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Maldiva atolls; their peculiar structure.
Dead and submerged reefs.
Areas of subsidence and elevation.
Distribution of volcanoes.
Subsidence slow and vast in amount.

APRIL 1, 1836.



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 (or atolls) of coral
formation similar to those in the Low Archipelago which we passed
near. 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, Mr. Hare, a 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 islet on which Mr. Hare was settled, and joined
Captain Ross's party. Mr. Hare upon this was ultimately obliged to
leave the place.

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 their discontented
state, from the repeated removals from islet to islet, and perhaps
also from a little mismanagement, things are not very prosperous.
The island has no domestic quadruped excepting the pig, and the
main vegetable production is the cocoa-nut. The whole prosperity of
the place depends on this tree; the only exports being oil from the
nut, and the nuts themselves, which are taken to Singapore and
Mauritius, where they are chiefly used, when grated, in making
curries. On the cocoa-nut, also, the pigs, which are loaded with
fat, almost entirely subsist, as do the ducks and poultry. Even a
huge land-crab is furnished by nature with the means to open and
feed on this most useful production.

The ring-formed reef of the 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 can pass to
the anchorage within. On entering, the scene was very curious and
rather pretty; its beauty, however, entirely depended 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 illumined by a vertical sun, of the most vivid
green. This brilliant expanse, several miles in width, is on all
sides divided, either by a line of snow-white breakers from the
dark heaving waters of the ocean, or from the blue vault of heaven
by the strips of land, crowned by the level 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 bands of living coral darken
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 in width;
on the lagoon side there is a white calcareous beach, the radiation
from which under this sultry climate was very oppressive; and on
the outer coast a solid broad flat of coral-rock served 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 first glance, seems to compose the whole wood;
there are however, five or six other trees. 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, and
grows near the beach, where, without doubt, the one seed was thrown
up by the waves. A Guilandina also grows on only one of the islets.
I do not include in the above list the sugar-cane, banana, some
other vegetables, fruit-trees, and imported grasses. As the islands
consist entirely of coral, and at one time must have existed as
mere water-washed reefs, all their terrestrial productions must
have been transported here by the waves of the sea. In accordance
with this, the Florula 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 families! (20/1. These plants are described in the
"Annals of Natural History" volume 1 1838 page 337.)

In Holman's "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. (20/2. Holman's "Travels" volume 4 page 378.)
"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
entwining 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 settled on
the islands. These are all supposed to have been driven by the
north-west monsoon to the coast of New Holland, and thence to these
islands by the south-east 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 these islands are common littoral species in the East
Indian archipelago. From the direction, however, of the winds and
currents, it seems scarcely possible that they could have come here
in a direct line. If, as suggested with much probability by Mr.
Keating, they were first carried towards the coast of New Holland,
and thence drifted back together with the productions of that
country, the seeds, before germinating, must have travelled between
1800 and 2400 miles.

Chamisso, when describing the Radack Archipelago, situated in the
western part of the 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." (20/3. Kotzebue's "First
Voyage" volume 3 page 155.) It is also said that palms and bamboos
from somewhere in the torrid zone, and trunks of northern firs, are
washed on shore; these firs must have come from an immense
distance. These facts are highly interesting. It cannot be doubted
that, if there were land-birds to pick up the seeds when first cast
on shore, and a soil better adapted for their growth than the loose
blocks of coral, the most isolated of the lagoon islands would in
time possess a far more abundant Flora than they now have.

The list of land animals is even poorer than that of the plants.
Some of the islets are inhabited by rats, which were brought in a
ship from the Mauritius, wrecked here. These rats are considered by
Mr. Waterhouse as identical with the English kind, but they are
smaller, and more brightly coloured. There are no true land-birds,
for a snipe and a rail (Rallus Phillippensis), though living
entirely in the dry herbage, belong to the order of Waders. Birds
of this order are said to occur on several of the small low islands
in the Pacific. At Ascension, where there is no land-bird, a rail
(Porphyrio simplex) was shot near the summit of the mountain, and
it was evidently a solitary straggler. At Tristan d'Acunha, where,
according to Carmichael, there are only two land-birds, there is a
coot. From these facts I believe that the waders, after the
innumerable web-footed species, are generally the first colonists
of small isolated islands. I may add that whenever I noticed birds,
not of oceanic species, very far out at sea, they always belonged
to this order; and hence they would naturally become the earliest
colonists of any remote point of land.

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. (20/4. The thirteen species belong to
the following orders: - In the Coleoptera, a minute Elater;
Orthoptera, a Gryllus and a Blatta; Hemiptera, one species;
Homoptera, two; Neuroptera, a Chrysopa; Hymenoptera, two ants;
Lepidoptera nocturna, a Diopaea, and a Pterophorus (?); Diptera,
two species.) Of these one only was a beetle. A small 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 has
described the natural history of a lagoon-island in the Radack
Archipelago (20/5. Kotzebue's "First Voyage" volume 3 page 222.);
and it is remarkable how closely its inhabitants, in number and
kind, resemble those of Keeling Island. There is one lizard and two
waders, namely, a snipe and curlew. Of plants there are nineteen
species, including a fern; and some of these are the same with
those growing here, though on a spot so immensely remote, and in a
different ocean.

