Chapter Vi.

Description of the coloured map.—Proximity of atolls and barrier-reefs.— Relation in form and position of atolls with ordinary islands.—Direct evidence of subsidence difficult to be detected.—Proofs of recent elevation where fringing-reefs occur.—Oscillations of level.—Absence of active volcanoes in the areas of subsidence.—Immensity of the areas which have been elevated and have subsided.—Their relation to the present distribution of the land.—Areas of subsidence elongated, their intersection and alternation with those of elevation.—Amount and slow rate of the subsidence.—Recapitulation.

It will be convenient to give here a short account of the appended map (Plate III.) [Inasmuch as the coloured map would have proved too costly to be given in this series, the indications of colour have been replaced by numbers referring to the dotted groups of reefs, etc. The author’s original wording, however, is retained in full, as it will be easy to refer to the map by the numbers, and thus the flow of the narrative is undisturbed.]: a fuller one, with the data for colouring each spot, is reserved for the Appendix; and every place there referred to may be found in the Index. A larger chart would have been desirable; but, small as the adjoined one is, it is the result of many months’ labour. I have consulted, as far as I was able, every original voyage and map; and the colours were first laid down on charts on a larger scale. The same blue colour, with merely a difference in the depth of tint, is used for atolls or lagoon-islands, and barrier-reefs, for we have seen, that as far as the actual coral-formation is concerned, they have no distinguishing character. Fringing-reefs have been coloured red, for between them on the one hand, and barrier-reefs and atolls on the other, there is an important distinction with respect to the depth beneath the surface, at which we are compelled to believe their foundations lie. The two distinct colours, therefore, mark two great types of structure.

The _dark blue colour_ [represented by (3) in our plate] represents atolls and submerged annular reefs, with deep water in their centres. I have coloured as atolls, a few low and small coral-islands, without lagoons; but this has been done only when it clearly appeared that they originally contained lagoons, since filled up with sediment: when there were not good grounds for this belief, they have been left uncoloured.

The _pale blue colour_ [represented by (2)] represents barrier-reefs. The most obvious character of reefs of this class is the broad and deep-water moat within the reef: but this, like the lagoons of small atolls, is liable to become filled up with detritus and with reefs of delicately branched corals: when, therefore, a reef round the entire circumference of an island extends very far into a profoundly deep sea, so that it can hardly be confounded with a fringing-reef which must rest on a foundation of rock within a small depth, it has been coloured pale blue, although it does not include a deep-water moat: but this has only been done rarely, and each case is distinctly mentioned in the Appendix.

The _red colour_ (4) represents reefs fringing the land quite closely where the sea is deep, and where the bottom is gently inclined extending to a moderate distance from it, but not having a deep-water moat or lagoon-like space parallel to the shore. It must be remembered that fringing-reefs are frequently _breached_ in front of rivers and valleys by deepish channels, where mud has been deposited. A space of thirty miles in width has been coloured round or in front of the reefs of each class, in order that the colours might be conspicuous on the appended map, which is reduced to so small a scale.

The _vermillion spots_, and streaks (1) represent volcanoes now in action, or historically known to have been so. They are chiefly laid down from Von Buch’s work on the Canary Islands; and my reasons for making a few alterations are given in the note below.[1]

[1] I have also made considerable use of the geological part of Berghaus’ “Physical Atlas.” Beginning at the eastern side of the Pacific, I have added to the number of the volcanoes in the southern part of the Cordillera, and have coloured Juan Fernandez according to observations collected during the voyage of the _Beagle_ (“Geological Transactions,” volume v., page 601.) I have added a volcano to Albemarle Island, one of the Galapagos Archipelago (the author’s “Journal of Researches,” page 457). In the Sandwich group there are no active volcanoes, except at Hawaii; but the Rev. W. Ellis informs me, there are streams of lava apparently modern on Maui, having a very recent appearance, which can be traced to the craters whence they flowed. The same gentleman informs me, that there is no reason to believe that any active volcano exists in the Society Archipelago; nor are there any known in the Samoa or Navigator group, although some of the streams of lava and craters there appear recent. In the Friendly group, the Rev. J. Williams says (“Narrative of Missionary Enterprise,” page 29) that Toofoa and Proby Islands are active volcanoes. I infer from Hamilton’s “Voyage in the ‘Pandora’” (Page 95), that Proby Island is synonymous with Onouafou, but I have not ventured to colour it. There can be no doubt respecting Toofoa, and Captain Edwards (Von Buch, page 386) found the lava of recent eruption at Amargura still smoking. Berghaus marks four active volcanoes actually within the Friendly group; but I do not know on what authority: I may mention that Maurelle describes Latte as having a burnt-up appearance: I have marked only Toofoa and Amargura. South of the New Hebrides lies Matthews Rock, which is drawn and described as an active crater in the “Voyage of the _Astrolabe_.” Between it and the volcano on the eastern side of New Zealand, lies Brimstone Island, which from the high temperature of the water in the crater, may be ranked as active (Berghaus “Vorbemerk,” II Lief. S. 56). Malte Brun, volume xii., page 231, says that there is a volcano near port St. Vincent in New Caledonia. I believe this to be an error, arising from a smoke seen on the _opposite_ coast by Cook (“Second Voyage,” volume ii., page 23) which smoke went out at night. The Mariana Islands, especially the northern ones, contain many craters (see Freycinet’s “Hydrog. Descript.”) which are not active. Von Buch, however, states (page 462) on the authority of La Peyrouse, that there are no less than seven volcanoes between these islands and Japan. Gemelli Creri (Churchill’s “Collect.” volume iv., page 458), says there are two active volcanoes in latitude 23° 30′, and in latitude 24°: but I have not coloured them. From the statements in Beechey’s “Voyage” (page 518, 4to edition) I have coloured one in the northern part of the Bonin group. M. S. Julien has clearly made out from Chinese manuscripts not very ancient (“Comptes Rendus,” 1840, page 832), that there are two active volcanoes on the eastern side of Formosa. In Torres Straits, on Cap Island (9° 48′ S., 142° 39′ E.) a volcano was seen burning with great violence in 1793 by Captain Bampton (see Introduction to Flinders’ “Voyage,” page 41). Mr. M’Clelland (Report of Committee for investigating Coal in India, page 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”, volume xxxviii., page 385). In Berghaus’ “Physical 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,” page 218) says that there is one at the mouth 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, page 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.

The _uncoloured coasts_ consist, first and chiefly, of those, where there are no coral-reefs, or such small portions as to be quite insignificant. Secondly, of those coasts where there are reefs, but where the sea is very shallow, for in this case the reefs generally lie far from the land, and become very irregular, in their forms: where they have not become 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, some reefs are left uncoloured from the want of information respecting them, and some because they are of an intermediate structure between the barrier and fringing classes. The value of the map is lessened, in proportion to the number of reefs which I have been obliged to leave uncoloured, although, in a theoretical point of view, few of them present any great difficulty: but their number is not very great, as will be found by comparing the map with the statements in the Appendix. I have experienced more difficulty in colouring fringing-reefs than in colouring barrier-reefs, as the former, from their much less dimensions, have less attracted the attention of navigators. As I have had to seek my information from all kinds of sources, and often from indirect ones, I do not venture to hope that the map is free from many errors. Nevertheless, I trust it will give an approximately correct view of the general distribution of the coral-reefs over the whole world (with the exception of some fringing-reefs on the coast of Brazil, not included within the limits of the map), and of their arrangement into the three great classes, which, though necessarily very imperfect from the nature of the objects classified, have been adopted by most voyagers. I may further remark, that the dark blue colour represents land entirely composed of coral-rock; the pale blue, land with a wide and thick border of coral-rock; and the red, a mere narrow fringe of coral-rock.

Looking now at the map under the theoretical point of view indicated in the last chapter, the two blue tints signify that the foundations of the reefs thus coloured have subsided to a considerable amount, at a slower rate than that of the upward growth of the corals, and that probably in many cases they are still subsiding. The red signifies that the shores which support fringing-reefs have not subsided (at least to any considerable amount, for the effects of a subsidence on a small scale would in no case be distinguishable); but that they have remained nearly stationary since the period when they first became fringed by reefs; or that they are now rising or have been upraised, with new lines of reefs successively formed on them: these latter alternatives are obviously implied, as newly formed lines of shore, after elevations of the land, would be in the same state with respect to the growth of fringing-reefs, as stationary coasts. If during the prolonged subsidence of a shore, coral-reefs grew for the first time on it, or if an old barrier-reef were destroyed and submerged, and new reefs became attached to the land, these would necessarily at first belong to the fringing class, and, therefore, be coloured red, although the coast was sinking: but I have no reason to believe, that from this source of error, any coast has been coloured wrongly with respect to movement indicated. Well characterised atolls and encircling barrier-reefs, where several occur in a group, or a single barrier-reef if of large dimensions, leave scarcely any doubt on the mind respecting the movement by which they have been produced; and even a small amount of subsequent elevation is soon betrayed. The evidence from a single atoll or a single encircling barrier-reef, must be received with some caution, for the former may possibly be based upon a submerged crater or bank, and the latter on a submerged margin of sediment, or of worn-down rock. From these remarks we may with greater certainty infer that the spaces, especially the larger ones, tinted blue in the map, have subsided, than that the red spaces have remained stationary, or have been upraised.

_On the grouping of the different classes of reefs_.—Having made these preliminary remarks, I will consider first how far the grouping of the different kinds of coral-islands and reefs is corroborative of the truth of the theory. A glance at the map shows that the reefs, coloured blue and red, produced under widely different conditions, are not indiscriminately mixed together. Atolls and barrier-reefs, on the other hand, as may be seen by the two blue tints, generally lie near each other; and this would be the natural result of both having been produced during the subsidence of the areas in which they stand. Thus, the largest group of encircled islands is that of the Society Archipelago; and these islands are surrounded by atolls, and only separated by a narrow space from the large group of Low atolls. In the midst of the Caroline atolls, there are three fine encircled islands. The northern point of the barrier-reef of New Caledonia seems itself, as before remarked, to form a complete large atoll. The great Australian barrier is described as including both atolls and small encircled islands. Captain King[2] mentions many atoll-formed and encircling coral-reefs, some of which lie within the barrier, and others may be said (for instance between latitude 16° and 13°) to form part of it. Flinders[3] has described an atoll-formed reef in latitude 10°, seven miles long and from one to three broad, resembling a boot in shape, with apparently very deep water within. Eight miles westward of this, and forming part of the barrier, lie the Murray Islands, which are high and are encircled. In the Corallian Sea, between the two great barriers of Australia and New Caledonia, there are many low islets and coral-reefs, some of which are annular, or horse-shoe shaped. Observing the smallness of the scale of the map, the parallels of latitude being nine hundred miles apart, we see that none of the large groups of reefs and islands supposed to have been produced by long-continued subsidence, lie near extensive lines of coast coloured red, which are supposed to have remained stationary since the growth of their reefs, or to have been upraised and new lines of reefs formed on them. Where the red and blue circles do occur near each other, I am able, in several instances, to show that there have been oscillations of level, subsidence having preceded the elevation of the red spots; and elevation having preceded the subsidence of the blue spots: and in this case the juxtaposition of reefs belonging to the two great types of structure is little surprising. We may, therefore, conclude that the proximity in the same areas of the two classes of reefs, which owe their origin to the subsidence of the earth’s crust, and their separation from those formed during its stationary or uprising condition, holds good to the full extent, which might have been anticipated by our theory.

[2] Sailing directions, appended to volume ii. of his “Surveying Voyage to Australia.”

[3] “Voyage to Terra Australis,” volume ii. page 336.

As groups of atolls have originated in the upward growth, at each fresh sinking of the land, of those reefs which primarily fringed the shores of one great island, or of several smaller ones; so we might expect that these rings of coral-rock, like so many rude outline charts, will still retain some traces of the general form, or at least general range, of the land, round which they were first modelled. That this is the case with the atolls in the Southern Pacific as far as their range is concerned, seems highly probable, when we observe that the three principal groups are directed in north-west and south-east lines, and that nearly all the land in the S. Pacific ranges in this same direction; namely, N. Western Australia, New Caledonia, the northern half of New Zealand, the New Hebrides, Saloman, Navigator, Society, Marquesas, and Austral archipelagoes: in the Northern Pacific, the Caroline atolls abut against the north-west line of the Marshall atolls, much in the same manner as the east and west line of islands from Ceram to New Britain do on New Ireland: in the Indian Ocean the Laccadive and Maldiva atolls extend nearly parallel to the western and mountainous coast of India. In most respects, there is a perfect resemblance with ordinary islands in the grouping of atolls and in their form: thus the outline of all the larger groups is elongated; and the greater number of the individual atolls are elongated in the same direction with the group, in which they stand. The Chagos group is less elongated than is usual with other groups, and the individual atolls in it are likewise but little elongated; this is strikingly seen by comparing them with the neighbouring Maldiva atolls. In the Marshall and Maldiva archipelagoes, the atolls are ranged in two parallel lines, like the mountains in a great double mountain-chain. Some of the atolls, in the larger archipelagoes, stand so near to each other, and have such an evident relationship in form, that they compose little sub-groups: in the Caroline Archipelago, one such sub-group consists of Pouynipète, a lofty island encircled by a barrier-reef, and separated by a channel only four miles and a half wide from Andeema atoll, with a second atoll a little further off. In all these respects an examination of a series of charts will show how perfectly groups of atolls resemble groups of common islands.

_On the direct evidence of the blue spaces in the map having subsided during the upward growth of the reefs so coloured, and of the red spaces having remained stationary, or having been upraised._—With respect to subsidence, I have shown in the last chapter, that we cannot expect to obtain in countries inhabited only by semi-civilised races, demonstrative proofs of a movement, which invariably tends to conceal its own evidence. But on the coral-islands supposed to have been produced by subsidence, we have proofs of changes in their external appearance—of a round of decay and renovation—of the last vestiges of land on some—of its first commencement on others: we hear of storms desolating them to the astonishment of their inhabitants: we know by the great fissures with which some of them are traversed, and by the earthquakes felt under others, that subterranean disturbances of some kind are in progress. These facts, if not directly connected with subsidence, as I believe they are, at least show how difficult it would be to discover proofs of such movement by ordinary means. At Keeling atoll, however, I have described some appearances, which seem directly to show that subsidence did take place there during the late earthquakes. Vanikoro, according to Chevalier Dillon,[4] is often violently shaken by earthquakes, and there, the unusual depth of the channel between the shore and the reef,—the almost entire absence of islets on the reef,— its wall-like structure on the inner side, and the small quantity of low alluvial land at the foot of the mountains, all seem to show that this island has not remained long at its present level, with the lagoon-channel subjected to the accumulation of sediment, and the reef to the wear and tear of the breakers. At the Society Archipelago, on the other hand, where a slight tremor is only rarely felt, the shoaliness of the lagoon-channels round some of the islands, the number of islets formed on the reefs of others, and the broad belt of low land at the foot of the mountains, indicate that, although there must have been great subsidence to have produced the barrier-reefs, there has since elapsed a long stationary period.[5]

[4] See Captain Dillon’s “Voyage in search of La Peyrouse.” M. Cordier in his “Report on the Voyage of the ‘Astrolabe’” (page cxi., volume i.), speaking of Vanikoro, says the shores are surrounded by reefs of madrepore, _“qu’on assure être de formation tout-a-fait moderne_.” I have in vain endeavoured to learn some further particulars about this remarkable passage. I may here add, that according to our theory, the island of Pouynipète (Plate I., Figure 7), in the Caroline Archipelago, being encircled by a barrier-reef, must have subsided. In the “New S. Wales Lit. Advert.” February 1835 (which I have seen through the favour of Dr. Lloghtsky), there is an account of this island (subsequently confirmed by Mr. Campbell), in which it is said, “At the N.E. end, at a place called Tamen, there are ruins of a town, _now only_ accessible by boats, the waves _reaching to the steps of the houses_.” Judging from this passage, one would be tempted to conclude that the island must have subsided, since these houses were built. I may, also, here append a statement in Malte Brun (volume ix., page 775, given without any authority), that the sea gains in an extraordinary manner on the coast of Cochin China, which lies in front and near the subsiding coral-reefs in the China Sea: as the coast is granitic, and not alluvial, it is scarcely possible that the encroachment of the sea can be owing to the washing away of the land; and if so, it must be due to subsidence.

[5] Mr. Couthouy states (“Remarks,” page 44) that at Tahiti and Eimeo the space between the reef and the shore has been nearly filled up by the extension of those coral-reefs, which within most barrier-reefs merely fringe the land. From this circumstance, he arrives at the same conclusion as I have done, that the Society Islands since their subsidence, have remained stationary during a long period; but he further believes that they have recently commenced rising, as well as the whole area of the Low Archipelago. He does not give any detailed proofs regarding the elevation of the Society Islands, but I shall refer to this subject in another part of this chapter. Before making some further comments, I may observe how satisfactory it is to me, to find Mr. Couthouy affirming, that “having personally examined a large number of coral-islands, and also residing eight months among the volcanic class, having shore and partially encircling reefs, I may be permitted to state that my own observations have impressed a conviction of the correctness of the theory of Mr. Darwin.”

This gentleman believes, that subsequently to the subsidence by which the atolls in the Low Archipelago were produced, the whole area has been elevated to the amount of a few feet; this would indeed be a remarkable fact; but as far as I am able to judge, the grounds of his conclusion are not sufficiently strong. He states that he found in almost every atoll which he visited, the shores of the lagoon raised from eighteen to thirty inches above the sea-level, and containing imbedded Tridacnae and corals standing as they grew; some of the corals were dead in their upper parts, but below a certain line they continued to flourish. In the lagoons, also, he frequently met with clusters of Madrepore, with their extremities standing from one inch to a foot above the surface of the water. Now, these appearances are exactly what I should have expected, without any subsequent elevation having taken place; and I think Mr. Couthouy has not borne in mind the indisputable fact, that corals, when constantly bathed by the surf, can exist at a higher level than in quite tranquil water, as in a lagoon. As long, therefore, as the waves continued at low water to break entirely over parts of the annular reef of an atoll, submerged to a small depth, the corals and shells attached on these parts might continue living at a level above the smooth surface of the lagoon, into which the waves rolled; but as soon as the outer edge of the reef grew up to its utmost possible height, or if the reef were very broad nearly to that height, the force of the breakers would be checked, and the corals and shells on the inner parts near the lagoon would occasionally be left dry, and thus be partially or wholly destroyed. Even in atolls, which have not lately subsided, if the outer margin of the reef continued to increase in breadth seaward (each fresh zone of corals rising to the same vertical height as at Keeling atoll), the line where the waves broke most heavily would advance outwards, and therefore the corals, which when living near the margin, were washed by the breaking waves during the whole of each tide, would cease being so, and would therefore be left on the backward part of the reef standing exposed and dead. The case of the madrepores in the lagoons with the tops of their branches exposed, seems to be an analogous fact, to the great fields of dead but upright corals in the lagoon of Keeling atoll; a condition of things which I have endeavoured to show, has resulted from the lagoon having become more and more enclosed and choked up with reefs, so that during high winds, the rising of the tide (as observed by the inhabitants) is checked, and the corals, which had formerly grown to the greatest possible height, are occasionally exposed, and thus are killed: and this is a condition of things, towards which almost every atoll in the intervals of its subsidence must be tending. Or if we look to the state of an atoll directly after a subsidence of some fathoms, the waves would roll heavily over the entire circumference of the reef, and the surface of the lagoon would, like the ocean, never be quite at rest, and therefore the corals in the lagoon, from being constantly laved by the rippling water, might extend their branches to a little greater height than they could, when the lagoon became enclosed and protected. Christmas atoll (2° N. latitude) which has a very shallow lagoon, and differs in several respects from most atolls, possibly may have been elevated recently; but its highest part appears (Couthouy, page 46) to be only ten feet above the sea-level. The facts of a second class, adduced by Mr. Couthouy, in support of the alleged recent elevation of the Low Archipelago, are not all (especially those referring to a shelf of rock) quite intelligible to me; he believes that certain enormous fragments of rock on the reef, must have been moved into their present position, when the reef was at a lower level; but here again the force of the breakers on any inner point of the reef being diminished by its outward growth without any change in its level, has not, I think, been borne in mind. We should, also, not overlook the occasional agency of waves caused by earthquakes and hurricanes. Mr. Couthouy further argues, that since these great fragments were deposited and fixed on the reef, they have been elevated; he infers this from the greatest amount of erosion not being near their bases, where they are unceasingly washed by the reflux of the tides, but at some height on their sides, near the line of high-water mark, as shown in an accompanying diagram. My former remark again applies here, with this further observation, that as the waves have to roll over a wide space of reef before they reach the fragments, their force must be greatly increased with the increasing depth of water as the tide rises, and therefore I should have expected that the chief line of present erosion would have coincided with the line of high-water mark; and if the reef had grown outwards, that there would have been lines of erosion at greater heights. The conclusion, to which I am finally led by the interesting observations of Mr. Couthouy is, that the atolls in the Low Archipelago have, like the Society Islands, remained at a stationary level for a long period: and this probably is the ordinary course of events, subsidence supervening after long intervals of rest.

