The living gelatinous covering of the calcareous fabric of the coral-trunks attracts fishes and even turtles in search of food. In the time of Columbus the now desolate district of the Jardines del Rey was animated by a singular branch of industry pursued by the inhabitants of the sea-coasts of Cuba, who availed themselves of a little fish, the Remora, or sucking-fish (the so-called Ship-holder), probably the Echeneis naucrates, for catching turtles. A long and strong line, made of the fibres of the palm, was attached to the tail of the fish. The Remora (called in Spanish Reves, or reversed, because at first sight the back and abdomen might easily be mistaken for each other), attaches itself by suction to the turtle through the indented and moveable cartilaginous plates of the upper shell that covers the head. The Remora, says Columbus, would rather let itself be torn to pieces than relinquish its prey, and the little fish and the turtle are thus drawn out of the water together. “Nostrates,” says Martin Anghiera, the learned secretary of Charles V, “piscem Reversum appellant, quod versus venatur. Non aliter ac nos canibus gallicis per æquora campi lepores insectamur, illi (incolæ Cubæ insulæ) venatorio pisce pisces alios capiebant.”[[LB]] We learn from Dampier and Commerson, that this artifice of employing a sucking-fish to catch other fishes is very common on the eastern coasts of Africa, near Cape Natal and Mozambique, as well as on the island of Madagascar.[[LC]] An acquaintance with the habits of animals, and the same necessities, lead to similar artifices and modes of capture amongst tribes having no connection with one another.
Although, as we have already remarked, the actual seat of the Lithophytes who build calcareous walls, lies within a zone extending from 22 to 24 degrees on either side of the equator, yet coral-reefs, favoured, it is supposed, by the warm Gulf Stream, are met with around the Bermudas in 32° 23′ lat., and these have been admirably described by Lieutenant Nelson.[[LD]] In the southern hemisphere corals (Millepores and Cellepores) are found singly as far as Chiloe and even to the Chonos-Archipelago and Tierra del Fuego, in 53° lat., while Retepores have even been found as far as 72½° lat.
Since Captain Cook’s second voyage, the hypothesis advanced by him as well as by Reinhold and George Forster, that the flat coral islands of the South Pacific have been built up by living agents from the depths of the sea’s bottom, has found numerous advocates. The distinguished naturalists Quoy and Gaimard, who accompanied Captain Freycinet on his voyage of circumnavigation in the frigate “Uranie,” were the first who expressed themselves, in 1823, with much freedom against the views advanced by the two Forsters (father and son), by Flinders, and Péron.[[LE]] “In directing the attention of naturalists to coral-animalcules,” they say, “we hope to be able to prove that all which has been hitherto affirmed or believed up to the present time, regarding the immense structures they are capable of raising, is for the most part inexact, and in all cases very greatly exaggerated. We are rather of opinion that coral-animalcules, instead of rearing perpendicular walls from the depths of the Ocean, only form strata or incrustrations of some few toises in thickness.” Quoy and Gaimard (p. 289) have also expressed an opinion, that Atolls (coral walls inclosing a lagoon) owe their origin to submarine volcanic craters. They have undoubtedly underrated the depth at which animals who construct coral-reefs (as for example the Astræa) can exist, as they place the extreme limits at from 26 to 32 feet below the level of the sea. Charles Darwin, a naturalist, who has known how to enhance the value of his own observations by a comparison with those of others in many parts of the world, places the region of living coral-animals at a depth of 20 or 30 fathoms,[[LF]] which corresponds with that in which Professor Edward Forbes found the greatest number of corals in the Ægean Sea. This is Professor Forbes’s fourth region of marine-animals, as given in his ingenious memoir on the Provinces of Depth, and the geographical distribution of Mollusca at perpendicular distances from the surface.[[LG]] It would appear, however, that the depth at which corals live is very different in the different species, especially in the more delicate ones which do not form such considerable structures.
