Narrative of the surveying voyages of His Majesty's Ships Adventure and Beagle, Vol. 3 [of 3] · Charles Darwin
CORAL FORMATIONS.
APRIL 1ST.--We arrived in view of the Keeling or Cocos Islands, situated in the Indian ocean, and about six hundred miles distant from the coast of Sumatra. This is one of the lagoon islands of coral formation, similar to those we passed in the Dangerous Archipelago. An excellent idea of the general appearance of these extraordinary rings of land, which rise out of the depths of the ocean, may be obtained from the characteristic sketch of Whitsunday Island, in Beechey’s Voyage. When the ship was in the channel at the entrance, Mr. Liesk, an English resident, came off in his boat. The history of the inhabitants of this place, in as few words as possible, is as follows. About nine years ago, a Mr. Hare, a very worthless character, brought from the East Indian archipelago a number of Malay slaves, which now, including children, amount to more than a hundred. Shortly afterwards, Captain Ross, who had before visited these islands in his merchant-ship, arrived from England, bringing with him his family and goods for settlement. Along with him came Mr. Liesk, who had been a mate in his vessel. The Malay slaves soon ran away from the island on which Mr. Hare was settled, and joined Captain Ross’s party. Mr. Hare upon this was ultimately obliged to leave these islands.
The Malays are now nominally in a state of freedom; and certainly are so, as far as regards their personal treatment; but in most other points they are considered as slaves. From the discontented state of the people, the repeated removals, and; perhaps, also from a little mismanagement, things are not very prosperous. The island has no quadruped, excepting the pig, and no vegetable in any quantity excepting the cocoa-nut. On the latter the whole prosperity of the place depends. The only exports are oil from the nut, and the cocoa-nut[1] itself. On it the pigs, which are loaded with fat, almost entirely subsist, as likewise do the poultry and ducks. Even a huge land-crab is furnished by nature with a curious instinct and form of legs to open and feed on this same fruit. The annular reef of this lagoon island is surmounted in the greater part of its length by linear islets. On the northern or leeward side there is an opening, through which vessels reach the anchorage. On entering, the scene was very curious and rather pretty; its beauty, however, being solely dependant on the brilliancy of the surrounding colours. The shallow, clear, and still water of the lagoon, resting in its greater part on white sand, is, when illuminated by a vertical sun, of a most vivid green. This brilliant expanse, several miles in width, is on all sides divided, either from the dark heaving water of the ocean by a line of snow-white breakers, or from the blue vault of heaven by the strips of land, crowned at an equal height by the tops of the cocoa-nut trees. As a white cloud here and there affords a pleasing contrast with the azure sky, so in the lagoon, dark bands of living coral appear through the emerald green water.
The next morning after anchoring, I went on shore on Direction Island. The strip of dry land is only a few hundred yards wide; on the lagoon side we have a white calcareous beach, the radiation from which in such a climate is very oppressive; and on the outer coast, a solid broad flat of coral rock, which serves to break the violence of the open sea. Excepting near the lagoon where there is some sand, the land is entirely composed of rounded fragments of coral. In such a loose, dry, stony soil, the climate of the intertropical regions alone could produce a vigorous vegetation. On some of the smaller islets, nothing could be more elegant, than the manner in which the young and full-grown cocoa-nut trees, without destroying each other’s symmetry, were mingled into one wood. A beach of glittering white sand formed a border to these fairy spots.
I will now give a sketch of the natural history of these islands, which, from its very paucity, possesses a peculiar interest. The cocoa-nut tree, at the first glance, seems to compose the whole wood; there are, however, five or six other kinds. One of these grows to a very large size, but, from the extreme softness of its wood, is useless; another sort affords excellent timber for ship-building. Besides the trees, the number of plants is exceedingly limited, and consists of insignificant weeds. In my collection, which includes, I believe, nearly the perfect Flora, there are twenty species, without reckoning a moss, lichen, and fungus. To this number two trees must be added; one of which was not in flower, and the other I only heard of. The latter is a solitary tree of its kind in the whole group, and grows near the beach, where, without doubt, the one seed was thrown up by the waves. I do not include in the above list, the sugar-cane, banana, some other vegetables, fruit-trees, and imported grasses. As these islands consist entirely of coral, and at one time probably existed as a mere water-washed reef, all the productions now living here, must have been transported by the waves of the sea. In accordance to this, the Flora has quite the character of a refuge for the destitute: Professor Henslow informs me, that of the twenty species, nineteen belong to different genera, and these again to no less than sixteen orders!