Turning now to the red colour; as on our map, the areas which have sunk slowly downwards to great depths are many and large, we might naturally have been led to conjecture, that with such great changes of level in progress, the coasts which have been fringed probably for ages (for we have no reason to believe that coral-reefs are of short duration), would not have remained all this time stationary, but would frequently have undergone movements of elevation. This supposition, we shall immediately see, holds good to a remarkable extent; and although a stationary condition of the land can hardly ever be open to proof, from the evidence being only negative, we are, in some degree, enabled to ascertain the correctness of the parts coloured red on the map, by the direct testimony of upraised organic remains of a modern date. Before going into the details on this head (printed in small type), I may mention, that when reading a memoir on coral formations by MM. Quoy and Gaimard[6] I was astonished to find, for I knew that they had crossed both the Pacific and Indian Oceans, that their descriptions were applicable only to reefs of the fringing class; but my astonishment ended satisfactorily, when I discovered that, by a strange chance, all the islands which these eminent naturalists had visited, though several in number, namely, the Mauritius, Timor, New Guinea, the Mariana, and Sandwich Archipelagoes, could be shown by their own statements to have been elevated within a recent geological era.

[6] “Annales des Sciences Nat.” tom. vi., page 279, etc.

In the eastern half of the Pacific, the _Sandwich Islands_ are all fringed, and almost every naturalist who has visited them, has remarked on the abundance of elevated corals and shells, apparently identical with living species. The Rev. W. Ellis informs me, that he has noticed round several parts of Hawaii, beds of coral-detritus, about twenty feet above the level of the sea, and where the coast is low they extend far inland. Upraised coral-rock forms a considerable part of the borders of Oahu; and at Elizabeth Island[7] it composes three strata, each about ten feet thick. Nihau, which forms the northern, as Hawaii does the southern end of the group (350 miles in length), likewise seems to consist of coral and volcanic rocks. Mr. Couthouy[8] has lately described with interesting details, several upraised beaches, ancient reefs with their surfaces perfectly preserved, and beds of recent shells and corals, at the islands of Maui, Morokai, Oahu, and Tauai (or Kauai) in this group. Mr. Pierce, an intelligent resident at Oahu, is convinced, from changes which have taken place within his memory, during the last sixteen years, “that the elevation is at present going forward at a very perceptible rate.” The natives at Kauai state that the land is there gaining rapidly on the sea, and Mr. Couthouy has no doubt, from the nature of the strata, that this has been effected by an elevation of the land.

[7] “Zoology of Captain Beechey’s Voyage,” page 176. See also MM. Quoy and Gaimard in “Annales de Scien. Nat.” tom. vi.

[8] “Remarks on Coral Formations,” page 51.

In the southern part of the Low Archipelago, Elizabeth Island is described by Captain Beechey,[9] 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[10] 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.

[9] Beechey’s “Voyage in the Pacific,” page 46, 4to edition.

[10] Couthouy’s “Remarks,” page 34.

_Savage Island_ (S.E. of the Friendly group), is about forty feet in height. Forster[11] describes the plants as _already_ growing out of the dead, but still upright and spreading trees of coral; and the younger Forster[12] 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.”[13] 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[14] 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[15] 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.

[11] “Observations made during Voyage round the World,” page 147.

[12] “Voyage,” volume ii., page 163.

[13] Cook’s “Third Voyage” (4to edition), volume i., page 314.

[14] Ibid., volume i., page 235.

[15] “Remarks on Coral-Formations,” page 50.

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 _Salomon Archipelago_, I have no information; but at New Ireland, which forms the northern point of the latter chain, both Labillardière and Lesson have described large beds of an apparently very modern madreporitic rock, with the form of the corals little altered. The latter author[16] 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,[17] and Chamisso,[18] 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.[19]

[16] “Voyage de la ‘Coquille’,” Part. Zoolog.

[17] Freycinet’s “Voyage autour du Monde.” See also the “Hydrographical Memoir,” page 215.

[18] Kotzebue’s “First Voyage.”

[19] Lutké’s “Voyage,” volume ii., page 304.

In the _East Indian Archipelago_, many authors have recorded proofs of recent elevation. M. Lesson[20] 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[21] 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,”[22] 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[23] 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[24] (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 _Phillippines_, 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[25] 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.

[20] Partie Zoolog., “Voyage de la ‘Coquille’.”

[21] “Ann. des Scien. Nat.” tom. vi., page 281.

[22] Translated by Windsor Earl, chapters vi., vii.

[23] “Geolog. Transact.” 2nd series, volume i., page 403. On the Peninsula of Malacca, in front of Pinang, 5° 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.

[24] “Notices of the East Indian Arch.” Singapore, 1828, page 6, and Append., page 43.

[25] Captain B. Hall, “Voyage to Loo Choo,” Append., pages xxi. and xxv. Captain Beechey’s “Voyage,” page 496.

Dr. Davy[26] describes the northern province of _Ceylon_ 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.[27] _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[28] 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° 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.

[26] “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.

[27] 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.

[28] 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.

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. Rüppell[29] 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°; but that south of 26°, 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° 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. Rüppell says that the modern beds attain a height of only thirty to forty feet, Mr. Burton[30] 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.

[29] Rüppell, “Reise in Abyssinien,” Band i., s. 141.

[30] Lyell’s “Principles of Geology,” 5th edition, volume iv., page 25.

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[31] 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.[32]

[31] Ainsworth’s “Assyria and Babylon,” page 217.

[32] 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.

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 remains, which seem, from evidence more or less satisfactory, to belong to a late tertiary period. It may, however, be objected, that similar proofs of elevation, perhaps, occur on the coasts coloured blue in our map: but this certainly is not the case with the few following and doubtful exceptions.

The entire area of the Red Sea appears to have been upraised within a modern period; nevertheless I have been compelled (though on unsatisfactory evidence, as given in the Appendix) to class the reefs in the middle part, as barrier-reefs; should, however, the statements prove accurate to the less height of the tertiary bed in this middle part, compared with the northern and southern districts, we might well suspect that it had subsided subsequently to the general elevation by which the whole area has been upraised. Several authors[33] have stated that they have observed shells and corals high up on the mountains of the Society Islands,—a group encircled by barrier-reefs, and, therefore, supposed to have subsided: at Tahiti Mr. Stutchbury found on the apex of one of the highest mountains, between 5,000 and 7,000 feet above the level of the sea, “a distinct and regular stratum of semi-fossil coral.” At Tahiti, however, other naturalists, as well as myself, have searched in vain at a low level near the coast, for upraised shells or masses of coral-reef, where if present they could hardly have been overlooked. From this fact, I concluded that probably the organic remains strewed high up on the surface of the land, had originally been embedded in the volcanic strata, and had subsequently been washed out by the rain. I have since heard from the Rev. W. Ellis, that the remains which he met with, were (as he believes) interstratified with an argillaceous tuff; this likewise was the case with the shells observed by the Rev. D. Tyerman at Huaheine. These remains have not been specifically examined; they may, therefore, and especially the stratum observed by Mr. Stutchbury at an immense height, be contemporaneous with the first formation of the Society Islands, and be of any degree of antiquity; or they may have been deposited at some subsequent, but probably not very recent, period of elevation; for if the period had been recent, the entire surface of the coast land of these islands, where the reefs are so extensive, would have been coated with upraised coral, which certainly is not the case. Two of the Harvey, or Cook Islands, namely, Aitutaki and Manouai, are encircled by reefs, which extend so far from the land, that I have coloured them blue, although with much hesitation, as the space within the reef is shallow, and the outline of the land is not abrupt. These two islands consist of coral-rock; but I have no evidence of their recent elevation, besides, the improbability of Mangaia, a fringed island in the same group (but distant 170 miles), having retained its nearly perfect atoll-like structure, during any immense lapse of time after its upheaval. The Red Sea, therefore, is the only area in which we have clear proofs of the recent elevation of a district, which, by our theory (although the barrier-reefs are there not well characterised), has lately subsided. But we have no reason to be surprised at oscillation, of level of this kind having occasionally taken place. There can be scarcely any doubt that Savage, Aurora,[34] and Mangaia Islands, and several of the islands in the Friendly group, existed originally as atolls, and these have undoubtedly since been upraised to some height above the level of the sea; so that by our theory, there has here, also, been an oscillation of level, —elevation having succeeded subsidence, instead of, as in the middle part of the Red Sea and at the Harvey Islands, subsidence having probably succeeded recent elevation.

[33] Ellis, in his “Polynesian Researches,” was the first to call attention to these remains (volume i., page 38), and the tradition of the natives concerning them. See also Williams, “Nar. of Missionary Enterprise,” page 21; also Tyerman and G. Bennett, “Journal of Voyage,” volume i., page 213; also Mr. Couthouy’s “Remarks,” page 51; but this principal fact, namely, that there is a mass of upraised coral on the narrow peninsula of Tiarubu, is from hearsay evidence; also Mr. Stutchbury, “West of England Journal,” No. i., page 54. There is a passage in Von Zach, “Corres. Astronom.” volume x., page 266, inferring an uprising at Tahiti, from a footpath now used, which was formerly impassable; but I particularly inquired from several native chiefs, whether they knew of any change of this kind, and they were unanimous in giving me an answer in the negative.

[34] Aurora Island is described by Mr. Couthouy (“Remarks,” page 58); it lies 120 miles north-east of Tahiti; it is not coloured in the appended map, because it does not appear to be fringed by living reefs. Mr. Couthouy describes its summit as “presenting a broad table-land which declines a few feet towards the centre, where we may suppose the lagoon to have been placed.” It is about two hundred feet in height, and consists of reef-rock and conglomerate, with existing species of coral embedded in it. The island has been elevated at two successive periods; the cliffs being marked halfway up with a horizontal water-worn line of deep excavations. Aurora Island seems closely to resemble in structure Elizabeth Island, at the southern end of the Low Archipelago.

It is an interesting fact, that Fais, which, from its composition, form, height, and situation at the western end of the Caroline Archipelago, one is strongly induced to believe existed before its upheaval as an atoll, lies exactly in the prolongation of the curved line of the Mariana group, which we know to be a line of recent elevation. I may add, that Elizabeth Island, in the southern part of the Low Archipelago, which seems to have had the same kind of origin as Fais, lies near Pitcairn Island, the only one in this part of the ocean which is high, and at the same time not surrounded by an encircling barrier-reef.

_On the absence of active Volcanoes in the areas of subsidence, and on their frequent presence in the areas of elevation._—Before making some concluding remarks on the relations of the spaces coloured blue and red, it will be convenient to consider the position on our map of the volcanoes historically known to have been in action. It is impossible not to be struck, first with the absence of volcanoes in the great areas of subsidence tinted pale and dark blue,—namely, in the central parts of the Indian Ocean, in the China Sea, in the sea between the barriers of Australia and New Caledonia, in the Caroline, Marshall, Gilbert, and Low Archipelagoes; and, secondly, with the coincidence of the principal volcanic chains with the parts coloured red, which indicates the presence of fringing-reefs; and, as we have just seen, the presence in most cases of upraised organic remains of a modern date. I may here remark that the reefs were all coloured before the volcanoes were added to the map, or indeed before I knew of the existence of several of them.

The volcano in Torres Strait, at the northern point of Australia, is that which lies nearest to a large subsiding area, although situated 125 miles within the outer margin of the actual barrier-reef. The Great Comoro Island, which probably contains a volcano, is only twenty miles distant from the barrier-reef of Mohila; Ambil volcano, in the Philippines, is distant only a little more than sixty miles from the atoll-formed Appoo reef: and there are two other volcanoes in the map within ninety miles of circles coloured blue. These few cases, which thus offer partial exceptions to the rule, of volcanoes being placed remote from the areas of subsidence, lie either near single and isolated atolls, or near small groups of encircled islands; and these by our theory can have, in few instances, subsided to the same amount in depth or area, as groups of atolls. There is not one active volcano within several hundred miles of an archipelago, or even a small group of atolls. It is, therefore, a striking fact that in the Friendly Archipelago, which owes its origin to the elevation of a group of atolls, two volcanoes, and, perhaps, others[35] are known to be in action: on the other hand, on several of the encircled islands in the Pacific, supposed by our theory to have subsided, there are old craters and streams of lava, which show the effects of past and ancient eruptions. In these cases, it would appear as if the volcanoes had come into action, and had become extinguished on the same spots, according as the elevating or subsiding movements prevailed.

[35] See the note at p. 121, on the authorities for colouring the volcanoes in the appended map.

There are some other coasts on the map, where volcanoes in a state of action concur with proofs of recent elevation, besides those coloured red from being fringed by coral-reefs. Thus I hope to show in a future volume, that nearly the whole line of the west coast of South America, which forms the greatest volcanic chain in the world, from near the equator for a space of between 2,000 and 3,000 miles southward, has undergone an upward movement during a late geological period. The islands on the north-western shores of the Pacific, which form the second greatest volcanic chain, are very imperfectly known; but Luzon, in the Philippines, and the Loo Choo Islands, have been recently elevated; and at Kamtschatka[36] there are extensive tertiary beds of modern date. Evidence of the same nature, but not very satisfactory, may be detected in Northern New Zealand where there are two volcanoes. The co-existence in other parts of the world of active volcanoes, with upraised beds of a modern tertiary origin, will occur to every geologist.[37] Nevertheless, until it could be shown that volcanoes were inactive, or did not exist in subsiding areas, the conclusion that their distribution depended on the nature of the subterranean movements in progress, would have been hazardous. But now, viewing the appended map, it may, I think, be considered as almost established, that volcanoes are often (not necessarily always) present in those areas where the subterranean motive power has lately forced, or is now forcing outwards, the crust of the earth, but that they are invariably absent in those, where the surface has lately subsided or is still subsiding.[38]

[36] At Sedanka, in latitude 58° N. (Von Buch’s “Descrip. des Isles Canaries,” page 455). In a forthcoming part, I shall give the evidence referred to with respect to the elevation of New Zealand.

[37] During the subterranean disturbances which took place in Chile, in 1835, I have shown (“Geolog. Trans.” 2nd Ser., vol. v., page 606) that at the same moment that a large district was upraised, volcanic matter burst forth at widely separated points, through both new and old vents.

[38] We may infer from this rule, that in any old deposit, which contains interstratified beds of erupted matter, there was at the period, and in the area of its formation, a _tendency_ to an upward movement in the earth’s surface, and certainly no movement of subsidence.

_On the relations of the areas of Subsidence and Elevation_.—The immense surfaces on the map, which, both by our theory and by the plain evidence of upraised marine remains, have undergone a change of level either downwards or upwards during a late period, is a most remarkable fact. The existence of continents shows that the areas have been immense which at some period have been upraised; in South America we may feel sure, and on the north-western shores of the Indian Ocean we may suspect, that this rising is either now actually in progress, or has taken place quite recently. By our theory, we may conclude that the areas are likewise immense which have lately subsided, or, judging from the earthquakes occasionally felt and from other appearances, are now subsiding. The smallness of the scale of our map should not be overlooked: each of the squares on it contains (not allowing for the curvature of the earth) 810,000 square miles. Look at the space of ocean from near the southern end of the Low Archipelago to the northern end of the Marshall Archipelago, a length of 4,500 miles, in which, as far as is known, every island, except Aurora which lies just without the Low Archipelago, is atoll-formed. The eastern and western boundaries of our map are continents, and they are rising areas: the central spaces of the great Indian and Pacific Oceans, are mostly subsiding; between them, north of Australia, lies the most broken land on the globe, and there the rising parts are surrounded and penetrated by areas of subsidence,[39] so that the prevailing movements now in progress, seem to accord with the actual states of surface of the great divisions of the world.

[39] I suspect that the Arru and Timor-laut Islands present an included small area of subsidence, like that of the China Sea, but I have not ventured to colour them from my imperfect information, as given in the Appendix.

The blue spaces on the map are nearly all elongated; but it does not necessarily follow from this (a caution, for which I am indebted to Mr. Lyell), that the areas of subsidence were likewise elongated; for the subsidence of a long, narrow space of the bed of the ocean, including in it a transverse chain of mountains, surmounted by atolls, would only be marked on the map by a transverse blue band. But where a chain of atolls and barrier-reefs lies in an elongated area, between spaces coloured red, which therefore have remained stationary or have been upraised, this must have resulted either from the area of subsidence having originally been elongated (owing to some tendency in the earth’s crust thus to subside), or from the subsiding area having originally been of an irregular figure, or as broad as long, and having since been narrowed by the elevation of neighbouring districts. Thus the areas, which subsided during the formation of the great north and south lines of atolls in the Indian Ocean,—of the east and west line of the Caroline atolls,—and of the north-west and south-east line of the barrier-reefs of New Caledonia and Louisiade, must have originally been elongated, or if not so, they must have since been made elongated by elevations, which we know to belong to a recent period.

I infer from Mr. Hopkins’ researches,[40] that for the formation of a long chain of mountains, with few lateral spurs, an area elongated in the same direction with the chain, must have been subjected to an elevatory movement. Mountain-chains, however, when already formed, although running in very different directions, it seems,[41] may be raised together by a widely-acting force: so, perhaps, mountain-chains may subside together. Hence, we cannot tell, whether the Caroline and Marshall Archipelagoes, two groups of atolls running in different directions and meeting each other, have been formed by the subsidence of two areas, or of one large area, including two distinct lines of mountains. We have, however, in the southern prolongation of the Mariana Islands, probable evidence of a line of recent elevation having intersected one of recent subsidence. A view of the map will show that, generally, there is a tendency to alternation in the parallel areas undergoing opposite kinds of movement; as if the sinking of one area balanced the rising of another.

[40] “Researches in Physical Geology,” Transact. Cambridge Phil. Soc., volume vi, part i.

[41] For instance in S. America from latitude 34°, for very many degrees southward there are upraised beds containing recent species of shells, on both the Atlantic and Pacific side of the continent, and from the gradual ascent of the land, although with very unequal slopes, on both sides towards the Cordillera, I think it can hardly be doubted that the entire width has been upraised in mass within the recent period. In this case the two W.N.W. and E.S.E. mountain-lines, namely the Sierra Ventana and the S. Tapalguen, and the great north and south line of the Cordillera have been together raised. In the West Indies the N. and S. line of the Eastern Antilles, and the E. and W. line of Jamaica, appear both to have been upraised within the latest geological period.

