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Memoir on the growth of Iithophyte polyps

considered geologically.

Jean René Quoy and Joseph-Paul Gaimard

Read to the Académie royale des Sciences, 14 July 1823.

Version reproduced in Zoologie, pp658-671, translated by John Milsom


  1. What has been said and written previously about corals is mostly wrong.

 AMONG the zoological phenomena related to the theory of the earth, those concerning plant-like animals (zoophytes) are still far from being fully understood. By calling the attention of naturalists to these creatures, we hope to demonstrate that everything that has been said or is believed to have been observed up to now regarding the immense structures that they are able to build, is inaccurate, always excessively exaggerated, and usually erroneous.

  1. What Péron said was based on his observations of small areas on Timor and Mauritius only, and he too readily believed what he was told by other people.

There can be no doubt that it has taken a great deal of effort on our part to reach a synthesis of the facts that we have examined with the greatest attention and which oblige us to combat assertions generally received and again presented by that indefatigable naturalist whose death has too soon disturbed the sciences. Péron, by some isolated observations on Timor and Mauritius, the only places where he himself studied the work of lithophytes, drew too general conclusions on the evidence of travellers concerning those animals that are believed to have raised, or be still raising, many archipelagos and dangerous obstacles from the depths of the ocean. What use are all the quotations he collected, if they rest on observations that were wrong or superficial, and to hide the truth and support the error by the influence of famous names.

Rather than believing, as Péron did, that the Pacific islands are wholly or partly coralline, we believe that they are made up mainly of the same sorts of rocks as other land masses.

Instead of believing that the Society Islands, some parts of New Ireland, the Louisiades, the Solomons, the Friendly Islands, the Marianas, Palau, the Samoas, Fiji, the Marquesas, etc. were partly or wholly constructed by zoophytes, we think that all these islands are formed of the same rocks that make up all other known islands and continents. There are shales, as on Timor and Waigeo, and sandstones, as on the coast of Australia. Elsewhere, horizontally-layered limestone forms the island of Boni and surrounds the volcanic peaks of the Marianas. Granite is also sometimes found, but most of the islands in the Southern Oceans were formed by volcanic activity. Mauritius, Réunion, some of the Moluccas, the Hawaiian Islands, Tahiti, and all those numerous archipelagos discovered by Bougainville and Cook, are partly volcanic, as evidenced by the rock samples that we brought back from a few of these places, and the reports of field scientists from those that we have not visited ourselves. What, then, has given rise to the belief that madrepores are widespread on the floors of the ocean basins, and have built up from them the low islands that are so dangerous to explorers! A brief review, a quick glance at the work of these zoophytes.

We examine how reefs form and show that corals are only a few feet thick.

We propose in this memoir:

  1. To examine how lithophytes build their structures on pre-existing bases, and define the circumstances favourable or unfavourable to their growth.
  2. To show that there are no large, permanently inhabited islands [pdf 694 p660] that are entirely formed of corals; and that, far from raising perpendicular walls from the depths of the ocean, as has been suggested, these animals form only layers or encrustations a few metres thick.

Warm shallow seas protected from excessive wave action favour reef growth.

Here is how this superposition of madrepores takes place. Saxigenic polyps multiply in places where the sea is always warm, and where there are bays enclosing calm shallow waters that are not likely to be disturbed by strong swells or by the regular breezes of the tropics. They build their dwellings on the underwater rocks, enveloping them in whole or in part, but do not form them. Thus, all these constructions, all these madreporic belts, which, in the South Seas, are met with frequently enough in the lee of the islands, are, according to us, shoals dependent on the configuration of the underlying rock. We recognize they belong to it whenever we have opportunity of observing the trends of mountains and hills, which they should continue to follow under the water. It is always where the sea floor slopes gently and where the sea is shallow that we find the largest masses of madrepores. They are prolific where the water is calm, and where it is not they form only isolated patches of species that are less affected the agitation of the waves.

There are reef cliffs in deep water where we can’t sound bottom

It has been said, and is common knowledge amongst sailors, that in the equatorial seas we find coral[ reefs* which rise like walls from depths too great to be reached by a sounding line.

