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THE VOYAGE OF THE BEAGLE
BY CHARLES DARWIN

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THE VOYAGE OF THE BEAGLE

PREFACE

I have stated in the preface to the first Edition of this work,
and in the Zoology of the Voyage of the Beagle, that it was in
consequence of a wish expressed by Captain Fitz Roy, of having
some scientific person on board, accompanied by an offer from
him of giving up part of his own accommodations, that I
volunteered my services, which received, through the kindness of
the hydrographer, Captain Beaufort, the sanction of the Lords of
the Admiralty. As I feel that the opportunities which I enjoyed
of studying the Natural History of the different countries we
visited, have been wholly due to Captain Fitz Roy, I hope I may
here be permitted to repeat my expression of gratitude to him;
and to add that, during the five years we were together, I
received from him the most cordial friendship and steady
assistance. Both to Captain Fitz Roy and to all the Officers of
the Beagle [1] I shall ever feel most thankful for the
undeviating kindness with which I was treated during our long
voyage.

This volume contains, in the form of a Journal, a history of
our voyage, and a sketch of those observations in Natural History
and Geology, which I think will possess some interest for the
general reader. I have in this edition largely condensed and
corrected some parts, and have added a little to others, in order
to render the volume more fitted for popular reading; but I trust
that naturalists will remember, that they must refer for details
to the larger publications which comprise the scientific results
of the Expedition. The Zoology of the Voyage of the Beagle
includes an account of the Fossil Mammalia, by Professor Owen;
of the Living Mammalia, by Mr. Waterhouse; of the Birds, by
Mr. Gould; of the Fish, by the Rev. L. Jenyns; and of the
Reptiles, by Mr. Bell. I have appended to the descriptions of
each species an account of its habits and range. These works,
which I owe to the high talents and disinterested zeal of the
above distinguished authors, could not have been undertaken, had
it not been for the liberality of the Lords Commissioners of Her
Majesty's Treasury, who, through the representation of the Right
Honourable the Chancellor of the Exchequer, have been pleased
to grant a sum of one thousand pounds towards defraying part
of the expenses of publication.

I have myself published separate volumes on the 'Structure
and Distribution of Coral Reefs;' on the 'Volcanic Islands
visited during the Voyage of the Beagle;' and on the 'Geology
of South America.' The sixth volume of the 'Geological
Transactions' contains two papers of mine on the Erratic
Boulders and Volcanic Phenomena of South America. Messrs.
Waterhouse, Walker, Newman, and White, have published several
able papers on the Insects which were collected, and I trust
that many others will hereafter follow. The plants from the
southern parts of America will be given by Dr. J. Hooker, in
his great work on the Botany of the Southern Hemisphere. The
Flora of the Galapagos Archipelago is the subject of a separate
memoir by him, in the 'Linnean Transactions.' The Reverend
Professor Henslow has published a list of the plants collected
by me at the Keeling Islands; and the Reverend J. M. Berkeley
has described my cryptogamic plants.

I shall have the pleasure of acknowledging the great assistance
which I have received from several other naturalists, in the
course of this and my other works; but I must be here allowed
to return my most sincere thanks to the Reverend Professor
Henslow, who, when I was an undergraduate at Cambridge, was
one chief means of giving me a taste for Natural History, --
who, during my absence, took charge of the collections I sent
home, and by his correspondence directed my endeavours, -- and
who, since my return, has constantly rendered me every
assistance which the kindest friend could offer.

DOWN, BROMLEY, KENT,
June 9, 1845

[1] I must take this opportunity of returning my sincere thanks
to Mr. Bynoe, the surgeon of the Beagle, for his very kind
attention to me when I was ill at Valparaiso.

THE VOYAGE OF THE BEAGLE

CHAPTER I

ST. JAGO -- CAPE DE VERD ISLANDS

Porto Praya -- Ribeira Grande -- Atmospheric Dust with
Infusoria -- Habits of a Sea-slug and Cuttle-fish -- St.
Paul's Rocks, non-volcanic -- Singular Incrustations --
Insects the first Colonists of Islands -- Fernando Noronha --
Bahia -- Burnished Rocks -- Habits of a Diodon -- Pelagic
Confervae and Infusoria -- Causes of discoloured Sea.