The existence in many parts of the world of high table-land, proves that large surfaces have been upraised in mass to considerable heights above the level of the ocean; although the highest points in almost every country consist of upturned strata, or erupted matter: and from the immense spaces scattered with atolls, which indicate that land originally existed there, although not one pinnacle now remains above the level of the sea, we may conclude that wide areas have subsided to an amount, sufficient to bury not only any formerly existing table-land, but even the heights formed by fractured strata, and erupted matter. The effects produced on the land by the later elevatory movements, namely, successively rising cliffs, lines of erosion, and beds of literal shells and pebbles, all requiring time for their production, prove that these movements have been very slow; we can, however, infer this with safety, only with respect to the few last hundred feet of rise. But with reference to the whole vast amount of subsidence, necessary to have produced the many atolls widely scattered over immense spaces, it has already been shown (and it is, perhaps, the most interesting conclusion in this volume), that the movements must either have been uniform and exceedingly slow, or have been effected by small steps, separated from each other by long intervals of time, during which the reef-constructing polypifers were able to bring up their solid frameworks to the surface. We have little means of judging whether many considerable oscillations of level have generally occurred during the elevation of large tracts; but we know, from clear geological evidence, that this has frequently taken place; and we have seen on our map, that some of the same islands have both subsided and been upraised. I conclude, however, that most of the large blue spaces, have subsided without many and great elevatory oscillations, because only a few upraised atolls have been observed: the supposition that such elevations have taken place, but that the upraised parts have been worn down by the surf, and thus have escaped observation, is overruled by the very considerable depth of the lagoons of all the larger atolls; for this could not have been the case, if they had suffered repeated elevations and abrasion. From the comparative observations made in these latter pages, we may finally conclude, that the subterranean changes which have caused some large areas to rise, and others to subside, have acted in a very similar manner.

_Recapitulation_.—In the three first chapters, the principal kinds of coral-reefs were described in detail, and they were found to differ little, as far as relates to the actual surface of the reef. An atoll differs from an encircling barrier-reef only in the absence of land within its central expanse; and a barrier-reef differs from a fringing-reef, in being placed at a much greater distance from the land with reference to the probable inclination of its submarine foundation, and in the presence of a deep-water lagoon-like space or moat within the reef. In the fourth chapter the growing powers of the reef-constructing polypifers were discussed; and it was shown, that they cannot flourish beneath a very limited depth. In accordance with this limit, there is no difficulty respecting the foundations on which fringing-reefs are based; whereas, with barrier-reefs and atolls, there is a great apparent difficulty on this head; in barrier-reefs from the improbability of the rock of the coast or of banks of sediment extending, in every instance, so far seaward within the required depth;—and in atolls, from the immensity of the spaces over which they are interspersed, and the apparent necessity for believing that they are all supported on mountain-summits, which although rising very near to the surface-level of the sea, in no one instance emerge above it. To escape this latter most improbable admission, which implies the existence of submarine chains of mountains of almost the same height, extending over areas of many thousand square miles, there is but one alternative; namely, the prolonged subsidence of the foundations, on which the atolls were primarily based, together with the upward growth of the reef-constructing corals. On this view every difficulty vanishes; fringing reefs are thus converted into barrier-reefs; and barrier-reefs, when encircling islands, are thus converted into atolls, the instant the last pinnacle of land sinks beneath the surface of the ocean.

Thus the ordinary forms and certain peculiarities in the structure of atolls and barrier-reefs can be explained;—namely, the wall-like structure on their inner sides, the basin or ring-like shape both of the marginal and central reefs in the Maldiva atolls—the union of some atolls as if by a ribbon—the apparent disseverment of others—and the occurrence, in atolls as well as in barrier-reefs, of portions of reef, and of the whole of some reefs, in a dead and submerged state, but retaining the outline of living reefs. Thus can be explained the existence of breaches through barrier-reefs in front of valleys, though separated from them by a wide space of deep water; thus, also, the ordinary outline of groups of atolls and the relative forms of the separate atolls one to another; thus can be explained the proximity of the two kinds of reefs formed during subsidence, and their separation from the spaces where fringing-reefs abound. On searching for other evidence of the movements supposed by our theory, we find marks of change in atolls and in barrier-reefs, and of subterranean disturbances under them; but from the nature of things, it is scarcely possible to detect any direct proofs of subsidence, although some appearances are strongly in favour of it. On the fringed coasts, however, the presence of upraised marine bodies of a recent epoch, plainly show, that these coasts, instead of having remained stationary, which is all that can be directly inferred from our theory, have generally been elevated.

Finally, when the two great types of structure, namely barrier-reefs and atolls on the one hand, and fringing-reefs on the other, were laid down in colours on our map, a magnificent and harmonious picture of the movements, which the crust of the earth has within a late period undergone, is presented to us. We there see vast areas rising, with volcanic matter every now and then bursting forth through the vents or fissures with which they are traversed. We see other wide spaces slowly sinking without any volcanic outburst, and we may feel sure, that this sinking must have been immense in amount as well as in area, thus to have buried over the broad face of the ocean every one of those mountains, above which atolls now stand like monuments, marking the place of their former existence. Reflecting how powerful an agent with respect to denudation, and consequently to the nature and thickness of the deposits in accumulation, the sea must ever be, when acting for prolonged periods on the land, during either its slow emergence or subsidence; reflecting, also, on the final effects of these movements in the interchange of land and ocean-water on the climate of the earth, and on the distribution of organic beings, I may be permitted to hope, that the conclusions derived from the study of coral-formations, originally attempted merely to explain their peculiar forms, may be thought worthy of the attention of geologists.

In the beginning of the last chapter I stated the principles on which the map is coloured. There only remains to be said, that it is an exact copy of one by M. C. Gressier, published by the Dépôt général de la Marine, in 1835. The names have been altered into English, and the longitude has been reduced to that of Greenwich. The colours were first laid down on accurate charts, on a large scale. The data, on which the volcanoes historically known to have been in action, have been marked with vermillion, were given in a note to the last chapter. I will commence my description on the eastern side of the map, and will describe each group of islands consecutively, proceeding westward across the Pacific and Indian Oceans, but ending with the West Indies.

The WESTERN SHORES OF AMERICA appear to be entirely without coral-reefs; south of the equator the survey of the “Beagle”, and north of it, the published charts show that this is the case. Even in the Bay of _Panama_, where corals flourish, there are no true coral-reefs, as I have been informed by Mr. Lloyd. There are no coral-reefs in the _Galapagos_ Archipelago, as I know from personal inspection; and I believe there are none on the _Cocos, Revilla-gigedo_, and other neighbouring islands. _Clipperton_ rock, 10° N., 109° W., has lately been surveyed by Captain Belcher; in form it is like the crater of a volcano. From a drawing appended to the MS. plan in the Admiralty, it evidently is not an atoll. The eastern parts of the Pacific present an enormous area, without any islands, except _Easter_, and _Sala_, and _Gomez_ Islands, which do not appear to be surrounded by reefs.

The LOW ARCHIPELAGO.—This group consists of about eighty atolls: it will be quite superfluous to refer to descriptions of each. In D’Urville and Lottin’s chart, one island (_Wolchonsky_) is written with a capital letter, signifying, as explained in a former chapter, that it is a high island; but this must be a mistake, as the original chart by Bellinghausen shows that it is a true atoll. Captain Beechey says of the thirty-two groups which he examined (of the greater number of which I have seen beautiful MS. charts in the Admiralty), that twenty-nine now contain lagoons, and he believes the other three originally did. Bellinghausen (see an account of his Russian voyage, in the “Biblioth. des Voyages,” 1834, page 443) says, that the seventeen islands which he discovered resembled each other in structure, and he has given charts on a large scale of all of them. Kotzebue has given plans of several; Cook and Bligh mention others; a few were seen during the voyage of the “Beagle”; and notices of other atolls are scattered through several publications. The _Actæon_ group in this archipelago has lately been discovered (“Geographical Journal”, volume vii., page 454); it consists of three small and low islets, one of which has a lagoon. Another lagoon-island has been discovered (“Naut. Mag.” 1839, page 770), in 22° 4′ S., and 136° 20′ W. Towards the S.E. part of the group, there are some islands of different formation: _Elizabeth_ Island is described by Beechey (page 46, 4to edition) as fringed by reefs, at the distance of between two and three hundred yards; coloured red. _Pitcairn_ Island, in the immediate neighbourhood, according to the same authority, has no reefs of any kind, although numerous pieces of coral are thrown up on the beach; the sea close to its shore is very deep (see “Zool. of Beechey’s Voyage,” page 164); it is left uncoloured. _Gambier_ Islands (see Plate I., Figure 8), are encircled by a barrier-reef; the greatest depth within is thirty-eight fathoms; coloured pale blue. _Aurora_ Island, which lies N.E. of Tahiti close to the large space coloured dark blue in the map, has been already described in a note (page 71), on the authority of Mr. Couthouy; it is an upraised atoll, but as it does not appear to be fringed by living reefs, it is left uncoloured.

The SOCIETY Archipelago is separated by a narrow space from the Low Archipelago; and in their parallel direction they manifest some relation to each other. I have already described the general character of the reefs of these fine encircled islands. In the “Atlas of the ‘Coquille’s’ Voyage” there is a good general chart of the group, and separate plans of some of the islands. _Tahiti_, the largest island in the group, is almost surrounded, as seen in Cook’s chart, by a reef from half a mile to a mile and a half from the shore, with from ten to thirty fathoms within it. Some considerable submerged reefs lying parallel to the shore, with a broad and deep space within, have lately been discovered (“Naut. Mag.” 1836, page 264) on the N.E. coast of the island, where none are laid down by Cook. At _Eimeo_ the reef “which like a ring surrounds it, is in some places one or two miles distant from the shore, in others united to the beach” (Ellis, “Polynesian Researches,” volume i., page 18, 12mo edition). Cook found deep water (twenty fathoms) in some of the harbours within the reef. Mr. Couthouy, however, states (“Remarks,” page 45) that both at Tahiti and Eimeo, the space between the barrier-reef and the shore, has been almost filled up,—“a nearly continuous fringing-reef surrounding the island, and varying from a few yards to rather more than a mile in width, the lagoons merely forming canals between this and the sea-reef,” that is the barrier-reef. _Tapamanoa_ is surrounded by a reef at a considerable distance from the shore; from the island being small it is breached, as I am informed by the Rev. W. Ellis, only by a narrow and crooked boat channel. This is the lowest island in the group, its height probably not exceeding 500 feet. A little way north of Tahiti, the low coral-islets of _Teturoa_ are situated; from the description of them given me by the Rev. J. Williams (the author of the “Narrative of Missionary Enterprise”), I should have thought they had formed a small atoll, and likewise from the description given by the Rev. D. Tyerman and G. Bennett (“Journal of Voyage and Travels,” volume i., page 183), who say that ten low coral-islets “are comprehended within one general reef, and separated from each other by interjacent lagoons;” but as Mr. Stutchbury (“West of England Journal,” volume i., page 54) describes it as consisting of a mere narrow ridge, I have left it uncoloured. _Maitea_, eastward of the group, is classed by Forster as a high encircled island; but from the account given by the Rev. D. Tyerman and G. Bennett (volume i., page 57) it appears to be an exceedingly abrupt cone, rising from the sea without any reef; I have left it uncoloured. It would be superfluous to describe the northern islands in this group, as they may be well seen in the chart accompanying the 4to edition of Cook’s “Voyages,” and in the “Atlas of the ‘Coquille’s’ Voyage.” _Maurua_ is the only one of the northern islands, in which the water within the reef is not deep, being only four and a half fathoms; but the great width of the reef, stretching three miles and a half southward of the land (which is represented in the drawing in the “Atlas of the ‘Coquille’s’ Voyage” as descending abruptly to the water) shows, on the principle explained in the beginning of the last chapter, that it belongs to the barrier class. I may here mention, from information communicated to me by the Rev. W. Ellis, that on the N.E. side of _Huaheine_ there is a bank of sand, about a quarter of a mile wide, extending parallel to the shore, and separated from it by an extensive and deep lagoon; this bank of sand rests on coral-rock, and undoubtedly was originally a living reef. North of Bolabola lies the atoll of _Toubai_ (Motou-iti of the “‘Coquille’s’ Atlas”) which is coloured dark blue; the other islands, surrounded by barrier-reefs, are pale blue; three of them are represented in Figures 3, 4, and 5, in Plate I. There are three low coral-groups lying a little E. of the Society Archipelago, and almost forming part of it, namely _Bellinghausen_, which is said by Kotzebue (“Second Voyage,” volume ii., page 255), to be a lagoon-island; _Mopeha_, which, from Cook’s description (“Second Voyage,” book iii., chapter i.), no doubt is an atoll; and the _Scilly_ Islands, which are said by Wallis (“Voyage,” chapter ix.) to form a _group_ of _low_ islets and shoals, and, therefore, probably, they compose an atoll: the two former have been coloured blue, but not the latter.

MENDANA or MARQUESAS Group.—These islands are entirely without reefs, as may be seen in Krusenstern’s Atlas, making a remarkable contrast with the adjacent group of the Society Islands. Mr. F.D. Bennett has given some account of this group, in the seventh volume of the “Geographical Journal”. He informs me that all the islands have the same general character, and that the water is very deep close to their shores. He visited three of them, namely, _Dominicana_, _Christiana_, and _Roapoa;_ their beaches are strewed with rounded masses of coral, and although no regular reefs exist, yet the shore is in many places lined by coral-rock, so that a boat grounds on this formation. Hence these islands ought probably to come within the class of fringed islands and be coloured red; but as I am determined to err on the cautious side, I have left them uncoloured.

COOK or HARVEY and AUSTRAL ISLAND.—_Palmerston_ Island is minutely described as an atoll by Captain Cook during his voyage in 1774; coloured blue. _Aitutaki_ was partially surveyed by the “Beagle” (see map accompanying “Voyages of ‘Adventure’ and ‘Beagle’”); the land is hilly, sloping gently to the beach; the highest point is 360 feet; on the southern side the reef projects five miles from the land: off this point the “Beagle” found no bottom with 270 fathoms: the reef is surmounted by many low coral-islets. Although within the reef the water is exceedingly shallow, not being more than a few feet deep, as I am informed by the Rev. J. Williams, nevertheless, from the great extension of this reef into a profoundly deep ocean, this island probably belongs, on the principle lately adverted to, to the barrier class, and I have coloured it pale blue; although with much hesitation.—_Manouai_ or _Harvey_ Island. The highest point is about fifty feet: the Rev. J. Williams informs me that the reef here, although it lies far from the shore, is less distant than at Aitutaki, but the water within the reef is rather deeper: I have also coloured this pale blue with many doubts.—Round _Mitiaro_ Island, as I am informed by Mr. Williams, the reef is attached to the shore; coloured red. —_Mauki_ or Maouti; the reef round this island (under the name of Parry Island, in the “Voyage of H.M.S. ‘Blonde’,” page 209) is described as a coral-flat, only fifty yards wide, and two feet under water. This statement has been corroborated by Mr. Williams, who calls the reef attached; coloured red.—_Aitu_, or Wateeo; a moderately elevated hilly island, like the others of this group. The reef is described in Cook’s “Voyage,” as attached to the shore, and about one hundred yards wide; coloured red.—_Fenoua-iti;_ Cook describes this island as very low, not more than six or seven feet high (volume i., book ii., chapter iii, 1777); in the chart published in the “‘Coquille’s’ Atlas,” a reef is engraved close to the shore: this island is not mentioned in the list given by Mr. Williams (page 16) in the “Narrative of Missionary Enterprise;” nature doubtful. As it is so near Atiu, it has been unavoidably coloured red.— _Rarotonga;_ Mr. Williams informs me that it is a lofty basaltic island with an attached reef; coloured red.—There are three islands, _Rourouti_, _Roxburgh_, and _Hull_, of which I have not been able to obtain any account, and have left them uncoloured. Hull Island, in the French chart, is written with small letters as being low.—_Mangaia;_ height about three hundred feet; “the surrounding reef joins the shore” (Williams, “Narrative,” page 18); coloured red.—_Rimetara;_ Mr. Williams informs me that the reef is rather close to the shore; but, from information given me by Mr. Ellis, the reef does not appear to be quite so closely attached to it as in the foregoing cases: the island is about three hundred feet high (“Naut. Mag.” 1839, page 738); coloured red.—_Rurutu;_ Mr. Williams and Mr. Ellis inform me that this island has an attached reef; coloured red. It is described by Cook under the name of Oheteroa: he says it is not surrounded, like the neighbouring islands by a reef; he must have meant a distant reef.—_Toubouai;_ in Cook’s chart (“Second Voyage,” volume ii., page 2) the reef is laid down in part one mile, and in part two miles from the shore. Mr. Ellis (“Polynes. Res.” volume iii., page 381) says the low land round the base of the island is very extensive; and this gentleman informs me that the water within the reef appears deep; coloured blue.—_Raivaivai_, or Vivitao; Mr. Williams informs me that the reef is here distant: Mr. Ellis, however, says that this is certainly not the case on one side of the island; and he believes that the water within the reef is not deep; hence I have left it uncoloured.—_Lancaster_ Reef, described in “Naut. Mag.” 1833 (page 693), as an extensive crescent-formed coral-reef. I have not coloured it.—_Rapa_, or Oparree; from the accounts given of it by Ellis and Vancouver, there does not appear to be any reef.—_I. de Bass_ is an adjoining island, of which I cannot find any account.—_Kemin_ Island; Krusenstern seems hardly to know its position, and gives no further particulars.

ISLANDS BETWEEN _the Low and Gilbert Archipelagoes_.

_Caroline_ Island (10° S., 150° W.) is described by Mr. F.D. Bennett (“Geographical Journal”, volume vii., page 225) as containing a fine lagoon; coloured blue.—_Flint_ Island (11° S., 151° W.); Krusenstern believes that it is the same with _Peregrino_, which is described by Quiros (Burney’s “Chron. Hist.” volume ii., page 283) as “a cluster of small islands connected by a reef, and forming a lagoon in the middle;” coloured blue.—_Wostock_ is an island a little more than half a mile in diameter, and apparently quite flat and low, and was discovered by Bellinghausen; it is situated a little west of Caroline Island, but it is not placed on the French charts; I have not coloured it, although I entertain little doubt from the chart of Bellinghausen, that it originally contained a small lagoon.—_Penrhyn_ Island (9° S., 158° W.); a plan of it in the “Atlas of the First Voyage” of Kotzebue, shows that it is an atoll; blue.— _Starbuck_ Island (5° S., 156° W.) is described in Byron’s “Voyage in the ‘Blonde’” (page 206) as formed of a flat coral-rock, with no trees; the height not given; not coloured.—_Malden_ Island (4° S., 154° W.); in the same voyage (page 205) this island is said to be of coral formation, and no part above forty feet high; I have not ventured to colour it, although, from being of coral-formation, it is probably fringed; in which case it should be red.—_Jarvis_, or _Bunker_ Island (0° 20′ S., 160° W.) is described by Mr. F.D. Bennett (“Geographical Journal”, volume vii., page 227) as a narrow, low strip of coral-formation; not coloured.—_Brook_, is a small low island between the two latter; the position, and perhaps even the existence of it is doubtful; not coloured.—_Pescado_ and _Humphrey_ Islands; I can find out nothing about these islands, except that the latter appears to be small and low; not coloured.—_Rearson_, or Grand Duke Alexander’s (10 S., 161° W.); an atoll, of which a plan is given by Bellinghausen; blue.— _Souvoroff_ Islands (13° S., 163° W.); Admiral Krusenstern, in the most obliging manner, obtained for me an account of these islands from Admiral Lazareff, who discovered them. They consist of five very low islands of coral-formation, two of which are connected by a reef, with deep water close to it. They do not surround a lagoon, but are so placed that a line drawn through them includes an oval space, part of which is shallow; these islets, therefore, probably once (as is the case with some of the islands in the Caroline Archipelago) formed a single atoll; but I have not coloured them.—_Danger_ Island (10° S., 166° W.); described as low by Commodore Byron, and more lately surveyed by Bellinghausen; it is a small atoll with three islets on it; blue.—_Clarence_ Island (9° S., 172° W.); discovered in the “Pandora” (G. Hamilton’s “Voyage,” page 75): it is said, “in running along the land, we saw several canoes crossing the _lagoons;_” as this island is in the close vicinity of other low islands, and as it is said, that the natives make reservoirs of water in old cocoa-nut trees (which shows the nature of the land), I have no doubt it is an atoll, and have coloured it blue. _York_ Island (8° S., 172° W.) is described by Commodore Byron (chapter x. of his “Voyage”) as an atoll; blue.—_Sydney_ Island (4° S., 172° W.) is about three miles in diameter, with its interior occupied by a lagoon (Captain Tromelin, “Annal. Marit.” 1829, page 297); blue.—_Phœnix_ Island (4° S., 171° W.) is nearly circular, low, sandy, not more than two miles in diameter, and very steep outside (Tromelin, “Annal. Marit.” 1829, page 297); it may be inferred that this island originally contained a lagoon, but I have not coloured it.—_New Nantucket_ (0° 15′ N., 174° W.). From the French chart it must be a low island; I can find nothing more about it or about _Mary_ Island; both uncoloured.—_Gardner_ Island (5° S., 174° W.) from its position is certainly the same as _Kemin_ Island described (Krusenstern, page 435, Appen. to Mem., published 1827) as having a lagoon in its centre; blue.

