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are large beds of Seriatopora. There is also a marked difference, according to Captain Moresby,* between the great branching corals of the Red Sea, and those on the reefs of the Maldiva atolls. These facts, which in themselves are deserving of notice, bear, perhaps, not very remotely on a remarkable circumstance which ... |
Moresby, * Capt. Moresby on the Northern Maldiva Atolls, Geograph. Journ. vol. v. p. 401. namely, that, with very few exceptions, none of the coral-knolls within the lagoons of Peros Banhos, Diego Garcia and the Great Chagos Bank, (all situated in the Chagos group,) rise to the surface of the water; whereas all those, ... |
and Egmont atolls in the same group, and likewise within the large southern Maldiva atolls, reach the surface. I make these statements, after having examined the charts of each atoll. In the lagoon of Peros Banhos, which is nearly twenty miles across, there is only one single reef which rises to the surface: in Diego G... |
several of these lie close to the margin of the lagoon, and need scarcely have been reckoned: in the great Chagos Bank there is not one. On the other hand, in the lagoons of some of the great southern Maldiva atolls, although thickly studded with reefs, every one without exception, rises to the surface; and on an avera... |
less than two submerged reefs in each atoll: in the northern atolls, however, the submerged lagoon-reefs are not quite so rare. The submerged reefs in the Chagos atolls generally have from one to seven fathoms water on them, but some have from seven to ten. Most of them are small, with very steep sides:* at Peros Banho... |
a depth of about thirty fathoms, and some of them in the Great Chagos Bank from above forty fathoms: they are covered, Capt. Moresby informs me, with living and healthy coral, two and three feet high, consisting of several species. Why then have not these lagoon-reefs reached the surface, like the innumerable ones in t... |
attempt to assign any difference in their external conditions, as the cause of this diversity, we are at once baffled: the lagoon of Diego Garcia is not deep, and is most wholly surrounded by its reef; Peros Banhos is very deep, much larger, with many wide passages communicating with the open sea. On the other hand, of... |
which all, or nearly all * Some of these statements were not communicated to me verbally by Capt. Moresby, but are taken from the MS. account, before alluded to, of the Chagos Group. the lagoon-reefs have reached the surface, some are small, others large, some shallow, others deep, some well enclosed, and others open. ... |
has seen a French chart of Diego Garcia made eighty years before his survey, and apparently very accurate; and from it he infers, that during this interval there has not been the smallest change in the depth on any of the knolls within the lagoon. It is, also, known that during the last fifty-one years, the eastern cha... |
lagoon, has neither become narrower, nor decreased in depth; and as there are numerous small knolls of living coral within it, some change might have been anticipated. Moreover, as the whole reef round the lagoon of this atoll has been converted into land—an unparalleled case, I believe, in an atoll of such large size,... |
for considerable spaces more than half a mile wide—also a very unusual circumstance,—we have the best possible evidence, that Diego Garcia has remained at its present level for a very long period. With this fact, and with the knowledge, that no sensible change has taken place during eighty years in the coral knolls, an... |
reached the surface in other atolls, which do not present the smallest appearance of being older that Diego Garcia and Peros Banhos, and which are placed under the same external conditions with them, one is led to conclude that these submerged reefs, although covered with luxuriant coral, have no tendency to grow upwar... |
present levels for an almost indefinite period. From the number of these knolls, from their position, size, and form,—many of them being only one or two hundred yards across, with a rounded outline, and precipitous sides,—it is indisputable that they have been formed by the growth of coral; and this makes the case much... |
in the Great Chagos bank, some of these almost columnar masses are 200 feet high, and their summits lie only from two to eight fathoms beneath the surface; there- fore, a small proportional amount more of growth would cause them to attain the surface, like those numerous knolls, which rise from an equally great depth w... |
can hardly suppose that time has been wanting for the upward growth of the coral, whilst in Diego Garcia, the broad annular strip of land, formed by the continued accumulation of detritus, shows how long this atoll has remained at its present level. We must look to some other cause than the rate of growth; and I suspec... |
be found in the reefs being formed of different species of corals, adapted to live at different depths. The Great Chagos bank is situated in the centre of the Chagos group, and the Pitt and Speaker banks at its two extreme points. These banks resemble atolls, except in their external rim being about eight fathoms subme... |
of dead rock, with very little living coral on it: a portion nine miles long of the annular reef of Peros Banhos atoll is in the same condition. These facts, as will hereafter be shown, render it very probable that the whole group at some former period subsided seven or eight fathoms; and that the coral perished on the... |