AFTER having been twice driven back by heavy southwestern
gales, Her Majesty's ship Beagle, a ten-gun
brig, under the command of Captain Fitz Roy, R. N.,
sailed from Devonport on the 27th of December, 1831. The
object of the expedition was to complete the survey of
Patagonia and Tierra del Fuego, commenced under Captain King
in 1826 to 1830, -- to survey the shores of Chile, Peru, and
of some islands in the Pacific -- and to carry a chain of
chronometrical measurements round the World. On the 6th
of January we reached Teneriffe, but were prevented landing,
by fears of our bringing the cholera: the next morning
we saw the sun rise behind the rugged outline of the Grand
Canary island, and suddenly illuminate the Peak of Teneriffe,
whilst the lower parts were veiled in fleecy clouds. This
was the first of many delightful days never to be forgotten.
On the 16th of January, 1832, we anchored at Porto Praya,
in St. Jago, the chief island of the Cape de Verd archipelago.

The neighbourhood of Porto Praya, viewed from the sea,
wears a desolate aspect. The volcanic fires of a past age,
and the scorching heat of a tropical sun, have in most places
rendered the soil unfit for vegetation. The country rises in
successive steps of table-land, interspersed with some truncate
conical hills, and the horizon is bounded by an irregular
chain of more lofty mountains. The scene, as beheld through
the hazy atmosphere of this climate, is one of great interest;
if, indeed, a person, fresh from sea, and who has just
walked, for the first time, in a grove of cocoa-nut trees, can
be a judge of anything but his own happiness. The island
would generally be considered as very uninteresting, but to
anyone accustomed only to an English landscape, the novel
aspect of an utterly sterile land possesses a grandeur which
more vegetation might spoil. A single green leaf can
scarcely be discovered over wide tracts of the lava plains;
yet flocks of goats, together with a few cows, contrive to
exist. It rains very seldom, but during a short portion of
the year heavy torrents fall, and immediately afterwards a
light vegetation springs out of every crevice. This soon
withers; and upon such naturally formed hay the animals
live. It had not now rained for an entire year. When the
island was discovered, the immediate neighbourhood of
Porto Praya was clothed with trees, [1] the reckless
destruction of which has caused here, as at St. Helena, and
at some of the Canary islands, almost entire sterility. The
broad, flat-bottomed valleys, many of which serve during a
few days only in the season as water-courses, are clothed
with thickets of leafless bushes. Few living creatures inhabit
these valleys. The commonest bird is a kingfisher (Dacelo
Iagoensis), which tamely sits on the branches of the castor-
oil plant, and thence darts on grasshoppers and lizards. It
is brightly coloured, but not so beautiful as the European
species: in its flight, manners, and place of habitation,
which is generally in the driest valley, there is also a wide
difference.

One day, two of the officers and myself rode to Ribeira
Grande, a village a few miles eastward of Porto Praya. Until
we reached the valley of St. Martin, the country presented
its usual dull brown appearance; but here, a very small rill
of water produces a most refreshing margin of luxuriant
vegetation. In the course of an hour we arrived at Ribeira
Grande, and were surprised at the sight of a large ruined
fort and cathedral. This little town, before its harbour was
filled up, was the principal place in the island: it now
presents a melancholy, but very picturesque appearance. Having
procured a black Padre for a guide, and a Spaniard who
had served in the Peninsular war as an interpreter, we visited
a collection of buildings, of which an ancient church
formed the principal part. It is here the governors and
captain-generals of the islands have been buried. Some of
the tombstones recorded dates of the sixteenth century. [2]

The heraldic ornaments were the only things in this retired
place that reminded us of Europe. The church or chapel
formed one side of a quadrangle, in the middle of which a
large clump of bananas were growing. On another side
was a hospital, containing about a dozen miserable-looking
inmates.

We returned to the Venda to eat our dinners. A considerable
number of men, women, and children, all as black as
jet, collected to watch us. Our companions were extremely
merry; and everything we said or did was followed by their
hearty laughter. Before leaving the town we visited the
cathedral. It does not appear so rich as the smaller church,
but boasts of a little organ, which sent forth singularly
inharmonious cries. We presented the black priest with a few
shillings, and the Spaniard, patting him on the head, said,
with much candour, he thought his colour made no great
difference. We then returned, as fast as the ponies would
go, to Porto Praya.

