CHAPTER I

THE VOYAGE OF THE BEAGLE BY

CHARLES DARWIN

About the online edition.

The degree symbol is represented as "degs." Italics are represented as

_italics_. Footnotes are collected at the end of each chapter.

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 mast-head. 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 sea-weed. 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.

The smallest rock in the tropical seas, by giving a foundation for the

growth of innumerable kinds of sea-weed and compound animals, supports

likewise a large number of fish. The sharks and the seamen in the boats

maintained a constant struggle which should secure the greater share of

the prey caught by the fishing-lines. I have heard that a rock near

the Bermudas, lying many miles out at sea, and at a considerable depth,

was first discovered by the circumstance of fish having been observed

in the neighbourhood.

FERNANDO NORONHA, Feb. 20th.--As far as I was enabled to observe,

during the few hours we stayed at this place, the constitution of the

island is volcanic, but probably not of a recent date. The most

remarkable feature is a conical hill, about one thousand feet high, the

upper part of which is exceedingly steep, and on one side overhangs its

base. The rock is phonolite, and is divided into irregular columns. On

viewing one of these isolated masses, at first one is inclined to

believe that it has been suddenly pushed up in a semi-fluid state. At

St. Helena, however, I ascertained that some pinnacles, of a nearly

similar figure and constitution, had been formed by the injection of

melted rock into yielding strata, which thus had formed the moulds for

these gigantic obelisks. The whole island is covered with wood; but

from the dryness of the climate there is no appearance of luxuriance.

Half-way up the mountain, some great masses of the columnar rock,

shaded by laurel-like trees, and ornamented by others covered with fine

pink flowers but without a single leaf, gave a pleasing effect to the

nearer parts of the scenery.

BAHIA, OR SAN SALVADOR. BRAZIL, Feb. 29th.--The day has passed

delightfully. Delight itself, however, is a weak term to express the

feelings of a naturalist who, for the first time, has wandered by

himself in a Brazilian forest. The elegance of the grasses, the

novelty of the parasitical plants, the beauty of the flowers, the

glossy green of the foliage, but above all the general luxuriance of

the vegetation, filled me with admiration. A most paradoxical mixture

of sound and silence pervades the shady parts of the wood. The noise

from the insects is so loud, that it may be heard even in a vessel

anchored several hundred yards from the shore; yet within the recesses

of the forest a universal silence appears to reign. To a person fond

of natural history, such a day as this brings with it a deeper pleasure

than he can ever hope to experience again. After wandering about for

some hours, I returned to the landing-place; but, before reaching it, I

was overtaken by a tropical storm. I tried to find shelter under a

tree, which was so thick that it would never have been penetrated by

common English rain; but here, in a couple of minutes, a little torrent

flowed down the trunk. It is to this violence of the rain that we must

attribute the verdure at the bottom of the thickest woods: if the

showers were like those of a colder climate, the greater part would be

absorbed or evaporated before it reached the ground. I will not at

present attempt to describe the gaudy scenery of this noble bay,

because, in our homeward voyage, we called here a second time, and I

shall then have occasion to remark on it.

Along the whole coast of Brazil, for a length of at least 2000 miles,

and certainly for a considerable space inland, wherever solid rock

occurs, it belongs to a granitic formation. The circumstance of this

enormous area being constituted of materials which most geologists

believe to have been crystallized when heated under pressure, gives

rise to many curious reflections. Was this effect produced beneath the

depths of a profound ocean? or did a covering of strata formerly extend

over it, which has since been removed? Can we believe that any power,

acting for a time short of infinity, could have denuded the granite

over so many thousand square leagues?

