wanderings in New South Wales"), informs me he found much coral at a great altitude, which he considered of recent origin. Respecting SANTA CRUZ, and the SOLOMON ARCHIPELAGO, I have no information; but at New Ireland, which forms the northern point of the latter chain, both Labillardiere and Lesson have described large beds of an apparently very modern madreporitic rock, with the form of the corals little altered. The latter author ("Voyage de la 'Coquille'," Part. Zoolog.) states that this formation composes a newer line of coast, modelled round an ancient one. There only remains to be described in the Pacific, that curved line of fringed islands, of which the MARIANAS form the main part. Of these Guam, Rota, Tiniam, Saypan, and some islets farther north, are described by Quoy and Gaimard (Freycinet's "Voyage autour du Monde." See also the "Hydrographical Memoir," page 215.), and Chamisso (Kotzebue's "First Voyage."), as chiefly composed of madreporitic limestone, which attains a considerable elevation, and is in several cases worn into successively rising cliffs: the two former naturalists seem to have compared the corals and shells with the existing ones, and state that they are of recent species. FAIS, which lies in the prolonged line of the Marianas, is the only island in this part of the sea which is fringed; it is ninety feet high, and consists entirely of madreporitic rock. (Lutke's "Voyage," volume ii., page 304.)
In the EAST INDIAN ARCHIPELAGO, many authors have recorded proofs of recent elevation. M. Lesson (Partie Zoolog., "Voyage de la 'Coquille'.") states, that near Port Dory, on the north coast of New Guinea, the shores are flanked, to the height of 150 feet, by madreporitic strata of modern date. He mentions similar formations at Waigiou, Amboina, Bourou, Ceram, Sonda, and Timor: at this latter place, MM. Quoy and Gaimard ("Ann. des Scien. Nat." tom. vi., page 281.) have likewise described the primitive rocks, as coated to a considerable height with coral. Some small islets eastward of Timor are said in Kolff's "Voyage," (translated by Windsor Earl, chapters vi., vii.) to resemble small coral islets upraised some feet above the sea. Dr. Malcolmson informs me that Dr. Hardie found in JAVA an extensive formation, containing an abundance of shells, of which the greater part appear to be of existing species. Dr. Jack ("Geolog. Transact." 2nd series, volume i., page 403. On the Peninsula of Malacca, in front of Pinang, 5 deg 30' N., Dr. Ward collected some shells, which Dr. Malcolmson informs me, although not compared with existing species, had a recent appearance. Dr. Ward describes in this neighbourhood ("Trans. Asiat. Soc." volume xviii., part ii., page 166) a single water-worn rock, with a conglomerate of sea-shells at its base, situated six miles inland, which, according to the traditions of the natives, was once surrounded by the sea. Captain Low has also described (Ibid., part i., page 131) mounds of shells lying two miles inland on this line of coast.) has described some upraised shells and corals, apparently recent, on Pulo Nias off SUMATRA; and Marsden relates in his history of this great island, that the names of many promontories, show that they were originally islands. On part of the west coast of BORNEO and at the SOOLOO Islands, the form of the land, the nature of the soil, and the water-washed rocks, present appearances ("Notices of the East Indian Arch." Singapore, 1828, page 6, and Append., page 43.) (although it is doubtful whether such vague evidence is worthy of mention), of having recently been covered by the sea; and the inhabitants of the Sooloo Islands believe that this has been the case. Mr. Cuming, who has lately investigated, with so much success, the natural history of the PHILIPPINES, found near Cabagan, in Luzon, about fifty feet above the level of the R. Cagayan, and seventy miles from its mouth, a large bed of fossil shells: these, he informs me, are of the same species with those now existing on the shores of the neighbouring islands. From the accounts given us by Captain Basil Hall and Captain Beechey (Captain B. Hall, "Voyage to Loo Choo," Append., pages xxi. and xxv. Captain Beechey's "Voyage," page 496.) of the lines of inland reefs, and walls of coral-rock worn into caves, above the present reach of the waves, at the LOO CHOO Islands, there can be little doubt that they have been upraised at no very remote period.