margin of those atolls which are now submerged, but that it continued alive, and grew up to the surface on those which are now perfect. If these atolls did subside, and if from the suddenness of the movement or from any other cause, those corals which are better adapted to live at a certain depth than at the surface, o... |
got possession of the knolls, supplanting the former occupants, they would exert little or no tendency to grow upwards. To illustrate this, I may observe, that if the corals of the upper zone on the outer edge of Keeling atoll were to perish, it is improbable that those of the lower zone would grow to the surface, and ... |
exposed to conditions for which they do not appear to be adapted. The conjecture, that the corals on the submerged knolls within the Chagos atolls have analogous habits with those of the lower zone outside Keeling atoll, received some support from a remark by Captain Moresby, namely, that they have a different appearan... |
Maldiva atolls, which, as we have seen, all rise to the surface: he compares the kind of difference to that of the vegetation under different climates. I have entered at considerable length into this case, although unable to throw much light on it, in order to show that an equal tendency to upward growth ought not to b... |
all coral-reefs,—to those situated at different depths,—to those forming the ring of an atoll or those on the knolls within a lagoon,—to those in one area and those in another. The inference, therefore, that one reef could not grow up to the surface within a given time, because another, not known to be covered with the... |
and not known to be placed under conditions exactly the same, has not within the same time reached the surface, is unsound. On the Rate of Growth of Coral-reefs. THE remark made at the close of the last section, naturally leads to this division of our subject, which has not, I think, hitherto been considered under a ri... |
view. Ehrenberg* has stated, that in the Red Sea, the corals only coat other rocks in a layer from one to two feet in thickness, or at most to a fathom and a half; and he disbelieves that, in any case, they form, by their own proper growth, great masses, stratum over stratum. A nearly similar observation has been made |
by MM. Quoy and Gaimard,† with respect to the thickness of some upraised beds of coral, which they examined at Timor and some other places. Ehrenberg‡ saw certain large massive corals in the Red Sea, which he imagines to be of such vast antiquity, that they might have been beheld by Pharaoh; and according to Mr. Lyell§... |
corals * Ehrenberg, as before cited, pp. 39, 46, and 50. † Annales des Sciences, Nat. tom. vi. p. 28. ‡ Ehrenberg, ut sup. p. 42. § Lyell's Principles of Geology, Book iii. ch. xviii. at Bermuda, which are known by tradition, to have been living for centuries. To show how slowly coral-reefs grow upwards, Captain Beeche... |
case of the Dolphin Reef off Tahiti, which has remained at the same depth beneath the surface, namely, about two fathoms and a half, for a period of sixty-seven years. There are reefs in the Red Sea, which certainly do not appear† to have increased in dimensions during the last half century, and from the comparison of ... |
recent surveys, probably not during the last two hundred years. These, and other similar facts, have so strongly impressed many with the belief of the extreme slowness of the growth of corals, that they have even doubted the possibility of islands in the great oceans having been formed by their agency. Others again, wh... |
difficulty, have admitted that it would require thousands, and tens of thousands of years, to form a mass even of inconsiderable thickness: but the subject has not, I believe, been viewed in the proper light. That masses of considerable thickness have been formed by the growth of coral, may be inferred with certainty f... |
lagoons of Peros Banhos and of the Great Chagos bank, there are, as already described, small steep-sided knolls covered with living coral. There are similar knolls in the southern Maldiva atolls, some of which, as Captain Moresby assures me, are less than a hundred yards in diameter, and rise to the surface from a dept... |
feet. Considering their number, form and position, it would be preposterous to suppose that they are based on pinnacles of any rock, not of coral formation; or that sediment could have been heaped up into such small and steep isolated cones. As no kind of living coral grows above the height of a few feet, we are compel... |
that these knolls have been formed by the successive growth and death of many individuals,—first one being broken off or killed by some accident, and then another, and * Beechey's Voyage to the Pacific, ch. viii. † Ehrenberg, ut sup. p. 43. one set of species being replaced by another set with different habits, as the ... |
surface, or as other changes supervened. The spaces between the corals would become filled up with fragments and sand, and such matter would probably soon be consolidated, for we learn from Lieut. Nelson,* that at Bermuda a process of this kind takes place beneath water, without the aid of evaporation. In reefs, also, ... |