ISLANDS SOUTH _of the Sandwich Archipelago_.

_Christmas_ Island (2° N., 157° W.). Captain Cook, in his “Third Voyage” (Volume ii., chapter x.), has given a detailed account of this atoll. The breadth of the islets on the reef is unusually great, and the sea near it does not deepen so suddenly as is generally the case. It has more lately been visited by Mr. F.D. Bennett (“Geographical Journal,” volume vii., page 226); and he assures me that it is low and of coral-formation: I particularly mention this, because it is engraved with a capital letter, signifying a high island, in D’Urville and Lottin’s chart. Mr. Couthouy, also, has given some account of it (“Remarks,” page 46) from the Hawaiian “Spectator”; he believes it has lately undergone a small elevation, but his evidence does not appear to me satisfactory; the deepest part of the lagoon is said to be only ten feet; nevertheless, I have coloured it blue.—_Fanning_ Island (4° N., 158° W.) according to Captain Tromelin (“Ann. Maritim.” 1829, page 283), is an atoll: his account as observed by Krusenstern, differs from that given in Fanning’s “Voyage” (page 224), which, however, is far from clear; coloured blue.— _Washington_ Island (4° N., 159° W.) is engraved as a low island in D’Urville’s chart, but is described by Fanning (page 226) as having a much greater elevation than Fanning Island, and hence I presume it is not an atoll; not coloured.—_Palmyra_ Island (6° N., 162° W.) is an atoll divided into two parts (Krusenstern’s “Mem. Suppl.” page 50, also Fanning’s “Voyage,” page 233); blue.—_Smyth’s_ or Johnston’s Islands (17° N., 170° W.). Captain Smyth, R.N., has had the kindness to inform me that they consist of two very low, small islands, with a dangerous reef off the east end of them. Captain Smyth does not recollect whether these islets, together with the reef, surrounded a lagoon; uncoloured.

SANDWICH ARCHIPELAGO.—_Hawaii;_ in the chart in Freycinet’s “Atlas,” small portions of the coast are fringed by reefs; and in the accompanying “Hydrog. Memoir,” reefs are mentioned in several places, and the coral is said to injure the cables. On one side of the islet of Kohaihai there is a bank of sand and coral with five feet water on it, running parallel to the shore, and leaving a channel of about fifteen feet deep within. I have coloured this island red, but it is very much less perfectly fringed than others of the group.—_Maui;_ in Freycinet’s chart of the anchorage of Raheina, two or three miles of coast are seen to be fringed; and in the “Hydrog. Memoir,” “banks of coral along shore” are spoken of. Mr. F.D. Bennett informs me that the reefs, on an average, extend about a quarter of a mile from the beach; the land is not very steep, and outside the reefs the sea does not become deep very suddenly; coloured red.—_Morotoi_, I presume, is fringed: Freycinet speaks of the breakers extending along the shore at a little distance from it. From the chart, I believe it is fringed; coloured red.—_Oahu;_ Freycinet, in his “Hydrog. Memoir,” mentions some of the reefs. Mr. F.D. Bennett informs me that the shore is skirted for forty or fifty miles in length. There is even a harbour for ships formed by the reefs, but it is at the mouth of a valley; red.—_Atooi_, in La Peyrouse’s charts, is represented as fringed by a reef, in the same manner as Oahu and Morotoi; and this, as I have been informed by Mr. Ellis, on part at least of the shore, is of coral-formation: the reef does not leave a deep channel within; red.—_Oneehow;_ Mr. Ellis believes that this island is also fringed by a coral-reef: considering its close proximity to the other islands, I have ventured to colour it red. I have in vain consulted the works of Cook, Vancouver, La Peyrouse, and Lisiansky, for any satisfactory account of the small islands and reefs, which lie scattered in a N.W. line prolonged from the Sandwich group, and hence have left them uncoloured, with one exception; for I am indebted to Mr. F.D. Bennett for informing me of an atoll-formed reef, in latitude 28° 22′, longitude 178° 30′ W., on which the “Gledstanes” was wrecked in 1837. It is apparently of large size, and extends in a N.W. and S.E. line: very few islets have been formed on it. The lagoon seems to be shallow; at least, the deepest part which was surveyed was only three fathoms. Mr. Couthouy (“Remarks,” page 38) describes this island under the name of _Ocean_ island. Considerable doubts should be entertained regarding the nature of a reef of this kind, with a very shallow lagoon, and standing far from any other atoll, on account of the possibility of a crater or flat bank of rock lying at the proper depth beneath the surface of the water, thus affording a foundation for a ring-formed coral-reef. I have, however, thought myself compelled, from its large size and symmetrical outline, to colour it blue.

SAMOA or NAVIGATOR GROUP.—Kotzebue, in his “Second Voyage,” contrasts the structure of these islands with many others in the Pacific, in not being furnished with harbours for ships, formed by distant coral-reefs. The Rev. J. Williams, however, informs me, that coral-reefs do occur in irregular patches on the shores of these islands; but that they do not form a continuous band, as round Mangaia, and other such perfect cases of fringed islands. From the charts accompanying La Peyrouse’s “Voyage,” it appears that the north shore of _Savaii_, _Maouna_, _Orosenga_, and _Mannua_, are fringed by reefs. La Peyrouse, speaking of Maouna (page 126), says that the coral-reef surrounding its shores, almost touches the beach; and is breached in front of the little coves and streams, forming passages for canoes, and probably even for boats. Further on (page 159), he extends the same observation to all the islands which he visited. Mr. Williams in his “Narrative,” speaks of a reef going round a small island attached to _Oyolava_, and returning again to it: all these islands have been coloured red.—A chart of _Rose_ Island, at the extreme west end of the group, is given by Freycinet, from which I should have thought that it had been an atoll; but according to Mr. Couthouy (“Remarks,” page 43), it consists of a reef, only a league in circuit, surmounted by a very few low islets; the lagoon is very shallow, and is strewed with numerous large boulders of volcanic rock. This island, therefore, probably consists of a bank of rock, a few feet submerged, with the outer margin of its upper surface fringed with reefs; hence it cannot be properly classed with atolls, in which the foundations are always supposed to lie at a depth, greater than that at which the reef-constructing polypifers can live; not coloured.

_Beveridge Reef_, 20° S., 167° W., is described in the “Naut. Mag.” (May 1833, page 442) as ten miles long in a N. and S. line, and eight wide; “in the inside of the reef there appears deep water;” there is a passage near the S.W. corner: this therefore seems to be a submerged atoll, and is coloured blue.

_Savage_ Island, 19° S., 170° W., has been described by Cook and Forster. The younger Forster (volume ii., page 163) says it is about forty feet high: he suspects that it contains a low plain, which formerly was the lagoon. The Rev. J. Williams informs me that the reef fringing its shores, resembles that round Mangaia; coloured red.

FRIENDLY ARCHIPELAGO. _Pylstaart_ Island. Judging from the chart in Freycinet’s “Atlas,” I should have supposed that it had been regularly fringed; but as nothing is said in the “Hydrog. Memoir” (or in the “Voyage” of Tasman, the discoverer) about coral-reefs, I have left it uncoloured.—_Tongatabou:_ In the “Atlas of the Voyage of the ‘Astrolabe’,” the whole south side of the island is represented as narrowly fringed by the same reef which forms an extensive platform on the northern side. The origin of this latter reef, which might have been mistaken for a barrier-reef, has already been attempted to be explained, when giving the proofs of the recent elevation of this island.— In Cook’s charts the little outlying island also of _Eoaigee_, is represented as fringed; coloured red.—_Eoua_. I cannot make out from Captain Cook’s charts and descriptions, that this island has any reef, although the bottom of the neighbouring sea seems to be corally, and the island itself is formed of coral-rock. Forster, however, distinctly (“Observations,” page 14) classes it with high islands having reefs, but it certainly is not encircled by a barrier-reef and the younger Forster (“Voyage,” volume i., page 426) says, that “a bed of coral-rocks surrounded the coast towards the landing-place.” I have therefore classed it with the fringed islands and coloured it red. The several islands lying N.W. of Tongatabou, namely _Anamouka_, _Komango_, _Kotou_, _Lefouga_, _Foa_, &c., are seen in Captain Cook’s chart to be fringed by reefs, in several of them are connected together. From the various statements in the first volume of Cook’s “Third Voyage,” and especially in the fourth and sixth chapters, it appears that these reefs are of coral-formation, and certainly do not belong to the barrier class; coloured red.—_Toufoua_ & _Kao_, forming the western part of the group, according to Forster have no reefs; the former is an active volcano.—_Vavao_. There is a chart of this singularly formed island, by Espinoza: according to Mr. Williams it consists of coral-rock: the Chevalier Dillon informs me that it is not fringed; not coloured. Nor are the islands of _Latte_ and _Amargura_, for I have not seen plans on a large scale of them, and do not know whether they are fringed.

_Niouha_, 16° S., 174° W., or _Keppel_ Island of Wallis, or _Cocos_ Island. From a view and chart of this island given in Wallis’s “Voyage” (4to edition) it is evidently encircled by a reef; coloured blue: it is however remarkable that _Boscawen_ Island, immediately adjoining, has no reef of any kind; uncoloured.

_Wallis Island_, 13° S., 176° W., a chart and view of this island in Wallis’s “Voyage” (4to edition) shows that it is encircled. A view of it in the “Naut. Mag.” July 1833, page 376, shows the same fact; blue.

_Alloufatou_, or _Horn_ Island, _Onouafu_, or _Proby_ Island, and _Hunter_ Islands, lie between the Navigator and Fidji groups. I can find no distinct accounts of them.

FIDJI or VITI GROUP.—The best chart of the numerous islands of this group, will be found in the “Atlas of the ‘Astrolabe’s’ Voyage.” From this, and from the description given in the “Hydrog. Memoir,” accompanying it, it appears that many of these islands are bold and mountainous, rising to the height of between 3,000 and 4,000 feet. Most of the islands are surrounded by reefs, lying far from the land, and outside of which the ocean appears very deep. The “Astrolabe” sounded with ninety fathoms in several places about a mile from the reefs, and found no bottom. Although the depth within the reef is not laid down, it is evident from several expressions, that Captain D’Urville believes that ships could anchor within, if passages existed through the outer barriers. The Chevallier Dillon informs me that this is the case: hence I have coloured this group blue. In the S.E. part lies _Batoa_, or _Turtle_ Island of Cook (“Second Voyage,” volume ii., page 23, and chart, 4to edition) surrounded by a coral-reef, “which in some places extends two miles from the shore;” within the reef the water appears to be deep, and outside it is unfathomable; coloured pale blue. At the distance of a few miles, Captain Cook (Ibid., page 24) found a circular coral-reef, four or five leagues in circuit, with deep water within; “in short, the bank wants only a few little islets to make it exactly like one of the half-drowned isles so often mentioned,”—namely, atolls. South of Batoa, lies the high island of _Ono_, which appears in Bellinghausen’s “Atlas” to be encircled; as do some other small islands to the south; coloured pale blue; near Ono, there is an annular reef, quite similar to the one just described in the words of Captain Cook; coloured dark blue.

_Rotoumah_, 13° S., 179° E.—From the chart in Duperrey’s “Atlas,” I thought this island was encircled, and had coloured it blue, but the Chevallier Dillon assures me that the reef is only a shore or fringing one; red.

_Independence_ Island, 10° S., 179° E., is described by Mr. G. Bennett, (“United Service Journal,” 1831, part ii., page 197) as a low island of coral-formation, it is small, and does not appear to contain a lagoon, although an opening through the reef is referred to. A lagoon probably once existed, and has since been filled up; left uncoloured.

ELLICE GROUP.—_Oscar_, _Peyster_, and _Ellice_ Islands are figured in Arrowsmith’s “Chart of the Pacific” (corrected to 1832) as atolls, and are said to be very low; blue.—_Nederlandisch_ Island. I am greatly indebted to the kindness of Admiral Krusenstern, for sending me the original documents concerning this island. From the plans given by Captains Eeg and Khremtshenko, and from the detailed account given by the former, it appears that it is a narrow coral-island, about two miles long, containing a small lagoon. The sea is very deep close to the shore, which is fronted by sharp coral-rocks. Captain Eeg compares the lagoon with that of other coral-islands; and he distinctly says, the land is “very low.” I have therefore coloured it blue. Admiral Krusenstern (“Memoir on the Pacific,” Append., 1835) states that its shores are eighty feet high; this probably arose from the height of the cocoa-nut trees, with which it is covered, being mistaken for land. —_Gran Cocal_ is said in Krusenstern’s “Memoir,” to be low, and to be surrounded by a reef; it is small, and therefore probably once contained a lagoon; uncoloured.—_St. Augustin_. From a chart and view of it, given in the “Atlas of the ‘Coquille’s’ Voyage,” it appears to be a small atoll, with its lagoon partly filled up; coloured blue.

GILBERT GROUP.—The chart of this group, given in the “Atlas of the ‘Coquille’s’ Voyage,” at once shows that it is composed of ten well characterised atolls. In D’Urville and Lottin’s chart, _Sydenham_ is written with a capital letter, signifying that it is high; but this certainly is not the case, for it is a perfectly characterised atoll, and a sketch, showing how low it is, is given in the “‘Coquille’s’ Atlas.” Some narrow strip-like reefs project from the southern side of _Drummond_ atoll, and render it irregular. The southern island of the group is called _Chase_ (in some charts, _Rotches_); of this I can find no account, but Mr. F.D. Bennett discovered (“Geographical Journal”, volume vii., page 229), a low extensive island in nearly the same latitude, about three degrees westward of the longitude assigned to Rotches, but very probably it is the same island. Mr. Bennett informs me that the man at the masthead reported an appearance of lagoon-water in the centre; and, therefore, considering its position, I have coloured it blue. —_Pitt_ Island, at the extreme northern point of the group, is left uncoloured, as its exact position and nature is not known.—_Byron_ Island, which lies a little to the eastward, does not appear to have been visited since Commodore Byron’s voyage, and it was then seen only from a distance of eighteen miles; it is said to be low; uncoloured.

_Ocean_, _Pleasant_, and _Atlantic_ Islands all lie considerably to the west of the Gilbert group: I have been unable to find any distinct account of them. Ocean Island is written with small letters in the French chart, but in Krusenstern’s “Memoir” it is said to be high.

MARSHALL GROUP.—We are well acquainted with this group from the excellent charts of the separate islands, made during the two voyages of Kotzebue: a reduced one of the whole group may be easily seen in Krusenstern’s “Atlas,” and in Kotzebue’s “Second Voyage.” The group consists (with the exception of two _little_ islands which probably have had their lagoon filled up) of a double row of twenty-three large and well-characterised atolls, from the examination of which Chamisso has given us his well-known account of coral-formations. I include _Gaspar-Rico_, or _Cornwallis_ Island in this group, which is described by Chamisso (Kotzebue’s “First Voyage,” volume iii., page 179) “as a low sickle-formed group, with mould only on the windward side.” Gaspard Island is considered by some geographers as a distinct island lying N.E. of the group, but it is not entered in the chart by Krusenstern; left uncoloured. In the S.W. part of this group lies _Baring_ Island, of which little is known (see Krusenstern’s “Appendix,” 1835, page 149). I have left it uncoloured; but _Boston_ Island I have coloured blue, as it is described (Ibid.) as consisting of fourteen small islands, which, no doubt, enclose a lagoon, as represented in a chart in the “‘Coquille’s’ Atlas.”—Two islands, _Aur Kawen_ and _Gaspar Rico_, are written in the French chart with capital letters; but this is an error, for from the account given by Chamisso in Kotzebue’s “First Voyage,” they are certainly low. The nature, position, and even existence, of the shoals and small islands north of the Marshall group, are doubtful.

NEW HEBRIDES.—Any chart, on even a small scale, of these islands, will show that their shores are almost without reefs, presenting a remarkable contrast with those of New Caledonia on the one hand, and the Fidji group on the other. Nevertheless, I have been assured by Mr. G. Bennett, that coral grows vigorously on their shores; as indeed, will be further shown in some of the following notices. As, therefore, these islands are not encircled, and as coral grows vigorously on their shores, we might almost conclude, without further evidence, that they were fringed, and hence I have applied the red colour with rather greater freedom than in other instances.—_Matthew’s Rock_, an active volcano, some way south of the group (of which a plan is given in the “Atlas of the ‘Astrolabe’s’ Voyage”) does not appear to have reefs of any kind about it.—_Annatom_, the southernmost of the Hebrides; from a rough woodcut given in the “United Service Journal” (1831, part iii., page 190), accompanying a paper by Mr. Bennett, it appears that the shore is fringed; coloured red.—_Tanna_. Forster, in his “Observations” (page 22), says Tanna has on its shores coral-rock and madrepores; and the younger Forster, in his account (volume ii., page 269) speaking of the harbour says, the whole S.E. side consists of coral-reefs, which are overflowed at high-water; part of the southern shore in Cook’s chart is represented as fringed; coloured red.—_Immer_ is described (“United Service Journal,” 1831, part iii., page 192) by Mr. Bennett as being of moderate elevation, with cliffs appearing like sandstone: coral grows in patches on its shore, but I have not coloured it; and I mention these facts, because Immer might have been thought from Forster’s classification (“Observations,” page 14), to have been a low island or even an atoll.— _Erromango_ Island; Cook (“Second Voyage,” volume ii., page 45, 4to edition) speaks of rocks everywhere _lining_ the coast, and the natives offered to haul his boat over the breakers to the sandy beach: Mr. Bennett, in a letter to the Editor of the “Singapore Chron.,” alludes to the _reefs_ on its shores. It may, I think, be safely inferred from these passages that the shore is fringed in parts by coral-reefs; coloured red.—_Sandwich_ Island. The east coast is said (Cook’s “Second Voyage,” volume ii., page 41) to be low, and to be guarded by a chain of breakers. In the accompanying chart it is seen to be fringed by a reef; coloured red.—_Mallicollo_; Forster speaks of the reef-bounded shore: the reef is about thirty yards wide, and so shallow that a boat cannot pass over it. Forster also (“Observations,” page 23) says, that the rocks of the sea-shore consist of madrepore. In the plan of Sandwich harbour, the headlands are represented as fringed; coloured red.—_Aurora_ and _Pentecost_ Islands, according to Bougainville, apparently have no reefs; nor has the large island of _S. Espiritu_, nor _Bligh_ Island or _Banks’_ Islands, which latter lie to the N.E. of the Hebrides. But in none of these cases, have I met with any detailed account of their shores, or seen plans on a large scale; and it will be evident, that a fringing-reef of only thirty or even a few hundred yards in width, is of so little importance to navigation, that it will seldom be noticed, excepting by chance; and hence I do not doubt that several of these islands, now left uncoloured, ought to be red.