Dr. Davy describes the northern province of CEYLON ("Travels in Ceylon," page 13. This madreporitic formation is mentioned by M. Cordier in his report to the Institute (May 4th, 1839), on the voyage of the "Chevrette", as one of immense extent, and belonging to the latest tertiary period.) as being very low, and consisting of a limestone with shells and corals of very recent origin; he adds, that it does not admit of a doubt that the sea has retired from this district even within the memory of man. There is also some reason for believing that the western shores of India, north of Ceylon, have been upraised within the recent period. (Dr. Benza, in his "Journey through the N. Circars" (the "Madras Lit. and Scient. Journ." volume v.) has described a formation with recent fresh-water and marine shells, occurring at the distance of three or four miles from the present shore. Dr. Benza, in conversation with me, attributed their position to a rise of the land. Dr. Malcolmson, however (and there cannot be a higher authority on the geology of India) informs me that he suspects that these beds may have been formed by the mere action of the waves and currents accumulating sediment. From analogy I should much incline to Dr. Benza's opinion.) MAURITIUS has certainly been upraised within the recent period, as I have stated in the chapter on fringing-reefs. The northern extremity of MADAGASCAR is described by Captain Owen (Owen's "Africa," volume ii., page 37, for Madagascar; and for S. Africa, volume i., pages 412 and 426. Lieutenant Boteler's narrative contains fuller particulars regarding the coral-rock, volume i., page 174, and volume ii., pages 41 and 54. See also Ruschenberger's "Voyage round the World," volume i., page 60.) as formed of madreporitic rock, as likewise are the shores and outlying islands along an immense space of EASTERN AFRICA, from a little north of the equator for nine hundred miles southward. Nothing can be more vague than the expression "madreporitic rock;" but at the same time it is, I think, scarcely possible to look at the chart of the linear islets, which rise to a greater height than can be accounted for by the growth of coral, in front of the coast, from the equator to 2 deg S., without feeling convinced that a line of fringing-reefs has been elevated at a period so recent, that no great changes have since taken place on the surface of this part of the globe. Some, also, of the higher islands of madreporitic rock on this coast, for instance Pemba, have very singular forms, which seem to show the combined effect of the growth of coral round submerged banks, and their subsequent upheaval. Dr. Allan informs me that he never observed any elevated organic remains on the SEYCHELLES, which come under our fringed class.
The nature of the formations round the shores of the RED SEA, as described by several authors, shows that the whole of this large area has been elevated within a very recent tertiary epoch. A part of this space in the appended map, is coloured blue, indicating the presence of barrier-reefs: on which circumstance I shall presently make some remarks. Ruppell (Ruppell, "Reise in Abyssinien," Band i., s. 141.) states that the tertiary formation, of which he has examined the organic remains, forms a fringe along the shores with a uniform height of from thirty and forty feet from the mouth of the Gulf of Suez to about latitude 26 deg; but that south of 26 deg, the beds attain only the height of from twelve to fifteen feet. This, however, can hardly be quite accurate; although possibly there may be a decrease in the elevation of the shores in the middle parts of the Red Sea, for Dr. Malcolmson (as he informs me) collected from the cliffs of Camaran Island (latitude 15 deg 30' S.) shells and corals, apparently recent, at a height between thirty and forty 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. Ruppell says that the modern beds attain a height of only thirty to forty feet, Mr. Burton (Lyell's "Principles of Geology," 5th edition, volume iv., page 25.) found a deposit replete with existing species of shells, at the height of 200 feet. In an admirable series of drawings by Captain 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 seems to have been subjected to the same elevatory movement, for 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 (Ainsworth's "Assyria and Babylon," page 217.) 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. (On Florida and the north shores of the Gulf of Mexico, Rogers' "Report to Brit. Assoc." volume iii., page 14.--On the shores of Mexico, Humboldt, "Polit. Essay on New Spain," volume i., page 62. (I have also some corroborative facts with respect to the shores of Mexico.)--Honduras and the Antilles, Lyell's "Principles," 5th edition, volume iv., page 22.--Santa Cruz and Barbadoes, Prof. Hovey, "Silliman's Journal", volume xxxv., page 74.--St. Domingo, Courrojolles, "Journ de Phys." tom. liv., page 106.--Bahamas, "United Service Journal", No. lxxi., pages 218 and 224. Jamaica, De la Beche, "Geol. Man." page 142.--Cuba, Taylor in "Lond. and Edin. Mag." volume xi., page 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.)