Reefs are not entirely built of madrepores, but all reef-building species require light, and cannot develop at depths of more than a few fathoms.

It is their depth that poses the greatest risk to ships, which when becalmed and at the mercy of the currents, cannot anchor in such places. But it is not true to say that these reefs are entirely madrepores. First of all, because the species which constantly form the most considerable benches, like some meanders, some caryophyllies, but especially the astreae, adorned with the most beautiful and velvety colours, need the influence of the light to acquire them are not seen growing below a few fathoms deep; and consequently  cannot develop at depths of a thousand or twelve hundred feet, as would be necessary for them to raise the escarpments in question. Besides, these various species of animals would therefore almost exclusively enjoy the prerogative of inhabiting all depths, under all pressures and, so to speak, at all temperatures.

.Because waves break up reefs, they cannot be very extensive in depth

Another circumstance that explorers have ignored, which strengthens our case and makes it more obvious, is that at great depths the sea is always stormy and breaks with force on the reefs, without any need for the wind to agitate it. And by simply applying the observations of these same travellers, who say (which is very true) that where the waves are agitated the lithophytes cannot grow, because their fragile structures are destroyed, we come to the certainty that these underwater escarpments are not due to these animalcules. But where, in these same places, there is a depression and some shelter, they will immediately raise their homes and help to reduce the small depth that already exists. This can be seen in almost all places where warm water allows these animals to grow in abundance. In localities where the tides are felt, the currents [pdf 696 p662] sometimes can irregular channels between the madrepores, without ever being blocked by them species, due to a combination of motion and cold water. On the other hand it is in these places that the flexible halcyons can multiply.

Coral cannot grow above low tide mark.

When we carefully observe their geological distribution, we see that the zoophytes rise to the sea surface, never above; after this point the ability to grow which has existed until then appears to be extinguished. It is destroyed  all the more if, by the effect of the tides, thecreatures are exposed to direct sunlight. Where, on these reefs of inert debris deprived of their inhabitants, there are small depressions which never dry out, some patches of these lithophytes shine in the brightest colours, having escaped the almost general destruction,. So spcies that are growing again, no longer able to build outside these reefs on which the sea breaks, are little by little approaching the sides where the damped waves have almost no effect on them, as we have seen at Mauritius, Timor, the Papuan Islands, the Marianas and the Hawaiian Islands; however, where the waters do not have a great depth, as is the case at Turtle Island, of which Cook speaks, where there is no bottom between the madreporic reefs and the island, despite the short distance between these two points.

If we examine these animals in the places most adapted to their growth, we shall see their different species, whose forms, as varied as they are elegant, become rounded into balls, spread out into fans or ramify into trees, mingle to blend and reflect the shades of red, yellow, blue and purple.

We know that all these so-called walls, entirely made up of corals, are interrupted by openings through which the sea enters and leaves with violence, and nobody is ignorant of the danger that Captain Cook ran on this occasion on the coasts of the New Holland, when he had no other resource, to escape the destruction but to take the sudden decision of sailing into one of those narrow passes, where one is always sure to find deep water. This again supports the idea that we are advancing; for if these perpendicular walls were entirely madreporic, there would be no deep openings in their continuity, because the peculiarity of the zoophytes is to build in uninterrupted masses; and that once more, if they could rise from very great depths, they would end up filling up and blocking these passages. This does not occur, and will probably not happen, for the reasons we suggest. If these facts prove that the madrepores cannot live at very great depths, the submarine mounds merely elevate them and are not exclusively formed by them.

The second proposition. There are no permanently inhabited islands of significant size that are formed of lithophytes, and the layers they build under the water are only a few toise thick. It is through the second part of our proposition that we will proceed. The impossibility of going under the water to examine to what precise depth the solid zoophytes are established, makes it necessary for us to be satisfied with what has taken place formerly. The monuments which the former revolutions of the globe have raised will serve to show what is happening nowadays. We will describe what we have seen in several places, and we shall speak first of the island which Péron took for the scene of the great labours of these polyps; we mean Timor.