sure, as I have shown, that masses of great thickness have been formed by the growth of coral: in the case of Vanikoro, judging only from the depth of the moat between the land and the reef, the wall of coral-rock must be at least 300 feet in vertical thickness. It is unfortunate that the upraised coral islands in the |
Pacific have not been examined by a geologist. The cliffs of Elizabeth Island, in the Low Archipelago, are eighty feet high, and appear from Captain Beechey's description, to consist of a homogeneous coral rock. From the isolated position of this island we may safely infer that it is an upraised atoll, and therefore th... |
of coral, grown together: Savage Island seems, from the description of the younger Forster,† to have a similar structure, and its shores are about forty feet high: some of the Cook Islands also appear‡ to be similarly composed. Capt. Belcher, R.N. in a letter, which Capt. Beaufort showed me at the Admiralty, speaking o... |
in boring forty-five feet through coral-sand, when the auger became jammed by the falling in of the surrounding creamy matter." On one of the Maldiva atolls, Capt. Moresby bored to a depth of twenty-six feet, when his auger also broke: he has had the kindness to give me the matter brought up; it is perfectly white, and... |
coral-rock. In my description of Keeling atoll, I have given some facts, which show that the reef probably has grown out- * Geological Transactions, vol. v. p. 113. † Forster's Voyage round the World with Cook, vol. ii. pp. 163, 167. ‡ Williams' Narrative of Missionary Enterprize, p. 30. wards; and I found, just within... |
mounds of Porites and of Millepora, with their summits lately killed, and their sides subsequently thickened by the growth of the coral: a layer, also, of Nullipora had already coated the dead surface. As the external slope of the reef, is the same round the whole of this atoll, and round many other atolls, the angle o... |
from an adaption between the growing powers of the coral, and the force of the breakers, and their action on the loose sediment. The reef, therefore, could not increase outwards, without a nearly equal addition to every part of the slope, so that the original inclination might be preserved, and this would require a lar... |
from the wear of corals and shells, to be added to the lower part. Moreover, at Keeling atoll, and probably in many other cases, the different kinds of corals would have to encroach on each other; thus the Nulliporæ cannot increase outwards without encroaching on the Porites and Millepora complanata, as is now taking p... |
on the strongly branched Madrepora, the Millepora alcicornis, and some Astræas; nor these again without a foundation being formed for them within the requisite depth, by the accumulation of sediment. How slow, then, must be the ordinary lateral or outward growth of such reefs. But off Christmas atoll, where the sea is ... |
good reason to believe that, within a period not very remote, the reef has increased considerably in width. The land has the extraordinary breadth of three miles; it consists of parallel ridges of shells and broken corals, which furnish "an incontestable proof," as observed by Cook,* "that the island has been produced ... |
a state of increase." The land is fronted by a coral-reef, and from the manner in which islets are known to be formed, we may feel confident that the reef was not three miles wide, when the first, or most backward ridge, was * Cook's Third Voyage, Book iii. ch. x. thrown up; and, therefore, we must conclude that the |
reef has grown outwards during the accumulation of the successive ridges. Here then, a wall of coral-rock of very considerable breadth has been formed by the outward growth of the living margin, within a period, during which ridges of shells and corals, lying on the bare surface, have not decayed. There can be little d... |
Capt. Beechey, that Matilda atoll, in the Low Archipelago, has been converted in the space of thirty-four years, from being, as described by the crew of a wrecked whaling vessel, a "reef of rocks," into a lagoon island, fourteen miles in length, with "one of its sides covered nearly the whole way with high trees."* The... |
atoll, it has been shown, have increased in length, and since the construction of an old chart, several of them have become united into one long islet: but in this case, and in that of Matilda atoll, we have no proof, and can only infer as probable, that the reef, that is the foundation of the islets, has increased as |
well as the islets themselves. After these considerations, I attach little importance, as indicating the ordinary and still less the possible rate of outward growth of coral-reefs, to the fact that certain reefs in the Red Sea have not increased during a long interval of time; or to other such cases, as that of Ouluthy... |
where every islet, described a hundred years before by Cantova, was found in the same state by Lutkè,†—without it could be shown that, in these cases, the conditions were favourable to the vigorous and unopposed growth of the corals living in the different zones of depth, and that a proper basis for the extension of th... |
former conditions must depend on many contingencies, and in the deep oceans where coral formations most abound, * Beechey's Voyage to the Pacific, ch. vii. and viii. † F. Lutkè's Voyage autour du monde. In the group Elato, however, it appears that what is now the islet Falipi, is called in Cantova's Chart, the Banc de ... |