Another day we rode to the village of St. Domingo, situated
near the centre of the island. On a small plain which
we crossed, a few stunted acacias were growing; their tops
had been bent by the steady trade-wind, in a singular
manner -- some of them even at right angles to their trunks.
The direction of the branches was exactly N. E. by N., and S. W.
by S., and these natural vanes must indicate the prevailing
direction of the force of the trade-wind. The travelling had
made so little impression on the barren soil, that we here
missed our track, and took that to Fuentes. This we did
not find out till we arrived there; and we were afterwards
glad of our mistake. Fuentes is a pretty village, with a small
stream; and everything appeared to prosper well, excepting,
indeed, that which ought to do so most -- its inhabitants.
The black children, completely naked, and looking very
wretched, were carrying bundles of firewood half as big as
their own bodies.

Near Fuentes we saw a large flock of guinea-fowl --
probably fifty or sixty in number. They were extremely
wary, and could not be approached. They avoided us, like
partridges on a rainy day in September, running with their
heads cocked up; and if pursued, they readily took to the
wing.

The scenery of St. Domingo possesses a beauty totally
unexpected, from the prevalent gloomy character of the rest
of the island. The village is situated at the bottom of a
valley, bounded by lofty and jagged walls of stratified lava.
The black rocks afford a most striking contrast with the
bright green vegetation, which follows the banks of a little
stream of clear water. It happened to be a grand feast-day,
and the village was full of people. On our return we overtook
a party of about twenty young black girls, dressed in
excellent taste; their black skins and snow-white linen being
set off by coloured turbans and large shawls. As soon as
we approached near, they suddenly all turned round, and
covering the path with their shawls, sung with great energy
a wild song, beating time with their hands upon their legs.
We threw them some vintems, which were received with
screams of laughter, and we left them redoubling the noise
of their song.

One morning the view was singularly clear; the distant
mountains being projected with the sharpest outline on a
heavy bank of dark blue clouds. Judging from the appearance,
and from similar cases in England, I supposed that the
air was saturated with moisture. The fact, however, turned
out quite the contrary. The hygrometer gave a difference
of 29.6 degs., between the temperature of the air, and the
point at which dew was precipitated. This difference was
nearly double that which I had observed on the previous
mornings. This unusual degree of atmospheric dryness was
accompanied by continual flashes of lightning. Is it not an
uncommon case, thus to find a remarkable degree of aerial
transparency with such a state of weather?

Generally the atmosphere is hazy; and this is caused by
the falling of impalpably fine dust, which was found to have
slightly injured the astronomical instruments. The morning
before we anchored at Porto Praya, I collected a little packet
of this brown-coloured fine dust, which appeared to have
been filtered from the wind by the gauze of the vane at the
masthead. Mr. Lyell has also given me four packets of dust
which fell on a vessel a few hundred miles northward of
these islands. Professor Ehrenberg [3] finds that this dust
consists in great part of infusoria with siliceous shields, and
of the siliceous tissue of plants. In five little packets which
I sent him, he has ascertained no less than sixty-seven
different organic forms! The infusoria, with the exception of
two marine species, are all inhabitants of fresh-water. I
have found no less than fifteen different accounts of dust
having fallen on vessels when far out in the Atlantic. From
the direction of the wind whenever it has fallen, and from
its having always fallen during those months when the harmattan
is known to raise clouds of dust high into the atmosphere,
we may feel sure that it all comes from Africa. It
is, however, a very singular fact, that, although Professor
Ehrenberg knows many species of infusoria peculiar to
Africa, he finds none of these in the dust which I sent him.
On the other hand, he finds in it two species which hitherto
he knows as living only in South America. The dust falls
in such quantities as to dirty everything on board, and to
hurt people's eyes; vessels even have run on shore owing to
the obscurity of the atmosphere. It has often fallen on
ships when several hundred, and even more than a thousand
miles from the coast of Africa, and at points sixteen hundred
miles distant in a north and south direction. In some
dust which was collected on a vessel three hundred miles
from the land, I was much surprised to find particles of
stone above the thousandth of an inch square, mixed with
finer matter. After this fact one need not be surprised
at the diffusion of the far lighter and smaller sporules of
cryptogamic plants.