As to the masses of madrepores which the sea has left uncovered by retreating from the land, we shall say that they acquired in these places an extent that we have not seen anywhere.The whole shore of Coupang is formed of them; and as one climbs the hills (and not the mountains) that surround the city, one finds them at every step. This is sufficient to us to conclude at  first that the whole island is formed of this substance, and that the mountain range of Anmfoa and Fateleou, which may be a thousand toises high, owes its origin. But on leaving the city, we have scarcely taken five hundred paces in ascending the heights, before we find, in place, vertical layers of a bluish gray shale veined with quartz Also, on the banks of the Bacanassi river.there are, blocks of smooth rock, coarse jasper, and in other places, compact limestone, substances which sufficiently demonstrate the bases on which the zoophytes have been raised. We cannot exactly determine the thickness of their massifs; but we think nothing of diminishing it by evaluating it from twenty-five to thirty feet.

Much further on, at heights of fifteen to  eighteen hundred feet, Péron found fossil shells. He does not say that the bedrock was madreporic; even if it had been, by examining these mountains carefully, we would soon have discovered the nature of the rocks which formed its foundations. This naturalist, in support of his opinion of the important role played by lithophytes, advances, on the basis of reports obtained from uneducated people, that high mountains, which he has only seen from a distance of ten leagues, are all madreporic. Certainly, on a fact of geology so surprising, we cannot believe the words either of Dutch colonists or of semi-civilised men, who do not understand questions of natural history. This is what he said when he was at Olinama, a few leagues from Coupang: “From this last point we were facing the great mountain range of Anmfoa and Fateleou; this broad plateau which dominates all this portion of Timor, is entirely composed of madreporic substances. From Oëna to Pacoula, the inhabitants say that everything is limestone [samougnia batoa capor], and the Dutch [pdf 699 p665]readily confirm this fact.” (Peron, Voyage de découvertes aux Terres Australes, 4th edition, Volume 2, p. 176.)

In such matters, one must have seen and reviewed, and properly noted the facts; for when we hasten to draw general conclusions, our pride always finds means to accommodate these same facts to our way of seeing.

All this indicates that there are no mountains on Timor formed exclusively of corals. Like all major land masses, the island is composed of a variety of different rocks. Having surveyed it for a distance of about fifty leagues, close enough for observation, we have seen it to be volcanic in several places. Besides, it has mines of gold and copper; which, added to what we have just said, also partly indicates the nature of the rocks.

We might perhaps add to this Bald Head, in Port King George, in New Holland, which Vancouver described in passing, and on the summit of which he saw intact, decorative branched corals. This is absolutely the same phenomenon as on Timor and in a thousand other places,**. Zoophytes have built on a base they have found, and they occupy only the surface. For why would Bald Head differ from Mount Gardner, which, next to it, is formed of primitive rocks? Besides, Péron said it has the same geological constitution (Péron, Voyage de découvertes aux Terres Australes, 4th edition, Volume 2, page 133)

On Rota, one of the Marianas Islands, our colleague M. Gaudichaud has sampled perfectly preserved branches of true madrepores  from calcareous rock about two hundred metres above sea level,. Here there are three localities where they are at great heights. We have observed them at very much lower elevations in several other places, as on the Isle de France, where they form a layer more than ten feet thick between two lava flows; on Oahu, one of the Sandwich Islands, where they are no higher but outcrop over several hundred metres. In all these cases, care must be taken to distinguish the lithophytes which, having been building uninterrupted masses, were able to increase, from those which, rolled and attenuated by the waters and mixed with the marine shells, contribute to form the deposits known as madreporic limestone. These remains are only the debris of the first. We have seen some in the Mariana Islands and on the Papuan Islands; they are found on the coasts of France and in several other places.

It is therefore Timor which, having provided us with the best exposures of zoophytes, leads us to conclude, by analogy with what has taken place in the past, that the species of the genus astrea, the only ones capable of covering immense areas, do not do not start their constructions at depths of more than  twenty-five or thirty feet, and then raise them to near the sea surface.

Never, either with the lead or with the anchors, have we brought fragments of these species; we have only seen them in places where the water was very shallow, the madrepores rameux, which do not form thick and consistent layers, either on the high places that the Ocean has abandoned, either on the shores where they still exist, live at quite great depths.