On a point not far from the city, where a rivulet entered the sea, I

observed a fact connected with a subject discussed by Humboldt. [7] At

the cataracts of the great rivers Orinoco, Nile, and Congo, the

syenitic rocks are coated by a black substance, appearing as if they

had been polished with plumbago. The layer is of extreme thinness; and

on analysis by Berzelius it was found to consist of the oxides of

manganese and iron. In the Orinoco it occurs on the rocks periodically

washed by the floods, and in those parts alone where the stream is

rapid; or, as the Indians say, "the rocks are black where the waters

are white." Here the coating is of a rich brown instead of a black

colour, and seems to be composed of ferruginous matter alone. Hand

specimens fail to give a just idea of these brown burnished stones

which glitter in the sun's rays. They occur only within the limits of

the tidal waves; and as the rivulet slowly trickles down, the surf must

supply the polishing power of the cataracts in the great rivers. In

like manner, the rise and fall of the tide probably answer to the

periodical inundations; and thus the same effects are produced under

apparently different but really similar circumstances. The origin,

however, of these coatings of metallic oxides, which seem as if

cemented to the rocks, is not understood; and no reason, I believe, can

be assigned for their thickness remaining the same.

One day I was amused by watching the habits of the Diodon antennatus,

which was caught swimming near the shore. This fish, with its flabby

skin, is well known to possess the singular power of distending itself

into a nearly spherical form. After having been taken out of water for

a short time, and then again immersed in it, a considerable quantity

both of water and air is absorbed by the mouth, and perhaps likewise by

the branchial orifices. This process is effected by two methods: the

air is swallowed, and is then forced into the cavity of the body, its

return being prevented by a muscular contraction which is externally

visible: but the water enters in a gentle stream through the mouth,

which is kept wide open and motionless; this latter action must,

therefore, depend on suction. The skin about the abdomen is much

looser than that on the back; hence, during the inflation, the lower

surface becomes far more distended than the upper; and the fish, in

consequence, floats with its back downwards. Cuvier doubts whether the

Diodon in this position is able to swim; but not only can it thus move

forward in a straight line, but it can turn round to either side. This

latter movement is effected solely by the aid of the pectoral fins; the

tail being collapsed, and not used. From the body being buoyed up with

so much air, the branchial openings are out of water, but a stream

drawn in by the mouth constantly flows through them.

The fish, having remained in this distended state for a short time,

generally expelled the air and water with considerable force from the

branchial apertures and mouth. It could emit, at will, a certain

portion of the water, and it appears, therefore, probable that this

fluid is taken in partly for the sake of regulating its specific

gravity. This Diodon possessed several means of defence. It could

give a severe bite, and could eject water from its mouth to some

distance, at the same time making a curious noise by the movement of

its jaws. By the inflation of its body, the papillae, with which the

skin is covered, become erect and pointed. But the most curious

circumstance is, that it secretes from the skin of its belly, when

handled, a most beautiful carmine-red fibrous matter, which stains

ivory and paper in so permanent a manner that the tint is retained with

all its brightness to the present day: I am quite ignorant of the

nature and use of this secretion. I have heard from Dr. Allan of

Forres, that he has frequently found a Diodon, floating alive and

distended, in the stomach of the shark, and that on several occasions

he has known it eat its way, not only through the coats of the stomach,

but through the sides of the monster, which has thus been killed. Who

would ever have imagined that a little soft fish could have destroyed

the great and savage shark?

March 18th.--We sailed from Bahia. A few days afterwards, when not far

distant from the Abrolhos Islets, my attention was called to a

reddish-brown appearance in the sea. The whole surface of the water,

as it appeared under a weak lens, seemed as if covered by chopped bits

of hay, with their ends jagged. These are minute cylindrical

confervae, in bundles or rafts of from twenty to sixty in each. Mr.

Berkeley informs me that they are the same species (Trichodesmium

erythraeum) with that found over large spaces in the Red Sea, and

whence its name of Red Sea is derived. [8] Their numbers must be

infinite: the ship passed through several bands of them, one of which

was about ten yards wide, and, judging from the mud-like colour of the

water, at least two and a half miles long. In almost every long voyage

some account is given of these confervae. They appear especially

common in the sea near Australia; and off Cape Leeuwin I found an

allied but smaller and apparently different species. Captain Cook, in

his third voyage, remarks, that the sailors gave to this appearance the

name of sea-sawdust.