In Holman’s[2] Travels, an account is given on the authority of Mr. A. S. Keating, who resided twelve months on these islands, of the various seeds, and other bodies, which have been known to have been washed on shore. “Seeds and plants from Sumatra and Java have been driven up by the surf on the windward side of the islands. Among them have been found the Kimiri, native of Sumatra and the peninsula of Malacca; the cocoa-nut of Balci, known by its shape and size; the Dadass, which is planted by the Malays with the pepper-vine, the latter intwining round its trunk, and supporting itself by the prickles on its stem; the soap-tree; the castor-oil plant; trunks of the sago palm; and various kinds of seeds unknown to the Malays who settled on the islands. These are all supposed to have been driven on shore by the N.W. monsoon to the coast of New Holland, and thence to these islands by the S.E. trade-wind. Large masses of Java teak, and yellow-wood, have also been found, besides immense trees, of red and white cedar, and the blue gum-wood of New Holland, in a perfectly sound condition. All the hardy seeds, such as creepers, retain their germinating power, but the softer kinds, among which is the mangostin, are destroyed in the passage. Fishing-canoes, apparently from Java, have at times been washed on shore.” It is interesting thus to discover how numerous the seeds are, which, coming from several countries, are drifted over the wide ocean. Professor Henslow tells me, he believes that nearly all the plants which I brought from this island, are common littoral species in the East Indian archipelago. From the direction, however, of the winds and currents, it seems scarcely possible that they can have come here in a direct line. If, as suggested with much probability by Mr. Keating, they have first been carried towards the coast of New Holland, and thence drifted back again, together with the productions of that country, the seeds, before germinating, must have travelled between 1800 and 2400 miles.
Chamisso,[3] when describing the Radack Archipelago, situated in the central part of the Western Pacific, states that, “The sea brings to these islands the seeds and fruits of many trees, most of which have yet not grown here. The greater part of these seeds appear to have not yet lost the capability of growing.” It is also said that trunks of northern firs are washed on shore, which must have been floated from an immense distance. These facts are highly interesting. It cannot be doubted, if there were land-birds to pick up the seeds when first cast on shore, and a soil more adapted for their growth than the loose blocks of coral, that such islands, although so isolated, would soon possess a more abundant Flora. The list of land-animals is even poorer than that of plants. Some of the islets are inhabited by rats; and their origin is known to be due to a ship from the Mauritius, which was wrecked here. These rats have rather a different appearance from the English kind; they are smaller and much more brightly coloured. There are no true land-birds; for a snipe and a rail (_Rallus phillippensis_), though living entirely among the dry herbage, belong to the order of Waders. Birds of this order are said to occur on several of the low islands in the Pacific. At Ascension a rail (_Porphyrio_?) was shot near the summit of the mountain; and it was evidently a solitary straggler. From these circumstances, I believe, the waders are the first colonists of any island, after the innumerable web-footed species. I may add, that whenever I have noticed birds, which were not pelagic, very far out at sea, they always belonged to this order; and hence they would naturally become the earliest colonist of any distant point.
Of reptiles, I saw only one small lizard. Of insects, I took pains to collect every kind. Exclusive of spiders, which were numerous, there were thirteen species.[4] Of these, one only was a beetle. A small species of ant, swarmed by thousands under the loose dry blocks of coral, and was the only true insect which was abundant. Although the productions of the land are thus scanty; if we look to the waters of the surrounding sea, the number of organic beings is indeed infinite. Chamisso[5] has described the natural history of Romanzoff, a lagoon island in the Radack Archipelago. The number and kind of productions there is very nearly the same with those here. One small lizard was seen: wading birds (Numenius and Scolopax) were numerous, and very tame. Of plants, he states there were nineteen species (including one fern); and some of them are the same species with those I collected here, although on an island situated in a different ocean.
These strips of land are raised only to that height, to which the surf can throw fragments, and the wind heap up sand. Their protection is due to the outward and lateral increase of the reef, which thus breaks the sea. The aspect and constitution of these islets at once call up the idea, that the land and the ocean are here struggling for mastery: although terra-firma has obtained a footing, the denizens of the other element think their claim at least equal. In every part one meets hermit-crabs of more than one species,[6] carrying on their backs the houses they have stolen from the neighbouring beach. Overhead, the trees are occupied by numbers of gannets, frigate-birds, and terns. From the many nests and smell of the atmosphere, this might be called a sea-rookery. The gannets, sitting on their rude nests, look at an intruder with a stupid, yet angry air. The noddies, as their name expresses, are silly little creatures. But there is one charming bird; it is a small and snow-white tern, which smoothly hovers at the distance of an arm’s length from your head; its large black eye scanning with quiet curiosity your expression. Little imagination is required to fancy, that so light and delicate a body must be tenanted by some wandering fairy spirit.