The long strips of land, forming the linear islets, have been
raised only to that height to which the surf can throw fragments of
coral, and the wind heap up calcareous sand. The solid flat of
coral rock on the outside, by its breadth, breaks the first
violence of the waves, which otherwise, in a day, would sweep away
these islets and all their productions. The ocean and the land seem
here struggling for mastery: although terra firma has obtained a
footing, the denizens of the water think their claim at least
equally good. In every part one meets hermit crabs of more than one
species, carrying on their backs the shells which they have stolen
from the neighbouring beach. (20/6. The large claws or pincers of
some of these crabs are most beautifully adapted, when drawn back,
to form an operculum to the shell, nearly as perfect as the proper
one originally belonging to the molluscous animal. I was assured,
and as far as my observations went I found it so, that certain
species of the hermit-crab always use certain species of shells.)
Overhead numerous gannets, frigate-birds, and terns, rest on the
trees; and the wood, from the many nests and from the smell of the
atmosphere, might be called a sea-rookery. The gannets, sitting on
their rude nests, gaze at one 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, snow-white tern, which
smoothly hovers at the distance of a few feet above one's 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 3, 1836.

After service I accompanied Captain Fitz Roy to the settlement,
situated at the distance of some miles, on the point of an islet
thickly covered 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, for 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 the inhabitants of Borneo, Celebes, Java, and Sumatra. In
colour they resemble the Tahitians, from whom they do not widely
differ in features. Some of the women, however, show a good deal of
the Chinese character. I liked both their general expressions 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 tides; and it
has even been imagined that sand has the power of filtering the
salt from the sea-water. These ebbing wells are common on some of
the low islands in the West Indies. The compressed sand, or porous
coral rock, is permeated like a sponge with the salt water, but the
rain which falls on the surface must sink to the level of the
surrounding sea, and must accumulate there, displacing an equal
bulk of the salt water. As the water in the lower part of the great
sponge-like coral mass rises and falls with the tides, so will the
water near the surface; and this will keep fresh, if the mass be
sufficiently compact to prevent much mechanical admixture; but
where the land consists of great loose blocks of coral with open
interstices, if a well be dug, the water, as I have seen, is
brackish.

After dinner we stayed to see a curious half superstitious scene
acted by the Malay women. A large wooden spoon dressed in garments,
and which had been carried to the grave of a dead man, they pretend
becomes inspired at the full of the moon, 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 movements. The dance did not commence till the moon had
risen, and it was well worth remaining to behold her bright orb so
quietly shining through the long arms of the cocoa-nut trees as
they waved in the evening breeze. These scenes of the tropics are
in themselves so delicious that they almost equal those dearer ones
at home, 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 over the outer flat of dead rock 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 form 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 6, 1836.

I accompanied Captain Fitz Roy 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 water was 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 bow 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 head foremost into the water trying to seize their
prey. Captain Moresby informs me that in the Chagos archipelago in
this same ocean, the natives, by a horrible process, take the shell
from the back of the living turtle. "It is covered with burning
charcoal, which causes the outer shell to curl upwards, it is then
forced off with a knife, and before it becomes cold flattened
between boards. After this barbarous process the animal is suffered
to regain its native element, where, after a certain time, a new
shell is formed; it is, however, too thin to be of any service, and
the animal always appears languishing and sickly."

When we arrived at the head of the lagoon we crossed a narrow islet
and found a great surf breaking on the windward coast. I can hardly
explain the reason, but there is to my mind much 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 dead coral-rock, strewed
here and there with great loose 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 heaped on the beach, whence the tall cocoa-nut springs,
plainly bespeak the unrelenting power of the waves. Nor are 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, almost equalling in force those
during a gale of wind in the 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 an irresistible power. Yet these
low, insignificant coral-islets stand and are victorious: for here
another power, as an antagonist, 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 that 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, for we stayed
a long time in the lagoon, examining the fields of coral and the
gigantic shells of the chama, into which, if a man were to put his
hand, he would not, as long as the animal lived, be able to
withdraw it. 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 delicately branching corals, which, though
standing upright, were 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
not 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 trees being younger on these portions. Under the 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 within the lagoon
not only is not increased by currents from the outside, but is
itself blown outwards by the force of the wind. Hence it is
observed that the tide near the head of the lagoon does not rise so
high during a strong breeze as it does when it is calm. This
difference of level, although no doubt very small, has, I believe,
caused the death of those coral-groves, which under the former and
more open condition of the outer reef had attained the utmost
possible limit of upward growth.

A few miles north of Keeling there is another small atoll, the
lagoon of which is nearly filled up with coral-mud. Captain Ross
found embedded in the conglomerate on 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 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 afraid of imagining a means of transport
apparently so improbable. It was therefore with great interest that
I found Chamisso, 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 upon 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 steal them. 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, attested by the value which the inhabitants, who are
such bold navigators, attach to a stone of any kind - and the
slowness of the currents of the open sea, are all considered, the
occurrence of pebbles thus transported does appear wonderful.
(20/7. Some natives carried by Kotzebue to Kamtschatka collected
stones to take back to their country.) Stones may often be thus
carried; 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
be 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. These facts
may possibly throw light on single stones, whether angular or
rounded, occasionally found embedded in fine sedimentary masses.

During another day I visited West Islet, on which the vegetation
was perhaps more luxuriant than on any other. 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



Online LibraryCharles DarwinThe Voyage of the Beagle → online text (page 45 of 51)