Near Keeling Atoll, in the Indian Ocean, I observed many little masses

of confervae a few inches square, consisting of long cylindrical

threads of excessive thinness, so as to be barely visible to the naked

eye, mingled with other rather larger bodies, finely conical at both

ends. Two of these are shown in the woodcut united together. They

vary in length from .04 to .06, and even to .08 of an inch in length;

and in diameter from .006 to .008 of an inch. Near one extremity of

the cylindrical part, a green septum, formed of granular matter, and

thickest in the middle, may generally be seen. This, I believe, is the

bottom of a most delicate, colourless sac, composed of a pulpy

substance, which lines the exterior case, but does not extend within

the extreme conical points. In some specimens, small but perfect

spheres of brownish granular matter supplied the places of the septa;

and I observed the curious process by which they were produced. The

pulpy matter of the internal coating suddenly grouped itself into

lines, some of which assumed a form radiating from a common centre; it

then continued, with an irregular and rapid movement, to contract

itself, so that in the course of a second the whole was united into a

perfect little sphere, which occupied the position of the septum at one

end of the now quite hollow case. The formation of the granular sphere

was hastened by any accidental injury. I may add, that frequently a

pair of these bodies were attached to each other, as represented above,

cone beside cone, at that end where the septum occurs.

I will add here a few other observations connected with the

discoloration of the sea from organic causes. On the coast of Chile, a

few leagues north of Concepcion, the Beagle one day passed through

great bands of muddy water, exactly like that of a swollen river; and

again, a degree south of Valparaiso, when fifty miles from the land,

the same appearance was still more extensive. Some of the water placed

in a glass was of a pale reddish tint; and, examined under a

microscope, was seen to swarm with minute animalcula darting about, and

often exploding. Their shape is oval, and contracted in the middle by

a ring of vibrating curved ciliae. It was, however, very difficult to

examine them with care, for almost the instant motion ceased, even

while crossing the field of vision, their bodies burst. Sometimes both

ends burst at once, sometimes only one, and a quantity of coarse,

brownish, granular matter was ejected. The animal an instant before

bursting expanded to half again its natural size; and the explosion

took place about fifteen seconds after the rapid progressive motion had

ceased: in a few cases it was preceded for a short interval by a

rotatory movement on the longer axis. About two minutes after any

number were isolated in a drop of water, they thus perished. The

animals move with the narrow apex forwards, by the aid of their

vibratory ciliae, and generally by rapid starts. They are exceedingly

minute, and quite invisible to the naked eye, only covering a space

equal to the square of the thousandth of an inch. Their numbers were

infinite; for the smallest drop of water which I could remove contained

very many. In one day we passed through two spaces of water thus

stained, one of which alone must have extended over several square

miles. What incalculable numbers of these microscopical animals! The

colour of the water, as seen at some distance, was like that of a river

which has flowed through a red clay district, but under the shade of

the vessel's side it was quite as dark as chocolate. The line where

the red and blue water joined was distinctly defined. The weather for

some days previously had been calm, and the ocean abounded, to an

unusual degree, with living creatures. [9]

In the sea around Tierra del Fuego, and at no great distance from the

land, I have seen narrow lines of water of a bright red colour, from

the number of crustacea, which somewhat resemble in form large prawns.

The sealers call them whale-food. Whether whales feed on them I do not

know; but terns, cormorants, and immense herds of great unwieldy seals

derive, on some parts of the coast, their chief sustenance from these

swimming crabs. Seamen invariably attribute the discoloration of the

water to spawn; but I found this to be the case only on one occasion.