The geology of this island is the most interesting part of
its natural history. On entering the harbour, a perfectly
horizontal white band, in the face of the sea cliff, may be seen
running for some miles along the coast, and at the height of
about forty-five feet above the water. Upon examination
this white stratum is found to consist of calcareous matter
with numerous shells embedded, most or all of which now
exist on the neighbouring coast. It rests on ancient volcanic
rocks, and has been covered by a stream of basalt, which
must have entered the sea when the white shelly bed was
lying at the bottom. It is interesting to trace the changes
produced by the heat of the overlying lava, on the friable
mass, which in parts has been converted into a crystalline
limestone, and in other parts into a compact spotted stone
Where the lime has been caught up by the scoriaceous fragments
of the lower surface of the stream, it is converted into
groups of beautifully radiated fibres resembling arragonite.
The beds of lava rise in successive gently-sloping plains,
towards the interior, whence the deluges of melted stone
have originally proceeded. Within historical times, no signs
of volcanic activity have, I believe, been manifested in any
part of St. Jago. Even the form of a crater can but rarely
be discovered on the summits of the many red cindery hills;
yet the more recent streams can be distinguished on the
coast, forming lines of cliffs of less height, but stretching
out in advance of those belonging to an older series: the
height of the cliffs thus affording a rude measure of the age
of the streams.

During our stay, I observed the habits of some marine
animals. A large Aplysia is very common. This sea-slug
is about five inches long; and is of a dirty yellowish colour
veined with purple. On each side of the lower surface, or
foot, there is a broad membrane, which appears sometimes
to act as a ventilator, in causing a current of water to flow
over the dorsal branchiae or lungs. It feeds on the delicate
sea-weeds which grow among the stones in muddy and shallow
water; and I found in its stomach several small pebbles,
as in the gizzard of a bird. This slug, when disturbed, emits
a very fine purplish-red fluid, which stains the water for the
space of a foot around. Besides this means of defence, an
acrid secretion, which is spread over its body, causes a
sharp, stinging sensation, similar to that produced by the
Physalia, or Portuguese man-of-war.

I was much interested, on several occasions, by watching
the habits of an Octopus, or cuttle-fish. Although common
in the pools of water left by the retiring tide, these animals
were not easily caught. By means of their long arms and
suckers, they could drag their bodies into very narrow crevices;
and when thus fixed, it required great force to remove
them. At other times they darted tail first, with the rapidity
of an arrow, from one side of the pool to the other, at the
same instant discolouring the water with a dark chestnut-brown
ink. These animals also escape detection by a very
extraordinary, chameleon-like power of changing their colour.
They appear to vary their tints according to the nature
of the ground over which they pass: when in deep water,
their general shade was brownish purple, but when placed on
the land, or in shallow water, this dark tint changed into one
of a yellowish green. The colour, examined more carefully,
was a French grey, with numerous minute spots of bright
yellow: the former of these varied in intensity; the latter
entirely disappeared and appeared again by turns. These
changes were effected in such a manner, that clouds, varying
in tint between a hyacinth red and a chestnut-brown, [4] were
continually passing over the body. Any part, being subjected
to a slight shock of galvanism, became almost black: a similar
effect, but in a less degree, was produced by scratching
the skin with a needle. These clouds, or blushes as they may
be called, are said to be produced by the alternate expansion
and contraction of minute vesicles containing variously
coloured fluids. [5]

This cuttle-fish displayed its chameleon-like power both
during the act of swimming and whilst remaining stationary
at the bottom. I was much amused by the various arts to
escape detection used by one individual, which seemed fully
aware that I was watching it. Remaining for a time motionless,
it would then stealthily advance an inch or two, like a
cat after a mouse; sometimes changing its colour: it thus
proceeded, till having gained a deeper part, it darted away,
leaving a dusky train of ink to hide the hole into which it
had crawled.

While looking for marine animals, with my head about
two feet above the rocky shore, I was more than once saluted
by a jet of water, accompanied by a slight grating noise. At
first I could not think what it was, but afterwards I found
out that it was this cuttle-fish, which, though concealed in a
hole, thus often led me to its discovery. That it possesses
the power of ejecting water there is no doubt, and it appeared
to me that it could certainly take good aim by directing the
tube or siphon on the under side of its body. From the
difficulty which these animals have in carrying their heads,
they cannot crawl with ease when placed on the ground. I
observed that one which I kept in the cabin was slightly
phosphorescent in the dark.