SANTA-CRUZ GROUP.—_Vanikoro_ (Figure 1, Plate I.) offers a striking example of a barrier-reef: it was first described by the Chevalier Dillon, in his voyage, and was surveyed in the “Astrolabe”; coloured pale blue.—_Tikopia_ and _Fataka_ Islands appear, from the descriptions of Dillon and D’Urville, to have no reefs; _Anouda_ is a low, flat island, surrounded by cliffs (“‘Astrolabe’ Hydrog.” and Krusenstern, “Mem.” volume ii., page 432); these are uncoloured. _Toupoua_ (_Otooboa_ of Dillon) is stated by Captain Tromelin (“Annales Marit.” 1829, page 289) to be almost entirely included in a reef, lying at the distance of two miles from the shore. There is a space of three miles without any reef, which, although indented with bays, offers no anchorage from the extreme depth of the water close to the shore: Captain Dillon also speaks of the reefs fronting this island; coloured blue.— _Santa-Cruz_. I have carefully examined the works of Carteret, D’Entrecasteaux, Wilson, and Tromelin, and I cannot discover any mention of reefs on its shores; left uncoloured.—_Tinakoro_ is a constantly active volcano without reefs.—_Mendana Isles_ (mentioned by Dillon under the name of _Mammee_, etc.); said by Krusenstern to be low, and intertwined with reefs. I do not believe they include a lagoon; I have left them uncoloured.—_Duff’s_ Islands compose a small group directed in a N.W. and S.E. band; they are described by Wilson (page 296, “Miss. Voy.” 4to edition), as formed by bold-peaked land, with the islands surrounded by coral-reefs, extending about half a mile from the shore; at a distance of a mile from the reefs he found only seven fathoms. As I have no reason for supposing there is deep water within these reefs, I have coloured them red. _Kennedy_ Island, N.E. of Duff’s. I have been unable to find any account of it.

NEW CALEDONIA.—The great barrier-reefs on the shores of this island have already been described (Figure 5, Plate II.). They have been visited by Labillardière, Cook, and the northern point by D’Urville; this latter part so closely resembles an atoll that I have coloured it dark blue. The _Loyalty_ group is situated eastward of this island; from the chart and description given in the “Voyage of the ‘Astrolabe’,” they do not appear to have any reefs; north of this group, there are some extensive low reefs (called _Astrolabe_ and _Beaupré_,) which do not seem to be atoll-formed; these are left uncoloured.

AUSTRALIAN BARRIER-REEF.—The limits of this great reef, which has already been described, have been coloured from the charts of Flinders and King. In the northern parts, an atoll-formed reef, lying outside the barrier, has been described by Bligh, and is coloured dark blue. In the space between Australia and New Caledonia, called by Flinders the Corallian Sea, there are numerous reefs. Of these, some are represented in Krusenstern’s “Atlas” as having an atoll-like structure; namely, _Bampton_ shoal, _Frederic_, _Vine_ or Horse-shoe, and _Alert_ reefs; these have been coloured dark blue.

LOUISIADE: the dangerous reefs which front and surround the western, southern, and northern coasts of this so-called peninsula and archipelago, seem evidently to belong to the barrier class. The land is lofty, with a low fringe on the coast; the reefs are distant, and the sea outside them profoundly deep. Nearly all that is known of this group is derived from the labours of D’Entrecasteaux and Bougainville: the latter has represented one continuous reef ninety miles long, parallel to the shore, and in places as much as ten miles from it; coloured pale blue. A little distance northward we have the _Laughlan_ Islands, the reefs round which are engraved in the “Atlas of the Voyage of the ‘Astrolabe’,” in the same manner as in the encircled islands of the Caroline Archipelago, the reef is, in parts, a mile and a half from the shore, to which it does not appear to be attached; coloured blue. At some little distance from the extremity of the Louisiade lies the _Wells_ reef, described in G. Hamilton’s “Voyage in H.M.S. ‘Pandora’” (page 100): it is said, “We found we had got embayed in a double reef, which will soon be an island.” As this statement is only intelligible on the supposition of the reef being crescent or horse-shoe formed, like so many other submerged annular reefs, I have ventured to colour it blue.

SALOMON ARCHIPELAGO: the chart in Krusenstern’s “Atlas” shows that these islands are not encircled, and as coral appears from the works of Surville, Bougainville, and Labillardière, to grow on their shores, this circumstance, as in the case of the New Hebrides, is a presumption that they are fringed. I cannot find out anything from D’Entrecasteaux’s “Voyage,” regarding the southern islands of the group, so have left them uncoloured.—_Malayta_ Island in a rough MS. chart in the Admiralty has its northern shore fringed.—_Ysabel_ Island, the N.E. part of this island, in the same chart, is also fringed: Mendana, speaking (Burney, volume i., page 280) of an islet adjoining the northern coast, says it is surrounded by reefs; the shores, also of Port Praslin appear regularly fringed.—_Choiseul_ Island. In Bougainville’s “Chart of Choiseul Bay,” parts of the shores are fringed by coral-reefs.— _Bougainville_ Island. According to D’Entrecasteaux the western shore abounds with coral-reefs, and the smaller islands are said to be attached to the larger ones by reefs; all the before-mentioned islands have been coloured red.—_Bouka_ Islands. Captain Duperrey has kindly informed me in a letter that he passed close round the northern side of this island (of which a plan is given in his “Atlas of the ‘Coquille’s’ Voyage”), and that it was “garnie d’une bande de récifs à fleur d’eau adherentes au rivage;” and he infers, from the abundance of coral on the islands north and south of Bouka, that the reef probably is of coral; coloured red.

Off the north coast of the Solomon Archipelago there are several small groups which are little known; they appear to be low, and of coral-formation; and some of them probably have an atoll-like structure; the Chevallier Dillon, however, informs me that this is not the case with the B. de _Candelaria_.—_Outong Java_, according to the Spanish navigator, Maurelle, is thus characterised; but this is the only one which I have ventured to colour blue.

NEW IRELAND.—The shores of the S.W. point of this island and some adjoining islets, are fringed by reefs, as may be seen in the “Atlases of the Voyages of the ‘Coquille’ and ‘Astrolabe’.” M. Lesson observes that the reefs are open in front of each streamlet. The _Duke of York’s_ Island is also fringed; but with regard to the other parts of _New Ireland_, _New Hanover_, and the small islands lying northward, I have been unable to obtain any information. I will only add that no part of New Ireland appears to be fronted by distant reefs. I have coloured red only the above specified portions.

NEW BRITAIN and the NORTHERN SHORE of NEW GUINEA.—From the charts in the “Voyage of the ‘Astrolabe’,” and from the “Hydrog. Memoir,” it appears that these coasts are entirely without reefs, as are the _Schouten Islands_, lying close to the northern shore of New Guinea. The western and south-western parts of New Guinea, will be treated of when we come to the islands of the East Indian Archipelago.

ADMIRALTY GROUP.—From the accounts by Bougainville, Maurelle, D’Entrecasteaux, and the scattered notices collected by Horsburgh, it appears, that some of the many islands composing it, are high, with a bold outline; and others are very low, small and interlaced with reefs. All the high islands appear to be fronted by distant reefs rising abruptly from the sea, and within some of which there is reason to believe that the water is deep. I have therefore little doubt they are of the barrier class.—In the southern part of the group we have _Elizabeth Island_, which is surrounded by a reef at the distance of a mile; and two miles eastward of it (Krusenstern, “Append.” 1835, page 42) there is a little island containing a lagoon.—Near here, also lies _Circular-reef_ (Horsburgh, “Direct.” volume i., page 691, 4th edition), “three or four miles in diameter having deep water inside with an opening at the N.N.W. part, and on the outside steep to.” I have from these data, coloured the group pale blue, and _circular-reef_ dark blue.—the _Anachorites_, _Echequier_, and _Hermites_, consist of innumerable low islands of coral-formation, which probably have atoll-like forms; but not being able to ascertain this, I have not coloured them, nor _Durour_ Island, which is described by Carteret as low.

The CAROLINE ARCHIPELAGO is now well-known, chiefly from the hydrographical labours of Lutké; it contains about forty groups of atolls, and three encircled islands, two of which are engraved in Figures 2 and 7, Plate I. Commencing with the eastern part; the encircling reef round _Ualen_ appears to be only about half a mile from the shore; but as the land is low and covered with mangroves (“Voyage autour du Monde,” par F. Lutké, volume i., page 339), the real margin has not probably been ascertained. The extreme depth in one of the harbours within the reef is thirty-three fathoms (see charts in “Atlas of ‘Coquille’s’ Voyage”), and outside at half a mile distant from the reef, no bottom was obtained with two hundred and fifty fathoms. The reef is surmounted by many islets, and the lagoon-like channel within is mostly shallow, and appears to have been much encroached on by the low land surrounding the central mountains; these facts show that time has allowed much detritus to accumulate; coloured pale blue.— _Pouynipète_, or _Seniavine_. In the greater part of the circumference of this island, the reef is about one mile and three quarters distant; on the north side it is five miles off the included high islets. The reef is broken in several places; and just within it, the depth in one place is thirty fathoms, and in another, twenty-eight, beyond which, to all appearance, there was “un porte vaste et sur” (Lutké, volume ii., page 4); coloured pale blue.—_Hogoleu_ or _Roug_. This wonderful group contains at least sixty-two islands, and its reef is one hundred and thirty-five miles in circuit. Of the islands, only a few, about six or eight (see “Hydrog. Descrip.” page 428, of the “Voyage of the ‘Astrolabe’,” and the large accompanying chart taken chiefly from that given by Duperrey) are high, and the rest are all small, low, and formed on the reef. The depth of the great interior lake has not been ascertained; but Captain D’Urville appears to have entertained no doubt about the possibility of taking in a frigate. The reef lies no less than fourteen miles distant from the northern coasts of the interior high islands, seven from their western sides, and twenty from the southern; the sea is deep outside. This island is a likeness on a grand scale to the Gambier group in the Low Archipelago. Of the groups of low[1] islands forming the chief part of the Caroline Archipelago, all those of larger size, have the true atoll-structure (as may be seen in the “Atlas” by Captain Lutké), and some even of the very small ones, as _Macaskill_ and _Duperrey_, of which plans are given in the “Atlas of the ‘Coquille’s’ Voyage.” There are, however, some low small islands of coral-formation, namely _Ollap_, _Tamatam_, _Bigali_, _Satahoual_, which do not contain lagoons; but it is probable that lagoons originally existed, but have since filled up: Lutké (volume ii., page 304) seems to have thought that all the low islands, with only one exception, contained lagoons. From the sketches, and from the manner in which the margins of these islands are engraved in the “Atlas of the Voyage of the ‘Coquille’,” it might have been thought that they were not low; but by a comparison with the remarks of Lutké (volume ii., page 107, regarding Bigali) and of Freycinet (“Hydrog. Memoir ‘L’Uranie’ Voyage,” page 188, regarding Tamatam, Ollap, etc.), it will be seen that the artist must have represented the land incorrectly. The most southern island in the group, namely _Piguiram_, is not coloured, because I have found no account of it. _Nougouor_, or _Monte Verdison_, which was not visited by Lutké, is described and figured by Mr. Bennett (“United Service Journal,” January 1832) as an atoll. All the above-mentioned islands have been coloured blue.

[1] In D’Urville and Lottin’s chart, Peserare is written with capital letters; but this evidently is an error, for it is one of the low islets on the reef of Namonouyto (see Lutké’s charts)—a regular atoll.

WESTERN PART OF THE CAROLINE ARCHIPELAGO.—_Fais_ Island is ninety feet high, and is surrounded, as I have been informed by Admiral Lutké, by a narrow reef of living coral, of which the broadest part, as represented in the charts, is only 150 yards; coloured red.— _Philip_ Island., I believe, is low; but Hunter, in his “Historical Journal,” gives no clear account of it; uncoloured.—_Elivi;_ from the manner in which the islets on the reefs are engraved, in the “Atlas of the ‘Astrolabe’s’ Voyage,” I should have thought they were above the ordinary height, but Admiral Lutké assures me this is not the case: they form a regular atoll; coloured blue.—_Gouap_ (_Eap_ of Chamisso), is a high island with a reef (see chart in “Voyage of the ‘Astrolabe’”), more than a mile distant in most parts from the shore, and two miles in one part. Captain D’Urville thinks that there would be anchorage (“Hydrog. Descript. ‘Astrolabe’ Voyage,” page 436) for ships within the reef, if a passage could be found; coloured pale blue.—_Goulou_, from the chart in the “‘Astrolabe’s’ Atlas,” appears to be an atoll. D’Urville (“Hydrog. Descript.” page 437) speaks of the low islets on the reef; coloured dark blue.

PELEW ISLANDS.—Krusenstern speaks of some of the islands being mountainous; the reefs are distant from the shore, and there are spaces within them, and not opposite valleys, with from ten to fifteen fathoms. According to a MS. chart of the group by Lieutenant Elmer in the Admiralty, there is a large space within the reef with deepish water; although the high land does not hold a central position with respect to the reefs, as is generally the case, I have little doubt that the reefs of the Pelew Islands ought to be ranked with the barrier class, and I have coloured them pale blue. In Lieutenant Elmer’s chart there is a horseshoe-formed shoal, laid down thirteen miles N.W. of Pelew, with fifteen fathoms within the reef, and some dry banks on it; coloured dark blue.—_Spanish_, _Martires_, _Sanserot_, _Pulo Anna_ and _Mariere_ Islands are not coloured, because I know nothing about them, excepting that according to Krusenstern, the second, third, and fourth mentioned, are low, placed on coral-reefs, and therefore, perhaps, contain lagoons; but Pulo Mariere is a little higher.

MARIANA ARCHIPELAGO, or LADRONES.—_Guahan_. Almost the whole of this island is fringed by reefs, which extend in most parts about a third of a mile from the land. Even where the reefs are most extensive, the water within them is shallow. In several parts there is a navigable channel for boats and canoes within the reefs. In Freycinet’s “Hydrog. Mem.” there is an account of these reefs, and in the “Atlas,” a map on a large scale; coloured red.—_Rota_. “L’ile est presque entièrement entourée des récifs” (page 212, Freycinet’s “Hydrog. Mem.”). These reefs project about a quarter of a mile from the shore; coloured red.—_Tinian_. The eastern coast is precipitous, and is without reefs; but the western side is fringed like the last island; coloured red.—_Saypan_. The N.E. coast, and likewise the western shores appear to be fringed; but there is a great, irregular, horn-like reef projecting far from this side; coloured red.—_Farallon de Medinilla_, appears so regularly and closely fringed in Freycinet’s charts, that I have ventured to colour it red, although nothing is said about reefs in the “Hydrographical Memoir.” The several islands which form the northern part of the group are volcanic (with the exception perhaps of Torres, which resembles in form the madreporitic island of Medinilla), and appear to be without reefs.—_Mangs_, however, is described (by Freycinet, page 219, “Hydrog.”) from some Spanish charts, as formed of small islands placed “au milieu des nombreux récifs;” and as these reefs in the general chart of the group do not project so much as a mile; and as there is no appearance from a double line, of the existence of deep water within, I have ventured, although with much hesitation, to colour them red. Respecting _Folger_ and _Marshall_ Islands which lie some way east of the Marianas, I can find out nothing, excepting that they are probably low. Krusenstern says this of Marshall Island; and Folger Island is written with small letters in D’Urville’s chart; uncoloured.

BONIN or ARZOBISPO GROUP.—_Peel Island_ has been examined by Captain Beechey, to whose kindness I am much indebted for giving me information regarding it: “At Port Lloyd there is a great deal of coral; and the inner harbour is entirely formed by coral-reefs, which extend outside the port along the coast.” Captain Beechey, in another part of his letter to me, alludes to the reefs fringing the island in all directions; but at the same time it must be observed that the surf washes the volcanic rocks of the coast in the greater part of its circumference. I do not know whether the other islands of the Archipelago are fringed; I have coloured Peel Island red.—_Grampus Island_ to the eastward, does not appear (Meare’s “Voyage,” page 95) to have any reefs, nor does _Rosario Island_ (from Lutké’s chart), which lies to the westward. Respecting the few other islands in this part of the sea, namely the _Sulphur Islands_, with an active volcano, and those lying between Bonin and Japan (which are situated near the extreme limit in latitude, at which reefs are formed), I have not been able to find any clear account.

WEST END OF NEW GUINEA.—_Port Dory_. From the charts in the “Voyage of the ‘Coquille’,” it would appear that the coast in this part is fringed by coral-reefs; M. Lesson, however, remarks that the coral is sickly; coloured red.—_Waigiou_. A considerable portion of the northern shores of these islands is seen in the charts (on a large scale) in Freycinet’s “Atlas” to be fringed by coral-reefs. Forrest (page 21, “Voyage to New Guinea”) alludes to the coral-reefs lining the heads of Piapis Bay; and Horsburgh (volume ii., page 599, 4th edition), speaking of the islands in Dampier Strait, says “sharp coral-rocks line their shores;” coloured red.—In the sea north of these islands, we have _Guedes_ (or _Freewill_, or _St. David’s_), which from the chart given in the 4to edition of Carteret’s “Voyage,” must be an atoll. Krusenstern says the islets are very low; coloured blue.—_Carteret’s Shoals_, in 2° 53′ N., are described as circular, with stony points showing all round, with deeper water in the middle; coloured blue.—_Aiou;_ the plan of this group, given in the “Atlas of the Voyage of the ‘Astrolabe’,” shows that it is an atoll; and, from a chart in Forrest’s “Voyage,” it appears that there is twelve fathoms within the circular reef; coloured blue.—The S.W. coast of New Guinea appears to be low, muddy, and devoid of reefs. The _Arru_, _Timor laut_, and _Tenimber_ groups have lately been examined by Captain Kolff, the MS. translation of which, by Mr. W. Earl, I have been permitted to read, through the kindness of Captain Washington, R.N. These islands are mostly rather low, and are surrounded by distant reefs (the Ki Islands, however, are lofty, and, from Mr. Stanley’s survey, appear without reefs); the sea in some parts is shallow, in others profoundly deep (as near Larrat). From the imperfection of the published charts, I have been unable to decide to which class these reefs belong. From the distance to which they extend from the land, where the sea is very deep, I am strongly inclined to believe they ought to come within the barrier class, and be coloured blue; but I have been forced to leave them uncoloured.—The last-mentioned groups are connected with the east end of Ceram by a chain of small islands, of which the small groups of _Ceram-laut_, _Goram_ and _Keffing_ are surrounded by very extensive reefs, projecting into deep water, which, as in the last case, I strongly suspect belong to the barrier class; but I have not coloured them. From the south side of Keffing, the reefs project five miles (Windsor Earl’s “Sailing Direct. for the Arafura Sea,” page 9).

CERAM.—In various charts which I have examined, several parts of the coast are represented as fringed by reefs.—_Manipa_ Island, between Ceram and Bourou, in an old MS. chart in the Admiralty, is fringed by a very irregular reef, partly dry at low water, which I do not doubt is of coral-formation; both islands coloured red.—_Bourou;_ parts of this island appear fringed by coral-reefs, namely, the eastern coast, as seen in Freycinet’s chart; and _Cajeli Bay_, which is said by Horsburgh (volume ii., page 630) to be lined by coral-reefs, that stretch out a little way, and have only a few feet water on them. In several charts, portions of the islands forming the AMBOINA GROUP are fringed by reefs; for instance, _Noessa_, _Harenca_, and _Ucaster_, in Freycinet’s charts. The above-mentioned islands have been coloured red, although the evidence is not very satisfactory.—North of Bourou the parallel line of the _Xulla Isles_ extends: I have not been able to find out anything about them, excepting that Horsburgh (volume ii., page 543) says that the northern shore is surrounded by a reef at the distance of two or three miles; uncoloured.—_Mysol Group;_ the Kanary Islands are said by Forrest (“Voyage,” page 130) to be divided from each other by deep straits, and are lined with coral-rocks; coloured red.—_Guebe_, lying between Waigiou and Gilolo, is engraved as if fringed; and it is said by Freycinet, that all the soundings under five fathoms were on coral; coloured red.—_Gilolo_. In a chart published by Dalrymple, the numerous islands on the western, southern (_Batchian_ and the _Strait of Patientia_), and eastern sides appear fringed by narrow reefs; these reefs, I suppose, are of coral, for it is said in “Malte Brun” (volume xii., page 156), “Sur les cotes (of Batchian) comme _dans le plupart_ des iles de cet archipel, il y a de rocs de medrepores d’une beauté et d’une variété infinies.” Forrest, also (page 50), says Seland, near Batchian, is a little island with reefs of coral; coloured red.—_Morty_ Island (north of Gilolo). Horsburgh (volume ii., page 506) says the northern coast is lined by reefs, projecting one or two miles, and having no soundings close to them; I have left it uncoloured, although, as in some former cases, it ought probably to be pale blue.—_Celebes_. The western and northern coasts appear in the charts to be bold and without reefs. Near the extreme northern point, however, an islet in the _Straits of Limbe_, and parts of the adjoining shore, appear to be fringed: the east side of the bay of _Manado_, has deep water, and is fringed by sand and coral (“‘Astrol.’ Voyage,” Hydrog. Part, pages 453-4); this extreme point, therefore, I have coloured red.—Of the islands leading from this point to Magindanao, I have not been able to find any account, except of _Serangani_, which appears surrounded by narrow reefs; and Forrest (“Voyage,” page 164) speaks of coral on its shores; I have, therefore, coloured this island red. To the eastward of this chain lie several islands; of which I cannot find any account, except of _Karkalang_, which is said by Horsburgh (volume ii., page 504) to be lined by a dangerous reef, projecting several miles from the northern shore; not coloured.