Sir James Ross, in his Antarctic expedition, brought up corals from a great depth with the lead; and these he remitted for accurate examination to Mr. Stokes and Professor Forbes. Westward of Victoria Land, in the neighbourhood of the Coulman Island, in 72° 31′ south lat., and at a depth of 270 fathoms, Retepora cellulosa, a Hornera, and Prymnoa Rossii. (the latter very similar to a species common to the coasts of Norway,) were found alive and in a perfectly fresh condition.[[LH]] In the far north too, the Greenland Umbellaria Grœnlandica has been brought up alive by whale fishers from a depth of 236 fathoms.[[LI]] The same relation between species and locality is met with among sponges, which however are now regarded as belonging more to plants than to zoophytes. On the shores of Asia Minor, the common marine sponge is brought up from depths varying from 5 to 36 fathoms, although one very small species of the same genus is only found at a depth of at least 180 fathoms.[[LJ]] It is difficult to divine what hinders the Astræas, Madrepores, Mæandrinas, and the whole group of tropical phyto-corals, which are capable of constructing large cellular calcareous walls, from living in very deep strata of water. The decrease of temperature is very gradual, the diminution of light nearly the same, and the existence of numerous Infusoria at great depths of the Ocean proves that there cannot here be any deficiency of food for polyps.
In opposition to the hitherto generally adopted opinion respecting the absence of all organisms and living creatures in the Dead Sea, it is worthy of notice that my friend and fellow-labourer, M. Valenciennes, has received, through the Marquis Charles de l’Escalopier, and through the French Consul Botta, beautiful specimens of Porites elongata from the Dead Sea. This fact is the more interesting, because this species is not found in the Mediterranean, but only in the Red Sea, which, according to Valenciennes, has but few organisms in common with the Mediterranean. As a sea-fish, a species of Pleuronectes, advances far into the interior of France, and accustoms itself to gill-respiration in fresh water, so also does a remarkable flexibility of organization exist in the above-mentioned coral-animal (Porites elongata of Lamarck), as the same species lives both in the Dead Sea, which is supersaturated with salt, and in the open ocean near the Séchelles Islands.[[LK]]
According to the most recent chemical analyses of the younger Silliman, the genus Porites, like many other cellular coral-trunks (Madrepores, Astræas, and Mæandrinas of Ceylon and the Bermudas), contains besides from 92 to 95 per cent. of carbonate of lime and magnesia, a portion of fluorine and phosphoric acid.[[LL]] The presence of fluorine in the hard skeleton of the polyps reminds us of the fluoride of calcium found in fish bones according to Morechini’s and Gay-Lussac’s experiments at Rome. Silex is mixed only in very small quantities, with the fluoride of calcium and phosphate of lime found in the coral-trunks; but one coral animal allied to the Horn corals (Gray’s Hyalonema, Glass thread) has an axis of fibres of pure silex, resembling a hanging tuft of hair. Professor Forchhammer, who has recently been engaged in a thorough analysis of sea-water in the most opposite parts of the earth’s surface, finds the quantity of lime in the Caribbean Sea remarkably small, it being only ²⁴⁷⁄₁₀₀₀₀, whilst in the Cattegat it amounts to ³⁷¹⁄₁₀₀₀₀. He is disposed to ascribe this difference to the numerous coral-banks near the West India Islands, which appropriate the lime to themselves, and thus exhaust the sea-water.[[LM]]
Charles Darwin has with great ingenuity developed the genetic connection between shore-reefs, island-encircling reefs, and lagoon islands, i. e., narrow, annular coral banks which surround inner lagoons. According to his views, these three kinds of structure depend upon the oscillating condition of the bottom of the sea, or on periodical elevations and subsidences. The often-advanced hypothesis, according to which the lagoon-islands, or atolls, mark by their circularly enclosed coral-reefs, the outline of a submarine crater, raised on a volcanic crater-margin, is opposed by the great extent of their diameters, which are in some instances upwards of 30, 40, or even 60 miles. Our fire-emitting mountains have no such craters, and if we would compare the lagoon, with its submerged mural surface and narrow encircling reef, with one of the annular lunar mountains, we must not forget that these annular mountains are not volcanoes, but tracts of land enclosed by walls. According to Darwin, the following is the process of formation. An island mountain closely encircled by a coral reef subsides, while the fringing reef that had sunk with it, is constantly recovering its level owing to the tendency of the coral animals to regain the surface by renewed perpendicular structures; these constitute first a reef encircling the island at a distance, and subsequently, when the inclosed island has wholly subsided, an atoll. According to this view, which regards islands as the most prominent parts, or the culminating points of the submarine land, the relative position of the coral islands would disclose to us what we could scarcely hope to discover by the sounding line, viz., the former configuration and articulation of the land. This attractive subject (to the connection of which with the migrations of plants and the distribution of the races of men we drew attention at the beginning of this note), can only be fully elucidated when we shall succeed in acquiring further knowledge of the depth and nature of the different rocks which serve as a foundation for the lower strata of the dead polyp-trunks.