ST. PAUL'S ROCKS. -- In crossing the Atlantic we hove-to
during the morning of February 16th, close to the island of
St. Paul's. This cluster of rocks is situated in 0 degs. 58'
north latitude, and 29 degs. 15' west longitude. It is 540
miles distant from the coast of America, and 350 from the island
of Fernando Noronha. The highest point is only fifty feet above
the level of the sea, and the entire circumference is under
three-quarters of a mile. This small point rises abruptly out
of the depths of the ocean. Its mineralogical constitution
is not simple; in some parts the rock is of a cherty, in others
of a felspathic nature, including thin veins of serpentine. It
is a remarkable fact, that all the many small islands, lying
far from any continent, in the Pacific, Indian, and Atlantic
Oceans, with the exception of the Seychelles and this little
point of rock, are, I believe, composed either of coral or of
erupted matter. The volcanic nature of these oceanic islands
is evidently an extension of that law, and the effect of those
same causes, whether chemical or mechanical, from which it
results that a vast majority of the volcanoes now in action
stand either near sea-coasts or as islands in the midst of the
sea.

The rocks of St. Paul appear from a distance of a brilliantly
white colour. This is partly owing to the dung of a
vast multitude of seafowl, and partly to a coating of a hard
glossy substance with a pearly lustre, which is intimately
united to the surface of the rocks. This, when examined
with a lens, is found to consist of numerous exceedingly
thin layers, its total thickness being about the tenth of an
inch. It contains much animal matter, and its origin, no
doubt, is due to the action of the rain or spray on the birds'
dung. Below some small masses of guano at Ascension, and
on the Abrolhos Islets, I found certain stalactitic branching
bodies, formed apparently in the same manner as the thin
white coating on these rocks. The branching bodies so closely
resembled in general appearance certain nulliporae (a family
of hard calcareous sea-plants), that in lately looking hastily
over my collection I did not perceive the difference. The
globular extremities of the branches are of a pearly texture,
like the enamel of teeth, but so hard as just to scratch plate-
glass. I may here mention, that on a part of the coast of
Ascension, where there is a vast accumulation of shelly sand,
an incrustation is deposited on the tidal rocks by the water
of the sea, resembling, as represented in the woodcut, certain
cryptogamic plants (Marchantiae) often seen on damp
walls. The surface of the fronds is beautifully glossy; and
those parts formed where fully exposed to the light are of a
jet black colour, but those shaded under ledges are only grey.
I have shown specimens of this incrustation to several
geologists, and they all thought that they were of volcanic
or igneous origin! In its hardness and translucency -- in
its polish, equal to that of the finest oliva-shell -- in the
bad smell given out, and loss of colour under the blowpipe -- it
shows a close similarity with living sea-shells. Moreover, in
sea-shells, it is known that the parts habitually covered and
shaded by the mantle of the animal, are of a paler colour
than those fully exposed to the light, just as is the case with
this incrustation. When we remember that lime, either as a
phosphate or carbonate, enters into the composition of the
hard parts, such as bones and shells, of all living animals, it
is an interesting physiological fact [6] to find substances
harder than the enamel of teeth, and coloured surfaces as well
polished as those of a fresh shell, reformed through inorganic
means from dead organic matter -- mocking, also, in
shape, some of the lower vegetable productions.

We found on St. Paul's only two kinds of birds -- the
booby and the noddy. The former is a species of gannet,
and the latter a tern. Both are of a tame and stupid
disposition, and are so unaccustomed to visitors, that I could
have killed any number of them with my geological hammer.
The booby lays her eggs on the bare rock; but the tern makes
a very simple nest with seaweed. By the side of many of
these nests a small flying-fish was placed; which I suppose,
had been brought by the male bird for its partner. It was
amusing to watch how quickly a large and active crab
(Graspus), which inhabits the crevices of the rock, stole the
fish from the side of the nest, as soon as we had disturbed
the parent birds. Sir W. Symonds, one of the few persons
who have landed here, informs me that he saw the crabs
dragging even the young birds out of their nests, and devouring
them. Not a single plant, not even a lichen, grows
on this islet; yet it is inhabited by several insects and
spiders. The following list completes, I believe, the
terrestrial fauna: a fly (Olfersia) living on the booby, and
a tick which must have come here as a parasite on the birds;
a small brown moth, belonging to a genus that feeds on feathers;
a beetle (Quedius) and a woodlouse from beneath the dung; and
lastly, numerous spiders, which I suppose prey on these small
attendants and scavengers of the water-fowl. The often repeated
description of the stately palm and other noble tropical
plants, then birds, and lastly man, taking possession of
the coral islets as soon as formed, in the Pacific, is probably
not correct; I fear it destroys the poetry of this story, that
feather and dirt-feeding and parasitic insects and spiders
should be the first inhabitants of newly formed oceanic
land.