stated whether this has been caused by the growth of coral, or by the accumulation of sand. a basis within the requisite depth can rarely be present. Nor do I attach any importance to the fact of certain submerged reefs, as those off Tahiti or those within Diego Garcia, not now being nearer the surface than they were m... |
ago, as an indication of the rate under favourable circumstances of the upward growth of reefs; after it has been shown, that all the reefs have grown to the surface in some of the Chagos atolls, but that in neighbouring atolls, which appear to be of equal antiquity and to be exposed to the same external conditions, ev... |
submerged; for we are almost driven to attribute this to a difference, not in the rate of growth, but in the habits of the corals in the two cases. In an old-standing reef, the corals, which are so different in kind on different parts of it, are probably all adapted to the stations they occupy, and hold their places, l... |
other organic beings, by a struggle one with another, and with external nature; hence we may infer that their growth would generally be slow, except under peculiarly favourable circumstances. Almost the only natural condition, allowing a quick upward growth of the whole surface of a reef, would be a slow subsidence of ... |
Keeling atoll were to subside two or three feet, can we doubt that the protecting margin of live coral, about half an inch in thickness, which surrounds the dead upper surfaces of the mounds of Porites, would in this case form a concentric layer over them, and the reef thus increase upwards, instead of, as at present, ... |
are now encroaching on the Porites and Millepora, but in this case might we not confidently expect that the latter would, in their turn, encroach on the Nulliporæ? After a subsidence of this kind, the sea would gain on the islets, and the great fields of dead but upright corals in the lagoon, would be covered by a shee... |
clear water; and might we not then expect that these reefs would rise to the surface, as they anciently did when the lagoon was less confined by islets, and as they did within a period of ten years in the schooner- channel, cut by the inhabitants. In one of the Maldiva atolls, a reef, which within a very few years |
existed as an islet bearing cocoa-nut trees, was found by Lieut. Prentice "entirely covered with live coral and Madrepore." The natives believe that the islet was washed away by a change in the currents, but if, instead of this, it had quietly subsided, surely every part of the island which offered a solid foundation, ... |
become coated with living coral. Through steps such as these, any thickness of rock, composed of a singular intermixture of various kinds of corals, shells, and calcareous sediment, might be formed; but without subsidence, the thickness would necessarily be determined by the depth at which the reef-building polypifers ... |
suppose a reef of coral favourably circumstanced could grow up from a given depth; I should answer, that we have no precise evidence on this point, and comparatively little concern with it. We see, in innumerable points over wide areas, that the rate has been sufficient, either to bring up the reefs from various depths... |
is more probable, to keep them at the surface, during progressive subsidences; and this is a much more important standard of comparison than any cycle of years. It may, however, be inferred from the following facts, that the rate in years under favourable circumstances would be very far from slow. Dr. Allan of Forres h... |
in the library of the Edinburgh University, (extracts from which I owe to the kindness of Dr. Malcolmson,) the following account of some experiments, which he tried during his travels in the years 1830 to 1832 on the East Coast of Madagascar. "To ascertain the rise and progress of the coral family, and fix the number o... |
at Foul Point (Lat. 17° 40') twenty species of coral were taken off the reef and planted apart on a sand-bank three feet deep at low water. Each portion weighed ten pounds, and was kept in its place by stakes. Similar quantities were placed in a clump and secured as the rest. This was done in December 1830. In July |
following, each detached mass was nearly level with the sea at low water, quite immoveable, and several feet long, stretching, as the parent reef, with the coast current from north to south. The masses accumulated in a clump were found equally increased, but some of the species in such unequal ratios, as to be growing ... |
of Dr. Allan's magnificent collection by shipwreck, unfortunately prevents its being known to what genera these corals belonged; but from the numbers experimented on, it is certain that all the more conspicuous kinds must have been included. Dr. Allan informs me, in a letter, that he believes it was a Madrepora, which ... |
suspect that the level of the sea might possibly have been somewhat different at the two stated periods; nevertheless, it is quite evident that the growth of the ten-pound masses, during the six or seven months, at the end of which they were found immoveably fixed* and several feet in length, must have been very great.... |
different kinds of coral, when placed in one clump, having increased in extremely unequal ratios, is very interesting, as it shows the manner in which a reef, supporting many species of coral, would probably be affected by a change in the external conditions favouring one kind more than another. The growth of the masse... |