ISLANDS NEAR TIMOR.—The account of the following islands is taken from Captain D. Kolff’s “Voyage,” in 1825, translated by Mr. W. Earl, from the Dutch.—_Lette_ has “reefs extending along shore at the distance of half a mile from the land.”—_Moa_ has reefs on the S.W. part.—_Lakor_ has a reef lining its shore; these islands are coloured red.—Still more eastward, _Luan_ has, differently from the last-mentioned islands, an extensive reef; it is steep outside, and within there is a depth of twelve feet; from these facts, it is impossible to decide to which class this island belongs.—_Kissa_, off the point of Timor, has its “shore fronted by a reef, steep too on the outer side, over which small proahs can go at the time of high water;” coloured red.—_Timor;_ most of the points, and some considerable spaces of the northern shore, are seen in Freycinet’s chart to be fringed by coral-reefs; and mention is made of them in the accompanying “Hydrog. Memoir;” coloured red.—_Savu_, S.E. of Timor, appears in Flinders’ chart to be fringed; but I have not coloured it, as I do not know that the reefs are of coral.— _Sandalwood_ Island has, according to Horsburgh (volume ii., page 607), a reef on its southern shore, four miles distant from the land; as the neighbouring sea is deep, and generally bold, this probably is a barrier- reef, but I have not ventured to colour it.

N.W. COAST OF AUSTRALIA.—It appears, in Captain King’s Sailing Directions (“Narrative of Survey,” volume ii, pages 325-369), that there are many extensive coral-reefs skirting, often at considerable distances, the N.W. shores, and encompassing the small adjoining islets. Deep water, in no instance, is represented in the charts between these reefs and the land; and, therefore, they probably belong to the fringing class. But as they extend far into the sea, which is generally shallow, even in places where the land seems to be somewhat precipitous; I have not coloured them. Houtman’s Abrolhos (latitude 28° S. on west coast) have lately been surveyed by Captain Wickham (as described in “Naut. Mag.” 1841, page 511): they lie on the edge of a steeply shelving bank, which extends about thirty miles seaward, along the whole line of coast. The two southern reefs, or islands, enclose a lagoon-like space of water, varying in depth from five to fifteen fathoms, and in one spot with twenty-three fathoms. The greater part of the island has been formed on their inland sides, by the accumulation of fragments of coral; the seaward face consisting of nearly bare ledges of rock. Some of the specimens, brought home by Captain Wickham, contained fragments of marine shells, but others did not; and these closely resembled a formation at King George’s Sound, principally due to the action of the wind on calcareous dust, which I shall describe in a forthcoming part. From the extreme irregularity of these reefs with their lagoons, and from their position on a bank, the usual depth of which is only thirty fathoms, I have not ventured to class them with atolls, and hence have left them uncoloured.—_Rowley Shoals_. These lie some way from the N.W. coast of Australia: according to Captain King (“Narrative of Survey,” volume i., page 60), they are of coral-formation. They rise abruptly from the sea, and Captain King had no bottom with 170 fathoms close to them. Three of them are crescent-shaped; they are mentioned by Mr. Lyell, on the authority of Captain King, with reference to the direction of their open sides. “A third oval reef of the same group is entirely submerged” (“Principles of Geology,” book iii. chapter xviii.); coloured blue.—_Scott’s Reefs_, lying north of Rowley Shoals, are briefly described by Captain Wickham (“Naut. Mag.” 1841, page 440): they appear to be of great size, of a circular form, and “with smooth water within, forming probably a lagoon of great extent.” There is a break on the western side, where there probably is an entrance: the water is very deep off these reefs; coloured blue.

Proceeding westward along the great volcanic chain of the East Indian Archipelago, _Solor Strait_ is represented in a chart published by Dalrymple from a Dutch MS., as fringed; as are parts of _Flores_, of _Adenara_, and of _Solor_. Horsburgh speaks of coral growing on these shores; and therefore I have no doubt that the reefs are of coral, and accordingly have coloured them red. We hear from Horsburgh (volume ii., page 602) that a coral-flat bounds the shores of _Sapy_ Bay. From the same authority it appears (page 610) that reefs fringe the island of _Timor-Young_, on the N. shore of Sumbawa; and, likewise (page 600), that _Bally_ town in _Lombock_, is fronted by a reef, stretching along the shore at a distance of a hundred fathoms, with channels through it for boats; these places, therefore, have been coloured red.—_Bally_ Island. In a Dutch MS. chart on a large scale of Java, which was brought from that island by Dr. Horsfield, who had the kindness to show it me at the India House, its western, northern, and southern shores appear very regularly fringed by a reef (see also Horsburgh, volume ii., page 593); and as coral is found abundantly there, I have not the least doubt that the reef is of coral, and therefore have coloured it red.

JAVA.—My information regarding the reefs of this great island is derived from the chart just mentioned. The greater part of _Madura_ is represented in it as regularly fringed, and likewise portions of the coast of Java immediately south of it. Dr. Horsfield informs me that coral is very abundant near _Sourabaya_. The islets and parts of the N. coast of Java, west of _Point Buang_, or _Japara_, are fringed by reefs, said to be of coral. _Lubeck_, or _Bavian_ Islands, lying at some distance from the shore of Java, are regularly fringed by coral-reefs. _Carimon Java_ appears equally so, though it is not directly said that the reefs are of coral; there is a depth between thirty and forty fathoms round these islands. Parts of the shores of _Sunda_ Strait, where the water is from forty to eighty fathoms deep, and the islets near _Batavia_ appear in several charts to be fringed. In the Dutch chart the southern shore, in the narrowest part of the island, is in two places fringed by reefs of coral. West of _Segorrowodee_ Bay, and the extreme S.E. and E. portions are likewise fringed by coral-reefs; all the above-mentioned places coloured red.

_Macassar Strait_; the east coast of _Borneo_ appears, in most parts, free from reefs, and where they occur, as on the east coast of _Pamaroong_, the sea is very shallow; hence no part is coloured. In _Macassar_ Strait itself, in about latitude 2° S., there are many small islands with coral-shoals projecting far from them. There are also (old charts by Dalrymple) numerous little flats of coral, not rising to the surface of the water, and shelving suddenly from five fathoms to no bottom with fifty fathoms; they do not appear to have a lagoon-like structure. There are similar coral-shoals a little farther south; and in latitude 4° 55′ there are two, which are engraved from modern surveys, in a manner which might represent an annular reef with deep water inside: Captain Moresby, however, who was formerly in this sea, doubts this fact, so that I have left them uncoloured: at the same time I may remark, that these two shoals make a nearer approach to the atoll-like structure than any other within the E. Indian Archipelago. Southward of these shoals there are other low islands and irregular coral-reefs; and in the space of sea, north of the great volcanic chain, from Timor to Java, we have also other islands, such as the _Postillions_, _Kalatoa_, _Tokan-Bessees_, &c., which are chiefly low, and are surrounded by very irregular and distant reefs. From the imperfect charts I have seen, I have not been able to decide whether they belong to the atoll or barrier-classes, or whether they merely fringe submarine banks, and gently sloping land. In the Bay of _Bonin_, between the two southern arms of Celebes, there are numerous coral- reefs; but none of them seem to have an atoll-like structure. 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.

SUMATRA.—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° 51′ S.) is surrounded by reefs of coral, partly dry at low water, (Horsburgh, volume ii., page 96).—_Trieste Island_ (4° 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°). 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° 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° 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.

NICOBAR ISLANDS.—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.

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 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 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.

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 space 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 shore; in some parts, however, the reef must be attached, since Lieutenant Boteler (“Narr.” volume i., page 161) describes a passage 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 shore (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 shore, with deep water. On the north-western coasts the reefs appear attached to the shores. 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 _shore_, from which expression I presume some parts are without reefs. From this description I apprehend the reef belongs to the barrier class; 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 latitude 25° S.) the coast for ten miles is fringed by a reef; coloured red. The shore 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 shore, with from four to ten fathoms within it. If this reef had been more extensive, it must have been classed as a barrier-reef; but as the line of coast falls inwards here, a submarine bank perhaps extends parallel to the shore, which has offered a foundation for the growth of the coral; I have left this part uncoloured. From _lat_. 22° 16′ _to_ 21° 37′, the shore 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 shore, 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 latitude 33° 15′; I have coloured the whole of this part of the coast red. The islands of _Juan de Nova_ (in latitude 17° 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 _Passandava Bays_ (14° 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° 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 class, 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 shore.” 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 space, 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° 1′ N.) there is a coral-reef extending four or five miles along the shore (Owen’s “Narr.” volume i, page 357) which in the chart lies at the distance of a quarter of a mile from the shore, 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° 20′ S.) “the coast and islands are formed of madrepore” (Owen’s “Narrative,” volume i., page 363). The chart of this part (entitled _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 spaces 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.” volume i., page 369) describes the muddy bay of _Patta_, which seems to resemble other parts of this coast, as fronted by small, narrow, level islets formed of decomposing coral, the margin of which is seldom of greater height than twelve feet, overhanging the rocky surface from which the islets rise. Knowing that the islets are formed of coral, it is, I think, scarcely possible to view the coast, and not at once conclude that we here see a fringing-reef, which has been upraised a few feet: the unusual depth of from two to four fathoms within some of these islets, is probably due to muddy rivers having prevented the growth of coral near the shore. There is, however, one difficulty on this view, namely, that before the elevation took place, which converted the reef into a chain of islets, the water must apparently have been still deeper; on the other hand it may be supposed that the formation of a nearly perfect barrier in front, of so large an extent of coast, would cause the currents (especially in front of the rivers), to deepen their muddy beds. When describing in the chapter on fringing-reefs, those of Mauritius, I have given my reasons for believing that the shoal spaces within reefs of this kind, must, in many instances, have been deepened. However this may be, as several parts of this line of coast are undoubtedly fringed by living reefs, I have coloured it red.— _Maleenda_ (3° 20′ S.). In the plan of the harbour, the south headland appears fringed; and in Owen’s chart on a larger scale, the reefs are seen to extend nearly thirty miles southward; coloured red.—_Mombas_ (4° 5′ S.). The island which forms the harbour, “is surrounded by cliffs of madrepore, capable of being rendered almost impregnable” (Owen’s “Narr.” volume i., page 412). The shore of the mainland N. and S. of the harbour, is most regularly fringed by a coral-reef at a distance from half a mile to one mile and a quarter from the land; within the reef the depth is from nine to fifteen feet; outside the reef the depth at rather less than half a mile is thirty fathoms. From the charts it appears that a space about thirty-six miles in length, is here fringed; coloured red.—_Pemba_ (5° S.) is an island of coral-formation, level, and about two hundred feet in height (Owen’s “Narr.” volume i., page 425); it is thirty-five miles long, and is separated from the mainland by a deep sea. The outer coast is represented in the chart as regularly fringed; coloured red. The mainland in front of Pemba is likewise fringed; but there also appear to be some outlying reefs with deep water between them and the shore. I do not understand their structure, either from the charts or the description, therefore have not coloured them.—_Zanzibar_ resembles Pemba in most respects; its southern half on the western side and the neighbouring islets are fringed; coloured red. On the mainland, a little S. of Zanzibar, there are some banks parallel to the coast, which I should have thought had been formed of coral, had it not been said (Boteler’s “Narr.” volume ii., page 39) that they were composed of sand; not coloured.—_Latham’s Bank_ is a small island, fringed by coral-reefs; but being only ten feet high, it has not been coloured.—_Monfeea_ is an island of the same character as Pemba; its outer shore is fringed, and its southern extremity is connected with Keelwa Point on the mainland by a chain of islands fringed by reefs; coloured red. The four last-mentioned islands resemble in many respects some of the islands in the Red Sea, which will presently be described.— _Keelwa_. In a plan of the shore, a space of twenty miles N. and S. of this place is fringed by reefs, apparently of coral: these reefs are prolonged still further southward in Owen’s general chart. The coast in the plans of the rivers _Lindy_ and _Monghow_ (9° 59′ and 10° 7′ S.) has the same structure; coloured red.—_Querimba Islands_ (from 10° 40′ to 13° S.). A chart on a large scale is given of these islands; they are low, and of coral-formation (Boteler’s “Narr.” volume ii., page 54); and generally have extensive reefs projecting from them which are dry at low water, and which on the outside rise abruptly from a deep sea: on their insides they are separated from the continent by a channel, or rather a succession of bays, with an average depth of ten fathoms. The small headlands on the continent also have coral-banks attached to them; and the Querimba islands and banks are placed on the lines of prolongation of these headlands, and are separated from them by very shallow channels. It is evident that whatever cause, whether the drifting of sediment or subterranean movements, produced the headlands, likewise produced, as might have been expected, submarine prolongations to them; and these towards their outer extremities, have since afforded a favourable basis for the growth of coral-reefs, and subsequently for the formation of islets. As these reefs clearly belong to the fringing class, the Querimba islands have been coloured red.—_Monabila_ (13° 32′ S.). In the plan of this harbour, the headlands outside are fringed by reefs apparently of coral; coloured red.—_Mozambique_ (150° S.) The outer part of the island on which the city is built, and the neighbouring islands, are fringed by coral-reefs; coloured red. From the description given in Owen’s “Narr.” (volume i., page 162), the shore from _Mozambique_ to _Delagoa Bay_ appears 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 India 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 sandbanks, 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 Captain Haines (“Geographical Journal,” 1839, page 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 India Company in 1836, from personal communication with Captain 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, seems to have no necessary connection with the presence of reefs; for Captain Moresby particularly observed to me, that, in latitude 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, chiefly on the eastern side; the space within being deep enough to admit a safe navigation in small vessels. The banks are generally of an oval form, and some miles in width; but some of them are very long in proportion to their width. Captain Moresby informs me that any one, who had not made actual plans of them, would be apt to think that they were much more elongated than they really are. Many of them rise to the surface, but the greater number lie from five to thirty fathoms beneath it, with irregular soundings on them. They consist of sand and living coral; coral on most of them, according to Captain Moresby, covering the greater part of their surface. They extend parallel to the shore, and they are not unfrequently connected in their middle parts by short transverse banks with the mainland. The sea is generally profoundly deep quite close to them, as it is near most parts of the coast of the mainland; but this is not universally the case, for between latitude 15° and 17° the water deepens quite gradually from the banks, both on the eastern and western shores, towards the middle of the sea. Islands in many parts arise from these banks; they are low, flat-topped, and consist of the same horizontally stratified formation with that forming the plain-like margin of the mainland. Some of the smaller and lower islands consist of mere sand. Captain Moresby informs me, that small masses of rock, the remnants of islands, are left on many banks where there is now no dry land. Ehrenberg also asserts that most of the islets, even the lowest, have a flat abraded basis, composed of the same tertiary formation: he believes that as soon as the surf wears down the protuberant parts of a bank, just beneath the level of the sea, the surface becomes protected from further abrasion by the growth of coral, and he thus accounts for the existence of so many banks standing on a level with the surface of this sea. It appears that most of the islands are certainly decreasing in size.

The form of the banks and islands is most singular in the part just referred to, namely, from latitude 15° to 17°, where the sea deepens quite gradually: the _Dhalac_ group, on the western coast, is surrounded by an intricate archipelago of islets and shoals; the main island is very irregularly shaped, and it includes a bay seven miles long, by four across, in which no bottom was found with 252 feet: there is only one entrance into this bay, half a mile wide, and with an island in front of it. The submerged banks on the eastern coast, within the same latitudes, round _Farsan_ Island, are, likewise, penetrated by many narrow creeks of deep water; one is twelve miles long, in the form of a hatchet, in which, close to its broad upper end, soundings were not struck with 360 feet, and its entrance is only half a mile wide: in another creek of the same nature, but even with a more irregular outline, there was no bottom with 480 feet. The island of Farsan, itself, has as singular a form as any of its surrounding banks. The bottom of the sea round the Dhalac and Farsan Islands consists chiefly of sand and agglutinated fragments, but, in the deep and narrow creeks, it consists of mud; the islands themselves consist of thin, horizontally stratified, modern tertiary beds, containing but little broken coral;[2] their shores are fringed by living coral-reefs.

[2] Rüppell, “Reise in Abyssinie,” Band. i., S. 247.

From the account given by Rüppell[3] of the manner in which Dhalac has been rent by fissures, the opposite sides of which have been unequally elevated (in one instance to the amount of fifty feet), it seems probable that its irregular form, as well as probably that of Farsan, may have been partly caused by unequal elevations; but, considering the general form of the banks, and of the deep-water creeks, together with the composition of the land, I think their configuration is more probably due in great part to strong currents having drifted sediment over an uneven bottom: it is almost certain that their form cannot be attributed to the growth of coral. Whatever may have been the precise origin of the Dhalac and Farsan Archipelagoes, the greater number of the banks on the eastern side of the Red Sea seem to have originated through nearly similar means. I judge of this from their similarity in configuration (in proof of which I may instance a bank on the east coast in latitude 22°; and although it is true that the northern banks generally have a less complicated outline), and from their similarity in composition, as may be observed in their upraised portions. The depth within the banks northward of latitude 17°, is usually greater, and their outer sides shelve more abruptly (circumstances which seem to go together) than in the Dhalac and Farsan Archipelagoes; but this might easily have been caused by a difference in the action of the currents during their formation: moreover, the greater quantity of living coral, which, according to Captain Moresby, exists on the northern banks, would tend to give them steeper margins.

[3] Rüppell, “Reise in Abyssinie,” Band. i., S. 245.

From this account, brief and imperfect as it is, we can see that the great chain of banks on the eastern coast, and on the western side in the southern portion, differ greatly from true barrier-reefs wholly formed by the growth of coral. It is indeed the direct conclusion of Ehrenberg (“Uber die,” etc., pages 45 and 51), that they are connected in their origin quite secondarily with the growth of coral; and he remarks that the islands off the coast of Norway, if worn down level with the sea, and merely coated with living coral, would present a nearly similar appearance. I cannot, however, avoid suspecting, from information given me by Dr. Malcolmson and Captain Moresby, that Ehrenberg has rather under-rated the influence of corals, in some places at least, on the formation of the tertiary deposits of the Red Sea.