[78]. p. 216—“Of the Samothracian Traditions.”
Diodorus has preserved to us these remarkable traditions, the probability of which has invested them with almost historical certainty in the eyes of geologists. The island of Samothrace, once also named Ethiopea, Dardania, and Leucania or Leucosia in the Scholiast of Apollonius Rhodius, the seat of the ancient mysteries of the Cabiri, was inhabited by the remnant of an aboriginal people, several words of whose vernacular language were preserved in later times in sacrificial ceremonies. The position of Samothrace, opposite to the Thracian Hebrus, and near the Dardanelles, explains why a more circumstantial tradition of the great catastrophe of an outburst of the waters of the Pontus (Euxine) should have been especially preserved in this island. Sacred rites were here performed at altars erected on the supposed limits of this inundation; and among the Samothracians, as well as the Bœetians, a belief in the periodical destruction of the human race (a belief which also prevailed among the Mexicans in their myth of the four destructions of the world) was associated with historical recollections of individual inundations.[[LN]] According to Diodorus, the Samothracians related that the Black Sea had been an inland lake, which, swelled by the influx of rivers (long prior to the inundations which had occurred among other nations) had burst, first through the straits of the Bosphorus, and subsequently through those of the Hellespont.[[LO]] These ancient revolutions of nature have been considered in a special treatise, by Dureau de la Malle, and all the facts known regarding them collected by Carl von Hoff, in an important work on the subject.[[LP]] The Samothracian traditions seem reflected as it were in the Sluice-theory of Strato of Lampsacus, according to which the swelling of the waters in the Euxine first formed the passage of the Dardanelles, and next the opening through the Pillars of Hercules. Strabo, in the first book of his Geography, has preserved among the critical extracts from the works of Eratosthenes, a remarkable fragment of the lost work of Strato, which presents views that embrace almost the whole circumference of the Mediterranean.
“Strato of Lampsacus,” says Strabo,[[LQ]] “enters more fully than the Lydian Xanthus (who has described the impressions of shells far from the sea) into a consideration of the causes of these phenomena. He maintains, that the Euxine had formerly no outlet at Byzantium, but that the pressure of the swollen mass of waters caused by the influx of rivers had opened a passage, whereupon the water rushed into the Propontis and the Hellespont. The same thing also happened to our sea (the Mediterranean), for here too a passage was opened through the isthmus at the Pillars of Hercules, in consequence of the filling of the sea by currents, which in flowing off left the former swampy banks uncovered and dry. In proof of this, Strato affirms, first, that the outer and inner bottoms of the sea are different; then that there is still a bank running under the sea from Europe to Lybia, which shows that the inner and outer sea were formerly not united; next that the Euxine is extremely shallow, while the Cretan, the Sicilian and the Sardinian seas are, on the contrary, very deep; the cause of this being that the former is filled with mud from the numerous large rivers flowing into it from the north. Hence too the Euxine is the freshest, and the streams flowing from it are directed towards the parts where the bottom is deepest. It would also appear that if these rivers continue to flow into the Euxine, it will some day be completely choked with mud, for even now, its left side is becoming marshy in the direction of Salmydessus (the Thracian Apollonia), at the part called by mariners ‘The Breasts,’ before the mouth of the Ister and the desert of Scythia. Perhaps, therefore, the Lybian Temple of Ammon may also have once stood on the sea-shore, its present position in the interior of the country being in consequence of such off-flowings of rivers. Strato also conjectures that the fame and celebrity of the Oracle (of Ammon) is more easily accounted for, on the supposition that the temple was on the sea-shore, since its great distance from the coast would otherwise make its present distinction and fame inexplicable. Egypt also was in ancient times overflowed by the sea as far as the marshes of Pelusium, Mount Casius, and Lake Serbonis; for whenever in digging it happened that salt-water was met with, the borings passed through strata of sea-sand and shells, as if the country had been inundated, and the whole district around Mount Casius and Gerrha had been a marshy sea, continuous with the Gulf of the Red Sea. When the sea (the Mediterranean) retreated, the country was uncovered, leaving, however, the present Lake Serbonis. Subsequently the waters of this lake also flowed off, converting its bed into a swamp. In like manner the banks of Lake Mœris resemble more the shores of a sea than those of a river.” An erroneous reading introduced as an emendation by Grosskurd, in consequence of a passage in Strabo,[[LR]] gives in place of Mœris, “the Lake Halmyris,” but the latter was situated near the southern mouth of the Danube.