SUNDAY, APRIL 3D.--After service I accompanied Captain FitzRoy to the settlement, situated at the distance of some miles, on a point thickly scattered over with tall cocoa-nut trees. Captain Ross and Mr. Liesk live in a large barn-like house open at both ends, and lined with mats made of woven bark. The houses of the Malays are arranged along the shore of the lagoon. The whole place had rather a desolate aspect, because there were no gardens to show the signs of care and cultivation. The natives belong to different islands in the East Indian Archipelago, but all speak the same language: we saw inhabitants of Borneo, Celebes, Java, and Sumatra. In the colour of their skin they resemble the Tahitians, nor do they widely differ from them in form of features. Some of the women, however, showed a good deal of the Chinese character. I liked both their general expression and the sound of their voices. They appeared poor, and their houses were destitute of furniture; but it was evident, from the plumpness of the little children, that cocoa-nuts and turtle afford no bad sustenance. On this island the wells are situated from which ships obtain water. At first sight it appears not a little remarkable that the fresh water should regularly ebb and flow with the usual tide.[7] We must believe that the compressed sand or porous coral rock acts like a sponge; and that the rain-water which falls on the ground being specifically lighter than the salt merely floats on its surface, and is subject to the same movements. There can be no actual attraction between salt and fresh water, and the spongy texture must tend to prevent all admixture from slight disturbances. On the other hand, where the foundation consists only of loose fragments, upon a well being dug, salt or brackish water enters; of which fact we saw an instance on this same island.
After dinner we stayed to see a half superstitious scene acted by the Malay women. They dress a large wooden spoon in garments, carry it to the grave of a dead man, and then at the full of the moon they pretend it becomes inspired, and will dance and jump about. After the proper preparations, the spoon held by two women became convulsed, and danced in good time to the song of the surrounding children and women. It was a most foolish spectacle, but Mr. Liesk maintained that many of the Malays believed in its spiritual movement. The dance did not commence till the moon had risen, and it was well worth remaining to behold her bright globe so quietly shining through the long arms of the cocoa-nuts, as they waved in the evening breeze. These scenes of the tropics are in themselves so delicious, that they almost equal those dearer ones to which we are bound by each best feeling of the mind. The next day I employed myself in examining the very interesting yet simple structure and origin of these islands. The water being unusually smooth I waded in as far as the living mounds of coral, on which the swell of the open sea breaks. In some of the gullies and hollows there were beautiful green and other coloured fishes, and the forms and tints of many of the zoophytes were admirable. It is excusable to grow enthusiastic over the infinite numbers of organic beings with which the sea of the tropics, so prodigal of life, teems; yet I must confess I think those naturalists who have described in well-known words the submarine grottoes decked with a thousand beauties, have indulged in rather exuberant language.
APRIL 6TH.--I accompanied Captain FitzRoy to an island at the head of the lagoon: the channel was exceedingly intricate, winding through fields of delicately branched corals. We saw several turtle, and two boats were then employed in catching them. The method is rather curious: the water is so clear and shallow, that although at first a turtle quickly dives out of sight, yet in a canoe, or boat under sail, the pursuers after no very long chase come up to it. A man standing ready in the bows, at this moment dashes through the water upon the turtle’s back; then clinging with both hands by the shell of its neck, he is carried away till the animal becomes exhausted and is secured. It was quite an interesting chase to see the two boats thus doubling about, and the men dashing into the water trying to seize their prey. When we arrived at the head of the lagoon, we crossed the narrow islet and found a great surf breaking on the windward coast. I can hardly explain the cause, but there is to my mind a considerable degree of grandeur in the view of the outer shores of these lagoon islands. There is a simplicity in the barrier-like beach, the margin of green bushes and tall cocoa-nuts, the solid flat of coral rock, strewed here and there with great fragments, and the line of furious breakers, all rounding away towards either hand. The ocean throwing its waters over the broad reef appears an invincible, all-powerful enemy, yet we see it resisted and even conquered by means which at first seem most weak and inefficient.
It is not that the ocean spares the rock of coral; the great fragments scattered over the reef, and accumulated on the beach, whence the tall cocoa-nut springs, plainly bespeak the unrelenting power of its waves. Nor are there any periods of repose granted. The long swell, caused by the gentle but steady action of the trade-wind always blowing in one direction over a wide area, causes breakers, which even exceed in violence those of our temperate regions, and which never cease to rage. It is impossible to behold these waves without feeling a conviction that an island, though built of the hardest rock, let it be porphyry, granite, or quartz, would ultimately yield and be demolished by such irresistible forces. Yet these low, insignificant coral islets stand and are victorious: for here another power, as antagonist to the former, takes part in the contest. The organic forces separate the atoms of carbonate of lime one by one from the foaming breakers, and unite them into a symmetrical structure. Let the hurricane tear up its thousand huge fragments; yet what will this tell against the accumulated labour of myriads of architects at work night and day, month after month. Thus do we see the soft and gelatinous body of a polypus, through the agency of the vital laws, conquering the great mechanical power of the waves of an ocean, which neither the art of man, nor the inanimate works of nature could successfully resist.