_The West Coast of the Red Sea between lat._ 19° _and_ 22°.—There are, in this space, reefs, which, if I had known nothing of those in other parts of the Red Sea, I should unhesitatingly have considered as barrier-reefs; and, after deliberation, I have come to the same conclusion. One of these reefs, in 20° 15′, is twenty miles long, less than a mile in width (but expanding at the northern end into a disc), slightly sinuous, and extending parallel to the mainland at the distance of five miles from it, with very deep water within; in one spot soundings were not obtained with 205 fathoms. Some leagues further south, there is another linear reef, very narrow, ten miles long, with other small portions of reef, north and south, almost connected with it; and within this line of reefs (as well as outside) the water is profoundly deep. There are also some small linear and sickle-formed reefs, lying a little way out at sea. All these reefs are covered, as I am informed by Captain Moresby, by living corals. Here, then, we have all the characters of reefs of the barrier class; and in some outlying reefs we have an approach to the structure of atolls. The source of my doubts about the classification of these reefs, arises from having observed in the Dhalac and Farsan groups the narrowness and straightness of several spits of sand and rock: one of these spits in the Dhalac group is nearly fifteen miles long, only two broad, and it is bordered on each side with deep water; so that, if worn down by the surf, and coated with living corals, it would form a reef nearly similar to those within the space under consideration. There is, also, in this space (latitude 21°) a peninsula, bordered by cliffs, with its extremity worn down to the level of the sea, and its basis fringed with reefs: in the line of prolongation of this peninsula, there lies the island of _Macowa_ (formed, according to Captain Moresby, of the usual tertiary deposit), and some smaller islands, large parts of which likewise appear to have been worn down, and are now coated with living corals. If the removal of the strata in these several cases had been more complete, the reefs thus formed would have nearly resembled those barrier-like ones now under discussion. Notwithstanding these facts, I cannot persuade myself that the many very small, isolated, and sickle-formed reefs and others, long, nearly straight, and very narrow, with the water unfathomably deep close round them, could possibly have been formed by corals merely coating banks of sediment, or the abraded surfaces of irregularly shaped islands. I feel compelled to believe that the foundations of these reefs have subsided, and that the corals, during their upward growth, have given to these reefs their present forms: I may remark that the subsidence of narrow and irregularly-shaped peninsulas and islands, such as those existing on the coasts of the Red Sea, would afford the requisite foundations for the reefs in question.

_The West Coast from lat._ 22° _to_ 24°.—This part of the coast (north of the space coloured blue on the map) is fronted by an irregularly shelving bank, from about ten to thirty fathoms deep; numerous little reefs, some of which have the most singular shapes, rise from this bank. It may be observed, respecting one of them, in latitude 23° 10′, that if the promontory in latitude 24° were worn down to the level of the sea, and coated with corals, a very similar and grotesquely formed reef would be produced. Many of the reefs on this part of the coast may thus have originated; but there are some sickle, and almost atoll-formed reefs lying in deep water off the promontory in latitude 24°, which lead me to suppose that all these reefs are more probably allied to the barrier or atoll classes. I have not, however, ventured to colour this portion of coast.—_On the west coast from lat._ 19° _to_ 17° (south of space coloured blue on the map), there are many low islets of very small dimensions, not much elongated, and rising out of great depths at a distance from the coast; these cannot be classed either with atolls, or barrier- or fringing-reefs. I may here remark that the outlying reefs on the west coast, between latitude 19° and 24°, are the only ones in the Red Sea, which approach in structure to the true atolls of the Indian and Pacific Oceans, but they present only imperfect miniature likenesses of them.

_Eastern Coast_.—I have felt the greatest doubt about colouring any portion of this coast, north of the fringing-reefs round the Farsan Islands in 16° 10′. There are many small outlying coral-reefs along the whole line of coast; but as the greater number rise from banks not very deeply submerged (the formation of which has been shown to be only secondarily connected with the growth of coral), their origin may be due simply to the growth of knolls of corals, from an irregular foundation situated within a limited depth. But between latitude 18° and 20°, there are so many linear, elliptic, and extremely small reefs, rising abruptly out of profound depths, that the same reasons, which led me to colour blue a portion of the west coast, have induced me to do the same in this part. There exist some small outlying reefs rising from deep water, north of latitude 20° (the northern limit coloured blue), on the east coast; but as they are not very numerous and scarcely any of them linear, I have thought it right to leave them uncoloured.

In the _southern parts_ of the Red Sea, considerable spaces of the mainland, and of some of the Dhalac islands, are skirted by reefs, which, as I am informed by Captain Moresby, are of living coral, and have all the characters of the fringing class. As in these latitudes, there are no outlying linear or sickle-formed reefs, rising out of unfathomable depths, I have coloured these parts of the coast red. On similar grounds, I have coloured red the _northern parts of the western coast_ (north of latitude 24° 30′), and likewise the shores of the chief part of the _Gulf of Suez_. In the _Gulf of Acaba_, as I am informed by Captain Moresby there are no coral-reefs, and the water is profoundly deep.

WEST INDIES.—My information regarding the reefs of this area, is derived from various sources, and from an examination of numerous charts; especially of those lately executed during the survey under Captain Owen, R.N. I lay under particular obligation to Captain Bird Allen, R.N., one of the members of the late survey, for many personal communications on this subject. As in the case of the Red Sea, it is necessary to make some preliminary remarks on the submerged banks of the West Indies, which are in some degree connected with coral-reefs, and cause considerable doubts in their classification. That large accumulations of sediment are in progress on the West Indian shores, will be evident to any one who examines the charts of that sea, especially of the portion north of a line joining Yucutan and Florida. The area of deposition seems less intimately connected with the debouchement of the great rivers, than with the course of the sea-currents; as is evident from the vast extension of the banks from the promontories of Yucutan and Mosquito.

Besides the coast-banks, there are many of various dimensions which stand quite isolated; these closely resemble each other, they lie from two or three to twenty or thirty fathoms under water, and are composed of sand, sometimes firmly agglutinated, with little or no coral; their surfaces are smooth and nearly level, shelving only to the amount of a few fathoms, very gradually all round towards their edges, where they plunge abruptly into the unfathomable sea. This steep inclination of their sides, which is likewise characteristic of the coast-banks, is very remarkable: I may give as an instance, the Misteriosa Bank, on the edges of which the soundings change in 250 fathoms horizontal distance, from 11 to 210 fathoms; off the northern point of the bank of Old Providence, in 200 fathoms horizontal distance, the change is from 19 to 152 fathoms; off the Great Bahama Bank, in 160 fathoms horizontal distance, the inclination is in many places from 10 fathoms to no bottom with 190 fathoms. On coasts in all parts of the world, where sediment is accumulating, something of this kind may be observed; the banks shelve very gently far out to sea, and then terminate abruptly. The form and composition of the banks standing in the middle parts of the W. Indian Sea, clearly show that their origin must be chiefly attributed to the accumulation of sediment; and the only obvious explanation of their isolated position is the presence of a nucleus, round which the currents have collected fine drift matter. Any one who will compare the character of the bank surrounding the hilly island of Old Providence, with those banks in its neighbourhood which stand isolated, will scarcely doubt that they surround submerged mountains. We are led to the same conclusion by examining the bank called Thunder Knoll, which is separated from the Great Mosquito Bank by a channel only seven miles wide, and 145 fathoms deep. There cannot be any doubt that the Mosquito Bank has been formed by the accumulation of sediment round the promontory of the same name; and Thunder Knoll resembles the Mosquito Bank, in the state of its surface submerged twenty fathoms, in the inclinations of its sides, in composition, and in every other respect. I may observe, although the remark is here irrelevant, that geologists should be cautious in concluding that all the outlyers of any formation have once been connected together, for we here see that deposits, doubtless of exactly the same nature, may be deposited with large valley-like spaces between them.

Linear strips of coral-reefs and small knolls project from many of the isolated, as well as coast-banks; sometimes they occur quite irregularly placed, as on the Mosquito Bank, but more generally they form crescents on the windward side, situated some little distance within the outer edge of the banks:—thus on the Serranilla Bank they form an interrupted chain which ranges between two and three miles within the windward margin: generally they occur, as on Roncador, Courtown, and Anegada Banks, nearer the line of deep water. Their occurrence on the windward side is conformable to the general rule, of the efficient kinds of corals flourishing best where most exposed; but their position some way within the line of deep water I cannot explain, without it be, that a depth somewhat less than that close to the outer margin of the banks, is most favourable to their growth. Where the corals have formed a nearly continuous rim, close to the windward edge of a bank some fathoms submerged, the reef closely resembles an atoll; but if the bank surrounds an island (as in the case of Old Providence), the reef resembles an encircling barrier-reef. I should undoubtedly have classed some of these fringed banks as imperfect atolls, or barrier-reefs, if the sedimentary nature of their foundations had not been evident from the presence of other neighbouring banks, of similar forms and of similar composition, but without the crescent-like marginal reef: in the third chapter, I observed that probably some atoll-like reefs did exist, which had originated in the manner here supposed.

Proofs of elevation within recent tertiary periods abound, as referred to in the sixth chapter, over nearly the whole area of the West Indies. Hence it is easy to understand the origin of the low land on the coasts, where sediment is now accumulating; for instance on the northern part of Yucutan, and on the N.E. part of Mosquito, where the land is low, and where extensive banks appear to be in progressive formation. Hence, also, the origin of the Great Bahama Banks, which are bordered on their western and southern edges by very narrow, long, singularly shaped islands, formed of sand, shells, and coral-rock, and some of them about a hundred feet in height, is easily explained by the elevation of banks fringed on their windward (western and southern) sides by coral-reefs. On this view, however, we must suppose either that the chief part of the surfaces of the great Bahama sandbanks were all originally deeply submerged, and were brought up to their present level by the same elevatory action, which formed the linear islands; or that during the elevation of the banks, the superficial currents and swell of the waves continued wearing them down and keeping them at a nearly uniform level: the level is not quite uniform; for, in proceeding from the N.W. end of the Bahama group towards the S.E. end, the depth of the banks increases, and the area of land decreases, in a very gradual and remarkable manner. The latter view, namely, that these banks have been worn down by the currents and swell during their elevation, seems to me the most probable one. It is, also, I believe, applicable to many banks, situated in widely distant parts of the West Indian Sea, which are wholly submerged; for, on any other view, we must suppose, that the elevatory forces have acted with astonishing uniformity.

The shore of the Gulf of Mexico, for the space of many hundred miles, is formed by a chain of lagoons, from one to twenty miles in breadth (“Columbian Navigator,” page 178, etc.), containing either fresh or salt water, and separated from the sea by linear strips of sand. Great spaces of the shores of Southern Brazil.[4] and of the United States from Long Island (as observed by Professor Rogers) to Florida have the same character. Professor Rogers, in his “Report to the British Association” (volume iii., page 13), speculates on the origin of these low, sandy, linear islets; he states that the layers of which they are composed are too homogeneous, and contain too large a proportion of shells, to permit the common supposition of their formation being simply due to matter thrown up, where it now lies, by the surf: he considers these islands as upheaved bars or shoals, which were deposited in lines where opposed currents met. It is evident that these islands and spits of sand parallel to the coast, and separated from it by shallow lagoons, have no necessary connection with coral-formations. But in Southern Florida, from the accounts I have received from persons who have resided there, the upraised islands seem to be formed of strata, containing a good deal of coral, and they are extensively fringed by living reefs; the channels within these islands are in some places between two and three miles wide, and five or six fathoms deep, though generally[5] they are less in depth than width. After having seen how frequently banks of sediment in the West Indian Sea are fringed by reefs, we can readily conceive that bars of sediment might be greatly aided in their formation along a line of coast, by the growth of corals; and such bars would, in that case, have a deceptive resemblance with true barrier-reefs.

[4] In the “London and Edinburgh Philosophical Journal,” 1841, page 257, I have described a singular bar of sandstone lying parallel to the coast off Pernambuco in Brazil, which probably is an analogous formation.

[5] In the ordinary sea-charts, no lagoons appear on the coast of Florida, north of 26°; but Major Whiting (“Silliman’s Journal,” volume xxxv., page 54) says that many are formed by sand thrown up along the whole line of coast from St. Augustine’s to Jupiter Inlet.

Having now endeavoured to remove some sources of doubt in classifying the reefs of the West Indies, I will give my authorities for colouring such portions of the coast as I have thought myself warranted in doing. Captain Bird Allen informs me, that most of the islands on the _Bahama Banks_ are fringed, especially on their windward sides, with living reefs; and hence I have coloured those, which are thus represented in Captain Owen’s late chart, red. The same officer informs me, that the islands along the southern part of _Florida_ are similarly fringed; coloured red. CUBA: Proceeding along the northern coast, at the distance of forty miles from the extreme S.E. point, the shores are fringed by reefs, which extend westward for a space of 160 miles, with only a few breaks. Parts of these reefs are represented in the plans of the harbours on this coast by Captain Owen; and an excellent description is given of them by Mr. Taylor (Loudon’s “Mag. of Nat. Hist.” volume ix., page 449); he states that they enclosed a space called the “_baxo_,” from half to three-quarters of a mile in width, with a sandy bottom, and a little coral. In most parts people can wade, at low water, to the reef; but in some parts the depth is between two and three fathoms. Close outside the reef, the depth is between six and seven fathoms; these well-characterised fringing-reefs are coloured red. Westward of longitude 77° 30′, on the northern side of Cuba, a great bank commences, which extends along the coast for nearly four degrees of longitude. In the place of its commencement, in its structure, and in the “_cays_,” or low islands on its edge, there is a marked correspondence (as observed by Humboldt, “Pers. Narr.” volume vii., page 88) between it and the Great Bahama and Sal Banks, which lie directly in front. Hence one is led to attribute the same origin to both these sets of banks; namely, the accumulation of sediment, conjoined with an elevatory movement, and the growth of coral on their outward edges; those parts which appear fringed by living reefs are coloured red. Westward of these banks, there is a portion of coast apparently without reefs, except in the harbours, the shores of which seem in the published plans to be fringed. The _Colorado Shoals_ (see Captain Owen’s charts), and the low land at the western end of Cuba, correspond as closely in relative position and structure to the banks at the extreme point of Florida, as the banks above described on the north side of Cuba, do to the Bahamas, the depth within the islets and reefs on the outer edge of the _Colorados_, is generally between two and three fathoms, increasing to twelve fathoms in the southern part, where the bank becomes nearly open, without islets or coral-reefs; the portions which are fringed are coloured red. The southern shore of Cuba is deeply concave, and the included space is filled up with mud and sandbanks, low islands and coral-reefs. Between the mountainous _Isle of Pines_ and the southern shore of Cuba, the general depth is only between two and three fathoms; and in this part small islands, formed of fragmentary rock and broken madrepores (Humboldt, “Pers. Narr.” volume vii. pages 51, 86 to 90, 291, 309, 320), rise abruptly, and just reach the surface of the sea. From some expressions used in the “Columbian Navigator” (volume i., part ii., page 94), it appears that considerable spaces along the outer coast of Southern Cuba are bounded by cliffs of coral-rock, formed probably by the upheaval of coral-reefs and sandbanks. The charts represent the southern part of the Isle of Pines as fringed by reefs, which the “Columb. Navig.” says extend some way from the coast, but have only from nine to twelve feet water on them; these are coloured red.—I have not been able to procure any detailed description of the large groups of banks and “cays” further eastward on the southern side of Cuba; within them there is a large expanse, with a muddy bottom, from eight to twelve fathoms deep; although some parts of this line of coast are represented in the general charts of the West Indies, as fringed, I have not thought it prudent to colour them. The remaining portion of the south coast of Cuba appears to be without coral-reefs.

YUCUTAN.—The N.E. part of the promontory appears in Captain Owen’s charts to be fringed; coloured red. The eastern coast, from 20° to 18° is fringed. South of latitude 18°, there commences the most remarkable reef in the West Indies: it is about one hundred and thirty miles in length, ranging in a N. and S. line, at an average distance of fifteen miles from the coast. The islets on it are all low, as I have been informed by Captain B. Allen; the water deepens suddenly on the outside of the reef, but not more abruptly than off many of the sedimentary banks: within its southern extremity (off _Honduras_) the depth is twenty-five fathoms; but in the more northern parts, the depth soon increases to ten fathoms, and within the northernmost part, for a space of twenty miles, the depth is only from one to two fathoms. In most of these respects we have the characteristics of a barrier-reef; nevertheless, from observing, first, that the channel within the reef is a continuation of a great irregular bay, which penetrates the mainland to the depth of fifty miles; and secondly, that considerable spaces of this barrier-like reef are described in the charts (for instance, in latitude 16° 45′ and 16° 12′) as formed of pure sand; and thirdly, from knowing that sediment is accumulating in many parts of the West Indies in banks parallel to the shore; I have not ventured to colour this reef as a barrier, without further evidence that it has really been formed by the growth of corals, and that it is not merely in parts a spit of sand, and in other parts a worn down promontory, partially coated and fringed by reefs; I lean, however, to the probability of its being a barrier-reef, produced by subsidence. To add to my doubts, immediately on the outside of this barrier-like reef, _Turneffe_, _Lighthouse_, and _Glover_ reefs are situated, and these reefs have so completely the form of atolls, that if they had occurred in the Pacific, I should not have hesitated about colouring them blue. _turneffe Reef_ seems almost entirely filled up with low mud islets; and the depth within the other two reefs is only from one to three fathoms. From this circumstance and from their similarity in form, structure, and relative position, both to the bank called _Northern Triangles_, on which there is an islet between seventy and eighty feet, and to _Cozumel_ Island, the level surface of which is likewise between seventy and eighty feet in height, I consider it more probable that the three foregoing banks are the worn down bases of upheaved shoals, fringed with corals, than that they are true atolls, wholly produced by the growth of coral during subsidence; left uncoloured.

In front of the eastern _Mosquito_ coast, there are between latitude 12° and 16° some extensive banks (already mentioned, page 148), with high islands rising from their centres; and there are other banks wholly submerged, both of which kinds of banks are bordered, near their windward margins, by crescent-shaped coral-reefs. But it can hardly be doubted, as was observed in the preliminary remarks, that these banks owe their origin, like the great bank extending from the Mosquito promontory, almost entirely to the accumulation of sediment, and not to the growth of corals; hence I have not coloured them.

_Cayman Island_: this island appears in the charts to be fringed; and Captain B. Allen informs me that the reefs extend about a mile from the shore, and have only from five to twelve feet water within them; coloured red.—_Jamaica_: judging from the charts, about fifteen miles of the S.E. extremity, and about twice that length on the S.W. extremity, and some portions on the S. side near Kingston and Port Royal, are regularly fringed, and therefore are coloured red. From the plans of some harbours on the N. side of Jamaica, parts of the coast appear to be fringed; but as these are not represented in the charts of the whole island, I have not coloured them.—_St. Domingo_: I have not been able to obtain sufficient information, either from plans of the harbours, or from general charts, to enable me to colour any part of the coast, except sixty miles from Port de Plata westward, which seems very regularly fringed; many other parts, however, of the coast are probably fringed, especially towards the eastern end of the island.—_Puerto Rico_: considerable portions of the southern, western, and eastern coasts, and some parts of the northern coast, appear in the charts to be fringed; coloured red.—Some miles in length of the southern side of the Island of _St, Thomas_ is fringed; most of the _Virgin Gorda_ Islands, as I am informed by Mr. Schomburgk, are fringed; the shores of _Anegada_, as well as the bank on which it stands, are likewise fringed; these islands have been coloured red. The greater part of the southern side of _Santa Cruz_ appears in the Danish survey to be fringed (see also Prof. Hovey’s account of this island, in “Silliman’s Journal,” volume xxxv., page 74); the reefs extend along the shore for a considerable space, and project rather more than a mile; the depth within the reef is three fathoms; coloured red.—The _Antilles_, as remarked by Von Buch (“Descrip. Iles Canaries,” page 494), may be divided into two linear groups, the western row being volcanic, and the eastern of modern calcareous origin; my information is very defective on the whole group. Of the eastern islands, _Barbuda_ and the western coasts of _Antigua_ and _Mariagalante_ appear to be fringed: this is also the case with _Barbadoes_, as I have been informed by a resident; these islands are coloured red. On the shores of the Western Antilles, of volcanic origin, very few coral-reefs appear to exist. The island of _Martinique_, of which there are beautifully executed French charts, on a very large scale, alone presents any appearance worthy of special notice. The south-western, southern, and eastern coasts, together forming about half the circumference of the island, are skirted by very irregular banks, projecting generally rather less than a mile from the shore, and lying from two to five fathoms submerged. In front of almost every valley, they are breached by narrow, crooked, steep-sided passages. The French engineers ascertained by boring, that these submerged banks consisted of madreporitic rocks, which were covered in many parts by thin layers of mud or sand. From this fact, and especially from the structure of the narrow breaches, I think there can be little doubt that these banks once formed living reefs, which fringed the shores of the island, and like other reefs probably reached the surface. From some of these submerged banks reefs of living coral rise abruptly, either in small detached patches, or in lines parallel to, but some way within the outer edges of the banks on which they are based. Besides the above banks which skirt the shores of the island, there is on the eastern side a range of linear banks, similarly constituted, twenty miles in length, extending parallel to the coast line, and separated from it by a space between two and four miles in width, and from five to fifteen fathoms in depth. From this range of detached banks, some linear reefs of living coral likewise rise abruptly; and if they had been of greater length (for they do not front more than a sixth part of the circumference of the island), they would necessarily from their position have been coloured as barrier-reefs; as the case stands they are left uncoloured. I suspect that after a small amount of subsidence, the corals were killed by sand and mud being deposited on them, and the reefs being thus prevented from growing upwards, the banks of madreporitic rock were left in their present submerged condition.