At the distance of several leagues from the Archipelago of the

Galapagos, the ship sailed through three strips of a dark yellowish, or

mud-like water; these strips were some miles long, but only a few yards

wide, and they were separated from the surrounding water by a sinuous

yet distinct margin. The colour was caused by little gelatinous balls,

about the fifth of an inch in diameter, in which numerous minute

spherical ovules were imbedded: they were of two distinct kinds, one

being of a reddish colour and of a different shape from the other. I

cannot form a conjecture as to what two kinds of animals these

belonged. Captain Colnett remarks, that this appearance is very common

among the Galapagos Islands, and that the directions of the bands

indicate that of the currents; in the described case, however, the line

was caused by the wind. The only other appearance which I have to

notice, is a thin oily coat on the water which displays iridescent

colours. I saw a considerable tract of the ocean thus covered on the

coast of Brazil; the seamen attributed it to the putrefying carcase of

some whale, which probably was floating at no great distance. I do not

here mention the minute gelatinous particles, hereafter to be referred

to, which are frequently dispersed throughout the water, for they are

not sufficiently abundant to create any change of colour.

There are two circumstances in the above accounts which appear

remarkable: first, how do the various bodies which form the bands with

defined edges keep together? In the case of the prawn-like crabs,

their movements were as co-instantaneous as in a regiment of soldiers;

but this cannot happen from anything like voluntary action with the

ovules, or the confervae, nor is it probable among the infusoria.

Secondly, what causes the length and narrowness of the bands? The

appearance so much resembles that which may be seen in every torrent,

where the stream uncoils into long streaks the froth collected in the

eddies, that I must attribute the effect to a similar action either of

the currents of the air or sea. Under this supposition we must believe

that the various organized bodies are produced in certain favourable

places, and are thence removed by the set of either wind or water. I

confess, however, there is a very great difficulty in imagining any one

spot to be the birthplace of the millions of millions of animalcula and

confervae: for whence come the germs at such points?--the parent bodies

having been distributed by the winds and waves over the immense ocean.

But on no other hypothesis can I understand their linear grouping. I

may add that Scoresby remarks that green water abounding with pelagic

animals is invariably found in a certain part of the Arctic Sea.

[1] I state this on the authority of Dr. E. Dieffenbach, in his German

translation of the first edition of this Journal.

[2] The Cape de Verd Islands were discovered in 1449. There was a

tombstone of a bishop with the date of 1571; and a crest of a hand and

dagger, dated 1497.

[3] I must take this opportunity of acknowledging the great kindness

with which this illustrious naturalist has examined many of my

specimens. I have sent (June, 1845) a full account of the falling of

this dust to the Geological Society.

[4] So named according to Patrick Symes's nomenclature.

[5] See Encyclop. of Anat. and Physiol., article Cephalopoda

[6] Mr. Horner and Sir David Brewster have described (Philosophical

Transactions, 1836, p. 65) a singular "artificial substance resembling

shell." It is deposited in fine, transparent, highly polished,

brown-coloured laminae, possessing peculiar optical properties, on the

inside of a vessel, in which cloth, first prepared with glue and then

with lime, is made to revolve rapidly in water. It is much softer,

more transparent, and contains more animal matter, than the natural

incrustation at Ascension; but we here again see the strong tendency

which carbonate of lime and animal matter evince to form a solid

substance allied to shell.

[7] Pers. Narr., vol. v., pt. 1., p. 18.

[8] M. Montagne, in Comptes Rendus, etc., Juillet, 1844; and Annal. des

Scienc. Nat., Dec. 1844

[9] M. Lesson (Voyage de la Coquille, tom. i., p. 255) mentions red

water off Lima, apparently produced by the same cause. Peron, the

distinguished naturalist, in the Voyage aux Terres Australes, gives no

less than twelve references to voyagers who have alluded to the

discoloured waters of the sea (vol. ii. p. 239). To the references

given by Peron may be added, Humboldt's Pers. Narr., vol. vi. p. 804;

Flinder's Voyage, vol. i. p. 92; Labillardiere, vol. i. p. 287; Ulloa's

Voyage; Voyage of the Astrolabe and of the Coquille; Captain King's

Survey of Australia, etc.