And it is even one of the questionable propositions of the naturalist whom we quote, of having wished to limit the habitats of these animals to the 34th degree of South latitude; for close to Cape Horn, at about 56 degrees latitude, at depths of between fifty and eighty  brasse, we found small madrepores rameux vivans. And, in a previous voyage, at an opposite meridian, on the Aiguilles Bank, we remember having seen rétépores at more than a hundred fathoms deep, es. It is true that in higher latitudes these animals occupy but little space, but they do live there, and the first of these two facts proves that they can withstand a very cold temperature, though probably not as cold as at the southern extremity of America, as is commonly believed.

It is very odd that the madrepores of the Southern Ocean and the Indian archipelago have been credited with forming steep underwater mountains, at the base of which there is no bottom; and much more surprising still that examination of the places where the same phenomenon is observed without the presence of these zoophytes did not cause anyone to doubt such an extraordinary fact.

It is known that rocks of any composition may form considerable escarpments. To prove that this arrangement exists under the water, we quote Guam Island, one of the Marianas, located at thirteen and a half degrees north latitude: where it is not volcanic, this island is surrounded by limestone cliffs so steep that they resemble perfect walls, arranged in a few places in successive terraces, which, en echelon, will be lost beneath the sea. If, by casting the lead, one encounters the summit of one of these walls, the bottom will be at around eight or ten brasse, more or less, while near by a hundred fathoms of line may not be enough. Now, suppose that, on the shallowest and most sheltered crests, the zoophytes come to build, they will rise until their progress is hindered by their own development, which, by forming an obstacle to the waves, will cause them to come crashing on them, then they will be reefs.

Adjacent to Guam, Rota Island is in the same situation. On its escarpments, which are much more considerable, there are madrepores, properly so called, of the species called staghorn, absolutely similar to those that abound in the surrounding sea.Thus, formerly, they multiplied on the land that the sea has since abandoned, as they grow daily on that which it still covers.

Other examples of these perpendicular submarine mountains are noticeable in various latitudes. We read in Pallas (Second Voyage, Volume 3, page 133 & page 220)***  that he saw in Tauris mountains so steep that they rise more than a thousand feet above the sea level, and that one cannot find bottom just offshre. Well! we repeat it, it is the summits of similar underwater mountains of the torrid zone, whatever their nature, that the zoophytes have taken for bases: and all these reefs of Tahiti, of the Dangerous and Navigators archipelagos(Tuamotus and Samoas respectively), of the Friendly Islands  etc. are madreporic only on the surface. Let us listen to Forster, who, one of the first, has accredited the opinion we are fighting, and we shall see that he furnishes arms against himself. “The Low Islands,” he says, “to the east of Tahiti, as well as the Society Islands, the Friendly Islands, the New Hebrides, and New Caledonia, with the intermediate islands of Scylli. Howe, Palliser, Palmeston, Wild, Turtle and those of Hope and Cocos, the Queen Charlotte Islands, Captain Carteret, and many others – as well as New Ireland, Nova Scotia Brittany and New Guinea also form, beneath the ocean, a great chain of mountains: they extend in an immense space which comprises three quarters of the whole South Sea. (Forster the elder, Observations, in Cook 5, page 24.)

Then appearing to forget what he has just said, and giving too much credit to the madrepores, he adds (page 136): “The reef, the first foundation of the islands, is formed by the animals that inhabit the lithophytes. They  build their homes up to a short distance from the surface of the sea, & c. ”

This irregular distribution of land may once have been our salvation when the corvette Uranie was driven at night by the currents into the passage that bears her name and was surrounded by a multitude of islands and rocks. In this difficult position, having no indications anywhere, we did not know which passage to choose to leave this archipelago, in the middle of all this confusion we found a madrepore shelf on which we anchored. From what we have just said, everything must lead us to suppose that this massif was raised on a base of nature similar to the rocks around us.

Thus we believe that we have shown that it is not likely that zoophytes have formed the vast pediments on which most of the islands of the deep ocean are based. It remains to consider how these animals can come together to form small islets. Forster has very well described how this is done.