lines parallel to the prevailing currents, whether due to the drifting of sediment or to the simple movement of the water, is, also, a very interesting circumstance. A fact, communicated to me by Lieut. Wellstead, I.N., in some degree corroborates the result of Dr. Allan's experiments: it is, that in the Persian Gulf a... |
in the course of twenty months with a layer of coral, two feet in thickness, which it required great force to remove, when the vessel was docked: it was not ascertained * It is stated by Mr. De la Beche (Geological Manual, p. 143.) on the authority of Mr. Lloyd, who surveyed the Isthmus of Panama, that some specimens o... |
Polypifers, placed by him in a sheltered pool of water, were found in the course of a few days firmly fixed by the secretion of a stony matter, to the bottom. to what order this coral belonged. The case of the schooner-channel, choked up with coral in an interval of less than ten years, in the lagoon of Keeling atoll, |
should be here borne in mind. We may also infer, from the trouble which the inhabitants of the Maldiva atolls take to root out, as they express it, the coral-knolls from their harbours, that their growth can hardly be very slow.* From the facts given in this section, it may be concluded, first, that considerable thickn... |
been formed within the present geological æra by the growth of coral and the accumulation of its detritus; and, secondly, that the increase of individual corals and of reefs, both outwards or horizontally and upwards or vertically, under the peculiar conditions favourable to such increase, is not slow, when referred ei... |
in the earth's crust, or to the more precise but less important one of a cycle of years. * Mr. Stuchbury (West of England Journal, No. I. p. 50.) has described a specimen of Agaricia, "weighing 2 lbs. 9 oz. which surrounds a species of oyster, whose age could not be more than two years, and yet is completely enveloped |
by this dense coral." I presume that the oyster was living when the specimen was procured; otherwise the fact tells nothing. Mr. Stuchbury also mentions an anchor, which had become entirely encrusted with coral in fifty years; other cases, however, are recorded of anchors which have long remained amidst coral reefs wit... |
in 1832, after having been down exactly one month at Rio de Janeiro, was so thickly coated by two species of Tubularia, that large spaces of the iron were entirely concealed; the tufts of this horny zoophyte were between two and three inches in length. It has been attempted to compute, but I believe erroneously, the ra... |
a reef, from the fact mentioned by Capt. Beechey of the Chama gigas being embedded in coral rock. But it should be remembered, that some species of this genus invariably live, both whilst young and old, in cavities, which the animal has the power of enlarging with its growth. I saw many of these shells thus embedded in... |
'flat' of Keeling atoll, which is composed of dead rock; and therefore the cavities in this case had no relation whatever with the growth of coral. M. Lesson, also, speaking of this shell (Partie Zoolog. Voyage de la Coquille) has remarked, "que constamment ses valves étaient engagés complètement dans la masse des Madr... |
live. I HAVE already described in detail, which might have appeared trivial, the nature of the bottom of the sea immediately surrounding Keeling atoll; and I will now describe with almost equal care the soundings off the fringing reefs of Mauritius. I have preferred this arrangement, for the sake of grouping together f... |
the wide bell-shaped lead which Capt. FitzRoy used at Keeling Island, but my examination of the bottom was confined to a few miles of coast (between Port Louis and Tomb Bay) on the leeward side of the island. The edge of the reef is formed of great shapeless masses of branching Madrepores, which chiefly consist of two ... |
and pocillifera,—mingled with a few other kinds of coral. These masses are separated from each other by the most irregular gullies and cavities, into which the lead sinks many feet. Outside this irregular border of Madrepores, the water deepens gradually to twenty fathoms, which depth generally is found at the distance... |
from the reef. A little further out the depth is thirty fathoms, and thence the bank slopes rapidly into the depths of the ocean. This inclination is very gentle compared with that outside Keeling and other atolls, but compared with most coasts it is steep. The water was so clear outside the reef, that I could distingu... |
the rugged bottom. In this part, and to a depth of eight fathoms, I sounded repeatedly, and at each cast pounded the bottom with the broad lead, nevertheless the arming invariably came up perfectly clean, but deeply indented. From eight to fifteen fathoms a little calcareous sand was occasionally brought up, but more f... |
all this space the two Madrepores above mentioned, and two species of Astræa, with rather large* stars, seemed the commonest kinds; and it must be noticed that twice at the depth of 15 fathoms, the arming was marked with a clean impression of an Astræa. Besides these lithophytes, some fragments of the Millepora alcicor... |