We did not return on board till late in the evening, as we staid some time in the lagoon collecting specimens of the giant Chama, and looking at the coral fields. Near the head of the lagoon I was much surprised to find a wide area, considerably more than a mile square, covered with a forest of branching coral, which though standing upright was all dead and rotten. At first I was quite at a loss to understand the cause; afterwards it occurred to me that it was owing to the following rather curious combination of circumstances. It should, however, first be stated, that corals are never able to survive even a short exposure in the air to the sun’s rays, so that their upward limit of growth is determined by that of lowest water at spring tides. It appears from some old charts, that the long island to windward was formerly separated by wide channels into several islets; this fact is likewise indicated by the less age of the trees in certain portions. Under this former condition of the reef, a strong breeze, by throwing more water over the barrier, would tend to raise the level of the lagoon. Now it acts in a directly contrary manner; for the water, not only is not increased by currents from the outside, but is blown outwards by the force of the wind. Hence, it is observed, that the tides near the head of the lagoon do not rise so high during strong breezes as on ordinary occasions. This difference of level, although no doubt very small, has I believe caused the death of those coral groves, which under the former condition of things had attained the utmost possible limit of upward growth.
A few miles north of Keeling there is another small lagoon island, the centre of which is nearly filled up. Captain Ross found in the conglomerate of the outer coast a well rounded fragment of greenstone, rather larger than a man’s head; he and the men with him were so much surprised at this, that they brought it away and preserved it as a curiosity. The occurrence of this one stone, where every other-particle of matter is calcareous, certainly is very puzzling. The island has scarcely ever been visited, nor is it probable that a ship had been wrecked there. From the absence of any better explanation, I came to the conclusion that it must have come there entangled in the roots of some large tree: when, however, I considered the great distance from the nearest land, the combination of chances against a stone thus being entangled, the tree washed into the sea, floated so far, then landed safely, and the stone finally so embedded as to allow of its discovery, I was almost ashamed of imagining a means of transport so improbable.
It was therefore with great interest that I found Chamisso,[8] the justly distinguished naturalist who accompanied Kotzebue, stating that the inhabitants of the Radack Archipelago, a group of lagoon islands in the midst of the Pacific, obtained stones for sharpening their instruments by searching the roots of trees which are cast up on the beach. It will be evident that this must have happened several times, since laws have been established that such stones belong to the chief, and a punishment is inflicted on any one who attempts to defraud him of this right. When the isolated position of these small islands in the midst of a vast ocean--their great distance from any land excepting that of coral formation, a fact well-attested by the value which the inhabitants, who are such bold navigators, attach to a stone of any kind,[9]--and the slowness of the currents of the open sea are all considered, the occurrence of pebbles thus transported does appear wonderful. Stones may often be thus transported; and if the island on which they are stranded is constructed of any other substance besides coral, they would scarcely attract attention, and their origin at least would never have been guessed. Moreover this agency may long escape discovery from the probability of trees, especially those loaded with stones, floating beneath the surface.
In the channels of Tierra del Fuego large quantities of drift timber are cast upon the beach, yet it is extremely rare to meet a tree swimming on the water. It is easy to conceive that waterlogged wood might be transported, when floating close to the bottom, and occasionally even just touching it. The knowledge of any result which (with sufficient time allowed) can be produced by causes, though appearing infinitely improbable, is valuable to the geologist, for he by his creed deals with centuries and thousands of years as others do with minutes. If a few isolated stones are discovered in a mass of fine sedimentary strata, it cannot, after the above facts, be considered as very improbable that they may have been drifted there by the floating timber of a former epoch. During another day I visited Horsburg and West Island. In the latter, the vegetation was perhaps more luxuriant than in any other part. The cocoa-nut trees generally grow separate, but here the young ones flourished beneath their tall parents, and formed with their long and curved fronds the most shady arbours. Those alone who have tried it know how delicious it is to be seated in such shade, and drink the cool pleasant fluid of the cocoa-nut, which hangs in great bunches close by. In this island there is a large bay or little lagoon, composed of the finest white sand: it is quite level, and is only covered by the tide at high water; from this large bay smaller creeks penetrated the surrounding woods. To see a field of glittering sand, representing water, and around the border of which the cocoa-nut trees extended their tall and waving trunks, formed a singular and very pretty view.
Text from Project Gutenberg, public domain in the United States.