Indeed, when remote from large land masses, these creatures have brought up to the surface, and remain in the ebb tide, the hurricanes which sometimes occur at the bottom of these shallow waters, carry the sands and the mud. engages in the anfractuosities of the corals, settles there, agglomerates, and as soon as the summit of this new island can remain constantly uncovered, that the waves can no longer destroy what they themselves have helped to form, then its contour is enlarged, its edges rise insensibly by the successive addition of the sands, and, according to the direction of the winds and currents, it may remain sterile for a long time, but if, by the action of these two causes, the seeds of the plants are brought to it from neighboring coasts, then, in latitudes which are so favorable to their development, it is soon to be covered with vegetation, the debris of which builds up layers of humus that contribute to the raising of the soil. This we could see for ourselves on the small island of Kera, located in the bay of Kupang, in Timor.

But if islands are to form in this way they must not be too far from larger landmasses, because if they are, then plants cannot reach them so easily. Such islets almost always remain bare and sterile. That is why the reports of sailors of  madreporic islands in the deep oceans which, although far from any other land, are yet covered with vegetation, has always seemed extraordinary to us; all the more so because in these immense spaces, the violence of the waves, which nothing can dampen, must prevent the work of zoophytes. However, we do not deny the existence of these islands, which it would be interesting to examine again; for as soon as the navigators encounter low islands in the tropics, informed by the generally accepted opinion, they do not hesitate to say that they are madreporic.

Nevertheless, islands where there is fresh water cannot be formed in this way! We will mention, for example, that of Boni, located close to the equator, where thick vegetation is rooted on limestone. It is the same on Cocos Island, off Guam, which is composed of the same material. In general, if they are inhabited by men, if they therefore have freshwater springs or lakes, we can almost assume that they are not or are only partially composed of lithophytes, because springs cannot form sources in their porous masses. Some of the Caroline Islands, in the midst of which we sailed without being able to stop , are excessively low; we suppose them encrusted with madrepores; and as they have inhabitants, there must be somewhere favourable to the accumulation of fresh water ****

By recognising the limitations on the power of these animals, by indicating the limits which nature has prescribed to them, we have no other object than to furnish more exact data to savants who rise to great hypothetical considerations on the conformation of the globe.  Considering these zoophytes again with more attention, they will no longer be seen to be filling the basins of the seas, raising islands, increasing the continents, and threatening future generations with a solid equatorial circle formed of their remains. Their influence, relative to the shallows in which they multiply, is already quite great, without exaggerating it, but compared to the masses on which they rest, what are their often discontinuous layers, which must be carefully sought to find them, when considered from the tops of the enormous volcanic peaks of the Hawaiian Islands and Réunion, the Moluccas, the Marianas, the mountains of Timor, New Guinea etc. Nothing, no doubt; and the solid zoophytes are far from being able to be compared to shells amongst the materials which both have furnished and still supply to the terrestrial envelope.

* We are aware that this word “coral” is commonly applied, very wrongly, to all lithogenic polyps; the word “madrepore”, which in zoology serves to designate a single genus, has nearly the same meaning. We will sometimes use one and sometimes the other for all these animals, mentioning the species wherever necessary.

**A most remarkable fact of this kind is that reported by M. Salt, Second Voyage to Abyssinia, Volume 1, pp. 216-217: “Amphila Bay in the Red Sea is formed,” he says, “of twelve islands, of which eleven are partly formed of alluvium, which consist of coralline, meprepora, echinites, and a great variety of shells common to this sea. The elevation of these islands is sometimes thirty feet above the high tide . . . . . . . .   The small island, which differs from the other eleven, is composed of a solid rock, of limestone, in which one notices veins of chalcedony. ” Does not this little island indicate that some cause has prevented the madrepores from covering it, while they have built their houses in the neighborhood, on bases which must probably be of the same nature as those of the one little island?.

***Presumably the French edition of « Voyages de M. P.S. Pallas en différentes provinces de l’empire de Russie et dans l’Asie septentrionale » but if so, the page references are incorrect.

**** On looking at the maps of Captain Kotzebue’s voyage, we are struck by seeing several of these islands grouped in circles, bound together by coral reefs, and presenting, by this arrangement, a small Inner and deep sea, entered through one or more openings. Would not this disposition be due to submarine craters on the edges of which the Iithophytes would have worked!