THE BERMUDA ISLANDS have been carefully described by Lieutenant Nelson, in an excellent Memoir in the “Geological Transactions” (volume v., part i., page 103). In the form of the bank or reef, on one side of which the islands stand, there is a close general resemblance to an atoll; but in the following respects there is a considerable difference,—first, in the margin of the reef not forming (as I have been informed by Mr. Chaffers, R.N.) a flat, solid surface, laid bare at low water, and regularly bounding the internal space of shallow water or lagoon; secondly, in the border of gradually shoaling water, nearly a mile and a half in width, which surrounds the entire outside of the reef (as is laid down in Captain Hurd’s chart); and thirdly, in the size, height, and extraordinary form of the islands, which present little resemblance to the long, narrow, simple islets, seldom exceeding half a mile in breadth, which surmount the annular reefs of almost all the atolls in the Indian and Pacific Oceans. Moreover, there are evident proofs (Nelson, Ibid., page 118), that islands similar to the existing ones, formerly extended over other parts of the reef. It would, I believe, be difficult to find a true atoll with land exceeding thirty feet in height; whereas, Mr. Nelson estimates the highest point of the Bermuda Islands to be 260 feet; if, however, Mr. Nelson’s view, that the whole of the land consists of sand drifted by the winds, and agglutinated together, were proved correct, this difference would be immaterial; but, from his own account (page 118), there occur in one place, five or six layers of red earth, interstratified with the ordinary calcareous rock, and including stones too heavy for the wind to have moved, without having at the same time utterly dispersed every grain of the accompanying drifted matter. Mr. Nelson attributes the origin of these several layers, with their embedded stones, to as many violent catastrophes; but further investigation in such cases has generally succeeded in explaining phenomena of this kind by ordinary and simpler means. Finally, I may remark, that these islands have a considerable resemblance in shape to Barbuda in the West Indies, and to Pemba on the eastern coast of Africa, which latter island is about two hundred feet in height, and consists of coral-rock. I believe that the Bermuda Islands, from being fringed by living reefs, ought to have been coloured red; but I have left them uncoloured, on account of their general resemblance in external form to a lagoon-island or atoll.

The names not in capitals are all names of places, and refer exclusively to the Appendix: in well-defined archipelagoes, or groups of islands, the name of each separate island is not given.

ABROLHOS, Brazil, coated by corals.

Abrolhos (Australia).

ABSENCE of coral-reefs from certain coasts.

Acaba, gulf of.

Admiralty group.

AFRICA, east coast, fringing-reef of. Madreporitic rock of.

Africa, east coast.

AGE of individual corals.

Aiou.

Aitutaki.

Aldabra.

Alert reef.

Alexander, Grand Duke, island.

ALLAN, Dr., on Holuthuriæ feeding on corals. On quick growth of corals at Madagascar. On reefs affected by currents.

Alloufatou.

Alphonse.

Amargoura. (Amargura.)

Amboina.

America, west coast.

Amirantes.

Anachorites.

Anambas.

ANAMOUKA, description of.

Anamouka.

Anadaman islands.

Antilles.

Appoo reef.

Arabia Felix.

AREAS, great extent of, interspersed with low islands. Of subsidence and of elevation. Of subsidence appear to be elongated. Of subsidence alternating with areas of elevation.

Arru group.

Arzobispo.

ASCIDIA, depth at which found.

Assomption.

Astova.

Atlantic islands.

ATOLLS, breaches in their reefs. Dimensions of. Dimensions of groups of. Not based on craters or on banks of sediment, or of rock. Of irregular forms. Steepness of their flanks. Width of their reef and islets. Their lowness. Lagoons. General range. With part of their reef submerged, and theory of.

Augustine, St.

AURORA island, an upraised atoll.

Aurora.

AUSTRAL islands, recently elevated.

Austral islands.

Australia, N.W. coast.

AUSTRALIAN barrier-reef.

Australian barrier.

Babuyan group.

Bahama banks.

Balahac.

Bally.

Baring.

BARRIER-REEF of Australia. Of New Caledonia.

BARRIER-REEFS, breaches through. Not based on worn down margin of rock. On banks of sediment. On submarine craters. Steepness of their flanks. Their probable vertical thickness. Theory of their formation.

Bampton shoal.

Banks islands.

Banks in the West Indies.

Bashee islands.

Bass island.

Batoa.

Beaupre reef.

BEECHEY, Captain, obligations of the author to. On submerged reefs. Account of Matilda island.

BELCHER, Captain, on boring through coral-reef.

Belize reef, off.

Bellinghausen.

Bermuda islands.

Beveridge reef.

Bligh.

BOLABOLA, view of.

Bombay shoal.

Bonin Bay.

Bonin group.

BORINGS through coral-reefs.

BORNEO, W. coast, recently elevated.

Borneo, E. coast. S.W. and W. coast N. coast. Western bank.

Boscawen.

Boston.

Bouka.

Bourbon.

Bourou.

Bouton.

BRAZIL, fringing-reefs on coast of.

BREACHES through barrier-reefs.

Brook.

Bunker.

Bunoa.

Cagayanes.

Candelaria.

Cargados Carajos.

Caroline archipelago.

Caroline island.

Carteret shoal.

CARYOPHYLLIA, depth at which it lives.

Cavilli.

Cayman island.

Celebes.

Ceram.

CEYLON, recently elevated.

Ceylon.

CHAGOS Great Bank, description and theory of.

CHAGOS group.

Chagos group.

CHAMA-SHELLS embedded in coral-rock.

CHAMISSO, on corals preferring the surf.

CHANGES in the state of Keeling atoll. Of atolls.

CHANNELS leading into the lagoons of atolls. Into the Maldiva atolls. Through barrier-reefs.

Chase.

China sea.

CHRISTMAS atoll.

Christmas atoll.

Christmas island (Indian Ocean).

Clarence.

Clipperton rock.

COCOS, or Keeling atoll.

Cocos (or Keeling).

Cocos island (Pacific).

COCHIN China, encroachments of the sea on the coast.

Cochin China.

Coetivi.

Comoro group.

COMPOSITION of coral-formations.

CONGLOMERATE coral-rock on Keeling atoll. On other atolls. Coral-rock.

COOK islands, recently elevated.

Cook islands.

CORAL-BLOCKS bored by vermiform animals.

CORAL-REEFS, their distribution and absence from certain areas. Destroyed by loose sediment.

CORAL-ROCK at Keeling atoll. Mauritius. Organic remains of.

CORALS dead but upright in Keeling lagoon. Depths at which they live. Off Keeling atoll. Killed by a short exposure. Living in the lagoon of Keeling atoll. Quick growth of, in Keeling lagoon. Merely coating the bottom of the sea. Standing exposed in the Low archipelago.

CORALLIAN sea.

Corallian sea.

Cornwallis.

Cosmoledo.

COUTHOUY, Mr., alleged proofs of recent elevation of the Low archipelago. On coral-rock at Mangaia and Aurora islands. On external ledges round coral-islands. Remarks confirmatory of the author’s theory.

CRESCENT-FORMED reefs.

Cuba.

CUMING, Mr., on the recent elevation of the Philippines.

Dangerous, or Low archipelago.

Danger islands.

DEPTHS at which reef-building corals live. At Mauritius, the Red Sea, and in the Maldiva archipelago. At which other corals and corallines can live.

Dhalac group.

DIEGO GARCIA, slow growth of reef.

DIMENSIONS of the larger groups of atolls.

DISSEVERMENT of the Maldiva atolls, and theory of.

DISTRIBUTION of coral-reefs.

Domingo, St.

DORY, Port, recently elevated.

Dory, Port.

Duff islands.

Durour.

Eap.

EARTHQUAKES at Keeling atoll. In groups of atolls. In Navigator archipelago.

EAST INDIAN ARCHIPELAGO, recently elevated.

Easter.

Echequier.

EHRENBERG, on the banks of the Red Sea. On depths at which corals live in the Red Sea. On corals preferring the surf. On the antiquity of certain corals.

Eimeo.

ELEVATED reef of Mauritius.

ELEVATIONS, recent proofs of. Immense areas of.

Elivi.

ELIZABETH island. Recently elevated.

Elizabeth island.

Ellice group.

ENCIRCLED ISLANDS, their height. Geological composition.

EOUA, description of.

Eoua.

ERUPTED MATTER probably not associated with thick masses of coral-rock.

FAIS, recently elevated.

Fais.

Fanning.

Farallon de Medinilla.

Farson group.

Fataka.

FIJI archipelago.

FISH, feeding on corals. Killed in Keeling lagoon by heavy rain.

FISSURES across coral-islands.

FITZROY, Captain, on a submerged shed at Keeling atoll. On an inundation in the Low archipelago.

Flint.

Flores.

Florida.

Folger.

Formosa.

FORSTER, theory of coral-formations.

Frederick reef.

Freewill.

FRIENDLY group recently elevated.

Friendly archipelago.

FRINGING-REEFS, absent where coast precipitous. Breached in front of streams. Described by MM. Quoy and Gaimard. Not closely attached to shelving coasts. Of east coast of Africa. Of Cuba. Of Mauritius. On worn down banks of rock. On banks of sediment. Their appearance when elevated. Their growth influenced by currents. By shallowness of sea.

Galapagos archipelago.

Galega.

GAMBIER islands, section of.

Gambier islands.

Gardner.

Gaspar rico.

GEOLOGICAL COMPOSITION of coral-formations.

Gilbert archipelago.

Gilolo.

Glorioso.

GLOUCESTER Island.

Glover reef.

Gomez.

Gouap.

Goulou.

Grampus.

Gran Cocal.

GREAT CHAGOS BANK, description and theory of.

GREY, Captain, on sandbars.

GROUPING of the different classes of reefs.

Guedes.

HALL, Captain B., on Loo Choo.

HARVEY islands, recently elevated.

HEIGHT of encircled islands.

Hermites.

Hervey or Cook islands.

Hogoleu.

HOLOTHURIAE (Holuthuriæ) feeding on coral.

HOUDEN island, height of.

Honduras, reef off.

Horn.

Houtman Abrolhos.

HUAHEINE; alleged proofs of its recent elevation.

Huaheine.

Humphrey.

Hunter.

HURRICANES, effects of, on coral-islands.

Immaum.

Independence.

INDIA, west coast, recently elevated.

India.

IRREGULAR REEFS in shallow seas.

ISLETS of coral-rock, their formation. Their destruction in the Maldiva atolls.

Jamaica.

Jarvis.

JAVA, recently elevated.

Java.

Johnston island.

Juan de Nova.

Juan de Nova (Madagascar).

Kalatoa.

KAMTSCHATKA, proofs of its recent elevation.

Karkalang.

KEELING atoll, section of reef.

Keeling, south atoll. North atoll.

Keffing.

Kemin.

Kennedy.

Keppel.

Kumi.

Laccadive group.

LADRONES, or Marianas, recently elevated.

Ladrones archipelago.

LAGOON of Keeling atoll.

LAGOONS bordered by inclined ledges and walls, and theory of their formation. Of small atolls filled up with sediment.

LAGOON-CHANNELS within barrier-reefs.

LAGOON-REEFS, all submerged in some atolls, and rising to the surface in others.

Lancaster reef.

Latte.

Lauglan islands.

LEDGES round certain lagoons.

Lette.

Lighthouse reef.

LLOYD, Mr., on corals refixing themselves.

LOO CHOO, recently elevated.

Loo Choo.

Louisiade.

LOW ARCHIPELAGO, alleged proofs of its recent elevation.

Low archipelago.

LOWNESS of coral-islands.

Loyalty group.

Lucepara.

LUTKE, Admiral, on fissures across coral-islands.

LUZON, recently elevated.

Luzon.

LYELL, Mr., on channels into the lagoons of atolls. On the lowness of their leeward sides. On the antiquity of certain corals. On the apparent continuity of distinct coral-islands. On the recently elevated beds of the Red Sea. On the outline of the areas of subsidence.

Macassar strait.

Macclesfield bank.

MADAGASCAR, quick growth of corals at. Madreporitic rock of.

Madagascar.

Madjiko-sima.

Madura (Java).

Madura (India).

MAHLOS MAHDOO, theory of formation.

MALACCA, recently elevated.

Malacca.

MALCOLMSON, Dr., on recent elevation of W. coast of India. On recent elevation of Camaran island.

Malden.

MALDIVA atolls, and theory of their formation. Steepness of their flanks. Growth of coral at.

Maldiva archipelago.

MANGAIA island. Recently elevated.

Mangaia.

Mangs.

MARIANAS, recently elevated.

Mariana archipelago.

Mariere.

Marquesas archipelago.

Marshall archipelago.

Marshall island.

Martinique.

Martires.

MARY’S ST., in Madagascar, harbour made in reefs.

Mary island.

Matia, or Aurora.

MATILDA atoll.

MAURITIUS, fringing-reefs of. Depths at which corals live there. Recently elevated.

Mauritius.

MAURUA, section of.

Maurua.

MENCHIKOFF atoll.

Mendana archipelago.

Mendana isles.

Mexico, gulf of.

MILLEPORA COMPLANATA at Keeling atoll.

Mindoro.

Mohilla. (Mohila.)

MOLUCCA islands, recently elevated.

Mopeha.

MORESBY, Captain, on boring through coral-reefs.

Morty.

Mosquito coast.

MUSQUILLO atoll.

Mysol.

NAMOURREK group.

Natunas.

NAVIGATOR archipelago, elevation of.

Navigator archipelago.

Nederlandisch.

NELSON, Lieutenant, on the consolidation of coral-rocks under water. Theory of coral-formations. On the Bermuda islands.

New Britain.

NEW CALEDONIA, steepness of its reefs. Barrier-reef of.

New Caledonia.

New Guinea (E. end).

New Guinea (W. end).

New Hanover.

NEW HEBRIDES, recently elevated.

New Hebrides.

NEW IRELAND, recently elevated.

New Ireland.

New Nantucket.

Nicobar islands.

Niouha.

NULLIPORAE at Keeling atoll. On the reefs of atolls. On barrier-reefs. Their wide distribution and abundance.

OBJECTIONS to the theory of subsidence.

Ocean islands.

Ono.

Onouafu. (Onouafou.)

Ormuz.

Oscar group.

OSCILLATIONS of level.

Ouallan, or Ualan. (Oualan.)

OULUTHY atoll.

Outong Java.

Palawan, S.W. coast. N.W. coast. Western bank.

Palmerston.

Palmyra.

Paracells.

Paraquas.

Patchow.

Pelew islands.

PEMBA island, singular form of.

Pemba.

Penrhyn.

Peregrino.

PERNAMBUCO, bar of sandstone at.

PERSIAN gulf, recently elevated.

Persian gulf.

Pescadores.

Peyster group.

Philip.

PHILIPPINE archipelago, recently elevated.

Philippine archipelago.

Phœnix.

Piguiram.

Pitcairn.

PITT’S bank.

Pitt island.

Platte.

Pleasant.

PORITES, chief coral on margin of Keeling atoll.

Postillions.

POUYNIPETE. Its probable subsidence.

Pouynipète.

Pratas shoal.

Proby.

Providence.

Puerto Rico.

Pulo Anna.

PUMICE floated to coral-islands.

Pylstaart.

PYRARD DE LAVAL, astonishment at the atolls in the Indian Ocean.

QUOY AND GAIMARD, depths at which corals live. Description of reefs applicable only to fringing-reefs.

RANGE of atolls.

Rapa.

Rearson.

RED SEA, banks of rock coated by reefs. Proofs of its recent elevation. Supposed subsidence of.

Red Sea.

REEFS, irregular in shallow seas. Rising to the surface in some lagoons and all submerged in others. Their distribution. Their absence from some coasts.

Revilla-gigedo.

RING-FORMED REEFS of the Maldiva atolls, and theory of.

Rodriguez.

Rosario.

Rose island.

Rotches.

Rotoumah.

Roug.

Rowley shoals.

RUPPELL, Dr., on the recent deposits of Red Sea.

Sable, ile de.

Sahia de Malha.

St. Pierre.

Sala.

Salomon archipelago. (Solomon.)

SAMOA, or Navigator archipelago, elevation of.

Samoa archipelago.

SAND-BARS parallel to coasts.

Sandal-wood.

SANDWICH archipelago, recently elevated.

Sandwich archipelago.

Sanserot.

Santa-Cruz group.

SAVAGE island, recently elevated.

Savage.

Savu.

Saya, or Sahia de Malha.

Scarborough shoal.

SCARUS feeding on corals.

Schouten.

Scilly.

SCORIAE floated to coral-islands.

Scott’s reef.

SECTIONS of islands encircled by barrier-reefs. Of Bolabola.

SEDIMENT in Keeling lagoon. In other atolls. Injurious to corals. Transported from coral-islands far seaward.

Seniavine.

Serangani.

Seychelles.

SHIP-BOTTOM quickly coated with coral.

SMYTH island.

SOCIETY archipelago, stationary condition of. Alleged proofs of recent elevation.

Society archipelago.

Socotra.

Solor.

SOOLOO islands, recently elevated.

Sooloo islands.

Souvaroff.

Spanish.

SPONGE, depths at which found.

Starbuck. (Slarbuck.)

STONES transported in roots of trees.

STORMS, effects of, on coral-islands.

STUTCHBURY, Mr., on the growth of an Agaricia. On upraised corals in Society archipelago.

SUBSIDENCE of Keeling atoll. Extreme slowness of. Areas of, apparently elongated. Areas of immense. Great amount of.

Suez, gulf of.

Sulphur islands.

SUMATRA, recently elevated.

Sumatra.

Sumbawa.

SURF favourable to the growth of massive corals.

Swallow shoal.

Sydney island.

TAHITI, alleged proofs of its recent elevation.

Tahiti.

TEMPERATURE of the sea at the Galapagos archipelago.

Tenasserim.

Tenimber island.

Teturoa.

THEORIES on coral-formations.

THEORY OF subsidence, and objections to.

THICKNESS, vertical, of barrier-reefs.

Thomas, St.

Tikopia.

TIMOR, recently elevated.

Timor.

Timor-laut.

Tokan-Bessees.

Tongatabou.

Tonquin.

Toubai.

Toufoa. (Toofoa.)

Toupoua.

TRADITIONS OF CHANGE in coral-islands.

TRIDACNAE embedded in coral-rock. Left exposed in the Low archipelago.

TUBULARIA, quick growth of.

Tumbelan.

Turneffe reef.

Turtle.

Ualan.

VANIKORO, section of. Its state and changes in its reefs.

Vanikoro.

Vine reef.

Virgin Gorda.

Viti archipelago.

VOLCANIC islands, with living corals on their shores. Matter, probably not associated with thick masses of coral-rock.

VOLCANOES, authorities for their position on the map. Their presence determined by the movements in progress. Absent or extinct in the areas of subsidence.

Waigiou.

Wallis island.

Washington.

Well’s reef.

WELLSTEAD, Lieutenant, account of a ship coated with corals.

WEST INDIES, banks of sediment fringed by reefs. Recently elevated.

West Indies.

WHITSUNDAY island, view of. Changes in its state.

WILLIAMS, Rev. J., on traditions of the natives regarding coral-islands. On antiquity of certain corals.

Wolchonsky.

Wostock.

Xulla islands.

York island.

Yucutan, coast of.

ZONES of different kinds of corals outside the same reefs.