position at Keeling Island, were brought up; and in the deeper parts there were large beds of a Seriatopora, different from S. subulata, but closely allied to it. On the beach within the reef, the rolled fragments consisted chiefly of the corals just mentioned, and of a massive Porites, like that at Keeling atoll, of a... |
of numerous fragments of Nullipora. From fifteen to twenty fathoms the bottom was, with few exceptions, either formed of sand, or thickly covered with Seriatopora: this delicate coral seems to form at these depths extensive beds, unmingled with any other kind. At 20 fathoms, one sounding brought up a fragment of Madrep... |
the same species (for I neglected to bring specimens from both stations) which mainly forms the upper margin of the reef; if so, it grows in depths varying from 0 to 20 fathoms. Between twenty and thirty-three fathoms I obtained several soundings and they all showed a sandy bottom, with one exception * Since the preced... |
I have received from Mr. Lyell a very interesting pamphlet, entitled Remarks upon Coral-Formations, &c., by J. Couthouy, Boston, United States, 1842. There is a statement (p. 6), on the authority of the Rev. J. Williams, corroborating the remarks made by Ehrenberg and Lyell, (p. 71 of this volume,) on the antiquity of ... |
and at Bermuda; namely, that at Upolu, one of the Navigator islands, "particular clumps of coral are known to the fishermen by name, derived from either some particular configuration or tradition attached to them, and handed down from time immemorial." With respect to the thickness of masses of coral-rock, it clearly a... |
34, 58), that Mangaia and Aurora islands are upraised atolls, composed of coral-rock: the level summit of the former is about 300 feet, and that of Aurora island is 200 feet above the sea-level. at 30 fathoms, when the arming came up scooped out, as if by the margin of a large Caryophyllia. Beyond 33 fathoms I sounded ... |
and from 86 fathoms, at the distance of one mile and a third from the edge of the reef, the arming brought up calcareous sand with a pebble of volcanic rock. The circumstance of the arming having invariably come up quite clean, when sounding within a certain number of fathoms off the reefs of Mauritius and Keeling atol... |
in the former case, and twelve in the latter), and of its having always come up (with one exception) smoothed and covered with sand, when the depth exceeded 20 fathoms, probably indicates a criterion, by which the limits of the vigorous growth of coral might in all cases be readily ascertained. I do not, however, suppo... |
number of soundings were obtained round these islands, the limit above assigned would be found never to vary, but I conceive the facts are sufficient to show, that the exceptions would be few. The circumstance of a gradual change, in the two cases, from a field of clean coral to a smooth sandy bottom, is far more impor... |
the depth at which the larger kinds of coral flourish, than almost any number of separate observations on the depth, at which certain species have been dredged up. For we can understand the gradation, only as a prolonged struggle against unfavourable conditions. If a person were to find the soil clothed with turf on th... |
water, but on going to some distance on one side of it, he observed the blades of grass growing thinner and thinner, with intervening patches of sand, until he entered a desert of sand, he would safely conclude, especially if changes of the same kind were noticed in other places, that the presence of the water was abso... |
the formation of a thick bed of turf: so may we conclude, with the same feeling of certainty, that thick beds of coral are formed only at small depths beneath the surface of the sea. I have endeavoured to collect every fact, which might either invalidate or corroborate this conclusion. Capt. Mores- by, whose opportunit... |
of the Maldiva and Chagos Archipelagoes have been unrivalled, informs me, that the upper part or zone of the steep-sided reefs, on the inner and outer coasts of the atolls in both groups, invariably consists of coral, and the lower parts of sand. At seven or eight fathoms depth, the bottom is formed, as could be seen t... |
water, of great living masses of coral, which at about ten fathoms generally stand some way apart from each other, with patches of white sand between them, and at a little greater depth these patches become united into a smooth steep slope, without any coral. Capt. Moresby, also, informs me in support of his statement,... |
coral on the Padua Bank (northern part of the Laccadive group) which has an average depth between 25 and 35 fathoms, but that on some other banks in the same group with only ten or twelve fathoms water on them, (for instance, the Tillacapeni bank), the coral was living. With regard to the coral-reefs in the Red Sea, Eh... |
the following passage. "The living corals do not descend there into great depths. On the edges of islets and near reefs, where the depth was small, very many lived; but we found no more even at six fathoms. The pearl-fishers at Yemen and Massaua asserted that there was no coral near the pearl-banks at nine fathoms dept... |
We were not able to institute any more special researches."* I am, however, assured both by Captain Moresby and Lieut. Wellstead, that in the more northern parts of the Red Sea, there are extensive beds of living coral at a depth of 25 fathoms, in which the anchors of their vessels were frequently entangled. Captain Mo... |
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